Computed Tomography (CT) Fundamentals

CT acquires data with an X-ray tube rotating around the patient, from which an image reconstruction process generates tomographic images of the patient’s cross-section. CT images, presented as CT numbers (Hounsfield Unit, HU), represent the intrinsic property of the human body interacting with X-ray photons. CT scanner is a sophisticated system including various components with different functionality to enable data acquisition and image reconstruction, with numerous parameters selectable by operators that impact image quality and radiation dose. In cardiac CT, ECG gating is required to image the beating heart. Both prospective and retrospective gating have been used in cardiac CT, together with various scan modes such as axial, sequential, helical/spiral, and Flash, depending on the scanner type and hardware.