Click on image to view larger version.

Figure 2 Principles of the three-dimensional paraboloid (3DP) method. a, A magnitude image is reproduced as obtained perpendicular to the longitudinal axis of the vessel. A preliminary lumen vessel edge is constructed as a perfect circle from two manually placed points. b, Pixels are identified at a distance of 0.3 to 1.3 mm (gray area) from the preliminary circle (dashed circle). Data for the 3DP fit are acquired from this ring of pixels. c, A plot of flow velocity, u, as a function of length in radial dimension, r, used for determination of wall shear rate. WSS is wall shear rate times the dynamic viscosity of the blood.