ABSTRACT
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.