Proc. SPIE. 3980, Medical Imaging 2000: PACS Design and Evaluation: Engineering and Clinical Issues
KEYWORDS: Medical imaging, Image compression, Picture Archiving and Communication System, Forward error correction, Receivers, Fractal analysis, Asynchronous transfer mode, Telecommunications, Networks, Imaging systems
In an ATM (Asynchronous Transfer Mode)-based PAC system, cell losses during the transmission might cause degradation on the quality of medical images. This in turn will affect the accuracy of the diagnosis. A three-step scheme to minimize the effect of cell losses on the quality of medical images is proposed in this paper. The first step is related to the medical imaging coding before it enters the network, in which, ROIs (Regions of Interest) of the medical imaging which are crucial to diagnosis are kept non-compressed and packetized with pixel-level inter-leaving. Non-compression can make the data of ROIs to be more robust to cell losses than any compression algorithms, while pixel-level inter-leaving is strong for bursty cell losses recovery combined with FEC (Forward Error Correction) at the receiver. The background part of the medical imaging will be compressed using fractal algorithm, which can get very high compression ratio to balance the large amount data of the ROIs. In the second step, the ROIs will be allocated the highest priority during transmission. While in the third step, FEC will be used to minimize the existed cell losses at the receiver. The balance and optimal of these three stages are discussed from the system-level point of view.
Dispersion in optical fibers and rise time in electro-optic components are very important parameters in the design of high speed optical communication systems. Dispersion parameter is used to determine the bandwidth capability of the optical fiber. Rise time parameter is used to estimate the bandwidth capacity of the overall transmission system comprising transmitter fiber and receiver. Both dispersion and rise time parameters are treated in isolation in technical literature. An approximate relation between these two parameters in conjunction with the bandwidth estimation has been derived and presented in the paper.
A novel coding scheme (DmB1M) proposed by Japanese researchers is analysed and compared with other coding techniques commonly adopted for optical communications. An experimental realization of the new code (D1OB1M m 10) using discrete components has been performed and the circuit test results for an information rate of 140 Mbps are presented. The design of speed converters and clock recovery circuits which are crucial for the code realization is described in the paper. The coding technique is suitable for optical transmission with data rates in the order of Gbps.