ESTRO 2023 - Abstract Book

S880

Digital Posters

ESTRO 2023

1 azienda ospedaliero universitaria pisana, fisica sanitaria, pisa, Italy; 2 università di pisa, fisica sanitaria, pisa, Italy; 3 università di pisa, fisica, pisa, Italy; 4 infn, sezione di catania, catania, Italy; 5 università di palermo, fisica, palermo, Italy; 6 università di pisa, radioterapia, pisa, Italy; 7 università roma la sapienza, ingegneria, roma, Italy; 8 università roma tor vergata, ingegneria, roma, Italy; 9 università di roma tor vergata, ingegneria, roma, Italy

Purpose or Objective Background

The Flash effect is a very attractive radiobiological effect from a clinical perspective; despite this, the mechanisms underlying the effect and its quantitative dependencies on beam parameters (Dose-per-Pulse, Instantaneous-Dose-per Pulse...) are still only partially known. To fully investigate these topics and optimize and speed up its clinical translation, it is necessary to carry out accurate quantitative radiobiological experiments. One of the main difficulties in carrying out quantitative experiments is the lack of dedicated Linacs. Purpose. The purpose of this work is to describe the architecture and the potential of a new Linac dedicated to Flash research, with unique features of its kind, installed and operational, thanks to the founding grant of Fondazione Pisa, within the CPFR in Pisa (Italy). EF with triode gun is equipped with an accurate monitoring system of both fluence and energy and, thanks to its triode gun, it can vary the beam current from conventional values up to extreme “Flash” values. This means being able to vary the various dosimetric parameters of the beam without modifying the experimental setup and one independently of the other, allowing the execution of experiments never carried out until now. Materials and Methods The trend of the dose-per-pulse and of the dose / UM were acquired daily for 2 months with the independent dose-per pulse dosimeter Flash diamond, to evaluate the short and long term stability of the output and of the monitoring system . For all available combinations of 1) optic of the beam (applicator used) -2) beam current 3) energy and 4) pulse duration, both water dose distribution and pulse time form were obtained by using different dosimeters, as ionization chambers, gafchromic films, flash diamond , alanine and SIC. Results The short-term and long-term stability of the output is 1% and 3%, respectively, while that of the dosimetric monitoring system is 2 and 4%. The effective duration time of the pulses can be varied in steps of 0.1 µ s, from an effective value of 0.5 up to 4. The frequency of the pulses can vary from 1 to 249 Hz, not affecting the stability of the output and of the monitoring system. It is possible to vary the beam current from a few mA up to 100 mA and varying the dose-per-pulse from conventional values (cGy / pulse) up to "extreme" flash values (over 20 Gy / pulse). Conclusion EF with triode gun presents fundamental innovations that allow to increase the accuracy of the quantitative radiobiological experiments necessary to understand the mechanisms underlying the flash effect and its quantitative dependencies on the beam parameters, need to optimize its clinical traslation. For example, it is possible, for the first time, to perform FLASH-CONV comparative experiments without changing the experimental setup, to study the volume effect while maintaining the dose-per-pulse and to study the possible dependence on the instantaneous dose-per-pulse. K. Bergfeldt 1 , S. Engelholm 2 , M. Hedman 3 , P. Fransson 4 , K. Ahlberg 5 , L. Beckman 6 , G. Gagliardi 7 , K. Vernmark 8 , P. Nodbrant 9 , A. Isaksson 10 , T. Nyholm 11 1 Skandion Clinic and Umeå University, Department of Radiation Sciences, Umeå, Sweden; 2 Skane University Hospital, Department of Hematoglogy, Oncology and Radiophysics, Lund, Sweden; 3 Karolinska University Hospital and Karolinska Institute, Department of Radiation Oncology, Stockholm, Sweden; 4 Norrlands University Hospital, Cancercenter and Department of Nursing, Umeå, Sweden; 5 The Sahlgrenska Academy at Gothenburg University, Institute of Health and Care Science, Gothenburg, Sweden; 6 Umeå University and Sundsvall County Hospital, Department of Radiation Sciences, Sundsvall, Sweden; 7 Karolinska University Hospital, Department of Radiotherapy Physics and Engineering, Stockholm, Sweden; 8 Linköping University, Department of Oncology, and Department of Biomedical and Clinical Sciences, , Linkoping, Sweden; 9 County hospital Ryhov, Department of Oncology , Jonkoping, Sweden; 10 Orebro University Hopsital, Department of Oncology, Örebro, Sweden; 11 Umeå University, Department of Radiation Sciences, Umeå, Sweden Purpose or Objective Several reports, including bibliometric reviews, have revealed an alarming situation within Swedish radiotherapy. From a former position as a front runner in scientific and technical development, Sweden of today has a limited number of oncologists specialised in radiotherapy and accordingly a decreased activity in research and development. The decreasing number of RTT:s create difficulties in providing radiotherapy for all patients. As a result of a multiprofessional effort the Swedish association of Radiation Oncology (SSOF) was formed in 2021, aiming to turn this decreasing trend. Materials and Methods Based on the five-point action plan presented by ESTRO in “the white paper” several actions have been planned and executed by SSOF in order to reach all stakeholders – governments and policymakers, healthcare professionals, patients and professional societies, along with national and international research funds to participate and support decision making in order to secure the valuable position of radiotherapy in comprehensive cancer care. PO-1099 Securing the future of radiotherapy by the ESTRO five point action plan - the Swedish experience

Results