Cardiac CT—basic principles

Computed tomography (CT) was introduced for clinical diagnostic radiology in 1971, and it was used as neuro and body scanner for about 20 years. Spatial and temporal resolution required to evaluate a dynamic structure such as the heart was not sufficient until 1998. Thanks to the technical developments in CT technology over the past 20 years cardiac CT (CCT) developed from an investigative tool into an established clinical tool primarily used as non-invasive clinical diagnostic test for coronary artery imaging. The key technical development occurred in the late 1990s with the introduction of multidetector CT (4 slices) scanners able to synchronize image acquisition and reconstruction with an electrocardiographic (ECG) track. However, 4-slice and also the following 16-slice CT technology had technical limitations, such as limited coverage and temporal resolution, but which allowed diagnostic image quality in selected patients with low and stable heart rate. Moreover, relatively high radiation exposure was required to obtain clinically valid image quality. For this reason, different technical strategies were developed in the following years and advances were also provided in the field of reconstruction algorithm with the introduction of iterative algorithms that allowed an image noise reduction and in the field of tissue characterization with the use of dual-energy CT. All these advances allowed CCT to become a pivotal tool in the cardiology daily practice to image the coronary arteries and beyond.