A local angle compensation method based on kinematics constraints for non-invasive vascular axial strain computations on human carotid arteries

Non invasive vascular elastography (NIVE) was developed to highlight atherosclerotic plaque constituents. However, NIVE motion estimates are affected by artifacts, such as an underestimation of deformations due to projected movement angles with respect to the ultrasound beam, movements of the operator or of the patient during image acquisition. The main objective of this work was to propose a local angle compensation method within small measurement windows for the axial strain based on kinematics constraints, and to introduce a filtering process on the strain time-varying curve to reduce as much as possible the impact of motion artifacts. With such preprocessing, we successfully quantified the strain behavior of near and far walls in longitudinal images of internal carotid arteries without (n=30) and with (n=21) significant atherosclerotic disease (greater than 50% stenosis). Maximum strain rates of 4.49%s^-1 for the healthy group and of 2.29%s^-1 for the atherosclerotic group were calculated on the far wall of internal carotid arteries; significant differences were found between these values (p=0.001). The minimum strain rates, also on the far wall of internal carotid arteries, of -3.68%s^-1 for the healthy group and of -1.89%s^-1 for the atherosclerotic group were significantly different as well (p=8×10^-4). The mean systolic, diastolic and cumulated axial strains could also distinguish the two groups after normalization by the pressure gradient between acquired images. To conclude, the proposed techniques allowed to differentiate healthy and atherosclerotic carotid arteries and may help to diagnose vulnerable plaques.