ESTRO 38 Abstract book

S278 ESTRO 38

Questionnaire A questionnaire about ease in moulding, positioning and removing the mask was answered by:  4 Mouldroom RTTs  5 CT RTTs  38 Treatment room RTTs 1. van Herk M, Remeijer P, Rasch C, et al: The probability of correct target dosage: Dose-population histograms for deriving treatment margins in radiotherapy. Int J Radiat Oncol Biol Phys 47:1121-1135, 2000 Results Stability The stability of the Nanor mask is slightly better than the Efficast Maxi and Micro mask. A reduction in intrafraction margin of 5mm is possible (Table 1).

Conclusion With AlignRT, left-sided breast cancer patients can be positioned accurately (on average 0.4 ± 1.3 (1SD) mm) based on comparison with CBCT data. Low intrafraction variability and good stability were observed for the active breathing coordinator guided breath holds. OC-0528 A clinical evaluation of the stablilty, patient comfort and ease in use of the new Nanor mask L. Mesch 1 , M. Essers 2 , T. Rozema 1 1 Dr. Bernard Verbeeten Instituut, Department of Radiation Oncology, Tilburg, The Netherlands; 2 Dr. Bernard Verbeeten Instituut, Department of Medical Physics and Engineering, Tilburg, The Netherlands Purpose or Objective The Nanor mask (Orfit Industries) is a mask with a “thin thermoplastic material that makes use of nanotechnology to improve the mechanical properties of the thermoplastic material”. The goals of this study were to compare the stability and patient comfort of the Nanor Mask with two Efficast mask materials, as well as the ease in use for the RTT. Material and Methods From January 2017 until December 2017, 48 patients referred for radiotherapy of the brain for at least 10 fractions were randomized to 3 categories: 1. Orfit Efficast mask 2 mm maxi perforation (16, 1 stopped) 2. Orfit Efficast mask 1,6 mm micro perforation (16, 2 stopped) 3. Orfit Nanor mask 1,6 mm micro perforation (16, 2 stopped) Each patient was immobilized with a mask in combination with Raycast® Head supports regular density with lateral neck flaps (Orfit Industries). Stability Two orthogonal kV images were acquired for daily image- guided patient setup (Varian Medical Systems). After the online correction, CBCT1 was acquired. After delivery of the treatment fields, CBCT2 was acquired to determine the intra fraction error. Proper PTV margins were determined taking these intrafraction errors into account 1 . Patient comfort After the treatment, the RTT marked the straining zones on a picture of the head and asked the patient where they felt any discomfort or pressure, which was also marked on another picture of the head. Figure 1 shows the colour scale (0-100%): 0% means there was no straining on any day and 100% means patient felt straining zones on each treatment day.

Patient comfort Patient comfort of all masks is good. The pressure felt by the patient is comparable for the Efficast Maxi and Nanor masks and slightly less for Efficast Micro mask. Similar results were found for compression seen by the RTT. Patient comfort is slightly better for the Nanor mask for fractions where patients use dexamethasone (figure 1). Questionnaire User friendlyness is comparable for all masks. There is a slight preference for Nanor mask, especially for positioning the patient in the mask at the CT and the treatment unit. Conclusion The stability and patient comfort for the Nanor, Efficast micro and Efficast maxi mask are good. Although the Nanor mask feels more comfortable and softer than the Efficast micro mask, in fact the stability is slightly improved. OC-0529 Evaluation of the potential treatment delivery benefits of Varian HyperArc for brain metastases A. Williamson 1 , A. James 1 , A. Chalmers 2 , R. Carruthers 2 , S. Nowicki 1 , P. McLoone 3 1 Beatson West of Scotland Cancer Centre, Radiotherapy, Glasgow, United Kingdom ; 2 Institute of Cancer Sciences- University of Glasgow, Radiotherapy, Glasgow, United Kingdom; 3 University of Glasgow, Statistics, Glasgow, United Kingdom Purpose or Objective Varian HyperArc is a stereotactic radiosurgery solution, designed to automate and simplify sophisticated treatments which became clinically available in October 2017. HyperArc uses the Encompass immobilisation device and 6DOF couch, with a single button delivery and automated couch movement eliminating the need to re-