PET positron emission tomography: what to know

PET is a functional imaging test. A radiotracer, often FDG, travels through the body and collects according to cellular activity. The scanner detects this signal and creates images; CT is commonly added to show where the signal sits anatomically. The information may support diagnosis, staging, treatment planning or assessment of response. It is not a stand-alone verdict: infection, inflammation and healing can also produce increased uptake. The radiologist and treating team interpret the pattern with symptoms, examination, blood tests and other imaging.

Check whether you need to fast and whether water is encouraged. Follow advice about medicines, exercise and keeping warm. Tell the department if you have diabetes, could be pregnant, are breastfeeding, have recently been unwell or need help remaining still. The visit usually includes registration, a tracer injection, quiet rest and imaging while you lie on a table. Bring the referral information requested by the centre. Read about the [FDG Radiotracer](/materials/fdg-radiotracer/) and the [PET-CT Scanner](/technology/pet-ct-scanner/) to understand the two parts of a common examination.

During the appointment, report severe nausea, dizziness, itching, swelling or breathing changes immediately. Seek emergency help for collapse, chest pain, severe breathlessness, or swelling of the lips, face or throat. Contact the imaging department if an injection site becomes increasingly painful or red, or if vomiting or a rash persists. These symptoms need assessment and cannot be used to predict the scan result. Arrange a results discussion with the clinician who requested the examination.

Ask what the PET study is looking for, whether CT or another scan will be performed at the same visit, how to manage medicines and diabetes, and how the findings will change the next step. Ask whether the test relates to [Lymphoma](/conditions/lymphoma/) or [Cancer of Unknown Primary](/conditions/cancer-of-unknown-primary/), and when you will receive the report.