The University of Oxford Centre for Clinical Magnetic Resonance Research (OCMR), University of Oxford, John Radcliffe Hospital, Oxford, UK.
Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), University of Oxford, Churchill Hospital, Oxford, UK.
NMR Biomed. 2019 Feb;32(2):e4030. doi: 10.1002/nbm.4030. Epub 2018 Nov 21.
Modified Look-Locker inversion recovery (MOLLI) T mapping sequences can be useful in cardiac and liver tissue characterization, but determining underlying water T is confounded by iron, fat and frequency offsets. This article proposes an algorithm that provides an independent water MOLLI T (referred to as on-resonance water T ) that would have been measured if a subject had no fat and normal iron, and imaging had been done on resonance. Fifteen NiCl -doped agar phantoms with different peanut oil concentrations and 30 adults with various liver diseases, nineteen (63.3%) with liver steatosis, were scanned at 3 T using the shortened MOLLI (shMOLLI) T mapping, multiple-echo spoiled gradient-recalled echo and H MR spectroscopy sequences. An algorithm based on Bloch equations was built in MATLAB, and water shMOLLI T values of both phantoms and human participants were determined. The quality of the algorithm's result was assessed by Pearson's correlation coefficient between shMOLLI T values and spectroscopically determined T values of the water, and by linear regression analysis. Correlation between shMOLLI and spectroscopy-based T values increased, from r = 0.910 (P < 0.001) to r = 0.998 (P < 0.001) in phantoms and from r = 0.493 (for iron-only correction; P = 0.005) to r = 0.771 (for iron, fat and off-resonance correction; P < 0.001) in patients. Linear regression analysis revealed that the determined water shMOLLI T values in patients were independent of fat and iron. It can be concluded that determination of on-resonance water (sh)MOLLI T independent of fat, iron and macroscopic field inhomogeneities was possible in phantoms and human subjects.
修正的 Look-Locker 反转恢复（MOLLI）T 映射序列可用于心脏和肝脏组织特征描述，但由于铁、脂肪和频率偏移，确定基础水 T 会受到干扰。本文提出了一种算法，该算法提供了一个独立的水 MOLLI T（称为共振下水 T），如果受试者没有脂肪且铁含量正常，并且在共振下进行成像，那么就可以测量到这个 T 值。使用缩短的 MOLLI（shMOLLI）T 映射、多回波扰相梯度回波和 H 磁共振波谱序列，在 3 T 对 15 个含有不同浓度花生油的 NiCl 掺杂琼脂体模和 30 名患有各种肝脏疾病的成年人进行扫描，其中 19 名（63.3%）患有肝脂肪变性。基于 Bloch 方程的算法是在 MATLAB 中构建的，并确定了体模和人体参与者的水 shMOLLI T 值。通过 Pearson 相关系数评估算法结果的质量，该系数表示 shMOLLI T 值与水的光谱确定 T 值之间的相关性，还通过线性回归分析进行评估。在体模中，shMOLLI 与基于光谱的 T 值之间的相关性增加，从 r = 0.910（P < 0.001）增加到 r = 0.998（P < 0.001），在患者中，从 r = 0.493（仅进行铁校正；P = 0.005）增加到 r = 0.771（进行铁、脂肪和失谐校正；P < 0.001）。线性回归分析表明，患者确定的水 shMOLLI T 值与脂肪和铁无关。可以得出结论，在体模和人体受试者中，有可能确定独立于脂肪、铁和宏观磁场不均匀性的共振下水（sh）MOLLI T。
