High-Resolution Quantitative Sodium Imaging at 9.4 Tesla

PurposeInvestigation of the feasibility to perform high-resolution quantitative sodium imaging at 9.4 Tesla (T). MethodsA proton patch antenna was combined with a sodium birdcage coil to provide a proton signal without compromising the efficiency of the X-nucleus coil. Sodium density weighted images with a nominal resolution of 1 x 1 x 5 mm(3) were acquired within 30 min with an ultrashort echo time sequence. The methods used for signal calibration as well as for B-0, B-1, and off-resonance correction were verified on a phantom and five healthy volunteers. ResultsAn actual voxel volume of roughly 40 L could be achieved at 9.4T, while maintaining an acceptable signal-to-noise ratio (8 for brain tissue and 35 for cerebrospinal fluid). The measured mean sodium concentrations for gray and white matter were 362 and 31 +/- 1 mmol/L of wet tissue, which are comparable to values previously reported in the literature. ConclusionThe reduction of partial volume effects is essential for accurate measurement of the sodium concentration in the human brain. Ultrahigh field imaging is a viable tool to achieve this goal due to its increased sensitivity. Magn Reson Med 73:342-351, 2015. (c) 2014 Wiley Periodicals, Inc.