ESTRO 38 Abstract book

S50 ESTRO 38

assess their visibility in CT, MRI and the verification system. Material and Methods The value of migration and change of the geometry of the system of implanted markers. The group of 66 patients was determined on the basis of a comparison of the distance between central points of all implanted markers during all treatment sessions. Measurement of the distance between the central points was carried out on the basis of images archived in the CyberKnife system. The usefulness of tags is defined by determining the number of intra-markers used to locate the disc volume by the CyberKnife verification system. The analysis included a group of 66 patients who are treated in the Department of Radiotherapy, Oncology Center, the Branch Gliwice, from January 2010 to June 2017. In each patient, 2 to 5 markers were implanted percutaneously into the liver. In total, 198 gold markers were implanted. On the basis of CT scans, on which the contours of the tumor and critical organs were drawn, a treatment plan was prepared in the MultiPlan system. During each therapeutic session, the patient was positioned using a vacuum mattress, an infrared camera marker system and a Synchrony Vest. After making verification images in the CyberKnife system, the golden markers were located automatically. All detected markers were marked as active in the treatment panel. The number of detected markers by the system in individual treatment fractions was estimated based on a retrospective analysis of 352 archived images. Results The average value of change in distance between markers along with the standard deviation was: 0.53 mm (SD = 0.86). The maximum value of change in distance between markers was 2.5 mm. In 57% of measurements, there was no change in the distance between individual markers during radiotherapy. In 39% of measurements, the measured change in distance was 1-2 mm, and in the case of 15% of measurements, the value was 3 mm. There was no case of tracer migration outside the liver area. In 50% of patients, despite the implantation of at least 3 markers, the system detected only 2 during the entire treatment, and in the group of 16% of patients, the system detected only one marker. In all patients, where it was impossible to verify at least 3 markers, the implanted markers were developed or occurred in both forms. In the case of patients in whom all markers were folded up, the system correctly detected at least 3 markers. In all cases, the markers were visible in CT and computed tomography images of nuclear magnetic resonance. Conclusion 1. The GoldAnchor® intra-tracer label applied in rolled form does not migrate in the liver parenchyma during the entire healing process, 2. The shape of the implanted tags determines the ability to detect them by the CyberKnife verification system; tags in the expanded form (line) are more often not recognized by the system than those that have a folded form, 3. The GoldAnchor® markers should be implanted in the liver only in rolled form (loops). OC-0098 Gated vs coached DIBH treatment in left sided breast cancer radiotherapy: a single centre study K. Crowther 1 , S. Osman 2 , S. O'Hare 1 , S. Gray 1 , D. Holland 1 , H. Vennard 1 , G. Hanna 1,2 1 Belfast Health and Social Care Trust, Cancer Centre- Radiotherapy, Belfast, United Kingdom ; 2 Queen's University, Centre for Cancer Research and Cell Biology, Belfast, United Kingdom Purpose or Objective Deep inspiration breath hold (DIBH) reduces cardiac and pulmonary dose during tangential-field left breast radiotherapy (RT). We report preliminary results of an ongoing study, comparing voluntary moderate (vm) DIBH

Results 5 patients were not suitable for DIBH. 2 did not meet training sessions criteria and 3 showed no dosimetric advantage when comparing both planning CT’s. For the 19 suitable patients the mean DIBH time during training session was 31s, adding 6s to the minimum requisite. The mean overall treatment time was 26min about twice the departmental time slot of a standard FB treatment. For the first patient, adaptations of the planned workflow were made, due to inaccurate positioning of the OSMS cameras. During gantry rotation, cameras are blocked between 20 o and 70 o , interrupting the treatment repeatedly resulting in longer treatment time. This was solved by increasing the ROI and therefore the detected surface. In the 285 treatment sessions delivered, DIBH CBCT after OSMS positioning was within tolerances for 254 sessions. The remaining 31 sessions required repositioning and image reacquisition. With DIBH, the mean dose to the heart was reduced by 1.4Gy (5Gy in FB vs 3,6Gy in DIBH). Conclusion DIBH using OSMS was successfully implemented in our department and is now a routine procedure. Careful selection of the patients is a key factor for a successful treatment delivery and the increased workflow has to be balanced out with its effective benefit. Our next aim is to implement SGRT in other thoracic treatment sites. OC-0097 Detection of GoldAnchor markers implanted in the liver during robotic radiosurgery in the CK system. K. Szczepanik 1 , M. Stapo-Fudzinska 2 , B. Jochymek 1 , D. Bodusz 1 , L. Kleszyk 1 , E. Telka 1 , M. Kijonka 3 1 Maria Sklodowska-Curie Memorial Cancer Center and Institute of Oncology, Department of Radiotherapy, Gliwice, Poland ; 2 Maria Sklodowska-Curie Memorial Cancer Center and Institute of Oncology, Department of Planning Radiotherapy and Brachytherapy, Gliwice, Poland ; 3 Maria Sklodowska-Curie Memorial Cancer Center and Institute of Oncology, Department of Medical Physics, Gliwice, Poland Purpose or Objective The study was to determine the migration values of applied GoldAnchor® intra-markers to the liver and to