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Efficiently Simulating an Endograft Deployment: A Methodology for Detailed CFD Analyses.

ABSTRACT: Numerical models of endografts for the simulation of endovascular aneurysm repair are increasingly important in the improvement of device designs and patient outcomes. Nevertheless, current finite element analysis (FEA) models of complete endograft devices come at a high computational cost, requiring days of runtime, therefore restricting their applicability. In the current study, an efficient FEA model of the Anaconda™ endograft (Terumo Aortic, UK) was developed, able to yield results in just over 4 h, an order of magnitude less than similar models found in the literature. The model was used to replicate a physical device that was deployed in a 3D printed aorta and comparison of the two shapes illustrated a less than 5 mm placement error of the model in the regions of interest, consistent with other more computationally intensive models in the literature. Furthermore, the final goal of the study was to utilize the deployed fabric model in a hemodynamic analysis that would incorporate realistic fabric folds, a feature that is almost always omitted in similar simulations. By successfully exporting the deployed graft geometry into a flow analysis, it was illustrated that the inclusion of fabric wrinkles enabled clinically significant flow patterns such as flow stagnation and recirculation to be detected, paving the way for this modelling methodology to be used in future for stent design optimisation.

SUBMITTER: Kyriakou F

PROVIDER: S-EPMC7505889 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature

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Efficiently Simulating an Endograft Deployment: A Methodology for Detailed CFD Analyses.

Kyriakou Faidon F Maclean Craig C Dempster William W Nash David D

Annals of biomedical engineering 20200511 10

Numerical models of endografts for the simulation of endovascular aneurysm repair are increasingly important in the improvement of device designs and patient outcomes. Nevertheless, current finite element analysis (FEA) models of complete endograft devices come at a high computational cost, requiring days of runtime, therefore restricting their applicability. In the current study, an efficient FEA model of the Anaconda™ endograft (Terumo Aortic, UK) was developed, able to yield results in just o ...[more]

PMID: 32394221

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Project description:IntroductionThe first live birth after uterus transplantation occurred in Sweden in 2014. Uterus transplantation has repeatedly, and at many centers worldwide, proven to be a feasible treatment for absolute uterine factor infertility. Hysterectomy in live donors and transplantation are well described in numerous reports. However, there are no reports of hysterectomy in the recipient after uterus transplantation, which will occur at either graft failure, after childbirth, or after numerous failed pregnancy attempts. We present the first report of hysterectomy in recipients after uterus transplantation with detailed analyses of findings in conjunction with graft failures.Material and methodsAn analysis of recipient hysterectomies (n = 10), performed in 2012-2020, was conducted. Data from the international uterus transplantation registry (ISUTx registry) were extracted, and medical records were systematically reviewed, to collect and compile characteristics of recipients and donors, as well as pre-, per-, and postoperative data, including clinical course of graft failures.ResultsHysterectomy in recipients was performed in conjunction with cesarean section (n = 3), 3-6 months after cesarean section (n = 3), or after failed pregnancy attempts (n = 1) or graft failure (n = 3). The durations of anesthesia (2 h 36 min to 7 h 35 min) and hysterectomy surgery (1 h 42 min to 5 h 52 min) ranged widely, with long perioperative interruptions for insertion of ureteral catheters in two cases. Adhesions to the uterus were abundant, the majority being mild. Three uteri that subsequently showed graft failure (hysterectomy at 1, 3, and 8 months post transplantation) showed histological signs of ischemia in biopsies taken 1-week post-transplant and early signs of central hypoperfusion by Doppler ultrasound. In these graft failure explants, there were no epithelial linings in the uterine cavity or in the cervix. The inner uterine wall was severely ischemic and/or necrotic, whereas outer parts were partly viable. There were signs of moderate atherosclerosis of uterine arteries but no rejection. Mild postoperative complications were frequent (6/10), with one supravaginal hematoma requiring surgical drainage.ConclusionsHysterectomy after uterus transplantation is a complex and time-consuming procedure, and perioperative ureteral catheters may be helpful. Histopathology of early cervical biopsies showing ischemic signs may indicate subsequent irreversible damage, leading to graft failure.

Project description:Existing in vivo experiments show significantly decreased acrolein uptake in rats with increasing inhaled acrolein concentrations. Considering that high-polarity chemicals are prone to bond with each other, it is hypothesized that molecular binding between acrolein and water will contribute to the experimentally observed deposition decrease by decreasing the effective diffusivity. The objective of this study is to quantify the probability of molecular binding for acrolein, as well as its effects on acrolein deposition, using multiscale simulations. An image-based rat airway geometry was used to predict the transport and deposition of acrolein using the chemical species model. The low Reynolds number turbulence model was used to simulate the airflows. Molecular dynamic (MD) simulations were used to study the molecular binding of acrolein in different media and at different acrolein concentrations. MD results show that significant molecular binding can happen between acrolein and water molecules in human and rat airways. With 72 acrolein embedded in 800 water molecules, about 48% of acrolein compounds contain one hydrogen bond and 10% contain two hydrogen bonds, which agreed favorably with previous MD results. The percentage of hydrogen-bonded acrolein compounds is higher at higher acrolein concentrations or in a medium with higher polarity. Computational dosimetry results show that the size increase caused by the molecular binding reduces the effective diffusivity of acrolein and lowers the chemical deposition onto the airway surfaces. This result is consistent with the experimentally observed deposition decrease at higher concentrations. However, this size increase can only explain part of the concentration-dependent variation of the acrolein uptake and acts as a concurrent mechanism with the uptake-limiting tissue ration rate. Intermolecular interactions and associated variation in diffusivity should be considered in future dosimetry modeling of high-polarity chemicals such as acrolein.

Dataset Information

Efficiently Simulating an Endograft Deployment: A Methodology for Detailed CFD Analyses.

Publications

Efficiently Simulating an Endograft Deployment: A Methodology for Detailed CFD Analyses.

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