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.

Motion estimation in ultrasound imaging applied to the diagnostic of pelvic floor disorders

“…In this paper, we propose a hybrid technique, taking advantage from the method called BDBM (Bilinear Deformable Block Matching) in [18] and the 2D delay estimator based on the monogenic signal phase presented in [24]. Moreover, the 2D dense motion fields estimated between pairs of consecutive images are added on the whole sequence [25]. The method proposed here to evaluate the motion of pelvic organs has several advantages: -Locally, the motion of one block of pixels is approximated by a bilinear model which takes into account rigid translations, rotations, dilatations and shear deformations.…”

Motion estimation-based image enhancement in ultrasound imaging

“…The motion estimation method used in this paper, referred to as Bilinear Deformable Block Matching (BDBM) [15,22], is adapted to complex tissue motion estimation and to small local deformations. Unlike classical block matching (BM), also called speckle tracking in US literature, BDBM is based on a local bilinear model and consequently takes into account the local deformations of the tissues.…”

“…The main steps of the BDBM method for estimating the motion between two images are summarized in Algorithm 1 and its comprehensive description can be found in [15]. Compute the dense motion field as detailed in [22].…”

“…The contrast resolution enhancement was assessed in terms of contrast-to-noise ratio (CNR), a criterion often involved in the evaluation of US image processing techniques [22,28]. The CNR is defined as…”

“…The average displacements between two consecutive frames are 0.031 mm and 0.046 mm in the axial and lateral directions, respectively. More details about the thyroid data may be found in [22]. The results are displayed in Fig.…”