Three-dimensional intracoronary ultrasound imaging. Methodology and clinical relevance for the assessment of coronary arteries and bypass grafts.

Three-dimensional (3-D) reconstruction of intracoronary ultrasound (ICUS) images has an increasing application as the applicability of systems of on-line analysis provides a superior guidance by coupling the advantages of a high-resolution cross-sectional imaging with an overview of stenosis and reference segments. Detection of the external contour of the vessel which is a prerequisite for measurements of coronary plaques is currently not provided by the algorithms for automated on-line analysis. Thus, off-line reconstruction is required for studies aiming at the assessment of progression/regression of atherosclerosis and of mechanisms of interventions or restenosis. Various 3-D reconstruction methods with specific advantages and limitations are able to meet the different requirements concerning applicability, quality of visualization, and accuracy of quantification. The use of 3-D ICUS in the assessment of cardiac transplant recipients permits a more reliable and accurate quantification of intimal hyperplasia as seen in cardiac allograft arteriopathy. In patients undergoing bypass surgery it may influence the therapeutic decision, since it allows to determine the longitudinal extent of calcification and frequently discovers atherosclerosis in angiographically normal segments. Vessel stenoses both of native coronary arteries and bypass grafts can be studied by 3-D ICUS and additional information can be obtained during catheter based interventions. Despite some remaining technical limitation 3-D reconstruction of ICUS images has the potential of becoming a practical tool to simplify the interpretation and quantification of ICUS images.