IS IMAGE SUBTRACTION NECESSARY IN THE CLINICAL INTERPRETATION OF SINGLE-DAY SPLIT-DOSE STRESS CEREBRAL PERFUSION SINGLE-PHOTON EMISSION TOMOGRAPHY USING TC-99M COMPOUNDS

The aim of this study was to validate a simplified semiquantitative me thod of evaluating a single-day stress cerebral perfusion test to obta in cerebrovascular reserve capacity (CVRC) for routine clinical uses, A split-dose protocol was tested in 36 pairs of technetium-99m hexamet hylpropylene amino oxime baseline (low dose) and acetazolamide (high d ose) stress brain single-photon emission tomographic (SPET) studies fr om 16 patients with cerebrovascular disease. The images were displayed on a semiquantitative color scale with (corrected) and without (uncor rected) image subtraction, dose adjustment, and decay correction. The representative CVRC was determined by placing 3x3 pixel regions of int erest on midthalamic and midcerebellar slices. The corrected and uncor rected relative changes in CVRC were correlated using linear regressio n. The relative changes of corrected (x) and uncorrected (y) CVRC by q uantitative analysis were highly correlated in a linear fashion (y=0.6 7x+0.002, r=0.998, P<0.0005). As predicted by theory, the slope was re lated to the ratio of split dose and independent of ROI sampling. Sing le-day split-dose stress brain SPET can be accurately performed withou t image subtraction and complicated dose adjustment or decay correctio n for clinical studies.