【作者】 肖坚；

【导师】 刘良；

【作者基本信息】 华中科技大学 ， 法医学， 2006， 博士

【摘要】 死亡时间(postmortem interval,PMI)推断是法医病理学科研和实践中主要问题之一,也是法医病理学研究的重点和难点。PMI推断是由诸多子系统有机结合的复杂、综合系统,各子系统既相互独立又相互联系,这给法医学实践中推断PMI带来极大困难。大多数情况下,综合利用尸斑、尸僵、体温等指标,基本可以得到有关早期PMI推断的可靠结果。但对于晚期PMI推断的研究,受尸体腐败的影响,常规的检测方法难以对尸体进行检测,无法建立相应的PMI推断方法。从上世纪70年代,法医学研究者已运用许多化学方法,对多种生物检材进行检测(如全血和血清、脑脊液、玻璃体液、骨骼肌、肝脏等),以改进有关PMI推断的精度和广度。对于处于晚期死亡时间内的尸体,特别是已发生腐败的尸体,如何建立一套客观的、重复性好、可定量分析的推断PMI的研究方法,一直是法医学研究亟待解决的难题。但到目前为止,对晚期PMI的推断国内外尚无公认的简易实用、准确可靠的推测方法。在自然条件下,尸体虽然受各种理化、生物因素的影响,各脏器组织结构在死亡后迅速自溶、腐败。但在大体上还可以在相当长的时间内保存。因此,利用处于晚期PMI段内尸体上残留的组织样本,是进行推断PMI研究的突破口。利用先进的手段对残存脏器样本,进行形态学及尸体化学观察,将是拓展PMI推断研究的有效方法。随着影像学技术手段的迅猛发展和成熟,计算机断层扫描(computed tomography,CT)、磁共振波谱检测(magnagi cresonance spectroscopy,MRS)等非介入性数字化检查手段,已可以对脏器进行形态及化学成分的定量分析。影像学检查手段技术具有快速、无创、客观、数据易保存的特点,目前已在法医病理尸检中运用。由于它有别于传统经典尸检方法,被称之为“虚拟尸检”(virtopsy,virtual autopsy)。通过本课题的研究发现,在法医病理学实践中虚拟尸检有其广阔的运用前景。它可以在不破坏尸体完整性的前提下,获取各种情况下尸体形态及尸体化学等相关的数字化信息。通过虚拟尸检,可以建立有关PMI推断研究的客观准确、简便实用、重复性好的的定量研究方法。并能有效的拓展PMI推断研究的精度和广度。本研究分为两个部分:在前期有关早期PMI推断研究的基础上,利用虚拟尸检技术(MRS,CT),对尸体腐败过程中的形态学变化和尸体化学变化进行检测。通过建立相关死亡动物模型,建立相关检测方法,分别进行高分辨率MRS及螺旋CT检测。第一部分研究:利用31P-MRS、1H-MRS,对空气栓塞致死大鼠模型的脑组织死亡代谢成分的变化进行检测,分析其中磷谱及氢谱中代谢成分的变化;探讨利用死亡后脑组织各种代谢成分的变化,进行PMI(特别是晚期PMI)推断的可行性。通过研究发现在磁共振波谱检测中,磷谱的变化主要在动物死亡24h以内,反映脑组织中能量代谢的变化;氢谱的检测可以持续到组织消失之前(本研究中只在死亡后0～240h内进行了研究),反映脑组织腐败过程中的代谢变化。本研究对死亡后脑组织氢谱检测所显示代谢物质的变化进行分析,并通过曲线优度拟合建立有关PMI推断的回归方程。本研究认为利用’H-MRS检测的虚拟尸检,对于推断晚期PMI具有重要意义。氢谱中显示的乳酸、丁酸等多种代谢产物均可进行晚期PMI推断研究。第二部分研究:在尸体化学研究的基础上,本研究利用普及率相当高的螺旋CT,对大型动物新西兰白兔死亡后的变化进行虚拟尸检检测。通过基于螺旋CT检测的虚拟尸检,探讨利用死亡后尸体组织脏器形态学变化进行推断PMI的研究方法。通过对空气栓塞致死新西兰白兔死亡后到白骨化全程进行监测的研究发现,在动物死亡后有多个脏器变化的数据可以用来推断PMI,特别是晚期PMI。建立相应的回归方程可能准确进行PMI推断。通过高分辨率MRS及螺旋CT的检测,本研究认为利用基于MRS检测、螺旋CT检测的虚拟尸检技术,进行PMI推断是可行的。本研究中取得的研究成果,可以为在大型动物及人尸体上进行相关研究,提供实验基础和理论依据;并为今后的虚拟尸检研究指示研究方向,为构建有关PMI推断综合系统进行了有益的探索。本研究的创新之处:1)首次将基于影像学检查的虚拟尸检技术,带进有关PMI推断的研究领域。利用MRS、螺旋CT从尸体化学及组织脏器形态学变化进行研究,全面探讨虚拟尸检技术在PMI推断研究中运用。目前国外学者已开展虚拟尸检的检测,但相关研究多限于个案的报道,没有有关PMI推断的系统研究。2)本研究首次将高分辨率MRS检测引入法医学研究中,对利用磁共振波谱检测结果,进行PMI推断进行了有益的探索。并对死亡后脑组织中代谢成分进行定量研究,为今后展开利用临床磁共振仪进行虚拟尸检研究指示研究方向,并为其提供了相应实验基础和理论依据。3)本研究将螺旋CT扫描及相关重建技术引入法医学研究中,构建利用螺旋CT检测结果,进行PMI推断做了有益的探索。利用螺旋CT获取的死后重要脏器的面积变化、CT值变化及重建图像,构建相应回归方程进行PMI推断的研究,为今后展开利用螺旋CT在人尸体上进行虚拟尸检研究,指示了研究方向,并提供了相应实验基础和理论依据。本研究受教育部博士点基金(基于磁共振波谱的死亡时间推断研究,编号:20040487049,2004年)资助。已在专业期刊上发表相关文章5篇,已接受待发表论文3篇。第一部分基于磁共振波谱检测推断死亡时间的实验研究实验一适用于磁共振波谱检测的死亡动物模型构建目的建立重要脏器无机械性损伤、致死因素单一且量化、无药物影响的大鼠死亡模型。方法通过在10秒钟内向大鼠尾静脉注入2ml空气,造成大鼠空气栓塞死亡模型。结果本模型建立的重要影响因素为注入空气的体积和速率。其操作方法简单、建模成功率100%,可确切造成各体重组大鼠的迅速死亡,且无重要脏器的机械性损伤。结论此动物模型,各脏器及组织中不含外源性药物成分,不会对磁共振波谱检测结果造成干扰。为进行基于磁共振波谱检测的虚拟尸检进行PMI推断研究的开展,提供了理想的动物死亡模型。实验二31P MRS、1H-MRS检测脑组织死后变化推断死亡时间的实验研究目的利用31P-MRS、1H-MRS检测脑组织死后代谢成分变化,探讨利用磁共振波谱检测结果,进行PMI推断的研究方法。方法通过空气栓塞处死成年大鼠;于动物死亡后0-240h内,摘取不同死亡时间组大鼠的全部脑组织,迅速置于液氮速冻;脑组织充分粉碎碾均后,每只动物称取1g脑组织粉末,制备高氯酸提取物;所得冻干粉溶于D20,分别用DSS和H3P04作为内标和外标,进行1H和31P磁共振波谱(MRS)检测和定量分析。结果脑组织高氯酸提取物的磁共振波谱分辨率良好,31P-MRS在死亡后的变化主要集中在死亡后24h以内;利用Pi、磷酸单脂的结果,可以进行死亡后24h内的PMI推断;其它物质如ATP、PCr、ADP等代谢物质变化迅速,只适合在0-12h内进行PMI推断的研究。1H-MRS检测结果显示,动物死亡后脑组织中多种代谢成分呈规律性变化。包括N-乙酰天冬氨酸(Naa)、肌酸(Cr)、乳酸(Lac)等的消失;丁酸(But)、异丁酸(iBut)、游离三甲基铵(fTMA)等的产生。Naa、Cr等物质,在动物死亡后初期即快速下降。Lac、Asp等代谢物质先上升再下降。But、iBut、fTMA、Ace等新生物质,出现后含量持续上升。大鼠死亡后60h是脑组织中多种新生代谢物质出现,及脑组织中原有化学物质接近消失的重要时间点。在动物死亡后,脑组织代谢过程中出现的But、iBut、fTMA、Ace等新生物质,及脑组织中Naa、Cho、Cr、Lac等消失的原有化学物质,对于推断PMI,特别是晚期PMI有重要意义;它们与死亡时间之间存在密切关系。结论利用磁共振波谱,可以准确监测大鼠死亡后脑组织代谢成分的变化。死后大鼠脑组织磷谱的检测主要用早期PMI推断。死后大鼠脑组织氢谱检测具有重要法医学意义,利用脑组织中产生和消失代谢物质,进行推断PMI的研究,可极大的拓展有关PMI推断研究的时间区段。在氢谱检测中死亡后60h是死亡大鼠脑组织代谢过程中的重要时间点,它预示着脑组织进入快速腐败阶段。死后大鼠脑组织代谢过程中产生的新生物质,及消失的化学成分是进行PMI推断(特别是晚期PMI)的有效指标。利用基于磁共振波谱检测的虚拟尸检技术,进行PMI推断研究有其广阔的运用前景和重要的法医学意义。第二部分基于螺旋CT的虚拟尸检推断死亡时间的实验研究实验一基于螺旋CT检测脑组织死后变化推断死亡时间的实验研究目的利用基于螺旋CT的虚拟尸检技术,动态观察空气栓塞致死新西兰白兔颅脑的数字化信息,建立通过脑组织CT值、脑组织/颅腔面积比变化推断PMI的方法。方法通过耳缘静脉注射空气,建立新西兰白兔死亡模型;于死亡后0～120h,运用CT进行头颅平描;选取颅顶层面测定脑组织CT值、脑组织/颅腔面积比。结果死亡后兔脑组织CT值呈双峰样上升、脑组织/颅腔面积比呈不断下降趋势;建立与死亡时间的回归方程:CT值=47.4780-0.1768T+0.0049T2(T/h,CT value/HU)、面积比=99.7368+0.3098T-0.01 18T2/100(T/h)。结论CT扫描检查可准确显示兔脑的死后变化;脑组织消失之前,综合运用CT检查指标可用于准确PMI推断。实验二基于螺旋CT检测腹腔死后变化推断死亡时间的实验研究目的利用基于螺旋CT的虚拟尸检技术,采集空气栓塞致死新西兰白兔腹腔的数字化信息,建立通过新西兰白兔死亡后腹腔/椎骨面积比的变化推断PMI的新方法方法建立新西兰白兔空气栓塞死亡模型;动物死亡后0～240小时间,运用螺旋CT进行全身扫描;选取第四腰椎(L4)层面图像进行分析。计算L4层面上腹腔/椎骨面积比。结果动物死亡到腹壁破溃前,CT检查L4层面图像中腹腔含气量面积不断增加。腹腔/椎骨面积比不断增大,直至PMI=108h。在PMI=120h,腹壁破溃。此后,腹腔/椎骨面积比总体趋势是减小但波动较大。起初由于腹腔中腐败气体溢出,腹腔/椎骨面积比减小;在PMI=144h时,腹腔/椎骨面积比又有所增加;此后腹腔/椎骨面积比不断减小,直至实验结束。利用面积比推断腹壁破溃之前PMI的回归方程为:面积比(腹腔/椎骨)=19.758+0.1951T+0.0012T2(T/h, R2=0.993F=482.42,PMI=0-108h)结论利用基于CT检查的虚拟尸检获取L4层面图像可以准确反映新西兰白兔死亡后腹腔的变化。利用腹腔/椎骨面积比可用于腹壁破溃前PMI推断的研究。关键词:法医病理;法医放射;兔;腹腔;CT;死亡时间;虚拟尸检实验三基于螺旋CT检测肝脏死后变化推断死亡时间的实验研究目的利用基于螺旋CT的虚拟尸检技术,采集的空气栓塞致死新西兰白兔肝脏的数字化信息,建立肝脏CT值及肝脏面积进行PMI的新方法。方法通过耳缘静脉注射空气,建立新西兰白兔空气栓塞死亡模型;动物死亡不同时间点(0,12,24,36,48,60,72,84,96,108,120,132,144,156,168,180,192,204,216,228,240h),运用螺旋CT进行全身扫描;利用第一腰椎(L1)层面CT图像,对肝脏死亡后CT值、肝脏/椎骨面积比进行计算,并与PMI进行曲线拟合建立相关回归方程。结果基于螺旋CT的虚拟尸检发现,肝脏最先发生CT值的变化,并随着PMI延长CT值逐渐下降;在PMI=108h到达最低值。此后CT略有上升后再次下降。在PMI=180h,CT已无法进行CT值的检测。肝脏死后肝脏/椎骨面积比,在动物死亡后最初0-48h变化不大。在PMI=48h以后,面积比迅速下降。在PMI=132h,CT图像上显示肝脏的面积有轻微增加,而后又开始下降。在PMI=180h,肝脏消失。利用CT值、面积比与PMI建立优化回归方程分别为:肝脏CT值=100.773-1.6026T+0.0018T2(CT值/HU,T/h,F=41.18,R2=0.882),肝脏/椎骨面积比=18.9310-0.1 181T+0.0002T2(T/h,R2=0.894, F=50.68)。在研究过程中,在CT图像上发现肝脏腐败过程中出现的重要征象——肝内胆管充气征。它在PMI=48h的肝脏CT图像上出现,它出现后肝脏面积迅速减小。当肝脏实质中出现腐败气体后,此征象逐渐消失。结论基于螺旋CT的虚拟尸检,可以全面采集肝脏死后变化的相关信息;肝脏的CT值、肝脏/椎骨面积比可以准确推断PMI;这两指标极大地拓展了晚期PMI推断的研究时间区间。基于螺旋CT的虚拟尸检技术,采集尸体信息进行PMI推断研究,具有传统经典尸检无法比拟的优势。肝脏死后肝脏/椎骨面积比,能准确反映脏动物死亡后肝脏体积的变化规律。肝脏CT图像上出现的肝内胆管充气征,对预示肝脏进入快速腐败阶段具有重要法医学意义。更多还原

【Abstract】 Postmortem interval （PMI） estimation is one of the most important and most difficult tasks in the practice and scientific research of forensic pathology. PMI estimation might be a complex system, which must be based on many independent and relative sub-systems. In most early PMI cases, the common indicators such as rigor mortis, livor mortis, and the body’s core temperature would achieve acceptable results. But in late PMI cases, the general pathologic method doesn’t work because of autolysis and putrefaction. So it’s a very difficult task of estimation PMI especially in late PMI. Since 1970s various chemical methods have been developed in order to ameliorate and extend PMI estimation, e.g., using blood and serum, cerebrospinal fluid, vireous humor, skeletal muscle and liver. By now, there aren’t convenient, practical, objective, feasible, quantitative, credible and acceptable methods in late PMI estimation.Under natural condition, all kinds of physical, chemical and biological factors would impact body. Organs would autolysis and putrefy; the volume of them would decrease. But postmortem organs would keep a long time during putrefaction. Many metabolic change and morphologic change would happen in organs. Using traditional methods such as pathologic section examinaction could not be effective. But rudimentary organ samples would be effective to estimate PMI. And detected their metabolic changes and morphologic changes by modern detective methods, the rudimentary organ samples would become the breakthrough point of estimation late PMI and could extend the research time span of estimation late PMI.With the radiology’s development, magnetic resonance spectroscopy （MRS）, and computed tomography （CT） could be used to exminate morphologic change and the metabolic change in all kinds of organs. The radiologic digital methods could be used to apply quantitative and qualitative analysis. Because they are non-invasive, rapid, objective, and its data were stored and copied easily. Virtopsy （virtual autopsy） based on CT and MRS has been used in forensic examination. Overseas scholars had used the virtopsy technology to definite individuals. But virtopsy is a new research fields, there was no reports on estimation PMI. We planed to use virtopsy based on MRS and spiral CT to perform the study of estimation PMI especially late PMI.The study was divided into two parts, including virtopsy based on high-resolution magnetic resonance spectroscopy and spiral CT. High-resolution MRS was used to detect body’s postmortem metabolic changes, and spiral CT was used to analyze body’s postmortem morphologic changes. During the study, animal death model and detective methods were established, and the results were used to establish mathematic models to estimate PMI.The study of part one: we used high-resolution ³¹P-MRS、¹H-MRS to detect the postmortem metabolic changes in rat death model. The proton spectrum and phosphate spectrum of brain postmortem metabolites were analyzed. The feasibility of PMI estimation （especially in late PMI） was explored by using metabolites postmortem changes. The results showed that phosphate spectrum’s change was during early PMI （≦ 24h）; the spectrum mostly reflected the energy change during postmortem change. And its results could be used to estimate early PMI. Proton spectrum’s change was during the whole study period （0～240h）, which reflected the whole body’s putrefaction process. There were many metabolites disappeared, e.g., Naa, lactate, etc. and there were many metabolites appeared, e.g. fTMA, butyrate, iso-butyrate, etc. By regressive analysis and curve fitting, the equation of them could be used to estimate PMI （especially late PMI）. The detective of ¹H-MRS was more important than that of ³¹P-MRS in the research of late PMI estimation. The disappeared and new appeared metabolites could be used to estimate PMI and could ameliorate and extend PMI estimation.The study of part two: the virtopsy was performed based on spiral computed tomography by using New Zealand rabbit death model. In this part, the postmortem morphologic digital data were used to establish the method of estimation PMI（especially late PMI）,e.g. CT value, the area of organs, reconstruction images etc. The postmortem morphologic changes were detected by virtopsy based on spiral CT form the beginning of death to sleletonized remains. The results showed that many vital organs could be used to estimate PMI, such as brain, liver, celiac cavity and so on. The regressive equations were established by the organs’ CT value and area, which could be used to estimate PMI （especially late PMI）.According to the results of high-resolution MRS and spiral CT, the feasibility of virtopsy based on MRS and spiral CT was confirmed. The preliminary archievement of virtopsy would become the experiment and theory base of other bigger animals and human bodys’ virtopsy. It also could indicate virtopsy research’s direction, and make a helpful explorement of establising complicate system on estimation PMI.The innovations of the study were as following. 1) the results of virtopsy based on radiologic methods was firstly used to estimate PMI. High-resolution ³¹P-MRS、¹H-MRS and spiral CT were used in the study to detect the morphologic and metabolic chemical postmortem changes. There were no reports on systemic research of estimation PMI by using virtospsy, expect for individual cases reports. 2) The high-resolution MRS was put into the research of forensic research by which we explore to establish the detective method of postmortem metabolites. By quantitative analysis of the metabolites postmortem change, the regressive equations were established and could be used to estimate PMI. The study would indicate the direction of the virtopsy forensic research; and it could become the base of experiment and theory of virtopsy based on clinical MR. 3) The spiral CT scan and reconstruction were put into forensic research, which became a helpful exploration of virtopsy based on spiral CT scan. The CT value, organs’ area and reconstructive images of brain, liver, celiac cavity etc could be used to estimate PMI especially late PMI. The results indicated the research direction of PMI estimation and would become the base of experiment and theory in human body by virtopsy based on spiral CT scan.The study was fund by Deparment of education doctor’s fund （the study of estimation PMI based on magnetic spectroscopy, serial number:20040487049, 2004） . The five articles were published on relative issues.Part OneAn Experimental Study of Applying Magnetic Resonance Spectroscopy to Estimate Postmortem IntervalExperiment IEstablishing the Rat Death Model Fit for Magnetic ResonanceSpectroscopy Detective Objective To establish the rat death model in which there was quantitative cause of death without vital organs’ mechanical injury and exogenous drugs’ interference. The model could be fit for MRS detect（magnetic resonance spectroscopy）. Methods The lateral tail veins were exposed, and the volume of 2 ml air was infused into them within 10 seconds to establish the rat death model of air embolism. Results The quantity of insufflated air and the velocity of infusion played a crucial role in the experiment. The procedure was simple and very successful （with success rate of 100%）, caused different weight group rats’ rapid death reliably and there were no mechanical injuries of vital organs. Conclusion The study could provide an ideal animal death model for the study of applying MRS to estimate PMI. Experiment IIAn Experimental Study of Applying ³¹P-MRS, ¹MRS to Detect Rat Brain Postmortem Change to Estimate Postmortem IntervalObjective To evaluate of ³¹P-MRS, ¹H-MRS postmortem metabolites changes in rat brain, use the results of MRS to explore the new methods of postmortem interval （PMI） estimation. Methods: the rat death model was made by air embolism. During 0～240h after death, the rats’ whole brain was picked out and put into liquid nitrogen to deepfreeze. The frozen brain was grinded into tissue powder. The perchloric acid extract was made by using 1g brain tissue powder and lyophilized. The lyophilized powder dissolved in D₂O. Using DSS/H₃PO₄ as internal/external standard, the extract was detected by ³¹P-MRS, ¹H-MRS respectively. The metabolites’ peaks were integrated; the relative values were used to estimation postmortem interval. Results: High-resolution MRS detective of postmortem brain tissue was achieved perfectly. ³¹P-MRS revealed ATP, ADP, phosphocreatine, inorganic orthophosphate, manifold aliphatic phosphates and sugar phosphates; the spectrum change of ³¹P-MRS was during 24h after death. The relative values of inorganic orthophosphate and phosphomonoeste could be used to estimate PMI within 24h. Other substances such as ATP, ADP, and PCr etc changed more rapidly; they could be used to estimate PMI during 0～12h. ¹H-MRS showed many resonance peaks, including lactate, N-acetylaspartate, choline, creatine, GABA, myo-inositol, succinate, acetate, butyrate, free trimethylammonium, iso-butyrate and other metabolic substances. During early postmortem interval, Naa and Cr decreased rapidly. After PMI=60h, But, iBut, fTMA appeared in the spectrum. They and Ace increased continuously till to the end of the research. During the whole research period, Lac、Asp went up then decreased till disappeared. The results showed that it was the important time point of PMI=60h, there were many new metabolic substances appeared and original substances in the brain would disappear mostly. For estimation PMI, there were significance of the new metabolic substances such as But、iBut、fTMA、Ace and of the original substances in brain such as Naa、Cho、Cr、Lac. There were closely relation between them and PMI. Conclusions High-resolution MRS could be used to detect the postmortem change of rat brain. The ³¹P-MRS result of rat brain could be used to estimate early PMI（≦24h）. The ¹H-MRS result could be used to estimate PMI especially late PMI; it had more important forensic significance than that of ³¹P-MRS; it could ameliorate and extend the span of estimation PMI. It was an important time point at PMI=60h, which suggested that brain would go into rapid putrefaction period. The appeared and disappeared metabolites were effective index to be used estimate PMI especially in late PMI. There were wide application prospects and important forensic significance of applying virtopsy based on magnetic resonance spectroscopy to estimate PMI. Part twoAn Experimental Study of Virtopsy to Estimate Postmortem Interval Based on Spiral CTExperiment IAn Experimental Study of Applying New Zealand WhiteRabbit’s Brain Postmortem Change Detected by Spiral CTto Estimate Postmortem IntervalObjective Investigate the postmortem changes of New Zealand white rabbit’s brain by spiral CT scan, and establish effective methods of estimating PMI by using brain CT value and the area rate of brain /cranial cavity. Methods The rabbit’s death model was established by venous air embolism. Virtopsy based on spiral CT scan was performed to investigate the brains’ postmortem change after death 0～120h. Results The values of brain tissue increased, the rate of brain area/cranial area decreased after death. The regression equations: CT value=47.4780-0.1768T+0.0049T² （ T/h , CT value/HU）、area rate =99.7368+0.3098T-0.0118T²/100（T/h）. Conclusion CT scan could show brain postmortem changes, the CT value and area rate were effective index to estimate PMI before brain disappearance. Experiment IIAn Experimental Study of Applying New Zealand WhiteRabbit’s Celiac Cavity Postmortem Change Detected by SpiralCT to Estimate Postmortem Interval Objective Investigate the postmortem changes of New Zealand white rabbit’s celiac cavity by virtopsy badsed on spiral CT scan, and establish effective methods of estimating PMI by using the area rate of celiac cavity /vertebra. Methods Virtopsy based on spiral CT scan was performed on rabbit’s death model to investigate the celiac cavity’s postmortem change after death 0～240h. The slice image of lumbar 4（L4） was chosen to analyze the postmortem changes of the area rate of celiac cavity/vertebra. Results the L4 image of CT scan showed that the volume of gas increased in the celiac cavity from the beginning of death to the abdomen wall’s perforation. The area rate of celiac cavity /vertebra increased continuously from Oh to 108h after death. At PMI=120h, the abdomen wall perforated and putrefaction gas went out, the rate decreased greatly. But At PMI=144h, the rate went up a little then went down. Before abdomen wall perforation （PMI=0～108h）, the regression equation: of the area rate could be used to estimate PMI. （the area rate=19.758+0.1951T+0.0012T²,T/h , R²=0.993 F=482.42, PMI=0～108h） Conclusions the image of L4 could reflect the New Zealand white rabbit’s celiac cavity postmortem change, obtained by virtopsy （spiral CT scan）. The area rate of celiac cavitya/vertebra （L4） could be used to estimate PMI during 0～108h. Experiment IIIAn Experimental Study of Applying New Zealand White Rabbit’s Liver Postmortem Change Detected by Spiral CTto Estimate Postmortem IntervalObjective Investigate the postmortem changes of New Zealand white rabbit’s liver by virtopsy based on spiral CT, and establish effective methods of estimating PMI by using liver CT value and the area rate of liver /vertebra. Methods Virtopsy based on spiral CT was performed on rabbit’s deathmodel to investigate the liver’s postmortem change after death 0²40h. The sliceimage of lumbar 1（L1） was chosen to analyze the postmortem changes of liver’sCT values and the rate area of liver/vertebra （L1）. CT value-PMI and arearate-PMI characteristic curve were fitted on detected data, the best regressionequations were established to estimate PMI. Results the results of virtopsy basedon spiral CT showed that liver’s CT value changed firstly during putrefaction.During the whole experiment, the liver’s CT values decreased continuously; andat PMI=108, the CT value reach the lowest point. The value increased a little,and then the value went down till it could not be detected by CT at PMI=180h.The area rate of liver /vertebra didn’t changed during 0～48h. After PMI=48h, therate of area deceased continuously; but at PMI=132h, the rate went up a littleand then went down till liver disappeared at PMI=180h. Regression equationswere established between CT value, the area rate and PMI: liver’s CTvalue=100.773-1.6026T+0.0018T²（CTvalue/HU, T/h, F=41.18, R²=0.882） ,the area rate of liver/ vertebra（L1）=18.9310-0.1181T+0.0002T²（T/h, F=50.68,R²=0.894, ）. An important CT sign （intra-hepatic bile duct dilation filled with air）was found at PMI=48h. After the sign appeared, the livers’ area decreasedgreatly. When the putrefaction gas appeared in the liver, the sign disappearedgradually. Conclusions virtopsy based on spiral CT could obtain all informationof liver’s postmortem changes. The liver’s CT value and the area rate ofliver/vertebra （L1） could be used to estimate PMI and the research span ofestimation PMI was extended. The CT sign（intra-hepatic bile duct dilation fillwith air） would be important significance for suggesting liver’s rapidputrefaction’s beginning. Virtopsy based on spiral CT could be morecomprehensive than traditional autopsy.更多还原