What Does SUV Mean on a PET Scan?

## What Is SUV? **SUV — Standardized Uptake Value** — is a measurement of how much radioactive tracer (FDG, or fluorodeoxyglucose) an area of your body has absorbed compared to your body as a whole. Since cancer cells are metabolically very active and consume glucose rapidly, they tend to absorb more FDG — and show up with higher SUV values on a PET scan. SUV is calculated by comparing: - The concentration of tracer in a specific area - The total amount of tracer injected, adjusted for your body weight ## SUV Numbers and What They Mean | SUV Value | General Interpretation | |---|---| | < 2.5 | Low metabolic activity — often normal tissue or benign process | | 2.5 – 5.0 | Borderline — warrants attention; could be inflammation, infection, or cancer | | 5.0 – 10.0 | Elevated — more suspicious for malignancy | | > 10.0 | High — very suspicious for active cancer | **Critical caveat:** These are general guidelines, not rules. The meaning of an SUV depends heavily on: - Which part of the body - The type of cancer you have - Previous treatment (treated tumors can have lower SUV) - Timing since your last scan ## Why SUV Isn't the Whole Story SUV values can be elevated for many non-cancer reasons: - **Infection and inflammation** — often show high FDG uptake - **Recent surgery** — healing tissue is metabolically active - **Normal structures** — the brain, heart, and urinary tract all have naturally high FDG uptake - **Blood sugar levels** — high blood glucose at the time of the scan reduces tracer uptake and affects accuracy ## SUVmax vs. SUVmean Reports often use two variants: - **SUVmax** — the single highest-uptake voxel in a lesion; most commonly reported; more sensitive to noise - **SUVmean** — average uptake across the lesion; more stable but requires precise lesion outlining ## Comparing SUVs Over Time The change in SUV from one scan to the next is often more meaningful than the absolute number: - **Decreasing SUV** on treatment → the cancer is responding - **Stable SUV** → disease is neither responding nor progressing - **Increasing SUV or new FDG-avid lesions** → possible progression Many oncologists look at the **Deauville Score** (in lymphoma) or **PERCIST criteria** for standardized response assessment rather than raw SUV numbers. ## Bottom Line Don't panic over a single SUV number — or assume a high number definitely means active cancer. Your oncologist interprets these values in the full clinical context of your cancer type, treatment history, and the specific body location.