Out-of-field doses in children treated for large arteriovenous malformations using hypofractionated gamma knife radiosurgery and intensity-modulated radiation therapy

(EURADOS) De Saint-Hubert, Marijke; Majer, Marija; Hršak, Hrvoje; Heinrich, Zdravko; Knežević, Željka; Miljanić, Saveta; Porwol, Paulina; Stolarczyk, Liliana; Vanhavere, Filip; Harrison, Roger M. (2018) Out-of-field doses in children treated for large arteriovenous malformations using hypofractionated gamma knife radiosurgery and intensity-modulated radiation therapy. Radiation Protection Dosimetry, 181 (2). pp. 100-110. ISSN 0144-8420

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Abstract

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 emphasize their importance.

Item Type:	Article
Uncontrolled Keywords:	Out-of-field organ doses ; TLD, OSL and RPL dosimetry ; radiotherapy
Subjects:	NATURAL SCIENCES > Physics NATURAL SCIENCES > Chemistry NATURAL SCIENCES > Interdisciplinary Natural Sciences > Radiation Science
Divisions:	Division of Materials Chemistry
Depositing User:	Željka Knežević Medija
Date Deposited:	06 May 2019 13:17
URI:	http://fulir.irb.hr/id/eprint/4507
DOI:	10.1093/rpd/ncx301

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