在3T场强下使用改良型Look-Locker反转恢复（MOLLI）方法时脂肪对肝脏T1测量的影响
Influence of fat on liver T1 measurements using modified Look-Locker inversion recovery (MOLLI) methods at 3T.
作者信息
Mozes Ferenc E, Tunnicliffe Elizabeth M, Pavlides Michael, Robson Matthew D
机构信息
University of Oxford Centre for Clinical Magnetic Resonance Research (OCMR), University of Oxford, John Radcliffe Hospital, Oxford, UK.
Translational Gastroenterology Unit, University of Oxford, John Radcliffe Hospital, Oxford, UK.
出版信息
J Magn Reson Imaging. 2016 Jul;44(1):105-11. doi: 10.1002/jmri.25146. Epub 2016 Jan 13.
PURPOSE
To characterize the effect of fat on modified Look-Locker inversion recovery (MOLLI) T1 maps of the liver. The balanced steady-state free precession (bSSFP) sequence causes water and fat signals to have opposite phase when repetition time (TR) = 2.3 msec at 3T. In voxels that contain both fat and water, the MOLLI T1 measurement is influenced by the choice of TR.
MATERIALS AND METHODS
MOLLI T1 measurements of the liver were simulated using the Bloch equations while varying the hepatic lipid content (HLC). Phantom scans were performed on margarine phantoms, using both MOLLI and spin echo inversion recovery sequences. MOLLI T1 at 3T and HLC were determined in patients (n = 8) before and after bariatric surgery.
RESULTS
At 3T, with HLC in the 0-35% range, higher fat fraction values lead to longer MOLLI T1 values when TR = 2.3 msec. Patients were found to have higher MOLLI T1 at elevated HLC (T1 = 929 ± 97 msec) than at low HLC (T1 = 870 ± 44 msec).
CONCLUSION
At 3T, MOLLI T1 values are affected by HLC, substantially changing MOLLI T1 in a clinically relevant range of fat content. J. Magn. Reson. Imaging 2016;44:105-111.
目的
描述脂肪对肝脏改良Look-Locker反转恢复（MOLLI）T1图谱的影响。在3T场强下，当重复时间（TR）=2.3毫秒时，平衡稳态自由进动（bSSFP）序列会使水和脂肪信号呈现相反的相位。在同时包含脂肪和水的体素中，MOLLI T1测量值会受到TR选择的影响。
材料与方法
利用布洛赫方程模拟肝脏的MOLLI T1测量，同时改变肝脏脂质含量（HLC）。使用MOLLI和自旋回波反转恢复序列对人造黄油模型进行体模扫描。在减肥手术前后对患者（n = 8）进行3T场强下的MOLLI T1和HLC测定。
结果
在3T场强下，当HLC在0 - 35%范围内，且TR = 2.3毫秒时，较高的脂肪分数值会导致MOLLI T1值更长。研究发现，患者在HLC升高时（T1 = 929 ± 97毫秒）的MOLLI T1值高于HLC较低时（T1 = 870 ± 44毫秒）。
结论
在3T场强下，MOLLI T1值受HLC影响，在临床相关的脂肪含量范围内会使MOLLI T1发生显著变化。《磁共振成像杂志》2016年；44:105 - 111。
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