Basal and activational Tc-99(m)-HMPAO brain SPECT in Alzheimer's disease

Early diagnosis in Alzheimer's disease (AD) is important for the administra tion of new treatments. The purpose of this study was to differentiate mild ly/moderately demented AD patients from normal controls by means of activat ional brain SPECT, and to investigate the correlation between regional cere bral blood flow and dementia severity. Activational brain SPECT was perform ed 1 week after basal brain SPECT in 12 mild/moderate AD patients according to NINCDS-ADRDA criteria (mean age 69 +/- 7 years) and in seven healthy, a ge-matched, volunteer controls (mean age 65+/-9 years). Ln order to activat e the parietal cortex, patients were asked to subtract serial 5's from 100, 2 min before and after the intravenous administration of 925 MBq technetiu m-99m labelled D,L-hexamethyl-propylene amine oxime (Tc-99(m)-HMPAO). Using a three-headed gamma camera equipped with high resolution collimators, 128 images of 35 s duration in a 64 x 64 matrix were obtained over 360 degrees . Region to whole brain ratios (R/WB) were calculated in three consecutive transaxial slices 2 pixels thick above the orbitomeatal line, and the activ ation percentage was calculated. No statistical difference was detected bet ween AD patients and normal controls for parietal cortex activation. The co rrelation coefficient between the Mini-Mental State Examination (MMSE) scor ing and the activation percentage was 0.475 in normal controls and 0.175 in AD patients for the left anterior parietal cortex, and 0.353 in normal con trols and 0.146 in AD patients for the right anterior parietal cortex. In a visual evaluation of parietal cortex activation, 50% of AD patients were a ble to activate the parietal cortex, whereas 86% of the normal controls cou ld do so. Ln our current study, the subtraction of serial 5's was not regar ded as a promising task. Further studies are needed to clarify the importan ce of such tasks in the differential diagnosis of mild/moderate AD patients from normal elderly. ((C) 2000 Lippincott Williams & Wilkins).