Guide To CT Imaging

X-ray computed tomography (CT) is a medical imaging technology that uses x-ray radiation to image the patient, allowing healthcare professionals to care for patients by seeing what is on the inside. CT images are used most often to diagnose a disease (for example traumatic injuries or cancer), and can also be used for treatment, including surgery and radiation therapy.

CT imaging consists of two main steps: acquisition and reconstruction. During the CT acquisition step, a patient (or, more generically, an object) is first positioned inside the CT scanner. Inside the scanner there is a x-ray radiation source and many small radiation detectors. As the object is exposed to radiation from the source, some of the radiation will be absorbed by the object, but much of it will pass through and is absorbed by the detectors. This radiation absorbed by the detectors creates a projection image. Many projection images are acquired as the source rotates around the object. During the reconstruction step, these projection images are used to try to make a best guess, or estimate, as to what object would have those projection images. The final result is CT images, which show how much radiation was transmitted through different parts of the object.

In the section below, explore CT imaging by looking at the answers to various questions you might have related to the description above. The questions start with the most surface-level questions at the top of the list, and become deeper, more fundamental as you move down the list. Choose a question that interests you, and get started!

Level I

See the basics of CT imaging by using the RayCT Lite web app. Design an object, choose the CT acquisition parameters, and see the resulting CT image.

Level II

Learn about how x-rays (also known as photons) interact with objects by reading the ionizing radiation tutorials.