Abstract book - ESTRO meets Asia

S24 ESTRO meets Asia 2018

V. Manoor Ural 1 1 Apollo Hospital, Radiation Oncology, Bangalore, India

report generation 3. Downstream processes: how the registered images are used 4. Management processes: human and technical organisation Based on this a modular image registration framework was developed that can be applied to multi-modality treatment planning, image guided radiotherapy, adaptive radiotherapy, response assessment, and accounting for retreatment. Results Failure mode with the highest level of relative risk in our department (risk priority number = 229) was image registration with accuracy levels that require error handling. This was due to the difficulties in detection of whether such error handling had occurred (detectability = 6), with error management issues occurring frequently (occurrence = 6), and moderate severity in the event it wasn’t picked up (severity = 5). The AAPM TG100 report recommends quality control strategies that included interlocks, automation, and protocols, among others. In addition to quality controls recommended by AAPM TG132, a quality management strategy integrating technical and human factors was implemented to address multiple causes in our risk profile (Table 1). Our system focused on enabling a feedback loop to improve quality iteratively by coordinating tasks by different staff specialities into the report. For our site, one of the most important risk mitigation controls is the generation of a patient specific report for each image registration event, which provides valuable information about the accuracy level and uncertainty of the registration for the end user. Using software, this report can also include screenshots, comments on upstream issues, and Oncologists decisions or findings.

Purpose or Objective Modern-day radiotherapy utilizes conformal delivery techniques, which necessitate more accurate patient positioning and tumor targeting to achieve a high therapeutic ratio. The aim of the study is to evaluate the daily displacement of prostate during the course of definitive radiotherapy, as the bladder and rectum influences the position of prostate. Material and Methods We retrospectively analyzed 15 Patients who underwent definitive radiotherapy of Ca Prostate implanted with 3 gold fiducials markers at different planes of prostate a week prior to Radiation-therapy. CT Simulations was performed 1 week after the implant to eliminate the migration of fiducials. These patients were delivered with 76Gy in 38 fractions. All the patients underwent RT followed institutional bladder filling protocol of drinking 500 ml of water 45 minutes prior to treatment to reproduce the bladder volume of the simulation day. Pre- treatment kV-kV & CBCT Image verification was done on Truebeam STx (V1.6) workstation. Marker match tool was used for 2D-2D matching followed by 3 dimensional cross verification with CBCT. Magnitude and direction of the shifts were measured and applied and treatment were executed with reference to the fiducials based on online shifts. The offline review was done on Aria OIS(V11). Results The average shift of prostate was ranging from 3 mm to 8 mm in anterior-posterior and cranio-caudal direction directions. The lateral displacement of the prostate was within 4 mm.The vertical, lateral and longitudinal mean of the marker shift was within 1 mm in comparison with CBCT. The image acquisition and setup time was reduced less than a minute for marker-based treatments. Conclusion Gold fiducial based treatments, reduce the image guidance timing and assures more accurate targeting of prostate by acting as good surrogate with a reduction of repeated over exposure with CBCT. The results of this study indicate that daily prostate localization using fiducial markers in kV radio graphs during radiation therapy for prostate cancer may offer better target localization. Fiducial markers can be considered as standard of care in the delivery of modern prostate RT, and their use is recommended especially when considering dose escalation and improving the institutional tumor margins. PV-059 A modular quality management program for image registration with a risk-based approach J. Yuen 1 , L. Schmidt 1 , R. Brown 1 , J. Poder 1 , A. Ralston 1 1 St George Public Hospital, Cancer Care Centre, Sydney- NSW, Australia Purpose or Objective The recently published AAPM TG132 report provides a technical consensus on registration algorithms, validation, and operation; however customisation is required for institutional-specific processes and risks. A framework for using risk-based quality management techniques was used to supplement image registration recommendations in AAPM TG132 to optimize the image registration workflow in our institution. Material and Methods Failure mode effects analysis (FMEA) was used to generate a map of image registration processes and their associated failures modes, focusing on four main areas: 1. Upstream processes: input image characteristics that affect registration 2. Image registration processes: registration, QA, and

Conclusion Supplementing AAPM TG132, the risk-based approach from AAPM TG100 was implemented into a quality management system that enables feedback and is modular in nature to support multiple use cases. Multiple registrations can be analysed with a report database and used as a feedback mechanism for quality improvement projects. Report data can reveal causes of suboptimal registration, which could be due to upstream factors, registration factors, downstream factors, or management factors. PV-060 Dosimetric characteristics of INTRABEAM using spherical applicators

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PV-061 Skin Dosimetry of Patient-tailored 3D-printed Bolus Application in Post-mastectomy Electron Beam RT S. Seol 1 , J. Shin 1 , W. Park 1 , K. Yang 1 , S. Ju 1 , D. Choi 1 ,