Abstract Book

S116

ESTRO 37

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Teaching Lecture: Oesophagus cancer

SP-0213 Oesophagus cancer A. Rovirosa Hospital Clinic I Provincal, Barcelona, Spain

Abstract not received

Teaching Lecture: Clinical implementation of adaptive radiotherapy

SP-0214 Clinical implementation of adaptive radiotherapy D. Moeller 1 , U.V. Elstrøm 1 , M.S. Assenholt 1 , L. Hoffmann 1 1 Aarhus University Hospital, Department of Medical Physics, Aarhus C, Denmark Abstract text When anatomical changes occur during the course of radiotherapy they can affect the dose to both tumour and normal tissues. The planned dose distribution can then be restored with the concept of adaptive radiotherapy. Strategies for treatment adaptation lead to more precise treatment delivery, in some cases even allowing for margin reduction. This in turn has been shown to reduce dose to organs at risk with the possibility to minimize toxicity, for example in the lung [1,2], bowel and rectum [3] and parotic glands [4]. Strategies for treatment adaptation can be geared towards either systematic or random changes. The choice of adaptation strategy should be based on clinically relevant trigger criteria which should be verified in a large scale clinical setting. The lecture outlines how to implement adaptive radiotherapy in clinical practice focussing on: * Selection of patients for adaptation. What evidence do we need? * What are the clinical relevant time points for adaptation? * How do we identify/define clinically relevant trigger criteria? * How do we adjust margins, treatment planning and setup to comply with the adaptive strategy? * How do we ensure consistent and efficient evaluation and clinical compliance? * Automation of an adaptive workflow. What tests are needed? [1] Tvilum M et al. Clinical outcome of image-guided adaptive radiotherapy in the treatment of lung cancer patients. Acta Oncol. 54:1430-7 (2015). [2] Møller DS et al. Adaptive radiotherapy for advanced lung cancer ensures target coverage and decreases lung dose. Radiother Oncol.121:32-38 (2016). [3] Thörnqvist S et al. Adaptive radiotherapy strategies for pelvic tumors - a systematic review of clinical implementations. Acta Oncol. 5:943-58 (2016). [4] Hvid CA et al. Cone-beam computed tomography (CBCT) for adaptive image guided head and neck radiation therapy. Acta Oncol. 10:1-5 (2017)

Teaching Lecture: Things radiotherapy physicists need to know about good PET imaging practice

SP-0215 Things radiotherapy physicists need to know about good PET imaging practice R. Boellaard 1 1 Boellaard R, Radiology and Nuclear Medicine, Amsterdam, The Netherlands Abstract text Metabolic activity or glucose consumption can be measured using FDG PET/CT. Quantification of FDG PET/CT studies is often based on so-called standardised uptake values (SUV) which is the FDG concentration observed by PET usually normalised by net injected activity per patient weight. SUVs or other metabolic parameters, such as metabolic volume and total lesion glycolysis can be used for metabolic phenotyping of the tumor. Moreover FDG PET/CT may be useful for radiotherapy purposes, e.g. to assist in tumor delineations or identify regions requiring a higher treatment dose. FDG uptake, its distribution and PET based tumor delineations are associated by various sources of bias and uncertainties [1]. Factor influencing tracer uptake can be described as technical, imaging physics related or biological uncertainties[1]. Use of PET for radiation therapy purposes requires that data or delineations derived from PET are repeatable and reproducible. The latter implies that the effects of the above mentioned factors on SUV should be mitigated and/or harmonized as much as possible [2,3]. Harmonization of PET/CT examinations aims at making SUV reads as exchangeable (comparable) and reproducible as possible by harmonizing imaging procedures, image quality and quantitation and harmonizing data analysis methods and interpretation. The main challenge of harmonisation efforts arises from differences in both PET/CT imaging procedures and in technology across multiple sites and users. To this end the European Association of Nuclear Medicine published FDG PET/CT imaging guidelines [2,3] and started a multicentre calibration/accreditation program to harmonise quantitative imaging system performance. Moreover, continuous monitoring of the FDG PET/CT data quality is warranted [4]. In this lecture the principles of metabolic imaging with PET, the mechanism of FDG uptake, various factors affecting FDG PET/CT tracer