How Does a CT Scan Work?

A computed topography scan, also known as a CT scan, uses rotating X-rays to create cross-sections of images of the body, according to the National Institute of Biomedical Imaging and Bioengineering. A computer compiles the sections of images into one three-dimensional image offering more details than a conventional X-ray.

The CT scan uses a motorized table to move the patient inside the imaging machine, notes the U.S. Food and Drug Administration. The sources moves around the circular entrance to the machine. The bed moves the patient through the opening as the X-ray source makes rotations around the entrance to capture each cross-sectional image. The X-ray source inside the machine uses a fan-shaped beam between 1 millimeter and 10 millimeters thick that passes through the body to detectors opposite the X-ray source. The detectors record the X-rays after they pass through the body to create the image of the internal body structures.

Contrast material is sometimes injected into the patient to aid in getting a clear image, says the National Institute of Biomedical Imaging and Bioengineering. This is particularly useful when the scan focuses on soft tissues that don't show up as vividly as dense structures such as bones. The circulatory and digestive systems are two examples that might require contract material during a CT scan.