Functional bolus-tracking arterial spin labeling: a new approach to quantitative fMRI

BOLD fMRI is the most widely used method for mapping neuronal activity in the brain. The alterations in the BOLD signal when cerebral blood flow (CBF), volume (CBV) and vascular structure change (e.g. due to aging and or neurovascular disease) are relatively unknown. This presents a considerable obstacle when interpreting certain BOLD fMRI studies (1). The purpose of this study is to develop a new quantitative fMRI technique, bolus-tracking arterial spin labeling (ASL) fMRI, which provides a more detailed assessment of the blood perfusion of an activated brain region. To this end, a novel derivation of the Fokker-Planck equation (Eq.1) was utilized that reduces the number of variables required to describe the physiological processes involved in cerebral perfusion. The solution to Eq.1 was fitted to ASL data (Fig.2) and the mean transit time (MTT) and capillary transit time (CTT) were calculated. A rat fMRI study was designed to establish if these parameters change during neuronal activation.