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SU‐E‐T‐714: Developing a TG‐43U1 Based Dose Calculation Treatment Planning Software for Cs‐137 LDR Brachytherapy
Author(s) -
Sina S,
Faghihi R,
Meigooni A,
Siavashpour Z,
MoslehShirazi M
Publication year - 2011
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 - 10.1118/1.3612676
Subject(s) - brachytherapy , radiation treatment planning , nuclear medicine , medical physics , software , medicine , computer science , radiation therapy , radiology , operating system
Purpose: Old treatment planning systems used for Cs‐137 LDR brachytherapy source use traditional dose calculation method, requiring the exposure rate constant considering each pellet as a point source, not accounting for encapsulation, applicators and spacersˈ effects. Utilizing such methods would introduce significant errors in dose estimation. The TG‐43 formalism is the main dose calculation formalism in most treatment planning softwares. The purpose of this work is to establish a new algorithm for treatment planning based on TG‐43U1 formalism. Methods: STPS software for brachytherapy treatment planning of Selectron Cs‐137 source in Iran, is based on old dose calculation formalism. In this study, a new dose calculation algorithm was esablished based on TG‐43 algorithm for treatment planning software. In this algorithm, the TG‐43 parameters of each active pellet in different places inside the source were obtained by MCNP4c code. Then the dose distribution around every combination of active and inactive pellets can be obtained by summing the dose of active sources. The accuracy of this algorithm was checked by comparing the results of this algorithm for special combination of active and inactive pellets with Monte Carlo simulations. Finally, the uncertainty of old dose calculation formalism was investigated by comparing the results of STPS software with those obtained by the new algorithm. Results: For a typical arrangement of 10 active pellets in the applicator, the percentage difference between doses obtained by the new algorithm at 1cm distance from the tip of the applicator and those obtained by old formalisms is 30%, while the difference between the results of MCNP and the new algorithm is less than 5% at this point. Conclusions: According to the results, dose calculation using “gamma‐ray” based dosimetry formalisms, overestimate the dose especially towards the tip of the applicator. While the new algorithm can perform the dose calculation more accurately.