ESTRO 36 Abstract Book

S971 ESTRO 36 _______________________________________________________________________________________________

treatment, in-vivo EPID transit images (movie files) were acquired during treatment for every field. After the first 3 fractions, in-vivo measurements were repeated on a weekly basis. The PerFRACTION analysis is almost fully automated. Treatment plans were calculated in version 10.6 of Eclipse TM TPS from Varian Medical Systems. The plan, the structure set, the dose distribution and the CT image set are exported to PF server. This server continually searches in R&V and ARIA TM oncology information system, from Varian Medical Systems, for the data of each patient. After each treatment the server gets the recorded log files and the measured EPID Dicom files which are processed and used for the 3D dose distribution calculation. PerFRACTION 3D uses a superposition/convolution type algorithm, the SDC Dose Calculator, to calculate back the dose on the CT image set or on the patient CBCT acquired at the treatment session. Following AAPM TG-218 report, we adopted a tolerance limit (treatable but further evaluation may be warranted) of 95 % of points passing the 3%Global/2mm/10% gamma analysis, and an action limit of 90% (requires additional analysis and may need corrective action). Dose-volume histograms (DVH) analysis obtained by 3D reconstructed dose on the planning CT or CBCT scans allow a clinical interpretation of the deviations and helps to find possible reasons for the discrepancies. PerFRACTION also demands goals definition for specific targets and/or organs at risk which are used to trigger failure email notifications. Results PerFRACTION 3D was launched in the beginning of 2016 and is in an early stage of clinical use, with constant software updates and corrections. In the first two months of the in-vivo dosimetry QA protocol implementation, 30 transit EPID images were acquired during the treatment fractions of 10 patients. PTV 3D overall gamma passing rate was equal to 97.3% ± 1% (1 SD), with all fractions within the adopted tolerance level of 95%. Conclusion The preliminary results for in-vivo dosimetry using PerFRACTION 3D suggests it as a promising tool for detection of treatment discrepancies and their clinical impact. This in-vivo dosimetry approach combined with plan pre-treatment verification can contribute to a more robust patient specific QA as well as to identify more clearly the possible causes of discrepancies such as machine and/or patient related ones. Electronic Poster: Brachytherapy: Breast EP-1766 First experiences using the new Papillon + TM Contact X-Ray Brachytherapy 50KVp (CXB) unit J.P. Gérard 1 , C. Dejean 2 , M.E. Chand 1 , D. Lam Cham Kee 1 , J. Doyen 1 , K. Benezery 1 , J.M. Hannoun-Levi 1 1 Centre Antoine Lacassagne, Radiotherapy, Nice, France 2 Centre Antoine Lacassagne, Physics, Nice, France Purpose or Objective The Papillon 50 TM unit was designed in 2009 to perform CXB treatment using 50 KVp X-Rays with short focus distance (FSD <4cm) and high dose rate (> 15 Gy/mn) aiming at replacing the Philips RT 50 TM to treat endoscopically rectal cancer. In order to treat breast cancer using an intra-operative radiotherapy (IORT) approach a new Papillon + TM ( P+ ) unit was designed (Ariane cpy. UK) and the first prototype was installed in Centre A Lacassagne in Nice during december 2016.

Material and Methods The P+ unit is a battery powered mobile X-Ray generator producing an X-Ray beam with a peak energy of 30 or 50 KVp. A tungsten transmission anode is liquid cooled to produce a dose rate of 8-18 Gy/ minute depending on distance and added filtration. The useable beam angle is 310° x360° and is well adapted to breast IORT. The tube incorporates a radiation delivery rod that is 22 cm long and 1.7 cm in diameter. The X ray tube and integrated high voltage generator are mounted on an articulated arm that incorporates electromagnetic brakes on all movements. A separated work station is used to remotely control the system using a wireless connection. Various applicators can be mounted on Treatment Application Adaptors to treat skin, breast and rectal tumors.