Challenges for the Implementation of Primary Standard Dosimetry in Proton Minibeam Radiation Therapy

John Cotterill; Samuel Flynn; Russell Thomas; Anna Subiel; Nigel Lee; Michael Homer; Hugo Palmans; Ludovic De Marzi; Yolanda Prezado; David Shipley; Ana Lourenço

doi:10.3390/cancers16234013

Challenges for the Implementation of Primary Standard Dosimetry in Proton Minibeam Radiation Therapy

Cancers (Basel). 2024 Nov 29;16(23):4013. doi: 10.3390/cancers16234013.

Authors

John Cotterill¹, Samuel Flynn^{1

2}, Russell Thomas^{1

3}, Anna Subiel^{1

4}, Nigel Lee¹, Michael Homer¹, Hugo Palmans^{1

5}, Ludovic De Marzi^{6

7}, Yolanda Prezado^{8

9

10

11}, David Shipley¹, Ana Lourenço^{1

4}

Affiliations

¹ Radiotherapy and Radiation Dosimetry, National Physical Laboratory, Teddington TW11 0LW, UK.
² Particle Physics Group, School of Physics and Astronomy, University of Birmingham, Edgbaston B15 2TT, UK.
³ Faculty of Engineering and Physical Sciences, University of Surrey, Guildford GU2 7XH, UK.
⁴ Department of Medical Physics and Biomedical Engineering, University College London, London WC1E 6BT, UK.
⁵ Medical Physics Group, MedAustron Ion Therapy Center, A-2700 Wiener Neustadt, Austria.
⁶ Laboratoire d'Imagerie Translationnelle en Oncologie (LITO), Institut Curie, Université Paris-Saclay, Inserm U1288, 91898 Orsay, France.
⁷ Radiation Oncology Department, Institut Curie, PSL Research University, 75005 Paris, France.
⁸ New Approaches in Radiotherapy Lab, Center for Research in Molecular Medicine and Chronic Diseases (CIMUS), Instituto de Investigación Sanitaria de Santiago de Compostela (IDIS), University of Santiago de Compostela, 15706 Santiago de Compostela, A Coruña, Spain.
⁹ Oportunius Program, Galician Agency of Innovation (GAIN), Xunta de Galicia, 15702 Santiago de Compostela, A Coruña, Spain.
¹⁰ Institut Curie, Université PSL, CNRS UMR3347, Inserm U1021, Signalisation Radiobiologie et Cancer, 91400 Orsay, France.
¹¹ Université Paris-Saclay, CNRS UMR3347, Inserm U1021, Signalisation Radiobiologie et Cancer, 91400 Orsay, France.

Abstract

Background/Objectives: Spatial fractionation of proton fields as sub-millimeter beamlets to treat cancer has shown better sparing of healthy tissue whilst maintaining the same tumor control. It is critical to ensure primary standard dosimetry is accurate and ready to support the modality's clinical implementation. Methods: This work provided a proof-of-concept, using the National Physical Laboratory's Primary Standard Proton Calorimeter (PSPC) to measure average absorbed dose-to-water in a pMBRT field. A 100 MeV mono-energetic field and a 2 cm wide SOBP were produced with a spot-scanned proton beam incident on a collimator comprising 15 slits of 400 µm width, each 5 cm long and separated by a center-to-center distance of 4 mm. Results: The results showed the uncertainty on the absorbed dose-to-water in the mono-energetic beam was dominated by contributions of 1.4% and 1.1% (k = 1) for the NPL PSPC and PTW Roos chambers, respectively, originating from the achievable positioning accuracy of the devices. In comparison, the uncertainty due to positioning in the SOBP for both the NPL PSPC and PTW Roos chambers were 0.4%. Conclusions: These results highlight that it may be more accurate and reliable to perform reference dosimetry measuring the Dose-Area Product or in an SOBP for spatially fractionated fields.

Keywords: SFRT; calorimetry; dosimetry; minibeams; pMBRT; proton.

Grants and funding

This research was partially funded by the UK Government’s Department for Science, Innovation, and Technology, a key contributor to the UK National Measurement System. Project 18HLT04 UHDpulse received funding from the EMPIR programme, co-financed by the Participating States and the European Union’s Horizon 2020 research and innovation programme. Additionally, this project received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant Agreement No. 817908) for Y. Prezado. This work has been carried out using the INSPIRE Research Infrastructures and is part of a project that has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 730983. Some simulations for this work were carried out using the access to the HPC resources of TGCC under allocation 2021-A0100312447 made by GENCI.