A three-Gaussian fit of phantom scatter correction data

Gasteren, van Jjm; Laarse, van der R; Venselaar, J.L.M.; Heukelom, S.; Jager, H.N.; Kleffens, van Hj Herman; Westermann, C.F.

doi:10.1088/0031-9155/43/3/009

Cited by 4 publications

(2 citation statements)

References 4 publications

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“…When tissue-phantom ratios (TPRs) are used for dose calculations, one needs the relative phantom scatter correction factors S p (s) as a function of equivalent square field size s at the depth of normalization d N . A model recently proposed by van Gasteren et al (1998) describes S p (r) for circular fields with radius r by a summation of three Gaussian distributions:…”

Section: Introductionmentioning

confidence: 99%

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Comparing two methods for calculating phantom scatter

McDonough

Xiao²,

Bjärngard³

1999

Phys. Med. Biol.

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Two methods are compared for calculating the field-size dependence of the phantom scatter component of dose for x-ray beams. One model sums three Gaussian distributions; the other model is a two-parameter function. With a measurement of the beam quality as input to determine parameters, both models accurately reproduce the relative phantom scatter. However, there are important differences between the models. For all beam energies, the two-parameter model characterizes the absolute phantom scatter as a function of depth and field size, while, also for all beam energies, the six-parameter Gaussian model characterizes the relative phantom scatter at a single depth of 10 cm. For small field sizes, the phantom scatter calculated from the two-parameter model agrees with Monte Carlo calculations better than the Gaussian model. In the Gaussian model, the parameters can be obtained for beam energies between 60Co and 25 MV by linear interpolation based on the measured beam quality. In the two-parameter model, and for energies above 4 MV, the parameters can be obtained using linear functions of the dose-weighted average linear attenuation coefficient, which is related to beam quality.

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Section: Introductionmentioning

confidence: 99%

“…The six free parameters are determined by fitting S p (r) at a depth of 10 cm for seven photon beams ranging in energy from 60 Co to 25 MV. Van Gasteren et al (1998) showed that the parameters for other photon beams can be interpolated from the results using the quality index (QI), i.e. the ratio of TPRs measured at 20 and 10 cm depths.…”

Section: Introductionmentioning

confidence: 99%

Comparing two methods for calculating phantom scatter

McDonough

Xiao²,

Bjärngard³

1999

Phys. Med. Biol.

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Photon pencil kernel parameterisation based on beam quality index

Nyholm

Olofsson

Ahnesjö

et al. 2006

Radiotherapy and Oncology

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Monitor unit calculation on the beam axis of open and wedged asymmetric high-energy photon beams

Georg

1999

Phys. Med. Biol.

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An ESTRO booklet and a report of the Netherlands Commission on Radiation Dosimetry have been published recently describing empirical methods for monitor unit (MU) calculations in symmetrical high-energy photon beams. Both documents support the same basic ideas; firstly the separation of head scatter and volume scatter components and secondly the determination of head scatter quantities in a mini-phantom. Based on these ideas the methods previously described for MU calculations in symmetrical beams are extended to asymmetrical open and wedged beams in isocentric treatment conditions. All required dosimetric parameters (normalized head scatter factors, phantom scatter correction factors, wedge factors, off-axis ratios, quality index, and depth dose parameters) are determined as a function of beam axis position in order to study their off-axis dependence. Measurements are performed for 6 MV and 18 MV photon beams provided by two different dual-energy linear accelerators, a GE Saturne 42 and a Varian 2100 CD linac.

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A three-Gaussian fit of phantom scatter correction data

Cited by 4 publications

References 4 publications

Comparing two methods for calculating phantom scatter

Comparing two methods for calculating phantom scatter

Photon pencil kernel parameterisation based on beam quality index

Monitor unit calculation on the beam axis of open and wedged asymmetric high-energy photon beams

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