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

Abstract

Objective: To demonstrate the capability of a clinical 3T 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 (T1) and transverse relaxation time (T2) measurements were set up at a spatial resolution of 0.3×0.3×1mm(3). Diffusion-weighted imaging was also applied and the evaluation included both mono- and biexponential approaches (b-value up to 6000s/mm(2)). Besides quantitative imaging, the rat brain was also scanned at a microscopic resolution of 130×130×130μm(3). Quantitative proton spectroscopy was also carried out on the rat brain with water as internal reference.

Results: T1 and T2 for the rat brain cortex were 1272±85ms and 75±2ms, 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.

Keywords: Brain; Clinical scanner; MRI; Rat; Spectroscopy.