Quantitative ²³Na MRI of human knee cartilage using dual-tuned ¹H/²³Na transceiver array radiofrequency coil at 7 tesla

Abstract

Purpose To develop quantitative dual-tuned (DT) 1H/ 23Na MRI of human knee cartilage in vivo at 7 Tesla (T). Materials and Methods A sensitive 23Na transceiver array RF coil was developed at 7T. B1 fields generated by the transceiver array coil were characterized and corrected in the 23Na images. Point spread function (PSF) of the 23Na images was measured, and the signal decrease due to partial-volume-effect was compensated in [23Na] quantification of knee cartilage. SNR and [23Na] in anterior femoral cartilage were measured from seven healthy subjects. Results SNR of 23Na image with the transceiver array coil was higher than that of birdcage coil. SNR in the cartilage at 2-mm isotropic resolution was 26.80 ± 3.69 (n = 7). B 1 transmission and reception fields produced by the DT coil at 7T were similar to each other. Effective full-width-half-maximum of 23Na image was ∼5 mm at 2-mm resolution. Mean [23Na] was 288.13 ± 29.50 mM (n = 7) in the anterior femoral cartilage of normal subjects. Conclusion We developed a new high-sensitivity 23Na RF coil for knee MRI at 7T. Our 1H/23Na MRI allowed quantitative measurement of [23Na] in knee cartilage by measuring PSF and cartilage thickness from 23Na and 1H image, respectively. J. Magn. Reson. Imaging 2013;38:1063-1072. © 2013 Wiley Periodicals, Inc. Copyright © 2013 Wiley Periodicals, Inc.