肢体枪弹伤的MRI表现及其病理形态学基础的实验研究

An experimental study on image findings of MRI and their pathomorphological basis in limb gunshot wound

目的 通过动物模型 ,观察肢体枪弹伤的MRI表现 ,并探讨其病理形态学基础。方法将 16只犬分成伤后 5、2 4、4 8和 72h组 ,手枪致伤犬后大腿制成动物模型后 ,进行MR多层面多序列扫描。观察各时相点损伤组织的病理形态学改变与MRI表现。结果 原发伤道为组织缺损区 ,5h组4只犬伤道内充填的血液与 2 4、4 8、72h组 12只犬充填的脓液在MRI上均表现为长T1和长T2 信号。挫伤区以均质样变的凝固性坏死为主 ,在MR各时相点的图像上均表现为不规则线样或点片状等T1和短T2 信号 ,静脉注入钆喷替酸葡甲胺 (Gd DTPA)后无强化。震荡区 :5h组的 4只犬以肌细胞水肿、变性、溶解及组织间隙内大量红细胞为主 ;2 4、4 8、72h组的 12只犬细胞间出现大量中性粒细胞和脓细胞 ,随着时间的增加 ,变性肌细胞的溶解逐渐加剧 ,组织水肿更加明显 ;各时相的震荡区在MRI上均呈T1稍低信号、T2 高信号 ,并有明显强化 ,且T2 信号随时间的增加而增高 ,使相邻的挫伤区显示更清楚。结论 在肢体枪弹伤后 72h内 ,MRI能较准确地显示组织的损伤状况 ,其中T2 WI和增强T1WI价值较大。枪弹伤特有的组织缺损、细胞凝固性坏死、大范围血管与细胞损伤是其不同于普通创伤MRI表现的重要病理形态学基础。

Objective To observe the MRI findings of limb gunshot wound and investigate their pathomorphological basis through animal models.Methods Sixteen mongrel dogs were divided into four groups randomly. The hind legs of dogs shot with handgun were undergone 0.5 T MRI scans at 5 h, 24 h, 48 h, and 72 h after wounded, respectively. The gross changes, HE staining light microscopic findings and MRI findings of wounds were observed.Results Permanent tract was a zone of tissue defect. In the tract, blood of 5 h group′s and pus of 24 h, 48 h, and 72 h groups showed T 1WI hypointense signal and T 2WI hyperintense signal. In contusion zone, the main pathological change was homogeneous coagulating necrosis of muscle fibers. MRI images showed irregular line, dot, or block T 1WI isointense signal, T 2WI hypointense signal, and no enhanced after Gd-DTPA injected in all groups. In concussion zone, the main pathological changes of 5 h group were edema, degeneration, and lysis of cells and lots of erythrocytes in the tissue interspace. Besides these, a large quantity of leucocytes and pus cells appeared, the lysis of degenerated cells near the contusion zone and the edema of such area, with passage of time, were more obviously in groups 24 h, 48 h, and 72 h. In MRI, concussion zone showed slightly hypointense T 1WI signal, hyperintense T 2WI, signal and T 2WI signal got higher and the adjacent contusion zone got clearer with time pass. Concussion zone could be enhanced obviously.Conclusion MRI can reflect the lesion of tissue in limb gunshot wound accurately during seventy-two hours after wound. The T 2WI and contrast-enhanced T 1WI are valuable. The special tissue-defect area, coagulating necrosis of cells, and large range injury of blood vessels and cells are the important pathomorphological basis which cause the MRI findings of gunshot wound different from normal trauma.