Research Summary
Data-driven approaches for discovering macroscopic rupture pattern of ascending thoracic aortic aneurysm (ATAA) based on early response features
It is known that the rupture of an aneurysm tissue begins at a certain local region, and then the crack continues to propagate under loading. We developed novel, data-driven approaches to differentiate macroscopic response patterns between rupture and non-rupture groups. To facilitate the application of this method in vivo, only tension-strain curves within the physiological blood pressure range were selected. It is hypothesized that the region prone to initiate rupture is associated with a high level of stress (tension) build-up. The results suggest that the proposed “stress (tension) build-up level” within the physiological pressure range can be exploited to estimate the rupture risk of ATAA. This work has shown promising results and may eventually pave the way for noninvasively assessing ATAA rupture risk.
Related Publications
He, X., Avril, S., & Lu, J. (2021). Prediction of local strength of ascending thoracic aortic aneurysms. Journal of the Mechanical Behavior of Biomedical Materials, 115, 104284.
He, X., Avril, S., & Lu, J. (2021). Estimating aortic thoracic aneurysm rupture risk using tension–strain data in physiological pressure range: an in vitro study. Biomechanics and Modeling in Mechanobiology, 20(2), 683-699.
He, X., Avril, S., & Lu, J. (2019). Machine learning prediction of tissue Strength and local Rupture risk in Ascending thoracic Aortic Aneurysms. Molecular & Cellular Biomechanics, 16(S2): 50 -52.
Constitutive Modeling of Vascular Tissue considering collagen recruitment
Our data-driven approaches imply that patterns observed during the transitional phase of response can be exploited to evaluate the rupture risk in aortic aneurysms. The transitional phase arises due to the gradual recruitment of crimped collagen fibers. In our work, we introduced an ‘effective stretch’ to account for collagen recruitment. It is a continuum-scale kinematic variable measuring, in an average sense, the uncrimped stretch of collagen fibers at the tissue level. In light of the effective stretch, we developed a family of constitutive models to describe the uniaxial and biaxial responses of vascular tissue. The models demonstrate excellent descriptive and predictive capabilities
Related Publications
Lu, J., & He, X. (2021). Incorporating fiber recruitment in hyperelastic modeling of vascular tissues by means of kinematic average. Biomech Model Mechanobiol, 20(5), 1833-1850
He, X., & Lu, J. (2022). Modeling planar response of vascular tissues using quadratic functions of effective strain. International Journal for Numerical Methods in Biomedical Engineering, e3653.
He, X., & Lu, J. (2022). Explicit consideration of fiber recruitment in vascular constitutive formulation using beta functions. Journal of the Mechanics and Physics of Solids, 163, 104837.
A strain based rupture metric for ATAA that emphasizes micro-structural connection
We advocated the use of effective strain in ATAA rupture assessment. The effective strain is a measure of net strain in the collagen network after waviness uncrimping. We analyzed bulge inflation data of ATAA samples. It was found that, while the total strains at rupture varied from sample to sample, the effective strains were closely clustered around 0.1. And the hotspots of effective strain matched the rupture sites well. The work underlines the importance of considering collagen fiber waviness and recruitment when evaluating the rupture risk using strain and suggests a new direction for developing sharper rupture metrics
Related Publications
He, X., Auricchio, F., Morganti, S., & Lu, J. (2021). Uniaxial properties of ascending aortic aneurysms in light of effective stretch. Acta Biomaterialia, 136, 306-313.
He, X., & Lu, J. (2022). On strain-based rupture criterion for ascending aortic aneurysm: The role of fiber waviness. Acta biomaterialia, 149, 51-59.
Patient-specific assessment of aortic wall growth and diseases
We developed computational methods to estimate in-vivo stiffness of aortic wall directly from dynamic CTA using a modified version of the Vascular Deformation Mapping (VDM) technique. More will come
Related Publications
- Kim, T.; Tjahjadi, N.S.; He, X.; van Herwaarden, J.; Patel, H.J.; Burris, N.S.; Figueroa, C.A. Three-Dimensional Characterization of Aortic Root Motion by Vascular Deformation Mapping. J. Clin. Med. 2023,
Modeling of the Interaction between Colon and Colonoscope during a Colonoscopy
We simulated the insertion process of colonoscopes in colon models via ANSYS-LSDYNA. An uni-axial tension test was carried out to provide the mechanical properties of a porcine colon. The model developed in this project serves as a starting point in understanding the efficacy of Small colonoscopes in reducing patient pain considering the effects of patient characteristics, including gender, age, and region.
Related Publications
Zhou, D., & He, X. (2019). Numerical evaluation of the efficacy of small-caliber colonoscopes in reducing patient pain during a colonoscopy. Computer methods in biomechanics and biomedical engineering, 22(1), 38-46.
He, X., Bai, J., & Zhou, D. (2019). Numerical Evaluation of the Performance Efficiency of Small-Caliber Colonoscopes in Reducing Patient Pain during a Colonoscopy: Influence of Gender. International Journal of Pharma Medicine and Biological Sciences, 8(2), 28-33.