ANALYSIS OF MAGNETIC-RESONANCE SPECTRA BY MOLE PERCENT - COMPARISON TO ABSOLUTE UNITS

A variety of metabolites present in perchloric acid extracts of brain tissue were measured by (1)h and P-31 magnetic resonance spectroscopy (MRS) and HPLC in the same tissue sample and the MRS results were expressed both in terms of mole % and mu more/g based on an internal standard. The levels of 16 metabolites were compared by linear regression analysis and the mole % results were found to correlate very well with the results expressed as mu mole/g. To compare the two units under typical experimental conditions, the percent change in metabolites in a group of Alzheimer's disease brains was compared to a control group using both units. The results were essentially identical for the mole % and mu mole/g methods. We conclude that the use of the more % method of expressing MRS data yields results which are equivalent to those expressed in absolute units and suggest that, for in vivo MRS studies, use of the mole % method is preferable because fewer artifacts, such as partial Volume effects, are introduced.