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Lookup NU author(s): Dr Roger Harrison
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© The Author(s) 2018. Published by Oxford University Press. All rights reserved. The purpose of this study was to measure out-of-field organ doses in two anthropomorphic child phantoms for the treatment of large brain arteriovenous malformations (AVMs) using hypofractionated gamma knife (GK) radiosurgery and to compare these with an alternative treatment using intensity-modulated radiation therapy (IMRT). Target volume was identical in size and shape in all cases. Radiophotoluminescent (RPL), thermoluminescent (TL) and optically stimulated luminescent (OSL) dosimeters were used for out-of-field dosimetry during GK treatment and a good agreement within 1-2% between results was shown. In addition, the use of multiple dosimetry systems strengthens the reliability of the findings. The number of GK isocentres was confirmed to be important for the magnitude of out-of-field doses. Measured GK doses for the same distance from the target, when expressed per target dose and isocentre, were comparable in both phantoms. GK out-of-field doses averaged for both phantoms were evaluated to be 120 mGy/Gy for eyes then sharply reduced to 20 mGy/Gy for mandible and slowly reduced up to 0.8 mGy/Gy for testes. Taking into account the fractionation regimen used to treat AVM patients, the total treatment organ doses to the out-of-field organs were calculated and compared with IMRT. The eyes were better spared with GK whilst for more distant organs doses were up to a factor of 2.8 and 4 times larger for GK compared to IMRT in 5-year and 10-year old phantoms, respectively. Presented out-of-field dose values are specific for the investigated AVM case, phantoms and treatment plans used for GK and IMRT, but provide useful information about out-of-field dose levels and emphasise their importance.
Author(s): De Saint-Hubert MD, Majer M, Hrsak H, Heinrich Z, Knezevic Z, Miljanic S, Porwol P, Stolarczyk L, Vanhavere F, Harrison RM
Publication type: Article
Publication status: Published
Journal: Radiation Protection Dosimetry
Year: 2018
Volume: 181
Issue: 2
Pages: 100-110
Print publication date: 01/10/2018
Online publication date: 17/01/2018
Acceptance date: 20/12/2017
ISSN (print): 0144-8420
ISSN (electronic): 1742-3406
Publisher: Oxford University Press
URL: https://doi.org/10.1093/rpd/ncx301
DOI: 10.1093/rpd/ncx301
PubMed id: 29351691
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