【摘要】 背景:基于自编写的Matlab程序实现了对兔股骨图像边缘的识别。但鉴于模型的复杂性,在UG三维软件中建立股骨实体模型后导入ANSYS软件中,能否构建相应的结构模型?目的:构建兔股骨三维生物力学模型的方法。设计:随机对照观察。单位:北京理工大学生物力学实验室。材料:实验用1只雌性新西兰大白兔,兔龄1年,体质量2.6kg,。实验用ACTIS400/225型工业CT扫描机为美国BIR公司生产。方法:实验于2005-07/12在北京理工大学生物力学实验室完成。①股骨影像轮廓提取:实验兔麻醉后处死,分离股骨。将工业CT扫描图像转换成*.bmp格式的图像文件,应用Photo shop图像处理软件,对原始图像进行对比度调整、平滑去噪等必要处理,以增强图像的可辨性和可分析性。再用磁性套索工具勾勒各层图像的内、外边界线,得到各层面股骨内、外轮廓曲线,采用CT扫描机对兔股骨进行扫描,自股骨头上端起,由近端向远端垂直于股骨纵轴行CT扫描,层间距为1mm。小转子下方第43层至股骨中段53层,由于形状比较规则,扫描层间距为2mm。共扫描87层,长度为9.9cm,输入计算机后经处理得到边界轮廓线,再通过自编程序,获取建模时所用的轮廓线坐标,将坐标数据输入建模软件,建立三维实体模型。②股骨有限元模型的建立:将UG中导出的*.IGES文件,导入至ANSYS软件,自动生成股骨实体模型,利用ANSYS软件布尔操作中的减操作,得到有空腔的实体模型。主要观察指标:兔股骨结构模型建立情况。结果:①利用UG三维造型软件,读取第1层轮廓数据*.dat文件,形成由多个数据点连接的自由曲线,依次读取第2层、第3层、第4层至第87层,形成兔股骨内、外轮廓的堆叠图。②采用自由网格划分法,应用ANSYS程序自动划分网格,生成有限元网格。网格划分后得到42221个节点及27768个单元。结论:实验模型真实模拟了兔股骨的解剖学形态。建立的三维生物力学模型为下一步通过有限元法确定振动对骨丢失影响的最佳参数奠定了实验学基础。更多还原

【Abstract】 BACKGROUND: The image edge of rabbit femur is identified using self-programmed Matlab program. But owing to the complexity of the model, can we set up a femoral structure model after the solid model of the femur created in UG three-dimensional (3D) software is put into ANSYS software? OBJECTIVE: To explore the method of constructing 3D biomechanical model of rabbit femur. DESIGN: Randomized controlled observation. SETTING: Biomechanics Laboratory of Beijing Institute of Technology. MATERIAL: One 1-year-old female New Zealand white rabbit weighing 2.6 kg. ACTIS 400/225 industry CT scanner (BIR, USA). METHODS: The experiment was performed at the Biomechanics Laboratory of Beijing Institute of Technology from July to December 2005. ①The rabbit was executed under anaesthesia to isolate the femur. The industry CT scanning images were transformed into .bmp format. Photoshop image processing software was applied for some essential processing on the original image, such as contrast control, smoothing and noise attenuation to strengthen the differentiability and analyzability of the image. In addition, the magnetic noose tool was used to outline the contour line of inside and outside boundary, and obtain the inside and outside contour line of every layer of the femur. The rabbit femur was scanned by industry CT starting from the upper extreme of the femur, vertical to femoral ordinate axis line (slice space=1 mm). The scanning slice space was adjusted to 2 mm from the 43rd layer below small trochanter to the 53rd layer of middle femur because the shape between these layers was relatively regular. Totally 87 slices of layer images were scanned 9.9 cm in length. The image was put into the computer and processed to get the boundary contour line; the contour line coordinate for modeling was obtained through programming, then the data were put into the model software to create the 3D solid model. ②.IGES document was imported from UG into ANSYS software. A solid model of the femur was produced automatically. Finally, the solid model with cavity was obtained using subtraction option of Boolean in ANSYS. MAIN OUTCOME MEASURES: Establishment of rabbit femoral structure model. RESULTS: ①The UG 3D modeling software was used to read the first layer data in . dat document, the free curve which connected by the multiple valid points was formed. The 2nd, 3rd, 4th until the 87th layers were read in turn, and the inside and outside contours of rabbit femur was formed. ②The free meshing method was adopted and ANSYS program to automatically divide the mesh to produce finite element meshes and 42 221 nodes and 27 768 elements were obtained. CONCLUSION: The 3D model of rabbit femur actually simulated the anatomic appearance of the femur. This model lays a foundation for identifying the optimal parameter of vibration that can improve bone mineral density by finite element analysis.更多还原