Out-of-Field Doses in Children Treated for Large Arteriovenous Malformations Using Hypofractionated Gamma Knife Radiosurgery and Intensity-Modulated Radiation Therapy

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.

Neutron Radiation Dose Measurements in a Scanning Proton Therapy Room: Can Parents Remain Near Their Children During Treatment?

“…For these measurements, extended-range Bonner sphere spectrometry systems, neutron rem counters, and tissue-equivalent proportional counters were used and benchmarked to help in selecting the optimal detector for proton therapy neutron spectra (15). In addition to environmental measurements, EURADOS WG9 also measured neutron doses in both water and anthropomorphic phantoms, using bubble, etched track, thermoluminescent, and radiophotoluminescent detectors (16)(17)(18)(19)(20).…”

Out-of-Field Doses Produced by a Proton Scanning Beam Inside Pediatric Anthropomorphic Phantoms and Their Comparison With Different Photon Modalities

“…Out-of-field doses following (IMPT) were compared with previous measurements carried out within EURADOS WG9 for different photon radiotherapy techniques: IMRT, 3D-CRT, and GK treatment. Photon measurements were performed on a Varian Clinac 2300 linear accelerator (LINAC) in the Centre of Oncology, Krakow, Poland, and on a Leksell Gamma Knife (GK) (Model 4 C, Elekta Instruments, Stockholm, Sweden) at University Hospital Centre Zagreb, Croatia ( 33 , 34 ). It is important to note that phantoms and detectors which were used in previous experiments as well as target location were the same as for proton irradiations.…”

“…Firstly, WG9 performed detailed characterization of the out-of-field doses, associated with proton PBS in a water phantom with both measurements and MC simulation, which clearly showed complexity associated with the secondary radiation field produced in proton PBS ( 22 , 29 – 31 ). The next step included measurement campaigns organized by WG9 in the Centre of Oncology, Krakow University Hospital Centre Zagreb, and University Hospital Osijek to study secondary radiation for different photon radiotherapy techniques ( 32 – 34 ). Those experiments were followed by a measurement campaign which is presented in this paper dedicated to proton radiotherapy with pencil beam scanning technique (PBS) carried out at the Cyclotron Centre Bronowice IFJ PAN (Krakow, Poland) ( 29 ).…”

The European radiation dosimetry group – Review of recent scientific achievements

“…The second study compares out-of-field doses in children treated for large arteriovenous malformations (AVMs) using hypofractionated GK radiosurgery and IMRT (De Saint-Hubert et al, 2018). This study employed similar materials and methods to Majer et al (2017), in that out-of-field organ doses in two anthropomorphic child phantoms (5 y and 10 y) were measured, using RPL, TL and optically stimulated luminescence (OSL).…”