Fundamental radiological and geometric performance of two types of proton beam modulated discrete scanning systems

Farr, J; Dessy, F.; Wilde, Olivier De; Bietzer, O; Schönenberg, D.

doi:10.1118/1.4807643

Cited by 34 publications

(44 citation statements)

References 9 publications

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“…In contrast to the parallel scanning PBS system at PSI,4 the IBA PBS systems have small incident angles according to spot scanning location. The initial scanning angle and projected offset coordinate at the source plane (see Fig.…”

Section: Methodsmentioning

confidence: 99%

“…The design of the dedicated PBS nozzle (IBA Particle Therapy, Louvain‐la‐Neuve, Belgium; model: Dedicated Pencil Beam Nozzle) used in this study has been described by Farr4 and Lin 23. A schematic view of the nozzle system is presented in Fig.…”

Section: Methodsmentioning

confidence: 99%

“…Rather than a detailed single‐spot profile validation of the halo,7, 12, 30, 31, 32 field size factors (FSF) for square fields with 4 mm spacing and 1 MU per spot of monoenergetic proton beams, described by Pedroni et al,4 Sawakuchi et al,33 Zhu et al,34 and Shen et al,35 were used to investigate the accuracy of the halo both with and without the range shifter. A water phantom (Digiphant,IBA Dosimetry, Schwarzenbruck, Germany), which combines a two‐dimensional ionization chamber array (MatriXX PT ® , IBA Dosimetry, Schwarzenbruck, Germany) dedicated to address the high‐dose rates in PBS, in a waterproof housing that can be scanned in a water phantom, was used to measure the two‐dimensional (2D) dose distributions in selected depth perpendicular to the beam incident direction 36.…”

Section: Methodsmentioning

confidence: 99%

“…Various technical constraints in the current delivery systems result in a minimum proton energy limitation of between 70 and 100 MeV,4 thus a range shifter is needed to degrade the proton range in order to treat tumors located shallower than the minimum range 5. It is well known that the energy spread (due to energy straggling) and spot size (due to MCS) increase at the exit of a range shifter 6.…”

Section: Introductionmentioning

confidence: 99%

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Validation and clinical implementation of an accurate Monte Carlo code for pencil beam scanning proton therapy

Huang

Kang

Souris

et al. 2018

J Applied Clin Med Phys

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Monte Carlo (MC)‐based dose calculations are generally superior to analytical dose calculations (ADC) in modeling the dose distribution for proton pencil beam scanning (PBS) treatments. The purpose of this paper is to present a methodology for commissioning and validating an accurate MC code for PBS utilizing a parameterized source model, including an implementation of a range shifter, that can independently check the ADC in commercial treatment planning system (TPS) and fast Monte Carlo dose calculation in opensource platform (MCsquare). The source model parameters (including beam size, angular divergence and energy spread) and protons per MU were extracted and tuned at the nozzle exit by comparing Tool for Particle Simulation (TOPAS) simulations with a series of commissioning measurements using scintillation screen/CCD camera detector and ionization chambers. The range shifter was simulated as an independent object with geometric and material information. The MC calculation platform was validated through comprehensive measurements of single spots, field size factors (FSF) and three‐dimensional dose distributions of spread‐out Bragg peaks (SOBPs), both without and with the range shifter. Differences in field size factors and absolute output at various depths of SOBPs between measurement and simulation were within 2.2%, with and without a range shifter, indicating an accurate source model. TOPAS was also validated against anthropomorphic lung phantom measurements. Comparison of dose distributions and DVHs for representative liver and lung cases between independent MC and analytical dose calculations from a commercial TPS further highlights the limitations of the ADC in situations of highly heterogeneous geometries. The fast MC platform has been implemented within our clinical practice to provide additional independent dose validation/QA of the commercial ADC for patient plans. Using the independent MC, we can more efficiently commission ADC by reducing the amount of measured data required for low dose “halo” modeling, especially when a range shifter is employed.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Validation and clinical implementation of an accurate Monte Carlo code for pencil beam scanning proton therapy

Huang

Kang

Souris

et al. 2018

J Applied Clin Med Phys

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“…For example, the Hitachi and IBA systems provide minimum proton energies of 70 MeV. 3,4 In order to apply the pencil beam scanning technique to tumors located proximal to the minimum range, a range shifter is needed to degrade the beam energy. 3,5,6 A range shifter is a uniform slab of material, usually plastic.…”

Section: Introductionmentioning

confidence: 99%

Impact of range shifter material on proton pencil beam spot characteristics

et al. 2015

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Purpose: To quantitatively investigate the effect of range shifter materials on single-spot characteristics of a proton pencil beam. Methods: An analytic approximation for multiple Coulomb scattering ("differential Moliere" formula) was adopted to calculate spot sizes of proton spot scanning beams impinging on a range shifter. The calculations cover a range of delivery parameters: six range shifter materials (acrylonitrile butadiene styrene, Lexan, Lucite, polyethylene, polystyrene, and wax) and water as reference material, proton beam energies ranging from 75 to 200 MeV, range shifter thicknesses of 4.5 and 7.0 g/cm 2 , and range shifter positions from 5 to 50 cm. The analytic method was validated by comparing calculation results with the measurements reported in the literature. Results: Relative to a water-equivalent reference, the spot size distal to a wax or polyethylene range shifter is 15% smaller, while the spot size distal to a range shifter made of Lexan or Lucite is about 6% smaller. The relative spot size variations are nearly independent of beam energy and range shifter thickness and decrease with smaller air gaps. Conclusions: Among the six material investigated, wax and polyethylene are desirable range shifter materials when the spot size is kept small. Lexan and Lucite are the desirable range shifter materials when the scattering power is kept similar to water. C 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.

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A benchmarking method to evaluate the accuracy of a commercial proton monte carlo pencil beam scanning treatment planning system

Lin

Huang

Kang

et al. 2017

J Applied Clin Med Phys

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AcurosPT is a Monte Carlo algorithm in the Eclipse 13.7 treatment planning system, which is designed to provide rapid and accurate dose calculations for proton therapy. Computational run‐time in minimized by simplifying or eliminating less significant physics processes. In this article, the accuracy of AcurosPT was benchmarked against both measurement and an independent MC calculation, TOPAS. Such a method can be applied to any new MC calculation for the detection of potential inaccuracies. To validate multiple Coulomb scattering (MCS) which affects primary beam broadening, single spot profiles in a Solidwater® phantom were compared for beams of five selected proton energies between AcurosPT, measurement and TOPAS. The spot Gaussian sigma in AcurosPT was found to increase faster with depth than both measurement and TOPAS, suggesting that the MCS algorithm in AcurosPT overestimates the scattering effect. To validate AcurosPT modeling of the halo component beyond primary beam broadening, field size factors (FSF) were compared for multi‐spot profiles measured in a water phantom. The FSF for small field sizes were found to disagree with measurement, with the disagreement increasing with depth. Conversely, TOPAS simulations of the same FSF consistently agreed with measurement to within 1.5%. The disagreement in absolute dose between AcurosPT and measurement was smaller than 2% at the mid‐range depth of multi‐energy beams. While AcurosPT calculates acceptable dose distributions for typical clinical beams, users are cautioned of potentially larger errors at distal depths due to overestimated MCS and halo implementation.

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Fundamental radiological and geometric performance of two types of proton beam modulated discrete scanning systems

Cited by 34 publications

References 9 publications

Validation and clinical implementation of an accurate Monte Carlo code for pencil beam scanning proton therapy

Validation and clinical implementation of an accurate Monte Carlo code for pencil beam scanning proton therapy

Impact of range shifter material on proton pencil beam spot characteristics

A benchmarking method to evaluate the accuracy of a commercial proton monte carlo pencil beam scanning treatment planning system

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