Particle therapy is ideal for the treatment of ocular melanomas

Mishra, Kavita; Chiu‐Tsao, Sou‐Tung; Orton, Colin G.

doi:10.1118/1.4939223

Cited by 7 publications

(3 citation statements)

References 24 publications

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“…A challenge in the widespread use of proton therapy to treat ocular melanoma has been the limited number of centers with the required infrastructure. 8 Spot scanning proton beams have become more widespread than passive scattered beams in recent years. 9 Since the OPTIC survey, an Italian center has used a raster scanning proton beam with a fixed horizontal beam line to treat ocular sites using a brass aperture.…”

Section: Introductionmentioning

confidence: 99%

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Design and characterization of an aperture system and spot configuration for ocular treatments with a gantry‐based spot scanning proton beam

et al. 2023

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Background and purpose: Proton therapy is a key modality used in the treatment of ocular melanoma. Traditionally ocular sites are treated using a dedicated eyeline with a passively scattered proton beam and a brass aperture. This work aims to design and characterize a beam-collimating aperture to treat ocular targets with a gantry-based spot scanning proton beam. Methods: A plastic aperture system that slides into the gantry nozzle of a spot scanning proton beam was designed and constructed. It consists of an intermediate scraper layer to attenuate stray protons and a 3D-printed patient-specific aperture positioned 5.7 cm from the surface of the eye. The aperture system was modeled in TOPAS and Monte Carlo simulations were validated with film measurements. Two different spot configurations were investigated for treatment planning and characterized based on lateral penumbra, central axis (CAX) dose and relative efficiency. Alignment and leakage were investigated through experimental film measurements. Range was verified using a multi-layer ionization chamber. Reference dose measurements were made with a PinPoint 3D ion chamber. Neutron dose was evaluated through Monte Carlo simulations. Results: Aperture alignment with radiation isocenter was determined to be within 0.31 mm at a gantry angle of 0 • . A single-spot configuration with a 10 mm diameter aperture yielded film-measured lateral penumbras of 1 mm to 1.25 mm, depending on depth in the spread-out Bragg peak. TOPAS simulations found that a single spot configuration results in a flat dose distribution for a 10 mm diameter aperture and provides a CAX dose of less than 106% for apertures less than 14 mm in diameter. For larger targets, adding four corner spots to fill in the dose distribution is beneficial. Trade-offs between lateral penumbra, CAX dose and relative efficiency were characterized for different spot configurations and can be used for future clinical decision-making. The aperture was experimentally determined to not affect proton beam range, and no concerning leakage radiation or neutron dose was identified. Reference dose measurements with a PinPoint ion chamber were within 2.1% of Monte Carlo calculated doses. Conclusion:The aperture system developed in this work provides a method of treating ocular sites on a gantry-based spot scanning proton system. Additional work to develop compatible gaze tracking and gating infrastructure is ongoing.

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Section: Introductionmentioning

confidence: 99%

“…A challenge in the widespread use of proton therapy to treat ocular melanoma has been the limited number of centers with the required infrastructure 8 . Spot scanning proton beams have become more widespread than passive scattered beams in recent years 9 .…”

Section: Introductionmentioning

confidence: 99%

Design and characterization of an aperture system and spot configuration for ocular treatments with a gantry‐based spot scanning proton beam

et al. 2023

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“…Clinical studies at various institutions, including ours, have confirmed that charged particles treat eye tumors very effectively. High local control rates of more than 96%, along with low enucleation rates and other complication rates, have been achieved with charged particle beams at dedicated centers such as ours with proton ocular beams [9] [10] [11] [12].…”

Section: Introductionmentioning

confidence: 99%

An Overview of the Control System for Dose Delivery at the UCSF Dedicated Ocular Proton Beam

Daftari¹,

Mishra²,

Singh³

et al. 2016

IJMPCERO

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Since 1978, the University of California San Francisco (UCSF) Ocular Tumor Program has been using particle therapy for treating ocular patients with malignant as well as benign eye disease. Helium ion beams were used initially and were produced by two synchrotron-based systems: first by the 184-inch synchro-cyclotron and later by the Bevalac, at the Lawrence Berkeley National Laboratory (LBNL). Since 1994, protons, produced by a cyclotron-based system at the Crocker Nuclear Laboratory (CNL) Eye Treatment Facility (ETF), have been used for this purpose. The CNL cyclotron produces a 67.5 MeV beam, allowing for a uniquely homogeneous beam for eye treatment, without degradation of the beam or manipulation of the beam line. This paper describes, in detail, the control system for beam delivery, as implemented for measuring and delivering the radiation to ocular tumors at CNL. The control system allows for optimal delivery and rapid termination of the irradiation after the desired dose is achieved. In addition, several safeguard systems are discussed, as these are essential for such a system in the event of failure of software, electronics, or other hardware. The QA analysis shows that the total range of the proton beam is 30.7 ± 1.0 mm in water at iso-center. The beam distal penumbra (80%-20%) is 1.1 mm for a range-modulated beam at a collimator to iso-center distance of 50 mm. Daily QA checks confirm that the range and modulation is within 0.1 mm. The beam flatness and symmetry in a 25 mm diameter beam are ±1%-2%. Variation in the daily dosimetry system, as compared to standard dosimetry, is within ±3.5%, with a mean variation of 0.72(±1.9)% and 0.85(±2.3)% for segmented transmission ionization chambers IC1 (upstream) and IC2 (downstream), respectively. From May 1994 to the end of 2015, UCSF has treated 1838 proton ocular patients at the Davis ETF. During this period, no treatments were missed due to any cyclotron or control system failures.

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