PET scanning (Positron Emission Tomography) is a medical technique that helps doctors see how organs are functioning and diagnose conditions like cancer. It shows areas of high metabolic activity, which can indicate where cancer cells are, as they grow and divide more rapidly than normal cells.

1. Tracer Injection:

• The patient is injected with a radioactive substance (like glucose) that contains a positron-emitting isotope. This acts as a tracer.
• The tracer moves through the bloodstream and collects in areas with high metabolism, such as cancer cells.

2. Positron Emission:

• As the positrons from the isotope move through the body, they meet electrons in the organs.
• When a positron meets an electron, they annihilate each other and release gamma rays in opposite directions.

3. Gamma Ray Detection:

• Special detectors around the patient pick up the pairs of gamma rays emitted.
• By detecting at least 3 pairs of gamma rays, the location of the tumour can be pinpointed using a method called triangulation.

4. Metabolic Activity:

• The distribution of radioactivity in the scan matches areas of high metabolic activity. Cancer cells show up clearly because they take up more of the radioactive glucose due to their high energy use.

The radioactive isotope used in PET scans has a short half-life, so it decays quickly and doesn't stay in the body for too long.