ESTRO 36 Abstract Book

S160 ESTRO 36 _______________________________________________________________________________________________

well as diffusion weighted (DW) and dynamic contrast enhanced (DCE) MR imaging. Voxel-based and regional correlation analysis of mutual parameter pairs showed moderate to low parameter correlations. However, on a patient-to-patient basis large variations were observed for most parameter correlations. Consequently, robust and accurate workflows and image acquisition protocols need to be identified in order to use multi-parametric functional PET/MR imaging in the future for adapted RT concepts in a clinical context. SP-0308 Metabolic and functional MRI integration for glioblastoma dose-painting trial. A. Laprie 1 1 Institut Claudius Regaud, Toulouse Cedex 09, France The ongoing spectro-glio trial (NCT01507506) is a phase III multicentric randomized trial for newly diagnosed glioblastoma. It has included 165 patients among the 220 planned. It compares arm A : STUPP protocol ( 60 GY + TMZ) with arm B that includes an additional SIB targeted at MR spectroscopic abnomalities ( CHO/NAA>2)+tumor bed at a dose of 72Gy/2.4Gy In this presentation we will discuss the original modalities, the difficulties met and the solutions found for the particularity of this trial : multicentric use of 3D MR spectroscopic imaging developement of an innovative technique of integration of MR spectroscopic imaging to RT-scan centralized delineation of arm B patients - online quality control of dosimetry in arm B patients database developement - analysis techniques of this large prospective database of anatomic, perfusion, diffusion and spectroscopic imaging of glioblastoma.( follow-up every 3 months until relapse) -preliminary imaging results SP-0309 Plan of the day and dose-escalation for bladder cancer (RAIDER Trial) H. McNair 1 1 The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, Sutton, United Kingdom The major challenge in delivering accurate radiotherapy to the bladder is to compensate for the daily variation in organ size, shape and position. This change is mainly due to differing degrees of bladder filling and can be influenced by change in rectal volume. The plan of the day approach has the potential to improve outcomes by improving target coverage and decrease the dose to bowel. However the unpredictable nature of bladder filling and changes in organ dimensions require confident and timely decision making for treatment delivery. This is of particular importance when the does to the tumour bed is escalated. This presentation will discuss the importance of achieving a representative reference image and the practicalities of the patient maintaining a consistent drinking protocol. Clinical examples will be used to illustrate common imaging problems with appropriate decision making, in particular when not to proceed to treatment. The importance of staff training and maintaining competency to achieve consistent image selection will also be discussed. Acknowledgements: Emma Hall, Robert Huddart and Shasita Hafeez and the RAIDER trials team. Radiotherapy Trials Quality Assurance (RTTQA) team. We also acknowledge funding to the NIHR Biomedical Research Centre at The Royal Marsden and The Institute of Cancer Research. Research at The Institute of Cancer Research is also supported by Cancer Research UK under Programme C33589/A19727. In addition the national trial (RAIDER) was funded by Cancer Research UK (CRUK/14/016)

Symposium: Registration and fusion techniques

SP-0310 Rigid registration techniques for different imaging modalities N. Nesvacil 1 1 Medical University of Vienna, Department of Radiotherapy- CCC- Christian Doppler Laboratory for Medical Radation Research for Radiation Oncology, Vienna, Austria Image registration has become an important part of treatment planning and execution in 3D image guided external beam radiotherapy (EBRT) and brachytherapy (BT) during the last decades. In principle, the same algorithms for rigid or non-rigid image registration can be applied to either type of radiotherapy. However, for their application in brachytherapy the presence of the brachytherapy delivery device, i.e. the applicator, plays an essential role. This presentation will provide an overview of rigid registration techniques in brachytherapy, compared to external beam radiotherapy. In gynaecological brachytherapy, where the applicator and CTV might move in relation to the bony anatomy during the course of a (multi-fractionated) treatment, applicator-based rigid registration can be used to combine images for treatment planning acquired with the same or different modalities at different time points. One of the most useful applications of this technique is to transfer target contours defined on a reference image, e.g. an MRI at the time of the first BT, to subsequent CT image volumes for planning of further BT fractions, if MRI is not always available for dose plan adaptation to the anatomy of the day. Requirements and pitfalls for clinical applications of this technique will be discussed. In order to analyse interfraction variations for target and organs at risk (OARs) based on image volumes acquired at different time points, rigid image registration can provide a good estimate of the dosimetric impact of anatomical changes between applicator, CTV and OARs. Clinical examples will be discussed for different treatment sites. Limitations of the technique will be summarized and special focus will be given to prostate and gynaecological BT treatment planning. Multi-modal rigid image registration for brachytherapy is also used to improve target delineation and dose plan optimization for a single fraction. MRI acquired before brachytherapy can be combined with CT images for treatment planning of prostate cancer, in order to visualize and delineate intraprostatic lesions as boost target volumes in HDR or LDR brachytherapy. In the setting of gynaecological cancer brachytherapy where only CT is available for visualization of the applicator and surrounding organs after implantation, rigid registration of ultrasound images obtained with applicator in situ could be used in the future for dual modality dose planning of a single fraction. Challenges and solutions for the registration of ultrasound and CT images, such as determining the applicator position in the ultrasound image volume, will be explored to conclude this presentation. SP-0311 Deformable registration for dose summation K. Tanderup 1 1 Aarhus University Hospital, Department of Oncology, Aarhus C, Denmark Dose summation across brachytherapy fractions and accumulation with external beam radiotherapy (EBRT) dose is essential for assessment of total dose to both targets and organs at risk in treatments with fractionated brachytherapy and in combinations with EBRT. Brachytherapy dose distributions are highly