scholarly journals Importance of initial aortic properties on the evolving regional anisotropy, stiffness and wall thickness of human abdominal aortic aneurysms

2012 ◽  
Vol 9 (74) ◽  
pp. 2047-2058 ◽  
Author(s):  
J. S. Wilson ◽  
S. Baek ◽  
J. D. Humphrey
Keyword(s):  
Wall Thickness ◽  
Computational Modelling ◽  
Wall Stress ◽  
Abdominal Aortic Aneurysms ◽  
Clinical Decision ◽  
Aortic Aneurysms ◽  
Patient Specific ◽  
Initial State ◽  
Non Invasive ◽  
Abdominal Aortic

Complementary advances in medical imaging, vascular biology and biomechanics promise to enable computational modelling of abdominal aortic aneurysms to play increasingly important roles in clinical decision processes. Using a finite-element-based growth and remodelling model of evolving aneurysm geometry and material properties, we show that regional variations in material anisotropy, stiffness and wall thickness should be expected to arise naturally and thus should be included in analyses of aneurysmal enlargement or wall stress. In addition, by initiating the model from best-fit material parameters estimated for non-aneurysmal aortas from different subjects, we show that the initial state of the aorta may influence strongly the subsequent rate of enlargement, wall thickness, mechanical behaviour and thus stress in the lesion. We submit, therefore, that clinically reliable modelling of the enlargement and overall rupture-potential of aneurysms may require both a better understanding of the mechanobiological processes that govern the evolution of these lesions and new methods of determining the patient-specific state of the pre-aneurysmal aorta (or correlation to currently unaffected portions thereof) through knowledge of demographics, comorbidities, lifestyle, genetics and future non-invasive or minimally invasive tests.

A Comparative Study of Biomechanical and Geometrical Attributes of Abdominal Aortic Aneurysms in the Asian and Caucasian Populations

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Tejas Canchi ◽  
Sourav S. Patnaik ◽  
Hong N. Nguyen ◽  
E. Y. K. Ng ◽  
Sriram Narayanan ◽  
...  
Keyword(s):  
Wall Thickness ◽  
Gaussian Curvature ◽  
Wall Stress ◽  
Aneurysm Rupture ◽  
Aortic Aneurysms ◽  
Patient Specific ◽  
Backward Elimination ◽  
Abdominal Aortic ◽  
Highly Correlated ◽  
Peak Wall Stress

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.

Local Mechanical Properties of Abdominal Aortic Aneurysms

2008 ◽  
Author(s):  
Evelyne van Dam ◽  
Marcel Rutten ◽  
Frans van de Vosse
Keyword(s):  
Mechanical Properties ◽  
Stress Analysis ◽  
Vessel Wall ◽  
Computational Models ◽  
Wall Stress ◽  
Abdominal Aortic Aneurysms ◽  
Aortic Aneurysms ◽  
Patient Specific ◽  
Rupture Risk ◽  
Abdominal Aortic

Rupture risk of abdominal aortic aneurysms (AAA) based on wall stress analysis may be superior to the currently used diameter-based rupture risk prediction [4; 5; 6; 7]. In patient specific computational models for wall stress analysis, the geometry of the aneurysm is obtained from CT or MR images. The wall thickness and mechanical properties are mostly assumed to be homogeneous. The pathological AAA vessel wall may contain collageneous areas, but also calcifications, cholesterol crystals and large amounts of fat cells. No research has yet focused yet on the differences in mechanical properties of the components present within the degrading AAA vessel wall.

Patient-specific initial wall stress in abdominal aortic aneurysms with a backward incremental method

2007 ◽  
Vol 40 (5) ◽  
pp. 1081-1090 ◽  
Author(s):  
S. de Putter ◽  
B.J.B.M. Wolters ◽  
M.C.M. Rutten ◽  
M. Breeuwer ◽  
F.A. Gerritsen ◽  
...  
Keyword(s):  
Wall Stress ◽  
Abdominal Aortic Aneurysms ◽  
Aortic Aneurysms ◽  
Patient Specific ◽  
Incremental Method ◽  
Abdominal Aortic

scholarly journals Patient-specific modelling of abdominal aortic aneurysms: The influence of wall thickness on predicted clinical outcomes

2016 ◽  
Vol 38 (6) ◽  
pp. 526-537 ◽  
Author(s):  
Noel Conlisk ◽  
Arjan J. Geers ◽  
Olivia M.B. McBride ◽  
David E. Newby ◽  
Peter R. Hoskins
Keyword(s):  
Clinical Outcomes ◽  
Wall Thickness ◽  
Abdominal Aortic Aneurysms ◽  
Aortic Aneurysms ◽  
Patient Specific ◽  
Abdominal Aortic

Discrimination of Vessel Wall Components of Abdominal Aortic Aneurysms by Multi-Contrast MRI

2008 ◽  
Author(s):  
Evelyne van Dam ◽  
Marcel Rutten ◽  
Frans van de Vosse
Keyword(s):  
Vessel Wall ◽  
Computational Models ◽  
Wall Stress ◽  
Abdominal Aortic Aneurysms ◽  
Aortic Aneurysms ◽  
Patient Specific ◽  
Western World ◽  
Atherosclerotic Plaques ◽  
Abdominal Aortic ◽  
Wall Components

Rupture of an abdominal aortic aneurysm (AAA) is a major cause of death in the Western world. When the AAA is diagnosed timely, rupture can be prevented by conventional surgical or by endovascular repair. To date, the decision to operate is based on geometry alone, but it has already been suggested that wall stress would be a better predictor [2]. Patient specific computational models have been developed to calculate wall stress [2; 5; 9; 8; 10]. In these models, the AAA wall is assumed to be homogeneous. Patient-specific inhomogeneities such as atherosclerotic plaques and calcifications have large effects on the maximum wall stress and wall stress distribution [6; 7]. Histological examination is not feasible for determining wall composition of patients.

scholarly journals Patient Specific Wall Stress Analysis and Mechanical Characterization of Abdominal Aortic Aneurysms Using 4D Ultrasound

2016 ◽  
Vol 52 (5) ◽  
pp. 635-642 ◽  
Author(s):  
E.M.J. van Disseldorp ◽  
N.J. Petterson ◽  
M.C.M. Rutten ◽  
F.N. van de Vosse ◽  
M.R.H.M. van Sambeek ◽  
...  
Keyword(s):  
Stress Analysis ◽  
Mechanical Characterization ◽  
Wall Stress ◽  
Abdominal Aortic Aneurysms ◽  
Aortic Aneurysms ◽  
Patient Specific ◽  
4D Ultrasound ◽  
Abdominal Aortic

Abstract 107: Increased Peak Wall Stress in Women With Abdominal Aortic Aneurysms

2017 ◽  
Vol 37 (suppl_1) ◽  
Author(s):  
Eric Shang ◽  
Grace Wang ◽  
Ronald Fairman ◽  
Benjamin Jackson
Keyword(s):  
Wall Thickness ◽  
Aortic Wall ◽  
Wall Stress ◽  
Aortic Aneurysms ◽  
Patient Specific ◽  
Rupture Risk ◽  
Intraluminal Thrombus ◽  
Abdominal Aortic ◽  
Aortic Wall Thickness ◽  
Peak Wall Stress

Objective: Women with abdominal aortic aneurysms (AAA) exhibit more rapid aneurysm growth and greater rupture risk at equivalent diameters relative to men. Evidence suggests that biomechanical peak wall stress (PWS) derived from finite element analysis of AAAs is a superior predictor of rupture compared to maximum transverse diameter (MTD). This study aimed to investigate differences in the calculated PWS of AAAs between men and women. Method: Men (n=35) and women (n=35) with infrarenal AAAs with 45-55mm MTD undergoing CTA were identified. Customized image processing algorithms extracted patient-specific AAA geometries from raw DICOM images. The resulting aortic reconstructions incorporated patient-specific and regionally resolved aortic wall thickness, intraluminal thrombus, and wall calcifications. Aortic models were loaded with 120mmHg blood pressure using commercially available FEA solvers. Results: Peak wall stress was found to be significantly higher in women (299±51 vs 257±53 kPA, P=0.001, see Figure). Neither MTD (50.5±3.1 vs 49.8±2.9 mm, P=0.34), mean aortic wall thickness (2.38±0.52 vs 2.34±0.50 mm, P=0.69), nor wall thickness at location of PWS (2.36±0.60 vs 2.20±0.46 mm, P=0.20) varied by sex. While there were no sex-associated differences in aneurysm volume (86.6±27.0 vs 94.8±25.5 cm 3 , P=0.76) or intraluminal thrombus volume (14.2±11.7 vs 16.3±13.4 mm, P=0.33), women’s AAAs had significantly increased maximum Gaussian curvature (0.032±0.011 vs 0.025±0.015 mm -2 , P=0.03). Conclusion: Comparably sized AAAs in women were shown to have significantly higher peak wall stress. Maximum gaussian curvature, a measure of aneurysm morphology, was significantly different between the two groups. These results suggest that men and women possess distinct aneurysm geometries, and that PWS-derived rupture risk prediction may provide a more reliable estimator of rupture risk in all patients.

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