Abstract

The treatment protocols of cancerous ocular diseases with proton therapy are well established, and dedicated eye-treatment systems can produce the clinical beam properties that meet the peculiar features required by eye-treatment modalities. However, for general-purpose multiroom systems comprising eye-treatment beamlines and nozzles, the design and commissioning procedures must be optimized to achieve the performances of fully dedicated systems in terms of depth-dose distal falloff, lateral penumbra, and dose rate. This paper presents a realistic start-to-end beam transport and particle-matter interactions model of the ion beam applications Proteus\textregistered{} Plus $(\mathrm{P}+)$ single-scattering eye-treatment room with Beam Delivery SIMulation (bdsim) using Geant4. The model is used to establish optimization patterns in terms of beam optics to achieve a smaller depth-dose distal falloff than the design baseline while maintaining a nominal dose rate and lateral flatness of the dose deposition profile. An alternative design is proposed to increase the dose rate further by up to a factor 3, allowing for delivering a complete hypofractionated treatment session under 60 s. It uses a beam-stopping device to complement the existing scattering features of the nozzle. An in-depth study of the system is performed using bdsim and the numerical simulations are discussed in detail.

Highlights

  • Proton therapy is a well-established method for the treatment of ocular melanomas [1]

  • This paper presents a numerical approach to tackle the step-by-step optimization of such passive scattering systems in the specific context of ocular tumors treatment

  • The features of its main components were discussed to highlight the close links between several machine parameters, the physical properties of the delivered beam, and the resulting clinical performances

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Summary

Introduction

Proton therapy is a well-established method for the treatment of ocular melanomas [1]. Ocular melanomas are the most common type of primary intraocular cancers. When located in the uveal tract, this malignant tumor is called an uveal melanoma and can arise in the iris, in the ciliary body, or within the choroid. All of these three melanoma types have the potential to metastasize to other parts of the body, most often to the liver. Ocular cancer treatment with proton beams started in 1972. It makes use of the sharp dose deposition profiles of protons to deliver a high-dose treatment field while sparing healthy tissues and nearby organs

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