Accurate assessment of regional cerebral blood volume (rCBV) is of critical
importance in the study of cerebrovascular disease and other disorders of
the central nervous system, Currently, magnetic resonance imaging [MRI) is
able to measure rCBV non-invasively with two commonly used methods: the dyn
amic imaging (DI) and steady state (SS) approaches. In this study, two ques
tions were investigated. First, how do partial volume effects between gray
matter (GM) and white matter (WM) and between epicortical vessels and brain
parenchyma affect the estimation of rCBV when using the SS approach? Secon
d, how comparable are the ratios of rCBV in GM to rCBV in WM (rCBV GM/WM) o
btained with the two methods? We used a paramagnetic contrast agent, OPTIMA
RK (Mallinckrodt, St. Louis, MO), at a dose of 0.2 mmol/kg in anesthetized
pigs (n = 6) to obtain rCBV maps using both methods. When a 10% rCBV thresh
old was used to minimize effects from large epicortical vessels, and tissue
segmentation was used to separate GM from WM, rCBV values of 4.8 +/- 0.3%
and 3.3 +/- 0.5% were obtained for GM and WM, respectively, with the SS app
roach. Significantly higher rCBV values for both GM (P < 0.001) and WM (P <
0.01) were observed when the contribution from large epicortical vessels w
as not removed. When tissue segmentation and rCBV thresholding were used on
SS data, an rCBV GM/WM ratio of 1.5 +/- 0.2 was obtained. This value did n
ot differ significantly from the rCBV GM/WM ratio of 1.8 +/- 0.6 obtained u
sing the DI approach. J, Magn, Reson, Imaging 1999;9:44-52, (C) 1999 Wiley-
Liss, Inc.