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

PurposePhosphor 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 methodsEight corpses, died of natural cause, were examined (5 males, 3 females; age: 73 ± 7 y, weight 65.8 ± 15.9 kg). A control group of 3 subjects (2 males, 1 female, mean age: 51 ± 24 y, range: 24–69 y, mean body weight: 84.0 ± 16.5 kg) was examined at a single time point as well. 31P MRS was performed on a 1.5 T MRI (TR 700 ms, TE 0.35 ms, averages 256, flip angle 90°). A standard 31P/1H heart/liver coil was employed (receiver coil diameter 12 cm). The 31P MRS scans were repeated in intervals of 1 h over a period from 4.5 to 24 h postmortem (p.m.). The core temperature was rectally measured throughout the MRI examination.ResultsThe 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.ConclusionThere 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.