3D ultrasound

A 3D ultrasound of a fetus aged 20 weeks

3D ultrasound is a medical ultrasound technique, often used during pregnancy, providing three dimensional images of the fetus.

There are several different scanning modes in medical and obstetric ultrasound. The standard common obstetric diagnostic mode is 2D scanning. In 3D fetal scanning, however, instead of the sound waves being sent straight down and reflected back, they are sent at different angles. The returning echoes are processed by a sophisticated computer program resulting in a reconstructed three dimensional volume image of fetus's surface or internal organs, in much the same way as a CT scan machine constructs a CT scan image from multiple x-rays. 3D ultrasounds allow one to see width, height and depth of images in much the same way as 3D movies but no movement is shown.

3D ultrasound was first developed by Olaf von Ramm and Stephen Smith at Duke University in 1987.

Clinical use of this technology is an area of intense research activity especially in fetal anomaly scanning but there are also popular uses that have been shown to improve fetal-maternal bonding. 4D baby scans are similar to 3D scans except that they show fetal movement as shown in the video clip.

If the system is used only in the Obstetrics Application, the ultrasound energy is limited by the manufacturer below FDA limits for obstetrical ultrasound, whether scanning 2, 3 or 4 dimensionally. (The FDA limit for obstetrical ultrasound is 94 mW/cm².) While there has been no conclusive evidence for harmful effects of 3D ultrasounds on a developing fetus, there still remains controversy over its use in non-medical situations, and generally, the AIUM recommends that 3D ultrasounds should be undertaken with the understanding that a risk may exist.

Elective 3D Ultrasound

Although 3D ultrasound technology may be used on any part of the body, elective 3D ultrasound conventionally refers to 3D ultrasounds performed on pregnant women for the sole purpose of the woman to see her unborn baby, what the baby looks like, or to see whether the baby will be a boy or a girl. In the medical literature, these elective 3D ultrasounds are also referred to as keepsake ultrasounds, although this term is rarely used in the lay population and only sometimes used in the media.

Benefits of elective 3D ultrasounds

Although there is no direct medical benefit of receiving an elective 3D ultrasound, there may be many indirect benefits, as listed below. It is important to note that there has been no conclusive evidence in the medical literature to support these benefits, and in fact, the medical literature shows conflicting studies on these benefits.

Controversially, Christian/Catholic non-profit organizations have employed 3D ultrasounds for young pregnant women in order to influence their decisions regarding abortion. Charitable donations or public funds help pay for the 3D ultrasound machine.

Risks of 3D ultrasounds

Generally, the risks of 3D ultrasounds mirror those of 2D ultrasounds, as it uses the same ultrasound waves at the same intensity. Unlike the comparison of CT scans to x-rays, 3D ultrasounds do not employ multiple snapshots of 2D ultrasounds but uses the 2D ultrasound images taken at various angles to construct an image. So the potential risk of 3D ultrasounds, if any, would depend on the duration of the ultrasound session rather than whether it is 2D or 3D.

The risk of ultrasounds, theoretically, would depend on the following factors:

• Duration of ultrasound exposure
• Intensity of ultrasound waves
• Frequency of ultrasound sessions

Duration

Although no set standard formally exists, there is a consensus among ob/gyn physicians and 3D ultrasound centers that ultrasound sessions should be limited to 1 hour at a time.

Intensity

The intensity of ultrasound waves are mechanically set into the machine to not exceed FDA standards. Ultrasound machines are constructed to either shut off or give a noticeable warning if any of the built-in barriers fail to limit the ultrasound waves to below the FDA standard. Generally, a higher intensity of ultrasound waves are used to detect the baby's heartbeat, and as these waves are also directed and focused onto a single organ in the fetus, it is generally advised that use of the ultrasound machine to detect and play the baby's heartbeat be done after 12 weeks of gestation, although it may be physically detectable as early as 9 weeks of gestation.

Frequency

The frequency of ultrasound sessions can also theoretically pose a risk. It is generally discouraged to perform elective 3D ultrasounds more frequently than once a month. It is important to note that women undergoing in vitro fertilization or who have possible fetal abnormalities undergo weekly 2D ultrasounds. Pregnant women in some European countries undergo monthly 2D ultrasounds as routine prenatal care.

Physical effects

Neither the mother nor the fetus can hear or feel ultrasounds produced by the ultrasound machine. It is known that ultrasound is a form of energy, like all sound waves, and may produce a slight amount of heat when focused in one spot over hours to days. Therapeutic ultrasounds have different ultrasound settings with higher intensities and are meant to create this slight warmth or vibration.

Medical effects

There has been no associated mental defects or medical harms to the mother or fetus directly attributed to 2D or 3D ultrasounds over the course of its 30-year history of medical ultrasound use. There is more than one report of a slight increase in left-handedness in boys whose mothers have received 3D ultrasounds.

Other risks

Other unintended harm caused by 3D ultrasounds may include the finding of false positives, which can be a significant source of distress to the mother. Cysts found on the fetus that would have been harmless and may not have been found otherwise may be detected on 3D ultrasound and lead to further more invasive exams as well as cause needless anxiety to the mother. Artifacts can be seen on 3D ultrasound, particularly by those with less experience, such as duplications of body parts, holes, clefts, and missing body parts. Usually, these artifacts go away by moving the ultrasound probe slightly, but when performed by an inexperienced technician, may produce needless anxiety to the mother.

Seeing the fetus too early, under 17 weeks, may cause some harm to the mother as it may actually decrease bonding and give a feeling to the mother that the baby is alien or "not really a baby yet." It is generally advised to perform 3D ultrasounds at or after 17 weeks of gestation for this reason (Kurjak et al., How useful is 3D and 4D ultrasound in perinatal medicine? J. Perinatal Medicine, 2007).

Other incidental harms to elective 3D ultrasounds include falls or back pain when getting on and off a bed not conducive to pregnant women in 3D ultrasound centers; aggressive manipulation of the belly by an inexperienced ultrasound technician; encouragement of the pregnant mother to drink caffeine-containing beverages to stimulate the baby for a "good photo shot." Caffeine, even in small amounts, have been implicated with some controversy to result in possible harm to the fetus. [citation needed]

Substitution of prenatal care

By far, the biggest potential risk to the pregnant woman in getting a 3D ultrasound is a false sense of reassurance. Pregnant women in the United States who can not otherwise afford health care and do not have health insurance may see the payment of an elective 3D ultrasound, which may cost around $100–$200, as a cheaper alternative to the artificially raised prices of prenatal care from a clinic or hospital, where lab work alone may exceed $1000. Women who receive a 3D ultrasound may be falsely reassured that "everything is okay" and may discontinue prenatal care or taking prenatal vitamins. This potential risk may be averted, at least partially, by repeated instructions that the 3D ultrasound does not take place of routine prenatal care. Many 3D ultrasound centers require signatures on statements of understanding to this fact or may require proof of prenatal care. Some 3D ultrasound centers go as far as to require a note or a prescription from a physician to perform the 3D ultrasounds.

Risk reduction of 3D ultrasounds

The following can help reduce the risks of elective 3D ultrasounds:

• Have a qualified medical director for 3D ultrasound centers.

Some states require that every 3D ultrasound center must have a medical director

• Employ only ARDMS-certified ultrasound technologists

Some ultrasound centers do not employ ultrasound technologists, and currently, there is no law that mandates that 3D ultrasounds must be performed by certified ultrasound technologists

• Provide adequate training to ultrasound technologists
• Have adequate communication with the ob/gyn's of the customers, and have policies put in place in regards to accidental discoveries of abnormalities
• Safety inspections of the clinic
• Regular inspections and maintenance of the ultrasound machine
• Limit ultrasound sessions to last no longer than 30 minutes
• Limit ultrasound sessions to no more than once a month
• Require proof of prenatal care prior to the 3D ultrasound session

Timing of 3D ultrasound

Gender checks

Although medical textbooks state that the gender of the baby can be seen on ultrasound as early as 12 weeks, practically speaking, most medical facilities and hospitals do not attempt to determine the gender of the baby until the 20-week ob/gyn visit. 3D/4D ultrasound centers bridge the gap and fulfill the niche market of pregnant women who can not wait to find out the sex of the baby, women who did not find out the gender of the baby at their medical visit and the insurance does not pay for any more ultrasounds, and women who simply want to confirm the sex of the baby.

Some ultrasound centers attempt to determine the gender of the baby as early as 15 weeks and advertise as such. The customer is required to pay at the first visit, but most of the time, the customer has to return when the baby is more mature. At 15 weeks, the success rate for being able to see the gender is around 50% at best, and the accuracy at that gestational age is questionable.

At 17 weeks, the ability to find the gender and accuracy rises to above 90%. Most ultrasound centers use 17 weeks as their cutoff to determine the gender. Gender determination is the most accurate at 20 weeks and beyond, with a rate of 95%, as reported in the medical literature based on ob/gyn visits generally done at 20 weeks.

Visualization of the baby

3D ultrasounds are best done at 20–32 weeks, and ideally between 24 and 30 weeks. Some centers advise customers to come in between 28 and 32 weeks or beyond in order to get closeup pictures.

After 32 weeks, there is an increased risk that the baby has already engaged (descended into the pelvis) and at that time, getting 3D images of the baby is nearly impossible.

Methods

Unlike the medical ultrasound visit, customers of 3D ultrasound centers are not advised to hold their urine or have a full bladder before their 3D ultrasound apppointment.

In order to get good images, ultrasound centers advise customers to drink adequate amounts of water (32 ounces/day) for the one to two weeks prior to their appointment. This is in order to ensure there is an adequate amount of amniotic fluid around the fetus and that the fluid is clear. Drinking large amounts of water immediately before the 3D ultrasound appointment does not help to have clearer 3D ultrasound images.

Future developments

3D ultrasounds may soon become a part of routine care. Indeed, many hospitals and clinics already provide 3D ultrasounds to pregnant women as a courtesy.

3D ultrasounds may soon be covered by FSA (flexible spending accounts) and may eventually be accepted by some insurance companies, as medical studies begin to show benefits of elective 3D ultrasounds.

State laws are developing to require oversight and restrictions on 3D ultrasound centers, including the requirement of a medical director, requiring verification of prenatal care, and/or requiring certified ultrasound technicians.

3D ultrasounds are already being used to detect fetal anomalies of the heart. 3D ultrasounds may be used in the near future for actual neurological and behavioral testing of the fetus to help diagnose or rule out cerebral palsy.

A novel technology enabling the use of 3D ultrasound in remote areas has been recently developed. This new technology leverages the ubiquitous mobile phone available even in the most remote corners of the world. By collecting the raw data at the patient location and sending it for processing and expert evaluation to the central processing station, this technology reduces equipment costs and reduces the hand-eye coordination skills normally required from the technician performing the procedure.

Opposing views

In 1999, the American Institute of Ultrasound in Medicine (AIUM) released the following statement: The AIUM strongly discourages the non-medical use of ultrasound for psychosocial or entertainment purposes. The use of either two-dimensional (2D) or three-dimensional (3D) ultrasound to only view the fetus, obtain a picture of the fetus, or determine the fetal gender without a medical indication is inappropriate and contrary to responsible medical practice.

In February 2004, the American Food and Drug Administration (FDA) issued the following statement: Persons who promote, sell or lease ultrasound equipment for making “keepsake” fetal videos should know that FDA views this as an unapproved use of a medical device. In addition, those who subject individuals to ultrasound exposure using a diagnostic ultrasound device (a prescription device) without a physician’s order may be in violation of state or local laws or regulations regarding use of a prescription medical device.

Regional Anesthesia

Real-time three dimensional ultrasound is used during peripheral nerve blockade procedures to identify relevant anatomy and monitor the spread of local anesthetic around the nerve. Peripheral nerve blockades prevent the transmission of pain signals from the site of injury to the brain without deep sedation, which makes them particularly useful for outpatient orthopedic procedures. Real-time 3D ultrasound allows muscles, nerves and vessels to be clearly identified while a needle or catheter is advanced under the skin. 3D ultrasound is able to view the needle regardless of the plane of the image, which is a substantial improvement over 2D ultrasound. Additionally, the image can be rotated or cropped in real time to reveal anatomical structures within a volume of tissue. Physicians at the Mayo Clinic in Jacksonville have been developing techniques using real time 3D ultrasound to guide peripheral nerve blocks for shoulder, knee, and ankle surgery.

Further reading

• Article: 3D and 4D Ultrasound Scanning
• Article: 4D: What the Medical Literature Says
• The History of Ultrasounds (including 3D ultrasounds)

External links

• The Endowment for Human Development provides numerous 4D ultrasounds that can be viewed online.
• Scans uncover secrets of the womb BBC News
• About the discovery of medical ultrasonography
• RadiologyTube - 3D and 4D Ultrasound Videos
• History of medical sonography (ultrasound)
• Safety Concerns Details a number of health concerns over this unregulated practice