American College of Cardiology/European Society of Cardiology international study of angiographic data compression phase II - The effects of varying JPEG data compression levels on the quantitative assessment of the degree of stenosis in digital coronary angiography

OBJECTIVES This report describes whether lossy Joint Photographic Experts G roup (JPEG) image compression/decompression has an effect on the quantitati ve assessment of vessel sizes by state-of-the-art quantitative corollary ar teriography (QCA). BACKGROUND The Digital Imaging and Communications in Medicine (DICOM) digit al exchange standard for angiocardiography prescribes that images must be s tored loss free, thereby limiting JPEC compression to a maximum ratio of 2: 1. For practical purposes it would he desirable to increase the compression ratio (CR), which would lead to lossy image compression. METHODS A series of 48 obstructed coronary segments were compressed/decompr essed at CR 1:1 (uncompressed), 6:1, 10:1 and 16:1 and analyzed blindly and in random order using the QCA-CMS analytical software. Similar catheter an d vessel start- and end points were used within each image quartet, respect ively. All measurements were repeated after several weeks using newly selec ted start- and end-points. Three different sub-analyses were carried out: t he intra-observer, fixed inter-compression and variable inter-compression a nalyses, with increasing potential error sources, respectively. RESULTS The intra-observer analysis showed significant systematic and rando m errors in the calibration factor at JPEG CR 10:1. The fixed inter-compres sion analysis demonstrated systematic errors in the calibration factor and recalculated vessel parameter results at CR 16:1 and for the random errors at CR 10:1 and 16:1. The variable inter-compression analysis presented syst ematic and random errors in the calibration factor and recalculated paramet er results at CR 10:1 and 16:1. Any negative effect at CR 6:1 was found onl y for the calibration factor of the variable inter-compression analysis, wh ich did not show up in the final vessel measurements. CONCLUSIONS Compression ratios of 10:1 and 16:1 affected the QCA results ne gatively and therefore should not be used in clinical research studies. (J Am Coil Cardiol 2000;35:1380-7) (C) 2000 by the American College of Cardiol ogy.