下肢有限元模型的建立及损伤机制重建

目的 建立完整的下肢有限元模型,探讨碾压及撞击情况下下肢的损伤机制,并利用此模型对一例真实交通事故中损伤下肢进行有限元分析.方法 基于交通事故受害者下肢完整的CT扫描图片,利用Mimics重建下肢长骨、髌骨、半月板、膝关节韧带以及软组织几何模型,利用结构化网格生成方法划分模型,并根据文献材料属性确定各部分的材料参数.通过长骨、大腿及小腿的三点弯曲模拟试验与文献试验结果对比验证模型的有效性.用轮胎模型分别以低、中、高的速度碾压大腿中段,及撞击大腿下段和股骨上段.通过碾压与撞击的模拟对比,得出下肢不同损伤的损伤机制,通过与真实交通事故中损伤下肢进行对比,分析验证该案例的损伤过程.结果 建立了一例完整的下肢有限元模型,主要以六面体网格进行单元划分.验证实验中,模型的接触力峰值,最大弯矩值以及弯矩曲线与文献报道的试验数据吻合.在轮胎碾压情况下,长骨可形成节段性骨折,股骨的骨折形态与案例中的骨折形态一致.结论 有限元模型及分析方法能应用于法医学损伤机制的分析与研究.     

人体损伤程度鉴定标准若干条文的理解与适用（第七讲骨盆与脊柱损伤）

1骨盆损伤的检验1.1活体检验损伤急性期进行鉴定时,应注意损伤部位有无肿胀、压痛、皮下淤血。表浅部位的骨折有时可及骨折断端。若耻骨联合明显分离时,可扪及间隙。骶髂关节脱位或髋关节骨折、脱位时,骨盆部或髋部可畸形,并可见关节活动受限,伤肢常缩短畸形。骨盆骨折者骨盆分离、挤压试验结果常呈阳性。会阴部瘀斑是耻骨、坐骨骨折的特有体征。尿道损伤时可存在急性尿潴留和尿道流血。骨盆损伤有时尚可累及膀胱、直肠、肛门、阴道、神经等,引起继发性损伤,有时可形成后腹膜血肿。     

人体胸廓骨骼三维有限元模型的构建及生物力学分析

目的建立完整的人体胸廓骨骼三维有限元模型,并探索力作用变化趋势。方法对尸体胸部进行多层螺旋CT(multislice computed tomography,MSCT)扫描,使用有限元建模软件根据CT图像数据对胸廓骨性结构进行三维重建并生成有限元模型,模拟胸廓右季肋部遭受速度为4、6与8m/s的钝性物体正面击打,分析胸廓受击打后的应力、应变分布情况。结果成功构建解剖学高仿真度的人体胸廓有限元模型,模型体网格平均质量0.7。生物力学分析结果显示胸廓受击打后发生局部弯曲及整体变形,应力与应变产生于初始打击部位肋骨,后沿肋骨向两侧传播,并于肋骨后侧及近胸骨处集中,6m/s与8m/s的打击速度可造成打击部位肋骨应变值超出相应强度极限,发生骨折。结论应用有限元建模分析软件能够建立符合真实情况的高质量的人体胸廓三维有限元模型,且模型可用于分析外力作用下胸廓骨性结构的应变趋势,为胸部损伤的致伤方式推断提供了新的途径和方法。     

膝关节损伤后MRI征象法医学分析48例

<正>磁共振成像(MRI)具有高度的软组织分辨率以及多平面成像和软骨、骨髓显示能力,能清晰地显示半月板、交叉韧带、关节软骨、骨膜、关节囊及内、外侧副韧带、骨骼和肌肉等解剖结构,在膝关节疾病诊断中具有独特优势。本文对48例膝关节损伤MRI征象及鉴定资料进行分析,希望为法医学鉴定提供     

基于数据挖掘算法的骨盆损伤判别模型

目的 利用主成分分析、偏最小二乘法对基于骨盆CT图像提取的特性信息进行降维,利用降维的数据建立判别骨盆是否受伤的支持向量机分类判别模型,评估其应用的可行性。方法 将采集的正常和受伤骨盆CT图像146例分别随机提取80%作为训练集,用于模型拟合;剩余20%作为测试集,用于模型准确性的检验。通过CT图像输入、图像预处理、特征提取、特征降维、特征选择、参数选择、模型建立和模型比较等步骤,建立骨盆是否受伤的判别模型。结果 偏最小二乘法降维方法优于主成分分析降维方法,支持向量机模型优于朴素贝叶斯模型。基于12个偏最小二乘因子建立的骨盆是否受伤支持向量机分类判别模型的建模集、留一法交叉验证和测试集结果准确率分别为100%、100%和93.33%。结论 基于CT图像建立的骨盆是否受伤数据挖掘模型在评估骨盆损伤中具有比较高的准确性,为骨盆损伤的自动快速识别奠定基础。     

有限元法在法医交通颅脑损伤中的应用

有限元法是一种基于计算机应用于医学领域的应力分析方法。通过建立颅脑有限元分析模型,可以很好地研究颅脑受力过程,在法医交通颅脑损伤的分析中显得愈加重要。本文将对近6年国内外在交通颅脑损伤方面有限元建模和分析方面的研究成果进行综述。     

MRI在膝关节损伤法医鉴定中应用25例

磁共振成像（magnetic resonance imaging,MRI）技术已广泛应用于临床诊断。其具有对比明显,层次分明的技术性能,对确诊膝关节韧带及关节软骨损伤等有明显优势。本文对25例膝关节损伤案例进行分析,并结合与X线、CT技术在实践中应用的比较,探讨MRI在膝关节损伤法医鉴定中的价值。1案例资料1.1病历资料25例关节损伤,男21例、女4例。所有案例均有明确的膝部外伤史,其中扭伤及跌伤15例,直接打击10例。     

基于MSCT和Mimics软件构建人体颅骨三维有限元模型

目的 建立人体颅骨的有限元三维模型,探索人体颅骨有限元模型在生物力学分析中的价值.方法 用MSCT对尸体头部扫描后.使用Mimics建模软件对CT二维图像进行三维重建,并对原始三维颅骨模型优化,然后对模型进行面网格和体网格划分,利用ANSYS有限元分析软件验证颅骨被物体打击和颅骨撞击地面的不同应力变化.结果 原始三维颅...     

有限元法研究高坠中躯干不同部位着地的肋骨骨折机制

目的利用有限元法研究躯干不同部位着地的肋骨损伤机制,对重建高坠过程提供新技术与新方法。方法采用有限元法观察全人类安全模型THUMS4.0在躯干部不同部位着地时的肋骨损伤情况,并与实际案例进行比较,从生物力学角度分析高坠导致的肋骨骨折形成机制。结果不同部位着地所形成的应力、应变分布及肋骨骨折部位存在一定差异。躯干前侧着地时双侧均发生肋骨骨折,骨折主要位于肋骨-肋软骨交界处和腋中线区域;躯干右前侧着地时,着地一侧首先发生肋骨骨折,骨折分布于右侧腋中线至腋后线区域以及双侧肋骨-肋软骨交界处;躯干后侧着地时,骨折主要位于双侧肋骨后侧;躯干右后侧着地时,着地部位易发生多发性肋骨骨折。塑性应变多集中于骨折处,von Mises应力除集中于骨折处,也可位于其他部位。结论躯干部不同部位着地时,肋骨骨折部位及损伤机制具有一定差异。     

骨盆后环不稳定伴骶丛损伤的法医学鉴定分析

交通伤所致的骨盆后环不稳定伴骶丛损伤,其早期临床诊断较为困难,原因在于伤者多合并头、胸、腹及下肢损伤,神经损伤的临床表现常被其他伤情所掩盖,到病情稳定后方才引起注意,临床上容易漏诊.由于骨盆后环不稳定伴骶丛损伤具有其特殊性,给法医鉴定带来了新的课题,应引起法医的高度重视.笔者对骨盆后环不稳定伴骶丛损伤案例的鉴定资料进行回顾性研究,并结合文献复习,现报告如下.     

Metric sex determination from the pelvis in modern Greeks

The ability to determine sex from unknown skeletal remains is vital, and methods to do this on the various bones of the human skeleton have been researched extensively. Many researchers have emphasized the need for population specific data for methods which are based on measurements, as there are vast differences in body size in various populations. The pelvis is known to be the most sexually dimorphic part of the human body, and no discriminant function formulae for this bone are available for Greek or other Mediterranean groups. The purpose of this study was therefore to develop discriminant functions which can be used for sex determination on measurements of the pelvis of modern Greeks. A sample of 97 male and 95 female pelves in a skeletal collection housed in Heraklion, Crete, was used. Measurements were taken from the articulated pelvis, single os coxae and the sacrum. Discriminant function formulae for all measurements and various combinations were used in order to assess the degree of sexual dimorphism in various parts of the pelvis, and to make the formulae usable on fragmented remains. For the single os coxae, average accuracies of 79.7-95.4% (79.1-93.5% on cross-validation) were found. However, it was found that measurements of the sciatic notch were unreliable and yielded poor results, and it is advisable that this characteristic must only be used as a last resort. Dimensions of the sacrum were not very dimorphic (average accuracy 60.9%), while measurements from the articulated pelvis yielded poorer results than that from single innominate bones. The diameter of the acetabulum was the single most dimorphic characteristic, providing on average 83.9% accuracy when used in isolation.     

骨骼CT三维重建图像性别判定和年龄推断研究

目的通过计算骨骼计算机断层扫描(Computed Tomography,CT)三维重建图像判定性别和推断年龄的准确率,评价利用骨骼CT三维重建图像判定性别和推断年龄的可行性。方法将法医人类学教材中性别判定和年龄推断的方法应用于539例骨骼CT三维重建图像样本,判定245例骨盆的性别,推断100例男性耻骨联合、100例男性胸骨和94例男性锁骨的年龄,计算准确率。结果骨盆性别判定准确率为98.4%,耻骨下角和坐骨大切迹是区分性别最好的两项指标。男性耻骨联合、胸骨、锁骨的年龄推断准确率在45%以上,其中锁骨双侧方程准确率最高为77%。结论利用骨骼CT三维重建图像判定性别和推断年龄具有可行性。使用大体标本建立的骨盆形态学性别判定方法可直接应用于骨骼CT三维重建图像。使用大体标本建立的男性耻骨联合、胸骨、锁骨形态学年龄推断指标、分级和评分标准以及方程需要修改和补充。     

3D Finite Element Model of Human Knee Injuries in the Traffic Accident

Objective To explore the injury mechanism of the human knee in a traffic accident by estab lishing a 3D finite element （FE） model. Methods The FE model, composed of femur, tibia, fibula, patel la, meniscus, knee ligaments and surrounding soft tissues, was reconstructed by CT scanning data from a male volunteer. Validation was performed by the lateral impact simulation, and the stress and strain re sults were obtained to be compared with those previously reported for injury prediction. Results The re suits derived from the FE model were found to be similar with those previously reported, most of the ligaments and meniscus wounded at 40 m/s collision, which was readily observed. Conclusion The simu lation results generated by FE model can be effectively used for the injury mechanism analysis of initial contact.     

Virtual determination of sex: metric and nonmetric traits of the adult pelvis from 3D computed tomography models

Examination of the adult os coxae and sacrum is one of the most common methods of sex estimation from bone. Medical imaging, such as computed tomography (CT), provides the opportunity for three-dimensional (3D) imaging of the skeleton from clinical scans of known individuals in situ. In this study, a randomly selected subset of abdominopelvic CT-derived models were used to evaluate simple, repeatable metric methods of sex estimation based on a combination of obstetric measurements and the traditionally nonmetric Phenice-derived traits. A four-variable discriminant function for sex estimation was developed based on statistical analyses. Overall, the cross-validated accuracy of this method was 100%, with inter-observer error showing an average of only 2.2%. Comparative analysis was run on the data set using FORDISC 3.0. This study shows that current sex determination standards from the pelvis should be updated to include more in vivo data to increase the accuracy of identification.     

Sex determination from os sacrum by postmortem CT

Sex determination in forensic practice is performed mostly on sexually dimorphic bones, including pelvic bones such as the os sacrum. Postmortem CT scan provides an easy and fast method for depicting and measuring bone structures prior to elaborate autopsy preparations. To develop a simple and objective method for sex determination in postmortem CT, metric data were evaluated from CT images of the pelvic-associated os sacrum of 95 corpses (49 men and 46 women) from the Canton of Bern, Switzerland. Discriminant function analysis of the data showed that the best accuracy in determining sex was 76.8% and 78.9% with two different observers. It is concluded that measuring the os sacrumin postmortem CT for sex determination has moderate accuracy and should only be applied in combination with other methods.     

Injury pattern in fatal automobile accident passengers due to rear-end collisions

The article reports on the injury pattern seen in fatally wounded car passengers after rear-end collisions on motorways. The study material included 5 rear-end collisions, in which 9 car occupants (5 drivers and 4 front-seat passengers) were killed. The change in velocity (delta v) was above 60 km/h in all the reported cases. The injury pattern showed the following characteristics: extensive soft-tissue traumatization (subcutaneous haematomas, blood-filled pockets, "décollements") not discernible from outside on the back of the trunk, mostly in the lumbosacral region; dorsal serial rib fractures, often combined with fractures of the spine (including the sacrum and the coccyx) and/or the pelvis; ruptures of the aorta at the typical sites of predisposition; ruptures of the liver and spleen (particularly at the visceral surfaces).     

重建耻骨联合三维结构用于活体年龄推断的技术方法

目的建立基于MRI成像的快速耻骨联合三维结构重建技术方法。方法利用3.0 T超导磁共振仪对成年男性志愿者骨盆进行T1小角度快速激发3D梯度回波序列扫描,进行二值化阈值分割、区域增长提取骨盆软组织图像;运算获得耻骨联合三维结构模型雏形,经逆向工程软件降噪处理建立耻骨联合三维结构模型,并与耻骨CT扫描三维结构重建模型进行比较。结果耻骨联合面沟嵴、下端、腹侧缘(斜面)、背侧缘(斜面)、耻骨结节等结构显示完整,无明显噪点,与CT扫描三维重建模型吻合较好。结论 MRI扫描成像可实现快速有效的耻骨联合三维结构重建,可为法医活体年龄推断提供安全无辐射作用的三维可视化影像学技术方法。     

Massive systemic fat embolism detected by postmortem imaging and biopsy*

Postmortem computed tomography (pmCT) and pmCT angiography (pmCTA) provide a minimally invasive method to determine the cause of death. Postmortem image-guided biopsy allows for precise sampling of histological specimens. This case study describes the findings of lethal systemic fat embolism (FE) on whole-body unenhanced pmCT, pmCTA, and image-guided biopsy, with autopsy and histopathologic correlation. Unenhanced pmCT revealed a distinct fat level on top of sedimented layers of corpuscular blood particles and serum in the arterial system and pulmonary trunk. Subsequent pmCTA showed reproducible results, and image-guided biopsy confirmed fatal FE. pm CT/pmCTA combined with image-guided biopsy established the cause of death as right heart failure as a result of systemic fatal FE prior to autopsy. All imaging findings were consistent with traditional autopsy and histological specimens. This unique case demonstrates new imaging findings in massive, fatal FE and highlights that postmortem imaging, supplemented by image-guided biopsy, may detect the cause of death prior to traditional autopsy.     

Whole body postmortem magnetic resonance angiography

Computed tomography (CT) and magnetic resonance (MR) imaging have become important elements of forensic radiology. Whereas the feasibility and potential of CT angiography have long been explored, postmortem MR angiography (PMMRA) has so far been neglected. We tested the feasibility of PMMRA on four adult human cadavers. Technical quality of PMMRA was assessed relative to postmortem CT angiography (PMCTA), separately for each body region. Intra-aortic contrast volumes were calculated on PMCTA and PMMRA with segmentation software. The results showed that technical quality of PMMRA images was equal to PMCTA in 4/4 cases for the head, the heart, and the chest, and in 3/4 cases for the abdomen, and the pelvis. There was a mean decrease in intra-aortic contrast volume from PMCTA to PMMRA of 46%. PMMRA is technically feasible and allows combining the soft tissue detail provided by MR and the information afforded by angiography.     

Post-mortem radiological CT identification based on classical ante-mortem X-ray examinations

Radiological identification is important in forensic medicine. Identification using comparison of individualising structures with ante- and post-mortem conventional radiographs has been known for a long time. New radiological procedures such as computed tomography (CT) and magnetic resonance imaging (MRI) are being increasingly used for identification. In this paper, a new comparative approach using various radiological methods is described and its application demonstrated. This new approach is the comparison of ante-mortem conventional radiographs with projected images calculated from post-mortem CT data. The identification procedure will be illustrated with reference to the frontal sinus and the pelvis.