中国数字人脑部体数据的任意切面绘制

目的:实现医学断层图像序列的三维重建及任意切面显示。方法:结合医学图像三维可视化的2种方法:表面绘制方法和体绘制方法,采用以三维矩阵数值运算与逻辑运算为基础的体数据面绘制算法。结果:可以从任意角度和位置来观察切面的形状、大小、灰度分布等各种生理病理特征。结论:通过分析子矩阵分解算法解决实时性要求与存储空间和运行时间的矛盾,克服了表面绘制不能体现内部数据的缺点,从一定程度上解决了体绘制的速度问题。     

医学体数据可视化的研究和实现

医学体数据可视化在临床上已成为辅助诊断和辅助治疗的重要手段,其技术也成为近年来研究和应用的热点.本文讨论了体数据可视化中的体绘制算法(volume rendering)中最常用的光线投射法,并利用Visualization Tool Kit(VTK)--一个包含了多种体绘制技术的基于面向对象方法设计的、功能强大的可视化类库,来实现断层医学图像的三维重建,并比较了这几种体绘制技术的各自特点.重建效果表明基于VTK的体绘制技术具有应用灵活、重建效果逼真、重建速度较快等优点.     

中国数字人连续断层图像的局部聚类分割方法

目的 介绍一种使用Photoshop CS(Adobe;San Jose,CA,Corel KnockOut 2.0 plug-in)和Matlab 7.0(Math Works;Worcester,MA)软件对中国数字人彩色图像的分割方法.方法 首先使用Photoshop中knockout滤镜,利用其强大蒙板功能,交互式提取目标区域.然后在Matlab中使用形态学处理函数和边缘检测算子,精确提取平滑的轮廓线.结果 对骨、肌、脏器及大的血管、神经等完成了分割与分类,获取的轮廓线保留了精确的细节,定位准确且比较平滑.结论 局部聚类分割方法可以快速、准确的对中国数字人彩色图像进行分割与分类.     

基于平面插值的快速光线投射算法

插值算法是光线投射法中基本的计算方法,计算量很大,直接影响成像速度.传统的三元线性插值比较费时,许多人对其进行改进.本文提出一种平面插值算法,可以明显地提高成像速度并且图像质量仍可以接受.     

医学图像光线投影体绘制中一种改进的快速算法

光线投影算法是体绘制算法中图像效果比较好的方法，但存在运算量大，绘制速度慢的问题。为此本文提出了一种新的光线投影体绘制的加速算法，利用重采样点在两坐标系中的矩阵变换特性。减少矩阵运算量，加快重采样计算过程，并且通过将Bresenham算法扩展至三维，利用包围盒技术避免对空体元的采样，从而加速了光线投影的效率。实验结果表明改进后的加速算法，既能保证绘制质量，又能显著减少计算量，提高体绘制的速度。     

基于多媒体技术的快速并行体绘制

体绘制的成像速度一直是影响其发展的关键因素。我们提出了一种基于多媒体单指令多数据(single instruction multiple data,SIMD)技术的加速算法。在保证成像质量的前提下,通过采用MMX、SSE、SSE2指令,分别加速光线扫描、采样和坐标变换等部分,使得光线跟踪算法的成像速度提高了3～6倍。实验表明,该算法具有成像速度快、成像稳定等显著优势,具有很高的应用价值。     

基于片段融合的医学图像光线投影体绘制技术

光线投影算法是医学图像三维可视化中常用的体绘制技术,算法原理简单,具有较高的成像质量,但绘制速度较慢。我们改进算法,利用投射光线与平面簇求交,快速确定融合片段,减少插值计算量,采用基于片段的融合绘制技术,加快融合速度,并且利用包围盒技术减少对无效平面的求交,提高了光线投影的效率。实验结果表明,改进后的算法既能保证绘制质量,又能显著减少计算量,提高体绘制的速度。     

基于GPU的医学图像快速体绘制算法

目的:将传统的光线投射体绘制算法在具有可编程管线的图形处理器(GPU)上重新实现,将耗时的三线性插值和采样过程放在GPU上进行,提高重建速度.方法:首先将体数据和传递函数映射为纹理并将其载入到显存,接着通过对顶点着色程序和像素着色程序的编写将光线进入点、离开点的计算以及图像的合成运算移入GPU中,最后通过调整传递函数来实现不同的绘制效果.通过使用渲染到纹理技术,将绘制的中间结果保存到纹理,并以此来避免使用着色器的动态分支功能.结果:与传统的光线投射算法相比,本文算法可快速重建出质量较高的图像.结论:实验表明,在同等绘制质量的前提下,该方法的绘制速度显著提高,能够满足医学影像可视化的实时交互需求,具有较好的临床应用前景.     

基于多重增量递推和采样点分解的求交算法

同一投射光线上相邻采样点间以及屏幕相邻像素点投射光线上的递推增量间都存在着递推关系,本文据此提出一种利用这些递推关系来快速计算采样点坐标的多重增量递推算法,使投射光线与采样平面间交点的计算完全避免了乘法运算,同时把采样点坐标分解为整数和浮点数两部分,避免了计算采样点坐标时浮点数的取整运算.综合应用多重增量递推和采样点分解技术,对于采用三线性插值方式和常规光线投射算法,渲染速度达到传统采样点计算方式的2倍以上,且不需要额外的内存消耗和预处理,也不损失图像质量,在虚拟内窥成像中有较大应用价值.     

基于片段融合的医学图像光线投影体绘制技术

光线投影算法是医学图像三维可视化中常用的体绘制技术,算法原理简单,具有较高的成像质量,但绘制速度较慢.我们改进算法,利用投射光线与平面簇求交,快速确定融合片段,减少插值计算量,采用基于片段的融合绘制技术,加快融合速度,并且利用包围盒技术减少对无效平面的求交,提高了光线投影的效率.实验结果表明,改进后的算法既能保证绘制质量,又能显著减少计算量,提高体绘制的速度.     

大规模医学序列图像体视化研究与实现

为了解决PC机上难以实现大规模数据的体视化问题,考虑到PC机内存小,显卡性能低的情况,提出了一种单片读取图像数据的体视化解决方案。采用光线投射体绘制法,实现了三维体视化所需的缩放、平移、旋转、剖切等操作,解决了因单片读取数据而出现的高角度失真问题。绘制过程中,充分利用序列图像的颜色信息,真实地再现了人体的内、外部结构。还与VolView、3Dmed软件进行了对比试验。在VC＋＋．net平台下初步完成了面向PC的医学图像体视化原型系统的开发工作。     

交互式虚拟内窥镜成像及应用

目的：作为虚拟内窥镜系统开发的基础性课题,本文针对虚拟内窥镜研究中交互式成像问题展开研究,以求得快速而优质的成像效果。方法：首先提出一种简单直观的坐标变换方法,便于进行交互式的虚拟内窥镜成像。其次,为解决交互式虚拟内窥镜成像的速度问题,使用精简后的光线投射法进行体绘制重建,在使其能够在保证一定图像精度的同时提高速度。结果：实验得到了满意的交互式成像效果。结论：所提出的方法是切实可行的,从而为进一步开发高精度的交互式虚拟内窥镜系统打下了坚实的基础。     

Three-dimensional volume rendering of the ankle based on magnetic resonance images enables the generation of images comparable to real anatomy

We have applied high-quality medical imaging techniques to study the structure of the human ankle. Direct volume rendering, using specific algorithms, transforms conventional two-dimensional (2D) magnetic resonance image (MRI) series into 3D volume datasets. This tool allows high-definition visualization of single or multiple structures for diagnostic, research, and teaching purposes. No other image reformatting technique so accurately highlights each anatomic relationship and preserves soft tissue definition. Here, we used this method to study the structure of the human ankle to analyze tendon–bone–muscle relationships. We compared ankle MRI and computerized tomography (CT) images from 17 healthy volunteers, aged 18–30 years (mean 23 years). An additional subject had a partial rupture of the Achilles tendon. The MRI images demonstrated superiority in overall quality of detail compared to the CT images. The MRI series accurately rendered soft tissue and bone in simultaneous image acquisition, whereas CT required several window-reformatting algorithms, with loss of image data quality. We obtained high-quality digital images of the human ankle that were sufficiently accurate for surgical and clinical intervention planning, as well as for teaching human anatomy. Our approach demonstrates that complex anatomical structures such as the ankle, which is rich in articular facets and ligaments, can be easily studied non-invasively using MRI data.     

Ventricular shape visualization using selective volume rendering of cardiac datasets

In this paper, we present a novel technique of improving volume rendering quality and speed by integrating original volume data and global model information attained by segmentation. The segmentation information prevents object occlusions that may appear when volume rendering is based on local image features only. Thus the presented visualization technique provides meaningful visual results that enable a clear understanding of complex anatomical structures. In the first part, we describe a segmentation technique for extracting the region of interest based on an active contour model. In the second part, we propose a volume rendering method for visualizing the selected portions of fuzzy surfaces extracted by local image processing methods. We show the results of selective volume rendering of left and right ventricle based on cardiac datasets from clinical routines. Our method offers an accelerated technique to accurately visualize the surfaces of segmented objects.     

三维医学图象数据的分析与显示

本文报告了一种在微机上实现的三维医学图象分析与显示系统，具体算法采用体积描绘，用光线跟踪进行三维显示，结合矩算子进行局部景物分割，能获得精确的表面法向参量，使显示结果更为逼真，对实际三维医学图像数据的分析，显示结果证明系统具有一定的实用性。     

Fast perspective volume ray casting method using GPU-based acceleration techniques for translucency rendering in 3D endoluminal CT colonography

Recent advances in graphics processing unit (GPU) have enabled direct volume rendering at interactive rates. However, although perspective volume rendering for opaque isosurface is rapidly performed using conventional GPU-based method, perspective volume rendering for non-opaque volume such as translucency rendering is still slow. In this paper, we propose an efficient GPU-based acceleration technique of fast perspective volume ray casting for translucency rendering in computed tomography (CT) colonography. The empty space searching step is separated from the shading and compositing steps, and they are divided into separate processing passes in the GPU. Using this multi-pass acceleration, empty space leaping is performed exactly at the voxel level rather than at the block level, so that the efficiency of empty space leaping is maximized for colon data set, which has many curved or narrow regions. In addition, the numbers of shading and compositing steps are fixed, and additional empty space leapings between colon walls are performed to increase computational efficiency further near the haustral folds. Experiments were performed to illustrate the efficiency of the proposed scheme compared with the conventional GPU-based method, which has been known to be the fastest algorithm. The experimental results showed that the rendering speed of our method was 7.72 fps for translucency rendering of 1024×1024 colonoscopy image, which was about 3.54 times faster than that of the conventional method. Since our method performed the fully optimized empty space leaping for any kind of colon inner shapes, the frame-rate variations of our method were about two times smaller than that of the conventional method to guarantee smooth navigation. The proposed method could be successfully applied to help diagnose colon cancer using translucency rendering in virtual colonoscopy.     

基于改进光线投射法的冠脉图像三维重建

传统光线投射算法虽然绘制图像时能取得良好的效果,但因为运算速度较慢,限制了其广泛应用。为了在图像三维重建时既能保证质量,又能提高实时交互性,本文提出一种基于改进光线投射算法的冠脉三维重建方法,利用检测原数据点的数据值来简化重采样中三线性插值的复杂性,并结合切比雪夫空体素跳跃法,进一步提高算法的效率。实验结果表明,该算法能够在提高运算速度的同时,保证绘制冠脉三维图像的质量。     

Volume rendering based on magnetic resonance imaging: advances in understanding the three-dimensional anatomy of the human knee

The choice of medical imaging techniques, for the purpose of the present work aimed at studying the anatomy of the knee, derives from the increasing use of images in diagnostics, research and teaching, and the subsequent importance that these methods are gaining within the scientific community. Medical systems using virtual reality techniques also offer a good alternative to traditional methods, and are considered among the most important tools in the areas of research and teaching. In our work we have shown some possible uses of three-dimensional imaging for the study of the morphology of the normal human knee, and its clinical applications. We used the direct volume rendering technique, and created a data set of images and animations to allow us to visualize the single structures of the human knee in three dimensions. Direct volume rendering makes use of specific algorithms to transform conventional two-dimensional magnetic resonance imaging sets of slices into see-through volume data set images. It is a technique which does not require the construction of intermediate geometric representations, and has the advantage of allowing the visualization of a single image of the full data set, using semi-transparent mapping. Digital images of human structures, and in particular of the knee, offer important information about anatomical structures and their relationships, and are of great value in the planning of surgical procedures. On this basis we studied seven volunteers with an average age of 25 years, who underwent magnetic resonance imaging. After elaboration of the data through post-processing, we analysed the structure of the knee in detail. The aim of our investigation was the three-dimensional image, in order to comprehend better the interactions between anatomical structures. We believe that these results, applied to living subjects, widen the frontiers in the areas of teaching, diagnostics, therapy and scientific research.     

An improved matched filter for blood vessel detection of digital retinal images

The matched filter has been widely used in the detection of blood vessels of the human retina digital image. In this paper, the matched filter response to the detection of blood vessels is increased by proposing better filter parameters. These filter parameters are found by using an optimization procedure on 20 retina images of the DRIVE database. Comparisons with other approaches show that the matched filter that uses the newly found parameters outperforms the matched filter that uses the classical filter parameters as well as some vessel detection techniques. A technique is also discussed to find the best threshold value for the continuous matched filter output image and hence the best segmented vessel image.