ESTRO 2022 - Abstract Book

S1350

Abstract book

ESTRO 2022

Radiotherapy, Marseille, France; 4 Aix Marseille Université, CNRS UMR 7258, INSERM UMR 1068, CRCM, Marseille, France; 5 Institut Paoli-Calmettes, Department of Radiotherapy , Marseille, France Purpose or Objective Optical fiber-based scintillating dosimetry is the most recent promising technique due to the miniature size dosimeter and improve quality assurance in modern radiation therapy. Despite several advantages, the major issue of using scintillating dosimeters is the Cerenkov Effect and predominantly requires extra measurement correction factors. Therefore, this work highlighted a novel micro-dosimetry technique to ensure Cerenkov-free measurement and provide quality treatment. Materials and Methods A micro-dosimetry technique was proposed with the performance evaluation of a novel infrared inorganic scintillator detector (IR-ISD). The detector essentially consists of a micro-scintillating head with a sensitive volume of 1.5x10 -6 mm 3 . The proposed system was evaluated under the 6/15 MV LINAC beam as well as 320KV- 192 Ir Brachytherapy (BT) source used in the patient treatment system. Overall measurements were performed using IBA TM water tank phantoms by following TRS- 398 protocol for radiotherapy and TG43U1 recommendations for BT. Cerenkov measurements were performed for different small fields from 0.5x0.5 cm 2 to 10x10cm 2 under LINAC as well as till 0.25cm distance from the BT source. In addition, several dosimetric parameters such as PDD, beam profiling, dose linearity, dose rate linearity, repeatability, and scintillation stability were investigated to realize the device’s performance. Finally, a comparative study will be shown using Monte-Carlo (MC) simulation, and data from recent literature. Results This study highlighted a complete removal of the Cerenkov Effect using a point-like miniature detector, especially for small field radiation beam treatment. Measurements demonstrated that IR-ISD has acceptable behavior with dose rate variability (maximum standard deviation ~ 0.15%) for the dose rate of 20 cGy/s to 1000 cGy/s. An entire linear response (R 2 =1) was obtained with the dose delivered in the range of 4cGy to 1000 cGy, independently of the field size selected from 4 x 4 cm ² to 0.5 x 0.5 cm ² . Perfect repeatability (0.15 % variation from average) with day-to-day reproducibility (0.25% variation) was observed. PDD profiles obtained in the water tank present identical behavior to the reference dosimeter with a build- up maximum depth dose at 1.5 cm. The small field of 0.5 x 0.5 cm ² profiles have been characterized to determine convolution and penumbra effect. Eventually, in BT, a comparison with MC simulations shows that measurement agrees within 0.65% till 0.25 cm source-to-detector distance. Conclusion Unlike recent advanced PSD systems (e.g., exradin W1/W2), the proposed micro-dosimetry system in this study requires no Cerenkov corrections and showed efficient performance for several dosimetric parameters. Therefore, it is expected that the IR-ISD system can be promoted to validate with direct clinical investigations, such as in the small-field dose verification, intra-beam characterizations, and BT treatment plan. M.N. Duma 1 , B. Vrou Offersen 2 , M. Bessermann Johansen 3 , K. Boye 4 , B.S. Kristensen 4 , I. Meattini 5 , L. Marrazzo 6 , V. Di Cataldo 7 , A. De Caluwé 8 , D. Teixeira 9 , P. Franco 10 , G. Loi 11 , I. Jensen 12 , M. Møller 13 , K. Verhoeven 14 , R. Marseguerra 15 , K. Legård Jakobsen 16 , S. Aziz-Jowad Al-Rawi 16 , Y. Kirova 17 , B.A. Jereczek-Fossa 18 , M.C. Leonardi 19 , R. Luraschi 20 , I. Kindts 21 , L. Goethals 21 , P. Loap 17 , J. Vu-Bezim 17 , S. Weimann 22 , T. Teichmann 22 , A. Wittig 22 1 University Hospital Jena, Department of radiotherapy and radiation oncology, Jena, Germany; 2 Aarhus University Hospital, Department of Experimental Clinical Oncology, Aarhus, Denmark; 3 Aarhus University Hospital, Department of Oncology, Aarhus, Denmark; 4 Rigshospitalet, Department of Oncology, Copenhagen, Denmark; 5 University of Florence; Careggi University Hospital, Experimental and Clinical Sciences “Mario Serio”; Radiation Oncology Unit, Florence, Italy; 6 Medical Physics Unit, Careggi University Hospital, Florence, Italy; 7 IFCA, Radiation Oncology Department, Florence, Italy; 8 Institut Jules Bordet, Université Libre de Bruxelles; AZ St Maarten, Radiation Oncology department, Brussels, Mechelen, Belgium; 9 Institut Jules Bordet, Université Libre de Bruxelles, Medical Physics department, Brussels, Belgium; 10 University of Eastern Piedmont; ‘Maggiore della Carità’ University Hospital, Department of Translational Medicine (DIMET), Department of Radiation Oncology, Novara, Italy; 11 ‘Maggiore della Carità’ University Hospital, Department of Medical Physics, Novara, Italy; 12 Aalborg University Hospital, Department of Medical Physics, Aalborg, Denmark; 13 Aalborg University Hospital, Department of Oncology, Aalborg, Denmark; 14 GROW School for Oncology, Maastricht University Medical Center, Department of Radiation Oncology (MAASTRO), Maastricht, The Netherlands; 15 Zealand University Hospital, Rigshospitalet, Department of Clinical Oncology and Palliative Care, Department of Oncology, Næstved, Copenhagen, Denmark; 16 Zealand University Hospital, Department of Clinical Oncology and Palliative Care, Næstved, Denmark; 17 Institut Curie, Department of Radiation Oncology, Paris, France; 18 IEO, European Institute of Oncology IRCCS; University of Milan, Division of Radiation Oncology, Department of Oncology and Hematoncology, Milan, Italy; 19 IEO, European Institute of Oncology IRCCS, Division of Radiation Oncology, Milan, Italy; 20 IEO, European Institute of Oncology IRCCS, Unit of Medical Physics, Milan, Italy; 21 Cancer Centre, General Hospital Groeninge, Department of Radiation Oncology, Kortrijk, Belgium; 22 University Hospital Jena, Department of radiotherapy and radiation oncology , Jena, Germany Purpose or Objective The inter-institutional variability in planning objectives and constraints are expected to be very large in regional nodal irradiation (RNI) since no international guidelines are available specific for breast cancer (BCa) treatment planning,. The aim of this international study was to assess the decision making process as well as the planning of RNI in experienced European BCa centers. PO-1569 An international, multicenter planning study on regional nodal irradiation in breast cancer

Materials and Methods