A new method for the relative quantification of rCBF examined by 99Tcm-HMPAO SPECT

A new method for the analysis of regional cerebral blood flow (rCBF) studies, the 'Min-Max' method, was compared with the conventional method, the 'Average' method. Regional CBF was examined by single photon emission computed tomography (SPECT) using 99Tcm-hexamethylpropyleneamine oxime (99Tcm-HMPAO). The two methods were used to quantify the rCBF in a population of patients with various dementia disorders, and in healthy controls. Results from a phantom were also used. In the Average method the average counts per pixel (cp-1) within irregular manually drawn regions of interest (ROIs) was registered. In the Min-Max method the minimum cp-1 and maximum cp-1 within rectangular ROIs were registered for white and grey matter, respectively. The relative rCBF (rrCBF) was calculated as the ratio between the regional and cerebellar values. The Min-Max method gave systematically lower values for rrCBF in the white matter, in both clinical studies, and in the phantom, compared to the Average method. No difference was found in the grey matter results. The variability in rrCBF in the phantom study was greater with the Min-Max method than with the Average method, but this effect was counteracted in the clinical studies by a smaller interobserver error. The average regional differences between patients and controls appeared greater with the Min-Max method than with the Average method. The Min-Max method proved to be more simple to execute, involved a smaller observer error, and with respect to ability to distinguish patients with dementia disorders from controls, it appears to function at least as well as the accepted Average method.