The clinical implementation of a method for calculating the output factor and per cent depth dose for an electron beam

Choi, D; Mobit, Paul N; Breitman, K.

doi:10.1088/0031-9155/48/7/307

Cited by 7 publications

(9 citation statements)

References 12 publications

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“…Hence, because the dose distribution can be changed due to the multiple scattering of electrons, studies on the multiple scattering have been carried out [11][12][13]. Lee et al studied the dose distribution of the electron beam according to the manufactured form of the cut-out block in the electron beam therapy.…”

Section: Discussionmentioning

confidence: 99%

A Study on Effective Source-Skin Distance using Phantom in Electron Beam Therapy

Kim¹,

Lee²,

Heo³

et al. 2014

Journal of Magnetics

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In this study, for 6-20 MeV electron beam energy occurring in a linear accelerator, the authors attempted to investigate the relation between the effective source-skin distance and the relation between the radiation field and the effective source-skin distance. The equipment used included a 6-20 MeV electron beam from a linear accelerator, and the distance was measured by a ionization chamber targeting the solid phantom. The measurement method for the effective source-skin distance according to the size of the radiation field changes the source-skin distance (100, 105, 110, 115 cm) for the electron beam energy (6,9,12, 16, 20 MeV). The effective source-skin distance was measured using the method proposed by Faiz Khan, measuring the dose according to each radiation field (6 × 6, 10 × 10, 15 × 15, 20 × 20 cm 2 ) at the maximum dose depth (1.3, 2.05, 2.7, 2.45, 1.8 cm, respectively) of each energy. In addition, the effective source-skin distance when cut-out blocks (6 × 6, 10 × 10, 15 × 15 cm 2 ) were used and the effective source-skin distance when they were not used, was measured and compared. The research results showed that the effective source-skin distance was increased according to the increase of the radiation field at the same amount of energy. In addition, the minimum distance was 60.4 cm when the 6 MeV electron beams were used with 6 × 6 cut-out blocks and the maximum distance was 87.2 cm when the 6 MeV electron beams were used with 20 × 20 cut-out blocks; thus, the largest difference between both of these was 26.8 cm. When comparing the before and after the using the 6 × 6 cut-out block, the difference between both was 8.2 cm in 6 MeV electron beam energy and was 2.1 cm in 20 MeV. Thus, the results showed that the difference was reduced according to an increase in the energy. In addition, in the comparative experiments performed by changing the size of the cut-out block at 6 MeV, the results showed that the source-skin distance was 8.2 cm when the size of the cut-out block was 6 × 6, 2.5 cm when the size of the cut-out block was 10 × 10, and 21.4 cm when the size of the cut-out block 15 × 15. In conclusion, it is recommended that the actual measurement is used for each energy and radiation field in the clinical dose measurement and for the measurement of the effective source-skin distance using cut-out blocks.

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Section: Discussionmentioning

confidence: 99%

A Study on Effective Source-Skin Distance using Phantom in Electron Beam Therapy

Kim¹,

Lee²,

Heo³

et al. 2014

Journal of Magnetics

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“…Since the enhanced sector integration model is, in some way, related to the sector integration model by Jursinic and Mueller 14 ͑later modified by Choi and co-workers 15,16 ͒, it would be beneficial to compare them to highlight differences and improvements in the accuracy of the calculations.…”

Section: Discussionmentioning

confidence: 99%

“…Apart from the empirical and theoretical models, there was a few published semiempirical models based on the sector integration concept. [13][14][15][16] The sector integration concept was similar to the one introduced by Clarkson 17 for the calculation of the output factor for photon beams. The original method by Jursinic and Mueller 14 has been further modified by Choi and co-workers 15,16 to allow for the calculation of ROF of irregular shaped electron fields in the case of extended source to surface distance.…”

Section: Introductionmentioning

confidence: 99%

“…[13][14][15][16] The sector integration concept was similar to the one introduced by Clarkson 17 for the calculation of the output factor for photon beams. The original method by Jursinic and Mueller 14 has been further modified by Choi and co-workers 15,16 to allow for the calculation of ROF of irregular shaped electron fields in the case of extended source to surface distance. Nevertheless, one of the limitations of their methods was the inability to calculate the depth of maximum dose d max shift to shallower depths for very small electron fields and the accuracy of ROF for the concaved shaped cutouts was rather poor ͑errorsϾ 3%͒.…”

Section: Introductionmentioning

confidence: 99%

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An enhanced sector integration model for output and dose distribution calculation of irregular concave shaped electron beams

Gajewski¹

2009

Medical Physics

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A comprehensive method of output factor and dose distribution calculation for electron beams has been developed. It allows one to calculate the output factors and isodose distributions in water of arbitrary shaped electron fields with excellent accuracy even for the cases of concaved, small, elongated beams, and extended source to surface distances (SSDs). The method requires two sets of data: Depth dose distribution per monitor unit for circular cutouts and depth dose distributions per monitor unit for circular blocks (plugs), both for two SSDs, one reference of 100 cm and second extended one. The method has been extensively tested using a combination of different irregular cutouts and various SSDs for the 6 and 9 MeV electron beams. The calculated values agreed with the measured data well within 1% for output factors and below 1 for gamma (gamma test) for isodose distributions. The computer program has been developed to facilitate the method for practical application. The method has been used for almost 8 years considerably cutting workload in the department.

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“…[1][2][3] Monte Carlo calculations have likewise been used to obtain accurate estimates of both ROF and PDD for clinical electron beams. [4][5][6][7][8] The published Monte Carlo methods require a separate simulation of individual inserts.…”

Section: Introductionmentioning

confidence: 99%

Final Aperture Superposition Technique applied to fast calculation of electron output factors and depth dose curves

Faddegon¹,

Villarreal-Barajas²

2005

Medical Physics

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The Final Aperture Superposition Technique (FAST) is described and applied to accurate, near instantaneous calculation of the relative output factor (ROF) and central axis percentage depth dose curve (PDD) for clinical electron beams used in radiotherapy. FAST is based on precalculation of dose at select points for the two extreme situations of a fully open final aperture and a final aperture with no opening (fully shielded). This technique is different than conventional superposition of dose deposition kernels: The precalculated dose is differential in position of the electron or photon at the downstream surface of the insert. The calculation for a particular aperture (x-ray jaws or MLC, insert in electron applicator) is done with superposition of the precalculated dose data, using the open field data over the open part of the aperture and the fully shielded data over the remainder. The calculation takes explicit account of all interactions in the shielded region of the aperture except the collimator effect: Particles that pass from the open part into the shielded part, or visa versa. For the clinical demonstration, FAST was compared to full Monte Carlo simulation of 10 x 10, 2.5 x 2.5, and 2 x 8 cm2 inserts. Dose was calculated to 0.5% precision in 0.4 x 0.4 x 0.2 cm3 voxels, spaced at 0.2 cm depth intervals along the central axis, using detailed Monte Carlo simulation of the treatment head of a commercial linear accelerator for six different electron beams with energies of 6-21 MeV. Each simulation took several hours on a personal computer with a 1.7 Mhz processor. The calculation for the individual inserts, done with superposition, was completed in under a second on the same PC. Since simulations for the pre calculation are only performed once, higher precision and resolution can be obtained without increasing the calculation time for individual inserts. Fully shielded contributions were largest for small fields and high beam energy, at the surface, reaching a maximum of 5.6% at 21 MeV. Contributions from the collimator effect were largest for the large field size, high beam energy, and shallow depths, reaching a maximum of 4.7% at 21 MeV. Both shielding contributions and the collimator effect need to be taken into account to achieve an accuracy of 2%. FAST takes explicit account of the shielding contributions. With the collimator effect set to that of the largest field in the FAST calculation, the difference in dose on the central axis (product of ROF and PDD) between FAST and full simulation was generally under 2%. The maximum difference of 2.5% exceeded the statistical precision of the calculation by four standard deviations. This occurred at 18 MeV for the 2.5 x 2.5 cm2 field. The differences are due to the method used to account for the collimator effect.

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The clinical implementation of a method for calculating the output factor and per cent depth dose for an electron beam

Cited by 7 publications

References 12 publications

A Study on Effective Source-Skin Distance using Phantom in Electron Beam Therapy

A Study on Effective Source-Skin Distance using Phantom in Electron Beam Therapy

An enhanced sector integration model for output and dose distribution calculation of irregular concave shaped electron beams

Final Aperture Superposition Technique applied to fast calculation of electron output factors and depth dose curves

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