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

DIAGNOSTIC NUCLEAR MEDICINE EXAMINATIONS: Radioisotope Scintillation Scanning
(Scintiscan)
In nuclear medicine, radioactive substances known as radioisotopes are administered to the patient
in order to diagnose disease. A radioactive isotope a disintegrates spontaneously (ultimately losing
its radioactivity) and emits gamma rays from within the body which enable the physician to visualize
internal abnormalities. This differs from x-ray procedures where the x-rays are passed through the
body from an external source.
Examples of radioactive isotopes, commonly used for isotope-imaging studies, are gallium, iodine,
and technetium. Sometimes non-radioactive compounds are simply labeled or tagged with a
radioactive isotope and sometimes radioactive tracers (radioactive pharmaceuticals) are given by
mouth or by vein. Some of the isotopes are selectively absorbed by tumors or by specific organs in
the body. The concentrated radioisotopes outline the tumor or organ making it visible on the
photoscanner by the emission of radioactive energy. Much research in nuclear medicine is concerned
with attempts to find new radioisotopes and to develop radioisotope-labeled compounds that will be
selectively absorbed in specific parts of the body.
A device called a photoscanner is used to measure the radioactivity from the nuclear substances
absorbed by various parts of the body. A two-dimensional representation or map can be made of the
rays emitted from the radioisotope which shows where it is concentrated in body tissue. Findings of
such an examination are photographically recorded and are referred to as scans. The more common
scans are illustrated in the diagram on the next page (Figure 1)--bone, kidney, thyroid, brain, salivary
glands, heart/lung, liver/spleen, and total body. Bone scanning with various bone-seeking isotopes is
advocated for earlier diagnosis of bone metastasis. Other names for these types of scans are
scintiscan, gallium scan, and lymphoscintography.
PRACTICAL
EXERCISES
Radioisotope scanning and tracer procedures are used frequently to diagnose cancer. In this
section we will concentrate on reports of scans. Abstract Examples E12-E14 and then compare with
the suggested abstractions on page 85.
lisotope--A form of a chemical element which varies from other forms of this element by the number of
neutrons in its nucleus. An isotope can be stable or radioactive depending upon the composition of
its nucleus.
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