SUVmax, SUVmean and SUVpeak: — What Each Number Measures

There is no single normal value. Different tissues absorb FDG at different rates as a matter of normal physiology — the brain and heart are naturally high, resting muscle is low. What your team looks for is whether a particular area absorbs more than the surrounding tissue or more than the same area on a previous scan. Crossing any specific number is not the question they are asking.

An individual number cannot be interpreted without context. The same value means something different depending on which organ is involved, your clinical history, what the previous scan showed, and whether you had any infection or inflammation at the time. Your reporting radiologist or oncologist is the right person to interpret this for your specific scan. Never use an SUV figure to draw your own conclusions before speaking to your team.

No. SUV describes metabolic activity — how much glucose a tissue is consuming — and many conditions other than cancer cause high uptake. A PET finding is always interpreted alongside clinical history, other imaging and often a tissue biopsy before any diagnosis is made. SNMMI and EANM guidance consistently states that metabolic imaging findings should not be used in isolation to confirm or exclude a malignant diagnosis.

Different centres and radiologists may default to different metrics, which is one reason comparing numbers across hospitals is unreliable. If your care has moved to a different centre or the reporting protocol has changed, the numbers are not directly comparable even if the lesion itself has not changed. Ask your oncologist which figure should be used consistently going forward, and whether the earlier scan can be re-reported using the same method if a direct comparison is needed.

A falling SUV after treatment generally means the lesion is absorbing less glucose, which may indicate the treatment is working. Formal response criteria from bodies including PERCIST and EORTC use a defined change in SUV to categorise a lesion as responding, stable or progressing. Your oncologist will tell you how they are interpreting the change in your specific case, and what the next step will be based on that assessment.

A rising SUV can indicate that a lesion is more metabolically active, which may mean it is progressing — but the size of the change, the method used, and whether the two scans were technically comparable all matter before that conclusion is drawn. Your oncologist will tell you whether the change is clinically meaningful at your review. If you are waiting for that review and are worried, call the clinic rather than interpreting the number yourself.