The diagnostic value of biexponential apparent diffusion coefficients in myopathy

To investigate the performance of a biexponential signal decay model using DWI in myopathies and to differentiate Polymyositis (PM)/Dermatomyositis (DM), Glycogen Storage Diseases (GSDs) and Muscular Dystrophies (MDs) utilizing diffusion-weighted imaging. 11 healthy volunteers (control group) and 46 patients with myopathy were enrolled in the retrospective study. 27 of 46 patients had PM/DM, 7 patients GSDs and 12 patients MDs. After conventional MR sequences, diffusion weighted imaging with a b-factor ranging from 0 to 1200 s/mm(2) was performed on both thighs. The intra-muscular signal-to-noise ratios (SNRs) on multiple-b DWI images were measured for 7 different muscles and compared among the different groups. The median T2 signal intensity and biexponential apparent diffusion coefficients (ADC), including standard ADC, fast ADC, and slow ADC values, were compared among the different groups. The intra-muscular SNRs were statistically significantly different depending on the b value, and also found among the 4 groups (p < 0.05). The median T2 signal intensity of the normal muscles in control group was statistically significantly lower than that of edematous muscles in the PM/DM, GSDs and MDs groups (p = 0.000), while there were no statistically significant differences among the PM/DM, GSDs, and MDs groups (p > 0.05). The median standard ADC value of the edematous muscles in GSDs was statistically significantly lower than that of normal muscles in the control group (p = 0.000) and the median ADC value of the edematous muscles in PM/DM patients was statistically significantly greater than that of the GSDs (p = 0.000) and MDs groups (p = 0.005). The median slow ADC value of the edematous muscles in MDs patients and PM/DM patients was statistically significantly greater than that of GSDs patients (p < 0.05). Intra-muscular SNR decay curves and biexponential ADC parameters are useful in distinguishing among PM/DM, GSDs, and MDs.

利用弥散加权成像（DWI）研究双指数信号衰减模型在肌病中的表现，并区分多发性肌炎（PM）/皮肌炎（DM）、糖原贮积病（GSDs）和肌营养不良症（MDs）。11名健康志愿者（对照组）和46名肌病患者参与了这项回顾性研究。46名患者中27人患有PM/DM，7人患有GSDs，12人患有MDs。在常规磁共振序列之后，对双侧大腿进行b值范围从0到1200 s/mm²的弥散加权成像。测量7种不同肌肉在多b值DWI图像上的肌内信噪比（SNRs），并在不同组间进行比较。比较不同组间的中位T2信号强度和双指数表观弥散系数（ADC），包括标准ADC、快速ADC和慢速ADC值。肌内SNRs根据b值有统计学显著差异，并且在4组间也存在差异（p < 0.05）。对照组正常肌肉的中位T2信号强度在统计学上显著低于PM/DM、GSDs和MDs组的水肿肌肉（p = 0.000），而PM/DM、GSDs和MDs组之间无统计学显著差异（p > 0.05）。GSDs组水肿肌肉的中位标准ADC值在统计学上显著低于对照组的正常肌肉（p = 0.000），PM/DM患者水肿肌肉的中位ADC值在统计学上显著大于GSDs组（p = 0.000）和MDs组（p = 0.005）。MDs患者和PM/DM患者水肿肌肉的中位慢速ADC值在统计学上显著大于GSDs患者（p < 0.05）。肌内SNR衰减曲线和双指数ADC参数有助于区分PM/DM、GSDs和MDs。