Abstract book - ESTRO meets Asia

S29 ESTRO meets Asia 2018

Purpose or Objective To test the recent Technical Report Series (TRS) 483, jointly developed by International Atomic Energy Agency (IAEA) and The American Association of Physicists in Medicine (AAPM), for the dosimetry of small static photon fields used in external beam radiotherapy. Material and Methods We tested the code of practice (CoP) through determination of beam quality index of the reference field [TPR 20,10 (10) and %dd (10) X ] from the small fields using Palman’s equation, cross calibration and reference dosimetry using a machine-specific reference (msr) fields and field output factors for field size ranging from 0.5 x 0.5 to 10 x 10 cm 2 . 6 MV and 10 MV with flattening filter (WFF) and flattening free filter (FFF) photon beams were tested using the CoP. The cross calibration for the msr field were carried out between the FC65-G farmer type chamber with CC-13 and CC-01 chambers. The output factors were measured using the photon field diodes, electron field diodes, CC-01 and CC13 for all the 6 WFF, 6FFF, 10WFF and 10FFF. Results Measurements were made with two linear accelerators True Beam and Clinac 2100 DMX (M/S Varian Medical systems, USA). There were two diodes and three ionization chambers were used in the testing of the CoP. The beam quality index TPR 20,10 (10) and %dd (10) X determined using the Palman’s equation from the small msr fields were with ± 0.1% from the measured values. The cross calibration in the msr fields between the chambers were resulted with ± 0.3%. The output factors measured using various detectors and corrected according to the CoP were resulted with ± 1%. Conclusion The preliminary results of the CoP were consistent and improve the variations between the detectors. The CoP has no issues in putting into clinical practice for reference and relative dosimetry in small static photon beams. OC-076 Australian Dosimetric Benchmarking in Radiation Oncology Audit: A Driver for Improved Treatment A. Alves 1 , C. Davey 1 , F. Kadeer 1 , J. Kenny 1 , M. Shaw 1 , J. Supple 1 , J. Lye 1 1 Australian Radiation Protection and Nuclear Safety Agen cy, Australian Clinical Dosimetry Service, Melbourne, Australia Purpose or Objective The Australian Clinical Dosimetry Service, (ACDS)— operating over 7 years with 100% national participation— offers an independent dosimetry audit program for radiation oncology clinics. A three-level audit program covers: (1) reference dosimetry, (2) beam model evaluation and (3) end-to-end testing. The gathered national dataset is used to benchmark the quality of treatment and serves as a driver for best-practice in radiation oncology. Material and Methods Auditors perform site visits to enable the highest accuracy measurements and also perform postal audits to enable large-scale coverage of the majority of treatment beams across the nation. Outcomes are based on the difference between the dose measured by the ACDS and the dose predicted by the clinic. The ACDS is located at the Australian Radiation Protection and Nuclear Safety Agency, where equipment is calibrated in the national standards laboratory. Results Outcomes have been used to directly advise clinics about practice, have generated information opaque to individual clinics, and have assisted decision making around equipment commissioning. Over 80 recommendations have been made based on initial audit findings. Trends across multiple audits required multi-clinic analysis, such

reduce this source of error, including periodic training for radiation oncologists, the use of shared delineation guidelines, quality assurance processes with online platform for centralized revision and new tools employing advanced technology. SP-072 Preoperative radiotherapy: where we stand V. Valentini 1 1 Università Cattolica del Sacro Cuore, Gemelli ART, Rome, Italy Abstract text The standard of care for locally advanced rectal cancer (LARC) is neoadjuvant radiotherapy (RT)+/- chemotherapy (CT), followed by total mesorectal excision (TME). Neoadjuvant treatment can reduce the risk of local recurrence, improving the downsizing of the tumor or the sphincter-preserving surgery. Rectal cancer management focuses on two strictly connected fields: increase of pathological complete response (pCR) and surgery de- escalation. Newest diagnostic and treatment technologies have led to major changes in the way patients with LARC are investigated and treated. The use and role of medical imaging technologies in clinical oncology has greatly expanded from primarily a diagnostic and qualitative tool to a quantitative one. In a similar way, gene expression profiles of pretreatment biopsies of LARC have been generated to define response predictors with promising features. Furthermore the tremendous advances in radiation therapy technology have allowed for remarkable precision in treatment delivery and for the realization of dose escalation. These improvements in diagnostic and treatment technology and the advances in individualized medicine justify the progressive and continuous effort to develop predictive models in oncology field. Decision Support Systems (DSS) could support clinicians in detecting real ypT0 cases and avoiding surgical overtreatment, basing on inter- and intra-patient tumor heterogeneity and advanced treatment personalization. The predictor may help clinicians in the management of LARC patients, supporting decisions and treatment strategies in a conservative approach. SP-073 Brachytherapy: where we stand A. Su Myint 1 1 Clatterbridge Cancer Centre, Papillon SuiteBebington, Wirral, UK

Abstract not received

Teaching lecture: LET, RBE, particles

SP-074 LET, RBE, particles A. Potter 1 1 St. Andrew's Hospital, Adelaide Radiotherapy Centre, Adelaide, Australia

Abstract not received

Proffered papers: Quality management and verification (physics) OC-075 Single institutional experience of TRS483 for small static fields used in external beam radiotherapy K.R. Mani 1 1 United hospital ltd, Radiation Oncology, Dhaka, Bangladesh