Spatial and spectral heterogeneity of time‐varying shear stress profiles in the carotid bifurcation by phase‐contrast MRI

Abstract

Purpose To determine the heterogeneity of the time‐varying shear stress profiles in the human carotid bifurcation, a region prone to atherosclerosis. Materials and Methods Lagrangian bicubic interpolation of phase‐contrast MRI images was used to determine the shear stress profiles for three adult healthy male volunteers. Frequency spectra for the common and internal carotid artery (CCA and ICA, respectively)‐derived shear stresses were examined in order to determine the presence of significant heterogeneity in the intensity distribution. Results Hemodynamic characteristics (peak, minimum, average shear stress, and oscillatory shear index [OSI]) were highly heterogeneous both along the length of the vessel as well as circumferentially around the CCA and ICA. In the frequency domain, intensities below 4 Hz were significantly higher in the CCA compared to the sinus region of the ICA, indicating that shear stress heterogeneity can be detected in the frequency domain. The harmonic index, a measure of the relative contributions of dynamic and static components of the shear stress signal, colocalizes with OSI, which implies a relationship between specific frequency components and atherosclerosis development. Conclusion These findings indicate that the time and frequency dependent parameters of in vivo shear stress have important implications for regional development of atherosclerosis. J. Magn. Reson. Imaging 2006.