Comparison of Flattening Filter (FF) and Flattening-Filter-Free (FFF) 6 MV photon beam characteristics for small field dosimetry using EGSnrc Monte Carlo code

Sangeetha, S.; Sureka, C.S.

doi:10.1016/j.radphyschem.2017.02.029

Cited by 17 publications

(13 citation statements)

References 59 publications

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“…Most previous works reported an increase in dose rate by factor of 2 [36–37] who worked on Siemens ONCOR Avant-Garde and Siemens Primus linacs, respectively. For the other vendors, recently Sangeetha et al [38] reported a relative dose rate of 2.52 (2.60) for the 10×10 cm 2 (20×20 cm 2 ) field for a Varian 600C/D and Dalaryd et al [39], observed that the dose rate of the FFF beams increased by a factor of 2.23 for an ElektaPrecise. Notably, the values for our Siemens Artiste were larger than previous ones with dose rate of 2.8 (2.96) for the 10×10 cm 2 (20×20 cm 2 ) fields.…”

Section: Discussionmentioning

confidence: 99%

Monte-Carlo simulation of the Siemens Artiste linear accelerator flat 6 MV and flattening-filter-free 7 MV beam line

et al. 2019

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The aim of our work is to provide the up-to-now missing information on the Siemens Artiste FFF 7 MV beam line using a Monte-Carlo model fit to the realistic dosimetric measurements at the linear accelerator in clinical use at our department. The main Siemens Artiste 6MV and FFF 7MV beams were simulated using the Geant4 toolkit. The simulations were compared with the measurements with an ionization chamber in a water phantom to verify the validation of simulation and tuning the primary electron parameters. Hereafter, other parameters such as surface dose, spectrum, electron contamination, symmetry, flatness/unflatness, slope, and characteristic off-axis changes were discussed for both Flat and FFF mode. The mean electron energy for the FFF beam was 8.8 MeV and 7.5 MeV for Flat 6 MV, the spread energy and spot size of the selected Gaussian distribution source were 0.4 MeV and 1mm, respectively. The dose rate of the FFF beam was 2.8 (2.96) times higher than for the flattened beam for a field size of 10×10 (20×20) cm2. The electron contamination has significant contribution to the surface dose especially for the flattened beam. The penumbra, surface dose and the mean energy of photons decrease by removing the flattening filter. Finally, the results show that off-axis changes have no strong effect on the mean energy of FFF beams, while this effect was more considerable for the flattened beam.

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Section: Discussionmentioning

confidence: 99%

Monte-Carlo simulation of the Siemens Artiste linear accelerator flat 6 MV and flattening-filter-free 7 MV beam line

et al. 2019

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“…On the other hand, the flattening filter is replaced with other filter material to maintain the signal received by monitor chambers on FFF linac design [ 4 ]; however, the filter design is not provided by manufacturers. Thus, many researchers have been predicted and simulated design of the FFF linac head especially on the flattening filter replacement material [ 5 - 7 ]. Several studies have been conducted to measure and compare 6MV photon beam characteristics, both on Monte Carlo simulations and measurements.…”

Section: Introductionmentioning

confidence: 99%

A Monte Carlo Study of Photon Beam Characteristics on Various Linear Accelerator Filters

2020

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Background: Intensity Modulated Radiation Therapy (IMRT) technique is an advanced method of radiotherapy leading into the development of Flattening Filter-Free (FFF) medical linear accelerators (Linacs). Monte Carlo simulation has been a standard method for calculation of particle transport due to precise geometry and material specifications. Objective: This study is to obtain the design optimization of Flattening Filter Free (FFF) for 6 MV Linac machine Material and Methods: In this simulating study, EGSnrc user code was used to simulate particles emitted from head of linac 6MV Varian to achieve the most suitable filter in FFF linac design. Monte Carlo simulation results of the PDD and profile, on the 10 × 10 cm 2 field, were compared with the measurements. Differences in small profile beams from Monte Carlo simulation were also evaluated between FF and FFF linac. Results: The spectrum on Monte Carlo simulation in isocenter was compared with Treatment Planning System (TPS) for each filter variation. The slight differences of average spectrum are simulated using 2 mm copper filter and FakeBeam with -1.52 ± 3.82% and -3.13 ± 3.61%. Whereas, for PDD and profiles, each variation has an average difference of 7.10 ± 0.70% and -5.99 ± 1.39%. Conclusion: FakeBeam filter is a proper filter for the use of linac design 6MV Varian. It is necessary to decrease the kinetic energy of electrons to perform MC simulations on FFF linac.

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“…The dose verification of single square-field and multifield irradiation of IMRT was also performed by the 3D gel dosimeters [15]. Nevertheless, the homogeneous dose delivery revealed disagreement with TPS when using small-field irradiation techniques [16,17]. The flattening filter free (FFF) beam irradiation increased the dose conformity and further reduced the treatment delivery time in radiosurgery by removing the flattening filter [1,18,19].…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional dose comparison of flattening filter (FF) and flattening filter-free (FFF) radiation therapy by using NIPAM gel dosimetry

et al. 2019

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Intensity-modulated radiotherapy and volumetric modulated arc therapy are modern radiation therapy technologies that can create the desired dose distribution by multileaf collimator movement and dose-rate control. However, the homogeneous dose delivery of small-field irradiation techniques shows disagreement with that of treatment planning system. The removal of the flattening filter by flattening filter free (FFF) beam irradiation increases dose conformity and further reduces treatment delivery time in radiosurgery. This study aims to investigate the dose distribution of FFF and flattened beams for small-field irradiation by using the 3D gel dosimeter. The N -isopropylacrylamide (NIPAM) polymer gel dosimeter was employed to record the 3D dose distribution. In addition, flattened and FFF beams were compared using the gamma evaluation technique. The use of an FFF accelerator resulted in excellent radiation treatments with short delivery times and low doses to normal tissues and organs. Results also showed that the passing rate increased with the decrease of field size (30 × 30, 20 × 20, and 10 × 10 mm 2 ) at post-irradiation times of 24, 48, 72, and 96 h. The passing rates for each field size were retained at the same level when gamma criteria, namely, distance-to-agreement (DTA) = 3 mm/dose difference (DD) = 3%, were used. Nevertheless, the passing rates for each field size decreased slowly after 48 h when DTA = 2 mm/DD = 2%. The Wilcoxon signed-rank test was used to determine statistical difference with a significant level of p < 0.05. The passing rates of flattened and FFF beams showed no significant difference. The edge enhancement effect in the flattened beam was more evident than in the FFF beam. The 3D NIPAM gel dosimeter can be used for dose verification of small field for radiation therapy with high dose rate.

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Comparison of Flattening Filter (FF) and Flattening-Filter-Free (FFF) 6 MV photon beam characteristics for small field dosimetry using EGSnrc Monte Carlo code

Cited by 17 publications

References 59 publications

Monte-Carlo simulation of the Siemens Artiste linear accelerator flat 6 MV and flattening-filter-free 7 MV beam line

Monte-Carlo simulation of the Siemens Artiste linear accelerator flat 6 MV and flattening-filter-free 7 MV beam line

A Monte Carlo Study of Photon Beam Characteristics on Various Linear Accelerator Filters

Three-dimensional dose comparison of flattening filter (FF) and flattening filter-free (FFF) radiation therapy by using NIPAM gel dosimetry

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