【作者】 吴正强；

【导师】 秦绪佳；

【作者基本信息】 浙江工业大学 ， 计算机软件与理论， 2009， 硕士

【摘要】 医学图像可视化是当前一个研究热点问题,它将计算机图形学和图像处理技术运用在生物医学工程中,在医学诊断、手术规划及模拟仿真等都方面都有着广泛的应用。体绘制技术已经成为医学图像可视化的重要方法。传输函数设计是体绘制算法中的关键步骤,它能突出显示体数据中人们感兴趣的特征。本文分析了传统一维传输函数难以提取复杂的特征,实现了基于灰度—梯度模直方图传输函数。针对灰度—梯度模直方图传输函数受噪声影响大和固定大小梯度计算的问题,设计将局部体素三维矩的特征值作为定义域的传输函数,该方法将体数据的局部形状特征引入传输函数设计。本文运用LH(Lower and High Intensity)来表示形成边界体素的两种物质,设计了将体素的LH值投射到直方图传输函数,LH直方图传输函数解决了灰度一梯度直方图传输函数当弧线相交时边界选取问题,实验表明使用LH直方图比现有得方法更有利于物质边界得选择。镜像LH直方图将边界分为两部分,而镜像LH直方图解决了物质边界归属问题,能够形成更清晰和准确的物质边界。本文提出了基于三切面和绘制空间的局部传输函数的设计,该方法有效的利用空间有效的解决了感兴趣区域和周围不感兴趣区域体数据值重叠的问题。本文还讨论和实现了基于硬件加速的二维和三维纹理体绘制算法,大大的提高体绘制的速度。三维纹理硬件技术算法有较好的绘制效果和达到实时交互的绘制能力。最后,本文实现了一个基于上述原理和方法的医学体视化系统,获得了良好的体绘制效果。更多还原

【Abstract】 Visualization on medical images is a hot spot field. It is an important application of computer graphics and image processing in biomedicine engineering. Visualization of medical images is widely used in diagnostic, surgery planning and simulating. Direct Volume Rendering is one of the most important techniques for visualizing medical volume data.Transfer function specification is arguably the most important task in volume visualization that will highlight those aspects of the volume data that are of interest to the user. As the traditional transfer function is difficult to extract the complex feature, this thesis implements a multidimensional transfer function base on the scalar value and the gradient magnitude. For this method is involved the problem of the noise impact and fixed size of the gradient calculation, a transfer function base local data features design method is presented in this thesis ,by examining relationships among three eigenvalues of inertia matrix.In this thesis, the two materials that form the boundary are labeled L and H. We design and implement a transfer function based on the LH histogram. The experiments tell that the LH transfer function is easy to select the boundaries while arches could be overlap in scalar value and gradient magnitude histogram. In mirrored LH space both sides of boundary can be classified independently.This thesis introduce two local transfer functions, their fields are users interactive selected in three sections or rendering space. They can easily isolate the regions of interesting while uninteresting regions contain the same range of data value. Finally, a medical image volume rendering system, which is based on texture-based hardware accelerated volume rendering technique, is designed and implemented with excellent result.更多还原