Nowadays, the radiation processing community is witnessing a growing use of Monte Carlo simulations, namely when it comes to the Performance Qualification (PQ) dose mapping inside of a specific product. Such simulations can be very time consuming in terms of calculation duration. However, in order to speed up simulation tools, Kerma water is often calculated and dose to water derived. This presentation compares measured and simulated dose to water for a 7 MV X-ray irradiation of a reference product of 0.1 g/cm³ density.

Simulations were performed with RayXpert^® software (TRAD, France) implementing the X-ray field modelled with its energy-angle spectrum. Irradiations were performed at the feerix^® irradiation platform (Aerial, France) using alanine physical dosimeters positioned in relevant locations of the reference product for comparison purposes.

Results show in general a good agreement between measured and calculated absorbed dose to water. A significant discrepancy was found as expected in the first layer of about 1 g/cm² thickness at the surface of the product. Elsewhere inside the reference product calculation and physical measurements match within 2%.

This means that the “Kerma water” quantity used in RayXpert^® can calculate an accurate delivered dose to a reference product in the present irradiation conditions. If this result can be confirmed in other irradiation cases, one can imagine several implications to the irradiation process control for the future. One can cite: anticipation of process parameters, reduction of number of physical dosimeters, limited work for PQ dose mapping, calibration of dosimetry systems with virtual reference dosimetry. These improvements can however exist only if relevant online process output verification tools are in place.