定量磁化率映射（QSM）可最大限度地减少细胞病理学对肝脏铁浓度 R2* 估计的干扰。
Quantitative susceptibility mapping (QSM) minimizes interference from cellular pathology in R2* estimation of liver iron concentration.
机构信息
Shanghai Key Laboratory of Magnetic Resonance and Department of Physics, East China Normal University, Shanghai, China.
Department of Radiology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
出版信息
J Magn Reson Imaging. 2018 Oct;48(4):1069-1079. doi: 10.1002/jmri.26019. Epub 2018 Mar 22.
BACKGROUND
A challenge for R2 and R2* methods in measuring liver iron concentration (LIC) is that fibrosis, fat, and other hepatic cellular pathology contribute to R2 and R2* and interfere with LIC estimation.
PURPOSE
To examine the interfering effects of fibrosis, fat, and other lesions on R2* LIC estimation and to use quantitative susceptibility mapping (QSM) to reduce these distortions.
STUDY TYPE
Prospective.
PHANTOMS, SUBJECTS: Water phantoms with various concentrations of gadolinium (Gd), collagen (Cl, modeling fibrosis), and fat; nine healthy controls with no known hepatic disease, nine patients with known or suspected hepatic iron overload, and nine patients with focal liver lesions.
FIELD STRENGTH/SEQUENCE: The phantoms and human subjects were imaged using a 3D multiecho gradient-echo on clinical 1.5T and 3T MRI systems.
ASSESSMENT
QSM and R2* images were postprocessed from the same gradient-echo data. Fat contributions to susceptibility and R2* were corrected in signal models for LIC estimation.
STATISTICAL TESTS
Polynomial regression analyses were performed to examine relations among susceptibility, R2* and true [Gd] and [Cl] in phantoms, and among susceptibility and R2* in patient livers.
RESULTS
In phantoms, R2* had a strong nonlinear dependency on [Cl], [fat], and [Gd], while susceptibility was linearly dependent (R > 0.98). In patients, R2* was highly sensitive to liver pathological changes, including fat, fibrosis, and tumors, while QSM was relatively insensitive to these abnormalities (P = 0.015). With moderate iron overload, liver susceptibility and R2* were not linearly correlated over a common R2* range [0, 100] sec (P = 0.35).
DATA CONCLUSION
R2* estimation of LIC is prone to substantial nonlinear interference from fat, fibrosis, and other lesions. QSM processing of the same gradient echo MRI data can effectively minimize the effects of cellular pathology.
LEVEL OF EVIDENCE
1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;48:1069-1079.
背景
R2 和 R2* 方法在测量肝脏铁浓度（LIC）时面临一个挑战，即纤维化、脂肪和其他肝内细胞病变会对 R2 和 R2*产生影响，并干扰 LIC 的估计。
目的
研究纤维化、脂肪和其他病变对 R2*LIC 估计的干扰作用，并利用定量磁化率映射（QSM）来减少这些扭曲。
研究类型
前瞻性。
体模和受试者
具有不同浓度钆（Gd）、胶原蛋白（Cl，模拟纤维化）和脂肪的水模体；9 名无已知肝病史的健康对照者，9 名已知或疑似肝铁过载患者，以及 9 名患有局灶性肝病变的患者。
磁场强度/序列：使用 3D 多回波梯度回波在临床 1.5T 和 3T MRI 系统上对体模和人体进行成像。
评估
从相同的梯度回波数据中对 QSM 和 R2图像进行后处理。在用于 LIC 估计的信号模型中，校正了脂肪对磁化率和 R2的贡献。
统计学检验
进行多项式回归分析，以研究体模中磁化率、R2与真实[Gd]和[Cl]之间的关系，以及患者肝脏中磁化率和 R2之间的关系。
结果
在体模中，R2与[Cl]、[脂肪]和[Gd]呈强非线性关系，而磁化率呈线性关系（R>0.98）。在患者中，R2对包括脂肪、纤维化和肿瘤在内的肝脏病理变化高度敏感，而 QSM 对这些异常相对不敏感（P=0.015）。在中度铁过载时，在常见的 R2范围[0，100] sec 内，肝脏磁化率和 R2之间没有线性相关性（P=0.35）。
数据结论
LIC 的 R2*估计容易受到脂肪、纤维化和其他病变的严重非线性干扰。对相同梯度回波 MRI 数据进行 QSM 处理可以有效地最小化细胞病理学的影响。
证据水平
1 技术功效：第 1 阶段 J. Magn. Reson. Imaging 2018;48:1069-1079.
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