In Vivo response to compression of 35 breast lesions observed with a two-dimensional locally regularized strain estimation method

Reconstructing the Spatial Distribution of the Relative Shear Modulus in Quasi-static Ultrasound Elastography: Plane Stress Analysis

Quasi-static ultrasound elastography (QSUE) is an imaging technique that mainly provides axial strain maps of tissues when the latter are subjected to compression. In this article, a method for reconstructing the relative shear modulus distribution within a linear elastic and isotropic medium, in QSUE, is introduced. More specifically, the plane stress inverse problem is considered. The proposed method is based on the variational formulation of the equilibrium equations and on the choice of adapted discretization spaces, and only requires displacement fields in the analyzed media to be determined. Results from plane stress and 3-D numerical simulations, as well as from phantom experiments, showed that the method is able to reconstruct the different regions within a medium, with shear modulus contrasts that unambiguously reveal whether inclusions are stiffer or softer than the surrounding material. More specifically, for the plane stress simulations, inclusion-to-background modulus ratios were found to be very accurately estimated, with an error lower than 3%. For the 3-D simulations, for which the plane stress conditions are no longer satisfied, these ratios were, as expected, less accurate, with an error that remained lower than 10% for two of the three cases analyzed but was around 34% for the last case. Concerning the phantom experiments, a comparison with a shear wave elastography technique from a clinical ultrasound scanner was also made. Overall, the inclusion-to-background shear modulus ratios obtained with our approach were found to be closer to those given by the phantom manufacturer than the ratios provided by the clinical system.

Reconstructing the shear modulus contrast of linear elastic and isotropic media in quasi-static ultrasound elastography

This study focuses on the reconstruction of the shear modulus contrast in linear elastic and isotropic media, in quasi-static ultrasound elastography. The method proposed is based on the variational formulation of the equilibrium equations and on the choice of adapted discretization spaces to estimate the parameters of interest. Experimental results obtained with CIRS phantoms are presented, for which regions with different mechanical properties can be clearly identified in the stiffness contrast maps. Elastic modulus images collected with a shear-wave elastography technique from a clinical ultrasound scanner (Aixplorer) are also provided for comparison. Results show very similar values for the modulus ratios determined by the two elastography approaches.

2D tissue strain tensor imaging in quasi-static ultrasound elastography. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2021;2021:2847-2851. [PMID: 34891841 DOI: 10.1109/embc46164.2021.9630570] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Accurately estimating all strain components in quasi-static ultrasound elastography is crucial for the full analysis of biological media. In this paper, 2D strain tensor imaging is investigated, using a partial differential equation (PDE)-based regularization method. More specifically, this method employs the tissue property of incompressibility to smooth the displacement fields and reduce the noise in the strain components. The performance of the method is assessed with phantoms and in vivo breast tissues. For all the media examined, the results showed a significant improvement in both lateral displacement and strain but also, to a lesser extent, in the shear strain. Moreover, axial displacement and strain were only slightly modified by the regularization, as expected. Finally, the easier detectability of the inclusion/lesion in the final lateral strain images is associated with higher elastographic contrast-to-noise ratios (CNRs), with values in the range [0.68 - 9.40] vs [0.09 - 0.38] before regularization.

Diagnostic utility of strain and shear wave ultrasound elastography in differentiation of benign and malignant solid breast lesions

Background

The purpose of our study was to assess diagnostic performance and comparison of strain and shear wave ultrasound elastography for differentiation of benign and malignant breast lesions compared to histopathological diagnosis as a reference standard. Our single center study involved 100 female patients with 132 solid breast masses. All patients underwent supervision of medical history, clinical examination, conventional B-mode ultrasound which was evaluated according to the BIRADS (Breast Imaging Reporting and Data System), and strain and shear wave ultrasound elastography. Strain ratio for strain elastography, mean elasticity value, and stiff ratio for shear wave elastography were calculated. All breast lesions were biopsied. Comparison of the elastography results with the histopathological diagnoses was done.

Results

There was no statistically significant difference as regard the AUCs for calculated values of strain and shear wave ultrasound elastography (strain ratio, 0.916; mean elasticity, 0.884; and stiff ratio, 0.872; P > 0.05). The AUCs for the combined use of B-mode US and elastography techniques were improved as the following: B-mode + strain, 0.920; B-mode + shear wave 0.952 with a significant P value < 0.001. Higher diagnostic accuracy was noted with the combination of strain and shear wave elastography than each single elastographic modality (P = 0.02).

Conclusions

Ultrasound elastography of breast masses is a non-invasive procedure with high sensitivity. Strain and shear wave elastography had almost similar diagnostic performance and displayed higher diagnostic performance if combined with B-mode ultrasound which helps in decreasing the number of unneeded breast biopsies.

Muscle elastography in multiple sclerosis spasticity

Ultrasound elastography is a novel imaging modality for evaluating the elasticity of biological tissues. The technique is widely used in oncology to detect and differentiate malignant lesions in soft tissues. Studies have explored use of ultrasound elastography to measure the mechanical properties of muscle in patients with multiple sclerosis spasticity. Real-time elastography was shown to correlate well with subjective scales commonly used to measure MS spasticity. Ultrasound elastography has the potential to become a new objective gold standard to monitor symptom evolution in patients with MS spasticity and to evaluate the efficacy of antispasticity treatment.

Comparison and Combination of Strain and Shear Wave Elastography of Breast Masses for Differentiation of Benign and Malignant Lesions by Quantitative Assessment: Preliminary Study

OBJECTIVES

To compare the diagnostic performance of strain and shear wave elastography of breast masses for quantitative assessment in differentiating benign and malignant lesions and to evaluate the diagnostic accuracy of combined strain and shear wave elastography.

METHODS

Between January and February 2016, 37 women with 45 breast masses underwent both strain and shear wave ultrasound (US) elastographic examinations. The American College of Radiology Breast Imaging Reporting and Data System (BI-RADS) final assessment on B-mode US imaging was assessed. We calculated strain ratios for strain elastography and the mean elasticity value and elasticity ratio of the lesion to fat for shear wave elastography. Diagnostic performances were compared by using the area under the receiver operating characteristic curve (AUC).

RESULTS

The 37 women had a mean age of 47.4 years (range, 20-79 years). Of the 45 lesions, 20 were malignant, and 25 were benign. The AUCs for elasticity values on strain and shear wave elastography showed no significant differences (strain ratio, 0.929; mean elasticity, 0.898; and elasticity ratio, 0.868; P > .05). After selectively downgrading BI-RADS category 4a lesions based on strain and shear wave elastographic cutoffs, the AUCs for the combined sets of B-mode US and elastography were improved (B-mode + strain, 0.940; B-mode + shear wave; 0.964; and B-mode, 0.724; P < .001). Combined strain and shear wave elastography showed significantly higher diagnostic accuracy than each individual elastographic modality (P = .031).

CONCLUSIONS

These preliminary results showed that strain and shear wave elastography had similar diagnostic performance. The addition of strain and shear wave elastography to B-mode US improved diagnostic performance. The combination of strain and shear wave elastography results in a higher diagnostic yield than each individual elastographic modality.

Specific Ultrasound Data Acquisition for Tissue Motion and Strain Estimation: Initial Results

Ultrasound applications such as elastography can benefit from 3-D data acquisition and processing. In this article, we describe a specific ultrasound probe, designed to acquire series of three adjacent imaging planes over time. This data acquisition makes it possible to consider the out-of-plane motion that can occur at the central plane during medium scanning, and is proposed with the aim of improving the results of strain imaging. In this first study, experiments were conducted on phantoms, and controlled axial and elevational displacements were applied to the probe using a motorized system. Radiofrequency ultrasound data were acquired at a 40-MHz sampling frequency with an Ultrasonix ultrasound scanner, and processed using a 3-D motion estimation method. For each of the 2-D regions of interest of the central plane in pre-compression data, a 3-D search was run to determine its corresponding version in post-compression data, with this search taking into account the region-of-interest deformation model chosen. The results obtained with the proposed ultrasound data acquisition and strain estimation were compared with results from a classic approach and illustrate the improvement produced by considering the medium's local displacements in elevation, with notably an increase in the mean correlation coefficients achieved.

Radiofrequency ultrasound data acquisition with a 640-element array transducer for strain imaging: Experimental results with phantoms and biological tissue samples

This paper presents ultrasound elastography results obtained with a 640-element array transducer we have recently developed. This probe allows the acquisition of series of three adjacent imaging planes over time and therefore makes possible the computation of 2-D elastograms, with consideration of out-of-plane motion. In this study, elastography experiments were conducted on phantoms and bovine tissue samples, and compression was manually applied to the media via the hand-held ultrasound transducer. The results obtained with the proposed data acquisition and 3-D processing are presented and compared to those from a classical 2-D approach.