Ultrasonic Strain Research Articles

Ultrasonic-induced amorphization and strengthening mechanisms of ultrasonic vibrations assisted friction stir Al/Ti welds

Integration of aluminum (Al) and titanium (Ti) alloys offers an effective approach to sustainable and high-quality development of the automotive and aviation industries. However, challenges arise when welding Al alloys to Ti alloys due to the formation of detrimental intermetallic compounds at the interface. With the implementation of ultrasonic vibrations, the temperature and strain rate were both increased during Al/Ti friction stir welding (FSW), leading to the formation of an amorphous interlayer, instead of intermetallic compound (IMC), at the interface. The interfacial microcracks were eliminated in the ultrasonic vibrations assisted friction stir welding (UVFSW). There were Ti particles separated from the Ti substrate and dispersed in the Al alloy, thereby resulting in a more gradual and moderate evolution of the interfacial microstructure. Due to the improved interfacial microstructure with ultrasonic vibrations, the lap shear strength was almost twice that of the conventional FSW welds within same welding conditions. Meanwhile, ultrasonic vibrations also improved the fabrication efficiency with a higher optimal traversing speed. The failure mode shifted from interface separation of FSW welds to a shear dimple fracture of the UVFSW welds, demonstrating the better plasticity and reliability of the UVFSW Al/Ti dissimilar joints.

Evaluation of Left Ventricular Systolic Function Using Layer-Specific Strain in Rats Performing Endurance Exercise: A Pilot Study.

The functional characteristics of exercise-induced myocardial hypertrophy were studied in a rat model in conjunction with ultrasound layered strain technique to investigate the hidden changes in the heart brought about by exercise. Forty specific pathogen free (SPF) adult Sprague-Dawley rats were selected and randomly divided into two groups of 20 exercise and 20 control rats. The longitudinal and circumferential strain parameters were measured using the ultrasonic stratified strain technique. The differences between the two groups and the predictive effect of stratified strain parameters on left ventricular systolic function were analyzed. The exercise group had significantly higher global endocardial myocardial longitudinal strain (GLSendo), global mid-myocardial global longitudinal strain (GLSmid) and global endocardial myocardial global longitudinal strain (GCSendo) values than the control group (p < 0.05). Even though global mid-myocardial circumferential strain (GCSmid) and global epicardial myocardial circumferential strain (GCSepi) were higher in the exercise group than in the control group, statistical significance was not reached (p > 0.05). Conventional echocardiography parameters were well correlated with GLSendo, GLSmid, and GCSendo (p < 0.05). GLSendo was the best predictor of left ventricular myocardial contractile performance in athletes determined using the receiver operating characteristic curve, with an area under the curve of 0.97, sensitivity of 95% and specificity of 90%. Rats performing endurance exercise exhibited subclinical changes in the heart after prolonged high-intensity exercise. A stratified strain parameter, GLSendo, played an important role in the evaluation of LV systolic performance in exercising rats.

Piezo-Activated Atomic-Thin Molybdenum Disulfide/MXene Nanoenzyme for Integrated and Efficient Tumor Therapy via Ultrasound-Triggered Schottky Electric Field.

Monolayer molybdenum disulfide (MoS2 ) nanoenzymes exhibit a piezoelectric polarization, which generates reactive oxygen species to inactivate tumors under ultrasonic strain. However, its therapeutic efficiency is far away from satisfactory, due to stackable MoS2 , quenching of piezo-generated charges, and monotherapy. Herein, chitosan-exfoliated monolayer MoS2 (Ch-MS) is composited with atomic-thin MXene, Ti3 C2 (TC), to self-assemble a multimodal nanoplatform, Ti3 C2 -Chitosan-MoS2 (TC@Ch-MS), for tumor inactivation. TC@Ch-MS not only inherits piezoelectricity from monolayer MoS2 , but also maintains remarkable stability. Intrinsic metallic MXene combines with MoS2 to construct an interfacial Schottky heterojunction, facilitating the separation of electron-hole pairs and endowing TC@Ch-MS increase-sensitivity magnetic resonance imaging responding. Schottky interface also leads to peroxidase mimetics with excellent catalytic performance toward H2 O2 in the tumor microenvironment under mechanical vibration. TC@Ch-MS possesses the superior photothermal conversion efficiency than pristine TC under near-infrared ray illumination, attributed to its enhanced interlaminar conductivity. Meanwhile, TC@Ch-MS realizes optimized efficiency on tumor apoptosis with immunotherapy. Therefore, TC@Ch-MS achieves an integrated diagnosis and multimodal treatment nanoplatform, whereas the toxicity to normal tissue cells is negligible. This work may shed fresh light on optimizing the piezoelectric materials in biological applications, and also give prominence to the significance of intrinsic metallicity in MXene.

Evaluation of left ventricular systolic function in patients with systemic lupus erythematosus using ultrasonic layer-specific strain technology and its association with cardiovascular events: a long-term follow-up study

BackgroundSystemic lupus erythematosus (SLE) is a multisystem, autoimmune disease with potential cardiovascular involvement. Layer-specific strain (LSS) analysis is a new method that allows early detection of subtle left ventricular (LV) systolic dysfunction. The aim of this study was to evaluate LV systolic function in patients with SLE using conventional echocardiographic measurements and longitudinal strain (LS) and circumferential strain (CS) by LSS. Furthermore, the association between echocardiographic parameters and the occurrence of cardiovascular events was assessed.MethodsA total of 162 patients with SLE (the SLE group) who underwent a dedicated multidisciplinary assessment, including echocardiography, were analyzed at the time of their first visits. The control group consisted of 68 age- and sex-matched healthy subjects. LS and CS on endocardial, mid-myocardial, and epicardial layers at 17 cardiac segments were measured. Transmural strain gradient was calculated as the differences in systolic strain between the endocardial and epicardial layers.ResultsCompared with control subjects, patients with SLE had significantly lower LV ejection fraction, LS, and CS values in all layers (P < 0.05); LV LS and CS gradient were all lower than control subjects (P < 0.05). During a median follow-up period of 83 months (interquartile range: 64–95 months), 59 patients (36.4%) developed cardiovascular events. Using multivariate Cox regression analysis, we found that LV endocardial LS (hazard ratio, 1.014; 95% CI, 1.002–1.035; P = 0.025) and CS (hazard ratio, 1.051; 95% CI, 1.027–1.077; P < 0.001) demonstrated independent associations with cardiovascular events; whereas LV ejection fraction was not significantly associated with cardiovascular events. The Kaplan–Meier survival curves showed that patients with SLE with lower LV endocardial LS and CS (based on the cutoff values of -21.5% and -29.0%, respectively) experienced higher cumulative rates of cardiovascular events compared with those with higher LV endocardial LS and CS.ConclusionsIn patients with SLE, LV systolic function measured by LV endocardial LS and CS were significantly lower than that of the control group and were associated with cardiovascular events, potentially representing a new technology to improve risk stratification in these patients

Investigation on characteristics of tensile damage and microstructure evolution of steel AISI 316L by nonlinear ultrasonic Lamb wave

In view of the high sensitivity to microstructure evolution of higher harmonics generated by the nonlinear ultrasonic method, the tensile damage in the stainless steel AISI 316L was evaluated by nonlinear ultrasonic Lamb wave. The effect of different degree of tensile deformation on nonlinear ultrasonic response in 316L was analyzed by considering the microstructure evolution and the test results. First, the power-law relation of nonlinear ultrasonic parameter and plastic strain is proposed. Meanwhile, martensitic transformation and the increasing of dislocation density can be observed in the micrographs of specimens with the increase of plastic deformation. Then, the same variation tendency of intergranularly averaged Kernel Average Misorientation (KAM), as well as the relative nonlinear ultrasonic parameter, demonstrated that the nonlinearity due to tensile damage is controlled by the evolution of microstructure that directly affects higher order elastic constant of stainless steel 316L. Furthermore, based on continuous damage mechanics, the method quantitatively characterizes the degradation of mechanical properties was proposed with a functional relation of damage variable and relative nonlinear parameter. The method proposed in this study provides a theoretical basis for online monitoring of the damage status of in-service equipment. It is of great significance for residual life assessment, structure integrity assessment, and service life extension of equipment.

Recent Advancement of Phase Shifted Fiber Bragg Grating Sensor for Ultrasonic Wave Application: A Review

Fiber Bragg grating (FBG) is gaining traction in the field of optical fiber sensors, either as a detection tool for ultrasonic waves or as a detection target. The significant contributions of the last few years are summarized in this overview, that includes setups based on wavelength and intensity. This article summarizes recent research and development activities in ultrasonic wave applications utilizing FBG sensors and makes recommendations for future research. Several different FBG strain sensor packing configurations are discussed. This article presents a comprehensive theoretical and mathematical analysis of a phase-shifted fiber Bragg grating (<inline-formula> <tex-math notation="LaTeX">$\pi $ </tex-math></inline-formula>-PS-FBG) for use in a structural health monitoring system that employs a longitudinal ultrasonic strain wave obtained via a natural single FBG. The effect of grating regulating factors (grating length, index change, and apodization), as well as ultrasonic acoustic wavelengths, on the <inline-formula> <tex-math notation="LaTeX">$\pi $ </tex-math></inline-formula>-PS-FBG&#x2019;s wavelength shift sensitivity have been investigated. Additionally, the slow-light effect in the <inline-formula> <tex-math notation="LaTeX">$\pi $ </tex-math></inline-formula>-PS-FBG acoustic sensor was investigated. Sensitivity, detection range, and limit of detection are all thoroughly examined and discussed with the objective of comparing various technologies and determining future directions in the field of phase shifted fiber optic sensors.

On the Dynamic Mechanical Behaviors of a Fault Unwelded Bimrock Exposed to Freeze-Thaw-Fatigue Loads: A Lab-Scale Testing

This work is aimed at investigating the mechanical behaviors of a fault unwelded bimrock subjected to coupled freeze-thaw (FT) and fatigue loads. The influence of FT cycle on rock strength, deformation, damage evolution, and failure morphology was detailed investigated. The testing results show that the soil-rock interface is sensitive to freeze-thaw condition. Interface damage and cracking contribute a lot to sample strength, volumetric deformation, and damage evolution. In addition, a sudden increase of stress amplitude results in the increase of damage, afterwards, the coupling degree of bimrock improves with the increase of loading cycles. A coupling freeze-thaw and mechanical damage evolution model was proposed using the damage index defined by ultrasonic velocity and axial strain. It is found that the evolution trend of the model is strongly related to the previous freeze-thaw damage. Moreover, failure mode of bimrock changes from shear failure to bulging failure with increasing FT cycles. The failure process of bimrock is the rearrangement of the fine soil particles and rock blocks, the soil matrix and rock block bear axial cyclic loads by their interactions.

Фазовые превращения в нержавеющей стали Сr-Mn-N, активированные наноструктурирующей поверхностной обработкой, и их влияние на деформационное поведение и разрушение при криогенной температуре

The structure of stainless austenitic Cr-Mn-N steel after deformation treatment of its surface by ultrasonic forging strain (UFS) has been studied. It is shown that UFS activates strain aging in the near-surface layer with the formation of CrN particles. Preliminary ultrasonic treatment of the steel surface contributes to an increase in the yield strength during tensile tests at a temperature of -196 ° C and provides ductile fracture of the near-surface layer.

Phase Transformations in Stainless Cr-Mn-N Steel Activated by Nanostructuring Surface Treatment and Their Influence on Deformation Behavior and Fracture at Cryogenic Temperatures

The structure of stainless austenitic Cr-Mn-N steel after deformation treatment of its surface by ultrasonic forging strain (UFS) has been studied. It is shown that UFS activates strain aging in the near-surface layer with the formation of CrN particles. Preliminary ultrasonic treatment of the steel surface contributes to an increase in the yield strength during tensile tests at a temperature of -196oC and provides ductile fracture of the near-surface layer. Keywords: high nitrogen steel, austenite, ultrasonic forgingstrain, strain aging, cryogenic temperature, martensitic transformation.

Effect of ultrasonic forging strain processing on the surface layer microstructure and temperature-dependent mechanical properties of high nitrogen austenitic steel

The paper presents the research results on the effect of ultrasonic forging strain (UFS) processing of the high-nitrogen Cr–Mn–N austenitic stainless steel on the surface layer microstructure and tensile properties in the temperature range from −80 up to 20 °C. The high dispersion microstructure, strain aging with the formation of both CrN and Fe2N nitrides, as well as twinning were revealed in the surface layer 2–3 μm thick using a transmission electron microscope (TEM). In addition, ε-martensite with the hcp lattice was observed at a depth of more than 80 μm from the surface after UFS processing. Tensile tests showed that UFS processing had increased the yield strength. Elongation level of about 40% did not differ over the entire test temperature range. A ductile type of the fracture surfaces was observed for all test temperatures down to −80 °C.

Ultrasonic and Optical Evaluation of Deformation Stages from the Beginning to Fracture: A Case Study of Low-Carbon Steels

This paper reports the results of acoustic parameter measurements in a deformed material with simultaneous recording of autowave patterns of localized plastic deformation for steels of various compositions. It discusses the possibility of using an autowave model for the derivation of structural strength criteria of materials. It was shown that the time and place of future fracture in steel specimens can be predicted from the kinetic dependences of localized deformation sites at the prefracture stage long before visible necking. It was found that the ultrasonic velocity vs. strain curve has a kink in the elastic–plastic transition in low-carbon steels. This kink may serve as an acoustic criterion for the onset of irreversible deformation in metal forming and non-destructive testing of components and structures.

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.

Mechanical meta-material-based polymer skin graft production by rapid prototyping and replica method

Purpose The purpose of this paper is the production of mechanical meta-material samples by rapid prototyping (RP) and replica technique for patient-specific skin graft or cranial implant applications in tissue engineering. Design/methodology/approach Positive moulds (patterns) were produced by stereolithography-based RP. Impression moulding method was used for the production of silicone products (skin grafts). Alginate was used as a moulding material (negative mould). Room temperature vulcanising silicone was poured into the cavity of alginate mould and then products were produced. TiO2 powder and carbon fibres were used as reinforcement. Meta-material structured polyurethane reinforced silicone composites were also produced. Liquid components (diisocyanate and polyol) were poured into the mould and then polyurethane was produced. Then, polyurethane was immersed in the liquid silicone. Findings It is found that non-destructive ultrasonic test is a fast and reliable method. Meta-material-based composites show dome-shaped tensile/synclastic surface properties which are important for the skin graft and cranial implants. Increasing the amounts of cross-linking agent and TiO2 particles increased the hardness and elastic modulus. Carbon fibre addition enhanced the elastic modulus. Originality/value Although there are studies on the meta-materials, there is limited study on the RP of the meta-materials for patient-specific implants (skin grafts). Auxetic surface shows perfect fit to curved surface of the skull. Although there are studies on the silicone and polyurethane composites, there is limited study on the characterisation of mechanical properties by ultrasonic tests and strain gauge analysis.

Combining laser transformation hardening and ultrasonic impact strain hardening for enhanced wear resistance of AISI 1045 steel

A medium-carbon steel AISI 1045 was hardened by a laser heat treatment (LHT), a multi-pin ultrasonic impact treatment (UIT), and two combined laser-ultrasonic surface treatments (UIT + LHT and LHT + UIT processes) to improve the wear resistance of the surface layer. The paper is focused on detecting the relationship between the surface roughness and microstructure, phase state, hardness, residual stress of the specimens hardened by the LHT, UIT and combined UI + LHT/LHT + UIT processes, and their wear and friction behaviors. The hardened plane specimens were examined after the short-term (15 min) and long-term (45 min) wear tests under oil-lubricated conditions in the quasi-static and dynamic loads. The analysis of the surface morphologies and cross-section profiles of the worn tracks were assessed by an optical 3D measurement system and scanning electron microscopy (SEM). The wear mechanisms are also discussed. Results showed that the combined LHT + UIT treatment provides a lower surface roughness (Ra ~0.25 μm) and a highest surface hardness (~11,000 HV0.05) while the combined UIT + LHT treatment leads to the deeper hardened zone by 1.5–2 times. As compared to the untreated specimen (dynamic tests), the wear loss magnitudes were respectively decreased by ~5%, 35%, 42%, and 84% after the UIT, LHT, combined UIT + LHT and LHT + UIT processes. The LHT + UIT-processed specimen has the highest wear resistance owing to the formation of the fine-grained martensitic microstructure, more flattened surface microrelief, and the absence of the oxide film.

Strain rate sensitivity of the ultrastrong gradient nanocrystalline 316L stainless steel and its rate-dependent modeling at nanoscale

We fabricate ultrastrong gradient nanocrystalline (NC) 316L stainless steel with an extremely fined grain size of 5 nm using the Ultrasonic Strain Engineering Technology (USET) at ambient temperature. We evaluate the strain rate sensitivity (SRS), an indicator of the rate controlling mechanism in the plastic deformation of metals and alloys, for the ultrastrong gradient NC 316L stainless steel by strain rate jump nanoindentation and micropillar compression test. The significant decrease of the SRS for the NC 316L stainless steel with a grain size of 5 nm is attributed to the phase transformation from the austenite face center cubic (FCC) to the martensite body center cubic (BCC) structures during the grain refinement process. In addition, the grain boundary activities in NC 316L stainless steel is largely suppressed by the embodied nanosized intermetallic phases and metal precipitates. We propose an in-situ grain structure stability mechanism to achieve such extremely fined NC stainless steel via USET at ambient temperature. We further adopt and validate a rate-dependent constitutive model for the NC 316L stainless steel. The work provides an efficient way to produce ultrastrong gradient NC 316L stainless steel that can be widely used in the light-weighting and mechanical strengthening of aerospace and transportation engineering.

Automatic Identification of Breast Ultrasound Image Based on Supervised Block-Based Region Segmentation Algorithm and Features Combination Migration Deep Learning Model.

Breast cancer is a high-incidence type of cancer for women. Early diagnosis plays a crucial role in the successful treatment of the disease and the effective reduction of deaths. In this paper, deep learning technology combined with ultrasound imaging diagnosis was used to identify and determine whether the tumors were benign or malignant. First, the tumor regions were segmented from the breast ultrasound (BUS) images using the supervised block-based region segmentation algorithm. Then, a VGG-19 network pretrained on the ImageNet dataset was applied to the segmented BUS images to predict whether the breast tumor was benign or malignant. The benchmark data for bio-validation were obtained from 141 patients with 199 breast tumors, including 69 cases of malignancy and 130 cases of benign tumors. The experiment showed that the accuracy of the supervised block-based region segmentation algorithm was almost the same as that of manual segmentation; therefore, it can replace manual work. The diagnostic effect of the combination feature model established based on the depth feature of the B-mode ultrasonic imaging and strain elastography was better than that of the model established based on these two images alone. The correct recognition rate was 92.95%, and the AUC was 0.98 for the combination feature model.

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.

Ultrasonic strain elastography for detecting abnormalities in the supraspinatus tendon: an intra- and inter-rater reliability study

ObjectivesThe reliability of ultrasonic strain elastography (SEL) used to detect abnormalities in the supraspinatus tendon is unclear. Thus, the aim of this study was to investigate the reliability of SEL...