2.2 : Computed Tomography

Tomography refers to imaging by sections. Computed tomography (CT) is a non-invasive imaging technique that uses computers to analyze several cross-sectional X-rays to reveal minute details about structures in the body.

The technique was invented in the 1970s and is based on the principle that as X-rays pass through the body, they are absorbed or reflected at different levels. In the technique, a patient lies on a motorized platform while a computerized axial tomography (CAT) scanner rotates 360 degrees around the patient, taking X-ray images. A computer combines these images into a two-dimensional view of the scanned area, or a "slice."

Recently, the development of more powerful computers and more sophisticated software has made CT scanning routine for many diagnostic evaluations. It is especially useful for soft tissue scanning in areas like the brain, thoracic, and abdominal viscera. Its level of detailing is so precise that it can allow physicians to measure the size of a tumor mass or tissue down to a millimeter. Furthermore, different anatomical planes, in addition to the axial, like sagittal and coronal, can be viewed using software that processes or reformats the image slices obtained. This reduces unnecessary exposure to more X-rays for studying different planes.

CT scanning exposes patients to a dose of radiation many times higher than X-rays. In fact, children who undergo CT scans are at increased risk of developing cancer, as are adults who have multiple CT scans.

This content is derived from Openstax, Anatomy and Physiology, Section 1.7: Medical Imaging