Radionuclide Metrology Landing page

Radionuclide Metrology

Helping ensure that measurements of radioactivity used in medicine, environmental monitoring, research and industry are trusted and are comparable worldwide.

 

Measuring radioactivity with confidence

Comparing national standards for radionuclide activity

Radioactive materials are used in fields ranging from nuclear medicine to environmental monitoring. Reliable use of these materials depends on confidence that an activity measured in one country is comparable with a measurement made elsewhere.

The BIPM operates international reference systems that allow National Metrology Institutes (NMIs) and Designated Institutes (DIs) to compare their primary activity standards and demonstrate their equivalence.

 

The BIPM’s radionuclide comparison systems

Different radionuclides need different routes to comparison

The BIPM operates three complementary comparison systems that enable national activity standards for different types of radionuclides to be compared internationally. Each provides a different route to comparison, depending on the properties of the radionuclide and how the standard can be measured.

SIR
 
International Reference System

International Reference System

SIR — gamma-ray emitting radionuclides

The BIPM maintains the International Reference System (SIR) as a stable international reference for comparing national standards of many gamma-ray emitting radionuclides over time.

Participating National Metrology Institutes (NMIs) and Designated Institutes (DIs) send a sample of their primary standard in solution to the BIPM, where a high-stability ionization chamber enables it to be compared with standards submitted by other institutes.

By maintaining the SIR as a continuous reference system, the BIPM enables degrees of equivalence to be established without requiring all participants to measure the same material at the same time.

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SIRTI
 
Transportable reference system

Transportable reference system

SIRTI — short-lived gamma-ray emitters

Some short-lived gamma-emitting radionuclides decay too quickly for samples to be transported to the BIPM. To enable these standards to be compared, the BIPM operates the SIR Transfer Instrument (SIRTI), a transportable comparison instrument that can be taken to participating institutes and, where possible, operated remotely from the BIPM.

By taking the comparison instrument to participating institutes, the BIPM can extend international comparison services to short-lived gamma-emitting radionuclides, including radionuclides important in nuclear medicine.

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ESIR
 
Extending the reference system

Extending the reference system

ESIR — extending comparisons to other radionuclides

For radionuclides that cannot be measured effectively with the SIR ionization chambers, the BIPM operates the Extension of the International Reference System (ESIR). Using liquid scintillation counting, ESIR extends international comparisons to pure beta-emitting and selected other radionuclides.

Through ESIR, the BIPM extends international comparison services to radionuclides not covered effectively by the SIR, including pure beta-emitting radionuclides relevant to healthcare, environmental monitoring and other applications.

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A growing measurement need

Measuring radionuclides used in nuclear medicine

Radionuclides are increasingly being used not only for medical imaging, but also in targeted treatments for cancer and other diseases. Accurate activity measurements and reliable standards are important for quantitative imaging, treatment planning and the safe use of radiopharmaceuticals.

The Radionuclide Therapy and Quantitative Imaging Working Group of the Consultative Committee for Ionizing Radiation (CCRI) brings together experts from metrology, nuclear medicine and medical physics to identify measurement priorities for radionuclide-based therapy and quantitative imaging. This includes measurement needs for alpha-emitting radionuclides being used or investigated for therapeutic nuclear medicine.

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For measurement specialists

Radionuclide comparison systems and technical resources

Go directly to technical information, participation documents and internationally recognized comparison results.

Frequently asked questions

Find quick answers to common questions about radionuclide metrology and the BIPM’s international comparison systems.

What is radionuclide metrology?

Radionuclide metrology is concerned with the accurate measurement of radioactivity. It supports applications including nuclear medicine, environmental monitoring, scientific research and industry.

What is the SIR?

The International Reference System (SIR) is the BIPM’s continuous comparison system for national activity standards of many gamma-ray emitting radionuclides.

Why is SIRTI needed?

Short-lived gamma-emitting radionuclides can decay too quickly for samples to be transported to the BIPM. SIRTI is a transportable comparison instrument that allows comparisons to be carried out at participating institutes.

What does ESIR add?

ESIR extends the BIPM reference system to radionuclides that cannot be measured effectively with the SIR ionization chambers. It uses liquid scintillation counting and enables comparisons for pure beta-emitting and selected other radionuclides.

How do BIPM radionuclide comparisons contribute to internationally recognized measurement capabilities?

Successful participation provides evidence of the equivalence of national standards and can contribute to the review of Calibration and Measurement Capabilities (CMCs) under the International Committee for Weights and Measures Mutual Recognition Arrangement (CIPM MRA).

Why is radionuclide metrology important for nuclear medicine?

Nuclear medicine relies on accurate measurements of radionuclide activity for quantitative imaging and radionuclide therapy. Traceable and comparable activity measurements provide confidence in the measurement results used across these applications.

Continue exploring ionizing radiation metrology

Explore other areas of the BIPM Ionizing Radiation Department’s work and international coordination.

Explore the BIPM Ionizing Radiation Department

Learn more about the Department’s measurement services, international activities and scientific programmes.

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