What should you know about an NM PET-CT scan?

An NM PET-CT scan combines a radiotracer with CT imaging to show body structure and areas of increased metabolic activity. Nuclear medicine staff give the tracer, often an FDG radiotracer, before the scan. The PET images show how tissues behave, while CT helps locate those changes precisely.

The scan may help clinicians look for cancer in a known area, check whether disease has spread, or investigate an abnormal finding whose origin is unclear. Increased tracer uptake can occur for reasons other than cancer, including inflammation, so the images need interpretation alongside symptoms, examination findings, and other tests. Learn about the [PET-CT Scanner](/technology/pet-ct-scanner/) and the [FDG Radiotracer](/materials/fdg-radiotracer/).

Your imaging team will give instructions about eating, drinking, medicines, and blood glucose. Wear comfortable clothing and tell staff if you are pregnant, might be pregnant, breastfeeding, diabetic, or unable to lie still. Plan time for the tracer to circulate quietly before imaging, followed by a period of remaining still during the scan. The [PET-CT Scan](/treatments/diagnostics-and-staging/pet-ct-scan/) page explains the appointment.

Contact the imaging centre before the appointment if you cannot follow fasting instructions, have a problem with blood glucose, or need help transferring or lying flat. After the scan, seek urgent medical help for trouble breathing, facial swelling, fainting, or another sudden severe symptom. A mild injection-site reaction should still be reported to the department for advice.

Ask what the scan is intended to answer, whether you need to change medicines, how long the visit may take, and when the report will reach your treating clinician. If the scan is for suspected lymphoma or cancer of unknown primary, ask how its findings will fit with biopsy and other imaging.