Talk:Magnetic resonance imaging/Archive 1

Archive 1

Archive 2

Reading an MRI signal

The comment below is partly true. When the external RF pulse is turned on there will be magnetization in the x-y plane. The atoms will now emit a radio frequency themselves - the energy coming from the external RF pulse. However, you can't measure this until the external RF pulse is turned off. As soon as this happens there is T1 and T2 relaxation of the signal.

So the signal is measured during T1 and T2 relaxation but it is caused by the magnetization vector in the x-y plane. Doregan 13:49, 30 November 2007 (UTC)

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The article contains the text:

"As the high-energy nuclei relax and realign, they emit energy which is recorded to provide information about their environment."

I believe that this is a popular misconception about how MRI machines work. What the MRI machine actually measures is the bulk magnetization in the X-Y plane, NOT a radio signal that is emitted by the relaxing protons. Protons actually emit virtually no electromagnetic radiation as they undergo T-1 relaxation; the energy that is lost when they realign along the Z-axis is transferred into the environment as thermal motion. That's why T-1 relaxation is sometimes called "spin-lattice relaxation" - the protons are transferring their excess energy into the lattice as heat via dipolar interactions, paramagnetic interactions, etc. So, it does not seem accurate to me to describe the MRI machine as recording “the energy that is emitted when the nuclei relax.” -July 20, 2005

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Hoping that some contributors may notice, I would like to propose one addition here (being not that bold for the moment):

The increasing number of MRI scans ordered has become a significant cost factor for healthcare. Even when a CAT examination would be able to answer the same questions, MRI scans are ordered where available.

Opinions whether this statement is NPOV and may be added? Pjacobi 15:43, 19 Jul 2004 (UTC)

• It may be worth rephrasing, but seems valid to add. It may also be worth noting that unlike CAT, MRI studies don't involve radioactive contrast materials. --Improv 14:30, 21 Feb 2005 (UTC)

Where I work, I feel MRI is in fact underutilized. The radiation dose and contrast load of enhanced CT are serious things. As mentioned above, MRI has neither of these risks, as far as we know, and in many cases -- not all -- provides superior diagnostic information. It is very true that cost and time (MRI is much more time intensive than CT, both in preparation and acquisition) are real factors, but this will only improve in the near future, as it has in CT. I would choose MRI over CT for my family any time I could. xiggelee 02:04, 1 Mar 2005 (UTC)

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"Such open bore magnets are often lower field magnets, typically in the 0.2 Tesla range, which decreases their sensitivity but also decreases the Radio Frequency power potentially absorbed by the patient during a protracted operation."

Is this true? I don't think the field strength of the large coil necessarily has anything to do with the intensity of the RF. - Omegatron 03:38, Feb 14, 2005 (UTC)

The frequency of the RF field is proportional to the main field of the magnet: lower field => lower RF freq. => lower SAR. Also the induced currents into the conducting instruments (such as needles) decrease with lowering of the frequency.

AFAIK, the only outcome of increased deposition of RF energy in a patient is increased heat deposition, and it is on a miniscule order of magnitude -- not enough heat to feel. (Any heat felt during the scan would most likely be from the equipment, not the RF pulse.) Importantly, the signal-to-noise ratio is wildly better on the stronger field magnets (usually 1.5 T). The open bore magnets yield lower quality images. xiggelee 02:04, 1 Mar 2005 (UTC)

Yes, the whole body SAR is typically not a factor at lower fields (excluding very small patients, such as babies). But the localized SAR, for example, at the tip of an antenna-like needle, can easily exceed the SAR limits - Evahala

SAR is definetly a factor at high field strength (3T and above) which is becoming more and more common now days. I am working with an MRA sequence (at 4T) that could run in 13min but takes about 30 min to spread out the power deposition from the RF energy. Also higher field strengths have much more strict limitations on what sort of implanted devices you can have in the magnet. Almost anything goes at 0.2T or even 1.5T, but you get up to 4T and only permanent dental work is allowed (somewhat due to the higher field, mostly due to the increase RF deposition). - SBarnes

MRI and depression

Might it be appropriate to mention the anecdotal evidence that MRI can alliviate depression? jScott 06:12, 2005 Feb 21 (UTC)

• I've never heard anything about this, but I'll mention it to my subjects :) Seriously though, unless it's at all a well known belief or happens to be true (I know of no studies on the topic, but I'll do a litsearch when I get to work), I doubt it's worth mentioning. It seems extremely unlikely to me that MRI could affect people that way given the physics involved, although it's possible that the novel experience of being in an enclosed space for the length of a study (or for a medical scan), or being around researchers/doctors, may make people feel better. Even if MRI were, on some off chance, actually capable of affecting things, it would be prohibitively expensive to do frequent treatment with it -- where I work, our scanner is typically backed up for weeks in advance, and costs around $700/hr to run. --Improv 14:30, 21 Feb 2005 (UTC)

• You may be referring to repetitive transcranial magnetic stimulation (rTMS). I don't know a lot about it, but while it does involve magnetism applied to the brain, it is otherwise a completely different technique than MRI. rTMS produces a transient high-strength rapidly-changing magnetic field in the brain, and it is a treatment alternative to electroconvulsive therapy (ECT). In MRI, the magnetic field is only the background: the magnet aligns the nuclei, an RF pulse knocks them out of alignment, and as they go back, you watch what happens and gather information. xiggelee 02:04, 1 Mar 2005 (UTC)

• It's actually a study from McLean Hospital in the US by Rohan et al. in 2004 that found bipolar patients reporting, in anecdotal fashion, an improvement in their depression following a MR spectroscopic imaging scan. Follow-up experiments indicated that only specific imaging parameters lead to the behavioural effect (that is, their MRSI sequence did, but another sequence, I believe it was PEPSI didn't). Am J Psychiatry. 2004 Jan;161(1):93-8. See Bioelectromagnetics Potatophysics 09:15, 8 November 2005 (UTC)

Spins of atomic nuclei

"When the object to be imaged is placed in a powerful, uniform magnetic field, the spins of the atomic nuclei ..." I may be rusty on NMR, but isn't it the spin of the electrons, and not the nuclei? --jag123 06:22, 1 Mar 2005 (UTC)

Nuclear Magnetic Resonance —jScott 23:47, 2005 Mar 17 (UTC)

It's the nuclei (*Nuclear* Magnetic Resonance). ESR (Electron Spin Resonance) uses electron spin. However, electrons do change the magnetic environment of the nuceli, which gives rise to tissue differences, etc...

Encoding of position information, and T1 and T2 evaluation

I've read through the article a couple of times, and the "technique" section could use clarification. Specific questions are:

• How are the T1 and T2 times measured, signal-wise? As a precessing proton is a quantum system, they shouldn't emit RF while precessing, but instead emit only when changing state. What are these state transitions, and what do emission spectra look like? Or are _absorption_ spectra what's measured? Some of this is covered in NMR spectroscopy, but what's measured here seems to be something different.
• It seems odd that RF of the frequency of ground-state resonance would bump the precessing nuclei into much-higher-energy states; I'd expect the energy applied to have to be the difference between source and destination states. There's some aspect of this I'm not seeing, which it would be handy to fold into the description.
• I'm having a great deal of trouble seeing how detailed spatial information is extracted in more than one dimension. Applying a field gradient in one direction would give you information by having resonant frequency change with position on that axis, but applying such fields sequentially gives you far less information than would be needed to unambiguously reconstruct the scanned object. I also don't see how you'd do phase encoding, or how frequency encoding wouldn't interfere with the coding resulting from the first applied field, or how you'd get 3D spatial frequency information to work with. Clarification of this (possibly including diagrams) would be very handy.

Thanks. --Christopher Thomas 17:34, 23 Jun 2005 (UTC)

Update - I see how you can get intensities for all of the spatial frequencies by varying the strength of the three gradient fields at once and checking different linear combinations of them, but you'd need to take a minimum of several hundred samples to do this, which means your subject would probably have moved enough during that time to muck up the results. Still waiting with interest for the actual answer.--Christopher Thomas 04:12, 24 Jun 2005 (UTC)

Quantum mechanically speaking, the system is a classic two-state system (see Feynman Lectures on Physics Vol 3). In the presence of a background magnetic field, the proton exists in two states of definite energy ie two stationary states (call it spin parallel and spin anti-parallel). In thermal equilibrium, slightly more protons are in the lower energy state. The presence of an oscillating polarized magnetic field at Larmor frequency (with energy corresponding to the energy gap between states) causes transitions between the states. If the field has amplitude B, the proton goes from one state to the other in a time $\pi /\gamma B$ where $\gamma$ is the gyromagnetic ratio. This corresponds to a "180 degree flip". At other times, the proton is in a superposition of both states. If the oscillating field is then switched off, in the presence of the background field, this superposition of two states will evolve a phase change which is identical to "precession". A quantum mechanical description of how this precessing system couples with a radio receiver to give a signal is beyond me.

Empirically, the system can be described as a magnetization vector that obeys the Bloch equations.

Spatial encoding: Usually only one slice of protons is excited by applying an oscillating B field with a narrow range of frequencies simultaneously with a "slice-select" gradient. Encoding is thus reduced to two dimensions. It is possible to obtain a one dimensional distribution (projection) of proton density over the entire slice with one excitation, by applying a "read" gradient (perpendicular to the slice-select gradient) during signal reception. The projection is then derived from the signal by a Fourier transform. The projection will be perpendicular to the direction of the read gradient. By rotating the direction of the read gradient following different excitations (typically ~128 or 256), projections at different angles are obtained, from which the 2d proton distribution in the slice can be calculated using the inverse Radon transform, similar to computed tomography. In practice, either filtered back-projection (a less computationally intensive form of the inverse Radon transform algorithm), or regridding, is used instead. Alternatively, it is possible to keep the read gradient during signal reception in the same direction, but to turn on, briefly (switch on after excitation but switch off before signal reception), a gradient in the direction perpendicular to both the read and slice-select gradients. By changing the strength of this "phase-encoding" gradient before every signal, projections at different phase encodings are obtained, from which the 2d proton distribution can be calculated using another Fourier transform in the phase-encoding direction. Note that in imaging it is important to change the strength rather than the time the phase encoding is left on: this keeps the echo time constant and is the basis of the classic "spin warp" technique (see Edelstein WA et al "Spin warp NMR imaging and applications to human whole-body imaging" Physics in Medicine and Biology 25(4):751-6 1980) - August 17, 2005

Thanks for the response. It cleared up a lot of confusion. --Christopher Thomas 06:11, 5 November 2005 (UTC)

T1 and T2 contrast: MRI machines don't measure the T1 and T2 times directly. Instead the T1/T2 properties are used to modify contrast already present. The T1 time represents the time constant for relaxation of the spins following excitation. T2 represents the time constant for disappearance of the bulk transverse magnetization (this is much quicker than T1 and is due to loss of phase coherence of the individual nuclei).

Consider the trivial case where the transverse magnetization is measured immediately following application of the exciting RF pulse. The intensity of the signal would depend only on the number of protons in the region of interest (hence a proton density image). Now consider, what occurs if there is a delay between measurement of the excitation and measurement of the signal - in this case, the signal will have faded from the previous scenario. However, the degree of fading is related to the T2 of the individual tissues - tissues with short T2 will fade more than tissues with long T2. An image obtained under these conditions is said to be T2-weighted because it now contains information about the T2, but is not in itself a measure of the T2. The degree of T2-weighting is controllable by changing the delay ('echo time' or TE).

Information on the T1 can be obtained if T1 relaxation is incomplete. Tissues with a long T1 time will recover longitudinal magnetisation slowly, hence there will be less LM with which to generate transverse magnetisation when the next pulse is applied. Long repetition times (TR) mean almost complete LM recovery, in all tissues, and hence very little influence of T1 on the signal. Short TR produces a large influence of T1 on the signal.

In practice, it isn't possible to separate Proton density, T1 and T2 effects completely - but it is possible to weight the image in one direction or other.

Similarly, in practice, the signal fades faster than T2, because of local magnetic field inhomogeneities and other effects. (A non-uniform field will cause non-uniform precession within a region, and hence rapid loss of phase coherence). This is called T2*. A technique called 'spin echo' can be used to recover the true T2 - the simple description is that the direction of precession is reversed mid-way between excitation and measurement - hence protons with a higher Larmor frequency, which had developed a phase lead, are flipped into a lagging phase at the mid point, before coming back into phase at the time of measurement. ChumpusRex 00:28, 7 February 2006 (UTC)

More on Phase Encoding

The Radon transform is not used in MRI. That would involve convoluting the data from projections through the patient. Typical single and multi slice techniques use a 2 Dimensional Fourier Transform for reconstruction (2dft). Christopher's observation about needing numerous samples is correct. That is the 128 to 256 excitations mentioned in the previous paragraph. Obviously, it has been possible to fit them into usable techniques covering a time for which most patients can remain still. However, these techniques cannot be used for things like imaging the intestines, which move on their own. Echo planar imaging is very fast and solves the motion problem. Maybe I'll look it up sometime and send in some info on it.

Some specifics on phase encoding: After each excitation, the signal is read with the frequency encoding gradient on and always at the same level. Thus, the correspondance of frequency across the fequency encoded direction remains constant. However, prior to the readout, an additional phase encoding gradient is turned on and then off. The amount of time that it remains on is different for each excitation. Usually it builds to a maximum in one direction, then goes to zero and builds again in the opposite direction. During the time that the gradient is on, the frequencies vary as a function of position in the third dimension. When the gradient is turned off, the frequencies return to a constant (the slice selection frequency). However, in the interim, the signals have acquired a phase difference along the PE (phase encoded) direction. Now, if you reorder these acquisitions so that the phase encoding increases monotonicly (spelling?) and examine a single frequency for each excitation, you will have a one dimensional signal which can be analysed with another fourier transform. The result of the transform gives the relative strength for the selected frequency encoding position as a function of the position in the phase encoding direction. This is what you need in order to sort out the final dimension.

Earlier in the discussion, someone cited the danger of injected radioactive substances in CT. That's in Nuclear Medicine (PET, SPECT, Bone Scans, Blood Scans, etc.). The radiation in CT comes from the X-Ray tube. The contrast agents in CT simply absorb more X-rays than normal tissue and therefore show up on the image.

About depression: At one time I got a whole lot of MRI during software development and (particularly) during testing. I don't know if I was less depressed during that period (I take Effexor now), but I know I did get more sleep because I always fell asleep in the scanner.

Bulk Magnetization: The first note on this discussion page talks about RF emissions and the measurement of bulk magnetization. The receiver coil on an MRI scanner is definately an RF antenna. It is not a magnetometer. It receives an RF signal at the Larmor frequency (actually the spread of frequencies dictated by the frequency encoding gradient). I can't think of any source for this RF other than the relaxing photons. Certainly the signal strength is low. Lots of people thought that usable diagnostic images could never be produced via MRI for this reason.

The T1 characteristics of this signal are tied to the properties of the local tissue. This indicates that the vast majority of the RF is absorbed locally and transformed to heat energy in the tissue. The receiver coil provides another energy absorption option for the nuclei to emit to. If the receiver could be made immensely more effective, then it would also dominate the T1 property,and at the least remove tissue T1 sensitivity from the image.

A great deal of mystery is due to the position of MRI at the cusp of classical and quantum physics. Most systems for which the quantum equations are reasonably simple cannot be analysed using classical physics without producing gross errors (the electronic shell structure of the atom is a good example). Conversely, most systems which can be correctly analysed using classical mechanics become absurdly complex when quantum mechanics is applied (did you ever try to compute the allowed energy levels for a bowling ball?). MRI can be approached from either direction. Therefore, most texts use both tools to illuminate the subject. Unfortunately, this require great precision in the definition and use of terms and it is sometimes lacking. I suspect that this is the cause of some of these misperceptions.

You can find a lot of this information in Bushberg's "Essential Physics of Medical Imaging." There is also an excellent (!!!) MRI online tutorial at http://www.cis.rit.edu/htbooks/mri/inside.htm, complete with lots of animated spin vectors.

P.S. I just created an account and this is my first interaction with Wikipedia, so please be ruthless in chopping out whatever doesn't belong. I won't be offended. My name is comming out like an ip address on the preview, so I am Ed Solem (edsolem) and my address is els@plexar.com. 67.23.4.116 16:29, 13 August 2005 (UTC)

Thanks for the additional clarification. It was very useful. --Christopher Thomas 06:12, 5 November 2005 (UTC)

Nobel Prize Controversy

Removed the words "Several MRI experts and university professors were quoted in the ads expressing their disappointment and dismay at the exclusion." from the article. In the MR community, a much larger number of scientists and MRI experts expressed no such disappointment (or rather, supported it), and without mentioning them, this seems to violate NPOV as an appeal to authority. Perhaps we should consider shortening this section and letting people read about in the Damadian article, rather than replicate it here?

• I added back in the text to the ad. I think that should be a link here at least, as it was a notable event. There could/should be a whole other article regarding the Damadian controversy. Semiconscious (talk · home) 18:37, 11 September 2005 (UTC)

• Someone's made significant edits to this section, and it reads quite poorly. Does someone want to volunteer to clean this up?

• There is far more about Damadian in the Nobel Prize section than either Lauterbur or Mansfield. There was much more noise than controversy, and many in the MR community feel the decision was sensible. Does anyone mind if I tidy up? Full disclosure - I work in Mansfields centre in Notts.

Animated image

Good though it is, it's not wise to have a rapidly- changing, animated image; they're problematic for some people with epilepsy (and other conditions); and of course such people may be particularly attracted to an article such as this. It's also contrary to the [[W3C] web accessibility standards, which we should strive to meet. Accordingly, I'm replacing it with a link. Andy Mabbett 11:33, 7 October 2005 (UTC)

I think the illustration is far more useful than any supposed problems it may cause. I suggest that you ask on the Village pump and seek to build a more general concensus that animations should be removed from Wikipedia, before making a decision like this. In the mean time I will restore the illustration. -- Solipsist 16:19, 10 October 2005 (UTC)

What mroe evidence do you need, than the WAI guidelines: 7.1 and 7.3 expecially? Note also my point about the likely audience for this subject Andy Mabbett 16:29, 10 October 2005 (UTC)

I suspect you are misunderstanding the W3C guidelines. Individual pixels flickering are not likely to cause problems of any sort. The guidelines are about flashing the whole screen on large blocks of text. -- Solipsist 16:37, 10 October 2005 (UTC)

Which part of avoid movement in pages do you think I am misunderstanding? Andy Mabbett 17:25, 10 October 2005 (UTC)

• The W3C page has this to say about these guidelines:

"These guidelines are a specification developed by the W3C, an international, vendor-neutral industry consortium, and have been developed under W3C process. W3C is not a legislative body and the Web Content Accessibility Guidelines specification is not a regulation. The guidelines may be informally or formally adopted by different kinds of organizations to clarify what level of accessibility that organization requires for particular Web sites. If you would like to learn more about specific laws or policies in different countries which have bearing on accessibility requirements for Web sites, some of these are available in the policy references section of the WAI site. Please contact the relevant legal authority for more details on obligations and/or enforcement."

The specific guideline in question here is 7.3, as it is fairly explicit that 7.1 does not apply for a slow-moving, small image.

7.3 is rated as "priority 2", defined as "A Web content developer should [note: emphasis theirs] satisfy this checkpoint. Otherwise, one or more groups will find it difficult to access information in the document. Satisfying this checkpoint will remove significant barriers to accessing Web documents." The animated gif image on this page does not inhibit one from accessing the page; that is, its inclusion does not prohibit one from reading the page in any browser.

If you feel there are certain disabled populations who will suffer accessibility to this page because of its inclusion, you should justify that and include your reasoning Andy. Given this is a priority 2 guideline and that its inclusion does not limit accessibility, I feel that the utility and merit of the image supersede any potential dangers or accessibility deficits the image may cause. semiconscious (talk · home) 18:20, 10 October 2005 (UTC)

• I concur with Semiconscious on this. Unless you can demonstrate that either Wikipedia has made a commitment to obey w3 recommendations or that there is other policy on animated images, I don't think you've demonstrated a good enough reason to have the image removed. --Improv 22:26, 11 October 2005 (UTC)

*User has had problems in the past, and just needs some attention. Please see the (RFC) filed against user, of which he has yet to answer; just ignore him, as he never creates any article, or has loaded any pictures, etc. Quote: "Which part of avoid movement in pages do you think I am misunderstanding"? Just look at his user page (user:Pigsonthewing). Scott 17:36, 17 October 2005 (UTC)

he never creates any article A bare-faced lie by User:Scottfisher. Andy Mabbett 19:23, 17 October 2005 (UTC)

• I don't even know why I'm bothering because it has nothing to do with the point at hand, but I find myself commenting never the less. Andy Mabbett seems to have contributed to many articles on Wikipedia. However—in the strictest sense at the time of this writing—Scott is correct: in reviewing his user contributions Andy has not created any articles. Can we please move on though and refrain from taking this... this whatever it is... any further? semiconscious (talk · home) 22:28, 17 October 2005 (UTC)

Scott is correct: in reviewing his user contributions Andy has not created any articles.: Poppycock. I look forward to your appology. Andy Mabbett 22:46, 17 October 2005 (UTC)

• I apologize for saying you have contributed many articles to Wikipedia. :) Just kidding. It would seem I was hasty in my previous declaration and my skills at using Wikipedia have not fully developed. You have indeed made many unique, new page contributions, so I apologize. Best. semiconscious (talk · home) 01:08, 18 October 2005 (UTC)

Source of the animated image

There is a more basic problem with the animated image. It is not from an MRI scan. The animated image is a cross-sectional series from a CT scan. There is no way to make bone light up like that using an MRI machine. I think it should be removed. —The preceding unsigned comment was added by HankD (talk • contribs) on 16:24, 1 March 2006.

It's a T1 weighted axial series from an MRI. I don't think there's any doubt about that. CT can't show the difference between grey and white matter as well as that. The reason it looks wrong is because it's a negative of the conventional way of displaying images. Thus, the bone, which produces almost no MR signal shows up white on this image (by convention no signal is shown as black - an exception is 'phase sensitive' inversion recovery imaging, where a 'negative' signal is usually shown as black and 'positive' as white).ChumpusRex 18:45, 1 March 2006 (UTC)

It's my head. It was scanned at UC Berkeley on their Varian 4T MRI. It's still a bad animation and should be removed though. :) Semiconscious • talk 06:19, 22 March 2006 (UTC)

The cine series has not been inverted. The white in these images is not bone but subcutaneous fat, which is hyperintense (bright) on sequences such as the spoiled gradient echo (SPGR) or MP-RAGE used here.

RFC request

Comment. I am responding to the RFC request on Wikipedia:Requests for comment/Maths, natural science, and technology. I think the animated image should stay. According to WAI, the "Web Accessibility Initiative (WAI) is an effort to improve the accessibility of the World Wide Web (WWW or Web), especially, but not only, for people with disabilities." In my opinon, the "not only" means we should consider all of those who may benefit from the image, not simply those who might. And in my understanding of epilepsy, it is extremely unlikely that this type of graphic would trigger a seizure in the very small percentage of epileptics who might be predisposed to photosensitive epilepsy anyway. Edwardian 05:46, 18 October 2005 (UTC)

• I am also responding to the RFC. As it is, the image does not seem to add anything to the article. Where is it discussed? How is having an animation more effective than having still pics? I would say remove. Physchim62 07:51, 28 October 2005 (UTC)
• I am responding to the RFC. Cross-sectional imaging is often only meaningful when slides are seen in a continuum. Radiologists see things with their scroll button that clinicians don't see when looking at printed films. I think an animated image is an excellent example of the uses of MRI and makes it a lot more tangible. JFW | T@lk 13:07, 31 October 2005 (UTC)
• Responding to the RFC. People with very severe photosensitive epilepsy are likely to use a browser that allows to disable animation, or a separate application that does the same. However, the best of both worlds would be allowing the reader to control the animation. Unfortunately it seems that MediaWiki can't do this. Maybe have a static placeholder on this page with a link to the animated version? Aapo Laitinen 18:38, 4 November 2005 (UTC)

I consider the animated image rather irritating, quite independent of the WAI aspect. I was wondering why it is still there, as I remember that it has been replaced with a still image and link to the animated version. Ahhhh, that was on de:! HAve a look at [1]. I propose switching to this solution. --Pjacobi 23:37, 5 November 2005 (UTC)

• Responding to the RFC: I don't think the image is large enough or fast-moving enough to pose a serious risk to people with photosensitive epilepsy. However, I think it should be buried a bit deeper in the article along with a relevant discussion of using MRI to take multiple cross-sections. When I first saw the RFC regarding a moving image on a MRI page, I expected to see a moving diagram of a precessing/dephasing set of spins. Also, the caption is "fMRI scan" and this doesn't appear to be a very good representation of an fMRI -- I'm much more used to seeing those with the false colour overlay indicating the regions of differential activation seen with the BOLD effect. Perhaps the image appearing at the bottom with the Nobel Prize discussion should head up the article. Potatophysics 10:27, 8 November 2005 (UTC)

In other words, swap the current two image around and improve the captions. This sounds like a good idea. And whilst I was at it I found a clearer fMRI image on Commons. -- Solipsist 11:06, 8 November 2005 (UTC)

MRI and tatoo

In one of the rerun episode of House on Fox, Dr. House told his patient (a tough guy from the death row) in the MRI that it would be very painful for him because of the metallic tatoo ink on his body. The show even dramatized the tough guy squirming in pain as the tatoo on the patient's body turning red hot during the MRI. How much of such dramatization was true? Kowloonese 20:12, 30 December 2005 (UTC)

If you have _conducting_ ink, you can get induction currents set up by the RF probe pulses, but my understanding is that that kind of ink is rare, if it's used at all. Normal inks won't do anything (there was an amusing "myth busters" episode where they did their best to put an MRI-sensitive tattoo on pig skin). Some inks contain magnetic particles that might be affected by the strong DC magnetic field, but I doubt this effect would be significant in the concentrations used (the MB team saw their tupperware tub full of ultra-magnetic dye move, but you're wearing about a hundred thousand times less ink than that). For purposes of the article, medical citations would be needed either way, of course (neither of our TV examples would count). --Christopher Thomas 22:06, 30 December 2005 (UTC)

When I scan people for my experiments, tattoos are considered potentially disqualifying because many inks used do cause burns, and while many others don't, it's better to be safe than sorry when you're scheduling time for something which costs about $700/hour to run. According to the MRI techs at the scanner, they've seen people who have had their tattoos burn them in the scanner. I realise that this still is hearsay, but it's a little bit less hearsayish on topics like these. --Improv 23:51, 30 December 2005 (UTC)

Hmm...what sort of power output do you get from the RF transmitter in an MRI? It seems unlikely to me that there would be enough power to heat something up like that.

• Here is a sample safety procedure guideline that isn't too dissimilar to the training information I received before I was permitted to scan. This site also has more info on the RF pulse levels -- the MR Techs do calculations based on weight and expected heating before the scan begins. It is important to note that when the subject is in the scanner for long periods of time (my experiments, with the structural parts added in, run nearly 2 hours), moderate heading could add up. --Improv 07:32, 11 February 2006 (UTC)

• The RF output for a typical medical MR scanner can be significant. In medical devices, transmitters with peak outputs of 15-35 kW are typical. In most cases the duty cycle is very low. However, certain rapid imaging techniques (e.g. fast spin echo) can require average output powers of over 1 kW. Current guidelines recommend that the SAR be limited (e.g. to 4 W/kg over the whole body averaged over 15 minutes). One challenge that many researchers/manufacturers are facing is how to accelerate image acquisition, or improve image quality, while still meeting these guidelines. This is particularly the case with the tendency for manufacturers to offer incresingly stronger magnets (SAR is approx proportional to B₀²) as a way to improve image quality. ChumpusRex 22:08, 15 February 2006 (UTC)

• I would echo Improv's reference to the ACR Guidance Document for Safe MR Practices: 2007 and its references to tattoos and safety. --Tgilk (talk) 15:59, 5 January 2008 (UTC)

Nomenclature

While the sentence about the cost of MRI equipment is important and valid, I think it is quite out of place under a subheading of nomenclature. Also, I don't think this sentence needs to start with "unfortunately." Perhaps this sentence should be brought up to the first paragraph? Faeanna 04:00, 8 January 2006

• I created a heading on 'Economics' of MRI providing some very general information on gross costs and information on recent changes to the way MRI scans are reimbursed in the US by the insurance providers. I welcome the thoughts and comments of others. --Tgilk (talk) 16:01, 5 January 2008 (UTC)

What can be inferred from this technique?

Correct me if I'm wrong, but I don't see any discussion in the article about what sort of information researchers may be able to/have discovered by using this technique. Without wanting to sound melodramatic, can this technique be used to read your thoughts, to some extent? I've been asked - and am inclined - to take part in an experiment using one of these things, so I'm kind of curious about it. --Kick the cat 12:33, 4 February 2006 (UTC)

No, MRI gives strictly anatomical information. fMRI may light up certain areas used in certain kinds of cognitive activity. As it involves no radiation, it is generally considered to be harmless (unless you've got metal clips somewhere). JFW | T@lk 05:23, 5 February 2006 (UTC)

Read thoughts? That one's new to me! :)--Zereshk 05:27, 30 March 2006 (UTC)

Nuclear technology template

Magnetic resonance is not a nuclear technology in the sense that nuclei are only used as sensors and are not modified as in radioactivity of in nuclear fission. No harmful high-energy radiation is involved in this technique, and this is precisely the reason why the word "nuclear" is avoided in the name of the technique in the context of its application in medicine (as opposed to the NMR, a term used in physics). Andreas 14:48, 19 March 2006 (UTC)

Damadian

Does the GE litigation mentioned in the Damadian part of the article belong to "1997" or "1979"?--Zereshk 05:25, 30 March 2006 (UTC)

So when was it invented?

The nobel price contoversy section hints at 1974, but thats not for a magnetic resonance imager. When was the design as we use today invented? Thought it should definatly be included both in the article and in here - Jak (talk) 16:52, 10 July 2006 (UTC)

Herman Carr invented the gradient technique used today and actually produced one-dimensional images in the 1950's. The key event was the discovery about 1970 of tissue relaxation times differences by first Freeman Cope with deuterium oxide and then Raymond Damadian with regular water. This meant "contrast", if a way could be found to effectively localize the signal. Lauderbur and Mansfield figured out how to do this, using a development of Carr's original technique. Sesquiculus1 00:45, 22 August 2006 (UTC)

Vested interest, but no-one ever seems to mention Professor John Mallard (plus Jim Hutchison, Bill Edelstein and Margaret Foster) - key figures in both MRI and PET development. They developed the spin-warp technology, imaged a mouse in 1974 and produced the first clinically useful images in 1980... don't want to add anything as yet as wanted a worldwide perspective first.

Hutchison JMS, Mallard JR, Goll CC. In-vivo imaging of body structures using proton resonance. Proceedings. 18th Ampère Congress. Magnetic resonance and related phenomena. Nottingham 9-14 September 1974. Amsterdam, Oxford: North-Holland Publishing Company. 283-284.

Edelstein WA, Hutchison JMS, Johnson G, Redpath TW. Spin-warp NMR imaging and applications to human whole-body imaging. Phys Med Biol 1980;25:751-756.

Mallard JR. Magnetic resonance imaging—the Aberdeen perspective on developments in the early years. Phys Med Biol 2006;51:R45-R60 PMJ 11:50, 06 November 2006 (GMT)

On the intro section, there is mention of the first MRI patient. Could someone post a date for that first patient scan?

Claustrophobia

People who are claustrophobic (whether they realize they are or not) often cannot undergo MRI scans without sedation (valium or similar). I think this should definitely be mentioned since it is a crucial part of any pre-MRI questionnaire.

If you look up claustrophobia on Wikipedia you'll see some good statistics (with citation) about MRI claustrophobia.

Parts of the claustrophobia section must be some sort of joke. Unless someone has recently invented ear phones that work without magnetic metals the whole part about relieving claustrophobia by watching a film or listening to music is absolute rubish. It may work in other circumstances but I don't think many MR techs would be too happy about an ear phone speaker punching a hole in their machine. —Preceding unsigned comment added by 92.25.231.24 (talk) 21:08, 25 February 2009 (UTC)

I can assure you it's not rubbish in the least. Dunno how they work, but you can definitely use earphones (special earphones, not your own) in an MRI scanner. A citation should still be provided, but from my own experience in a scanner with headphones, I can tell you it happens. _TalkIslander 22:28, 25 February 2009 (UTC)

Headphones are useful to distract patients, but also vital for many fMRI experiments that involve playing sounds, voices, etc to the subject. There are two problems. The most obvious is that most speaker elements are very magnetic, and not welcome inside the bore. The second is that adding magnetic elements close to the volume-of-interest ruins the shim (makes the main B0 field very inhomogeneous). I have seen two different ways of making MR compatible headphones. The first is to put the speaker element outside the magnetic field, and run air-tubes to the headphones. It works surprisingly well and is easy to make, but does distort the sound somewhat. The second is to use electrostatic, rather than magnetic, elements. Some high-end headphones do this for improved accoustic quality (so the manufacturers say, at least). Electrostatic elements can be operated in the main field, so long as all magnetic parts have been replaced.GyroMagician (talk) 15:09, 27 February 2009 (UTC)

Headphones are standard equipment on every MRI scanner. They work, like GyroMagician mentioned, by running air-tubes from an external speaker to the headphones. The headphones are routinely used to advise the patient to hold his breath (for cardiac or body mri), but also quite commonly used to play calming music. —Preceding unsigned comment added by 173.88.132.201 (talk) 23:58, 29 May 2009 (UTC)

MRI scanners?

There is plenty of discussion of the physics involved but I couldn't find any description of what an MRI scanner consists of or why it is so expensive to acquire and maintain. In the safety section there is the first and only mention of superconducting magnets and cryogens. A picture of a scanner and a diagram of its important components would be nice. Pretzelpaws 02:24, 28 July 2006 (UTC)

I have added a picture of a MRI scanner. --WS 21:00, 22 November 2006 (UTC)

The picture is wholly inadequate. It gives no clue as to how 3 orthogonal gradients are set up in what is a solenoidal configuration. Where are the coils (if that is what is used) to set up the gradients? How are they aligned, powered and controlled?

Where is the RF feed?

And for MRI patients who also happen to be physicists, what is the cause of the pulsing sound? I am assuming it is magnetostriction somewhere, but would like to know more.

Yes, I'm an experimental physicist.

Peter.zimmerman (talk) 15:42, 9 May 2008 (UTC)

WOW!

Has anyone ever seen this before?!! [2] I had no idea that real time several Hz MRI images could even possibly be taken like this. I was completely shocked when I saw this video the first time to the point that I thought it might be fake. But it is apparently real! [3]. Can someone work this into the article? --Deglr6328 07:00, 19 August 2006 (UTC)

Effects of titanium

I removed this addition because it had no source and didn't make sense to me:

However, There is a 50/50 chance that the space where the titanium is will cause a blank space in the MRI. While this poses NO risk to the patient it deems the MRI useless in that part of the body.

Why in the world would there be a "50/50 chance"? —Keenan Pepper 00:09, 23 August 2006 (UTC)

Recent edits

A recent edit [4] removed large amounts of text, and left a stray t in the middle. Someone who knows the subject needs to review.

Also why does Lauterbur become Lauderbur ? -- Beardo 23:14, 10 October 2006 (UTC)

MRI measures and intelligence

The article Francis Galton claims there was a 0.4 correlation between intelligence and MRI measures. Is that true? If yes, please add a reference. Further the article claims this had proven Daltons hypothesis that head size was an reliable indicator of intelligence. Is there empirical support for this hypothesis? I don't think so but don't have any references. Thanks in advance, Falk Lieder 14:09, 23 October 2006 (UTC)

Yeah, that Dalton guy was one crazy mother. There was a whole movement back in his day in which many anthropologists and neuroscientists were trying to figure out exactly which traits meant you were intelligent, be it your race, the shape of your features, the nature of the bumps on your head and where they were, and, of course, the size of your head. What is meant, exactly, by a "0.4" correlation? Is this a value of beta in some kind of linear regression? That's not a very strong correlation. I believe I read that, upon Dalton's autopsy, it was found that his brain was actually quite small... I highly recommend that anyone interested or intruiged by this read Steven Jay Gould's book The Mismeasure of Man. 74.245.67.106 22:01, 16 March 2007 (UTC)

EU EMF Directive

The original text was a little partial here. Maybe a little too political also. I've edited it to better reflect both sides of a very complex issue.

Fixed Phil 08:49, 30 October 2006 (UTC)

CT versus MRI

A recent addition, (Also MRI can generate cross-sections that CT cannot, such as diagonal slices through the body.) The concept of MRI providing better 2D and 3D reconstructions in comparison to CT is debateable, however, CT and MR are two different modalities, useful for imaging different anatomical and physiological properties and processes.

Reconstruction algorithms for both CT and MR images can provide images with almost equal useability to a surgeon. In some cases fusion images (blended CT and MRI images), along with Nuclear Medicine scans provide accurate simulation maps for radiotherapy treatment. One modality is not necessarily better or worse, just different.

--Read-write-services 01:01, 3 November 2006 (UTC)

This section (CT vs MRI) ends with the phrase "farts and legs". As a layman who knows nothing about this topic, I have a vision of a polar graph with a starfish shaped contour on it. But the reference is not at all clear. Can someone explain this a bit better. Thanks.

Ccalvin 20:59, 26 January 2007 (UTC)

Hi there, it is vandalism-a sad fact with this medium-well spotted, but I think it has been rectified since, regards,--Read-write-services 23:07, 28 January 2007 (UTC)

Magnetic field strength and resolution?

What are the relationships between:

1. magnetic field strength & spatial resolution and
2. magnetic field strength & temporal resolution?

I think the above questions would be interesting to examine in the article. The article proclaims that MRI scanners with up to 20 Tesla fields are in use in research settings. What does 20 Teslas get you? What is the compromise that is made when using a weaker field-- is it just less cost? If the issue is more complex than just cost, it would be interesting to understand the pros and cons of a stronger field. Nephron  T|C 21:04, 25 November 2006 (UTC)

The most important impact of field strength is signal to noise ratio (SNR). Higher static field strengths result in a larger population of spins aligning parallel to the field, thus the net magnetization is greater. Net magnetization is approximately proportional to B₀²; thus doubling the field strength quadruples the signal strength.

Temporal resolution and spatial resolution are both related to the SNR. By recording the signal more quickly, you receive less information and hence have a poorer SNR. Similarly, by using smaller pixels you divide your signal more finely - the result of which is poorer SNR. SNR is important because it determines the minimum contrast that is visible in the image. The benefit of higher field strength is therefore the ability to increase spatial resolution or decrease scan time without degrading image noise.

Spectroscopy is a technique which can provide information as to the chemical composition of a tissue, and is an important tool in diagnosis of brain diseases - particularly tumors. Spectroscopy gains particular benefit from high field strengths, not just because it samples only a very small volume of tissue (and hence has intrinsically poor SNR) but also because the chemical shift effect (on which spectroscopy depends) is proportional to the field strength.

Increasing field is not without problems:

- Higher field means a higher Larmor frequency. A higher RF frequency means greater RF absorption in tissue causing greater tissue heating and poorer penetration into the body. At field strengths above 1.5 T, RF heating effects are a serious problem - and get worse proportional to B₀². This is a particular problem for metal implants, which suffer significant heating - in general, few implants are regarded as safe above 1.5 T.

- Chemical shift and magnetic susceptibility effects are more evident at high fields. This is further exacerbated by the fact that spin echo techniques (which are tolerant to chemical shift and susceptibility effects) are limited by RF heating, and need to be replaced by gradient echo techniques (which are highly sensitive to these effects).

- Relaxation times are prolonged at high field - because scan times and contrast are related to the tissue relaxation times, the scan time must either be prolonged to compensate or image contrast degraded (particularly T1 contrast).

- Increased risk of side effects - exposure to fields above 3 T have been reported to cause nausea and dizziness. At higher strengths Lenz law and magnetohydrodynamic effects on the cardiovascular system are potentially significant - causing marked distortion of the ECG waveform and raising blood pressure (due to MHD effects causing an apparent increase in blood viscosity).

- Considerably increased cost of the magnet; both installation and maintenance costs.

- There are limits to the field strength at which ancillary equipment (e.g. patient monitoring devices, or remote injector devices) can operate.

In practice, general medical scanners are usually 1.5 T or less - the drawbacks of higher fields tend to outweigh the benefits. However, 3 T scanners are used for specialist work (e.g. brain imaging/spectroscopy, cardiac imaging) and for research.

Even higher field machines (e.g. 4 - 7 T or even 9.4 T) are not used for clinical work (nor are they approved as safe for clinical work) and are purely research tools. Machines using fields higher than 9.4 T are reserved for laboratory small animal or specimen use (partly due to the impracticality of making human sized high-field magnets, but also due to safety concerns).ChumpusRex 02:09, 26 November 2006 (UTC)

The underlying fundamental is that the imaging volume decreases with increase in magnetic field. At a field of 11.7T(500 MHz), the imaging volume is 89 mm. Thus, such high fields are only for small animal imaging - mouse only. Research clinical scanners are available at field strength of 7T, but have smaller bores - small enough to hardly fit a human with a large nose! In addition, larger field magnets are not just astronomically expensive (each Tesla adds about $1 million to cost!), but also more difficult to shim. Many Steady State pulse sequences are run only on 1.5T and run into field inhomogenity problems at higher fields. Navdeep o 19:10, 14 August 2007 (UTC)

Wow. Very detailed answer-- that well surpassed my expectations. Sounds like you're very knowledgable about the subject; I'd bet you have a degree or two in physics or engineering. Any how, it will take me a while to digest what you've written. Also, I'm unfortunately terribly busy with school... but after things look better on that front, perhaps we can somehow integrate your nuggets of wisdom into the article in language that is relatively easy to digest for joe average and makes the article even better (if someone doesn't beat us to it). Nephron  T|C 22:44, 1 December 2006 (UTC)

More basic, non-technical info

This article needs much more background. For example: why are MRIs round? In a machine where is the magnet? Where do the radio waves originate and where do they go? Other simple things. Kevlar67 05:50, 3 January 2007 (UTC)

• Hi there,

NOT all MRI machines are round, some are "C" shaped, some are donut shaped while the usual older style technology has a cylindrical bore for the patient to lay inside. The typical cylindrical machine uses helium cooled, superconductive wire that forms the intense magnetic feild-it is an electromagnet that one it is ramped up (energised with current), the cables are removed and due to superconducxtivity, the magnet remains energised (provided that the helium level is maintaned). The Magnet is the whole unit that you typically see in a picture of the machine. The RF (radio frequency energy) is sent in via the transmitter located outside the magnet room itself. The transmitter is connected to the machine via low loss coaxial cable. The RF energy is 'coupled' to the body using the coil surrounding the patient's head or other region of interest, or may be transmitted from the Body coil located just inside the internal skin of the machine's bore.

I hope this helps-don't know if we need such simplistic explanations though on the actual article? any comments? if so I would be delighted to create an introduction to MRI systems for the article if there is interest! cheers!--Read-write-services 09:34, 4 January 2007 (UTC)

Agree on the more basic info!

K-space? What the heck is that? Has anyone noticed that thi spage only makes sense if you're a physicist? Can't someone explain MRI in terms that a regular person can understand? You know - without the math...

Split page ?

It may be time to split the page into multiple pages, which can then address issues relevant to different communities (laymen, patients, physcicists, doctors etc) more effectively. This will also address issues raised by comments above on "more basic info" and "construction of MR machines". What do others think ?Abecedare 18:28, 6 January 2007 (UTC)

• Agree article should be split. That said, WP (WP:NOT) isn't a manual for experts; so, I disagree with the idea of splitting the article to address different communities.

Here is a proposal for a split:

• Safety of MRI
• Physics of MRI
• Magnetic Resonance Angiography (which already exists)
• Functional MRI
• Interventional MRI
• Magnetic resonance guided focused ultrasound

I think it should be like renal failure or dialysis -- with "main" article links, e.g. {{main|Safety of MRI}}. Nephron  T|C 18:52, 6 January 2007 (UTC)

I concur. I think it may be useful to create the red-linked articles listed by Nephron, and maybe others such as Cardiac MRI (which covers cine imaging, currently unaddressed). Then we can move some of the details to these articles and to others like Diffusion MRI, Diffusion tensor imaging etc.

A useful guideline to follow is WP:Summary style. Abecedare 19:08, 6 January 2007 (UTC)

I agree. The main article is becoming very large and daunting. As previous authos, I don't think that different articles for different audiences are appropriate. While some of the technical details are somewhat arcane, this is perhaps best addressed by a short paragraph, for the layman, in the main article linking to a more in-depth article.

I've also just added a section on scanner design/construction. Again, this is probably something that could have its own article. ChumpusRex 23:42, 6 January 2007 (UTC)

I don't know about splitting the page, but I do know that the lay-person's write-up is too simple and the technical write-up jumps too fast into advanced topics and needs bridging and better definition of symbols (e.g. vector-G; I guess it's the gradient). Let me say that I'm a PhD physicist, knew Felix Bloch well, and even did an experiment in an undergrad lab using the discovery apparatus. I still find it too hard to make the jump from the lay description to the technical one. Wikipedia shouldn't just be reference for the cognoscenti. —Preceding unsigned comment added by Peter.zimmerman (talk • contribs) 15:51, 9 May 2008 (UTC)

Sorry; forgot to sign above para.

Peter.zimmerman (talk) 15:55, 9 May 2008 (UTC)

Requested move

Magnetic resonance imaging → Magnetic Resonance Imaging — The obvious title of this article seems like it should be Magnetic Resonance Imaging because that's how it's used in the article, but I think a few people might disagree so I'm suggesting it before moving. Vicarious 05:28, 18 January 2007 (UTC)

Survey

Add  # '''Support'''  or  # '''Oppose'''  on a new line in the appropriate section followed by a brief explanation, then sign your opinion using ~~~~. Please remember that this survey is not a vote, and please provide an explanation for your recommendation.

Survey - in support of the move

1. Support I am sure that MRI is an abbreviation of Magnetic Resonance Imaging, therefore it would be suitable to change it to MRI. Personally, I'd change the heading to read Magnetic Resonance Imaging or MRI, when using the abbreviation in the body text. --Read-write-services 00:22, 23 January 2007 (UTC)

Survey - in opposition to the move

1. Oppose. I think it is alright the way it is. Also, I think it is as per naming convention see Wikipedia:Naming_conventions_(capitalization) and WP:NAME. Nephron  T|C 07:33, 18 January 2007 (UTC)
2. Oppose move. Current name is as per naming convention + system anyway redirects from "Magnetic Resonance Imaging". Also see: Computed tomography. Abecedare 08:03, 18 January 2007 (UTC)

Discussion

Add any additional comments:

I'm not sure I understand either of your arguments. The naming conventions page says only capitalize if it's a proper noun, which this clearly is. If it's not a proper noun than someone should go through the article and make it lower case in all the many places it's currently upper. As for listing another article that is currently also incorrect, I think the only proper reply is to list a random article that is correct, e.g. Kyoto Protocol. Vicarious 09:14, 18 January 2007 (UTC)

• "Magnetic resonance imaging" is not a proper noun but rather than argue that issue, I would request you to check the usage in (not the title alone) standard MRI textbooks such as "Magnetic resonance imaging" by Haacke et al; or journals such as "Magnetic resonance in medicine" or "IEEE Transactions on medical imaging" or "Radiology"; or in other encyclopedias such as "Britannica" [5] to confirm that MRI is almost universally spelled out as "magnetic resonance imaging" in academic usage except possibly when it is used for the first time in an article/book and the abbreviation is introduced. The same principle holds for other medical imaging technologies including CT, PET and SPECT, as well as other relevant terms including RF, SNR, GRAPPA, SENSE, FOV, CBF, MRA, NMR etc (the exceptions being terms such as DFT or FFT in whose expansion Fourier alone is capitalized as it is a proper noun). So yes, someone should go through the article and convert the terminology to lowercase. Hope this clears the confusion. Regards. Abecedare 10:27, 18 January 2007 (UTC)
  • Now that's some reasoning I can get behind. Vicarious 23:12, 18 January 2007 (UTC)

Principle

Was thinking of perhaps layifying some of the language a bit:

Medical MRI most frequently relies on the relaxation properties of excited hydrogen nuclei in water and lipids.

Does the MRI work only with hydrogen atoms? Does it work only with hydrogen atoms in water and lipids? Are there any hydrogen atoms in a human (or other things commonly scanned) which are not contained in water or lipids? (i.e., could this be changed to state simply it relies on relaxation properties of hydrogen nuclei (or perhaps any nuclei with net non-zero spin)?

It can work on any nuclei with a net nuclear spin (see multinuclear imaging in the main article). However, hydrogen is a major constituent of the body, and the scanner requires dedicated RF hardware tuned to the resonance frequency of each nuclear isotope to be imaged. While all Hydrogen atoms will be excited by the scanner, only 'free' molecules produce a useful signal - where there is a tight lattice (e.g. bones, tendons and ligaments), the MR signal decays so quickly that it has faded before the scanner can become ready to detect it. (This is used to great effect in diagnosis, because injury to tendons/ligaments allows free fluid into the tissue causing a dramatic change in signal characteristics).

---

When the object to be imaged is placed in a powerful, uniform magnetic field, the spins of atomic nuclei with a resulting non-zero spin have to arrange in a particular manner with the applied magnetic field according to quantum mechanics. Hydrogen atoms (= protons) have a simple spin 1/2 and therefore align either parallel or antiparallel to the magnetic field.

My understanding of spin is a little rusty; "with resulting non-zero spin" - what does the word 'resulting' mean here? The spin is created as a result of applying the magentic field? Any given proton may obtain either spin 0, 1/2 or -1/2? Is the direction of alignment (parallel/antiparallel) arbitrary or a result of some other property of the proton which will precisely determine the direction (+ or - spin)?

Within the nuclei protons (and neutrons), in the same shell, pair off with opposing spins. E.g. Helium-4 contains 2 paired protons (1 spin +1/2 and 1 spin -1/2) and 2 paired neutrons with no net nuclear spin; but Helium-3 contains an unpaired neutron so has a net nuclear spin of 1/2.

The alignment of an individual proton with the magnetic field can be either parallel or anti-parallel. The result is a dynamic equilibrium with some protons aligning parallel, and the rest anti-parallel, with a constant exchange between the 2 states. However, because nuclei have lower energy when aligned parallel than anti-parallel, the equilibrium is not symmetrical, with a very slight excess of nuclei aligned in the parallel direction.

---

Common magnetic field strengths range from 0.3 to 3 T, although field strengths as high as 9.4 T are used in research scanners [6] and research instruments for animals or only small test tubes range as high as 20 T. Commercial suppliers are investing in 7 T platforms. For comparison, the Earth's magnetic field averages around 50 μT, less than 1/100,000 times the field strength of a typical MRI.

Is this paragraph appropriate/needed in the principal section?

I think it provides a bit of perspective. Magnets in typical MR scanners are many times stronger than magnets that most people typically handle, not to mention very much larger. It is their magnetic property that is the most recognised 'feature' of the scanners.

---

The spin polarization determines the basic MRI signal strength. For protons, it refers to the population difference of the two energy states that are associated with the parallel and antiparallel alignment of the proton spins in the magnetic field and governed Boltzmann's statistics.

Is this saying that spin polarization is the integral difference in protons in one state versus the other? So, if I have 500,001 protons that are parallel and 500,000 protons that are antiparallel then my spin polarization is 1? What is Boltzmann's statistics and what does that have to do with the calculation of spin polarization? What is the cause for the descrepancy; is it arbitrary or is it a result of some fundemental property of protons?

Spin polarization is more usually called net magnetization. This is perhaps a better term. It essentially represents the residual magnetic alignment after those protons aligned parallel and anti-parallel have cancelled. In your example above, it would be 1 spin per million in the parallel direction. The Boltzman distribution is a mathematical description of the equilibrium that forms when particles can occupy different energy levels (see above).

---

In a 1.5 T magnetic field (at room temperature) this difference refers to only about one in a million nuclei since the thermal energy far exceeds the energy difference between the parallel and antiparallel states. Yet the vast quantity of nuclei in a small volume sum to produce a detectable change in field.

The thermal energy causes protons to switch between parallel and antiparallel? (which seems to argue that the state is arbitrary) If the selection of parallel and antiparallel is arbitrary than each "small volume" would statistically cancel out each other "small volume" (since that would not be helpful; seems to argue that the selection isnt arbitrary and must favor either parallel or antiparallel statistically. If so, why?) '...detectable change in magnetic field...'?

It is the thermal energy that allows the protons to change state, hence allows an equilibrium to form. Because of a very slight preponderance in the parallel direction, then the net magnetization doesn't completely cancel - there is a tiny residual. However, the sheer number of protons is so high, that even this tiny residual is sufficient for detection.

---

Most basic explanations of MRI will say that the nuclei align parallel or anti-parallel with the static magnetic field though, because of quantum mechanical reasons, the individual nuclei are actually set off at an angle from the direction of the static magnetic field. The bulk collection of nuclei can be partitioned into a set whose sum spin are aligned parallel and a set whose sum spin are anti-parallel.

This is describing the heisenberg effect? Each proton could never be precisely in a specific alignment, but simply has a probablity cloud of alignments which is centered along the magnetic field? If thats the case then there is a certain probablity that a given proton is precisely aligned with the magnetic field and the probablity cloud is statistically parallel with the magnetic field? Can be partitioned theoretically or is partitioned in practice during the scan?

My knowledge of QM is limited, and I don't think I've seen this issue discussed at any length in general MR texts. The spins are already partitioned parallel and anti-parallel by the magnetic field. The point made here is that regarding all the spins as being aligned either perfectly parallel or anti-parallel is adequate to predict the aggregate behavior (which is all that can be detected), even though the true direction of an individual spin is uncertain.

---

The magnetic dipole moment of the nuclei then precesses around the axial field. While the proportion is nearly equal, slightly more are oriented at the low energy angle. The frequency with which the dipole moments precess is called the Larmor frequency.

Ok, starting to get really lost... Is this saying that similar to -- electron orbitals around a nuclei--, the proton's axis has multiple quantized "orbitals" which effect the probablity cloud of its angle of incidence with the magnetic field? Ok, all my previous theories start to breakdown when adding that the proton precesses at a specific rate. And the angle of incidence with the magnetic field is a function of energy level. Perhaps the higher level orbitals are donuts centered around the magnetic field which allows for a specific frequency, but then it seems that the 0 level orbital should still have no frequency (and should still include the magnetic axis itself). ...the proportion is nearly equal... Proportion of 0 level to 1 level? Why would it be nearly equal? Why are the protons in the level 1 state at all? Aren't there states above level 1? Larmor frequency is specific to the level 1 state or all states precess at the same frequency?

Each spin has a magnetic dipole moment. This can be imagined as a bar magnet aligned with the spin. The bar magnet rotates around the axis of the spin at the precession rate (Larmor frequency) of the spin. To further simplify matters, it is only necessary to imagine a single bar magnet for the whole net magnetization of a region.

Under equilibrium conditions the spins are aligned with the external magnetic field - this means that the net magnetization is aligned with the magnetic field. Because the net magnetization rotates along its own axis, this rotation does not result in any net change in the magnetic field produced by the net magnetization.

---

The tissue is then briefly exposed to pulses of electromagnetic energy (RF pulses) in a plane perpendicular to the magnetic field, causing some of the magnetically aligned hydrogen nuclei to assume a temporary non-aligned high-energy state. Or in other words, the steady-state equilibrium established in the static magnetic field becomes perturbed and the population difference of the two energy levels is altered. The frequency of the pulses is governed by the Larmor equation to match the required energy difference between the two spin states.

Is the EM applied from a single direction or radially? The EM waves hit the protons and move them from level 0 to level 1? How are the states measured; photons created when the proton relaxes and released in a random direction as opposed to the original direction of the source beam? What does that information tell one about the material being scanned? What is really being measured; proportion of hyrdrogen atoms at every given location? Different regions are detected by measuring intensity of photons detected bouncing randomly? I have no idea how far off from reality I am at this point, but if that's the case how does measurement work in 3D?

The EM only needs to be applied perpendicularly. Essentially, the RF energy allows some protons to be moved from the low energy level, into the high energy level. It would be possible to apply a measured amount of energy and equalise the parallel/anti-parallel proportions discussed earlier (saturation) or even apply more and reverse the net magnetization.

However, the actual effect is more subtle. The EM pulse results in a change in the angle of precession of the individual spins. Recall that the net magnetization is rotating about its axis (but the symmetrical nature of the dipole magnetic field means that this rotation has no net effect). However, the change in spin precession angle causes the net magnetization to tilt on its axis of rotation. EM pulses are constructed in such a way as to rotate or 'flip' the net magnetization by a specified angle.

Commonly a '90 degree' pulse may be used. This tilts net magnetization so that it is perpendicular to the static magnetic field, yet the rotation axis continues to be aligned with the field. This results in a rotating magnetic dipole - imagine a bar magnet attached to a rotor shaft as in a simple permanent magnet alternator. Just as in an alternator, this rotating magnetic field is induces an AC voltage in wire coils placed around it. It is this AC voltage that forms the basis of the MRI signal, and is what is detected by the scanner.

Other flip angles are possible and are used for special purposes. 180 degree pulses completely reverse the direction of the net magnetization and on their own result in no detectable signal - but can be used as part of more complex sequences of pulses to improve performance. Low angle pulses can also be used, but produce a weaker signal (because only the transverse component of the rotating magnetization is detectable).

Up to now we haven't discussed localisation of the spins at all. Localisation is more complex - but the fundamental concept is that while the spins have been flipped transversely, the magnetic field of the scanner is changed so that the field changes across the scanner (a gradient). The Larmor frequency is related to the magnetic field strength that the spin experiences - and it is the Larmor frequency that determines the frequency of the EM pulse that will flip the spins, and also the frequency of the signal that the spins will subsequently produce. By applying a magnetic field gradient across the scanner, the Larmor frequency of spins will vary across the scanner. It is therefore possible selectively to flip spins within regions of the scanner and analyse the received signal to receive positional information.

---

Anyway, I'm sure I'll have more questions and if this goes well I'd like to try and tackle the k-space section also. Aepryus 07:33, 23 January 2007 (UTC)

It might be useful to split this section off next - I'll probably do it when i have a bit more time. In the meantime, if you think you can understand it, why not have a go at simplifying the text? ChumpusRex 20:11, 25 January 2007 (UTC)

Noises

While the article makes it clear that an MRI machine produces the rumbling/growling noises because of the rapid expansion/contraction of the magnets, it doesn't explain something that I've wondered for years: When the machine pauses between the various stages of a scan and the rumbling/growling stops, there is the single, occasional, very loud "clack" sound, like a piece of wood being struck by a hammer, or perhaps a really *really* loud slap stick. Since the magnets are essentially idle (or so I understand) during this time, what then makes this sound? Vanessaezekowitz 17:19, 15 March 2007 (UTC)

You are most probably referring to the "RF scaling" of the scanner, this is to test the duration and energy level of the RF pulse to achieve the transition to 90 degrees away from the static feild. i.e. to provide the maximum received energy in the antenna, the magnetic lines of force must cross the coil perpendicularly. the ultimate aim is to set up the RF system to receive the best possible signal and (to a lesser degree) to minimise patient RF exposure.--Read-write-services 00:44, 16 March 2007 (UTC)

Contrast Agent Safety

With respect to, I believe, gadolinium contrast agents, someone wrote the following (which was unreferenced and, in my opnion, is off tone and unlikely to be true):

However, one should be careful with the anaphylactoids. It has to be pumped in to the bloodstream, usually through a vein in the arm, the same place as where you take bloodsamples. If it is pumped into a muscle, it will have enormous consequences, and an amputation may be needed.

Seriously. How enormous, exactly, will the consequences be? As enormous as a house, or more like a mountain? And what class of substances are the "anaphylactoids"? If it's "pumped" into the extravascular space, it'd make its way into the lymphatic system and very soon make its way back into the vasculature, soon to be removed by the kidneys. Cajolingwilhelm 22:14, 16 March 2007 (UTC)

Vitamin E

Does anyone here no why vitamin E, of all substances, is used as a marker in (f)MRI? One idea I've heard is that it was easily available in capsule form from health food stores, and for that reason became commonly used, and eventually it became the standard and some entrepreneur lept at the opportunity to market specially-made capsules. This seems rather fantastic, and even if it is true it doesn't address the question of why vitamin E in the first place.

Any information belongs in the relevant section of the vitamin E article. --Eitch 21:59, 8 April 2007 (UTC)

Vitamin E capsules are filled with Vitamin E oil. The capsules are cheap and exhibit hyperintensity (bright on some MR images), so they may mark a location on the body/region of interest.Cheers--Read-write-services 23:27, 2 May 2007 (UTC)

I guess I'm asking more a p-chem question and a historical one. 1) Why the hyperintensity? 2) Why vitamin E over other potential markers? - now, I'm sure, it's because it's the standard. But are there no comparably inexpensive substances that would mark as well? Was the first MRI researcher to use it down the hall from and good friends with a vitamin E researcher?

And another vitamin E question: is any specific one of the four forms of vitamin E used in the capsules? --Eitch 04:36, 3 May 2007 (UTC)

There's nothing really clever here. All a marker has to do is sit safely on the skin, and show a characteristic, easily identifiable, signal on the MRI images.

Anything that returns an easily identifiable signal will do. Lipids (fat and oils) are substances that do just this: they contain a high concentration of hydrogen atoms (protons) and have a short T1 relaxation time, as a result they return a 'hyperintense' (strong) signal on a number of different image acquisition methods.

Fish oil and Vitamin E capsules are conveniently packaged portions of lipid, which makes them suitable. Their low cost and easy availability makes them the obvious choice. ChumpusRex 17:56, 3 May 2007 (UTC)

MRI vs CT availability/cost

The article notes that CT is more widely available and less expensive, how regional is that and is it dated? In many parts of the USA private MRI facilities are fairly common; in the Chicago area it's unlikely that anyone is more than 5-6 miles from a private MRI facility. Fencepost 19:43, 15 July 2007 (UTC)

As of 2002, CT scanners[7] still outnumbered MRI scanners[8] by a factor of about 2 to 1 in the OECD nations. I can't find more recent figures for the United States, but as of January 1, 2006 Canada had 196 MRI scanners and 378 CT scanners[9]. TenOfAllTrades(talk) 17:36, 17 July 2007 (UTC)

Magnetic Resonqance Venography or Angiography

"Magnetic resonance venography (MRV) is a similar procedure that is used to image veins. In this method the tissue is now excited inferiorly while signal is gathered in the plane immediately superior to the excitation plane, and thus imaging the venous blood which has recently moved from the excited plane."

This quote stands in contrast to the one on arteries, but I'm really not sure how it's supposed to work. If veins contrast with arteries, it's because fluid moves more slowly through veins and higher pressure is in arteries. Is this a technique to measure oxygenation of the blud? Brewhaha@edmc.net

Veins contrast in arteries according to their direction of flow. Arteries tend to flow from the neck upwards and veins from the head downwards (there is a bit of variation inside the head, but the major vessels follow this rule).

The technique described is 'time-of-flight' angiography which works due to flow effects. If you saturate all the spins in a slice, then imaging that slice shortly afterwards, will return no signal because the spins were already saturated. However, blood which flows into the imaging slice after saturation, but before imaging, will not be saturated and will return a signal. This technique will tend to show any blood flow, as long as there is some flow perpendicular to the plane of the imaging (so that spin-unsaturated blood from outside the slice can flow in).

Sometimes, it is not desirable to see all flow, and the process can be modified to be direction sensitive. This allows seperate arteriography and venography. If the excitation (saturation) slice extends further down than does the imaging slice (or a second saturation is applied lower down) then blood flowing up and about to enter the imaging slice will be saturated, and will not return a signal. However, blood flowing down will avoid saturation and return a signal. ChumpusRex 17:09, 17 July 2007 (UTC)

11 August revisions by "Smartwords"

The additions are all unsourced, and I do not recognize them from any source on the matter that I have read. I have for instance never heard of the AdHoc-group of friends before. I think that these new statements need sources, or they should be removed. In order to not start a revert-war, I will give it a graceperiod of a week. Mossig 20:18, 14 August 2007 (UTC)

Possible long-term health effects

To my knowledge, the possible long-term health effects of heavy magnetic interaction on the Human body (And indeed, the Human brain) are not yet known, and theoretically could be harmfull. As such I'd appreciate somebody better versed on the subject to write a sub-section under Safty reflecting that possibility, and citing research into the matter. Neobros 03:22, 18 September 2007 (UTC)

See the conversation "is MRI safe" here on the discussion page, higher up, for a quick summary of why we will never be able to prove the absence of adverse effects. Also, there's information on concerns over long-term effects in the 'European Directive' section of the entry. I hope that helps. Tgilk (talk) 14:54, 16 November 2008 (UTC)

MRI and the expanded acronym must be capitalized

I'm surprised this has slipped by. Phrases expanded from all-capitals acronyms are themselves capitalized. I suppose I will begin to search for all articles which do not follow this form. This is my first discovery on this subject. However minor this edit may seem, a collaborative encyclopedia should conform to the same rules of grammer, punctuation, etc. as the real world. Also, the title of the article should be capitalized, but I don't know how to do that. Can anyone explain how to capitalize the article header ? I don't see that code in the HTML. Please explain and assist. If you don't think the article should be capitalized, don't bother to respond because you are wrong. Just wanted to eliminate discussion which could be absurd, such as a response arguing that expanded acronyms are not capitalized if they contain proper nouns or formal process description titles. Promodulus 19:48, 25 September 2007 (UTC)

Here are a couple respectable sources:

"These scientists use functional magnetic resonance imaging (fMRI) to take pictures of the active brain…" (Their emphasis.)

Huettel, S.A., Song, A.W., & McCarthy, G. (2004). Functional magnetic resonance imaging. Sunderland, MA: Sinauer Associates, Inc. (p. 2).

"The advent of functional brain imaging, both positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), has made it possible…" (Their emphasis.)

Rodman, H.R., Pessoa, L., & Ungerlieder, L.G. (2003) Visual Perception of Objects. In Squire, L.R., Bloom, F.E., McConnell, S.K., Roberts, J.L., Spitzer, N.C., & Zigmond, M.J. (Eds.), Fundamental neuroscience (p. 1215). San Diego, CA: Academic Press.

"Magnetic resonance imaging (MRI) and spectroscopy (MRS) provide noninvasive tools…"

Storey, P. (2006). Introduction to magnetic resonance imaging and spectroscopy . In Prasad, P.V. (Ed.), Magnetic Resonance Imaging: Methods and Biologic Applications (p. 3). Totowa, NJ: Humana Press.

Or, if we want to get into the habit of using Google Books, check out the capitalization in the quotes returned with the results of a "magnetic resonance imaging (mri)" search.

(See also the AMA Style Guide, which is not necessarily applicable to WP but which does seem to reflect the real world's grammar.) — eitch 15:48, 26 September 2007 (UTC)

There is a difference when you are mentioning the concept or process in standard prose versus the title of the process, which is a proper noun, and proper nouns are capitalized. Again, how can the title of this article be fixed ? What Wikipedia policy page instructs how to edit headers ? Promodulus 15:59, 26 September 2007 (UTC)

It seems like you're getting stuck on titling conventions (no offense, if this diagnosis is right — what I'm imaging you're stuck on is something I was stuck on once). Take book titles: In English, every word in a "Book Title" is capitalized. In some other places (e.g. Germany) only the first word of a "Book title" is capitalized. It happens in some English contexts, too: some journals capitalize only the first word of each article's title. And it's the convention WP has opted for. To pick two examples at random (I don't know why these are the examples that came to mind), we have the articles titled Set dance and Ice hockey.

For an example of something commonly referred to by an acronym, there's the article Obsessive-compulsive disorder ("OCD"). (As far as 'acronyms and their expansions' go, it's useful to remember it's really 'a term and its compression' and that the acronym rule in question is 'put acronyms in all-caps' — "OCD is a psychopathology. Researchers study OCD," not "Ocd is a psychopathology. Researchers study ocd.") — eitch 14:23, 27 September 2007 (UTC)

This issue has also been raised before. See the discussion above and also wikipedia's naming conventions, for reasons why the current capitalization is correct. Abecedare 16:45, 27 September 2007 (UTC)

You're right that phrases expanded from acronyms are often capitalized, but it's not strictly correct. When my group has submitted papers that do this, they come back from the editors with the caps changed to lower case. That's how I found out not to capitalize such phrases in the future - before that, I would have agreed with you. On a less substantive note, comments on grammar will usually get a lot more traction if you spell "grammar" correctly. --Reuben (talk) 02:58, 18 December 2007 (UTC)

Question

I have recently undergone an MRI scan and I turned to Wikipedia for a simple explanation of how the technology works. I was considerably disappointed by this article. I have no problem with an article that goes into some depth and detail, but this is riduculous - there is nothing there for the general reader, no generalised introduction. Having read the start of the article I have little conception of how an MRI scanner forms an image - even though I have a physics degree! AB

Moved here from the top of the discussion page by NCurse _work 12:52, 29 September 2007 (UTC)

Yes, there is definetly too much jargon in this article. Could someone please translate this article into English?66.159.69.132 17:57, 22 October 2007 (UTC)

Translation of page to English

There is too much jargon on the main article. I can barely understand one word in five. Could someone please translate this article into layman's terms?66.159.69.132 18:08, 23 October 2007 (UTC)

Medical/clinical MRI versus research MR machines

A recent edit to the purported 21 tesla machine area of the article may wish to note that 3T is about the strongest field that can safely be used on humans.

Increased risk of side effects - exposure to fields above 3 T have been reported to cause nausea and dizziness. At higher strengths Lenz law and magnetohydrodynamic effects on the cardiovascular system are potentially significant - causing marked distortion of the ECG waveform and raising blood pressure (due to MHD effects causing an apparent increase in blood viscosity). - Considerably increased cost of the magnet; both installation and maintenance costs. - There are limits to the field strength at which ancillary equipment (e.g. patient monitoring devices, or remote injector devices) can operate. In practice, general medical scanners are usually 1.5 T or less - the drawbacks of higher fields tend to outweigh the benefits. However, 3 T scanners are used for specialist work (e.g. brain imaging/spectroscopy, cardiac imaging) and for research. Even higher field machines (e.g. 4 - 7 T or even 9.4 T) are not used for clinical work (nor are they approved as safe for clinical work) and are purely research tools. Machines using fields higher than 9.4 T are reserved for laboratory small animal or specimen use (partly due to the impracticality of making human sized high-field magnets, but also due to safety concerns).ChumpusRex 02:09, 26 November 2006 (UTC)

kind regards,--Read-write-services (talk) 21:35, 4 December 2007 (UTC)

• Actually, the US FDA has approved magnetic field strengths of up to 8 Tesla for use on humans, and a new 9.4 Tesla head-only scanner at the University of Illinois apparently just completed safety trials (you can Google 'worlds strongest MRI' and find it - even though that headline is grossly inaccurate).

--Tgilk (talk) 19:15, 9 January 2008 (UTC)

Even number of nucleons

The statement "If the number of nucleons within an isotope is even then there is no net spin.", in the "Principle" section, is wrong. E.g.: deuterium, hydrogen isotope of mass 2, has 2 nucleons, a proton and a neutron, and a spin of 1. When the number of protons and the number of neutrons are both even, then the net spin is zero. E.g. He⁴. (But I am not sure what exactly is the rule. Whether double-even is logically equivalent to spin = 0.) —Preceding unsigned comment added by 137.138.201.73 (talk) 00:08, 19 December 2007 (UTC)

You are certainly correct. We would need a good source to show whether there are any examples of an isotope with an even number of neutrons and an even number of protons, but which has a net spin, or an isotope with an odd number of neutrons and an odd number of protons, but with zero net spin. I doubt a full discussion is needed in this article, so I just replaced the previous text (which was, as you noted, imprecise) with another specific and relevant example. --Reuben (talk) 18:33, 19 December 2007 (UTC)

Poking through the Table of Isotopes I found at least one interesting case: rubidium-90 has 37 protons and 53 neutrons, and is spin-zero, with a half-life of 158 s. For the converse case, where a nucleus with even protons and even neutrons has a nonzero spin, you have to look at some long-lived excited states like lead-202-m1. --Reuben (talk) 18:53, 19 December 2007 (UTC)

RF System

The article currently states:

The power of the transmitter is variable, but high-end scanners may have a peak output power of up to 35 kW, and be capable of sustaining average power of 1 kW

35kW sounds a bit high. The (human) research system I currently use has an 8kW amplifier. Anything above 10kW is surprising. I would also hope any RF system would cut out if I tried to apply a sustained output of 1kW. Modern MRI systems all use pulsed power, pulses typically lasting a few ms. RF power is limited by the heating it causes in the subject (Specific Absorption Rate). A sustained kW would be dangerous.

While I'm here, I've also changed RF to Radio Frequency in the title. —Preceding unsigned comment added by 85.218.28.5 (talk) 23:25, 13 January 2008 (UTC)

Having worked as an MRI physicist for 2 MRI companies, I can confirm that high field (1.5T and above) whole body MRI scanners require peak output RF power of 20-30 kW or more. The effective width of the RF pulses (equivalent width of a square pulse) is usually around 0.5-1 msec and the duty cycle approaches 5%. --PloniAlmoni (talk) 13:05, 17 January 2008 (UTC)

Gradients

Perhaps someone could clear up some confusion I have regarding the explanation of magnetic field gradients:

"Magnetic gradients are generated by three orthogonal coils, oriented in the x, y and z directions of the scanner. These are usually resistive electromagnets powered by sophisticated amplifiers which permit rapid and precise adjustments to their field strength and direction."

This to me suggests that the x,y,z coils produce magnetic fields in orthogonal directions, but I was of the impression that the magnetic field was always in the same direction as the permanent field, only the gradients were orthogonal. Is my impression correct? Maybe this could be rephrased. —Preceding unsigned comment added by 124.170.114.4 (talk) 02:47, 3 February 2008 (UTC)

I've tried to update the Gradient section to make things a little clearer. You are exactly correct, the gradient fields are all aligned with B₀, it's the field gradients that are orthogonal. A picture would help, I'll see if I have one. GyroMagician (talk) 11:30, 5 May 2008 (UTC)

MRI vs CT not quite correct

The article's comment "For purposes of tumor detection and identification, MRI is generally superior.[14][15][16] However, CT usually is more widely available, faster, much less expensive, and may be less likely to require the person to be sedated or anesthetized." implies that MRI is all-around superior to CT and would be used for all cancer detection were it not for its cost relative to CT.

That's not quite true. If you look at the author's citations, all of the articles talk about brain tumors. CT scan is the radiologist and radiation oncologist's diagnostic of choice for thoracic cancers (lung cancer) and GI.

MRI is less helpful than CT when you are trying to plan a radiotherapy regimen because you are interested in tissue density of the patient (since that determines how much radiation is deposited at what parts of the body). CT scans will give you a readout of the tissue densities within a patient--MRI's cannot do that.

(I am 90% sure of this but could be wrong, which is why I'm posting this here instead of editing the article--somebody who is more expert, please feel free to confirm/deny/correct anything I have said.) —Preceding unsigned comment added by 132.183.19.59 (talk) 17:54, 8 February 2008 (UTC)

Radio waves or radio frequency magnetic fields?

It is technically wrong to describe the RF signals that the patient is exposed to as radio waves. If they were they would cook the patient, like a microwave cooker, (see previous remarks). The RF signals are generated by inductors, so are RF magnetic fields. The perturbing RF magnetic field is orthogonal to the polarising magnetic field. As the perturbing magnetic field is restricted to the near-field region, no significant electric field is generated. The fields are described as non-radiative evanescent waves. See also NMR. GilesW (talk) 13:00, 18 February 2008 (UTC)

I suggest editing the introduction along these lines: Any comments?:

The scanner creates a powerful polarising magnetic field which aligns the magnetization of hydrogen atoms in the body. A radio frequency magnetic field, orthogonal to the polarising magnetic field, is used to perturb the nuclei at their resonant frequency. This causes the hydrogen atoms to emit a weak magnetic signal which is amplified by the scanner. This signal can be manipulated by additional magnetic fields to build up enough information to reconstruct an image of the body. GilesW (talk) 13:10, 18 February 2008 (UTC)

I've reverted these edits in the introduction! The opening paragraphs need to be in plain language with as little jargon and physics as possible. Let's keep the detailed physics for the Principals section. It is not incorrect to say that the scanner emits radiowaves (around 64 MHz at 1.5T), but the comments about the near-field effects are correct. Doregan (talk) 21:32, 18 February 2008 (UTC)

I accept that my wording could be clarified. However the name of the effect is MAGNETIC resonance. It is easy to understand (simplistically I know) how a powerful polarizing magnetic field can applied to a nucleus, and that nucleus can be caused to spin by applying an alternating magnetic field perpendicular (or orthogonal) to the polarizing field, at the resonant frequency of the nucleus. Calling an alternating magnetic field "radio waves" does not aid understanding; it is an unnecessary "white lie" that obscures the basic principle. Radio waves would "microwave" the patient: the use of magnetic fields without an electric component avoids that.

Incidentally, in the case of Earth's field MRI, the frequency of the alternating magnetic field ("radio waves") is around 2kHz, i.e. they are at audible frequencies.

Statements should where possible be genuinely understandable by our target readership, and if not the whole truth, at least "not wrong". GilesW (talk) 00:06, 6 March 2008 (UTC)

Wavelengths. The frequencies used in hospital MRI scanners must be such that the patient is within a small fraction of a wavelength from the transmit coils, well within their near field region, where the field is overwhelmingly magnetic, and the electric field cannot develop to a significant extent. Over the same distances, shorter wavelengths would allow stronger electric fields to develop, increasing heating effects within the patient. 1.5T => 63MHz, so that wavelength =~5m.GilesW (talk) 15:05, 13 March 2008 (UTC)

Hrmm. Some reality check: An RF field does not necessarily cook a person, it depends on the power. (Which is lucky, using mobile phones would be lethal otherwise.) And you will not have an alternating magnetic field without a corresponding electric field, see Maxwell. And please refrain from calling low frequency EM fields for "audible" - they are not, as they are not pressure waves.

Finally: the wavelength changes with the dielectric properties of the propagation medium - in the body it is much shorter than outside. Mossig (talk) 17:37, 13 March 2008 (UTC)

Maybe it is a subtle point, but GilesW is highlighting something important. The art of RF probe design is to produce a strong magnetic field inside the load (the patient) while keeping the electric field elsewhere (outside the patient, usually within the probe). The difference between near and far field is important. Once a far field is produced, the wave will propagate - i.e. it won't come back, and we've lost the energy. RF probes are deliberately designed to avoid this. In contrast, the near field is conservative. Ignoring losses due to eddy currents in the sample, the RF field generated inside the sample is entirely recoverable.

Yes, it is true that the permittivity of tissue reduces the RF wavelength inside the body, such that λ = λ0/sqrt(εr). If we take εr=60, then λ = ~60cm at 63MHz. This is still well within the near field limit. Current research machines operate in the region of 7T, giving a proton resonance at 300MHz. This equates to a wavelength of about 13cm. While we are now on the boundary between near and far field, we are still trying to use the near field - well designed RF probes at 300MHz still do not radiate significantly.

Oh yes, and there is a difference between 'audible' and 'audible frequencies'. To say that something happens at audible frequencies is useful to an electronic engineer, as it says something about the kind of circuit design required. It is not meant to imply that it makes a noise, but it's interesting to note that, if hooked up to a loudspeaker, the amplified received signal would indeed be audible.

I like the proposed paragraph. The only change I would make would be to change 'amplified by the scanner' to 'detected by the scanner'. —Preceding unsigned comment added by 128.178.53.61 (talk) 17:14, 27 March 2008 (UTC)

"Open MRI"...

needs to be defined and distinguished from regular MRI. The brief paragraph on open MRI just uses the term without describing what it refers to exactly. —Preceding unsigned comment added by 65.212.108.131 (talk) 19:00, 26 March 2008 (UTC)

Medication?patches with MRI

Do medication patches have to be removed before MRI's? What are the effects?

Patches made with electrically conductive foils may be subject to rapid heating and the patch may prove to be a contraindication for an MR exam. Also, some topical drug-delivery systems are affected by heating and may accelerate / decelerate the delivery to outside the clinical levels. Each patch should be reviewed by the MRI provider in concert with the proscribing physician. Collaboratively, these two healthcare providers should make the determination of whether the patch should be removed, left on, and whether the MR exam should go forward.Tgilk (talk) 15:01, 16 November 2008 (UTC)

MRI is not a medical imaging technique only

NMR = spectroscopy + imaging, and MRI is the imaging part. It was developed in other fields, and now applies perfectly to medicine. But MRI can be applied on any kind of sample, including non-biological ones. Nergaal (talk) 18:24, 24 June 2008 (UTC)

I disagree with the change to the title. While it is true that MRI has non-medical applications they are minor, both in quantity, and in impact on the respective fields. Medical MRI has over 10000 scanners worldwide, each performing typically 30 scans a day. It is one of the most important innovations in medicine (Fuchs and Sox, 2001) and attracted the Nobel prize in physiology and medicine. By contrast non-medical MRI (in geology, chemstry, botany, physics) is a minor activity which has only modest impact on the respective disciplines. MRI is the term almost universally recognised by the lay public, Wikipedia's readership. Brownturkey (talk) 18:37, 24 June 2008 (UTC)

I agree with the name change. The technique is indeed nuclear magnetic resonance imaging, even though the "N" was dropped. NMR was developed (starting in the 1930s, through the 40s, 50s and 60s) as a general technique, applicable in many other fields of physics, chemistry and biology. However, MRI was developed and continues to be used almost exclusively as a tool for diagnostic medical imaging. After all, that's what the "I" in MRI stands for (I = Imaging). So the real name should be NMRI, and so the technology was called in the 1970s and early 1980s. The "N" was only dropped from the name to avoid associating the technology with anything nuclear (this happened not long after the Three Mile Island accident). PloniAlmoni (talk) 06:16, 26 June 2008 (UTC)

It is true that in the early days MRI was NMR Imaging (or Zeumatography), but many techniques have had different names in the early days e.g. Roentgenology and Skiagraphy for what is now known as X-radiography. You could argue the "correct" name for NMR is Nuclear Induction if you read Felix Bloch's papers. On Google "magnetic resonance imaging" gets 9,320,000 hits but "nuclear magnetic resonance imaging"gets 860,000, so if you follow the WP:NAME policy then "magnetic resonance imaging" wins. Brownturkey (talk) 19:24, 26 June 2008 (UTC)

Incidentally another possible reason for dropping the "N" is that, in the early days, it wasn't clear whether (N)MRI would end up in hospital radiology departments or nuclear medicine departments. MRI was very profitable in the USA and some folk believe that the radiologists engineered the loss of the "N" to keep it out of the hands of the nuclear medicine departments! Brownturkey (talk) 19:24, 26 June 2008 (UTC)

There is a good reason to keep the word nuclear in the title, to indicate that signal is indeed magnetic resonance of the nucleus (and not,say, the electron).--PloniAlmoni (talk) 06:33, 29 June 2008 (UTC)

I disagree with the name change. While one could argue that the "correct" name is NMRI, it is never normally called that. I think adding nuclear to the name will only confuse. Someone reading the article could come away with the impression that "nuclear magnetic resonance imaging" is the common name, which simply isn't true. Anyone who has worked out that other things have spin and could also generate images will have grasped that MRI refers to the nucleus, and usually (although not exclusively) medical imaging. Equally, MRS usually refers to medical nuclear magnetic resonance spectroscopy, and NMR usually refers to what chemists do. The underlying methods (nutation, relaxation, etc) are usually described as spin physics, or sometimes as NMR. The whole lot is commonly called "magnetic resonance", as in the "International Society for Magnetic Resonance in Medicine". GyroMagician (talk) 16:06, 30 June 2008 (UTC)

Having worked on this article a bit it is clear that the whole piece is focussed on biomedical MRI. This isn't such a bad thing - it's a big topic, and I think most people visiting the page will be looking for biomedical MRI. I suggest reverting back to the old name (i.e. dropping nuclear), and adding a new page dealing with non-biomedical MRI. Non-biomed use is outside my expertise, so if somebody else out there would like to start such a page, that would be excellent. GyroMagician (talk) 09:28, 9 July 2008 (UTC)

I have reverted from NMRI to MRI on the grounds that MRI complies with WP:NAME. If folk disagree with this, please can we discuss here Brownturkey (talk) 07:23, 26 July 2008 (UTC)

Experimental Techniques

If nobody disagrees I'll delete this section. I think all the information is now contained, in more detail, in the the surrounding sections (SWI, DTI, etc). GyroMagician (talk) 17:39, 6 July 2008 (UTC)

I agree although I've been thinking that this section need some more radical surgery. I think it would be helpful to divide into (a) techniques that are routinely used in medical diagnosis (T1W, T2W, PDW, fat suppression, MRA, approved contrast media etc) and (b) techniques which are used in medical research but would not normally be encountered in routine diagnostic radiology in a non-research hospital (e.g. SWI, MTC, DWI, DTI, MRE, MRS, CDI, Xenospin, Helispin, investigational contrast media etc). Brownturkey (talk) 19:05, 6 July 2008 (UTC)

I like it. I think the whole page needs quite a bit of work. I'll delete "experimental techniques" - we could then have two sections under "applications" called maybe "clinical imaging methods" and "research imaging methods". We could then try to order "reserach imaging methods" roughly into order of importance (that'll start a flame war!). Do you fancy trying to reorder and rewrite the intro to applications? It seems to overlap quite a lot with "MR vs. CT", and is not as clear as it might be. I'm currently trying to rewrite the imaging section - you can see my current attempt here. BTW, what the heck is Helispin? That's a new one for me. GyroMagician (talk) 17:14, 7 July 2008 (UTC)

Happy so to do. I was thinking of alphabetical order, though! Helispin and Xenospin are the brand names GEHC has chosen for hyperpolarised He and Xe. Brownturkey (talk) 18:56, 7 July 2008 (UTC)

Excellent. The trouble I see with alphabetical ordering is that something like Current Density Imaging will appear before fMRI, which is clearly more significant. However, I guess it's not as clear-cut for many of the examples. Maybe three sections: basic imaging, advanced imaging, experimental imaging? GyroMagician (talk) 08:44, 8 July 2008 (UTC)

History

It's good to see the new history section. However I think for WP:NPOV we need to expand to mention contributions by Gabillard, Carr, Lauterbur, Mansfield, Mallard, Ernst and others Brownturkey (talk) 20:08, 14 July 2008 (UTC)

I like the idea of a history section (and agree that it needs filling out), but can we delete the "Future of MRI" section? It is (necessarily) speculation, and doesn't really belong in an encyclopedia. Specific methods (fMRI, Xe) have their own sections. GyroMagician (talk) 22:38, 14 July 2008 (UTC)

Why don't we make "History of MRI" a separate page? It is likely to be quite long, and the current page is already a bit too long for Wikipedia. I think it should make an interesting read. This might make a good starting point: http://emrf.org/New%20Site/FAQs/FAQs%20History%20of%20MRI%20page02.htm or here: http://www.mr-tip.com/serv1.php?type=db1&dbs=MRI%20History GyroMagician (talk) 13:26, 15 July 2008 (UTC)

The history-section is totally amero-BIASED in Damadian`s favor, and I cannot see how it could belong to a main article on MRI without further expansion and mention of other, equal or more iportant, contributors.

Yes, it is. I'd love to see someone write a descent history of MRI page - but I don't have time to do it myself. That's why I suggested the (self-admittedly Euro-biased) link above. Do you think it would be better to delete the current history section, add something brief to it to make it a little more fair, or would you be interested in writing a more in-depth history? I also think a "history of MRI" belongs on a separte page - this one is already too long. GyroMagician (talk) 12:22, 29 July 2008 (UTC)

Well, from the European Radiology Association Damadian is credited for filing the first patent on a MR scanner(not a true imager), based on a technology which sooner rather than later became obsolete and replaced/outcompeted by gradient-eccho-techniques.

Damadian was neither the first to measure magnetic resonance in biological tissues, and probably not the originator of the idea to use magnetic resonance to create an image of living tissue(an idea which he patented). Later he was rather alienated by the scientific community for his self-righteousness on the topic of the discovery of MRI, which most certainly was not his credit, but the credit of decades of scientific endeavours. As it stands now, Damadians contributions are grossly OVERemphasized, he was one out of hundreds behind the development of MRI, and therefore it should be removed. I think the History section and all references to the Nobel prize controversy is completely unnecessary in an article on MRI and belong to an own "History of MRI"-page and the Damadian-page Regards, Ynot —Preceding unsigned comment added by 84.202.16.231 (talk) 20:16, 29 July 2008 (UTC)

Diffusion MRI

The DWI enhancement appears within 5-10 minutes of the onset of stroke symptoms (as compared with 64 slice computed tomography, which often does not detect changes of acute infarct for up to 4-6 hours) and remains for up to two weeks.

I removed "64 slice" (undid the edit) because it doesn't seem relevant. If I understand correctly the quoted section is pointing out an advantage in the detection mechanism of DWI vs. CT, rather than overcoming a technical limitation due to readout speed or sensitivity. I may be misunderstanding - if so, please correct me and undo my undo ;-) GyroMagician (talk) 18:54, 15 July 2008 (UTC)

Gadolinium : para- or ferro- magnetic

In this article it is stated that Gadolinium is paramagnetic. However the reference on Wikipedia and Webelements states it is ferromagnetic. I don't know which it is, but ferromagnetic makes more sense to me, and this should be consistent. 92.238.100.42 (talk) 16:52, 25 July 2008 (UTC)

The Gd contrast media (e.g. Gadopentetate dimeglumine are definitely paramagnetic. You can find the following on the manufacturer's website: "Gadopentetate dimeglumine is a paramagnetic agent and, as such, it develops a magnetic moment when placed in a magnetic field. The relatively large magnetic moment produced by the paramagnetic agent results in a relatively large local magnetic field, which can enhance the relaxation rates of water protons in the vicinity of the paramagnetic agent. (Magnevist prescribing infomation (c) Bayer-Schering 2008, fair use)" Brownturkey (talk) 17:18, 25 July 2008 (UTC)

It is widely accepted that Gd is ferromagnetic, with a Curie Temperature (the temperature above which a ferromagnetic material is no longer ferromagnmetic) that is around room temperature. So, so the body's temperature of 98.6 F, Gd would be paramagnetic. Several years ago there was an article in Nature suggesting that Gd is actually antiferromagnetic, and there is a lot of anecdotal evidence in the Materials community that supports this. However, these effects are all observed at temperatures less than room temperature. —Preceding unsigned comment added by 76.120.248.242 (talk) 17:04, 30 July 2008 (UTC)

There is a confusion here. The contrast agents are chemical compounds of gadolinium such as gadopentetate dimeglumine which are always paramagnetic. They are sometimes referred to casually as "gadolinium" in the same way that sodium ion in the diet is referred to as "sodium". You would never inject gadolinium metal into a patient, nor would you add sodium metal to your diet! Brownturkey (talk) 19:43, 7 August 2008 (UTC)

Article title dispute - page move protected

This is getting out of hand - it seems that every time I look at my watchlist, this article has been moved back or forth from one title to another. Please discuss this issue below, come to a consensus regarding the name, and realise that should editors continue to move the page back and forth once the protection expires, I'll just protect it for longer. _TalkIslander 10:57, 26 July 2008 (UTC)

Thank you Islander. This started when Nergaal moved without discussion on 2008-06-24. Some arguments are stated above but for me the key point is to follow WP:NCON and WP:NAME: Google "magnetic resonance imaging" gets 9,320,000 hits but "nuclear magnetic resonance imaging"gets 860,000; and in the scientific and lay literature, MRI clearly wins. Brownturkey (talk) 14:07, 26 July 2008 (UTC)

I did one of the name changes back to MRI and agree with BrownTurkey. If someone wants an article on the non-medical uses of nuclear magnetic resonance imaging called NMRI, with a disambiguation of some form, that is fine. But the present article describes the medical imaging technique which is most commonly called MRI. 86.162.227.198 (talk) 18:43, 27 July 2008 (UTC)

I'd like to agree with the above. This article is clearly about biomedical magnetic resonance imaging, which is universally called MRI. I think there is a good case for a non-biomedical NMRI article, but it should be a separate article. GyroMagician (talk) 08:56, 28 July 2008 (UTC)

The techincal term is NMRI but due to stupid American public they discarded the N part so the short term of Nuclear Mad=gnetic resonance imaging is MRI. Go ask somebody who builds MRIs and he will tell you the correct name. Nergaal (talk) 22:28, 8 August 2008 (UTC)

The issue is not whether the Americal public is "stupid". The issue is what name for the article most correctly follows Wikipedia's naming policies. The technical term is actually MRI not NMRI, as evidenced by its almost universal use in the technical literature in "Magnetic Resonance in Medicine" http://www3.interscience.wiley.com/journal/10005196/home%7C and other high impact factor technical journals in the field. If you actually go to the websites of the three leading builders of MRIs - GEHC, Philips or Siemens - you will indeed find MRI not NMRI. Brownturkey (talk) 08:35, 9 August 2008 (UTC)

Let's hope we can leave this silliness alone now and keep the name as MRI. I have worked with Philips, Siemens and Varian systems, all of which were called MRI machines by both the manufacturers and users (hospitals and universities). If the American public (and scientific community) are stupid for discarding the N, then Europeans are just as stupid. Nergaal, you don't have to like the name, but surely you have to accept common usage? GyroMagician (talk) 09:51, 9 August 2008 (UTC)

We appear to have three votes for MRI (Brownturkey, 86.162.227.198 and GyroMagician) and one vote for NMRI (Nergaal). Can we call an end to this dispute, keep the current name (MRI) and remove the banner? GyroMagician (talk) 14:43, 11 August 2008 (UTC)

The banner was out of date anyway (protection lapsed on Saturday), so I've removed it. There does appear to be consensus on this issue, though, which is good. _TalkIslander 15:04, 11 August 2008 (UTC)

Sorry for missing for a while, but I never argued that the MRI labeling is wrong or that is should be changed. I just argued that MRI=Nuclear Magnetic Resonance Imaging. I am not disputing the acronym, just that the correct name or meaning. Regardless weather the name remains this or not, I think there needs to be a section with regards of the correct nomenclature and with reasons why the wrong name was publicized or used. Nergaal (talk) 11:36, 12 August 2008 (UTC)

As for the manufacturers reasoning, it has no strength: why would manufacturers call their product Nuclear.... when the decided in the first place not to call it that way in order not to scare the people away from accepting its use. What universities and scientific community are you talking about? I have talked with professors of NMR and some of those who pioneered the machine and they call it, or at least argue that the correct name is Nuclear Magnetic Resonance Imaging. Nergaal (talk) 11:45, 12 August 2008 (UTC)

Everyone knows it as MRI, so I say let's keep it as MRI, but give the correct technical term in the lead in bold. Headbomb {ταλκ – WP Physics: PotW} 13:17, 12 August 2008 (UTC)

Although NMRI is the more correct term for the technique, both MRI and NMRI are frequently used. However MRI is the term that is more commonly known among the greater public, so it should probably be used as the main article title. The lead should however mention the alternative name to comply with wikipedia policy. (TimothyRias (talk) 13:34, 12 August 2008 (UTC))

It's demonstrably not true that MRI is universally known by specialists to be an abbreviation for "nuclear magnetic resonance imaging", and not "magnetic resonance imaging". For example, here is a paper recently published in Magnetic Resonance in Medicine. (I'm one of the coauthors.) In the first paragraph, it says "...using magnetic resonance imaging (MRI)". Many many more examples can very easily be found. Maybe there was a time when "magnetic resonance imaging" was an incorrect shorthand, but that time has passed: its current usage by specialists and everyone else indicates that the term is correct both with and without the "nuclear". Nergaal, you say: "there needs to be a section with regards of the correct nomenclature and with reasons why the wrong name was publicized or used." Does the current third paragraph satisfy this? If not, what other information do you propose including that's not already in the third paragraph? --Steve (talk) 16:06, 12 August 2008 (UTC)

ferromagnetic materials

"Conventional magnets made from ferromagnetic materials (e.g., steel alloys containing rare earth elements such as Neodymium)" I do not know which specific magnets are used in the construction of MRIs, but this is clearly an incorrect statement. Steel alloys cannot produce the fields required for MRI. Because the author refers to Nd, I think he really means rare earth-iron based materials such as Nd2Fe14B. This is not a steel alloy (remember that steel must contain both Iron and Carbon), but it is the most commonly used permanent magnetic material. Nd-Fe-B alloys are used almost every place that magnets are required in our daily lives. Wherever there is a motor you probably will find a Nd-Fe-B magnet. —Preceding unsigned comment added by 76.120.248.242 (talk) 17:09, 30 July 2008 (UTC)

MRI Economics

The existing article has a section entitled: "MRI Economics." This section provides, in whole:

"Economics of MRI

MRI equipment is expensive. New 1.5 tesla scanners often cost between $1,000,000 USD and $1,500,000 USD. New 3.0 tesla scanners often cost between $2,000,000 and $2,300,000 USD. Construction of MRI suites can cost $500,000 USD.

For over a dozen years, MRI scanners have been significant sources of revenue for healthcare providers in the US. This is because of favorable reimbursement rates from insurers, both private and federal government programs. Insurance reimbursement has historically been provided in two components, technical for the actual performance of the MRI scan and professional for the radiologist's review of the images and/or data.

In the US, the 2007 Deficit Reduction Act (DRA) significantly reduced reimbursement rates paid by federal insurance programs for the technical component of many scans, shifting the economic landscape. Many private insurers have followed suit.

Currently, in the US, there is increasing interest in reducing the costs associated with MRI services and simultaneously improving the ability to effectively and efficiently provide MRI examination services to larger numbers of patients with the same equipment. The primary plan to accomplish this goal involves speeding up the motor that moves the patient in and out of the MRI machine."

The last paragraph consists of one sentence that appears to be written in the style of bureaucratic BS providing no substantive information whatsoever. Apparently, an eagle-eyed Wikipedia reader noticed this and appended a final sentence which is nothing more than sarcastic vandalism. Perhaps before deleting the vandalism, the offending information-less paragraph should be improved or deleted. —Preceding unsigned comment added by 71.155.150.123 (talk) 02:19, 5 August 2008 (UTC)

I'd vote to delete the section - it doesn't add much, it's very US-centric and the whole page is already rather long. GyroMagician (talk) 07:28, 8 August 2008 (UTC)

While I can see some reason for providing information about the approximate cost of MRI equipment, I agree that there's no point to including the rest of the material. It could be summarized in two sentences, which apply universally to all medical equipment and procedures: "Changes in public and private funding practices affect use of and access to costly equipment and procedures. In general, there will be pressure to use costly equipment as efficiently as possible by minimising procedure times and maximising throughput." TenOfAllTrades(talk) 01:12, 14 August 2008 (UTC)

I agree that it's useful to provide some information about the cost of MRI. I suggest we cut the fluff the section, but keep "MRI equipment is expensive. New 1.5 tesla scanners often cost between $1,000,000 USD and $1,500,000 USD. New 3.0 tesla scanners often cost between $2,000,000 and $2,300,000 USD. Construction of MRI suites can cost $500,000 USD." What I'm not sure about about is where to put it. Maybe we should keep this as a separate section and add some information about the running costs of a clinical scanner. I know they are fairly high, but couldn't put numbers to that. GyroMagician (talk) 10:11, 14 August 2008 (UTC)

I'm slightly uncomfortable about this. Actally pretty much everything in medicine is expensive... surgical suites, drugs, even physicians... people think of MRI as expensive because it looks big and exotic but of course MRI is very cost-effective because it avoids even more expensive invasive techniques... but this health economics is quite difficult and subtle - not easy to summarise in a couple of sentences Brownturkey (talk) 16:16, 14 August 2008 (UTC)

Hi Brownturkey, I can see your hesitation. I agree that the costing of anything medical is somewhat complex and never cheap. I don't think we're aiming to give an in-depth costing though. It's a fairly widely-heard comment that MRI is expensive, so it'd be good to put some approximate figures to that, and explain where the cost comes from (installation and running). Of course we would also have to include a note to the effect that a good image can save a much more expensive surgical procedure -- we could probably find a ref to that effect. Does that sound acceptable? GyroMagician (talk) 21:24, 20 August 2008 (UTC)

Greetings, all. As the person who originated the 'economics' section, my intention had been to try and communicate some of the underlying cost structure that is relevant to discussions of the cost : benefit of MRI. I have seen this section abused, and I think that it may be wise to provide some cursory information about the costs of operation, but weed-out other comments which don't add materially to the content - as others have stated clearly in prior notes, above. However, I don't have access to information that would provide an idea of those operational costs. Anyone else?Tgilk (talk) 14:38, 16 November 2008 (UTC)

RfC: Nuclear or not

• Not - whatever the "correct" name, there is only one name this has to the world "MRI"; to change it would fly in the face of common sense. However, I do have a sneaking regard for editors who wish the truth to be known. Abtract (talk) 12:52, 12 August 2008 (UTC)

• Not - walk into any hospital, you will find signs pointing you to the MRI suite, never the NMRI suite. As for academic centres, the following all talk about 'magnetic resonance' without nuclear:
  • FMRIB, Oxford [10]
  • SPMMRC Nottingham (Sir Peter Mansfields lab) [11]
  • FIL, University College London [12]
  • MGH, Boston [13]
  • CMRR, Minnesota [14]
  • CMR, Queensland [15]
  • BIC, University of Illinois at Urbana-Champaign (founded by Paul Lauterbur) [16]
  • (this is a random selection of labs that sprung to mind - sorry if I missed yours :-)

There is a clear distinction in the field between NMR and MRI although they are, of course, basically the same thing. This is currently well reflected in Wikipedia, where we have a page for NMR and a page for MRI. There is a good arguement for changing the MRI page to talk less about NMR and more about image formation, but that is a separate discussion. The name of the page should reflect common usage. To quote from WP:NAME, "Use the most easily recognized name". I think that says it - MRI. GyroMagician (talk) 15:05, 12 August 2008 (UTC)

• Not It is true that in the early days MRI was sometimes called NMR Imaging, but many techniques have had different names in the early days e.g. Roentgenology and Skiagraphy for what is now known as X-radiography. To a pedant the correct name would be zeugmatography since that is the name devised by the inventor of the technique (though I'm not proposing that we use that name!). (You could argue the "correct" name for NMR is Nuclear Induction if you read Felix Bloch's papers). On Google "magnetic resonance imaging" gets 9,320,000 hits but "nuclear magnetic resonance imaging"gets 860,000, so if you follow the WP:NAME policy then "magnetic resonance imaging" wins. Brownturkey (talk) 20:15, 12 August 2008 (UTC)

• Not Adding "or NMRI" to the first sentence would be fine, but really the article is perfectly clear that this medical technique consists of imaging using NMR. - Eldereft (cont.) 22:41, 12 August 2008 (UTC)
  • I agree with Eldereft. MRI is the most common English term and thus should be the article title. --Gimme danger (talk) 11:03, 13 August 2008 (UTC)

• Magnetic Resonance Imaging is the current term, the N is a historical footnote. It should clearly redirect here, and I don't see a problem with including NMRI as a bolded alternate name in the lead, but WP:COMMONSENSE says we should use the current common name. SDY (talk) 23:22, 13 August 2008 (UTC)

• Not Perhaps I'm the only one who thinks this way, but I believe that the 'n' is still very alive and well, but that it is used (and useful) in distinguishing clinical / medical MR from biochemistry MR. I would agree that clinical MR is just-plain-old 'MR' or 'MRI' (I prefer MR as there are a number of non-imaging, at least not in the conventional sense, capabilities... but I realize most people know MR as MRI). For the dedicated spectrometers used in biochemistry, I do see NMR or nMR (demoting the word 'nuclear'). Tgilk (talk) 15:08, 16 November 2008 (UTC)

Tooth fillings

Perhaps someone could explain why metallic tooth fillings do not appear to be a problem for MRI.RayJohnstone (talk) 05:10, 24 September 2008 (UTC)

Because the amalgam filling material that is used is not ferromagnetic. It does degrade the image quality though. Gold and certain orthodontic appliances can be problematic. --WS (talk) 22:40, 12 October 2008 (UTC)

Signal manipulated by magnetic fields?

Does this sentance in the abstract make sense?

"This signal can be manipulated by additional magnetic fields to build up enough information to construct an image of the body."

What is this referring to? --Nowa (talk) 12:12, 13 November 2008 (UTC)

The additional magnetic fields are generated by the gradient coils RF coils. Without them it would not be possible to resolve the image spatially. The use of gradients for spatial resolution was demonstrated by Paul Lauterbur in 1973.

TomyDuby (talk) 17:34, 13 November 2008 (UTC)

Thanks. I think what threw me was the use of the word "signal". --Nowa (talk) 23:04, 13 November 2008 (UTC)

Section on Claustrophobia and discomfort

Contains the following sentence: ...The good news is that modern scanners have short bores - (70mm for example) and scan times are much quicker... Surely there is a mistake: 70 mm?

TomyDuby (talk) 19:47, 22 December 2008 (UTC)

The main msitake I'm seeing there is the use of the term "The good news is...". As for the 70mm, it seems plausible to me, but should be backed up by a reference. _TalkIslander 20:26, 22 December 2008 (UTC)

70mm is a bit short for a human system - I'm guessing that should read 70cm ;-) I agree that the phrase 'the good news is' should go. GyroMagician (talk) 20:46, 23 December 2008 (UTC)

Thanks for your comments. I managed to find a reference to compact length of only 125 cm and expanded 70 cm bore diameter [[17]]. I am modifying the main article.

TomyDuby (talk) 09:31, 24 December 2008 (UTC)

Open Reference to "TI" in FLAIR section

In section on "Fluid attenuated inversion recovery" there is a uncorrelated reference to TI.

"By carefully choosing the TI, the signal from any particular tissue can be nulled."

What's a TI?

Lastrunk (talk) 19:30, 20 January 2009 (UTC)

TI is the inversion time. The pulse sequence goes 180---90---180. TI is the time between the 180 and the 90 (either one, the sequence is symmetric about the 90). I've tried to update the main article, but it would be clearer with a pulse sequence diagram - I'll try and add one. GyroMagician (talk) 20:32, 21 January 2009 (UTC)

Adding new section under "2.1 Traditional Scans" or "2.1 Types of Contrast"

The article has NO discussion of traditional scans with traditional types of contrast: T1 weighted scan, T2 weighted scan, T2* weighted scan, and Spin density. These are the vast majority of scans that are performed and they are not even mentioned, despite a lengthy section talking about "specialized scans". I will add this section in the next few days unless anyone objects. I plan on adding images of the same brain showing different types of contrast (there is a nice set on wikicommons), I think that will be a nice illustration. I also want to add pages on gradient echo sequence, and spin echo sequence, both fundamental MR and both missing if anyone wants to help out. SBarnes (talk) 17:48, 12 February 2009 (UTC)

Thanks for the new section - an excellent addition, and something the page badly needed.GyroMagician (talk) 14:46, 8 March 2009 (UTC)

2D-FT NMRI and Spectroscopy

User BCI2 has added a link at three different point in the article to this page 2D-FT NMRI and Spectroscopy. I'm not sure what the page aims to add to the main article - I think it looks like a second attempt at this page (in case anyone missed it, all current MRI is of the Fourier transform variety, almost all 2D). I would like to remove the links, but as anything linked to the name NMRI has previously proved contentious, I thought I'd ask for comments here first. Does anyone mind if I delete the links? GyroMagician (talk) 10:13, 3 March 2009 (UTC)

Raymond Damadian's Contributions

Thank you for agreeing to talk. Let's try to work out fair content for the contributions I Raymond Damadian.

Over the past couple of years, I have made various attempts to make the section on MRI accord with the truth of history. When I make postings, the entire article is automatically reverted, even though each statement is validly footnoted. Here are two quotes from respected textbooks that I hope make the point:

“The initial concept for the medical application of NMR, as it was then called, originated with the discovery by Raymond Damadian in 1971 that certain mouse tumours displayed elevated relaxation times compared with normal tissues in vitro. This exciting discovery opened the door for a complete new way of imaging the human body where the potential contrast between tissues and disease was many times greater than that offered by X-ray technology and ultrasound …. NMR developed into a laboratory spectroscopic technique capable of examining the molecular structure of compounds, until Damadian’s ground-breaking discovery in 1971.” MRI from Picture to Proton, Cambridge University Press, 2003

Making Modern Science, A Historical Review, The University of Chicago Press, 2005“By the final few decades of the twentieth century, medical practitioners were exploiting developments in nuclear physics to provide a range of new ways of peering inside the human body …. Another technique developed during the 1970s was MRI (magnetic resonance imaging). The technique was initially developed by Raymond Damadian (1936 -), working at the Downstate Medical Center in New York, making use of the fact that different atomic nuclei emit radio waves of predictable frequencies when exposed to a magnetic field. Damadian noted that tumorous cells emitted signals different from those emitted by healthy tissue and used this as the basis for a new technique for identifying cancers. Damadian and his fellow workers produced the first MRI scan of the human body in 1977.” Making Modern Science, A Historical Review, The University of Chicago Press, 2005.

In addition, the footnotes on the changes I made are here for examination. Magnetic resonance imaging is a relatively new technology. It began in 1969 when Raymond V. Damadian, a medical doctor who did post-doctoral studies in biophysics at Harvard, proposed scanning the human body by NMR (MR). [1] He conducted experiments on cancer tissue and normal tissues in rats and discovered the marked differences in the T1 and T2 relaxation times between cancer tissue and the normal tissues themselves. Damadian reported his findings in Science. The signals from these tissue relaxation differences are the source of every MRI made. They provide the pixel brightness and therefore the image contrast that enables visualization of the body’s vital organs at a level of detail unprecedented in medical history. The first MR image was published in 1973[3]. Damadian built the first whole-body MR scanner at New York's Downstate Medical Center, with the help of two postdoctoral fellows, and achieved the first scan of a live human, a cross section of the human chest. [4][5] Tomattea (talk) 22:54, 28 April 2009 (UTC)

Please, get back to me with your thoughts. Tomattea (talk) 23:10, 28 April 2009 (UTC)

Comment It would be appropriate in my opinion to add a 2-3 paragraph section to this article on the history of MR (starting from NMR, MRI, medical applications, FMRI, parallel MRI etc). That section can then mention Damadian's contribution to the area (along with Purcell, Ernst, Bloch, Lauterbur, Mansfield, Ogawa, etc) giving them due weight. Would you like to attempt writing a draft ? Abecedare (talk) 16:32, 29 April 2009 (UTC)

A history section would certainly improve the article, good idea. It will be interesting to tease out the timeline too. GyroMagician (talk) 17:39, 29 April 2009 (UTC)

Oh dear, here we go again. I think it is useful to start this discussion (which I feel may be a long one) by including this letter from Herman Carr:

"Field Gradients in Early MRI", Physics Today 57(7), July 2004, Letters to the editor

Prof. Carr had a reasonable claim to be the first using field gradients, published in 1952. Now, back to Damadian. Damadian was the first to publish the idea that different tissue (and specifically cancerous vs. normal tissue) have different relaxation times, giving image contrast - this is the 1971 Science publication. If you get hold of a copy of the article, you will notice it contains no images - it is plain old NMR. Lauterbur used projection-reconstruction to generate images (of a phantom), which he published in 1973. Damadian later tried to localise the NMR signal using his so called 'field focusing' technique "Field-Focusing Nuclear Magnetic Resonace (FONAR)", Naturwissenschaften, 65(5), May 1978. To quote "shaping of the static field across the sample confines the signal-producing region of the sample to a small volume, called the resonance aperture". There is not much detail here, but the principle is to 'shape' the static field such that only a small region of the sample is on-resonance. It works, but it is hard to produce a small, well defined region. This has nothing to do with modern MRI, which uses field gradients to localise the excitation (slice selection) and spin signal - which is the work that earned Mansfield and Lauterbur a nobel prize. In this case the whole sample is within the RF bandwidth of the system and on resonance. Damadian may have been the first to build a whole-body human NMR machine, but critically it wasn't an MRI machine. In this case the distinction is important - Damadian didn't know how to do MRI. The results Damadian & co. show in 1978 are already at the limit of what field-focusing can do. By contrast, the equally low-res images generated by the Fourier method were only the begining. The stunning images we produce today still use the same priciples introduced by Mansfield and Lauterbur, and still use the same k-space framework set out by Mansfield in (I think) 1977.

Damadian is good at making a lot of noise. He did some good work, I do not argue against that. But he is not the 'father of modern MRI' that he would have you beleive he is. You can find publications out there that support and refute Damadians view. I think we will have to argue this out using the original papers - modern review articles are often inaccurate. Modern MRI was built up by many people, and of course builds directly on NMR. I'll consider that Herman Carr may have been overlooked, but not Damadian. I think the Nobel prize went to the right people, and I don't think my view is unusual in the MR field. But if you can prove otherwise, we can change the page. GyroMagician (talk) 17:37, 29 April 2009 (UTC)

I agree with every word you said.

TomyDuby (talk) 20:14, 29 April 2009 (UTC)

I've been pleased to see your comments. My only intention is for us to arrive at a history section that is based on the truth of scientific discovery. I am sure we agree on the goal. I expect the road will be bumpy.

During the next week, I will be posting referenced information for your consideration. The most critical material will all be from original source material. As an optional extra, I will quote from the 1985 NY Times book by the NY Times reporter, Sonny Kleinfeld, A Machine Called Indomitable. He interviewed the main participants.

Here is a glimpse of what's to come:

While delighted by the openness of some, I expected the slams, such as, "Damadian is good at making a lot of noise." I believe he has been mis-characterized over the years by a community that has sought to own what it feels it should rightfully own. Perhaps understandable from an egoistic point of view but not from a scientific one.

Actually, if you think about it, it took an MD with biophysical training at Harvard, with a relative who had died of cancer, to stand at an NMR machine as Freeman Cope and he did potassium experiments together at NMR Specialties, be astonished by the capability, know the potassium and water content of tumor cells is different than normal cells, and intuit that NMR might be able to detect cancer. Cope declined to embark on the research with him because he felt it was too enormous an undertaking. Damadian was foolish enough to return to NMR Specialties a couple of weeks later with rat tumors. His research led to his paper in Science.

In regard to priority, here is a quote from Damadian's grant proposal of 1969. I cannot paste it here but can tell you where you can see an image of the original.

It is dated September 17, 1969, and addressed to The Health Research Council of the City of New York: "I will make every effort myself and through collaborators to establish that all tumors can be recognized by their potassium relaxation times or H20-proton spectra and proceed with the development of instrumentation and probes that can be used to scan the human body externally for early signs of malignancy."

A couple of notes on our Nobel Laureates. The first, expressed for the nonce and for the sake of brevity in my own words, is in the New York Times book by Sonny Kleinfield. The second is taken from Mansfield's own writing:

Paul Lauterbur became the chairman of the NMR company where Damadian did his experiments. When Hollis went there from Johns Hopkins to confirm or disprove Damadian's results, Lauterbur asked Hollis about the experiments. Hollis explained them. Shortly, thereafter Lauterbur went to the Big Boy with one of his VP's, Donald Vickers, and had his big idea. That's why Lauterbur credited Damadian at the end of the notation he made in his notebook. I have a copy of his notebook, which I can share an image of. Yet he did not credit Damadian in the paper he published in Nature. He said he "didn't have room." Nor did he credit Damadian in about 250 papers he wrote over the years. In fact, he subsequently referred to Damadian in such terms as "a promotion artist" or "businessman."

Regarding Mansfield, I will provide a quote from him about his awareness of Damadian's work, also from Kleinfeld's book. Sonny interviewed him as well. Right now here is a quote from Mansfield's own book. Perhaps it will prompt you to reevaluate if Damadian's technique was the first-ever way to scan the human body, available for technical improvement, or, as it's often mischaracterized as, "a dead end."

The following is from NMR Imaging in Biomedicine, by P. Mansfield and P. G. Morris, Academic Press, Inc., 1982,p. 6. Mansfield is referring to Damadian's technique. After he notes its shortcomings, he writes: "Nevertheless, one can obtain images by this point scan method, although the scan time is inevitably long."

To approach another touchy subject, please keep in mind that Alfred Nobel's will specifies that the award in Physiology and Medicine can only be given for "discovery," not technological improvements. My contention is that Damadian did the "discovery." He envisioned the whole-body MR scanner, did the experiments to see if the technology would work on tumors and normal tissues, and built the scanner that achieved the first image of a live human, a cross section of the chest of one of his postdoctoral fellows. Yes, the image was crude. More NMR technology had to be applied to it. That is what Lauterbur and Mansfield did. When challenged, the spokesman from the Nobel Committee said, "We only gave it for the image." Apparently, he did not realize that today every MRI image is derived from the signals from tissue that Damadian discovered. No signal, no image. Meanwhile, he also neglected to note that the techniques of Lauterbur and Mansfield have been surpassed.

If any of the information I provide startles or upsets you, I trust you'll confirm the posting with your own look at the source material before you make up your minds.

I trust you're still on board and look forward to working with you.

Let the truth prevail.

Tomattea (talk) 21:25, 30 April 2009 (UTC)

Hello Tomattea. I'd be interested to know where the following line came from (I thought the Nobel committee famously refused to comment on their decisions): When challenged, the spokesman from the Nobel Committee said, "We only gave it for the image.". However, that is what I had assumed to be the case. The Nobel prize was awarded for the imaging method, not for tissue relaxation. The method for encoding signal source location was developed by Mansfield and Lauterbur (and probably Carr). In it's exact same form, this method is still used today in every hospital with an MR machine, and by almost every research machine (it is also the method now used by FONAR's own scanners). This was innovation or discovery, and did not build on Damadians method - it is fundamentally quite different.

Sorry if I come across as hostile, but I have been through this argument before, and it gets a little repetitive. However, if we can lay down a timeline, listing the many major contributions in the history of MRI, that would make the discussion worthwhile. I'm happy to look over any source material you suggest (if I can get hold of it). If we are to produce a detailed history, can I suggest we put it on a separate page? The MRI page is already rather long, and I think this new section may also be a reasonable size. GyroMagician (talk) 07:58, 1 May 2009 (UTC)

Thank you for your response. I remember reading the newspaper report with the line in it during the period right after the award was announced, but I think it would be difficult to locate. Thankfully, we agree that the prize was given for the image. The Nobel awards speech admits as much.

I do not, however, wish our discussion to center around the Nobel Prize. It drags science by the nose enough as it is. Additionally, I am disinclined to accept the Nobel decision as if the committee were the final arbiter of scientific truth, which it has often proved not to be and, I believe in this case, that it erred in not including Damadian, very likely for scientifically unacceptable reasons. Damadian's insight that NMR might have a medical application in the detection of cancer and the signals he discovered from cancer tissue and from the normal tissues were the contributions that first interested Lauterbur and Mansfield in the medical application of NMR. Furthermore, Damadian's contributions remained foundational to both men's contributions. If I had a much improved camera but no light, what pictures could I make? The general literature seems little cognizant of these facts.

I will address your point about "The method for encoding signal source location was developed by Mansfield and Lauterbur (and probably Carr)." First, the gradient with the capacity for spatial localization was invented by Gabillard and subsequently by Carr but for one dimension only. Lauterbur devised a way to employ it in two dimensions. Garroway, Grannell, and Mansfield provided a means for pulsing the gradients in sequence, which enabled the further development of spatial phase encoding.

I think an important thing to keep in mind is that the gradient and the Fourier tranform of the NMR signal were around for decades. But nobody considered the medical application of NMR for the detection of disease in the human body until Damadian, a logical contribution for a medical doctor with biophysical training.

The fact is, there has been an egregious amount of misrepresentation in the category. Lauterbur did not credit Damadian, and here's an instance where Mansfield inappropriately claimed priority over Lauterbur. Take a look at Mansfield's May-June 1984 paper in RNM Images, p 22. The first sentence reads "Since the principle of magnetic resonance (MR) imaging of discrete structures was first proposed by Mansfield and Grannell in 1973..." The paper by Mansfield and Grannell that he cites was received by the publisher of the Journal of Solid State Physics in August 1973. Lauterbur's Nature paper was published in March 1973, or five months earlier.

Clearly, there's some sorting out to do.

When you have time, I would like you to look into the little-heralded work of Kudravcev at NIH in the 1950s, as reported by Chen and Hoult, in Biomedical Magnetic Resonance Technology, IOP Publishing, 1989, p 38. To wit: "... Kudravcev, a Latvian emigre to the United States and an electrical engineer, had been involved in television technology and, combining the two disciplines, he devised in 1959 a crude method for displaying on a television screen what is essentially a Mercator projection [image] of a quail egg with embryo with the aid of what would now be called a surface coil. The idea of magnetic resonance imaging is clearly contained in the following excerpt from a National Heart Institute (1960) progress report: "Preliminary experiments on the use of NMR absorption for determining the distribution of hydrogen and some other NMR susceptible nuclei in living tissue have yielded interesting results. This work will be continued in the hope that a scanning technique will give coarse pictures (in intensity variation) of muscle, arteries and other structures...." Having problems with the homogeneity of the magnetic field, Kudravcev realized that field inhomogeneity could be used to localise the volume of interest, and in 1961 performed experiments which successfully demonstrated that fact, using both static and alternating field gradients.".... However, as his work was deemed a curiosity [until Damadian did his work in 1970, they couldn't envision a medical application for it], he was forced to abandon his efforts ..." The story becomes quite interesting when one realizes that Kudravcev reported to Edwin Becker, a friend of Lauterbur's, and both Becker and Lauterbur served on the committee deciding Damadian's grants. Somehow, they never approved them.

I'm glad you're cognizant that you can sound hostile. I try to be self-aware of the same. Hopefully, it means we can have a civil, fact-based discussion.

I do not believe you have been through the material to the point of it being tiresome. Your timeline suggestion is a good one. I can get hold of a lot of original source material but don't know an easy way to share it. I could email you pdf's or we could establish a neutral gmail account, such as mrihist@gmail.com and have mutual access to it. You could email docs and PDFs and I could, too. Everyone could access the material with ease.

I also think your suggestion for a separate page for a detailed history is a good one, but the present article on MRI conspicuously lacks a brief history. I think we can add one without excessively encumbering the article; in fact, I believe it will round out the form of it.

Tomattea (talk) 21:20, 1 May 2009 (UTC)

Could we step back a bit. It is clear that many people including Raymond Damadian have contributed to the development of MRI. Raymond Damadian and his supporters consider his contributions have not been adequately recognised and have attempted to marshal evidence to support their position. Others then marshal evidence (e.g. concerning Carr or Kuravcev) to support a contrary position. I have no doubt this debate will continue for a very long time, partly because because of unstated ad hominem attitudes. The point I would like to make is that Wikipedia is not the place to conduct a debate by gathering evidence in support of one case or the other - even if the evidence is a verifiable primary source. See WP:NOR - "articles may not contain any new analysis or synthesis of published material that serves to advance a position not clearly advanced by the sources". If Tomattea is mailing pdfs this sounds a bit like original research. There are several scholarly histories of MR (David Hoult, and the David Grant / Robin Harris volume ISBN-13: 978-0471958390 come to mind). It seems to me that a good article should reflect the consensus in those scholarly histories, and minority views have to be stated and accepted as such. Brownturkey (talk) 22:32, 1 May 2009 (UTC)

I think the goal is to get a well-proportioned history, based on the facts. The scholarly books obviously play a central role. It's considerate that you're leaving a place for minority views to be stated. The challenge is to decide what they are. I do not take the Nobel decision as history but as politics and an inexcusable slight.

I mentioned two books when I initiated the possibility of a history section. Here again is just one of them, which is from the U. of Chicago Press:

“By the final few decades of the twentieth century, medical practitioners were exploiting developments in nuclear physics to provide a range of new ways of peering inside the human body …. Another technique developed during the 1970s was MRI (magnetic resonance imaging). The technique was initially developed by Raymond Damadian (1936 -), working at the Downstate Medical Center in New York, making use of the fact that different atomic nuclei emit radio waves of predictable frequencies when exposed to a magnetic field. Damadian noted that tumorous cells emitted signals different from those emitted by healthy tissue and used this as the basis for a new technique for identifying cancers. Damadian and his fellow workers produced the first MRI scan of the human body in 1977.” Making Modern Science, A Historical Review, The University of Chicago Press, 2005.

I do think we must acknowledge that much of the history of the category has been written by the NMR community, a fact that has perhaps understandably, but not validly, led to some downplaying and distortion of Damadian's contribution. Yet credit for his work has survived decades of it and is likely to strengthen over time. It has also resulted in a caricature of him as being irrascible. But there is a difference between that and justifiable outrage. What would you do if, on one hand, experts were poo-pooing your work, while, on the other hand, other experts were attempting to appropriate it?

There have also been some unintended consequences of this sort of history. For instance, just a few months ago there was an article in The Journal of Urology about the subject, where the medical doctors who authored it were particularly disheartened that the frequent lack of credit going to Damadian, along with the Nobel decision, would likely discourage future M. D.'s from pursuing original research. I will provide a reference to the article as I get time.

One of the books you mention, by Chen and Hoult, is an example of the prejudice, as well as the thin ice it's on. When he downplays Damadian's contribution, Hoult makes the same error that many make when they say Damadian's technique couldn't work. They fail to distinguish between the two components of the electromagnetic field - the electric component and the magnetic component. The magnetic component is the near field and can be focused. It's the only field Damadian was focusing.

It is also rather bizarre to dismiss that the validity of Damadian's patent was argued before The U. S. Supreme Court, during which a long train of NMR experts were recruited by GE to testify against the patent's validity. Over a million pages of documentary evidence were scrutinized. Damadian had to prove his technique worked. The fact that he was successful in doing so is the only reason his patent was upheld and why GE, as well as other major companies that had entered the field, such as J & J, agreed to pay for infringement.

I think if we decide that the distinguished thing to do is present the truth of discovery, without bias, we can produce a history that is worthy of the science. That is my only goal. It strikes me as ironic that it will apparently be a bit of a struggle. I hope it becomes more of a cordial process. Tomattea (talk) 20:22, 4 May 2009 (UTC)

I have recently written a history of MRI article for the journal Neurosurgical Focus and provide a link to the Nature Precedings version. I believe that it fairly placed Damadian's specific contributions in their appropriate historical context. It also explores the difficulty of knowing how invention and priority are based.[[[User:Afiller|Afiller]] (talk)} —Preceding undated comment added 00:39, 18 July 2009 (UTC).

Mednovus

Before splitting this out to its own article, as per http://en.wikipedia.org/w/index.php?title=Magnetic_resonance_imaging&curid=19446&diff=294983287&oldid=294979786, the company's notability (per WP:CORP) should be established. --ClickRick (talk) 15:17, 7 June 2009 (UTC)

Removed content for now. If notability can be established then it can always be restored. --ClickRick (talk) 15:25, 7 June 2009 (UTC)

I read the reference you provided to notability, but it isn't terribly helpful, particularly as it applies to smaller, privately-held companies. Acknowledging that 'notability' is not equivalent to 'fame', I would contend that this company is notable within the context of the MRI world (which is why I chose this article to which to append the stub). The company is one of very few working exclusively in the realm of MRI safety, collaborated with the National Research Council of Canada on the development of perhaps the worlds most sensitive pass through ferromagnetic detection instrument the 9000-C, and the company is represented by its president, Tobias Gilk on the American College of Radiology's MR Safety Committee. Mr. Gilk has also contributed to / authored numerous publications on MRI safety, including the US Department of Veterans Affairs MRI Design Guide, the ASHE monograph, Designing and Engineering MRI Safety, and numerous others. Kemp Massengill, MD, co-founder of the company and its former president, was sought-out as an authority when the New York Times did an article on MRI accidents in 2005. Please advise as to whether you feel that this achieves the 'notability' benchmark relative to this company's involvement in the MRI industry or, if it does not, please advise as to what other materials would be appropriate to establishing 'notability' for a smaller, privately-held company. Thank you. Tgilk (talk) 20:52, 7 June 2009 (UTC)

Most of those links are not WP:Secondary sources and could not be seen as being "neutral". Is there perhaps a periodical within the health sector which discusses MRI and Mednovus in particular, perhaps with an (independently-written) article reviewing the company's work or products? --ClickRick (talk)

Diffusion MRI

A 'lively' discussion has broken out between two editors on the Diffusion MRI page (see the talk page and history). I don't know anything about diffusion, so I'm not much help - but I'm guessing someone watching this page does. Could you go over there and take a look? Thx GyroMagician (talk) 07:20, 22 July 2009 (UTC)