scholarly journals Identification of in vivo nonlinear anisotropic mechanical properties of ascending thoracic aortic aneurysm from patient-specific CT scans

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Minliang Liu ◽  
Liang Liang ◽  
Fatiesa Sulejmani ◽  
Xiaoying Lou ◽  
Glen Iannucci ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Aortic Aneurysm ◽  
Thoracic Aortic Aneurysm ◽  
Aortic Wall ◽  
Inverse Methods ◽  
Ct Scans ◽  
Patient Specific ◽  
Accurate Identification ◽  
Anisotropic Mechanical Properties

Abstract Accurate identification of in vivo nonlinear, anisotropic mechanical properties of the aortic wall of individual patients remains to be one of the critical challenges in the field of cardiovascular biomechanics. Since only the physiologically loaded states of the aorta are given from in vivo clinical images, inverse approaches, which take into account of the unloaded configuration, are needed for in vivo material parameter identification. Existing inverse methods are computationally expensive, which take days to weeks to complete for a single patient, inhibiting fast feedback for clinicians. Moreover, the current inverse methods have only been evaluated using synthetic data. In this study, we improved our recently developed multi-resolution direct search (MRDS) approach and the computation time cost was reduced to 1~2 hours. Using the improved MRDS approach, we estimated in vivo aortic tissue elastic properties of two ascending thoracic aortic aneurysm (ATAA) patients from pre-operative gated CT scans. For comparison, corresponding surgically-resected aortic wall tissue samples were obtained and subjected to planar biaxial tests. Relatively close matches were achieved for the in vivo-identified and ex vivo-fitted stress-stretch responses. It is hoped that further development of this inverse approach can enable an accurate identification of the in vivo material parameters from in vivo image data.

scholarly journals A Probabilistic and Anisotropic Failure Metric for Ascending Thoracic Aortic Aneurysm Risk Stratification

2020 ◽  
Author(s):  
Minliang Liu ◽  
Liang Liang ◽  
Qing Zou ◽  
Yasmeen Ismail ◽  
Xiaoying Lou ◽  
...  
Keyword(s):  
Aortic Aneurysm ◽  
Risk Stratification ◽  
Thoracic Aortic Aneurysm ◽  
Aortic Wall ◽  
Experimental Studies ◽  
Biomechanical Analysis ◽  
Patient Specific ◽  
Uniaxial Tensile ◽  
Joint Probability Distribution ◽  
P Value

AbstractExperimental studies have shown that aortic wall tensile strengths in circumferential and longitudinal directions are different (i.e., anisotropic), and vary significantly among patients with aortic aneurysm. To assess aneurysm rupture and dissection risk, material failure metric of the aortic wall needs to be accurately defined and determined. Previously such risk assessment methods have largely relied on deterministic or isotropic failure metric. In this study, we develop a novel probabilistic and anisotropic failure metric for risk stratification of ascending thoracic aortic aneurysm (ATAA). To this end, uniaxial tensile tests were performed using aortic tissue samples of 84 ATAA patients, from which a joint probability distribution of the anisotropic wall strengths was obtained. Next, the anisotropic failure probability (FP) based on the Tsai−Hill (TH) failure criterion was derived. The novel FP metric, which incorporates uncertainty in the anisotropic failure properties, can be evaluated after the aortic wall stresses are computed from patient-specific biomechanical analysis. For method validation, “ground-truth” risks of additional 41 ATAA patients were numerically-reconstructed using corresponding CT images and tissue testing data. Performance of different risk stratification methods (e.g., with and without patient-specific hyperelastic properties) was compared using p-value and receiver operating characteristic (ROC) curve. The results show that: (1) the probabilistic FP metric outperforms the deterministic TH metric; and (2) patient-specific hyperelastic properties can help to improve the performance of probabilistic FP metric in ATAA risk stratification.

Abstract 3054: Comparison of Transforming Growth Factor-β1 Expression in Aortic Wall of Thoracic Aortic Aneurysm Versus Dissection

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Shouguo Yang ◽  
Guanggen Cui ◽  
Ramin Beygui ◽  
Fardad Esmailian ◽  
Abbas Ardehali ◽  
...  
Keyword(s):  
Aortic Aneurysm ◽  
Thoracic Aortic Aneurysm ◽  
Aortic Wall ◽  
Transforming Growth Factor ◽  
Smooth Muscle Actin ◽  
Underlying Mechanism ◽  
Transforming Growth Factor Β1 ◽  
Fluorescent Intensity ◽  
Nucleus Density ◽  
Tgf Β1

Background The underlying mechanism of thoracic aortic aneurysm (TAA) and dissection(TAD) was undetermined, and one controversy lies in whether they represent the different dvelopement period of the same disorder or totally diferent diseases. This study is in aim to compare the expression and distribution of Transforming Growth Factors(TGF) β1 in the aortic wall of TAA versus TAD patients. Method Aortic specimens were obtained from patients underwent to aortic procedures for TAA (n=38) and TAD (n=20) at UCLA , and control aorta (CN) from organ donnor (n=20). Double immunofluorescent stainning of TGF-β1 and α-smooth muscle actin were performed with paraffin embeded slides for all aortic samples and semiquantified by fluorescent intensity analysis. Histopathologic examination were performed with HE, Verhoeff van-Gieson and Masson’s trichrome stain. Results TAA and TAD patients exhibited an up-regulation of TGF-β1 to 120.3% and 109.6% compared with CN separately (P<0.05), with TAA higher than TAD (P<0.05). TGF-β1 distributed unevenly across aortic wall with the highest levels expression in tunica media, followed by intima then adventitia. In intima, TGF-β1 was expressed at the same level for TAD as CN, but was increased to 115.2% for TAA compared to CN (P<0.05). In media, TGF-β1 increased by 127.2% in TAA and 116.1% in TAD compared to CN (P<0.01), with TAA being higher than TAD (P<0.05). In adventitia, TGF- β1 was up-regulated to 119.6% and 116.7% for TAA and TAD compared to CN (P<0.05). Nucleus density analysis showed cellular plasia in adventitia of TAA and TAD than CN (P<0.05 ), while TAD patients demonstrated a higher nucleus density than TAA in intima and adventitia (P<0.05). α-actin was increased in media of TAA and TAD to 164.5% and 120% than CN (P<0.01 and P<0.05). Attenuated and interrupted elastin and mild to severe cystic medial degeneration were characteristic histopathologic finding in 29 (76.3%) TAA and 17(85%) TAD patients. Conclusions TGF- β1 expression was up-regulated in aortic wall of TAA and TAD compared to CN. The significant higher levels of TGF- β1 in intima and media in TAA versus TAD patients implicated a probable positive effect of TGF- β1 to maintain aortic wall integrity, and/or greater comsamption of TGF- β1 in the aortic dissection.

scholarly journals In Vivo Quantification of Regional Circumferential Green Strain in the Thoracic and Abdominal Aorta by Two-Dimensional Spiral Cine DENSE MRI

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
John S. Wilson ◽  
Xiaodong Zhong ◽  
Jackson Hair ◽  
W. Robert Taylor ◽  
John N. Oshinski
Keyword(s):  
Abdominal Aorta ◽  
Aortic Wall ◽  
Patient Specific ◽  
Peak Strain ◽  
Ssfp Cine ◽  
Green Strain ◽  
The Mean ◽  
Thoracic And Abdominal ◽  
Cine Dense

Regional tissue mechanics play a fundamental role in the patient-specific function and remodeling of the cardiovascular system. Nevertheless, regional in vivo assessments of aortic kinematics remain lacking due to the challenge of imaging the thin aortic wall. Herein, we present a novel application of displacement encoding with stimulated echoes (DENSE) magnetic resonance imaging (MRI) to quantify the regional displacement and circumferential Green strain of the thoracic and abdominal aorta. Two-dimensional (2D) spiral cine DENSE and steady-state free procession (SSFP) cine images were acquired at 3T at either the infrarenal abdominal aorta (IAA), descending thoracic aorta (DTA), or distal aortic arch (DAA) in a pilot study of six healthy volunteers (22–59 y.o., 4 females). DENSE data were processed with multiple custom noise reduction techniques including time-smoothing, displacement vector smoothing, sectorized spatial smoothing, and reference point averaging to calculate circumferential Green strain across 16 equispaced sectors around the aorta. Each volunteer was scanned twice to evaluate interstudy repeatability. Circumferential Green strain was heterogeneously distributed in all volunteers and locations. The mean spatial heterogeneity index (standard deviation of all sector values divided by the mean strain) was 0.37 in the IAA, 0.28 in the DTA, and 0.59 in the DAA. Mean (homogenized) peak strain by DENSE for each cross section was consistent with the homogenized linearized strain estimated from SSFP cine. The mean difference in peak strain across all sectors following repeat imaging was −0.1±2.3%, with a mean absolute difference of 1.7%. Aortic cine DENSE MRI is a viable noninvasive technique for quantifying heterogeneous regional aortic wall strain and has significant potential to improve patient-specific clinical assessments of numerous aortopathies, as well as to provide the lacking spatiotemporal data required to refine patient-specific computational models of aortic growth and remodeling.

Region-Specific Medial Fiber Micro-Architecture in the Longitudinal-Radial and Circumferential-Radial Planes of Ascending Thoracic Aortic Aneurysm Among Bicuspid and Tricuspid Aortic Valve Patients

2013 ◽  
Author(s):  
Alkiviadis Tsamis ◽  
Julie A. Phillippi ◽  
Ryan G. Koch ◽  
Jeffrey T. Krawiec ◽  
Antonio D’Amore ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Aortic Valve ◽  
Aortic Aneurysm ◽  
Thoracic Aortic Aneurysm ◽  
Aortic Wall ◽  
False Lumen ◽  
True Lumen ◽  
Life Threatening ◽  
The Media ◽  
Intimal Tear

Aortic dissection is a life-threatening cardiovascular emergency with a high potential for death. It usually begins with an intimal tear which permits blood to enter the wall, split the media and create a false lumen, which can reenter the true lumen or exit through the adventitia causing complete rupture. A possible mechanism for dissection of ascending thoracic aortic aneurysm (ATAA) can be the occurrence of blood pressure-induced wall stresses in excess to the adhesive strength between the degenerated aortic wall layers.

On the RANS modelling of the patient-specific thoracic aortic aneurysm

2021 ◽  
pp. 98-102
Author(s):  
A. Mourato ◽  
M. Brito ◽  
J. Xavier ◽  
L. Gil ◽  
A. Tomás
Keyword(s):  
Aortic Aneurysm ◽  
Thoracic Aortic Aneurysm ◽  
Patient Specific

scholarly journals Genetic and Epigenetic Mechanisms Underlying Vascular Smooth Muscle Cell Phenotypic Modulation in Abdominal Aortic Aneurysm

2020 ◽  
Vol 21 (17) ◽  
pp. 6334
Author(s):  
Rijan Gurung ◽  
Andrew Mark Choong ◽  
Chin Cheng Woo ◽  
Roger Foo ◽  
Vitaly Sorokin
Keyword(s):  
Smooth Muscle ◽  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Smooth Muscle Cells ◽  
Aortic Wall ◽  
Epigenetic Mechanisms ◽  
Phenotypic Modulation ◽  
Abdominal Aortic

Abdominal aortic aneurysm (AAA) refers to the localized dilatation of the infra-renal aorta, in which the diameter exceeds 3.0 cm. Loss of vascular smooth muscle cells, degradation of the extracellular matrix (ECM), vascular inflammation, and oxidative stress are hallmarks of AAA pathogenesis and contribute to the progressive thinning of the media and adventitia of the aortic wall. With increasing AAA diameter, and left untreated, aortic rupture ensues with high mortality. Collective evidence of recent genetic and epigenetic studies has shown that phenotypic modulation of smooth muscle cells (SMCs) towards dedifferentiation and proliferative state, which associate with the ECM remodeling of the vascular wall and accompanied with increased cell senescence and inflammation, is seen in in vitro and in vivo models of the disease. This review critically analyses existing publications on the genetic and epigenetic mechanisms implicated in the complex role of SMCs within the aortic wall in AAA formation and reflects the importance of SMCs plasticity in AAA formation. Although evidence from the wide variety of mouse models is convincing, how this knowledge is applied to human biology needs to be addressed urgently leveraging modern in vitro and in vivo experimental technology.

Mechanical Properties Characterization of Abdominal Aortic Aneurysm Tissue Using Biaxial Testing

2002 ◽  
Author(s):  
Steven P. Marra ◽  
Francis E. Kennedy ◽  
Mark F. Fillinger
Keyword(s):  
Mechanical Properties ◽  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Imaging Techniques ◽  
Constitutive Law ◽  
Patient Specific ◽  
Biaxial Testing ◽  
Abdominal Aortic ◽  
Mechanical Properties Characterization

An abdominal aortic aneurysm (AAA) is an abnormal, localized enlargement of the aorta. If untreated, a AAA will continue to enlarge in size and eventually rupture. Currently, AAA diameter is used as the principal indicator of impending rupture. However, this method it is not totally reliable. In an effort to improve the estimation of rupture risk, some researchers are currently studying the mechanical wall stresses of AAAs using patient-specific medical imaging techniques and finite element modeling [1,2]. The accuracy of these models depends significantly on the constitutive law used to describe the mechanical properties of the AAA tissue. To date, only isotropic constitutive laws have been used in these models.

Sign in / Sign up

Export Citation Format

Share Document