de Heer Paul, Bizino Maurice B, Lamb Hildo J, Webb Andrew G
C.J. Gorter Center for High Field MR, Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands.
Department of Radiology, Leiden University, Medical Center, Leiden, the Netherlands.
J Magn Reson Imaging. 2016 Nov;44(5):1151-1158. doi: 10.1002/jmri.25254. Epub 2016 Mar 26.
To optimize data acquisition parameters in cardiac proton MR spectroscopy, and to evaluate the intra- and intersession variability in myocardial triglyceride content.
Data acquisition parameters at 3 Tesla (T) were optimized and reproducibility measured using, in total, 49 healthy subjects. The signal-to-noise-ratio (SNR) and the variance in metabolite amplitude between averages were measured for: (i) global versus local power optimization; (ii) static magnetic field (B ) shimming performed during free-breathing or within breathholds; (iii) post R-wave peak measurement times between 50 and 900 ms; (iv) without respiratory compensation, with breathholds and with navigator triggering; and (v) frequency selective excitation, Chemical Shift Selective (CHESS) and Multiply Optimized Insensitive Suppression Train (MOIST) water suppression techniques. Using the optimized parameters intra- and intersession myocardial triglyceride content reproducibility was measured. Two cardiac proton spectra were acquired with the same parameters and compared (intrasession reproducibility) after which the subject was removed from the scanner and placed back in the scanner and a third spectrum was acquired which was compared with the first measurement (intersession reproducibility).
Local power optimization increased SNR on average by 22% compared with global power optimization (P = 0.0002). The average linewidth was not significantly different for pencil beam B shimming using free-breathing or breathholds (19.1 Hz versus 17.5 Hz; P = 0.15). The highest signal stability occurred at a cardiac trigger delay around 240 ms. The mean amplitude variation was significantly lower for breathholds versus free-breathing (P = 0.03) and for navigator triggering versus free-breathing (P = 0.03) as well as for navigator triggering versus breathhold (P = 0.02). The mean residual water signal using CHESS (1.1%, P = 0.01) or MOIST (0.7%, P = 0.01) water suppression was significantly lower than using frequency selective excitation water suppression (7.0%). Using the optimized parameters an intrasession limits of agreement of the myocardial triglyceride content of -0.11% to +0.04%, and an intersession of -0.15% to +0.9%, were achieved. The coefficient of variation was 5% for the intrasession reproducibility and 6.5% for the intersession reproducibility.
Using approaches designed to optimize SNR and minimize the variation in inter-average signal intensities and frequencies/phases, a protocol was developed to perform cardiac MR spectroscopy on a clinical 3T system with high reproducibility. J. Magn. Reson. Imaging 2016;44:1151-1158.
优化心脏质子磁共振波谱的数据采集参数，并评估心肌甘油三酯含量的 session 内和 session 间变异性。
在3特斯拉（T）下优化数据采集参数，并使用总共49名健康受试者测量其可重复性。针对以下情况测量信噪比（SNR）和平均值之间代谢物幅度的方差：（i）全局与局部功率优化；（ii）在自由呼吸或屏气期间进行的静磁场（B）匀场；（iii）R波峰值后50至900毫秒的测量时间；（iv）不进行呼吸补偿、屏气和导航触发；（v）频率选择性激发、化学位移选择性（CHESS）和多重优化不敏感抑制序列（MOIST）水抑制技术。使用优化参数测量 session 内和 session 间心肌甘油三酯含量的可重复性。以相同参数采集两个心脏质子波谱并进行比较（session 内可重复性），之后将受试者从扫描仪中移出并重新放置回扫描仪中，采集第三个波谱并与第一次测量进行比较（session 间可重复性）。
与全局功率优化相比，局部功率优化平均使 SNR 提高了22%（P = 0.0002）。使用自由呼吸或屏气进行铅笔束B匀场时，平均线宽无显著差异（19.1赫兹对17.5赫兹；P = 0.15）。在心脏触发延迟约240毫秒时出现最高信号稳定性。屏气时的平均幅度变化显著低于自由呼吸（P = 0.03），导航触发时的平均幅度变化显著低于自由呼吸（P = 0.03），以及导航触发时的平均幅度变化显著低于屏气（P = 0.02）。使用CHESS（1.1%，P = 0.01）或MOIST（0.7%，P = 0.01）水抑制时的平均残留水信号显著低于使用频率选择性激发水抑制时（7.0%）。使用优化参数，心肌甘油三酯含量的 session 内一致性界限为-0.11%至+0.04%，session 间为-0.15%至+0.9%。session 内可重复性的变异系数为5%，session 间可重复性的变异系数为6.5%。
使用旨在优化SNR并最小化平均间信号强度和频率/相位变化的方法，开发了一种在临床3T系统上以高可重复性进行心脏磁共振波谱检查的方案。《磁共振成像杂志》2016年；44：1151 - 1158。
