Ultrasound Image Sequence Registration and its Application for Thyroid Nodular Disease

Abstract

Ultrasound elastography is a promising technique that can assist in diagnosis of thyroid cancer. However, the tissue movements generated by the freehand compression are complex and difficult to estimate. Therefore, the aim of this study was to propose a motion estimation technique adapted to our application. First, a parametric deformable block matching is introduced and shown to provide better results than classical block matching. Afterwards, the extension of this method to motion estimation with image sequences is presented. Moreover, motion analysis using a technique of compression orientation detection led us to introduce a new parameter based on the angle of estimated motion vectors. The accuracy of our methods was tested on simulated and in-vivo ultrasound images. The in-vivo data sets correspond to thyroid gland images acquired using freehand tissue compression by ultrasound probe of a clinical ultrasound scanner modified for research. Thus, we show how our method improves the contrast between the healthy part of the thyroid and the malignant tumor by a factor of 3 compared to ultrasound images and by a factor of 2 compared to classical strain images.