1 Department of Radiology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave, Cincinnati, OH 45229-3039.
2 Department of Mathematical Sciences, University of Cincinnati, Cincinnati, OH.
AJR Am J Roentgenol. 2015 Aug;205(2):W216-23. doi: 10.2214/AJR.14.13755.
The purpose of this study is to validate the use of MR spectroscopy (MRS) in measuring muscular fat and to compare it with T2 maps in differentiating boys with Duchenne muscular dystrophy (DMD) from healthy boys.
Forty-two boys with DMD and 31 healthy boys were evaluated with MRI with (1)H-MRS and T2 maps. Grading of muscle fat and edema on conventional images, calculation of fat fractions ([fat / fat] + water) on MRS, and calculation of T2 fat values on T2 maps of the gluteus maximus and vastus lateralis muscles were performed. Group comparisons were made. The 95% reference interval (RI) of fat fraction for the control group was applied and compared with T2 map results.
Minimal fat on T1-weighted images was seen in 90.3% (gluteus maximus) and 71.0% (vastus lateralis) of healthy boys, versus 33.3% (gluteus maximus) and 52.4% (vastus lateralis) of boys with DMD. Muscle edema was seen in none of the healthy boys versus 52.4% (gluteus maximus) and 57.1% (vastus lateralis) of the boys with DMD. Fat fractions were higher in the DMD group (52.7%, gluteus maximus; 27.3%, vastus lateralis) than in the control group (12.8%, gluteus maximus; 13.7%, vastus lateralis) (p < 0.001). The 95% RI for gluteus maximus (38.7%) resulted in 61.9% sensitivity and 100% specificity for differentiating boys with DMD from healthy boys, whereas the value for vastus lateralis (17.8%) resulted in 76.2% sensitivity and 100% specificity; both had lower accuracy than did T2 maps (100% sensitivity and specificity). There was a positive correlation between T2 fat values and fat fractions (p < 0.0001).
In differentiation of the two groups, T2 maps were more accurate than MRS. Fat fractions can underestimate the actual amount of fat because of coexisting muscle edema in DMD.
本研究旨在验证磁共振波谱（MRS）测量肌肉脂肪的应用，并将其与 T2 图谱进行比较，以区分杜氏肌营养不良症（DMD）男孩和健康男孩。
42 名 DMD 男孩和 31 名健康男孩接受了 MRI 检查，包括（1）H-MRS 和 T2 图谱。对常规图像上的肌肉脂肪和水肿进行分级，在 MRS 上计算脂肪分数[脂肪/（脂肪+水）]，并计算臀大肌和股外侧肌 T2 图谱上的 T2 脂肪值。进行组间比较。对照组的脂肪分数 95%参考区间（RI）适用于与 T2 图谱结果进行比较。
90.3%（臀大肌）和 71.0%（股外侧肌）的健康男孩在 T1 加权图像上可见最小脂肪，而 33.3%（臀大肌）和 52.4%（股外侧肌）的 DMD 男孩可见脂肪。在所有健康男孩中均未见肌肉水肿，而 52.4%（臀大肌）和 57.1%（股外侧肌）的 DMD 男孩可见肌肉水肿。DMD 组的脂肪分数较高（臀大肌 52.7%，股外侧肌 27.3%），对照组较低（臀大肌 12.8%，股外侧肌 13.7%）（p<0.001）。臀大肌的 95%RI（38.7%）用于区分 DMD 男孩和健康男孩，灵敏度为 61.9%，特异性为 100%，而股外侧肌的 RI（17.8%）则分别为 76.2%和 100%；两者的准确性均低于 T2 图谱（100%的灵敏度和特异性）。T2 脂肪值与脂肪分数之间存在正相关（p<0.0001）。
在两组之间的区分中，T2 图谱比 MRS 更准确。由于 DMD 中存在共存的肌肉水肿，脂肪分数可能会低估实际脂肪量。
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