Department of Physical Therapy, University of Florida, Gainesville, FL, USA.
NMR Biomed. 2013 Mar;26(3):320-8. doi: 10.1002/nbm.2851. Epub 2012 Oct 9.
Skeletal muscles of children with Duchenne muscular dystrophy (DMD) show enhanced susceptibility to damage and progressive lipid infiltration, which contribute to an increase in the MR proton transverse relaxation time (T₂). Therefore, the examination of T₂ changes in individual muscles may be useful for the monitoring of disease progression in DMD. In this study, we used the mean T₂, percentage of elevated pixels and T₂ heterogeneity to assess changes in the composition of dystrophic muscles. In addition, we used fat saturation to distinguish T₂ changes caused by edema and inflammation from fat infiltration in muscles. Thirty subjects with DMD and 15 age-matched controls underwent T₂ -weighted imaging of their lower leg using a 3-T MR system. T₂ maps were developed and four lower leg muscles were manually traced (soleus, medial gastrocnemius, peroneal and tibialis anterior). The mean T₂ of the traced regions of interest, width of the T₂ histograms and percentage of elevated pixels were calculated. We found that, even in young children with DMD, lower leg muscles showed elevated mean T₂, were more heterogeneous and had a greater percentage of elevated pixels than in controls. T₂ measures decreased with fat saturation, but were still higher (P < 0.05) in dystrophic muscles than in controls. Further, T₂ measures showed positive correlations with timed functional tests (r = 0.23-0.79). The elevated T₂ measures with and without fat saturation at all ages of DMD examined (5-15 years) compared with unaffected controls indicate that the dystrophic muscles have increased regions of damage, edema and fat infiltration. This study shows that T₂ mapping provides multiple approaches that can be used effectively to characterize muscle tissue in children with DMD, even in the early stages of the disease. Therefore, T₂ mapping may prove to be clinically useful in the monitoring of muscle changes caused by the disease process or by therapeutic interventions in DMD.
患有杜氏肌营养不良症 (DMD) 的儿童的骨骼肌易受损，且脂质逐渐浸润，这会导致磁共振质子横向弛豫时间 (T₂) 延长。因此，检测个体肌肉的 T₂变化可能有助于监测 DMD 疾病的进展。在本研究中，我们使用平均 T₂、高信号像素百分比和 T₂异质性来评估病变肌肉的组成变化。此外，我们使用脂肪饱和来区分由水肿和炎症引起的 T₂变化与肌肉中的脂肪浸润。30 名 DMD 患儿和 15 名年龄匹配的健康对照者使用 3T 磁共振系统对其小腿进行 T₂ 加权成像。生成 T₂ 图并手动勾画出 4 条小腿肌肉（比目鱼肌、腓肠肌内侧头、腓肠肌外侧头和胫骨前肌）的感兴趣区。计算所勾画区域的平均 T₂、T₂ 直方图的宽度和高信号像素百分比。我们发现，即使是患有 DMD 的年幼儿童，其小腿肌肉的平均 T₂ 也较高，异质性更大，高信号像素百分比也更高。T₂ 测量值在脂肪饱和后会降低，但在病变肌肉中仍高于对照组（P < 0.05）。此外，T₂ 测量值与计时功能测试呈正相关（r = 0.23-0.79）。在 DMD 所有检查年龄（5-15 岁）与未受影响的对照组相比，T₂ 值升高，这表明病变肌肉中损伤、水肿和脂肪浸润的区域增加。本研究表明，T₂ 映射提供了多种方法，可以有效地用于描述 DMD 患儿的肌肉组织，即使在疾病的早期阶段也是如此。因此，T₂ 映射可能在监测由疾病进程或治疗干预引起的肌肉变化方面具有临床应用价值。
