Transit time, trailing time, and cerebral blood flow during brain activation: Measurement using multislice, pulsed spin-labeling perfusion imaging

Transit time and trailing time in pulsed spin-labeling perfusion imaging ar e likely to be modulated by local blood flow changes, such as those accompa nying brain activation. The majority of transit/trailing time is due to the passage of the tagged blood bolus through the arteriole/capillary regions, because of lower blood flow velocity in these regions. Changes of transit/ trailing time during activation could affect the quantification of CBF in f unctional neuroimaging studies, and are therefore important to characterize . In this work, the measurement of transit and trailing times and CBF durin g sensorimotor activation using multislice perfusion imaging with pulsed ar terial spin-labeling is described. While CBF elevated dramatically (similar to 80.7%) during the sensorimotor activation, sizable reductions of transi t time (similar to0.11 sec) and trailing time (similar to0.26 sec) were obs erved. Transit and trailing times were dependent on the distances from the leading and trailing edges of the tagged blood bolus to the location of the imaging slices, The effects of transit/trailing time changes on CBF quanti fication during brain activation were analyzed by simulation studies, signi ficant errors can be caused in the estimation of CBF if such changes of tra nsit/trailing time are not taken into account. (C) 2000 Wiley-Liss, Inc.