Spatial coefficient of variation in pseudo-continuous arterial spin labeling cerebral blood flow images as a hemodynamic measure for cerebrovascular steno-occlusive disease: A comparative 15O positron emission tomography study

Pseudo-continuous arterial spin labeling (pCASL) is a completely non-invasive method of cerebral perfusion measurement. However, cerebral blood flow (CBF) quantification is hampered by arterial transit artifacts characterized by bright vascular signals surrounded by decreased signals in tissue regions, which commonly appear in patients with reduced cerebral perfusion pressure. The spatial coefficient of variation (CoV) of pCASL CBF images has been proposed as an alternative region-of-interest (ROI)-based hemodynamic measure to predict prolonged arterial transit time (ATT). This retrospective study investigates the utility of spatial CoV by comparison with O-15 positron emission tomography (PET). For patients with cerebrovascular steno-occlusive disease (n = 17), spatial CoV was positively correlated with ATT independently measured by pulsed arterial spin labeling (r = 0.597, p < 0.001), confirming its role as an ATT-like hemodynamic measure. Comparisons with O-15 PET demonstrated that spatial CoV was positively correlated with vascular mean transit time (r = 0.587, p < 0.001) and negatively correlated with both resting CBF (r = -0.541, p = 0.001) and CBF response to hypercapnia (r = -0.373, p = 0.030). ROI-based spatial CoV calculated from single time-point pCASL can potentially detect subtle perfusion abnormalities in clinical settings.