Abstract
PURPOSE: By leveraging the small-vessel specificity of velocity-selective arterial spin labeling (VSASL), we present a novel technique for measuring cerebral MicroVascular Pulsatility named MVP-VSASL. THEORY AND METHODS: We present a theoretical model relating the pulsatile, cerebral blood flow-driven VSASL signal to the microvascular pulsatility index ( PI ), a widely used metric for quantifying cardiac-dependent fluctuations. The model describes the dependence of the PI of VSASL signal (denoted PIVS ) on bolus duration τ (an adjustable VSASL sequence parameter) and provides guidance for selecting a value of τ that maximizes the SNR of the PIVS measurement. The model predictions were assessed in humans using data acquired with retrospectively cardiac-gated VSASL sequences over a broad range of τ values. In vivo measurements were also used to demonstrate the feasibility of whole-brain voxel-wise pulsatility mapping, assess intrasession repeatability of PIVS , and illustrate the potential of this method to explore an association with age. RESULTS: The theoretical model showed excellent agreement to the empirical data in a gray matter region of interest (average R2 value of 0.898 ± 0.107 across six subjects). We further showed excellent intrasession repeatability of the pulsatility measurement ( ICC = 0.960 , p < 0.001 ) and the potential to characterize associations with age ( r = 0.554 , p = 0.021 ). CONCLUSION: We have introduced a novel, VSASL-based cerebral microvascular pulsatility technique, which may facilitate investigation of cognitive disorders where damage to the microvasculature has been implicated.