scholarly journals The Fluid-Dynamics of Endo Vascular Aneurysm Sealing (EVAS) System failure

2021 ◽  
Author(s):  
F. Battista ◽  
R. Ficarelli ◽  
A. Perrotta ◽  
P. Gualtieri ◽  
C. M. Casciola ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Fluid Mechanics ◽  
Velocity Fields ◽  
The Other ◽  
Recirculation Region ◽  
Computational Fluid Mechanics ◽  
Pressure Gradients ◽  
Pressure Drops ◽  
Flow Recirculation ◽  
Before And After

Abstract Purpose The main objective of this work is to investigate hemodynamics phenomena occurring in EVAS (Endo Vascular Aneurysm Sealing), to understand if and how they could lead to type 1a endoleaks and following re-intervention. To this aim, methods based on computational fluid mechanics are implemented as a tool for checking the behavior of a specific EVAS configuration, starting from the post-operative conditions. Pressure and velocity fields are detailed and compared, for two configurations of the Nellix, one as attained after correct implantation and the other in pathological conditions, as a consequence of migration or dislocation of endobags. Methods The computational fluid dynamics (CFD) approach is used to simulate the behavior of blood within a segment of the aorta, before and after the abdominal bifurcation. The adopted procedure allows reconstructing the detailed vascular geometry from high-resolution computerized tomography (CT scan) and generating the mesh on which the equations of fluid mechanics are discretized and solved, in order to derive pressure and velocity field during heartbeats. Results The main results are obtained in terms of local velocity fields and wall pressures. Within the endobags, velocities are usually quite regular during the whole cardiac cycle for the post-implanted condition, whereas they are more irregular for the migrated case. The largest differences among the two cases are observed in the shape and location of the recirculation region in the rear part of the aorta and the region between the endobags, with the formation of a gap due to the migration of one or both of the two. In this gap, the pressure fields are highly different among the two conditions, showing pressure peaks and pressure gradients at least four times larger for the migrated case in comparison to the post-implanted condition. Conclusions In this paper, the migration of one or both endobags is supposed to be related to the existing differential pressures acting in the gap formed between the two, which could go on pushing the two branches one away from the other, thus causing aneurysm re-activation and endoleaks. Regions of flow recirculation and low-pressure drops are revealed only in case of endobag migration and in presence of an aneurysm. These regions are supposed to lead to possible plaque formation and atherosclerosis.

Cognitive apprenticeship and T-shaped instructional design in computational fluid mechanics: Student perspectives on learning

2020 ◽  
pp. 030641902091572
Author(s):  
Sónia IS Pinto ◽  
Susan M Zvacek
Keyword(s):  
Fluid Mechanics ◽  
Cognitive Apprenticeship ◽  
Student Perspectives ◽  
Theory And Practice ◽  
Learning Theories ◽  
Computational Fluid Mechanics ◽  
Education Theory ◽  
Before And After ◽  
Development Course ◽  
Previous Iteration

The goal of the present work was to explore student perspectives about a course module designed with cognitivist and constructivist learning theories, the cognitive apprenticeship instructional model, and a T-shaped design, specifically the first module of a Computational Fluid Mechanics curricular unit within a Master of Computational Mechanics program. This module was redesigned accordingly after the professor participated in a faculty development course, Engineering Education Theory and Practice, at the Faculty of Engineering, University of Porto. Student perspectives on the efficacy of the redesigned course were solicited, along with those from students who had previously taken the course. Students who participated in the revised course module reported higher levels of satisfaction than students from the previous iteration of the course and were more likely to recognize the value of specific instructional activities. This paper describes the revision of the course module and a comparison of the student feedback before and after those revisions.

Computational Fluid Dynamics Simulation of Airflow Alteration in the Trachea Before and After Vascular Ring Surgery

2013 ◽  
Author(s):  
Tzu-Ching Shih ◽  
Tzyy-Leng Horng ◽  
Fong-Lin Chen
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Vascular Ring ◽  
Dynamics Simulation ◽  
Positive Pressure ◽  
Local Pressure ◽  
Pressure Drops ◽  
Vascular Rings ◽  
Before And After ◽  
Key Factor

Vascular rings, congenital intracardic anomalies of the aortic arch and the vessels emerging from the heart, completely encircle the trachea and esophagus [1]. The vascular ring results in narrowing and obstruction of the trachea and the esophagus. Due to the existence of a complete or partial vascular ring compressing either the trachea or esophagus, symptoms of a vascular ring in children include cough, stridor, chronic cough, dysphagia, persistent wheeze, and noisy breathing [2]. Some studies reported that the vascular ring surgery provides an excellent chance to improve the patient respiration conditions, especially for relief of symptoms [1–3]. Al-Bassam et al. reported that the thoracoscopic division of vascular rings in infants and children is a safe and effective surgery rather than an open thoracotomy[4]. Even after the treatment of a surgical division of the vascular ring, however, the fixed obstruction is relieved but the patient continues to have dynamic collapse because the compressed trachea segment is always malacic. Airway resistance to flow in the airway, thus, is a key factor for not only clinical diagnosis severity assessment but also therapeutic decision in tracheal stenosis. Furthermore, Malvè et al. (2011) utilized the finite element-based commercial software code (ADINA R&D Inc.) to model the fluid structure interaction of a human trachea under different ventilation conditions [5]. They also found that the positive pressure in the trachea does not result in the airway collapse during the time period of mechanical breathing. Therefore, the purpose of this study is to use the computational fluid dynamics (CFD) technique to calculate the local pressure drops in the tracheal segment for different inspiratory and expiratory flow rates due to preoperative and preoperative vascular ring surgery.

C. The Continuous Spectrum of Pulsating Variable Stars

1967 ◽  
Vol 28 ◽  
pp. 177-206
Author(s):  
J. B. Oke ◽  
C. A. Whitney
Keyword(s):  
Continuous Spectrum ◽  
Variable Stars ◽  
Velocity Fields ◽  
The Other ◽  
Line Spectrum ◽  
Direct Information ◽  
Thermodynamic Structure ◽  
Diagnostic Interpretation ◽  
Pulsating Variable Stars ◽  
The Continuum

Pecker:The topic to be considered today is the continuous spectrum of certain stars, whose variability we attribute to a pulsation of some part of their structure. Obviously, this continuous spectrum provides a test of the pulsation theory to the extent that the continuum is completely and accurately observed and that we can analyse it to infer the structure of the star producing it. The continuum is one of the two possible spectral observations; the other is the line spectrum. It is obvious that from studies of the continuum alone, we obtain no direct information on the velocity fields in the star. We obtain information only on the thermodynamic structure of the photospheric layers of these stars–the photospheric layers being defined as those from which the observed continuum directly arises. So the problems arising in a study of the continuum are of two general kinds: completeness of observation, and adequacy of diagnostic interpretation. I will make a few comments on these, then turn the meeting over to Oke and Whitney.

Some uses of direct solvers in computational fluid mechanics

1987 ◽  
Author(s):  
HARRY DWYER ◽  
KENICHI MATSUMO ◽  
SOKOL IBRANI ◽  
M. HAFEZ
Keyword(s):  
Fluid Mechanics ◽  
Computational Fluid Mechanics ◽  
Direct Solvers

Arthroscopy in Arthrosis: Is It Worth it? A case Presentation

2018 ◽  
Vol 69 (8) ◽  
pp. 2232-2235
Author(s):  
Marius Moga ◽  
Mark Edward Pogarasteanu ◽  
Antoine Edu
Keyword(s):  
Clinical Status ◽  
Loose Body ◽  
Point Of View ◽  
The Other ◽  
Joint Range Of Motion ◽  
Objective Evidence ◽  
Before And After ◽  
Total Knee ◽  
Joint Range

The role of arthroscopy in incipient and mild arthrosis, even combined with proximal tibial ostetomy, is well known and well documented. On the other hand, its role in the treatment of advanced arthrosis of the large joints, especially the knee, is a subject of controversy. The proponents of the use of arthroscopy in advanced arthrosis claim that meniscectomy, synovectomy, ostophytectomy, chondral lesion stabilization, arthroscopic release, plica and loose body removal greatly improve the quality of life for most patients, especially if followed by the use of viscoelastic injection, by diminishing pain and improving joint range of motion. The opponents claim that, even though the advantages are clear in the cases that refuse arthroplasty, in all the other cases the surgical indication should be total knee arthroplasty, as the clinical relief is temporary, but with all the risks of a surgical intervention. We have conducted an overview of the recent literature, in order to find objective evidence to sustain either point of view. We focused on articles published that included an objective measurement of before and after clinical status through clinical scores and objective measurements. We also focused on the follow-up period and on the evolution of the pathology after arthroscopy.

Antimicrobial Effect of 940 nm Diode Laser based on Photolysis of Hydrogen Peroxide in the Treatment of Periodontal Disease

2018 ◽  
Vol 69 (8) ◽  
pp. 2081-2088 ◽  
Author(s):  
Alin Alexandru Odor ◽  
Edwin Sever Bechir ◽  
Deborah Violant ◽  
Victoria Badea
Keyword(s):  
Hydrogen Peroxide ◽  
Laser Therapy ◽  
Diode Laser ◽  
Antimicrobial Effect ◽  
The Other ◽  
Control Group ◽  
Group 4 ◽  
Periodontal Bacteria ◽  
Severe Periodontitis ◽  
Before And After

Moderate and severe periodontitis represents a challenge in the non-surgical periodontal therapy. Due to the lack of evidence regarding the antimicrobial effectiveness of 940 nm diode laser in periodontal treatment, this study aimed to evaluate the antimicrobial effect of hydrogen peroxide (H2O2) photolysis performed with 940 nm diode laser in the treatment of moderate and severe periodontitis. Twenty-five patients with 100 teeth were selected for this pilot study. The test teeth were randomly assigned to one of the four treatment groups: Group 1: scaling and root planning (SRP) (control group); and the following experimental groups: Group 2: H2O2; Group 3: 940 nm diode laser therapy; Group 4: 940 nm diode laser therapy and H2O2. Clinical examinations, like probing depth (PD), clinical attachment level (CAL) and bleeding on probing (BOP) were performed before and after the treatment. The microbiological evaluation, effectuated before and after the treatment, included nine periodontal bacteria species and investigated by means of real-time PCR assay. The clinical and bacterial differences in the tested groups, was assessed between control group and the other three experimental groups, as well as between the experimental groups. The total bacteria load was reduced for all four studied groups. Group 4 (diode laser + H2O2) showed significant bacterial reduction of the major periodontal bacteria like Pg., Tf., Td., Pi., Pm., Fn (p[0.001) than the other 3 groups (p]0.001). Also the periodontal clinical parameters, like PD, CAL and BOP showed a significant reduction after the photolysis of H2O2 with the 940 nm diode laser (p[0.001). Differences between tested groups showed a significant beneficial results in regard to Group 4.It is suggested that the photoactivation of H2O2 with the 940 nm diode laser can be used successfully in adjunctive to the non-surgical periodontal treatment as a bactericidal tool.

scholarly journals Enhancement of cerebrovascular 4D flow MRI velocity fields using machine learning and computational fluid dynamics simulation data

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
David R. Rutkowski ◽  
Alejandro Roldán-Alzate ◽  
Kevin M. Johnson
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Velocity Fields ◽  
Dynamics Simulation ◽  
Patient Specific ◽  
4D Flow Mri ◽  
4D Flow ◽  
Flow Phase ◽  
Flow Mri ◽  
Trained Network

AbstractBlood flow metrics obtained with four-dimensional (4D) flow phase contrast (PC) magnetic resonance imaging (MRI) can be of great value in clinical and experimental cerebrovascular analysis. However, limitations in both quantitative and qualitative analyses can result from errors inherent to PC MRI. One method that excels in creating low-error, physics-based, velocity fields is computational fluid dynamics (CFD). Augmentation of cerebral 4D flow MRI data with CFD-informed neural networks may provide a method to produce highly accurate physiological flow fields. In this preliminary study, the potential utility of such a method was demonstrated by using high resolution patient-specific CFD data to train a convolutional neural network, and then using the trained network to enhance MRI-derived velocity fields in cerebral blood vessel data sets. Through testing on simulated images, phantom data, and cerebrovascular 4D flow data from 20 patients, the trained network successfully de-noised flow images, decreased velocity error, and enhanced near-vessel-wall velocity quantification and visualization. Such image enhancement can improve experimental and clinical qualitative and quantitative cerebrovascular PC MRI analysis.

USNCCM-11: Computational fluid mechanics for free and moving boundary problems

2013 ◽  
Vol 87 ◽  
pp. 1
Author(s):  
Rekha R. Rao ◽  
S.A. Roberts ◽  
David R. Noble ◽  
Patrick D. Anderson ◽  
Jean-Francois Hétu
Keyword(s):  
Fluid Mechanics ◽  
Moving Boundary ◽  
Computational Fluid Mechanics ◽  
Moving Boundary Problems ◽  
Boundary Problems

scholarly journals Management of chronic periodontitis: an interdisciplinary approach

2016 ◽  
Vol 4 (2) ◽  
pp. 65
Author(s):  
Sneha Dani ◽  
Savitha A.N ◽  
Kenneth Tan ◽  
Anand Naik ◽  
Charan Chhatrala ◽  
...  
Keyword(s):  
Public Interest ◽  
Orthodontic Treatment ◽  
Interdisciplinary Approach ◽  
Primary Objective ◽  
Periodontal Therapy ◽  
The Other ◽  
Periodontal Health ◽  
Orthodontic Therapy ◽  
Single Tooth ◽  
Before And After

Objective: In recent years, advances in technique as well as a growing public interest in developing and maintaining a healthy and attractive smile, has resulted in a greater understanding of the interrelationships between periodontics and orthodontics. The primary objective of periodontal therapy is to restore and maintain the health and integrity of the attachment apparatus of teeth. In adults, the loss of teeth or periodontal support can result in pathological teeth migration involving either a single tooth or a group of teeth. This may result in the development of a diastema, incisal proclination, rotation with collapse of the posterior occlusion.Materials and methods: This case report is of a 32 year old female patient who reported with swollen gums, generalized spacing between the teeth and extruded upper anterior tooth. Periodontal therapy followed by fixed orthodontic therapy was planned.Results: At the end of 2 years a stable healthy periodontium was established that was both functional and esthetic.Conclusion: Adjunctive orthodontic therapy is often necessary for successful restoration of periodontal health. On the other hand, successful orthodontic treatment will depend on the periodontal preparation before and after treatment and the maintenance of periodontal health throughout all phases of mechano-therapy.

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