CAIE A-Level Physics 24.3.6 PET Gamma-Ray Detection

Practise explaining how opposing gamma photons are detected and timed in PET, relating the data to an image of tracer concentration in tissue.

Exam points

explain how opposing gamma photons are detected and their arrival times processed
relate PET photon detection data to an image of tracer concentration in tissue

[Maximum number: 2]

Fluorine-18 $\left({ }_{9}^{18} \mathrm{~F}\right)$ is a radioactive nuclide that is used as a tracer in positron emission tomography (PET scanning). Fluorine-18 decays to a nuclide of oxygen ( O ) according to

{ }_{9}^{18} \mathrm{~F} \longrightarrow{ }_{P}^{Q} \mathrm{X}+{ }_{8}^{R} \mathrm{O} \text {. }

Explain how the detection of the gamma-ray photons is used to produce an image of the tissue being examined.

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24.3.6—The gamma-ray photons from an annihilation event travel outside the body and question 1