The treatment by gamma rays allows to modify the physical, chemical and / or biological properties of the irradiated materials, even in their final packaging, thanks to the great penetration capacity of the photons.
It is compatible with numerous materials, does not produce waste from the process and does not induce radioactivity.
Gamma rays are a form of electromagnetic radiation, with extremely high energy because it has a very short wavelength (100 x 10-12 m); that is why it has the capacity to cause changes in the atoms of the matter with which it interacts (ionizing radiation).
The process by which a material is deliberately exposed to the action of a radiation source in a controlled manner is known as irradiation.
Industrial irradiators that use a power source or radionuclide, mainly Cobalt-60, incorporate the technology of ionizing radiation in order to take advantage of the energy emitted by photons to controlly modify the physical, chemical and / or biological properties of the irradiated materials.
The unit of measurement of the irradiation process is defined as the energy absorbed by matter per unit mass (J / kg) and is Gray, usually expressed in kGy. Formerly the rad (absorbed dose rate) unit of measure was used.
The product to be irradiated accesses the irradiation cell through the input labyrinth, moves around the sources through an automatic transport system integrating doses along the route, and leaves, once the treatment is done, through the labyrinth of exit.
The transport route is chosen in such a way that the photons penetrate the product on both sides, with the received radiation (the absorbed dose) being as uniform as possible.
A large part of the industrial irradiators are used as sterilization facilities. The main advantages are the following:
High penetrability / Final sterilization
Due to the high penetrating power of the gamma photons emitted by the Cobalt-60 (1.17 and 1.33 MeV), products packed in hermetic containers are irradiated in their final packaging.
Process in "cold"
Slight increase in the temperature of the product during the process.
Safe and clean
Does not leave residues in the product (energy of the photons emitted is less than 10 MeV)
Monitoring and control of a single variable
The only variable parameter to control is time. The dose absorbed (Gy - Gray) by the product to be irradiated is a function of the time of exposure to radioactive sources.
By using dosimeters (film or PMMA) the dose received by the product is guaranteed and allows its parametric release
Does not require quarantine
The treated product can be used immediately (dosimetric release and absence of residues)
The effect of gamma radiation on microorganisms is well known and quantified.
Highly accurate and reproducible process.
One of the most developed applications is the use of this technology for the sterilization process.
Gamma irradiation is a physical means of decontamination - sterilization, since it kills bacteria by breaking down bacterial DNA, which inhibits bacterial division. Gamma rays, emitted from Cobalt-60, are pure energy, similar in many ways to microwaves and X-rays. Gamma rays administered during radiation sterilization destroy chemical bonds by interacting with the electrons of the atomic components. Although gamma rays are highly effective at killing microorganisms, they do not create waste, nor do they have enough energy to induce radioactivity.
For sterility purposes, the microbiological population of the raw materials and / or components must be taken into account, the microbial barrier properties of the containers, and the control of the environment in which it is manufactured, assembled, packed and / or stored. product.
The ultimate responsibility for ensuring that all sterilization operations and product quality control checks are appropriate, appropriate and correctly carried out rests with the manufacturer. However, the irradiator is responsible for supplying the required dose to the product according to validated process specifications.
Validation of the sterilization process is carried out according to the following regulations:
UNE EN-ISO-11137 "Sterilization of products for healthcare"
Standards of Proper Manufacture of Medicines for Human and Veterinary Use and Application Annexes.
AAMI TIR29 "Guide for process characterization and control in radiation sterilization of medical devices"
AAMI / ISO TIR13004 Sterilization of health care products - Radiation - Substantiation of a selected sterilization dose: Method VDmaxSD
The Validation of a product (PQ-CCF) is composed mainly of the stages:
- Study of the compatibility of materials with gamma radiation
- Determination of the dose of verification and establishment of the sterilization dose according to the bioburden of the product (bioburden) and chosen method (See table).
- Establishment of the maximum acceptable dose
- Dose map: Study of the dose distribution in the product to determine the location and magnitude of the minimum and maximum absorbed dose as well as the determination of the relationships between the doses and the routine verification position to establish the limits of control.
- Determination of the loading model of the product in the irradiation containers
- Issuance and final approval of the product treatment specification.
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