1Radiology, Brigham and Women's Hospital, Boston, MA, USA
The short T2 component of the T2 curve measured in white matter is commonly assigned to myelin-associated water. A problem with this assignment is that water exchange times through the myelin sheath are not known even minimal exchange would greatly reduce the size of this component to below the measured levels. Diffusion measurements indicate that such exchange exists. This incompatibility is described and solutions proposed.