SEER Training Modules

Computerized Tomography

Computerized (Axial) Tomography (CT)

Computerized scanners are used for the examination of body tissues. Most well known are EMI scans, Delta-Scans, and Acta-Scanner. Unlike a conventional x-ray that sends a broad beam of radiation over a large area, the CT scanner's x-ray tube directs a thin, concentrated beam of radiation through a cross section of the body detectors. The technique involves recording of "slices" of the body with an x-ray scanner; theses records are then integrated by computer to give a cross-sectional image. A complete study of a patient usually takes 8 to 15 separate scans of 13 mm-thick slices of the body.

From the readings, the computer constructs an image which is displayed on a television screen where it can be photographed for a permanent record. The precision of the scanner permits a more accurate diagnosis of the extent of disease than any other external means. It can discover tumors at an early stage and pinpoint their exact location. It may avert the risk of exploratory surgery to determine if an organ is diseased. CT scans can be performed with or without the use of contrast media.

Here is an example report of a CT scan (sometimes called CAT scan) of the chest. Abstract what you think is pertinent in the report and then compare with the suggested abstraction.

Emission Computerized Tomography (ECT)

SPECT: Single Photon ECT

Selected planes can be analyzed without interfering overlap from other planes. For example: in liver scanning for metastasis, smaller, deeper lesions can be better identified than with conventional scans.

PET: Position Emission Tomography

Some elements, for example, oxygen, carbon and nitrogen, do not have a single photon-emitting isotope suitable for conventional imaging. PET permits investigation of cerebral glucose metabolism and cerebral blood and, thus, measures chemical compounds of the body.