We reconstructed three-dimensional (3D) surface images from single photon emission computed tomography (SPECT) data with N-isopropyl-p [123I]-iodo-amphetamine (123I-IMP) in 27 patients with Parkinson's disease, 16 patients with Alzheimer's disease, 9 patients with Binswanger's disease, and 11 elderly normal subjects. Three-D reconstruction was performed with Starcam 3000 XC/T using distance-shaded method at the threshold levels at intervals of 5% from 45% to 80%. In normal control subjects, no perfusion defects were found in any region at threshold values below 60%, although the frontal and temporal cortices occasionally showed perfusion defects at threshold levels from 60% to 80%. In patients with Parkinson's disease with dementia, perfusion defects were diffuse, particularly in the parietal and temporal cortices even at a threshold of 45%. Patients with Alzheimer's disease also showed diffuse perfusion defects, particularly in parietal and temporal cortices even at threshold levels as low as 45%. The primary visual cortex was less affected in these patients. The demented Parkinson's disease patients demonstrated perfusion defects similar to those of patients with Alzheimer's disease, although perfusion defects were more prominent in patients with Alzheimer's disease. In patients with Binswanger's disease, patchy perfusion defects were found most frequently in the frontal region. In addition, perfusion defects in the cerebellum and sensory motor cortex were more frequent in the Binswanger's disease patients than in patients with Alzheimer's or Parkinson's disease and normal subjects. The demented Parkinson's disease patients showed perfusion defects in the temporal and parietal cortices and demonstrated a perfusion pattern similar to that of patients with Alzheimer's disease.(ABSTRACT TRUNCATED AT 250 WORDS)