ESTRO 37 Abstract book

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ESTRO 37

treatment planning system is based on the TG-43 formalism introduced by AAPM10-12 for cylindrical and symmetric sources. However, this formalism only takes into account the dose distribution around the sealed source, considering the surroundings as water. Besides this technological evolution, the role and importance of the Radiotherapist, as well as his/her skills and responsibilities, have become fundamental throughout the course of the patient and in the therapeutic act. At the same time, research projects are developed with the involvement of a multidisciplinary team, aiming to offer a continuous improvement in the health care provided to the cancer patient. SP-0135 The RTT´s advanced role in image guided adaptive brachytherapy for cervix cancer in clinical routine B. Wisgrill 1 , N. Nesvacil 1 , D. Berger 1 , M. Schmid 1 , A. Osztavics 1 1 Universitätsklinik für Strahlentherapie, Brachytherapy, Wien, Austria Image guided adaptive brachytherapy for cervix cancer is a complex and extensive treatment-option which requires the collaboration between physicians, medical physicists and RTTs. The purpose of the presentation is to point out the role of the RTTs in the different steps of the workflow and outline specific knowledge and skills. Material and Methods The workflow chart out of Applicator based-image registration to support image guided adaptive cervix brachytherapy in clinical routine published by J. Bör et al. served as base for the survey of RTTs’ required skills and knowledge. For this purpose the activities of the RTTs were recorded in every step of the workflow for a total of ten treatments. Afterwards the results were allocated into the main fields of duties Documentation, Imaging, Treatment-planning and Treatment-delivery. In addition the collected information was divided into basic and advanced skills and knowledge. In the last step the results were compared with the clinic’s internal RTT requirement profile and the ESTRO RTT benchmarking. Results Except for target delineation (physicians), plan optimization and approval of the plan (medical physicists and physicians), activities of the RTTs were detected in every step of the workflow. In case of Documentation the main tasks are the recordings during the insertion of the BT-implant and treatment-delivery. Beside the documentation of the used applicator, the records contain a clinical/technical drawing of the positions and insertion depths of the needles to simplify the reconstruction of the implant. The preparation of these drawings requires advanced knowledge about anatomical structures and different versions and sizes of the predominantly used VIENNA applicators and needles. Radiographs in ap and lateral direction are produced to identify the needles in the patient body and give a better overview for the implant reconstruction and verify the catheter labelling. The 3D-Imaging for treatment planning realized using MRI appeared as a complex matter from the RTTs’ point of view. In our department the MR scanner is directly located in the BT clinical area. In addition to the basic understanding of the image modality, a close cooperation between BT RTT and MR operators is required to adjust the MRI acquisition to achieve optimal image quality. Also a fundamental knowledge about the applicator structure and application technique is required by all RTTs involved in the imaging process. In case of Treatment-planning the basic tasks contain Abstract text Purpose/Objective

the case administration and import of the required image data. As it is nowadays our standard to treat patients with combined intracavitary and interstitial implants, RTTs are trained to routinely performing the MR-only based applicator reconstruction, aided by specialised physicists in case of more complex implants . In addition RTTs prepare all basic treatment plan parameters and create a standard dose plan, which is later optimized by the physicists and radiation oncologists. The delineation process of the OARs on MR images is currently done by physicians. RTTs are currently trained to support this task in the future. The right Treatment-delivery is the RTT’s field of responsibility. The basic tasks include the loading of the patient specific treatment plan, the correct connection between patient and the after-loader and the handling of the device. The advanced role of the RTT provides that in addition to the patient data also the plausibility of treatment parameters like source strength, treatment time and total reference air kerma are checked. This induces an advanced knowledge and sense for dose parameters. The RTT serves as last validation instance of the correct preparation of the patient, like bladder filling and state of urinary catheter. In several cases the preparations were also performed by RTTs. Finally the last optical control and preparation of the in-vivo- measurement of OAR (bladder and rectum) are in RTT’s responsibility. Prior to delivery of the 2 nd fraction, a new MRI is acquired and registered with planning MRI from day one based on the intracavitary applicator position by the RTT. Based on the registration the interdisciplinary team assesses implant stability, variation of the anatomy relative to the implant and decides if treatment adaptation is necessary. Conclusion RTTs specific roles in Documentation, Imaging, Treatment-planning and Treatment-delivery require knowledge of anatomy, medical physics and BT-specific medical engineering, beyond basic RT skills. Clinics which perform complex treatment forms shall schedule extra time for training and offer postgraduate professional education in treatment specific knowledge domains. PV-0136 Comparison of secondary cancer risks of whole and various partial breast irradiation techniques N. Hoekstra 1 , E. Fleury 1 , P. Van der Baan 1 , A. Bahnerth 1 , M. Hoogeman 1 , J.P. Pignol 1 1 Erasmus Medical Center Rotterdam Daniel den Hoed Cancer Center, Radiotherapy, Rotterdam, The Netherlands Purpose or Objective With the increased detection of breast cancer at an early stage, the overall survival has steeply increased, so preventing radiation-induced secondary cancers is becoming an important issue. There is concern that total body radiation exposure from new radiotherapy techniques might result in increased secondary cancer risks. These new techniques include accelerated partial breast irradiation (APBI), delivered as VMAT, stereotactic radiotherapy or HDR brachytherapy. The aim of this study is to compare the risk of secondary cancer of whole breast irradiation (WBI) and various APBI techniques. Material and Methods We conducted a phantom study using a Rando-Alderson anthropomorphic phantom that was modified to hold realistic tissue-equivalent breasts. Treatment plans were generated for 3D-conformal WBI (42.56 Gy in 16 fractions), 3D-conformal APBI (38.5 Gy in 10 fractions), Poster Viewing : Poster viewing 3: Dosimetry