Yufen Chen1, Danny J. J. Wang2,
John A. Detre1
1Center for Functional
Neuroimaging, University of Pennsylvania, Philadelphia, PA, United States; 2Department
of Neurology, University of California Los Angeles, Los Angeles, CA, United
States
Transit time refers to the time needed for labeled spins to travel from the label region to the imaging region in ASL. Here, we investigate the effects of labeling position on the arterial and microvascular transit times of two efficient transit time mapping techniques: LL-ASL and FEAST. Our results demonstrate a linear relationship between label position and arterial transit time, with the slope related to the average blood velocity from label to image region. A 650ms discrepancy was observed between arterial and microvascular transit times, likely the result of controlled oxygen transport to facilitate exchange at the capillary bed.