Design and implementation of full-frame, bit-allocation image-compression hardware module. Work in progress

Technical considerations in planning a distributed teleradiology system

A large-scale teleradiology project is under way to link a Florida imaging center to the UCLA Department of Radiology. The initial goal is to provide Florida patients in a routine clinical practice environment with subspecialty consultation by academic radiologists. The plan then calls for the addition of other domestic and international sites. Technical issues in planning to establish the necessary teleradiology infrastructure include wide area network design, image compression, distributed archiving, and special viewing station features. Special emphasis is placed on archive design that makes intelligent use of information, such as triggering events from the radiological information system (RIS) for image prefetching and visual cues from photo-icons for full-size image retrieval. Concepts such as teleconsultation and remote procedure monitoring are aimed at providing the same level of services at distant sites that would be available in-house. This article highlights the system design parameters that must be considered to engineer a scalable distributed teleradiology system.

Video compression of coronary angiograms based on discrete wavelet transform with block classification

A new method of video compression for angiographic images has been developed to achieve high compression ratio (~20:1) while eliminating block artifacts which leads to loss of diagnostic accuracy. This method adopts motion picture experts group's (MPEGs) motion compensated prediction to takes advantage of frame to frame correlation. However, in contrast to MPEG, the error images arising from mismatches in the motion estimation are encoded by discrete wavelet transform (DWT) rather than block discrete cosine transform (DCT). Furthermore, the authors developed a classification scheme which label each block in an image as intra, error, or background type and encode it accordingly. This hybrid coding can significantly improve the compression efficiency in certain eases. This method can be generalized for any dynamic image sequences applications sensitive to block artifacts.

Data clustering and other archive retrieval strategies for teleradiology and picture archiving and communication systems

A key advantage in the conversion from film-based to digital radiology is the possibility of a long-term on line electronic archival of patient studies. The popular approach based on optical disk jukeboxes for the long-term archive and magnetic disk storage for data caching is not economically attractive because of the cost of both the jukebox and the medium. Strategies for extending the archival system design with a tape jukebox have been studied. The proposed strategy calls for the use of high-ratio lossy compression together with low-cost tape storage to make long-term on line archiving more affordable. An intelligent prefetching algorithm based on hospital information system and radiologic information system triggers, which in turn are augmented by manual case preparation, can effectively overcome the longer latency of ad hoc retrievals. This longer latency is caused by both system-level bottlenecks and the sequential access constraint of the tape drive. Strategies for image clustering and tape allocation by patient classification also enhance retrieval efficiency. This archival design using image compression, prefetching, and clustering could be implemented in many of the existing teleradiology and picture archiving and communication systems.