Kevin Kreeger

High-quality volume rendering using texture mapping hardware

Wt present a method Jor volume rendering of regular grids cclhic~h takes advantage of <?D texture mapping hardware currc,rhlly available on graphics workstations. Our method products accurate shadang for arbitrary and dynamically changing directionul lights, viewing parameters, and transfer funclior~. TIlis is achieved by hardware interpolating the data values and gradients before software classification and shadrng. The method works equally well for parallel and perspective projections. We present two approaches for OUT method: one which takes advantage of software ray casting optimitaIrons nnd another which takes advantage of hardware blending (Acceleration. CR Categories: 13.1 [Computer Graphics]: Hardware Architecture; 1.3.3 [Computer Graphics]: Picture/Image Generation; 1.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism-Color, shading, shadowing, and texture

Mixing translucent polygons with volumes

We present an algorithm which renders opaque and/or translucent polygons embedded within volumetric data. The processing occurs such that all objects are composited in the correct order, by rendering thin slabs of the translucent polygons between volume slices using slice-order volume rendering. We implemented our algorithm with OpenGL on current general-purpose graphics systems. We discuss our system implementation, speed and image quality, as well as the renderings of several mixed scenes.

Image segmentation approach to extract colon lumen through colonic material tagging and hidden Markov random field model for virtual colonoscopy

Virtual colonoscopy provides a safe, minimal-invasive approach to detect colonic polyps using medical imaging and computer graphics technologies. Residual stool and fluid are problematic for optimal viewing of the colonic mucosa. Electronic cleansing techniques combining bowel preparation, oral contrast agents, and image segmentation were developed to extract the colon lumen from computed tomography (CT) images of the colon. In this paper, we present a new electronic colon cleansing technology, which employs a hidden Markov random filed (MRF) model to integrate the neighborhood information for overcoming the non-uniformity problems within the tagged stool/fluid region. Prior to obtaining CT images, the patient undergoes a bowel preparation. A statistical method for maximum a posterior probability (MAP) was developed to identify the enhanced regions of residual stool/fluid. The method utilizes a hidden MRF Gibbs model to integrate the spatial information into the Expectation Maximization (EM) model-fitting MAP algorithm. The algorithm estimates the model parameters and segments the voxels iteratively in an interleaved manner, converging to a solution where the model parameters and voxel labels are stabilized within a specified criterion. Experimental results are promising.

Hybrid volume and polygon rendering with cube hardware

Hybrid Volume and Polygon Rendering with Cube Hardware Kevin Kreeger and Arie Kaufman* Center for Visual Computing (CVC) and Department of Computer Science State University of New York at Stony Brook Stony Brook, NY 11794-4400 We present two methods which connect today’s polygon graphics hardware accelerators to Cube-5 volume rendering hardware, the successor to Cube4 The proposed methods allow mixing of both opaque and translucent polygons with volumes on PC class machines, while ensuring the correct compositing order of all objects. Both implementations connect the two hardware acceleration subsystems at the frame buffer. One shares a common DRAM buffer and one run-length encodes images of thin slabs of polygonal data and then combines them in the Cube composite buffer In both realizations, we take advantage of the predictable ordered access to frame buffer storage that is utilized by Cube-5 and the rest of the family of volume rendering accelerators based on the Cube design. CR Categories: 1.3.1 [Computer Graphics]: Hardware Architecture-Graphics Processors; 1.3.3 [Computer Graphics]: Picture/Image Generation-Display algorithms; 1.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism;

Adaptive perspective ray casting

We present a method to accurately and efficiently perform perspective volumetric ray casting of uniform regular datasets, called Exponential-Region (ER) Perspective. Unlike previous methods which undersample, oversample, or approximate the data, our method near uniformly samples the data throughout the viewing volume. In addition, it gains algorithmic advantages from a regular sampling pattern and cache-coherent read access, making it an algorithm well suited for implementation on hardware architectures for volume rendering. We qualify the algorithm by its filtering characteristics and demonstrate its effectiveness by contrasting its antialiasing quality and timing with other perspective ray casting methods.

Interactive electronic biopsy for 3D virtual colonscopy

We propose an interactive electronic biopsy technique for more accurate colon cancer diagnoses by using advanced volume rendering technologies. The volume rendering technique defines a transfer function to map different ranges of sample values of the original volume data to different colors and opacities, so that the interior structure of the polyps can be clearly recognized by human eyes. Specifically, we provide a user- friendly interface for physicians to modify various parameters in the transfer function, so that the physician can interactively change the transfer function to observe the interior structures inside the abnormalities. Furthermore, to speed up the volume rendering procedure, we propose an efficient space-leaping technique by observing that the virtual camera parameters are often fixed when the physician modifies the transfer function. In addition, we provide an important tool to display the original 2D CT image at the current 3D camera position, so that the physician is able to double check the interior structure of a polyp with the density variation in the corresponding CT image for confirmation. Compared with the traditional biopsy in the procedure of optical colonoscopy, our method is more flexible, noninvasive, and therefore without risk.

PAVLOV: a programmable architecture for volume processing

We present a purullel 2D mesh connected architecture with SIML) processing elements. The design allows for real-time volume rendering as well as interactive 30 segmentation and .1D feature extraction. Thas zs possible because the SIMD processing elements are programmable, a feature which also ullows the use of many different rendering algorithms. We present an algorithm which, with the addition of hardware re,sources, provides conflict free access to volume slices along any of the three major axes. The volume access conflict bus been the main reason why previous similar architectures could not perform real-time volume rendering. We present the performance of preliminary algorithms on a software simulator of the architecture design. CR Categories: C.1.2 [Processor Architectures]: Mult,iple Data Stream .4rchitectures (Multiprocessors)-Singleirlst,rllc:tion-streanl, multiple-data-stream processors (SIMD) ; 1.3.1 [Computer Graphics]: Hardware ArchitectureGraphics processors, Parallel processing; 1.4.6 [Image Proc.rssillg And Computer Vision]: Segmentation;

Interactive navigation for PC-based virtual colonscopy

Virtual colonoscopy on powerful workstations has the distinct advantage of interactive navigation, as opposed to passive viewing of cine loops or pre-computed movies. Because of the prohibitive cost of hardware, only passive displays have been feasible for the wide-scale deployment required for mass screening. The purpose of our work is to compare low-cost commodity hardware as an effective tool for interactive colonographic navigation versus the expensive workstations.

3D virtual colonoscopy with real-time volume rendering

In our previous work, we developed a virtual colonoscopy system on a high-end 16-processor SGI Challenge with an expensive hardware graphics accelerator. The goal of this work is to port the system to a low cost PC in order to increase its availability for mass screening. Recently, Mitsubishi Electric has developed a volume-rendering PC board, called VolumePro, which includes 128 MB of RAM and vg500 rendering chip. The vg500 chip, based on Cube-4 technology, can render a 2563 volume at 30 frames per second. High image quality of volume rendering inside the colon is guaranteed by the full lighting model and 3D interpolation supported by the vg500 chip. However, the VolumePro board is lacking some features required by our interactive colon navigation. First, VolumePro currently does not support perspective projection which is paramount for interior colon navigation. Second, the patient colon data is usually much larger than 2563 and cannot be rendered in real-time. In this paper, we present our solutions to these problems, including simulated perspective projection and axis aligned boxing techniques, and demonstrate the high performance of our virtual colonoscopy system on low cost PCs.

Real-time volume rendering for virtual colonoscopy

We present a volume rendering system that is capable of generating high-quality images of large volumetric data (e.g., 5123) in real time (30 frames or more per second). The system is particularly suitable for applications that generate densely occluded scenes of large data sets, such as virtual colonoscopy. The central idea is to divide the volume into sets of axis-aligned slabs. The union of the slabs approximates the shape of a colon. We render sub-volumes enclosed by the slabs and blend the slab images. We use the slab structure to accelerate volume rendering in various aspects. First, empty voxels outside the slabs are skipped. Second, fast view-volume clipping and occlusion culling are applied based on the slabs. Third, slab images are reused for nearby viewpoints. In addition, the slabs can be created very efficiently and they can be used to approximate perspective rendering with parallel projection, so that our system can benefit from fast parallel projection hardware and algorithms. We use image-warping to reduce the artifacts due to the approximation.