Real-time ultrasound elastography in evaluating dynamic changes of rabbit skeletal muscle injury induced by microwave ablation of different powers / 第二军医大学学报

ABSTRACT

Objective: To use ultrasound elastography for observing the natural recovery of rabbit muscle elasticity after skeletal muscle injury induced by microwave ablation of different powers. Methods: Forty New Zealand white rabbits were randomly divided into 30 W group and 50 W group, with 20 in each group. Another 4 rabbits served as normal controls (normal group). Rabbit models of skeletal muscle injury were established by microwave thermocoagulation with different powers (30 W and 50 W) for the right medial femoral muscle for 3 min using the KY-2100 microwave ablation instrument (2 450 MHz). One hour, and 1, 2, 7 and 28 d after microwave ablation, ultrasound elastography feature strain ratio (SR) values in ablation areas were calculated. At each time point, the thermocoagulated muscle tissue of the right medial femoral muscle in the 30 W and 50 W groups and the muscle tissue of the same area on the same side in the normal group were harvested for pathological observation. Results: The ablation areas extracted from ultrasound elastography were mainly blue in the 30 W and 50 W groups, while green area appeared in those areas 7 d after microwave ablation. More blue areas were seen in 50 W group compared with 30 W group 28 d after microwave ablation. Compared with the normal group, the SR values in the 30 W and 50 W groups were significantly increased 1 h, 1 d, and 2 d after microwave ablation (P0.05). H-E staining showed different degrees of tissue damage, carbonization, and coagulation necrosis of peripheral muscle fibers. Inflammatory cell infiltration was seen at the injured junction 1-2 d after microwave ablation, and the macrophages in the 50 W group was more than that in the 30 W group. A large number of neovascularization, fibroblasts and scar formation were observed at the junction 7-28 d after microwave ablation, and inflammation and turbidity swelling were alleviated in the 30 W and 50 W groups. Masson staining showed less fiber contents and no obvious fiber proliferation 1 h after microwave ablation in the 30 W and 50 W groups. At 1-2 d after microwave ablation, different degrees of new collagen fibers and muscle interstitial fiber proliferation were observed in the 30 W and 50 W groups. At 7-28 d after microwave ablation, a large number of newborn collagen fibers were observed in the 30 W and 50 W groups, accompanied by a significant increase in peripheral fibers of vascular wall. Sirius red staining showed that a large number of newborn collagen gradually appeared in the 30 W and 50 W groups. Immediately and 1 d after microwave ablation, there were mainly type I collagen fibers, and type II collagen fibers were found 2 d after microwave ablation. At 7 d and 28 d after microwave ablation, there were more type II collagen fibers reticulated in the 30 W and 50 W groups. Conclusion: Microwave ablation with different powers can cause acute muscle injury in rabbits, the injury intensifes during 1-2 d after microwave ablation, and begin to repair 7-28 d after microwave ablation; the repair of 50 W group is later than the 30 W group. The dynamic changes of ultrasound elastography are consistent with the pathological findings. Ultrasound elastography can noninvasively evaluate the dynamic changes of skeletal muscle tissue repair after muscle injury, and it is a complement to the conventional ultrasound examination.