Dosimetry in X-ray sterilization is of paramount importance to guarantee an appropriate safety level of the product being qualified and then processed. However, dosimetry is a manual or semi-manual task requiring significant budget and manpower. It is also subject to intrinsic uncertainties, such as the alanine mass, the EPR accuracy and reproducibility, and the positioning accuracy, limiting the overall efficiency and reproducibility [1].

This paper describes a real-time detector that could help improving current practices. The study consists in a proof-of-concept system for enhanced measurement of the beam flux delivered to the product using real-time sensor monitoring. It includes both a theoretical approach and an experimental validation.

The prototype was tested at Aerial under a 7 MV X-ray beam. After successful characterization, the detector was tested by processing dummy pallets mimicking the irradiation process of products. The detector demonstrated the ability to measure the beam flux and to record a signature of the product being treated. With its excellent accuracy and reproducibility, the detector was able to easily detect fluctuations of the signal on the order of 1% and density fluctuations on the order of 5%. The preliminary tests also confirmed the ability of such detector to detect deviation in photon flux, scan amplitude and conveyor speed and even to detect misloading of a product.

A roadmap to include the detector signals in a broader parametric release and Process Control Systems roadmap will be presented and discussed.

Reference:

[1] Josef Mittendorfer and Bernhard Gallnböck-Wagner, “Process control in electron beam sterilization of medical devices and a pathway to parametric release”, Radiation Physics and Chemistry, 173 (2020) 108870