Elena Vescovo1, Andrew Levick2, Sha Zhao1, Graham Machin2, Charmaine Childs3, Timothy Rainey3, Steve Williams1
1Imaging Science and Biomedical Engineering, The University of Manchester, Manchester, Greater Manchester, United Kingdom; 2Temperature Group, National Physical Laboratory, Teddington, Middlesex, United Kingdom; 3Brain Injury Research Group, The University of Manchester, Manchester, Greater Manchester, United Kingdom
Estimation of temperature by MRS from the chemical shift of water relative to N-acetylaspartate (NAA) relies on a calibration curve. To date these have never been related back to primary standards. We describe extremely stable temperature control of an MRS phantom at 1.5T using a circulating water bath and organic fixed-point materials, with measurements related back to the International Temperature Scale 1990 (ITS-90) at the UK National Physical Laboratory. Frequency differences (water-NAA) were highly reproducible (SD<10-4 ppm) at fixed temperature and R2 for the fit was 0.9996. Ionic strength affected the intercept but not slope of the temperature calibration.