Abstract #1275

Imaging artefacts during simultaneous in-beam MR imaging and proton pencil beam irradiation

Sebastian Gantz^1,2, Volker Hietschold³, Sergej Schneider^1,2,4, and Aswin Louis Hoffmann^1,2,5

¹Institute of Radiooncology-OncoRay, Helmholtz-Zentrum Dresden - Rossendorf, Dresden, Germany, ²OncoRay – National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany, ³Department of Radiology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany, ⁴Technische Universität Dresden, Carl Gustav Carus Faculty of Medicine, Dresden, Germany, ⁵Department of Radiotherapy and Radiation Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany

The targeting precision of proton therapy is expected to benefit from real-time MRI guidance. We developed a setup of a first prototype in-beam MRI scanner with a proton pencil beam scanning nozzle. Dipole magnets in the nozzle used for beam steering produce time-dependent magnetic fringe fields that may interfere with the MR image acquisition. In this study, we show that vertical beam steering shows no degradation of the MR image quality, whereas horizontal beam steering introduces severe ghosting artefacts in phase encoding direction. The origin of these artefacts is unraveled and strategies to eliminate or correct these artefacts are proposed.

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