High-speed lossless compression for angiography image sequences

High speed processing of large amounts of data is a requirement for many diagnostic quality medical imaging applications. A demanding example is the acquisition, storage and display of image sequences in angiography. The functional and performance requirements for handling angiography data were identified. A new lossless image compression algorithm was developed, implemented in 'C++' for the Intel Pentium / MS-Windows environment and optimised for speed of operation. Speeds of up to 6M pixels per second for compression and 12M pixels per second for decompression were measured. This represents an improvement of up to 400% over the next best high-performance algorithm (LOCO-I) without significant reduction in compression ratio. Performance tests were carried out at St. James's Hospital using actual angiography data. Results were compared with the lossless JPEG standard and other leading methods such as JPEG-LS (LOCO-I) and the lossless wavelet approach proposed for JPEG 2000. Our new algorithm represents a significant improvement in the performance of lossless image compression technology without using specialised hardware. It has been applied successfully to image sequence decompression at video rate for angiography; one of the most challenging application areas in medical imaging.