As already mentioned in Chapter 4, postmortem imaging has proved to be a particular success in cases of gunshot injury. The technical improvement allows more information to be gathered than ever before, regarding the reconstruction of the scene. Seventeen cases of gunshot injury of the head/brain (Oehmi-chen et al. 2003) studied with imaging techniques revealed the following:
1. Entrance (Fig. 8.17a) and exit wound (Fig. 8.17c) in the skull could be differentiated in nearly all cases by imaging methods alone, by for example 3D reconstruction (Fig. 8.17b, d, e) of the internal and/or external surfaces of the skull. Involvement of the base of the skull, which happens for example if the gun is fired with the muzzle in the victim's mouth, was found.
2. Change in density of the trail of opaque bone and projectile fragments marks the direction of the missile track in CCT scans, or in 3D reconstructions of the skull's interior.
3. The patterning of skull fracture lines provides clues regarding bullet velocity or the muzzle-to-head distance.
4. The missile track itself can be traced along the distance from the entrance wound to the exit wound in axial/coronal CCT scans (Figs. 8.18, 8.20d), in 3D reconstructions, or by demonstrating the path of destruction through the parenchyma, both in situ prior to autopsy and in the isolated, formalin-fixed brain (Figs. 8.20d, 8.19). Special changes in the brain parenchyma are also important:
- Entry of air into the skull and the (secondary) collapse of the brain ventricles or the missile track and (possible) displacement of the brain depending on the position of the head at the time of wounding (Fig. 8.20a-d).
- Deformation of the brain as an artifact of formalin fixation.
5. Secondary changes, such as bleeding, air bubbles, edema (cf. Carey et al. 1990) and/or hypoxia or tissue destruction (Fig. 8.19d) can be demonstrated both in situ and in the isolated, formalin-fixed brain by MRI.
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