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PET Scan
A PET (positron emission tomography) scan uses a small amount of radioactive tracer to show how active tissues are. It is often combined with CT and is especially useful in cancer care.
Causes & risk factors
- To find or stage cancers
- To check how well cancer treatment is working
- To look for cancer spread in the body
- To assess some heart and brain conditions
- To help tell active disease from scar tissue
- To guide biopsy or treatment planning
Common symptoms
- Usually done to investigate a known or suspected cancer
- Unexplained weight loss (as part of cancer work-up)
- Swollen glands under investigation
Tests & diagnosis
- CT scan (often combined as PET-CT)
- MRI for certain areas
- Biopsy to confirm findings
Treatment & management
- A small amount of radioactive tracer is injected first
- You rest quietly for about an hour while it spreads
- The scan itself is painless and takes around 30 minutes
- You may be asked not to eat beforehand and to avoid strenuous activity
- The radiation leaves the body within hours — you may be asked to avoid close contact with pregnant women and young children briefly
When to see a doctor urgently
- When your specialist needs to stage a cancer or check treatment
- To look for whether a cancer has spread
- As part of planning cancer treatment
Frequently asked questions
Is the radioactive tracer in a PET scan harmful?
The amount used is small and leaves your body within hours. As a precaution you may be asked to keep your distance from pregnant women and young children for a short time afterwards.
Why combine PET with CT?
A PET scan shows how active tissue is, while CT shows detailed anatomy. Combining them (PET-CT) pinpoints exactly where active disease is, which is very useful in cancer care.
Explore more
Sources & further reading
- World Health Organization (WHO)
- MedlinePlus — U.S. National Library of Medicine
- Ministry of Health & Family Welfare, India
- Indian Council of Medical Research (ICMR)
Reviewed by Dr. Sanjay Anbu, MBBS. MedDroid is an AI medical assistant and can make mistakes. It provides general health information, not a diagnosis or medical advice — always consult a qualified clinician. In an emergency, contact your local emergency number immediately.