应用死后肾脏CT值变化规律推断死亡时间

Estimation of the postmortem interval by the changes in the value of kidney CT scans

目的检测死后不同时间点新西兰兔肾脏CT值(单位:Hounsfield Unit,HU),获得其死后变化规律,建立死亡时间推断方程。方法采用健康成年新西兰兔10只,利用耳缘静脉空气栓塞法处死后放入20℃恒温箱内保存,在死后0~168h内,采取每隔12h进行一次CT扫描,检测肾脏CT值随时间的变化情况,采用回归分析方法确定肾脏CT值与PMI的关系。结果 PMI在0~168h之内,肾脏CT值随PMI的延长呈现先增加后下降的趋势,使用曲线拟合分析,x:肾脏整体CT值,单位为HU;y:PMI,单位为h,其中二次方程的拟合效果最好,拟合回归方程为:y=2266.973-93.180x+0.974x2(R2=0.758,P <0.001)。结论本研究表明,肾脏CT值随着死亡时间的逐渐延长存在明显的死后变化规律,PMCT测量肾脏整体CT值可作为法医学推断PMI的新方法之一,具有很好的应用前景,值得进一步研究。

Objective To detect the density in Hounsfield Unit(HU) of rabbit kidney computed tomography(CT) scans at different time after death, and establish an equation used to infer the time of death. Methods Ten healthy adult New Zealand rabbits were sacrificed by air embolization and stored in a 20℃ incubator. Within 168 h after death, CT scanning was performed every 12 h to detect the HU value of the kidney. Regression analysis was used to determine the relationship between the HU value of the kidney and PMI. Results Within 168 h of PMI, the HU value of kidney increased first and then decreased with the extension of PMI. Curve fitting analysis showed that quadratic equation had the best fitting capability. The fitting regression equation was: y=2266.973-93.180 x+0.974 x2(x: CT density of kidney in HU, y: PMI in hour, R2=0.758, P < 0.001). Conclusion This study indicated that the CT HU value of the kidney was obviously changed after death with the gradual extension of the time of death. Using postmortem CT to measure HU value of the kidney is a new method to estimate PMI, which has a good application prospect and is worthy of further study.