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

Kapur, Ajay; M., C.; Mok, E; Findley, David O.; Boyer, Arthur L.

doi:10.1088/0031-9155/43/12/007

Cited by 77 publications

(85 citation statements)

References 34 publications

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“…An example of the latter is given by Kapur et al 44 These types of systems are not in widespread clinical use, but may become more prevalent in the future. Details of these approaches are also discussed in the AAPM TG 70 report.…”

Section: B2 Field-size Determinationmentioning

confidence: 99%

Monitor unit calculations for external photon and electron beams: Report of the AAPM Therapy Physics Committee Task Group No. 71

et al. 2014

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A protocol is presented for the calculation of monitor units (MU) for photon and electron beams, delivered with and without beam modifiers, for constant source-surface distance (SSD) and source-axis distance (SAD) setups. This protocol was written by Task Group 71 of the Therapy Physics Committee of the American Association of Physicists in Medicine (AAPM) and has been formally approved by the AAPM for clinical use. The protocol defines the nomenclature for the dosimetric quantities used in these calculations, along with instructions for their determination and measurement. Calculations are made using the dose per MU under normalization conditions, D 0 , that is determined for each user's photon and electron beams. For electron beams, the depth of normalization is taken to be the depth of maximum dose along the central axis for the same field incident on a water phantom at the same SSD, where D 0 = 1 cGy/MU. For photon beams, this task group recommends that a normalization depth of 10 cm be selected, where an energy-dependent D 0 ≤ 1 cGy/MU is required. This recommendation differs from the more common approach of a normalization depth of d m , with D 0 = 1 cGy/MU, although both systems are acceptable within the current protocol. For photon beams, the formalism includes the use of blocked fields, physical or dynamic wedges, and (static) multileaf collimation. No formalism is provided for intensity modulated radiation therapy calculations, although some general considerations and a review of current calculation techniques are included. For electron beams, the formalism provides for calculations at the standard and extended SSDs using either an effective SSD or an air-gap correction factor. Example tables and problems are included to illustrate the basic concepts within the presented formalism.

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Section: B2 Field-size Determinationmentioning

confidence: 99%

Monitor unit calculations for external photon and electron beams: Report of the AAPM Therapy Physics Committee Task Group No. 71

et al. 2014

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“…( 9 – 12 ) Insert correction factors have dose components from both direct and scattered particles. Direct electrons, which typically contribute 80% to 90% of the dose at

R_{100}

, are the primary influence on the shape of the ICF curve.…”

Section: Resultsmentioning

confidence: 99%

“…A number of successful attempts were made ( 9 – 12 ) to predict the values of OFs for a given insert using Monte Carlo methods. Most of the work was done for regular inserts (circle, square, and rectangle).…”

Section: Methodsmentioning

confidence: 99%

“…More recently, a number of investigators ( 9 – 12 ) have been evaluating Monte Carlo methods to calculate OFs for electron beams shaped using square, rectangular, and circular inserts. The consensus among investigators is that the Monte Carlo methods have the potential to accurately predict the OFs for electron beams (13) .…”

Section: Introductionmentioning

confidence: 99%

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Monte Carlo calculations of output factors for clinically shaped electron fields

Turian

Smith

Bernard

et al. 2004

J Applied Clin Med Phys

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We report on the use of the EGS4/BEAM Monte Carlo technique to predict the output factors for clinically relevant, irregularly shaped inserts as they intercept a linear accelerator's electron beams. The output factor for a particular combination—energy, cone, insert, and source‐to‐surface distance (SSD)—is defined in accordance with AAPM TG‐25 as the product of cone correction factor and insert correction factor, evaluated at the depth of maximum dose. Since cone correction factors are easily obtained, we focus our investigation on the insert correction factors (ICFs). An analysis of the inserts used in routine clinical practice resulted in the identification of a set of seven “idealized” shapes characterized by specific parameters. The ICFs for these shapes were calculated using a Monte Carlo method (EGS4/BEAM) and measured for a subset of them using an ion chamber and well‐established measurement methods. Analytical models were developed to predict the Monte Carlo–calculated ICF values for various electron energies, cone sizes, shapes, and SSDs. The goodness‐of‐fit between predicted and Monte Carlo–calculated ICF values was tested using the Kolmogorov–Smirnoff statistical test. Results show that Monte Carlo–calculated ICFs match the measured values within 2.0% for most of the shapes considered, except for few highly elongated fields, where deviations up to 4.0% were recorded. Predicted values based on analytical modeling agree with measured ICF values within 2% to 3% for all configurations. We conclude that the predicted ICF values based on modeling of Monte Carlo–calculated values could be introduced in clinical use.PACS numbers: 87.53.Wz, 87.53.Hv

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“…To demonstrate this, we compare the model calculated cutout factors with those measured and calculated by Kapur et al using a full Monte Carlo simulation. 45 …”

Section: Model Verificationmentioning

confidence: 99%

A Multileaf Collimator for Modulated Electron Radiation Therapy for Breast Cancer

Song¹,

Jiang²

2002

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

Cited by 77 publications

References 34 publications

Monitor unit calculations for external photon and electron beams: Report of the AAPM Therapy Physics Committee Task Group No. 71

Monitor unit calculations for external photon and electron beams: Report of the AAPM Therapy Physics Committee Task Group No. 71

Monte Carlo calculations of output factors for clinically shaped electron fields

A Multileaf Collimator for Modulated Electron Radiation Therapy for Breast Cancer

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