A Method to Design Custom-Fit Stent Graft for Abdominal Aortic Aneurism

2015 ◽  
Author(s):  
Giorgio Colombo ◽  
Simone Bartesaghi ◽  
Eduardo Pallares
Keyword(s):  
Stent Graft ◽  
Cross Sections ◽  
Cfd Simulation ◽  
Design Method ◽  
Geometric Model ◽  
Endovascular Aneurysm Repair ◽  
Specific Patient ◽  
Aorta Aneurysm ◽  
Optimal Behavior ◽  
Geometric Data

Abdominal Aorta Aneurysm (AAA) affects aorta, especially above the iliac bifurcation where the Wall Shear Stress (WSS) is greater. Consequence may be fatal in case of breakage; a way to treat it is Endovascular Aneurysm Repair (EVAR) where a stent graft is placed inside the aorta without open surgery requirement. Because of the standards, stent graft can be chosen between several sizes: in some cases, this device cannot fit perfectly with the anatomy of the patient and this can lead to a not optimal behavior of the prosthesis and further complications. This study present a method to design and test specific custom-fit stent graft able to better adapt to the patient artery improving the efficiency of the prosthesis and reducing the risk of the migration of the graft as well as the fabric torn. The design method is based on a 3D geometric model of the aorta, generated from CT scan data. Centrelines and geometric data for cross sections along the aorta are the inputs necessary to define the mesh of the stent. A custom algorithm is developed to size the stent in relation to the geometric data of the specific patient; when the frame of the prosthesis is defined, a CAD-based Loft Surface has used to define surfaces between the stent rings. For the bifurcation, again CAD-based Boundary Surfaces is used. The described procedure has been also applied in a Augmented Virtual Reality simulation of the EVAR and, finally, it permits a CFD simulation to evaluate the behavior of the prosthesis inserted into the aorta.

scholarly journals Lightweight and maintainable rotary-wing UAV frame from configurable design to detailed design

2021 ◽  
Vol 13 (7) ◽  
pp. 168781402110349
Author(s):  
Huiqiang Guo ◽  
Mingzhe Li ◽  
Pengfei Sun ◽  
Changfeng Zhao ◽  
Wenjie Zuo ◽  
...  
Keyword(s):  
Design Method ◽  
Geometric Model ◽  
Optimization Method ◽  
Frame Structure ◽  
Manufacturing Cost ◽  
Detailed Design ◽  
High Manufacturing Cost ◽  
The Military ◽  
Rotary Wing ◽  
Novel Design

Rotary-wing unmanned aerial vehicles (UAVs) are widespread in both the military and civilian applications. However, there are still some problems for the UAV design such as the long design period, high manufacturing cost, and difficulty in maintenance. Therefore, this paper proposes a novel design method to obtain a lightweight and maintainable UAV frame from configurable design to detailed design. First, configurable design is implemented to determine the initial design domain of the UAV frame. Second, topology optimization method based on inertia relief theory is used to transform the initial geometric model into the UAV frame structure. Third, process design is considered to improve the manufacturability and maintainability of the UAV frame. Finally, dynamic drop test is used to validate the crashworthiness of the UAV frame. Therefore, a lightweight UAV frame structure composed of thin-walled parts can be obtained and the design period can be greatly reduced via the proposed method.

scholarly journals Simulation of Hydraulic Cylinder Cushioning

2021 ◽  
Vol 13 (2) ◽  
pp. 494
Author(s):  
Antonio Algar ◽  
Javier Freire ◽  
Robert Castilla ◽  
Esteban Codina
Keyword(s):  
Dynamic Model ◽  
Cfd Simulation ◽  
Fluid Dynamic ◽  
Computational Fluid Dynamic Simulation ◽  
Hydraulic Cylinder ◽  
Outlet Port ◽  
Optimal Behavior ◽  
Radial Movement ◽  
Mechanical Shocks ◽  
Radial Gap

The internal cushioning systems of hydraulic linear actuators avoid mechanical shocks at the end of their stroke. The design where the piston with perimeter grooves regulates the flow by standing in front of the outlet port has been investigated. First, a bond graph dynamic model has been developed, including the flow throughout the internal cushion design, characterized in detail by computational fluid-dynamic simulation. Following this, the radial movement of the piston and the fluid-dynamic coefficients, experimentally validated, are integrated into the dynamic model. The registered radial movement is in coherence with the significant drag force estimated in the CFD simulation, generated by the flow through the grooves, where the laminar flow regime predominates. Ultimately, the model aims to predict the behavior of the cushioning during the movement of the arm of an excavator. The analytical model developed predicts the performance of the cushioning system, in coherence with empirical results. There is an optimal behavior, highly influenced by the mechanical stress conditions of the system, subject to a compromise between an increasing section of the grooves and an optimization of the radial gap.

Endoleaks: current concepts and treatments

2021 ◽  
Author(s):  
Zia Ur Rehman
Keyword(s):  
Stent Graft ◽  
Treatment Options ◽  
Endovascular Aneurysm Repair ◽  
Aneurysm Rupture ◽  
Special Situation ◽  
Type V ◽  
Aneurysm Repair ◽  
Benign Course ◽  
Selection Of

Endoleaks are the most common complications following endovascular aneurysm repair. Depending upon their origin, there are five types of endoleaks, types I-V, which can also be classified as direct and indirect endoleaks. Direct endoleaks type 1 and III have higher risk of aneurysm rupture due to rapid sac expansion, and require immediate correction.  Indirect endoleaks types II, IV and V have a relatively benign course compared to direct endoleaks. Most of them resolve with time and very few of them need interventions upon sac enlargement. Type V endotension is a special situation where there is sac enlargement despite no demonstrable endoleak. Proper planning and appropriate selection of stent-graft can prevent most of these endoleaks. With improvement in stent-graft technology, the incidence of endoleaks has been reduced. The current narrative review was planned to describe the pathophysiology, risk factors and treatment options for each type of endoleak. Continuous...

scholarly journals Endovascular Aneurysm Sealing of a Collapsed and Thrombosed Aortic Stent-Graft With Renovisceral Chimney Stent-Grafts

2018 ◽  
Vol 26 (1) ◽  
pp. 72-75
Author(s):  
Fabien Lareyre ◽  
Claude Mialhe ◽  
Carine Dommerc ◽  
Juliette Raffort
Keyword(s):  
Stent Graft ◽  
Mesenteric Artery ◽  
Endovascular Aneurysm Repair ◽  
Stent Grafts ◽  
Aortic Thrombosis ◽  
Aortic Stent Graft ◽  
Aneurysm Repair ◽  
Stent Graft Implantation ◽  
Graft Implantation

Purpose: To report the use of the Nellix endovascular aneurysm sealing (EVAS) system in the management of proximal stent-graft collapse associated with thrombosis following endovascular aneurysm repair (EVAR). Case Report: A 76-year-old man was admitted for proximal collapse of an aortic extension following bifurcated AFX stent-graft implantation associated with chimney grafts in both renal arteries and the superior mesenteric artery 1 month prior. Imaging identified thrombosis of the aortic stent-graft and the iliac limbs. A Nellix EVAS was placed into the AFX stent-graft to recanalize the aneurysm lumen and address the aortic thrombosis. There was no endoleak, and the renovisceral chimney stent-grafts remained patent over a follow-up of 25 months. Conclusion: While further studies are required to generalize its use, EVAS appears to be feasible in the management of aortic stent-graft collapse.

Lactation in the Human Breast From a Fluid Dynamics Point of View

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
S. Negin Mortazavi ◽  
Donna Geddes ◽  
Fatemeh Hassanipour
Keyword(s):  
Fluid Dynamics ◽  
Clinical Data ◽  
Flow Rate ◽  
Cfd Simulation ◽  
Geometric Model ◽  
Milk Intake ◽  
Vacuum Pressure ◽  
Cfd Modeling ◽  
Human Breast ◽  
Milk Flow

This study is a collaborative effort among lactation specialists and fluid dynamic engineers. The paper presents clinical results for suckling pressure pattern in lactating human breast as well as a 3D computational fluid dynamics (CFD) modeling of milk flow using these clinical inputs. The investigation starts with a careful, statistically representative measurement of suckling vacuum pressure, milk flow rate, and milk intake in a group of infants. The results from clinical data show that suckling action does not occur with constant suckling rate but changes in a rhythmic manner for infants. These pressure profiles are then used as the boundary condition for the CFD study using commercial ansys fluent software. For the geometric model of the ductal system of the human breast, this work takes advantage of a recent advance in the development of a validated phantom that has been produced as a ground truth for the imaging applications for the breast. The geometric model is introduced into CFD simulations with the aforementioned boundary conditions. The results for milk intake from the CFD simulation and clinical data were compared and cross validated. Also, the variation of milk intake versus suckling pressure are presented and analyzed. Both the clinical and CFD simulation show that the maximum milk flow rate is not related to the largest vacuum pressure or longest feeding duration indicating other factors influence the milk intake by infants.

scholarly journals Endovascular repair of aortic aneurysm: Preliminary results

2009 ◽  
Vol 137 (1-2) ◽  
pp. 10-17 ◽  
Author(s):  
Lazar Davidovic ◽  
Momcilo Colic ◽  
Igor Koncar ◽  
Dejan Markovic ◽  
Dusan Kostic ◽  
...  
Keyword(s):  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Stent Graft ◽  
Endovascular Aneurysm Repair ◽  
Aortic Aneurysms ◽  
Endovascular Stent ◽  
Stent Grafts ◽  
Graft Thrombosis ◽  
Abdominal Aortic

Introduction. Endovascular aneurysm repair (EVAR) has been introduced into clinical practice at the beginning of the 90's of the last century. Because of economic, political and social problems during the last 25 years, the introduction of this procedure in Serbia was not possible. Objective. The aim of this study was to present preliminary experiences and results of the Clinic for Vascular Surgery of the Serbian Clinical Centre in Belgrade in endovascular treatment of thoracic and abdominal aortic aneurysms. Methods. The procedure was performed in 33 patients (3 female and 30 male), aged from 42 to 83 years. Ten patients had a descending thoracic aorta aneurysm (three atherosclerotic, four traumatic - three chronic and one acute as a part of polytrauma, one dissected, two penetrated atherosclerotic ulcers), while 23 patients had the abdominal aortic aneurysm, one ruptured and two isolated iliac artery aneurysms. The indications for EVAR were isthmic aneurismal localisation, aged over 80 years and associated comorbidity (cardiac, pulmonary and cerebrovasular diseases, previous thoracotomy or multiple laparotomies associated with abdominal infection, idiopatic thrombocitopaenia). All of these patients had three or more risk factors. The diagnosis was established using duplex ultrasonography, angiography and MSCT. In the case of thoracic aneurysm, a Medtronic-Valiant? endovascular stent graft was implanted, while for the abdominal aortic aneurysm Medtronic-Talent? endovascular stent grafts with delivery systems were used. In three patients, following EVAR a surgical repair of the femoral artery aneurysm was performed, and in another three patients femoro-femoral cross over bypass followed implantation of aortouniiliac stent graft. Results. During procedure and follow-up period (mean 1.6 years), there were: one death, one conversion, one endoleak type 1, six patients with endoleak type 2 that disappeared during the follow-up period, one early graft thrombosis. No other complications, including aneurysm expansion, collapse, deformity and migration of the endovascular stent grafts, were registered. Conclusion. According to all medical and economic aspects, we recommend EVAR to treat acute traumatic thoracic aortic aneurysm, as well as in elderly and high-risk patients with abdominal or thoracic aneurysms, when open surgery is related to a significantly higher mortality and morbidity.

Cide-A Gene Expression in Patients with Obesity Qualified for Endovascular Treatment of Abdominal Aorta Aneurysm

2015 ◽  
Vol 86 (10) ◽  
Author(s):  
Marcin Feldo ◽  
Janusz Kocki ◽  
Jan Feldo ◽  
Sylwia Łukasik ◽  
Jacek Bogucki ◽  
...  
Keyword(s):  
Gene Expression ◽  
Endovascular Aneurysm Repair ◽  
The Body ◽  
Control Group ◽  
Study Group ◽  
Aorta Aneurysm ◽  
Group Play ◽  
Aneurysm Repair ◽  
Adipose Tissue Cells

Abstractgene and the genes of LRP group play a key role in the regulation of the body weight and lipid metabolism in mammals.was to define the role of. The study group consisted of 38 subjects, including 27 men and 11 women qualified for endovascular aneurysm repair (EVAR). The subjects with abdominal aortic aneurysm were enrolled in the study group, depending on the body mass index (BMI); in obese patients (BMI > 30). The control group (n = 16) included subjects without lipid disorders. One-step isolation of RNA from lymphocytes and adipose tissue cells was performed using the modified TRI method by Chomc-zynski and Sacchi, and then the gene expression was tested by real-time PCR.. The highest mean relative of the gene expression for. Due to the important role of the

Incomplete Expansion of Chimney Stent Graft during Chimney-Thoracic Endovascular Aneurysm Repair

2017 ◽  
Vol 39 ◽  
pp. 293.e1-293.e5 ◽  
Author(s):  
Athanasios Katsargyris ◽  
Domenico Spinelli ◽  
Kyriakos Oikonomou ◽  
Hozan Mufty ◽  
Eric LG. Verhoeven
Keyword(s):  
Stent Graft ◽  
Endovascular Aneurysm Repair ◽  
Thoracic Endovascular Aneurysm Repair ◽  
Aneurysm Repair
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