Ultrasonic Strain Imaging Research Articles

Evaluation of the diagnostic performance of contrast-enhanced ultrasound combined with BRAF V600E gene detection in nodules of unclear significance by thyroid fine-needle aspiration.

Our study aims to test the diagnostic performance of contrast-enhanced ultrasound (CEUS) combined with the detection of serine/threonine-protein kinase V600E (BRAF V600E) in nodules of unclear significance by thyroid fine-needle aspiration (FNA). From January 2015 to December 2019, 244 patients were subjected to ultrasonic strain imaging and elastography, CEUS, and BRAF V600E gene detection at Lishui Hospital of Zhejiang University. Thyroid FNA does not confirm the benignancy and malignancy of the thyroid nodules. With postoperative pathology as the gold standard, the diagnostic value of CEUS, BRAF V600E detection, and the combination in differentiating benign and malignant thyroid nodules were evaluated. The negative predictive value (NPV) and accuracy of CEUS, BRAF V600E detection, and the combination were calculated along with sensitivity, specificity, and positive predictive value (PPV). In this study, the sensitivity, specificity, PPV, NPV, accuracy, and AUC of CEUS alone in predicting benign and malignant thyroid nodules were 69.8%, 94.9%, 98.6%, 37.4%, 73.8% and 0.884, respectively. The sensitivity, specificity, PPV, NPV, accuracy and AUC of BRAF V600E detection alone were 65.4%, 100%, 100%, 35.5%, 70.9% and 0.827, respectively. The sensitivity, specificity, PPV, NPV, accuracy and AUC of the combination were 73.2%, 94.9%, 98.7%, 40.2%, 76.6% and 0.923, respectively. Therefore, compared with CEUS or BRAF V600E gene detection alone, the combination of CEUS and BRAF V600E gene detection has a higher sensitivity, NPV, and accuracy in the diagnosis of thyroid nodules.

Visualization and quantification of myocardial mechanical changes of left ventricle in systemic lupus erythematosus patients using ultrasonic layer-specific strain imaging

Objective To evaluate the damage of longitudinal mechanical parameters of left ventricular myocardium by ultrasonic layer-specific strain imaging in patients with systemic lupus erythematosus (SLE) without conventional evidence of cardiovascular system involvement. Methods Seventy-eight patients suffered from SLE without conventional evidence of cardiovascular system involvement (SLE group) and 48 healthy volunteers with age and sex matched (control group) were selected for this study. The left ventricular conventional structure and functional parameters were measured by conventional echocardiography. Then layer-specific strain imaging was performed in both groups to obtain left ventricular endocardial myocardial global longitudinal strain (GLSendo), mid-myocardial GLS (GLSmid), epicardial GLS (GLSepi) and basal segment, middle segment and apex longitudinal strain (LS) of all three layers of the myocardium. Then the transmural difference of the GLS (ΔLS=GLSendo-GLSepi) were calculated. The related parameters between these two groups were compared for difference and correlation analysis of related mechanical parameters were also made. Results ①There was no significant difference in the left ventricular ejection fraction (LVEF) and left ventricular stroke volume (LVSV ) between the two groups (all P>0.05); Compared with the control group, the mean E/e in the SLE group was increased and the E/A, E, e were decreased (all P 0.05). ②The myocardial global longitudinal strain(GLS) of the two groups were decreased from endocardial to epicardial gradient; the values of GLS and segmental LS of all three layers in the SLE group were decreased (all P<0.05); the ΔLS of the SLE group was decreased compared with the control group (P<0.05); the value of peak strain dispersion (PSD) were increased in SLE patients (P<0.05). ③The correlation analysis showed the GLS of each layer of myocardium in SLE patients were negatively correlated with disease duration (rs=-0.34~-0.36, all P<0.05) and SLE disease activity index(SLEDAI) (rs=-0.25~-0.30, all P<0.05). Conclusions The ultrasonic layer-specific strain imaging can quantitatively detect the damage of mechanical parameters of left ventricle in SLE patients, which is more sensitive than the conventional echocardiography in evaluating left ventricular systolic function. It may provide visual evidence for early diagnosis of cardica dysfunction in SLE patients. Key words: Ultrasonography; Systemic lupus erythematosus; Myocardium; Layer-specific strain

Evaluation of left ventricular myocardial systolic dysfunction in patients with obstructive sleep apnea hypopnea syndrome using three-dimensional strain echocardiography

Objective To evaluate left ventricular myocardial systolic function in patients with obstructive sleep apnea hypopnea syndrome (OSAHS) with normal left ventricular ejection fraction(LVEF) using three-dimensional strain echocardiography. Methods One hundred patients with OSAHS were divided into mild group, moderate group and severe group according to apnea hypopnea index(AHI) while matched with 32 healthy people as control group. The parameters such as three-dimensional LVEF, global longitudinal strain(GLS), global circumferential strain(GCS), global area strain(GAS), global radial strain (GRS), twist and torsion based on standard three-dimensional echocardiography were measured by three-dimensional strain echocardiography, the above parameters among the four groups were compared for difference.Linear correlationship between AHI, LVEF and the three dimensional strain parameters was analyzed respectively. Results ①There was no significant difference in three-dimensional LVEF, twist and torsion between each groups(P>0.05). ②GLS, GAS and GRS were lower in mild, moderate and severe group compared with control group, decreasing along with the disease severity (P<0.01 or P<0.05). GCS in severe group was lower than that in control group (P<0.01). ③GLS and GAS in severe group were lower than those in mild group (all P<0.05). GRS in moderate and severe group were lower than that in mild group(all P<0.05), GAS, GRS in severe group was lower than those in moderate group(P<0.05). ④There was a mild correlation between GLS and AHI (r=0.342, P<0.01), GAS and AHI (r=0.294, P<0.01), GRS and AHI (r=-0.411, P<0.01). There was a mild correlation between GCS and three-dimensional LVEF (r=-0.354, P<0.01), GAS and three-dimensional LVEF (r=-0.326, P<0.01), GRS and three-dimensional LVEF (r=0.300, P<0.01). Conclusions The left ventricular myocardial systolic function is impaired in all patients with OSAHS even with normal LVEF and the dysfunction is aggravating with the disease severity. Ultrasonic three-dimensional strain imaging technology can be used to detect the subclinical myocardial systolic dysfunction quantitatively in the early stage of OSAHS patients. Key words: Ultrasonography; Obstructive sleep apnea hypopnea syndrom; Ventricular function, left; Myocardial contraction; Strain

Artifacts detection-based adaptive filtering to noise reduction of strain imaging

Strain imaging in medical ultrasound is the imaging modality of elastic properties of biological tissue. In general, strain image will suffer from artifacts noise, which degrades lesion detectability and increases the likelihood of misdiagnosis. How to both suppress artifacts effectively and preserve the structure is vital for diagnosis and also for image post-processing. The bilateral filtering can reduce artifact noise and, at the same time, maintain the tissue structure. However, the balance between noise suppression and edge preservation often makes the threshold selection difficult. This paper is to solve the problem of difficult threshold selection in bilateral filtering. The probability distribution function of amplitude modulation noise in this paper is derived from the statistics of uncompressed speckle. The statistical model of artifact formation is useful for designing an adaptive fast bilateral filter for artifact reduction in ultrasound strain imaging. Both simulation and phantom testing show that the proposed method can improve the quality of ultrasonic strain imaging. Furthermore, the elastographic signal-to-noise ratio was increased by 129.91% and 52.36% for simulated and phantom strain images. The elastographic contrast-to-noise ratio was increased by 521.42% and 218.07% for simulated and phantom strain images, respectively. As indicated by the profiles, the proposed method produces a better result for the purpose of visualization.

Edge-preserving ultrasonic strain imaging with uniform precision.

Ultrasound elastography involves measuring the mechanical properties of tissue, and has many applications in diagnostics and intervention. A common step in different elastography methods is imaging the tissue while it undergoes deformation and estimating the displacement field from the images. A popular next step is to estimate tissue strain, which gives clues into the underlying tissue elasticity modulus. To estimate the strain, one should compute the gradient of the displacement image, which amplifies the noise. The noise is commonly minimized by least square estimation of the gradient from multiple displacement measurements, which reduces the noise by sacrificing image resolution. In this work, we adaptively adjust the level and orientation of the smoothing using two different mechanisms. First, the precision of the displacement field decreases significantly in the regions with high signal decorrelation, which requires increasing the smoothness. Second, smoothing the strain field at the boundaries between different tissue types blurs the edges, which can render small targets invisible. To minimize blurring and noise, we perform anisotropic smoothing parallel to the direction of edges. The first mechanism ensures that textures/variations in the strain image reflect underlying tissue properties and are not caused by errors in the displacement estimation. The second mechanism keeps the edges between different tissue structures sharp while minimizing the noise. We validate the proposed method using phantom and in-vivo clinical data.

Stochastic precision analysis of 2D cardiac strain estimation in vivo

Ultrasonic strain imaging has been applied to echocardiography and carries great potential to be used as a tool in the clinical setting. Two-dimensional (2D) strain estimation may be useful when studying the heart due to the complex, 3D deformation of the cardiac tissue. Increasing the framerate used for motion estimation, i.e. motion estimation rate (MER), has been shown to improve the precision of the strain estimation, although maintaining the spatial resolution necessary to view the entire heart structure in a single heartbeat remains challenging at high MERs. Two previously developed methods, the temporally unequispaced acquisition sequence (TUAS) and the diverging beam sequence (DBS), have been used in the past to successfully estimate in vivo axial strain at high MERs without compromising spatial resolution. In this study, a stochastic assessment of 2D strain estimation precision is performed in vivo for both sequences at varying MERs (65, 272, 544, 815 Hz for TUAS; 250, 500, 1000, 2000 Hz for DBS). 2D incremental strains were estimated during left ventricular contraction in five healthy volunteers using a normalized cross-correlation function and a least-squares strain estimator. Both sequences were shown capable of estimating 2D incremental strains in vivo. The conditional expected value of the elastographic signal-to-noise ratio (E(SNRe|ε)) was used to compare strain estimation precision of both sequences at multiple MERs over a wide range of clinical strain values. The results here indicate that axial strain estimation precision is much more dependent on MER than lateral strain estimation, while lateral estimation is more affected by strain magnitude. MER should be increased at least above 544 Hz to avoid suboptimal axial strain estimation. Radial and circumferential strain estimations were influenced by the axial and lateral strain in different ways. Furthermore, the TUAS and DBS were found to be of comparable precision at similar MERs.

The potential role of ultrasonic strain imaging and immunophenotyping in diagnosing acute rejection after heart transplantation

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A hybrid displacement estimation method for ultrasonic elasticity imaging

Axial displacement estimation is fundamental to many freehand quasistatic ultrasonic strain imaging systems. In this paper, we present a novel estimation method that combines the strengths of quality-guided tracking, multi-level correlation, and phase-zero search to achieve high levels of accuracy and robustness. The paper includes a full description of the hybrid method, in vivo examples to illustrate the method's clinical relevance, and finite element simulations to assess its accuracy. Quantitative and qualitative comparisons are made with leading single- and multi-level alternatives. In the in vivo examples, the hybrid method produces fewer obvious peak-hopping errors, and in simulation, the hybrid method is found to reduce displacement estimation errors by 5 to 50%. With typical clinical data, the hybrid method can generate more than 25 strain images per second on commercial hardware; this is comparable with the alternative approaches considered in this paper.

Initial clinical experience of an ultrasonic strain imaging system with novel noise-masking capability

Quasistatic strain imaging is a form of elastography that can produce qualitative images of tissue stiffness with only software modifications to conventional ultrasound hardware. Unlike current commercial offerings, the novel strain-imaging system that is the subject of this paper displays regions of signal decorrelation using an overlaid colour mask and can also produce three-dimensional (3D) strain images. In illustrative studies of the breast, testis and thyroid, the colour mask is seen to reduce the potential to misinterpret noise as meaningful stiffness information, and also helps to differentiate cystic and solid lesions. High-quality imaging of the testis in vivo demonstrates that 3D strain imaging is feasible.

3-D ultrasonic strain imaging using freehand scanning and a mechanically-swept probe - correspondence

This paper compares 2 approaches to 3-D ultrasonic axial strain imaging: a tracked ultrasound probe swept manually over a volume, and a mechanically-swept 3-D probe. We find that high-quality data are more easily obtained using the 3-D probe, but the freehand approach may be more practical in certain scanning situations.

A Generalized Speckle Tracking Algorithm for Ultrasonic Strain Imaging Using Dynamic Programming

This study developed an improved motion estimation algorithm for ultrasonic strain imaging that employs a dynamic programming technique. In this article, we model the motion estimation task as an optimization problem. Since tissue motion under external mechanical stimuli often should be reasonably continuous, a set of cost functions combining correlation and various levels of motion continuity constraint were used to regularize the motion estimation. To solve the optimization problem with a reasonable computational load, a dynamic programming technique that does not require iterations was used to obtain displacement vectors in integer precision. Then, a subsample estimation algorithm was used to calculate local displacements in fractional precision. Two implementation schemes were investigated with in vivo ultrasound echo data sets. We found that the proposed algorithm provides more accurate displacement estimates than our previous algorithm for in vivo clinical data. In particular, the new algorithm is capable of tracking motion in more complex anatomy and increases strain image consistency in a sequence of images. Preliminary results also suggest that a significantly longer sequence of high contrast strain images could be obtained with the new algorithm compared with the previous algorithm. The new algorithm can also tolerate larger motion discontinuities ( e.g., cavity in an anthropomorphic uterine phantom). (E-mail: jjiang2@wisc.edu)

Patent Foramen Ovale Closure

Setting aside the controversial questions of whether closing a patent foramen ovale (PFO) is indicated or effective for the prevention of recurrent stroke or the treatment of migraine headaches, what is the physiological impact of implanting a transcatheter device in the atrial septum? In this issue of Circulation , Wohrle and his colleagues address 1 aspect of this question, reporting the results of a study in which they assessed atrioventricular and semilunar valve function in 102 patients before and after transcatheter PFO closure.1 The authors evaluated valvar competence before, the day following, and 12 months after PFO closure and found no significant change in aortic regurgitation (AR) or regurgitation of the other cardiac valves. On their own, these findings might be passed off as predictable and modestly novel. Viewed in the context of a recent article by Schoen et al in Heart , however, they are noteworthy.2 Accordingly, to appreciate the study by Wohrle et al fully, it should be read as a counterpoint to the report by Schoen et al, which was a surprise to many in its description of new or increased AR in 10% of 170 patients who underwent transcatheter closure of a PFO and 9% of 70 in whom a device was placed to close an atrial septal defect.2 Article see p 3002 Before simply accepting the apparently contradictory findings of these 2 studies, however, it is worth acknowledging several basic methodological differences. The first difference is the means by which valvar regurgitation was assessed. In contrast to Schoen et al, who evaluated valvar function with transesophageal echocardiography 3, 6, and 12 months after catheterization, Wohrle et al assessed the function of the aortic and other valves with cardiac magnetic resonance imaging. Schoen et al graded AR according to a standard ordinal scale, …

Ultrasonic Viscoelasticity Imaging of Nonpalpable Breast Tumors: Preliminary Results

Improvements in the diagnosis of early breast cancers depend on a physician's ability to obtain the information necessary to distinguish nonpalpable malignant and benign tumors. Viscoelastic features that describe mechanical properties of tissues may help to distinguish these types of lesions. Twenty-one patients with nonpalpable, pathology-confirmed Breast Imaging Reporting and Data System (BIRADS) 4 or 5 breast lesions (10 benign, 11 malignant) detected by mammography were studied. Viscoelastic parameters were extracted from a time sequence of ultrasonic strain images, and differences in the parameters between malignant and benign tumors were compared. Parametric data were color coded and superimposed on sonograms. The strain retardance time parameter, T(1), provided the best discrimination between malignant and benign tumors (P < .01). T(1) measures the time required for tissues to fully deform (strain) once compressed; therefore, it describes the time-varying viscous response of tissue to a small deforming force. Compared to the surrounding background tissues, malignant lesions have smaller average T(1) values, whereas benign lesions have higher T(1) values. This tissue-specific contrast correlates with known changes in the extracellular matrix of breast stroma. Characterization of nonpalpable breast lesions is improved by the addition of viscoelastic strain imaging parameters. The differentiation of malignant and benign BI-RADS 4 or 5 tumors is especially evident with the use of the retardation time estimates, T(1).

An Intelligent Interface for Freehand Strain Imaging

We present a new, intelligent interface for freehand strain imaging, which has been designed to support clinical trials investigating the potential of ultrasonic strain imaging for diagnostic purposes across a broad range of target pathologies. The aim with this interface is to make scanning easier and to help clinicians learn the necessary scanning technique quickly, by providing real time feedback indicating the quality of the strain data as they are produced. The methods require a pixel-level indicator of estimation precision, which can be calculated in-line with strain estimation. This is exploited in novel approaches to normalisation, persistence and display. The effect of each component is indicated in the results with examples from in vitro and in vivo scanning. As well as providing real-time feedback, the images are easier to interpret because data at unacceptably low signal-to-noise ratios do not reach the display. Additionally, the level of noise in the displayed images is actually reduced compared with other methods that use the same strain estimates with the same level of persistence. The interface also considerably reduces the difficulty in producing volumes of strain data from freehand three-dimensional scans. (E-mail: jel35@eng.cam.ac.uk)

Dynamic Resolution Selection in Ultrasonic Strain Imaging

Ultrasonic strain imaging promises to be a valuable tool in medical diagnostics. Reliability and ease-of-use have become important considerations. These depend on selection of appropriate imaging parameters. Two tasks are undertaken here. The tradeoff between resolution and estimation precision is examined closely to establish models for the relationships with imaging parameters and data properties. These models are then applied in a system that automatically sets the imaging parameters responsive to the data quality and the required estimation precision, so as to produce more meaningful images under varying scan conditions. The new system is applied to simulation, in vitro and in vivo data for validation. It reduces the complexity of the sonographer's role in strain imaging, and produces images of reliable quality even when the level of signal decorrelation varies throughout the ultrasound data. (E-mail: jel35@eng.cam.ac.uk)

Arterial Stiffness Is Associated With Left Ventricular Diastolic Function in Patients With Cardiovascular Risk Factors: Early Detection With the Use of Cardio-Ankle Vascular Index and Ultrasonic Strain Imaging

Background It is well known that left ventricular (LV) diastolic function declines in the elderly, especially in patients with cardiovascular risk factors. However, few data are available on the early detection of relationship between arterial stiffness and LV diastolic dysfunction. Methods and Results The common carotid artery intima-media thickness (IMT) and cardio-ankle vascular index (CAVI) were measured to determine the presence of subclinical atherosclerosis in 30 patients (13 men and 17 women; mean age 59 ± 5.7 years) with 1 or more cardiovascular risk factors. LV systolic and diastolic function also were determined by measuring transmitral flow velocity, mitral annular motion velocity, and myocardial strain and strain rate profiles using pulsed Doppler, tissue velocity, and ultrasonic strain imaging. The CAVI correlated with the peak early diastolic velocity of transmitral flow velocity ( r = −0.50, P < .01), the ratio of peak early to late diastolic transmitral flow velocity ( r = −0.37, P < .05), the deceleration time from peak to baseline of the early diastolic transmitral flow velocity ( r = 0.57, P < .01), the peak early diastolic mitral annular motion velocity ( r = −0.41, P < .05), and the peak early diastolic strain rates at the endocardial sites of the LV posterior and inferior walls ( r = 0.61, P < .001; r = 0.56, P < .001, respectively). There were no relationships between CAVI and LV ejection fraction, peak systolic mitral annular motion velocity, or peak systolic strain rates of the LV walls. Multiple regression analysis revealed that the early diastolic strain rates at the endocardial sites of the LV walls are strongly correlated with CAVI. There were no relationships between the IMT and the LV systolic and diastolic parameters. Conclusion These results suggest that cardiovascular risk factors interact to affect arterial stiffness and LV relaxation, and therefore support the importance of screening using CAVI and ultrasonic strain imaging and early intervention in this patient population.

Estimation of Displacement Location for Enhanced Strain Imaging

Ultrasonic strain imaging usually begins with displacement estimates computed using finite-length sections of RF ultrasound signals. Amplitude variations in the ultrasound are known to perturb the location at which the displacement estimate is valid. If this goes uncorrected, it is a significant source of estimation noise, which is amplified when displacement fields are converted into strain images. We present a study of this effect based on theoretical analysis and practical experiments. A correction method based on the analysis is tested on phase zero and correlation coefficient strain imaging, and compared to the amplitude compression techniques of earlier studies. We also test adaptive strain estimation to provide a benchmark, but the performance of our new method matches or surpasses this benchmark under normal scanning conditions. Furthermore, the new correction is suitable for real time applications owing to its extreme computational simplicity.

Performance Evaluation of Displacement Estimators for Real-Time Ultrasonic Strain and Blood Flow Imaging With Improved Spatial Resolution

Ultrasonic strain and blood flow imaging has great potential to improve early tumor detection. Both methods have the same task of estimating echo signal displacements. To be able to resolve tissue stiffness and vascularity of tumors while they are still small, spatial resolution must be improved. Moreover, ultrasonic real-time imaging is vital in clinical practice. In this paper, we evaluate the estimation performances of one novel and several established displacement estimators with real-time capability and compare these with results from cross-correlation-based standard estimators when echo signals that are typically available with a commercial ultrasound scanner set to yield the highest spatial resolution are used. Estimation errors are investigated as a function of sampling rate, signal-to-noise ratio, displacement and strain magnitudes, and frequency-dependent tissue attenuation. Results are from simulations using the FIELD II program to generate ultrasonic echo signals and tissue-mimicking phantom experiments using a Voluson 730 medical ultrasound scanner (GE medical systems Kretztechnik, Austria) that is equipped with a digital research interface that enables the export of beam-formed radio frequency echo data.

Predictive Value of Associations Between Carotid Arterial Sclerosis and Left Ventricular Diastolic Dysfunction in Patients with Cardiovascular Risk Factors

It is well known that arterial stiffness affects the morbidity and mortality associated with cardiovascular disease. However, there are limited data addressing the relationship between arterial stiffness and left ventricular (LV) diastolic function in patients with cardiovascular risk factors. Subclinical atherosclerosis was determined by measuring the intima-media thickness and stiffness (beta) of the left and right common carotid arteries using B- and M-mode ultrasonography in 30 patients with one or more cardiovascular risk factors. LV systolic and diastolic function were also determined by measuring transmitral flow velocity, mitral annular motion velocity, and myocardial strain and strain rate profiles using pulsed Doppler, tissue velocity, and ultrasonic strain imaging. The carotid stiffness beta was greater and the peak early diastolic strain rates of the LV posterior and inferior walls were lower in these patients than in the age-matched control group. The carotid intima-media thickness correlated only with body mass index and LV wall thickness. The carotid stiffness beta correlated with age, peak early diastolic velocity and deceleration time of the transmitral flow, peak early diastolic mitral annular motion velocity, and peak early diastolic strain rates of the LV walls. Multiple linear regression analysis revealed that early diastolic strain rates of the LV walls are strongly related to carotid stiffness beta. In conclusion, LV relaxation is significantly associated with carotid arterial atherosclerosis, particularly sclerosis, in patients with cardiovascular risk factors. These results support the importance of screening using ultrasonic strain imaging and early intervention in this patient population.

A parallelizable real-time motion tracking algorithm with applications to ultrasonic strain imaging

Ultrasound-based mechanical strain imaging systems utilize signals from conventional diagnostic ultrasound systems to image tissue elasticity contrast that provides new diagnostically valuable information. Previous works (Hall et al 2003 Ultrasound Med. Biol. 29 427, Zhu and Hall 2002 Ultrason. Imaging 24 161) demonstrated that uniaxial deformation with minimal elevation motion is preferred for breast strain imaging and real-time strain image feedback to operators is important to accomplish this goal. The work reported here enhances the real-time speckle tracking algorithm with two significant modifications. One fundamental change is that the proposed algorithm is a column-based algorithm (a column is defined by a line of data parallel to the ultrasound beam direction, i.e. an A-line), as opposed to a row-based algorithm (a row is defined by a line of data perpendicular to the ultrasound beam direction). Then, displacement estimates from its adjacent columns provide good guidance for motion tracking in a significantly reduced search region to reduce computational cost. Consequently, the process of displacement estimation can be naturally split into at least two separated tasks, computed in parallel, propagating outward from the center of the region of interest (ROI). The proposed algorithm has been implemented and optimized in a Windows® system as a stand-alone ANSI C++ program. Results of preliminary tests, using numerical and tissue-mimicking phantoms, and in vivo tissue data, suggest that high contrast strain images can be consistently obtained with frame rates (10 frames s−1) that exceed our previous methods.