Urgent challenges in quantification and interpretation of brain grey matter atrophy in individual MS patients using MRI - Amiri, Houshang (Department of Radiology and Nuclear Medicine, VU University Medical Center, Amsterdam, The Netherlands) ; de Sitter, Alexandra (Department of Radiology and Nuclear Medicine, VU University Medical Center, Amsterdam, The Netherlands) ; Bendfeldt, Kerstin (Medical Image Analysis Center (MIAC AG) Basel, Switzerland) ; Battaglini, Marco (Department of Medicine, Surgery and Neuroscience, University of Siena, Siena, Italy) ; Gandini Wheeler-Kingshott, Claudia A. M. (NMR Research Unit, Department of Neuroinflammation, Queen Square MS Centre, UCL Institute of Neurology, London, UK) ; Calabrese, Massimiliano (Multiple Sclerosis Centre, Neurology Section, Department of Neurosciences, Biomedicine and Movements, University of Verona, Italy) ; Geurts, Jeroen J. G. (Amsterdam UMC. University Medical Center) ; Rocca, Maria A. (Neuroimaging Research Unit, Institute of Experimental Neurology, Division of Neuroscience, San Raffaele Scientific Institute, Vita-Salute San Raffaele University, Milan, Italy) ; Sastre-Garriga, Jaume (Hospital Universitari Vall d'Hebron) ; Enzinger, Christian (Department of Neurology & Division of Neuroradiology, Vascular and Interventional Radiology, Department of Radiology, Medical University of Graz, Austria) ; De Stefano, Nicola (Department of Medicine, Surgery and Neuroscience, University of Siena, Siena, Italy) ; Filippi, Massimo (Neuroimaging Research Unit, Institute of Experimental Neurology, Division of Neuroscience, San Raffaele Scientific Institute, Vita-Salute San Raffaele University, Milan, Italy) ; Rovira, Álex (Hospital Universitari Vall d'Hebron) ; Barkhof, Frederik (University College London. Institutes of Neurology & Healthcare Engineering) ; Vrenken, Hugo (Department of Radiology and Nuclear Medicine, VU University Medical Center, Amsterdam, The Netherlands) ; Universitat Autònoma de Barcelona