Christof Reinhart

VIRIM: a massively parallel processor for real-time volume visualization in medicine

Architecture and applications of a massively parallel processor are described. Volumes of 256×256×128 voxels can be visualized at a frame rate of 10 Hz using volume oriented visualization algorithms. A prototype of the scalable and modular system is currently set up. 3D rotation around an arbilrary rotation axis, perspective, zooming, and arbilrary gray value mapping are provided in real-time. Multiuser access over high-speed networks is possible. A volume oriented visualization algorithm is used that is tailored to the requirements in medicine [5]. With this algorithm, small structures of a size down to the pixel resolution, and structures without defined surfaces can be visualized as well as semitransparent objects. One application of the system is therapy planning in heart surgery.

Virim: A massively parallel processor for real-time volume visualization in medicine

Abstract Architecture and applications of a massively parallel system currently developed are described, which allows real-time visualization using volume oriented visualization algorithms. Volumes of 256 × 256 × 128 voxels can be visualized with a frame rate of 10 Hz. The system is scalable and modular, and will allow a multi-user access over high-speed networks. 3D-rotation around arbitrary rotation axis, perspective, zooming and arbitrary grey value mapping are provided in real-time. A volume oriented algorithm is used that is tailored to the requirements in medicine [H.-P. Meinzer et al., IEEE Comp. Graph. Appl. , 34 (Nov. 1991)]. With this algorithm, small structures without defined surfaces, e.g. , tumours, can be visualized as well as semi-transparent objects. One planned application of the system is heart surgery.

Evaluation of a real-time direct volume rendering system

VIRIM, a real-time direct volume rendering system is evaluated for medical applications. Experiences concerning the hardware architecture are discussed. The issues are the flexibility of VIRIM, the restriction to two gradient components only, the duplication of the volume data sets on different modules, the size of the volume data set, the gray-value segmentation tool, and the support of algorithmic improvements like space-leaping, early ray-termination and others. It turned out that flexibility is the main benefit and absolutely necessary for VIRIM. Given this flexibility the application areas of real-time rendering systems increase dramatically: Most of the user requirements focus now not on visualization but on general volume data processing. The most serious bottleneck of VIRIM is the limited volume memory that is integrated on the first prototype. The most frequently used tool of VIRIM is gray-value segmentation. It is highly useful if original, i.e. unsegmented data have to be dealt with, and if pre-segmented data have to be investigated. All other benefits and architectural shortcomings are not critical for the application areas of VIRIM, i.e. operation simulation and control in head surgery.