P5D-5 Principal Component Analysis of Shear Strain Effects

Shear stresses are always present during a applied axial compression, since tissue slippage occurs along both the lateral and elevational directions. The shear stress component along the axial compression axes, adds to the axial compression, while the perpendicular components introduce both lateral and elevational motion and deformation introducing additional noise artifacts into the axial and lateral strain images. We evaluate the impact of the lateral shear stress component within the image plane on the normal strain tensors by varying the shear angle during axial compression. For small axial compressions, shearing strains can significantly reduce strain image quality, quantified using the elastographic signal-to-noise and contrast-to-noise ratio. Shear strain effects also increase the noise level in the strain tensor images for larger axial compressions. On the other hand, principal component analysis can be used to project the strain tensor images into the first and second principal component images that provide reproducible strain images with significantly higher elastographic signal and contrast-to-noise ratios.