Collapsed cone dose calculations for heterogeneous tissues in brachytherapy using primary and scatter separation source data
2017 (English)In: Computer Methods and Programs in Biomedicine, ISSN 0169-2607, E-ISSN 1872-7565, Vol. 139, 17-29 p.Article in journal (Refereed) Published
Background and Objective: Brachytherapy is a form of radiation therapy using sealed radiation sources inserted within or in the vicinity of the tumor of, e.g., gynecological, prostate or head and neck cancers. Accurate dose calculation is a crucial part of the treatment planning. Several reviews have called for clinical software with model-based algorithms that better take into account the effects of patient individual distribution of tissues, source-channel and shielding attenuation than the commonly employed TG-43 formalism which simply map homogeneous water dose distributions onto the patient. In this paper we give a comprehensive and thorough derivation of such an algorithm based on collapsed cone point-kernel superposition, and describe details of its implementation into a commercial treatment planning system for clinical use. Methods: A brachytherapy version of the collapsed-cone algorithm using analytical raytraces of the primary photon radiation followed by successive scattering dose calculation for once and multiply scattered photons is described in detail, including derivation of the corresponding set of recursive equations for energy transport along cone axes/transport lines and the coupling to clinical source modeling. Specific implementation issues for setting up of the calculation grid, handling of intravoxel gradients and voxels partly containing non patient applicator material are given. Results: Sample runs for two clinical cases are shown, one being a gynecological application with a tungsten-shielded applicator and one a breast implant. These two cases demonstrate the impact of improved dose calculation versus TG-43 formalism. Conclusions: Use of model-based dose calculation algorithms for brachytherapy taking the three-dimensional treatment geometry into account increases the dosimetric accuracy in planning and follow up of treatments. The comprehensive description and derivations provided gives a rigid background for further clinical, educational and research applications. (C) 2016 Elsevier Ireland Ltd. All rights reserved.
Place, publisher, year, edition, pages
ELSEVIER IRELAND LTD , 2017. Vol. 139, 17-29 p.
Brachytherapy; Radiotherapy treatment planning; Model-based dose calculation; Advanced collapsed cone engine; Point kernel superposition
Radiology, Nuclear Medicine and Medical Imaging
IdentifiersURN: urn:nbn:se:liu:diva-136324DOI: 10.1016/j.cmpb.2016.10.022ISI: 000395223200003PubMedID: 28187887OAI: oai:DiVA.org:liu-136324DiVA: diva2:1087926
Funding Agencies|Swedish Cancer Foundation [CAN 2015/618]2017-04-102017-04-102017-04-10