PERCIST Calculator

PERCIST 1.0 metabolic response from FDG PET/CT: checks that the baseline lesion is measurable, compares the hottest lesion's SULpeak between scans, and assigns CMR, PMR, SMD or PMD.

Enter SUL values (SUV normalized to lean body mass). The hottest lesion at follow-up may be a different lesion from baseline, as long as it was present at baseline.

Input Parameters

Use blood pool only when metastases keep a clean 3 cm liver ROI from being drawn; fatty liver or cirrhosis does not count as diseased.

Baseline

SULpeak: mean SUL in a ~1 cm³ sphere (1.2 cm diameter) over the hottest part of the lesion

Follow-up

Not explained by infection, inflammation or treatment effect
For non-target lesions, at least the same rise as the target rule (30% and 0.8 SUL), e.g., SULpeak 2.0 to 6.0
Optional: total lesion glycolysis (exploratory) and scan comparability

Calculated Response

Measurability threshold --
Baseline lesion measurable --
SULpeak change --
Liver SULmean change --
PERCIST response --
Threshold = 1.5 × liver SULmean + 2 × SD

Interpretation

Enter baseline reference values and the SULpeak at both scans to see the response.

PERCIST 1.0 rules used

  • Measurable lesion: baseline SULpeak at least 1.5 × liver SULmean + 2 SD (3 cm ROI in the right lobe). If the liver is diseased, use 2.0 × blood-pool SULmean + 2 SD.
  • Lesion compared: the hottest lesion at baseline against the hottest lesion at follow-up, which need not be the same lesion.
  • CMR: target uptake below liver SULmean and indistinguishable from surrounding background, all other lesions back to background, and no new lesions. SULpeak need not reach zero.
  • PMR: SULpeak decrease of at least 30% and at least 0.8 SUL, with no new lesions and no progression of target size or non-target lesions.
  • PMD: SULpeak increase of at least 30% and at least 0.8 SUL; a new FDG-avid lesion typical of cancer; target lesion size up 30% or more; or unequivocal non-target progression. New lesions or unequivocal progression count as PMD even when the baseline lesion was not measurable.
  • SMD: SULpeak change of less than 30% in either direction, or a drop that misses the 0.8 SUL requirement.
  • Assessable pair of scans: liver SULmean differs by no more than 20% of the larger value and no more than 0.3 SUL; both uptake times 50–70 min and within 15 min of each other; same scanner, protocol and software; injected dose within 20%; fasting at least 4 hours with glucose under 200 mg/dL.
  • Exploratory: a TLG increase of more than 75% is listed as PMD, but Practical PERCIST treats TLG as exploratory data.
  • Confirmation: new FDG-avid foci without a CT correlate should usually be verified by follow-up PET/CT or another method about 1 month later.

References

  • Wahl RL, Jacene H, Kasamon Y, Lodge MA. From RECIST to PERCIST: evolving considerations for PET response criteria in solid tumors. J Nucl Med. 2009;50 Suppl 1:122S-150S. doi:10.2967/jnumed.108.057307
  • O JH, Lodge MA, Wahl RL. Practical PERCIST: a simplified guide to PET response criteria in solid tumors 1.0. Radiology. 2016;280(2):576-584. doi:10.1148/radiol.2016142043

For education and as a reading aid. Trial protocols and imaging charters take precedence.