1. Department of Medical, Surgical and Neuro Sciences, Diagnostic Imaging, University of Siena, Viale Bracci 10, 53100 Siena, Italy
2. Division of Radiology, European Institute of Oncology, University of Milan, Via Ripamonti 435, 20141 Milan, Italy
3. Department of Neuroradiology, Medical University of South Carolina, Charleston, SC 29425, USA
4. Department of Neuroradiology, Neurocenter of Italian Switzerland, 6903 Lugano, Switzerland