According to the FDA, CAT scans rotate an x-ray source mounted opposite a detector around a patient, producing a thin, fan-shaped beam of x-rays that pass through patients' bodies one small section at a time. The detectors register the x-rays as they pass through a patient's body and transmit them to a computer that reconstructs them into one or multiple cross-sectional images of the internal organs and tissues.
The FDA states that CAT, which stands for computed axial tomography, scan machines have a motorized table to move the patient through the rotating x-ray and detector assembly, which makes a rotation each second or less. Each rotation takes an image of a small section or slice of the body. These computed tomography (CT) images provide clearer and more detailed pictures of internal organs, bones, soft tissue and blood vessels than conventional x-ray images, and they can be used for both diagnostic and therapeutic purposes. The National Institutes for Health note that the images can be stacked on one another to create a three-dimensional image of the body. According to the NIH, some exams require a special contrast dye to be delivered orally, rectally or by IV into a patient's body before the test to provide better imaging.