What Is a PET Scan?
A PET (positron emission tomography) scan is an imaging test that uses a radioactive tracer to show how tissues and organs are functioning. In oncology, PET scans are used to detect cancer, see if cancer has spread, evaluate whether treatment is working, and detect recurrence.
Understanding SUV (Standardized Uptake Value)
The most important number in your PET report is the SUV — Standardized Uptake Value. SUV measures how much radioactive tracer a specific area of tissue absorbed. Cancer cells are metabolically active and absorb more tracer, appearing as "hot spots."
- SUV max: The highest uptake value in a lesion. Higher numbers generally indicate more metabolically active tissue.
- SUVmax < 2.5: Often considered low, may be normal tissue or benign process
- SUVmax 2.5–10: May indicate malignancy — context matters
- SUVmax > 10: Highly suspicious for active cancer
Important: SUV values alone do not diagnose cancer. Your oncologist interprets them in the context of your full clinical picture.
Key Terms in PET Reports
- Avid / FDG-avid: The area absorbs significant tracer — often cancer or inflammation
- Hypermetabolic: Increased metabolic activity — suspicious area
- Hypometabolic: Decreased activity compared to surrounding tissue
- Mediastinum: The space between the lungs containing the heart, lymph nodes
- No evidence of distant metastatic disease: No spread to distant organs detected
- Physiologic uptake: Normal expected tracer absorption in certain organs
Comparing PET Scans Over Time
When your report compares to a prior PET scan, look for terms like: interval decrease (improvement), interval increase (progression), stable (no change), or complete metabolic response (no detectable cancer activity — a very positive finding).
What to Ask Your Oncologist
Ask your oncologist to walk you through your PET results. Ask what the findings mean for your treatment plan, whether any areas need biopsy, and how these results compare to your previous scans.