Arterial spin labelling
Arterial spin labeling (ASL), also known as arterial spin tagging, is a magnetic resonance imaging method for measuring perfusion using water already in the subject as tracers by setting and tracking magnetic spin. Perfusion MRI is perfusion scanning by the use of a particular MRI sequence. ASL specifically refers to magnetic labeling of arterial blood below the imaging slab, without the need of gadolinium contrast, instead inferring perfusion from a drop in signal observed in the imaging slice arising from inflowing spins (outside the imaging slice) having been selectively saturated. A number of ASL schemes are possible, the simplest being flow alternating inversion recovery (FAIR) which requires two acquisitions of identical parameters with the exception of the out-of-slice saturation; the difference in the two images is theoretically only from inflowing spins, and may be considered a 'perfusion map'. The technique was developed by John Detre, Alan P. Koretsky and coworkers in 1992.
In cerebral infarction, the penumbra has decreased perfusion. Besides acute and chronic neurovascular diseases, the value of ASL has been demonstrated in brain tumors, epilepsy and neurodegenerative disease, such as Alzheimer’s disease, frontotemporal dementia and Parkinson disease.
ASL is in general a safe technique, although injuries may occur as a result of failed safety procedures or human error like other MRI techniques.
- Fortin F, Gaillard F. "Arterial spin labelling (ASL) MR perfusion". Radiopaedia. Retrieved 2017-10-15.
- "Arterial spin labeling". University of Michigan. Retrieved 2017-10-27.
- Koretsky AP (August 2012). "Early development of arterial spin labeling to measure regional brain blood flow by MRI". NeuroImage. 62 (2): 602–7. doi:10.1016/j.neuroimage.2012.01.005. PMC 4199083. PMID 22245338.
- Chen F, Ni YC (March 2012). "Magnetic resonance diffusion-perfusion mismatch in acute ischemic stroke: An update". World Journal of Radiology. 4 (3): 63–74. doi:10.4329/wjr.v4.i3.63. PMID 22468186.
- Grade M, Hernandez Tamames JA, Pizzini FB, Achten E, Golay X, Smits M (December 2015). "A neuroradiologist's guide to arterial spin labeling MRI in clinical practice". Neuroradiology. 57 (12): 1181–202. doi:10.1007/s00234-015-1571-z. PMC 4648972. PMID 26351201.
- Huettel SA, Song AW, McCarthy G (2009). Functional Magnetic Resonance Imaging (2nd ed.). Sunderland, Massachusetts: Sinauer Associates. p. 26. ISBN 978-0-87893-286-3.
- Detre JA, Rao H, Wang DJ, Chen YF, Wang Z (May 2012). "Applications of arterial spin labeled MRI in the brain". Journal of Magnetic Resonance Imaging. 35 (5): 1026–37. doi:10.1002/jmri.23581. PMC 3326188. PMID 22246782.
- Watson RE (2015-10-01). "Lessons Learned from MRI Safety Events". Current Radiology Reports. 3 (10): 37. doi:10.1007/s40134-015-0122-z. ISSN 2167-4825.
- mriquestions.com