Mammogram JPEG quantisation matrix optimisation for PACS

Clinical procedures and legal requirements increasingly demand greater performance in JPEG compression of digitised grayscale medical images without loss of visual fidelity or without exceeding a bounded error metric. Current JPEG common practice uses a default general-purpose luminance quantisation matrix. As an initial investigation into defining more suitable quantisation matrices for different medical image modalities, a new candidate matrix has been derived for mammograms. For a given SNR, the new quantisation matrix achieves a relative compression ratio performance improvement of approximately 22% for a quality factor of 95% and 15% for a quality factor of 85%. This study paves the way for a computationally intelligent approach to optimising the quantisation matrix for each medical image modality in both batch mode and adaptively on an image-by-image basis.