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Mercado-Shekhar KP, Kleven RT, Aponte Rivera H, Lewis R, Karani KB, Vos HJ, Abruzzo TA, Haworth KJ, Holland CK. Effect of Clot Stiffness on Recombinant Tissue Plasminogen Activator Lytic Susceptibility in Vitro. ULTRASOUND IN MEDICINE & BIOLOGY 2018; 44:2710-2727. [PMID: 30268531 PMCID: PMC6551517 DOI: 10.1016/j.ultrasmedbio.2018.08.005] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Revised: 08/01/2018] [Accepted: 08/10/2018] [Indexed: 05/05/2023]
Abstract
The lytic recombinant tissue plasminogen activator (rt-PA) is the only drug approved by the Food and Drug Administration for treating ischemic stroke. Less than 40% of patients with large vessel occlusions who are treated with rt-PA have improved blood flow. However, up to 6% of all patients receiving rt-PA develop intracerebral hemorrhage. Predicting the efficacy of rt-PA treatment a priori could help guide therapeutic decision making, such that rt-PA is administered only to those individuals who would benefit from this treatment. Clot composition and structure affect the lytic efficacy of rt-PA and have an impact on elasticity. However, the relationship between clot elasticity and rt-PA lytic susceptibility has not been adequately investigated. The goal of this study was to quantify the relationship between clot elasticity and rt-PA susceptibility in vitro. Human and porcine highly retracted and mildly retracted clots were fabricated in glass pipettes. The rt-PA lytic susceptibility was evaluated in vitro using the percent clot mass loss. The Young's moduli of the clots were estimated using ultrasound-based single-track-location shear wave elasticity imaging. The percent mass loss in mildly retracted porcine and human clots (28.9 ± 6.1% and 45.2 ± 7.1%, respectively) was significantly higher (p < 0.05) than in highly retracted porcine and human clots (10.9 ± 2.1% and 25.5 ± 10.0%, respectively). Furthermore, the Young's moduli of highly retracted porcine and human clots (5.33 ± 0.92 and 3.21 ± 1.97 kPa, respectively) were significantly higher (p < 0.05) than those of mildly retracted porcine and human clots (2.66 ± 0.55 and 0.79 ± 0.21 kPa, respectively). The results revealed an inverse relationship between the percent clot mass loss and Young's modulus. These findings motivate continued investigation of ultrasound-based methods to assess clot stiffness in order to predict rt-PA thrombolytic efficacy.
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Affiliation(s)
- Karla P Mercado-Shekhar
- Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, Cincinnati, Ohio, USA.
| | - Robert T Kleven
- Department of Biomedical Engineering, University of Cincinnati, Cincinnati, Ohio, USA
| | - Hermes Aponte Rivera
- Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, Cincinnati, Ohio, USA
| | - Ryden Lewis
- Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, Cincinnati, Ohio, USA
| | - Kunal B Karani
- Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, Cincinnati, Ohio, USA
| | - Hendrik J Vos
- Department of Biomedical Engineering, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Todd A Abruzzo
- Department of Radiology, Cincinnati Children's Hospital, Cincinnati, Ohio, USA
| | - Kevin J Haworth
- Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, Cincinnati, Ohio, USA; Department of Biomedical Engineering, University of Cincinnati, Cincinnati, Ohio, USA
| | - Christy K Holland
- Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, Cincinnati, Ohio, USA; Department of Biomedical Engineering, University of Cincinnati, Cincinnati, Ohio, USA
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Wang Y, Jiang J. Influence of Tissue Microstructure on Shear Wave Speed Measurements in Plane Shear Wave Elastography: A Computational Study in Lossless Fibrotic Liver Media. ULTRASONIC IMAGING 2018; 40:49-63. [PMID: 28720056 DOI: 10.1177/0161734617719055] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Shear wave elastography (SWE) has been used to measure viscoelastic properties for characterization of fibrotic livers. In this technique, external mechanical vibrations or acoustic radiation forces are first transmitted to the tissue being imaged to induce shear waves. Ultrasonically measured displacement/velocity is then utilized to obtain elastographic measurements related to shear wave propagation. Using an open-source wave simulator, k-Wave, we conducted a case study of the relationship between plane shear wave measurements and the microstructure of fibrotic liver tissues. Particularly, three different virtual tissue models (i.e., a histology-based model, a statistics-based model, and a simple inclusion model) were used to represent underlying microstructures of fibrotic liver tissues. We found underlying microstructures affected the estimated mean group shear wave speed (SWS) under the plane shear wave assumption by as much as 56%. Also, the elastic shear wave scattering resulted in frequency-dependent attenuation coefficients and introduced changes in the estimated group SWS. Similarly, the slope of group SWS changes with respect to the excitation frequency differed as much as 78% among three models investigated. This new finding may motivate further studies examining how elastic scattering may contribute to frequency-dependent shear wave dispersion and attenuation in biological tissues.
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Affiliation(s)
- Yu Wang
- 1 Department of Biomedical Engineering, Michigan Technological University, Houghton, MI, USA
| | - Jingfeng Jiang
- 1 Department of Biomedical Engineering, Michigan Technological University, Houghton, MI, USA
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Bernard S, Cloutier G. Forward and inverse viscoelastic wave scattering by irregular inclusions for shear wave elastography. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2017; 142:2346. [PMID: 29092551 DOI: 10.1121/1.5007729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Inversion methods in shear wave elastography use simplifying assumptions to recover the mechanical properties of soft tissues. Consequently, these methods suffer from artifacts when applied to media containing strong stiffness contrasts, and do not provide a map of the viscosity. In this work, the shear wave field recorded inside and around an inclusion was used to estimate the viscoelastic properties of the inclusion and surrounding medium, based on an inverse problem approach assuming local homogeneity of both media. An efficient semi-analytical method was developed to model the scattering of an elastic wave by an irregular inclusion, based on a decomposition of the field by Bessel functions and on a decomposition of the boundaries as Fourier series. This model was validated against finite element modeling. Shear waves were experimentally induced by acoustic radiation force in soft tissue phantoms containing stiff and soft inclusions, and the displacement field was imaged at a high frame rate using plane wave imaging. A nonlinear least-squares algorithm compared the model to the experimental data and adjusted the geometrical and mechanical parameters. The estimated shear storage and loss moduli were in good agreement with reference measurements, as well as the estimated inclusion shape. This approach provides an accurate estimation of geometry and viscoelastic properties for a single inclusion in a homogeneous background in the context of radiation force elastography.
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Affiliation(s)
- Simon Bernard
- Laboratory of Biorheology and Medical Ultrasonics, University of Montréal Hospital Research Center (CRCHUM), 900 St-Denis, Suite R11.720, Montréal, Québec H2X 0A9, Canada
| | - Guy Cloutier
- Laboratory of Biorheology and Medical Ultrasonics, University of Montréal Hospital Research Center (CRCHUM), 900 St-Denis, Suite R11.720, Montréal, Québec H2X 0A9, Canada
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Ouared A, Kazemirad S, Montagnon E, Cloutier G. Ultrasound viscoelasticity assessment using an adaptive torsional shear wave propagation method. Med Phys 2016; 43:1603. [PMID: 27036560 DOI: 10.1118/1.4942813] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
PURPOSE Different approaches have been used in dynamic elastography to assess mechanical properties of biological tissues. Most techniques are based on a simple inversion based on the measurement of the shear wave speed to assess elasticity, whereas some recent strategies use more elaborated analytical or finite element method (FEM) models. In this study, a new method is proposed for the quantification of both shear storage and loss moduli of confined lesions, in the context of breast imaging, using adaptive torsional shear waves (ATSWs) generated remotely with radiation pressure. METHODS A FEM model was developed to solve the inverse wave propagation problem and obtain viscoelastic properties of interrogated media. The inverse problem was formulated and solved in the frequency domain and its robustness to noise and geometric constraints was evaluated. The proposed model was validated in vitro with two independent rheology methods on several homogeneous and heterogeneous breast tissue-mimicking phantoms over a broad range of frequencies (up to 400 Hz). RESULTS Viscoelastic properties matched benchmark rheology methods with discrepancies of 8%-38% for the shear modulus G' and 9%-67% for the loss modulus G″. The robustness study indicated good estimations of storage and loss moduli (maximum mean errors of 19% on G' and 32% on G″) for signal-to-noise ratios between 19.5 and 8.5 dB. Larger errors were noticed in the case of biases in lesion dimension and position. CONCLUSIONS The ATSW method revealed that it is possible to estimate the viscoelasticity of biological tissues with torsional shear waves when small biases in lesion geometry exist.
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Affiliation(s)
- Abderrahmane Ouared
- Laboratory of Biorheology and Medical Ultrasonics, University of Montréal Hospital Research Center (CRCHUM), Montréal, Québec H2X 0A9, Canada and Institute of Biomedical Engineering, University of Montréal, Montréal, Québec H3T 1J4, Canada
| | - Siavash Kazemirad
- Laboratory of Biorheology and Medical Ultrasonics, University of Montréal Hospital Research Center (CRCHUM), Montréal, Québec H2X 0A9, Canada
| | - Emmanuel Montagnon
- Laboratory of Biorheology and Medical Ultrasonics, University of Montréal Hospital Research Center (CRCHUM), Montréal, Québec H2X 0A9, Canada
| | - Guy Cloutier
- Laboratory of Biorheology and Medical Ultrasonics, University of Montréal Hospital Research Center (CRCHUM), Montréal, Québec H2X 0A9, Canada; Department of Radiology, Radio-Oncology and Nuclear Medicine, University of Montréal, Montréal, Québec H3T 1J4, Canada; and Institute of Biomedical Engineering, University of Montréal, Montréal, Québec H3T 1J4, Canada
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Schwartz BL, Yin Z, Yasar TK, Liu Y, Khan AA, Ye AQ, Royston TJ, Magin RL. Scattering and Diffraction of Elastodynamic Waves in a Concentric Cylindrical Phantom for MR Elastography. IEEE Trans Biomed Eng 2016; 63:2308-2316. [PMID: 26886963 DOI: 10.1109/tbme.2016.2527825] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
AIM The focus of this paper is to report on the design and construction of a multiply connected phantom for use in magnetic resonance elastography (MRE)-an imaging technique that allows for the noninvasive visualization of the displacement field throughout an object from externally driven harmonic motion-as well as its inverse modeling with a closed-form analytic solution which is derived herein from first principles. METHODS Mathematically, the phantom is described as two infinite concentric circular cylinders with unequal complex shear moduli, harmonically vibrated at the exterior surface in a direction along their common axis. Each concentric cylinder is made of a hydrocolloid with its own specific solute concentration. They are assembled in a multistep process for which custom scaffolding was designed and built. A customized spin-echo-based MR elastography sequence with a sinusoidal motion-sensitizing gradient was used for data acquisition on a 9.4 T Agilent small-animal MR scanner. Complex moduli obtained from the inverse model are used to solve the forward problem with a finite-element method. RESULTS Both complex shear moduli show a significant frequency dependence (p 0.001) in keeping with previous work. CONCLUSION The novel multiply connected phantom and mathematical model are validated as a viable tool for MRE studies. SIGNIFICANCE On a small enough scale much of physiology can be mathematically modeled with basic geometric shapes, e.g., a cylinder representing a blood vessel. This study demonstrates the possibility of elegant mathematical analysis of phantoms specifically designed and carefully constructed for biomedical MRE studies.
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Ingle A, Varghese T. Three-dimensional sheaf of ultrasound planes reconstruction (SOUPR) of ablated volumes. IEEE TRANSACTIONS ON MEDICAL IMAGING 2014; 33:1677-88. [PMID: 24808405 PMCID: PMC4207375 DOI: 10.1109/tmi.2014.2321285] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
This paper presents an algorithm for 3-D reconstruction of tumor ablations using ultrasound shear wave imaging with electrode vibration elastography. Radio-frequency ultrasound data frames are acquired over imaging planes that form a subset of a sheaf of planes sharing a common axis of intersection. Shear wave velocity is estimated separately on each imaging plane using a piecewise linear function fitting technique with a fast optimization routine. An interpolation algorithm then computes velocity maps on a fine grid over a set of C-planes that are perpendicular to the axis of the sheaf. A full 3-D rendering of the ablation can then be created from this stack of C-planes; hence the name "Sheaf Of Ultrasound Planes Reconstruction" or SOUPR. The algorithm is evaluated through numerical simulations and also using data acquired from a tissue mimicking phantom. Reconstruction quality is gauged using contrast and contrast-to-noise ratio measurements and changes in quality from using increasing number of planes in the sheaf are quantified. The highest contrast of 5 dB is seen between the stiffest and softest regions of the phantom. Under certain idealizing assumptions on the true shape of the ablation, good reconstruction quality while maintaining fast processing rate can be obtained with as few as six imaging planes suggesting that the method is suited for parsimonious data acquisitions with very few sparsely chosen imaging planes.
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Affiliation(s)
- Atul Ingle
- Corresponding author: , phone: 408-823-7537
| | - Tomy Varghese
- Departments of Medical Physics and Electrical and Computer Engineering, University of Wisconsin– Madison, Madison, wi, 53706 USA
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Montagnon E, Hadj-Henni A, Schmitt C, Cloutier G. Rheological assessment of a polymeric spherical structure using a three-dimensional shear wave scattering model in dynamic spectroscopy elastography. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2014; 61:277-287. [PMID: 24474134 DOI: 10.1109/tuffc.2014.6722613] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
With the purpose of assessing localized rheological behavior of pathological tissues using ultrasound dynamic elastography, an analytical shear wave scattering model was used in an inverse problem framework. The proposed method was adopted to estimate the complex shear modulus of viscoelastic spheres from 200 to 450 Hz. The inverse problem was formulated and solved in the frequency domain, allowing assessment of the complex viscoelastic shear modulus at discrete frequencies. A representative rheological model of the spherical obstacle was determined by comparing storage and loss modulus behaviors with Kelvin-Voigt, Maxwell, Zener, and Jeffrey models. The proposed inversion method was validated by using an external vibrating source and acoustic radiation force. The estimation of viscoelastic properties of three-dimensional spheres made softer or harder than surrounding tissues did not require a priori rheological assumptions. The proposed method is intended to be applied in the context of breast cancer imaging.
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Montagnon E, Hadj-Henni A, Schmitt C, Cloutier G. Viscoelastic characterization of elliptical mechanical heterogeneities using a semi-analytical shear-wave scattering model for elastometry measures. Phys Med Biol 2013; 58:2325-48. [DOI: 10.1088/0031-9155/58/7/2325] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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Schmitt C, Montagnon E, Henni AH, Qi S, Cloutier G. Shear wave induced resonance elastography of venous thrombi: a proof-of-concept. IEEE TRANSACTIONS ON MEDICAL IMAGING 2013; 32:565-577. [PMID: 23232414 DOI: 10.1109/tmi.2012.2231093] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Shear wave induced resonance elastography (SWIRE) is proposed for deep venous thrombosis (DVT) elasticity assessment. This new imaging technique takes advantage of properly polarized shear waves to induce resonance of a confined mechanical heterogeneity. Realistic phantoms (n = 9) of DVT total and partial clot occlusions with elasticities from 406 to 3561 Pa were built for in vitro experiments. An ex vivo study was also performed to evaluate the elasticity of two fresh porcine venous thrombi in a pig model. Transient shear waves at 45-205 Hz were generated by the vibration of a rigid plate (plane wavefront) or by a needle to simulate a radiation pressure on a line segment (cylindrical wavefront). Induced propagation of shear waves was imaged with an ultrafast ultrasound scanner and a finite element method was developed to simulate tested experimental conditions. An inverse problem was then formulated considering the first resonance frequency of the DVT inclusion. Elasticity agreements between SWIRE and a reference spectroscopy instrument (RheoSpectris) were found in vitro for total clots either in plane (r(2) = 0.989) or cylindrical (r(2) = 0.986) wavefront configurations. For total and partial clots, elasticity estimation errors were 9.0 ±4.6% and 9.3 ±11.3%, respectively. Ex vivo, the blood clot elasticity was 498 ±58 Pa within the inferior vena cava and 436 ±45 Pa in the right common iliac vein (p = 0.22). To conclude, the SWIRE technique seems feasible to quantitatively assess blood clot elasticity in the context of DVT ultrasound imaging.
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Affiliation(s)
- Cédric Schmitt
- Laboratory of Biorheology and Medical Ultrasonics, University of Montreal Hospital Research Center (CRCHUM), Montréal, QC, Canada.
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Doyle TE, Factor RE, Ellefson CL, Sorensen KM, Ambrose BJ, Goodrich JB, Hart VP, Jensen SC, Patel H, Neumayer LA. High-frequency ultrasound for intraoperative margin assessments in breast conservation surgery: a feasibility study. BMC Cancer 2011; 11:444. [PMID: 21992187 PMCID: PMC3209468 DOI: 10.1186/1471-2407-11-444] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Accepted: 10/12/2011] [Indexed: 12/22/2022] Open
Abstract
Background In addition to breast imaging, ultrasound offers the potential for characterizing and distinguishing between benign and malignant breast tissues due to their different microstructures and material properties. The aim of this study was to determine if high-frequency ultrasound (20-80 MHz) can provide pathology sensitive measurements for the ex vivo detection of cancer in margins during breast conservation surgery. Methods Ultrasonic tests were performed on resected margins and other tissues obtained from 17 patients, resulting in 34 specimens that were classified into 15 pathology categories. Pulse-echo and through-transmission measurements were acquired from a total of 57 sites on the specimens using two single-element 50-MHz transducers. Ultrasonic attenuation and sound speed were obtained from time-domain waveforms. The waveforms were further processed with fast Fourier transforms to provide ultrasonic spectra and cepstra. The ultrasonic measurements and pathology types were analyzed for correlations. The specimens were additionally re-classified into five pathology types to determine specificity and sensitivity values. Results The density of peaks in the ultrasonic spectra, a measure of spectral structure, showed significantly higher values for carcinomas and precancerous pathologies such as atypical ductal hyperplasia than for normal tissue. The slopes of the cepstra for non-malignant pathologies displayed significantly greater values that differentiated them from the normal and malignant tissues. The attenuation coefficients were sensitive to fat necrosis, fibroadenoma, and invasive lobular carcinoma. Specificities and sensitivities for differentiating pathologies from normal tissue were 100% and 86% for lobular carcinomas, 100% and 74% for ductal carcinomas, 80% and 82% for benign pathologies, and 80% and 100% for fat necrosis and adenomas. Specificities and sensitivities were also determined for differentiating each pathology type from the other four using a multivariate analysis. The results yielded specificities and sensitivities of 85% and 86% for lobular carcinomas, 85% and 74% for ductal carcinomas, 100% and 61% for benign pathologies, 84% and 100% for fat necrosis and adenomas, and 98% and 80% for normal tissue. Conclusions Results from high-frequency ultrasonic measurements of human breast tissue specimens indicate that characteristics in the ultrasonic attenuation, spectra, and cepstra can be used to differentiate between normal, benign, and malignant breast pathologies.
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Affiliation(s)
- Timothy E Doyle
- Department of Physics, Utah Valley University, Orem, UT 84058, USA.
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Aldrin JC, Blodgett MP, Lindgren EA, Steffes GJ, Knopp JS. Scattering of obliquely incident shear waves from a cylindrical cavity. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2011; 129:3661-3675. [PMID: 21682391 DOI: 10.1121/1.3583540] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Prior work has proposed the use of ultrasonic angle-beam shear wave techniques to detect cracks of varying angular location around fastener sites by generating and detecting creeping waves. To better understand the nature of the scattering problem and quantify the role of creeping waves in fastener site inspections, a 3D analytical model was developed for the propagation and scattering of an obliquely incident plane shear wave from a cylindrical cavity with arbitrary shear wave polarization. The generation and decay of the spiral creeping waves was found to be dependent on both the angle of incidence and polarization of the plane shear wave. A difference between the angle of displacement in 3D and the direction of propagation for the spiral creeping wave was observed and attributed to differences in the curvature of the cavity surface for the tangential and vertical (z) directions. Using the model, practical insight was presented on measuring the displacement response in the far-field from the hole. Both analytical and experimental results highlighted the value of the diffracted and leaky spiral creeping wave signals for nondestructive evaluation of a crack located on the cavity. Last, array and signal processing methods are discussed to improve the resolution of the weaker creeping wave signals in the presence of noise.
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Affiliation(s)
- John C Aldrin
- Computational Tools, 4275 Chatham Avenue, Gurnee, Illinois 60031, USA.
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Hadj Henni A, Schmitt C, Tremblay MÉ, Hamdine M, Heuzey MC, Carreau P, Cloutier G. Hyper-frequency viscoelastic spectroscopy of biomaterials. J Mech Behav Biomed Mater 2011; 4:1115-22. [PMID: 21783120 DOI: 10.1016/j.jmbbm.2011.03.020] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Revised: 03/14/2011] [Accepted: 03/15/2011] [Indexed: 01/26/2023]
Abstract
With the emergence of new biomaterials and elastography imaging techniques, there is a need for innovative instruments dedicated to viscoelasticity measurements. In this work, we introduce a novel hyper-frequency viscoelastic spectroscopy (HFVS) technique dedicated to characterize soft media subjected to mid-to-very-high frequency stress ranges (or, equivalently, to probe short-to-very-short relaxation times). HFVS, which has been implemented in an analytical instrument performing non-contact measurements in less than 1 s between 10 and 1000 Hz, is a suitable tool to study viscoelasticity for bio-applications. In this context, HFVS has been compared to classical oscillatory rheometry on several classes of soft materials currently encountered in tissue repair, bioengineering and elastography imaging on a frequency range between 10 and 100 Hz. After having demonstrated the good correspondence between HFVS and rheometry, this study has been completed by exploring the sensitivity of HFVS to physicochemically induced variations of viscoelasticity. HFVS opens promising perspectives in the challenging field of biomaterial science and for viscoelasticity-based quality control of materials.
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Affiliation(s)
- Anis Hadj Henni
- Laboratory of Biorheology and Medical Ultrasonics, University of Montreal Hospital Research Center, Montreal, QC, Canada.
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Schmitt C, Hadj Henni A, Cloutier G. Characterization of blood clot viscoelasticity by dynamic ultrasound elastography and modeling of the rheological behavior. J Biomech 2010; 44:622-9. [PMID: 21122863 DOI: 10.1016/j.jbiomech.2010.11.015] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2010] [Revised: 11/08/2010] [Accepted: 11/10/2010] [Indexed: 11/29/2022]
Abstract
Dynamic elastography (DE) is a new tool to study mechanical behavior of soft tissues via their motion response to propagating shear waves. This technique characterized viscoelasticity of 9 porcine whole blood samples (3 animals) during coagulation for a shearing frequency of 70Hz, and after complete clot formation between 50 and 160Hz. Clot storage (G') and loss (G″) moduli were calculated from shear wave velocity and attenuation. Temporal evolutions of G' and G″ during coagulation were typified with 4 parameters: maximum change in elasticity (G' slope(max)), elasticity after 120min of coagulation (G'(max)), time occurrence of G″ maximum (t(e)) and G″ at the plateau (G″(plateau)). G' and G″ frequency dependence of completely formed blood clots was fitted with 5 standard rheological models: Maxwell, Kelvin-Voigt, Jeffrey, Zener and third-order generalized Maxwell. DE had sufficient sensitivity to follow the coagulation kinetics described by a progressive increase in G', while G″ transitory increased followed by a rapid stabilization. Inter- and intra-animal dispersions (InterAD and IntraAD) of G'(max) (InterAD=15.9%, IntraAD=9.1%) showed better reproducibility than G' slope(max) (InterAD=40.4%, IntraAD=21.9%), t(e) (InterAD=27.4%, IntraAD=18.7%) and G″(plateau) (InterAD=58.6%, IntraAD=40.2%). G' evolution within the considered range of frequency exhibited an increase, followed by stabilization to a plateau, whereas G″ presented little variations with convergence at a quasi-constant value at highest frequencies. Residues χ(⁎), describing the goodness of fit between models and experimental data, showed statistically (p<0.05) that the Kelvin-Voigt model was less in agreement with experimental data than other models. The Zener model is recommended to predict G' and G″ dispersion of coagulated blood over the explored frequency range.
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Affiliation(s)
- Cédric Schmitt
- Laboratory of Biorheology and Medical Ultrasonics, Research Center, Centre Hospitalier de l'Université de Montréal (CRCHUM), Montréal, Québec, Canada H2L2W5
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Zahiri Azar R, Baghani A, Salcudean SE, Rohling R. 2-D high-frame-rate dynamic elastography using delay compensated and angularly compounded motion vectors: preliminary results. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2010; 57:2421-2436. [PMID: 21041130 DOI: 10.1109/tuffc.2010.1709] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
This paper describes a new ultrasound-based system for high-frame-rate measurement of periodic motion in 2-D for tissue elasticity imaging. Similarly to conventional 2-D flow vector imaging, the system acquires the RF signals from the region of interest at multiple steering angles. A custom sector subdivision technique is used to increase the temporal resolution while keeping the total acquisition time within the range suitable for real-time applications. Within each sector, 1-D motion is estimated along the beam direction. The intra- and inter-sector delays are compensated using our recently introduced delay compensation algorithm. In-plane 2-D motion vectors are then reconstructed from these delay-compensated 1-D motions. We show that Young's modulus images can be reconstructed from these 2-D motion vectors using local inversion algorithms. The performance of the system is validated quantitatively using a commercial flow phantom and a commercial elasticity phantom. At the frame rate of 1667 Hz, the estimated flow velocities with the system are in agreement with the velocity measured with a pulsed-wave Doppler imaging mode of a commercial ultrasound machine with manual angle correction. At the frame rate of 1250 Hz, phantom Young's moduli of 29, 6, and 54 kPa for the background, the soft inclusion, and the hard inclusion, are estimated to be 30, 11, and 53 kPa, respectively.
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Affiliation(s)
- Reza Zahiri Azar
- Department of Electrical and Computer Engineering, University of British Columbia, Vancouver, BC, Canada.
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Schmitt C, Hadj Henni A, Cloutier G. Ultrasound dynamic micro-elastography applied to the viscoelastic characterization of soft tissues and arterial walls. ULTRASOUND IN MEDICINE & BIOLOGY 2010; 36:1492-1503. [PMID: 20800176 DOI: 10.1016/j.ultrasmedbio.2010.06.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2009] [Revised: 06/02/2010] [Accepted: 06/13/2010] [Indexed: 05/29/2023]
Abstract
Quantitative noninvasive methods that provide in vivo assessment of mechanical characterization of living tissues, organs and artery walls are of interest because information on their viscoelastic properties in the presence of disease can affect diagnosis and treatment options. This article proposes the dynamic micro-elastography (DME) method to characterize viscoelasticity of small homogeneous soft tissues, as well as the adaptation of the method for vascular applications [vascular dynamic micro-elastography (VDME)]. The technique is based on the generation of relatively high-frequency (240-1100 Hz) monochromatic or transient plane shear waves within the medium and the tracking of these waves from radio-frequency (RF) echoes acquired at 25 MHz with an ultrasound biomicroscope (Vevo 770, Visualsonics). By employing a dedicated shear wave gated strategy during signal acquisition, postprocessed RF sequences could achieve a very high frame rate (16,000 images per s). The proposed technique successfully reconstructed shear wave displacement maps at very high axial (60 mum) and lateral (250 mum) spatial resolutions for motions as low as a few mum. An inverse problem formulated as a least-square minimization, involving analytical simulations (for homogenous and vascular geometries) and experimental measurements were performed to retrieve storage (G') and loss (G'') moduli as a function of the shearing frequency. Viscoelasticity measurements of agar-gelatin materials and of a small rat liver were proven feasible. Results on a very thin wall (3 mm thickness) mimicking artery enabled to validate the feasibility and the reliability of the vascular inverse problem formulation. Subsequently, the G' and G'' of a porcine aorta showed that both parameters are strongly dependent on frequency, suggesting that the vascular wall is mechanically governed by complex viscoelastic laws.
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Affiliation(s)
- Cédric Schmitt
- University of Montreal Hospital Research Center, Montréal, Québec, Canada
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Shear wave induced resonance elastography of soft heterogeneous media. J Biomech 2010; 43:1488-93. [PMID: 20171643 DOI: 10.1016/j.jbiomech.2010.01.045] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2009] [Revised: 01/20/2010] [Accepted: 01/21/2010] [Indexed: 11/22/2022]
Abstract
In the context of ultrasound dynamic elastography imaging and characterization of venous thrombosis, we propose a method to induce mechanical resonance of confined soft heterogeneities embedded in homogenous media. Resonances are produced by the interaction of horizontally polarized shear (SH) waves with the mechanical heterogeneity. Due to such resonance phenomenon, which amplifies displacements up to 10 times compared to non-resonant condition, displacement images of the underlying structures are greatly contrasted allowing direct segmentation of the heterogeneity and a more precise measurement of displacements since the signal-to-noise ratio is enhanced. Coupled to an analytical model of wave scattering, the feasibility of shear wave induced resonance (SWIR) elastography to characterize the viscoelasticity of a mimicked venous thrombosis is demonstrated (with a maximum variability of 3% and 11% for elasticity and viscosity, respectively). More generally, the proposed method has the potential to characterize the viscoelastic properties of a variety of soft biological and industrial materials.
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