Validation of tomographic measurement of cerebral blood volume with C-11-labeled carboxyhemoglobin.

Abstract

Red blood cells, tagged with C-11 administration of /sup 11/CO gas, have been used to portray the distribution of blood in the brain. To date, however, the accuracy of this approach has not been validated. We have performed in vitro measurements of regional cerebral blood volume (CBV) with red blood cells labeled with C-11 and Cr-51 in four dogs and two rhesus monkeys. These studies yielded a ratio of CBV/sub C-1/ to CBV/sub Cr-11/ of 1.02 +- 0.03 (s.d.) from 92 samples. A least-squares fit to these data showed CBV/sub C-11/ = 1.01 CBV/sub Cr-51/ + 0.037; P much < 0.001. The ratio of CBV in gray matter to that in white matter was 2.8 +- 0.4 (n = 12) and 3.1 +- 0.6 (n = 8). In vivo studies with emission computed tomography (ECT) and /sup 11/CO-RBC gave coefficients of variation of +- 2.8% and +- 4.8% for cross-sectional CBV and regional (approx.4 cm/sup 2/) CBV over an 80-min period. The average human CBV was found to be 4.2 +- 0.4 cc blood per 100 g tissue. Clear tomographic delineation of the distribution of CBV in human subjects is achieved with ECT, which provides a ''live'' measurement of thismore » parameter of cerebral hemodynamics. These data demonstrate that /sup 11/CO administered by single-breath inhalation is a reliable and accurate blood tracer for measurement of CBV with ECT.« less