Interactive three-dimensional region of interest analysis of HMPAO SPECT brain studies.

An interactive computer program has been developed to align a three-dimensional region of interest (ROI) model to technetium-99m-hexamethylpropylenamine oxime (99mTc-HMPAO) single-photon emission computed tomography (SPECT) studies of the brain. The ROI model subdivides the human brain into fourteen discrete regions. A study was performed to determine normal ranges for HMPAO uptake in the ROIs defined by the model, and to assess the relative interobserver variability using the fitting program. HMPAO SPECT studies of twelve normal volunteers were independently analyzed by four observers. Small but significant differences between operators occurred primarily because of difficulty in defining the angle of the orbitomeatal plane on sagittal SPECT images. Despite this difficulty, the program and model have proven useful in defining ranges for normal cerebral perfusion in a healthy adult population. A study of a small group of patients with Alzheimer's dementia suggests that this procedure may be of use in the diagnosis of this disease.