Quantitative proton MRI and MRS of the rat brain with a 3 T clinical MR scanner

Summary Objective To demonstrate the capability of a clinical 3 T human scanner in performing quantitative MR experiments in the rat brain. Material and methods In vivo, measurements on eight Wistar rats were performed. Longitudinal relaxation time ( T 1 ) and transverse relaxation time ( T 2 ) measurements were set up at a spatial resolution of 0.3 × 0.3 × 1 mm3 . Diffusion-weighted imaging was also applied and the evaluation included both mono- and biexponential approaches ( b-value up to 6000 s/mm2 ). Besides quantitative imaging, the rat brain was also scanned at a microscopic resolution of 130 × 130 × 130 μm3 . Quantitative proton spectroscopy was also carried out on the rat brain with water as internal reference. Results T 1 and T 2 for the rat brain cortex were 1272 ± 85 ms and 75 ± 2 ms, respectively. Diffusion-weighted imaging yielded accurate diffusion coefficient measurements at both low and high b -value ranges. The concentrations of MR visible metabolites were determined for the major resonances (i.e., N-acetyl-aspartate, choline and creatine) with acceptable accuracy. Conclusion The results suggest that quantitative imaging and spectroscopy can be carried out on small animals on high-field clinical scanners.