Online PC-based integration of digital intracoronary ultrasound images into angiographic images during cardiac catheterization

Lossy JPEG compression in quantitative angiography: the role of X-ray quantum noise

In medical imaging, contrary to applications in the consumer market, the use of irreversible or lossy compression is still in its beginnings. This is due to the suspected risk of compromising the diagnostic content. Many studies have been performed, but it was not until 2008 that national activities in different countries resulted in recommendations for the safe use of irreversible image compression in clinical practice. Quantitative coronary angiography (QCA), however, poses a special problem, since here a large variation in published maximum compression factors has strengthened the general concerns about the use of lossy techniques. Up to now, the reason for the variation has not been thoroughly investigated. Reasons for the discrepancies in published compression factors are determined in this study. Since JPEG compression reduces the quantum noise of the X-ray images, the impact of compression is overestimated when interpreting any change in local diameter as an error. By taking into consideration the quantitative effect of quantum noise in QCA, it is shown that the influence of JPEG compression can be neglected for compression factors up to ten at clinically applicable X-ray doses. This limit is comparable to that found by visual analysis for aesthetic image quality. Future studies on image compression effects should take the interaction with quantum noise explicitly into consideration.

Quantitative coronary angiography in the current era: principles and applications

Coronary angiography, despite its inherent invasiveness and need for contrast media and radiographic exposure, is still routinely employed every year for the diagnostic and therapeutic management of millions of patients with or at risk for coronary artery disease. Whereas approximate visual estimation is the most common way to evaluate coronary angiography findings, since the late 1980s a number of investigators have developed and investigated methods of quantitative coronary angiography (QCA) analysis exploiting automated or semi-automated edge detection. Despite the inherent drawback of QCA due to its focus on the contrast-filled lumen of the vessel, QCA has offered and continues to offer important insights for clinical research and, in selected cases, clinical practice. This review aims thus to provide a comprehensive and updated viewpoint on the actual role of QCA.