Constitutive modeling of the passive inflation-extension behavior of the swine colon

Patel, Bhavesh; Chen, Huan; Ahuja, Aashish; Krieger, Joshua; Noblet, Jillian N.; Chambers, Sean; Kassab, Ghassan S.

doi:10.1016/j.jmbbm.2017.08.031

Cited by 26 publications

(19 citation statements)

References 28 publications

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“…Geometrical and material properties of swine descending colon tissues were used for the models. In our previous study of swine tissue behavior, we established the first anisotropic material constitutive model for the descending swine colon based on simultaneous inflation and extension tests 15 . This material constitutive model was used in the simulations.…”

Section: Resultsmentioning

confidence: 99%

“…All simulations were performed on a Dell Workstation T7810 with two Intel Xeon processors and 32 GBytes of memory. In our previous study of swine tissue behavior, we established an anisotropic material constitutive model for the descending and spiral regions of the swine colon based on simultaneous inflation and extension tests 15 . This model has been shown in several previous studies to capture adequately the anisotropic behavior of the colon 19,[34][35][36] .…”

Section: Discussionmentioning

confidence: 99%

“…Boundary conditions. The boundary conditions were imposed based on our previous study of swine colon 15 .…”

Section: Discussionmentioning

confidence: 99%

“…Material parameters used in the computational model. They were established in a previous study for five swine descending colon samples15 .…”

mentioning

confidence: 99%

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Computational analysis of mechanical stress in colonic diverticulosis

Patel

Guo

Noblet

et al. 2020

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Diverticulosis results from the development of pouch-like structures, called diverticula, over the colon. The etiology of the disease is poorly understood resulting in a lack of effective treatment approaches. It is well known that mechanical stress plays a major role in tissue remodeling, yet its role in diverticulosis has not been studied. Here, we used computational mechanics to investigate changes in stress distribution engendered over the colon tissue by the presence of a pouch-like structure. the objectives of the study were twofold: (1) observe how stress distribution changes around a single pouch and (2) evaluate how stress elevation correlates with the size of the pouch. Results showed that high stresses are concentrated around the neck of a pouch, and their values and propagation increase with the size of the pouch neck rather than the pouch surface area. These findings suggest that stress distribution may change in diverticulosis and a vicious cycle may occur where pouch size increases due to stress elevation, which in turn elevates stress further and so on. Significant luminal pressure reduction would be necessary to maintain stress at normal level according to our results and therapeutic approaches aimed directly at reducing stress should rather be sought after.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Computational analysis of mechanical stress in colonic diverticulosis

Patel

Guo

Noblet

et al. 2020

Sci Rep

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“…The present study created artificial dissections in porcine aortas, conducted planar biaxial testing on tissue segments from different regions and then used a novel non-linear regression modeling interface to fit the five parameter HGO model for hyperelastic materials against measured data. The constitutive modeling for soft tissues has been widely utilized to understand its mechanical response and perform computational modeling for developing virtual therapies for treating diseases (Raghavan and Vorp, 2000 ; Holzapfel et al, 2004 ; Speelman et al, 2009 ; Patel et al, 2018 ). The algorithm introduced in this study utilized data from various protocols (i.e., 1:1, 1:1.5, 1:2, 1.5:1, 2:1) to develop an enriched HGO constitutive model relation that was trained on larger data set for achieving higher stress-stretch predictive capabilities (Table 1 ).…”

Section: Discussionmentioning

confidence: 99%

Biomechanical Material Characterization of Stanford Type-B Dissected Porcine Aortas

et al. 2018

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Aortic dissection (AD) involves tearing of the medial layer, creating a blood-filled channel called false lumen (FL). To treat dissections, clinicians are using endovascular therapy using stent grafts to seal the FL. This procedure has been successful in reducing mortality but has failed in completely re-attaching the torn intimal layer. The use of computational analysis can predict the radial forces needed to devise stents that can treat ADs. To quantify the hyperelastic material behavior for therapy development, we harvested FL wall, true lumen (TL) wall, and intimal flap from the middle and distal part of five dissected aortas. Planar biaxial testing using multiple stretch protocols were conducted on tissue samples to quantify their deformation behavior. A novel non-linear regression model was used to fit data against Holzapfel–Gasser–Ogden hyperelastic strain energy function. The fitting analysis correlated the behavior of the FL and TL walls and the intimal flap to the stiffness observed during tensile loading. It was hypothesized that there is a variability in the stresses generated during loading among tissue specimens derived from different regions of the dissected aorta and hence, one should use region-specific material models when simulating type-B AD. From the data on material behavior analysis, the variability in the tissue specimens harvested from pigs was tabulated using stress and coefficient of variation (CV). The material response curves also compared the changes in compliance observed in the FL wall, TL wall, and intimal flap for middle and distal regions of the dissection. It was observed that for small stretch ratios, all the tissue specimens behaved isotropically with overlapping stress–stretch curves in both circumferential and axial directions. As the stretch ratios increased, we observed that most tissue specimens displayed different structural behaviors in axial and circumferential directions. This observation was very apparent in tissue specimens from mid FL region, less apparent in mid TL, distal FL, and distal flap tissues and least noticeable in tissue specimens harvested from mid flap. Lastly, using mixed model ANOVAS, it was concluded that there were significant differences between mid and distal regions along axial direction which were absent in the circumferential direction.

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