Objective: Application of a quantitative MR-spectroscopic method for 3T clinical scanners based on tissue water content as an internal reference.
Patients and methods: Six (22 +/- 2 yrs) volunteers were involved in the study. We performed T1 relaxation time measurements in a particular slice of the brain at 1T and 3T. Based on the validated water content measurement at 1T, the correlation of relaxation time T1 and water content was determined at 3T. The resulting water content served as internal reference for the quantification of localizated MR-spectroscopic measurement.
Results: At 3T our method resulted in 37.6 +/- 0.5 mol/l and 46.4 +/- 1.5 mol/l tissue water content in the white and gray matter, respectively. Calibration based on water content led to following metabolite concentrations: N-acetyl-aspartate 7.79 +/- 0.67 mmol/l; creatine 3.76 +/- 0.28 mmol/l; choline 3.68 +/- 0.47 mmol/l; myo-inositol 10.35 +/- 3.70 mmol/l in the white matter; and N-acetyl-aspartate 8.20 +/- 0.45 mmol/l; creatine 4.76 +/- 0.18 mmol/l; choline 2.64 +/- 0.35 mmol/l; myo-inositol 8.32 +/- 1.42 mmol/l in the grey matter.
Conclusions: Tissue water content based on T value at 3T shows good accordance with gravimetric or other MR methods in the literature. Using it as an internal reference resulted in white matter metabolite concentrations that are in the range of previously published data. Comparing metabolite values of grey matter is more difficult because data in the literature substantially differ. The presented method is simple and easily applicable on any MR scanner without complicated correction and calibration steps.