# Krenning score

Source: https://nuclide.cc/terms/krenning-score/  
Nuclide record `krenning-score` (Term). Data CC BY-NC 4.0, attribute "Data from Nuclide (nuclide.cc)"; commercial use needs a licence.

## TL;DR

A 0-to-4 scale doctors use to describe how strongly a tumour lights up on a somatostatin receptor scan, by comparing it with the normal liver and spleen. A higher score generally means the tumour is a good candidate for peptide receptor radionuclide therapy.

## Summary

The Krenning score is a five-point visual grading system (0-4) developed for planar and SPECT imaging with 111In-pentetreotide (OctreoScan), which grades tumour uptake of a somatostatin receptor tracer against two internal reference tissues: normal liver (grades 1-3) and spleen or kidney (grade 4). Grade 0 is no uptake; grade 1 is uptake below liver; grade 2 is uptake equal to or slightly less than liver; grade 3 is uptake greater than liver; grade 4 is uptake greater than spleen or kidney. The NETTER-1 trial required tumour uptake at least equal to normal liver (Krenning grade 2 or above) for enrolment, and a score greater than 2 is the practical threshold most centres use when selecting patients for PRRT with lutetium-177 dotatate.

The score has been extrapolated to gallium-68 and copper-64 DOTATATE PET/CT as a "modified Krenning score", but the correlation between the original scintigraphy-derived score and the PET-derived score is limited: PET is more sensitive, is acquired around one hour after injection rather than 24 hours, and tends to grade the same lesion higher. For lesions larger than 2 cm the modified score is considered more reliable; centres should state which imaging method and which reference organ underlie a reported grade.

The score is lesion-level and visual rather than quantitative, so heterogeneous disease (some lesions with low uptake alongside others with high uptake) requires reporting each discordant lesion separately rather than a single summary number, since a single index-lesion grade can misrepresent overall receptor status across the body.

## Fields

- Kind: Term
- Last checked: 2026-09-22
- Tags: scoring system; SSTR imaging; PRRT eligibility

## Sources

- Radiopaedia: Krenning score of neuroendocrine tumour uptake: https://radiopaedia.org/articles/krenning-score-of-neuroendocrine-tumour-uptake?lang=us
- Somatostatin receptor imaging and theranostics: current practice and future prospects (JNM/PMC, 2021): https://pmc.ncbi.nlm.nih.gov/articles/PMC9364764/

## Connected records

- drugs: [177Lu-edotreotide](https://nuclide.cc/drugs/itm-11/), [Gallium-68 DOTATATE (and Cu-64 DOTATATE)](https://nuclide.cc/drugs/ga68-dotatate/), [Lutetium-177 dotatate](https://nuclide.cc/drugs/lutathera/)
- technologies: [Peptide receptor radionuclide therapy (PRRT)](https://nuclide.cc/technologies/prrt/), [Somatostatin receptor PET (68Ga/64Cu-DOTATATE)](https://nuclide.cc/technologies/sstr-pet/)
- indications: [Neuroendocrine tumours](https://nuclide.cc/indications/neuroendocrine/)
- trials: [NETTER-1](https://nuclide.cc/trials/netter-1/)
- isotopes: [Copper-64](https://nuclide.cc/isotopes/cu-64/), [Gallium-68](https://nuclide.cc/isotopes/ga-68/), [Indium-111](https://nuclide.cc/isotopes/in-111/), [Lutetium-177](https://nuclide.cc/isotopes/lu-177/)
- terms: [Tumour-to-background ratio (TBR)](https://nuclide.cc/terms/tumour-to-background-ratio/)

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