What a PET scan can show about cancer in the body

The FDG radiotracer is taken up by many active cells. PET shows where activity is concentrated, while CT supplies detailed information about anatomy. Together, the images can help locate a primary tumour, show involved lymph nodes, look for disease in other areas, and assess how a known tumour is responding to treatment.

Increased uptake does not automatically mean cancer. Infection, inflammation, healing tissue, and some normal organs can also appear active. A radiologist and the treating team interpret the pattern alongside symptoms, examination findings, blood tests, prior scans, and sometimes a biopsy.

Follow the centre's instructions about fasting, fluids, medicines, and physical activity. Tell staff about diabetes, pregnancy, breastfeeding, recent illness, or trouble remaining still. Bring earlier imaging reports if available. After the scan, ask when the report will be reviewed and whether another test is needed before treatment decisions are made.

Learn more about the [PET-CT Scanner](/technology/pet-ct-scanner/) and the [FDG Radiotracer](/materials/fdg-radiotracer/).

The scan itself is not an emergency test for new severe symptoms. Seek urgent medical help for sudden weakness, severe breathlessness, chest pain, collapse, or new confusion. Contact the imaging or oncology team about persistent injection-site swelling, increasing pain, or a new symptom after the appointment.

What question is this scan intended to answer? Which body regions will be included? Could inflammation affect interpretation? Will a tissue sample be needed? How will the findings change staging or the next treatment discussion?