OUT-OF-FIELD DOSE MEASUREMENTS FOR 3D CONFORMAL AND INTENSITY MODULATED RADIOTHERAPY OF A PAEDIATRIC BRAIN TUMOUR.
The purpose of this study was to measure out-of-field organ doses in clinical conditions in anthropomorphic paediatric phantoms which received a simulated treatment of a brain tumour with intensity modulated radiotherapy (IMRT) and 3D conformal radiotherapy (3D CRT). Organ doses measured with radiophotoluminescent and thermoluminescent dosemeters were on average 1.6 and 3.0 times higher for the 5 y-old than for the 10 y-old phantom for IMRT and 3D CRT, respectively. A larger 5-y to 10-y organ dose ratio for 3D CRT can be explained because the use of a mechanical wedge for the 5-y-old 3D CRT phantom treatment increased out-of-field doses. Due to different configurations of the radiation fields, for both phantoms, the IMRT technique resulted in a higher non-target brain dose and higher eye doses but lower thyroid doses compared to 3D CRT. For 3D CRT (which used a non-coplanar field configuration), eye doses were 3-6% and for IMRT (which used a coplanar field configuration) 27-30% of the treatment dose, respectively. For thyroid and more distant organs, doses were less than 1% of the treatment dose. Comparison of measured doses and doses calculated by the treatment planning system (TPS) showed that the TPS underestimated out-of-field doses both for IMRT and 3D CRT.
Ruder Boškovic Institute, Bijenicka cesta 54, 10000 Zagreb, Croatia.
Marija
M
Majer
Institute of Nuclear Physics PAN, Radzikowskiego 152, 31-342 Krakow, Poland.
Liliana
L
Stolarczyk
Belgium Nuclear Research Center (SCK-CEN), Boeretang 200, BE-2400 Mol, Belgium.
Marijke
M
De Saint-Hubert
Centre of Oncology M. Sklodowska-Curie Memorial Institute, Garncarska 11, 31-115 Krakow, Poland.
Damian
D
Kabat
Ruder Boškovic Institute, Bijenicka cesta 54, 10000 Zagreb, Croatia.
Željka
Ž
Kneževic
Ruder Boškovic Institute, Bijenicka cesta 54, 10000 Zagreb, Croatia.
Saveta
S
Miljanic
Institute of Nuclear Physics PAN, Radzikowskiego 152, 31-342 Krakow, Poland.
Natalia
N
Mojzeszek
University of Newcastle, Faculty of Medical Sciences, Newcastle upon Tyne NE2 4HH, UK.
Roger
R
Harrison
D001932:Brain Neoplasms / Q000532:radiotherapy*; D002648:Child; D002675:Child, Preschool; D061888:Craniospinal Irradiation / Q000379:methods*; D006801:Humans; D008953:Models, Anatomic; D058958:Organs at Risk / Q000528:radiation effects; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal; D050397:Radiotherapy, Intensity-Modulated