MR T_2 mapping成像在Duchenne肌营养不良症中的应用

Application of MR T_2 mapping in patients with Duchenne muscular dystrophy

目的探讨MRI对Duchenne肌营养不良的应用价值,并将T_2mapping成像与T_1脂肪评分系统进行比较研究。方法收集2012年11月—2013年6月经病理或基因确诊的Duchenne肌营养不良病人27例,均为男性,平均年龄(8.53±6.25)岁,平均病程为(4.17±3.79)年。同期选择12例健康人作为对照组,其中男7例,女5例,平均年龄(25.67±1.23)岁。均行下肢MRI检查,评价其MRI表现,并应用T_1脂肪评分系统进行脂肪浸润分级,T_2mapping成像测定T_2值。采用独立样本t检验比较病例组及对照组T_2值差异。采用Pearson相关分析病例组T_2值与T_1脂肪评分,以及两者分别与年龄、病程、肌酸激酶水平的相关性;采用Spearman秩相关分析病例组的T_2值及T_1脂肪评分分别与临床分级的相关性。结果 22例病人MRI表现为受累肌肉呈不同程度脂肪浸润,T_1WI呈高信号,5例MRI表现正常。22例病人各块肌肉的受累程度不同,但T_2值与T_1脂肪评分分布趋势相似,两者均反映受累最重者为大收肌(T_2值243 ms,T_1评分2.8),其次为臀大肌(T_2值243 ms,T_1评分2.7)、股外侧肌(T_2值225 ms,T_1评分1.9),受累较轻的有股薄肌(T_2值171 ms,T_1评分0.3)、缝匠肌(T_2值170 ms,T_1评分0.6)及长收肌(T_2值175 ms,T_1评分0.4)。病例组的T_2值[(211.9±65.2)ms]明显高于对照组[(141.6±16.7)ms](t=5.228,P<0.001)。MRI表现正常的病人,其T_2值[(158.1±15.4)ms]比对照组[(141.6±16.7)ms]稍高,但差异无统计学意义(t=1.89,P=0.078)。T_2值与T_1脂肪评分、病程及临床分级均呈正相关(均P<0.05),与年龄和肌酸激酶水平无相关性(均P>0.05)。T_1脂肪评分与年龄、病程及临床分级均呈正相关(均P<0.05),与肌酸激酶水平无相关性(P>0.05)。结论 T_2mapping成像与T_1脂肪评分系统均能很好地评价Duchenne肌营养不良病人的肌肉受累分布特征及病情的严重程度,Duchenne肌营养不良病人的下肢肌肉T_2值与T_1脂肪浸润程度呈正相关,T_2值比T_1脂肪评分更为客观。

Objective To evaluate and compare the diagnostic value of magnetic resonance imaging T2 mapping and T1WI fatty score system in patients with Duchenne muscular dystrophy(DMD).Methods Twenty-seven patients with pathologically or gene proved DMD were enrolled in this study from November 2012 to June 2013.All the patients were male with an average age of 8.53±6.25 years,and the average course of disease was 4.17±3.79 years.Twelve healthy volunteers were recruited as the control group,including 7 male and 5 female,with an average age of 25.67±1.23 years.All subjects were underwent MRI examination of the lower extremities and MRI performance were evalulated.The T1 fat scoring system was used to classify the fat infiltration,and the T2 mapping imaging was used to deteminre the T2 value.The difference in T2 value was tested by independent sample t test between the patient and the control groups.Pearson correlation analysis was used to investigate the correlation between the T2 values and T1 fat score,and the correlation between two group with age,course of disease,and creatine kinase level.Spearman rank correlation analysis was used to explore the correlation between the T2 value and the T1 fat score with the clinical grade of the case group.Results In 22 patients,MRI showed a different degree of fatty infiltration in the affected muscles and the T1WI showed high signal.No abnormal MRI features were observed in five patients.The degree of involvement of the muscles varied.The T1 fat score and T2 value have similar distribution,both showing the most frequently involved muscle was the adductor magnus(T2 value=243 ms,T1 fat score=2.8),followed by the gluteus maximus(T2 value=243 ms,T1 fat score=2.7),vastus lateralis(T2 value=225 ms,T1 fat score=1.9).The least affected muscle was the gracilis(T2 value=171 ms,T1 fat score=0.3),the sartorius muscle(T2 value=170 ms,T1 fat score=0.6),and the adductor longus(T2 value=175 ms,T1 fat score=0.4).The average T2 value(211.9±65.2 ms)of the patients was significantly higher than that of the control group(141.6±16.7 ms)(t=5.228,P<0.001).The T2 value of the patients with normal MR features(158.1±15.4 ms)was mildly higher than that of control group(141.6±16.7 ms),but the difference was not statistically significant(t=1.89,P=0.078).The T2 value was positively correlated with the T1 fat score,course of disease and clinical grade(all P<0.05),while was negatively correlated with age and creatine kinase value(all P>0.05).The T1 fat score was positively correlated with age,course of disease,and clinical grade(all P<0.05),while was negative correlated with creatine kinase value(P>0.05).Conclusions T2 mapping and T1 fat scoring system both can well evaluate the distribution of muscle involvement and the severity of the disease in patients with Duchenne muscular dystrophy.The T2 value is positively correlated with the T1 fat score of the lower limb muscles in patients with Duchenne muscular dystrophy,while the T2 value is more objective than T1 fat score.