Proc. SPIE. 7264, Medical Imaging 2009: Advanced PACS-based Imaging Informatics and Therapeutic Applications
KEYWORDS: Image compression, Video, Diagnostics, Computer programming, Medical imaging, Telecommunications, Video compression, Computed tomography, Data communications, Picture Archiving and Communication System
Digital medical images are rapidly growing in size and volume. A typical study includes multiple image "slices." These
images have a special format and a communication protocol referred to as DICOM (Digital Imaging Communications in
Medicine). Storing, retrieving, and viewing these images are handled by DICOM-enabled systems. DICOM images are
stored in central repository servers called PACS (Picture Archival and Communication Systems). Remote viewing
stations are DICOM-enabled applications that can query the PACS servers and retrieve the DICOM images for viewing.
Modern medical images are quite large, reaching as much as 1 GB per file. When the viewing station is connected to the
PACS server via a high-bandwidth local LAN, downloading of the images is relatively efficient and does not cause
significant wasted time for physicians. Problems arise when the viewing station is located in a remote facility that has a
low-bandwidth link to the PACS server. If the link between the PACS and remote facility is in the range of 1 Mbit/sec,
downloading medical images is very slow. To overcome this problem, medical images are compressed to reduce the size
for transmission. This paper describes a method of compression that maintains diagnostic quality of images while
significantly reducing the volume to be transmitted, without any change to the existing PACS servers and viewer
software, and without requiring any change in the way doctors retrieve and view images today.
In this paper we consider Wyner-Ziv video compression using rateless LDPC codes. It is shown that the advantages of using rateless LDPC codes in Wyner-Ziv video compression, in comparison to using traditional fixed-rate LDPC codes, are at least threefold: 1) it significantly reduces the storage complexity; 2) it allows seamless integration with mode selection; and 3) it greatly improves the overall system's performance. Experimental results on the standard CIF-sized sequence <i>mobile_and_calendar</i> show that by combining rateless LDPC coding with simple skip mode selection, one can build a Wyner-Ziv video compression system that is, at rate 0.2 bits per pixel, about 2.25dB away from the standard JM software implementation of the H.264 main profile, more than 8.5dB better than H.264 Intra where all frames are H.264 coded intrapredicted frames, and about 2.3dB better than the same Wyner-Ziv system using fixed-rate LDPC coding. In terms of encoding complexity, the Wyner-Ziv video compression system is two orders of magnitude less complex than the JM implementation of the H.264 main profile.
We analyze challenges in the current approaches to digital video surveillance solutions, both technically and financially.
We propose a Cell Processor based digital video surveillance platform to overcome those challenges and address ever
growing needs in enterprise class surveillance solutions capable of addressing multiple thousands camera installations.
To improve the compression efficiency we have chosen H.264 video compression algorithm which outperforms all
standard video compression schemes as of today.