Comparing SUV Between Two Scans: — Is It Meaningful?

Not necessarily. A rise in SUV only reliably points to increased metabolic activity if both scans were done on the same scanner with the same protocol. A different scanner, a higher blood glucose level, a longer injection-to-scan delay, or a change in reconstruction settings can all raise the number without any change in disease. Your oncologist looks at whether the number changed, where it changed, whether new lesions appeared, and what the images show visually — not the number alone. Bring this question directly to your next appointment so the team can walk you through the specific comparison.

Not directly. A number-to-number comparison is unreliable when conditions differ. Your oncologist can still read both scans and look for qualitative changes — whether previously active lesions look quieter, whether new ones appeared — but will treat the raw numbers with caution. Bring the image files from both scans to your appointment if you can, rather than only the printed reports. For future follow-up, asking whether scans can be done consistently at one centre is a reasonable question for your care team.

No. SUV does not have a normal range the way a blood count does. The same tissue will produce a different number depending on the scanner, blood glucose level, timing, and reconstruction method. It is not a cancer score. What matters is the change from your own baseline under comparable conditions, and your oncologist's overall assessment of what the scan shows. A number that seems alarming in isolation may be unremarkable in context — which is why individual values should never be interpreted without the full clinical picture.

PERCIST — PET Response Criteria in Solid Tumours — is a standardised framework from the Society of Nuclear Medicine for classifying whether a treatment response has occurred on PET imaging. It uses percent change in SUV from a baseline scan to define response categories. It applies when scans are done under matched technical conditions, which is exactly why the same-scanner, same-protocol requirement matters in practice. Not every report will mention PERCIST by name; ask your oncologist which criteria they are using to assess your response.

SUVmax is the single highest uptake point in the measured area. SUVpeak is an average over a small fixed volume near the hottest spot, and is considered slightly more reproducible because it is less sensitive to a single noisy measurement. Which one a department uses depends on their local protocol. What matters when comparing scans is that both reports used the same measure — mixing SUVmax from one scan with SUVpeak from another adds another layer of variation to an already complex comparison. If your reports differ, ask the nuclear medicine team which measure was used each time.

Yes, and it is worth asking. Keeping follow-up scans at the same centre, on the same scanner, with the same preparation instructions removes the single largest source of variation in serial comparisons. If you need to move between centres — because of travel, cost, or a change of hospital — ask whether the original centre can share the scan acquisition parameters with the new one, so the nuclear medicine team there knows what conditions to match as closely as possible.