This volume is the fifth in a series on quantitative coronary arteriography (QCA). The following topics, which all currently are and continue to be issues of extensive discussions in the research and clinical communities, are covered in great detail in this volume: endothelial function; comparisons between digital and cine coronary arteriography; inter-laboratory variation between QCA Core Laboratories; the developments in digital archival media; intracoronary pressure, coronary blood flow and flow reserve; quantitative and qualitative features in regression/progression studies; QCA in recanalization studies; and finally the current position of rivalling modalities as coronary angioscopy, intraluminal imaging with ultrasound and fluorescence spectroscopy. This book provides a comprehensive, overview for all clinicians and physicists actively involved or otherwise interested in current developments in quantitative coronary arteriography.