Abstract Book

S118

ESTRO 37

This approach requires Rapid Learning Health Care systems. Conclusion The model-based approach is an alternative evidence- based methodology to select patients for protons therapy and to test if the new technology eventually results in lower rates of radiation-induced side effects SP-0219 EPTN WP2: Dosimetry and quality assurance S. Safai 1 , O. Jäkel 2 , S. Menkel 3 1 Paul Scherrer Institute PSI, Center for Proton Therapy, Villigen PSI, Switzerland 2 Deutsches Krebsforschungszentrum, Medical Physics in Radiation Oncology, Heidelberg, Germany 3 Universitätsklinikum Carl Gustav Carus, Proton Therapy Center, Dresden, Germany Abstract text WP2 is the second work package of the European Particle Therapy Network (EPTN) referred to as “WP2: dose assessment, quality assurance, dummy runs and technology inventory”. The focus of this work package is on dosimetry and quality assurance in particle therapy. As of today 14 centres of 8 different countries are represented in WP2. During the WP2 workshop held in March 2017 in Brussels six working groups within WP2 have been created to cover different aspects of dosimetry as listed below. This abstract contains extracts from the ESTRO newsletter No. 113 (July – August 2017) pertain to WP2. The 6 working groups (WG) 1) Quality assurance/equipment survey : a questionnaire has been prepared and distributed across the centres in Europe to collect information on the dosimetric quality assurance tests performed on particle machines, including the type of test, the frequency, the tolerance, the duration, the resources required, the level of satisfaction and the equipment used. The aim is to become aware of the spectrum of approaches used in the different centres, to learn from the experience of such centres and to encourage discussions targeted to harmonize the QA program in Europe. The survey will also help to better identify the dosimetry areas in which WP2 could contribute to. 2) Reference dosimetry : the current standards (code of practice) on reference dosimetry do not cover in a satisfactory way the particular needs of particle scanning machines with regard to reference dosimetry and primary monitor calibration. We are therefore glad that other committees outside of EPTN are currently addressing and updating the definition of such standards. The role for this working group is to gather the experience from different centres by sharing the results on this topic to provide valuable inputs to the existing committees. We are therefore closely following the update of the Technical Reports Series (TRS), where members of the WG are involved. The WG, among others, will propose well-defined tests for a better interpretation of the results across the institutes. 3) Audits : the aim is to create a network of centres interested in participating in reference dosimetry audits and end-to-end audits. Similar to “Reference dosimetry” this working group is defining standard tests to be performed with an anthropomorphic phantom, which can be shared between centres. 4) Patient specific verification : this WG aims at understanding how patient specific verification is currently performed and which tools and criteria are used for comparison between planned and measured dose in order to understand the needs in this area. The EPTN WP5 on treatment planning system is addressing this topic as well and a dedicated questionnaire has been prepared. As such WP2 will not include patient specific verification questions on its survey but will profit from the results of WP5.

5) Dosimetry tools : as a results of the QA/equipment survey a database for dosimetry equipment used in particle therapy will be created and maintained. 6) Ocular treatments : dedicated working group on the dosimetry aspects of ocular treatments. The aims and status of activities of each working group will be presented with particular attention to the preliminary results of the QA/equipment survey. SP-0220 EPTN WP4: Image Guidance in Particle Therapy A. Hoffmann 1 , A. Bolsi 2 , M. Peroni 2 1 OncoRay - Center for Radiation Research in Oncology, Medical Radiation Physics, Dresden, Germany 2 Paul Scherrer Institute, Centre for Proton Therapy, Villigen, Switzerland Abstract text The finite range of a particle beam makes the dose delivered by particle therapy (PT) more sensitive to morphological (i.e. geometric and anatomical) variations than for photon therapy (XT). To reduce this range uncertainty, PT can benefit from incorporating image- guidance techniques in the treatment delivery phase. Currently, imaging guidance in particle therapy (IGPT) lags behind photon therapy (IGXT) as the translation of imaging tools and techniques from XT to PT is not always straightforward. At present, clinical IGPT mainly involves daily orthogonal kilovoltage (kV) X-ray imaging, which lacks soft-tissue contrast. Consequently, CT scans have been included to assess the impact of anatomical changes during the course of therapy (with schedules varying on a centre-by-centre basis). In some centres, in-room CT imaging is available both for positioning and for offline monitoring of anatomy changes. Recently, the ability to perform on-board cone-beam CT (CBCT) has come available on some systems. Although CBCT has been widely implemented for IGXT, for IGPT it is nowhere near a standardized approach. Moreover, the value of in-room CT versus CBCT has to be established. Given the lack of standardized procedures, most PT centres have developed their own strategies for IGPT, which is based on to their available infrastructure, technical implementation and delivery strategy. The need to cooperate among centres and exchange knowledge on IGPT as an integral part of modern image- guided radiation therapy has been acknowledged as being of importance to bring PT forward. Within ESTRO’s EPTN Task Force, the goal of working group on “ Image Guidance in Particle Therapy ” is to assess the current status of IGPT in clinical practice, to identify bottlenecks and challenges of IGPT, and to drive harmonization through guidelines based on consensus between the European centres. Moreover, an inventory of current research activities in IGPT will be provided, with the intent of facilitating translation of innovative techniques into clinical practice. Furthermore, a strategy proposal for future IGPT research that would require a European network of PT centres will be developed. As a first step, contact persons interested to participate in the IGPT-WP have been identified within 19 participating European PT centres. A survey on the status and future perspectives of IGPT has been filled out by all of these centres in February 2016. Topics covered in the survey include: patient immobilization, imaging for treatment planning, patient positioning and dose delivery, imaging for moving targets, research activities and future perspectives of IGPT. Secondly, a first workshop of the IGPT-WP has been organized in 2017 with representatives of 12 PT centres. During this meeting, three sub-working groups have been defined based on body site: 1) brain, head and neck, 2) thorax, 3) abdomen and pelvis. The coordinators for the sub-working groups have participated in the analysis of the results of the questionnaire relevant to their field. A detailed