Simultaneous Imaging Of Cbf Change And Bold With Saturation-Recovery-T-1 Method

A neuroimaging technique based on the saturation-recovery (SR)-T-1 MRI method was applied for simultaneously imaging blood oxygenation level dependence (BOLD) contrast and cerebral blood flow change (Delta CBF), which is determined by CBF-sensitive T-1 relaxation rate change (Delta R-1(CBF)). This technique was validated by quantitatively examining the relationships among Delta R1CBF,Delta CBF, BOLD and relative CBF change (rCBF), which was simultaneously measured by laser Doppler flowmetry under global ischemia and hypercapnia conditions, respectively, in the rat brain. It was found that during ischemia, BOLD decreased 23.1 +/- 2.8% in the cortical area; Delta R-1(CBF) decreased 0.020 +/- 0.004s(-1) corresponding to a Delta CBF decrease of 1.07 +/- 0.24 ml/g/min and 89.5 +/- 1.8% CBF reduction (n=5), resulting in a baseline CBF value (=1.18 ml/g/min) consistent with the literature reports. The CBF change quantification based on temperature corrected Delta R-1 CBF had a better accuracy than apparent R-1 change (Delta R-1(app)); nevertheless, Delta R-1(app) without temperature correction still provides a good approximation for quantifying CBF change since perfusion dominates the evolution of the longitudinal relaxation rate (R-1(app)). In contrast to the excellent consistency between Delta CBF and rCBF measured during and after ischemia, the BOLD change during the post-ischemia period was temporally disassociated with Delta CBF, indicating distinct CBF and BOLD responses. Similar results were also observed for the hypercapnia study. The overall results demonstrate that the SR-T-1 MRI method is effective for noninvasive and quantitative imaging of both Delta CBF and BOLD associated with physiological and/or pathological changes.