Computer tomography, positron emission tomography and nuclear magnetic resonance in cardiology

Ultrafast CT scanning, due to short exposure time, high repetition rate and multiple projections, is well-suited for studies of the heart. A typical ultrafast CT study is composed of three different series of images: volume mode, flow mode and motion mode. With the equipment on this service, using volume mode and EKG triggering, a series of eight contiguous 1 cm-thick slices are generated within 240 ms with and without contrast medium. This imaging technique serves for localization of structures. In flow mode, EKG-triggered slices at multiple levels are generated after a bolus injection of contrast dye. Consequently, the passage of the contrast medium can be followed from the right to the left heart and the circulation time can be estimated, the knowledge of which is advantageous for planning of the subsequent motion study. On use of the motion mode, up to 17 slice images per second can be generated at four, six or eight levels during maximal contrast opacification of both ventricles. Possibilities for clinical application of fast CT scanning can be found in diseases of the aorta and pericardium, cardiac tumors and thrombi as well as for use in assessing cardiac chambers and wall thickness, temporal changes in wall thickness, regional wall motion impairment and quantification of cardiac output and shunt flow. Due to the short imaging time, the technique can also be used for exercise studies and to evaluate pharmacological interventions. According to preliminary results, myocardial blood flow can also be reliably quantitated. Coronary bypass grafts can be directly visualized after injection of contrast dye and, through use of the peak arrival time at various levels, information with regard to blood flow velocity as well as estimations of cross-sectional area in the grafts can be obtained. The sensitivity and specificity of assessment of patency of coronary bypass grafts is currently at approximately 95%.