LAUSR

Most clinicians do not routinely remove bullets from patients with gunshot wounds to avoid the risks of surgical intervention. There are considered to be only a few medical indications for removing a bullet. In criminal investigations in which surgical intervention to recover a lodged bullet is not advocated, radiological images can provide important information on the type of ammunition used. In the last century, X-ray imaging has become a standard procedure to locate bullets that are lodged inside the body, and retained bullets are among the most frequently encountered metallic foreign bodies detected on X-ray imaging. The radiographic depiction of a bullet on the X-ray image can be used to classify a bullet according to its shape and size. For this purpose, magnification factors have to be considered, since the radiographic depiction of a bullet can be magnified compared to the actual size of the lodged bullet, depending on the distances from the X-ray tube focal spot to the X-ray film and to the bullet. Furthermore, an X-ray image allows only a twodimensional summation image representing the degree of X-ray absorption along the X-ray beam path. Thus, at least three orthogonal X-ray images are required for calibre calculations. Three-dimensional computed tomography (CT) data largely bypass these limitations, as an object can be rotated and aligned to any desired plane using multiplanar reconstructions (two-dimensional view) or volume renderings (three-dimensional view). Furthermore, CT data are increasingly available, as CT scanning is increasingly applied in emergency departments. Nevertheless, the opportunity of a virtual investigation of a lodged bullet by means of CT images is frequently not considered, since it is well known that metallic objects cause severe artefacts on CT. Thus, the image quality of a delineated bullet on standard CT differs greatly from the familiar detailed depiction of a bullet on planar X-ray images. However, special reconstructions that are provided by all main CT manufacturers still enable a very detailed depiction of metallic objects on CT and allow Hounsfield unit (HU) measurements of such radiopaque material.