Reproducibility of liver iron concentration estimates in MRI through R2* measurement determined by least-squares curve fitting.
Reproducibility of liver iron concentration estimates in MRI through R2* measurement determined by least-squares curve fitting.
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DOI：
10.1002/acm2.13096
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发表时间：
2020-12
影响因子：
2.1
通讯作者：
Pickens DR
中科院分区：
文献类型：
--
作者：
Headley AM;Grice JV;Pickens DR
通过MRI测量横向弛豫率（R2* = 1/T2*）可以无创评估多个临床参数，包括肝脏铁浓度（LIC）和脂肪分数。脂肪和铁都有助于弥漫性肝病时，储存在肝脏中过量。这种肝损伤会导致纤维化和肝硬化，增加患肝细胞癌的风险。肝脏铁浓度与使用MRI的R2* 测量值线性相关。构建体模以评估1.5 T和3 T MRI系统上的R2* 量化变异性。使用最小二乘曲线拟合技术进行量化。体模使用现成的低成本材料制成。它包含四个小瓶，R2* 值涵盖临床相关范围（1.5 T下100 - 420 Hz）。使用玻璃小瓶中的氯化铁溶液获得铁含量，每个玻璃小瓶固定在三维（3D）打印的聚乳酸（PLA）结构中，周围是蒸馏水，所有溶液都装在密封的丙烯酸圆柱体中。还使用PLA 3D打印了多个体模支架，以使体模相对于静磁场方向精确定向。对不同体模角度、多个MRI系统和不同脉冲序列参数下的采集进行了评价。在1.5 T MRI系统上，在这些不同的采集条件下，在同一小瓶中进行的任何两个R2* 测量值之间的变异性对于四个小瓶中的每一个都<7%。对于3 T MRI系统，所有情况下的变异性均小于14%。当使用不变的脉冲序列参数时，1.5 T和3 T采集的变异性均<6%。体模可用于模拟使用MRI测量的一系列临床相关水平的R2* 弛豫率。在几种不同的图像采集条件下，这些测量结果相对于金标准方法（肝活检）具有重现性。
Measuring transverse relaxation rate (R2* = 1/T2*) via MRI allows for noninvasive evaluation of multiple clinical parameters, including liver iron concentration (LIC) and fat fraction. Both fat and iron contribute to diffuse liver disease when stored in excess in the liver. This liver damage leads to fibrosis and cirrhosis with an increased risk of developing hepatocellular carcinoma. Liver iron concentration is linearly related to R2* measurements using MRI. A phantom was constructed to assess R2* quantification variability on 1.5 and 3 T MRI systems. Quantification was executed using least‐squares curve fitting techniques. The phantom was created using readily available, low‐cost materials. It contains four vials with R2* values that cover a clinically relevant range (100 to 420 Hz at 1.5 T). Iron content was achieved using ferric chloride solutions contained in glass vials, each affixed in a three‐dimensional (3D)‐printed polylactide (PLA) structure, surrounded by distilled water, all housed in a sealed acrylic cylinder. Multiple phantom stands were also 3D‐printed using PLA for precise orientation of the phantom with respect to the direction of the static magnetic field. Acquisitions at different phantom angles, across multiple MRI systems, and with different pulse sequence parameters were evaluated. The variability between any two R2* measurements, taken in the same vial under these various acquisition conditions, on a 1.5 T MRI system, was <7% for each of the four vials. For 3 T MRI systems, variability was less than 14% in all cases. Variability was <6% for both 1.5 and 3 T acquisitions when unchanged pulse sequence parameters were used. The phantom can be used to mimic a range of clinically relevant levels of R2* relaxation rates, as measured using MRI. These measurements were found to be reproducible relative to the gold‐standard method, liver biopsy, across several different image acquisition conditions.
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