Variation in output factor caused by secondary blocking for 7–16 MeV electron beams

Choi, Myung Chul; Purdy, James A.; Gerbi, Bruce J.; Abrath, Fred G.; Glasgow, Glenn P.

doi:10.1118/1.594545

Cited by 12 publications

(2 citation statements)

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“…Energy deposition by electron beams in a medium is significantly affected by the beam characteristics and collimation and by the medium geometry and construction due to multiple Coulomb scattering (Bethe et al 1938, Berger 1963, Lanzl 1981. Consequently, output factors for electron beams vary in a complicated manner with beam energy and field geometry (Biggs et al 1979, Choi et al 1979, Hogstrom et al 1981, Nair et al 1983, Meyer et al 1984, Mills et al 1985, AAPM 1991, Al-Ghazi and Tavares 1993, Shiu et al 1994. In particular, the prediction of output factors for small-field electron beams is complicated by the lack of lateral scatter equilibrium (McGinley et al 1979, AAPM 1983, 1991, Sharma et al 1984, ICRU 1984a, Niroomand-Rad 1989, Rashid et al 1990.…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo calculations of electron beam output factors for a medical linear accelerator

Kapur

Mok

et al. 1998

Phys. Med. Biol.

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The purpose of this study was to investigate the application of the Monte Carlo technique to the calculation and analysis of output factors for electron beams used in radiotherapy. The code EGS4/BEAM was used to obtain phase-space files for 6, 12 and 20 MeV clinical electron beams from a scattering-foil linac (Varian Clinac 2100C) for a clinically representative range of applicator and square or rectangular insert combinations. The source-to-surface distance used was 100 cm. The field sizes ranged from 1 x 1 cm2 to 20 x 20 cm2. These phase-space files were analysed to study the intrinsic beam characteristics and used as source input for relative dose and output factor computations in homogeneous water phantoms using the code EGS4/DOSXYZ. The calculated relative central-axis depth-dose and transverse dose profiles at various depths of clinical interest agreed with the corresponding measured dose profiles to within 2% of the maximum dose. Calculated output factors for the fields studied agreed with measured output factors to about 2%. This demonstrated that for the Varian Clinac 2100C linear accelerator, electron beam dose calculations in homogeneous water phantoms can be performed accurately at the 2% level using Monte Carlo simulations.

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Section: Introductionmentioning

confidence: 99%

Monte Carlo calculations of electron beam output factors for a medical linear accelerator

Kapur

Mok

et al. 1998

Phys. Med. Biol.

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“…The dose delivered by electron beams has complex dependence on the shape of the field, design of collimator systems, and energy of the beam. [1][2][3][4][5] This complicated dependence arises because the electrons undergo multiple scatter in the accelerator head, in the collimator systems, in the intervening air between the collimator and the patient, off the walls of the applicator, off the field shaping cerrobend inserts ͑cutouts͒, and finally in the patient. The dosimetry for regular circular, square, or rectangular fields is straightforward.…”

Section: Introductionmentioning

confidence: 99%

The root percent depth dose method for calculating monitor units for irregularly shaped electron fields

Kehwar

Huq

2008

Medical Physics

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This study outlines an improved method for calculating dose per monitor unit values for irregularly shaped electron fields using the nth root percent depth dose method. This method calculates the percent depth dose and output factors for an irregularly shaped electron field directly from the measured electron beam percent depth dose curves and output factors for circular fields. The percent depth dose curves and output factors for circular fields are normalized and measured at a fixed depth of maximum dose for a reference field, respectively. When compared with the sector integral lateral buildup ratio method, the percent depth dose data calculated using the nth root method accounts more accurately for the change in lateral scatter with decreasing field size. Therefore, it provides more accurate values of dose per monitor unit at different depths for all type of field shapes and beam energies. For beam energies in the range of 6-21 MeV, the differences between measured and calculated dose per monitor unit values, at different depths, were found to be within +/- 1.0% when the nth root percent depth dose method was used for calculation and 12.6% when the sector integral lateral buildup ratio method was used. The nth root percent depth dose method was tested and compared with the sector integral lateral buildup ratio method for ten clinically used irregularly shaped inserts (cutouts). For small irregularly shaped fields, a maximum difference of 2% was found between calculated dose per monitor unit values and measurements when the nth root percent depth dose method was used; this difference changed to 7% when comparisons were made between measurements and calculations based on the sector integral lateral buildup ration method. For large irregular fields this difference was found to be within 1.5% and 3.5%, respectively.

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A Monte Carlo Study of the Particle Angular Distributions from the Electron Applicators of a Medical Linear Accelerator

Jabbari

Hashemi

2009

IFMBE Proceedings

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Variation in output factor caused by secondary blocking for 7–16 MeV electron beams

Cited by 12 publications

References 0 publications

Monte Carlo calculations of electron beam output factors for a medical linear accelerator

Monte Carlo calculations of electron beam output factors for a medical linear accelerator

The root percent depth dose method for calculating monitor units for irregularly shaped electron fields

A Monte Carlo Study of the Particle Angular Distributions from the Electron Applicators of a Medical Linear Accelerator

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