Local cerebral blood volume determined by three-dimensional reconstruction of radionuclide scan data

We developed a method to determine in man absolute values of local cerebral blood volume (LCBV) localized throughout the brain in three dimensions and presented in a cross-sectional picture format. Previously, absolute values of LCBV have been determined in vivo by stimulated X-ray fluorescence, but these determinations have been limited to one point in the brain at a time. All other previous estimates of LCBV by external emission counting have been contaminated by the significant contribution of blood in the overlying scalp and cranium. In our method, a transverse section scan is made after the injection of -99m-Tc-labeled red blood cells into a peripheral vein. Data processing then gives a point-to-point estimate of absolute radionuclide concentration analogous to an autoradiograph. After the concentration of blood activity is determined, counting data are converted to a two-dimensional map of LCBV representing a cross section at a known level of the brain. In a series of five baboons, the following equation was obtained for the regression plane that relates LCBV in the center of the brain to arterial carbon dioxide tension (P-ALPHA-CO2) and mean arterial blood pressure (MABP): LCBV equals 2.88 + 0.049P-ALPHA-CO2 MINUS 0.013MABP. In patients, LCBE values ranged from 2 to 4 ml/100 g depending on location; higher values corresponded to regions of cerebral cortex. Differences in blood volumes of focal brain lesions were also quantified.