Quantitation of brain perfusion with 99mTc-bicisate and single SPECT scan: comparison with microsphere measurements

This study describes and validates in a preliminary manner a method to measure the steady-state influx constant (Ki) of 99mTc-bicisate with one single photon emission computed tomography (SPECT) scan. The method is based on the analysis of the arterial concentration of the radioactivity. The results of this quantitation procedure were compared with regional CBF (rCBF) measurements made using 99mTc-microspheres (MI). Two quantitative indexes of perfusion, fractional brain uptake (FBU) and normalized (with cerebellum) brain uptake (NBU), were also evaluated. Two SPECT studies were performed on seven cardiovascular patients who had no signs of neurological disease. In the first of these, 99mTc-bicisate was used, while in the other, which was performed 2 days later, MI were injected into the left heart ventricle. The values of the FBU, NBU, and Ki of 99mTc-bicisate were calculated in several gray and white matter brain regions of interest (ROIs) and compared with the rCBF values measured with MI in coupled ROIs. Mean FBU values were 0.00008 +/- 0.00002 and 0.00004 +/- 0.00001 in the gray and the white matter, respectively. Mean NBU values were 0.99 +/- 0.04 and 0.54 +/- 0.05, mean Ki values were 0.36 +/- 0.06 and 0.19 +/- 0.03 ml g-1 min-1 and mean rCBF values were 0.51 +/- 0.04 and 0.27 +/- 0.04 ml g-1 min-1 in gray and white matter, respectively. Analysis of variance of the regression gave different F values for the regressions with rCBF of FBU (F = 19, n = 126), NBU (F = 289, n = 112), and Ki (F = 117, n = 126).(ABSTRACT TRUNCATED AT 250 WORDS)