QUANTITATIVE IN-VIVO P-31 MAGNETIC-RESONANCE SPECTROSCOPY OF ALZHEIMER-DISEASE

The purpose of this study was to determine whether, in Alzheimer disea se (AD) patients, abnormalities in energy charge or phospholipid metab olism could be detected during life with quantitative phosphorus magne tic resonance spectroscopy (P-31 MRS). We performed in vivo P-31 MRS i n 16 patients with a clinical diagnosis of probable AD with mild to mo derate dementia severity (mean Blessed Dementia Score = 17.5, range = 7-37) and in 8 healthy, nondemented, age-matched, control subjects. MR studies were performed on a commercial 1.5 T MR imager using a volume head coil. We acquired brain spectra by sampling a 6-cm-thick axial s lice through the cerebrum (a region that includes similar to 900 ml of brain tissue); we measured beta-nucleoside triphosphate (beta-NTP), p hosphocreatine (PCr), phosphomonoesters (PME), phosphodiesters (PDE), and inorganic phosphate (P-i) concentrations, then calculated ratios o f these resonances. The beta-NTP, PCr, and P-i resonances in AD and co ntrol subjects were not significantly different. These data indicate t hat brain energy stores are not depleted in AD. No significant differe nces were detected in the absolute measurements of PME and PDE between the AD and control groups. However, among the calculated ratios, an i ncrease in the PME/PDE ratio of similar to 50%, mostly due to a decrea se in the PDE signal, was statistically significant (AD PME/PDE mean = 0.35, range 0.13-0.71; normal PME/PDE mean = 0.22, range 0.16-0.34). We speculate that the difference in PDE reflects changes in the biophy sical state of membrane phospholipids in AD.