[Estimation of postmortem interval with single-voxel proton 1H-MR spectroscopy at different temperature].

OBJECTIVE: To find an objective method for estimation of postmortem interval (PMI) with single-voxel proton MR spectroscopy at different temperature.
METHODS: Changes of metabolite peak area and peak area ratio of the N-acetylaspartate (Naa), choline (Cho) and total creatine (Cr) in the brain of 24 rabbit models were measured by 1H-MR spectroscopy (1H-MRS) at 0.5, 1, 2, 4, 6, 8, 12, 16 and 24 h, respectively after death.
RESULTS: Naa and Cr decreased continuously with the extension of PMI, and the ratios of Naa/Cr and Cho/Cr also decreased continuously with the extension of PMI within 24 h. The quadratic polynomial regression equation is y=0.0019x2-0.803x+1.4498 (R2=0.962) (Equation 1) with the Naa/Cr used as an independent variable, while the quadratic polynomial regression equation is y=-0.0024x2+0.926x+1.1777 (R2=0.986) (Equation 2) with the Cho/Cr used as an independent variable. The average deviations were about 2.10-37.90 min and 1.69-40.87 min, respectively if the PMI was estimated by Equation 1 and Equation 2, respectively.
CONCLUSION: Our study indicates that there is a strong correlation between Naa/Cr, Cho/Cr and PMI, which may be used for estimation of PMI at different temperature.