Technical Note: Dosimetric characteristics of the ocular beam line and commissioning data for an ocular proton therapy planning system at the Proton Therapy Center Houston

Titt, Uwe; Suzuki, Kazumichi; Li, Yupeng; Gillin, Michael; Zhu, Xiaorong Ronald

doi:10.1002/mp.12605

Cited by 8 publications

(11 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Clinical SOBPs are generated by properly weighting beams extracted from the accelerator at discrete energy levels from 63 to 90 MeV; our finding in terms of distal fall‐off (1.0 to 1.5 mm) is consistent with values between 0.7 and 3 mm reported for most ocular dedicated beamlines . Similarly, our results of LP width and secondary neutron dose are similar to those described in the literature and appear clinically acceptable. In particular, penumbra width is compatible with the usual 2.5 mm lateral expansion of the target defined as block margin in treatment planning.…”

Section: Discussionsupporting

confidence: 89%

See 1 more Smart Citation

Design and commissioning of the non‐dedicated scanning proton beamline for ocular treatment at the synchrotron‐based CNAO facility

et al. 2019

View full text Add to dashboard Cite

Purpose: Only few centers worldwide treat intraocular tumors with proton therapy, all of them with a dedicated beamline, except in one case in the USA. The Italian National Center for Oncological Hadrontherapy (CNAO) is a synchrotron-based hadrontherapy facility equipped with fixed beamlines and pencil beam scanning modality. Recently, a general-purpose horizontal proton beamline was adapted to treat also ocular diseases. In this work, the conceptual design and main dosimetric properties of this new proton eyeline are presented. Methods: A 28 mm thick water-equivalent range shifter (RS) was placed along the proton beamline to shift the minimum beam penetration at shallower depths. FLUKA Monte Carlo (MC) simulations were performed to optimize the position of the RS and patient-specific collimator, in order to achieve sharp lateral dose gradients. Lateral dose profiles were then measured with radiochromic EBT3 films to evaluate the dose uniformity and lateral penumbra width at several depths. Different beam scanning patterns were tested. Discrete energy levels with 1 mm water-equivalent step within the whole ocular energy range (62.7-89.8 MeV) were used, while fine adjustment of beam range was achieved using thin polymethylmethacrylate additional sheets.Depth-dose distributions (DDDs) were measured with the Peakfinder system. Monoenergetic beam weights to achieve flat spread-out Bragg Peaks (SOBPs) were numerically determined. Absorbed dose to water under reference conditions was measured with an Advanced Markus chamber, following International Atomic Energy Agency (IAEA) Technical Report Series (TRS)-398 Code of Practice. Neutron dose at the contralateral eye was evaluated with passive bubble dosimeters. Results: Monte Carlo simulations and experimental results confirmed that maximizing the air gap between RS and aperture reduces the lateral dose penumbra width of the collimated beam and increases the field transversal dose homogeneity. Therefore, RS and brass collimator were placed at about 98 cm (upstream of the beam monitors) and 7 cm from the isocenter, respectively. The lateral 80%-20% penumbra at middle-SOBP ranged between 1.4 and 1.7 mm depending on field size, while 90%-10% distal fall-off of the DDDs ranged between 1.0 and 1.5 mm, as a function of range. Such values are comparable to those reported for most existing eye-dedicated facilities. Measured SOBP doses were in very good agreement with MC simulations. Mean neutron dose at the contralateral eye was 68 lSv/Gy. Beam delivery time, for 60 Gy relative biological effectiveness (RBE) prescription dose in four fractions, was around 3 min per session. Conclusions: Our adapted scanning proton beamline satisfied the requirements for intraocular tumor treatment. The first ocular treatment was delivered in August 2016 and more than 100 patients successfully completed their treatment in these 2 yr.

show abstract

Section: Discussionsupporting

confidence: 89%

“…Finally, the strategy of combining MC simulations and experimental data acquisition in supporting our beamline design and ocular treatment start‐up phase appeared highly successful, as already reported for other scenarios as well as dedicated eyelines …”

Section: Discussionsupporting

confidence: 66%

Design and commissioning of the non‐dedicated scanning proton beamline for ocular treatment at the synchrotron‐based CNAO facility

et al. 2019

View full text Add to dashboard Cite

show abstract

“…This beam line's non-FLASH performance has been characterized previously using Monte Carlo simulations and measurements. 18 The simulated dose distributions were found to be in excellent agreement with measurements.…”

Section: Accelerator and Beam Linementioning

confidence: 53%

“…The incident proton beam is nearly a Gaussian, and the maximum charge for the ocular beam line is about 10 nC per spill. This beam line's non‐FLASH performance has been characterized previously using Monte Carlo simulations and measurements 18 . The simulated dose distributions were found to be in excellent agreement with measurements.…”

Section: Methodsmentioning

confidence: 68%

Design and validation of a synchrotron proton beam line for FLASH radiotherapy preclinical research experiments

et al. 2021

Self Cite

View full text Add to dashboard Cite

The main purpose of this work was to generate and validate the dosimetric accuracy of proton beams of dimensions that are appropriate for in vivo small animal and in vitro ultrahigh dose rate (FLASH) radiotherapy experiments using a synchrotron-based treatment delivery system.This study was performed to enable future investigations of the relevance of a spread-out Bragg peak (SOBP) under FLASH conditions. Methods: The spill characteristics of the small field fixed horizontal beam line were modified to deliver accelerated protons in times as short as 2 ms and to control the dose delivered. A Gaussian-like transverse beam profile was transformed into a square uniform one at FLASH dose rates, while avoiding low-dose regions, a crucial requirement to protect normal tissue during FLASH irradiation. Novel beam-shaping devices were designed using Monte Carlo techniques to produce up to about 6 cm 3 of uniform dose in SOBPs while maximizing the dose rate. These included a scattering foil, a conical flattening filter to maximize the flux of protons into the region of interest, energy filters, range compensators, and collimators.The shapes,sizes,and positions of the components were varied to provide the required field sizes and SOBPs. Results: The designed and fabricated devices were used to produce 10-, 15-, and 20-mm diameter, circular field sizes and 10-, 15-, and 20-mm SOBP modulation widths at uniform physical dose rates of up to 375 Gy/s at the center of the SOBP and a minimum dose rate of about 255 Gy/s at the entrance, respectively, in cylindrical volumes. The flatness of lateral dose profiles at the center could be adjusted to within ±1.5% at the center of the SOBP. Assessment of systematic uncertainties, such as impact of misalignments and positioning uncertainties, was performed using simulations, and the results were used to provide appropriate adjustments to ensure high-accuracy FLASH beam delivery for both in vitro and in vivo preclinical experiments. Conclusions: It is feasible to use synchrotron-generated proton beams of sufficient dimensions for FLASH radiobiology experiments. We expect to use the system we developed to acquire in vitro and in vivo small animal FLASH radiobiology data as a function of dose, dose rate, oxygen content, and linear energy transfer to help us understand the underlying mechanisms of the FLASH phenomenon.

show abstract

“…Pencil beam scanning is the most advanced proton beam therapy techniques. The underlying physics of the pencil beam scanning nozzle is relatively simple and straightforward, but a wide variety of different scanning nozzles are available in proton therapy centers worldwide [1][2][3][4]. Daily quality-assurance (QA) assessment of the proton beam nozzle is an important part of proton beam therapy, especially for pencil beam scanning nozzles, as the sharp dose distribution is sensitive to a small error [5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Development of an Assemblable, Daily, Quality-Assurance Device for Line-Scanning Proton Therapy

Chung

Park

Ahn

et al. 2019

J. Korean Phys. Soc.

View full text Add to dashboard Cite

Proton beam therapy requires a reliable and efficient method of daily quality assurance. Various daily quality-assurance systems were developed for a simple and efficient quality assurance of spot-scanning proton therapy nozzles. To promote the same effectiveness in daily quality assurance of line-scanning proton therapy nozzles, we developed an assemblable, all-in-one, daily, quality-assurance system for line-scanning proton therapy nozzles. The system uses a high-density polyethylene device mounted on a two-dimensional ionization chamber array detector. The device is modularized for routine daily quality-assurance activities (output measurements, range verifications, and scan pattern measurements). A proton beam delivery plan was created for daily quality assurance based on the CT-scanned image of the device. Each step of the daily quality-assurance procedure was tested with the developed system. Using the developed system, proton beam range verifications and gamma analysis of the scan pattern test were combined into a measurement with a single beam delivery. The developed system will improve the efficiency of daily quality assurance for line-scanning nozzles while using an assemblable design to add flexibility.

show abstract

Technical Note: Dosimetric characteristics of the ocular beam line and commissioning data for an ocular proton therapy planning system at the Proton Therapy Center Houston

Abstract: We have completed a comprehensive characterization of the beam line. The data will be useful to characterize proton beams in clinical and experimental small-field applications.

Cited by 8 publications

References 15 publications

Design and commissioning of the non‐dedicated scanning proton beamline for ocular treatment at the synchrotron‐based CNAO facility

Design and commissioning of the non‐dedicated scanning proton beamline for ocular treatment at the synchrotron‐based CNAO facility

Design and validation of a synchrotron proton beam line for FLASH radiotherapy preclinical research experiments

Development of an Assemblable, Daily, Quality-Assurance Device for Line-Scanning Proton Therapy

Contact Info

Product

Resources

About