Ischemic stroke due to atherosclerotic disease has been studied widely in the recent past. Most studies focus on either the correlation between stroke risk and stenosis severity (narrowing of the plaque in the vessel) or mechanisms affecting platelet activation and aggregation. Shear stress has been identified as a strong indicator for platelet activation/aggregation, resulting in both thrombus formation and plaque growth. This has subsequently been correlated with regions of elevated turbulence.
Doppler ultrasound offers a method of characterizing these flow disturbances using a well-established parameter—turbulence intensity (Tl), which is the root mean squared deviation in the spectral mean velocity. Using an in-house in vitro flow system, Doppler spectra are obtained at each of over 1000, 1-mm3 isotropically spaced sites in the central plane of seven Teflon phantoms simulating varying degrees of arterial disease. An average of Tl over a 25 mm2 region of interest, as well as the volume of Tl and the cumulative Tl over the internal carotid artery showed that downstream turbulence increased significantly with both stenosis severity (30% - 650% increase) and plaque asymmetry (10% - 30% increase)
