Abstract Book

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ESTRO 37

Mean treatment time was 20 min and 35 min for FT and STM respectively. Positional deviations are shown in Table 2. Average positional accuracy of 0.2, 0.2, and 0.2mm for FT (range 0 to 0.9 mm) and 0.3,0.2 and 0.1 mm for STM(range 0 to 0.9 mm) in the lateral, vertical, and longitudinal directions respectively were found. In the rotational directions, the positional accuracy were 0.1°, 0.3°, and 0.2° for FT( range 0° to 0.4° ) and 0.1°, 0.2°, and 0.2° for STM( range 0° to 0.9°) in the pitch, roll, and yaw respectively.

The first group of patients received two standard dark ink tattoos, and were positioned aligning the tattoos with a measured point on the breast board, with lasers. The second group had no tattoos, and positioned using Surface Guided Technology (SGRT), Align RT (Vision RT, London, UK). A daily 3D-CBCT was completed for each patient for both groups, reviewed and matched online. The longitudinal, lateral and vertical shifts determined from the online match were recorded and analysed. Results 22 patients/ 402 fractions were set up for treatment using tattoo based method and 21 patients/392 fractions had no tattoos and were set up for treatment using SGRT. Within each group the data was divided between left and right sided breasts, as the left breast patients were treated under Deep Inspiration Breath Hold (DIBH) and the right breast patients were treated in free breathing. All three translational shifts (longitudinal, lateral, vertical) and the 3D vector magnitude were then plotted on graphs. The patients set up with tattoos and lasers, for the right sided patients the 3D magnitude mean 0.5 cm, the min 0.1cm and the max 1.4cm. For the left sided patients, the 3D magnitude the mean 0.8cm, min 0.1cm and the max 3.6cm. The patients with no tattoos and set up using SGRT, for the right sided patient the 3D magnitude mean 0.5cm, min 0.1cm, max 1.9cm. For the left sided patients, the 3D magnitude mean 0.4cm, min 0.1cm and max 1.4cm. Conclusion No tattoos together with SGRT offers set up accuracy for right breast set-up comparable to that of the traditional tattoo method, and shows a marked improvement for the left breast DIBH patients. With our current imaging regime, this work shows that going tattoo-less is appropriate and safe. This in turn may improve patient experience of having breast Radiotherapy by addressing the cosmetic and psychological concerns associated with dark ink tattoos. EP-2339 Evaluation of a new mask system for stereotactic radiotherapy in brain lesions M. Buitelaar-Gallé 1 , J. Van Egmond 1 , J. Van Santvoort 1 , J. Roos 1 , L. Versluis 1 , S. De Vet 1 , M. Van Hameren 1 , T. Van Oorschot 1 , R. Wiggenraad 1 , J. Van Wingerden 1 , M. Mast 1 1 Haaglanden Medical Centre, Radiotherapy, Leidschendam, The Netherlands Purpose or Objective In our institute we have 12 years’ experience with stereotactic radiotherapy (SRT) for brain lesions on a Novalis (Varian medical systems) using a Brainlab mask system. Results of the accuracy of this Brainlab system were reported in 2008 [1]. In 2016 we started with SRT on an Elekta accelerator. Therefore, we had to change our procedures, including our mask system. We wanted to evaluate if the positioning results with this new system were comparable with the previous system. We compared our previous and newly adopted SRT Twenty patients treated on the Novalis accelerator were immobilised with a Brainlab mask with a vacuum mouth piece (figure 1A). ExcacTrac (ET) imaging (Brainlab) was used before and after radiation treatment. A 3D correction was performed using the ET system [1]. Repositioning of the patient was performed if the rotations were ≥ 2°. positioning methods. Material and Methods

Conclusion The mean positional accuracy for the full thermoplastic mask were found similar to those with a short thermoplastic mask with mouthpiece, while the overall patient management was significantly longer when using a mouthpiece. Therefore, we conclude that using a full thermoplastic mask is efficient and accurate for frameless radiosurgery treatments. EP-2338 To Evaluate the Accuracy of Delivering Breast Radiotherapy without Tattoos. J. Rigley 1 , P. Robertson 1 1 Genesis Care Nottingham, Radiotherapy, Nottingham, United Kingdom Purpose or Objective During radiotherapy breast cancer patients are traditionally set-up using permanent tattoos. Several studies report these marks can cause anxiety and body confidence issues. The purpose of this study was to assess the feasibility of having no tattoos and using Surface Guided Radiotherapy (SGRT) (VisionRT, London UK) as an alternative to the traditional tattoo based set-up method Material and Methods All patients receiving whole breast/chest wall Radiotherapy between November 2016 and June 2017 at Genesis Care Nottingham were included in this evaluation.