FY2014 has seen significant progress toward accomplishing all of the Specific Aims; some of this progress is detailed here. For Aim 1, the first project focuses on the early development of MS lesions. Previously, we studied two critical aspects of lesion development: the small veins around which white matter lesions form, and the spatiotemporal dynamics of vascular permeability as manifested in gadolinium-enhanced MRI. To understand whether the presence of a central vein may help distinguish MS lesions from their mimickers an idea that remains controversial and to which we only partially subscribe we developed a rapid imaging approach for clinical 3T MRI called FLAIR*. Studies to assess the utility of FLAIR* for diagnosis and characterization of MS lesions are currently underway in our lab and in several other labs worldwide. With respect to vascular permeability, we have established that there are two spatiotemporal patterns in MS lesions: a centrifugal pattern, in which serum contents leak from the center of the lesion and then proceed outward, over the course of minutes to hours, to fill the entire lesion; and a centripetal pattern, in which serum contents first appear on the periphery of the lesion and then proceed inward. These findings have important implications for understanding lesion development and its association with blood-brain-barrier permeability. In further work published in the past year, we have described how these permeability patterns help to determine the fashion in which acute MS lesions evolve into their chronic counterparts. Additionally under Aim 1, we have completed and published work on the evolution of inflammatory demyelinating lesions in the brains of marmoset monkeys with experimental autoimmune encephalomyelitis. We have specifically demonstrated that the blood-brain barrier becomes locally permeable up to four weeks prior to the onset of demyelination, and we have shown that this permeability is associated with a perivascular lymphocytic and mononuclear infiltrate with parenchymal activation of microglia and astrocytes. Finally, we have continued recruitment of asymptomatic first-degree relatives of MS patients in collaboration with the nationwide Genes and Environment in Multiple Sclerosis (GEMS) study that is headquartered at the Brigham & Womens Hospital of Harvard University. At NIH, we are characterizing individuals believed to be at relatively high and low risk for development of clinical MS. This study is ongoing, and the initial results are expected to be available in the next year. For Aim 2, work in FY14 has focused on development of methodology for radiological-pathological correlation studies. We have implemented high-resolution imaging of formalin-fixed brains using a variety of MRI approaches and developed a system to use those images to guide the histopathological analysis. This is accomplished by generating a 3D-printed brain-cutting box that allows precise sectioning of the brain, such that small lesions observed on MRI (either in vivo or postmortem) can be localized and studied. We have demonstrated the value of this device for analyzing areas of neocortical demyelination and leptomeningeal inflammation. An additional project under Aim 2 has been the high-resolution assessment of brain volume using an MRI technique we developed called brain-free water imaging. With this technique, we can greatly improve the standard approach to MRI-based brain volume measurement, uncovering, in the process, stronger links between imaging findings and clinical status of MS patients. Finally, we have continued work on assessing the myelin specificity of T2* magnitude and phase imaging, initiating a study of acute and chronic MS lesions on the 7 tesla MRI scanner. This study, in collaboration with Jeff Duyns group, is ongoing; results are expected within the next year.