Validation of a virtual source model for Monte Carlo dose calculations of a flattening filter free linac

Cashmore, J.; Golubev, S. A.; Dumont, J; Sikora, Marcin; Alber, M.; Ramtohul, M.

doi:10.1118/1.4709601

Cited by 23 publications

(22 citation statements)

References 19 publications

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“…Removing the filter results in a highly forward‐peaked beam profile, increases the dose rate, and softens the beam. While several recent papers have summarized the dosimetric characteristics of these beams 1 , 2 , 3 and others have reported commissioning results of the anisotropic analytical algorithm (4) or Monte Carlo, 5 , 6 , 7 scarce data exist on modeling these beams with the collapsed cone convolution superposition (CCCS) algorithm as implemented in the widely used Pinnacle 3 treatment planning system (Philips Radiation Oncology Systems, Fitchburg, WI). Stathakis et al (8) reported their experience commissioning the CCCS algorithm for 6 and 18 MV unflattened beams by overriding interlocks related to the flattening filter, but no patients were treated with this configuration.…”

Section: Introductionmentioning

confidence: 99%

Commissioning and verification of the collapsed cone convolution superposition algorithm for SBRT delivery using flattening filter‐free beams

Foster

Speiser

Solberg

2014

J Applied Clin Med Phys

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Linacs equipped with flattening filter‐free (FFF) megavoltage photon beams are now commercially available. However, the commissioning of FFF beams poses challenges that are not shared with traditional flattened megavoltage X‐ray beams. The planning system must model a beam that is peaked in the center and has an energy spectrum that is softer than the flattened beam. Removing the flattening filter also increases the maximum possible dose rates from 600 MU/min up to 2400 MU/min in some cases; this increase in dose rate affects the recombination correction factor, Pion, used during absolute dose calibration with ionization chambers. We present the first‐reported experience of commissioning, verification, and clinical use of the collapsed cone convolution superposition (CCCS) dose calculation algorithm for commercially available flattening filter‐free beams. Our commissioning data are compared to previously reported measurements and Monte Carlo studies of FFF beams. Commissioning was verified by making point‐dose measurement of test plans, irradiating the RPC lung phantom, and performing patient‐specific QA. The average point‐dose difference between calculations and measurements of all test plans and all patient specific QA measurements is 0.80%, and the RPC phantom absolute dose differences for the two thermoluminescent dosimeters (TLDs) in the phantom planning target volume (PTV) were 1% and 2%, respectively. One hundred percent (100%) of points in the RPC phantom films passed the RPC gamma criteria of 5% and 5 mm. Our results show that the CCCS algorithm can accurately model FFF beams and calculate SBRT dose distributions using those beams.PACS number: 87.55.kh

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Section: Introductionmentioning

confidence: 99%

Commissioning and verification of the collapsed cone convolution superposition algorithm for SBRT delivery using flattening filter‐free beams

Foster

Speiser

Solberg

2014

J Applied Clin Med Phys

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“…As shown in Figure 4b and c, the off-axis profiles have convex distributions that agree with the literature. [310131516181920] The profile in the off-axis direction at the 0.7-cm depth, where many contamination electrons are contained, differs from the profiles at deeper positions under the influence of entrained electrons. This is because the electron beam spreads laterally after entering water and is larger than X-rays, as shown in Figure 4a.…”

Section: Resultsmentioning

confidence: 99%

“…The dose distribution for FFF linacs determined using Monte Carlo (MC) simulations,[34567891011] as well as measured data from treatment apparatuses in clinical use,[89101112131415161718] has been published. Most of such experimental studies employed commercial linacs with a metal plate, such as copper or aluminum, inserted to absorb the primary and secondary electrons created in materials in the linac head.…”

Section: Introductionmentioning

confidence: 99%

Beam characterization of 10-MV photon beam from medical linear accelerator without flattening filter

et al. 2017

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Aim:This work investigated the dosimetric properties of a 10-MV photon beam emitted from a medical linear accelerator (linac) with no flattening filter (FF). The aim of this study is to analyze the radiation fluence and energy emitted from the flattening filter free (FFF) linac using Monte Carlo (MC) simulations.Materials and Methods:The FFF linac was created by removing the FF from a linac in clinical use. Measurements of the depth dose (DD) and the off-axis profile were performed using a three-dimensional water phantom with an ionization chamber. A MC simulation for a 10-MV photon beam from this FFF linac was performed using the BEAMnrc code.Results:The off-axis profiles for the FFF linac exhibited a chevron-like distribution, and the dose outside the irradiation field was found to be lower for the FFF linac than for a linac with an FF (FF linac). The DD curves for the FFF linac included many contaminant electrons in the build-up region.Conclusion:Therefore, for clinical use, a metal filter is additionally required to reduce the effects of the electron contamination. The mean energy of the FFF linac was found to be lower than that of the FF linac owing to the absence of beam hardening caused by the FF.

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“…One of the possible solutions is to ignore all the details of the hardware and adopt a source model based on the parameters obtained by fitting the energy spectrum, the radial, and angular distributions with analytical functions to measured data. We may refer this kind of method to as a virtual analytical source model (VASM) . In this work, we developed an alternative approach, for which we call a virtual machine source model (VMSM) to distinguish it from a VASM.…”

Section: Introductionmentioning

confidence: 99%

Technical Note: An approach to building a Monte Carlo simulation model for a double scattering proton beam system

2018

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Validation of a virtual source model for Monte Carlo dose calculations of a flattening filter free linac

Cited by 23 publications

References 19 publications

Commissioning and verification of the collapsed cone convolution superposition algorithm for SBRT delivery using flattening filter‐free beams

Commissioning and verification of the collapsed cone convolution superposition algorithm for SBRT delivery using flattening filter‐free beams

Beam characterization of 10-MV photon beam from medical linear accelerator without flattening filter

Technical Note: An approach to building a Monte Carlo simulation model for a double scattering proton beam system

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