The application of the RA-index is easy. The score is calculated following examination of the seven sites using the radiological data. It is very important to note that the image analysis is performed dynamically on successive slices of the MDCT. For each site, the grade of gas present (0, I, II, or III) has to be defined, which is possible even for a forensic pathologist without experience in the interpretation of radiological data. For vessels, the quantification of gas includes examination of the entire length of the vessel. Once a grade is assigned for each defined site, the corresponding scores are summed up usint this interactive table; a site with no gas corresponds to a score of zero. Finally, the scores of each site are added, giving the RA-index. The RA-index is a useful tool for postmortem diagnosis of the presence of possibly vital gas on PMCT. The presence of gas grade III in the heart with an RA-index below 50 is a clear indication to proceed to further investigations (i.e., gas chromatography). Although, it should also be noted that an RA-index over 50 does not mean that a vital air embolism was not present before the development of postmortem gas. [1]
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