The present invention relates to a system, method and apparatus for measuring vascular parameters and, more particularly, but not exclusively, to a system, method and apparatus for monitoring changes in the equivalent inner diameter of small branching arteries and arterioles. An aspect of some embodiments of the invention concerns finding a measure of a blood flow dependent parameters in small arteries, and in arterioles that branch off them, and using them and differences between them to find information about the equivalent inner diameter of said arterioles, and/or about changes in said diameter of the arterioles.
