In Vitro Effects of Photon Beam and Carbon Ion Radiotherapy on the Perineural Invasion of Two Cell Lines of Neurotropic Tumours oleh Alexandra Charalampopoulou, Amelia Barcellini, Giuseppe Emanuele Frittitta, Giorgia Fulgini, Giovanni Battista Ivaldi, Giuseppe Magro, Marco Liotta, Ester Orlandi, Marco Giuseppe Pullia, Paola Tabarelli de Fatis, Angelica Facoetti