Monte Carlo simulation of TrueBeam flattening-filter-free beams using Varian phase-space files: Comparison with experimental data

Belosi, M.F.; Rodríguez, Miguel; Fogliata, Antonella; Cozzi, Luca; Sempau, J.; Clivio, Alessandro; Nicolini, G.; Vanetti, Eugenio; Krauss, H.; Khamphan, C.; Fénoglietto, P.; Puxeu, Josep; Fedele, David A.; Mancosu, P.; Brualla, L.

doi:10.1118/1.4871041

Cited by 44 publications

(43 citation statements)

References 23 publications

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“…For version‐2, the phase‐space files are stored in a

6.5 \times 6.5 {cm}^{2}

two‐dimensional plane located 26.7 cm from the source. Recent studies by Belosi et al (17) and Rodrigues et al (18) validated these version‐2 phase‐space files with measurement data for photon and electron beams, respectively. In this study, we report a comparison of the Monte Carlo simulations with measurements by small field detectors of output factors for Varian SRS system with conical collimators for energy of 6 MV flattening filter‐free (6 MV) and 10 MV flattening filter‐free (10 MV) on the Varian TrueBeam accelerator.…”

Section: Introductionmentioning

confidence: 88%

Output factor comparison of Monte Carlo and measurement for Varian TrueBeam 6 MV and 10 MV flattening filter‐free stereotactic radiosurgery system

Cheng

Ning

Arora

et al. 2016

J Applied Clin Med Phys

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The dose measurements of the small field sizes, such as conical collimators used in stereotactic radiosurgery (SRS), are a significant challenge due to many factors including source occlusion, detector size limitation, and lack of lateral electronic equilibrium. One useful tool in dealing with the small field effect is Monte Carlo (MC) simulation. In this study, we report a comparison of Monte Carlo simulations and measurements of output factors for the Varian SRS system with conical collimators for energies of 6 MV flattening filter‐free (6 MV) and 10 MV flattening filter‐free (10 MV) on the TrueBeam accelerator. Monte Carlo simulations of Varian's SRS system for 6 MV and 10 MV photon energies with cones sizes of 17.5 mm, 15.0 mm, 12.5 mm, 10.0 mm, 7.5 mm, 5.0 mm, and 4.0 mm were performed using EGSnrc (release V4 2.4.0) codes. Varian's version‐2 phase‐space files for 6 MV and 10 MV of TrueBeam accelerator were utilized in the Monte Carlo simulations. Two small diode detectors Edge (Sun Nuclear) and Small Field Detector (SFD) (IBA Dosimetry) were applied to measure the output factors. Significant errors may result if detector correction factors are not applied to small field dosimetric measurements. Although it lacked the machine‐specific kQitalicclin,Qitalicmsrfitalicclin,fitalicmsr correction factors for diode detectors in this study, correction factors were applied utilizing published studies conducted under similar conditions. For cone diameters greater than or equal to 12.5 mm, the differences between output factors for the Edge detector, SFD detector, and MC simulations are within 3.0% for both energies. For cone diameters below 12.5 mm, output factors differences exhibit greater variations.PACS number(s): 87.55.k, 87.55.Qr

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“…For version‐2, the phase‐space files are stored in a

6.5 \times 6.5 {cm}^{2}

Section: Introductionmentioning

confidence: 88%

Output factor comparison of Monte Carlo and measurement for Varian TrueBeam 6 MV and 10 MV flattening filter‐free stereotactic radiosurgery system

Cheng

Ning

Arora

et al. 2016

J Applied Clin Med Phys

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“…Validation results in water exhibited 99.9% and 99.0% of data passing the 2%/2 mm gamma criterion for 6 MV FFF and 10 MV FFF beams, respectively. Previous work performed by Belosi et al compared Varian provided phase space files to measurement using the same 2%/2 mm gamma criterion and yielded passing rates of 99.9% and 100.0% for 6 MV FFF and 10 MV FFF beams, respectively. Profile comparisons of our multiple source model to measurement exhibited gamma passing rates of 97.8% and 97.9% for the respective models.…”

Section: Discussionmentioning

confidence: 99%

Development of a flattening filter free multiple source model for use as an independent, Monte Carlo, dose calculation, quality assurance tool for clinical trials

et al. 2017

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“…Published phase space files for 6 MV FFF and flattened beams, generated using the actual geometry of the TrueBeam accelerator (Varian Medical System, Palo Alto, CA, USA) above the collimator moving jaws,16 were used as the input radiation source to BEAMnrc. Those phase space files were validated with measurements17 and successfully used in previous studies 9, 18, 19. Water phantom was simulated using DOSXYZnrc for dose distribution calculations 20…”

Section: Methodsmentioning

confidence: 99%

Superficial and peripheral dose in compensator‐based FFF beam IMRT

Zhang

Feygelman

Moros

et al. 2016

J Applied Clin Med Phys

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Flattening filter‐free (FFF) beams produce higher dose rates. Combined with compensator‐based intensity modulated radiotherapy (IMRT) techniques, the dose delivery for each beam can be much shorter compared to the flattened beam MLC‐based or flattened beam compensator‐based IMRT. This ‘snap shot’ IMRT delivery is beneficial to patients for tumor motion management. Due to softer energy, superficial doses in FFF beam treatment are usually higher than those from flattened beams. Due to no flattening filter, thus less photon scattering, peripheral doses are usually lower in FFF beam treatment. However, in compensator‐based IMRT using FFF beams, the compensator is in the beam pathway. Does it introduce beam hardening effects and scattering such that the superficial dose is lower and peripheral dose is higher compared to FFF beam MLC‐based IMRT? This study applied Monte Carlo techniques to investigate the superficial and peripheral doses in compensator‐based IMRT using FFF beams and compared it to the MLC‐based IMRT using FFF beams and flattened beams. Besides varying thicknesses of brass slabs to simulate varying thicknesses of compensators, a simple cone‐shaped compensator was simulated to mimic a clinical application. The dose distribution in water phantom by the cone‐shaped compensator was then simulated by multiple MLC‐defined FFF and flattened beams with varying apertures. After normalization to the maximum dose, Dmax, the superficial and peripheral doses were compared between the FFF beam compensator‐based IMRT and FFF/flattened beam MLC‐based IMRT. The superficial dose at the central 0.5 mm depth was about 1% (of Dmax) lower in the compensator‐based 6 MV FFF (6FFF) IMRT compared to the MLC‐based 6FFF IMRT, and about 8% higher than the flattened 6 MV MLC‐based IMRT dose. At 8 cm off‐axis at depth of central maximum dose, dmax, the peripheral dose between the 6FFF and flattened 6 MV MLC demonstrated similar doses, while the compensator dose was about 1% (of Dmax) higher. Compensators reduce the superficial doses slightly compared to open FFF beams, but increases the peripheral doses due to scatter in the compensator.

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Monte Carlo simulation of TrueBeam flattening-filter-free beams using Varian phase-space files: Comparison with experimental data

Cited by 44 publications

References 23 publications

Output factor comparison of Monte Carlo and measurement for Varian TrueBeam 6 MV and 10 MV flattening filter‐free stereotactic radiosurgery system

Output factor comparison of Monte Carlo and measurement for Varian TrueBeam 6 MV and 10 MV flattening filter‐free stereotactic radiosurgery system

Development of a flattening filter free multiple source model for use as an independent, Monte Carlo, dose calculation, quality assurance tool for clinical trials

Superficial and peripheral dose in compensator‐based FFF beam IMRT

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