Medical rapid prototyping and 3D CT in the manufacture of custom made cranial titanium plates

This report describes a new method of custom making cranial titanium plates for the repair of skull defects. We have combined 3D CT imaging and surface modelling with rapid prototyping (RP) technology to produce physical models of our patients' skulls from which custom titanium plates were made. We have expanded the use of image processing tools applied to the CT image data to fabricate a representation of the skull defect. Medical RP models are relatively expensive and particular attention has been paid to developing image processing methods to reduce costs. Our technique used the patient as their own model and generated data from the contralateral side of the head where appropriate. We present the results of 10 patients who have had a custom made cranial titanium plate fitted and discuss the models for these cases. The benefits of our custom made titanium plates are reduced patient attendances to hospital and a more accurate titanium plate which has improved fitting and cosmesis.     

CT三维重建技术在颅骨缺损修补术中的应用

目的 探讨CT三维重建技术在颅骨缺损修补术中的临床价值。方法 收集2013年3月~2016年4月行钛板颅骨缺损修补术患者11例。均于术前采用螺旋CT薄层扫描和颅骨三维成像,根据CT采集的数据进行颅骨缺损部位的数字化模拟塑形,制作出成型三维钛板。根据术中钛板与颅骨缺损吻合程度、术后头颅外形对称性评价钛骨嵌合度是否良好,根据患者满意程度、外观美感、咬合感、头部舒适度等医患互动方式评价手术效果是否满意。结果 11例患者手术顺利,无一例出现术后感染。仅1例（9.09%）术后并发硬膜外积液。所有的塑形钛板均与颅骨缺损部嵌合度良好,患者的手术效果满意度为100.00%。结论 利用CT三维重建技术的成型钛板具有良好的嵌合度,且手术效果佳,该CT技术在颅骨缺损修补术中具有临床实用价值。     

数字化钛网颅骨成形198例分析

背景：传统的颅骨缺损修复方法存在反复修整塑形时间长、修复后外观不满意等弊端。计算机辅助设计及成型技术(即数字化塑形)引入神经外科,使颅骨缺损个体化修复获得满意效果。 目的：观察应用数字化塑形钛网进行颅骨成形的临床效果。 方法：应用钛网进行Ⅱ期颅骨成形198例,数字化塑形钛网组(96例)进行头颅CT扫描取得颅骨及缺损的数据,传至数字化塑型钛网制造公司,获得个体化的预制钛网材料进行颅骨修复;传统手工成形组(102例)术中临时对钛网用手工裁剪、塑形进行颅骨修复。 结果与结论：数字化组钛网置于颅骨缺损处,达到与骨窗缘紧密贴合,外形满意度达100%,每台手术时间较传统组平均少用约45 min,术后无头皮下积血、感染、修补材料裸露等并发症,传统组修补材料裸露1例,切口感染2例,头皮下积血4例。结果可见数字化塑形钛网进行颅骨成形缩短了手术时间,降低了修补材料裸露、继发性感染等并发症,可获得满意的成形效果。 关键词：数字化塑形;钛网;颅骨缺损;颅骨成形术;并发症 doi:10.3969/j.issn.1673-8225.2012.04.043     

Design and fabrication of custom mandible titanium tray based on rapid prototyping

During the past few years, the combination of medical imaging and rapid manufacturing technique has proven to be a very important development. On the other hand, the conventional method has some drawbacks. For example, it takes longer time to complete an operation and it also presents some difficulty in matching the repaired contours. With advanced software and hardware, an image of an undamaged bone similar to that of the patient can be made from computerised tomography (CT); and a physical object constructed by the mirror-processed image data can be quickly fabricated with a high degree of fitting with the patient's bone. This paper presents a methodology for the design and fabrication of an individual titanium tray for the repair of mandible defects. Methods for the tray modeling using CAD system are presented: A 3D model of the bony defect is generated after the acquisition of helical CT data. An individual tray is designed using freeform surfaces geometries and fabricated by rapid prototyping (RP) technology. The results of tray filling with bone-grafting materials are then presented. Result: the tray is inserted into the patient mandible segment. The symmetry and reconstruction quality contour of the repaired mandible was satisfactory. Thus, the patient is able to eat normally. The bone-grafting material harvested from the anterior ilium was low. The clinical experience showed that rapid prototyping and reverse engineering software are effective methods of fabricating custom trays for mandibular reconstruction after bone loss due to a tumor.     

快速成型钛板结合自体骨移植修复犬下颌骨缺损

背景：近年来,快速成型技术被迅速的应用于医学重建领域,利用快速成型技术可为组织缺损患者制作个体化的植入物,可达到空间尺寸上的精确修复。 目的：利用快速成型技术制作个体化钛板,结合自体松质骨移植,修复犬下颌骨节段性缺损。 方法：9只杂种犬行螺旋CT扫描获取头颅骨骼数据,建立数字3D模型,在模型上模拟右侧下颌骨体部切除术,并制作个体化板状修复体,经快速成型加工制造,获得个体化的钛板。然后行动物实验,手术制造右侧下颌骨体部4 cm长节段性缺损,同期手术切取自体髂骨块固定于快速成型钛板的舌侧,修复下颌骨缺损。采用核医学、力学、影像学和组织学等方法评估骨移植后的转归。 结果与结论：应用快速成型支架重建了左右对称的下颌骨形态,自体髂骨移植后逐渐皮质化,植骨和钛板之间形成纤维结缔组织间隔层。在下颌骨缺损修复中,应用快速成型钛板能够达到形态和功能兼顾的效果。 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程全文链接：     

Using three-dimensional multigrid-based snake and multiresolution image registration for reconstruction of cranial defect

In cranioplasty, neurosurgeons use bone grafts to repair skull defects. To ensure the protection of intracranial tissues and recover the original head shape for aesthetic purposes, a custom-made pre-fabricated prosthesis must match the cranial incision as closely as possible. In our previous study (Liao et al. in Med Biol Eng Comput 49:203–211, 2011), we proposed an algorithm consisting of the 2D snake and image registration using the patient’s own diagnostic low-resolution and defective high-resolution computed tomography (CT) images to repair the impaired skull. In this study, we developed a 3D multigrid snake and employed multiresolution image registration to improve the computational efficiency. After extracting the defect portion images, we designed an image-trimming process to remove the bumped inner margin that can facilitate the placement of skull implants without manual trimming during surgery. To evaluate the performance of the proposed algorithm, a set of skull phantoms were manufactured to simulate six different conditions of cranial defects, namely, unilateral, bilateral, and cross-midline defects with 20 or 40 % skull defects. The overall image processing time in reconstructing the defect portion images can be reduced from 3 h to 20 min, as compared with our previous method. Furthermore, the reconstruction accuracies using the 3D multigrid snake were superior to those using the 2D snake.     

Three-dimensional reconstruction and rapid prototyping of femur bone using multiple digital X-rays

The medical industry has made great strides in offering healthcare services, and rapid prototyping (RP) is an example of a tool that has experienced tremendous growth in the medical field. RP technologies are used for building models that provide visual and tactile information. The linking of scanning technology and RP technologies now permit anatomical image data to be viewed in a completely different manner. The feasibility of producing RP models using digital X-rays is explained in this work. Digital X-rays taken at regular angular intervals of the anatomical object are used as input data to reconstruct the anatomical object. Software to detect the edge of the bone projection and export it to two-dimensional coordinates was developed using Visual Basic 6.0. This coordinate data of the image is used for creating the spline of the two-dimensional projections of the bone. Then, using extrusion and Boolean intersection operations, the three-dimensional model of the bone without concavities is reconstructed. In order to incorporate the concavities, a unique method is applied. Using grey-level histograms, the concavities are detected, and using subtraction Boolean operation the concavities are incorporated in the model. The CAD model obtained is converted to stl file format, which is the defacto standard for RP. Using FDM 2000 machine the prototype of the bone is fabricated. The reconstructed model is compared with the CT model of the actual bone. The CT model and X-ray model are compared using the slices taken with a constant inter-slice distance. The fabricated bone model is used as visual-tactile representation, surgical planning and simulation tool for doctors. This would enhance the doctor – patient relationship and reduce the time for surgery.     

Three-dimensional reconstruction and rapid prototyping of femur bone using multiple digital X-rays

The medical industry has made great strides in offering healthcare services, and rapid prototyping (RP) is an example of a tool that has experienced tremendous growth in the medical field. RP technologies are used for building models that provide visual and tactile information. The linking of scanning technology and RP technologies now permit anatomical image data to be viewed in a completely different manner. The feasibility of producing RP models using digital X-rays is explained in this work. Digital X-rays taken at regular angular intervals of the anatomical object are used as input data to reconstruct the anatomical object. Software to detect the edge of the bone projection and export it to two-dimensional coordinates was developed using Visual Basic 6.0. This coordinate data of the image is used for creating the spline of the two-dimensional projections of the bone. Then, using extrusion and Boolean intersection operations, the three-dimensional model of the bone without concavities is reconstructed. In order to incorporate the concavities, a unique method is applied. Using grey-level histograms, the concavities are detected, and using subtraction Boolean operation the concavities are incorporated in the model. The CAD model obtained is converted to stl file format, which is the defacto standard for RP. Using FDM 2000 machine the prototype of the bone is fabricated. The reconstructed model is compared with the CT model of the actual bone. The CT model and X-ray model are compared using the slices taken with a constant inter-slice distance. The fabricated bone model is used as visual-tactile representation, surgical planning and simulation tool for doctors. This would enhance the doctor - patient relationship and reduce the time for surgery.     

基于薄层CT数据的胫骨近端接骨板标准件库的建立及意义

目的　探讨胫骨近端接骨板标准件库建立的方法及临床意义。 方法　采集6套全规格胫骨近端接骨板薄层CT扫描的原始数据,导入Mimics14.0中进行三维重建,以STL格式文件输出至Geomagic对三维模型进行形态学优化。在Mimics中进行体积恢复。利用MedCAD绘制圆柱体状钉道模拟现实锁定钉方向,并完成带钉接骨板形态学标准件库建立。 结果　 (1) 完成186块带钉的接骨板标准件的建立;(2) 经Geomagic外观优化以及Mimics体积恢复,使接骨板三维模型具有较高仿真度。 结论　(1) 基于CT扫描的数据,通过逆向工程软件处理可以实现骨科接骨板的标准件库制备; (2) 接骨板与钉道选择性的组合方式适用于骨折内固定植入手术的数字化设计。     

生物活性人工骨结合CAD/CAM技术重建颅骨板制作系统

目的 通过CAD／CAM技术和快速成型技术并结合生物活性人工骨材料的应用，建立个性化设计制造具有良好骨融合性的颅骨板制作系统。方法 通过螺旋CT扫描、CAD三维重建成像、快速成型机加工，制成与患者颅骨缺损部位几何形态相同的个性化实体模型，应用石膏翻模工艺和EH复合人工骨材料，制成患者骨修补治疗用颅骨板。结果 CAD／CAM技术重建的人工骨颅骨板几何外形与骨缺损部位非常吻合，与健康侧对称，临床效果非常满意。结论 生物活性人工骨结合CAD／CAM技术重建颅骨板制作系统为治疗颅骨缺损患者提供了一种新手段，可有效提高临床治疗效果和修复美学效果。     

基于CT断层影像的颅骨解剖结构三维重建

目的:基于CT颅脑断面连续影像,利用Mimics 8.01软件对颅骨进行三维重建,为解剖学教学和研究提供模型.方法:利用Mimics软件对CT颅脑影像中的骨组织进行自动阈值分割后,对重建出的颅骨进行自动分割,分割出舌骨结构.对于其他颅骨结构,在Mimics软件中的三个方位CT图像中,利用定位线结合解剖学中的颅骨毗邻关系,找出区分毗邻颅骨之间的定位点.然后,根据事先规划的不同结构的分割颜色,人工描出相应的颅骨所在区域.随后,对分割出的各个颜色区域进行三维重建,重建出主要的脑颅骨和面颅骨结构,并分别在计算机上对上述结构进行观察.结果:成功对颅骨的结构分别以不同颜色进行分割,并分别重建出额骨、颞骨、枕骨、顶骨、蝶骨、筛骨、鼻骨、泪骨、上颌骨、下颌骨、腭骨、舌骨结构,在计算机中进行任意角度和单独观察.结论:基于CT颅脑断面影像可以对颅骨进行三维重建,为数字化颅骨解剖教学及颅脑手术导航奠定基础.     

数字几何处理技术及在颌骨缺损修复手术中的应用

提出一种精确匹配的定制型医用内植物设计与制造方法。采用医学图像处理和数字几何处理技术从CT图像序列中获得以三角面描述的骨组织面模型。对几何模型进行三角面精简、碎片清除、切割、镜像和合并等几何运算后,用LOM法制作实际大小的快速原型模型。快速原型有利于精确匹配的内植物制作,对手术实施也有导向作用。利用该技术已进行30多例颌骨修复手术,效果良好。     

不同修复材料在颅骨成型中的应用

背景：临床上,颅骨修补的材料种类繁多,分为自体骨及人工材料,后者包括高分子聚合材料(硅胶板)及钛合金网。那么,哪种材料最具临床应用价值呢？ 目的：探讨各种颅骨修补材料在颅骨成型中的应用价值。 方法：回顾性分析2000-02/2010-06因颅骨缺损而行颅骨成型的78例临床资料,其中硅胶板修补颅骨19例,二维钛网26例,数字化三维钛网33例。主要从修补时间、费用、患者的美容及心理康复程度进行分析比较。 结果与结论：数字化三维钛网组较硅胶板及二维钛网组在手术时间上明显缩短,外观上完全恢复解剖,但数字化三维钛网组费用明显高于硅胶板及二维钛网组,而且数字化三维钛网硬度较弱,抗碰撞能力较二维钛网组低。结果提示,数字化二维钛网可以避免在手术中塑型,缩短手术时间,外观上完全恢复解剖,费用较低,且硬度大,抗碰撞能力强。     

Three-dimensional reconstruction of cranial defect using active contour model and image registration

In neurosurgery, cranial incisions during craniotomy can be recovered by cranioplasty—a surgical operation using cranial implants to repair skull defects. However, surgeons often encounter difficulties when grafting prefabricated cranial plates into defective areas, since a perfect match to the cranial incision is difficult to achieve. Previous studies using mirroring technique, surface interpolation, or deformed template had limitations in skull reconstruction to match the patient’s original appearance. For this study, we utilized low-resolution and high-resolution computed tomography images from the patient to repair skull defects, whilst preserving the original shape. Since the accuracy of skull reconstruction was associated with the partial volume effects in the low-resolution images and the percentage of the skull defect in the high-resolution images, the low-resolution images with intact skull were resampled and thresholded followed by active contour model to suppress partial volume artifacts. The resulting low-resolution images were registered with the high-resolution ones, which exhibited different percentages of cranial defect, to extract the incised cranial part. Finally, mesh smoothing refined the three-dimensional model of the cranial defect. Simulation results indicate that the reconstruction was 93.94% accurate for a 20% skull material removal, and 97.76% accurate for 40% skull material removal. Experimental results demonstrate that the proposed algorithm effectively creates a customized implant, which can readily be used in cranioplasty.     

计算机辅助设计数字化三维成形钛网修补颅骨缺损

目的探讨利用计算机辅助设计与制造（CAD/CAM）技术进行个性化塑形颅骨缺损修补术的临床价值。方法2007年6月～2008年6月,选择笔者所在医院颅骨缺损患者20例作为计算机辅助设计组,其中男性12例,女性8例,年龄20。57岁,平均年龄33岁。术前将其颅骨缺损前后CT数据在计算机上分别进行三维重建,采用颅骨缺损部位的三维几何模型数据．应用人工智能技术,设计补片几何形状,制作出凸凹2个模具,利用模具将颅骨修补材料钛网压制成形,用成形好的钛网修补颅骨缺损。另选20例颅骨缺损患者作为对照组。结果塑形、麻醉及手术操作时间明显减少,术后无一例出现因塑形欠佳造成的并发症,复查头颅CT修复以后的颅骨形状与原颅骨形状完全一致。结论颅骨缺损修补手术应用CAD／CAM技术塑形颅骨修补材料实现了个体化配置修补颅骨缺损,使患者颅骨修补后头颅形状最大限度恢复生理原貌,患者满意度100％。此方法重复性强,具有一定的创新性和实用性,值得在临床大力推广。     

The display of three-dimensional anatomy with stereolithographic models

Stereolithography, a new technique of prototype fabrication developed for the aerospace industry, offers a unique way to display patient anatomy. Like current computer aided design (CAD) systems, it uses digital image data from computed tomography (CT) and magnetic resonance (MR) to produce a physical model. Unlike conventional CAD it does not require a cutting tool and, therefore, CAD toolpath limitations do not exist. The stereolithography apparatus uses an ultraviolet laser to selectively polymerize and solidify a polymeric liquid plastic solution under computer control. The device was used to produce a model of cranial bony anatomy from CT image data, providing full internal detail in the constructed model, including encased sinuses, foramen, and potentially complete internal anatomy within a closed skull. The advantages and disadvantages of this technology are reviewed with an emphasis on future development.     

应用数字化钛网塑形修补颅骨缺损

背景：颅骨修补的材料种类繁多,而修补效果也不尽相同,采用何种修补材料、如何将颅骨缺损修复的更加完美是当前国内外学者研究的热点。 目的：针对数字化三维塑形钛网在颅骨缺损修补中的临床应用进行探索。 方法：以“tissue engineering,craniocerebral trauma,CAD/CAM和titanium armor plate”为检索词,检索Medline数据库(2000/2011-06),“头颅骨损伤,数字化三维成形,钛网”为检索词,检索CNKI数据库。将近年发表的针对性强的文章纳入研究范围,同一领域的文献则选择近期发表或权威杂志的文章。排除与传统材料或方法修复头颅骨损伤和陈旧的文献。对查阅到的最新研究及临床应用有实用价值的文献详细分析并加以总结概括。 结果与结论：初次检索到236篇文献,最终纳入27篇文献进行分析。传统方法修复颅骨损伤已暴露很多问题,而钛网作为近几年临床应用广泛的颅骨修补材料显示了很多优点,尤其是随着数字化技术的广泛应用,头颅CT扫描数据、三维重建模拟缺损颅骨形状和曲度、个性化设计缺损颅骨的钛网补片,制造出了与缺损处吻合良好的修补物,使患者颅骨缺损修补后头颅形状恢复解剖原貌,无论是整形外观还是相容性方面均可取得满意效果。     

A unified model for the speed of sound in cranial bone based on genetic algorithm optimization

The density and structure of bone is highly heterogeneous, causing wide variations in the reported speed of sound for ultrasound propagation. Current research on the propagation of high intensity focused ultrasound through an intact human skull for non-invasive therapeutic action on brain tissue requires a detailed model for the acoustic velocity in cranial bone. Such models have been difficult to derive empirically due to the aforementioned heterogeneity of bone itself. We propose a single unified model for the speed of sound in cranial bone based upon the apparent density of bone by CT scan. This model is based upon the coupling of empirical measurement, theoretical acoustic simulation and genetic algorithm optimization. The phase distortion caused by the presence of skull in an acoustic path is empirically measured. The ability of a theoretical acoustic simulation coupled with a particular speed-of-sound model to predict this phase distortion is compared against the empirical data, thus providing the fitness function needed to perform genetic algorithm optimization. By performing genetic algorithm optimization over an initial population of candidate speed-of-sound models, an ultimate single unified model for the speed of sound in both the cortical and trabecular regions of cranial bone is produced. The final model produced by genetic algorithm optimization has a nonlinear dependency of speed of sound upon local bone density. This model is shown by statistical significance to be a suitable model of the speed of sound in bone. Furthermore, using a skull that was not part of the optimization process, this model is also tested against a published homogeneous speed-of-sound model and shown to return an improved prediction of transcranial ultrasound propagation.