The influence of cardiac triggering time and an optimization strategy for improved cardiac MR spectroscopy

Purpose: To study how cardiac motion affects the spectral quality in cardiac MR spectroscopy and to establish an optimization strategy for the cardiac triggering time for improved quality and success rate of cardiac MRS. Method: Water spectra were acquired while the cardiac triggering tune was varied over the cardiac cycle, and five different spectral quality parameters were studied (frequency, phase, linewidth, amplitude and noise). Furthermore, three different optimization strategies for the cardiac triggering time were tested, and finally, a comparison was made between water suppressed lipid spectra acquired in systole and diastole. Results: The cardiac triggering time had a high impact on the spectral quality, especially on the mean signal amplitude and the standard deviation of the signal amplitude, phase and linewidth. Generally, the highest spectral quality was observed for spectra acquired in mid to end systole, at approximately 23% of the cardiac cycle. The exact optimal triggering time differed between subjects and needed to be individually optimized. To optimize the triggering time with our proposed MRS-method gave in average 13% higher signal than when the triggering time was determined through imaging. Lipid spectra acquired in systole demonstrated higher quality with improved SNR compared with acquisitions made in diastole. Conclusion: This study shows that the spectral quality in cardiac MRS is strongly dependent on the cardiac triggering time, and that the spectral quality as well as the repeatability between acquisitions is greatly improved when the cardiac triggering time is individually optimized in mid to end systole using MRS.