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Dosimetric accuracy of a deterministic radiation transport based I 192 r brachytherapy treatment planning system. Part II: Monte Carlo and experimental verification of a multiple source dwell position plan employing a shielded applicator
Author(s) -
Petrokokkinos L.,
Zourari K.,
Pantelis E.,
Moutsatsos A.,
Karaiskos P.,
Sakelliou L.,
Seimenis I.,
Georgiou E.,
Papagiannis P.
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 - 10.1118/1.3567507
Subject(s) - shielded cable , dosimetry , monte carlo method , brachytherapy , imaging phantom , radiation treatment planning , ionization chamber , electromagnetic shielding , physics , nuclear medicine , dose profile , dwell time , optics , computer science , radiation therapy , mathematics , medicine , ion , telecommunications , clinical psychology , statistics , quantum mechanics , ionization
Purpose: The aim of this work is the dosimetric validation of a deterministic radiation transport based treatment planning system ( BRACHYVISION ™ v. 8.8, referred to as TPS in the following) for multipleI192 r source dwell position brachytherapy applications employing a shielded applicator in homogeneous water geometries.Methods: TPS calculations for an irradiation plan employing seven VS2000 I192 r high dose rate (HDR) source dwell positions and a partially shielded applicator (GM11004380) were compared to corresponding Monte Carlo (MC) simulation results, as well as experimental results obtained using the VIP polymer gel–magnetic resonance imaging three‐dimensional dosimetry method with a custom made phantom.Results: TPS and MC dose distributions were found in agreement which is mainly within ±2%. Considerable differences between TPS and MC results (greater than 2%) were observed at points in the penumbra of the shields (i.e., close to the edges of the “shielded” segment of the geometries). These differences were experimentally verified and therefore attributed to the TPS. Apart from these regions, experimental and TPS dose distributions were found in agreement within 2 mm distance to agreement and 5% dose difference criteria. As shown in this work, these results mark a significant improvement relative to dosimetry algorithms that disregard the presence of the shielded applicator since the use of the latter leads to dosimetry errors on the order of 20%–30% at the edge of the “unshielded” segment of the geometry and even 2%–6% at points corresponding to the potential location of the target volume in clinical applications using the applicator (points in the unshielded segment at short distances from the applicator).Conclusions: Results of this work attest the capability of the TPS to accurately account for the scatter conditions and the increased attenuation involved in HDR brachytherapy applications employing multiple source dwell positions and partially shielded applicators.