Quantitative sodium MRI of the mouse prostate

A method was developed for quantitative sodium MRI of the mouse prostate at 9.4 T. A small loop‐gap radiofrequency coil was constructed and dual‐tuned to both the proton and sodium frequencies. The location and boundary of the mouse prostate were localized using high‐resolution T 2 ‐weighted proton images, and sodium images were acquired with 1mm isotropic resolution using a short echo time (0.6 ms) and a long pulse repetition time (300 ms) for sodium density weighting with minimal T 1 and T 2 contrast. Sodium concentration in the prostate was estimated by comparing pixel intensities within the prostate to the pixel intensities in a pair of reference vials with known sodium concentrations, and a radiofrequency field inhomogeneity correction was performed based on field maps of a homogeneous phantom. In a group of five healthy, 5‐month‐old BALB/c mice, the average sodium concentration within their prostates was measured to be 173 ± 38 mM. Muscle tissue and bladder were also clearly visible in the sodium images, and their sodium concentrations were estimated to be 40 ± 15 mM and 210 ± 72 mM, respectively. Magn Reson Med 63:822–827, 2010. © 2010 Wiley‐Liss, Inc.