SPECT image analysis using statistical parametric mapping: comparison of technetium-99m-HMPAO and technetium-99m-ECD.

UNLABELLED: The goal of this study was to examine the apparent differences in regional cerebral blood flow (rCBF) between two groups of normal individuals who received either of the two tracers, 99mTc-D,L-hexamethylpropylene amine oxide (99mTc-HMPAO, or exametazime) or 99mTc-ethylene-dicysteine diethylester (99mTc-ECD, or bicisate).

METHODS: Individuals were screened for drug use, head injury, medication status and other psychiatric and medical illnesses. The two groups were matched for age, sex and race. SPECT measurement of brain perfusion was performed in 35 individuals who received 99mTc-HMPAO and in 55 who received 99mTc-ECD. Subsequent analysis of these scans was done using computer software including Statistical Parametric Mapping and Analyze. Images were intensity-thresholded and spatially normalized to a standardized stereotactic (Talairach) space. This allowed for the objective, quantitative analysis of these data, demonstrating the extent and magnitude of rCBF changes.

RESULTS: Our results showed significant changes between these two groups of normal individuals, presumably due to differences in pharmacokinetics between the two radiolabeled tracers. Specifically, large areas of the parietal, occipital and superior temporal cortices were significantly lower in the 99mTc-HMPAO group than in the 99mTc-ECD group. Increases were seen in the subcortical nuclei, parts of the brain stem, hippocampus and small areas of the cerebellum in the 99mTc-HMPAO group as compared to the 99mTc-ECD group.

CONCLUSION: We present a method of image analysis to semiquantitatively measure rCBF in SPECT images and the changes seen due to differences between the two radiotracers.