Comparison of post-mortem metabolic changes in sheep brain tissue in isolated heads and whole animals using 1H-MR spectroscopy--preliminary results.

By means of in situ proton magnetic resonance spectroscopy ((1)H-MRS) time-dependent metabolic changes in brain are measured for the estimation of post-mortem intervals (PMIs). An isolated whole head and a whole young sheep from an abattoir with known time of death were stored at approximately 21°C, and localized (1)H-MRS (TR/TE 2,500/25 ms) of the brain was performed at various PMIs with a clinical 1.5 T whole-body scanner using a quadratur head coil. In the isolated head, additional metabolites including free trimethylammonium (fTMA), propionate, and butyrate, and especially acetate, could be detected as described in previous studies. In the head of the whole animal, especially fTMAs and lactate were found in the late PMI but no further metabolites of relevance. These preliminary findings support the hypothesis that in a whole-body corpse, the distribution of bacteria from the gastrointestinal tract up to the brain in the late post-mortem interval can influence the metabolic decomposition of brain tissues. In further studies, it should be kept in mind that an isolated head does not represent authentic circumstances and is, therefore, not an ideal model for brain decomposition in intact corpses.