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Visualisation of the heart and coronary arteries requires high spatial and temporal resolution. In the past, this has been a tremendous challenge for computed tomography (CT), which is an inherently slow imaging technique because a heavy x-ray tube and detectors needed to rotate around the patient. However, in the past 10 years, CT technology has progressed rapidly and, at present, allows relatively stable visualisation of the coronary artery lumen—so-called ‘coronary CT angiography’. Technology progressed from single slice CT to 4-, 16- and 64-slice CT and even beyond. Currently, 64-slice CT with gantry rotation times between 330 and 420 ms constitutes the widely accepted minimum requirement for coronary CT angiography.^w1–w3 The limited temporal resolution of these CT systems is one of their main limitations. It has been convincingly shown that low heart rates improve image quality in 64-slice CT.^w3–w7 Consequently, it is currently recommended to lower the patient's heart rate to below 60/min in order to achieve optimal image quality when coronary CT angiography is performed with 64-slice CT equipment.^{w1 w2}

Beyond 64-slice CT, manufacturers have chosen different approaches to develop cardiac CT technology further. Two manufacturers have chosen to increase the number of simultaneously acquired slices by creating 256-slice and 320-slice systems. This is meant to allow coverage of the entire volume of the heart in one single rotation,1 ^{w8 w9} requiring only one single heart beat for data acquisition while spatial and temporal resolutions of each individual cross-sectional image remain unchanged. This approach makes cardiac CT imaging less susceptible to arrhythmias, and will potentially reduce radiation dose.

Another manufacturer has designed a CT system which combines two x-ray tubes and detectors in a single gantry, arranged at an angle of 90°. This ‘dual source CT’ (DSCT) provides a temporal resolution of 83 ms, twice as high as compared …