不同消融功率致兔骨骼肌急性微波热损伤修复的超声影像演变特征

Ultrasonic changes of injured and repaired rabbit skeletal muscle induced by different power of microwave thermal ablation

目的建立兔骨骼肌急性微波热损伤模型,观察兔骨骼肌因不同消融功率所致损伤修复不同时期肌肉组织的超声影像特征,并探讨其病理组织学、血清标志物的变化。方法根据不同消融功率,40只新西兰白兔随机分为30 W组与50 W组。高频超声引导下采用2450 MHz的微波治疗仪电针插入兔双侧股内侧肌肉,2组分别启动30 W或50 W微波热凝右侧肌肉3 min。于损伤前和损伤后1 h、1 d、2 d、7 d、28 d行二维超声、彩色多普勒血流显像、超声造影检查。在每个时间节点每组各处死4只兔,切取右侧损伤肌肉组织进行光镜病理组织学观察,抽取耳缘静脉血,检测损伤前后血清肌酸肌酶（CK）,乳酸脱氢酶（LDH）,肌钙蛋白（Tn T）的含量。结果 （1）超声影像改变：损伤后1 h消融区域回声一过性增高,而后减低,1 d时达最低回声,2组1 d、2 d时损伤区内肌纹理消失,损伤最大径线值依次增大,与1 h时比较均增大[30 W组：（23.1±5.8 vs 10.0±3.1）mm,50 W组：（32.4±4.6 vs 16.0±4.1）mm,t=-7.72、-8.31,P均〈0.01],30 W组2 d时达最大值,与1 d比增大[（25.7±1.8 vs 23.1±5.8）mm,t=-2.35,P〈0.05],50 W组1 d时达最大值,7 d、28 d时2组损伤区最大径线值依次变小,30 W组7 d较2 d时变小[（20.8±3.4 vs 25.7±1.8）mm,t=-2.23,P〈0.05],50 W组28 d较7 d时变小[（23.6±2.6 vs 28.5±4.6）mm,t=-4.32,P〈0.01]。在不同时间节点50 W组的损伤区最大径线值,均大于30 W组,2组比较,差异有统计学意义[（16.0±4.1 vs 10.0±3.1）mm,（32.4±4.6 vs 23.1±5.8）mm,（31.0±5.0 vs 25.7±1.8）mm,（28.5±4.6 vs 20.8±3.4）mm,（23.6±2.6 vs18.2±1.5）mm,t=-3.23、-3.59、-2.99、-6.53、-2.17,P均〈0.05]。损伤后肌肉内彩色多普勒血流信号0级,超声造影显示消融区域无造影剂充填,与30 W组相比,彩色多普勒血流信号消失及超声造影无灌注区所显示的范围更大,持续时间长。随着肌纤维的修复,损伤后7~28 d 2组声像图上回声逐渐增高,肌纹理逐渐清晰,在消融区域周边出现Ⅱ~Ⅲ级血流信号,超声造影显示造影剂包绕消融区,无造影剂充填区逐渐缩小,但50 W组晚于30 W组。（2）HE染色光镜下可见由炭化坏死、浊肿变性区逐渐向正常肌纤维组织过渡,50 W组变性坏死区域较大,修复期损伤交界处大量新生血管和胶原纤维形成,28 d时多于7 d,肌纤维凝固性坏死、浊肿等较损伤2 d少。（3）血清标志物检测：与损伤前比较,损伤后1 h,2组血清CK含量均升高[30 W组：（1.58±0.67 vs 0.64±0.31）k U/L,50 W组：（1.84±1.19 vs 0.64±0.31）k U/L,t=-4.623、-4.768,P均〈0.01];50 W组血清LDH含量升高[7049.60±3328.60 vs 4155.80±1745.80）U/L,t=-2.594,P〈0.05];损伤后1 d,2组血清LDH与Tn T含量均升高[LDH 30 W组：（8486.82±2438.90 vs 4155.8±1745.8）U/L,LDH 50 W组：（9091.86±1068.50 vs 4155.8±1745.8）U/L,t=-4.762、-6.515,P均〈0.05];Tn T 30 W组：（21.67±8.80 vs12.37±4.34）μg/L,Tn T 50 W组：（25.64±4.19 vs 12.37±4.34）μg/L,t=-3.306、-5.194,P均〈0.01）;损伤后2 d,2组血清LDH含量均升高[30 W组：（7116.2±1887.2 vs 4155.8±1745.8）U/L,50 W组：（8494.57.86±1199.30 vs 4155.8±1745.8）U/L,t=-3.283、-5.910,P均〈0.01）,差异均有统计学意义。结论兔骨骼肌急性损伤在微波热消融后1~2 d进行性加重,7~28 d呈修复趋势,消融功率50 W组修复晚于30 W组。超声成像可动态观察受损后肌肉相应的组织结构、血流分布的超声影像演变特征,与病理组织学、血清生化指标变化趋势也较为一致,从而形象直观地反映骨骼肌损伤修复过程。

Objective To investigate the ultrasonic features of rabbit skeletal muscle injury and regeneration induced by microwave thermal ablation, and to observe histological findings and laboratory tests respectively. Methods Experimental rabbit models of skeletal muscle injured by microwave ablation（2450 MHz） with different power were established. 40 rabbits were randomly divided into two groups with 20 rabbits in each group, group 30 W and group 50 W. At different time points, before injury and one hour, one day, two days, 7 days, 28 days after injury, the corresponding 2D sonograms, color Doppler flow imaging（CDFI）, contrast-enhanced ultrasound（CEUS） features and microscopic findings from the region of interest（ROI） taken from either model were analyzed and compared statistically, laboratory tests of serum markers CK, LDH and Tn T level were also be detected dynamically. Results（1） After different power microwave ablation, 2D sonograms showed there were distinct changes of the textures in both injured regions compared to the normal status, characterized in disappearance of their regular arrangement and directions. The echo level in ablation regions of two groups increased one hour after injury, but decreased gradually later, especially at one day after injury. Compared with regions of one hour after injury, the maximum diameters became larger significantly in two groups at one, two hour after injury [the maximum diameter of group 30 W, one day vs one hour：（23.1±5.8 vs 10.0±3.1） mm; the maximum diameter of group 50 W, one day vs one hour：（32.4±4.6 vs 16.0±4.1） mm, t=-7.72,-8.31, P 0.01; the maximum diameter of group 30 W, 2 day vs one day：（25.7±1.8 vs 23.1±5.8） mm, t=-2.35, P 0.05], while the maximum diameters became smaller significantly in two groups at 7 days, 28 days after injury respectively [the maximum diameter of group 30 W, 7 days vs 2 days：（20.8±3.4 vs 25.7±1.8） mm, t=-2.23, P 0.05; the maximum diameter of group 50 W, 28 days vs 7 days：（23.6±2.6 vs 28.5±4.6） mm, t=-4.32, P 0.01]. At different time points after injury, the maximum diameter in group 50 W was significantly larger than in group 30 W [（16.0±4.1 vs 10.0±3.1） mm,（32.4±4.6 vs 23.1±5.8） mm,（31.0±5.0 vs 25.7±1.8） mm,（28.5±4.6 vs 20.8±3.4） mm,（23.6±2.6 vs 18.2±1.5） mm, t=-3.23,-3.59,-2.99,-6.53,-2.17, all P 0.05]. There were no blood signal and contrast agents displayed on CDFI or CEUS images after injury, and group 50 W images often showed larger filling-defect areas compared with group 30 W. However, 7~28 days after injury, with the regeneration of muscular fibers, injured regions of the two groups were repaired gradually. The injured muscle texture appeared clearly and peripheral blood signals could be detected as grade Ⅱ- Ⅲ on CDFI images. No contrast agents area on CEUS images became smaller.（2） The corresponding histopathology revealed identifiable alterations such as muscular fibers degeneration, necrosis, regeneration, fibrosis or nourishing blood vessels variation, which contribute to the differentiation to normal status and between the two groups on ultrasonograms.（3） Compared with normal status, one hour after injury, serum CK level increased significantly in two groups [group 30 W：（1.58±0.67 vs 0.64±0.31） k U/L; group 50 W：（1.84±1.19 vs 0.64±0.31） k U/L, t=-4.623,-4.768, all P 0.01], while serum LDH level in group 50 W was also obviously higher than in group 30 W [（7049.60±3328.60 vs 4155.80±1745.80） U/L, t=-2.594, P 0.05]; one day after injury, serum LDH and Tn T level in both two groups increased significantly [LDH in group 30 W：（8486.82±2438.90 vs 4155.8±1745.8） U/L; LDH in group 50 W：（9091.86±1068.50 vs 4155.8±1745.8） U/L, t=-4.762,-6.515, P 0.05; Tn T in group 30 W：（21.67±8.80 vs 12.37±4.34） μg/L, Tn T in group 50 W：（25.64±4.19 vs 12.37±4.34） μg/L, t=-3.306,-5.194, all P 0.01]; two days after injury, serum LDH level in both groups increased significantly [group 30 W：（7116.2±1887.2 vs 4155.8±1745.8） U/L, group 50 W：（8494.57.86±1199.30 vs 4155.8±1745.8） U/L, t=-3.289,-5.910, all P 0.01]. Conclusions Different power of Microwave thermal ablation can cause different histopathologic changes and laboratory tests results in correspondence with various features on multimode ultrasonograms. It is visible and useful for ultrasonography to demonstrate the texture characteristics of skeletal muscle injured by thermal factors, and it will be helpful to guide the explorative ultrasound diagnosis and evaluation, and to provide complementary information of skeletal muscles injury and repair characterization.