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

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 microL in seven minutes and "high-resolution" scans in 30 minutes with a voxel size of 570 microL 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 microL; 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.