Abstract
Two recently published methods of blood‐brain barrier permeability measurement using Gd‐DTPA scanning are compared by authors representing each group. The physiological models are reconciled. Results from both groups agree. These show that the transfer constant (the permeability surface area product per unit volume of tissue) of the defective blood‐brain barrier in multiple sclerosis is in the range 1‐12·10−4s−1 © 1992 Academic Press, Inc.