Improved Wall Shear Rate method for robust measurements

The Wall Shear Rate (WSR) represents an important parameter correlated with cardiovascular diseases, like, for example the atherosclerotic plaque formation. The WSR can be obtained as the radial blood velocity gradient assessed in the wall proximity. The WSR is typically approximated by using flow models like Poiseuille and/or Womersley applied to the measured center-line velocity. However these models cannot account for the complex flow configurations generated by the real geometry of the vessel, and the WSR estimate is inaccurate. The direct measurement of the velocity gradient through a Doppler high-resolution multigate technique can achieve a better accuracy, but the signal near the wall is affected by clutter. In this work an improved velocity reconstruction method for WSR measurement is proposed. It is based on the measurement of the actual velocity profile and a two-step interpolation that reconstructs the velocity in the wall proximity. The method, verified through realistic multiphysics simulations of a carotid artery, achieves a 5% RMS error for velocity reconstruction and a -10.5% underestimation in WSR assessment. The method was also tested on 14 healthy volunteers.