BRAINCAKEMedical Tracers
A medical tracer is a compound labelled with a radioactive nuclide. It is injected, swallowed or inhaled, and the compound is chosen so that the body carries it to the organ or tissue being studied. The radiation it emits is detected outside the body, showing where the tracer has gone and how quickly. This gives information about how organs are working, not just their shape.
A good tracer should:
• emit gamma rays, which pass out of the body to the detector. Alpha and beta particles would be absorbed in the body, causing ionisation damage without producing an image (the exception is a positron emitter, whose positrons produce gamma photons, used in PET)
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Key terms in this lesson
- half-life
- The average time taken for the number of nuclei of a radioactive isotope in a sample, or its activity, to halve.
- activity
- The number of nuclei of a radioactive isotope that disintegrate per second, measured in becquerels.
More in Medical Imaging
- Photoelectric Effect, Compton Scattering and Pair Production
- Attenuation of X-rays
- Contrast Media
- CAT Scanning
- Technetium-99m and Fluorine-18
- The Gamma Camera
- Diagnosis with a Gamma Camera
- PET Scanning
All 20 lessons in Medical Imaging · All OCR A-level Physics topics