COMPRESSION OF DIGITAL CORONARY ANGIOGRAMS DOES NOT AFFECT VISUAL OR QUANTITATIVE ASSESSMENT OF CORONARY-ARTERY STENOSIS SEVERITY

Digital coronary angiographic techniques are now widely used in many c ardiac catheterization laboratories. However, the full potential of di gital imaging technology remains to be achieved because of its enormou s storage and exchange requirements. Compression of digital imaging da ta allows a reduction in the volume of data so that storage and transm ission are more efficient and cost-effective. Three angiographers revi ewed the original and compressed formats of 96 coronary angiographic s equences in a blinded fashion to assess coronary lesion severity. Comp ression was achieved using the Joint Photographic Experts Group (JPEG) standard, which resulted in a compression ratio of approximately 15:1 . The original format was reviewed in a blinded fashion a second time to assess for intraobserver variability of similar formats. Lesion sev erity was graded in quartiles. Coronary stenosis >50% was considered ' 'significant.'' In parallel, the reproducibility of quantitative coron ary angiographic (QCA) measurements of coronary artery dimensions was also evaluated. For the visual assessment of lesion severity in the co mpressed versus original formats, kappa=0.52, suggesting moderate agre ement. When lesions were assessed as significant versus ''insignifican t,'' however, kappa=0.88, suggesting excellent agreement. In the 2 sep arate readings of the original data formats, kappa=0.44 for assessment of lesion severity by quartiles and kappa=0.72 for lesions assessed a s significant versus insignificant. Analysis of the compressed versus original data sets using QCA resulted in on excellent correlation for the measurement of lesion severity (r=0.99). The correlation was equal ly strong when the original format was analyzed sequentially (r=0.98). Lossy JPEG (15:1) compression is a valid means for reducing storage a nd exchange requirements of coronary angiographic date. The variabilit y in assessing lesion severity between the original and compressed for mats is comparable to the reported variability in visual assessment of lesion severity in sequential analysis of cine film.