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The collapsed cone superposition algorithm applied to scatter dose calculations in brachytherapy
Author(s) -
Carlsson Åsa K.,
Ahnesjö Anders
Publication year - 2000
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.1290485
Subject(s) - superposition principle , imaging phantom , monte carlo method , brachytherapy , physics , scattering , photon , dosimetry , computational physics , fluence , optics , mathematics , nuclear medicine , radiation therapy , statistics , medicine , laser , quantum mechanics
Methods for scatter dose calculations in brachytherapy have been developed based on the collapsed cone superposition algorithm. The methods account for effects on the scatter dose caused by the three‐dimensional distribution of heterogeneities in the irradiated volume and are considerably faster than methods based on straightforward superposition of kernels or direct Monte Carlo simulations. Use of a successive‐scattering approach, in which the dose contribution from once‐ and multiply scattered photons are calculated separately, was found superior to conventional superposition using a single point kernel for all scatter generations. Use of the successive‐scattering approach significantly reduces artifacts stemming from steep fluence gradients, typical of the brachytherapy geometry and critical for the collapsed cone approximation. The algorithm is tested versus Monte Carlo simulations for point sources of energies 28.4, 100, 350, and 662 keV. Results agree well for both a homogeneous water phantom and an air–water half‐phantom.