  Ultrasound elastography is the method to image the elasticity of compliant
tissues due to a mechanical compression applied to it. In elastography, the
local strain of explored tissue is estimated by analyzing the echo signals.
This is accomplished by a sonographer who uses ultrasound transducer to apply
pressure on the tissue area causing displacement of the tissue. A set of data
is obtained before and after the compression. This stress along the axial
direction not only causes deformation in that direction but it can also cause
lateral deformation in the tissue. This relative deformation is later
calculated using tracking algorithms. Finally, estimating the elasticity,
images are formed. In this paper, we introduce a novel strain estimator. The
proposed 1.5D strain estimator uses 1D windows for swift computations and
searches the lateral direction for taking the non-axial movement into account.
We have investigated the performance of our estimator using simulated and
in-vivo data of breast tissue. The performance of our method is verified by
comparing with different methods up to 16\% applied strain. The proposed
estimator has exhibited a superior performance compared to the conventional
methods. The image quality significantly improves, especially in the presence
of higher applied strain, when the non-axial motion is significant.
