Tc-99m HMPAO SPECT in the evaluation of Alzheimer's disease: correlation between neuropsychiatric evaluation and CBF images.

The purpose of this study was to evaluate the effects of various covariants on the distribution pattern of Tc-99m HMPAO in patients with Alzheimer's disease by correlation analysis. Twenty patients with Alzheimer's disease and 15 age matched normal subjects participated. Tc-99m HMPAO brain SPECT and x ray computed tomography (CT) were acquired for each subject. SPECT images were transformed to a standard size and shape by automated image registration (AIR) and were used for group comparison by means of SPM96. Voxel based covariance analysis was performed on standardised images taking the age of patients, severity of disease (clinical dementia rating scale, mini mental state examination, physical self maintenance scale), and atrophy indices as variables. There was significantly decreased regional cerebral blood flow (rCBF) in the frontal, parietal, and temporal regions in the patient group (p<0.001), more marked in those patients having severe dementia. Covariance analysis disclosed that aging and severity of disease have a pronounced effect on rCBF, especially that of the left parietal region.