90. Diagnostic Use of Radionuclides in medicine

yaboiemil's version from 2016-02-04 14:09

Radionuclide Tracing

1.Used to calculate compartment volumes.
2. A sample/known amount of radionuclide is injected or given orally. Time is given to
allow it to distribute evenly.
3. A sample is then taken and the radioactivity of it is measured. This can then be used
to calculate the entire volume of the of the compartment.


4, Antibodies/hormones (substance with trace amounts) are labelled with Radionuclides.
5. The radioacitivity is then measured to asses how much of the molecule is in the blood.

Scintillation counter

6. A scintillation counter contains a collimator which allows the sample to be taken from
just one direction (preventing contamination of results with random radiation)
7. The counter produces a voltage pulse for every photon of Gamma ray Radiation, which
is recorded by a computer.
8. The detector can be STILL or MOVING.
9. A still detector gives figures for the rate of capture of gamma photons, giving info on
the time-course of local metabolic activity
10. A moving detector moves around an organ in a zig-zag pattern, and gives info on the
distribution of bonded radionuclides within the area. Often used for the Thyroid Gland and
the Kidneys.

Gamma Camera

11. Made using a large (40cm) crystal of Sodium iodide, which counts how many gamma
photons make contact with the crystal.
12. Also produces an image quickly, giving an idea of distribution changes of the
radionuclide within say the bloodstream.

Methods where the x-rays originate from within the patient


Question Answer
SPECTSingle Photon Emission Computed Tomography
PETPositron Emission Tomography


13. When a positron meets and electron the 2 annihilate each other and 2 gamma photons
are formed. These are detected by detectors. Positrons therefore have a very short life in the