Methods for quantification of coronary artery calcifications with electronbeam and conventional CT and pushing the spiral CT envelope: New cardiac applications

Detection of coronary artery calcifications with slice by slice prospective ECG triggering is feasible with electron beam CT as well as with single an d multi-row-detector CT (MDCT). The radiation exposure to the patient to ob tain comparable image quality is similar for all three modalities utilizing this prospective acquisition technique. Alternatively, coronary screening can be performed by MDCT with retrospecti ve EKG spiral gating. Radiation exposure to the patient with this technique is significantly higher than with prospective triggering. Nevertheless, ac quisition of the entire volume of the heart with retrospective gating holds promise to improve reproducibility of coronary calcium measurements, espec ially in patients with a low amount of coronary calcium and in patients wit h atrial fibrillation. If retrospective gating is used for CT angiography (CTA) with MDCT this all ows to use thin slices (1.25 mm) and to perform the acquisition within one breath hold period (app. 35 s). This technique is currently limited by the temporal resolution per slice (250 ms). In order to achieve diagnostic imag e quality the heart rate of the patient thus needs to be sufficiently low. Therefore, in cases with heart rates significantly higher than 70 beats/min betablocker have to be administered for patient preparation as long as the re are no contraindications for such a regimen. Because of low image noise and high spatial resolution CTA with MDCT is abl e to display the entire extent of atherosclerosis allowing to visualize cal cified as well as non-calcified plaques of the coronary arteries. Under cli nical conditions CTA has the potential to accurately rule out or diagnose s ignificant coronary stenoses of the proximal and mid-segments of the corona ry artery tree when compared to conventional selective coronary angiography .