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,[1] 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'.[2] The technique was developed by John Detre, Alan P. Koretsky and coworkers in 1992.[3]

Clinical use

In cerebral infarction, the penumbra has decreased perfusion.[4] 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.[5]

Although the primary form of fMRI uses the blood-oxygen-level dependent (BOLD) contrast,[6] ASL is another method of obtaining contrast.[7]

Safety

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.[8]

References

  1. ↑ Fortin F, Gaillard F. "Arterial spin labelling (ASL) MR perfusion". Radiopaedia. Retrieved 2017-10-15.
  2. ↑ "Arterial spin labeling". University of Michigan. Retrieved 2017-10-27.
  3. ↑ 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.
  4. ↑ 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.
  5. ↑ 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.
  6. ↑ 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.
  7. ↑ 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.
  8. ↑ 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.
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