Linking computer-aided design (CAD) to Geant4-based Monte Carlo simulations for precise implementation of complex treatment head geometries

Constantin, Magdalena; Constantin, Dragoş; Keall, Paul J.; Narula, Anisha; Svatos, M

doi:10.1088/0031-9155/55/8/n03

Cited by 31 publications

(36 citation statements)

References 23 publications

(26 reference statements)

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“…The head shielding model of the existing detailed GEANT4 Monte Carlo model of the Varian TrueBeam accelerator was refined based on manufacturer's proprietary drawings. This modified model has been made accessible via Amazon cloud computing services.…”

Section: Methodsmentioning

confidence: 99%

“…This is the case for all aspects of the TrueBeam (Varian Medical Systems, Palo Alto, CA) linac. In order to provide a way to conduct Monte Carlo (MC) studies of this linac, the Varian Medical systems’ Monte Carlo group has worked together with institutions to create a MC model and to validate it against existing experimental data . Varian has made this VirtuaLinac MC available on Amazon Web services cloud to researchers to perform direct Monte Carlo simulations of TrueBeam.…”

Section: Introductionmentioning

confidence: 99%

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Part II: Verification of the TrueBeam head shielding model in Varian VirtuaLinac via out‐of‐field doses

et al. 2019

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Purpose A good Monte Carlo model with an accurate head shielding model is important in estimating the long‐term risks of unwanted radiation exposure during radiation therapy. The aim of this paper was to validate the Monte Carlo simulation of a TrueBeam linear accelerator (linac) head shielding model. We approach this by evaluating the accuracy of out‐of‐field dose predictions at extended distances which are comprised of scatter from within the patient and treatment head leakage and thus reflect the accuracy of the head shielding model. We quantify the out‐of‐field dose of a TrueBeam linac for low‐energy photons, 6X and 6X‐FFF beams, and compare measurements to Monte Carlo simulations using Varian VirtuaLinac that include a realistic head shielding model, for a variety of jaw sizes and angles up to a distance of 100 cm from the isocenter, in both positive and negative directions. Given the high value and utility of the VirtuaLinac model, it is critical that this model is validated thoroughly and the results be available to the medical physics community. Materials and method Simulations were done using VirtuaLinac, the GEANT4‐based Monte Carlo model of the TrueBeam treatment head from Varian Medical Systems, and an in‐house GEANT4‐based code. VirtuaLinac included a detailed model of the treatment head shielding and was run on the Amazon Web Services cloud to generate spherical phase space files surrounding the treatment head. These phase space files were imported into the in‐house code, which modeled the measurement setup with a solid water buildup, the carbon fiber couch, and the gantry stand. For each jaw size (2 × 2 cm2, 4 × 4 cm2, 10 × 10 cm2, and 20 × 20 cm2) and angular setting (0°, 90°, 45°, 135°), the dose was calculated at intervals of 5 cm along each measurement direction. Results For the 10 × 10 cm2 jaw size, both 6X and 6X‐FFF showed very good agreement between simulation and measurement in both in‐plane directions, with no apparent systematic bias. The percentage deviations for these settings were as follows: (mean, STDEV, maximum) (8.34, 6.44, 24.84) for 6X and (13.21, 8.93, 35.56) for 6X‐FFF. For all jaw sizes, simulation agreed well in the in‐plane direction going away from the gantry, but, some deviations were observed moving toward the gantry at larger distances. At larger distances, for the jaw sizes smaller than 10 × 10 cm2, the simulation underestimates the dose compared with measurement, while for jaw sizes larger than 10 × 10 cm2, it overestimates dose. For all comparisons between ±50 cm from isocenter, average absolute agreement between simulation and measurement was better than 28%. Conclusion We have validated the Varian VirtuaLinac's head shielding model via out‐of‐field doses and quantified the differences between TrueBeam head shielding model created out‐of‐field doses and measurements for an extended distance of 100 cm.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Part II: Verification of the TrueBeam head shielding model in Varian VirtuaLinac via out‐of‐field doses

et al. 2019

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“…Currently, International Atomic Energy Agency (IAEA) format phase space files for individual clinical photon beams (4,6,8,10, and 15 MV, plus 10 and 15 MV flattening filter free) are available from the manufacturer (at myvarian.com/montecarlo), generated using the Geant4 Monte Carlo code 14 and geometry input from computer aided designs. 15,16 While the phase space files have been shown to produce accurate dose distributions compared to measurement, 17 they are not useful for investigating novel target designs in TrueBeam since they correspond to a location just above the secondary collimation (jaws). However, Varian has developed a cloud based web application, called "VirtuaLinac," which allows for Monte Carlo simulation without releasing the full description of the Linac in this section.…”

Section: Introductionmentioning

confidence: 99%

A Monte Carlo investigation of low‐Z target image quality generated in a linear accelerator using Varianˈs VirtuaLinac^a)

2014

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Purpose: The focus of this work was the demonstration and validation of VirtuaLinac with clinical photon beams and to investigate the implementation of low-Z targets in a TrueBeam linear accelerator (Linac) using Monte Carlo modeling. Methods: VirtuaLinac, a cloud based web application utilizing Geant4 Monte Carlo code, was used to model the Linac treatment head components. Particles were propagated through the lower portion of the treatment head using BEAMnrc. Dose distributions and spectral distributions were calculated using DOSXYZnrc and BEAMdp, respectively. For validation, 6 MV flattened and flattening filter free (FFF) photon beams were generated and compared to measurement for square fields, 10 and 40 cm wide and at d max for diagonal profiles. Two low-Z targets were investigated: a 2.35 MeV carbon target and the proposed 2.50 MeV commercial imaging target for the TrueBeam platform. A 2.35 MeV carbon target was also simulated in a 2100EX Clinac using BEAMnrc. Contrast simulations were made by scoring the dose in the phosphor layer of an IDU20 aSi detector after propagating through a 4 or 20 cm thick phantom composed of water and ICRP bone. Results: Measured and modeled depth dose curves for 6 MV flattened and FFF beams agree within 1% for 98.3% of points at depths greater than 0.85 cm. Ninety three percent or greater of points analyzed for the diagonal profiles had a gamma value less than one for the criteria of 1.5 mm and 1.5%. The two low-Z target photon spectra produced in TrueBeam are harder than that from the carbon target in the Clinac. Percent dose at depth 10 cm is greater by 3.6% and 8.9%; the fraction of photons in the diagnostic energy range (25-150 keV) is lower by 10% and 28%; and contrasts are lower by factors of 1.1 and 1.4 (4 cm thick phantom) and 1

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“…It is also possible to directly read in computer-aided design into the MC code. 65 In addition, the dedicated implementation depends on the MC code used. Treatment head simulations for proton beams include also dynamic components, e.g.…”

Section: Monte Carlo Simulation Of the Radiation Fieldmentioning

confidence: 99%

Treatment planning aspects and Monte Carlo methods in proton therapy

Fix

Manser

2015

Mod. Phys. Lett. A

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Over the last years, the interest in proton radiotherapy is rapidly increasing. Protons provide superior physical properties compared with conventional radiotherapy using photons. These properties result in depth dose curves with a large dose peak at the end of the proton track and the finite proton range allows sparing the distally located healthy tissue. These properties offer an increased flexibility in proton radiotherapy, but also increase the demand in accurate dose estimations. To carry out accurate dose calculations, first an accurate and detailed characterization of the physical proton beam exiting the treatment head is necessary for both currently available delivery techniques: scattered and scanned proton beams. Since Monte Carlo (MC) methods follow the particle track simulating the interactions from first principles, this technique is perfectly suited to accurately model the treatment head. Nevertheless, careful validation of these MC models is necessary. While for the dose estimation pencil beam algorithms provide the advantage of fast computations, they are limited in accuracy. In contrast, MC dose calculation algorithms overcome these limitations and due to recent improvements in efficiency, these algorithms are expected to improve the accuracy of the calculated dose distributions and to be introduced in clinical routine in the near future. Keywords: Proton radiotherapy; Monte Carlo; dose calculation. 1540022-1 Mod. Phys. Lett. A 2015.30. Downloaded from www.worldscientific.com by CAMBRIDGE UNIVERSITY on 08/18/15. For personal use only.

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Linking computer-aided design (CAD) to Geant4-based Monte Carlo simulations for precise implementation of complex treatment head geometries

Cited by 31 publications

References 23 publications

Part II: Verification of the TrueBeam head shielding model in Varian VirtuaLinac via out‐of‐field doses

Part II: Verification of the TrueBeam head shielding model in Varian VirtuaLinac via out‐of‐field doses

A Monte Carlo investigation of low‐Z target image quality generated in a linear accelerator using Varianˈs VirtuaLinac^a)

Treatment planning aspects and Monte Carlo methods in proton therapy

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Linking computer-aided design (CAD) to Geant4-based Monte Carlo simulations for precise implementation of complex treatment head geometries

Cited by 31 publications

References 23 publications

Part II: Verification of the TrueBeam head shielding model in Varian VirtuaLinac via out‐of‐field doses

Part II: Verification of the TrueBeam head shielding model in Varian VirtuaLinac via out‐of‐field doses

A Monte Carlo investigation of low‐Z target image quality generated in a linear accelerator using Varianˈs VirtuaLinaca)

Treatment planning aspects and Monte Carlo methods in proton therapy

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A Monte Carlo investigation of low‐Z target image quality generated in a linear accelerator using Varianˈs VirtuaLinac^a)