Schematic diagram illustrates the continuous arterial
spin labeling (CASL) method. This technique is very similar to positron
emission tomography (PET) scanning, but is entirely non-invasive
and does not require injections or radioactivity. In this elegant
technique, water molecules in the patient's own blood are 'tagged'
by the functional magnetic resonance imaging (fMRI) magnet and used
as the natural contrast agent in order to measure cerebral blood-flow.
Image Courtesy: Jiongjiong Wang, PhD, and John A. Detre, MD,
University of Pennsylvania School of Medicine