【作者】 康健超；

【导师】 康宝生；

【作者基本信息】 西北大学 ， 计算机应用技术， 2011， 硕士

【摘要】 医学图像三维可视化技术为医生提供直观、逼真和具有真实感的三维器官体数据,从而有效的提高诊断效率,帮助医生明确诊断并指导手术,因此已经成为近年来的研究热点。本文在对可视化技术进行研究基础上,围绕国家自然科学基金项目《基于三维统计变形和有限元混合模型的颌骨手术计划和仿真》中的三维医学图像的体重建及体数据可视化展开工作,主要研究内容如下：1.采用预合成体绘制积分技术分析体绘制原理,对体绘制的光照模型、光学模型和体绘制的加速技术进行了系统研究。重点介绍了三种经典的体绘制算法,并对传统的抛雪球法做了仿真实验。2.针对传统光线投射算法绘制速度慢、精度差等缺点,提出一种改进的基于GPU编程的光线投射算法。算法采用新的采样合成函数,结合经典的Blinn-Phong光照模型,采用不透明度提前截止判断光线终止,算法使用Cg语言编写顶点程序和片段程序来实现。实验结果表明该算法既可以增强传统光线投射算法的绘制效果,也可以加快算法的速度。3.针对传统的GPU光线投射算法绘制效果差、效率低等问题,提出一种基于八叉树编码的CUDA光线投射算法。首先,采用八叉树对体数据进行编码,有效地剔除体数据中对重建图像无贡献的部分；其次,将体数据绑定到三维纹理上,根据体数据大小分配线程,每条光线与体数据求交时采用并行计算；最后,在CUDA内核中实现光线投射算法。实验结果证明该算法不仅可以增强传统的GPU光线投射算法的绘制效果,而且可以加快算法的绘制速度。本文所提出的算法在医生进行辅助检测、术前分析、术中监测等方面提供了良好的可视化工具。更多还原

【Abstract】 Three-dimensional Visualization technologies of medical images can provide intuitive、distinct and realistic volume data of anatomical structures. They can increase the efficiency of diagnosis effectively, and can help doctors confirm the diagnosis, as well as guide the surgery. Therefore, they have become the hotspot in medical fields in recent years. In this thesis, based on the research on the technologies of visualization, and under grant of the National Natural Science Fund Project "An orthognathic surgical planning and simulation based on 3D statistical deformation and finite element hybrid model", we focus on the subject of Volumeric rendering of 3D medical images. The main contents of this thesis are listed as follows:1. The principle of volumetric rendering is analyzed by the pre-integral synthesis, and Optical models、Ⅲumination models and the acceleration technique of volumetric rendering have been studied systematically. We introduce three classical algorithms of the volume rendering, and simulate the Splatting algorithm.2. To improve low sampling and poor sampling efficiency in the traditional ray casting algorithm, an improved ray casting algorithm based on GPU is proposed. The algorithm combines Blinn-Phong illumination model with a new sample synthesis function and early opacity termination condition, which is implemented by vertex programs and fragment programs in Cg language. The experimental results show that the algorithm can not only enhance the visualization effect of traditional ray-casting algorithm, but also accelerate the speed of volumetric rendering. 3. To improve the low efficiency and poor visualization results in the traditional ray casting algorithm based on GPU, an Octree Encoding based ray casting algorithm is proposed in CUDA, First, in this algorithm, the volume data is structured by Octree, which can eliminate a part of voxels that have no contribution to the reconstructed image efficiently. Secondly, the voxels are bound to 3D texture, and the threads are distributed according to the size of Volume data, parallel computing is used when finding out the intersection of each of the light and the volume data. Finally, the ray casting algorithm is implemented in CUDA kernel. The experimental results show that the proposed algorithm can not only enhance the visualization effect of GPU based traditional ray-casting algorithm, but also accelerate the speed of volumetric rendering.The algorithm proposed in this thesis provide a good visualization tool in helping doctors adjutant detection、pre-operative analysis and intra-operative monitor.更多还原