【作者】 张翼；

【导师】 宋志坚；

【作者基本信息】 复旦大学 ， 生物医学工程， 2008， 博士

【摘要】 脊柱手术是一类风险较大且病例较多的外科手术,在手术导航技术问世之前,医生在手术中主要是依靠病人术前CT断层图像或术中X射线透视获得病人的解剖信息。虽然这些方法对手术起到了一定的辅助指导作用,但是,医生需要通过这些影像在自己头脑中构建人体器官的三维形态与手术过程,手术质量很大程度上依赖于医生的临床经验,而对术中操作是否正确缺少科学依据。并且,应用术中X射线透视会使医生与病人受到较大剂量的辐射,增加了手术的时间和感染的风险。手术导航技术正是为解决上述问题而产生的,它以医学影像数据为基础,通过建立虚拟现实空间,结合三维可视化技术模拟手术中的关键步骤,借助空间定位仪跟踪手术器械相对于病变组织的位置关系,并将其实时反映在病人术前或术中的影像上,从而实现对手术的引导。该技术在提高手术定位精度,减少手术损伤,降低手术失误率方面等有重要的临床应用价值,也成为计算机辅助治疗领域里的重要研究内容。本文以解决脊柱外科手术导航系统的关键技术,实现脊柱外科手术导航系统的建立为研究目的,根据导航模式不同,分为基于X射线透视图像的导航、基于CT图像的三维导航、基于3D/2D配准的微创导航三部分进行了研究。在第一部分基于X射线透视图像导航的研究中,本文首先应用改进后维纳滤波以及图像噪声综合抑制方法,对X射线透视图像进行了预处理,提高了图像的清晰度。然后对X射线成像系统的标定算法进行改进,提出一种适用于C型臂X射线透视系统的在线标定技术,同时对影像增强器引起的图像失真进行了校正。该技术解决了图像变形对导航精度的不利影响,减少了术前的准备环节,提高了C型臂X射线机应用灵活性。最后本文应用坐标转换技术建立了基于X射线透视图像的手术导航系统。在第二部分基于CT图像的三维手术导航中,本文主要解决了图像三维重建与空间配准速度较慢的问题。首先通过应用基于纹理映射的体绘制方法加快了CT图像三维重建速度,然后提出应用点配准与迭代最近点配准结合的方法进行CT图像空间到病人空间的配准,并对迭代最近点算法进行了改进,通过构造最小外接球树进行最近点寻找的方法,提高了配准精度与效率。基于上述关键技术建立了三维手术导航系统。本文的第三部分是围绕着在微创条件下进行脊柱手术导航工作而开展的。微创手术是脊柱外科发展的重要方向,对手术导航也提出了新的要求。本文通过将CT图像(3D)与X射线透视图像(2D)的配准,解决了传统手术导航中的开放式配准与微创手术相矛盾的问题,实现了微创条件下的手术导航。在配准的步骤中,本文提出一种适用于脊柱微创手术导航的3D/2D分步式配准方法。首先应用点特征、面特征进行快速粗配准,对配准误差进行限制,然后采用一种基于图像梯度特征的配准算法进行精配准,这种算法是根据CT图像梯度在成像平面的投影强度构造最优化函数,能获得较稳定的局部极值,减小了X射线图像对配准精度的影响,提高了系统的稳定性。另外,由于该算法只对形成图像边缘的光线进行追踪,因此配准速度得到了大幅提升。通过以脊柱标本为模型的导航实验,本文分别对三类导航系统的注册误差,定位误差,准备时间等指标进行了测试,并与国外同类产品进行了对照。结果表明本文建立的手术导航系统达到了临床应用的标准。本文最后分别从硬件与软件两个方面对手术导航进行了系统集成,形成了能够应用于临床的脊柱外科手术导航系统。更多还原

【Abstract】 Spine surgery is considered as a common yet risky surgical treatment. Before the Image-guided surgery (IGS) technology was introduced, the surgeons could only rely on the anatomical information obtained from the preoperative CT images or inoperative X-ray fluoroscopes which can only offer limited help for the surgeons in terms of reconstruction of the 3D image of the patients. The quality of the surgery mainly reckons on the surgeons’ experiences. Besides, X-ray Fluoroscopy during the surgery increases the radiation exposure to both the patients and the surgeons. To obtain different views, it necessary to reposition the C-arm X-ray machine, prolongs the operating time and increases the infection risks. IGS technology is aimed to solve these problems. Based on medical image data and with the help of virtual reality technology, IGS uses dimensional position sensor to track the medical instruments and the pathological tissue and to correlate the operative field to the preoperative medical imaging data and leads to the real time guide during the surgery. IGS provides important clinic value in improving surgical positioning precision, lowering surgical trauma and error rate and has become one of the most important research directions in computer-aided therapy field.The goal of this dissertation is to implement IGS system for spine surgery by solving the key technologies. Based on imaging modality, we focus on three different image guided systems, which are based on fluoroscopy image, CT image and 3D/2D imaging registration respectively.1. X-ray fluoroscopy based IGSWe increase image definition by restoring fluoroscopy images using a modified Wiener filter and wavelet synthetic filter. Then, we improve the calibration algorithm for the C-arm fluoroscopy image system, propose an "on line" calibration technique and revise the image distortion caused by the image intensifier. This technology eliminates the disadvantage caused by the image distortion, shortens the preparation time before surgery and improves the flexibility of the C-arm X-ray machine. Finally, we develop a system of X-ray fluoroscopy based IGS combined with coordinate transform.2. CT image based 3D IGSWe mainly focus on two problems. First, we use a texture mapping-rendering algorithm to accelerate the 3D images reconstruction. Second, we propose a registration method combing of point matching and surface matching registration method. We also modify the Iterative Closest Point (ICP) algorithm to register the surface of bony structures of CT to patient, which increases the precision and efficiency of the IGS proceeding. Applying above technologies, we develop a system of CT image based IGS.3. 3D/2D images registration based mini invasive IGSMinimal invasive surgery is the future of spine surgery and brings new challenge to IGS. We present a novel multi-step 3D/2D images registration method. After using point and surface feature based registration method for coarse registration, we use an improved gradient feature based registration method for fine registration. This gradient feature based method provides a feasible way of determining the global solution. Besides, the speed of registration is greatly accelerated since this method only samples the rays passing through the edge of X-ray image.Further experiment is performed using a lumbar spine phantom to evaluate our IGS system. We have tested the registration error, location error, preparation time and other indicators. The test result demonstrates that our IGS system has met with the clinical application standard after comparing our data with the similar products abroad.Finally, we develop a IGS system for clinical spine surgery after integrating hardware and software.更多还原