Cerebral perfusion and arterial transit time changes during task activation determined with continuous arterial spin labeling

Perfusion imaging by arterial spin labeling (ASL) can be highly sensitive t o the transit time from the labeling site to the tissue. We report the resu lts of a study designed to separate the transit time and perfusion contribu tions to activation in ASL images accompanying motor and visual stimulation . Fractional transit time decreases were found to be comparable to fraction al perfusion increases and the transit time change was found to be the grea test contributor to ASL signal change in ASL sequences without delayed acqu isition. The implications for activation imaging with ASL and the arterial control of flow are discussed. Magn Reson Med 43:739-746, 2000. (C) 2000 Wi ley-Liss, Inc.