Analysis of physical parameters and determination of inflection point for Flattening Filter Free beams in medical linear accelerator

Pichandi, A.; Ganesh, K M; Amalraj, Jerrin; Balaji, K.; Kilara, G.

doi:10.1016/j.rpor.2014.01.004

Cited by 21 publications

(22 citation statements)

References 7 publications

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“…Recently, there has been a growing interesting in operating medical linear accelerators without a flattening filter (FFF). The main advantages of FFF beams are increased dose rate, reduced scatter radiation, reduced leaf transmission and treatment head leakage 7 . Numerous literatures reported that the increased dose rate of FFF beams is particularly beneficial for stereotactic body radiotherapy (SBRT) due to reduction of the treatment times of large fraction doses [8.9,10].…”

Section: Introductionmentioning

confidence: 99%

Comparison of treatment plan quality of VMAT for esophageal carcinoma with: flattening filter beam versus flattening filter free beam

et al. 2018

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Purpose: To investigate the difference in treatment plan quality of volumetric modulated arc treatment (VMAT) for esophageal carcinoma with flattening filter beam (FF) and flattening filter free beam (FFF).Material and methods: A total of fifty-six treatment plans were generated for twenty eight esophageal carcinoma patients with flattening filter beam and flattening filter free beam, using same optimal parameters. The homogeneity index (HI) and conformal index (CI) of targets, and some special points on Dose-Volume Histogram (DVH) curves were used to compare the plan quality. The coverage volumes of 45 Gy, 30 Gy and 20 Gy outside targets (V45Gy, V30Gy and V20Gy) were used to compare the targets peripheral dose. The MU numbers, measured delivery time and averaged dose rates were used to evaluate the delivery efficiency of treatment plans.Results: A significant decreasing in peripheral dose around targets was found using FFF beams while the dose distributions in targets were equivalent to the plans with FF beams. V45Gy, V30Gy and V20Gy were decreased by 6.46%, 88.18% and 4.40%, respectively. A significant increase in MUs and decrease in treatment time were also found in delivery test. The average MUs was increased by 21.83% and the average treatment time was reduced by down to 11.9%.Conclusions: For esophageal carcinoma, the research showed that the treatment plans with FFF beams could get comparable dose distribution in targets and could significantly reduce the peripheral dose around targets compared to the plans with FF beams.

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Section: Introductionmentioning

confidence: 99%

Comparison of treatment plan quality of VMAT for esophageal carcinoma with: flattening filter beam versus flattening filter free beam

et al. 2018

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“…The limitation of the current measurement is time consuming to apply a fine scanning step of 0.1 cm in the QA and commissioning process. MSM, techniques by Pönisch et al and the method of the re-normalization, which is a typical definition methods for the FFF beam field size, could contain uncertainty arising the scanning step [9,[15][16][17]. The uncertainty at the location of the inflection point may occur from the measured data for using less fine scanning step.…”

Section: Discussionmentioning

confidence: 99%

“…There have been several studies to define the field sizes of a FFF beam [13,14]. The most representative method to determine the field size of the FFF beam is the use of the inflection point (IP) on the penumbra region of the beam's profile [15,16]. Nevertheless, there are some uncertainties to obtain correct IP from beam data measurement.…”

Section: Introductionmentioning

confidence: 99%

Simplified sigmoidal curve fitting for 6 MV FFF photon beam of Halcyon to determine field size for beam commissioning and quality assurance

Choi

Law

Yoon

et al. 2020

Preprint

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Background Delivery of a single energy 6 MV flattening filter free (FFF) photon beam is a main characteristic of an O-ring gantry type linear accelerator (linac) Halcyon. The purpose of this study is to determine the field size of the beam through an application of the simplified sigmoidal curve fitting (SCF) to the beam profiles obtained from the preconfigured reference data of Halcyon, and then to compare its parametrization with the measured beam data from Halcyon. Methods After a mathematical definition of the SCF using four coefficients, the defined curves were fitted to both the reference and measured data. When a high agreement between the fitting curve and the profiles in each data, the field sizes were determined by identifying the maximum point along the third derivative of the fitting curve. The curve fitting included the field sizes for beam profiles as 2 × 2, 4 × 4, 6 × 6, 8 × 8, 10 × 10, 20 × 20 and 28 × 28 cm 2 as a function of depths (at 1.3, 5, 10, 20 cm). The results of the field size from the reference data were compared with the results in the measured data using same condition. Results All fitting curves show an average agreement ratio higher than 97% and the values of goodness of fit, R 2 , as better than 0.99. The differences of the field size between the reference data and the measured data were within the range of 0 to 0.2 cm. The least difference of the field sizes at depth 10 cm which is a surface to axis distance was reported. Conclusion The application of the SCF has been proved to accurately obtain the field size of the preconfigured reference and of measured FFF photon beam data for Halcyon. The current work can be useful to the beam commissioning as a countercheck methodology to the field size from the reference data in the treatment planning system of a newly installed Halcyon and to the routine quality assurance to ascertain the correctness of field sizes clinically used with the Halcyon.

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“…The most representative method to determine the eld size of the FFF beam is the use of the in ection point (IP) on the penumbra region of the beam's pro le. [9,10] Nevertheless, there are some uncertainties in obtaining a correct IP from beam data measurement. To consider this uncertainty, Pönisch et al proposed a method to identify the IP at the eld edge of the FFF beam with the same level of the FF beam.…”

Section: Introductionmentioning

confidence: 99%

Simplified sigmoidal curve fitting for a 6 MV FFF photon beam of Halcyon to determine the field size for beam commissioning and quality assurance

Choi

Law

Yoon

et al. 2020

Preprint

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Background : An O-ring gantry-type linear accelerator (Linac) with a 6 MV flattening filter-free (FFF) photon beam, Halcyon, includes a reference beam containing the representative information regarding the percent depth dose, profile, output factor, etc. for commissioning and quality assurance. However, because it does not provide the information of the field size, we proposed a method to determine all field sizes according to all depths for radiation therapy using simplified sigmoidal curve fitting (SCF). Methods : After a mathematical definition of the SCF using four coefficients, the defined curves were fitted to both the reference and measured data. For a high agreement between the fitting curve and the profiles in each data set, the field sizes were determined by identifying the maximum point along the third derivative of the fitting curve. The curve fitting included the field sizes for beam profiles of 2 × 2, 4 × 4, 6 × 6, 8 × 8, 10 × 10, 20 × 20 and 28 × 28 cm 2 as a function of depth (at 1.3, 5, 10, 20 cm). The results of the field size from the reference data were compared with the results in the measured data using the same condition. Results : All fitting curves show values of goodness of fit, R 2 , better than 0.99. The differences in the field size between the reference data and the measured data were within the range of 0 to 0.2 cm. The lowest difference in the field sizes at a depth of 10 cm, which is a surface-to-axis distance, was reported. Conclusion : The application of the SCF has been proven to accurately obtain the field size of the preconfigured reference and of the measured FFF photon beam data for the Halcyon system. The current work can be useful for beam commissioning as a counte-rcheck methodology to determine the field size from the reference data in the treatment planning system of a newly installed Halcyon system and for the routine quality assurance to ascertain the correctness of field sizes clinically used with the Halcyon system.

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Analysis of physical parameters and determination of inflection point for Flattening Filter Free beams in medical linear accelerator

Abstract: a b s t r a c tBackground: Medical Linear accelerators manufactured without flattening filters are increas-

Cited by 21 publications

References 7 publications

Comparison of treatment plan quality of VMAT for esophageal carcinoma with: flattening filter beam versus flattening filter free beam

Comparison of treatment plan quality of VMAT for esophageal carcinoma with: flattening filter beam versus flattening filter free beam

Simplified sigmoidal curve fitting for 6 MV FFF photon beam of Halcyon to determine field size for beam commissioning and quality assurance

Simplified sigmoidal curve fitting for a 6 MV FFF photon beam of Halcyon to determine the field size for beam commissioning and quality assurance

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