How does a PET scanner work?

A PET scanner works by detecting gamma rays emitted from a patient's body after injection of a radioactive tracer.

Positron Emission Tomography (PET) is a medical imaging technique used to visualise the metabolic activity of cells in the body. It is commonly used in the diagnosis and treatment of cancer, heart disease and neurological disorders. The PET scanner detects gamma rays emitted from a patient's body after injection of a radioactive tracer. The tracer is a compound that is metabolised by the body and emits positrons, which are positively charged particles. When a positron collides with an electron, they annihilate each other, releasing two gamma rays in opposite directions. These gamma rays are detected by the PET scanner and used to create an image of the body.

The PET scanner consists of a ring of detectors that surround the patient. Each detector is made up of a scintillator crystal and a photomultiplier tube. When a gamma ray enters the scintillator crystal, it produces a burst of light. The photomultiplier tube amplifies this signal and converts it into an electrical signal that can be processed by a computer. By measuring the time difference between the detection of the two gamma rays, the PET scanner can determine the location of the tracer in the body.

The computer then uses this information to create a 3D image of the body, showing the distribution of the tracer and therefore the metabolic activity of cells in different parts of the body. PET scans are often combined with CT scans to provide more detailed images of the body. PET/CT scans can help doctors to diagnose and monitor the progression of diseases, and to evaluate the effectiveness of treatments.