These findings suggest that thalamic atrophy is a clinically relevant biomarker of the neurodegenerative disease process in multiple sclerosis.

The signal decay with increasing b‐factor at fixed echo time from brain tissue in vivo has been measured using a line scan Stejskal–Tanner spin echo diffusion approach in eight healthy adult volunteers. The use of a 175 ms echo time and maximum gradient strengths of 10 mT/m allowed 64 b‐factors to be sampled, ranging from 5 to 6000 s/mm2, a maximum some three times larger than that typically used for diffusion imaging. The signal decay with b‐factor over this extended range showed a decidedly non‐exponential behavior well‐suited to biexponential modeling. Statistical analyses of the fitted biexponential parameters from over 125 brain voxels (15 × 15 × 1 mm3 volume) per volunteer yielded a mean volume fraction of 0.74 which decayed with a typical apparent diffusion coefficient around 1.4 µm2/ms. The remaining fraction had an apparent diffusion coefficient of approximately 0.25 µm2/ms. Simple models which might explain the non‐exponential behavior, such as intra‐ and extracellular water compartmentation with slow exchange, appear inadequate for a complete description. For typical diffusion imaging with b‐factors below 2000 s/mm2, the standard model of monoexponential signal decay with b‐factor, apparent diffusion coefficient values around 0.7 µm2/ms, and a sensitivity to diffusion gradient direction may appear appropriate. Over a more extended but readily accessible b‐factor range, however, the complexity of brain signal decay with b‐factor increases, offering a greater parametrization of the water diffusion process for tissue characterization. Copyright © 1999 John Wiley & Sons, Ltd.

At present, the diagnosis of multiple sclerosis (MS) relies heavily on the use of MRI, which can demonstrate disease dissemination in space and time [1][2][3][4] . The current 2010 McDonald criteria have enabled earlier diagnosis 5,6 and initiation of disease-modifying treatment, with substantial benefits for disease outcome 7,8 , but they still have imperfect sensitivity and specificity 9,10 . The limited accuracy of the criteria results in challenging cases and misdiagnosis, which are prevalent problems in MS 11,12 . Therefore, more-accurate and pathologically specific MRI criteria are still needed to exclude other disorders that can mimic MS 13,14 .The MRI-detectable central vein inside white matter lesions has recently been proposed as a biomarker of inflammatory demyelination and, thus, may aid the diagnosis of MS 15 . The 'central vein sign' (CVS) has been investigated in various neurological conditions by several groups, and evidence has accumulated that the CVS may have the ability to accurately differentiate MS from its mimics [15][16][17][18][19][20][21] . As a consequence, recent guidelines from the Magnetic Resonance Imaging in MS (MAGNIMS) group 1,4 and the Consortium of MS Centers (CMSC) task force 22 have acknowledged the potential of the CVS and its dedicated MRI acquisitions for the differential diagnosis of MS, while calling for further research before considering a possible modification of the diagnostic criteria. However, the lack of standardization for the definition and imaging of the CVS, as well as a dearth of large-scale prospective studies evaluating the CVS for MS diagnosis, are currently preventing the clinical validation of this potential biomarker 1,23 .This Consensus Statement aims to provide recommendations for the definition, standardization and clinical evaluation of the CVS in the diagnosis of MS. These statements are based on a thorough review of the existing literature on the CVS and the consensus opinion of the members of the North American Imaging in Multiple Sclerosis (NAIMS) Cooperative. E X P E RT C O N S E N S U S D O C U M E N T on behalf of the NAIMS CooperativeAbstract | Over the past few years, MRI has become an indispensable tool for diagnosing multiple sclerosis (MS). However, the current MRI criteria for MS diagnosis have imperfect sensitivity and specificity. The central vein sign (CVS) has recently been proposed as a novel MRI biomarker to improve the accuracy and speed of MS diagnosis. Evidence indicates that the presence of the CVS in individual lesions can accurately differentiate MS from other diseases that mimic this condition. However, the predictive value of the CVS for the development of clinical MS in patients with suspected demyelinating disease is still unknown. Moreover, the lack of standardization for the definition and imaging of the CVS currently limits its clinical implementation and validation. On the basis of a thorough review of the existing literature on the CVS and the consensus opinion of the members of the North American Imaging in Mult...