Björn Gudmundsson

Display of Density Volumes

The advent of inexpensive, high-speed processing and storage has fueled interest in new ways to process and display 3D images. This new discipline of 3D imaging promises to produce a wealth of exciting applications in many fields. For three years, engineers at Linkoping University have experimented with algorithms and methods to display 3D images obtained from a variety of sources, including computer-aided tomography, transmission electron microscopy, and laser microscopy. This article reviews the applicability of different display methods for different types of volumes, the advantages and disadvantages of different techniques, and the results of experiments when image processing techniques were applied before the images were displayed.

An interactive high-level language system for picture processing

Efficient work in a picture processing laboratory requires an interactive system. An interactive high-level language system for the PICAP laboratory, Linko¨ping University, is described. The system consists of a monitor, a text editor, a translator for incremental translation of a structured high-level language, an interpreterm and a procedure library. The language includes constructs for parallel picture operators. Incremental translation makes it possible for the users to execute and modify procedures in rapid sequence.

Presentation and perception of 3D images

In our paper we describe some experiments in processing and display of 3-D images. The experiments have been carried ont on the PICAP II system.

Interactive Display Of 3D-Images In Picap II

In this paper we present some experiments in processing and display of true 3D-images (density volumes). The experiments have been carried out on the PICAP II image processing system.

Compression of Sequences of 3D-Volume Surface Projections

The large data sets constituting 3D-volumes of reasonable resolution inflict high costs in terms of storage space and computation time. In this paper we describe an algorithm for data compression of sequences of 3D-volume projections where the projection angle increment is small and the surfaces of the objects in the volume are rendered using depth-only shading. The algorithm is based on a ray-casting method for incremental generation of such sequences. Experiments on a specific CT-volume yielded a compression factor of 32 for an angle increment of 1 degree and grid-point accuracy in object surface localization.

Manipulation And Display Of 3-D Images For Surgical Planning

In this paper we describe some of our experiments in the processing and display of 3-D images from CT-scanners. In the first part of the paper we describe the implemented surface displays and in the second part we discuss some applications of 3-D image transformations.

Fast Shadowing of Volume Data

An algorithm for fast generation of shadows in volume rendering is presented. The algorithm is an extension of a method for incremental generation of rotation sequences of volume projections. A sequence is generated as a viewer followed by a light-source moves along a circular orbit around the volume. The points in shadow in a certain projection are those that are visible from the viewers position but not from that of the light-source. The incremental method allows us to exploit the coherence between successive projections in order to reduce the number of costly raycasting operations that are neccessary to determine if points are in shadow or not. The shadowing algorithm has been implemented and tested. The results show significant reductions in computational cost compared to “brute force” generation of shadows.

An Interactive Visualization System for SPECT-Volumes

A system for fast interactive visualization of volumes is presented. The system is implemented on a SUN Sparc work station under X-windows. Volumes can be viewed either by browsing through the stack of slices or by generating projections of the volumes using a number of different techniques. Surfaces of objects in the volume can be shaded by means of an illumination model (e.g. Phong-shading). Rotation sequences are generated by an algorithm that yields a speed-up factor of about 10 over traditional ray-casting methods. To further enhance the viewers perception of the third dimension, the algorithm also allows for fast generation of rotation sequences with shadows. In our implementation, rotation-sequences are simultaneously generated and displayed at a sustained rate of about 5 projections per second on a standard SUN Sparc IPC. The angle increment between successive projections is set by the user. Sequences can be saved for later replay at even higher animation rates (up to 25 frames per second). Other features of the system include variable thresholding and pseudo- colouring of intensity intervals interactively defined by the user.

Some Aspects of a Viewing System for Radio Therapy Dose Planning

The PICAP II Image Processing System (1) at Linkoping University has been used to process and display true 3-D images, e.g. a stack of X-ray tomograms (2). Projections of the 3-D volume are computed and displayed under interactive user control. This paper discusses the possibilities to use the PICAP II system in radio therapy dose planning, where the image data is represented by a volume made up of tomograms.