Diagnostic PET scan

For many cancer scans, FDG radiotracer is injected into a vein. Cells take up FDG according to their use of glucose, and the scanner detects that distribution. PET can help locate active disease, assess its extent or evaluate response to treatment, depending on the clinical question.

An area of increased uptake is not automatically cancer. Infection, inflammation, healing tissue and normal organs can also take up radiotracer. Some tumours show little FDG activity. A radiologist or nuclear medicine physician therefore compares the PET pattern with the CT images, earlier scans and the reason for testing.

The report may describe where uptake occurs, whether it corresponds to a structure on CT and whether the pattern has changed. PET-CT can assist the work-up of conditions such as lymphoma or cancer of unknown primary, but biopsy or another imaging test may still be needed to establish what an area represents.

Follow the imaging centre's specific instructions about eating, water, exercise and medicines. Tell the team if you have diabetes, are pregnant or could be pregnant, are breastfeeding, have trouble lying flat, or recently had an infection, operation or cancer treatment. These details can affect preparation or interpretation.

Wear comfortable clothing and leave metal accessories at home if asked. After the injection, you will rest quietly while the radiotracer circulates, then lie still as the PET-CT scanner moves over the required body area. Follow the centre's advice about fluids and contact with others after leaving.

Tell the imaging staff immediately if you feel unwell, become short of breath, develop itching or swelling, or have pain around the injection site. Also speak up if anxiety, pain or breathing difficulty makes it hard to remain still; the team may be able to adjust positioning or provide support.

After leaving, seek urgent care for breathing difficulty, facial or throat swelling, fainting or rapidly worsening symptoms. For mild injection-site discomfort that persists or spreads, contact the imaging centre for advice and explain that you recently had a PET-CT scan.

Beforehand, ask which body areas will be scanned, which radiotracer and CT contrast are planned, and how to manage regular medicines. When the report is ready, ask whether any uptake could reflect recent treatment or inflammation, how it compares with prior imaging, and whether the finding calls for observation, another scan or tissue sampling.