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 emphasise
their importance.
Original language | English |
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Pages (from-to) | 1-11 |
Journal | Radiation protection dosimetry |
Volume | 181 |
Issue number | 2 |
DOIs | |
State | Published - 17 Jan 2018 |