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Czerpak CA, Ling YTT, Jefferys JL, Quigley HA, Nguyen TD. The Curvature, Collagen Network Structure, and Their Relationship to the Pressure-Induced Strain Response of the Human Lamina Cribrosa in Normal and Glaucoma Eyes. J Biomech Eng 2023; 145:101005. [PMID: 37382629 PMCID: PMC10405282 DOI: 10.1115/1.4062846] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 06/14/2023] [Accepted: 06/21/2023] [Indexed: 06/30/2023]
Abstract
The lamina cribrosa (LC) is a connective tissue in the optic nerve head (ONH). The objective of this study was to measure the curvature and collagen microstructure of the human LC, compare the effects of glaucoma and glaucoma optic nerve damage, and investigate the relationship between the structure and pressure-induced strain response of the LC in glaucoma eyes. Previously, the posterior scleral cups of 10 normal eyes and 16 diagnosed glaucoma eyes were subjected to inflation testing with second harmonic generation (SHG) imaging of the LC and digital volume correlation (DVC) to calculate the strain field. In this study, we applied a custom microstructural analysis algorithm to the maximum intensity projection of SHG images to measure features of the LC beam and pore network. We also estimated the LC curvatures from the anterior surface of the DVC-correlated LC volume. Results showed that the LC in glaucoma eyes had larger curvatures p≤0.03), a smaller average pore area (p = 0.001), greater beam tortuosity (p < 0.0001), and more isotropic beam structure (p = 0.01) than in normal eyes. The difference measured between glaucoma and normal eyes may indicate remodeling of the LC with glaucoma or baseline differences that contribute to the development of glaucomatous axonal damage.
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Affiliation(s)
- Cameron A Czerpak
- Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, MD 21218
| | - Yik Tung Tracy Ling
- Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, MD 21218
| | - Joan L Jefferys
- Wilmer Ophthalmological Institute, School of Medicine, The Johns Hopkins University, Baltimore, MD 21287
| | - Harry A Quigley
- Wilmer Ophthalmological Institute, School of Medicine, The Johns Hopkins University, Baltimore, MD 21287
| | - Thao D Nguyen
- Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, MD 21218; Wilmer Ophthalmological Institute, School of Medicine, The Johns Hopkins University, Baltimore, MD 21287
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Guo Y, Wang Y, Ma J, Li X. Effect of Solution pH on the Biomechanics of Intact Cornea From Inflation Tests. Curr Eye Res 2023:1-7. [PMID: 37070384 DOI: 10.1080/02713683.2023.2199447] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/19/2023]
Abstract
PURPOSE To investigate the effect of different pH phosphate buffer solution (PBS) drops on intact corneal biomechanics. METHODS Intact rabbit cornea with a 3 mm scleral skirt was sampled and immediately applied in inflation tests within 5 min. After preconditioning, a stable loading cycle from 0.3 to 6 kPa was performed followed by a 10 min interval. During the interval, the samples were randomized into four groups, with one control group receiving no drops and three groups with PBS drops of pH 6.9, 7.4 or 7.9 administration on the surface once per minute. The pressure and displacement were collected at the baseline and 10, 20 and 30 min following the administration. RESULTS Continuous corneal thickness increase was manifested following the administration of PBS but not in the control group. There was significant swelling-independent corneal modulus reduction after PBS administration, which occurred mainly in the first 10 min. PBS of pH 6.9 achieved significantly smaller modulus reduction than that with pH 7.4 PBS adjusted for thickness changes (p < 0.05). Pressure-modulus curve linear fitting demonstrated that the curve coefficient significantly reduced following PBS administration, and the coefficient decline was smallest with pH 6.9 PBS among three PBS administration groups (p < 0.05). CONCLUSIONS The study demonstrated that the PBS drops of various pH administration could decrease the corneal stiffness independent of corneal swelling. Following the PBS administration, the stiffness changes were more prominent as the posterior pressure increased, and the minimal effect was achieved with slightly acidic PBS. The research provides the essence for stabilizing the corneal biomechanical properties by regulating the pH value of tear film and intraocular pressure.
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Affiliation(s)
- Yining Guo
- Department of Ophthalmology, Peking University Third Hospital, Beijing, China
- Beijing Key Laboratory of Restoration of Damaged Ocular Nerve, Peking University Third Hospital, Beijing, China
| | - Yuexin Wang
- Department of Ophthalmology, Peking University Third Hospital, Beijing, China
- Beijing Key Laboratory of Restoration of Damaged Ocular Nerve, Peking University Third Hospital, Beijing, China
| | - Jiahui Ma
- Department of Ophthalmology, Peking University People's Hospital, Beijing, China
- Eye Diseases and Optometry Institute, Peking University Health Science Center, Beijing, China
| | - Xuemin Li
- Department of Ophthalmology, Peking University Third Hospital, Beijing, China
- Beijing Key Laboratory of Restoration of Damaged Ocular Nerve, Peking University Third Hospital, Beijing, China
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Guvenir Torun S, Torun HM, Hansen HHG, Gandini G, Berselli I, Codazzi V, de Korte CL, van der Steen AFW, Migliavacca F, Chiastra C, Akyildiz AC. Multicomponent Mechanical Characterization of Atherosclerotic Human Coronary Arteries: An Experimental and Computational Hybrid Approach. Front Physiol 2021; 12:733009. [PMID: 34557112 PMCID: PMC8452922 DOI: 10.3389/fphys.2021.733009] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 08/17/2021] [Indexed: 12/15/2022] Open
Abstract
Atherosclerotic plaque rupture in coronary arteries, an important trigger of myocardial infarction, is shown to correlate with high levels of pressure-induced mechanical stresses in plaques. Finite element (FE) analyses are commonly used for plaque stress assessment. However, the required information of heterogenous material properties of atherosclerotic coronaries remains to be scarce. In this work, we characterized the component-wise mechanical properties of atherosclerotic human coronary arteries. To achieve this, we performed ex vivo inflation tests on post-mortem human coronary arteries and developed an inverse FE modeling (iFEM) pipeline, which combined high-frequency ultrasound deformation measurements, a high-field magnetic resonance-based artery composition characterization, and a machine learning-based Bayesian optimization (BO) with uniqueness assessment. By using the developed pipeline, 10 cross-sections from five atherosclerotic human coronary arteries were analyzed, and the Yeoh material model constants of the fibrous intima and arterial wall components were determined. This work outlines the developed pipeline and provides the knowledge of non-linear, multicomponent mechanical properties of atherosclerotic human coronary arteries.
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Affiliation(s)
- Su Guvenir Torun
- Department of Biomedical Engineering, Erasmus Medical Center, Rotterdam, Netherlands
| | - Hakki M Torun
- School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA, United States
| | - Hendrik H G Hansen
- Department of Medical Imaging, Radboud University Medical Center, Nijmegen, Netherlands
| | - Giulia Gandini
- Department of Biomedical Engineering, Erasmus Medical Center, Rotterdam, Netherlands.,Laboratory of Biological Structure Mechanics, Department of Chemistry, Materials and Chemical Engineering "Giulio Natta," Politecnico di Milano, Milan, Italy
| | - Irene Berselli
- Department of Biomedical Engineering, Erasmus Medical Center, Rotterdam, Netherlands.,Laboratory of Biological Structure Mechanics, Department of Chemistry, Materials and Chemical Engineering "Giulio Natta," Politecnico di Milano, Milan, Italy
| | - Veronica Codazzi
- Department of Biomedical Engineering, Erasmus Medical Center, Rotterdam, Netherlands.,Laboratory of Biological Structure Mechanics, Department of Chemistry, Materials and Chemical Engineering "Giulio Natta," Politecnico di Milano, Milan, Italy
| | - Chris L de Korte
- Department of Medical Imaging, Radboud University Medical Center, Nijmegen, Netherlands.,Physics of Fluids Group, TechMed Centre, University of Twente, Enschede, Netherlands
| | | | - Francesco Migliavacca
- Laboratory of Biological Structure Mechanics, Department of Chemistry, Materials and Chemical Engineering "Giulio Natta," Politecnico di Milano, Milan, Italy
| | - Claudio Chiastra
- PolitoBIOMed Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy
| | - Ali C Akyildiz
- Department of Biomedical Engineering, Erasmus Medical Center, Rotterdam, Netherlands.,Department of Biomechanical Engineering, Delft University of Technology, Delft, Netherlands
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Carniel EL, Mencattelli M, Bonsignori G, Fontanella CG, Frigo A, Rubini A, Stefanini C, Natali AN. Analysis of the structural behaviour of colonic segments by inflation tests: Experimental activity and physio-mechanical model. Proc Inst Mech Eng H 2015; 229:794-803. [PMID: 26396226 DOI: 10.1177/0954411915606484] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Accepted: 08/25/2015] [Indexed: 12/19/2022]
Abstract
A coupled experimental and computational approach is provided for the identification of the structural behaviour of gastrointestinal regions, accounting for both elastic and visco-elastic properties. The developed procedure is applied to characterize the mechanics of gastrointestinal samples from pig colons. Experimental data about the structural behaviour of colonic segments are provided by inflation tests. Different inflation processes are performed according to progressively increasing top pressure conditions. Each inflation test consists of an air in-flow, according to an almost constant increasing pressure rate, such as 3.5 mmHg/s, up to a prescribed top pressure, which is held constant for about 300 s to allow the development of creep phenomena. Different tests are interspersed by 600 s of rest to allow the recovery of the tissues' mechanical condition. Data from structural tests are post-processed by a physio-mechanical model in order to identify the mechanical parameters that interpret both the non-linear elastic behaviour of the sample, as the instantaneous pressure-stretch trend, and the time-dependent response, as the stretch increase during the creep processes. The parameters are identified by minimizing the discrepancy between experimental and model results. Different sets of parameters are evaluated for different specimens from different pigs. A statistical analysis is performed to evaluate the distribution of the parameters and to assess the reliability of the experimental and computational activities.
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Affiliation(s)
- Emanuele L Carniel
- Department of Industrial Engineering, Centre for Mechanics of Biological Materials, University of Padova, Padova, Italy
| | | | | | | | - Alessandro Frigo
- Department of Industrial Engineering, Centre for Mechanics of Biological Materials, University of Padova, Padova, Italy
| | - Alessandro Rubini
- Department of Industrial Engineering, Centre for Mechanics of Biological Materials, University of Padova, Padova, Italy Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Cesare Stefanini
- The BioRobotics Institute, Scuola Superiore Sant'Anna, Pisa, Italy
| | - Arturo N Natali
- Department of Industrial Engineering, Centre for Mechanics of Biological Materials, University of Padova, Padova, Italy
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Kok S, Botha N, Inglis HM. Calibrating corneal material model parameters using only inflation data: an ill-posed problem. Int J Numer Method Biomed Eng 2014; 30:1460-1475. [PMID: 25112972 DOI: 10.1002/cnm.2667] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Revised: 07/29/2014] [Accepted: 07/31/2014] [Indexed: 06/03/2023]
Abstract
Goldmann applanation tonometry (GAT) is a method used to estimate the intraocular pressure by measuring the indentation resistance of the cornea. A popular approach to investigate the sensitivity of GAT results to material and geometry variations is to perform numerical modelling using the finite element method, for which a calibrated material model is required. These material models are typically calibrated using experimental inflation data by solving an inverse problem. In the inverse problem, the underlying material constitutive behaviour is inferred from the measured macroscopic response (chamber pressure versus apical displacement). In this study, a biomechanically motivated elastic fibre-reinforced corneal material model is chosen. The inverse problem of calibrating the corneal material model parameters using only experimental inflation data is demonstrated to be ill-posed, with small variations in the experimental data leading to large differences in the calibrated model parameters. This can result in different groups of researchers, calibrating their material model with the same inflation test data, drawing vastly different conclusions about the effect of material parameters on GAT results. It is further demonstrated that multiple loading scenarios, such as inflation as well as bending, would be required to reliably calibrate such a corneal material model.
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Affiliation(s)
- S Kok
- Department of Mechanical and Aeronautical Engineering, University of Pretoria, Pretoria, 0002, South Africa
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Li K, Wang Q, Pham T, Sun W. Quantification of structural compliance of aged human and porcine aortic root tissues. J Biomed Mater Res A 2013; 102:2365-74. [PMID: 23894117 DOI: 10.1002/jbm.a.34884] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Accepted: 07/15/2013] [Indexed: 11/08/2022]
Abstract
The structural compliance of the aortic root has a significant implication for valve procedures such as transcatheter aortic valve implantation and valve-sparing aortic root replacement. However, a detailed quantification of human aortic root structural compliance, particularly in different regions, has been incomplete. In this study, the structural properties of human aortic roots (81 ± 8.74 years, n = 10) were characterized and compared with those of porcine ones (6-9 months, n = 10) using a vessel pressure-inflation test. The test involved tracking three-dimensional deformation of the markers affixed on the different surface regions of the aortic roots, including the three sinuses: the noncoronary sinus (NCS), the left-coronary sinus (LCS), and the right-coronary sinus (RCS), and at three regions along the longitudinal direction of each sinus: the upper sinus (US), the middle sinus (MS), and the lower sinus (LS), and the ascending aorta (AA) region above the NCS. We found that tissue stiffness in physiological pressure range was similar among the three human sinuses. A variation in regional structural stiffness of human aorta was observed. In the circumferential direction, the LS regions were the stiffest in the LCS and RCS, whereas NCS had relatively uniform stiffness. In the longitudinal direction, the human AA regions were more compliant than all sinuses. There was a significant difference in tissue stiffness between human and porcine aortic tissues, suggesting that the mechanical properties of porcine tissues may not be analogous to aged human ones.
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Affiliation(s)
- Kewei Li
- Tissue Mechanics Laboratory, Biomedical Engineering Program and Department of Mechanical Engineering, University of Connecticut, Storrs, Connecticut, 06269
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