磁共振肌肉脂肪化色阶直方图评估法的临床应用

Clinical application of MRI histogram in evaluation of muscle fatty infiltration

目的：建立磁共振（magnetic resonance imaging,MRI）T1加权像（T1-weighted imaging,T1WI）图像中肌肉脂肪化程度的色阶直方图评估法,分析其临床应用价值。方法：对25例抗肌萎缩蛋白病患者行大腿肌肉MRI检查,分别采取直视分级法和色阶直方图评估法对肌肉脂肪化程度进行评估,比较两种方法的肌肉脂肪化评估结果及其与年龄、肌力的相关性。用组内相关系数检验两种评估法的不同评估者之间的一致性。结果：色阶直方图评估法与直视分级法均显示抗肌萎缩蛋白病患者大腿中段的肌肉脂肪化规律相同,即大收肌最严重,股薄肌、缝匠肌和长收肌最轻。色阶直方图评估法与直视分级法的结果存在显著正相关（r=0.854,P〈0.001）。色阶直方图评估及直视分级的肌肉脂肪化程度与年龄的相关系数分别为0.730（P〈0.001）和0.753（P〈0.001）,股四头肌脂肪化程度评估结果与伸膝肌力的相关系数分别为-0.468（P=0.024）和-0.460（P=0.027）。色阶直方图评估法的两位评估者之间的组内相关系数为0.998（95%CI：0.997～0.998,P〈0.001）,而直视分级法的两位评估者之间的组内相关系数为0.958（95%CI：0.946～0.967,P〈0.001）。结论：MRI肌肉脂肪化程度的色阶直方图评估法可以客观评估肌肉脂肪化程度。

Objective： To describe a method based on analysis of the histogram of intensity values produced from the magnetic resonance imaging（ MRI） for quantifying the degree of fatty infiltration.Methods： The study included 25 patients with dystrophinopathy. All the subjects underwent muscle MRI test at thigh level. The histogram M values of 250 muscles adjusted for subcutaneous fat,representing the degree of fatty infiltration,were compared with the expert visual reading using the modified Mercuri scale. Results： There was a significant positive correlation between the histogram M values and the scores of visual reading（ r = 0. 854,P〈0. 001）. The distinct pattern of muscle involvement detected in the patients with dystrophinopathy in our study of histogram M values was similar to that of visual reading and results in literature. The histogram M values had stronger correlations with the clinical data than the scores of visual reading as follows： the correlations with age（ r = 0. 730,P〈0. 001） and（ r = 0. 753,P〈0. 001）; with strength of knee extensor（ r =- 0. 468,P = 0. 024） and（ r =- 0. 460,P = 0. 027）respectively. Meanwhile,the histogram M values analysis had better repeatability than visual reading with the interclass correlation coefficient was 0. 998（ 95% CI： 0. 997- 0. 998,P〈0. 001） and 0. 958（ 95%CI： 0. 946- 0. 967,P〈0. 001） respectively. Conclusion： Histogram M values analysis of MRI with the advantages of repeatability and objectivity can be used to evaluate the degree of muscle fatty infiltration.