QUANTITATION OF ARTERIAL SPIN LABELING MRI LABELING EFFICIENCY IN HIGH CERVICAL VELOCITY CONDITIONS USING PHASE CONTRAST ANGIOGRAPHY

摘要

The objective of this study is to measure flow velocities in the four major vessels supplying the brain using phase contrast angiography (PCA) MRI and to use these measurements to estimate labeling efficiency in the popular cerebral blood flow (CBF)-weighted arterial spin labeling (ASL) approach in patient cervical vessels with variable flow velocity. ASL and PCA scans were performed on controls (n=7), and patients with sickle cell disease (SCD) with known, elevated flow velocity (n=19). Mean blood flow velocities were computed for the internal carotid and vertebral arteries using PCA. ASL labeling efficiencies were calculated by requiring that the CBF be identical between PCA and ASL. The results showed that ASL labeling efficiencies in patients with SCD are significantly lower (p<0.05) than in controls, causing an underestimation of CBF from ASL when using labeling efficiencies that do not control for flow velocity; solutions for this fundamental limitation are proposed.