ESTRO 36 Abstract Book

S243 ESTRO 36 2017 _______________________________________________________________________________________________

Leiden, The Netherlands 3 University Medical Center Utrecht, Radiotherapy, Utrecht, The Netherlands Purpose or Objective In 2006 four Radiation therapy technologist (RTT) heads of Radiation Oncology departments agreed to create an E- learning environment. Their goal was to introduce a learning method for RTTs involved in new radiation techniques for whom the learning environment would be easily accessible, relatively cheap and offer new teaching and learning techniques. Material and Methods From 2006 till 2008 a dedicated group of four RTTs created a web-based environment called “Ortello”. By December 2015 Ortello had been fully revised and updated to current website standards. In 2008 Ortello started with 8 Radiotherapy case studies (CS), 3 games and a multiple- choice test. Radiotherapy was highlighted in these CS, but other treatment modalities, such as surgery and chemotherapy, were also represented. Each CS consists of a patient’s pathway during their cancer treatment. Ortello now contains 21 different E-learning CS, which are categorized in Radiotherapy, Techniques, Imaging, and Radiobiology, coupled to 21 multiple-choice tests to examine the gained knowledge. The e-learning environment is linked to the Dutch Register for Paramedics to automatically register credit points obtained after completing a CS and the corresponding test. Every 2 years, reapplication for accreditation is required to guarantee the quality and relevance of each CS. Results Since it’s introduction, Ortello has gained more than 1100 users in 21 departments; 19 in The Netherlands and 2 in Suriname and Curacao. Each year new CS are launched on the website. Up to now, Ortello contains 11 CS in the category Radiotherapy: prostate-, oropharyngeal-, larynx carcinoma, 2 in the category Technique: ”Photons vs electrons” and ”Teaching & Brachytherapy”, 2 in the category Imaging: MRI and MRI & bone tumors and 3 in the category Radiobiology: Radiobiology, Linac & Radioactivity and Radiotherapy side effects. Currently, Ortello is no longer exclusive for RTTs, but can also be used by Diagnostic radiographers. Conclusion The E-learning environment Ortello is fully operational. On the Ortello website, RTTs can train their skills, maintain their knowledge, learn newly introduced technologies, and have the opportunity to learn techniques used in other departments. Furthermore, Ortello provides CS with the accreditation points to ensure RTTs continuous competence. OC-0463 In vitro prediction of DNA repair defects reveals association with poor clinical outcome in HNSCC P. Essers 1 , C. Verhagen 1 , M. Van der Heijden 1 , M. Van den Brekel 2 , H. Bartelink 3 , M. Verheij 3 , C. Vens 1 1 Netherlands Cancer Institute Antoni van Leeuwenhoek Hospital, Division of Biological Stress Response, Amsterdam, The Netherlands 2 Netherlands Cancer Institute Antoni van Leeuwenhoek Hospital, Department of Head and Neck Surgery / Department of Maxillofacial Surgery, Amsterdam, The Netherlands 3 Netherlands Cancer Institute Antoni van Leeuwenhoek Hospital, Department of Radiation Oncology, Amsterdam, The Netherlands Award Lecture: Donal Hollywood Award

bladder cancer. Integrative MRI technology has the potential to improve tumour and normal soft tissue visualisation at treatment planning and delivery. This work investigates the degree of inter and intra observer variation in image registration between experts, using a biological target volume (BTV) defined on diffusion weighted MRI (DW-MRI), in patients muscle invasive bladder cancer. Material and Methods Twenty-two patients with muscle invasive bladder cancer recruited prospectively to a phase I image guided radiotherapy protocol (NCT01124682). Prior to radiotherapy, all patients underwent MRI on a 1.5T magnet prior to to acquire T1-weighed, and T2-weighted DW-MRI with b values of 0, 50, 100, 250, 500 and 750s/mm 2 . The BTV was delineated on b 750 s/mm 2 images and transferred to the treatment planning system (Pinnacle v9.6, Philips Medical Systems), where DW-MR images were registered to the corresponding ADC map and planning CT by three observers (one oncologist and two radiographers). Registration was guided using the bladder, and BTV.

Results Nineteen of the 22 patients accrued to the study had BTVs visible on DW MRI and were included in this analysis. The most notable inter-observer variation in image registration of the BTV occurred in the caudal-cranial (C- C) direction with a mean difference of 5.4 mm (standard deviation (sd) 4.7 mm), followed by the anterior-posterior (A-P) direction (mean 4.5 mm, sd 4.9 mm). The inter- observer registration variation was minimal in the right- left (R-L) direction (mean, 2.8mm, sd 2.4 mm). Overall, on Anova analysis, there were no statistically significant differences in inter-observer registration (p = 0.8214, 0.3136, and 0.3270, in the R-L, A-P and C-C directions respectively). To determine intra-observer variability, each observer performed repeat image registrations on 5 patients at 3 separate time-points. The observers mean reproducibility of ≤ 4mm, 2.5 mm and 5 mm in all directions, respectively (Figure 1). Conclusion Despite the limitations in geometric fidelity of DW MRI, it is a potentially useful tool for the generation of BTV and image registration for adaptive bladder radiotherapy. In this study we quantified the inter-observer variation to <5mm +/- 5mm, in image registration of BTV generated using DW-MRI to planning CT. Current application to clinical practice may necessitate revision of PTV margins but further quantification of geometric distortions and validation is on going. We acknowledge NHS funding to the NIHR Biomedical Research Centre for Cancer and to Cancer Research UK (CRUK). PV-0462 E-learning in the Radiotherapy Department- Ortello J.P. De Jong 1 , P. De Boer 1 , D. Ages 2 , F. Telgenhof 3 , D. Hasken 3 1 Netherlands Cancer Institute Antoni van Leeuwenhoek Hospital, Radiotherapy, Amsterdam, The Netherlands 2 Leiden University Medical Center, Radiotherapy,

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