Geometrical Model to improve Accuracy of the IBA Prompt Gamma Camera

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Histogram showing the observed range shift in a water measurement with and without applying the geometrical correction.
Histogram showing the observed range shift in a water measurement with and without applying the geometrical correction.

OMA Fellow Johannes Petzoldt with co-authors from OncoRay and IBA successfully published a study on a correction model that helps to improve accuracy and precision of a prompt gamma (PG) camera for range verification in proton therapy. The peer-reviewed paper is included in the special issue Diagnostics for Beam and Patient Monitoring of Instruments and is available online through open access.

While in theory with an infinite camera system, a Bragg peak shift directly translates into a shift of the PG profiles, small geometry depending variations of the profiles have been observed in measurements with the PG camera. Those variations are a result of the finite dimensions of the system and need to be corrected for in order to improve the comparison of the measurement with the fast analytical model which is used to determine the absolute range of a proton beam. In order to reduce those variations, the OMA Fellow at IBA developed a model that better resembles the geometrical response of the PG camera as some geometrical effects are not fully described in the analytical simulation. To validate the model, he performed a benchmark experiment together with researchers from OncoRay in Dresden, Germany. The developed model increases the range retrieval precision and the benchmark experiment could be used to fine-tune the analytical simulation in order to improve the absolute range accuracy of the PG camera.