ESTRO 38 Abstract book

S177 ESTRO 38

be restored. Daily cone-beam CT scans based on soft tissue match are used for patient setup at Aarhus University Hospital. The combination of soft tissue match and an adaptive strategy allows for reduction in treatment margins, reduction in dose to normal tissue and enables dose escalation. This lecture focusses on the clinical implementation of image-guided adaptive radiotherapy in the treatment of lung cancer patients. It presents both the dosimetric and clinical outcome of the first patients treated with the strategy at Aarhus University Hospital. SP-0355 Selection of lung cancer patients for adaptive radiotherapy using cone-beam CT imaging D. Hattu 1 1 Maastricht Radiation Oncology Maastro Clinic, Radiotherapy, Maastricht, The Netherlands Abstract text Image-guided radiotherapy using cone-beam CT (CBCT) allows for precise patient set-up procedures and accurate treatment delivery. Besides image-guided patient set-up, CBCT can detect anatomical changes previously not visible on lateral port films. This additional information leads to an increased workload and decision criteria when to adapt need to be in place. Therefore in our department a traffic light protocol is part of the online matching protocol for lung cancer patients and is used for the evaluation of the correct positioning of the patient. It also serves as a decision support tool to guide Radiation Therapy Technologists (RTT) with potential follow- up investigations to be undertaken for e.g. changes in lung density, changes in tumor volume or tumor shifts. Requests for follow-up investigations are collected and reviewed offline by a dedicated RTT and a radiation oncologist specialized in lung cancer treatment to determine if further action is necessary (e.g. dose (re)calculation, new CT or even an adapted treatment plan). In this presentation an overview of the current protocol is given but also practical examples will be shown. SP-0356 Image-guided radiotherapy and motion management in lung cancer V. Gram 1 1 University Hospital of Copenhagen- Rigshospitalet, section of Radiotherapy- Clinic of Oncology, Copenhagen, Denmark Abstract text Modern radiotherapy techniques as IMRT and VMAT have already contributed to a reduction of the radiation dose to the lungs and heart for patients with lung cancer, and there are still modern techniques that are being explored for this patient group today. Image guidance and motion management offer great advantages for lung cancer patients, including the ability of monitoring tumour size and motion. Motion management techniques, such as DIBH offer advantages including a reduced dose to the healthy part of the lung and the heart, improved image quality and intra-fractional motion management of the tumour and have been used for breast cancer patients for over a decade with good results, as this technique expands the lungs and pushes the heart down with the diaphragm. The use of breath hold techniques is however not a standard approach in lung cancer, despite its advantages. There are a number of considerations to be evaluated in the implementation of breath-hold techniques; both technical, practical and patient-related. This presentation will include clinical experience in implementing DIBH for lung cancer patients from the perspective of an RTT and include ethical aspects, choice of technique, patient selection, patient and staff training, patient compliance and extra time required for adding this technique.

keV. Currently only a few large third generation synchrotrons around the world, such as the European Synchrotron in Grenoble (France) provide such beam properties. Various alternative approaches have been discussed in the past, including inverse Compton scattering sources and carbon nanotube x-ray tubes. Another strategy is the Line-Focus x-ray tube (LFxT), a source based on classical x-ray tubes, where the electron beam is focused to an extremely eccentric focal spot on a rapidly rotating tungsten target. The rapid relative movement between target and focal spot leads to a change in the energy transport within the target. Our simulations show that such a source can provide up to 200 Gy/s MRT peak entrance dose rate in a clinical setting.

Figure 1: Hybrid dose calculation approaches can calculate complex MRT treatment geometries within a few minutes. The resulting dose distributions can be used to calculate the equivalent uniform dose a promising predictor for normal tissue reactions.

Figure 2: The concept of the line focus x-ray tube is based on conventional x-ray tube technology. An eccentric focal spot hits a fast rotating target cylinder.

Symposium: Focus on the lung

SP-0354 Image-guided adaptive radiotherapy in the treatment of lung cancer patients M. Tvilum 1 , M. Marquard Knap 1 , L. Hoffmann 2 , A. Ahmed Khalil 1 , C.M. Lutz 2 , D. Sloth Møller 2 1 Aarhus University Hospital, Department Of Oncology, Aarhus C, Denmark; 2 Aarhus University Hospital, Department Of Medical Physics, Aarhus C, Denmark Abstract text Anatomical changes often occur during treatment of lung cancer patients with curative intended radiotherapy. These changes affect both the dose delivered to the tumour and to the normal tissue. By using the concepts of adaptive radiotherapy, the planned dose distribution can