Abstract: 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 Nacetylaspartateand(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=0.001 9 x2-0.803 x+1.449 8(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+1.177 7(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.

Key words: forensic pathology, postmortem interval, manneticresonance spectroscopy