Improved cardiac sodium MR imaging by density-weighted phase-encoding

Abstract

Purpose: To show that density-weighted (DW) k-space sampling improves the quality of human cardiac sodium imaging, a novel method was implemented that combines the high signal-to-noise efficiency of three-dimensional phase-encoding with the advantageous localization performance of nonuniform sampling. A simulation demonstrates substantially reduced blood contamination in the myocardium. Materials and Methods: At 2.0 T, DW cardiac "fast" sodium images with a voxel size of 844 μL in seven minutes and "high- resolution" scans in 30 minutes with a voxel size of 570 μL were acquired. For comparison, conventional gradient-echo imaging was also performed. Results: In the DW images, a myocardial signal-to-noise ratio (SNR) of 16.0 in the left ventricle and 8.5 in the septum (N = 4) was measured. With longer experimental duration (about 30 minutes; N = 3), the image quality and the SNR could be further improved (voxel size: 570 μL; SNR: blood 16.1, septum 10.6). Compared to the gradient-echo images, the image quality was substantially improved. Conclusion: This new method for human cardiac sodium imaging provides high image quality combined with optimal sensitivity and thus may improve the clinical applicability of 23Na cardiac MRI.