1. Department of Radiology, Fondazione IRCCS Policlinico San Matteo, Pavia, Italy
2. Department of Radiology, Civil Hospital, Vigevano, Italy
3. Diagnostic Imaging Unit, National Centre of Oncological Hadrontherapy, Pavia, Italy
4. Department of Radiology, Ospedale Maggiore di Lodi, Lodi, Italy