OBJECTIVES: The purpose of this study was to investigate the pattern of longitudinal changes in cerebral blood perfusion defects using SPECT in patients with dementia of Alzheimer's type . METHOD: Twelve patients with dementia of Alzheimer's type(10 male, 2 female; mean age 73.25+/- 10.62 years), diagnosed by the criteria of the DSM IV and the NINCDS-ADRDA, and ten normal comparison subjects(7 male, 3 female; mean age 75.10+/-5.76 years) were recruited. They were rated by Mini-Mental Status Examination, Mattis dementia Rating Scale, and Hamilton Depression Rating Scale. rCBF(regional cerebral blood flow) was measured using 99mTc-HMPAO SPECT at the initial study in all subjects, but rCBF was remeasured only in the patients after the follow-up period of average 2 years. SPECT scans of dementia patients and comparison subjects were analyzed by three- dimensional volume of interest method. RESULTS: Results were as follows. 1) There were significant perfusion defects in the bilateral frontal and temporoparietal areas in patients with dementia compared with normal comparison subjects at the baseline evaluation. More extensive perfusion defects including left superior frontal and medial temporal areas were observed in the follow-up SPECT scan compared with baseline scan. 2) There was significant negative correlation between rCBF of bilateral temporal lobe at the baseline scan and the rate of decline of scores of MMSE-K and Mattis dementia rating scale. 3) Various areas of the brain showed correlations between rCBF at the baseline scan and the rate of decline of scores of five subscales of Mattis dementia rating scale. CONCLUSIONS: Three-dimensional VOI approach using SPM analysis showed the characteristic perfusion defects and pattern of longitudinal changes in the patients of dementia of Alzheimer's type, which may be overlooked by the conventional region-of-interest technique. This alteration in rCBF may be closely related to the pathophysiological process of dementia of Alzheimer's type.