To monitor progression of cerebral blood flow deterioration, this study used consecutive surface SPECT to evaluate the feasibility of brain surface displays (BSD) to follow Alzheimer’s disease (AD) to determine whether overtime is a consistent feature of the disease.Methods
Eighteen men (mean age, 75.7 years) with probable Alzheimer’s disease (AD), with moderate to profound dementia indicated by the Mini-Mental State Examination (MMSE; median score, 10; range, 0 to 19), underwent brain Tc-99m ethyl cysteinate dimer SPECT. Brain SPECTs were obtained using a three-head gamma camera. Brain surface displays (BSD) were reconstructed from transaxial data using a threshold of 55% of the maximum pixel count. A second series of SPECTs were obtained after 5 to 23 months (except for one, which was done after 60 months). Each BSD was graded semiquantitatively, by visual interpretation, from zero to 8 (normal = 0, mild = 2, moderate = 4, severe = 6, and profound = 8) depending on the extent of the perfusion defects in the frontal, temporal, or parietal (or all of these) pattern of AD. MMSE scores were used to calculate “time index” values for estimating severity at the time of the SPECTs.Results
The initial BSD scores correlated significantly with dementia severity (r = 0.71, P < 0.001). All 18 patients had decreased blood flow on consecutive SPECTs. Scores for BSD progressed at a rate of 2.5 ± 1.7 points per year and correlated significantly with the time interval between the scans (r = 0.71;P < 0.001).Conclusions
The BSDs of SPECT scan data have considerable objective discriminatory power for assessing the severity and progression of AD-related hypoperfusion, particularly in the moderate to profound dementia ranges, and is potentially more reliable than the MMSE. Consecutive BSDs simplify SPECT image interpretation for measuring loss of brain function over time and could be useful for assessing the efficacy of therapeutic interventions for AD patients such as vitamin E and cholinesterase inhibitors.