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An equivalent square field formula for determining head scatter factors of rectangular fields.

S Kim·T C Zhu·J R Palta
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Abstract

A simple formula is derived for the calculation of an equivalent square field that gives the same head scatter factor as a given rectangular field. This formula is based strictly on the configuration of a medical linear accelerator treatment head. The geometric parameters used are the distances between the target and the top of each field-defining aperture. The formula accounts for both the effect of field elongation and the collimator exchange effect. This method predicts the output to within 1% accuracy for both open and wedged fields and does not require any new measured data other than the field size dependence of head scatter for a range of square field sizes. Interestingly, the formula we derived has the same format as the formula that was empirically obtained by Vadash and Bjärngard [Med. Phys. 20, 733-734 (1993)].

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Biophysical PhenomenaBiophysicsHumansModels, TheoreticalParticle AcceleratorsRadiotherapy, High-EnergyScattering, RadiationJournal Article

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S Kim, T C Zhu, J R Palta. 1997. An equivalent square field formula for determining head scatter factors of rectangular fields.. https://doi.org/10.1118/1.597963

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