Conventional Elastography Research Articles

Magnetomotive Ultrasound Shear Wave Elastography (MMUS-SWE): A Validation Study From Simulations to Experiments.

Ultrasound elastography is a functional imaging method that enables the measurement of soft tissue elasticity, which is associated with the pathological process of many diseases. However, the measurement area of the conventional elastography method is subjectively selected. Inspired by the targeted imaging technology, we propose a method of magnetomotive ultrasound shear wave elastography (MMUS-SWE). This method utilizes the magnetic force between the magnetic nanoparticles (MNPs) and the external magnetic field to generate shear waves. Then, it can detect the distribution of MNPs and the elasticity of the tissue around the MNPs. As MNPs have been widely used for targeted labeling, the strategy to induce local vibration by MNPs will be more specific than that of the conventional SWE. In this study, the theoretical feasibility was verified by the finite element simulation model. Then, an experimental system was built, and the experimental feasibility of the method was demonstrated through phantom experiments, in vitro tissue experiments, and in vivo experiments. The results show that the distribution of the MNPs and the elastic information of tissues surrounding the MNPs can be detected simultaneously. This technology is expected to realize targeted elasticity measurement based on the MNPs and has potential applications for disease diagnosis.

Asynchronous magnetic resonance elastography: Shear wave speed reconstruction using noise correlation ofincoherent waves.

The noninvasive measurement of biological tissue elasticity is an evolving technology that enables the robust characterization of soft tissue mechanics for a wide array of biomedical engineering and clinical applications. We propose, design, and implement here a new MRI technique termed asynchronous magnetic resonance elastography (aMRE) that pushes the measurement technology toward a driverless implementation. This technique can be added to clinical MRI scanners without any additional specialized hardware. Asynchronous MRE is founded on the theory of diffuse wavefields and noise correlation previously developed in ultrasound to reconstruct shear wave speeds using seemingly incoherent wavefields. Unlike conventional elastography methods that solve an inverse problem, aMRE directly reconstructs a pixel-wise mapping of wave speed using the spatial-temporal statistics of the measured wavefield. Incoherent finger tapping served as the wave-generating source for all aMRE measurements. Asynchronous MRE was performed on a phantom using a Siemens Prismafit as an experimental validation of the theory. It was further performed on thigh muscles as a proof-of-concept implementation of in vivo imaging using a Siemens Skyra scanner. Numerical and phantom experiments show an accurate reconstruction of wave speeds from seemingly noisy wavefields. The proof-of-concept thigh experiments also show that the aMRE protocol can reconstruct a pixel-wise mapping of wave speeds. Asynchronous MRE is shown to accurately reconstruct shear wave speeds in phantom experiments and remains at the proof-of-concept stage for in vivo imaging. After further validation and improvements, it has the potential to lower both the technical and monetary barriers of entry to measuring tissue elasticity.

Comparative study between conventional ultrasound strain elastography and an AI-enabled elastography software in differentiating breast masses

BackgroundConventional ultrasound elastography is a relatively novel noninvasive imaging study that assesses tissue stiffness and helps in the characterization of breast lesions. However, strain elastography is not available in some ultrasound machines especially those before 2003 and is susceptible by motion artifacts. Our aim was to compare the results of conventional ultrasound elastography and the results of an advanced intelligence-enabled elastography software. Also, we aimed to assess the feasibility of the AI-enabled elastography software to overcome the unavailability of the conventional elastography software in some new ultrasound machines.ResultsThe study included 53 patients, who had breast lesions either clinically felt or detected during screening. All patients were subjected to both grayscale US imaging and conventional ultrasound elastography; quasi-static compression was applied during acquiring one of the cine-loops of the grayscale US imaging. Also, the cine-loops of the grayscale US imaging while quasi-static compression were processed by an AI-enabled elastography software. Then, the results of the strain ratio (SR) calculated by conventional elastography software and those by AI-enabled elastography software were compared. The strain ratio calculated using the AI-enabled elastography software showed better results than conventional ultrasound elastography strain ratio. The AI-enabled software shows better specificity, sensitivity, positive predictive values, and negative predictive values than the conventional ultrasound elastography.ConclusionThe AI-enabled elastography software shows promising results compared to the conventional US elastography. Elastography does not have the potential to replace conventional B-mode US for the detection of breast cancer but may complement the conventional US to improve diagnostic performance.

Ultrasound Strain Elastography and Contrast-Enhanced Ultrasound in Predicting the Efficacy of Neoadjuvant Chemotherapy for Breast Cancer: A Nomogram Integrating Ki-67 and Ultrasound Features.

To explore whether conventional elastography and contrast-enhanced ultrasound (CEUS) combined with histopathology can monitor the efficacy of neoadjuvant chemotherapy (NAC) for breast cancer (BC), and develop a Nomogram prediction model monitoring response to NAC. From February 2010 to November 2015, 91 BC patients who received NAC were recruited. The maximum diameter, stiffness, and CEUS features were assessed. Core biopsy, surgical pathology immunophenotype, and Miller-Payne (MP) evaluation were documented. Univariate and multivariate analysis was performed using receiver operating characteristic (ROC) analysis and logistic regression analysis. There were 37 cases showing pathological complete response (pCR) and 54 of non-pCR. The changes of maximal diameter were correlated with MP (P < .05). The sensitivity (SEN), specificity (SPE), and area under the ROC curve (AUC) of baseline size predicting pCR were 57.40%, 70.30%, and 0.64 (P=.024). Baseline Ki-67 index of pCR group is significantly higher than that of non-pCR group (P=.029), and the ROC analysis of baseline Ki-67 indicates the SEN, SPE, and AUC of 51.70%, 78.00%, and 0.638 (P=.050). When combined with size, CEUS features, stiffness, and Ki-67 of baseline, the ROC curve shows good performance with SEN, SPE, and AUC of 70.00%, 76.19%, 0.821 (P=.004). Incorporating the change of characteristics into multivariate regression analysis, the results demonstrate excellent performance (SEN 100.00%, SPE 95.24%, AUC 0.986, P=.000). The change of the maximum size was correlated with MP score, which can provide reference to predict efficacy of NAC and evaluate residual lesions. When combining with elastography, CEUS, and Ki-67, better performance in predicting pathological response was shown.

Predicting the expression level of Ki-67 in breast cancer using multi-modal ultrasound parameters

ObjectiveThis study investigated the feasibility of predicting the expression levels of Ki-67 in breast cancer using ultrasonographic findings and clinical features.MethodsFifty-eight breast cancer patients, with 82 lesions confirmed by surgical pathology, were selected retrospectively for this study. Conventional ultrasound examination and elastography examination were performed before surgery. Clinical features (age, estrogen receptor (ER), progesterone receptor, and human epidermal growth factor receptor-2 expression levels), ultrasonographic findings, and elastography scores, including the maximum size, location, number, margin, borderline, blood flow, and elastography score of the mass, were collected. The expression of Ki-67 was recorded using immunohistochemical staining, and the patients were divided into a high (≥ 20%) expression group and a low (< 20%) expression group. SPSS 23.0 software was used for statistical analysis. An independent sample t-test was used for measurement data, and a χ2 test was used for enumeration data. Logistic regression analysis was performed for meaningful indicators, and the receiver operating characteristic curve was used to calculate the best diagnostic cut-off point.ResultsMonofactorial analysis showed that there was a statistically significant difference (p < 0.05) between the high expression of Ki-67 and the maximum diameter of the mass, the margin of the mass, the color Doppler flow imaging of the blood flow, and the resistance index of the blood flow. There were no significant differences in age, mass location, number, morphology, borderline, microcalcification, and elastography score (p > 0.05). Multiple factor regression analysis showed that a large mass and a mass with a rich blood flow had an independent predictive value for Ki-67. When the diameter was > 21.5 mm, the diagnostic sensitivity and specificity were 91.9% and 71.3%, respectively. The expression level of Ki-67 was negatively correlated with that of ER.ConclusionThe tumor size and blood flow of breast cancer is correlated with the expression level of Ki-67 and, thus, it could be used to predict the expression level of Ki-67 in ultrasound diagnosis. The margin condition and the expression level of ER of an ultrasonic mass could also indirectly reflect the Ki-67 expression level of the mass.

Dynamic X-ray elastography: A new tool for characterizing soft materials

Dynamic X-ray elastography using propagating shear waves is a novel technique to visualize the spatial distribution of elasticity in soft materials. We demonstrate that it can be applied to a gel sample with a fine structure. We prepared a viscoelastic gel sample with a two-dimensional lattice structure filled with ZrO2 particles, and applied the technique to map storage and loss moduli. The obtained storage modulus map successfully distinguished the harder lattice structure from the soft gel matrix with a spatial resolution much higher than those of other conventional elastography techniques using magnetic resonance and ultrasound.

Finite deformation elastography of articular cartilage and biomaterials based on imaging and topology optimization

Tissues and engineered biomaterials exhibit exquisite local variation in stiffness that defines their function. Conventional elastography quantifies stiffness in soft (e.g. brain, liver) tissue, but robust quantification in stiff (e.g. musculoskeletal) tissues is challenging due to dissipation of high frequency shear waves. We describe new development of finite deformation elastography that utilizes magnetic resonance imaging of low frequency, physiological-level (large magnitude) displacements, coupled to an iterative topology optimization routine to investigate stiffness heterogeneity, including spatial gradients and inclusions. We reconstruct 2D and 3D stiffness distributions in bilayer agarose hydrogels and silicon materials that exhibit heterogeneous displacement/strain responses. We map stiffness in porcine and sheep articular cartilage deep within the bony articular joint space in situ for the first time. Elevated cartilage stiffness localized to the superficial zone is further related to collagen fiber compaction and loss of water content during cyclic loading, as assessed by independent T2 measurements. We additionally describe technical challenges needed to achieve in vivo elastography measurements. Our results introduce new functional imaging biomarkers, which can be assessed nondestructively, with clinical potential to diagnose and track progression of disease in early stages, including osteoarthritis or tissue degeneration.

Changes in the Viscoelastic Properties of the Vastus Lateralis Muscle With Fatigue.

We investigated the in vivo effects of voluntary fatiguing isometric contractions of the knee extensor muscles on the viscoelastic properties of the vastus lateralis (VL). Twelve young males (29.0 ± 4.5 years) performed an intermittent voluntary fatigue protocol consisting of 6 sets × 10 repetitions of 5-s voluntary maximal isometric contractions with 5-s passive recovery periods between repetitions. Voluntary and evoked torque were assessed before, immediately after, and 20 min after exercise. The shear modulus (μ) of the VL muscle was estimated at rest and during a ramped isometric contraction using a conventional elastography technique. An index of active muscle stiffness was then calculated (slope from the relationship between shear modulus and absolute torque). Resting muscle viscosity (η) was quantified using a shear-wave spectroscopy sequence to measure the shear-wave dispersion. Voluntary and evoked torque decreased by ∼37% (P < 0.01) immediately after exercise. The resting VL μ was lower at the end of the fatigue protocol (−57.9 ± 5.4%, P < 0.001), whereas the resting VL η increased (179.0 ± 123%, P < 0.01). The active muscle stiffness index also decreased with fatigue (P < 0.05). By 20 min post-fatigue, there were no significant differences from the pre-exercise values for VL η and the active muscle stiffness index, contrary to the resting VL μ. We show that the VL μ is greatly reduced and η greatly enhanced by fatigue, reflecting a more compliant and viscous muscle. The quantification of both shear μ and η moduli in vivo may contribute to a better understanding of the mechanical behavior of muscles during fatigue in sports medicine, as well as in clinical situations.

Global Ultrasound Elastography in Spatial and Temporal Domains.

In this paper, a novel computationally efficient quasi-static ultrasound elastography technique is introduced by optimizing an energy function. Unlike conventional elastography techniques, three radio frequency (RF) frames are considered to devise a nonlinear cost function consisting of data intensity similarity term, spatial regularization terms and, most importantly, temporal continuity terms. We optimize the aforesaid cost function efficiently to obtain the time-delay estimation (TDE) of all samples between the first two and last two frames of ultrasound images simultaneously, and spatially differentiate the TDE to generate axial strain map. A novelty in our spatial and temporal regularizations is that they adaptively change based on the data, which leads to substantial improvements in TDE. We handle the computational complexity resulting from incorporation of all samples from all three frames by converting our optimization problem to a sparse linear system of equations. Consideration of both spatial and temporal continuity makes the algorithm more robust to signal decorrelation than the previous algorithms. We name the proposed method GUEST: Global Ultrasound Elastography in Spatial and Temporal directions. We validated our technique with simulation, experimental phantom, and in vivo liver data and compared the results with two recently proposed TDE methods. In all the experiments, GUEST substantially outperforms other techniques in terms of signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and strain ratio (SR) of the strain images.

The clinical utility of ARFI imaging for the differential diagnosis of salivary gland tumors

Objective Elastography is expected to be useful as an additional diagnostic aid for differentiating between benign and malignant tumors, but the diagnostic accuracy of conventional elastography is low in the salivary gland. Acoustic radiation force impulse (ARFI) imaging is a kind of elastography with a new mechanism. The purpose of this study is to clarify the clinical usefulness of ARFI imaging in distinguishing salivary gland tumors. Patients and Methods This study included patients who underwent ultrasonography and cytological or histological evaluation of salivary gland tumors at our department between July 2014 and February 2019. ARFI imaging was performed using Virtual Touch imaging (VTI), which was presented in grayscale, with dark color indicating hard. VTI images were divided into the following scores: score 1, mostly white color or white honeycomb; score 2, gray color with light parts; score 3, gray color; score 4, dark gray or black color with light parts; and score 5, dark gray or black color. The VTI images of different tumors were compared. Results Overall, 151 cases were benign tumors (87 Warthin tumors, 59 pleomorphic adenomas, 3 oncocytomas, 1 basal cell adenoma, 1 myoepithelioma) and 21 cases were malignant tumors. In the benign tumor group, 10, 56, 32, 34, and 19 VTI images were classified as score 1, 2, 3, 4, and 5, respectively, while the corresponding numbers were 0, 1, 5, 5, and 10 in the malignant group. If scores 4 and 5 were defined as malignant tumors, the sensitivity, specificity, and diagnostic accuracy for differentiating benign and malignant tumors were 76.5%, 67.6%, and 68.8%, respectively. In benign tumors, among Warthin tumors, 88.5% were included in scores 1–3, while among pleomorphic adenomas, 72.9% were included in scores 4 and 5. Among the malignant tumors, 71.4% were included in scores 4 and 5. Malignant tumors of scores 2 and 3 were located deeper site than those of scores 4 and 5. Conclusion Regarding salivary gland tumors at shallow site, AFRI imaging was considered useful technique because scores 1–3 of VTI system can be predicted benign tumors, especially Warthin tumors.

Elastography for portable ultrasound.

Portable wireless ultrasound has been emerging as a new ultrasound device due to its unique advantages including small size, lightweight, wireless connectivity and affordability. Modern portable ultrasound devices can offer high quality sonogram images and even multiple ultrasound modes such as color Doppler, echocardiography, and endovaginal examination. However, none of them can provide elastography function yet due to the limitations in computational performance and data transfer speed of wireless communication. Also phase-based strain estimator (PSE) that is commonly used for conventional elastography cannot be adopted for portable ultrasound, because ultrasound parameters such as data dumping interval are varied significantly in the practice of portable ultrasound. Therefore, this research aims to propose a new elastography method suitable for portable ultrasound, called the robust phase-based strain estimator (RPSE), which is not only robust to the variation of ultrasound parameters but also computationally effective. Performance and suitability of RPSE were compared with other strain estimators including time-delay, displacement-gradient and phase-based strain estimators (TSE, DSE and PSE, respectively). Three types of raw RF data sets were used for validation tests: two numerical phantom data sets modeled by an open ultrasonic simulation code (Field II) and a commercial FEA (Abaqus), and the one experimentally acquired with a portable ultrasound device from a gelatin phantom. To assess image quality of elastograms, signal-to-noise (SNRe) and contrast-to-noise (CNRe) ratios were measured on the elastograms produced by each strain estimator. The computational efficiency was also estimated and compared. Results from the numerical phantom experiment showed that RPSE could achieve highest values of SNRe and CNRe (around 5.22 and 47.62dB) among all strain estimators tested, and almost 10 times higher computational efficiency than TSE and DSE (around 0.06 vs. 5.76s per frame for RPSE and TSE, respectively).

Elastic modulus estimation based on local displacement observation of elastic body.

A method is proposed that provides estimates of the spatial variation of elastic moduli using local displacements of the elastic body. A central issue of elastography imaging has been the limited area of measurement. With the proposed method, stiffness parameter estimations are considered as minimization problems using finite-element models. The sparseness of the gradient of tissue elasticity is also exploited to improve estimation accuracy. Simulation experiments show that based on a 5% area of observation of a simple plate model with non-uniform elasticity the spatial variation of Young's modulus is reconstructed to within 5% accuracy. This result suggests that the proposed framework significantly extends the area of estimation overcoming the limitations of conventional elastography techniques.

High-resolution analysis of the mechanical behavior of tissue

The mechanical behavior and properties of biomaterials, such as tissue, have been directly and indirectly connected to numerous malignant physiological states. For example, an increase in the Young's Modulus of tissue can be indicative of cancer. Due to the heterogeneity of biomaterials, it is extremely important to perform these measurements using whole or unprocessed tissue because the tissue matrix contains important information about the intercellular interactions and the structure. Thus, developing high-resolution approaches that can accurately measure the elasticity of unprocessed tissue samples is of great interest. Unfortunately, conventional elastography methods such as atomic force microscopy, compression testing, and ultrasound elastography either require sample processing or have poor resolution. In the present work, we demonstrate the characterization of unprocessed salmon muscle using an optical polarimetric elastography system. We compare the results of compression testing within different ...

Abstract P4-02-11: Can ultrasound replace sentinel lymph node biopsy in breast cancer staging of the axilla? Results from a single center retrospective review of axillary evaluation with conventional sonography and ultrasound elastography

Abstract Background and objective Sentinel lymph node biopsy (SLNB) is the gold standard for axillary staging in clinically node negative breast cancer patients. Although generally safe and accurate, SLNB is an additional surgical procedure with occasional instances of false negatives and complications arising. Hence, there is interest in finding less invasive alternatives to SLNB. The aim of the study is to determine if ultrasound (US), together with adjunct US elastography (EI), has the potential to replace SLNB by evaluating its overall accuracy as well as the nodal disease burden in false negative cases. Materials and methods Axillary US evaluations in breast cancer patients performed in a single center institution over a 7 year period (2009-2015) were reviewed. Lymph nodes with histological assessments from percutaneous or surgical biopsies were included in the study. Cases which had histology obtained only after neoadjuvant chemotherapy were excluded. US assessment was based on the retrospective review of the attending radiologists' US reports. EI was based on the elastographic size ratio calculated from available elastographic images obtained before US percutaneous biopsy of lymph nodes. The sensitivity, specificity and false negative rates were correlated with histology as the gold standard. For false negative cases, the number of nodes involved and the size of the largest metastatic focus were recorded from available pathology reports. Results 608 axillary US studies performed on 578 patients with invasive breast cancers were reviewed. 254 (41.8%) cases had nodal metastases and 354 (58.2%) had benign histology. Overall US sensitivity, specificity and false negative rates were 74.8%, 91.0% and 25.2% respectively. Comparison of the ultrasound evaluation of lymph nodes against the final nodal status after histological evaluation Ultrasound impression MalignantBenignTotalNode statusMalignant190 (74.8%)64 (25.2%)254 Benign32 (9.0%)322 (91.0%)354 Total222386608 Of the 64 false negative cases, 81.3% (52/64) involved only 1 or 2 nodes, while false negative cases involving &amp;gt; 2 nodes constituted 4.7% (12/254) of all nodal metastases. 32.1%, 19.6%, 26.8% and 21.4% of the false negatives had a nodal metastatic size of 0.2-2mm, &amp;gt;2-5mm, &amp;gt;5-10mm and &amp;gt;10mm respectively (p=0.414). EI performed in 70 cases showed a sensitivity of 93.5% vs 97.8% (p=0.617) and specificity of 100% vs 58.3% (p&amp;lt;0.001) when compared against conventional US. Comparison of the diagnostic accuracy between conventional US and EI US impression EI impression malignantBenignMalignantBenignP-valueLymph node malignant (n=46)45 (97.8%)1 (2.2%)43 (93.5%)3 (6.5%)0.617Lymph node benign (n=24)10 (41.7%)14 (58.3%)0 (0%)24 (100%)&amp;lt;0.001 Conclusion US is fairly accurate in the evaluation of axillary nodal disease. Even in false negative cases, the nodal disease burden is low, potentially not affecting prognosis. Hence, axillary US staging has the potential to replace SLNB. Adding EI to conventional US evaluation will not significantly reduce the false negative rate but may help reduce unnecessary biopsies. Citation Format: Leong L, Upadhyaya V. Can ultrasound replace sentinel lymph node biopsy in breast cancer staging of the axilla? Results from a single center retrospective review of axillary evaluation with conventional sonography and ultrasound elastography [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-02-11.

A Modified 2D Multiresolution Hybrid Algorithm for Ultrasound Strain Imaging.

Ultrasound elastography is an imaging modality to evaluate elastic properties of soft tissue. Recently, 1D quasi-static elastography method has been commercialized by some companies. However, its performance is still limited on high strain level. In order to improve the precision of estimation during high compression, some algorithms have been proposed to expand the 1D window to a 2D window for avoiding the side-slipping. But they are usually more computationally expensive. In this paper, we proposed a modified 2D multiresolution hybrid method for displacement estimation, which can offer an efficient strain imaging with stable and accurate results. A FEM phantom with a stiffer circular inclusion is simulated for testing the algorithm. The elastographic contrast-to-noise rate (CNRe) is calculated for quantitatively comparing the performance of the proposed algorithm with conventional 1D elastography using phase zero estimation and the 1D elastography using downsampled (d-s) baseband signals. Results show that the proposed method is robust and performs similarly as other algorithms in low strain but is superior when high level strain is applied. Particularly, the CNRe of our algorithm is 15 times higher than original method under 4% strain level. Furthermore, the execution time of our algorithm is five times faster than other algorithms.

Neck Muscles and Content of Carotid Artery as Reference Tissue for Strain Ratio – a Novel Approach to Improve the Diagnostic Performance of Thyroid Elastography?

Measurement of thyroid nodule stiffness by strain elastography already showed promising results. The aim of our study was to evaluate the diagnostic performance of elastography in predicting thyroid cancer by determination of strain ratio comparing nodule stiffness with thyroid tissue and surrounding neck tissues as well (carotid artery, neck muscles). Totally, 310 thyroid nodules in 275 patients were examined by conventional ultrasound and elastography prior to aspiration biopsy. 22(7.1%) thyroid carcinomas were histologically confirmed and included in the study. 39 benign nodules (27 confirmed by histology and 12 with benign cytology and at least 2 years stable ultrasound finding) formed control group. Elastography was evaluated qualitatively using 6-grade score and strain ratio to surrounding thyroid tissue, carotid artery and neck muscles was determined. High-risk elastographic score (4,5) was more frequent in carcinomas (67%) compared with benign nodules (11%, p<0.001). Significant differences in distribution of strain were found in all studied parameters except comparison with thyroid tissue in transversal dimension. Strain ratio comparing the stiffness with neck muscles had a higher negative predictive value than elastographic score and conventional ultrasound (92 vs. 83 and 82% respectively). Moreover, the combination of ultrasound and strain ratio to neck muscles increased sensitivity and negative predictive value to 100%. Our results suggest, that strain ratio to neck muscles in combination with ultrasound seems to have good sensitivity and negative predictive value for predicting thyroid cancer and may be beneficial in cases when comparison to surrounding thyroid tissue is problematic (Hashimoto thyroiditis, multinodular goiter, large nodule).

The performance of conventional and elasticity ultrasonography of papillary thyroid microcarcinoma under different background

Objective To investigate the conventional ultrasonic and elastographic characteristics of papillary thyroid micro-carcinomas(PTMC) suffered in normal and Hashimoto's thyroiditis(HT). Methods A total of 227 patients with 249 nodules that were confirmed by surgery or biopsy were included in this study. The cases were divided into normal group and HT group. All patients underwent conventional ultrasound and elastography (static pressure). The sonographic characteristics and strain ratio (SR) value were evaluated. Results In the normal group, the ratio between male and female was 1∶2.9, while in HT group, it was 1∶11, which was significant different between the two group (P=0.002). Sonographic characteristics that had no significant difference between the two groups (P>0.05) include: boundary, shape, vertical and horizontal ratio, halo, echogenicity, calcification, posterior shadowing, vascularity on color Doppler ultrasonography. The strain ratio value was statistically different between the two groups (P=0.034), with 3.44±1.03 in normal group and 3.13±1.13 in HT group. Conclusions The conventional ultrasonographic features of PTMC were similar in both normal thyroid and HT.However, females suffering HT were more susceptible to PTMC, and the strain ratio value of PTMC concomitant HT decreased. Key words: Ultrasonography; Thyroid neoplasms; Hashimoto disease; Elastography

A PDE-Based Regularization Algorithm Toward Reducing Speckle Tracking Noise: A Feasibility Study for Ultrasound Breast Elastography.

Obtaining accurate ultrasonically estimated displacements along both axial (parallel to the acoustic beam) and lateral (perpendicular to the beam) directions is an important task for various clinical elastography applications (e.g., modulus reconstruction and temperature imaging). In this study, a partial differential equation (PDE)-based regularization algorithm was proposed to enhance motion tracking accuracy. More specifically, the proposed PDE-based algorithm, utilizing two-dimensional (2D) displacement estimates from a conventional elastography system, attempted to iteratively reduce noise contained in the original displacement estimates by mathematical regularization. In this study, tissue incompressibility was the physical constraint used by the above-mentioned mathematical regularization. This proposed algorithm was tested using computer-simulated data, a tissue-mimicking phantom, and in vivo breast lesion data. Computer simulation results demonstrated that the method significantly improved the accuracy of lateral tracking (e.g., a factor of 17 at 0.5% compression). From in vivo breast lesion data investigated, we have found that, as compared with the conventional method, higher quality axial and lateral strain images (e.g., at least 78% improvements among the estimated contrast-to-noise ratios of lateral strain images) were obtained. Our initial results demonstrated that this conceptually and computationally simple method could be useful for improving the image quality of ultrasound elastography with current clinical equipment as a post-processing tool.

Conventional, Doppler Ultrasound and Real Time Elastography in Diagnostic of Thyroid Solitary Nodules

Conventional, Doppler Ultrasound and Real Time Elastography in Diagnostic of Thyroid Solitary Nodules

Low-cost quasi-real-time elastography using B-mode ultrasound images.

A low cost, quasi real-time elastography system, displacement-gradient elastography (DGE), was developed by applying digital image correlation (DIC) method and smoothing algorithm to B-mode ultrasound images. In order to achieve quasi real-time elastogram display, a new fast pattern matching algorithm, decoupled cross-correlation (DCC), was proposed and validated. By applying the DGE to various phantoms, elastograms were generated to identify the lesion with wide variations of stiffness ratio and applied strain. The performance of DGE was qualitatively compared with those from a high-end ultrasound scanner using the elastograms of a commercial elastography breast phantom. DGE was also applied to the ultrasound images of human breast lesions in various BI-RADS categories. This study suggests that DGE may have comparable performance to conventional elastography in detecting breast cancer, while it can be easily implemented onto conventional ultrasound scanners.