Cardiac applications of multislice computed tomography.

Netherlands Multislice CT (MSCT) is gaining clinical acceptance for cardiac imaging owing to improved temporal and spatial resolution of the latest 16-slice and 64-slice technology. Although the cardiac MSCT applications are promising, there is still room for further technical improvements and optimization of post-processing techniques for cardiac evaluation. Interestingly, the data acquired for CT angiography of the coronary arteries can also be used to create volumetric cine loops of cardiac function. The functional data are available without the need for repeat scanning or for administration of additional contrast material [1]. Furthermore, MSCT allows assessment of first-pass perfusion and delayed enhancement imaging in patients with subacute myocardial infarction. Recently, it has been reported that MSCT reveals microvascular obstruction or the so-called no-reflow phenomenon as a late perfusion defect in patients with re-perfused acute infarctions, similar to observations made by other techniques like MRI [2]. With further development MSCT may allow combined assessment of the presence and extent of coronary atherosclerosis, the percent diameter stenosis, plaque characterization and the effect of the lesion on perfusion and myocardial function. In this review, the technical requirements of cardiac MSCT and some frequent clinical applications are discussed. Requirements for cardiac MSCT image acquisition depend strongly on the clinical problem. For example, CT coronary angiography requires excellent spatial and temporal resolution, whereas only modest spatial and temporal resolution is sufficient for the assessment of the anatomy of pulmonary veins and the left atrium. In general, the higher the requirements for image quality become, the more complex the acquisition, the longer scan time and the higher patient dose. Main aspects with regard to imaging performance are low-contrast and spatial resolution, temporal resolution, and scan time. Patient dose and radiation risk should always be considered as the counterpart of image acquisition and image quality. Low-contrast resolution is the ability to visualize structures that demonstrate only a small difference in Hounsfield units compared with their direct environment. In cardiac applications of CT, native tissue contrasts are in general not sufficient to differentiate between, for example, the vessel wall and its unenhanced lumen, or the heart and the inner chambers. Contrast enhancement is thus mandatory for visualizing the lumen of coronary arteries, the heart chambers, pathology of the myocardium or anatomy of pulmonary veins. Low-contrast resolution depends on tube current (mA), the reconstructed slice thickness, tube voltage, beam filtration and the reconstruction algorithm, and is strongly correlated to radiation exposure. …