Perfusion fMRI for functional neuroimaging

Arterial spin labeling perfusion functional magnetic resonance imaging (fMRI) is a noninvasive method of obtaining time-series measurements; of regional cerebral perfusion. Magnetically tagged protons in arterial water are labeled and allowed to perfuse the cerebral tissue. The perfusion-fMRI data are then generated from measurements of the difference between sequentially obtained label images and control images. This differencing step bestows signal properties upon perfusion data that are quite different from those of blood oxygen level-dependent (BOLD) fMRI. Unlike with BOLD, the resulting time-series data are quantifiable and stable over long time scales. As a consequence, perfusion fMRI is well suited to the stud), of mental operations and neural changes that evolve slowly, over a period of hours to days. The technique is currently limited by a low signal-to-noise ratio (SNR) and slow image acquisition. Ways to improve both of these weaknesses are available, including scanning at higher field strength, using surface coils, and using optimized three-dimensional image acquisition.