Radiation Verification and Sterilization Dose Transfer
Executive Summary: Radiation Verification and Sterilization Dose Transfer
Radiation verification doses and sterilization doses can be transferred between qualifying gamma, X-ray, and electron beam facilities in accordance with ISO 11137-1:2025, providing greater flexibility for dose audits and validation activities.
For products that do not contain liquid water, evidence shows microbicidal effectiveness is solely dose dependant and independent of radiation source, enabling verification work to be performed at specialized facilities such as STERIS Radiation Technology Centers (RTCs), which offer high-precision processing and rapid turnaround for validation and research applications.
This TechTip whitepaper answers the following questions:
- How to demonstrate the continued effectiveness of the established sterilization dose?
- What are the requirements for transferring verification dose and sterilization dose between radiation facilities?
- What is the Radiation Verification Dose Transfer Guidance from ISO 11137-1:2025?
What is the Sterilization Dose and Why is There a Need for Periodic Audit?
The sterilization dose is defined in ISO11137-1:2025 as ‘minimum dose to achieve the specified requirements for sterility’. (ISO 11137-1:2025 3.4.1). It is the minimum dose applied to ensure the required minimum Sterility Assurance Level (SAL) is achieved.
During validation using one of methods described in ISO 11137-2, the minimum sterilization dose is established based on the microbiological challenge of the product being sterilized.
Periodic audits are performed to confirm that the established minimum dose remains appropriate to the microbiological challenge.
Audits are the application of a lower dose (SAL 10-1 or SAL 10-2) to products representative of the typical microbiological challenge of the routine product.
How do I Demonstrate the Continued Effectiveness of the Established Sterilization Dose?
To demonstrate continued effectiveness of the established sterilization dose, a dose audit is required to be performed at defined frequencies.
This audit requires the treatment of samples at a dose specific to the medical device. In performing such studies, lower dose must be performed at verification levels on SAL 10-1 or 10-2, typically at doses less than 10kGy.
Additionally, the dose range of the applied verification dose (i.e. dose audit) is lower than the routine processing dose range to verify sterility assurance.
To achieve this tighter dose range, the product configuration and/or irradiator processing parameters may need to be adjusted and qualified.
What are the Requirements for Transferring Verification Dose and Sterilization Dose Between Radiation Facilities?
According to ISO 11137-1:2025, the sterilization dose qualification and dose audit do not need to be performed at the same facility and with the same radiation technology as the site used for routine product processing, provided product does not contain water in the liquid state.
Thus, a sterilization dose qualification or a dose audit irradiation may be performed in a radiation processing facility capable of delivering the specified verification dose: For example, a gamma or X-ray facility may be used to perform the verification dose for product routinely processed in an E-beam facility.
To meet the needs of our Customers, STERIS has consolidated dose verification work into our dedicated Radiation Technology Centers (RTC), which specialize in the high precision-processing of non-routine samples with a rapid turnaround.
Our Radiation Technology Centers specialise in dose delivery for dose verification, dose audit and research purposes.
The following information details the ISO requirements for transferring radiation verification dose work from a production processing facility to a STERIS RTC.
ISO 11137-1:2025 defines the requirements necessary to transfer doses from one plant to another and must be complied with to warrant any transfer of dose.
The requirements are detailed below:
What is the Radiation Verification Dose or Sterilization Dose Transfer Guidance from ISO 11137-1:2025?
The guidance from ISO 11137-1:2025 is as follows:
8.4.2 Transference of verification dose or sterilization dose
8.4.2.1
Transference of a verification dose or a sterilization dose to a radiation source different from that on which the dose was originally established is permitted provided that the product does not contain water in the liquid state.
8.4.2.2
For product that contains water in the liquid state, transference of the verification dose or sterilization dose is not permitted unless data are available to demonstrate that differences in operating conditions of the two radiation sources have no effect on microbicidal effectiveness.
Additional guidance is provided in Annex A of ISO 11135-1:2025. See Annex A.8.4.2
Summary: Radiation Verification and Sterilization Dose Transfer
In summary, this TechTip explains that ISO 11137-1:2025 permits radiation verification doses and sterilization doses to be transferred between qualifying gamma, X-ray, and electron beam facilities, provided key product conditions are met.
It highlights that, for products without liquid water, microbicidal effectiveness is generally independent of radiation source, enabling dose audits and validation work to be completed at specialized facilities such as .
Learn more about our contract sterilization services including E-beam, gamma and X-ray, and our technical support services that guide our Customers through the detailed and complex sterilization and laboratory testing processes, from product development through routine processing.
September 2026 Reviewed and updated by Pierre Reppert, Senior Manager, Radiation Technology Centers EMEA-APAC, STERIS Applied Sterilization Technologies.