Abstract Book

ESTRO 37

S554

printing technology. Gafchromic EBT3 films were used for measurements of the dose distribution. They were cut as like shape of applicator and fixed around the applicator mounted to miniature brachytherapy source. EBT3 films were irradiated in the water for 5 minutes. Results Fabricated electronic brachytherapy source was stably operated at 50 kV, the current of brachytherapy source was 253 mA. The X-ray energy spectra was measured at 40kV and 50 kV. Both X-ray spectra have tungsten characteristics and broad bremsstrahlung X-rays with the energies up to 40keV and 50 keV respectively. The x-ray angular dose distribution was measured from +122.4° to - 122.4° at 1 cm in the air. The X-ray intensity difference in the range of 244.8° was about 20% with decrease 108.1 to 87.0±0.9 Gy/min. Percent depth doses(PDD) were measured without x-ray filter and with 1mm, 2mm x-ray filter. The PDD of without filter was more steeper dose gradient than PDDs of 1mm, 2 mm x-ray filter. The suitable treatment range can be controlled by changing of x-ray filter thickness and tube voltage. A dose of 9.8 Gy was delivered at 5 mm to hemisphere direction and average dose of 8.45±0.21 Gy was delivered to linear direction. The delivered dosage can be controlled by changing irradiation time, x-ray energy and dwell position of fabricated electronic brachytherapy source. Conclusion The study results show that the fabricated cylindrical applicator mounted miniature electronic brachytherapy source based on CNT field emission can potentially be applied for electronic intravaginal brachytherapy because of its low energy, steep dose gradient, dose distribution. Further work is needed to get homogeneous dose distribution around cylindrical applicator to verify optimization of dwell position and X-ray energy. PO-0996 Dynamic Wave Arc for lung SBRT: compliance with RTOG dosimetric criteria. C. Collen 1 , M. Burghelea 2 , R. Van den Begin 1 , G. Coussement 1 , B. Engels 1 , T. Gevaert 1 , M. De Ridder 1 1 Universitair Ziekenhuis Brussel, Radiotherapy, Brussels, Belgium 2 Universitair Ziekenhuis Brussel, Radiation Oncology, Brussels, Belgium Purpose or Objective Dynamic Wave Arc (DWA) is a novel non-coplanar VMAT solution clinically implemented in our department. We report on the compliance with RTOG 0813 and 0915 dosimetric criteria for lung SBRT using DWA. Material and Methods

Conclusion A proof of concept of an automated sanity check for online plan adaptation was successfully demonstrated. Our algorithm was able to identify poor quality plans resulting from the target moving out of reach of the beam, using the center of mass of the fluence distribution. Other parameters that are approximately conserved during plan adaptation were identified. PO-0995 Development of cylindrical applicator for CNT based miniature electronic brachytherapy source H.J. Kim 1 , J.H. Lee 2 , C.Y. Jeong 1 , J.W. Kwak 1 , S.O. Cho 2 , B.C. Cho 2 , S.W. Lee 1 1 ASAN Medical Center, Department of Radiation Oncology, Songpa-gu- Seoul, Korea Republic of 2 Korea Advanced Institute of Science and Technology, Department of Nuclear and Quantum Engineering, Daegeon, Korea Republic of Purpose or Objective Electronic brachytherapy source based on thermionic emission type is promising new technology to replace brachytherapy using isotopes because of its low energy and steep dose gradient. Recently, miniature X-ray sources using carbon nanotube (CNT) field emission is developed for some clinical applications. The purpose of this study was to fabricate cylindrical applicator of CNT based miniature electronic brachytherapy source with homogeneous X-ray dose distribution around cylindrical applicator for intravaginal brachytherapy. Material and Methods The miniature electronic brachytherapy source based on CNT field emission was fabricated for electronic brachytherapy. The diameter of the fabricated miniature brachytherapy source is 7 mm and the length is 47 mm. The cylindrical application was designed using a Monte Carlo N-Particle eXtended (MCNPX) to create homogeneous X-ray dose distribution along the cylindrical applicator. The optimized design was fabricated with 3D

This study evaluated the lung SBRT plans of patients enrolled in a prospective trial (NCT 02224547). Internal target volumes (ITVs) were generated combining gross tumor volumes of all 10 respiratory phases on a 4DCT. Planning target volumes (PTVs) consisting of ITV + 5 mm margin and all organs at risk (OARs) were delineated on