三维人体模拟内窥的实验研究

目的 对三维人体虚拟内窥系统进行初步的实验研究。方法 建立了虚拟摄像机几何模型和定位方法,根据人体的三维影像数据,以不同分辨率对虚拟人体进行不同角度的观察。并对虚拟内窥镜的观察结果用光线跟踪方法检测表面和三线性插值方法绘制表面图。结果 实现虚拟内窥结果的可视化,研制出基于微机的虚拟内窥系统和对三维人体影像数据虚拟内窥的结果。结论 虚拟内窥是实现医学虚拟诊断、虚拟治疗和虚拟教学的很有前任的手段之一。     

基于PC机的虚拟内窥镜成像算法

目的对现有的虚拟内窥镜成像方法进行改进 ,使之能够在PC机上运行。方法传统算法在观察点位置变化时 ,应先对所有原始体数据进行三维坐标变换后再作透视投影 ,本文算法只对被观察的那部分数据进行处理 ,减少不必要的坐标变换 ,并将坐标变换、表面检测、透视投影等紧密结合 ,在一次光线跟踪过程中完成这些计算以减小计算量 ;直接对原始体数据进行投影 ,无需先对体数据进行插值 ,因此不用保留插值的中间结果 ,减少了内存消耗 ;在成像过程中自动排除与成像结果无关的数据 ,使它们不参与插值 ,不参与投影 ,进一步提高了计算速度。结果设计出基于PC机的虚拟内窥镜系统 ,并用大小为 5 1 2× 5 1 2的CT图片 ,绘制了胸部气管的内窥图像 ,以验证本文算法的有效性。结论所提出的算法能够在PC机上实现 ,有助于虚拟内窥镜系统的推广应用     

虚拟内窥镜系统中的自动导航

目的 研究基于PC机的虚拟内窥系统中的自动导航方法。方法 首先设计了一种基于位编码和坐标变换的快速3D细化算法来提高提取器官骨架的运算速度；然后采用2次跟踪技术裁剪骨架分支得到所需的导航路径；最后提出一种3遍3次Bezier平滑导航路径算法和Bezier插值算法，使导航路径至少能达到C1连续且较为平坦，并以平滑的导航路径上的点控制虚拟摄像机位置，以对应点处的切线(一阶导数)控制虚拟摄像机方向。结果 对经过分割后获得的人体气管体数据进行自动导航实验，结果表明，在自动导航中虚拟摄像机能保持远离气管内壁，而且相邻帧之间过渡比较平滑，能产生效果很好的自动导航动画。结论 方法实现简单。基本上能满足虚拟内窥镜系统临床应用的要求．     

基于表面点的高分辨率体数据三维重建

目的对高分辨率体数据实现高质量的实时三维表面浏览。方法本算法用结合阈值和形态学的分割方法提取体数据中单个器官的三维表面点集,再根据体数据中灰度梯度得到表面点的法向量。通过用表面点代替三角形面片来描述器官表面,在用户定义器官表面的颜色和透明度后,利用显卡OpenGL接口对表面点集进行三维显示。结果在微机环境下对中国数字人男性一号的CT数据集的骨骼和体表进行了三维重建,在保证图像质量的前提下重建速度超过25帧/s。结论本文提出的三维表面重建算法能对512×512×1720的高分辨率体数据进行高质量的实时三维表面浏览。     

面向航天虚拟操作分析的航天员人体建模与姿态仿真技术

目的建立支持虚拟操作分析的航天员三维人体模型。方法研究了层次化、关节化和参数化人体建模方法;通过CATIA软件建立人体骨骼层、皮肤层和服饰层静态模型,并将其导入到JACK环境当中进行关联处理,赋予人体关节运动特性。结果生成了可根据百分位和各体段参数进行调整的航天员模型,并实现了姿态仿真。结论建立的航天员人体模型具有几何外观特性和基本动力学特性,结合JACK软件环境,可以实现航天操作的可视性、可达性、疲劳度等分析。     

应用三维造型软件建立脑动脉瘤虚拟三维模型的研究

目的探讨应用三维造型软件建立脑动脉瘤虚拟三维模型的方法。方法分别对20例正常脑血管和216例脑动脉瘤的DSA资料进行分析整理,选取具有代表性的DSA资料作为蓝本,利用三维制作软件3D Studio MAX R3分别创建虚拟的脑动脉系统和动脉瘤模型。结果①虚拟脑动脉系统与DSA图像相比,在形态上具有相似性,在视觉上更容易理解血管的三维空间关系;能够在血管半透明的状态下显示虚拟的导丝、导管;通过将该虚拟模型文件复制成多个副本,稍加修改即可建立具有不同解剖变异的多个模型。②虚拟动脉瘤与DSA图像相比,能正确表现动脉瘤的发生部位、生长方向和形态特点;通过将该虚拟模型文件复制成多个副本,稍加修改即可建立发生部位、生长方向和形态各不相同的多个模型。结论由软件方法建立的脑动脉瘤虚拟三维模型能够逼真显示脑动脉系统和瘤体的三维空间关系,对于形态学研究和指导临床工作具有重要作用。     

基于人在回路感知的房颤导管消融训练器研究

目的 为解决三维标测指导下房颤导管消融手术医生缺乏训练手段的问题,根据常用的三维标测CARTO房颤手术系统原理,研制一种基于人在回路感知的房颤导管消融训练器.方法 分析人在回路的CARTO系统手术过程,提出训练器系统总体结构,并给出实现该系统的关键技术,包括:与实际手术用消融导管手感一致的训练用消融导管实现方法、基于实际病人数据的虚拟病人心脏几何模型和心电数据仿真方法、基于质点弹簧模型的虚拟消融导管仿真方法和基于OBB(oriented bounding box,方向包围盒)包围盒碰撞检测算法的两层虚拟手术交互操作模型.系统集成后邀请专家试用并对其评价.结果 该训练器与实际手术系统的操作方法、硬件操作界面和视觉信息一致,该系统交互操作实时、灵活.结论 该训练器能完成人在回路的房颤手术过程交互仿真,并可用于医生的手术训练和术前手术预演.     

医学体视化的三维旋转绘制法

目的 实现三维医学图像数据场的快速旋转体绘制。方法 由源一衰减模型、朗伯漫反射余弦定律和Phong镜面反射模型，推导出计算数据场中每一点的不透明度和明暗度的计算公式,通过旋转光源和视点,来自不同观察方向的感兴趣结构的体绘图被满意地生成。结果 通过对人体头部CT图像数据场进行三维旋转绘制，结果比较理想。结论 由于不需要对整个数据场进行分类和旋转，该方法具有速度快、所需内存少和绘制质量高的特点，是一种较好的医学体视化方法。     

基于虚拟专用网的互动式影像远程会诊体系的创建与初步应用

目的探讨互动式影像远程会诊系统的创建及其特点。方法下级医院局域网、防火墙[含虚拟专用网(virtual private network，VPN)功能]及不对称数字线路调制解调器(ADSL Modem)1套，联入Intemet，通过贵阳医学院附属医院防火墙接入本院VPN服务器，获得VPN隧道联入本院医学影像存储与传输系统(picture archiving and communication systems，PACS)服务器，使本院影像科诊断终端及下级医院能够共享同一影像数据。结果下级医院影像数据及检查信息能安全、无损的上传到本院PACS保存和管理，并进行会诊后将会诊结果以报告方式返回给下级医院。影像上传速度快，质量优良，操作互动性好。结论基于VPN的互动式远程会诊系统具有安全、快捷、互动性好、操作简便、实用可靠和优良的性价比等优点，值得推广。     

双能CT虚拟平扫进展及临床应用

双能CT主要包括双源CT与能谱CT,两种CT可以根据不同的原理实现虚拟平扫。虚拟平扫的优点包括降低辐射剂量,同时获得多组影像等。双能CT虚拟平扫已经在头颈部、胸部、腹部等全身多个系统得到应用。就双能CT虚拟平扫原理、优势及临床应用与进展予以综述,重点介绍双能CT虚拟平扫在各系统的应用价值。     

胎儿三维磁共振成像技术的初步应用

目的：探讨三维磁共振成像（3D-MRI）技术在显示胎儿体表正常解剖和先天畸形方面的应用价值。方法：对40例18~37周的胎儿在超声检查后1~2d内行MRI检查,应用单次激发快速自旋回波序列（SSFSE）行胎儿轴面、矢状面和冠状面二维MRI（2D-MRI）,三维稳态进动快速成像（3D-FIESTA）序列MRI,均使用并行采集技术（ASSET）,在工作站对原始数据进行多平面重组（MPR）、容积重组（VR）和磁共振仿真内窥镜技术（MRVE）等三维图像后处理。将MRI和随访、尸检结果进行比较。结果：36例孕妇3D-MRI检查成功率为94.4%（34/36）,34例胎儿经随访和尸检证实46处畸形。胎儿体表先天畸形2D-MRI正确诊断37处,诊断符合率80.4%（37/46）;误诊1处,假阳性率为2.1%（1/46）;漏诊8处,漏诊率17.4%（8/46）。3D-MRI正确诊断43处,诊断符合率93.5%（43/46）;误诊1处,假阳性率2.1%（1/46）;漏诊2处,漏诊率为4.3%（2/46）。两种方法诊断胎儿体表先天畸形差异无统计学意义（χ2=2.40,P〉0.05）,但3D-MRI对于面部畸形如唇裂和其他复杂畸形如体蒂异常、骶尾部畸胎瘤、联体双胎等显示更直观清楚。结论：3D-MRI一次扫描可直观反映胎儿体表结构的表面特征、立体形态及相互间的位置关系,VR、MRVE对胎儿正常面部、外生殖器、脐带、肢体等的评价有较高价值,MPR可对兴趣区进行多角度观察。磁共振三维成像对显示胎儿正常体表结构和病变及产前咨询和围产期手术具有重要的临床价值。     

磁共振仿真内窥镜成像技术临床应用的初步探讨

目的探讨ＭＲ仿真内窥镜（ＶＥ）技术与方法的临床应用。方法 将６２例ＭＲ水成像（尿路３３例,胰胆管１６例,椎管８例,脑室５例）和２０例ＭＲ血管造影（脑,腹部各１０例）二维或三维扫描数据传输至工作站,用寻航软件选择适当成像方式,阈值,视角及方向和人工伪彩色重建沿管腔长轴行进的内表面图像。结果 ＭＲ ＶＥ获得了逼真的尿路,胰胆管,椎管,脑室和血管纤维内窥镜样管腔内表面图像,较好地显示了内腔,分叉处及出口     

舱外航天服视野设计中的虚拟视域仿真建模

目的探讨一种用于舱外航天服视野设计和分析的虚拟视域仿真建模方法。方法利用Solidworks软件建立三维人体模型,在对软件进行二次开发的基础上,充分利用软件提供的聚光源特性,建立了模拟人眼视锥及人眼运动的仿真算法,从而在Solidworks软件中实现人穿着舱外服后的虚拟视域仿真分析。结果将所建立的模型用于舱外服视野分析,其结果与人-服试验过程视野工效测试结果相一致。结论该模型可应用于舱外航天服设计过程中,对于其它具有工效要求的产品设计具有参考意义。     

Hybrid segmentation and virtual bronchoscopy based on CT images

RATIONALE AND OBJECTIVES: Introduction of combination of the segmentation tool SegoMeTex and the virtual endoscopy system VIVENDI to perform virtual endoscopic inspections of the human lung. This virtual bronchoscopy system enables visualization of the tracheobronchial tree down to seventh generation. Furthermore, the modified virtual system visualizes hidden structures such as segmented vascular system or tumors. MATERIALS AND METHODS: The segmentation is based on image data acquired by a multislice computed tomography scanner. SegoMeTex is used to segment the tracheobronchial tree by a hybrid system with minimal user action. Similarly, the complementary pulmonary arterial can be segmented, whereas additional structures such as tumors are marked manually. On this dataset, subsequently, data structures of the inner surface for virtual endoscopy are generated. Finally, the dataset can be explored by a virtual bronchoscopy procedure using the VIVENDI system. RESULTS: The segmentation method was successfully tested on 22 patients. The hybrid segmentation system identified bronchi up to the sixth generation with a sensitivity of more than 58%, and a positive predictive value of more than 90%. After the segmentation, the datasets are explored interactively (>30 fps on a standard personal computer platform in real-time rendering) using the virtual endoscopy software. The exploration exposed a high-quality reconstruction, even of small structures throughout the dataset. CONCLUSION: Virtual bronchoscopy in combining with a highly sensitive segmentation is a valuable tool for the localization and measurement of stenosis for resection planning.     

Evaluation of the middle and inner ear structures: comparison of hybrid rendering, virtual endoscopy and axial 2D source images

Recent developments in 3D reconstructions can enhance the quality and diagnostic value of axial 2D image data sets with direct benefits for clinical practice. To show the possible advantages of a hybrid rendering method [color-coded 3D shaded-surface display (SSD)- and volume rendering method] with the possibility of virtual endoscopy we have specifically highlighted the use in relation to the middle and inner ear structures. We examined 12 patients with both normal findings and postoperative changes, using image data sets from high-resolution spiral computed tomography (HRSCT). The middle and inner ear was segmented using an interactive threshold interval density volume-growing method and visualized with a color-coded SSD rendering method. The temporal bone was visualized using a transparent volume rendering method. The 3D- and virtual reconstructions were compared with the axial 2D source images. The evaluated middle and inner ear structures could be seen in their complete form and correct topographical relationship, and the 3D- and virtual reconstructions indicated an improved representation and spatial orientation of these structures. A hybrid and virtual endoscopic method could add information and improve the value of imaging in the diagnosis and management of patients with middle or inner ear diseases making the understanding and interpretation of axial 2D CT image data sets easier. The introduction of an improved rendering algorithm aids radiological diagnostics, medical education, surgical planning, surgical training, and postoperative assessment. Received: 22 July 1998; Revised: 15 April 1999; Accepted: 19 April 1999     

Error estimation on extracorporeal trajectory determination from body scans

This study explores the magnitude of two sources of error that are introduced when extracorporeal bullet trajectories are based on post-mortem computed tomography (PMCT) and/or surface scanning of a body. The first source of error is caused by an altered gravitational pull on soft tissue, which is introduced when a body is scanned in another position than it had when hit. The second source of error is introduced when scanned images are translated into a virtual representation of the victim’s body. To study the combined magnitude of these errors, virtual shooting trajectories with known vertical angles through five “victims” (live test persons) were simulated. The positions of the simulated wounds on the bodies were marked, with the victims in upright positions. Next, the victims were scanned in supine position, using 3D surface scanning, similar to a body’s position when scanned during a PMCT. Seven experts, used to working with 3D data, were asked to determine the bullet trajectories based on the virtual representations of the bodies. The errors between the known and determined trajectories were analysed and discussed. The results of this study give a feel for the magnitude of the introduced errors and can be used to reconstruct actual shooting incidents using PMCT data.

     

构建国人头颈三维有限元模型

目的研究构建国人头颈三维有限元模型。方法依据正常国人头颅CT、MRI断层扫描图像，识别确定重建对象，对皮肤、颅骨采用灰度阈值法、轮廓跟踪算法及B样条曲线拟合法进行自动重建；对其他结构采用人机对话方式提取边界关键点，进行重建实体。定义结构材料参数后划分网格。筛选相邻体积交接面节点，粘连节点完成建模。结果完成包含皮肤、颅骨、硬膜、静脉窦、脑灰白质、脑干、小脑、脑室系统、颈椎及颈髓的国人头颈三维有限元模型。模型单元及节点数分别为168733，80535，总质量约5．14kg。结论利用医学影像资料，采用轮廓跟踪算法等数字图像技术可半自动实现人颅脑复杂结构的三维重建。     

Virtual radiographs computed from TACT volume data as a gold standard for image registration prior to subtraction

OBJECTIVE: To develop a three-dimensional (3D) model for quantitative analysis of image subtraction methods simulating clinical conditions and relevant to dental radiology. METHOD: A high-resolution volume representation of a formalin-preserved segment of a human maxilla was synthesized from a set of 51 digital radiographs equidistantly covering the entire sampling aperture by means of Tuned-Aperture Computed Tomography (TACT). Two-dimensional (2D) projection renderings of a 3D model were generated yielding arbitrary but well-known 2D projections with, and without, structured noise producing 'virtual radiographs'. RESULTS: Virtual radiographs were found to be similar to actual clinical images with respect to appearance, structure, and texture. Because the TACT reconstruction process allows all possible positions and orientations of source, specimen, and image plane to be simulated with negligible under sampling over a reasonable range of solid angles (sampling aperture), the resulting 3D model provided a rigorous method for establishing a truly objective gold standard (ground truth) for testing different registration techniques. CONCLUSIONS: TACT image registration can be assessed quantitatively by comparing actually observed vs theoretically professed parameters that presumably constrain the underlying projection geometries. Other attributes that vary from one method to the next, such as the use of nonlinear or region-specific techniques to facilitate registration, likewise, now can be rigorously measured by context-based methods such as quantitative determination of image similarity. Hence, a 3D model that renders idealized virtual radiographs from any desired projection geometry makes possible truly objective comparison of various digital subtraction techniques.     

16层螺旋CT后处理技术在儿童气管、支气管异物的诊断价值

目的：研究16层螺旋CT三维重建及仿真内窥镜技术对儿童气管、支气管异物的诊断价值。方法：使用螺旋CT对22例怀疑儿童气管、支气管异物的病例行胸部CT平扫,图像重建后传送至工作站处理,使用多平面重建（MPR）及仿真内窥镜技术（CTVB）进行分析,全部病例经纤维支气管镜（FOB）或临床证实。结果：22例中,CTVB显示I～III级气管支气管100%,显示第IV级支气管45.5%;MPR显示I～III级气管支气管100%,显示第IV级支气管50.0%;FOB显示I～II级气管支气管100%,显示第III级支气管72.7%。结论：多层螺旋CT三维重建及仿真内窥镜技术能准确显示气管、支气管异物的位置、大小、形态及阻塞程度,是一种准确、安全的无创性诊断方法,给临床诊断、治疗提供直观的影像学资料,具有较高的诊断价值。