Advancing proton minibeam radiation therapy: magnetically focussed proton minibeams at a clinical centre

Tim Schneider,Ludovic De Marzi,Annalisa Patriarca,Yolanda Prezado

doi:10.1038/s41598-020-58052-0

Abstract

Proton minibeam radiation therapy (pMBRT) is a novel therapeutic strategy that has proven to significantly increase dose tolerances and sparing of normal tissue. It uses very narrow proton beams (diameter ≤1 mm), roughly one order of magnitude smaller than state-of-the-art pencil beams. The current implementation of pMBRT with mechanical collimators is suboptimal as it is inflexible, decreases efficiency and produces additional secondary neutrons. As a potential solution, we explore in this article minibeam generation through magnetic focussing and investigate possibilities for the integration of such a technique at existing clinical centres. For this, a model of the pencil beam scanning (PBS) nozzle and beam at the Orsay Proton Therapy Centre was established and Monte Carlo simulations were performed to determine its focussing capabilities. Moreover, various modifications of the nozzle geometry were considered. It was found that the PBS nozzle in its current state is not suitable for magnetic minibeam generation. Instead, a new, optimised nozzle design has been proposed and conditions necessary for minibeam generation were benchmarked. In addition, dose simulations in a water phantom were performed which showed improved dose distributions compared to those obtained with mechanical collimators.

Highlights

Proton minibeam radiation therapy is a novel therapeutic strategy that has proven to significantly increase dose tolerances and sparing of normal tissue
PMBRT was implemented at the Orsay Proton Therapy Centre (ICPO) using a multislit collimator attached at the end of the nozzle
We considered the generation of purely magnetically focussed minibeams and investigated how such a method could be integrated at existing clinical centres

Summary

Introduction

Proton minibeam radiation therapy (pMBRT) is a novel therapeutic strategy that has proven to significantly increase dose tolerances and sparing of normal tissue It uses very narrow proton beams (diameter ≤1 mm), roughly one order of magnitude smaller than state-of-the-art pencil beams. PMBRT was implemented at the Orsay Proton Therapy Centre (ICPO) using a multislit collimator attached at the end of the nozzle This method has been tested both in passive scattering[8,9] and pencil beam scanning mode[10]. While other groups have recently explored the use of narrow proton beams (diameter ≥3 mm) to improve conventional PBS treatment[11] and proton beam radiosurgery[12], this work is the first one to evaluate magnetically focussed proton minibeams for pMBRT at a clinical centre

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Results

Conclusion