Reliability of MRSI brain temperature mapping at 1.5 and 3 T.
Bottom Line: Temperature data were analysed using a linear mixed effects model to determine variance components and systematic temperature changes during the scanning sessions.Components of apparent in vivo temperature variability at 1.5 T/3 T caused by inter-subject (0.18/0.17 °C), inter-session (0.18/0.15 °C) and within-session (0.36/0.14 °C) effects, as well as voxel-to-voxel variation (0.59/0.54 °C), were determined.The mean brain temperature at 3 T was weakly associated with aural (R = 0.55, p = 0.002) and oral (R = 0.62, p < 0.001) measurements of head temperature.
Affiliation: Brain Research Imaging Centre, Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, UK.Show MeSH
Mentions: A spherical acrylic phantom (diameter, 18 cm) divided into two hemispheres, each containing a smaller sphere (diameter, 6 cm), was constructed (Fig. 2a). The two inner spheres were filled with an aqueous solution containing metabolites at approximate physiological concentrations [10.3 mm NAA, 1.7 mmN-acetylaspartylglutamate, 10 mm creatine hydrate, 3 mm choline chloride, 7.5 mm myo-inositol, 12.5 mm glutamate, 5 mm lactate, 0.1% w/v sodium azide and 0.1% v/v gadoteric acid (0.5 m; DOTAREM, Guerbet, France), buffered with 50 mm monobasic potassium phosphate and 56 mm sodium hydroxide]. Heated water baths were used to circulate water around the outside of the metabolite compartments, maintaining the temperature of the left and right hemispheres at 37.0 and 37.5 °C, respectively. The true metabolite temperatures were monitored using MR-compatible fluoroptic thermometer probes (Luxtron 812, LumaSense Technologies Inc., Santa Clara, CA, USA; 0.1 °C accuracy). Five MRSI temperature scans were obtained back-to-back on four occasions at both 1.5 and 3 T. Phantom data were acquired and processed as described above, with the volume of interest covering the two inner spheres (Fig. 2b); the central 3 × 3 voxels in each inner sphere were analysed. Drifts in apparent MR temperature relative to the gold standard fibre-optic temperature measurements were estimated using a linear mixed effects model.
Affiliation: Brain Research Imaging Centre, Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, UK.