994-94 Use of Moderately Lossy JPEG Compression Does Not Result in Loss of Diagnostic Information in Digital Coronary Angiograms

Digital image compression is a means of reducing storage and exchange requirements for coronary angiograms. In order to assess the diagnostic accuracy of image compression, digital coronary arteriograms were analyzed in compressed and noncompressed formats. The effect on visual assessment of stenosis severity of digital coronary angiograms was evaluated on a set of 100 image sequences using lossy (15: 1) Joint Photographic Experts Group (JPEG) compression software. A panel of 3 angiographers reviewed 6200 frames from 10 clinical exams both with and without standard JPEG compression. Original and compressed versions of each sequence were viewed in random order by all panel members blinded to compression status. Images were viewed on the same display used for digital acquisition with the Philips Digital Cardiac Imaging (DCI) System. Panelists identified and graded severity of 99 stenoses in quartiles with >50% considered to be significant. There was no significant difference in the number of lesions identified with each modality. Overall agreement for severity of all lesions between compressed and non-compressed modalities was 0.60 and Kappa = 0.52. If lesions were dichotomized into “significant” (>50%) or “insignificant” (≤50%), agreement was 0.94 and Kappa = 0.88, suggesting that when disagreement occurred, it tended to be within one severity grade. These agreement statistics are consistent with previously reported intra-observer variability in the review of cine-coronary angiograms. The significant reduction in digital storage and exchange requirements provided by lossy JPEG does not result in a decrease in diagnostic quality of digital coronary angiograms. Variability in visual assessment from original and compressed data formats is comparable to intra-observer variability from identical data formats. Therefore, JPEG compression does not result in loss of diagnostic information and is a valid means of reducing storage and exchange requirements of coronary angiograms.