A sector‐integration method for calculating the output factors of irregularly shaped electron fields

Abstract

Articles you may be interested inFinal Aperture Superposition Technique applied to fast calculation of electron output factors and depth dose curves Med. A practical method for the calculation of multileaf collimator shaped fields output factors Med. Phys. 26, 2385 (1999); 10.1118/1.598754 Monte Carlo investigation of electron beam output factors versus size of square cutout Med. Phys. 26, 743 (1999); 10.1118/1.598582Calculating output factors for photon beam radiotherapy using a convolution/superposition method based on a dual source photon beam model Med.An empirical model is presented that uses a sector-integration method for calculating the output factors of irregularly shaped electron fields. The sector-integration method accounts for changes in electron fluence, lateral scatter equilibrium, and scatter from the edge of a cutout shield. This method is tested for elliptical and rectangular fields with a ratio of the long-to-short axis as great as 4 to 1. Differences between measured and calculated values for output factors were less than Ϯ1%.Comparisons were also carried out for a large number of cutout shields that were used in the clinic and similar levels of accuracy were obtained. © 1997 American Association of Physicists in Medicine. ͓S0094-2405͑97͒01211-X͔

Parameterization of electron beam output factor

“…Khan et al [9] reported a method for predicting ROF with irregular field using lateral build-up ratio concept. The sector integration concept [4,5,21], which is similar to Clarkson's model for calculation of the output factor for photon beams [22], has also been reported with accurate prediction of ROF. Even though we have not verified, sector integration similar to Khan et al [9] could be used with our equation and will be reported in a separate study.…”

“…This accuracy will be sufficient for double check of MUs in a clinical application and as such high energy electron beams with small fields are not often used. Previously several studies reported the use of polynomial functions for fitting to ROF curves [4,19]. Chow et al [20] reported an in-house software for ROF prediction using exponential approximation.…”

“…As a result, the ROF of a specific treatment is usually measured individually in order to achieve an acceptable accuracy. These patient-specific electron measurements are time consuming and prone for significant error due to selection of detector and respective d max .There are many publications on analytical methods to calculate the percent depth dose (PDD) [3] and/or ROF for electron beams, including the sector-integration method [4,5], Gaussian pencil model plus collimator scattering [6,7], two-source model [8], and a method based on the lateral build-up ratio [9e11]. The current generation of treatment planning systems for clinical use depend on pencil-beam algorithms [12,13].…”

Convolution‐based modified Clarkson integration (CMCI) for electron cutout factor calculation

“…In the literature, the methods for predicting cutout output factors for electron beams include the equivalent square,10, 11 square root,12 one‐dimensional,13 and sector‐integration methods 14. These algorithms predict the output factor of an irregular electron field using a database of parameters based on measurements.…”

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

“…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.…”