Modeling the Effect of Flow Dispersion in Continuous Arterial Spin Labeling

Weiying Dai¹, Ajit Shankaranarayanan², David Alsop¹

Quantification of perfusion with arterial spin labeling (ASL) requires knowledge of the label delivery over time. Standard ASL perfusion quantification assumes simple plug flow, i.e., all labeled blood takes the same time to travel from the labeling plane to the imaging region. Simple plug flow may not well approximate the tracer delivery. Here, we show that approximating the transit time distribution with a gamma variate function produces a relatively simple analytic solution to the modified Bloch equations. Pixel-by pixel fitting to in-vivo data was used to measure transit time dispersion. Using a dispersion model provided better fits to the multiple delay data compared with the standard model. Dispersion varies with spatial locations: deep gray matter regions have less dispersion and posterior regions have more.