Use of a standardized uptake value for parametric in vivo imaging of benzodiazepine receptor distribution on [11C]flumazenil brain PET.

To simplify the acquisition protocol of carbon-11 labeled flumazenil (FMZ) positron emission tomography (PET) for distribution volume (DV) images, we attempted to obtain standardized uptake value (SUV) images compatible with DV images, and assessed the applicability of this method in patients with unilateral cerebrovascular diseases (CVD). [(11)C]FMZ PET was performed in ten normal subjects. A DV image and ten sequential 5-min SUV images were generated for each subject. We investigated the correlation coefficient (r) and standard estimation of error (SEE) between the latter ten static images and the DV image using the pixel-by-pixel method, thereby determining the optimum acquisition phase. The same FMZ PET procedure was performed in 15 patients with unilateral CVD. Twenty regions of interest (ROIs) were positioned both in lesioned areas and in symmetrical regions. DV and SUV in the optimum phase for each ROI were calculated to compare the lesion-to-normal (L/N) ratio of DV and that of SUV. The highest r and a low SEE (r=0.957, SEE=633) were observed from 30 to 35 min after tracer administration in the study of normal subjects. A high r (0.945) and a low SEE (0.0438) between the DV L/N ratio and the SUV L/N ratio were obtained in the study of patients. Our study suggests that SUV images acquired from 30 to 35 min after FMZ administration are a suitable alternative to DV images not only in normal subjects but also in patients with unilateral CVD. This simple method seems to be valuable for the identification of altered neuronal activity in patients with CVD.