基于二次误差测度的特征保持简化算法

三维人脸模型通常具有很高的分辨率，而且人脸表面特征分布具有不均匀性，需要对模型进行简化，去除冗余信息，提高计算效率。但是现有的模型简化算法在特征保持方面并不能令人满意。本文将基于曲率信息的三维顶点特征表示度量加入模型顶点收缩代价的估计过程，在简化模型的同时保留特征丰富区域的信息。同时，本文在边折叠过程中加入了检测与再折叠操作，解决了简化过程中出现的重叠三角面问题。实验表明，本算法能够在可靠地生成高质量的简化模型的同时，更好地保持特征丰富区域的细节信息。     

满三维图像重建的卷积反投影算法

本文用构造δ序列的方法,给出了一种n维Radon变换反演的卷积反投影算法,证明了该算法在图像的连续点收敛于原图像,当n=2时,就是广泛用于图像重建的卷积反投影算法,由此也给出了卷积反投影方法收敛性的另一种推导。当n=3时,是新的满三维重建的卷积反投影算法,由于三维反演公式具有局部性,该算法对研究三维局部重建有启示。并基于三维情形,利用模拟数据进行了数值仿真,说明该算法是一种有效的三维图像重建算法。     

基于三维人脸模型装配的表情驱动算法

为了实现三维人脸模型中的面部表情控制，本文提出了一种基于人脸模型装配的表情驱动方法。该方法利用FACS编码系统计算出各动作单元AU对应的表情基参数，结合生物解剖学与运动学的相关知识，将肌肉与骨骼装配到三维人脸模型上，通过驱动控制点完成面部的表情驱动。与传统基于手工建模或数据驱动方法相比，本方法不需要大量的人工参与和训练数据。因此，该方法在数字娱乐、虚拟人物和人机交互等领域有着广泛的应用前景，为相关领域的研究和应用提供了一定的参考。     

前列腺癌图像引导放疗中骨骼对锥形束CT校准的影响研究

目的 利用前列腺癌患者治疗前锥形束CT(CBCT)获取的内植标记物位移信息,量化盆腔区域骨骼对图像引导放疗(IGRT)造成的影响.方法 对10例内植标记物前列腺癌患者进行治疗前CBCT扫描,记录标记物于左右(LR)、头脚(SI)、前后(AP)3个方向上的位移,利用算法量化盆腔区域骨骼对CBCT校准的影响.结果 标记物于LR、SI、AP 3个方向上的位移平均值分别为0.51、1.33、1.36 mm;10例患者骨骼对校准影响量化指标误差均方根(RMS)于LR、SI、AP 3个方向上的平均值分别为0.02、0.06、0.07 mm.结论 盆腔区域骨骼对前列腺癌IGRT治疗中CBCT校准影响甚微,但仍需提高软硬件和图像处理水平.     

基于视觉运动捕获数据的三维模型驱动方法

基于视觉运动捕获数据的三维模型驱动涉及到将三维位置数据转化为模型运动数据,和三维模型的动作驱动。视觉运动捕获的三维运动数据,由于缺乏骨架各关节点间的旋转信息,不能直接用于三维模型的驱动。本文提出了依据各关节点的相关性,求解骨架关节点的旋转信息,并计算出各关节点的欧拉角,将原始据转换为模型运动数据。然后,将转换后的运动数据应用于三维模型,通过改进后的线性混合皮肤变形算法（LBS）,实现了基于三维运动参数的三维模型驱动。文中实验结果验证了算法的有效性。     

基于简化机头模型与筒串卷积算法的调强计划独立三维剂量验算

目的 建立医用直线加速器的双点源机头模型,结合筒串卷积算法实现调强治疗计划三维独立剂量验算。 方法 分别对瓦里安、医科达直线加速器建立双点源机头模型,结合筒串卷积剂量算法计算三维剂量分布。与电离室水箱扫描数据比较规则野的Scp、PDD、离轴剂量分布确认计算模型。两种加速器分别各选取 12例共 24例调强治疗计划进行比较,对TPS计算结果进行独立验算,并且与探测器矩阵测量结果进行比较。 结果 矩形野中心点剂量偏差均<1%,射野内相同位置二者剂量偏差≤1%,半影区域位置偏差≤1 mm。采用3%/3 mm标准γ通过率均>90%。 结论 建立了基于双点源机头模型结合筒串卷积算法实现调强治疗计划三维独立剂量验算,对规则射野及调强治疗计划的验证比较,表明该方法和计算模型可用于临床计划的三维独立剂量验算。     

计算机三维重建在医学图像分析中的应用

本文主要是介绍我们自行开发的三维医学图像处理与分析系统在医学CT、MR图像中的应用。我们应用模糊聚类均值对医学图像进行处理 ,增强了对薄骨和关节接合处骨骼的识别能力 ,取得了较好的三维重建效果。重建的三维模型可清晰再现解剖结构 ,大大增加了医学图像分析系统的临床实用价值。     

盆腔肿瘤三维可视化

目的 探讨基于CTA断层图像重建盆腔肿瘤及周围结构数字模型及三维可视化的方法.方法 盆腔肿瘤患者1例,应用多层螺旋CT动脉造影技术(MSCTA),以层厚0.50mm进行腰骶椎薄层平扫,得到Dicom数据,导入Mimics软件,对盆腔肿瘤、供血血管、骨骼等进行半自动分割,以进行三维重建.结果 成功建立盆腔肿瘤及周围结构的三维数字可视化模型.结论 结合应用MSCTA二维图像与Mimics三维重建软件,建立的骶骨、盆腔肿瘤及其供血动脉等模型,既能够显示盆腔血管系统的空间位置关系,又可显示盆腔肿瘤的大小、位置、性质、供血动脉及其骶骨破坏情况,有助于术前模拟和预测.     

基于像素采样不足的伪迹处理方法

在实际的三维锥束CT重建中，受扫描结构的限制，当连续X射线穿过物体时，像素对射线的采样间隔不能满足Nyqust采样定理，这样通道信号产生混叠，使得重建图像出现伪迹。本论文针对这一问题，在用splatting算法计算代数重建算法权系数的基础上，分析了伪迹产生的原因并对对应的内插函数作了适当的变换，提出了适用于3-D锥束圆轨迹CT扫描系统的去伪处理方法。结果表明，经过去伪处理后，重建图像的分辨率明显提高。     

基于Android智能手机的彩色图像盲数字水印算法

针对智能手机上的图像版权保护问题,提出了一种适用于Android系统的彩色图像盲水印算法。算法根据DCT系数和图像灰度值之间的线性关系直接在空域中修改DCT系数。这种方法无需进行DCT变换和反DCT变换,可大幅度降低计算量。此外,该算法提取水印时不需要原始载体图像,能够实现盲提取。在Android手机上对该算法进行了大量实验,实验结果表明,提出的算法具有良好的透明性和鲁棒性。     

B-样条子波在图像边缘检测中的应用

由于经典的边缘提取算子的处理结果不是十分令人满意,本文采用基于微分算子的思想以B-样条子波为处理函数的边缘提取算法。该算法充分的利用了B-样条函数在边缘拟合上的优势以及小波方法的多尺度优势,算法的处理结果令人满意。     

自适应模糊增强的乳腺癌CISH细胞边缘检出

目的提出一种自适应设定可调参数的双线性广义模糊增强的细胞Canny边缘检出方法。方法根据乳腺癌CISH病理图像组织灰度分布特征,自动选取阈值设置双线性广义模糊增强的可调参数,并用自适应模糊增强算法代替Canny算法中的高斯滤波器,在计算梯度的幅值和方向以及抑制非极大值梯度幅值的基础上,利用最大类别方差法求双阈值进行细胞的强弱边缘检出。结果实现了乳腺癌CISH细胞的强弱边缘检出。结论实验结果表明该方法提取细胞边缘效果理想,比较固定模糊增强参数而言,更具有效性和实用性。     

Immediate maxillary reconstruction after malignant tumor extirpation.

AIMS: Immediate maxillary reconstruction after malignant tumor extirpation differs from other types of maxillary reconstruction. Our reconstruction algorithm is described in this article. METHODS: One hundred ninety-four patients who had undergone maxillectomy for malignant tumors were reviewed, and maxillectomy defects were classified with the method of Cordeiro and Santamaria. RESULTS: Mean total blood loss was 848 ml, and 71 patients died within 2 years after surgery. For type IIIa defects of the orbital floor, titanium mesh or vascularized bone or cartilage was used for reconstruction, but the rate of postoperative complications did not differ between titanium and autografts. Therefore, to reconstruct orbital floor defects we have recently used only titanium mesh. For type I or II defects, we use autografts for only selected cases. CONCLUSIONS: We strive to perform less-invasive reconstructive surgery after resection for maxillary malignancy.     

光学体视显微图像立体测量系统研究与开发

根据立体视觉的原理,设计实现了基于光学体视显微镜图像的立体测量系统。从图像采集、摄像机标定、立体匹配到深度图生成,建立了完整的系统。对系统中的摄像机模型进行了线性标定,达到了亚像素的标定精度。在立体匹配中实现了三种不同的算法:改进的区域相关性匹配算法、基于边界特征的概率松弛迭代匹配方法、新序数测度法(New Ordinal Measure),并对结果的精度进行了分析和比较。     

钛网及同种异体骨联合植入术在胸腰椎结核术中的应用价值

目的探讨钛网及同种异体骨联合应用植入术在胸腰椎结核手术中的应用价值。方法2002～2007年采用一期病灶清除,前、后路内固定,钛网及同种异体骨联合应用植入术治疗胸腰椎结核患者23例,术后观察伤口愈合、结核中毒症状及神经功能的恢复,固定融合及复发情况。结果23例患者获得1～3年随访,伤口均一期愈合,结核中毒症状明显改善或消失,神经功能完全恢复,固定融合情况良好,无结核复发迹象,6～12周带支具下床活动,6个月恢复正常生活及工作。结论胸腰椎结核一期前路病灶清除后应用钛网及同种异体骨联合重建并结合节段性内固定是一种值得推广的手术方法。     

An accurate, convective energy equation based automated meshing technique for analysis of blood vessels and tissues.

An automated three-element meshing method for generating finite element based models for the accurate thermal analysis of blood vessels imbedded in tissue has been developed and evaluated. The meshing method places eight noded hexahedral elements inside the vessels where advective flows exist, and four noded tetrahedral elements in the surrounding tissue. The higher order hexahedrals are used where advective flow fields occur, since high accuracy is required and effective upwinding algorithms exist. Tetrahedral elements are placed in the remaining tissue region, since they are computationally more efficient and existing automatic tetrahedral mesh generators can be used. Five noded pyramid elements connect the hexahedrals and tetrahedrals. A convective energy equation (CEE) based finite element algorithm solves for the temperature distributions in the flowing blood, while a finite element formulation of a generalized conduction equation is used in the surrounding tissue. Use of the CEE allows accurate solutions to be obtained without the necessity of assuming ad hoc values for heat transfer coefficients. Comparisons of the predictions of the three-element model to analytical solutions show that the three-element model accurately simulates temperature fields. Energy balance checks show that the three-element model has small, acceptable errors. In summary, this method provides an accurate, automatic finite element gridding procedure for thermal analysis of irregularly shaped tissue regions that contain important blood vessels. At present, the models so generated are relatively large (in order to obtain accurate results) and are, thus, best used for providing accurate reference values for checking other approximate formulations to complicated, conjugated blood heat transfer problems.     

An accurate,convective energy equation based automated meshing technique for analysis of blood vessels and tissues

An automated three-element meshing method for generating finite element based models for the accurate thermal analysis of blood vessels imbedded in tissue has been developed and evaluated. The meshing method places eight noded hexahedral elements inside the vessels where advective flows exist, and four noded tetrahedral elements in the surrounding tissue. The higher order hexahedrals are used where advective flow fields occur, since high accuracy is required and effective upwinding algorithms exist. Tetrahedral elements are placed in the remaining tissue region, since they are computationally more efficient and existing automatic tetrahedral mesh generators can be used. Five noded pyramid elements connect the hexahedrals and tetrahedrals. A convective energy equation (CEE) based finite element algorithm solves for the temperature distributions in the flowing blood, while a finite element formulation of a generalized conduction equation is used in the surrounding tissue. Use of the CEE allows accurate solutions to be obtained without the necessity of assuming ad hoc values for heat transfer coefficients. Comparisons of the predictions of the three-element model to analytical solutions show that the three-element model accurately simulates temperature fields. Energy balance checks show that the three-element model has small, acceptable errors. In summary, this method provides an accurate, automatic finite element gridding procedure for thermal analysis of irregularly shaped tissue regions that contain important blood vessels. At present, the models so generated are relatively large (in order to obtain accurate results) and are, thus, best used for providing accurate reference values for checking other approximate formulations to complicated, conjugated blood heat transfer problems.     

Level of detail technique for plant models

1 IntroductionPlant is a basic element in our environment,andit is also a specific phenomenon in the nature with com-plex shapes and colours,and with rich details of small,isolated and non-manifold geometry.Modelling,simulation and visualization of forestlandscape is a new multidisciplinary research of com-puter science,agric-forestry,and ecosystem.Interac-tive and realistic visualization of plant community be-come challenging problem in computer graphics andvirtual reality[1,2].The difficulti…     

基于小波变换极大模的多模医学图像融合

多模态医学图像融合由于其对医学临床诊断的意义已引起广泛的关注,基于图像边缘特性的融合方法逐渐成为研究的重点。本文提出了一种基于离散二进小波变换的多尺度边缘检测和图像融合的方法,实现了特征级图像融合。不同于以往的从极大模值点直接重建图像,本文的算法利用极大模值点建立有效的融合规则,然后从融合的小波系数重构信号。融合图像的交互信息和峰值信噪比等检测指标表明此方法优于传统融合算法。