Investigation of out-of-plane motion artifacts in 2D noninvasive vascular ultrasound elastography

Abstract

Ultrasound noninvasive vascular elastography (NIVE) has shown its potential to measure strains of carotid arteries to predict plaque instability. When two-dimensional (2D) strain estimation is performed, either in longitudinal or cross-sectional view, only in-plane motions are considered. The motions in elevation direction (i.e. perpendicular to the imaging plane), can induce estimation artifacts affecting the accuracy of 2D NIVE. The influence of such out-of-plane motions on the performance of axial strain and axial shear strain estimations has been evaluated in this study. For this purpose, we designed a diseased carotid bifurcation phantom with a 70% stenosis and an in vitro experimental setup to simulate orthogonal out-of-plane motions of 1 mm, 2 mm and 3 mm. The Lagrangian speckle model estimator (LSME) was used to estimate axial strains and shears under pulsatile conditions. As anticipated, in vitro results showed more strain estimation artifacts with increasing magnitudes of motions in elevation. However, even with an out-of-plane motion of 2.0 mm, strain and shear estimations having inter-frame correlation coefficients higher than 0.85 were obtained. To verify findings of in vitro experiments, a clinical LSME dataset obtained from 18 participants with carotid artery stenosis was used. Deduced out-of-plane motions (ranging from 0.25 mm to 1.04 mm) of the clinical dataset were classified into three groups: small, moderate and large elevational motions. Clinical results showed that pulsatile time-varying strains and shears remained reproducible for all motion categories since inter-frame correlation coefficients were higher than 0.70, and normalized cross-correlations (NCC) between radiofrequency (RF) images were above 0.93. In summary, the performance of LSME axial strain and shear estimations appeared robust in the presence of out-of-plane motions (<2 mm) as encountered during clinical ultrasound imaging.

Interframe Echo Intensity Variation of Subregions and Whole Plaque in Two‐Dimensional Carotid Ultrasonography

“…Thus, for small scattering structures, the out‐of‐plane motion should be the main maker of cardiac cycle‐induced intensity changes in the 2D B‐mode image sequence of arterial plaques. In a related study by Li et al, 33 the authors evaluated the influence of out‐of‐plane motion on elastography using a tissue‐mimicking phantom. They found that out‐of‐plane motions up to 2 mm did not influence strain estimations.…”

“…Thus, for small scattering structures, the out-of-plane motion should be the main maker of cardiac cycle-induced intensity changes in the 2D B-mode image sequence of arterial plaques. In a related study by Li et al, 33 the authors The entries are described by mean AE SD (min; max). GSM, grayscale median; CC, correlation coefficient; SD-map, standard deviation map; CC-map, correlation coefficient map; CV, coefficient of variation; AUC, area under the curve.…”

Deep learning in ultrasound elastography imaging: A review

“…Out-of -plane motion is another potential factor causing estimation artifacts in the context of NIVE. 30 In addition, it is not easy to perform 2D estimations in the frequency domain as lateral phase information is not available as there is no carrier frequency in the lateral direction with conventional ultrasound images. As an alternative, a dedicated transverse oscillation image reconstruction method 31,32 can be used for image reconstruction before strain estimations, as in Ref.…”

An integrated ultrasound imaging and abdominal compression device for respiratory motion management in radiation therapy

“…First, US usually works in planar imaging mode and has limited field of view, 23,24 often resulting in in-plane and/or cross-plane loss of tracking targets. 16,25,26 Second, respiratory motion can cause organ deformation 27 and change the appearance of tracking targets, 12,28 relationship between targets and surrogates. In addition, the positioning of US probe is user-dependent and has considerable inter-fraction uncertainty.…”