Postmortem ³¹P magnetic resonance spectroscopy of the skeletal muscle: α-ATP/Pi ratio as a forensic tool?

Purpose: Phosphor magnetic resonance spectroscopy (³¹P MRS) is an established method for metabolic examinations of resting and exercising skeletal muscle. So far, there are few MRS investigations of human corpses. The aim of this study was to investigate the temporal postmortem pattern of phosphor metabolites in the adductor magnus muscle and to check the value of MRS as a forensic tool, especially for the determination of the time of death. Material and methods: Eight corpses, died of natural cause, were examined (5 males, 3 females; age: 73±7y, weight 65.8±15.9kg). A control group of 3 subjects (2 males, 1 female, mean age: 51±24y, range: 24-69y, mean body weight: 84.0±16.5kg) was examined at a single time point as well. ³¹P MRS was performed on a 1.5T MRI (TR 700ms, TE 0.35ms, averages 256, flip angle 90°). A standard ³¹P/¹H heart/liver coil was employed (receiver coil diameter 12cm). The ³¹P MRS scans were repeated in intervals of 1h over a period from 4.5 to 24h postmortem (p.m.). The core temperature was rectally measured throughout the MRI examination. Results: The mean core temperature decreased from 36.0. °C to 25.7. °C. In vivo and ex vivo spectra showed characteristic differences, especially the PCr metabolite was no longer detectable after 10. h p.m. The α-ATP/Pi ratio decreased with time from 0.445 to 0.032 over 24. h p.m. Conclusion: There is a characteristic postmortem time pattern of the phosphor metabolites. Especially the acquired α-ATP/Pi ratio could be described by a significant exponential time course (r²=0.92, p<0.001). ³¹P MRS might be added to the postmortem imaging methods.