18F-Fluorodeoxyglucose (FDG) PET/CT for Tumor Localization — Intravenous Administration
A PET/CT scan that uses an FDG radiotracer to identify areas of increased metabolic activity and help locate tumors or suspicious tissue.
["This scan can show where cells are using extra glucose, which may help assess tumors, although abnormal uptake is not specific to cancer."]
Key facts at a glance
- LOINC
- 87915-5
- Short code
- PET+CT Vert-thgh Guid tum loc 18F-FDG IV
- Synonyms
- PET+CT Vert-thgh Guid tum loc 18F-FDG IV
- Category
- liver
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- pt-ct
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
What is this test?
18F-FDG PET/CT is a combined imaging test. A radioactive form of glucose, called FDG, is given through a vein, and a PET scanner measures how much tracer collects in different tissues. A CT scanner provides detailed images of anatomy that can be compared with the PET findings.
Why might I need this test?
This test may be used to help locate a known tumor, evaluate suspicious lymph nodes or other areas, stage certain cancers, or monitor treatment. It may also be performed when cancer is suspected but its location or extent is unclear.
How is the test performed?
After the FDG tracer is injected through an intravenous line, you usually rest quietly for a period while the tracer is absorbed. You then lie on a table while the machine collects PET and CT images, which are usually combined for review by a nuclear medicine physician and radiologist.
How do I prepare for the test?
Follow the facility's specific instructions, which may include fasting for several hours before the appointment and limiting strenuous activity beforehand. Tell the imaging team if you are pregnant, might be pregnant, or are breastfeeding, and ask about diabetes medications, recent surgeries, or other FDG tracers because these can affect the images.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Increased FDG uptake may occur in tumors, but it can also result from inflammation, infection, or normal tissue activity. The PET images are interpreted together with the CT images, the medical history, and other tests. Areas without increased uptake are not always free of disease, so results should be discussed with the ordering clinician.
Short name
18F-FDG PET/CT for Tumor Localization
Frequently asked questions
Does this test use radiation?
Does increased FDG uptake always mean cancer?
How long does an FDG PET/CT take?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
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Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy