Current development of cardiac imaging with multidetector-row CT

Abstract

Multidector-row CT (MDCT) with retrospective ECG gating allows scanning the entire heart with 1.25 mm slice thickness and 250 ms effective exposure time within 35 s investigation time. The resulting images allow for an accurate high-resolution assessment of morphological detail of both the coronary arteries and the cardiac chambers. Performing a contrast-enhanced MDCT angiography (MD-CTA) in addition to a non-enhanced scan for the detection and quantification of coronary calcifications may be indicated in patients with atypical chest pain and in young patients with high cardiovascular risk. This group of patients may show non-calcified plaques as the first sign of their coronary artery disease. As the proximal part of the coronary arteries is well displayed by MD-CTA it also helps to delineate the course in anomalous coronary vessels. Additional information is drawn from the preoperative use of MD-CTA do determine the distance of the left internal mammarian artery to the left anterior descending coronary artery prior to minimal invasive bypass grafting. Additional indications for MD-CTA are the non-invasive follow up after venous bypass grafting, PTCA, and coronary stent interventions. MD-CTA allows following the course of the coronary vessels to the level of third generation coronary segmental arteries. A definite diagonis to rule out coronary artery disease can be reliably made in vessels with a diameter of 1.5 mm or greater. With MDCT a number of different atherosclerotic changes can be observed in diseased coronary arteries. Non-stenotic lesions may show tiny calcifications surrounded by large areas of irregularly distributed soft tissue. Calcifications in this type of atherosclerotic coronary artery wall changes appear as ‘the tip of iceberg’. Heavy calcifications usually tend to be non-stenotic because of vessel remodelling resulting in a widening of the coronary vessel lumen. Therefore, heavy calcifications appear to ack like an ‘internal stent’ for a coronary vessel segment. Humps of soft tissue either with or without calcifications are more likely to cause significant coronary artery disease and correlate with stenoses of >50% on selective coronary catheter. These humps consist of well-defined soft tissue in the coronary artery wall. The density of this soft tissue may vary between 30–70 HU. In cases where a coronary vessel is occluded by thrombotic material, a typical sign is found with enlargement of the coronary vessel, a hypodense center and a hyperdense rim. Vessel occlusion without thrombus may also appear within a collapsed and dense lumen. In addition to the investigation of the coronary arteries, CTA with MDCT is well suited to assess the presence and morphology of myocardial scars and aneurysms, intracardial tumors and thrombi.