骨质疏松股骨三维有限元模型的建立

背景:通常的力学实验手法基本上无法直接应用于人体且模型间可比性低,对人体的力学行为进行有限元数值模拟就成为深化对人体认识的一种有效手段。目的:建立骨质疏松股骨三维有限元模型。方法:根据国人股骨平均参数,选择重度骨质疏松老年男性患者1例,年龄86岁,排除髋关节疾患。通过螺旋CT扫描获得骨质疏松股骨图像数据,将图像数据导入图像处理软件Mimics11.1进行图像处理,生成股骨骨皮质内、外表面的轮廓曲线;再将轮廓曲线数据导入建模软件Unigraphic NX4.0进行实体建模,得到具有骨皮质、骨松质、骨髓腔的股骨三维模型;将三维模型数据导入有限元分析软件Ansys11.0进行赋值、网格划分、定义接触等操作建立骨质疏松股骨三维有限元模型。结果与结论:建立了骨质疏松股骨三维有限元模型,为骨质疏松股骨限元模型的建立提供了切实可靠的方法,为研究骨质疏松股骨骨折的固定方法、关节置换等创造了条件。     

髋关节外展角度对股骨颈应力分布的影响

关节应力分布与外展角度关系密切,研究二者内在联系可为临床关节损伤的预防、治疗提供力学依据。本研究应用逆向工程软件Mimics14.0,基于正常人体髋关节CT图像数据,经一系列处理,建立髋关节三维模型;再划分网格,赋材质,生成三维有限元模型;再导入有限元分析软件Ansys13.0,加载体重负荷,求解、计算正立位与髋关节外展5°、10°、15°、20°、25°、30°等7个体位下股骨颈的应力值,并统计分析。结果表明:正立位或外展某一不同角度下,股骨颈内、外侧区域的应力值均高于前、后方区域;随外展角度的增加,股骨颈前方区域应力值基本不变,后方区域应力值逐渐减小,内、外侧区域的应力值逐渐增大,外侧区域变化较明显。股骨颈应力大部分集中于内、外侧皮质,髋关节外展可导致应力分布发生变化,为髋关节损伤患者选取合理的手术方案及预防举措具有指导作用。     

CroweⅣ型髋关节发育不良骨盆有限元模型的构建

背景:骨骼生物力学数字有限元分析方法,因其有限元模型作为虚拟标本可重复使用而不被破坏,可以降低实验成本。目的:探索一种利用三维有限元软件快速建立骨盆三维有限元模型的方法,并对发育性髋关节脱位患者假髋臼周围的受力情况进行初步分析。方法:采用发育性髋关节脱位患者的骨盆CT数据,在Mimics10.0软件中进行三维重建面网格划分,在Ansys10.0软件中进行体网格划分后导入Mimics10.0中赋予材料属性,从而建立发育性髋关节脱位患者的双髋臼半骨盆有限元模型。在Ansys10.0中,模拟患者患侧单下肢站立的情况对假臼关节面施加静力载荷,对该模型进行初步的力学分析及验证。结果与结论:基于DICOM格式CT数据建立了发育性髋关节脱位患者的双髋臼半骨盆三维有限元模型,模型精确可用,包括147167个节点,113898个单元,假臼位置与骶髂关节的关节面相对。患侧单下肢站立的情况下,骨盆应力主要集中在假髋臼和骶髂关节面之间的骨质。利用Mimics及Ansys软件可简单有效地建立骨盆的有限元模型,此建模过程同样适用于人体其他骨骼有限元模型的建立。利用有限元模型可以方便有效的模拟人体骨骼生理及病理状态下的受力情况,对于临床提供参考和指导。     

采用体绘制方法建立人股骨三维有限元模型及其应力分析

背景：目前股骨三维有限元研究建模方法有多种,而采用体绘制分体建模方法还未曾报道过。 目的：采用体绘制方法建立股骨三维有限元实体模型,对所建实体模型模拟力学载荷得出股骨应力分布,并与既往股骨力学实验比较,评估体绘制方法的可行性。 方法：将CT扫描图像去噪等预处理后,采用体绘制技术,利用Mimics和Ansys软件建立人股骨有限元模型,并在Mimics软件中赋予股骨材质,并模拟人体正常站立位时股骨载荷情况。 结果与结论：采用体绘制方法建立的人股骨三维有限元模型,包括皮质骨、松质骨及髓腔解剖结构,网格化后共生成63 900个节点,43 552个实体单元;模拟载荷显示股骨压应力区域主要集中在股骨内侧、尤其是股骨距部位,张应力主要集中于股骨颈外侧、股骨干外侧。表明体绘制方法可以建立高仿真、接近股骨解剖结构股骨三维有限元模型实体模型,可以探索股骨的内部结构,展现其内部细节,模拟股骨生物力学分布。关键词：体绘制;股骨;实体模型;有限元;力学分布 doi:10.3969/j.issn.1673-8225.2012.17.003     

表面髋关节置换三维有限元模型的建立及意义

背景:目前髋关节的三维有限元模型大都是基于人体尸骨数据或通过CAD重建获得的,其效果不够理想。目的:通过64排螺旋CT扫描提供数据,建立表面髋关节置换的三维有限元模型,拟为生物力学实验提供标准数学模型。方法:选择1名行表面髋关节置换后的成年男性志愿者,经X射线检查排除健侧髋关节疾患。螺旋CT扫描表面髋关节置换后患者所得数据导入Mimics软件。采用域值法建立三维立体模型,之后导入Abaqus软件,进行网格划分。建立起表面髋关节置换术后的三维有限元模型。结果与结论:建立了表面髋关节置换术后三维几何和有限元模型。表面髋关节置换模型分为三维六面体单元165886个,节点213343个。可见,通过Mimics软件、Abaqus软件可以利用表面髋关节置换术后患者薄层断面图像构建出其三维几何模型与三维有限元模型。该模型具有较高的形态学及力学仿真度。     

股骨头坏死有限元模型的建立

背景：股骨头坏死有限元分析法已经被许多研究者应用,但作为分析的数字模型还存在几何以及物理相似性不够等不足。 目的：借助股骨头坏死患者的CT扫描图片建立更加逼真的股骨头坏死有限元模型。 方法：将以各向同性扫描所得的层厚0.625 mm股骨头坏死髋关节连续断层142层Dicom格式CT图像,直接读入Mimics后界定骨组织阈值、提取各层面轮廓线、图像边缘分割、选择性编辑及补洞处理,去除冗余数据,三维化处理后获得股骨头坏死三维几何面网格模型,将其保存为后缀名.lis的Ansys文件,直接导入Ansys有限元分析软件进行体网格划分,再将体网格转入Mimics根据CT值给予赋值,再次导入Ansys 生成有限元模型。 结果与结论：快捷建立了外形逼真、计算精确的股骨头坏死三维有限元模型。提示应用精细CT扫描技术,Mimics软件根据CT值直接赋值使股骨头坏死三维有限元模型的建立更加快捷、精确。     

基于Composite Femur三维有限元股骨模型的建立及实验验证

背景:随着计算机技术的发展,三维有限元分析越来越多地应用于骨骼生物力学的研究,股骨作为人体最大最粗的长骨具有典型生理意义,其生物力学问题需要深入研究。目的:建立长管状骨的有限元分析模型,并通过力学实验验证有关参数。方法:通过CT扫描3rd generation composite femurs,获得连续断层图片,导入MIMICS医学建模软件生成实体模型后,应用通用有限元分析软件进行网格划分、材料属性赋值生成有限元模型,约束边界条件,模拟受力状态进行加载,得出有限元模型上的应力与应变结果,并与实测实验结果对比。结果与结论:股骨有限元生成节点数为52 772,单元格为45 127,进行股骨干单向压缩实验仿真,有限元模型相对位移与验证实验和实验计算结果一致性良好。提示用MIMICS建立的股骨模型,在Ansys下进行有限元分析,得到的结果与生物力学基本吻合,说明建立的股骨模型是可靠的。     

人工股骨头置换治疗严重股骨转子间骨折的有限元分析

目的　建立股骨转子间骨折、人工关节假体的三维数字模型,应用有限元对人工股骨头置换术后的股骨应力分布进行分析,评价置换术后的初始稳定性。 方法　利用螺旋CT对志愿者的左侧股骨进行断层扫描获取图像数据,经Mimics软件和Unigraphics建模软件处理,重建股骨三维模型。在此基础上,建立股骨转子间骨折、标准柄股骨假体三维实体模型,最后利用有限元分析软件Ansys10.0建立人工股骨头置换术治疗股骨转子间骨折的三维有限元模型,并对该模型进行生物力学分析。 结果　应力分析显示：正常股骨的应力由近端向远端逐渐上升,并于中下段达到最高。同时人工股骨头假体的应力集中于中段,与正常股骨的应力变化基本一致。人工股骨头置换没有改变股骨总体的应力模式,股骨距部位未见明显的应力集中区,依然是由近端向远端逐渐增加,应力峰值区域亦于全长股骨的中下段。 结论　标准柄人工股骨头置换治疗股骨转子间骨折不会引起股骨应力分布的明显改变,可以获得重建后的初期稳定。     

腰椎—骨盆—髋关节有限元模型建立及生物力学分析

背景：髋腰疾病的发病率不断增加,给临床治疗带来一定的挑战,需要完善的腰椎-骨盆-髋关节模型以分析其生物力学特点。目的：建立正常成人腰椎-骨盆-髋关节三维有限元模型进行生物力学分析,为研究髋腰疾病和相关手术治疗提供实验依据和参考。方法：获取正常成人CT数据,利用Mimics、Geomagic、Hypermesh、Abaqus等软件构建正常的腰椎-骨盆-髋关节三维有限元模型,将所得模型进行各个工况分析,得到椎体活动度、椎间盘及股骨头应力分布进行模型有效性验证。之后进一步构建坐位模型,比较分析站立位和坐位2种姿势下的生物力学分布特点和变化趋势。结果与结论：(1)成功建立了正常成人腰椎-骨盆-髋关节三维有限元模型;(2)构建的模型在各工况分析中结果均在既往文献数据的参考范围内,确认模型有效,可进一步用于后续的实验研究;(3)从站立位到坐位姿势变化后,L₄-L₅及L₅-S₁椎间盘的应力呈上升趋势,其中L₅-S₁应力变化最明显;对于髋关节应力分布而言,在站立位时,应力...     

基于CT及逆向工程软件构建正常人体骨盆三维有限元模型

背景:骨盆是人体骨骼中形态及结构最复杂的部分,许多学者一直致力于其生物力学的研究。由于骨盆形状极其不规则,所附着肌肉及韧带解剖结构复杂,建立精确的包含主要肌肉及人韧带的骨盆有限元模型十分困难。目的:建立正常成年人骨盆的三维有限元模型,为后续骨盆的生物力学分析提供数字模型。方法:采集健康成年男性志愿者的骨盆CT数据,将DICOM格式的CT图像导入医学影像三维重建软件Mimics10.0进行图像的分割及三维重建,将导出文件导入逆向工程软件Geomagic studio 11中对图像进行曲面化处理,建立曲面模型,使其更加光顺,将生成的曲面模型导入有限元分析软件Ansys 14.0中进行有限元网格划分。结果与结论:建立了正常成年人骨盆的三维有限元模型,总单元数为818 294个,总节点数为149 290个。课题基于健康成年男性志愿者的骨盆CT图像建立骨盆有限元模型,所得的模型精确度高、逼真、具有良好的解剖及几何相似性,可为下一步骨盆的生物力学分析提供基础。     

Survival analysis

Survival analysis is the analysis of data involving times to some event of interest. The distinguishing features of survival, or time-to-event, data and the objectives of survival analysis are described. Some fundamental concepts of survival analysis are introduced and commonly used methods of analysis are described.     

Sperm analysis

Human semen analysis is the first biological step of male fertility assessment. Its performance requires the use of standardized and objective procedures. The results of the tests may allow to conclude to a man's sterility when they reveal e.g. an azoospermia or an alteration of sperm morphology or motility incompatible with fertilization. More often however, it is difficult to precisely determine the relationships between the observed sperm anomalies and infertility. In a follow-up study of 520 infertile men over 3 years, the pregnancy rate was found to be significantly lower only in the cases where sperm concentration values were less than 5.10(6)/ml and unchanged for concentrations above this value. No threshold values were found for sperm motility and morphology, although the chances of conception were closely related to these two parameters for sperm concentration values above 5.10(6)/ml. Various tests have been described to evaluate the human sperm ability to migrate through the female genital tract and fertilize the oocyte. These tests and the human in vitro fertilization assay allow a better understanding of the structural and dynamical parameters mostly involved in sperm function.     

Modeling masticatory muscle force in finite element analysis: sensitivity analysis using principal coordinates analysis

Our work on a finite element model of the skull of Macaca aims to investigate the functional significance of specific features of primate skulls and to determine to which of the input variables (elastic properties, muscle forces) the model behavior is most sensitive. Estimates of muscle forces acting on the model are derived from estimates of physiological cross-sectional areas (PCSAs) of the jaw muscles scaled by relative electromyographic (EMG) amplitudes recorded in vivo. In this study, the behavior of the model was measured under different assumptions regarding the PCSAs of the jaw muscles and the latency between EMG activity in those muscles and the resulting force production. Thirty-six different loading regimes were applied to the model using four different PCSA sets and nine different PCSA scaling parameters. The four PCSA sets were derived from three different macaque species and one genus average, and the scaling parameters were either EMGs from 10, 20, 30, 40, 50 and 60 msec prior to peak bite force, or simply 100%, 50%, or 25% of peak muscle force. Principal coordinates analysis was used to compare the deformations of the model produced by the 36 loading regimes. Strain data from selected sites on the model were also compared with in vivo bone strain data. The results revealed that when varying the external muscle forces within these boundaries, the majority of the variation in model behavior is attributable to variation in the overall magnitude rather than the relative amount of muscle force generated by each muscle. Once this magnitude-related variation in model deformation was accounted for, significant variation was attributable to differences in relative muscle recruitment between working and balancing sides. Strain orientations at selected sites showed little variation across loading experiments compared with variation documented in vivo. These data suggest that in order to create an accurate and valid finite element model of the behavior of the primate skull at a particular instant during feeding, it is important to include estimates of the relative recruitment levels of the masticatory muscles. However, a lot can be learned about patterns of skull deformation, in fossil species for example, by applying external forces proportional to the estimated relative PCSAs of the jaw adductors.     

Morphological analysis of adrenal glands: a prospective analysis

There is a lack of studies to document the weight range of normal adrenal glands. The aims of the current study are to find out the weight range of normal adrenal glands in Chinese patients and to analyze any potential factors affecting it. Adrenal glands not affected by disease were prospectivelly collected from autopsies on 333 Chinese patients (208 men, 125 women). The weight and longest dimension of each adrenal gland were noted. The impact of various clinicopathological factors on the adrenal weight was studied. In addition, the morphometric features of these adrenal glands were compared with that of 28 surgically resected adrenal glands with cortical adenomas. The mean combined weight of adrenal glands was 11.8 g (range=5.8 g to 19.9 g). The left adrenal gland was often heavier than the right (mean weight=6.1 g and 5.7 g respectively) and with a greater longitudinal length than the right (mean length=5.2 cm and 4.8 cm respectively). Adrenal glands were often heavier in male, younger age group (less than 60-yr-old) and patients with history of hypertension or lung cancers. In comparison, the mean weight of right adrenal gland with cortical adenoma was 11.7 g (range=6 g to 26 g) and that of left adrenal gland with cortical adenoma was 9.4 g (range=4.6 g to 25 g). This is the first study in the English literature that provides data on the weight of normal adrenal glands in a solely Chinese population. Adrenal weight may be affected by patients' gender, age, laterality of adrenal gland and presence of systemic disease.     

多体素模式分析在fMRI数据分析中的应用

用多体素模式分析（multivariatepatternanalysis,MVPA）方法分析功能磁共振成像（functionalmagneticresonanceimaging,fMRI）数据是近年来认知神经科学领域的研究热点。MVPA可分析大脑的解剖信息、大脑的功能活动以及人们的行为表现三者之间的关系,从而对人们某个认知行为背后的神经机制进行探讨。本文主要介绍以下内容：①如何用MVPA方法对fMRI数据进行处理和分析,主要包括数据预处理、特征提取和样本创建、分类器的选择与测试。②如何对MVPA的分析结果进行解释：结合认知心理学的相关知识对MVPA的分析结果进行解释。通过本文,可以对MVPA的基本理论,应用特点和发展趋势,以及如何用MVPA方法进行fMRI数据处理和分析有一个较为全面的认识。