Comparison Between Total CBF Values Measured by ASL and Phase Contrast Over Increased Range of CBF Values

Introduction Arterial spin labeling (ASL) utilizes the water in arterial blood as endogenous contrast agent to assess cerebral blood perfusion and therefore is becoming more commonly used. A perfusion image is generated by subtracting a tagged image from a control image, where the tagged image is acquired following the “labeling” of the blood upstream using an inversion pulse. The time delay between the labeling and the image acquisition, which is the transient time, allows the labeled blood to reach the imaging volume. While ASL is sensitive to changes in cerebral blood flow (CBF), derived absolute CBF values are influenced, among others, by the choice of the transient time and by the actual blood flow velocities. This project aims to compare between measurements of total CBF obtained with ASL and phase contrast MRI (PCMRI). The comparison was done over a wide range of CBF values by manipulating the end tidal pCO2 level following the application of continuous positive airways pressure (CPAP).