Comparison of contrast-to-noise ratios of axial strain, shear modulus, and inverse of shear modulus estimated by axial strain ratio

Abstract

Occasionally, an axial strain image is dealt with as an image of relative shear modulus. However, we previously confirmed that the imaging of the 1-D relative shear modulus reconstruction obtained by the ratio of the axial strain in the axial direction (i.e., axial strain ratio) can yield a larger contrast-to-noise ratio (CNR) than that of the axial strain, although both the axial strain ratio and the axial strain have smaller relative contrasts than that of the original shear modulus. We also reported the imaging of the inverse of the relative shear modulus (i.e., the inverse of the axial strain ratio). In this report, the evaluations of CNRs on simulated phantoms clarify that, for local tumors, immediately after strain measurement, we can determine whether we should image the axial strain ratio or the inverse of the axial strain ratio, i.e., by using the statistical evaluations of measured strains in the tumor and the surrounding region. This also shows that the evaluations of CNRs of the strain ratio and the inverse of the strain ratio are effective. We also confirmed that reference regions should be properly set in the homogeneous neighborhood in front of or behind the target by viewing B-mode and strain images.