Combined radio-colour contrast in the examination of ballistic head models.

The conventional analysis of ballistic gelatine is performed by transillumination and scanning of 1-cm-thick slices. Previous research demonstrated the advantages of colour and radio contrast in gelatine for computed tomography (CT). The aim of this study was to determine whether this method could be applied to head models in order to facilitate their examination. Four head models of about 14 cm in diameter were prepared from two acryl hollow spheres and two polypropylene hollow spheres. Acryl paint was mixed with barium meal and sealed in a thin foil bag which was attached to the gelatine-filled sphere which was covered with about 3-mm-thick silicone. The head models were shot at using 9 mm × 19 expanding bullets from 4 m distance. The models were examined via multislice CT. The gelatine core was removed; the bullet track was photographed and cut into consecutive slices which were scanned optically. CT images were processed with Corel Photo-Paint. Optical and radiological images were analysed using the AxioVision software. The disruption of the gelatine within the head model was visualised by extensive distribution of paint up to the end of the finest cracks and fissures and along the whole bullet track. CT imaging with excellent radio contrast in the gelatine cracks caused by the temporary cavity allowed for multiplanar reconstruction. We conclude that the combination of colour contrast in gelatine with contrast material-enhanced CT facilitates accurate measurements in ballistic head models.