A novel proton counting detector and method for the validation of tissue and implant material maps for Monte Carlo dose calculation

Chang, Chung‐Cheng; Harms, Joseph; Oancea, Cristina; Yoon, S. Tim; Yang, Xiaofeng; Zhang, Tiezhi; Zhou, Jun; Lin, Liyong

doi:10.1088/1361-6560/abd22e

Cited by 17 publications

(8 citation statements)

References 43 publications

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“…We independently verified the dose measurement using EBT-XD radiochromic film for one of the fields. Verification measurements of the irradiation time were also performed for 1 field using a fast, pixelated spectral detector AdvaPIX-TPX3 (TPX3) [ 25 ] placed well beyond the primary beam. DR dependence on beam current measurements was performed using a 35 × 35-mm 2 field size, with square spot arrangement and a 6-mm spot spacing to deliver 17.5 Gy at a 10-cm depth.…”

Section: Methodsmentioning

confidence: 99%

Characterization of 250 MeV Protons from the Varian ProBeam PBS System for FLASH Radiation Therapy

Zhou

Chang

Zhu

et al. 2023

International Journal of Particle Therapy

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Shoot-through proton FLASH radiation therapy has been proposed where the highest energy is extracted from a cyclotron to maximize the dose rate (DR). Although our proton pencil beam scanning system can deliver 250 MeV (the highest energy), this energy is not used clinically, and as such, 250 MeV has yet to be characterized during clinical commissioning. We aim to characterize the 250-MeV proton beam from the Varian ProBeam system for FLASH and assess the usability of the clinical monitoring ionization chamber (MIC) for FLASH use. We measured the following data for beam commissioning: integral depth dose curve, spot sigma, and absolute dose. To evaluate the MIC, we measured output as a function of beam current. To characterize a 250 MeV FLASH beam, we measured (1) the central axis DR as a function of current and spot spacing and arrangement, (2) for a fixed spot spacing, the maximum field size that achieves FLASH DR (ie, > 40 Gy/s), and (3) DR reproducibility. All FLASH DR measurements were performed using an ion chamber for the absolute dose, and irradiation times were obtained from log files. We verified dose measurements using EBT-XD films and irradiation times using a fast, pixelated spectral detector. R90 and R80 from integral depth dose were 37.58 and 37.69 cm, and spot sigma at the isocenter were σx = 3.336 and σy = 3.332 mm, respectively. The absolute dose output was measured as 0.343 Gy*mm2/MU for the commissioning conditions. Output was stable for beam currents up to 15 nA and gradually increased to 12-fold for 115 nA. Dose and DR depended on beam current, spot spacing, and arrangement and could be reproduced with 6.4% and 4.2% variations, respectively. Although FLASH was achieved and the largest field size that delivers FLASH DR was determined as 35 × 35 mm2, the current MIC has DR dependence, and users should measure dose and DR independently each time for their FLASH applications.

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Section: Methodsmentioning

confidence: 99%

Characterization of 250 MeV Protons from the Varian ProBeam PBS System for FLASH Radiation Therapy

Zhou

Chang

Zhu

et al. 2023

International Journal of Particle Therapy

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“…However, current DECT techniques cannot provide the mass density and material composition that is needed for MC. Furthermore, a pixilated proton counting detector has been introduced to validate derived material information for anthropomorphic phantoms [ 35 ]. DECT and TPS vendors are encouraged to provide a solution to extract and implement material information for human and artificial tissues so that MC can be properly used in clinics.…”

Section: Discussionmentioning

confidence: 99%

NRG Oncology Survey of Monte Carlo Dose Calculation Use in US Proton Therapy Centers

Lin

Taylor

Shen

et al. 2021

International Journal of Particle Therapy

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Purpose/Objective(s) Monte Carlo (MC) dose calculation has appeared in primary commercial treatment-planning systems and various in-house platforms. Dual-energy computed tomography (DECT) and metal artifact reduction (MAR) techniques complement MC capabilities. However, no publications have yet reported how proton therapy centers implement these new technologies, and a national survey is required to determine the feasibility of including MC and companion techniques in cooperative group clinical trials. Materials/Methods A 9-question survey was designed to query key clinical parameters: scope of MC utilization, validation methods for heterogeneities, clinical site-specific imaging guidance, proton range uncertainties, and how implants are handled. A national survey was distributed to all 29 operational US proton therapy centers on 13 May 2019. Results We received responses from 25 centers (86% participation). Commercial MC was most commonly used for primary plan optimization (16 centers) or primary dose evaluation (18 centers), while in-house MC was used more frequently for secondary dose evaluation (7 centers). Based on the survey, MC was used infrequently for gastrointestinal, genitourinary, gynecology and extremity compared with other more heterogeneous disease sites (P < .007). Although many centers had published DECT research, only 3/25 centers had implemented DECT clinically, either in the treatment-planning system or to override implant materials. Most centers (64%) treated patients with metal implants on a case-by-case basis, with a variety of methods reported. Twenty-four centers (96%) used MAR images and overrode the surrounding tissue artifacts; however, there was no consensus on how to determine metal dimension, materials density, or stopping powers. Conclusion The use of MC for primary dose calculation and optimization was prevalent and, therefore, likely feasible for clinical trials. There was consensus to use MAR and override tissues surrounding metals but no consensus about how to use DECT and MAR for human tissues and implants. Development and standardization of these advanced technologies are strongly encouraged for vendors and clinical physicists.

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“…Another approach to measure the MCS angles would be the use of the AdvaPIX-TPX3 semiconductor sensor from the work of Granja et al and Charyyev et al [46,47]. The AdvaPIX-TPX3 measures directly the angles of the scattered protons, whereby the conversion of the spot profiles into an angular distribution by equation 8 is unnecessary.…”

Section: Discussionmentioning

confidence: 99%

Experiments and Monte Carlo simulations on multiple Coulomb scattering of protons

et al. 2021

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Background and purpose: Monte Carlo simulations as well as analytical computations of proton transport in material media require accurate values of multiple Coulomb scattering (MCS) angles. High-quality experimental data on MCS angles in the energy range for proton therapy are, however, sparse. In this work MCS modeling in proton transport was evaluated employing an experimental method to measure these angles on a medical proton beamline in clinically relevant materials. Results are compared to Monte Carlo simulations and analytical models.Materials and methods: Aluminum, brass and lucite (PMMA) scatterers of clinically relevant thicknesses were irradiated with protons at 100, 160 and 220 MeV. Resulting spatial distributions of individual pencil beams were measured with a scintillating screen. The MCS angles were determined by deconvolution and a virtual point source approach. Results were compared to those obtained with the Monte Carlo codes PENH, TOPAS and RayStation Monte Carlo, as well as the analytical models RayStation Pencil Beam Algorithm and the Molière/Fano/Hanson variant of the Molière theory.Results: Experimental data obtained with the presented methodology agree with previously published results within 6%, with an average deviation of 3%. The combined average uncertainty of the experimental data yielded 1.8%, while the combined maximum uncertainty was below 4%. The obtained Monte Carlo results for PENH, TOPAS and RayStation deviate on average for all considered energies, materials and thicknesses, by 2.5%, 3.4% and 2.8% from the experimental data, respectively. For the analytical models the average deviations amount to 4.5% and 2.9% for the RayStation Pencil Beam Algorithm and the Molière/Fano/Hanson model, respectively.Conclusion: The experimental method developed for the present work allowed to measure MCS angles in clinical proton facilities with good accuracy. The presented method permits to extend the database on experimental MCS angles which is rather limited. This work further provides benchmark data for lucite in thicknesses relevant for clinical applications. The data may serve to validate dose engines of treatment planning systems and secondary dose check software. The Monte Carlo and analytical algorithms studied are capable of reproducing MCS data within the required accuracy for clinical applications.

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A novel proton counting detector and method for the validation of tissue and implant material maps for Monte Carlo dose calculation

Cited by 17 publications

References 43 publications

Characterization of 250 MeV Protons from the Varian ProBeam PBS System for FLASH Radiation Therapy

Characterization of 250 MeV Protons from the Varian ProBeam PBS System for FLASH Radiation Therapy

NRG Oncology Survey of Monte Carlo Dose Calculation Use in US Proton Therapy Centers

Experiments and Monte Carlo simulations on multiple Coulomb scattering of protons

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