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  4. Update of the CLRP TG-43 Parameter Database for Brachytherapy Sources

Update of the CLRP TG-43 Parameter Database for Brachytherapy Sources

H Safigholi1*, M J P Chamberland1,2, R E P Taylor1,3, C H Allen1, M P Martinov1, D W O Rogers1, R W Thomson1, (1) Carleton Laboratory for Radiotherapy Physics, Department of Physics, Carleton University, Ottawa, ON, CA (2) The University of Vermont Medical Center, Burlington, VT, USA (3) Multi Leaf Consulting, Port Elgin, ON, CA

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: update the CLRP TG-43 dosimetry database for low- and high-energy brachytherapy sources using the open-source EGSnrc application egs_brachy. Version 2 of the CLRP database, CLRPv2, updates and improves the 2008 version, CLRPv1, which was calculated using the BrachyDose code. CLRPv2 currently includes datasets for 45 sources (17 Pd-103, 21 I-125, 1 Cs-131, 5 Ir-192), and will contain the datasets for other high-energy sources. For validation, results are compared with CLRPv1 data and other literature data.


Methods: include calculated values of DRCs, radial dose functions, 1D and 2D anisotropy functions, along-away dose-rate tables, Primary-scatter separation dose tables (for some sources), and the mean photon energy escaping the sources. The source geometry modelling has been systematically checked and updated. Unlike CLRPv1, the datasets include statistical uncertainty on the source volume corrections needed for phantom voxels containing part of the source.


Results: uncertainties, source volume corrections, and source geometry models have all been improved. To date, the CLRPv2 DRC values agreed with the CLRPv1 values results within 0.6% when no changes in the geometry were needed. Updates of the geometry models were required for 4 sources leading to DRC changes of up to 4.2%. The calculated DRCs for I-125 sources are, on average 2.7% less than recommended TG-43 consensus values, ranging from -6.1% to 1.5% different. Similarly, for Pd-103 sources the DRCs are on average 3.3% less, ranging from -5.9% to -0.3% different than the consensus values. For Ir-192, consensus DRCs are based only on calculated values and for the 3 cases with comparable values, the average difference is only 0.2%. Details for other dosimetry parameters will be provided at https://physics.carleton.ca/clrp/egs_brachy/seed_database_v2


Conclusion: CLPv2 database provides accurate TG-43 dosimetry parameters, complementing the source models freely distributed with egs_brachy. This database has applications in research, dosimetry, and brachytherapy planning.

Funding Support, Disclosures, and Conflict of Interest: This work was supported by the Natural Sciences and Engineering Research Council of Canada, the Canada Research Chairs program, the Ministry of Research and Innovation of Ontario, and a Compute Canada National Resource Allocation.

Keywords

Dosimetry Protocols, Monte Carlo, Brachytherapy

Taxonomy

TH- Brachytherapy: Computational dosimetry: Monte Carlo

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