ESTRO 36 Abstract Book

S8 ESTRO 36 2017 _______________________________________________________________________________________________

which a more thorough investigation is probably needed. For the high contrast detection task, the FOM used for this task (d’ of a NPWE model) yields results that are way too sensitive to the NPS, and work on improving the FOM is currently being performed. Conclusion The use of a model observer for objective and clinical task-based metrics might tackle the current problems encountered with iterative CT image reconstruction, for which the classical physical metrics are less pertinent. However, tuning model observer performance in order to estimate human observer performance remains cumbersome, in particular because it relies on the introduction of internal noise mimicking human uncertainty in decision taking. One improvement would be the use of Gabor channels (rather than DDoG), which are even more anthropomorphic. The CHO model showed that the majority of units assessed using this method performed reasonably well when searching focal liver lesions. However, the limited spread in objective image quality was associated with a large spread in the chosen dose indicator. On the other hand, high contrast detection still suffers from conceptual flaws that will have to be improved. Ultimately, the goal is to set up an open web server where users could upload their images, the CHO or NPWE calculation being performed online, for immediate objective image quality assessment and thus continuous immediate dose optimisation. SP-0024 The potential of new CT technologies for radiotherapy with photons and protons W. Van Elmpt 1 1 MAASTRO Clinic, Department of Radiation Oncology, Maastricht, The Netherlands Computed tomography (CT) imaging is a the core of the radiotherapy process: diagnosis, delineation, treatment planning and follow-up imaging. New CT techniques are introduced at many radiology departments such as Dual Energy CT (DECT) scanners, iterative CT reconstructions and automated selection of tube potential and imaging dose. These techniques are also finding their way towards radiotherapy departments. In this presentation a focus will be on the developments in CT imaging that have an application for radiotherapy purposes. To improve delineation accuracy, mono-energetic reconstructions from DECT imaging are being investigated, metal artifact reduction techniques are employed to reduce scatter from metal implants and iterative reconstruction improve image quality that could allow better contouring. For dose calculation in treatment planning, various options are becoming available that reconstruct electron or mass density images directly from the CT scanner or reduce the uncertainty in stopping power ratios (SPR) for proton therapy dose calculations by using DECT imaging.

of ablative treatment of metastatic disease are encouraging but variable so far, due to heterogeneity of patients’ group, lack of clear differentiation between oligometastatic and disseminated disease and different endpoints of studies: from overall survival to stabilization of the disease. Nevertheless, SBRT is now accepted, valuable solution for these patients, despite its limitation. Yet still there is a need to define, factors that will help clinicians to keep the balance between the benefit for patients and overtreatment. Finding biomarkers, patient, disease and technology related parameters would be of value for decision-making process and selection those who benefit most from ablative treatment. SP-0026 Optimizing the workflow of palliative treatment using Lean Six Sigma methodology M. Kamphuis 1 1 Academic Medical Center, Department of Radiation Therapy, Amsterdam, The Netherlands Introduction Palliative radiotherapy for painful bony metastases is mostly performed with a simple one or two field treatment technique. Nowadays this procedure is performed based on CT-images and is often time consuming. At the AMC in Amsterdam the procedure is during working hours organized in a so called “one stop shop” (OSS). This means that patients are seen by the radiation oncologist, simulated and being treated in one day. The processing time (PT) of the whole procedure is 4:30 hours on average, but in about 15 % of the cases more than 6 hours is necessary. The PT was considered undesirable, especially since patients are often in a poor condition. The aim of this study was to decrease the average length of the procedure by at least two hours. Methods Lean Six Sigma methodology was used to improve the OSS protocol. First, a baseline time measurement was performed in 30 patients to quantify the performance of the different steps of the procedure. At the same time factors influencing the length of the procedure were registered (e.g. the treatment techniques used, the number of RTTs involved and the number of sites being treated). Patients were asked to fill in a form measuring the perceived quality of the OSS. A multidisciplinary working group created an extensive list of influencing factors. Different techniques like Failure Mode and Effect Analysis were used. Most important influencing factors were identified e.g. using statistical analyses on the baseline time measurement. Based on these insights, the process was of the One Stop Shop was redesigned. The redesigned process was tested in a pilot study. Results In the baseline measurement, the PT ranged from 2:16h to 7:00h. In the analysis of influencing factors, the vital few could be identified: number of RTTs involved in the whole procedure, the use of a treatment planning instead of a manual calculation, as well as the fact that patients were scheduled of a fixed time slot on the treatment machine. Different important factors, not foreseen at forehand, could be identified using the methodology. The redesigned process consisted of a small team existing of two RTTs and one or two MDs performing the OSS. Team composition was determined the day before the OSS procedure, taking educational level and experience into account. This team was responsible for the whole process. The fixed time slot on the treatment was abolished, patients were being treated as soon as the preparations were finished and space was available on the treatment machine. Results of the pilot study will be presented during the conference. Conclusion Lean Six Sigma methodology provided the tools to quantify, analyze and re-optimize the One Stop Shop procedure. Furthermore, the methodology provided

Symposium: High tech or low tech for metastatic disease, how does one decide and what is the cost- benefit?

SP-0025 High tech approaches for curative treatment, when is enough enough? J. Kazmierska 1 1 Greater Poland Cancer Centre, Radiotherapy Dept, Poznan, Poland The idea to cure metastatic disease using local ablative treatment is compelling, especially in an era of fast technological progress in imaging and radiotherapy allowing for delivering high radiation doses with high precision. However, there are still important open questions regarding the rationale for such treatment, integration with systemic treatment and toxicity. Results