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Imaging biomarkers

What turns a measurement into a biomarker, how SUV and PET quantification behave, and the structured reporting systems used in research and trials.

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On this page, in one line each
  • What makes a measurement an imaging biomarker: A biomarker is a defined characteristic measured as an indicator of a biological process, disease or response. Imaging biomarkers need technical and clinical validation.
  • SUV and PET quantification: The standardised uptake value normalises PET activity to the injected amount and body size. It is useful and easy to over-trust.
  • Structured reporting systems: RECIST, Deauville, Krenning, PSMA-RADS, PI-RADS and others standardise how findings are described.
introductoryImaging Biomarkers & Radiomicsstudentresearcherregulatory

What makes a measurement an imaging biomarker

In short: A biomarker is a defined characteristic measured as an indicator of a biological process, disease or response. Imaging biomarkers need technical and clinical validation.

Categories

The FDA–NIH BEST glossary sorts biomarkers by use: susceptibility or risk, diagnostic, monitoring, prognostic, predictive, pharmacodynamic or response, and safety. The same measurement can serve different uses, and each use needs its own evidence.

Validation in layers

  • Technical validation: is the measurement repeatable and reproducible across scanners and sites?
  • Clinical validation: does it relate to the clinical quantity of interest in the intended population?
  • Utility: does using it improve decisions or outcomes?

Standardisation efforts

Groups such as the RSNA Quantitative Imaging Biomarkers Alliance write profiles that specify how to acquire and measure a biomarker so that values can be compared.

RadioGx can help you
  • Show biomarker definitions, reporting systems and related trials
RadioGx cannot
  • Interpret a biomarker value for anyone

Read more at the source

Glossary: Imaging biomarker, Quantitative imaging biomarker, Test-retest repeatability

Check your understanding

Technical validation of an imaging biomarker asks whether…

This lesson is general education. It does not interpret anyone’s images, results or treatment, and it is not medical advice.

intermediateImaging Biomarkers & Radiomicsphysicisttechnologistresearcher

SUV and PET quantification

In short: The standardised uptake value normalises PET activity to the injected amount and body size. It is useful and easy to over-trust.

The idea

SUV divides the measured activity concentration in tissue by the injected activity per unit body weight (or lean body mass, or body surface area). A value near one means uptake similar to a uniform distribution through the body.

What changes SUV

  • Time between injection and scan
  • Blood glucose for FDG
  • Scanner, reconstruction method and smoothing
  • Partial volume effects in small lesions
  • Region definition: maximum, peak or mean

Harmonisation

Programmes such as EANM’s EARL accreditation harmonise scanner performance so that SUVs are more comparable across sites. Response frameworks such as PERCIST specify how to measure change. Volume measures such as metabolic tumour volume depend on the segmentation threshold.

MythA higher SUV always means more aggressive disease.
FactSUV is affected by technical and physiological factors and must be interpreted by qualified professionals in context.
RadioGx can help you
  • Explain SUV variants and link PERCIST and harmonisation resources
RadioGx cannot
  • Interpret anyone’s SUV

Read more at the source

Glossary: Standardised uptake value (SUV), Metabolic tumour volume (MTV), Total lesion glycolysis (TLG), PERCIST, Partial volume effect

Check your understanding

Which factor does NOT usually change a measured SUV?

This lesson is general education. It does not interpret anyone’s images, results or treatment, and it is not medical advice.

introductoryImaging Biomarkers & Radiomicsstudentresearcherclinician

Structured reporting systems

In short: RECIST, Deauville, Krenning, PSMA-RADS, PI-RADS and others standardise how findings are described.

Why structure helps

Structured systems give readers a shared vocabulary and categories, which makes reports more consistent and research easier to compare. Trials often use them to define endpoints.

A few examples

  • RECIST 1.1: anatomic tumour response in solid tumours, widely used as a trial endpoint.
  • Deauville five-point scale: visual FDG uptake scoring used in lymphoma response assessment.
  • Krenning score: visual grading of somatostatin receptor uptake.
  • PSMA-RADS and PROMISE: frameworks for PSMA PET reporting.
  • PI-RADS, BI-RADS, LI-RADS, Lung-RADS: organ-specific reporting systems.

What they are not

These are reporting frameworks used by trained readers. RadioGx explains them; it does not assign categories to anyone’s images.

RadioGx can help you
  • Recognise these systems in queries and link to trials using them
RadioGx cannot
  • Assign a category to any image

Read more at the source

Glossary: RECIST 1.1, Deauville five-point scale, Krenning score

Check your understanding

RECIST 1.1 primarily measures…

This lesson is general education. It does not interpret anyone’s images, results or treatment, and it is not medical advice.

Key terms

Imaging biomarker
A characteristic measured on images as an indicator of a biological process, disease or response.
Quantitative imaging biomarker
An imaging biomarker expressed as a number on a defined scale.
Test-retest repeatability
Agreement between measurements repeated under the same conditions.
Standardised uptake value (SUV)
PET activity concentration normalised to injected activity per body size.
Metabolic tumour volume (MTV)
The volume of tissue above a chosen uptake threshold on PET.
Total lesion glycolysis (TLG)
MTV multiplied by the mean SUV of that volume.
PERCIST
PET Response Criteria in Solid Tumors: a framework for measuring metabolic response.
Partial volume effect
Underestimation of activity in objects small relative to scanner resolution.
RECIST 1.1
Response Evaluation Criteria in Solid Tumors: anatomic size-based response categories.
Deauville five-point scale
Visual FDG-PET uptake scoring used in lymphoma response assessment.
Krenning score
Visual grading of somatostatin receptor uptake relative to reference organs.

Myth and fact

MythA higher SUV always means a worse prognosis.
FactSUV depends on technical and physiological factors and needs professional interpretation in context.