POTENTIALS AND LIMITATIONS OF ELECTRON-BEAM COMPUTED-TOMOGRAPHY (EBCT)

Electron beam CT, which does not require mechanical movement of an X-r ay tube, has a temporal resolution which exceeds that of conventional computed tomography by a factor of about ten. Axial images of the hear t can be acquired within 50 to 100 ms with a spatial resolution below 0.5 mm(2) and permit precise visualization of all cardiac structures. ECG-triggered acquisition of 30 to 40 axial images (3 mm slice thickne ss) in a short inspiratory breathhold allows one to sample a 3-dimensi onal volume data set which covers the complete heart. Overall acquisit ion times are approximately 30 to 50 seconds. While electron beam CT i n general permits a complete cardiac investigation, including morpholo gy, function, and perfusion, the method's most important application i s non-invasive imaging of the coronary arteries. Without contrast enha ncement, coronary calcifications by EBCT currently constitutes the mos t sensitive non-invasive marker for the presence even of very early fo rms of coronary atherosclerosis. Intraveneous injection of contrast ag ent during image acquisition additionally permits the selective visual ization of the coronary artery lumen and detection of significant sten oses. This method is especially well suited in the follow-up of corona ry interventions and coronary bypass grafting. Breathhold and movement artifacts, superposition of coronary arteries and veins, as well as s even coronary calcifications currently constitute the method's main pr oblems. In spite of these limitations, electron beam CT has been shown to permit clinically valuable non-invasive investigations of the coro nary arteries, which may be further refined as technology progresses.