A Method to Measure Shear Strain with High Spatial Resolution in the Arterial Wall Non-Invasively in vivo by Tracking Zero-Crossings of B-Mode Intensity Gradients

We have previously shown that there is a distinct longitudinal movement of the arterial wall during a cardiac cycle. This movement is larger in the intima-media region than in the adventitial region which introduces a substantial shear strain within the arterial wall. Our previously developed echo-tracking algorithm measured this shear strain by tracking two separate echoes, one in the intima-media region and one in the adventitia region and thus only a linear distribution was evaluated. The objective of this study was to suggest and evaluate a new improved method which can measure the intramural shear strain with higher spatial resolution and thereby provide more information on this new and rather unknown phenomenon. The mean maximum shear strain was 0.82 radians with a standard deviation of 0.17 radians and a CV-value of 14.2%. The total mean difference in measured longitudinal movement between the new and previous method was 10μm with a standard deviation of 90μm and a CV-value of 12.8%. The spatial distribution of the intramural shear strain seems to be very non-linear with a large amount of shear strain occurring in a small section around the transition between the media and adventitia layers.