Validation of linear energy transfer computed in a Monte Carlo dose engine of a commercial treatment planning system

Wagenaar, Daniel A.; Tran, Linh T.; Meijers, Artürs; Marmitt, Gabriel Guterres; Souris, Kevin; Bolst, David; James, Benjamin; Biasi, Giordano; Povoli, Marco; Kok, Angela; Traneus, E.; Goethem, Marc-Jan van; Langendijk, Johannes A.; Rosenfeld, Anatoly B.; Both, Stefan

doi:10.1088/1361-6560/ab5e97

Cited by 46 publications

(50 citation statements)

References 30 publications

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“…2,5,6 Thus, clinics have transitioned to using TPS with Monte Carlo (MC)-based dose calculation algorithms, which agree with measured dose to within 5%. Recently, there has been increasing interest in calculation of linear energy transfer (LET) by TPS, [8][9][10][11] specifically because it is well known that proton beams exhibit greater relative biological effectiveness (RBE) at the distal edge of the Bragg peak, due to increased LET. The implementation of LET calculation in the TPS can better quantify the biologically equivalent dose of the treatment plan.…”

Section: Introductionmentioning

confidence: 99%

Producing a Beam Model of the Varian ProBeam Proton Therapy System using TOPAS Monte Carlo Toolkit

et al. 2020

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Purpose A Geant4‐based TOPAS Monte Carlo toolkit was utilized to model a Varian ProBeam proton therapy system, with the aim of providing an independent computational platform for validating advanced dosimetric methods. Materials and Methods The model was tested for accuracy of dose and linear energy transfer (LET) prediction relative to the commissioning data, which included integral depth dose (IDD) in water and spot profiles in air measured at varying depths (for energies of 70 to 240 MeV in increments of 10 MeV, and 242 MeV), and absolute dose calibration. Emittance was defined based on depth‐dependent spot profiles and Courant–Snyder’s particle transport theory, which provided spot size and angular divergence along the inline and crossline plane. Energy spectra were defined as Gaussian distributions that best matched the range and maximum dose of the IDD. The validity of the model was assessed based on measurements of range, dose to peak difference, mean point to point difference, spot sizes at different depths, and spread‐out Bragg peak (SOBP) IDD and was compared to the current treatment planning software (TPS). Results Simulated and commissioned spot sizes agreed within 2.5%. The single spot IDD range, maximum dose, and mean point to point difference of each commissioned energy agreed with the simulated profiles generally within 0.07 mm, 0.4%, and 0.6%, respectively. A simulated SOBP plan agreed with the measured dose within 2% for the plateau region. The protons/MU and absolute dose agreed with the current TPS to within 1.6% and exhibited the greatest discrepancy at higher energies. Conclusions The TOPAS model agreed well with the commissioning data and included inline and crossline asymmetry of the beam profiles. The discrepancy between the measured and TOPAS‐simulated SOBP plan may be due to beam modeling simplifications of the current TPS and the nuclear halo effect. The model can compute LET, and motivates future studies in understanding equivalent dose prediction in treatment planning, and investigating scintillation quenching.

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Section: Introductionmentioning

confidence: 99%

Producing a Beam Model of the Varian ProBeam Proton Therapy System using TOPAS Monte Carlo Toolkit

et al. 2020

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“…These will face the same challenges that are relevant for the quality control of dose distributions that are destined for three-dimensional geometries in heterogeneous media, while verification is often performed in two-dimensional geometries in the homogeneous media. Possible improvements could be achieved from independent dose and LET d calculation engines that will go through a separate validation and control, removing the need for individual validation [41]. In this respect, Monte Carlo calculation appears to be the most useful tool to calculate LET d , while microdosimetric methods could be a promising way to benchmark how different MC based engines can accurately predict LET d distributions [42][43][44].…”

Section: Discussionmentioning

confidence: 99%

RBE for proton radiation therapy – a Nordic view in the international perspective

et al. 2020

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Background: This paper presents an insight into the critical discussions and the current strategies of the Nordic countries for handling the variable proton relative biological effectiveness (RBE) as presented at The Nordic Collaborative Workshop for Particle Therapy that took place at the Skandion Clinic on 14th and 15th of November 2019. Material and methods: In the current clinical practice at the two proton centres in operation at the date, Skandion Clinic, and the Danish Centre for Particle Therapy, a constant proton RBE of 1.1 is applied. The potentially increased effectiveness at the end of the particle range is however considered at the stage of treatment planning at both places based on empirical observations and knowledge. More elaborated strategies to evaluate the plans and mitigate the problem are intensely investigated internationally as well at the two centres. They involve the calculation of the dose-averaged linear energy transfer (LET d ) values and the assessment of their distributions corroborated with the distribution of the dose and the location of the critical clinical structures. Results: Methods and tools for LET d calculations are under different stages of development as well as models to account for the variation of the RBE with LET d , dose per fraction, and type of tissue. The way they are currently used for evaluation and optimisation of the plans and their robustness are summarised. A critical but not exhaustive discussion of their potential future implementation in the clinical practice is also presented. Conclusions: The need for collaboration between the clinical proton centres in establishing common platforms and perspectives for treatment planning evaluation and optimisation is highlighted as well as the need of close interaction with the research academic groups that could offer a complementary perspective and actively help developing methods and tools for clinical implementation of the more complex metrics for considering the variable effectiveness of the proton beams.

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“…In MCSquare calculation, the ‘stopping power’ method ( 35 ) was selected, in which LET d was scored by dose-weighted average of the stopping power of particles through each voxel ( 36 ). Secondary particles were handled by specifying the options in the configuration file as: secondary photons and neutrons are not taken into account while the secondary electrons are considered as locally absorbed.…”

Section: Methodsmentioning

confidence: 99%

Linear Energy Transfer Incorporated Spot-Scanning Proton Arc Therapy Optimization: A Feasibility Study

Ding

Zheng

et al. 2021

Front. Oncol.

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PurposeTo integrate dose-averaged linear energy transfer (LETd) into spot-scanning proton arc therapy (SPArc) optimization and to explore its feasibility and potential clinical benefits.MethodsAn open-source proton planning platform (OpenREGGUI) has been modified to incorporate LETd into optimization for both SPArc and multi-beam intensity-modulated proton therapy (IMPT) treatment planning. SPArc and multi-beam IMPT plans with different beam configurations for a prostate patient were generated to investigate the feasibility of LETd-based optimization using SPArc in terms of spatial LETd distribution and plan delivery efficiency. One liver and one brain case were studied to further evaluate the advantages of SPArc over multi-beam IMPT.ResultsWith similar dose distributions, the efficacy of spatially optimizing LETd distributions improves with increasing number of beams. Compared with multi-beam IMPT plans, SPArc plans show substantial improvement in LETd distributions while maintaining similar delivery efficiency. Specifically, for the liver case, the average LETd in the GTV was increased by 124% for the SPArc plan, and only 9.6% for the 2-beam IMPT plan compared with the 2-beam non-LETd optimized IMPT plan. In case of LET optimization for the brain case, the SPArc plan could effectively increase the average LETd in the CTV and decrease the values in the critical structures while smaller improvement was observed in 3-beam IMPT plans.ConclusionThis work demonstrates the feasibility and significant advantages of using SPArc for LETd-based optimization, which could maximize the LETd distribution wherever is desired inside the target and averts the high LETd away from the adjacent critical organs-at-risk.

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Validation of linear energy transfer computed in a Monte Carlo dose engine of a commercial treatment planning system

Cited by 46 publications

References 30 publications

Producing a Beam Model of the Varian ProBeam Proton Therapy System using TOPAS Monte Carlo Toolkit

Producing a Beam Model of the Varian ProBeam Proton Therapy System using TOPAS Monte Carlo Toolkit

RBE for proton radiation therapy – a Nordic view in the international perspective

Linear Energy Transfer Incorporated Spot-Scanning Proton Arc Therapy Optimization: A Feasibility Study

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