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Marino M, Sauty B, Vairo G. Unraveling the complexity of vascular tone regulation: a multiscale computational approach to integrating chemo-mechano-biological pathways with cardiovascular biomechanics. Biomech Model Mechanobiol 2024:10.1007/s10237-024-01826-6. [PMID: 38507180 DOI: 10.1007/s10237-024-01826-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Accepted: 02/09/2024] [Indexed: 03/22/2024]
Abstract
Vascular tone regulation is a crucial aspect of cardiovascular physiology, with significant implications for overall cardiovascular health. However, the precise physiological mechanisms governing smooth muscle cell contraction and relaxation remain uncertain. The complexity of vascular tone regulation stems from its multiscale and multifactorial nature, involving global hemodynamics, local flow conditions, tissue mechanics, and biochemical pathways. Bridging this knowledge gap and translating it into clinical practice presents a challenge. In this paper, a computational model is presented to integrate chemo-mechano-biological pathways with cardiovascular biomechanics, aiming to unravel the intricacies of vascular tone regulation. The computational framework combines an algebraic description of global hemodynamics with detailed finite element analyses at the scale of vascular segments for describing their passive and active mechanical response, as well as the molecular transport problem linked with chemo-biological pathways triggered by wall shear stresses. Their coupling is accounted for by considering a two-way interaction. Specifically, the focus is on the role of nitric oxide-related molecular pathways, which play a critical role in modulating smooth muscle contraction and relaxation to maintain vascular tone. The computational framework is employed to examine the interplay between localized alterations in the biomechanical response of a specific vessel segment-such as those induced by calcifications or endothelial dysfunction-and the broader global hemodynamic conditions-both under basal and altered states. The proposed approach aims to advance our understanding of vascular tone regulation and its impact on cardiovascular health. By incorporating chemo-mechano-biological mechanisms into in silico models, this study allows us to investigate cardiovascular responses to multifactorial stimuli and incorporate the role of adaptive homeostasis in computational biomechanics frameworks.
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Affiliation(s)
- Michele Marino
- Department of Civil Engineering and Computer Science Engineering, University of Rome Tor Vergata, Via del Politecnico 1, 00133, Rome, Italy.
| | - Bastien Sauty
- Department of Civil Engineering and Computer Science Engineering, University of Rome Tor Vergata, Via del Politecnico 1, 00133, Rome, Italy
- Mines Saint-Etienne, Université Jean Monnet, INSERM, U1059 SAINBIOSE, F-42023, Saint-Etienne, France
| | - Giuseppe Vairo
- Department of Civil Engineering and Computer Science Engineering, University of Rome Tor Vergata, Via del Politecnico 1, 00133, Rome, Italy
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2
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Chung TK, Gueldner PH, Aloziem OU, Liang NL, Vorp DA. An artificial intelligence based abdominal aortic aneurysm prognosis classifier to predict patient outcomes. Sci Rep 2024; 14:3390. [PMID: 38336915 PMCID: PMC10858046 DOI: 10.1038/s41598-024-53459-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Accepted: 01/31/2024] [Indexed: 02/12/2024] Open
Abstract
Abdominal aortic aneurysms (AAA) have been rigorously investigated to understand when their clinically-estimated risk of rupture-an event that is the 13th leading cause of death in the US-exceeds the risk associated with repair. Yet the current clinical guideline remains a one-size-fits-all "maximum diameter criterion" whereby AAA exceeding a threshold diameter is thought to make the risk of rupture high enough to warrant intervention. However, between 7 and 23.4% of smaller-sized AAA have been reported to rupture with diameters below the threshold. In this study, we train and assess machine learning models using clinical, biomechanical, and morphological indices from 381 patients to develop an aneurysm prognosis classifier to predict one of three outcomes for a given AAA patient: their AAA will remain stable, their AAA will require repair based as currently indicated from the maximum diameter criterion, or their AAA will rupture. This study represents the largest cohort of AAA patients that utilizes the first available medical image and clinical data to classify patient outcomes. The APC model therefore represents a potential clinical tool to striate specific patient outcomes using machine learning models and patient-specific image-based (biomechanical and morphological) and clinical data as input. Such a tool could greatly assist clinicians in their management decisions for patients with AAA.
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Affiliation(s)
- Timothy K Chung
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
| | - Pete H Gueldner
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
| | - Okechukwu U Aloziem
- School of Medicine, University of Pittsburgh Medical Center, Pittsburgh, PA, USA
| | - Nathan L Liang
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
- Division of Vascular Surgery, Department of Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA, USA
- Department of Surgery, University of Pittsburgh, Pittsburgh, PA, USA
| | - David A Vorp
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA.
- Department of Surgery, University of Pittsburgh, Pittsburgh, PA, USA.
- McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA.
- Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, PA, USA.
- Department of Cardiothoracic Surgery, University of Pittsburgh, Pittsburgh, PA, USA.
- Clinical & Translational Sciences Institute, University of Pittsburgh, Pittsburgh, PA, USA.
- Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA, USA.
- Center for Vascular Remodeling and Regeneration, University of Pittsburgh, Pittsburgh, PA, USA.
- Bioengineering, Cardiothoracic Surgery, Surgery, Chemical and Petroleum Engineering and the Clinical and Translational Sciences Institute, Center for Bioengineering, University of Pittsburgh, 300 Technology Drive, Suite 300, Pittsburgh, PA, 15219, USA.
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3
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Vander Linden K, Vanderveken E, Van Hoof L, Maes L, Fehervary H, Dreesen S, Hendrickx A, Verbrugghe P, Rega F, Meuris B, Famaey N. Stiffness matters: Improved failure risk assessment of ascending thoracic aortic aneurysms. JTCVS OPEN 2023; 16:66-83. [PMID: 38204617 PMCID: PMC10775041 DOI: 10.1016/j.xjon.2023.09.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 09/07/2023] [Accepted: 09/11/2023] [Indexed: 01/12/2024]
Abstract
Objectives Rupture and dissection are feared complications of ascending thoracic aortic aneurysms caused by mechanical failure of the wall. The current method of using the aortic diameter to predict the risk of wall failure and to determine the need for surgical resection lacks accuracy. Therefore, this study aims to identify reliable and clinically measurable predictors for aneurysm rupture or dissection by performing a personalized failure risk analysis, including clinical, geometrical, histologic, and mechanical data. Methods The study cohort consisted of 33 patients diagnosed with ascending aortic aneurysms without genetic syndromes. Uniaxial tensile tests until failure were performed to determine the wall strength. Material parameters were fitted against ex vivo planar biaxial data and in vivo pressure-diameter relationships at diastole and systole, which were derived from multiphasic computed tomography (CT) scans. Using the resulting material properties and in vivo data, the maximal in vivo stress at systole was calculated, assuming a thin-walled axisymmetric geometry. The retrospective failure risk was calculated by comparing the peak wall stress at suprasystolic pressure with the wall strength. Results The distensibility coefficient, reflecting aortic compliance and derived from blood pressure measurements and multiphasic CT scans, outperformed predictors solely based on geometrical features in assessing the risk of aneurysm failure. Conclusions In a clinical setting, multiphasic CT scans followed by the calculation of the distensibility coefficient are of added benefit in patient-specific, clinical decision-making. The distensibility derived from the aneurysm volume change has the best predictive power, as it also takes the axial stretch into account.
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Affiliation(s)
| | - Emma Vanderveken
- Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium
| | - Lucas Van Hoof
- Department of Cardiac Surgery, University Hospitals Leuven, Leuven, Belgium
| | - Lauranne Maes
- Department of Mechanical Engineering, KU Leuven, Leuven, Belgium
| | - Heleen Fehervary
- Department of Mechanical Engineering, KU Leuven, Leuven, Belgium
- FIBEr, KU Leuven Core Facility for Biomechanical Experimentation, Leuven, Belgium
| | - Silke Dreesen
- Department of Mechanical Engineering, KU Leuven, Leuven, Belgium
| | - Amber Hendrickx
- Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium
| | - Peter Verbrugghe
- Department of Cardiac Surgery, University Hospitals Leuven, Leuven, Belgium
| | - Filip Rega
- Department of Cardiac Surgery, University Hospitals Leuven, Leuven, Belgium
| | - Bart Meuris
- Department of Cardiac Surgery, University Hospitals Leuven, Leuven, Belgium
| | - Nele Famaey
- Department of Mechanical Engineering, KU Leuven, Leuven, Belgium
- FIBEr, KU Leuven Core Facility for Biomechanical Experimentation, Leuven, Belgium
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4
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Wang X, Carpenter HJ, Ghayesh MH, Kotousov A, Zander AC, Amabili M, Psaltis PJ. A review on the biomechanical behaviour of the aorta. J Mech Behav Biomed Mater 2023; 144:105922. [PMID: 37320894 DOI: 10.1016/j.jmbbm.2023.105922] [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: 03/06/2023] [Revised: 05/14/2023] [Accepted: 05/20/2023] [Indexed: 06/17/2023]
Abstract
Large aortic aneurysm and acute and chronic aortic dissection are pathologies of the aorta requiring surgery. Recent advances in medical intervention have improved patient outcomes; however, a clear understanding of the mechanisms leading to aortic failure and, hence, a better understanding of failure risk, is still missing. Biomechanical analysis of the aorta could provide insights into the development and progression of aortic abnormalities, giving clinicians a powerful tool in risk stratification. The complexity of the aortic system presents significant challenges for a biomechanical study and requires various approaches to analyse the aorta. To address this, here we present a holistic review of the biomechanical studies of the aorta by categorising articles into four broad approaches, namely theoretical, in vivo, experimental and combined investigations. Experimental studies that focus on identifying mechanical properties of the aortic tissue are also included. By reviewing the literature and discussing drawbacks, limitations and future challenges in each area, we hope to present a more complete picture of the state-of-the-art of aortic biomechanics to stimulate research on critical topics. Combining experimental modalities and computational approaches could lead to more comprehensive results in risk prediction for the aortic system.
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Affiliation(s)
- Xiaochen Wang
- School of Electrical and Mechanical Engineering, The University of Adelaide, Adelaide, South Australia 5005, Australia.
| | - Harry J Carpenter
- School of Electrical and Mechanical Engineering, The University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Mergen H Ghayesh
- School of Electrical and Mechanical Engineering, The University of Adelaide, Adelaide, South Australia 5005, Australia.
| | - Andrei Kotousov
- School of Electrical and Mechanical Engineering, The University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Anthony C Zander
- School of Electrical and Mechanical Engineering, The University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Marco Amabili
- Department of Mechanical Engineering, McGill University, Montreal H3A 0C3, Canada
| | - Peter J Psaltis
- Adelaide Medical School, The University of Adelaide, Adelaide, South Australia 5005, Australia; Department of Cardiology, Central Adelaide Local Health Network, Adelaide, South Australia 5000, Australia; Vascular Research Centre, Heart Health Theme, South Australian Health & Medical Research Institute (SAHMRI), Adelaide, South Australia 5000, Australia
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5
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He X, Lu J. Modeling planar response of vascular tissues using quadratic functions of effective strain. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2023; 39:e3653. [PMID: 36164831 DOI: 10.1002/cnm.3653] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 05/13/2022] [Accepted: 09/24/2022] [Indexed: 05/12/2023]
Abstract
Simulation-based studies of the cardiovascular structure such as aorta have become increasingly popular for many biomedical problems such as predictions of aneurysm rupture. A critical step in these simulations is the development of constitutive models that accurately describe the tissue's mechanical behavior. In this work, we present a new constitutive model, which explicitly accounts for the gradual recruitment of collagen fibers. The recruitment is considered using an effective stretch, which is a continuum-scale kinematic variable measuring the uncrimped stretch of the tissue in an average sense. The strain energy of a fiber bundle is described by a quadratic function of the effective strain. Constitutive models formulated in this manner are applied to describe the responses of ascending thoracic aortic aneurysm and porcine thoracic aorta tissues. The heterogeneous properties of the ATAA tissue are extracted from bulge inflation test data, and then used in finite element analysis to simulate the inflation test. The descriptive and predictive capabilities are further assessed using planar testing data of porcine thoracic aortic tissues. It is found that the constitutive model can accurately describe the stress-strain relations. In particular, the finite element simulation replicates the displacement, strain, and stress distributions with excellent fidelity.
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Affiliation(s)
- Xuehuan He
- Department of Mechanical Engineering, The University of Iowa, Iowa City, Iowa, USA
| | - Jia Lu
- Department of Mechanical Engineering, The University of Iowa, Iowa City, Iowa, USA
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6
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Gasser TC, Miller C, Polzer S, Roy J. A quarter of a century biomechanical rupture risk assessment of abdominal aortic aneurysms. Achievements, clinical relevance, and ongoing developments. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2023; 39:e3587. [PMID: 35347895 DOI: 10.1002/cnm.3587] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Revised: 01/28/2022] [Accepted: 03/03/2022] [Indexed: 05/12/2023]
Abstract
Abdominal aortic aneurysm (AAA) disease, the local enlargement of the infrarenal aorta, is a serious condition that causes many deaths, especially in men exceeding 65 years of age. Over the past quarter of a century, computational biomechanical models have been developed towards the assessment of AAA risk of rupture, technology that is now on the verge of being integrated within the clinical decision-making process. The modeling of AAA requires a holistic understanding of the clinical problem, in order to set appropriate modeling assumptions and to draw sound conclusions from the simulation results. In this article we summarize and critically discuss the proposed modeling approaches and report the outcome of clinical validation studies for a number of biomechanics-based rupture risk indices. Whilst most of the aspects concerning computational mechanics have already been settled, it is the exploration of the failure properties of the AAA wall and the acquisition of robust input data for simulations that has the greatest potential for the further improvement of this technology.
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Affiliation(s)
- T Christian Gasser
- Department of Engineering Mechanics, KTH Royal Institute of Technology, Stockholm, Sweden
- Faculty of Health Sciences, University of Southern Denmark, Odense, Denmark
| | - Christopher Miller
- Department of Engineering Mechanics, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Stanislav Polzer
- Department of Applied Mechanics, VSB-Technical University of Ostrava, Ostrava-Poruba, Czech Republic
| | - Joy Roy
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
- Department of Vascular Surgery, Karolinska University Hospital, Stockholm, Sweden
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7
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Mutlu O, Salman HE, Al-Thani H, El-Menyar A, Qidwai UA, Yalcin HC. How does hemodynamics affect rupture tissue mechanics in abdominal aortic aneurysm: Focus on wall shear stress derived parameters, time-averaged wall shear stress, oscillatory shear index, endothelial cell activation potential, and relative residence time. Comput Biol Med 2023; 154:106609. [PMID: 36724610 DOI: 10.1016/j.compbiomed.2023.106609] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Revised: 01/19/2023] [Accepted: 01/22/2023] [Indexed: 01/24/2023]
Abstract
An abdominal aortic aneurysm (AAA) is a critical health condition with a risk of rupture, where the diameter of the aorta enlarges more than 50% of its normal diameter. The incidence rate of AAA has increased worldwide. Currently, about three out of every 100,000 people have aortic diseases. The diameter and geometry of AAAs influence the hemodynamic forces exerted on the arterial wall. Therefore, a reliable assessment of hemodynamics is crucial for predicting the rupture risk. Wall shear stress (WSS) is an important metric to define the level of the frictional force on the AAA wall. Excessive levels of WSS deteriorate the remodeling mechanism of the arteries and lead to abnormal conditions. At this point, WSS-related hemodynamic parameters, such as time-averaged WSS (TAWSS), oscillatory shear index (OSI), endothelial cell activation potential (ECAP), and relative residence time (RRT) provide important information to evaluate the shear environment on the AAA wall in detail. Calculation of these parameters is not straightforward and requires a physical understanding of what they represent. In addition, computational fluid dynamics (CFD) solvers do not readily calculate these parameters when hemodynamics is simulated. This review aims to explain the WSS-derived parameters focusing on how these represent different characteristics of disturbed hemodynamics. A representative case is presented for spatial and temporal formulation that would be useful for interested researchers for practical calculations. Finally, recent hemodynamics investigations relating WSS-related parameters with AAA rupture risk assessment are presented. This review will be useful to understand the physical representation of WSS-related parameters in cardiovascular flows and how they can be calculated practically for AAA investigations.
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Affiliation(s)
- Onur Mutlu
- Biomedical Research Center, Qatar University, Doha, Qatar
| | - Huseyin Enes Salman
- Department of Mechanical Engineering, TOBB University of Economics and Technology, Ankara, Turkey
| | - Hassan Al-Thani
- Department of Surgery, Trauma and Vascular Surgery, Hamad General Hospital, Hamad Medical Corporation, P.O. Box 3050, Doha, Qatar
| | - Ayman El-Menyar
- Department of Surgery, Trauma and Vascular Surgery, Hamad General Hospital, Hamad Medical Corporation, P.O. Box 3050, Doha, Qatar; Clinical Medicine, Weill Cornell Medical College, Doha, Qatar
| | - Uvais Ahmed Qidwai
- Department of Computer Science Engineering, Qatar University, Doha, Qatar
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8
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Dynamic Loading-A New Marker for Abdominal Aneurysm Growth? MEDICINA (KAUNAS, LITHUANIA) 2023; 59:medicina59020404. [PMID: 36837605 PMCID: PMC9967562 DOI: 10.3390/medicina59020404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 02/07/2023] [Accepted: 02/16/2023] [Indexed: 02/22/2023]
Abstract
The growing possibilities of non-invasive heart rate and blood pressure measurement with mobile devices allow vital data to be continuously collected and used to assess patients' health status. When it comes to the risk assessment of abdominal aortic aneurysms (AAA), the continuous tracking of blood pressure and heart rate could enable a more patient-specific approach. The use of a load function and an energy function, with continuous blood pressure, heart rate, and aneurysm stiffness as input parameters, can quantify dynamic load on AAA. We hypothesise that these load functions correlate with aneurysm growth and outline a possible study procedure in which the hypothesis could be tested for validity. Subsequently, uncertainty quantification of input quantities and derived quantities is performed.
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Biomechanical Rupture Risk Assessment in Management of Patients with Abdominal Aortic Aneurysm in COVID-19 Pandemic. Diagnostics (Basel) 2022; 13:diagnostics13010132. [PMID: 36611424 PMCID: PMC9818825 DOI: 10.3390/diagnostics13010132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2022] [Revised: 10/18/2022] [Accepted: 12/27/2022] [Indexed: 01/04/2023] Open
Abstract
Background: The acute phase of the COVID-19 pandemic requires a redefinition of healthcare system to increase the number of available intensive care units for COVID-19 patients. This leads to the postponement of elective surgeries including the treatment of abdominal aortic aneurysm (AAA). The probabilistic rupture risk index (PRRI) recently showed its advantage over the diameter criterion in AAA rupture risk assessment. Its major improvement is in increased specificity and yet has the same sensitivity as the maximal diameter criterion. The objective of this study was to test the clinical applicability of the PRRI method in a quasi-prospective patient cohort study. Methods: Nineteen patients (fourteen males, five females) with intact AAA who were postponed due to COVID-19 pandemic were included in this study. The PRRI was calculated at the baseline via finite element method models. If a case was diagnosed as high risk (PRRI > 3%), the patient was offered priority in AAA intervention. Cases were followed until 10 September 2021 and a number of false positive and false negative cases were recorded. Results: Each case was assessed within 3 days. Priority in intervention was offered to two patients with high PRRI. There were four false positive cases and no false negative cases classified by PRRI. In three cases, the follow-up was very short to reach any conclusion. Conclusions: Integrating PRRI into clinical workflow is possible. Longitudinal validation of PRRI did not fail and may significantly decrease the false positive rate in AAA treatment.
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10
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He X, Lu J. On strain-based rupture criterion for ascending aortic aneurysm: the role of fiber waviness. Acta Biomater 2022; 149:51-59. [PMID: 35760348 DOI: 10.1016/j.actbio.2022.06.034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 05/29/2022] [Accepted: 06/20/2022] [Indexed: 11/01/2022]
Abstract
We propose a new approach for constructing strain-based rupture criterion for ascending thoracic aortic aneurysm. The rupture metric is formulated using an effective strain, which is a measure of net strain that the collagen bundles experience after fiber uncrimping. The effective strain is a function of the total strain and the waviness properties of the collagen fibers. In the present work, the waviness properties are obtained from fitting biaxial response data to constitutive models that explicitly consider the collagen waviness and fiber recruitment. Inflation test data from 10 ascending thoracic aortic aneurysm specimens are analyzed. For each specimen, tension-strain data at ∼2300 material points are garnered. The effective strain fields in the configuration immediately before rupture are computed. It is found that the hotspots of the effective strain match the rupture sites very well in all 10 samples. More importantly, the values of effective strain at the hotsopts are closely clustered around 0.1, in contrast to a much wider distribution of the total strain. The study underscores the importance of considering the fiber recruitment in formulating strain-based rupture metric, and suggests that ϵ¯≈0.1, where ϵ¯ is the effective strain metric defined in this work, can be considered as a criterion for assessing the imminent rupture risk of ascending aortic aneurysms.
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Affiliation(s)
- Xuehuan He
- Department of Mechanical Engineering, and Iowa Technology Institute The University of Iowa, Iowa City, IA 52242, USA
| | - Jia Lu
- Department of Mechanical Engineering, and Iowa Technology Institute The University of Iowa, Iowa City, IA 52242, USA.
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11
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Wittek A, Alkhatib F, Vitásek R, Polzer S, Miller K. On stress in abdominal aortic aneurysm: Linear versus non-linear analysis and aneurysm rupture risk. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2022; 38:e3554. [PMID: 34806314 DOI: 10.1002/cnm.3554] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 11/14/2021] [Indexed: 06/13/2023]
Abstract
We present comprehensive biomechanical analyses of abdominal aortic aneurysms (AAA) for 43 patients. We compare stress magnitudes and stress distributions within arterial walls of abdominal aortic aneurysms (AAA) obtained using two simulation and modelling methods: (a) Fully automated and computationally very efficient linear method embedded in the software platform Biomechanics based Prediction of Aneurysm Rupture Risk (BioPARR), freely available from https://bioparr.mech.uwa.edu.au/; (b) More complex and much more computationally demanding Non-Linear Iterative Stress Analysis (Non-LISA) that uses a non-linear inverse iterative approach and strongly non-linear material model. Both methods predicted localised high stress zones with over 90% of AAA model volume fraction subjected to stress below 20% of the 99th percentile maximum principal stress. However, for the non-linear iterative method, the peak maximum principal stress (and 99th percentile maximum principal stress) was higher and the stress magnitude in the low stress area lower than for the automated linear method embedded in BioPARR. Differences between the stress distributions obtained using the two methods tended to be particularly pronounced in the areas where the AAA curvature was large. Performance of the selected characteristic features of the stress fields (we used 99th percentile maximum principal stress) obtained using BioPARR and Non-LISA in distinguishing between the AAAs that would rupture and remain intact was for practical purposes the same for both methods.
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Affiliation(s)
- Adam Wittek
- Intelligent Systems for Medicine Laboratory, The University of Western Australia, Perth, Western Australia, Australia
| | - Farah Alkhatib
- Intelligent Systems for Medicine Laboratory, The University of Western Australia, Perth, Western Australia, Australia
| | - Radek Vitásek
- Department of Applied Mechanics, VSB Technical University of Ostrava, Ostrava, Czech Republic
| | - Stanislav Polzer
- Department of Applied Mechanics, VSB Technical University of Ostrava, Ostrava, Czech Republic
| | - Karol Miller
- Intelligent Systems for Medicine Laboratory, The University of Western Australia, Perth, Western Australia, Australia
- Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
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12
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Avril S, Gee MW, Hemmler A, Rugonyi S. Patient-specific computational modeling of endovascular aneurysm repair: State of the art and future directions. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2021; 37:e3529. [PMID: 34490740 DOI: 10.1002/cnm.3529] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Accepted: 08/30/2021] [Indexed: 06/13/2023]
Abstract
Endovascular aortic repair (EVAR) has become the preferred intervention option for aortic aneurysms and dissections. This is because EVAR is much less invasive than the alternative open surgery repair. While in-hospital mortality rates are smaller for EVAR than open repair (1%-2% vs. 3%-5%), the early benefits of EVAR are lost after 3 years due to larger rates of complications in the EVAR group. Clinicians follow instructions for use (IFU) when possible, but are left with personal experience on how to best proceed and what choices to make with respect to stent-graft (SG) model choice, sizing, procedural options, and their implications on long-term outcomes. Computational modeling of SG deployment in EVAR and tissue remodeling after intervention offers an alternative way of testing SG designs in silico, in a personalized way before intervention, to ultimately select the strategies leading to better outcomes. Further, computational modeling can be used in the optimal design of SGs in cases of complex geometries. In this review, we address some of the difficulties and successes associated with computational modeling of EVAR procedures. There is still work to be done in all areas of EVAR in silico modeling, including model validation, before models can be applied in the clinic, but much progress has already been made. Critical to clinical implementation are current efforts focusing on developing fast algorithms that can achieve (near) real-time solutions, as well as ways of dealing with inherent uncertainties related to patient aortic wall degradation on an individualized basis. We are optimistic that EVAR modeling in the clinic will soon become a reality to help clinicians optimize EVAR interventions and ultimately reduce EVAR-associated complications.
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Affiliation(s)
- Stéphane Avril
- Mines Saint-Étienne, Univ Lyon, Univ Jean Monnet, INSERM, Saint-Étienne, France
| | - Michael W Gee
- Mechanics & High Performance Computing Group, Department of Mechanical Engineering, Technical University of Munich, Garching, Germany
| | - André Hemmler
- Mechanics & High Performance Computing Group, Department of Mechanical Engineering, Technical University of Munich, Garching, Germany
| | - Sandra Rugonyi
- Biomedical Engineering Department, Oregon Health & Science University, Portland, Oregon, USA
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13
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Lindquist Liljeqvist M, Bogdanovic M, Siika A, Gasser TC, Hultgren R, Roy J. Geometric and biomechanical modeling aided by machine learning improves the prediction of growth and rupture of small abdominal aortic aneurysms. Sci Rep 2021; 11:18040. [PMID: 34508118 PMCID: PMC8433325 DOI: 10.1038/s41598-021-96512-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 08/02/2021] [Indexed: 12/17/2022] Open
Abstract
It remains difficult to predict when which patients with abdominal aortic aneurysm (AAA) will require surgery. The aim was to study the accuracy of geometric and biomechanical analysis of small AAAs to predict reaching the threshold for surgery, diameter growth rate and rupture or symptomatic aneurysm. 189 patients with AAAs of diameters 40–50 mm were included, 161 had undergone two CTAs. Geometric and biomechanical variables were used in prediction modelling. Classifications were evaluated with area under receiver operating characteristic curve (AUC) and regressions with correlation between observed and predicted growth rates. Compared with the baseline clinical diameter, geometric-biomechanical analysis improved prediction of reaching surgical threshold within four years (AUC 0.80 vs 0.85, p = 0.031) and prediction of diameter growth rate (r = 0.17 vs r = 0.38, p = 0.0031), mainly due to the addition of semiautomatic diameter measurements. There was a trend towards increased precision of volume growth rate prediction (r = 0.37 vs r = 0.45, p = 0.081). Lumen diameter and biomechanical indices were the only variables that could predict future rupture or symptomatic AAA (AUCs 0.65–0.67). Enhanced precision of diameter measurements improves the prediction of reaching the surgical threshold and diameter growth rate, while lumen diameter and biomechanical analysis predicts rupture or symptomatic AAA.
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Affiliation(s)
- Moritz Lindquist Liljeqvist
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden. .,Department of Vascular Surgery, Karolinska University Hospital, Stockholm, Sweden.
| | - Marko Bogdanovic
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| | - Antti Siika
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| | - T Christian Gasser
- Department of Engineering Mechanics, Royal Institute of Technology, Stockholm, Sweden
| | - Rebecka Hultgren
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden.,Department of Vascular Surgery, Karolinska University Hospital, Stockholm, Sweden
| | - Joy Roy
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden.,Department of Vascular Surgery, Karolinska University Hospital, Stockholm, Sweden
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Liu M, Liang L, Ismail Y, Dong H, Lou X, Iannucci G, Chen EP, Leshnower BG, Elefteriades JA, Sun W. Computation of a probabilistic and anisotropic failure metric on the aortic wall using a machine learning-based surrogate model. Comput Biol Med 2021; 137:104794. [PMID: 34482196 DOI: 10.1016/j.compbiomed.2021.104794] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2021] [Revised: 08/20/2021] [Accepted: 08/21/2021] [Indexed: 01/15/2023]
Abstract
Scalar-valued failure metrics are commonly used to assess the risk of aortic aneurysm rupture and dissection, which occurs under hypertensive blood pressures brought on by extreme emotional or physical stress. To compute failure metrics under an elevated blood pressure, a classical patient-specific computer model consists of multiple computation steps involving inverse and forward analyses. These classical procedures may be impractical for time-sensitive clinical applications that require prompt feedback to clinicians. In this study, we developed a machine learning-based surrogate model to directly predict a probabilistic and anisotropic failure metric, namely failure probability (FP), on the aortic wall using aorta geometries at the systolic and diastolic phases. Ascending thoracic aortic aneurysm (ATAA) geometries of 60 patients were obtained from their CT scans, and biaxial mechanical testing data of ATAA tissues from 79 patients were collected. Finite element simulations were used to generate datasets for training, validation, and testing of the ML-surrogate model. The testing results demonstrated that the ML-surrogate can compute the maximum FP failure metric, with 0.42% normalized mean absolute error, in 1 s. To compare the performance of the ML-predicted probabilistic FP metric with other isotropic or deterministic metrics, a numerical case study was performed using synthetic "baseline" data. Our results showed that the probabilistic FP metric had more discriminative power than the deterministic Tsai-Hill metric, isotropic maximum principal stress, and aortic diameter criterion.
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Affiliation(s)
- Minliang Liu
- Tissue Mechanics Laboratory, The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Liang Liang
- Department of Computer Science, University of Miami, Coral Gables, FL, USA
| | - Yasmeen Ismail
- Tissue Mechanics Laboratory, The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Hai Dong
- Tissue Mechanics Laboratory, The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Xiaoying Lou
- Emory University School of Medicine, Atlanta, GA, USA
| | - Glen Iannucci
- Emory University School of Medicine, Atlanta, GA, USA
| | - Edward P Chen
- Emory University School of Medicine, Atlanta, GA, USA
| | | | | | - Wei Sun
- Tissue Mechanics Laboratory, The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA.
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Rengarajan B, Patnaik SS, Finol EA. A Predictive Analysis of Wall Stress in Abdominal Aortic Aneurysms Using a Neural Network Model. J Biomech Eng 2021; 143:1115051. [PMID: 34318314 DOI: 10.1115/1.4051905] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2021] [Indexed: 11/08/2022]
Abstract
Rupture risk assessment of abdominal aortic aneurysms (AAAs) by means of quantifying wall stress is a common biomechanical strategy. However, the clinical translation of this approach has been greatly limited due to the complexity associated with the computational tools required for its implementation. Thus, being able to estimate wall stress using nonbiomechanical markers that can be quantified as a direct outcome of clinical image segmentation would be advantageous in improving the potential implementation of said strategy. In the present work, we investigated the use of geometric indices to predict patient-specific AAA wall stress by means of a novel neural network (NN) modeling approach. We conducted a retrospective review of existing clinical images of two patient groups: 98 asymptomatic and 50 symptomatic AAAs. The images were subject to a protocol consisting of image segmentation, processing, volume meshing, finite element modeling, and geometry quantification, from which 53 geometric indices and the spatially averaged wall stress (SAWS) were calculated. SAWS estimated from finite element analysis was considered the gold standard for the predictions. We developed feed-forward NN models composed of an input layer, two dense layers, and an output layer using Keras, a deep learning library in python. The NN models were trained, tested, and validated independently for both AAA groups using all geometric indices, as well as a reduced set of indices resulting from a variable reduction procedure. We compared the performance of the NN models with two standard machine learning algorithms (MARS: multivariate adaptive regression splines and GAM: generalized additive model) and a linear regression model (GLM: generalized linear model). With the reduced sets of indices, the NN-based approach exhibited the highest mean goodness-of-fit (for the symptomatic group 0.71 and for the asymptomatic group 0.79) and lowest mean relative error (17% for both groups). In contrast, MARS yielded a mean goodness-of-fit of 0.59 for the symptomatic group and 0.77 for the asymptomatic group, with relative errors of 17% for the symptomatic group and 22% for the asymptomatic group. GAM had a mean goodness-of-fit of 0.70 for the symptomatic group and 0.80 for the asymptomatic group, with relative errors of 16% for the symptomatic group and 20% for the asymptomatic group. GLM did not perform as well as the other algorithms, with a mean goodness-of-fit of 0.53 for the symptomatic group and 0.70 for the asymptomatic group, with relative errors of 19% for the symptomatic group and 23% for the asymptomatic group. Nevertheless, the NN models required a reduced set of 15 and 13 geometric indices to predict SAWS for the symptomatic and asymptomatic AAA groups, respectively. This was in contrast to the reduced set of nine and eight geometric indices required to predict SAWS with the MARS and GAM algorithms for each AAA group, respectively. The use of NN modeling represents a promising alternative methodology for the estimation of AAA wall stress using geometric indices as surrogates, in lieu of finite element modeling. The performance metrics of NN models are expected to improve with significantly larger group sizes, given the suitability of NN modeling for "big data" applications.
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Affiliation(s)
- Balaji Rengarajan
- Department of Mechanical Engineering, University of Texas at San Antonio, San Antonio, TX 78249
| | - Sourav S Patnaik
- Department of Mechanical Engineering, University of Texas at San Antonio, San Antonio, TX 78249; Department of Bioengineering, University of Texas at Dallas, Richardson, TX 75080
| | - Ender A Finol
- Department of Mechanical Engineering, University of Texas at San Antonio, San Antonio, TX 78249
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Singh TP, Moxon JV, Gasser TC, Golledge J. Systematic Review and Meta-Analysis of Peak Wall Stress and Peak Wall Rupture Index in Ruptured and Asymptomatic Intact Abdominal Aortic Aneurysms. J Am Heart Assoc 2021; 10:e019772. [PMID: 33855866 PMCID: PMC8174183 DOI: 10.1161/jaha.120.019772] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Accepted: 02/19/2021] [Indexed: 12/31/2022]
Abstract
Background Prior studies have suggested aortic peak wall stress (PWS) and peak wall rupture index (PWRI) can estimate the rupture risk of an abdominal aortic aneurysm (AAA), but whether these measurements have independent predictive ability over assessing AAA diameter alone is unclear. The aim of this systematic review was to compare PWS and PWRI in participants with ruptured and asymptomatic intact AAAs of similar diameter. Methods and Results Web of Science, Scopus, Medline, and The Cochrane Library were systematically searched to identify studies assessing PWS and PWRI in ruptured and asymptomatic intact AAAs of similar diameter. Random-effects meta-analyses were performed using inverse variance-weighted methods. Leave-one-out sensitivity analyses were conducted to assess the robustness of findings. Risk of bias was assessed using a modification of the Newcastle-Ottawa scale and standard quality assessment criteria for evaluating primary research papers. Seven case-control studies involving 309 participants were included. Meta-analyses suggested that PWRI (standardized mean difference, 0.42; 95% CI, 0.14-0.70; P=0.004) but not PWS (standardized mean difference, 0.13; 95% CI, -0.18 to 0.44; P=0.418) was greater in ruptured than intact AAAs. Sensitivity analyses suggested that the findings were not dependent on the inclusion of any single study. The included studies were assessed to have a medium to high risk of bias. Conclusions Based on limited evidence, this study suggested that PWRI, but not PWS, is greater in ruptured than asymptomatic intact AAAs of similar maximum aortic diameter.
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Affiliation(s)
- Tejas P. Singh
- Queensland Research Centre for Peripheral Vascular DiseaseCollege of Medicine and DentistryJames Cook UniversityTownsvilleQueenslandAustralia
- The Department of Vascular and Endovascular SurgeryThe Townsville University HospitalTownsvilleQueenslandAustralia
| | - Joseph V. Moxon
- Queensland Research Centre for Peripheral Vascular DiseaseCollege of Medicine and DentistryJames Cook UniversityTownsvilleQueenslandAustralia
- The Australian Institute of Tropical Health and MedicineJames Cook UniversityTownsvilleQueenslandAustralia
| | - T. Christian Gasser
- Department of Engineering MechanicsKTH Solid MechanicsKTH Royal Institute of TechnologyStockholmSweden
| | - Jonathan Golledge
- Queensland Research Centre for Peripheral Vascular DiseaseCollege of Medicine and DentistryJames Cook UniversityTownsvilleQueenslandAustralia
- The Department of Vascular and Endovascular SurgeryThe Townsville University HospitalTownsvilleQueenslandAustralia
- The Australian Institute of Tropical Health and MedicineJames Cook UniversityTownsvilleQueenslandAustralia
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Polzer S, Kracík J, Novotný T, Kubíček L, Staffa R, Raghavan ML. Methodology for Estimation of Annual Risk of Rupture for Abdominal Aortic Aneurysm. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2021; 200:105916. [PMID: 33503510 DOI: 10.1016/j.cmpb.2020.105916] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Accepted: 12/18/2020] [Indexed: 06/12/2023]
Abstract
BACKGROUND AND OBJECTIVE Estimating patient specific annual risk of rupture of abdominal aortic aneurysm (AAA) is currently based only on population. More accurate knowledge based on patient specific data would allow surgical treatment of only those AAAs with significant risk of rupture. This would be beneficial for both patients and health care system. METHODS A methodology for estimating annual risk of rupture (EARR) of abdominal aortic aneurysms (AAA) that utilizes Bayesian statistics, mechanics and patient-specific blood pressure monitoring data is proposed. EARR estimation takes into consideration, peak wall stress in AAA computed by patient-specific finite element modeling, the probability distributions of wall thickness, wall strength, systolic blood pressure and the period of time that the patient is known to have already survived with the intact AAA. Initial testing of proposed approach was performed on fifteen patients with intact AAA (mean maximal diameter 51mm±8mm). They were equipped with a pressure holter and their blood pressure was recorded over 24 hours. Then, we calculated EARR values for four possible scenarios - without considering any days of survival prior identification of AAA at computed tomography scans (EARR_0), considering past survival of 30 (EARR_30), 90 (EARR_90) and 180 days (EARR_180). Finally, effect of patient-specific blood pressure variability was analyzed. RESULTS Consideration of past survival does indeed significantly improve predictions of future risk: EARR_30 (1.04%± 0.87%), EARR_90 (0.67%± 0.56%) and EARR_180 (0.47%± 0.39%) which are unrealistically high otherwise (EARR_0 5.02%± 5.24%). Finally, EARR values were observed to vary by an order as a consequence of blood pressure variability and by factor of two as a consequence of neglected growth. CONCLUSIONS Methodology for computing annual risk of rupture of AAA was developed for the first time. Sensitivity analyses showed respecting patient specific blood pressure is important factor and should be included in the AAA rupture risk assessment. Obtained EARR values were generally low and in good agreement with confirmed survival time of investigated patients so proposed method should be further clinically validated.
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Affiliation(s)
- Stanislav Polzer
- Department of Applied Mechanics, VSB-Technical University of Ostrava, 17.listopadu 2172/15, Ostrava-Poruba, 708 33, Czech Republic.
| | - Jan Kracík
- Department of Applied Mathematics, VSB-Technical University of Ostrava, 17.listopadu 2172/15, Ostrava-Poruba, 708 33, Czech Republic
| | - Tomáš Novotný
- 2nd Department of Surgery, St. Anne's University Hospital and Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Luboš Kubíček
- 2nd Department of Surgery, St. Anne's University Hospital and Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Robert Staffa
- 2nd Department of Surgery, St. Anne's University Hospital and Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Madhavan L Raghavan
- Department of Biomedical Engineering, University of Iowa, 5605 Seamans Center, Iowa City, IA, 52242, USA
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18
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Prediction of local strength of ascending thoracic aortic aneurysms. J Mech Behav Biomed Mater 2020; 115:104284. [PMID: 33348213 DOI: 10.1016/j.jmbbm.2020.104284] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Revised: 12/08/2020] [Accepted: 12/14/2020] [Indexed: 12/12/2022]
Abstract
Knowledges of both local stress and strength are needed for a reliable evaluation of the rupture risk for ascending thoracic aortic aneurysm (ATAA). In this study, machine learning is applied to predict the local strength of ATAA tissues based on tension-strain data collected through in vitro inflation tests on tissue samples. Inputs to machine learning models are tension, strain, slope, and curvature values at two points on the low strain region of the tension-strain curve. The models are trained using data from locations where the tissue ruptured, and subsequently applied to data from intact sites to predict the local rupture strength. The predicted strengths are compared with the known strength at rupture sites as well as the highest tension the tissues experienced at the intact sites. A local rupture index, which is the ratio of the end tension to the predicted rupture strength, is computed. The 'hot spots' of the rupture index are found to match the rupture sites better than those of the peak tension. The study suggests that the strength of ATAA tissue could be reliably predicted from early phase response features defined in this work.
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19
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Vitásek R, Gossiho D, Polzer S. Sources of inconsistency in mean mechanical response of abdominal aortic aneurysm tissue. J Mech Behav Biomed Mater 2020; 115:104274. [PMID: 33421951 DOI: 10.1016/j.jmbbm.2020.104274] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Revised: 11/20/2020] [Accepted: 12/12/2020] [Indexed: 10/22/2022]
Abstract
INTRODUCTION There is a striking difference in the reported mean response of abdominal aortic aneurysm tissue in academic literature depending on the type of tests (uniaxial vs biaxial) performed. In this paper, the hypothesis variability caused by differences in experimental protocols is explored using porcine aortic tissue as a substitute for aneurysmal tissue. METHODS Nine samples of porcine aorta were created and both uniaxial and biaxial tests were performed. Three effects were investigated. (i) Effect of sample (non) preconditioning, (ii) effect of objective function used (normalised vs non-normalised), and (iii) effect of chosen procedure used for mean response calculation: constant averaging (CA) vs fit to averaged response (FAR) vs fit to all data (FAD). Both the overall shape of mean curve and mean initial stiffness were compared. RESULTS (i) Non-preconditioning led to a much stiffer response, and initial stiffness was about three times higher for a non-preconditioned response based on uniaxial data compared to a preconditioned biaxial response. (ii) CA led to a much stiffer response compared to FAR and FAD procedures which gave similar results. (iii) Normalised objective function produced a mean response with six times lower initial stiffness and more pronounced nonlinearity compared to non-normalised objective function. DISCUSSION It is possible to reproduce a mechanically inconsistent response purely by using the chosen experimental protocol. Non-preconditioned data from failure tests should be used for FE simulation of the elastic response of aneurysms. CA should not be used to obtain a mean response.
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Affiliation(s)
- Radek Vitásek
- Department of Applied Mechanics, VSB-Technical University of Ostrava, 17.listopadu 2172/15, Ostrava-Poruba, 708 00, Czech Republic.
| | - Didier Gossiho
- Department of Biomedical Engineering, University of Iowa, 5605 Seamans Center, Iowa City, IA, 52242, USA
| | - Stanislav Polzer
- Department of Applied Mechanics, VSB-Technical University of Ostrava, 17.listopadu 2172/15, Ostrava-Poruba, 708 00, Czech Republic
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20
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Bruder L, Pelisek J, Eckstein HH, Gee MW. Biomechanical rupture risk assessment of abdominal aortic aneurysms using clinical data: A patient-specific, probabilistic framework and comparative case-control study. PLoS One 2020; 15:e0242097. [PMID: 33211767 PMCID: PMC7676745 DOI: 10.1371/journal.pone.0242097] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 10/26/2020] [Indexed: 11/18/2022] Open
Abstract
We present a data-informed, highly personalized, probabilistic approach for the quantification of abdominal aortic aneurysm (AAA) rupture risk. Our novel framework builds upon a comprehensive database of tensile test results that were carried out on 305 AAA tissue samples from 139 patients, as well as corresponding non-invasively and clinically accessible patient-specific data. Based on this, a multivariate regression model is created to obtain a probabilistic description of personalized vessel wall properties associated with a prospective AAA patient. We formulate a probabilistic rupture risk index that consistently incorporates the available statistical information and generalizes existing approaches. For the efficient evaluation of this index, a flexible Kriging-based surrogate model with an active training process is proposed. In a case-control study, the methodology is applied on a total of 36 retrospective, diameter matched asymptomatic (group 1, n = 18) and known symptomatic/ruptured (group 2, n = 18) cohort of AAA patients. Finally, we show its efficacy to discriminate between the two groups and demonstrate competitive performance in comparison to existing deterministic and probabilistic biomechanical indices.
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Affiliation(s)
- Lukas Bruder
- Mechanics & High Performance Computing Group, Technical University of Munich, Garching, Germany
| | - Jaroslav Pelisek
- Department of Vascular Surgery, University Hospital Zurich, Zurich, Switzerland
- Clinic for Vascular and Endovascular Surgery, Technical University of Munich, Munich, Germany
| | - Hans-Henning Eckstein
- Clinic for Vascular and Endovascular Surgery, Technical University of Munich, Munich, Germany
| | - Michael W. Gee
- Mechanics & High Performance Computing Group, Technical University of Munich, Garching, Germany
- * E-mail:
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21
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Sigaeva T, Polzer S, Vitásek R, Di Martino ES. Effect of testing conditions on the mechanical response of aortic tissues from planar biaxial experiments: Loading protocol and specimen side. J Mech Behav Biomed Mater 2020; 111:103882. [DOI: 10.1016/j.jmbbm.2020.103882] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 05/22/2020] [Accepted: 05/23/2020] [Indexed: 01/15/2023]
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22
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Liu M, Dong H, Lou X, Iannucci G, Chen EP, Leshnower BG, Sun W. A Novel Anisotropic Failure Criterion With Dispersed Fiber Orientations for Aortic Tissues. J Biomech Eng 2020; 142:1086084. [PMID: 32766773 DOI: 10.1115/1.4048029] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2020] [Indexed: 12/14/2022]
Abstract
Accurate failure criteria play a fundamental role in biomechanical analyses of aortic wall rupture and dissection. Experimental investigations have demonstrated a significant difference of aortic wall strengths in the circumferential and axial directions. Therefore, the isotropic von Mises stress and maximum principal stress, commonly used in computational analysis of the aortic wall, are inadequate for modeling of anisotropic failure properties. In this study, we propose a novel stress-based anisotropic failure criterion with dispersed fiber orientations. In the new failure criterion, the overall failure metric is computed by using angular integration (AI) of failure metrics in all directions. Affine rotations of fiber orientations due to finite deformation are taken into account in an anisotropic hyperelastic constitutive model. To examine fitting capability of the failure criterion, a set of off-axis uniaxial tension tests were performed on aortic tissues of four porcine individuals and 18 human ascending thoracic aortic aneurysm (ATAA) patients. The dispersed fiber failure criterion demonstrates a good fitting capability with the off-axis testing data. Under simulated biaxial stress conditions, the dispersed fiber failure criterion predicts a smaller failure envelope comparing to those predicted by the traditional anisotropic criteria without fiber dispersion, which highlights the potentially important role of fiber dispersion in the failure of the aortic wall. Our results suggest that the deformation-dependent fiber orientations need to be considered when wall strength determined from uniaxial tests are used for in vivo biomechanical analysis. More investigations are needed to determine biaxial failure properties of the aortic wall.
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Affiliation(s)
- Minliang Liu
- Tissue Mechanics Laboratory, The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA 30313
| | - Hai Dong
- Tissue Mechanics Laboratory, The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA 30313
| | - Xiaoying Lou
- Emory University School of Medicine, Atlanta, GA 30332
| | - Glen Iannucci
- Emory University School of Medicine, Atlanta, GA 30332
| | - Edward P Chen
- Emory University School of Medicine, Atlanta, GA 30332
| | | | - Wei Sun
- Tissue Mechanics Laboratory, The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Technology Enterprise Park, Room 206 387 Technology Circle, Atlanta, GA 30313
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23
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de Hoop H, Petterson NJ, van de Vosse FN, van Sambeek MRHM, Schwab HM, Lopata RGP. Multiperspective Ultrasound Strain Imaging of the Abdominal Aorta. IEEE TRANSACTIONS ON MEDICAL IMAGING 2020; 39:3714-3724. [PMID: 32746118 DOI: 10.1109/tmi.2020.3003430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Current decision-making for clinical intervention of abdominal aortic aneurysms (AAAs) is based on the maximum diameter of the aortic wall, but this does not provide patient-specific information on rupture risk. Ultrasound (US) imaging can assess both geometry and deformation of the aortic wall. However, low lateral contrast and resolution are currently limiting the precision of both geometry and local strain estimates. To tackle these drawbacks, a multiperspective scanning mode was developed on a dual transducer US system to perform strain imaging at high frame rates. Experimental imaging was performed on porcine aortas embedded in a phantom of the abdomen, pressurized in a mock circulation loop. US images were acquired with three acquisition schemes: Multiperspective ultrafast imaging, single perspective ultrafast imaging, and conventional line-by-line scanning. Image registration was performed by automatic detection of the transducer surfaces. Multiperspective images and axial displacements were compounded for improved segmentation and tracking of the aortic wall, respectively. Performance was compared in terms of image quality, motion tracking, and strain estimation. Multiperspective compound displacement estimation reduced the mean motion tracking error over one cardiac cycle by a factor 10 compared to conventional scanning. Resolution increased in radial and circumferential strain images, and circumferential signal-to-noise ratio (SNRe) increased by 10 dB. Radial SNRe is high in wall regions moving towards the transducer. In other regions, radial strain estimates remain cumbersome for the frequency used. In conclusion, multiperspective US imaging was demonstrated to improve motion tracking and circumferential strain estimation of porcine aortas in an experimental set-up.
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Failure properties of abdominal aortic aneurysm tissue are orientation dependent. J Mech Behav Biomed Mater 2020; 114:104181. [PMID: 33153925 DOI: 10.1016/j.jmbbm.2020.104181] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Revised: 08/12/2020] [Accepted: 10/23/2020] [Indexed: 10/23/2022]
Abstract
INTRODUCTION Biomechanical rupture risk assessment of abdominal aortic aneurysm (AAA) requires information about failure properties of aneurysmal tissue. There are large differences between reported values. Among others, studies vary in using either axially or circumferentially oriented samples. This study investigates the effect of sample orientation on failure properties. METHODS Aneurysmal tissues from 45 patients (11 females) were harvested during open AAA repair, cut into uniaxial samples (90) and tested mechanically within 3 h. If possible, the samples were cut in both axial (49 samples) and circumferential (41 samples) directions. Wall thickness, First Piola-Kirchhoff strength Pult and ultimate tension Tult were recorded. Influence of sample orientation and other clinical parameters were investigated using non parametric tests. RESULTS Medians of Pult (values 1100 kPa for circumferential vs. 715 kPa for axial direction, p < 10-4) and Tult (17.4 N/cm in circumferential vs. 11.2 N/cm in axial direction, p < 10-4) were significantly higher in circumferential direction. For paired data, the median of difference was 411 kPa (p < 10-3) in Pult and 7.4 N/cm (p < 10-4) in Tult in favor of circumferential direction. CONCLUSIONS In this first study of anisotropy in AAA wall failure properties using paired comparisons, the strength in circumferential orientation was found to be higher than in axial orientation.
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Miller K, Mufty H, Catlin A, Rogers C, Saunders B, Sciarrone R, Fourneau I, Meuris B, Tavner A, Joldes GR, Wittek A. Is There a Relationship Between Stress in Walls of Abdominal Aortic Aneurysm and Symptoms? J Surg Res 2020; 252:37-46. [DOI: 10.1016/j.jss.2020.01.025] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2019] [Revised: 01/17/2020] [Accepted: 01/31/2020] [Indexed: 10/24/2022]
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26
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Canchi T, Patnaik SS, Nguyen HN, Ng EYK, Narayanan S, Muluk SC, De Oliveira V, Finol EA. A Comparative Study of Biomechanical and Geometrical Attributes of Abdominal Aortic Aneurysms in the Asian and Caucasian Populations. J Biomech Eng 2020; 142:061003. [PMID: 31633169 PMCID: PMC10782868 DOI: 10.1115/1.4045268] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2019] [Revised: 09/24/2019] [Indexed: 11/08/2022]
Abstract
In this work, we provide a quantitative assessment of the biomechanical and geometric features that characterize abdominal aortic aneurysm (AAA) models generated from 19 Asian and 19 Caucasian diameter-matched AAA patients. 3D patient-specific finite element models were generated and used to compute peak wall stress (PWS), 99th percentile wall stress (99th WS), and spatially averaged wall stress (AWS) for each AAA. In addition, 51 global geometric indices were calculated, which quantify the wall thickness, shape, and curvature of each AAA. The indices were correlated with 99th WS (the only biomechanical metric that exhibited significant association with geometric indices) using Spearman's correlation and subsequently with multivariate linear regression using backward elimination. For the Asian AAA group, 99th WS was highly correlated (R2 = 0.77) with three geometric indices, namely tortuosity, intraluminal thrombus volume, and area-averaged Gaussian curvature. Similarly, 99th WS in the Caucasian AAA group was highly correlated (R2 = 0.87) with six geometric indices, namely maximum AAA diameter, distal neck diameter, diameter-height ratio, minimum wall thickness variance, mode of the wall thickness variance, and area-averaged Gaussian curvature. Significant differences were found between the two groups for ten geometric indices; however, no differences were found for any of their respective biomechanical attributes. Assuming maximum AAA diameter as the most predictive metric for wall stress was found to be imprecise: 24% and 28% accuracy for the Asian and Caucasian groups, respectively. This investigation reveals that geometric indices other than maximum AAA diameter can serve as predictors of wall stress, and potentially for assessment of aneurysm rupture risk, in the Asian and Caucasian AAA populations.
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Affiliation(s)
- Tejas Canchi
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798
| | - Sourav S. Patnaik
- Department of Mechanical Engineering, University of Texas at San Antonio, San Antonio, TX 78249
| | - Hong N. Nguyen
- Department of Biomedical Engineering, University of Texas at San Antonio, San Antonio, TX 78249
| | - E. Y. K. Ng
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798
| | - Sriram Narayanan
- The Harley Street Heart and Vascular Centre, Gleneagles Hospital, Singapore 258500
| | - Satish C. Muluk
- Department of Thoracic & Cardiovascular Surgery, Allegheny Health Network, Pittsburgh, PA 15212
| | - Victor De Oliveira
- Department of Management and Statistics, University of Texas at San Antonio, San Antonio, TX 78249
| | - Ender A. Finol
- Department of Mechanical Engineering, University of Texas at San Antonio, One UTSA Circle, EB 3.04.08, San Antonio, TX 78249
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Commentary: Do not "futz" with Laplace. J Thorac Cardiovasc Surg 2020; 162:1463-1466. [PMID: 32448689 DOI: 10.1016/j.jtcvs.2020.03.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Accepted: 03/04/2020] [Indexed: 11/20/2022]
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Biomechanical indices are more sensitive than diameter in predicting rupture of asymptomatic abdominal aortic aneurysms. J Vasc Surg 2020; 71:617-626.e6. [DOI: 10.1016/j.jvs.2019.03.051] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Accepted: 03/07/2019] [Indexed: 11/23/2022]
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Rengarajan B, Wu W, Wiedner C, Ko D, Muluk SC, Eskandari MK, Menon PG, Finol EA. A Comparative Classification Analysis of Abdominal Aortic Aneurysms by Machine Learning Algorithms. Ann Biomed Eng 2020; 48:1419-1429. [PMID: 31980998 DOI: 10.1007/s10439-020-02461-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Accepted: 01/20/2020] [Indexed: 12/14/2022]
Abstract
The objective of this work was to perform image-based classification of abdominal aortic aneurysms (AAA) based on their demographic, geometric, and biomechanical attributes. We retrospectively reviewed existing demographics and abdominal computed tomography angiography images of 100 asymptomatic and 50 symptomatic AAA patients who received an elective or emergent repair, respectively, within 1-6 months of their last follow up. An in-house script developed within the MATLAB computational platform was used to segment the clinical images, calculate 53 descriptors of AAA geometry, and generate volume meshes suitable for finite element analysis (FEA). Using a third party FEA solver, four biomechanical markers were calculated from the wall stress distributions. Eight machine learning algorithms (MLA) were used to develop classification models based on the discriminatory potential of the demographic, geometric, and biomechanical variables. The overall classification performance of the algorithms was assessed by the accuracy, area under the receiver operating characteristic curve (AUC), sensitivity, specificity, and precision of their predictions. The generalized additive model (GAM) was found to have the highest accuracy (87%), AUC (89%), and sensitivity (78%), and the third highest specificity (92%), in classifying the individual AAA as either asymptomatic or symptomatic. The k-nearest neighbor classifier yielded the highest specificity (96%). GAM used seven markers (six geometric and one biomechanical) to develop the classifier. The maximum transverse dimension, the average wall thickness at the maximum diameter, and the spatially averaged wall stress were found to be the most influential markers in the classification analysis. A second classification analysis revealed that using maximum diameter alone results in a lower accuracy (79%) than using GAM with seven geometric and biomechanical markers. We infer from these results that biomechanical and geometric measures by themselves are not sufficient to discriminate adequately between population samples of asymptomatic and symptomatic AAA, whereas MLA offer a statistical approach to stratification of rupture risk by combining demographic, geometric, and biomechanical attributes of patient-specific AAA.
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Affiliation(s)
- Balaji Rengarajan
- Department of Mechanical Engineering, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX, 78249, USA
| | - Wei Wu
- Department of Mechanical Engineering, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX, 78249, USA
| | - Crystal Wiedner
- Department of Management Science and Statistics, University of Texas at San Antonio, San Antonio, TX, USA
| | - Daijin Ko
- Department of Management Science and Statistics, University of Texas at San Antonio, San Antonio, TX, USA
| | - Satish C Muluk
- Department of Thoracic & Cardiovascular Surgery, Allegheny Health Network, Allegheny General Hospital, Pittsburgh, PA, USA
| | - Mark K Eskandari
- Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Prahlad G Menon
- Department of Mathematics and Data Analytics, Carlow University, Pittsburgh, PA, USA
| | - Ender A Finol
- Department of Mechanical Engineering, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX, 78249, USA.
- UTSA/UTHSA Joint Graduate Program in Biomedical Engineering, University of Texas at San Antonio, San Antonio, TX, USA.
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Sherifova S, Holzapfel GA. Biomechanics of aortic wall failure with a focus on dissection and aneurysm: A review. Acta Biomater 2019; 99:1-17. [PMID: 31419563 PMCID: PMC6851434 DOI: 10.1016/j.actbio.2019.08.017] [Citation(s) in RCA: 73] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 08/05/2019] [Accepted: 08/08/2019] [Indexed: 12/12/2022]
Abstract
Aortic dissections and aortic aneurysms are fatal events characterized by structural changes to the aortic wall. The maximum diameter criterion, typically used for aneurysm rupture risk estimations, has been challenged by more sophisticated biomechanically motivated models in the past. Although these models are very helpful for the clinicians in decision-making, they do not attempt to capture material failure. Following a short overview of the microstructure of the aorta, we analyze the failure mechanisms involved in the dissection and rupture by considering also traumatic rupture. We continue with a literature review of experimental studies relevant to quantify tissue strength. More specifically, we summarize more extensively uniaxial tensile, bulge inflation and peeling tests, and we also specify trouser, direct tension and in-plane shear tests. Finally we analyze biomechanically motivated models to predict rupture risk. Based on the findings of the reviewed studies and the rather large variations in tissue strength, we propose that an appropriate material failure criterion for aortic tissues should also reflect the microstructure in order to be effective. STATEMENT OF SIGNIFICANCE: Aortic dissections and aortic aneurysms are fatal events characterized by structural changes to the aortic wall. Despite the advances in medical, biomedical and biomechanical research, the mortality rates of aneurysms and dissections remain high. The present review article summarizes experimental studies that quantify the aortic wall strength and it discusses biomechanically motivated models to predict rupture risk. We identified contradictory observations and a large variation within and between data sets, which may be due to biological variations, different sample sizes, differences in experimental protocols, etc. Based on the findings of the reviewed literature and the rather large variations in tissue strength, it is proposed that an appropriate criterion for aortic failure should also reflect the microstructure.
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Affiliation(s)
- Selda Sherifova
- Institute of Biomechanics, Graz University of Technology, Stremayrgasse 16/2, 8010 Graz, Austria
| | - Gerhard A Holzapfel
- Institute of Biomechanics, Graz University of Technology, Stremayrgasse 16/2, 8010 Graz, Austria; Department of Structural Engineering, Norwegian Institute of Science and Technology (NTNU), 7491 Trondheim, Norway.
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31
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Romary DJ, Berman AG, Goergen CJ. High-frequency murine ultrasound provides enhanced metrics of BAPN-induced AAA growth. Am J Physiol Heart Circ Physiol 2019; 317:H981-H990. [PMID: 31559828 PMCID: PMC6879923 DOI: 10.1152/ajpheart.00300.2019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Revised: 09/11/2019] [Accepted: 09/18/2019] [Indexed: 12/12/2022]
Abstract
An abdominal aortic aneurysm (AAA), defined as a pathological expansion of the largest artery in the abdomen, is a common vascular disease that frequently leads to death if rupture occurs. Once diagnosed, clinicians typically evaluate the rupture risk based on maximum diameter of the aneurysm, a limited metric that is not accurate for all patients. In this study, we worked to evaluate additional distinguishing factors between growing and stable murine aneurysms toward the aim of eventually improving clinical rupture risk assessment. With the use of a relatively new mouse model that combines surgical application of topical elastase to cause initial aortic expansion and a lysyl oxidase inhibitor, β-aminopropionitrile (BAPN), in the drinking water, we were able to create large AAAs that expanded over 28 days. We further sought to develop and demonstrate applications of advanced imaging approaches, including four-dimensional ultrasound (4DUS), to evaluate alternative geometric and biomechanical parameters between 1) growing AAAs, 2) stable AAAs, and 3) nonaneurysmal control mice. Our study confirmed the reproducibility of this murine model and found reduced circumferential strain values, greater tortuosity, and increased elastin degradation in mice with aneurysms. We also found that expanding murine AAAs had increased peak wall stress and surface area per length compared with stable aneurysms. The results from this work provide clear growth patterns associated with BAPN-elastase murine aneurysms and demonstrate the capabilities of high-frequency ultrasound. These data could help lay the groundwork for improving insight into clinical prediction of AAA expansion.NEW & NOTEWORTHY This work characterizes a relatively new murine model of abdominal aortic aneurysms (AAAs) by quantifying vascular strain, stress, and geometry. Furthermore, Green-Lagrange strain was calculated with a novel mapping approach using four-dimensional ultrasound. We also compared growing and stable AAAs, finding peak wall stress and surface area per length to be most indicative of growth. In all AAAs, strain and elastin health declined, whereas tortuosity increased.
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MESH Headings
- Aminopropionitrile
- Animals
- Aorta, Abdominal/diagnostic imaging
- Aorta, Abdominal/pathology
- Aorta, Abdominal/physiopathology
- Aortic Aneurysm, Abdominal/chemically induced
- Aortic Aneurysm, Abdominal/diagnostic imaging
- Aortic Aneurysm, Abdominal/pathology
- Aortic Aneurysm, Abdominal/physiopathology
- Biomechanical Phenomena
- Dilatation, Pathologic
- Disease Models, Animal
- Disease Progression
- Hemodynamics
- Male
- Mice, Inbred C57BL
- Pancreatic Elastase
- Predictive Value of Tests
- Stress, Mechanical
- Time Factors
- Ultrasonography
- Vascular Remodeling
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Affiliation(s)
- Daniel J Romary
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana
| | - Alycia G Berman
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana
| | - Craig J Goergen
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana
- Purdue Center for Cancer Research, Purdue University, West Lafayette, Indiana
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Ayyalasomayajula V, Pierrat B, Badel P. A computational model for understanding the micro-mechanics of collagen fiber network in the tunica adventitia. Biomech Model Mechanobiol 2019; 18:1507-1528. [PMID: 31065952 PMCID: PMC6748894 DOI: 10.1007/s10237-019-01161-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Accepted: 04/26/2019] [Indexed: 12/11/2022]
Abstract
Abdominal aortic aneurysm is a prevalent cardiovascular disease with high mortality rates. The mechanical response of the arterial wall relies on the organizational and structural behavior of its microstructural components, and thus, a detailed understanding of the microscopic mechanical response of the arterial wall layers at loads ranging up to rupture is necessary to improve diagnostic techniques and possibly treatments. Following the common notion that adventitia is the ultimate barrier at loads close to rupture, in the present study, a finite element model of adventitial collagen network was developed to study the mechanical state at the fiber level under uniaxial loading. Image stacks of the rabbit carotid adventitial tissue at rest and under uniaxial tension obtained using multi-photon microscopy were used in this study, as well as the force-displacement curves obtained from previously published experiments. Morphological parameters like fiber orientation distribution, waviness, and volume fraction were extracted for one sample from the confocal image stacks. An inverse random sampling approach combined with a random walk algorithm was employed to reconstruct the collagen network for numerical simulation. The model was then verified using experimental stress-stretch curves. The model shows the remarkable capacity of collagen fibers to uncrimp and reorient in the loading direction. These results further show that at high stretches, collagen network behaves in a highly non-affine manner, which was quantified for each sample. A comprehensive parameter study to understand the relationship between structural parameters and their influence on mechanical behavior is presented. Through this study, the model was used to conclude important structure-function relationships that control the mechanical response. Our results also show that at loads close to rupture, the probability of failure occurring at the fiber level is up to 2%. Uncertainties in usually employed rupture risk indicators and the stochastic nature of the event of rupture combined with limited knowledge on the microscopic determinants motivate the development of such an analysis. Moreover, this study will advance the study of coupling microscopic mechanisms to rupture of the artery as a whole.
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Affiliation(s)
- Venkat Ayyalasomayajula
- Mines Saint-Étienne, Univ Lyon, Univ Jean Monnet, INSERM, U1059 SAINBIOSE, Centre CIS, 42023, Saint-Étienne, France.
| | - Baptiste Pierrat
- Mines Saint-Étienne, Univ Lyon, Univ Jean Monnet, INSERM, U1059 SAINBIOSE, Centre CIS, 42023, Saint-Étienne, France
| | - Pierre Badel
- Mines Saint-Étienne, Univ Lyon, Univ Jean Monnet, INSERM, U1059 SAINBIOSE, Centre CIS, 42023, Saint-Étienne, France
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33
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Hemmler A, Reeps C, Lutz B, Gee MW. Der digitale Zwilling in der endovaskulären Versorgung. GEFÄSSCHIRURGIE 2019. [DOI: 10.1007/s00772-019-00569-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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34
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Jalalahmadi G, Helguera M, Mix DS, Hodis S, Richards MS, Stoner MC, Linte CA. (PEAK) WALL STRESS AS AN INDICATOR OF ABDOMINAL AORTIC ANEURYSM SEVERITY. PROCEEDINGS. IEEE WESTERN NEW YORK IMAGE AND SIGNAL PROCESSING WORKSHOP 2019; 2018. [PMID: 31342015 DOI: 10.1109/wnyipw.2018.8576453] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Abdominal aortic aneurysms, which consist of dilatations of the infra-renal aorta by at least 1.5 times of its normal diameter, are becoming a leading cause of death worldwide. Rupture often occurs unexpectedly, before a repair procedure is conducted. The AAA maximum diameter has been used as a clinical criterion to monitor AAA severity. However, assessment of AAA rupture risk requires knowledge of wall stress and wall strength at the potential rupture location. We conducted a study on 37 patient specific CT datasets to investigate the benefits of using peak wall stress instead of Dmax for AAA rupture severity. Correlation between PWS and 24 geometric indices and biomechanical factors was studied where eleven of them showed a statistically significant correlation with PWS. A Finite Element Analysis Rupture Index was used to conclude that the use of D max as a single predictor of AAA behavior and severity may be insufficient based on our patient population with a Dmax smaller than the 5.5 cm, clinically recommended repair threshold.
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Affiliation(s)
- Golnaz Jalalahmadi
- Chester F. Carlson Center for Imaging Science, Rochester Institute of Technology, Rochester, USA
| | - María Helguera
- Chester F. Carlson Center for Imaging Science, Rochester Institute of Technology, Rochester, USA.,Instituto Tecnológico José Mario Molina Pasquel y Henríquez - Unidad Lagos de Moreno, Jalisco, México
| | - Doran S Mix
- Biomedical Engineering Department, Rochester Institute of Technology, Rochester, USA.,Department of Surgery, Division of Vascular Surgery, University of Rochester Medical Center, Rochester, USA
| | - Simona Hodis
- Department of Mathematics, Texas A&M University-Kingsville, Kingsville, TX, USA
| | - Michael S Richards
- Biomedical Engineering Department, Rochester Institute of Technology, Rochester, USA.,Department of Surgery, Division of Vascular Surgery, University of Rochester Medical Center, Rochester, USA
| | - Michael C Stoner
- Department of Surgery, Division of Vascular Surgery, University of Rochester Medical Center, Rochester, USA
| | - Cristian A Linte
- Chester F. Carlson Center for Imaging Science, Rochester Institute of Technology, Rochester, USA.,Biomedical Engineering Department, Rochester Institute of Technology, Rochester, USA
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LEACH JOSEPHR, ZHU CHENGCHENG, SALONER DAVID, HOPE MICHAELD. COMPARISON OF TWO METHODS FOR ESTIMATING THE UNLOADED STATE FOR ABDOMINAL AORTIC ANEURYSM STRESS CALCULATIONS. J MECH MED BIOL 2019. [DOI: 10.1142/s0219519419500155] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Biomechanical analyses can be used to better understand the rupture risk of abdominal aortic aneurysms (AAAs) on a patient-specific basis using vascular geometries obtained from medical imaging. Methodologies of varying complexity are used to estimate the unloaded state of the imaged vessel to provide a reference configuration for finite element simulations. In this work, we compare the implementation and results of two of these methods, one based on geometric scaling and the other using an iterative determination of unloaded vessel geometry. We find that the two methods result in significantly different stress predictions, and that the iterative method offers superior geometric accuracy. Our findings lend context to the variation in finite element results presented in the AAA stress analysis literature.
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Affiliation(s)
- JOSEPH R. LEACH
- Department of Radiology and Biomedical Imaging, University of California, 505 Parnassus Avenue, M-391 San Francisco, CA 94143-0628, USA
| | - CHENGCHENG ZHU
- Department of Radiology and Biomedical Imaging, University of California, 505 Parnassus Avenue, M-391 San Francisco, CA 94143-0628, USA
| | - DAVID SALONER
- Department of Radiology and Biomedical Imaging, University of California, 505 Parnassus Avenue, M-391 San Francisco, CA 94143-0628, USA
- Department of Radiology, Veterans Affairs Medical Center, 4150 Clement Street, San Francisco, CA 94121, USA
| | - MICHAEL D. HOPE
- Department of Radiology and Biomedical Imaging, University of California, 505 Parnassus Avenue, M-391 San Francisco, CA 94143-0628, USA
- Department of Radiology, Veterans Affairs Medical Center, 4150 Clement Street, San Francisco, CA 94121, USA
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36
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Wall Stress and Geometry Measures in Electively Repaired Abdominal Aortic Aneurysms. Ann Biomed Eng 2019; 47:1611-1625. [PMID: 30963384 DOI: 10.1007/s10439-019-02261-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 03/29/2019] [Indexed: 10/27/2022]
Abstract
Abdominal aortic aneurysm (AAA) is a vascular disease characterized by the enlargement of the infrarenal segment of the aorta. A ruptured AAA can cause internal bleeding and carries a high mortality rate, which is why the clinical management of the disease is focused on preventing aneurysm rupture. AAA rupture risk is estimated by the change in maximum diameter over time (i.e., growth rate) or if the diameter reaches a prescribed threshold. The latter is typically 5.5 cm in most clinical centers, at which time surgical intervention is recommended. While a size-based criterion is suitable for most patients who are diagnosed at an early stage of the disease, it is well known that some small AAA rupture or patients become symptomatic prior to a maximum diameter of 5.5 cm. Consequently, the mechanical stress in the aortic wall can also be used as an integral component of a biomechanics-based rupture risk assessment strategy. In this work, we seek to identify geometric characteristics that correlate strongly with wall stress using a sample space of 100 asymptomatic, unruptured, electively repaired AAA models. The segmentation of the clinical images, volume meshing, and quantification of up to 45 geometric measures of each AAA were done using in-house Matlab scripts. Finite element analysis was performed to compute the first principal stress distributions from which three global biomechanical parameters were calculated: peak wall stress, 99th percentile wall stress and spatially averaged wall stress. Following a feature reduction approach consisting of Pearson's correlation matrices with Bonferroni correction and linear regressions, a multivariate stepwise regression analysis was conducted to find the geometric measures most highly correlated with each of the biomechanical parameters. Our findings indicate that wall stress can be predicted by geometric indices with an accuracy of up to 94% when AAA models are generated with uniform wall thickness and up to 67% for patient specific, non-uniform wall thickness AAA. These geometric predictors of wall stress could be used in lieu of complex finite element models as part of a geometry-based protocol for rupture risk assessment.
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Urrutia J, Roy A, Raut SS, Antón R, Muluk SC, Finol EA. Geometric surrogates of abdominal aortic aneurysm wall mechanics. Med Eng Phys 2018; 59:43-49. [PMID: 30006003 DOI: 10.1016/j.medengphy.2018.06.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Revised: 06/06/2018] [Accepted: 06/29/2018] [Indexed: 11/16/2022]
Abstract
The maximum diameter criterion is the most important factor in the clinical management of abdominal aortic aneurysms (AAA). Consequently, interventional repair is recommended when an aneurysm reaches a critical diameter, typically 5.0 cm in the United States. Nevertheless, biomechanical measures of the aneurysmal abdominal aorta have long been implicated in AAA risk of rupture. The purpose of this study is to assess whether other geometric characteristics, in addition to maximum diameter, may be highly correlated with the AAA peak wall stress (PWS). Using in-house segmentation and meshing algorithms, 30 patient-specific AAA models were generated for finite element analysis using an isotropic constitutive material for the AAA wall. PWS, evaluated as the spatial maximum of the first principal stress, was calculated at a systolic pressure of 120 mmHg. The models were also used to calculate 47 geometric indices characteristic of the aneurysm geometry. Statistical analyses were conducted using a feature reduction algorithm in which the 47 indices were reduced to 11 based on their statistical significance in differentiating the models in the population (p < 0.05). A subsequent discriminant analysis was performed and 7 of these indices were identified as having no error in discriminating the AAA models with a significant nonlinear regression correlation with PWS. These indices were: Dmax (maximum diameter), T (tortuosity), DDr (maximum diameter to neck diameter ratio), S (wall surface area), Kmedian (median of the Gaussian surface curvature), Cmax (maximum lumen compactness), and Mmode (mode of the Mean surface curvature). Therefore, these characteristics of an individual AAA geometry are the highest correlated with the most clinically relevant biomechanical parameter for rupture risk assessment. We conclude that the indices can serve as surrogates of PWS in lieu of a finite element modeling approach for AAA biomechanical evaluation.
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Affiliation(s)
- Jesús Urrutia
- The University of Texas at San Antonio, Department of Biomedical Engineering, San Antonio, TX, USA; University of Navarra-Tecnun, Department of Mechanical Engineering, San Sebastian, Spain
| | - Anuradha Roy
- The University of Texas at San Antonio, Department of Management Science and Statistics, San Antonio, TX, USA
| | - Samarth S Raut
- Carnegie Mellon University, Department of Mechanical Engineering, Pittsburgh, PA, USA
| | - Raúl Antón
- University of Navarra-Tecnun, Department of Mechanical Engineering, San Sebastian, Spain
| | - Satish C Muluk
- Allegheny Health Network, Department of Thoracic and Cardiovascular Surgery, Pittsburgh, PA, USA
| | - Ender A Finol
- The University of Texas at San Antonio, Department of Mechanical Engineering, Room EB 3.04.08, One UTSA Circle, San Antonio, TX 78249, USA.
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38
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Chen Q, Chen Q, Li L, Lin X, Chang SI, Li Y, Tian Z, Liu W, Huang K. Serum anion gap on admission predicts intensive care unit mortality in patients with aortic aneurysm. Exp Ther Med 2018; 16:1766-1777. [PMID: 30186400 PMCID: PMC6122415 DOI: 10.3892/etm.2018.6391] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Accepted: 06/22/2018] [Indexed: 12/31/2022] Open
Abstract
It has been widely reported that the serum anion gap is significantly associated with mortality in intensive care unit (ICU); however, it remains unknown whether the association is present in aortic aneurysm (AA) patients. The present study aimed to investigate the association between the admission serum anion gap and ICU mortality in AA patients. Data extracted from a publicly accessible clinical database using a modifiable data mining technique were analyzed retrospectively, mainly by employing multivariable logistic regression analysis. The primary study outcome was ICU mortality. A total of 273 patient records were analyzed. The ICU mortality was 8.79% (24/273). The median serum anion gap was significantly higher in non-survivors [17.50 mEq/l, interquartile range (IQR) 15.75-22.50 mEq/l] compared with survivors [13.00 mEq/l, IQR 11.00-15.00 mEq/l, P<0.001]. Multivariate analysis resulted in identification of a clear association between admission serum anion gap and ICU mortality in AA patients [odds ratio (OR) 1.38 per 1 mEq/l increase, 95% confidence interval (CI) 1.08-1.76]. The area under the receiver operating characteristic curve showed an outstanding discrimination ability in predicting ICU mortality (area under curve 0.8513, 95% CI 0.7698-0.9328). In conclusion, admission serum anion gap may serve as a strong predictor of ICU mortality for AA patients.
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Affiliation(s)
- Qinchang Chen
- Division of Vascular and Thyroid Surgery, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, Guangdong 510120, P.R. China
| | - Qingui Chen
- Department of Medical Intensive Care Unit, First Affiliated Hospital of Sun Yat-Sen University, Guangzhou, Guangdong 510080, P.R. China
| | - Lingling Li
- Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, Guangdong 510080, P.R. China
| | - Xixia Lin
- Division of Vascular and Thyroid Surgery, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, Guangdong 510120, P.R. China
| | - Shih-I Chang
- Division of Vascular and Thyroid Surgery, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, Guangdong 510120, P.R. China
| | - Yonghui Li
- Division of Vascular and Thyroid Surgery, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, Guangdong 510120, P.R. China
| | - Zhenluan Tian
- Division of Vascular and Thyroid Surgery, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, Guangdong 510120, P.R. China
| | - Wei Liu
- Division of Vascular and Thyroid Surgery, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, Guangdong 510120, P.R. China
| | - Kai Huang
- Division of Vascular and Thyroid Surgery, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, Guangdong 510120, P.R. China
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Man V, Polzer S, Gasser T, Novotny T, Bursa J. Impact of isotropic constitutive descriptions on the predicted peak wall stress in abdominal aortic aneurysms. Med Eng Phys 2018; 53:49-57. [DOI: 10.1016/j.medengphy.2018.01.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Revised: 12/24/2017] [Accepted: 01/03/2018] [Indexed: 12/16/2022]
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Jalalahmadi G, Helguera M, Mix DS, Linte CA. Toward modeling the effects of regional material properties on the wall stress distribution of abdominal aortic aneurysms. PROCEEDINGS OF SPIE--THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING 2018; 10578. [PMID: 31213733 DOI: 10.1117/12.2294558] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
The overall geometry and different biomechanical parameters of an abdominal aortic aneurysm (AAA), contribute to its severity and risk of rupture, therefore they could be used to track its progression. Previous and ongoing research efforts have resorted to using uniform material properties to model the behavior of AAA. However, it has been recently illustrated that different regions of the AAA wall exhibit different behavior due to the effect of the biological activities in the metalloproteinase matrix that makes up the wall at the aneurysm site. In this work, we introduce a non-invasive patient-specific regional material property model to help us better understand and investigate the AAA wall stress distribution, peak wall stress (PWS) severity, and potential rupture risk. Our results indicate that the PWS and the overall wall stress distribution predicted using the proposed regional material property model, are higher than those predicted using the traditional homogeneous, hyper-elastic model (p <1.43E-07). Our results also show that to investigate AAA, the overall geometry, presence of intra-luminal thrombus (ILT), and loading condition in a patient specific manner may be critical for capturing the biomechanical complexity of AAAs.
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Affiliation(s)
- Golnaz Jalalahmadi
- Chester F. Carlson Center for Imaging Science, Rochester Institute of Technology, Rochester, USA
| | - María Helguera
- Chester F. Carlson Center for Imaging Science, Rochester Institute of Technology, Rochester, USA.,Instituto Tecnológico José Mario Molina Pasquel y Henríquez - Unidad Lagos de Moreno, Jalisco, México
| | - Doran S Mix
- Chester F. Carlson Center for Imaging Science, Rochester Institute of Technology, Rochester, USA.,Department of Surgery, Division of Vascular Surgery, University of Rochester Medical Center, Rochester, USA
| | - Cristian A Linte
- Chester F. Carlson Center for Imaging Science, Rochester Institute of Technology, Rochester, USA.,Biomedical Engineering Department, Rochester Institute of Technology, Rochester, USA
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Biehler J, Wall WA. The impact of personalized probabilistic wall thickness models on peak wall stress in abdominal aortic aneurysms. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2018; 34:e2922. [PMID: 28796436 DOI: 10.1002/cnm.2922] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Revised: 07/04/2017] [Accepted: 08/06/2017] [Indexed: 06/07/2023]
Abstract
If computational models are ever to be used in high-stakes decision making in clinical practice, the use of personalized models and predictive simulation techniques is a must. This entails rigorous quantification of uncertainties as well as harnessing available patient-specific data to the greatest extent possible. Although researchers are beginning to realize that taking uncertainty in model input parameters into account is a necessity, the predominantly used probabilistic description for these uncertain parameters is based on elementary random variable models. In this work, we set out for a comparison of different probabilistic models for uncertain input parameters using the example of an uncertain wall thickness in finite element models of abdominal aortic aneurysms. We provide the first comparison between a random variable and a random field model for the aortic wall and investigate the impact on the probability distribution of the computed peak wall stress. Moreover, we show that the uncertainty about the prevailing peak wall stress can be reduced if noninvasively available, patient-specific data are harnessed for the construction of the probabilistic wall thickness model.
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Affiliation(s)
- J Biehler
- Institute for Computational Mechanics, Technische Universität München, Boltzmannstraße 15, Garching, 85748, Germany
| | - W A Wall
- Institute for Computational Mechanics, Technische Universität München, Boltzmannstraße 15, Garching, 85748, Germany
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Kemmerling EMC, Peattie RA. Abdominal Aortic Aneurysm Pathomechanics: Current Understanding and Future Directions. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1097:157-179. [DOI: 10.1007/978-3-319-96445-4_8] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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The Association Between Geometry and Wall Stress in Emergently Repaired Abdominal Aortic Aneurysms. Ann Biomed Eng 2017; 45:1908-1916. [PMID: 28444478 DOI: 10.1007/s10439-017-1837-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Accepted: 04/18/2017] [Indexed: 10/19/2022]
Abstract
Abdominal aortic aneurysm (AAA) is a prevalent cardiovascular disease characterized by the focal dilation of the aorta, which supplies blood to all the organs and tissues in the systemic circulation. With the AAA increasing in diameter over time, the risk of aneurysm rupture is generally associated with the size of the aneurysm. If diagnosed on time, intervention is recommended to prevent AAA rupture. The criterion to decide on surgical intervention is determined by measuring the maximum diameter of the aneurysm relative to the critical value of 5.5 cm. However, a more reliable approach could be based on understanding the biomechanical behavior of the aneurysmal wall. In addition, geometric features that are proven to be significant predictors of the AAA wall mechanics could be used as surrogates of the AAA biomechanical behavior and, subsequently, of the aneurysm's risk of rupture. The aim of this work is to identify those geometric indices that have a high correlation with AAA wall stress in the population of patients who received an emergent repair of their aneurysm. In-house segmentation and meshing algorithms were used to model 75 AAAs followed by estimation of the spatially distributed wall stress by performing finite element analysis. Fifty-two shape and size geometric indices were calculated for the same models using MATLAB scripting. Hypotheses testing were carried out to identify the indices significantly correlated with wall stress by constructing a Pearson's correlation coefficient matrix. The analyses revealed that 12 indices displayed high correlation with the wall stress, amongst which wall thickness and curvature-based indices exhibited the highest correlations. Stepwise regression analysis of these correlated indices indicated that wall stress can be predicted by the following four indices with an accuracy of 76%: maximum aneurysm diameter, aneurysm sac length, average wall thickness at the maximum diameter cross-section, and the median of the wall thickness variance. The primary outcome of this work emphasizes the use of global measures of size and wall thickness as geometric surrogates of wall stress for emergently repaired AAAs.
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Novak K, Polzer S, Krivka T, Vlachovsky R, Staffa R, Kubicek L, Lambert L, Bursa J. Correlation between transversal and orthogonal maximal diameters of abdominal aortic aneurysms and alternative rupture risk predictors. Comput Biol Med 2017; 83:151-156. [PMID: 28282590 DOI: 10.1016/j.compbiomed.2017.03.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Revised: 02/07/2017] [Accepted: 03/03/2017] [Indexed: 11/29/2022]
Abstract
PURPOSE There is no standard for measuring maximal diameter (Dmax) of abdominal aortic aneurysm (AAA) from computer tomography (CT) images although differences between Dmax evaluated from transversal (axialDmax) or orthogonal (orthoDmax) planes can be large especially for angulated AAAs. Therefore we investigated their correlations with alternative rupture risk indicators as peak wall stress (PWS) and peak wall rupture risk (PWRR) to decide which Dmax is more relevant in AAA rupture risk assessment. MATERIAL AND METHODS The Dmax values were measured by a trained radiologist from 70 collected CT scans, and the corresponding PWS and PWRR were evaluated using Finite Element Analysis (FEA). The cohort was ordered according to the difference between axialDmax and orthoDmax (Da-o) quantifying the aneurysm angulation, and Spearman's correlation coefficients between PWS/PWRR - orthoDmax/axialDmax were calculated. RESULTS The calculated correlations PWS/PWRR vs. orthoDmax were substantially higher for angulated AAAs (with Da-o≥3mm). Under this limit, the correlations were almost the same for both Dmax values. Analysis of AAAs divided into two groups of angulated (n=38) and straight (n=32) cases revealed that both groups are similar in all parameters (orthoDmax, PWS, PWRR) with the exception of axialDmax (p=0.024). CONCLUSIONS It was confirmed that orthoDmax is better correlated with the alternative rupture risk predictors PWS and PWRR for angulated AAAs (DA-O≥3mm) while there is no difference between orthoDmax and axialDmax for straight AAAs (DA-O<3mm). As angulated AAAs represent a significant portion of cases it can be recommended to use orthoDmax as the only Dmax parameter for AAA rupture risk assessment.
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Affiliation(s)
- Kamil Novak
- Institute of Solid Mechanics, Mechatronics and Biomechanics, Brno University of Technology, Czech Republic.
| | - Stanislav Polzer
- Institute of Solid Mechanics, Mechatronics and Biomechanics, Brno University of Technology, Czech Republic
| | - Tomas Krivka
- Department of Medical Imaging, St. Anne´s University Hospital and Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Robert Vlachovsky
- 2(nd) Department of Surgery, St. Anne's University Hospital and Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Robert Staffa
- 2(nd) Department of Surgery, St. Anne's University Hospital and Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Lubos Kubicek
- 2(nd) Department of Surgery, St. Anne's University Hospital and Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Lukas Lambert
- Department of Radiology, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Czech Republic
| | - Jiri Bursa
- Institute of Solid Mechanics, Mechatronics and Biomechanics, Brno University of Technology, Czech Republic
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Weller GB, Lovely J, Larson DW, Earnshaw BA, Huebner M. Leveraging electronic health records for predictive modeling of post-surgical complications. Stat Methods Med Res 2017; 27:3271-3285. [PMID: 29298612 DOI: 10.1177/0962280217696115] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Hospital-specific electronic health record systems are used to inform clinical practice about best practices and quality improvements. Many surgical centers have developed deterministic clinical decision rules to discover adverse events (e.g. postoperative complications) using electronic health record data. However, these data provide opportunities to use probabilistic methods for early prediction of adverse health events, which may be more informative than deterministic algorithms. Electronic health record data from a set of 9598 colorectal surgery cases from 2010 to 2014 were used to predict the occurrence of selected complications including surgical site infection, ileus, and bleeding. Consistent with previous studies, we find a high rate of missing values for both covariates and complication information (4-90%). Several machine learning classification methods are trained on an 80% random sample of cases and tested on a remaining holdout set. Predictive performance varies by complication, although an area under the receiver operating characteristic curve as high as 0.86 on testing data was achieved for bleeding complications, and accuracy for all complications compares favorably to existing clinical decision rules. Our results confirm that electronic health records provide opportunities for improved risk prediction of surgical complications; however, consideration of data quality and consistency standards is an important step in predictive modeling with such data.
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Affiliation(s)
| | - Jenna Lovely
- 2 Pharmacy Services, Mayo Clinic, Rochester, MN, USA
| | - David W Larson
- 3 Department of Colon and Rectal Surgery, Mayo Clinic, Rochester, MN, USA
| | | | - Marianne Huebner
- 4 Department of Statistics and Probability, Michigan State University, East Lansing, MI, USA
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