Substitute ellipse of the permanent cavity in gelatin blocks and debridement of gunshot wounds.

A new method in terminal ballistics is presented that allows precise numerical analysis of characteristics of the permanent cavity by computed tomography (CT). Shots were made with a Russian AK-74 assault rifle (5.45 mm) into gelatin used as a tissue simulant. CT scans were made of the gelatin blocks, transferred into digital format, and analyzed using computer software. CT scans of the permanent cavity are characterized by markedly irregular shapes, and an attempt was made to simplify these forms and to link them with surgical debridement of gunshot wounds. An assumption was made that the zone of debridement has the form of an ellipse. Using the information from the CT images, a substitute ellipse was constructed as an approximation of the a vital tissue surrounding the wound channel with the aim of approaching a more exact definition of the zone of necessary debridement of gunshot wounds.