Timeline of GM imaging in MS. A schematic overview of developments in the field of GM imaging in MS from the beginning of the 20th century until now. A, B, D) Reproduced from Kidd et al. , Kutzelnigg et al. , and Schmierer et al.  respectively, all with permission from Oxford University Press. C) Reproduced from Cifelli et al.  with permission from John Wiley and Sons. E, F) Reproduced from Geurts et al.  and Roosendaal et al.  respectively, both with permission of the Radiological Society of North America.