Abstract：
BACKGROUND: We investigated the potential of magnetic resonance elastography (MRE) stiffness measurements in skeletal muscles as an outcome measure, by determining its test-retest reliability, as well as its sensitivity to change in a longitudinal follow-up study.
METHODS: We assessed test-retest reliability of muscle MRE in 20 subjects with (n = 5) and without (n = 15) muscle diseases and compared this to Dixon proton density fat fraction (PDFF) and volume measurements. Next, we measured MRE muscle stiffness in 21 adults with Becker muscular dystrophy (BMD) and 21 age-matched healthy controls at baseline, and after 9 and 18 months. We compared two different methods of analysing MRE data in this study: \'Method A\' used the stiffness maps generated by the Philips MRE software, and \'Method B\' applied a custom-made procedure based on wavelength measurements on the MRE images.
RESULTS: Intraclass correlation coefficients (ICC) of muscle stiffness ranged from good (0.83 for left vastus medialis, P < 0.001) to poor (0.19 for right rectus femoris, P = 0.212) for the examined thigh muscles with Method A, but we did not find a significant test-retest reliability with Method B (P > 0.050 for all). The ICC of muscle PDFF and volume measurements was excellent (>0.90; P < 0.001) for all muscles. At baseline, the average stiffness of all thigh muscles was significantly lower in adults with BMD than in controls for both Method A (-0.2 kPa, P = 0.025) and Method B (-0.6 kPa, P < 0.001). Regardless of which method was used, there was no significant difference in the evolution of muscle stiffness in patients and controls over 18 months.
CONCLUSIONS: Test-retest reliability of muscle MRE using a simple 2D technique was suboptimal, and did not reliably measure muscle stiffness changes in adults with BMD as compared with controls over 18 months. While the results provide motivation for testing more advanced 3D MRE methods, we conclude that the simple 2D MRE implementation used in this study is not suitable as an outcome measure for characterizing thigh muscle in clinical trials.
METHODS: We assessed test-retest reliability of muscle MRE in 20 subjects with (n = 5) and without (n = 15) muscle diseases and compared this to Dixon proton density fat fraction (PDFF) and volume measurements. Next, we measured MRE muscle stiffness in 21 adults with Becker muscular dystrophy (BMD) and 21 age-matched healthy controls at baseline, and after 9 and 18 months. We compared two different methods of analysing MRE data in this study: \'Method A\' used the stiffness maps generated by the Philips MRE software, and \'Method B\' applied a custom-made procedure based on wavelength measurements on the MRE images.
RESULTS: Intraclass correlation coefficients (ICC) of muscle stiffness ranged from good (0.83 for left vastus medialis, P < 0.001) to poor (0.19 for right rectus femoris, P = 0.212) for the examined thigh muscles with Method A, but we did not find a significant test-retest reliability with Method B (P > 0.050 for all). The ICC of muscle PDFF and volume measurements was excellent (>0.90; P < 0.001) for all muscles. At baseline, the average stiffness of all thigh muscles was significantly lower in adults with BMD than in controls for both Method A (-0.2 kPa, P = 0.025) and Method B (-0.6 kPa, P < 0.001). Regardless of which method was used, there was no significant difference in the evolution of muscle stiffness in patients and controls over 18 months.
CONCLUSIONS: Test-retest reliability of muscle MRE using a simple 2D technique was suboptimal, and did not reliably measure muscle stiffness changes in adults with BMD as compared with controls over 18 months. While the results provide motivation for testing more advanced 3D MRE methods, we conclude that the simple 2D MRE implementation used in this study is not suitable as an outcome measure for characterizing thigh muscle in clinical trials.
摘要：
背景：我们研究了骨骼肌磁共振弹性成像（MRE）刚度测量作为结果测量的潜力，通过确定其测试-重测可靠性，以及它在纵向随访研究中对变化的敏感性。
方法：我们评估了20名患有（n=5）和没有（n=15）肌肉疾病的受试者的肌肉MRE的测试-重测可靠性，并将其与Dixon质子密度脂肪分数（PDFF）和体积测量值进行比较。接下来,我们在基线测量了21名Becker肌营养不良（BMD）成人和21名年龄匹配的健康对照者的MRE肌肉硬度，9个月和18个月后。我们在这项研究中比较了分析MRE数据的两种不同方法：“方法A”使用了飞利浦MRE软件生成的刚度图，和\'方法B\'应用基于MRE图像上的波长测量的定制程序。
结果：肌肉僵硬度的组内相关系数（ICC）范围为良好（左股中肌为0.83，P<0.001)至较差(右股直肌为0.19，P=0.212）对于使用方法A检查的大腿肌肉，但我们没有发现方法B的测试-重测可靠性(全部P>0.050)。对于所有肌肉,肌肉PDFF和体积测量的ICC都是优异的(>0.90;P<0.001)。在基线,对于两种方法A，BMD成人的所有大腿肌肉的平均刚度均显着低于对照组（-0.2kPa，P=0.025）和方法B（-0.6kPa，P<0.001)。不管使用哪种方法，18个月以上患者和对照组的肌肉僵硬度变化无显著差异.
结论：使用简单的2D技术对肌肉MRE的重测可靠性不理想，与18个月以上的对照组相比，没有可靠地测量BMD成人的肌肉硬度变化。虽然结果为测试更先进的3DMRE方法提供了动力，我们得出的结论是,本研究中使用的简单的2DMRE实施不适合作为临床试验中表征大腿肌肉的结果指标.
方法：我们评估了20名患有（n=5）和没有（n=15）肌肉疾病的受试者的肌肉MRE的测试-重测可靠性，并将其与Dixon质子密度脂肪分数（PDFF）和体积测量值进行比较。接下来,我们在基线测量了21名Becker肌营养不良（BMD）成人和21名年龄匹配的健康对照者的MRE肌肉硬度，9个月和18个月后。我们在这项研究中比较了分析MRE数据的两种不同方法：“方法A”使用了飞利浦MRE软件生成的刚度图，和\'方法B\'应用基于MRE图像上的波长测量的定制程序。
结果：肌肉僵硬度的组内相关系数（ICC）范围为良好（左股中肌为0.83，P<0.001)至较差(右股直肌为0.19，P=0.212）对于使用方法A检查的大腿肌肉，但我们没有发现方法B的测试-重测可靠性(全部P>0.050)。对于所有肌肉,肌肉PDFF和体积测量的ICC都是优异的(>0.90;P<0.001)。在基线,对于两种方法A，BMD成人的所有大腿肌肉的平均刚度均显着低于对照组（-0.2kPa，P=0.025）和方法B（-0.6kPa，P<0.001)。不管使用哪种方法，18个月以上患者和对照组的肌肉僵硬度变化无显著差异.
结论：使用简单的2D技术对肌肉MRE的重测可靠性不理想，与18个月以上的对照组相比，没有可靠地测量BMD成人的肌肉硬度变化。虽然结果为测试更先进的3DMRE方法提供了动力，我们得出的结论是,本研究中使用的简单的2DMRE实施不适合作为临床试验中表征大腿肌肉的结果指标.
