Which Radiation Validation Method Should I Use?

What is Gamma Sterilization?

This method utilizes a Cobalt-60 radio isotope to provide ionizing radiation that is used to sterilize a product.  The radiation alters the genetic material of microorganisms killing them and preventing further reproduction.  The high product penetration of gamma radiation makes gamma sterilization particularly effective for dense products.

What is E-Beam Sterilization?

This sterilization method utilizes high energy electrons generated by linear electron accelerators to create free radicals that alter and destroy microorganism genetic material killing and preventing further reproduction.  E-Beam sterilization is very gentle on product material and packaging when compared to gamma sterilization and is compatible with most materials. Although, E-Beam product penetration is highly dependent on electron energy and has reduced penetration for dense products.

The Sterilization Validation Process

C.G. Laboratories provides the necessary guidance to help you choose the proper sterilization dose and testing methods to meet your needs.  Trained microbiologists and scientists handle products from start to finish to ensure accurate and efficient testing.  Following validation of the sterilization dose, additional testing of the product (every quarter) is required to remain compliant and demonstrate continued sterility, this is known as a Quarterly Dose Audit (QDA).  C.G. Laboratories provides QDA testing services to ensure you remain compliant throughout your product’s life cycle.

Method One:  This validation method allows for a fully customizable sterilization dose for your product.  However, this method requires a large amount of product and tends to make this a more expensive method due to loss of product and additional testing. This method tends to be used for products with very low or very high bioburden.

The VDmax Method requires roughly half the number of product sample and testing compared to Method One.  There is a common misconception that there are only 2 VDmax options (VDmax15 and VDmax25), however this is incorrect.  There are customizable VDmax methods available to C.G. Laboratories customers that are extrapolated from ISO testing standards and are far more economically viable compared to Method One (see “Table 3” from ISO/TS 13004:2012(E) below).  C.G. Laboratory Scientists can assist you in choosing which VDmax option is best for your validation needs.

Tests Performed VDmax Method One
Bioburden 30 30
Bioburden Recovery 3 3
Bacteriostasis/Fungistasis 6 6
Sterility Testing 10 100
Total # of Product Samples 49 139
Table 3 – Upper limit of average bioburden for selection of a given sterilization dose
Upper limit for average bioburden
(SIP equal to 1,0)
Selected sterilization dose
9,0 17,5
45 20
220 22,5
5000 27,5
23000 30
100000 32,5
440000 35