Non-coronary findings in cardiac CT

Gated multi-detector CT (MDCT) is now recognised as an excellent and robust application for non-invasive assessment of coronary arteries, and in many centres is routinely used. Some studies have shown that MDCT scanners with 64-detector row have a 99% negative predictive value for the detection of coronary artery stenosis. MDCT images obtained with ECG gating are superior to the standard (non-ECG-gated) studies due to reduction in blurring secondary to cardiac and respiratory motion.

One issue with gated MDCT was the dose. Previously, gated MDCT was routinely acquired with retrospective ECG-gating, with data acquired throughout the entire cardiac cycle. This was at the expense of increased radiation dose, although not all data was used for postprocessing or reconstructions. Now routinely prospective ECG-gating is used by turning off the x-ray beam during most of the cardiac cycle, with only a portion of the cardiac cycle that is radiated selected before the scan, resulting in significant reduction in radiation dose compared to retrospective ECG-gating.

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