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1.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 2071-2074, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018413

RESUMO

Ultrasound elastography is a non-invasive technique for detecting pathological alterations in tissue. It is known that pathological alteration of tissue often has a direct impact on its elastic modulus, which can be revealed using elastography. For estimating elastic modulus, we need to estimate both axial and lateral displacement accurately. Current state of the art elastography techniques provide a substantially less accurate lateral displacement field as compared to the axial displacement field. One of the most important factors in poor lateral estimation is a low sampling frequency in the lateral direction. In this paper, we use synthetic aperture beamforming to benefit from its capability of high sampling frequency in the lateral direction. We compare highly sampled data and focused line per line beam formed data by feeding them to our recently published elastography method, OVERWIND [1]. According to simulation and phantom experiments, not only the lateral displacement estimation is substantially improved, but also the axial displacement estimation is improved.


Assuntos
Técnicas de Imagem por Elasticidade , Módulo de Elasticidade , Imagens de Fantasmas
2.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 2079-2083, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018415

RESUMO

The placenta is a vital organ for growth and development of the fetus. Shear Wave Absolute Vibro-Elastography (SWAVE) is a new elastography technique proposed to detect placenta disorders. Elastography involves applying a force on the tissue and measuring the resulting tissue deformation. All types of compression cause the tissue to expand in three directions given the biological tissues are nearly incompressible. Hence, 3D displacement estimation should lead to the most accurate elasticity reconstruction compared to the traditional 1D methods. Previous studies estimated 3D displacements over ultrasound volumes mostly for quasi-static compression to generate strain images. However, accurate displacement tracking of dynamic motion continues to be a challenge. In this work, a novel volumetric regularized algorithm, 3D GLobal Ultrasound Elastography (GLUE3D), is presented to estimate the 3D displacement over a volume of ultrasound data, following by a 3D Young's modulus reconstruction. The proposed method outperforms the previous 2D method over a volume and is compared with a 3D technique using phantom data for which the elasticity are provided by the values from magnetic resonance elastography on the same phantom and also the manufacturer reference numbers. We then present Young's modulus reconstruction results obtained from clinical data of placenta which shows more uniform elasticity maps compared to the traditional 1D displacement measurements over a volume of ultrasound data. Furthermore, the dependency of the elasticity values to the frequency is investigated in this study.


Assuntos
Técnicas de Imagem por Elasticidade , Módulo de Elasticidade , Elasticidade , Feminino , Humanos , Imagens de Fantasmas , Placenta/diagnóstico por imagem , Gravidez
3.
Dental Press J Orthod ; 25(4): 44-50, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32965386

RESUMO

OBJECTIVE: To perform a numerical simulation using FEM to study the von Mises stresses on Mushroom archwires. METHODS: Mushroom archwires made of titanium-molybdenum alloy with 0.017 x 0.025-in cross-section were used in this study. A YS of 1240 MPa and a Young's modulus of 69 GPa were adopted. The archwire was modeled in Autodesk Inventor software and its behavior was simulated using the finite element code Ansys Workbench (Swanson Analysis Systems, Houston, Pennsylvania, USA). A large displacement simulation was used for non-linear analysis. The archwires were deformed in their extremities with 0° and 45°, and activated by their vertical extremities separated at 4.0 or 5.0 mm. RESULTS: Tensions revealed a maximum of 1158 MPa at the whole part of the loop at 5.0mm of activation, except in a very small area situated at the top of the loop, in which a maximum of 1324 Mpa was found. CONCLUSIONS: Mushroom loops are capable to produce tension levels in an elastic range and could be safely activated up to 5.0mm.


Assuntos
Agaricales , Incisivo , Fenômenos Biomecânicos , Módulo de Elasticidade , Análise de Elementos Finitos , Estresse Mecânico
4.
J Int Acad Periodontol ; 22(4): 231-235, 2020 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-32980835

RESUMO

AIMS: This study evaluated the mechanical properties of mandibular bone tissue retrieved from postmenopausal women under alendronate treatment. METHODS: Twenty postmenopausal women were divided into two groups: healthy postmenopausal subjects (control group) and osteoporotic subjects treated with alendronate (alendronate group). Mandibular bone samples were retrieved with a trephine bur at the time of dental implant placement and fixed in 4% formalin. Samples were processed for hard tissue histology, and the bone surface was analyzed for nanohardness measurement. Nanohardness and elastic modulus were evaluated by using a Berkovich tip with elastic modulus of 1.016x106 MPa, Poisson coefficient of 0.3, and a load of 100 mN. Each cycle was configured with a load time of 18 seconds (speed of 1 mN/second), the discharge time of 18 seconds, and a rest time of 5 seconds during indentation at a depth of 10 µm. RESULTS: The control group presented the highest values for nanohardness and elastic modulus (p less than 0.05) in relation to the osteoporotic subjects. CONCLUSIONS: Within the limitations of the study, it can be concluded that treatment with alendronate negatively influenced the mechanical properties of mandibular bone in postmenopausal women by reducing bone nanohardness and elastic modulus.


Assuntos
Alendronato , Pós-Menopausa , Módulo de Elasticidade , Feminino , Dureza , Humanos , Mandíbula
5.
PLoS One ; 15(9): e0238590, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32941456

RESUMO

The aim of this study was to evaluate the effect of silver diamine fluoride and grape seed extract on the microstructure and mechanical properties of carious dentin following exposure to acidic challenge. Ninety-eight molars with occlusal caries were used. In the control group the specimens were kept in distilled water. In the GSE group, the specimens were immersed in 6.5% grape seed extract solution for 30 minutes. In the SDF group, the specimens were immersed in 30% SDF solution for 4 minutes. In the GSE+SDF group, the specimens were immersed in 6.5% grape seed extract solution for 30 minutes and then exposed to 30% SDF solution for 4 minutes. All the groups underwent pH cycling model for 8 days. Microhardness measurements were taken at the baseline before surface treatments and after pH cycling. Elastic modulus was measured, after pH cycling. In the control group, the final hardness was significantly lower than the initial hardness (P = 0.001). In the SDF group, the final hardness was significantly higher than the initial hardness (P < 0.001). There was no significant difference between the initial and final hardness values in the GSE and GSE + SDF groups (p = 0.92, p = 0.07). The H1-H0 in the SDF group was significantly higher than the other groups (P<0.05). Moreover, elastic modulus of the experimental groups except GSE+SDF group was significantly higher than control. The highest mean elastic modulus was detected in the SDF group (P<0.001). The use of SDF and GSE prior to the acid challenge improved mechanical properties. Microstructural investigation, using scanning electron microscope showed dentin structure protection against acid challenges with SDF treatment and collagen matrix stabilization with GSE treatment. However combined use of these agents was not beneficious.


Assuntos
Ácidos/efeitos adversos , Dentina/efeitos dos fármacos , Extrato de Sementes de Uva/farmacologia , Proantocianidinas/farmacologia , Substâncias Protetoras/farmacologia , Compostos de Amônio Quaternário/farmacologia , Compostos de Prata/farmacologia , Fenômenos Biomecânicos/efeitos dos fármacos , Dentina/ultraestrutura , Módulo de Elasticidade/efeitos dos fármacos , Fluoretos Tópicos/farmacologia , Humanos
6.
Braz Oral Res ; 34: e099, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32785474

RESUMO

The composition of infiltrants can influence their physical properties, viscosity and depth of penetration (DP). Strategies are used to increase the DP, such as the addition of diluents or the use of heat. This study aimed to evaluate the effect of preheating and composition on physical properties and DP of infiltrants in demineralized enamel. The groups were assigned, and the following experimental formulations were made: 25%BisEMA +75%TEGDMA; 25%BisEMA +65%TEGDMA +10%ethanol; 25%BisEMA +65%TEGDMA +10%HEMA; 100%TEGDMA; 90%TEGDMA +10%ethanol; 90%TEGDMA +10%HEMA. The samples were photoactivated at two temperatures (25°C and 55°C). Degree of conversion (DC) was performed using an infrared spectrophotometer. Elastic modulus (E), flexural strength (FS) and contact angle (CA) tests were also performed. The DP of an infiltrant in demineralized enamel was determined by confocal laser scanning microscopy (CLSM) using an indirect labeling technique. The data were analyzed by two-way ANOVA and Tukey's test. DC increased after preheating in all the groups; however, 90%TEGDMA+10%ethanol showed the lowest DC for both temperatures, and the lowest E. Preheating did not influence E or FS. The CA increased at 55°C for most groups, but decreased for groups containing HEMA. Temperature did not seem to influence DP, and Icon showed the lowest DP values. The 100%TEGDMA composition showed more homogeneous penetration, whereas Icon showed heterogeneous and superficial penetration. The preheating technique does not improve all properties in all the material compositions. The composition of a material can influence and improve its properties.


Assuntos
Esmalte Dentário , Bis-Fenol A-Glicidil Metacrilato , Resinas Compostas , Módulo de Elasticidade , Teste de Materiais , Metacrilatos , Polietilenoglicóis , Ácidos Polimetacrílicos , Viscosidade
7.
Ultrasonics ; 108: 106223, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32771811

RESUMO

Quantitative ultrasound can be used to characterize the evolution of the bone-implant interface (BII), which is a complex system due to the implant surface roughness and to partial contact between bone and the implant. The determination of the constitutive law of the BII would be of interest in the context of implant acoustical modeling in order to take into account the imperfect characteristics of the BII. The aim of the present study is to propose an analytical effective model describing the interaction between an ultrasonic wave and a rough BII. To do so, a spring model was considered to determine the equivalent stiffness K of the BII. The stiffness contributions related (i) to the partial contact between the bone and the implant and (ii) to the presence of soft tissues at the BII during the process of osseointegration were assessed independently. K was found to be comprised between 1013 and 1017 N/m3 depending on the roughness and osseointegration of the BII. Analytical values of the reflection and transmission coefficients at the BII were derived from values of K. A good agreement with numerical results obtained through finite element simulation was obtained. This model may be used for future finite element bone-implant models to replace the BII conditions.


Assuntos
Interface Osso-Implante , Osseointegração , Ondas Ultrassônicas , Módulo de Elasticidade , Análise de Elementos Finitos , Modelos Teóricos , Propriedades de Superfície , Resistência à Tração , Titânio
8.
Nat Commun ; 11(1): 4000, 2020 08 10.
Artigo em Inglês | MEDLINE | ID: mdl-32778657

RESUMO

Additive manufacturing permits innovative soft device architectures with micron resolution. The processing requirements, however, restrict the available materials, and joining chemically dissimilar components remains a challenge. Here we report silicone double networks (SilDNs) that participate in orthogonal crosslinking mechanisms-photocurable thiol-ene reactions and condensation reactions-to exercise independent control over both the shape forming process (3D printing) and final mechanical properties. SilDNs simultaneously possess low elastic modulus (E100% < 700kPa) as well as large ultimate strains (dL/L0 up to ~ 400 %), toughnesses (U ~ 1.4 MJ·m-3), and strengths (σ ~ 1 MPa). Importantly, the latent condensation reaction permits cohesive bonding of printed objects to dissimilar substrates with modulus gradients that span more than seven orders of magnitude. We demonstrate soft devices relevant to a broad range of disciplines: models that simulate the geometries and mechanical properties of soft tissue systems and multimaterial assemblies for next generation wearable devices and robotics.


Assuntos
Teste de Materiais , Impressão Tridimensional , Silicones/química , Tecnologia Biomédica , Módulo de Elasticidade , Fenômenos Mecânicos , Polímeros , Reologia , Robótica , Resistência à Tração , Fatores de Tempo , Dispositivos Eletrônicos Vestíveis
9.
PLoS One ; 15(8): e0236802, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32785277

RESUMO

The static mechanical properties of coal rock show anisotropism, which makes the permeability have anisotropic characteristics partly. The dynamic impact mechanical characteristics of structural anisotropic coal under low and medium strain rates were studied by using self-made vertical Split Hopkinson Bar (SHPB) equipment. The peak stress, the strain rate, dynamic elastic modulus and failure characteristics of raw coal with three coring directions were analyzed under the influence of five impact loads and structural anisotropy. The peak stress increases linearly with impact load, and the maximum strain rate and the dynamic elastic modulus increase exponentially with impact load. The coal samples display anisotropic mechanical characteristics. The values of maximum strain rate, peak stress and dynamic elastic modulus are ranked with directions by the perpendicular to bedding direction (Z direction), the parallel to bedding direction (X direction), and the oblique 45° to bedding direction (Y direction). Dynamic mechanical properties of structural anisotropic coal provide a theoretical basis for gas seepage in far-blasting field.


Assuntos
Carvão Mineral/análise , Módulo de Elasticidade , Gases/química , Estresse Mecânico
10.
Int J Nanomedicine ; 15: 4333-4350, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32606681

RESUMO

Background: Different diseases affect both mechanical and chemical features of the involved tissue, enhancing the symptoms. Methods: In this study, using atomic force microscopy, we mechanically characterized human ovarian tissues with four distinct pathological conditions: mucinous, serous, and mature teratoma tumors, and non-tumorous endometriosis. Mechanical elasticity profiles were quantified and the resultant data were categorized using K-means clustering method, as well as fuzzy C-means, to evaluate elastic moduli of cellular and non-cellular parts of diseased tissues and compare them among four disease conditions. Samples were stained by hematoxylin-eosin staining to further study the content of different locations of tissues. Results: Pathological state vastly influenced the mechanical properties of the ovarian tissues. Significant alterations among elastic moduli of both cellular and non-cellular parts were observed. Mature teratoma tumors commonly composed of multiple cell types and heterogeneous ECM structure showed the widest range of elasticity profile and the stiffest average elastic modulus of 14 kPa. Samples of serous tumors were the softest tissues with elastic modulus of only 400 Pa for the cellular part and 5 kPa for the ECM. Tissues of other two diseases were closer in mechanical properties as mucinous tumors were insignificantly stiffer than endometriosis in cellular part, 1300 Pa compared to 1000 Pa, with the ECM average elastic modulus of 8 kPa for both. Conclusion: The higher incidence of carcinoma out of teratoma and serous tumors may be related to the intense alteration of mechanical features of the cellular and the ECM, serving as a potential risk factor which necessitates further investigation.


Assuntos
Microscopia de Força Atômica , Nanopartículas/química , Ovário/patologia , Ovário/ultraestrutura , Adulto , Fenômenos Biomecânicos , Módulo de Elasticidade , Matriz Extracelular/metabolismo , Feminino , Humanos , Pessoa de Meia-Idade
11.
PLoS One ; 15(7): e0236324, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32706841

RESUMO

As the main actuator of high-speed running, the ostrich feet are highly capable of cushioning and shock absorption. In this study, based on the elastic modulus scales and assembly order of the 3rd toe soft tissues and the functions of the metatarsophalangeal (MTP) joint, we designed fourteen bio-inspired feet. The impact process on loose sand was simulated on the finite element software Abaqus. Also the stress distributions and deformations of each component of the bio-inspired feet were clarified. With the peak acceleration as the index, the cushioning performances of the bio-inspired feet were compared on both loose sand and solid ground through height-variable impact tests. The 15-15-15 HA (hardness unit) bio-inspired foot showed lower peak acceleration and thereby better cushioning performance, but larger deformation, less-uniform stress distribution and thereby lower stability than the 15-35-55 HA bio-inspired foot. In fact, the silicon rubbers with different hardness degrees (which simulate the elasticity modulus scales of the digital cushions, fascia and skin) and the spring mechanism (which simulates the functions of the MTP joint) work as an "integrated system" of cushioning and shock absorption.


Assuntos
Aceleração , Membros Artificiais , Modelos Anatômicos , Corrida , Struthioniformes/anatomia & histologia , Animais , Módulo de Elasticidade , Pé/anatomia & histologia , Dureza , Humanos , Articulação Metatarsofalângica/anatomia & histologia , Dedos do Pé/anatomia & histologia
12.
PLoS One ; 15(7): e0235768, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32634166

RESUMO

The implementation of multiple drives for belt conveyors can solve the problems associated with motor overpower and the excessive tension of conveyor belts powered by a single drive. However, multiple drives can suffer from uneven driving power allocation. Among various factors, the selection of the type of conveyor belt particularly affects the power allocation. The current study aims to investigate the influence of the elastic modulus of a conveyor belt on the power allocation of multi-drive conveyors. Based on the Kelvin-Voigt viscoelastic model, a discrete model of an entire machine is established. Kelvin-Voigt software is used to simulate the working conditions of conveyor belts with different elastic moduli under full loads. The driving forces of individual rollers are obtained and then compared. Compared to other types of belts, a steel wire core conveyor belt, whose elastic modulus is relatively high, effectively improves the stability of the conveyor belt under a full load after start-up to achieve a reasonable power allocation. The results of this study provide a foundation for conveyor belt selection for multi-drive conveyors.


Assuntos
Módulo de Elasticidade , Equipamentos e Provisões
13.
PLoS One ; 15(7): e0235842, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32639989

RESUMO

Biodegradable stents are promising treatments for many diseases, e.g., coronary artery disease, urethral diseases, tracheal diseases, and esophageal strictures. The mechanical properties of biodegradable stent materials play a key role in the safety and efficacy of treatment. In particular, insufficient creep resistance of the stent material could result in premature stent collapse or narrowing. Commercially available biodegradable self-expandable SX-ELLA stents made of polydioxanone monofilament were tested. A new, simple, and affordable method to measure the shear modulus of tiny viscoelastic wires is presented. The important mechanical parameters of the polydioxanone filament were obtained: the median Young's modulus was [Formula: see text] = 958 (922, 974) MPa and the shear modulus was [Formula: see text] = 357 (185, 387) MPa, resulting in a Poisson's ratio of ν = 0.34. The SX-ELLA stents exhibited significant force relaxation due to the stress relaxation of the polydioxanone monofilament, approximately 19% and 36% 10 min and 48 h after stent application, respectively. However, these results were expected, and the manufacturer and implanting clinician should be aware of the known behavior of these biodegradable materials. If possible, a biodegradable stent should be designed considering therapeutic force rather than initial force. Additionally, new and more advanced biodegradable shape-memory polymers should be considered for future study and use.


Assuntos
Implantes Absorvíveis , Materiais Biocompatíveis/química , Polidioxanona/química , Stents , Módulo de Elasticidade , Humanos , Teste de Materiais , Fenômenos Mecânicos , Desenho de Prótese
14.
J Vis Exp ; (161)2020 07 03.
Artigo em Inglês | MEDLINE | ID: mdl-32716389

RESUMO

The analysis of thermal processes associated to the curing of adhesives and the study of mechanical behavior once cured, provide key information to choose the best option for any specific application. The proposed methodology for the curing characterization, based on thermal analysis and rheology, is described through the comparison of three commercial adhesives. The experimental techniques used here are Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Rheology. TGA provides information about the thermal stability and filler content, DSC allows the evaluation of some thermal events associated to the cure reaction and to thermal changes of the cured material when subjected to temperature changes. Rheology complements the information of the thermal transformations from a mechanical point of view. Thus, the curing reaction can be tracked through the elastic modulus (mainly the storage modulus), the phase angle and the gap. In addition, it is also shown that although DSC is of no use to study the curing of moisture curable adhesives, it is a very convenient method to evaluate the low temperature glass transition of amorphous systems.


Assuntos
Adesivos/química , Varredura Diferencial de Calorimetria , Módulo de Elasticidade , Teste de Materiais , Reologia , Termogravimetria
15.
Am J Orthod Dentofacial Orthop ; 157(6): 745-753, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32487304

RESUMO

INTRODUCTION: The mechanical properties of Invisalign material have rarely been explored because of the inaccessibility of the patent-protected raw material. The purpose of this study was to systematically evaluate the Invisalign thermoformed aligner material before and after clinical application, including mechanical properties, surface morphology, internal structure, and chemical composition changes. METHODS: Twenty sets of "as-received" (0-week) and retrieved (2-week; worn for 2 weeks, 20 ± 2 hours per day) Invisalign aligners were randomly collected from 4 different patients. Tensile tests, stress relaxation, and creep tests were carried out with a dynamic mechanical analyzer to characterize the changes in the mechanical properties of this material, Fourier transform infrared spectroscopy was used to capture the molecular changes on the surface of these aligners, scanning electron microscopy and transmission electron microscopy were used to observe the changes in surface morphology and internal structure, and scanning transmission electron microscopy-energy dispersive x-ray analysis was used to detect any changes in the chemical composition of this material before and after clinical application. RESULTS: The elastic modulus of 0-week and 2-week samples were 842 ± 63 MPa and 806 ± 19 MPa, respectively, with no significant difference. In addition, the relative stress after stress relaxation of 2 hours was 19.89 ± 2.25% and 15.91 ± 6.04% for 0-week and 2-week groups, respectively, with no significant difference. Scanning electron microscopy observations showed voids and signs of delamination on the surface of the 2-week samples, and scanning transmission electron microscopy-energy dispersive x-ray analysis indicated the possible release of trace elements during clinical use, such as aluminum. Results of Fourier transform infrared spectroscopy analysis, and transmission electron microscopy observations were quite stable, indicating that the molecular structure on the surface and the internal structure of this material were relatively stable under the oral environment. CONCLUSIONS: The surface morphology showed some defects after the clinical use of 2 weeks; however, there was no significant difference in mechanical properties. Trace elements may release out during clinical use and may pose a specific danger to allergic patients.


Assuntos
Aparelhos Ortodônticos Removíveis , Módulo de Elasticidade , Humanos , Teste de Materiais , Microscopia Eletrônica de Varredura , Espectroscopia de Infravermelho com Transformada de Fourier , Propriedades de Superfície
16.
Food Chem ; 330: 127182, 2020 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-32526648

RESUMO

In this paper we report the importance of swelling on gastric digestion of protein gels, which is rarely recognized in literature. Whey protein gels with NaCl concentrations 0-0.1 M were used as model foods. The Young's modulus, swelling ratio, acid uptake and digestion rate of the gels were measured. Pepsin transport was observed by confocal laser scanning microscopy using green fluorescent protein (GFP). With the increase of NaCl in gels, Young's modulus increased, swelling was reduced and digestion was slower, with a reduction of acid transport and less GFP present both at surface and in the gels. This shows that swelling affects digestion rate by enhancing acid diffusion, but also by modulating the partitioning of pepsin at the food-gastric fluid interface and thereby the total amount of pepsin in the food particle. This perspective on swelling will provide new insight for designing food with specific digestion rate for targeted dietary demands.


Assuntos
Mucosa Gástrica , Proteínas do Soro do Leite/metabolismo , Difusão , Digestão , Módulo de Elasticidade , Alimentos , Géis/química , Pepsina A/metabolismo , Estômago , Proteínas do Soro do Leite/química
17.
Ultrasonics ; 108: 106179, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32504988

RESUMO

The viscoelastic properties of tissues can reflect human physiological and pathological conditions. During and after the high-intensity focused ultrasound (HIFU) treatment, measuring the viscoelasticity of HIFU ablated tissue is important for therapy evaluation. Two-dimensional Fourier transform (2DFT) method has been reported to quantify elasticity and viscosity. However, a deviation is induced by under-sampling in practical application. This work proposes an approach based on the convolution theorem and model fitting to solve the finite spatial data problem. A model using the convolution theorem was constructed, and mean-square error (MSE) was calculated to determine the optimal fitting between the model and experimental data. For validation, HIFU therapeutic experiments were conducted in polyacrylamide-bovine serum (BAS) transparent tissue-mimicking phantoms. This approach was used to quantify the viscoelasticity of HIFU ablation and untreated phantoms. Acoustic-radiation-force (ARF) shear wave was generated by the same HIFU therapeutic transducer, and laser Doppler vibrometer (LDV) was used for the high-resolution measurement of shear wave signals. Results suggest that the shear elasticity and viscosity of untreated phantoms are generally smaller than those of HIFU ablation. Thus, the proposed method may be helpful for HIFU treatment monitoring.


Assuntos
Ablação por Ultrassom Focalizado de Alta Intensidade/métodos , Animais , Bovinos , Módulo de Elasticidade , Elasticidade , Desenho de Equipamento , Análise de Fourier , Modelos Teóricos , Imagens de Fantasmas , Processamento de Sinais Assistido por Computador , Viscosidade
18.
PLoS One ; 15(6): e0234359, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32520959

RESUMO

PURPOSE: Shear-wave elastography has been recognized a useful tool for quantifying muscle stiffness, commonly reported as shear modulus, however the reports on reliability are often limited to test-retest correlations. In this study, we explored the reliability of shear-wave elastography for assessment of the trapezius muscle stiffness and its relationship with low-level muscle activity. METHODS: Twenty participants were included in a two-session experiment. Measurements of shear modulus and muscle activity were performed at rest and during low-level activity, induced by shoulder abduction without additional external resistance. RESULTS: Good to excellent intra-session repeatability (ICC > 0.80) and moderate inter-rater and inter-session reproducibility (ICC = 0.66-0.74) were observed. Typical errors were acceptable (7.6% of the mean value) only for intra-session measurements in resting conditions, but not acceptable for all conditions with low-level muscle activity (10.2-16.6% of the mean value). Inverse relationships between shear modulus and muscle activity at 40° and 60° of shoulder abduction (r = -0.53 and -0.57) were observed on a group level. We also found higher shear modulus in males compared to females, for the parallel probe position compared to the perpendicular position (in relation to muscle fiber orientation), and for the dominant side of the body compared to the non-dominant side. CONCLUSIONS: This study showed an inverse relationship between muscle activity in low-level range and shear modulus on a group level, suggesting inherent passive stiffness could account for a larger portion of the variance (compared to muscle activity) in shear modulus when the muscle activity is low. Our results imply that shear-wave elastography can be used in research exploring muscle stiffness, however, caution is needed since only intra-session examination in resting conditions showed acceptable within-participant typical errors. The secondary analyses of the study showed higher shear modulus for males, for the non-dominant side of the body and for the parallel orientation of the ultrasound probe.


Assuntos
Técnicas de Imagem por Elasticidade/métodos , Força Muscular/fisiologia , Músculos Superficiais do Dorso/fisiologia , Adulto , Módulo de Elasticidade/fisiologia , Feminino , Voluntários Saudáveis , Humanos , Masculino , Movimento/fisiologia , Músculo Esquelético/fisiologia , Reprodutibilidade dos Testes , Ombro/fisiologia , Ultrassonografia/métodos
19.
Comput Methods Biomech Biomed Engin ; 23(13): 981-986, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32583688

RESUMO

Abdominal malignant tumors originated from cancers, such as vater ampulla carcinoma (VAC) and pancreatic cancer (PC), often invades the portal vein (PV) and the superior mesenteric vein (SMV) upon metastasis. Surgical removal of these tumors leads to sacrifice of parts of these vessels that need to be reconstructed with autograft tissues. Current options for the replacement tissue all have their limitations in certain aspects. Therefore, improved interstitial material for the reconstruction with better tissue compatibility is urgently needed. In the present study, we explored the potential of hepatic round ligament (HRL) as a candidate tissue for the task from the biomechanical point of view. We reveal that HRL and PV share similar geometrical parameters in terms of vascular cavity diameter and wall thickness. In addition, they also have similar elastic properties and tissue flexibility and intensity upon increased cavity pressure. Our study strongly supports HRL as potential replacement tissue for PV reconstruction in term of mechanical properties and encourages further biological studies to be performed on these two tissues for further verification.


Assuntos
Veias Mesentéricas/cirurgia , Veia Porta/cirurgia , Ligamento Redondo do Fígado/cirurgia , Adolescente , Adulto , Módulo de Elasticidade , Humanos , Veias Mesentéricas/patologia , Pessoa de Meia-Idade , Maleabilidade , Veia Porta/patologia , Adulto Jovem
20.
Medicine (Baltimore) ; 99(20): e20091, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32443319

RESUMO

This study aims to evaluate the changes of fragility and ultrastructure of amniotic membrane after cross-linking by UVA/riboflavin.Forty-nine fresh amniotic membranes were randomly divided into 3 groups. Eighteen were in group A (CX group) and immersed in 0.1% riboflavin solution for 10 min for UVA/riboflavin cross-linking. Sixteen were in group B (B2 group), soaked for 10 min with 0.1% riboflavin. After soaking, membranes in group A and B were transferred into corneal preservation solution. Fifteen pieces were in group C, directly into corneal preservation solution. The biomechanical and ultrastructural changes of the amniotic tissue before and after cross-linking were examined (CX group = 13, B2 group = 11, C group = 15). The amniotic membrane tissue of group A (n = 5) and B (n = 5) was transplanted into 16 eyes of the rabbits, respectively, and the dissolution time of the amniotic membrane tissue was investigated.After cross-linking, compared with the control group, the elastic modulus of the low-stress area of the amniotic membrane (Elow) was higher, while the elastic modulus of the high-stress area of the amniotic membrane (Ehigh) was lower, with no significant difference in the tensile strength. Also, the collagen fibers showed coarse and bamboo-like changes. In group A, amniotic membranes began to dissolve 4 weeks after conjunctiva transplantation, and all amniotic membranes were dissolved and absorbed 6 weeks after conjunctiva transplantation. In group B, some amniotic membrane tissues were still visible 6 weeks after conjunctiva transplantation.This study suggested that after amniotic membrane cross-linking, the brittleness was increased, the hardness was enhanced, and the morphology of the collagen fiber was changed. The cross-linked amniotic membrane showed resistance to tissue dissolution.


Assuntos
Âmnio/fisiologia , Âmnio/ultraestrutura , Reagentes para Ligações Cruzadas , Riboflavina , Transplante , Raios Ultravioleta , Implantes Absorvíveis , Âmnio/efeitos dos fármacos , Âmnio/transplante , Animais , Colágeno/efeitos dos fármacos , Colágeno/efeitos da radiação , Módulo de Elasticidade , Olho , Humanos , Procedimentos Cirúrgicos Oftalmológicos , Soluções para Preservação de Órgãos , Coelhos , Distribuição Aleatória
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