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Akbarzadeh Khorshidi M, Bose S, Watschke B, Mareena E, Lally C. Characterisation of human penile tissue properties using experimental testing combined with multi-target inverse finite element modelling. Acta Biomater 2024; 184:226-238. [PMID: 38945188 DOI: 10.1016/j.actbio.2024.06.035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2024] [Revised: 06/05/2024] [Accepted: 06/24/2024] [Indexed: 07/02/2024]
Abstract
This paper presents an inverse finite element (FE) approach aimed at estimating multi-layered human penile tissues. The inverse FE approach integrates experimental force-displacement and boundary deformation data of penile tissues with a developed FE model and uses new experimental data on human penile tissue. The experimental study encompasses whole organ plate-compression tests and individual layer tensile and compression tests, providing comprehensive insights into the tissue's mechanical behaviour. The biomechanical characterisation of penile tissue is of crucial significance for understanding its mechanical behaviour under various physiological and pathological conditions. The FE model is constructed using the realistic geometry of the penile segment and appropriate constitutive models for each tissue layer to leverage the accuracy and consistency of the model. Through systematic variation of tissue parameters in the inverse FE algorithm, simulations achieve the best match with both force-displacement and deformed boundary results obtained from the whole organ plate-compression tests. Test results from individual tissue layers are also utilised to assess the estimated parameters. The proposed inverse FE approach allows for the estimation of penile tissue parameters with high precision and reliability, shedding light on the mechanical properties of this complex biological organ. This work has applications not only in urology but also for researchers in various disciplines of biomechanics. As a result, our study contributes to advancing the understanding of human penile tissue mechanics whilst the methodology could also be applied to a range of other soft biological tissues. STATEMENT OF SIGNIFICANCE: This research uses a multi-target inverse finite element (FE) approach for estimating the material parameters of human penile tissues. By integrating experimental data and a realistic FE model, this study achieves high-precision constitutive model parameter estimation, offering key insights into penile tissue mechanics under various loading conditions. The significance of this work lies in the use of this inverse FE approach for fresh-frozen human penile tissues, to identify the mechanical properties and constitutive models for both segregated tunica albuginea and corpus cavernosum as well as intact penile tissue segments. The study's scientific impact lies in its advancement of the understanding of human urological tissue mechanics, impacting researchers and clinicians alike.
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Affiliation(s)
- Majid Akbarzadeh Khorshidi
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland; Department of Mechanical, Manufacturing and Biomedical Engineering, School of Engineering, Trinity College Dublin, Dublin 2, Ireland; Advanced Materials and BioEngineering Research Centre (AMBER), Royal College of Surgeons in Ireland and Trinity College Dublin, Dublin 2, Ireland
| | - Shirsha Bose
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland; Department of Mechanical, Manufacturing and Biomedical Engineering, School of Engineering, Trinity College Dublin, Dublin 2, Ireland; Advanced Materials and BioEngineering Research Centre (AMBER), Royal College of Surgeons in Ireland and Trinity College Dublin, Dublin 2, Ireland
| | - Brian Watschke
- Urology, Boston Scientific Corp, Inc, Minnetonka, MN, USA
| | - Evania Mareena
- Urology, Boston Scientific Corp, Inc, Clonmel Co, Tipperary, Ireland
| | - Caitríona Lally
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland; Department of Mechanical, Manufacturing and Biomedical Engineering, School of Engineering, Trinity College Dublin, Dublin 2, Ireland; Advanced Materials and BioEngineering Research Centre (AMBER), Royal College of Surgeons in Ireland and Trinity College Dublin, Dublin 2, Ireland.
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2
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Bose S, Akbarzadeh Khorshidi M, Johnston RD, Watschke B, Mareena E, Lally C. Experimental testing combined with inverse-FE for mechanical characterisation of penile tissues. Acta Biomater 2024; 179:180-191. [PMID: 38494081 DOI: 10.1016/j.actbio.2024.03.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Revised: 02/29/2024] [Accepted: 03/11/2024] [Indexed: 03/19/2024]
Abstract
Erectile dysfunction (ED) predominantly affects men in their 40-70s and can lead to poor quality of life. One option for ED treatment is surgical implantation of an inflatable penile prosthesis (IPP). However, they can be associated with negative outcomes including infection, migration or fibrosis. To improve outcomes, the interaction between the IPP device and surrounding tissues needs further investigation and this could be achieved using pre-clinical testbeds, but they need to be informed by extensive tissue testing. In this study, an experimental approach is adopted to characterise the mechanics of horse penile tissue and establish a testing protocol for penile tissue. The whole penis segments were tested in plate compression tests to obtain whole penis behaviour which is necessary for validation of a pre-clinical testbed, whilst tensile and compression tests were performed on individual penile tissues, namely corpus cavernosa and tunica albuginea. The second part of the paper deals with the development of a computational model employing an inverse finite element approach to estimate the material parameters of each tissue layer. These material parameters are in good agreement with the experimental results obtained from the individual tissue layers and whole organ tissue tests. This paper presents the first study proposing realistic nonlinear elastic material parameters for penile tissues and offers a validated testbed for IPPs. STATEMENT OF SIGNIFICANCE: Erectile Dysfunction (ED) affects over half the male population aged 40-70 potentially leading to poor quality of life. Patients not responding to conventional treatments of ED, are advised to use penile prostheses which can create an erection using implanted inflatable cylinders. A significant drawback of such prostheses, however, is the substantial tissue damage they can induce during their usage. Preclinical testbeds, including computational and bench-top models, could offer an efficient means of improving device designs to mitigate this damage but such testbeds require extensive knowledge of penile tissue properties. In this study, the authors determine penile tissue mechanics and apply an inverse FE approach to characterise the penile material properties required to validate preclinical models of the penis.
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Affiliation(s)
- Shirsha Bose
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland; Department of Mechanical, Manufacturing and Biomedical Engineering, School of Engineering, Trinity College Dublin, Dublin 2, Ireland; Advanced Materials and BioEngineering Research Centre (AMBER), Royal College of Surgeons in Ireland and Trinity College Dublin, Dublin 2, Ireland
| | - Majid Akbarzadeh Khorshidi
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland; Department of Mechanical, Manufacturing and Biomedical Engineering, School of Engineering, Trinity College Dublin, Dublin 2, Ireland; Advanced Materials and BioEngineering Research Centre (AMBER), Royal College of Surgeons in Ireland and Trinity College Dublin, Dublin 2, Ireland
| | - Robert D Johnston
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland; Department of Mechanical, Manufacturing and Biomedical Engineering, School of Engineering, Trinity College Dublin, Dublin 2, Ireland; Advanced Materials and BioEngineering Research Centre (AMBER), Royal College of Surgeons in Ireland and Trinity College Dublin, Dublin 2, Ireland
| | - Brian Watschke
- Urology, Boston Scientific Corp, Inc, Minnetonka, MN, USA
| | - Evania Mareena
- Urology, Boston Scientific Corp, Inc, Clonmel Co, Tipperary, Ireland
| | - Caitríona Lally
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland; Department of Mechanical, Manufacturing and Biomedical Engineering, School of Engineering, Trinity College Dublin, Dublin 2, Ireland; Advanced Materials and BioEngineering Research Centre (AMBER), Royal College of Surgeons in Ireland and Trinity College Dublin, Dublin 2, Ireland.
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3
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Wang M, Ching-Johnson JA, Yin H, O’Neil C, Li AX, Chu MWA, Bartha R, Pickering JG. Mapping microarchitectural degeneration in the dilated ascending aorta with ex vivo diffusion tensor imaging. EUROPEAN HEART JOURNAL OPEN 2024; 4:oead128. [PMID: 38162403 PMCID: PMC10755346 DOI: 10.1093/ehjopen/oead128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Revised: 10/26/2023] [Accepted: 11/30/2023] [Indexed: 01/03/2024]
Abstract
Aims Thoracic aortic aneurysms (TAAs) carry a risk of catastrophic dissection. Current strategies to evaluate this risk entail measuring aortic diameter but do not image medial degeneration, the cause of TAAs. We sought to determine if the advanced magnetic resonance imaging (MRI) acquisition strategy, diffusion tensor imaging (DTI), could delineate medial degeneration in the ascending thoracic aorta. Methods and results Porcine ascending aortas were subjected to enzyme microinjection, which yielded local aortic medial degeneration. These lesions were detected by DTI, using a 9.4 T MRI scanner, based on tensor disorientation, disrupted diffusion tracts, and altered DTI metrics. High-resolution spatial analysis revealed that fractional anisotropy positively correlated, and mean and radial diffusivity inversely correlated, with smooth muscle cell (SMC) and elastin content (P < 0.001 for all). Ten operatively harvested human ascending aorta samples (mean subject age 61.6 ± 13.3 years, diameter range 29-64 mm) showed medial pathology that was more diffuse and more complex. Nonetheless, DTI metrics within an aorta spatially correlated with SMC, elastin, and, especially, glycosaminoglycan (GAG) content. Moreover, there were inter-individual differences in slice-averaged DTI metrics. Glycosaminoglycan accumulation and elastin degradation were captured by reduced fractional anisotropy (R2 = 0.47, P = 0.043; R2 = 0.76, P = 0.002), with GAG accumulation also captured by increased mean diffusivity (R2 = 0.46, P = 0.045) and increased radial diffusivity (R2 = 0.60, P = 0.015). Conclusion Ex vivo high-field DTI can detect ascending aorta medial degeneration and can differentiate TAAs in accordance with their histopathology, especially elastin and GAG changes. This non-destructive window into aortic medial microstructure raises prospects for probing the risks of TAAs beyond lumen dimensions.
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Affiliation(s)
- Mofei Wang
- Robarts Research Institute, Schulich School of Medicine and Dentistry, Western University, 1151 Richmond St. N. London, Canada, N6A 5B7
- Department of Biochemistry, Western University, 1151 Richmond St. N. London, Canada, N6A 3K7
| | - Justin A Ching-Johnson
- Robarts Research Institute, Schulich School of Medicine and Dentistry, Western University, 1151 Richmond St. N. London, Canada, N6A 5B7
- Department of Medical Biophysics, Western University, 1151 Richmond St. N. London, Canada, N6A 3K7
| | - Hao Yin
- Robarts Research Institute, Schulich School of Medicine and Dentistry, Western University, 1151 Richmond St. N. London, Canada, N6A 5B7
| | - Caroline O’Neil
- Robarts Research Institute, Schulich School of Medicine and Dentistry, Western University, 1151 Richmond St. N. London, Canada, N6A 5B7
| | - Alex X Li
- Robarts Research Institute, Schulich School of Medicine and Dentistry, Western University, 1151 Richmond St. N. London, Canada, N6A 5B7
| | - Michael W A Chu
- Department of Surgery, Western University, 1151 Richmond St. N. London, Canada, N6A 3K7
- London Health Sciences Centre, 339 Windermere Rd, London, Ontario, Canada, N6A 5A5
| | - Robert Bartha
- Robarts Research Institute, Schulich School of Medicine and Dentistry, Western University, 1151 Richmond St. N. London, Canada, N6A 5B7
- Department of Medical Biophysics, Western University, 1151 Richmond St. N. London, Canada, N6A 3K7
| | - J Geoffrey Pickering
- Robarts Research Institute, Schulich School of Medicine and Dentistry, Western University, 1151 Richmond St. N. London, Canada, N6A 5B7
- Department of Biochemistry, Western University, 1151 Richmond St. N. London, Canada, N6A 3K7
- Department of Medical Biophysics, Western University, 1151 Richmond St. N. London, Canada, N6A 3K7
- London Health Sciences Centre, 339 Windermere Rd, London, Ontario, Canada, N6A 5A5
- Department of Medicine, Western University, 1151 Richmond St. N. London, Canada N6A 3K7
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Torun SG, Munoz PDM, Crielaard H, Verhagen HJM, Kremers GJ, van der Steen AFW, Akyildiz AC. Local Characterization of Collagen Architecture and Mechanical Failure Properties of Fibrous Plaque Tissue of Atherosclerotic Human Carotid Arteries. Acta Biomater 2023; 164:293-302. [PMID: 37086826 DOI: 10.1016/j.actbio.2023.04.022] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Revised: 04/05/2023] [Accepted: 04/13/2023] [Indexed: 04/24/2023]
Abstract
Atherosclerotic plaque rupture in carotid arteries is a major cause of cerebrovascular events. Plaque rupture is the mechanical failure of the heterogeneous fibrous plaque tissue. Local characterization of the tissue's failure properties and the collagen architecture are of great importance to have insights in plaque rupture for clinical event prevention. Previous studies were limited to average rupture properties and global structural characterization, and did not provide the necessary local information. In this study, we assessed the local collagen architecture and failure properties of fibrous plaque tissue, by analyzing 30 tissue strips from 18 carotid plaques. Our study framework entailed second harmonic generation imaging for local collagen orientation and dispersion, and uniaxial tensile testing and digital image correlation for local tissue mechanics. The results showed that 87% of the imaged locations had collagen orientation close to the circumferential direction (0°) of the artery, and substantial dispersion locally. All regions combined, median [Q1:Q3] of the predominant angle measurements was -2° [-16°:16°]. The stretch ratio measurements clearly demonstrated a nonuniform stretch ratio distribution in the tissue under uniaxial loading. The rupture initiation regions had significantly higher stretch ratios (1.26 [1.15-1.40]) than the tissue average stretch ratio (1.11 [1.10-1.16]). No significant difference in collagen direction and dispersion was identified between the rupture regions and the rest of the tissue. The presented study forms an initial step towards gaining better insights into the characterization of local structural and mechanical fingerprints of fibrous plaque tissue in order to aid improved assessment of plaque rupture risk. STATEMENT OF SIGNIFICANCE: Plaque rupture risk assessment, critical to prevent cardiovascular events, requires knowledge on local failure properties and structure of collagenous plaque tissue. Our current knowledge is unfortunately limited to tissue's overall ultimate failure properties with scarce information on collagen architecture. In this study, local failure properties and collagen architecture of fibrous plaque tissue were obtained. We found predominant circumferential alignment of collagen fibers with substantial local dispersion. The tissue showed nonuniform stretch distribution under uniaxial tensile loading, with high stretches at rupture spots. This study highlights the significance of local mechanical and structural assessment for better insights into plaque rupture and the potential use of local stretches as risk marker for plaque rupture for patient-specific clinical applications.
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Affiliation(s)
- Su Guvenir Torun
- Department of Biomedical Engineering, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Pablo de Miguel Munoz
- Department of Biomedical Engineering, Erasmus Medical Center, Rotterdam, The Netherlands; Department of Biomechanical Engineering, Delft University of Technology, Delft, The Netherlands
| | - Hanneke Crielaard
- Department of Biomedical Engineering, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Hence J M Verhagen
- Department of Vascular Surgery, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Gert-Jan Kremers
- Erasmus Optical Imaging Center, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Antonius F W van der Steen
- Department of Biomedical Engineering, Erasmus Medical Center, Rotterdam, The Netherlands; Department of Biomechanical Engineering, Delft University of Technology, Delft, The Netherlands
| | - Ali C Akyildiz
- Department of Biomedical Engineering, Erasmus Medical Center, Rotterdam, The Netherlands; Department of Biomechanical Engineering, Delft University of Technology, Delft, The Netherlands.
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5
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Tornifoglio B, Stone AJ, Kerskens C, Lally C. Ex Vivo Study Using Diffusion Tensor Imaging to Identify Biomarkers of Atherosclerotic Disease in Human Cadaveric Carotid Arteries. Arterioscler Thromb Vasc Biol 2022; 42:1398-1412. [PMID: 36172867 PMCID: PMC9592180 DOI: 10.1161/atvbaha.122.318112] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
BACKGROUND This study aims to address the potential of ex vivo diffusion tensor imaging to provide insight into the microstructural composition and morphological arrangement of aged human atherosclerotic carotid arteries. METHODS In this study, whole human carotid arteries were investigated both anatomically and by comparing healthy and diseased regions. Nonrigid image registration was used with unsupervised segmentation to investigate the influence of elastin, collagen, cell density, glycosaminoglycans, and calcium on diffusion tensor imaging derived metrics (fractional anisotropy and mean diffusivity). Early stage atherosclerotic features were also investigated in terms of microstructural components and diffusion tensor imaging metrics. RESULTS All vessels displayed a dramatic decrease in fractional anisotropy compared with healthy animal arterial tissue, while the mean diffusivity was sensitive to regions of advanced disease. Elastin content strongly correlated with both fractional anisotropy (r>0.7, P<0.001) and mean diffusivity (r>-0.79, P<0.0002), and the thickened intima was also distinguishable from arterial media by these metrics. CONCLUSIONS These different investigations point to the potential of diffusion tensor imaging to identify characteristics of arterial disease progression, at early and late-stage lesion development.
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Affiliation(s)
- Brooke Tornifoglio
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute (B.T., A.J.S., C.K., C.L.), Ireland.,Department of Mechanical, Manufacturing and Biomedical Engineering, School of Engineering (B.T., A.J.S., C.L.), Ireland
| | - Alan J. Stone
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute (B.T., A.J.S., C.K., C.L.), Ireland.,Department of Mechanical, Manufacturing and Biomedical Engineering, School of Engineering (B.T., A.J.S., C.L.), Ireland.,Department of Medical Physics and Clinical Engineering, St. Vincent’s University Hospital, Dublin, Ireland (A.J.S.)
| | - Christian Kerskens
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute (B.T., A.J.S., C.K., C.L.), Ireland.,Trinity College Institute of Neuroscience (C.K.), Ireland
| | - Caitríona Lally
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute (B.T., A.J.S., C.K., C.L.), Ireland.,Department of Mechanical, Manufacturing and Biomedical Engineering, School of Engineering (B.T., A.J.S., C.L.), Ireland.,Advanced Materials and Bioengineering Research Centre (AMBER), Royal College of Surgeons in Ireland and Trinity College Dublin (C.L.), Ireland
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6
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Ghasemi M, Johnston RD, Lally C. Development of a Collagen Fibre Remodelling Rupture Risk Metric for Potentially Vulnerable Carotid Artery Atherosclerotic Plaques. Front Physiol 2021; 12:718470. [PMID: 34776999 PMCID: PMC8586512 DOI: 10.3389/fphys.2021.718470] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 09/22/2021] [Indexed: 11/24/2022] Open
Abstract
Atherosclerotic plaque rupture in carotid arteries can lead to stroke which is one of the leading causes of death or disability worldwide. The accumulation of atherosclerotic plaque in an artery changes the mechanical properties of the vessel. Whilst healthy arteries can continuously adapt to mechanical loads by remodelling their internal structure, particularly the load-bearing collagen fibres, diseased vessels may have limited remodelling capabilities. In this study, a local stress modulated remodelling algorithm is proposed to explore the mechanical response of arterial tissue to the remodelling of collagen fibres. This stress driven remodelling algorithm is used to predict the optimum distribution of fibres in healthy and diseased human carotid bifurcations obtained using Magnetic Resonance Imaging (MRI). In the models, healthy geometries were segmented into two layers: media and adventitia and diseased into four components: adventitia, media, plaque atheroma and lipid pool (when present in the MRI images). A novel meshing technique for hexahedral meshing of these geometries is also demonstrated. Using the remodelling algorithm, the optimum fibre patterns in various patient specific plaques are identified and the role that deviations from these fibre configurations in plaque vulnerability is shown. This study provides critical insights into the collagen fibre patterns required in carotid artery and plaque tissue to maintain plaque stability.
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Affiliation(s)
- Milad Ghasemi
- Trinity Centre for Biomedical Engineering, Trinity College Dublin, Dublin, Ireland.,Department of Mechanical, Manufacturing and Biomedical Engineering, School of Engineering, Trinity College Dublin, Dublin, Ireland
| | - Robert D Johnston
- Trinity Centre for Biomedical Engineering, Trinity College Dublin, Dublin, Ireland.,Department of Mechanical, Manufacturing and Biomedical Engineering, School of Engineering, Trinity College Dublin, Dublin, Ireland
| | - Caitríona Lally
- Trinity Centre for Biomedical Engineering, Trinity College Dublin, Dublin, Ireland.,Department of Mechanical, Manufacturing and Biomedical Engineering, School of Engineering, Trinity College Dublin, Dublin, Ireland.,Advanced Materials and Bioengineering Research Centre (AMBER), Royal College of Surgeons in Ireland and Trinity College Dublin, Dublin, Ireland
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7
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Exploring arterial tissue microstructural organization using non-Gaussian diffusion magnetic resonance schemes. Sci Rep 2021; 11:22247. [PMID: 34782651 PMCID: PMC8593063 DOI: 10.1038/s41598-021-01476-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 10/13/2021] [Indexed: 12/02/2022] Open
Abstract
The purpose of this study was to characterize the alterations in microstructural organization of arterial tissue using higher-order diffusion magnetic resonance schemes. Three porcine carotid artery models namely; native, collagenase treated and decellularized, were used to estimate the contribution of collagen and smooth muscle cells (SMC) on diffusion signal attenuation using gaussian and non-gaussian schemes. The samples were imaged in a 7 T preclinical scanner. High spatial and angular resolution diffusion weighted images (DWIs) were acquired using two multi-shell (max b-value = 3000 s/mm2) acquisition protocols. The processed DWIs were fitted using monoexponential, stretched-exponential, kurtosis and bi-exponential schemes. Directionally variant and invariant microstructural parametric maps of the three artery models were obtained from the diffusion schemes. The parametric maps were used to assess the sensitivity of each diffusion scheme to collagen and SMC composition in arterial microstructural environment. The inter-model comparison showed significant differences across the considered models. The bi-exponential scheme based slow diffusion compartment (Ds) was highest in the absence of collagen, compared to native and decellularized microenvironments. In intra-model comparison, kurtosis along the radial direction was the highest. Overall, the results of this study demonstrate the efficacy of higher order dMRI schemes in mapping constituent specific alterations in arterial microstructure.
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8
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Giudici A, Wilkinson IB, Khir AW. Review of the Techniques Used for Investigating the Role Elastin and Collagen Play in Arterial Wall Mechanics. IEEE Rev Biomed Eng 2021; 14:256-269. [PMID: 32746366 DOI: 10.1109/rbme.2020.3005448] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The arterial wall is characterised by a complex microstructure that impacts the mechanical properties of the vascular tissue. The main components consist of collagen and elastin fibres, proteoglycans, Vascular Smooth Muscle Cells (VSMCs) and ground matrix. While VSMCs play a key role in the active mechanical response of arteries, collagen and elastin determine the passive mechanics. Several experimental methods have been designed to investigate the role of these structural proteins in determining the passive mechanics of the arterial wall. Microscopy imaging of load-free or fixed samples provides useful information on the structure-function coupling of the vascular tissue, and mechanical testing provides information on the mechanical role of collagen and elastin networks. However, when these techniques are used separately, they fail to provide a full picture of the arterial micromechanics. More recently, advances in imaging techniques have allowed combining both methods, thus dynamically imaging the sample while loaded in a pseudo-physiological way, and overcoming the limitation of using either of the two methods separately. The present review aims at describing the techniques currently available to researchers for the investigation of the arterial wall micromechanics. This review also aims to elucidate the current understanding of arterial mechanics and identify some research gaps.
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9
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Tornifoglio B, Stone AJ, Johnston RD, Shahid SS, Kerskens C, Lally C. Diffusion tensor imaging and arterial tissue: establishing the influence of arterial tissue microstructure on fractional anisotropy, mean diffusivity and tractography. Sci Rep 2020; 10:20718. [PMID: 33244026 PMCID: PMC7693170 DOI: 10.1038/s41598-020-77675-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Accepted: 10/26/2020] [Indexed: 12/11/2022] Open
Abstract
This study investigates diffusion tensor imaging (DTI) for providing microstructural insight into changes in arterial tissue by exploring how cell, collagen and elastin content effect fractional anisotropy (FA), mean diffusivity (MD) and tractography. Five ex vivo porcine carotid artery models (n = 6 each) were compared-native, fixed native, collagen degraded, elastin degraded and decellularised. Vessels were imaged at 7 T using a DTI protocol with b = 0 and 800 s/mm2 and 10 isotopically distributed directions. FA and MD were evaluated in the vessel media and compared across models. FA values measured in native (p < 0.0001), fixed native (p < 0.0001) and collagen degraded (p = 0.0018, p = 0.0016, respectively) were significantly higher than those in elastin degraded and decellularised arteries. Native and fixed native had significantly lower MD values than elastin degraded (p < 0.0001) and decellularised tissue (p = 0.0032, p = 0.0003, respectively). Significantly lower MD was measured in collagen degraded compared with the elastin degraded model (p = 0.0001). Tractography yielded helically arranged tracts for native and collagen degraded vessels only. FA, MD and tractography were found to be highly sensitive to changes in the microstructural composition of arterial tissue, specifically pointing to cell, not collagen, content as the dominant source of the measured anisotropy in the vessel wall.
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Affiliation(s)
- B Tornifoglio
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
- Department of Mechanical, Manufacturing and Biomedical Engineering, School of Engineering, Trinity College Dublin, Dublin, Ireland
| | - A J Stone
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
- Department of Mechanical, Manufacturing and Biomedical Engineering, School of Engineering, Trinity College Dublin, Dublin, Ireland
| | - R D Johnston
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
- Department of Mechanical, Manufacturing and Biomedical Engineering, School of Engineering, Trinity College Dublin, Dublin, Ireland
| | - S S Shahid
- Department of Radiology and Imaging Sciences, Indiana University School of Medicine, Indianapolis, IN, USA
| | - C Kerskens
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
- Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin, Ireland
| | - C Lally
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland.
- Department of Mechanical, Manufacturing and Biomedical Engineering, School of Engineering, Trinity College Dublin, Dublin, Ireland.
- Advanced Materials and Bioengineering Research Centre (AMBER), Royal College of Surgeons in Ireland and Trinity College Dublin, Dublin, Ireland.
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10
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Gaul RT, Nolan DR, Lally C. The use of small angle light scattering in assessing strain induced collagen degradation in arterial tissue ex vivo. J Biomech 2018; 81:155-160. [PMID: 30392528 DOI: 10.1016/j.jbiomech.2018.10.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Revised: 10/09/2018] [Accepted: 10/10/2018] [Indexed: 01/13/2023]
Abstract
Collagen is the predominant load bearing component in many soft tissues including arterial tissue and is therefore critical in determining the mechanical integrity of such tissues. Degradation of collagen fibres is hypothesized to be a strain dependent process whereby the rate of degradation is affected by the magnitude of strain applied to the collagen fibres. The aim of this study is to investigate the ability of small angle light scattering (SALS) imaging to identify strain dependent degradation of collagen fibres in arterial tissue ex vivo, and determine whether a strain induced protection mechanism exists in arterial tissue as observed in pure collagen and other collagenous tissues. SALS was used in combination with histological and second harmonic generation (SHG) analysis to determine the collagen fibre architecture in arterial tissue subjected to strain directed degradation. SALS alignment analysis identified statistically significant differences in fibre alignment depending on the strain magnitude applied to the tissue. These results were also observed using histology and SHG. Our findings suggest a strain protection mechanism may exist for arterial collagen at intermediate strain magnitudes between 0% and 25%. These findings may have implications for the onset and progression of arterial disease where changes in the mechanical environment of arterial tissue may lead to changes in the collagen degradation rate.
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Affiliation(s)
- R T Gaul
- Trinity Centre for Bioengineering, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland; Department of Mechanical and Manufacturing Engineering, School of Engineering, Trinity College Dublin, Dublin 2, Ireland
| | - D R Nolan
- Trinity Centre for Bioengineering, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland; Department of Mechanical and Manufacturing Engineering, School of Engineering, Trinity College Dublin, Dublin 2, Ireland
| | - C Lally
- Trinity Centre for Bioengineering, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland; Department of Mechanical and Manufacturing Engineering, School of Engineering, Trinity College Dublin, Dublin 2, Ireland.
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11
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Owen B, Bojdo N, Jivkov A, Keavney B, Revell A. Structural modelling of the cardiovascular system. Biomech Model Mechanobiol 2018; 17:1217-1242. [PMID: 29911296 PMCID: PMC6154127 DOI: 10.1007/s10237-018-1024-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Accepted: 04/25/2018] [Indexed: 02/02/2023]
Abstract
Computational modelling of the cardiovascular system offers much promise, but represents a truly interdisciplinary challenge, requiring knowledge of physiology, mechanics of materials, fluid dynamics and biochemistry. This paper aims to provide a summary of the recent advances in cardiovascular structural modelling, including the numerical methods, main constitutive models and modelling procedures developed to represent cardiovascular structures and pathologies across a broad range of length and timescales; serving as an accessible point of reference to newcomers to the field. The class of so-called hyperelastic materials provides the theoretical foundation for the modelling of how these materials deform under load, and so an overview of these models is provided; comparing classical to application-specific phenomenological models. The physiology is split into components and pathologies of the cardiovascular system and linked back to constitutive modelling developments, identifying current state of the art in modelling procedures from both clinical and engineering sources. Models which have originally been derived for one application and scale are shown to be used for an increasing range and for similar applications. The trend for such approaches is discussed in the context of increasing availability of high performance computing resources, where in some cases computer hardware can impact the choice of modelling approach used.
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Affiliation(s)
- Benjamin Owen
- School of Mechanical, Aerospace and Civil Engineering, University of Manchester, George Begg Building, Manchester, M1 3BB, UK.
| | - Nicholas Bojdo
- School of Mechanical, Aerospace and Civil Engineering, University of Manchester, George Begg Building, Manchester, M1 3BB, UK
| | - Andrey Jivkov
- School of Mechanical, Aerospace and Civil Engineering, University of Manchester, George Begg Building, Manchester, M1 3BB, UK
| | - Bernard Keavney
- Division of Cardiovascular Sciences, University of Manchester, AV Hill Building, Manchester, M13 9PT, UK
| | - Alistair Revell
- School of Mechanical, Aerospace and Civil Engineering, University of Manchester, George Begg Building, Manchester, M1 3BB, UK
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Shahid SS, Gaul RT, Kerskens C, Flamini V, Lally C. Quantifying the ultrastructure of carotid arteries using high-resolution micro-diffusion tensor imaging—comparison of intact versus open cut tissue. ACTA ACUST UNITED AC 2017; 62:8850-8868. [DOI: 10.1088/1361-6560/aa9159] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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13
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Collagen fibre characterisation in arterial tissue under load using SALS. J Mech Behav Biomed Mater 2017; 75:359-368. [DOI: 10.1016/j.jmbbm.2017.07.036] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Revised: 07/13/2017] [Accepted: 07/25/2017] [Indexed: 01/06/2023]
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14
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Akyildiz AC, Chai CK, Oomens CWJ, van der Lugt A, Baaijens FPT, Strijkers GJ, Gijsen FJH. 3D Fiber Orientation in Atherosclerotic Carotid Plaques. J Struct Biol 2017; 200:28-35. [PMID: 28838817 DOI: 10.1016/j.jsb.2017.08.003] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Revised: 07/18/2017] [Accepted: 08/20/2017] [Indexed: 11/26/2022]
Abstract
Atherosclerotic plaque rupture is the primary trigger of fatal cardiovascular events. Fibrillar collagen in atherosclerotic plaques and their directionality are anticipated to play a crucial role in plaque rupture. This study aimed assessing 3D fiber orientations and architecture in atherosclerotic plaques for the first time. Seven carotid plaques were imaged ex-vivo with a state-of-the-art Diffusion Tensor Imaging (DTI) technique, using a high magnetic field (9.4Tesla) MRI scanner. A 3D spin-echo sequence with uni-polar diffusion sensitizing pulsed field gradients was utilized for DTI and fiber directions were assessed from diffusion tensor measurements. The distribution of the 3D fiber orientations in atherosclerotic plaques were quantified and the principal fiber orientations (circumferential, longitudinal or radial) were determined. Overall, 52% of the fiber orientations in the carotid plaque specimens were closest to the circumferential direction, 34% to the longitudinal direction, and 14% to the radial direction. Statistically no significant difference was measured in the amount of the fiber orientations between the concentric and eccentric plaque sites. However, concentric plaque sites showed a distinct structural organization, where the principally longitudinally oriented fibers were closer to the luminal side and the principally circumferentially oriented fibers were located more abluminally. The acquired unique information on 3D plaque fiber direction will help understanding pathobiological mechanisms of atherosclerotic plaque progression and pave the road to more realistic biomechanical plaque modeling for rupture assessment.
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Affiliation(s)
- Ali C Akyildiz
- Department of Biomedical Engineering, Erasmus Medical Center, Rotterdam, The Netherlands.
| | - Chen-Ket Chai
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - Cees W J Oomens
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - Aad van der Lugt
- Department of Radiology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Frank P T Baaijens
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - Gustav J Strijkers
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands; Biomedical Engineering and Physics, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Frank J H Gijsen
- Department of Biomedical Engineering, Erasmus Medical Center, Rotterdam, The Netherlands
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15
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Fiber-based modeling of in situ ankle ligaments with consideration of progressive failure. J Biomech 2017; 61:102-110. [DOI: 10.1016/j.jbiomech.2017.07.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 04/13/2017] [Accepted: 07/10/2017] [Indexed: 11/23/2022]
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16
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Douglas GR, Brown AJ, Gillard JH, Bennett MR, Sutcliffe MPF, Teng Z. Impact of Fiber Structure on the Material Stability and Rupture Mechanisms of Coronary Atherosclerotic Plaques. Ann Biomed Eng 2017; 45:1462-1474. [PMID: 28361184 PMCID: PMC5415591 DOI: 10.1007/s10439-017-1827-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Accepted: 03/22/2017] [Indexed: 12/19/2022]
Abstract
The rupture of an atherosclerotic plaque in the coronary circulation remains the main cause of heart attack. As a fiber-oriented structure, the fiber structure, in particular in the fibrous cap (FC), may affect both loading and material strength in the plaque. However, the role of fiber orientation and dispersion in plaque rupture is unclear. Local orientation and dispersion of fibers were calculated for the shoulder regions, mid FC, and regions with intimal thickening (IT) from histological images of 16 human coronary atherosclerotic lesions. Finite element analysis was performed to assess the effect of these properties on mechanical conditions. Fibers in shoulder regions had markedly reduced alignment (Median [interquartile range] 12.9° [6.6, 18.0], p < 0.05) compared with those in mid FC (6.1° [5.5, 9.0]) and IT regions (6.7° [5.1, 8.6]). Fiber dispersion was highest in shoulders (0.150 [0.121, 0.192]), intermediate in IT (0.119 [0.103, 0.144]), and lowest in mid FC regions (0.093 [0.081, 0.105], p < 0.05). When anisotropic properties were considered, stresses were significantly higher for the mid FC (p = 0.030) and IT regions (p = 0.002) and no difference was found for the shoulder or global regions. Shear (sliding) stress between fibers in each region and their proportion of maximum principal stress were: shoulder (25.8 kPa [17.1, 41.2], 12.4%), mid FC (13.9 kPa [5.8, 29.6], 13.8%), and IT (36.5 kPa [25.9, 47.3], 15.5%). Fiber structure within the FC has a marked effect on principal stresses, resulting in considerable shear stress between fibers. Fiber structure including orientation and dispersion may determine mechanical strength and thus rupture of atherosclerotic plaques.
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Affiliation(s)
- Graeham R Douglas
- Department of Engineering, University of Cambridge, Trumpington Street, Cambridge, CB2 1PZ, UK
| | - Adam J Brown
- Division of Cardiovascular Medicine, University of Cambridge, Cambridge, UK
| | - Jonathan H Gillard
- Department of Radiology, School of Clinical Medicine, University of Cambridge, Box 218, Cambridge Biomedical Campus, Cambridge, CB2 0QQ, UK
| | - Martin R Bennett
- Division of Cardiovascular Medicine, University of Cambridge, Cambridge, UK
| | - Michael P F Sutcliffe
- Department of Engineering, University of Cambridge, Trumpington Street, Cambridge, CB2 1PZ, UK.
| | - Zhongzhao Teng
- Department of Engineering, University of Cambridge, Trumpington Street, Cambridge, CB2 1PZ, UK. .,Department of Radiology, School of Clinical Medicine, University of Cambridge, Box 218, Cambridge Biomedical Campus, Cambridge, CB2 0QQ, UK.
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17
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Opriessnig P, Mangge H, Stollberger R, Deutschmann H, Reishofer G. In vivo cardiovascular magnetic resonance of 2D vessel wall diffusion anisotropy in carotid arteries. J Cardiovasc Magn Reson 2016; 18:81. [PMID: 27876066 PMCID: PMC5120527 DOI: 10.1186/s12968-016-0304-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2016] [Accepted: 11/02/2016] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND Diffusion weighted (DW) cardiovascular magnetic resonance (CMR) has shown great potential to discriminate between healthy and diseased vessel tissue by evaluating the apparent diffusion coefficient (ADC) along the arterial axis. Recently, ex vivo studies on porcine arteries utilizing diffusion tensor imaging (DTI) revealed a circumferential fiber orientation rather than an organization in axial direction, suggesting dominant diffusion perpendicular to the slice direction. In the present study, we propose a method to access tangential and radial diffusion of carotids in vivo by utilizing a pulse sequence that enables high resolution DW imaging in combination with a two-dimensional (2D) diffusion gradient direction sampling scheme perpendicular to the longitudinal axis of the artery. METHODS High resolution DTI of 12 healthy male volunteers (age: 25-60 years) was performed on one selected axial slice using a read-out segmented EPI (rs-EPI) sequence on a 3T MR scanner. RESULTS It was found consistently for all 12 volunteers, that the tangential component as the principle direction of diffusion. Mean vessel wall fractional anisotropy (FA) values ranged from 0.7 for the youngest to 0.56 for the oldest participant. Linear regression analysis between the FA values and volunteers age revealed a highly significant (P < 0.01) linear relationship with an adjusted R2 of 0.52. In addition, a linear trend (P < 0.1) could be observed between radial diffusivity (RD) and age. CONCLUSION These results point to FA being a sensitive parameter able to capture changes in the vascular architecture with age. In detail, the data demonstrate a decrease in FA with advancing age indicating possible alterations of tissue microstructural integrity. Moreover, analyzing 2D diffusion tensor directions is sufficient and applicable in a clinical setup concerning the overall scan time.
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Affiliation(s)
- Peter Opriessnig
- Clinical Institute for Medical and Chemical Laboratory Diagnosis, Medical University of Graz, Auenbruggerplatz 15, A-8036 Graz, Austria
| | - Harald Mangge
- Clinical Institute for Medical and Chemical Laboratory Diagnosis, Medical University of Graz, Auenbruggerplatz 15, A-8036 Graz, Austria
| | - Rudolf Stollberger
- Institute of Medical Engineering, Graz University of Technology, Stremayrgasse 16/III, A-8010 Graz, Austria
| | - Hannes Deutschmann
- Department of Radiology, Division of Neuroradiology, Vascular and Interventional Radiology, Medical University of Graz, Auenbruggerplatz 9, A-8036 Graz, Austria
| | - Gernot Reishofer
- Department of Radiology, Division of Neuroradiology, Vascular and Interventional Radiology, Medical University of Graz, Auenbruggerplatz 9, A-8036 Graz, Austria
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18
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Noble C, Smulders N, Green NH, Lewis R, Carré MJ, Franklin SE, MacNeil S, Taylor ZA. Creating a model of diseased artery damage and failure from healthy porcine aorta. J Mech Behav Biomed Mater 2016; 60:378-393. [DOI: 10.1016/j.jmbbm.2016.02.018] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Revised: 02/05/2016] [Accepted: 02/10/2016] [Indexed: 01/24/2023]
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19
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Agger P, Lass T, Smerup M, Frandsen J, Pedersen M. Optimal preservation of porcine cardiac tissue prior to diffusion tensor magnetic resonance imaging. J Anat 2015; 227:695-701. [PMID: 26391195 DOI: 10.1111/joa.12377] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/13/2015] [Indexed: 11/26/2022] Open
Abstract
The effects of ex vivo preservation techniques on the quality of diffusion tensor magnetic resonance imaging in hearts are poorly understood, and the optimal handling procedure prior to investigation remains to be determined. Therefore, 24 porcine hearts were examined in six groups treated with different preservation techniques, including chemical fixation and freezing. Diffusion properties of each heart were assessed with diffusion tensor imaging in terms of fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (Da) and radial diffusivity (Dr). Tractography was performed to visualize the course of the cardiomyocytes, assuming greater diffusivity in the longitudinal than the transverse axis of individual cardiomyocytes. Significant differences in MD, Da and Dr were found, as well as in FA between groups (P < 0.001). Freezing of specimens resulted in the lowest mean FA of 0.21 (0.06) and highest Dr of 8.92 (1.5) mm2 s(-1) . The highest mean FA was found to be 0.43 (0.11) in hearts perfusion-fixed with formalin. Calculated tractographies were indistinguishable among groups except in frozen specimens, where no fibres could be tracked. Perfusion fixation with formalin provided the best tractography, but immersion fixation yielded diffusion data most similar to fresh hearts. These findings suggest that parameters derived from diffusion tensor imaging in ex vivo hearts are sensitive to fixation and storage methods. In particular, freezing of specimens should be avoided prior to diffusion tensor imaging investigation due to significant changes in diffusion parameters and subsequent image deteriorations.
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Affiliation(s)
- Peter Agger
- Department of Cardiothoracic & Vascular Surgery, Aarhus University Hospital, Aarhus, Denmark.,Comparative Medicine Lab, Aarhus University Hospital, Aarhus, Denmark.,Department of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark
| | - Thomas Lass
- Department of Cardiothoracic & Vascular Surgery, Aarhus University Hospital, Aarhus, Denmark
| | - Morten Smerup
- Department of Cardiothoracic & Vascular Surgery, Aarhus University Hospital, Aarhus, Denmark
| | - Jesper Frandsen
- Center for Functionally Integrative Neuroscience, Aarhus University Hospital, Aarhus, Denmark
| | - Michael Pedersen
- Comparative Medicine Lab, Aarhus University Hospital, Aarhus, Denmark.,Department of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark.,MR Research Center, Aarhus University Hospital, Aarhus, Denmark
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20
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Novak K, Polzer S, Tichy M, Bursa J. Automatic Evaluation of Collagen Fiber Directions from Polarized Light Microscopy Images. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2015; 21:863-875. [PMID: 25951852 DOI: 10.1017/s1431927615000586] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Mechanical properties of the arterial wall depend largely on orientation and density of collagen fiber bundles. Several methods have been developed for observation of collagen orientation and density; the most frequently applied collagen-specific manual approach is based on polarized light (PL). However, it is very time consuming and the results are operator dependent. We have proposed a new automated method for evaluation of collagen fiber direction from two-dimensional polarized light microscopy images (2D PLM). The algorithm has been verified against artificial images and validated against manual measurements. Finally the collagen content has been estimated. The proposed algorithm was capable of estimating orientation of some 35 k points in 15 min when applied to aortic tissue and over 500 k points in 35 min for Achilles tendon. The average angular disagreement between each operator and the algorithm was -9.3±8.6° and -3.8±8.6° in the case of aortic tissue and -1.6±6.4° and 2.6±7.8° for Achilles tendon. Estimated mean collagen content was 30.3±5.8% and 94.3±2.7% for aortic media and Achilles tendon, respectively. The proposed automated approach is operator independent and several orders faster than manual measurements and therefore has the potential to replace manual measurements of collagen orientation via PLM.
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Affiliation(s)
- Kamil Novak
- 1Institute of Solid Mechanics,Mechatronics and Biomechanics,Brno University of Technology,Czech Republic
| | - Stanislav Polzer
- 1Institute of Solid Mechanics,Mechatronics and Biomechanics,Brno University of Technology,Czech Republic
| | - Michal Tichy
- 22nd Department of Pathology and Anatomy,St. Anne's University Hospital,Czech Republic
| | - Jiri Bursa
- 1Institute of Solid Mechanics,Mechatronics and Biomechanics,Brno University of Technology,Czech Republic
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21
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Flamini V, Creane AP, Kerskens CM, Lally C. Imaging and finite element analysis: a methodology for non-invasive characterization of aortic tissue. Med Eng Phys 2014; 37:48-54. [PMID: 25453602 DOI: 10.1016/j.medengphy.2014.10.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Revised: 09/08/2014] [Accepted: 10/10/2014] [Indexed: 02/04/2023]
Abstract
Characterization of the mechanical properties of arterial tissues usually involves an invasive procedure requiring tissue removal. In this work we propose a non-invasive method to perform a biomechanical analysis of cardiovascular aortic tissue. This method is based on combining medical imaging and finite element analysis (FEA). Magnetic resonance imaging (MRI) was chosen since it presents relatively low risks for human health. A finite element model was created from the MRI images and loaded with systolic physiological pressures. By means of an optimization routine, the structural material properties were changed until average strains matched those measured by MRI. The method outlined in this work produced an estimate of the in situ properties of cardiovascular tissue based on non-invasive image datasets and finite element analysis.
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Affiliation(s)
- Vittoria Flamini
- New York University Polytechnic School of Engineering, Brooklyn, NY, United States; School of Mechanical & Manufacturing Engineering, Dublin City University, Dublin, Ireland
| | - Arthur P Creane
- School of Mechanical & Manufacturing Engineering, Dublin City University, Dublin, Ireland
| | | | - Caitríona Lally
- School of Mechanical & Manufacturing Engineering, Dublin City University, Dublin, Ireland.
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22
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Nierenberger M, Fargier G, Ahzi S, Rémond Y. Evolution of the three-dimensional collagen structure in vascular walls during deformation: an in situ mechanical testing under multiphoton microscopy observation. Biomech Model Mechanobiol 2014; 14:693-702. [DOI: 10.1007/s10237-014-0630-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Accepted: 10/24/2014] [Indexed: 10/24/2022]
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23
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Holzapfel GA, Mulvihill JJ, Cunnane EM, Walsh MT. Computational approaches for analyzing the mechanics of atherosclerotic plaques: a review. J Biomech 2014; 47:859-69. [PMID: 24491496 DOI: 10.1016/j.jbiomech.2014.01.011] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/13/2014] [Indexed: 11/18/2022]
Abstract
Vulnerable and stable atherosclerotic plaques are heterogeneous living materials with peculiar mechanical behaviors depending on geometry, composition, loading and boundary conditions. Computational approaches have the potential to characterize the three-dimensional stress/strain distributions in patient-specific diseased arteries of different types and sclerotic morphologies and to estimate the risk of plaque rupture which is the main trigger of acute cardiovascular events. This review article attempts to summarize a few finite element (FE) studies for different vessel types, and how these studies were performed focusing on the used stress measure, inclusion of residual stress, used imaging modality and material model. In addition to histology the most used imaging modalities are described, the most common nonlinear material models and the limited number of models for plaque rupture used for such studies are provided in more detail. A critical discussion on stress measures and threshold stress values for plaque rupture used within the FE studies emphasizes the need to develop a more location and tissue-specific threshold value, and a more appropriate failure criterion. With this addition future FE studies should also consider more advanced strain-energy functions which then fit better to location and tissue-specific experimental data.
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Affiliation(s)
- Gerhard A Holzapfel
- Graz University of Technology, Institute of Biomechanics, Kronesgasse 5-I, 8010 Graz, Austria.
| | - John J Mulvihill
- Centre for Applied Biomedical Engineering Research, Department of Mechanical, Aeronautical and Biomedical Engineering and the Materials and Surface Science Institute, University of Limerick, Ireland
| | - Eoghan M Cunnane
- Centre for Applied Biomedical Engineering Research, Department of Mechanical, Aeronautical and Biomedical Engineering and the Materials and Surface Science Institute, University of Limerick, Ireland
| | - Michael T Walsh
- Centre for Applied Biomedical Engineering Research, Department of Mechanical, Aeronautical and Biomedical Engineering and the Materials and Surface Science Institute, University of Limerick, Ireland
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