Self Instructional Manual for Cancer Registrars - SEER - National ...

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 to detectors. The technique involves recording of
"slices" of the body with an x-ray scanner; these 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 made with or without the use of contrast media.
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: Positron Emission Tomography
Some elements, for example, oxygen, carbon and nitrogen, do not have single photonemitting
isotopes suitable for conventional imaging. PET permits investigation Of
cerebral glucose metabolism and cerebral blood and, thus, measures chemical compounds
of the body.
On the next page is a report (Example Eli) of a CT (sometimes called CAT) scan of the chest.
Abstract what you think is pertinent in the report and then compare with the suggested abstraction
on page 75.
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