Positron Emission Tomography or PET scan is defined as a type of imaging technology to understand various organs' and tissues' functioning. In this method, a substance that is radioactive will be injected to help trace an organ's function. The substance that collects in high activity areas is shown as bright spots reflecting disease activity. This technique is useful in early disease detection.

The person is provided a radioactive tracer substance which can be injected, ingested or inhaled depending on the organ which is to be visualised. The person is then kept under a scanner machine which will then record images of the organs or tissues.

After the tracer is given, the person is asked to wait for 30 to 60 minutes for the substance to be absorbed by the body. The actual PET scan will take another 45-60 minutes. So, the total time for the test will be approximately 2 hours.

A PET scan allows a doctor to assess chemical activities in the body. High chemical activity in some areas is represented as bright spots. Diseases such as cancers can be diagnosed earlier than usual from this method as fast cell multiplication rate is represented as bright spots denoting abnormal activity. Other diseases such as Alzheimer's disease, tumours, and epilepsy can also be diagnosed.

A PET scan can record the slightest changes that can occur at the cellular level as diseases start with functional disturbances before there are structural changes. This is particularly useful in diagnosing various cancers and diseases earlier than a CT or MRI scan to begin prompt treatment and improve prognostic outcomes.