Advances in percutaneous coronary interventions have increased the demand for accurate evaluation of coronary artery disease. Over the last years new developments in signal processing and miniaturization of medical devices has permitted the development of numerous invasive and non-invasive imaging modalities which allow a detailed visualization of coronary anatomy and morphology. However, though these techniques provide additional information regarding the coronary pathophysiology and plaque distribution, they also have significant limitations which do not permit complete vessel representation. To overcome these drawbacks fusion of different imaging modalities has been proposed. This book describes a unique methodology for comprehensive three dimensional coronary representation which is based on the fusion of intravascular ultrasound and X-ray angiographic data. It also presents the validation method which was implemented to assess the reliability of the reconstruction methodology and discusses its current research applications and its future potentialities aiming to highlight its value in the clinical and research arena.