What should you know about a PET body scan?

A small amount of radiotracer is given before the scan. After a quiet waiting period, the PET camera records where the tracer collects. Many oncology scans cover from the head or neck through the upper legs, although the exact range depends on the referral. A CT portion may show the body's structure beside the activity map.

The scan can help assess the extent of a known cancer, check how treatment is affecting active tissue, or search for a possible source when cancer has been found elsewhere. [Lymphoma](/conditions/lymphoma/) and [Cancer of Unknown Primary](/conditions/cancer-of-unknown-primary/) are examples where this type of imaging may be part of a wider assessment. A scan cannot replace tissue sampling when a diagnosis requires a biopsy.

Use the preparation instructions from your imaging centre, which may include avoiding food for a set period and limiting strenuous activity beforehand. Tell staff about diabetes, pregnancy, breastfeeding, recent illness, medicines, and difficulty staying still. Keep warm and comfortable during the waiting period, because shivering can affect image quality.

The tracer is injected, then you rest without unnecessary talking or walking before imaging. The scan itself is quiet and requires you to lie still. Follow the department's advice about fluids and contact with young children or pregnant people afterwards. Read about the [FDG Radiotracer](/materials/fdg-radiotracer/) and [PET-CT Scanner](/technology/pet-ct-scanner/) for related terms.

During or soon after injection, report itching, hives, swelling, dizziness, or breathing trouble to the staff straight away. After the appointment, urgent help is appropriate for severe breathing difficulty, fainting, or rapidly worsening swelling. A mild injection-site sensation may have another explanation, but contact the imaging centre if it persists or worsens.

Ask which body areas will be scanned, whether fasting is required, how diabetes treatment should be managed, and when the report will reach your referring doctor. Ask what other test may clarify an area of uptake and whether you can take usual medicines on the day.