基于逆向工程技术的体表器官仿真修复重建研究

【作者】 张海林；

【导师】 乔群；

【作者基本信息】 中国协和医科大学 ， 外科学， 2007， 博士

【摘要】 体表器官缺损是现代整形外科领域的治疗重点和难点，体表器官的仿真修复重建是整形外科水平的最高体现。在传统的整形外科模式中，医生主要依靠自己的主观经验完成诊断分析和手术设计，整个过程缺乏客观评判指标和有效辅助手段，极大地影响到手术的效果和安全性。本研究借鉴工业领域逆向工程思想的先进技术，建立体表快速立体成像、手术仿真模拟设计、疗效客观评价系统，以期为体表组织器官修复重建提供一种全新的治疗模式，达到个性化治疗的目的。论文主要研究内容如下：1人体体表组织器官的三维数据采集高效、高精度地实现被测对象的三维数据获取，是逆向工程的第一环节，也是实现计算机辅助手术模拟的基础。基于相位偏移测量原理的莫尔条纹测量方法解决了传统测量方法不适合采集活体表面三维数据采集的问题。应用CT扫描获取器官内部结构的二维图像信息，用数学方法经过电子计算机处理而重建断层截面图象，根据不同位置的断层图像建立被测器官的三维信息。这两种方法相互补充，可以根据不同需求分别获取器官表面或内部结构的三维数据信息，充分满足器官再造的需求。2数据预处理针对相位偏移测量原理采集的人体点云数据，数据处理主要包括滤波和拼接。结合人体数据的自身特点，设计了矩形窗口加权中值滤波器，使用滤波器可以以较高的精度剔出大部分噪声数据。3构建三维曲面模型将经预处理后的一组点云数据导入逆向工程软件，通过对多视点云的拼接拟合，融合构建成为三角面片组成的曲面；再将构成曲面进行补洞、平滑、细分、曲面拟合、曲面光顺等处理，构建精确完整的数字化曲面模型。应用数据转换软件和三维重建软件完成了基于DICOM标准的CT图像数据采集和三维重建，获得了颅骨模型的三维数字化曲面模型。4制作三维实体模型将三维数字化曲面模型转换为STL格式后输入到激光快速成型机，制造出三维实体模型。实体模型能够精确地复制和再现被测对象的形貌状态，直观、详尽的表达解剖结构和周围关系。对于复杂病例，手术前可以在三维实体模型上进行手术模拟。5精度和误差分析对精度的追求是逆向工程技术在人体体表器官仿真修复重建中应用的首要目标。本研究通过对人体器官相应三维形貌信息进行传统方法测量和计算机辅助测量，验证构建的三维数字化模型和三维实体模型的精度均小于0.2mm，能够满足临床应用的要求。6临床应用研究本研究分别对颜面部软组织畸形、小耳畸形、颅骨缺损以及乳房整形进行了临床应用研究。(1)在逆向工程软件中对三维数字模型人工交互曲面变形方法或镜像模拟法设计手术后效果，并测量分析出需要整形修复的量化数据，为手术提供参考。(2)应用快速原型技术，制作正常的实体模型，为手术前设计和手术中修复重建提供直观的参考。(3)应用CAD软件分析缺损和畸形部位，设计植入体的三维数字模型，应用数控机床生产出与缺损或畸形部位完全契合的个性化植入体，无需再在手术台上对植入体进行裁剪、塑形，缩短手术时间，降低手术难度，提高手术安全性。(4)将患者手术前、手术模拟和手术后的三维数字模型应用逆向工程软件进行配准、分析，验证手术效果和手术设计方案的实现程度，(5)将患者手术后的颜面部数字化曲面模型和模拟的手术后曲面模型导入逆向工程软件，进行配准比较，验证手术设计方案的实现程度。课题引入逆向工程思想的先进知识，建立了体表快速立体成像、手术仿真模拟设计、疗效客观评价系统。经精度验证完全可以满足临床需求。通过试验研究和临床应用研究验证了该系统在体表组织器官仿真修复重建中的可行性，获得了良好的手术效果。但是本研究尚未能建立成为一个完整的计算机系统，进行手术预测和模拟时还比较复杂。此外，器官再造手术前后组织的形态变化是手术精确化的重大障碍，手术前模拟以及模型外科都是将组织器官认为是刚性结构，预测不够精确。在进一步地研究中我们要将现有的系统和程序结合起来，并构建人体体表器官的三维数据库和数据自动分析程序，建立组织生物力学的三维有限元分析模型，为体表组织器官的修复重建建立一个界面友好的计算机辅助三维虚拟现实的计算机系统。更多还原

【Abstract】 The restoration and reconstruction of surface organs remains the challenging field inmordern plastic surgery. There are still many technical obstacles for plastic surgeons to makea new vividely substitute. In traditional way, surgeons make the diagnostic analysis andoperative plan mainly depending on theire limitied personal experiences, which seems moresubjective and may jeopardize the final outcome. Originated from the idea of industrialreverse engineering, a new therapeutic model is developed with the aim to make a quickpreoperative three-dimensional imaging, a mimic model shaping, and a objectivepost-operative outcome evaluation. This dissertation includes the following 6 major parts:1.3-dimantional data acquisition3-dimantional data collection is the primary step in reverse project and based thecomputer-asisted operative manipulation. Two kind of method is adopted to efficiently andprecisely obtain the 3-dimantional data. The first method is Moire-fringe technology, which isbased on the phase measuring profilometry, to collect the 3-D surface data on a livingobjective. The other method is CT. CT scan can easily get the 2-dimentional data of a organ’sinternal structure. Processed by some special software, these data can be used to reestablishthe internal 3-D framwork of a specific organ. In reconstructive surgery, no matter external3-D data or the underface, internal 3-D data is required, the surgeon can readily get what theydesired through these two reliable methods, making a solid basis for further work.2. Data preprocessingAiming at character of body points cloud data measured by optical photogrammetryscanner, data disposal include mainly filter and registration. Combined with self-character ofbody data, this paper designed a Rectangle Window Weighted Median Fiter. Using of Fitercan eliminate most noise data with higher accuracy.3. Surface entity model constructionAfter scanning, point cloud is transmitted to work space and modelling under software ofreverse engineering. Several point cloud from different visual angle is obtained. Data registration can transform them to the same coordinate system and obtain registered 3D trigon.These trigonal patches can be processed further, such as hole-filling, smoothing, subdivision,surface merger, surface smoothing. Finally a precision intergrated digital surface entity modelis formed.The obtained CT scan data, which fulfill the DICOM standard, are modelling undersoftware of data transformation and 3-D reconstruction, and further produce the surface entitymodel of craniofacial bone.4. Body entity model reconstructionTransformed into STL format, the 3-D digital surface entity model is put into astereolithography and the body entity model is then manufactured. This model presents theprecise topograghy of the prototype, including the anatomic features and the surroundingrelationships. It is also beneficial to some complicated surgical cases, for preoperativepractice being feasible.5. Precision and erroe analysisThe primary goal of plastic surgical reverse engineering is to make a high precision finalmodel. In this study, traditional mearsuring method and computer-asisted mearsuring methodare used respectively to reveal the dimentional differences between the prototype and the finalmodel. In both method, less than 0.2 mm differences are found, which obviously meet theclinicla requirement.6. Clinical applicationOne part of this research is its clinical application. Some patients, such as those presentwith facial soft tissue deformities, microtia, cranial bone defects, breast deformities, arebeneficial from this study.(1) In some cases, artificial interact surface transformation of the 3-D digital model, ormirror simulation method is used. So the surgeons can get the desired post-operativeappearance and the specific data which need to be altered during operation. This methodprovides an objective basis for operative plan. (2) A body entity model can readily be obtained with the rapid-prototyping technique insome patients. On this model, the surgeons can make practice and whatever modification ifneeded, to fulfill the operative plan.(3) Also the implant can be produced with the modelling of CAD software and digitalmanufacturing. This kind of implant has the exact defect dimention, concaves andconcvexness, which apparently avoid in-operation shaping and tailoring, and make theoperative outcome more satisfactory.(4) A objective evaluation system can be established through the comparision of pre-op3-D imaging, in-op models, post-op 3D imaging. Also the feasibility of such kind of operationcan be appraised, if large sample is provieded.This study first introduces reverse engineering into plastic surgery, and successfullyestablished a new dianostic and therapeutic system consisting of rapid prototyping of surfaceorgans, computer-asisted preoperative design and objective outcome evaluation. The precisionof this system is high enough for clinical application. The feasibility is also confirmed by thelaboratory and clinic experiments, besides the satisfactory operative results being obtained.But this new system is not yet perfect. One disavantage is the too complicated process insimulation and manipulation. The other disavantage relate to the presumed tissue’s physicalcharacter. In this system, not only the prototype’s but also the substitute’s tissue is presumedto be rigid, not as pliable as real one. This inevitably affects the final result of reconstruction.In further studies, the present system will evolve into a more friendly interface, easycontrolling, computer-asisted virtual 3-D modeling, biological physical limited elementsanalysis system.更多还原