去神经骨骼肌退变的T2弛豫时间的实验研究

Experimental study of T2 relaxation time in denervated muscle

目的 探讨T2弛豫时间（T2值）测定在不同时间段去神经骨骼肌退变中的诊断价值.方法 35只新西兰兔随机分为七组,每组5只,切断右侧坐骨神经建立去神经支配腓肠肌实验模型,于模型制成后1、24、48 h,1、2、4、6周不同时间段行双侧下肢MR扫描,测量不同时间段腓肠肌的T2值,扫描后分别取材进行病理学检查.结果 去神经肌肉1及24 h各扫描序列上信号均无异常,去神经侧腓肠肌1～24 h的 T2值：（31.76±1.23）ms,假手术侧T2值为：（30.65±1.05） ms,T2值与假手术侧无明显统计学差异（F=3.884,P〉0.05）.48 h后T2图上可显示去神经支配腓肠肌信号轻度增高,T2值为 （40.75±1.02） ms;1～2周时肌肉T2值继续升高,6周达高峰（57.04±1.79） ms,T2值时间曲线呈缓慢上升型.假手术侧T2值与48 h的T2值有明显统计学差异（F=346.903,P〈0.01）;T2值增加与病理上出现肌肉水肿、变性,肌细胞间毛细血管增多,扩张相一致.结论 损伤后48 h的T2值测定可早期发现去神经肌肉的异常改变,明显早于肌肉萎缩的形态学改变,T2值随着去神经骨骼肌时间的延长而升高,T2值时间曲线可客观反应去神经后肌肉的退变,可作为检侧去神经肌肉异常的敏感、可靠指标.

Objective To evaluate the diagnostic value of T2 relaxation time （T2 value ） in different time quantum of acute denervated muscle models in rabbits. Methods Thirty-five adult rabbits were randomly divided into seven groups according to different time quantum, 5 rabbits in each group. Acute sciatic nerve denervated muscle models were set up by transecting the right sciatic nerves. After surgery, the bilateral lower extremities of each group were examined by MRI at 1 hour, 24 hours, 48 hours, 1 week, 2 weeks, 4 weeks and 6 weeks respectively. The left sciatic nerves were served as sham- operated sides. T2 relaxation time was measured, and then denervated muscle was examined pathologically. Results There were no obvious changes on MRI sequences at 1 hour and 24 hours on the denervated muscle sides. There was no statistically significant difference between transected and shamoperated sides in T2 value in the peroneal muscles （31.76 ±1.23 ） ms vs （ 30. 65 ±1.05 ） ms, （ F = 3. 884, P 〉 0. 05 ）. The denervated muscle showed slight hyperintense signals on T2 maps as early as 48 hours, which was （40. 75 ±1.02） ms, and further increased during 1 -2 weeks, until reached a maximum at 6 weeks （57. 04 ±1.79） ms. The time-signal curve of the T2 values was a slow-rise type. There was statistically significant difference between 48 hour and sham-operated side in T2 value in the peroneal muscles （ F = 346. 903, P 〈 0. 01 ）. The rise of T2 values was consistent with edema, degeneration of muscle fiber and enlargement of muscle capillaries. Conclusions The study that prolongation of the T2 values in denervated muscle happened as early as 48 hours after transaction. T2 relaxation time pronlongation is an early sign of muscle denervation, which markedly precede muscle atrophy. T2 value increases with the denevated muscle time. Dynamic T2 value measurement of denervated muscles is a sensitive and reliable method to monitor the change of denevated muscles.