Spoerk Jakob, Bergmann Helmar, Wanschitz Felix, Dong Shuo, Birkfellner Wolfgang
University of Applied Sciences Technikum Wien, Vienna, Austria.
Med Phys. 2007 Nov;34(11):4302-8. doi: 10.1118/1.2789500.
Digitally rendered radiographs (DRR) are a vital part of various medical image processing applications such as 2D/3D registration for patient pose determination in image-guided radiotherapy procedures. This paper presents a technique to accelerate DRR creation by using conventional graphics hardware for the rendering process. DRR computation itself is done by an efficient volume rendering method named wobbled splatting. For programming the graphics hardware, NVIDIAs C for Graphics (Cg) is used. The description of an algorithm used for rendering DRRs on the graphics hardware is presented, together with a benchmark comparing this technique to a CPU-based wobbled splatting program. Results show a reduction of rendering time by about 70%-90% depending on the amount of data. For instance, rendering a volume of 2 x 10(6) voxels is feasible at an update rate of 38 Hz compared to 6 Hz on a common Intel-based PC using the graphics processing unit (GPU) of a conventional graphics adapter. In addition, wobbled splatting using graphics hardware for DRR computation provides higher resolution DRRs with comparable image quality due to special processing characteristics of the GPU. We conclude that DRR generation on common graphics hardware using the freely available Cg environment is a major step toward 2D/3D registration in clinical routine.
数字重建射线照片（DRR）是各种医学图像处理应用的重要组成部分，例如在图像引导放射治疗程序中用于确定患者体位的二维/三维配准。本文提出了一种通过使用传统图形硬件进行渲染过程来加速DRR创建的技术。DRR计算本身是通过一种名为抖动体素绘制的高效体绘制方法完成的。为了对图形硬件进行编程，使用了NVIDIA的图形C语言（Cg）。本文介绍了一种用于在图形硬件上渲染DRR的算法描述，并给出了将该技术与基于CPU的抖动体素绘制程序进行比较的基准测试。结果表明，根据数据量的不同，渲染时间可减少约70%-90%。例如，使用传统图形适配器的图形处理单元（GPU），与基于英特尔的普通PC上6Hz的更新速率相比，以38Hz的更新速率渲染2×10⁶体素的体积是可行的。此外，由于GPU的特殊处理特性，使用图形硬件进行抖动体素绘制以计算DRR可提供具有可比图像质量的更高分辨率的DRR。我们得出结论，在临床常规中，使用免费的Cg环境在普通图形硬件上生成DRR是迈向二维/三维配准的重要一步。
