Continuous Arterial Spin Labeling by a Separate Neck Coil with Inversion-Recovery Suppression of Static Tissue Signals (ir- cASL)

INTRODUCTION Arterial spin labeling (ASL) technique has been widely used to measure cerebral blood flow (CBF) in animals and humans. This approach uses “pair-wise” subtraction of alternate images taken with labeled and non-labeled conditions to obtain a difference signal that arises only from inflowing “labeling” water. Although the static tissue signal from static brain water is subtracted out in the CBF determination, instabilities in the static tissue signal can add substantial noise to the difference signal which is typically less than 5% of the total signal intensity. Reduction or elimination of the static tissue signal in an ASL study could improve sensitivity, contrast and reproducibility. Such static tissue signal reduction can be achieved using single or multiple inversion pulses (1–4) based on the fluid-attenuated inversion recovery (FAIR) and other ASL techniques. In this work, we implemented the inversion-recovery suppression of static tissue to the two-coil continuous ASL (ir-cASL) to image baseline CBF and stimulus-evoked CBF fMRI. This approach compares favorably with existing methods because static tissue suppression is independent of labeling efficiency. Comparisons with cASL were made in the same animals.