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Li Z, Luo T, Wang S, Jia H, Gong Q, Liu X, Sutcliffe MPF, Zhu H, Liu Q, Chen D, Xiong J, Teng Z. Mechanical and histological characteristics of aortic dissection tissues. Acta Biomater 2022; 146:284-294. [PMID: 35367380 DOI: 10.1016/j.actbio.2022.03.042] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Revised: 03/23/2022] [Accepted: 03/24/2022] [Indexed: 12/14/2022]
Abstract
AIMS This study investigated the association between the macroscopic mechanical response of aortic dissection (AoD) flap, its fibre features, and patient physiological features and clinical presentations. METHODS Uniaxial test was performed with tissue strips in both circumferential and longitudinal directions from 35 patients with (AoD:CC) and without (AoD:w/oCC) cerebral/coronary complications, and 19 patients with rheumatic or valve-related heart diseases (RH). A Bayesian inference framework was used to estimate the expectation of material constants (C1, D1, and D2) of the modified Mooney-Rivlin strain energy density function. Histological examination was used to visualise the elastin and collagen in the tissue strips and image processing was performed to quantify their area percentages, fibre misalignment and waviness. RESULTS The elastin area percentage was negatively associated with age (p = 0.008), while collagen increased about 6% from age 40 to 70 (p = 0.03). Elastin fibre was less dispersed and wavier in old patients and no significant association was found between patient age and collagen fibre dispersion or waviness. Features of fibrous microstructures, either elastin or collagen, were comparable between AoD:CC and AoD:w/oCC group. Elastin and collagen area percentages were positively correlated with C1 and D2, respectively, while the elastin and collagen waviness were negatively correlated with C1 and D2, respectively. Elastin dispersion was negatively correlated to D2. Multivariate analysis showed that D2 was an effective parameter which could differentiate patient groups with different age and clinical presentations, as well as the direction of tissue strip. CONCLUSION Fibre dispersion and waviness in the aortic dissection flap changed with patient age and clinical presentations, and these can be captured by the material constants in the strain energy density function. STATEMENT OF SIGNIFICANCE Aortic dissection (AoD) is a severe cardiovascular disease. Understanding the mechanical property of intimal flap is essential for its risk evaluation. In this study, mechanical testing and histology examination were combined to quantify the relationship between mechanical presentations and microstructure features. A Bayesian inference framework was employed to estimate the expectation of the material constants in the modified Mooney-Rivlin constitutive equation. It was found that fibre dispersion and waviness in the AoD flap changed with patient age and clinical presentations, and these could be captured by the material constants. This study firstly demonstrated that the expectation of material constants can be used to characterise tissue microstructures and differentiate patients with different clinical presentations.
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An inverse method for mechanical characterization of heterogeneous diseased arteries using intravascular imaging. Sci Rep 2021; 11:22540. [PMID: 34795350 PMCID: PMC8602310 DOI: 10.1038/s41598-021-01874-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2021] [Accepted: 10/27/2021] [Indexed: 11/08/2022] Open
Abstract
The increasing prevalence of finite element (FE) simulations in the study of atherosclerosis has spawned numerous inverse FE methods for the mechanical characterization of diseased tissue in vivo. Current approaches are however limited to either homogenized or simplified material representations. This paper presents a novel method to account for tissue heterogeneity and material nonlinearity in the recovery of constitutive behavior using imaging data acquired at differing intravascular pressures by incorporating interfaces between various intra-plaque tissue types into the objective function definition. Method verification was performed in silico by recovering assigned material parameters from a pair of vessel geometries: one derived from coronary optical coherence tomography (OCT); one generated from in silico-based simulation. In repeated tests, the method consistently recovered 4 linear elastic (0.1 ± 0.1% error) and 8 nonlinear hyperelastic (3.3 ± 3.0% error) material parameters. Method robustness was also highlighted in noise sensitivity analysis, where linear elastic parameters were recovered with average errors of 1.3 ± 1.6% and 8.3 ± 10.5%, at 5% and 20% noise, respectively. Reproducibility was substantiated through the recovery of 9 material parameters in two more models, with mean errors of 3.0 ± 4.7%. The results highlight the potential of this new approach, enabling high-fidelity material parameter recovery for use in complex cardiovascular computational studies.
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Jannasch A, Rix J, Welzel C, Schackert G, Kirsch M, König U, Koch E, Matschke K, Tugtekin SM, Dittfeld C, Galli R. Brillouin confocal microscopy to determine biomechanical properties of SULEEI-treated bovine pericardium for application in cardiac surgery. Clin Hemorheol Microcirc 2021; 79:179-192. [PMID: 34487036 DOI: 10.3233/ch-219119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Heart valves are exposed to a highly dynamic environment and underlie high tensile and shear forces during opening and closing. Therefore, analysis of mechanical performance of novel heart valve bioprostheses materials, like SULEEI-treated bovine pericardium, is essential and usually carried out by uniaxial tensile tests. Nevertheless, major drawbacks are the unidirectional strain, which does not reflect the in vivo condition and the deformation of the sample material. An alternative approach for measurement of biomechanical properties is offered by Brillouin confocal microscopy (BCM), a novel, non-invasive and three-dimensional method based on the interaction of light with acoustic waves. OBJECTIVE BCM is a powerful tool to determine viscoelastic tissue properties and is, for the first time, applied to characterize novel biological graft materials, such as SULEEI-treated bovine pericardium. Therefore, the method has to be validated as a non-invasive alternative to conventional uniaxial tensile tests. METHODS Vibratome sections of SULEEI-treated bovine pericardium (decellularized, riboflavin/UV-cross-linked and low-energy electron irradiated) as well as native and GA-fixed controls (n = 3) were analyzed by BCM. In addition, uniaxial tensile tests were performed on equivalent tissue samples and Young's modulus as well as length of toe region were analyzed from stress-strain diagrams. The structure of the extracellular matrix (ECM), especially collagen and elastin, was investigated by multiphoton microscopy (MPM). RESULTS SULEEI-treated pericardium exhibited a significantly higher Brillouin shift and hence higher tissue stiffness in comparison to native and GA-fixed controls (native: 5.6±0.2 GHz; GA: 5.5±0.1 GHz; SULEEI: 6.3±0.1 GHz; n = 3, p < 0.0001). Similarly, a significantly higher Young's modulus was detected in SULEEI-treated pericardia in comparison to native tissue (native: 30.0±10.4 MPa; GA: 31.8±10.7 MPa; SULEEI: 42.1±7.0 MPa; n = 3, p = 0.027). Native pericardia showed wavy and non-directional collagen fibers as well as thin, linear elastin fibers generating a loose matrix. The fibers of GA-fixed and SULEEI-treated pericardium were aligned in one direction, whereat the SULEEI-sample exhibited a much denser matrix. CONCLUSION BCM is an innovative and non-invasive method to analyze elastic properties of novel pericardial graft materials with special mechanical requirements, like heart valve bioprostheses.
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Affiliation(s)
- Anett Jannasch
- Department of Cardiac Surgery, Carl Gustav Carus Faculty of Medicine, Technische Universität Dresden, Heart Centre Dresden, Dresden, Germany
| | - Jan Rix
- Clinical Sensoring and Monitoring, Department of Anesthesiology and Intensive Care Medicine, Carl Gustav Carus Faculty of Medicine, Technische Universität Dresden, Dresden, Germany
| | - Cindy Welzel
- Department of Cardiac Surgery, Carl Gustav Carus Faculty of Medicine, Technische Universität Dresden, Heart Centre Dresden, Dresden, Germany
| | - Gabriele Schackert
- Neurosurgery, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - Matthias Kirsch
- Neurosurgery, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany.,Klinik für Neurochirurgie, Asklepios Kliniken Schildautal, Seesen, Germany
| | - Ulla König
- Department of Medical and Biotechnological Applications, Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology, Dresden, Germany
| | - Edmund Koch
- Clinical Sensoring and Monitoring, Department of Anesthesiology and Intensive Care Medicine, Carl Gustav Carus Faculty of Medicine, Technische Universität Dresden, Dresden, Germany
| | - Klaus Matschke
- Department of Cardiac Surgery, Carl Gustav Carus Faculty of Medicine, Technische Universität Dresden, Heart Centre Dresden, Dresden, Germany
| | - Sems Malte Tugtekin
- Department of Cardiac Surgery, Carl Gustav Carus Faculty of Medicine, Technische Universität Dresden, Heart Centre Dresden, Dresden, Germany
| | - Claudia Dittfeld
- Department of Cardiac Surgery, Carl Gustav Carus Faculty of Medicine, Technische Universität Dresden, Heart Centre Dresden, Dresden, Germany
| | - Roberta Galli
- Department of Medical Physics and Biomedical Technology, Carl Gustav Carus Faculty of Medicine, Technische Universität Dresden, Dresden, Germany
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A multiphysics approach for modeling early atherosclerosis. Biomech Model Mechanobiol 2017; 17:617-644. [PMID: 29159532 DOI: 10.1007/s10237-017-0982-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Accepted: 11/04/2017] [Indexed: 01/03/2023]
Abstract
This work is devoted to the development of a mathematical model of the early stages of atherosclerosis incorporating processes of all time scales of the disease and to show their interactions. The cardiovascular mechanics is modeled by a fluid-structure interaction approach coupling a non-Newtonian fluid to a hyperelastic solid undergoing anisotropic growth and a change of its constitutive equation. Additionally, the transport of low-density lipoproteins and its penetration through the endothelium is considered by a coupled set of advection-diffusion-reaction equations. Thereby, the permeability of the endothelium is wall-shear stress modulated resulting in a locally varying accumulation of foam cells triggering a novel growth and remodeling formulation. The model is calibrated and applied to an murine-specific case study, and a qualitative validation of the computational results is performed. The model is utilized to further investigate the influence of the pulsatile blood flow and the compliance of the artery wall to the atherosclerotic process. The computational results imply that the pulsatile blood flow is crucial, whereas the compliance of the aorta has only a minor influence on atherosclerosis. Further, it is shown that the novel model is capable to produce a narrowing of the vessel lumen inducing an adaption of the endothelial permeability pattern.
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Larin KV, Sampson DD. Optical coherence elastography - OCT at work in tissue biomechanics [Invited]. BIOMEDICAL OPTICS EXPRESS 2017; 8:1172-1202. [PMID: 28271011 PMCID: PMC5330567 DOI: 10.1364/boe.8.001172] [Citation(s) in RCA: 221] [Impact Index Per Article: 31.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Revised: 01/18/2017] [Accepted: 01/19/2017] [Indexed: 05/18/2023]
Abstract
Optical coherence elastography (OCE), as the use of OCT to perform elastography has come to be known, began in 1998, around ten years after the rest of the field of elastography - the use of imaging to deduce mechanical properties of tissues. After a slow start, the maturation of OCT technology in the early to mid 2000s has underpinned a recent acceleration in the field. With more than 20 papers published in 2015, and more than 25 in 2016, OCE is growing fast, but still small compared to the companion fields of cell mechanics research methods, and medical elastography. In this review, we describe the early developments in OCE, and the factors that led to the current acceleration. Much of our attention is on the key recent advances, with a strong emphasis on future prospects, which are exceptionally bright.
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Affiliation(s)
- Kirill V Larin
- Department of Biomedical Engineering, University of Houston, 3605 Cullen Blvd., Houston, Texas 77204-5060, USA; Department of Molecular Physiology and Biophysics, Baylor College of Medicine, 1 Baylor Plaza, Houston, Texas 77030, USA;
| | - David D Sampson
- Optical + Biomedical Engineering Laboratory, School of Electrical, Electronic & Computer Engineering, The University of Western Australia, 35 Stirling Highway, Perth, WA 6009, Australia; Centre for Microscopy, Characterisation & Analysis, The University of Western Australia, 35 Stirling Highway, Perth, WA 6009, Australia;
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Qiu Y, Zaki FR, Chandra N, Chester SA, Liu X. Nonlinear characterization of elasticity using quantitative optical coherence elastography. BIOMEDICAL OPTICS EXPRESS 2016; 7:4702-4710. [PMID: 27896009 PMCID: PMC5119609 DOI: 10.1364/boe.7.004702] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Revised: 10/22/2016] [Accepted: 10/22/2016] [Indexed: 05/02/2023]
Abstract
Optical coherence elastography (OCE) has been used to perform mechanical characterization on biological tissue at the microscopic scale. In this work, we used quantitative optical coherence elastography (qOCE), a novel technology we recently developed, to study the nonlinear elastic behavior of biological tissue. The qOCE system had a fiber-optic probe to exert a compressive force to deform tissue under the tip of the probe. Using the space-division multiplexed optical coherence tomography (OCT) signal detected by a spectral domain OCT engine, we were able to simultaneously quantify the probe deformation that was proportional to the force applied, and to quantify the tissue deformation. In other words, our qOCE system allowed us to establish the relationship between mechanical stimulus and tissue response to characterize the stiffness of biological tissue. Most biological tissues have nonlinear elastic behavior, and the apparent stress-strain relationship characterized by our qOCE system was nonlinear an extended range of strain, for a tissue-mimicking phantom as well as biological tissues. Our experimental results suggested that the quantification of force in OCE was critical for accurate characterization of tissue mechanical properties and the qOCE technique was capable of differentiating biological tissues based on the elasticity of tissue that is generally nonlinear.
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Affiliation(s)
- Yi Qiu
- Department of Electrical and Computer Engineering, New Jersey Institute of Technology, Newark, NJ 07102, USA
| | - Farzana R. Zaki
- Department of Electrical and Computer Engineering, New Jersey Institute of Technology, Newark, NJ 07102, USA
| | - Namas Chandra
- Department of Biomedical Engineering, New Jersey Institute of Technology, Newark, NJ 07102, USA
| | - Shawn A. Chester
- Department of Mechanical and Industrial Engineering, New Jersey Institute of Technology, Newark, NJ 07102, USA
| | - Xuan Liu
- Department of Electrical and Computer Engineering, New Jersey Institute of Technology, Newark, NJ 07102, USA
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Mascarenhas EJ, Peters MF, Nijs J, Rutten MC, van de Vosse FN, Lopata RG. Assessment of mechanical properties of porcine aortas under physiological loading conditions using vascular elastography. J Mech Behav Biomed Mater 2016; 59:185-196. [DOI: 10.1016/j.jmbbm.2015.12.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2015] [Revised: 12/01/2015] [Accepted: 12/10/2015] [Indexed: 01/11/2023]
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Akyildiz AC, Hansen HHG, Nieuwstadt HA, Speelman L, De Korte CL, van der Steen AFW, Gijsen FJH. A Framework for Local Mechanical Characterization of Atherosclerotic Plaques: Combination of Ultrasound Displacement Imaging and Inverse Finite Element Analysis. Ann Biomed Eng 2015; 44:968-79. [PMID: 26399991 PMCID: PMC4826666 DOI: 10.1007/s10439-015-1410-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2015] [Accepted: 07/24/2015] [Indexed: 02/07/2023]
Abstract
Biomechanical models have the potential to predict plaque rupture. For reliable models, correct material properties of plaque components are a prerequisite. This study presents a new technique, where high resolution ultrasound displacement imaging and inverse finite element (FE) modeling is combined, to estimate material properties of plaque components. Iliac arteries with plaques were excised from 6 atherosclerotic pigs and subjected to an inflation test with pressures ranging from 10 to 120 mmHg. The arteries were imaged with high frequency 40 MHz ultrasound. Deformation maps of the plaques were reconstructed by cross correlation of the ultrasound radiofrequency data. Subsequently, the arteries were perfusion fixed for histology and structural components were identified. The histological data were registered to the ultrasound data to construct FE model of the plaques. Material properties of the arterial wall and the intima of the atherosclerotic plaques were estimated using a grid search method. The computed displacement fields showed good agreement with the measured displacement fields, implying that the FE models were able to capture local inhomogeneities within the plaque. On average, nonlinear stiffening of both the wall and the intima was observed, and the wall of the atheroslcerotic porcine iliac arteries was markedly stiffer than the intima (877 ± 459 vs. 100 ± 68 kPa at 100 mmHg). The large spread in the data further illustrates the wide variation of the material properties. We demonstrated the feasibility of a mixed experimental–numerical framework to determine the material properties of arterial wall and intima of atherosclerotic plaques from intact arteries, and concluded that, due to the observed variation, plaque specific properties are required for accurate stress simulations.
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Affiliation(s)
- Ali C. Akyildiz
- />Biomechanics Lab, Department of Biomedical Engineering, Thoraxcenter, Erasmus Medical Center, PO Box 2040, 3000 CA Rotterdam, The Netherlands
- />Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, USA
| | - Hendrik H. G. Hansen
- />Medical UltraSound Imaging Center (MUSIC), Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Harm A. Nieuwstadt
- />Biomechanics Lab, Department of Biomedical Engineering, Thoraxcenter, Erasmus Medical Center, PO Box 2040, 3000 CA Rotterdam, The Netherlands
| | - Lambert Speelman
- />Biomechanics Lab, Department of Biomedical Engineering, Thoraxcenter, Erasmus Medical Center, PO Box 2040, 3000 CA Rotterdam, The Netherlands
| | - Chris L. De Korte
- />Medical UltraSound Imaging Center (MUSIC), Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Antonius F. W. van der Steen
- />Biomechanics Lab, Department of Biomedical Engineering, Thoraxcenter, Erasmus Medical Center, PO Box 2040, 3000 CA Rotterdam, The Netherlands
- />Department of Applied Sciences, Delft University of Technology, Delft, The Netherlands
| | - Frank J. H. Gijsen
- />Biomechanics Lab, Department of Biomedical Engineering, Thoraxcenter, Erasmus Medical Center, PO Box 2040, 3000 CA Rotterdam, The Netherlands
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Yuan J, Teng Z, Feng J, Zhang Y, Brown AJ, Gillard JH, Jing Z, Lu Q. Influence of material property variability on the mechanical behaviour of carotid atherosclerotic plaques: a 3D fluid-structure interaction analysis. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2015; 31:e02722. [PMID: 25940741 PMCID: PMC4528233 DOI: 10.1002/cnm.2722] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 03/10/2015] [Accepted: 04/27/2015] [Indexed: 06/04/2023]
Abstract
Mechanical analysis has been shown to be complementary to luminal stenosis in assessing atherosclerotic plaque vulnerability. However, patient-specific material properties are not available and the effect of material properties variability has not been fully quantified. Media and fibrous cap (FC) strips from carotid endarterectomy samples were classified into hard, intermediate and soft according to their incremental Young's modulus. Lipid and intraplaque haemorrhage/thrombus strips were classified as hard and soft. Idealised geometry-based 3D fluid-structure interaction analyses were performed to assess the impact of material property variability in predicting maximum principal stress (Stress-P1 ) and stretch (Stretch-P1 ). When FC was thick (1000 or 600 µm), Stress-P1 at the shoulder was insensitive to changes in material stiffness, whereas Stress-P1 at mid FC changed significantly. When FC was thin (200 or 65 µm), high stress concentrations shifted from the shoulder region to mid FC, and Stress-P1 became increasingly sensitive to changes in material properties, in particular at mid FC. Regardless of FC thickness, Stretch-P1 at these locations was sensitive to changes in material properties. Variability in tissue material properties influences both the location and overall stress/stretch value. This variability needs to be accounted for when interpreting the results of mechanical modelling.
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Affiliation(s)
- Jianmin Yuan
- Department of Radiology, University of Cambridge, Cambridge, CB2 0QQ, UK
| | - Zhongzhao Teng
- Department of Radiology, University of Cambridge, Cambridge, CB2 0QQ, UK
- Department of Engineering, University of Cambridge, Cambridge, CB2 1PZ, UK
| | - Jiaxuan Feng
- Department of Vascular Surgery, Changhai Hospital, Changhai Road, Shanghai, 200433, China
| | - Yongxue Zhang
- Department of Radiology, University of Cambridge, Cambridge, CB2 0QQ, UK
- Department of Vascular Surgery, Changhai Hospital, Changhai Road, Shanghai, 200433, China
| | - Adam J Brown
- Division of Cardiovascular Medicine, University of Cambridge, Cambridge, CB2 1TN, UK
| | - Jonathan H Gillard
- Department of Radiology, University of Cambridge, Cambridge, CB2 0QQ, UK
| | - Zaiping Jing
- Department of Vascular Surgery, Changhai Hospital, Changhai Road, Shanghai, 200433, China
| | - Qingsheng Lu
- Department of Vascular Surgery, Changhai Hospital, Changhai Road, Shanghai, 200433, China
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Nieuwstadt HA, Fekkes S, Hansen HHG, de Korte CL, van der Lugt A, Wentzel JJ, van der Steen AFW, Gijsen FJH. Carotid plaque elasticity estimation using ultrasound elastography, MRI, and inverse FEA - A numerical feasibility study. Med Eng Phys 2015; 37:801-7. [PMID: 26130603 DOI: 10.1016/j.medengphy.2015.06.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Revised: 06/02/2015] [Accepted: 06/07/2015] [Indexed: 12/13/2022]
Abstract
The material properties of atherosclerotic plaques govern the biomechanical environment, which is associated with rupture-risk. We investigated the feasibility of noninvasively estimating carotid plaque component material properties through simulating ultrasound (US) elastography and in vivo magnetic resonance imaging (MRI), and solving the inverse problem with finite element analysis. 2D plaque models were derived from endarterectomy specimens of nine patients. Nonlinear neo-Hookean models (tissue elasticity C1) were assigned to fibrous intima, wall (i.e., media/adventitia), and lipid-rich necrotic core. Finite element analysis was used to simulate clinical cross-sectional US strain imaging. Computer-simulated, single-slice in vivo MR images were segmented by two MR readers. We investigated multiple scenarios for plaque model elasticity, and consistently found clear separations between estimated tissue elasticity values. The intima C1 (160 kPa scenario) was estimated as 125.8 ± 19.4 kPa (reader 1) and 128.9 ± 24.8 kPa (reader 2). The lipid-rich necrotic core C1 (5 kPa) was estimated as 5.6 ± 2.0 kPa (reader 1) and 8.5 ± 4.5 kPa (reader 2). A scenario with a stiffer wall yielded similar results, while realistic US strain noise and rotating the models had little influence, thus demonstrating robustness of the procedure. The promising findings of this computer-simulation study stimulate applying the proposed methodology in a clinical setting.
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Affiliation(s)
- H A Nieuwstadt
- Department of Biomedical Engineering, Erasmus MC, Rotterdam, The Netherlands.
| | - S Fekkes
- Department of Radiology and Nuclear Medicine, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - H H G Hansen
- Department of Radiology and Nuclear Medicine, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - C L de Korte
- Department of Radiology and Nuclear Medicine, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - A van der Lugt
- Department of Radiology, Erasmus MC, Rotterdam, The Netherlands
| | - J J Wentzel
- Department of Biomedical Engineering, Erasmus MC, Rotterdam, The Netherlands
| | - A F W van der Steen
- Department of Biomedical Engineering, Erasmus MC, Rotterdam, The Netherlands; Department of Imaging Science and Technology, Delft University of Technology, Delft, The Netherlands
| | - F J H Gijsen
- Department of Biomedical Engineering, Erasmus MC, Rotterdam, The Netherlands.
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11
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Brezinski ME. Practical Challenges of Current Video Rate OCT Elastography: Accounting for Dynamic and Static Tissue Properties. JOURNAL OF LASERS, OPTICS & PHOTONICS 2014; 1:112. [PMID: 29286052 PMCID: PMC5743221 DOI: 10.4172/2469-410x.1000112] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Optical coherence tomography (OCT) elastography (OCTE) has the potential to be an important diagnostic tool for pathologies including coronary artery disease, osteoarthritis, malignancies, and even dental caries. Many groups have performed OCTE, including our own, using a wide range of approaches. However, we will demonstrate current OCTE approaches are not scalable to real-time, in vivo imaging. As will be discussed, among the most important reasons is current designs focus on the system and not the target. Specifically, tissue dynamic responses are not accounted, with examples being the tissue strain response time, preload variability, and conditioning variability. Tissue dynamic responses, and to a lesser degree static tissue properties, prevent accurate video rate modulus assessments for current embodiments. Accounting for them is the focus of this paper. A top-down approach will be presented to overcome these challenges to real time in vivo tissue characterization. Discussed first is an example clinical scenario where OTCE would be of substantial relevance, the prevention of acute myocardial infarction or heart attacks. Then the principles behind OCTE are examined. Next, constrains on in vivo application of current OCTE are evaluated, focusing on dynamic tissue responses. An example is the tissue strain response, where it takes about 20 msec after a stress is applied to reach plateau. This response delay is not an issue at slow acquisition rates, as most current OCTE approaches are preformed, but it is for video rate OCTE. Since at video rate each frame is only 30 msec, for essentially all current approaches this means the strain for a given stress is changing constantly during the B-scan. Therefore the modulus can't be accurately assessed. This serious issue is an even greater problem for pulsed techniques as it means the strain/modulus for a given stress (at a location) is unpredictably changing over a B-scan. The paper concludes by introducing a novel video rate approach to overcome these challenges.
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Affiliation(s)
- Mark E Brezinski
- Center for Optics and Modern Physics, Brigham and Women’s Hospital, 75 Francis Street, Boston, M.A. 02115, USA
- Harvard Medical School, 25 Shattuck Street, Boston, M.A. 02115, USA
- Department of Electrical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, M.A. 02139, USA
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Lipid crystals mechanically stimulate adjacent extracellular matrix in advanced atherosclerotic plaques. Atherosclerosis 2014; 237:769-76. [PMID: 25463119 DOI: 10.1016/j.atherosclerosis.2014.10.018] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Revised: 09/29/2014] [Accepted: 10/06/2014] [Indexed: 11/22/2022]
Abstract
OBJECTIVE Although lipid crystals (LCs) have received attention as a causative factor of plaque rupture, the mechanisms by which they increase plaque vulnerability are unknown. We examined whether solid-state LCs physically affect the adjacent extracellular matrix (ECM) using a combination of multimodal nonlinear optical (MNLO) imaging and finite element analysis (FEA). METHODS The changes of ECMs affected by lipids in atherosclerotic arteries in apolipoprotein E-deficient mice (n = 32) fed a high-fat diet for 20-30 weeks were micro-anatomically visualized by a 3D MNLO imaging platform including CARS for lipids, TPEF for elastin, and SHG for collagen. RESULTS AND CONCLUSION The TPEF signal of elastin was increased at the peripheral regions of LCs (<10 μm) compared with foam cell regions. In order to confirm the increase of elastin, biochemical assay (western blot) was performed. The protein level of elastin was increased approximately 2.25-fold (p = 0.024) in LC-rich arteries. Under the hypothesis that the increase of elastin resulted from the mechanical stimulus from solid-state LCs, MNLO images were subjected to FEA to simulate the displacement according to the expanding magnitude of the vessel during cardiac cycles. We found that microscale focal stress was increased specifically around the LCs. These FEA results corresponded with the increase of elastin observed by TPEF. These data suggest that LCs mechanically stimulate the adjacent ECM to alter the composition of ECM and cause vessel remodeling. The combination of MNLO imaging and FEA has great potential to verify the mechanical predictions in cardiovascular diseases.
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13
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Lopata RGP, Peters MFJ, Nijs J, Oomens CWJ, Rutten MCM, van de Vosse FN. Vascular elastography: a validation study. ULTRASOUND IN MEDICINE & BIOLOGY 2014; 40:1882-1895. [PMID: 24798385 DOI: 10.1016/j.ultrasmedbio.2014.02.029] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Revised: 01/13/2014] [Accepted: 02/23/2014] [Indexed: 06/03/2023]
Abstract
Vascular elastography techniques are promising tools for mechanical characterization of diseased arteries. These techniques are usually validated with simulations or phantoms or by comparing results with histology or other imaging modalities. In the study described here, vascular elastography was applied to porcine aortas in vitro during inflation testing (n = 10) and results were compared with those of standard bi-axial tensile testing, a technique that directly measures the force applied to the tissue. A neo-Hookean model was fit to the stress-strain data, valid for large deformations. Results indicated good correspondence between the two techniques, with GUS = 110 ± 11 kPa and GTT = 108 ± 10 kPa for ultrasound and tensile testing, respectively. Bland-Altman analysis revealed little bias (GUS-GTT = 2 ± 20 kPa). The next step will be the application of a non-linear material model that is also adaptable for in vivo measurements.
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Affiliation(s)
- Richard G P Lopata
- Cardiovascular Biomechanics, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands.
| | - Mathijs F J Peters
- Cardiovascular Biomechanics, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - Jan Nijs
- Department of Cardiac Surgery, University Hospital Brussels, Brussels, Belgium
| | - Cees W J Oomens
- Soft Tissue Biomechanics & Engineering, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - Marcel C M Rutten
- Cardiovascular Biomechanics, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - Frans N van de Vosse
- Cardiovascular Biomechanics, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
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14
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Biomechanical properties of native and tissue engineered heart valve constructs. J Biomech 2014; 47:1949-63. [DOI: 10.1016/j.jbiomech.2013.09.023] [Citation(s) in RCA: 179] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Revised: 09/09/2013] [Accepted: 09/10/2013] [Indexed: 11/18/2022]
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15
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Teng Z, Sadat U, Brown AJ, Gillard JH. Plaque hemorrhage in carotid artery disease: pathogenesis, clinical and biomechanical considerations. J Biomech 2014; 47:847-58. [PMID: 24485514 PMCID: PMC3994507 DOI: 10.1016/j.jbiomech.2014.01.013] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/13/2014] [Indexed: 12/21/2022]
Abstract
Stroke remains the most prevalent disabling illness today, with internal carotid artery luminal stenosis due to atheroma formation responsible for the majority of ischemic cerebrovascular events. Severity of luminal stenosis continues to dictate both patient risk stratification and the likelihood of surgical intervention. But there is growing evidence to suggest that plaque morphology may help improve pre-existing risk stratification criteria. Plaque components such a fibrous tissue, lipid rich necrotic core and calcium have been well investigated but plaque hemorrhage (PH) has been somewhat overlooked. In this review we discuss the pathogenesis of PH, its role in dictating plaque vulnerability, PH imaging techniques, marterial properties of atherosclerotic tissues, in particular, those obtained based on in vivo measurements and effect of PH in modulating local biomechanics.
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Affiliation(s)
- Zhongzhao Teng
- University Department of Radiology, University of Cambridge, UK; Department of Engineering, University of Cambridge, UK.
| | - Umar Sadat
- Department of Surgery, Cambridge University Hospitals NHS Foundation Trust, UK
| | - Adam J Brown
- Department of Cardiovascular Medicine, University of Cambridge, UK
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16
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Sadat U, Teng Z, Gillard JH. Biomechanical structural stresses of atherosclerotic plaques. Expert Rev Cardiovasc Ther 2014; 8:1469-81. [DOI: 10.1586/erc.10.130] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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17
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Li W, Hill N, Ogden R, Smythe A, Majeed A, Bird N, Luo X. Anisotropic behaviour of human gallbladder walls. J Mech Behav Biomed Mater 2013; 20:363-75. [DOI: 10.1016/j.jmbbm.2013.02.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2012] [Revised: 02/11/2013] [Accepted: 02/20/2013] [Indexed: 10/27/2022]
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18
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McCormick M, Varghese T, Wang X, Mitchell C, Kliewer MA, Dempsey RJ. Methods for robust in vivo strain estimation in the carotid artery. Phys Med Biol 2012; 57:7329-53. [PMID: 23079725 DOI: 10.1088/0031-9155/57/22/7329] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A hierarchical block-matching motion tracking algorithm for strain imaging is presented. Displacements are estimated with improved robustness and precision by utilizing a Bayesian regularization algorithm and an unbiased subsample interpolation technique. A modified least-squares strain estimator is proposed to estimate strain images from a noisy displacement input while addressing the motion discontinuity at the wall-lumen boundary. Methods to track deformation over the cardiac cycle incorporate a dynamic frame skip criterion to process data frames with sufficient deformation to produce high signal-to-noise displacement and strain images. Algorithms to accumulate displacement and/or strain on particles in a region of interest over the cardiac cycle are described. New methods to visualize and characterize the deformation measured with the full 2D strain tensor are presented. Initial results from patients imaged prior to carotid endarterectomy suggest that strain imaging detects conditions that are traditionally considered high risk including soft plaque composition, unstable morphology, abnormal hemodynamics and shear of plaque against tethering tissue can be exacerbated by neoangiogenesis. For example, a maximum absolute principal strain exceeding 0.2 is observed near calcified regions adjacent to turbulent flow, protrusion of the plaque into the arterial lumen and regions of low echogenicity associated with soft plaques. Non-invasive carotid strain imaging is therefore a potentially useful tool for detecting unstable carotid plaque.
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Affiliation(s)
- M McCormick
- Department of Medical Physics, University of Wisconsin-Madison, Madison, WI 53705, USA
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19
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Li WG, Luo XY, Hill NA, Ogden RW, Smythe A, Majeed AW, Bird N. A Quasi-Nonlinear Analysis of the Anisotropic Behaviour of Human Gallbladder Wall. J Biomech Eng 2012; 134:101009. [PMID: 23083200 DOI: 10.1115/1.4007633] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Estimation of biomechanical parameters of soft tissues from noninvasive measurements has clinical significance in patient-specific modeling and disease diagnosis. In this work, we present a quasi-nonlinear method that is used to estimate the elastic moduli of the human gallbladder wall. A forward approach based on a transversely isotropic membrane material model is used, and an inverse iteration is carried out to determine the elastic moduli in the circumferential and longitudinal directions between two successive ultrasound images of gallbladder. The results demonstrate that the human gallbladder behaves in an anisotropic manner, and constitutive models need to incorporate this. The estimated moduli are also nonlinear and patient dependent. Importantly, the peak stress predicted here differs from the earlier estimate from linear membrane theory. As the peak stress inside the gallbladder wall has been found to strongly correlate with acalculous gallbladder pain, reliable mechanical modeling for gallbladder tissue is crucial if this information is to be used in clinical diagnosis.
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Affiliation(s)
- W. G. Li
- School of Mathematics and Statistics, University of Glasgow, Glasgow, G12 8QW, UK
| | - X. Y. Luo
- School of Mathematics and Statistics, University of Glasgow, Glasgow, G12 8QW, UK
| | - N. A. Hill
- School of Mathematics and Statistics, University of Glasgow, Glasgow, G12 8QW, UK
| | - R. W. Ogden
- School of Mathematics and Statistics, University of Glasgow, Glasgow, G12 8QW, UK; School of Engineering, University of Aberdeen, Aberdeen, AB24 3UE, UK
| | - A. Smythe
- Academic Surgical Unit, Royal Hallamshire Hospital, Sheffield, S10 2JF, UK
| | - A. W. Majeed
- Academic Surgical Unit, Royal Hallamshire Hospital, Sheffield, S10 2JF, UK
| | - N. Bird
- Academic Surgical Unit, Royal Hallamshire Hospital, Sheffield, S10 2JF, UK
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20
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Robertson C, Lee SW, Ahn YC, Mahon S, Chen Z, Brenner M, George SC. Investigating in vivo airway wall mechanics during tidal breathing with optical coherence tomography. JOURNAL OF BIOMEDICAL OPTICS 2011; 16:106011. [PMID: 22029358 PMCID: PMC3210193 DOI: 10.1117/1.3642006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Optical coherence tomography (OCT) is a nondestructive imaging technique offering high temporal and spatial resolution, which makes it a natural choice for assessing tissue mechanical properties. We have developed methods to mechanically analyze the compliance of the rabbit trachea in vivo using tissue deformations induced by tidal breathing, offering a unique tool to assess the behavior of the airways during their normal function. Four-hundred images were acquired during tidal breathing with a custom-built endoscopic OCT system. The surface of the tissue was extracted from a set of these images via image processing algorithms, filtered with a bandpass filter set at respiration frequency to remove cardiac and probe motion, and compared to ventilatory pressure to calculate wall compliance. These algorithms were tested on elastic phantoms to establish reliability and reproducibility. The mean tracheal wall compliance (in five animals) was 1.3±0.3×10(-5) (mm Pa)(-1). Unlike previous work evaluating airway mechanics, this new method is applicable in vivo, noncontact, and loads the trachea in a physiological manner. The technique may have applications in assessing airway mechanics in diseases such as asthma that are characterized by significant airway remodeling.
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Affiliation(s)
- Claire Robertson
- University of California, Irvine, Department of Biomedical Engineering, Irvine, California 92697, USA
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21
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Lawlor MG, O'Donnell MR, O'Connell BM, Walsh MT. Experimental determination of circumferential properties of fresh carotid artery plaques. J Biomech 2011; 44:1709-15. [PMID: 21497353 DOI: 10.1016/j.jbiomech.2011.03.033] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2010] [Revised: 03/07/2011] [Accepted: 03/28/2011] [Indexed: 10/18/2022]
Abstract
Carotid endarterectomy (CEA) is currently accepted as the gold standard for interventional revascularisation of diseased arteries belonging to the carotid bifurcation. Despite the proven efficacy of CEA, great interest has been generated in carotid angioplasty and stenting (CAS) as an alternative to open surgical therapy. CAS is less invasive compared with CEA, and has the potential to successfully treat lesions close to the aortic arch or distal internal carotid artery (ICA). Following promising results from two recent trials (CREST; Carotid revascularisation endarterectomy versus stenting trial, and ICSS; International carotid stenting study) it is envisaged that there will be a greater uptake in carotid stenting, especially amongst the group who do not qualify for open surgical repair, thus creating pressure to develop computational models that describe a multitude of plaque models in the carotid arteries and their reaction to the deployment of such interventional devices. Pertinent analyses will require fresh human atherosclerotic plaque material characteristics for different disease types. This study analysed atherosclerotic plaque characteristics from 18 patients tested on site, post-surgical revascularisation through endarterectomy, with 4 tissue samples being excluded from tensile testing based on large width-length ratios. According to their mechanical behaviour, atherosclerotic plaques were separated into 3 grades of stiffness. Individual and group material coefficients were then generated analytically using the Yeoh strain energy function. The ultimate tensile strength (UTS) of each sample was also recorded, showing large variation across the 14 atherosclerotic samples tested. Experimental Green strains at rupture varied from 0.299 to 0.588 and the Cauchy stress observed in the experiments was between 0.131 and 0.779 MPa. It is expected that this data may be used in future design optimisation of next generation interventional medical devices for the treatment and revascularisation of diseased arteries of the carotid bifurcation.
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Affiliation(s)
- Michael G Lawlor
- Centre for Applied Biomedical Engineering Research, Department of Mechanical, Aeronautical and Biomedical Engineering and the Materials and Surface Science Institute, University of Limerick, Limerick, Ireland
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22
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Sun C, Standish B, Yang VXD. Optical coherence elastography: current status and future applications. JOURNAL OF BIOMEDICAL OPTICS 2011; 16:043001. [PMID: 21529067 DOI: 10.1117/1.3560294] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Optical coherence tomography (OCT) has several advantages over other imaging modalities, such as angiography and ultrasound, due to its inherently high in vivo resolution, which allows for the identification of morphological tissue structures. Optical coherence elastography (OCE) benefits from the superior spatial resolution of OCT and has promising applications, including cancer diagnosis and the detailed characterization of arterial wall biomechanics, both of which are based on the elastic properties of the tissue under investigation. We present OCE principles based on techniques associated with static and dynamic tissue excitation, and their corresponding elastogram image-reconstruction algorithms are reviewed. OCE techniques, including the development of intravascular- or catheter-based OCE, are in their early stages of development but show great promise for surgical oncology or intravascular cardiology applications.
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Affiliation(s)
- Cuiru Sun
- Department of Electrical and Computer Engineering, Biophotonics and Bioengineering Laboratory, Ryerson University, Toronto, Ontario M5B 2K3, Canada
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23
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LIANG XING, CRECEA VASILICA, BOPPART STEPHENA. DYNAMIC OPTICAL COHERENCE ELASTOGRAPHY: A REVIEW. JOURNAL OF INNOVATIVE OPTICAL HEALTH SCIENCES 2010; 3:221-233. [PMID: 22448192 PMCID: PMC3311124 DOI: 10.1142/s1793545810001180] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
With the development of optical coherence tomography, the application optical coherence elastography (OCE) has gained more and more attention in biomechanics for its unique features including micron-scale resolution, real-time processing, and non-invasive imaging. In this review, one group of OCE techniques, namely dynamic OCE, are introduced and discussed including external dynamic OCE mapping and imaging of ex vivo breast tumor, external dynamic OCE measurement of in vivo human skin, and internal dynamic OCE including acoustomotive OCE and magnetomotive OCE. These techniques overcame some of the major drawbacks of traditional static OCE, and broadened the OCE application fields. Driven by scientific needs to engineer new quantitative methods that utilize the high micron-scale resolution achievable with optics, results of biomechanical properties were obtained from biological tissues. The results suggest potential diagnostic and therapeutic clinical applications. Results from these studies also help our understanding of the relationship between biomechanical variations and functional tissue changes in biological systems.
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Affiliation(s)
- XING LIANG
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign Urbana, IL, 61801, USA
- Biophotonics Imaging Laboratory, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign Urbana, IL, 61801, USA
| | - VASILICA CRECEA
- Department of Physics, University of Illinois at Urbana-Champaign Urbana, IL, 61801, USA
- Biophotonics Imaging Laboratory, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign Urbana, IL, 61801, USA
| | - STEPHEN A. BOPPART
- Departments of Electrical and Computer Engineering, Bioengineering, and Internal Medicine, University of Illinois at Urbana-Champaign Urbana, IL, 61801, USA
- Biophotonics Imaging Laboratory, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign Urbana, IL, 61801, USA
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24
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Le Floc'h S, Cloutier G, Finet G, Tracqui P, Pettigrew RI, Ohayon J. On the potential of a new IVUS elasticity modulus imaging approach for detecting vulnerable atherosclerotic coronary plaques: in vitro vessel phantom study. Phys Med Biol 2010; 55:5701-21. [PMID: 20826899 DOI: 10.1088/0031-9155/55/19/006] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Peak cap stress amplitude is recognized as a good indicator of vulnerable plaque (VP) rupture. However, such stress evaluation strongly relies on a precise, but still lacking, knowledge of the mechanical properties exhibited by the plaque components. As a first response to this limitation, our group recently developed, in a previous theoretical study, an original approach, called iMOD (imaging modulography), which reconstructs elasticity maps (or modulograms) of atheroma plaques from the estimation of strain fields. In the present in vitro experimental study, conducted on polyvinyl alcohol cryogel arterial phantoms, we investigate the benefit of coupling the iMOD procedure with the acquisition of intravascular ultrasound (IVUS) measurements for detection of VP. Our results show that the combined iMOD-IVUS strategy: (1) successfully detected and quantified soft inclusion contours with high positive predictive and sensitivity values of 89.7 ± 3.9% and 81.5 ± 8.8%, respectively, (2) estimated reasonably cap thicknesses larger than ∼300 µm, but underestimated thinner caps, and (3) quantified satisfactorily Young's modulus of hard medium (mean value of 109.7 ± 23.7 kPa instead of 145.4 ± 31.8 kPa), but overestimated the stiffness of soft inclusions (mean Young`s moduli of 31.4 ± 9.7 kPa instead of 17.6 ± 3.4 kPa). All together, these results demonstrate a promising benefit of the new iMOD-IVUS clinical imaging method for in vivo VP detection.
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Affiliation(s)
- Simon Le Floc'h
- Laboratory TIMC-DynaCell, UJF, CNRS UMR 5525, In3S, Grenoble, France
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25
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Balocco S, Camara O, Vivas E, Sola T, Guimaraens L, Gratama van Andel HAF, Majoie CB, Pozo JM, Bijnens BH, Frangi AF. Feasibility of estimating regional mechanical properties of cerebral aneurysmsin vivo. Med Phys 2010; 37:1689-706. [DOI: 10.1118/1.3355933] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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26
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Leach JR, Rayz VL, Soares B, Wintermark M, Mofrad MRK, Saloner D. Carotid atheroma rupture observed in vivo and FSI-predicted stress distribution based on pre-rupture imaging. Ann Biomed Eng 2010; 38:2748-65. [PMID: 20232151 PMCID: PMC2900591 DOI: 10.1007/s10439-010-0004-8] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2009] [Accepted: 03/04/2010] [Indexed: 11/13/2022]
Abstract
Atherosclerosis at the carotid bifurcation is a major risk factor for stroke. As mechanical forces may impact lesion stability, finite element studies have been conducted on models of diseased vessels to elucidate the effects of lesion characteristics on the stresses within plaque materials. It is hoped that patient-specific biomechanical analyses may serve clinically to assess the rupture potential for any particular lesion, allowing better stratification of patients into the most appropriate treatments. Due to a sparsity of in vivo plaque rupture data, the relationship between various mechanical descriptors such as stresses or strains and rupture vulnerability is incompletely known, and the patient-specific utility of biomechanical analyses is unclear. In this article, we present a comparison between carotid atheroma rupture observed in vivo and the plaque stress distribution from fluid–structure interaction analysis based on pre-rupture medical imaging. The effects of image resolution are explored and the calculated stress fields are shown to vary by as much as 50% with sub-pixel geometric uncertainty. Within these bounds, we find a region of pronounced elevation in stress within the fibrous plaque layer of the lesion with a location and extent corresponding to that of the observed site of plaque rupture.
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Affiliation(s)
- Joseph R Leach
- UC Berkeley/UC San Francisco Joint Graduate Group in Bioengineering, Berkeley, CA, USA.
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27
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Kolipaka A, McGee KP, Manduca A, Romano AJ, Glaser KJ, Araoz PA, Ehman RL. Magnetic resonance elastography: Inversions in bounded media. Magn Reson Med 2009; 62:1533-42. [PMID: 19780146 PMCID: PMC2849111 DOI: 10.1002/mrm.22144] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2009] [Accepted: 06/24/2009] [Indexed: 01/08/2023]
Abstract
Magnetic resonance elastography is a noninvasive imaging technique capable of quantifying and spatially resolving the shear stiffness of soft tissues by visualization of synchronized mechanical wave displacement fields. However, magnetic resonance elastography inversions generally assume that the measured tissue motion consists primarily of shear waves propagating in a uniform, infinite medium. This assumption is not valid in organs such as the heart, eye, bladder, skin, fascia, bone and spinal cord, in which the shear wavelength approaches the geometric dimensions of the object. The aim of this study was to develop and test mathematical inversion algorithms capable of resolving shear stiffness from displacement maps of flexural waves propagating in bounded media such as beams, plates, and spherical shells, using geometry-specific equations of motion. Magnetic resonance elastography and finite element modeling of beam, plate, and spherical shell phantoms of various geometries were performed. Mechanical testing of the phantoms agreed with the stiffness values obtained from finite element modeling and magnetic resonance elastography data, and a linear correlation of r(2) >or= 0.99 was observed between the stiffness values obtained using magnetic resonance elastography and finite element modeling data. In conclusion, we have demonstrated new inversion methods for calculating shear stiffness that may be more appropriate for waves propagating in bounded media.
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Affiliation(s)
| | | | | | - Anthony J. Romano
- Acoustics Division, Naval Research Laboratory, Washington, DC, United States
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