Human brain MR spectroscopy thermometry using metabolite aqueous-solution calibrations

Abstract

Purpose: To estimate absolute brain temperature using proton MR spectroscopy ( 1 H-MRS) and mean brain-body temperature difference of healthy human volunteers. Materials and Methods: Chemical shift difference between temperature-dependent water spectral line position and temperature-stable metabolite spectral reference was used for the estimations of absolute brain temperature. Temperature calibrations constants were obtained from the spectra of the N-acetyl aspartate (NAA line at ∼2.0 ppm), glycero-phosphocholine (GPC line at ∼3.2 ppm), and creatine (Cr line at ∼3.0 ppm) aqueous solutions with pH values within physiologically pertinent ranges. Single-voxel PRESS sequence (TR/TE 2000/80 ms) was used for this purpose. Brain temperature was determined by averaging the temperatures computed from water-Cho, water-Cr, and water-NAA chemical shift differences. Results: The mean brain temperature of 18 healthy volunteers was 38.1 ± 0.4°C and mean brain-body (rectal) temperature difference was 1.3 ± 0.4°C. Conclusion: Improved accuracy of the temperature constants and averaging the temperatures computed from water-Cho, water-Cr, and water-NAA chemical shift differences increased the reliability of the brain temperature estimations. © 2010 Wiley-Liss, Inc.