ISO 11137 – An Overview of Gamma Sterilization Validation

calendar15 Apr, 2023
timeReading Time: 4 Minutes
ISO 11137 - An Overview of Gamma Sterilization Validation

A medical device is considered sterile if it is free of live microorganisms. When it’s necessary to supply a sterile medical device, international standards mandate that accidental microbiological contamination of a medical device prior to sterilization be minimized. These standards define the requirements for validation and routine control of sterilization processes. Nevertheless, even after sterilization, there may be a small amount of microorganisms on medical devices made under standard manufacturing circumstances and in accordance with the specifications for quality control systems (see, for instance, ISO 13485). These medical instruments lack sterility. The objective of sterilization is to render non-sterile medical devices sterile by inactivating the microbiological contaminants. One of the last hurdles that many medical device manufacturers must clear before their product can be released is sterilization. This does not, however, imply that it can or ought to be treated as an extra. Equipment that has not been properly or thoroughly sterilized puts patients and users in peril. Fortunately, there are numerous effective methods for cleansing medical equipment.  Gamma illumination as a sanitization method and its specialized ISO standard, ISO 11137, will specifically be covered in this blog.

What is Sterilization?

All living microbes, including bacterial spores, are destroyed during sterilization. There are physical and chemical techniques for sterilization. A technique used to reduce microbial growth and illness transmission from one person to another. The use of disinfection methods in the environment reduces the growth of bacteria on surfaces, which reduces the spread of organisms among the populace. These methods are still widely employed in the medicinal and food industries today. 

What is ISO 11137?

A global federation of state standards organizations exists under the name ISO (the International Organization for Standardization). Technical groups under ISO are typically used to prepare International Standards. The ability to be represented on a technical committee exists for each member body interested in a topic for which one has been created. Governmental and non-governmental international organizations collaborate with ISO to complete the task. On all issues relating to electrotechnical regulation, ISO works closely with the International Electrotechnical Commission[1] (IEC).

Radiation sterilization of medical devices is governed by the worldwide standard ISO 11137. This section of ISO 11137 outlines specifications that, if fulfilled, will result in a radiation sterilization process designed to sterilize medical devices and that has the proper microbicidal activity. A low degree of probability of a viable microorganism remaining on a product after sterilization can also be predicted with reasonable certainty thanks to compliance with the requirements, which guarantees that this activity is both dependable and reproducible. Regulatory officials are responsible for defining this probability, and this determination may differ from nation to nation. Each of its three sections, which each focus on a distinct aspect of medical device radiation sterilization, is as follows:

  • ISO 11137-1: Outlines the requirements for establishing, validating, and controlling the radiation sterilization procedure. The two most frequently used gamma emitting radionuclides, cobalt 60 and cesium 137, are described along with directions for sterilization.
  • ISO 11137-2: The procedure that manufacturers will use to determine the minimal dose necessary to attain sterility is covered in the second section of the standard. Additionally, it describes how to prove a sterilizing dosage of 25 or 15 kilograms. (kGy). KiloGrays are the units used to quantify the gamma rays that are released during radionuclide decay.
  • ISO 11137-3: Standard’s section 3 instructs manufacturers on how to meet the requirements of part one, which deal with dosimetry (the measurement of gamma radiation dose) and its function in organizing, validating, and overseeing the sterilization procedure.

How Does Gamma Sterilization Medical Device Work?

Gamma irradiation is one of the most popular processes for sterilizing medical devices. Gamma rays are an example of electromagnetic energy, just like X-rays. To kill germs on previously packaged equipment, gamma rays, on the other hand, have a significantly greater energy and can penetrate materials like plastic. To start the sterilizing process, the radiation source (typically Cobalt 60, but occasionally Caesium 137) is put in a radiation-shielded chamber. Then, packaged medical equipment is carried in and moved around the radiation source to expose every surface to gamma rays.

Contrary to other sterilizing methods like ethylene oxide (EO), gamma irradiation does not necessitate particular humidity, temperature, or pressure limits. The gamma sterilization method is also ideal for heat-sensitive devices because it doesn’t increase the temperature of the items being sterilized. It should be noted that the availability of the necessary elements in the future is uncertain. The capacity of gamma irradiation facilities is constrained because the global supply of cobalt-60 is presently inadequate to keep up with the rate of decay.

What Is The Interaction For Gamma Sterilization Validation As Per ISO 11137?

The ISO 11137 gamma disinfection approval procedure is designed to ensure two key outcomes:

  • Utilizing a minimal dose of radiation, the intended Sterilization Assurance Level (SAL) is achieved. The SAL that is most frequently mentioned is 10-6, or one potentially contaminated device per million.
  • Overdosing on radiation dose is not detrimental to a product’s usefulness. Because gamma rays have the potential to break down the polymer used in many single-use medical devices that need sterilization, a maximum dose must be set and not surpassed during gamma sterilization.

The ISO 11137-2 standard outlines three procedures for calculating a radiation dose that meets both of these requirements. The first two techniques are comparable in that they both involve determining the natural bio burden – the amount of microorganisms on a product—and sterility testing to validate the correct dosage.

These procedures are designed to be used with items that need at least 100 units of the product and are produced in big batches. When it is impossible to group hundreds of devices together, the third technique, known as VDmax, is used for products produced in smaller batches. Instead of determining the lowest dose necessary to achieve SAL 10-6, this method assesses a predetermined dose: either 25 kGy or 15 kGy for objects with a lower tolerance for gamma rays. Regardless of the technique used, manufacturers must carry out quarterly dosage audits as part of ongoing process validation.


One of the many aspects that distinguishes the manufacturing of medical devices from other industries is the intricate and precise processes required for the sterilization validation process. It only makes sense to use an industry-specific platform to plan, carry out, and record all of your quality and risk management activities given the number of laws and standards, including ISO 11137, that medical device manufacturers must comprehend and adhere to.

Read Our Article: Important Aspect Of ISO Certification That Every Manufacturer Needs To Remember

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