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. 2021 Sep 16;13(18):4657.
doi: 10.3390/cancers13184657.

Conceptual Design of a Novel Nozzle Combined with a Clinical Proton Linac for Magnetically Focussed Minibeams

Tim Schneider  1 , Annalisa Patriarca  2 , Alberto Degiovanni  3 , Manuel Gallas  3 , Yolanda Prezado  1
Affiliations

Conceptual Design of a Novel Nozzle Combined with a Clinical Proton Linac for Magnetically Focussed Minibeams

Tim Schneider et al. Cancers (Basel). .

Abstract

(1) Background: Proton minibeam radiation therapy (pMBRT) is a novel therapeutic approach with the potential to significantly increase normal tissue sparing while providing tumour control equivalent or superior to standard proton therapy. For reasons of efficiency, flexibility and minibeam quality, the optimal implementation of pMBRT should use magnetically focussed minibeams which, however, could not yet be generated in a clinical environment. In this study, we evaluated our recently proposed minibeam nozzle together with a new clinical proton linac as a potential implementation. (2) Methods: Monte Carlo simulations were performed to determine under which conditions minibeams can be generated and to evaluate the robustness against focussing magnet errors. Moreover, an example of conventional pencil beam scanning irradiation was simulated. (3) Results: Excellent minibeam sizes between 0.6 and 0.9 mm full width at half maximum could be obtained and a good tolerance to errors was observed. Furthermore, the delivery of a 10 cm × 10 cm field with pencil beams was demonstrated. (4) Conclusion: The combination of the new proton linac and minibeam nozzle could represent an optimal implementation of pMBRT by allowing the generation of magnetically focussed minibeams with clinically relevant parameters. It could furthermore be used for conventional pencil beam scanning.

Keywords: Monte Carlo; clinical minibeams; linac; magnetic focussing; minibeam radiation therapy; pMBRT; protons.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
Schematic of the new nozzle design with dimensions in cm. Abbreviations: VBS - virtual beam source, Q—quadrupole, SM—scanning (dipole) magnet, IC—ionisation chamber.
Figure 2
Figure 2
Comparison of minimum beam sizes: (a) For 100 and 200 MeV beams and the three different air gaps using the base beam model. (b) For 100 and 200 MeV beams and the four different beam model variations. The air gap was 10 cm in all cases.
Figure 3
Figure 3
Lateral and longitudinal dose maps/profiles for an example pencil beam pattern at 100 MeV (top) and 200 MeV (bottom) assuming a 50 cm air gap. The vertical dotted line in the top left panel indicates the position in the Bragg peak where the lateral dose map was sampled.
See this image and copyright information in PMC

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