Editorial Better Late than Never The Long Journey for Noncontrast Arterial Spin Labeling Perfusion Imaging in Acute Stroke

See related article, page xxx. This report1 describes the authors ’ experience using anoncontrast brain perfusion method, arterial spin labeling (ASL), in patients with acute ischemic stroke and compares this with dynamic susceptibility contrast MRI. This latter technique is also sometimes referred to simply as perfusion-weighted imaging (PWI) to emphasize its complementary nature to diffusion-weighted imaging. The authors found excellent overlap between imaging information available with PWI and ASL with no measurable difference in per-ceived signal-to-noise ratio or lesion conspicuity. They also found that the effects of slow flow on the ASL signal, although present, were not an insurmountable impediment to image interpretation in that they correlated with the changes seen in the PWI time-to-maximum of the residue function (Tmax) and the nondelay-corrected cerebral blood flow maps