1. San Raffaele Scientific Institute, Experimental Imaging Centre, Via Olgettina N. 60, Milan 20182 Italy
2. Neurological Institute C. Besta, Neurosurgery unit 2, Via Celoria 11, Milano 20133, Italy
3. European Institute of Oncology, Nuclear Medicine Department, Via Ripamonti 435, Milan 20141, Italy
4. European Institute of Oncology, Medical Physics Unit, Via Ripamonti 435, Milan 20141, Italy
5. University of Verona, Department of Computer Science, Strada Le Grazie 15, Verona 37134, Italy