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1 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 PI on bolus duration τ (an adjustable VSASL sequence parameter) and provides guidance for selecting a value of τ that maximizes the SNR of the PI 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 PI mapping, assess intrasession repeatability of the PI measurement, 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 R 2 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.
Chen et al. (Sun,) studied this question.