851
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Zhang X, Li H, Shen S, Cai M. Investigation of the flow-field in the upper respiratory system when wearing N95 filtering facepiece respirator. J Occup Environ Hyg 2016; 13:372-82. [PMID: 26653154 DOI: 10.1080/15459624.2015.1116697] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
This article presents a reverse modeling of the headform when wearing a filtering facepiece respirator (FFR) and a computational fluid dynamics (CFD) simulation based on the modeling. The whole model containing the upper respiratory airway, headform, and FFR was directly recorded by computed tomography (CT) scanning, and a medical contrast medium was used to make the FFR "visible." The FFR was normally worn by the subject during CT scanning so that the actual deformation of both the FFR and the face muscles during contact can be objectively conserved. The reverse modeling approach was introduced to rebuild the geometric model and convert it into a CFD solvable model. In this model, we conducted a transient numerical simulation of air flow containing carbon dioxide, thermal dynamics, and pressure and wall shear stress distribution in the respiratory system taking into consideration an individual wearing a FFR. The breathing cycle was described as a time-dependent profile of the air velocity through the respiratory airway. The result shows that wearing the N95 FFR results in CO2 accumulation, an increase in temperature and pressure elevation inside the FFR cavity. The volume fraction of CO2 reaches 1.2% after 7 breathing cycles and then is maintained at 3.04% on average. The wearers re-inhale excessive CO2 in every breathing cycle from the FFR cavity. The air temperature in the FFR cavity increases rapidly at first and then stays close to the exhaled temperature. Compared to not wearing an FFR, wearers have to increase approximately 90 Pa more pressure to keep the same breathing flow rate of 30.54 L/min after wearing an FFR. The nasal vestibule bears more wall shear stress than any other area in the airway.
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Affiliation(s)
- Xiaotie Zhang
- a School of Power and Mechanical Engineering, Wuhan University , Wuhan , China
| | - Hui Li
- a School of Power and Mechanical Engineering, Wuhan University , Wuhan , China
| | - Shengnan Shen
- a School of Power and Mechanical Engineering, Wuhan University , Wuhan , China
| | - Mang Cai
- a School of Power and Mechanical Engineering, Wuhan University , Wuhan , China
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852
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Frösen J. Flow Dynamics of Aneurysm Growth and Rupture: Challenges for the Development of Computational Flow Dynamics as a Diagnostic Tool to Detect Rupture-Prone Aneurysms. Acta Neurochir Suppl 2016; 123:89-95. [PMID: 27637634 DOI: 10.1007/978-3-319-29887-0_13] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
Saccular intracranial aneurysm (sIA) is a relatively common disease that can potentially cause a devastating, life-threatening intracranial hemorrhage. Many sIAs never rupture and thus do not necessitate interventions, making the detection of rupture-prone sIAs a very relevant clinical problem. Moreover, because currently available methods to prevent sIA rupture have significant risks of morbidity and mortality, diagnostic tools that can predict imminent rupture and help plan proper timing of prophylactic interventions, can improve patient care. Hemorrhage from an sIA occurs when hemodynamic stress exceeds sIA wall strength. Computational fluid dynamics (CFD) is a tool with which the hemodynamic stress to which the sIA wall is exposed can be determined non-invasively. Studies using CFD in sIAs have demonstrated associations of wall shear stress (WSS) with aneurysm growth, fragile sIA wall, and sIA rupture; these studies show the potential of CFD as a diagnostic tool. This review discusses the limitations of CFD and of the studies performed, and what needs to be done in order to develop CFD into a useful diagnostic tool to determine aneurysm-specific rupture risk.
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Affiliation(s)
- Juhana Frösen
- Department of Neurosurgery, Kuopio University Hospital, Puijonlaaksontie 2, Kuopio, 00029, Finland.
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853
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Abstract
This paper reviews unsteady flow conditions in human swimming and identifies the limitations and future potential of the current methods of analysing unsteady flow. The capability of computational fluid dynamics (CFD) has been extended from approaches assuming steady-state conditions to consideration of unsteady/transient conditions associated with the body motion of a swimmer. However, to predict hydrodynamic forces and the swimmer's potential speeds accurately, more robust and efficient numerical methods are necessary, coupled with validation procedures, requiring detailed experimental data reflecting local flow. Experimental data obtained by particle image velocimetry (PIV) in this area are limited, because at present observations are restricted to a two-dimensional 1.0 m(2) area, though this could be improved if the output range of the associated laser sheet increased. Simulations of human swimming are expected to improve competitive swimming, and our review has identified two important advances relating to understanding the flow conditions affecting performance in front crawl swimming: one is a mechanism for generating unsteady fluid forces, and the other is a theory relating to increased speed and efficiency.
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Affiliation(s)
- Hideki Takagi
- a Faculty of Health and Sport Sciences , University of Tsukuba , Tsukuba , Ibaraki , Japan
| | - Motomu Nakashima
- b Department of Mechanical and Control Engineering , Tokyo Institute of Technology , Tokyo , Japan
| | - Yohei Sato
- c Nuclear Energy and Safety , Paul Scherrer Institute , Villigen , Switzerland
| | - Kazuo Matsuuchi
- d Emeritus Professor, University of Tsukuba , Tsukuba , Ibaraki , Japan
| | - Ross H Sanders
- e Exercise and Sport Science , The University of Sydney , Sydney , Australia
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854
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Bozzetto M, Ene-Iordache B, Remuzzi A. Transitional Flow in the Venous Side of Patient-Specific Arteriovenous Fistulae for Hemodialysis. Ann Biomed Eng 2015; 44:2388-2401. [PMID: 26698581 DOI: 10.1007/s10439-015-1525-y] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Accepted: 11/29/2015] [Indexed: 01/28/2023]
Abstract
Arteriovenous fistula (AVF) is the first choice for providing vascular access for hemodialysis patients, but maintaining its patency is challenging. AVF failure is primarily due to development of neointimal hyperplasia (NH) and subsequent stenosis. Using idealized models of AVF we previously suggested that reciprocating hemodynamic wall shear is implicated in vessel stenosis. The aim of the present study was to investigate local hemodynamics in patient-specific side-to-end AVF. We reconstructed realistic geometrical models of four AVFs from magnetic resonance images acquired in a previous clinical study. High-resolution computational fluid dynamics simulations using patient-specific blood rheology and flow boundary conditions were performed. We then characterized the flow field and categorized disturbed flow areas by means of established hemodynamic wall parameters. In all AVF, either in upper or lower arm location, we consistently observed transitional laminar to turbulent-like flow developing in the juxta-anastomotic vein and damping towards the venous outflow, but not in the proximal artery. High-frequency fluctuations of the velocity vectors in these areas result in eddies that induce similar oscillations of wall shear stress vector. This condition may importantly impair the physiological response of endothelial cells to blood flow and be responsible for NH formation in newly created AVF.
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Affiliation(s)
- Michela Bozzetto
- Department of Biomedical Engineering, IRCCS - Istituto di Ricerche Farmacologiche "Mario Negri", Via G.B. Camozzi, 3, 24020, Ranica, BG, Italy
| | - Bogdan Ene-Iordache
- Department of Biomedical Engineering, IRCCS - Istituto di Ricerche Farmacologiche "Mario Negri", Via G.B. Camozzi, 3, 24020, Ranica, BG, Italy
| | - Andrea Remuzzi
- Department of Biomedical Engineering, IRCCS - Istituto di Ricerche Farmacologiche "Mario Negri", Via G.B. Camozzi, 3, 24020, Ranica, BG, Italy. .,Department of Management, Information and Production and Engineering, University of Bergamo, Viale Marconi, 5, Dalmine, 24044, BG, Italy.
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855
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Zhang Q, Xue S, Yan C, Wu X, Wen S, Cong W. Installation of flow deflectors and wing baffles to reduce dead zone and enhance flashing light effect in an open raceway pond. Bioresour Technol 2015; 198:150-156. [PMID: 26386417 DOI: 10.1016/j.biortech.2015.08.144] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Revised: 08/28/2015] [Accepted: 08/29/2015] [Indexed: 06/05/2023]
Abstract
To reduce the dead zone and enhance the flashing light effect, a novel open raceway pond with flow deflectors and wing baffles was developed. The hydrodynamics and light characteristics in the novel open raceway pond were investigated using computational fluid dynamics. Results showed that, compared with the control pond, pressure loss in the flow channel of the pond with optimized flow deflectors decreased by 14.58%, average fluid velocity increased by 26.89% and dead zone decreased by 60.42%. With wing baffles built into the raceway pond, significant swirling flow was produced. Moreover, the period of average L/D cycle was shortened. In outdoor cultivation of freshwater Chlorella sp., the biomass concentration of Chlorella sp. cultivated in the raceway pond with wing baffles was 30.11% higher than that of the control pond.
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Affiliation(s)
- Qinghua Zhang
- National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
| | - Shengzhang Xue
- National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
| | - Chenghu Yan
- National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
| | - Xia Wu
- National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
| | - Shumei Wen
- National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
| | - Wei Cong
- National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China.
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856
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Dimasi A, Rasponi M, Sheriff J, Chiu WC, Bluestein D, Tran PL, Slepian MJ, Redaelli A. Microfluidic emulation of mechanical circulatory support device shear-mediated platelet activation. Biomed Microdevices 2015; 17:117. [PMID: 26578003 PMCID: PMC4855287 DOI: 10.1007/s10544-015-0015-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Thrombosis of ventricular assist devices (VADs) compromises their performance, with associated risks of systemic embolization, stroke, pump stop and possible death. Anti-thrombotic (AT) drugs, utilized to limit thrombosis, are largely dosed empirically, with limited testing of their efficacy. Further, such testing, if performed, typically examines efficacy under static conditions, which is not reflective of actual shear-mediated flow. Here we adopted our previously developed Device Thrombogenicity Emulation methodology to design microfluidic platforms able to emulate representative shear stress profiles of mechanical circulatory support (MCS) devices. Our long-term goal is to utilize these systems for point-of-care (POC) personalized testing of AT efficacy under specific, individual shear profiles. First, we designed different types of microfluidic channels able to replicate sample shear stress patterns observed in MCS devices. Second, we explored the flexibility of microfluidic technology in generating dynamic shear stress profiles by modulating the geometrical features of the channels. Finally, we designed microfluidic channel systems able to emulate the shear stress profiles of two commercial VADs. From CFD analyses, the VAD-emulating microfluidic systems were able to replicate the main characteristics of the shear stress waveforms of the macroscale VADs (i.e., shear stress peaks and duration). Our results establish the basis for development of a lab-on-chip POC system able to perform device-specific and patient-specific platelet activation state assays.
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Affiliation(s)
- Annalisa Dimasi
- Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milan, 20133, Italy
| | - Marco Rasponi
- Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milan, 20133, Italy
| | - Jawaad Sheriff
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, 11794-8151, USA
| | - Wei-Che Chiu
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, 11794-8151, USA
| | - Danny Bluestein
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, 11794-8151, USA
| | - Phat L Tran
- Department of Medicine and Biomedical Engineering, Sarver Heart Center, University of Arizona, 1501 North Campbell Avenue, Tucson, AZ, 85724, USA
| | - Marvin J Slepian
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, 11794-8151, USA.
- Department of Medicine and Biomedical Engineering, Sarver Heart Center, University of Arizona, 1501 North Campbell Avenue, Tucson, AZ, 85724, USA.
| | - Alberto Redaelli
- Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milan, 20133, Italy
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857
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Pasquarella C, Balocco C, Pasquariello G, Petrone G, Saccani E, Manotti P, Ugolotti M, Palla F, Maggi O, Albertini R. A multidisciplinary approach to the study of cultural heritage environments: Experience at the Palatina Library in Parma. Sci Total Environ 2015; 536:557-567. [PMID: 26245537 DOI: 10.1016/j.scitotenv.2015.07.105] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Revised: 07/16/2015] [Accepted: 07/22/2015] [Indexed: 06/04/2023]
Abstract
The aim of this paper is to describe a multidisciplinary approach including biological and particle monitoring, and microclimate analysis associated with the application of the Computational Fluid Dynamic (CFD). This approach was applied at the Palatina historical library in Parma. Monitoring was performed both in July and in December, in the absence of visitors and operators. Air microbial monitoring was performed with active and passive methods. Airborne particles with a diameter of ≥0.3, ≥0.5, ≥1 and ≥5 μm/m3, were counted by a laser particle counter. The surface contamination of shelves and manuscripts was assessed with nitrocellulose membranes. A spore trap sampler was used to identify both viable and non-viable fungal spores by optical microscope. Microbiological contaminants were analyzed through cultural and molecular biology techniques. Microclimatic parameters were also recorded. An infrared thermal camera provided information on the surface temperature of the different building materials, objects and components. Transient simulation models, for coupled heat and mass-moisture transfer, taking into account archivist and general public movements, combined with the related sensible and latent heat released into the environment, were carried out applying the CFD-FE (Finite Elements) method. Simulations of particle tracing were carried out. A wide variability in environmental microbial contamination, both for air and surfaces, was observed. Cladosporium spp., Alternaria spp., Aspergillus spp., and Penicillium spp. were the most frequently found microfungi. Bacteria such as Streptomyces spp., Bacillus spp., Sphingomonas spp., and Pseudoclavibacter as well as unculturable colonies were characterized by molecular investigation. CFD simulation results obtained were consistent with the experimental data on microclimatic conditions. The tracing and distribution of particles showed the different slice planes of diffusion mostly influenced by the convective airflow. This interdisciplinary research represents a contribution towards the definition of standardized methods for assessing the biological and microclimatic quality of indoor cultural heritage environments.
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Affiliation(s)
- C Pasquarella
- Department of Biomedical, Biotechnological and Translational Sciences, University of Parma, Italy
| | - C Balocco
- Department of Industrial Engineering, University of Florence, Italy
| | - G Pasquariello
- Central Institute of Graphic Arts, Ministry of Cultural Heritage and Activities and Tourism, Rome, Italy
| | - G Petrone
- Department of Industrial Engineering, University of Catania, Italy
| | - E Saccani
- Department of Biomedical, Biotechnological and Translational Sciences, University of Parma, Italy
| | - P Manotti
- Department of Biomedical, Biotechnological and Translational Sciences, University of Parma, Italy
| | - M Ugolotti
- Hygiene Unit, University Hospital of Parma, Italy
| | - F Palla
- STEBICEF Department, Laboratory of Biology and Biotechnology for Cultural Heritage, University of Palermo, Italy
| | - O Maggi
- Department of Environmental Biology, "Sapienza" University of Rome, Italy
| | - R Albertini
- Department of Clinical and Experimental Medicine, University of Parma, Italy
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858
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Nair P, Chong BW, Indahlastari A, Lindsay J, DeJeu D, Parthasarathy V, Ryan J, Babiker H, Workman C, Gonzalez LF, Frakes D. Hemodynamic characterization of geometric cerebral aneurysm templates. J Biomech 2015; 49:2118-2126. [PMID: 26654674 DOI: 10.1016/j.jbiomech.2015.11.034] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Accepted: 11/13/2015] [Indexed: 10/22/2022]
Abstract
Hemodynamics are currently considered to a lesser degree than geometry in clinical practices for evaluating cerebral aneurysm (CA) risk and planning CA treatment. This study establishes fundamental relationships between three clinically recognized CA geometric factors and four clinically relevant hemodynamic responses. The goal of the study is to develop a more combined geometric/hemodynamic basis for informing clinical decisions. Flows within eight idealized template geometries were simulated using computational fluid dynamics and measured using particle image velocimetry under both steady and pulsatile flow conditions. The geometric factor main effects were then analyzed to quantify contributions made by the geometric factors (aneurysmal dome size (DS), dome-to-neck ratio (DNR), and parent-vessel contact angle (PV-CA)) to effects on the hemodynamic responses (aneurysmal and neck-plane root-mean-square velocity magnitude (Vrms), aneurysmal wall shear stress (WSS), and cross-neck flow (CNF)). Two anatomical aneurysm models were also examined to investigate how well the idealized findings would translate to more realistic CA geometries. DNR made the greatest contributions to effects on hemodynamics including a 75.05% contribution to aneurysmal Vrms and greater than 35% contributions to all responses. DS made the next greatest contributions, including a 43.94% contribution to CNF and greater than 20% contributions to all responses. PV-CA and several factor interactions also made contributions of greater than 10%. The anatomical aneurysm models and the most similar idealized templates demonstrated consistent hemodynamic response patterns. This study demonstrates how individual geometric factors, and combinations thereof, influence CA hemodynamics. Bridging the gap between geometry and flow in this quantitative yet practical way may have potential to improve CA evaluation and treatment criteria. Agreement among results from idealized and anatomical models further supports the potential for a template-based approach to play a useful role in clinical practice.
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Affiliation(s)
- Priya Nair
- School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ, United States.
| | - Brian W Chong
- School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ, United States; Mayo Clinic Hospital, Phoenix, AZ, United States
| | - Aprinda Indahlastari
- School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ, United States
| | - James Lindsay
- School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ, United States
| | - David DeJeu
- School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ, United States
| | - Varsha Parthasarathy
- School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ, United States
| | - Justin Ryan
- School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ, United States
| | | | - Christopher Workman
- School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ, United States
| | - L Fernando Gonzalez
- Department of Neurosurgery, Duke University School of Medicine, Durham, NC, United States
| | - David Frakes
- School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ, United States; School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe, AZ, United States
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859
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Karmonik C, Anderson JR, Beilner J, Ge JJ, Partovi S, Klucznik RP, Diaz O, Zhang YJ, Britz GW, Grossman RG, Lv N, Huang Q. Relationships and redundancies of selected hemodynamic and structural parameters for characterizing virtual treatment of cerebral aneurysms with flow diverter devices. J Biomech 2015; 49:2112-2117. [PMID: 26654675 DOI: 10.1016/j.jbiomech.2015.11.035] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Accepted: 11/13/2015] [Indexed: 11/28/2022]
Abstract
BACKGROUND AND PURPOSE To quantify the relationship and to demonstrate redundancies between hemodynamic and structural parameters before and after virtual treatment with a flow diverter device (FDD) in cerebral aneurysms. METHODS Steady computational fluid dynamics (CFD) simulations were performed for 10 cerebral aneurysms where FDD treatment with the SILK device was simulated by virtually reducing the porosity at the aneurysm ostium. Velocity and pressure values proximal and distal to and at the aneurysm ostium as well as inside the aneurysm were quantified. In addition, dome-to-neck ratios and size ratios were determined. Multiple correlation analysis (MCA) and hierarchical cluster analysis (HCA) were conducted to demonstrate dependencies between both structural and hemodynamic parameters. RESULTS Velocities in the aneurysm were reduced by 0.14m/s on average and correlated significantly (p<0.05) with velocity values in the parent artery (average correlation coefficient: 0.70). Pressure changes in the aneurysm correlated significantly with pressure values in the parent artery and aneurysm (average correlation coefficient: 0.87). MCA found statistically significant correlations between velocity values and between pressure values, respectively. HCA sorted velocity parameters, pressure parameters and structural parameters into different hierarchical clusters. HCA of aneurysms based on the parameter values yielded similar results by either including all (n=22) or only non-redundant parameters (n=2, 3 and 4). CONCLUSION Hemodynamic and structural parameters before and after virtual FDD treatment show strong inter-correlations. Redundancy of parameters was demonstrated with hierarchical cluster analysis.
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Affiliation(s)
- C Karmonik
- MRI Core, Houston Methodist Research Institute, Houston, TX, USA; Cerebrovascular Center, Neurosurgery, Houston Methodist, Houston, TX, USA.
| | - J R Anderson
- MRI Core, Houston Methodist Research Institute, Houston, TX, USA
| | | | - J J Ge
- Siemens AX, Shanghai, China
| | - S Partovi
- Department of Radiology, University Hospitals Case Medical Center, Case Western Reserve University, Cleveland, OH, USA
| | - R P Klucznik
- Cerebrovascular Center, Radiology, Houston Methodist, Houston, TX, USA
| | - O Diaz
- Cerebrovascular Center, Radiology, Houston Methodist, Houston, TX, USA
| | - Y J Zhang
- Cerebrovascular Center, Neurosurgery, Houston Methodist, Houston, TX, USA
| | - G W Britz
- Cerebrovascular Center, Neurosurgery, Houston Methodist, Houston, TX, USA
| | - R G Grossman
- Cerebrovascular Center, Neurosurgery, Houston Methodist, Houston, TX, USA
| | - N Lv
- Neurosurgery, The Affiliated Changhai Hospital of Second Military Medical University, Shanghai, China
| | - Q Huang
- Neurosurgery, The Affiliated Changhai Hospital of Second Military Medical University, Shanghai, China
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860
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Lindemann J, Reichert M, Kröger R, Schuler P, Hoffmann T, Sommer F. Numerical simulation of humidification and heating during inspiration in nose models with three different located septal perforations. Eur Arch Otorhinolaryngol 2015; 273:1795-800. [PMID: 26545380 DOI: 10.1007/s00405-015-3818-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Accepted: 10/22/2015] [Indexed: 10/22/2022]
Abstract
Nasal septum perforations (SP) are characterized by nasal obstruction, bleeding and crusting. The disturbed heating and humidification of the inhaled air are important factors, which cause these symptoms due to a disturbed airflow. Numerical simulations offer a great potential to avoid these limitations and to provide valid data. The aim of the study was to simulate the humidification and heating of the inhaled air in digital nose models with three different SPs and without SP. Four realistic bilateral nose models based on a multi-slice CT scan were created. The SP were located anterior caudal, anterior cranial and posterior caudal. One model was without SP. A numerical simulation was performed. Boundary conditions were based on previous in vivo measurements. Heating and humidification of the inhaled air were displayed, analyzed in each model and compared to each other. Anterior caudal SPs cause a disturbed decrease of temperature and humidity of the inhaled air. The reduced temperature and humidity values can still be shown in the posterior nose. The anterior cranial and the posterior caudal perforation have only a minor influence on heating and humidification. A reduced humidification and heating of the air can be shown by numerical simulations due to SP depending on their localization. The anterior caudal SP representing a typical localization after previous surgery has the biggest influence on heating and humidification. The results explain the typical symptoms such as crusting by drying-out the nasal mucosa. The size and the localization of the SP are essential for the symptoms.
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Affiliation(s)
- Jörg Lindemann
- Department of ORL, Head and Neck Surgery, Ulm University Medical Center, Frauensteige 12, 89075, Ulm, Germany
| | - Michael Reichert
- Department of ORL, Head and Neck Surgery, Ulm University Medical Center, Frauensteige 12, 89075, Ulm, Germany.
| | | | - Patrick Schuler
- Department of ORL, Head and Neck Surgery, Ulm University Medical Center, Frauensteige 12, 89075, Ulm, Germany
| | - Thomas Hoffmann
- Department of ORL, Head and Neck Surgery, Ulm University Medical Center, Frauensteige 12, 89075, Ulm, Germany
| | - Fabian Sommer
- Department of ORL, Head and Neck Surgery, Ulm University Medical Center, Frauensteige 12, 89075, Ulm, Germany
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861
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Abstract
An optimization method suitable for improving the performance of Archimedes screw axial rotary blood pumps is described in the present article. In order to achieve a more robust design and to save computational resources, this method combines the advantages of the established pump design theory with modern computer-aided, computational fluid dynamics (CFD)-based design optimization (CFD-O) relying on evolutionary algorithms and computational fluid dynamics. The main purposes of this project are to: (i) integrate pump design theory within the already existing CFD-based optimization; (ii) demonstrate that the resulting procedure is suitable for optimizing an Archimedes screw blood pump in terms of efficiency. Results obtained in this study demonstrate that the developed tool is able to meet both objectives. Finally, the resulting level of hemolysis can be numerically assessed for the optimal design, as hemolysis is an issue of overwhelming importance for blood pumps.
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Affiliation(s)
- Hai Yu
- Laboratory of Fluid Dynamics & Technical Flows, University of Magdeburg "Otto von Guericke, Magdeburg, Germany
| | - Gábor Janiga
- Laboratory of Fluid Dynamics & Technical Flows, University of Magdeburg "Otto von Guericke, Magdeburg, Germany
| | - Dominique Thévenin
- Laboratory of Fluid Dynamics & Technical Flows, University of Magdeburg "Otto von Guericke, Magdeburg, Germany
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862
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Vorobtsova N, Chiastra C, Stremler MA, Sane DC, Migliavacca F, Vlachos P. Effects of Vessel Tortuosity on Coronary Hemodynamics: An Idealized and Patient-Specific Computational Study. Ann Biomed Eng 2016; 44:2228-39. [PMID: 26498931 DOI: 10.1007/s10439-015-1492-3] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Accepted: 10/16/2015] [Indexed: 01/09/2023]
Abstract
Although coronary tortuosity can influence the hemodynamics of coronary arteries, the relationship between tortuosity and flow has not been thoroughly investigated partly due to the absence of a widely accepted definition of tortuosity and the lack of patient-specific studies that analyze complete coronary trees. Using a computational approach we investigated the effects of tortuosity on coronary flow parameters including pressure drop, wall shear stress, and helical flow strength as measured by helicity intensity. Our analysis considered idealized and patient-specific geometries. Overall results indicate that perfusion pressure decreases with increased tortuosity, but the patient-specific results show that more tortuous vessels have higher physiological wall shear stress values. Differences between the idealized and patient-specific results reveal that an accurate representation of coronary tortuosity must account for all relevant geometric aspects, including curvature imposed by the heart shape. The patient-specific results exhibit a strong correlation between tortuosity and helicity intensity, and the corresponding helical flow contributes directly to the observed increase in wall shear stress. Therefore, helicity intensity may prove helpful in developing a universal parameter to describe tortuosity and assess its impact on patient health. Our data suggest that increased tortuosity could have a deleterious impact via a reduction in coronary perfusion pressure, but the attendant increase in wall shear stress could afford protection against atherosclerosis.
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863
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Janiga G, Daróczy L, Berg P, Thévenin D, Skalej M, Beuing O. An automatic CFD-based flow diverter optimization principle for patient-specific intracranial aneurysms. J Biomech 2015; 48:3846-52. [PMID: 26472308 DOI: 10.1016/j.jbiomech.2015.09.039] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Revised: 09/18/2015] [Accepted: 09/24/2015] [Indexed: 11/26/2022]
Abstract
The optimal treatment of intracranial aneurysms using flow diverting devices is a fundamental issue for neuroradiologists as well as neurosurgeons. Due to highly irregular manifold aneurysm shapes and locations, the choice of the stent and the patient-specific deployment strategy can be a very difficult decision. To support the therapy planning, a new method is introduced that combines a three-dimensional CFD-based optimization with a realistic deployment of a virtual flow diverting stent for a given aneurysm. To demonstrate the feasibility of this method, it was applied to a patient-specific intracranial giant aneurysm that was successfully treated using a commercial flow diverter. Eight treatment scenarios with different local compressions were considered in a fully automated simulation loop. The impact on the corresponding blood flow behavior was evaluated qualitatively as well as quantitatively, and the optimal configuration for this specific case was identified. The virtual deployment of an uncompressed flow diverter reduced the inflow into the aneurysm by 24.4% compared to the untreated case. Depending on the positioning of the local stent compression below the ostium, blood flow reduction could vary between 27.3% and 33.4%. Therefore, a broad range of potential treatment outcomes was identified, illustrating the variability of a given flow diverter deployment in general. This method represents a proof of concept to automatically identify the optimal treatment for a patient in a virtual study under certain assumptions. Hence, it contributes to the improvement of virtual stenting for intracranial aneurysms and can support physicians during therapy planning in the future.
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Affiliation(s)
- Gábor Janiga
- Laboratory of Fluid Dynamics and Technical Flows, University of Magdeburg "Otto von Guericke" Universitätsplatz, 2 D-39106 Magdeburg, Germany.
| | - László Daróczy
- Laboratory of Fluid Dynamics and Technical Flows, University of Magdeburg "Otto von Guericke" Universitätsplatz, 2 D-39106 Magdeburg, Germany
| | - Philipp Berg
- Laboratory of Fluid Dynamics and Technical Flows, University of Magdeburg "Otto von Guericke" Universitätsplatz, 2 D-39106 Magdeburg, Germany
| | - Dominique Thévenin
- Laboratory of Fluid Dynamics and Technical Flows, University of Magdeburg "Otto von Guericke" Universitätsplatz, 2 D-39106 Magdeburg, Germany
| | - Martin Skalej
- Institute for Neuroradiology, University of Magdeburg "Otto von Guericke", Germany
| | - Oliver Beuing
- Institute for Neuroradiology, University of Magdeburg "Otto von Guericke", Germany
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864
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Rudnick S, McDevitt J, Hunt G, Stawnychy M, Vincent R, Brickner P. Influence of ceiling fan's speed and direction on efficacy of upperroom, ultraviolet germicidal irradiation: Experimental. Build Environ 2015; 92:756-763. [PMID: 32288032 PMCID: PMC7127731 DOI: 10.1016/j.buildenv.2014.03.025] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Revised: 03/22/2014] [Accepted: 03/24/2014] [Indexed: 05/22/2023]
Abstract
Increasing a ceiling fan's speed from its lowest setting of 61 rpm, which resulted in 0.77 m3/s of airflow, to its highest setting of 176 rpm, which resulted in 2.5 m3/s of airflow, or having the fan blow either upward or downward had no statistically significant effect on the efficacy of upper-room ultraviolet germicidal irradiation (UVGI). This outcome suggests that air circulation due to the ceiling fan was sufficient and that any additional increase would not improve efficacy. Numerous experimental studies on upper-room UVGI in which fans were used to provide air mixing have been published. However, none have quantified the air movement produced by these fans or described their tests in sufficient detail to allow results to be compared to predictions using computational fluid dynamics (CFD). The present work provides the required information. In addition to the usual boundary conditions needed for CFD, we made experimental measurements of UV susceptibility of the microorganisms used in the upper-room UVGI tests. We measured UV susceptibilities for Mycobacterium parafortuitum and Bacillus atrophaeus spores to be 0.074 and 0.018 m2/J, respectively. In a previous publication, we reported the spatial distribution of fluence rate, which is also needed for predicting efficacy from CFD. In a companion paper referred to as Part II, upper-room UVGI efficacy was predicted by both Eulerian and Lagrangian CFD and compared to the experimental results from the present study.
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Affiliation(s)
- S.N. Rudnick
- Department of Environmental Health, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115, USA
| | - J.J. McDevitt
- Department of Environmental Health, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115, USA
| | - G.M. Hunt
- Department of Environmental Health, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115, USA
| | - M.T. Stawnychy
- Department of Environmental Health, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115, USA
| | - R.L. Vincent
- Department of Medicine, Section of General Internal Medicine, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1087, New York, NY 10029, USA
- Corresponding author.
| | - P.W. Brickner
- Department of Medicine, Section of General Internal Medicine, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1087, New York, NY 10029, USA
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865
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Anzai H, Yoshida Y, Sugiyama S, Endo H, Matsumoto Y, Ohta M. Porosity dependency of an optimized stent design for an intracranial aneurysm. Technol Health Care 2015; 23:547-56. [PMID: 26410116 DOI: 10.3233/thc-151007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Optimal design of stents for a cerebral aneurysm is desired for efficient flow reduction in the aneurysm. OBJECTIVE In this study, we aimed to optimize stent design at several porosities, estimate the influence of stent design on aneurysm flow, and evaluate the ability of stents to reduce flow. METHODS Stent models were constructed as sets of squares or rectangles in the necks of a two-dimensional (2D) and realistic aneurysm. Then, automated optimization was performed using a combination of simulated annealing and lattice Boltzmann flow simulation. RESULTS By simulated annealing, stents were gradually modified to reduce the average velocity in an aneurysm. As a result of optimization, stents of all porosities demonstrated an inhomogeneous distribution with dense struts in the inflow area. Flow reduction was increased compared with the initial stent. Under the condition of high porosity, flow reduction by the stent drastically increased as porosity decreased. Under low porosity, the increase of velocity reduction was moderate even as porosity decreased. CONCLUSIONS Optimization can enhance flow reduction by stents. However, the increase in reduction associated with decreasing porosity is moderate under lower-porosity conditions. This threshold may help in the choice of stent porosity for each specific aneurysm.
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Affiliation(s)
- H Anzai
- Frontier Research Institute of Interdisciplinary Sciences, Tohoku University, Sendai, Japan.,Institute of Fluid Science, Tohoku University, Sendai, Japan
| | - Y Yoshida
- Graduate School of Engineering, Tohoku University, Sendai, Japan
| | - S Sugiyama
- Department of Neurosurgery, Kohnan Hospital, Sendai, Japan.,Graduate School of Biomedical Engineering, Tohoku University, Sendai, Japan
| | - H Endo
- Department of Neurosurgery, Kohnan Hospital, Sendai, Japan
| | - Y Matsumoto
- Department of Neuroendovascular Therapy, Kohnan Hospital, Sendai, Japan
| | - M Ohta
- Institute of Fluid Science, Tohoku University, Sendai, Japan
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866
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Browne LD, Walsh MT, Griffin P. Experimental and Numerical Analysis of the Bulk Flow Parameters Within an Arteriovenous Fistula. Cardiovasc Eng Technol 2015; 6:450-62. [PMID: 26577478 DOI: 10.1007/s13239-015-0246-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2015] [Accepted: 09/16/2015] [Indexed: 11/25/2022]
Abstract
The creation of an arteriovenous fistula for hemodialysis has been reported to generate unstable to turbulent flow behaviour. On the other hand, the vast majority of computational fluid dynamic studies of an arteriovenous fistula use low spatial and temporal resolutions resolution in conjunction with laminar assumptions to investigate bulk flow and near wall parameters. The objective of the present study is to investigate if adequately resolved CFD can capture instabilities within an arteriovenous fistula. An experimental model of a representative fistula was created and the pressure distribution within the model was analysed for steady inlet conditions. Temporal CFD simulations with steady inflow conditions were computed for comparison. Following this verification a pulsatile simulation was employed to assess the role of pulsatility on bulk flow parameters. High frequency fluctuations beyond 100 Hz were found to occupy the venous segment of the arteriovenous fistula under pulsatile conditions and the flow within the venous segment exhibited unstable behaviour under both steady and pulsatile inlet conditions. The presence of high frequency fluctuations may be overlooked unless adequate spatial and temporal resolutions are employed. These fluctuations may impact endothelial cell function and contribute to the cascade of events leading to aggressive intimal hyperplasia and the loss of functionality of the vascular access.
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Affiliation(s)
- Leonard D Browne
- Department of Mechanical, Aeronautical and Biomedical Engineering, Materials and Surface Science Institute, Centre for Applied Biomedical Engineering Research (CABER), University of Limerick, Limerick, Ireland
| | - Michael T Walsh
- Department of Mechanical, Aeronautical and Biomedical Engineering, Materials and Surface Science Institute, Centre for Applied Biomedical Engineering Research (CABER), University of Limerick, Limerick, Ireland
| | - Philip Griffin
- Department of Mechanical, Aeronautical and Biomedical Engineering, Materials and Surface Science Institute, Centre for Applied Biomedical Engineering Research (CABER), University of Limerick, Limerick, Ireland.
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867
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Cheng Z, Kidher E, Jarral OA, O'Regan DP, Wood NB, Athanasiou T, Xu XY. Assessment of Hemodynamic Conditions in the Aorta Following Root Replacement with Composite Valve-Conduit Graft. Ann Biomed Eng 2016; 44:1392-404. [PMID: 26369636 DOI: 10.1007/s10439-015-1453-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 09/07/2015] [Indexed: 10/23/2022]
Abstract
This paper presents the analysis of detailed hemodynamics in the aortas of four patients following replacement with a composite bio-prosthetic valve-conduit. Magnetic resonance image-based computational models were set up for each patient with boundary conditions comprising subject-specific three-dimensional inflow velocity profiles at the aortic root and central pressure waveform at the model outlet. Two normal subjects were also included for comparison. The purpose of the study was to investigate the effects of the valve-conduit on flow in the proximal and distal aorta. The results suggested that following the composite valve-conduit implantation, the vortical flow structure and hemodynamic parameters in the aorta were altered, with slightly reduced helical flow index, elevated wall shear stress and higher non-uniformity in wall shear compared to normal aortas. Inter-individual analysis revealed different hemodynamic conditions among the patients depending on the conduit configuration in the ascending aorta, which is a key factor in determining post-operative aortic flow. Introducing a natural curvature in the conduit to create a smooth transition between the conduit and native aorta may help prevent the occurrence of retrograde and recirculating flow in the aortic arch, which is particularly important when a large portion or the entire ascending aorta needs to be replaced.
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868
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Kato T, Sone S, Funamoto K, Hayase T, Kadowaki H, Taniguchi N. Effects of inflow velocity profile on two-dimensional hemodynamic analysis by ordinary and ultrasonic-measurement-integrated simulations. Med Biol Eng Comput 2015; 54:1331-9. [PMID: 26307203 DOI: 10.1007/s11517-015-1376-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 08/12/2015] [Indexed: 11/29/2022]
Abstract
Two-dimensional ultrasonic-measurement-integrated (2D-UMI) simulation correctly reproduces hemodynamics even with an inexact inflow velocity distribution. This study aimed to investigate which is superior, a two-dimensional ordinary (2D-O) simulation with an accurate inflow velocity distribution or a 2D-UMI simulation with an inaccurate one. 2D-O and 2D-UMI simulations were performed for blood flow in a carotid artery with four upstream velocity boundary conditions: a velocity profile with backprojected measured Doppler velocities (condition A), and velocity profiles with a measured Doppler velocity distribution, a parabolic one, and a uniform one, magnitude being obtained by inflow velocity estimation (conditions B, C, and D, respectively). The error of Doppler velocity against the measurement data was sensitive to the inflow velocity distribution in the 2D-O simulation, but not in the 2D-UMI simulation with the inflow velocity estimation. Among the results in conditions B, C, and D, the error in the worst 2D-UMI simulation with condition D was 31 % of that in the best 2D-O simulation with condition B, implying the superiority of the 2D-UMI simulation with an inaccurate inflow velocity distribution over the 2D-O simulation with an exact one. Condition A resulted in a larger error than the other conditions in both the 2D-O and 2D-UMI simulations.
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Affiliation(s)
- Takaumi Kato
- Graduate School of Biomedical Engineering, Tohoku University, Sendai, 980-8579, Japan
| | - Shusaku Sone
- Graduate School of Biomedical Engineering, Tohoku University, Sendai, 980-8579, Japan
| | - Kenichi Funamoto
- Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan.
| | - Toshiyuki Hayase
- Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan
| | - Hiroko Kadowaki
- Graduate School of Engineering, Tohoku University, Sendai, 980-8579, Japan
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869
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Jo G, Chung SK, Na Y. Numerical study of the effect of the nasal cycle on unilateral nasal resistance. Respir Physiol Neurobiol 2015; 219:58-68. [PMID: 26315663 DOI: 10.1016/j.resp.2015.08.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Revised: 08/19/2015] [Accepted: 08/19/2015] [Indexed: 10/23/2022]
Abstract
We used computational fluid dynamics to study the effects of the nasal cycle on the modification of unilateral nasal resistance using nasal cavity models from 2 different patients with chronic rhinosinusitis. A steady airflow field with an inspiratory flow rate of 250 mL/s was simulated using ANSYS-FLUENT v14.5. The distribution of local unilateral nasal resistance showed different shapes of variation and magnitudes of resistance depending on the distribution of cross-sectional area in the nasal cavity models. The highest local resistance on the congested side was found near the nasal valve area in the first patient, whereas the highest value was found in the nasal vestibule for the second patient. The relative importance of nasal resistance in the turbinated air passage differed for the 2 patients. The unilateral resistance of the congested state was in the range of 0.0229-0.221 Pas/mL. In the inferior meatus, greater flow rate was allowed during the congested state than during the decongested state if an extensive backflow developed.
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Affiliation(s)
- Gyehwan Jo
- Department of Mechanical Engineering, Konkuk University, Seoul 143-701, Republic of Korea
| | - Seung-Kyu Chung
- Department of Otorhinolaryngology: Head and Neck Surgery, Samsung Medical Center, Sungkyunkwan University, School of Medicine, Seoul, Republic of Korea
| | - Yang Na
- Department of Mechanical Engineering, Konkuk University, Seoul 143-701, Republic of Korea.
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870
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Cibis M, Jarvis K, Markl M, Rose M, Rigsby C, Barker AJ, Wentzel JJ. The effect of resolution on viscous dissipation measured with 4D flow MRI in patients with Fontan circulation: Evaluation using computational fluid dynamics. J Biomech 2015; 48:2984-9. [PMID: 26298492 DOI: 10.1016/j.jbiomech.2015.07.039] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Revised: 07/03/2015] [Accepted: 07/30/2015] [Indexed: 10/23/2022]
Abstract
Viscous dissipation inside Fontan circulation, a parameter associated with the exercise intolerance of Fontan patients, can be derived from computational fluid dynamics (CFD) or 4D flow MRI velocities. However, the impact of spatial resolution and measurement noise on the estimation of viscous dissipation is unclear. Our aim was to evaluate the influence of these parameters on viscous dissipation calculation. Six Fontan patients underwent whole heart 4D flow MRI. Subject-specific CFD simulations were performed. The CFD velocities were down-sampled to isotropic spatial resolutions of 0.5mm, 1mm, 2mm and to MRI resolution. Viscous dissipation was compared between (1) high resolution CFD velocities, (2) CFD velocities down-sampled to MRI resolution, (3) down-sampled CFD velocities with MRI mimicked noise levels, and (4) in-vivo 4D flow MRI velocities. Relative viscous dissipation between subjects was also calculated. 4D flow MRI velocities (15.6 ± 3.8 cm/s) were higher, although not significantly different than CFD velocities (13.8 ± 4.7 cm/s, p=0.16), down-sampled CFD velocities (12.3 ± 4.4 cm/s, p=0.06) and the down-sampled CFD velocities with noise (13.2 ± 4.2 cm/s, p=0.06). CFD-based viscous dissipation (0.81 ± 0.55 mW) was significantly higher than those based on down-sampled CFD (0.25 ± 0.19 mW, p=0.03), down-sampled CFD with noise (0.49 ± 0.26 mW, p=0.03) and 4D flow MRI (0.56 ± 0.28 mW, p=0.06). Nevertheless, relative viscous dissipation between different subjects was maintained irrespective of resolution and noise, suggesting that comparison of viscous dissipation between patients is still possible.
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Affiliation(s)
- Merih Cibis
- Biomedical Engineering, Erasmus Medical Center, Rotterdam, Netherlands.
| | - Kelly Jarvis
- Radiology, Northwestern University, Feinberg School of Medicine, Chicago, IL, United States; Biomedical Engineering, Northwestern University, Chicago, IL, United States
| | - Michael Markl
- Radiology, Northwestern University, Feinberg School of Medicine, Chicago, IL, United States; Biomedical Engineering, Northwestern University, Chicago, IL, United States
| | - Michael Rose
- Radiology, Northwestern University, Feinberg School of Medicine, Chicago, IL, United States
| | - Cynthia Rigsby
- Radiology, Northwestern University, Feinberg School of Medicine, Chicago, IL, United States; Medical Imaging, Ann & Robert H Lurie Children's Hospital of Chicago, Chicago, IL, United States
| | - Alex J Barker
- Radiology, Northwestern University, Feinberg School of Medicine, Chicago, IL, United States
| | - Jolanda J Wentzel
- Biomedical Engineering, Erasmus Medical Center, Rotterdam, Netherlands
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871
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Zheng Y, Thiruvengadam M, Lan H, Tien JC. Design of push-pull system to control diesel particular matter inside a dead-end entry. Int J Coal Sci Technol 2015; 2:237-244. [PMID: 27069716 PMCID: PMC4811165 DOI: 10.1007/s40789-015-0076-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Revised: 06/02/2015] [Accepted: 06/05/2015] [Indexed: 06/05/2023]
Abstract
Diesel particulate matter (DPM) is considered to be carcinogenic after prolonged exposure. With more diesel-powered equipment used in underground mines, miners' exposure to DPM has become an increasing concern. This paper used computational fluid dynamics method to study the DPM dispersion in a dead-end entry with loading operation. The effects of different push-pull ventilation systems on DPM distribution were evaluated to improve the working conditions for underground miners. The four push-pull systems considered include: long push and short pull tubing; short push and long pull tubing, long push and curved pull tubing, and short push and curved pull tubing. A species transport model with buoyancy effect was used to examine the DPM dispersion pattern with unsteady state analysis. During the 200 s of loading operation, high DPM levels were identified in the face and dead-end entry regions. This study can be used for mining engineer as guidance to design and setup local ventilation, select DPM control strategies and for DPM annual training for underground miners.
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Affiliation(s)
- Yi Zheng
- />Department of Mining & Nuclear Engineering, Missouri University of Science and Technology, Rolla, MO 65401 USA
| | - Magesh Thiruvengadam
- />Department of Mining & Nuclear Engineering, Missouri University of Science and Technology, Rolla, MO 65401 USA
| | - Hai Lan
- />Clean Air Power Inc., Poway, CA 92064 USA
| | - Jerry C. Tien
- />Division of Mining and Resources Engineering, Department of Civil Engineering, Monash University, Clayton Campus, Wellington Road, Clayton, VIC 3800 Australia
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872
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Wilson JT, van Loon R, Wang W, Zawieja DC, Moore JE. Determining the combined effect of the lymphatic valve leaflets and sinus on resistance to forward flow. J Biomech 2015; 48:3584-90. [PMID: 26315921 DOI: 10.1016/j.jbiomech.2015.07.045] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Revised: 07/23/2015] [Accepted: 07/30/2015] [Indexed: 10/23/2022]
Abstract
The lymphatic system is vital to a proper maintenance of fluid and solute homeostasis. Collecting lymphatics are composed of actively contracting tubular vessels segmented by bulbous sinus regions that encapsulate bi-leaflet check valves. Valve resistance to forward flow strongly influences pumping performance. However, because of the sub-millimeter size of the vessels with flow rates typically <1 ml/h and pressures of a few cmH2O, resistance is difficult to measure experimentally. Using a newly defined idealized geometry, we employed an uncoupled approach where the solid leaflet deflections of the open valve were computed and lymph flow calculations were subsequently performed. We sought to understand: 1) the effect of sinus and leaflet size on the resulting deflections experienced by the valve leaflets and 2) the effects on valve resistance to forward flow of the fully open valve. For geometries with sinus-to-root diameter ratios >1.39, the average resistance to forward flow was 0.95×10(6)[g/(cm4 s)]. Compared to the viscous pressure drop that would occur in a straight tube the same diameter as the upstream lymphangion, valve leaflets alone increase the pressure drop up to 35%. However, the presence of the sinus reduces viscous losses, with the net effect that when combined with leaflets the overall resistance is less than that of the equivalent continuing straight tube. Accurately quantifying resistance to forward flow will add to the knowledge used to develop therapeutics for treating lymphatic disorders and may eventually lead to understanding some forms of primary lymphedema.
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Affiliation(s)
- John T Wilson
- Department of Bioengineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
| | - Raoul van Loon
- College of Engineering, Swansea University, Singleton Park, Swansea SA2 8PP, UK
| | - Wei Wang
- Department of Medical Physiology, Texas A&M Health Science Center, 702 Southwest H.K. Dodgen Loop, Temple, TX 76504, USA
| | - David C Zawieja
- Department of Medical Physiology, Texas A&M Health Science Center, 702 Southwest H.K. Dodgen Loop, Temple, TX 76504, USA
| | - James E Moore
- Department of Bioengineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK.
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873
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Peach TW, Spranger K, Ventikos Y. Towards Predicting Patient-Specific Flow-Diverter Treatment Outcomes for Bifurcation Aneurysms: From Implantation Rehearsal to Virtual Angiograms. Ann Biomed Eng 2015; 44:99-111. [PMID: 26240061 PMCID: PMC4690836 DOI: 10.1007/s10439-015-1395-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 07/15/2015] [Indexed: 12/14/2022]
Abstract
Despite accounting for the majority of all cerebral aneurysm cases, bifurcation aneurysms present many challenges to standard endovascular treatment techniques. This study examines the treatment of bifurcation aneurysms endovascularly with flow-diverting stents and presents an integrative computational modeling suite allowing for rehearsing all aspects of the treatment. Six bifurcation aneurysms are virtually treated with 70% porosity flow-diverters. Substantial reduction (>50%) in aneurysm inflow due to device deployment is predicted in addition to reductions in peak and average aneurysm wall shear stress to values considered physiologically normal. The subsequent impact of flow-diverter deployment on daughter vessels that are jailed by the device is investigated further, with a number of simulations conducted with increased outlet pressure conditions at jailed vessels. Increased outlet pressures at jailed daughter vessels are found to have little effect on device-induced aneurysm inflow reduction, but large variation (13–86%) is seen in the resulting reduction in daughter vessel flow rate. Finally, we propose a potentially powerful approach for validation of such models, by introducing an angiographic contrast model, with contrast transport modeled both before and after virtual treatment. Virtual angiograms and contrast residence curves are created, which offer unique clinical relevance and the potential for future in vivo verification of simulated results.
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Affiliation(s)
- T W Peach
- Department of Mechanical Engineering, University College London, London, UK.,Department of Engineering Science, University of Oxford, Oxford, UK
| | - K Spranger
- Department of Mechanical Engineering, University College London, London, UK
| | - Y Ventikos
- Department of Mechanical Engineering, University College London, London, UK.
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874
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Rodriguez GY, Valverde-Ramírez M, Mendes CE, Béttega R, Badino AC. Global performance parameters for different pneumatic bioreactors operating with water and glycerol solution: experimental data and CFD simulation. Bioprocess Biosyst Eng 2015; 38:2063-75. [PMID: 26227509 DOI: 10.1007/s00449-015-1446-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Accepted: 07/19/2015] [Indexed: 10/23/2022]
Abstract
Global variables play a key role in evaluation of the performance of pneumatic bioreactors and provide criteria to assist in system selection and design. The purpose of this work was to use experimental data and computational fluid dynamics (CFD) simulations to determine the global performance parameters gas holdup ([Formula: see text]) and volumetric oxygen transfer coefficient (k L a), and conduct an analysis of liquid circulation velocity, for three different geometries of pneumatic bioreactors: bubble column, concentric-tube airlift, and split tube airlift. All the systems had 5 L working volumes and two Newtonian fluids of different viscosities were used in the experiments: distilled water and 10 cP glycerol solution. Considering the high oxygen demand in certain types of aerobic fermentations, the assays were carried out at high flow rates. In the present study, the performances of three pneumatic bioreactors with different geometries and operating with two different Newtonian fluids were compared. A new CFD modeling procedure was implemented, and the simulation results were compared with the experimental data. The findings indicated that the concentric-tube airlift design was the best choice in terms of both gas holdup and volumetric oxygen transfer coefficient. The CFD results for gas holdup were consistent with the experimental data, and indicated that k L a was strongly influenced by bubble diameter and shape.
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Affiliation(s)
- G Y Rodriguez
- Graduate Program of Chemical Engineering, Federal University of São Carlos, C.P. 676, São Carlos, SP, 13565-905, Brazil
| | - M Valverde-Ramírez
- Graduate Program of Chemical Engineering, Federal University of São Carlos, C.P. 676, São Carlos, SP, 13565-905, Brazil
| | - C E Mendes
- Graduate Program of Chemical Engineering, Federal University of São Carlos, C.P. 676, São Carlos, SP, 13565-905, Brazil
| | - R Béttega
- Graduate Program of Chemical Engineering, Federal University of São Carlos, C.P. 676, São Carlos, SP, 13565-905, Brazil
| | - A C Badino
- Graduate Program of Chemical Engineering, Federal University of São Carlos, C.P. 676, São Carlos, SP, 13565-905, Brazil.
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875
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Wilhelm D, Purea A, Engelke F. Fluid flow dynamics in MAS systems. J Magn Reson 2015; 257:51-63. [PMID: 26073599 DOI: 10.1016/j.jmr.2015.05.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Revised: 05/15/2015] [Accepted: 05/18/2015] [Indexed: 06/04/2023]
Abstract
The turbine system and the radial bearing of a high performance magic angle spinning (MAS) probe with 1.3mm-rotor diameter has been analyzed for spinning rates up to 67kHz. We focused mainly on the fluid flow properties of the MAS system. Therefore, computational fluid dynamics (CFD) simulations and fluid measurements of the turbine and the radial bearings have been performed. CFD simulation and measurement results of the 1.3mm-MAS rotor system show relatively low efficiency (about 25%) compared to standard turbo machines outside the realm of MAS. However, in particular, MAS turbines are mainly optimized for speed and stability instead of efficiency. We have compared MAS systems for rotor diameter of 1.3-7mm converted to dimensionless values with classical turbomachinery systems showing that the operation parameters (rotor diameter, inlet mass flow, spinning rate) are in the favorable range. This dimensionless analysis also supports radial turbines for low speed MAS probes and diagonal turbines for high speed MAS probes. Consequently, a change from Pelton type MAS turbines to diagonal turbines might be worth considering for high speed applications. CFD simulations of the radial bearings have been compared with basic theoretical values proposing considerably smaller frictional loss values. The discrepancies might be due to the simple linear flow profile employed for the theoretical model. Frictional losses generated inside the radial bearings result in undesired heat-up of the rotor. The rotor surface temperature distribution computed by CFD simulations show a large temperature gradient over the rotor.
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Affiliation(s)
- Dirk Wilhelm
- Zurich University of Applied Sciences, Institute of Applied Mathematics and Physics, Techikumstrasse 9, 8400 Winterthur, Switzerland.
| | - Armin Purea
- Bruker Biospin GmbH, Am Silberstreifen 4, 76287 Rheinstetten, Germany
| | - Frank Engelke
- Bruker Biospin GmbH, Am Silberstreifen 4, 76287 Rheinstetten, Germany
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876
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Abstract
We present a computational model of three-dimensional and unsteady hemodynamics within the primary large arteries in the human on 1,572,864 cores of the IBM Blue Gene/Q. Models of large regions of the circulatory system are needed to study the impact of local factors on global hemodynamics and to inform next generation drug delivery mechanisms. The HARVEY code successfully addresses key challenges that can hinder effective solution of image-based hemodynamics on contemporary supercomputers, such as limited memory capacity and bandwidth, flexible load balancing, and scalability. This work is the first demonstration of large fluid dynamics simulations of the aortofemoral region of the circulatory system at resolutions as small as 10 μm.
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Affiliation(s)
- Amanda Randles
- Lawrence Livermore National Laboratory, Livermore, CA, USA
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877
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Kheyfets VO, Rios L, Smith T, Schroeder T, Mueller J, Murali S, Lasorda D, Zikos A, Spotti J, Reilly JJ, Finol EA. Patient-specific computational modeling of blood flow in the pulmonary arterial circulation. Comput Methods Programs Biomed 2015; 120:88-101. [PMID: 25975872 PMCID: PMC4441565 DOI: 10.1016/j.cmpb.2015.04.005] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Revised: 03/15/2015] [Accepted: 04/14/2015] [Indexed: 06/04/2023]
Abstract
Computational fluid dynamics (CFD) modeling of the pulmonary vasculature has the potential to reveal continuum metrics associated with the hemodynamic stress acting on the vascular endothelium. It is widely accepted that the endothelium responds to flow-induced stress by releasing vasoactive substances that can dilate and constrict blood vessels locally. The objectives of this study are to examine the extent of patient specificity required to obtain a significant association of CFD output metrics and clinical measures in models of the pulmonary arterial circulation, and to evaluate the potential correlation of wall shear stress (WSS) with established metrics indicative of right ventricular (RV) afterload in pulmonary hypertension (PH). Right Heart Catheterization (RHC) hemodynamic data and contrast-enhanced computed tomography (CT) imaging were retrospectively acquired for 10 PH patients and processed to simulate blood flow in the pulmonary arteries. While conducting CFD modeling of the reconstructed patient-specific vasculatures, we experimented with three different outflow boundary conditions to investigate the potential for using computationally derived spatially averaged wall shear stress (SAWSS) as a metric of RV afterload. SAWSS was correlated with both pulmonary vascular resistance (PVR) (R(2)=0.77, P<0.05) and arterial compliance (C) (R(2)=0.63, P<0.05), but the extent of the correlation was affected by the degree of patient specificity incorporated in the fluid flow boundary conditions. We found that decreasing the distal PVR alters the flow distribution and changes the local velocity profile in the distal vessels, thereby increasing the local WSS. Nevertheless, implementing generic outflow boundary conditions still resulted in statistically significant SAWSS correlations with respect to both metrics of RV afterload, suggesting that the CFD model could be executed without the need for complex outflow boundary conditions that require invasively obtained patient-specific data. A preliminary study investigating the relationship between outlet diameter and flow distribution in the pulmonary tree offers a potential computationally inexpensive alternative to pressure based outflow boundary conditions.
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Affiliation(s)
- Vitaly O Kheyfets
- Department of Bioengineering, UC Denver - Anschutz Medical Campus, Children's Hospital Colorado, 13123 E. 16th Ave B100, Aurora, CO 80045, United States.
| | - Lourdes Rios
- The University of Texas at San Antonio, Department of Biomedical Engineering, San Antonio, TX 78249, United States; The University of Texas at San Antonio, Department of Biological Sciences, San Antonio, TX 78249, United States.
| | - Triston Smith
- Western Pennsylvania Allegheny Health System, Allegheny General Hospital, McGinnis Cardiovascular Institute, Department of Radiology, Pittsburgh, PA 15212, United States; Western Pennsylvania Allegheny Health System, Allegheny General Hospital, McGinnis Cardiovascular Institute, Department of Cardiology, Pittsburgh, PA 15212, United States.
| | - Theodore Schroeder
- Western Pennsylvania Allegheny Health System, Allegheny General Hospital, McGinnis Cardiovascular Institute, Department of Radiology, Pittsburgh, PA 15212, United States; Western Pennsylvania Allegheny Health System, Allegheny General Hospital, McGinnis Cardiovascular Institute, Department of Cardiology, Pittsburgh, PA 15212, United States.
| | - Jeffrey Mueller
- Western Pennsylvania Allegheny Health System, Allegheny General Hospital, McGinnis Cardiovascular Institute, Department of Radiology, Pittsburgh, PA 15212, United States; Western Pennsylvania Allegheny Health System, Allegheny General Hospital, McGinnis Cardiovascular Institute, Department of Cardiology, Pittsburgh, PA 15212, United States.
| | - Srinivas Murali
- Western Pennsylvania Allegheny Health System, Allegheny General Hospital, McGinnis Cardiovascular Institute, Department of Radiology, Pittsburgh, PA 15212, United States; Western Pennsylvania Allegheny Health System, Allegheny General Hospital, McGinnis Cardiovascular Institute, Department of Cardiology, Pittsburgh, PA 15212, United States.
| | - David Lasorda
- Western Pennsylvania Allegheny Health System, Allegheny General Hospital, McGinnis Cardiovascular Institute, Department of Radiology, Pittsburgh, PA 15212, United States; Western Pennsylvania Allegheny Health System, Allegheny General Hospital, McGinnis Cardiovascular Institute, Department of Cardiology, Pittsburgh, PA 15212, United States.
| | - Anthony Zikos
- Western Pennsylvania Allegheny Health System, Allegheny General Hospital, McGinnis Cardiovascular Institute, Department of Radiology, Pittsburgh, PA 15212, United States; Western Pennsylvania Allegheny Health System, Allegheny General Hospital, McGinnis Cardiovascular Institute, Department of Cardiology, Pittsburgh, PA 15212, United States.
| | - Jennifer Spotti
- Western Pennsylvania Allegheny Health System, Allegheny General Hospital, McGinnis Cardiovascular Institute, Department of Radiology, Pittsburgh, PA 15212, United States; Western Pennsylvania Allegheny Health System, Allegheny General Hospital, McGinnis Cardiovascular Institute, Department of Cardiology, Pittsburgh, PA 15212, United States.
| | - John J Reilly
- University of Pittsburgh, Department of Medicine, Pittsburgh, PA 15261, United States.
| | - Ender A Finol
- The University of Texas at San Antonio, Department of Biomedical Engineering, San Antonio, TX 78249, United States.
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878
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Pahlavian SH, Loth F, Luciano M, Oshinski J, Martin BA. Neural Tissue Motion Impacts Cerebrospinal Fluid Dynamics at the Cervical Medullary Junction: A Patient-Specific Moving-Boundary Computational Model. Ann Biomed Eng 2015; 43:2911-23. [PMID: 26108203 DOI: 10.1007/s10439-015-1355-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 06/05/2015] [Indexed: 11/24/2022]
Abstract
Central nervous system (CNS) tissue motion of the brain occurs over 30 million cardiac cycles per year due to intracranial pressure differences caused by the pulsatile blood flow and cerebrospinal fluid (CSF) motion within the intracranial space. This motion has been found to be elevated in type 1 Chiari malformation. The impact of CNS tissue motion on CSF dynamics was assessed using a moving-boundary computational fluid dynamics (CFD) model of the cervical-medullary junction (CMJ). The cerebellar tonsils and spinal cord were modeled as rigid surfaces moving in the caudocranial direction over the cardiac cycle. The CFD boundary conditions were based on in vivo MR imaging of a 35-year old female Chiari malformation patient with ~150-300 µm motion of the cerebellar tonsils and spinal cord, respectively. Results showed that tissue motion increased CSF pressure dissociation across the CMJ and peak velocities up to 120 and 60%, respectively. Alterations in CSF dynamics were most pronounced near the CMJ and during peak tonsillar velocity. These results show a small CNS tissue motion at the CMJ can alter CSF dynamics for a portion of the cardiac cycle and demonstrate the utility of CFD modeling coupled with MR imaging to help understand CSF dynamics.
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Affiliation(s)
- Soroush Heidari Pahlavian
- Conquer Chiari Research Center, Department of Mechanical Engineering, The University of Akron, Akron, OH, 44325-3903, USA.,Department of Mechanical Engineering, The University of Akron, Akron, OH, USA
| | - Francis Loth
- Conquer Chiari Research Center, Department of Mechanical Engineering, The University of Akron, Akron, OH, 44325-3903, USA.,Department of Mechanical Engineering, The University of Akron, Akron, OH, USA
| | - Mark Luciano
- Department of Pediatric Neurosurgery, Cleveland Clinic Foundation, Cleveland, OH, USA
| | - John Oshinski
- Department of Radiology, Emory University, Atlanta, GA, USA
| | - Bryn A Martin
- Conquer Chiari Research Center, Department of Mechanical Engineering, The University of Akron, Akron, OH, 44325-3903, USA. .,Department of Mechanical Engineering, The University of Akron, Akron, OH, USA.
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879
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Xiang J, Antiga L, Varble N, Snyder KV, Levy EI, Siddiqui AH, Meng H. AView: An Image-based Clinical Computational Tool for Intracranial Aneurysm Flow Visualization and Clinical Management. Ann Biomed Eng 2016; 44:1085-96. [PMID: 26101034 DOI: 10.1007/s10439-015-1363-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Accepted: 06/11/2015] [Indexed: 10/23/2022]
Abstract
Intracranial aneurysms (IAs) occur in around 3% of the entire population. IA rupture is responsible for the most devastating type of hemorrhagic strokes, with high fatality and disability rates as well as healthcare costs. With increasing detection of unruptured aneurysms, clinicians are routinely faced with the dilemma whether to treat IA patients and how to best treat them. Hemodynamic and morphological characteristics are increasingly considered in aneurysm rupture risk assessment and treatment planning, but currently no computational tools allow routine integration of flow visualization and quantitation of these parameters in clinical workflow. In this paper, we introduce AView, a prototype of a clinician-oriented, integrated computation tool for aneurysm hemodynamics, morphology, and risk and data management to aid in treatment decisions and treatment planning in or near the procedure room. Specifically, we describe how we have designed the AView structure from the end-user's point of view, performed a pilot study and gathered clinical feedback. The positive results demonstrate AView's potential clinical value on enhancing aneurysm treatment decision and treatment planning.
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880
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Mori F, Hanida S, Kumahata K, Miyabe-Nishiwaki T, Suzuki J, Matsuzawa T, Nishimura TD. Minor contributions of the maxillary sinus to the air-conditioning performance in macaque monkeys. ACTA ACUST UNITED AC 2015; 218:2394-401. [PMID: 26034122 DOI: 10.1242/jeb.118059] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Accepted: 05/18/2015] [Indexed: 11/20/2022]
Abstract
The nasal passages mainly adjust the temperature and humidity of inhaled air to reach the alveolar condition required in the lungs. By contrast to most other non-human primates, macaque monkeys are distributed widely among tropical, temperate and subarctic regions, and thus some species need to condition the inhaled air in cool and dry ambient atmospheric areas. The internal nasal anatomy is believed to have undergone adaptive modifications to improve the air-conditioning performance. Furthermore, the maxillary sinus (MS), an accessory hollow communicating with the nasal cavity, is found in macaques, whereas it is absent in most other extant Old World monkeys, including savanna monkeys. In this study, we used computational fluid dynamics simulations to simulate the airflow and heat and water exchange over the mucosal surface in the nasal passage. Using the topology models of the nasal cavity with and without the MS, we demonstrated that the MS makes little contribution to the airflow pattern and the air-conditioning performance within the nasal cavity in macaques. Instead, the inhaled air is conditioned well in the anterior portion of the nasal cavity before reaching the MS in both macaques and savanna monkeys. These findings suggest that the evolutionary modifications and coetaneous variations in the nasal anatomy are rather independent of transitions and variations in the climate and atmospheric environment found in the habitats of macaques.
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Affiliation(s)
- Futoshi Mori
- Interfaculty Initiative in Information Studies, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan Earthquake Research Institute, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Sho Hanida
- Kanazawa Institute of Technology, Nonoichi, Ishikawa 921-8501, Japan
| | - Kiyoshi Kumahata
- RIKEN Advanced Institute for Computational Science, Kobe, Hyogo 650-0047, Japan
| | | | - Juri Suzuki
- Primate Research Institute, Kyoto University, Inuyama, Aichi 484-8506, Japan
| | - Teruo Matsuzawa
- Japan Advanced Institute of Science and Technology, Nomi, Ishikawa 923-1292, Japan
| | - Takeshi D Nishimura
- Primate Research Institute, Kyoto University, Inuyama, Aichi 484-8506, Japan
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881
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Hwang T, Oh YK, Kim B, Han JI. Dramatic improvement of membrane performance for microalgae harvesting with a simple bubble-generator plate. Bioresour Technol 2015; 186:343-347. [PMID: 25870035 DOI: 10.1016/j.biortech.2015.03.111] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Revised: 03/23/2015] [Accepted: 03/24/2015] [Indexed: 06/04/2023]
Abstract
To overcome fouling issue in membrane-based algae harvesting and thus make an otherwise promising harvesting option more competitive, a bubble-generator plate was developed. According to computational fluid dynamics analysis, the plate generated substantial hydrodynamic power in terms of high pressure, velocity, and shear stress. When installed in a membrane filtration system with membranes of different surface and structural characteristics (one prepared by the phase inversion method, and a commercial one) the bubble-generator was indeed effective in reducing fouling. Without the plate, the much cheaper homemade membrane had the similar performance as the commercial one. Use of the bubble-generator considerably improved the performance of both membranes, and revealed a valuable synergy with the asymmetrical structure of the homemade membrane. This result clearly showed that the ever-problematic fouling could be mitigated in a rather easy manner, and in so doing, that membrane technology could indeed become a practical option for algae harvesting.
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Affiliation(s)
- Taewoon Hwang
- Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, South Korea
| | - You-Kwan Oh
- Clean Fuel Department Bioenergy Research Group, Korea Institute of Energy Research, 152 Gajeong-ro, Yuseong-gu, Daejeon 305-343, South Korea
| | - Bohwa Kim
- Clean Fuel Department Bioenergy Research Group, Korea Institute of Energy Research, 152 Gajeong-ro, Yuseong-gu, Daejeon 305-343, South Korea
| | - Jong-In Han
- Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, South Korea.
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882
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Chauhan N, Chauhan RP. Active-passive measurements and CFD based modelling for indoor radon dispersion study. J Environ Radioact 2015; 144:57-61. [PMID: 25817925 DOI: 10.1016/j.jenvrad.2015.03.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Revised: 02/24/2015] [Accepted: 03/06/2015] [Indexed: 06/04/2023]
Abstract
Computational fluid dynamics (CFD) play a significant role in indoor pollutant dispersion study. Radon is an indoor pollutant which is radioactive and inert gas in nature. The concentration level and spatial distribution of radon may be affected by the dwelling's ventilation conditions. Present work focus at the study of indoor radon gas distribution via measurement and CFD modeling in naturally ventilated living room. The need of the study is the prediction of activity level and to study the effect of natural ventilation on indoor radon. Two measurement techniques (Passive measurement using pin-hole dosimeters and active measurement using continuous radon monitor (SRM)) were used for the validation purpose of CFD results. The CFD simulation results were compared with the measurement results at 15 points, 3 XY planes at different heights along with the volumetric average concentration. The simulation results found to be comparable with the measurement results. The future scope of these CFD codes is to study the effect of varying inflow rate of air on the radon concentration level and dispersion pattern.
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Affiliation(s)
- Neetika Chauhan
- Department of Physics, National Institute of Technology, Kurukshetra 136119, India.
| | - R P Chauhan
- Department of Physics, National Institute of Technology, Kurukshetra 136119, India
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883
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Tan GX, Jamil M, Tee NG, Zhong L, Yap CH. 3D Reconstruction of Chick Embryo Vascular Geometries Using Non-invasive High-Frequency Ultrasound for Computational Fluid Dynamics Studies. Ann Biomed Eng 2015; 43:2780-93. [PMID: 26014359 DOI: 10.1007/s10439-015-1339-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2015] [Accepted: 05/13/2015] [Indexed: 12/17/2022]
Abstract
Recent animal studies have provided evidence that prenatal blood flow fluid mechanics may play a role in the pathogenesis of congenital cardiovascular malformations. To further these researches, it is important to have an imaging technique for small animal embryos with sufficient resolution to support computational fluid dynamics studies, and that is also non-invasive and non-destructive to allow for subject-specific, longitudinal studies. In the current study, we developed such a technique, based on ultrasound biomicroscopy scans on chick embryos. Our technique included a motion cancelation algorithm to negate embryonic body motion, a temporal averaging algorithm to differentiate blood spaces from tissue spaces, and 3D reconstruction of blood volumes in the embryo. The accuracy of the reconstructed models was validated with direct stereoscopic measurements. A computational fluid dynamics simulation was performed to model fluid flow in the generated construct of a Hamburger-Hamilton (HH) stage 27 embryo. Simulation results showed that there were divergent streamlines and a low shear region at the carotid duct, which may be linked to the carotid duct's eventual regression and disappearance by HH stage 34. We show that our technique has sufficient resolution to produce accurate geometries for computational fluid dynamics simulations to quantify embryonic cardiovascular fluid mechanics.
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884
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Choi HW, Navia JA, Kassab GS. Thrombus deflector stent for stroke prevention: A simulation study. J Biomech 2015; 48:1789-95. [PMID: 26049978 DOI: 10.1016/j.jbiomech.2015.05.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Revised: 05/05/2015] [Accepted: 05/06/2015] [Indexed: 11/29/2022]
Abstract
Atrial fibrillation (AF) is a dysfunction of heart rhythm and represents an increased predisposition to ischemic stroke in AF patients. It has been shown that the AF-induced hemodynamic conditions may contribute to the increased embolic propensity through the carotid arteries. We simulated a stroke-prevention device with a unique strut structure to deflect the trajectory of a blood clot to the carotid artery. We identified the important determinants of functionality in a device design using computational fluid dynamics simulations. Quantitative assessment of deflection efficacy over various clot dimensions was carried out for the device with different strut configurations under AF flow conditions. The simulations demonstrate that the trajectory of a clot destined to the left common carotid artery (LCCA) can be deflected by a strut-structured device at the LCCA inlet with virtually no change in flow resistance. The deflection efficacy of the device is dependent on the clot properties and strut designs of the device. A configuration of 0.75 mm thick and 0.75 mm distant struts with 50% of surface convexity were found to provide maximum deflection efficacy (e.g., 36% greater deflection efficacy than a flat filter) among the strut structures considered. The results suggest that a deflector stent implanted in the aortic branch may be an effective stroke-prevention device. The present simulations motivate pre-clinical animal studies as well as further studies on patient-specific design of the device that maximize the deflection efficacy while minimizing device safety issues.
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Affiliation(s)
- Hyo Won Choi
- The California Medical Innovations Institute, 11107 Roselle Street, San Diego, CA 92121, United States
| | - Jose A Navia
- Department of Surgery, Austral University, Buenos Aires, Argentina
| | - Ghassan S Kassab
- The California Medical Innovations Institute, 11107 Roselle Street, San Diego, CA 92121, United States.
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885
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Abstract
Conveyor belt fires in an underground mine pose a serious life threat to miners. Water sprinkler systems are usually used to extinguish underground conveyor belt fires, but because of the complex interaction between conveyor belt fires and mine ventilation airflow, more effective engineering designs are needed for the installation of water sprinkler systems. A computational fluid dynamics (CFD) model was developed to simulate the interaction between the ventilation airflow, the belt flame spread, and the water spray system in a mine entry. The CFD model was calibrated using test results from a large-scale conveyor belt fire suppression experiment. Simulations were conducted using the calibrated CFD model to investigate the effects of sprinkler location, water flow rate, and sprinkler activation temperature on the suppression of conveyor belt fires. The sprinkler location and the activation temperature were found to have a major effect on the suppression of the belt fire, while the water flow rate had a minor effect.
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Affiliation(s)
- Liming Yuan
- Mine Safety and Health Research, National Institute for Occupational Safety and Health, P.O. Box 18070, Pittsburgh, PA 15236, USA
| | - Alex C Smith
- Mine Safety and Health Research, National Institute for Occupational Safety and Health, P.O. Box 18070, Pittsburgh, PA 15236, USA
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886
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Abstract
Conveyor belt fires in an underground mine pose a serious life threat to miners. Water sprinkler systems are usually used to extinguish underground conveyor belt fires, but because of the complex interaction between conveyor belt fires and mine ventilation airflow, more effective engineering designs are needed for the installation of water sprinkler systems. A computational fluid dynamics (CFD) model was developed to simulate the interaction between the ventilation airflow, the belt flame spread, and the water spray system in a mine entry. The CFD model was calibrated using test results from a large-scale conveyor belt fire suppression experiment. Simulations were conducted using the calibrated CFD model to investigate the effects of sprinkler location, water flow rate, and sprinkler activation temperature on the suppression of conveyor belt fires. The sprinkler location and the activation temperature were found to have a major effect on the suppression of the belt fire, while the water flow rate had a minor effect.
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Affiliation(s)
- Liming Yuan
- Corresponding author. Tel.: +1 412 3864961. (L. Yuan)
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887
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Kopanidis A, Pantos I, Theodorakakos A, Tzanalaidou E, Katritsis D. Fractional flow reserve derived from conventional coronary angiograms and computational fluid dynamics. Int J Cardiol 2015; 190:187-9. [PMID: 25920021 DOI: 10.1016/j.ijcard.2015.04.132] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 04/15/2015] [Indexed: 11/19/2022]
Affiliation(s)
- Anastasios Kopanidis
- Department of Mechanical Engineering, University of Western Macedonia, Kozani, Greece; Department of Cardiology, Athens Euroclinic, Athens, Greece
| | - Ioannis Pantos
- Department of Cardiology, Athens Euroclinic, Athens, Greece; Medical and Radiation Physics, Department of Radiology, University of Athens, Greece
| | - Andreas Theodorakakos
- Department of Mechanical Engineering, Technological Education Institute of Piraeus, Egaleo, Greece
| | | | - Demosthenes Katritsis
- Department of Cardiology, Athens Euroclinic, Athens, Greece; Beth Israel Deaconess Medical School, Harvard Medical School, Boston, MA,USA.
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888
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Fortuny G, Herrero J, Puigjaner D, Olivé C, Marimon F, Garcia-Bennett J, Rodríguez D. Effect of anticoagulant treatment in deep vein thrombosis: A patient-specific computational fluid dynamics study. J Biomech 2015; 48:2047-53. [PMID: 25917201 DOI: 10.1016/j.jbiomech.2015.03.026] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Revised: 03/05/2015] [Accepted: 03/22/2015] [Indexed: 11/19/2022]
Abstract
A methodology that might help physicians to establish a diagnostic and treatment tailored for each specific patient with a pathological thrombus is presented. A realistic model for the geometry of a popliteal vein with a thrombus just above the knee was reconstructed from in vivo computed tomography images acquired from one specific patient and then it was used to perform computational fluid dynamics (CFD) simulations. The wall shear stress (WSS) response to the administration of anticoagulant drugs and the influence of viscosity on the shape of the velocity distribution were investigated. Both a Newtonian and a non-Newtonian viscosity model were implemented for different blood flow rates in the range 3-7 cm(3)/s. The effect of anticoagulants on the blood was simulated by setting three different levels of viscosity in the Newtonian model (μ/μ∞=0.60, 0.80 and 1 with μ∞=3.45×10(-3) Pas). A reduction of μ by a given amount always led to a more modest reduction, typically by a factor of two, of the resulting WSS levels. Moreover, for a given flow rate the calculation with the non-Newtonian viscosity model yielded WSS levels between 20% and 40% larger than those obtained in the corresponding Newtonian fluid simulation. It was also found that blood moves slowly in the region between the thrombus and the vein wall, a fact that will favor the growth of the thrombotic mass. Both the mean WSS levels and the degree of sluggishness of the blood flow can be described by functions of the Reynolds number.
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Affiliation(s)
- Gerard Fortuny
- Departament d׳ Enginyeria Informàtica i Matemàtiques, Universitat Rovira i Virgili, Av Països Catalans 26, Tarragona, Catalunya, Spain.
| | - Joan Herrero
- Departament d׳ Enginyeria Quimica, Universitat Rovira i Virgili, Av Països Catalans 26, Tarragona, Catalunya, Spain.
| | - Dolors Puigjaner
- Departament d׳ Enginyeria Informàtica i Matemàtiques, Universitat Rovira i Virgili, Av Països Catalans 26, Tarragona, Catalunya, Spain.
| | - Carme Olivé
- Departament d׳ Enginyeria Informàtica i Matemàtiques, Universitat Rovira i Virgili, Av Països Catalans 26, Tarragona, Catalunya, Spain.
| | - Francesc Marimon
- Departament de Medicina i Cirurgia, Universitat Rovira i Virgili, Hospital Sant Joan, Reus, Catalunya, Spain.
| | - Josep Garcia-Bennett
- Servei de Radiologia i Diagnòstic per la Imatge, Hospital Sant Joan, Reus, Catalunya, Spain.
| | - Daniel Rodríguez
- Servei de Radiologia i Diagnòstic per la Imatge, Hospital Sant Joan, Reus, Catalunya, Spain.
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889
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Nicklas AP, Schilling D, Bader MJ, Herrmann TR, Nagele U; Training and Research in Urological Surgery and Technology (T.R.U.S.T.)-Group. The vacuum cleaner effect in minimally invasive percutaneous nephrolitholapaxy. World J Urol 2015; 33:1847-53. [PMID: 25833660 DOI: 10.1007/s00345-015-1541-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Accepted: 03/16/2015] [Indexed: 10/23/2022] Open
Abstract
INTRODUCTION Percutaneous stone removal increasingly plays an important role among the different approaches of interventional stone therapy, particularly since the development of miniaturized instruments is resulting in lower morbidity for the patients. One major drawback of smaller instruments is the increased difficulty of stone retrieval after disintegration due to the reduced tract diameter. This results in longer operation time and the need of additional tools such as disposable retrieval baskets. One of the key factors in the development of minimally invasive percutaneous nephrolitholapaxy (MIP) was the design of an Amplatz sheath which provides a built-in vacuum cleaner effect for stone retrieval. METHODS A series of flow analyses with the gauges and shapes of the most commonly used nephroscopes and sheaths in percutaneous nephrolitholapaxy was performed by computational fluid dynamics. Flow velocity and direction in front of the nephroscope were computed and visualized by the software. RESULTS In our study, the vacuum cleaner effect developed exclusively when a round-shaped nephroscope was used (Nagele Miniature Nephroscope System, Karl Storz GmbH & Co. KG) and depended on the relation between nephroscope diameter and inner sheath diameter. The strongest effect was observed with a 12 F nephroscope and an inner sheath diameter of 15 F. It did not develop when an oval- or crescent-shaped nephroscope was used. In front of the distal end of the round-shaped nephroscope, a slipstream develops, induced by the excursive change of width of the fluid flow on the outlet of the flushing canal. This allows the adhesion of a stone fragment in the eddy while the fluid flow is circulating around the stone. CONCLUSION This study illustrates and explains the vacuum cleaner effect which has been detected in the development of the Nagele Miniature Nephroscope System used in MIP. It combines the reduced morbidity of smaller kidney puncture diameters with the benefit of quick and complete stone removal.
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890
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Huang J, Feng F, Wan M, Ying J, Li Y, Qu X, Pan R, Shen G, Li W. Improving performance of flat-plate photobioreactors by installation of novel internal mixers optimized with computational fluid dynamics. Bioresour Technol 2015; 182:151-159. [PMID: 25689309 DOI: 10.1016/j.biortech.2015.01.067] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Revised: 01/15/2015] [Accepted: 01/16/2015] [Indexed: 06/04/2023]
Abstract
A novel mixer was developed to improve the performance of flat-plate photobioreactors (PBRs). The effects of mixer were theoretically evaluated using computational fluid dynamics (CFD) according to radial velocity of fluid and light/dark cycles within reactors. The structure parameters, including the riser width, top clearance, clearance between the baffles and walls, and number of the chambers were further optimized. The microalgae culture test aiming at validating the simulated results was conducted indoor. The results showed the maximum biomass concentrations in the optimized and archetype reactors were 32.8% (0.89 g L(-1)) and 19.4% (0.80 g L(-1)) higher than that in the control reactor (0.67 g L(-1)). Therefore, the novel mixer can significantly increase the fluid velocity along the light attenuation and light/dark cycles, thus further increased the maximum biomass concentration. The PBRs with novel mixers are greatly applicable for high-efficiency cultivation of microalgae.
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Affiliation(s)
- Jianke Huang
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, PR China.
| | - Fei Feng
- State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, PR China
| | - Minxi Wan
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, PR China
| | - Jiangguo Ying
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, PR China
| | - Yuanguang Li
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, PR China.
| | - Xiaoxing Qu
- State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, PR China
| | - Ronghua Pan
- JiaxingZeyuan Bio-products Co., Ltd., Jiaxing 314007, PR China
| | - Guomin Shen
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, PR China
| | - Wei Li
- State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, PR China
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891
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Quinn NP, Ackerman JD. The effect of bottom roughness on scalar transport in aquatic ecosystems: implications for reproduction and recruitment in the benthos. J Theor Biol 2015; 369:59-66. [PMID: 25596514 DOI: 10.1016/j.jtbi.2015.01.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Revised: 01/06/2015] [Accepted: 01/07/2015] [Indexed: 10/24/2022]
Abstract
Bottom roughness can influence gamete and larval transport in benthic organisms. For example the ratio of the roughness spacing (λ) and roughness height (k) determines the type of roughness flow regime created in two dimensional (2D) flows: λ/k<8 results in skimming flow; λ/k~8 results in wake interference flow; and λ/k>8 results in isolated roughness flow. Computational fluid dynamic modeling (COMSOL K-ε) was used to examine the effect of roughness geometry (e.g., a gradient in angularity provided by square, triangular and round 2D bottom roughness elements) on the prediction of roughness flow regime using biologically relevant λ/k ratios. In addition, a continuously released scalar (a proxy for gametes and larvae) in a coupled convection-diffusion model was used to determine the relationship among roughness geometry, λ/k ratios, and scalar transport (relative scalar transport, RT=ratio of scalar measured downstream in a series of roughness elements placed in tandem). The modeled roughness flow regimes fit closely with theoretical predictions using the square and triangle geometries, but the round geometry required a lower λ/k ratio than expected for skimming flow. Relative transport of the scalar was consistent with the modeled flow regimes, however significant differences in RT were found among the roughness flows for each geometry, and significantly lower RT values were observed for skimming flow in the round geometry. The λ/k ratio provides an accurate means of classifying flow in and around the roughness elements, whereas RT indicates the nature of scalar transport and retention. These results indicate that the spatial configuration of bottom roughness is an important determinant of gamete/larval transport in terms of whether the scalar will be retained among roughness elements or transported downstream.
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Affiliation(s)
- Noel P Quinn
- Department of Integrative Biology, University of Guelph, Guelph, ON, Canada N1G 2W1
| | - Josef D Ackerman
- Department of Integrative Biology, University of Guelph, Guelph, ON, Canada N1G 2W1.
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892
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Tangen KM, Hsu Y, Zhu DC, Linninger AA. CNS wide simulation of flow resistance and drug transport due to spinal microanatomy. J Biomech 2015; 48:2144-54. [PMID: 25888012 DOI: 10.1016/j.jbiomech.2015.02.018] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Revised: 02/04/2015] [Accepted: 02/15/2015] [Indexed: 11/21/2022]
Abstract
Spinal microstructures are known to substantially affect cerebrospinal fluid patterns, yet their actual impact on flow resistance has not been quantified. Because the length scale of microanatomical aspects is below medical image resolution, their effect on flow is difficult to observe experimentally. Using a computational fluid mechanics approach, we were able to quantify the contribution of micro-anatomical aspects on cerebrospinal fluid (CSF) flow patterns and flow resistance within the entire central nervous system (CNS). Cranial and spinal CSF filled compartments were reconstructed from human imaging data; microscopic trabeculae below the image detection threshold were added artificially. Nerve roots and trabeculae were found to induce regions of microcirculation, whose location, size and vorticity along the spine were characterized. Our CFD simulations based on volumetric flow rates acquired with Cine Phase Contrast MRI in a normal human subject suggest a 2-2.5 fold increase in pressure drop mainly due to arachnoid trabeculae. The timing and phase lag of the CSF pressure and velocity waves along the spinal canal were also computed, and a complete spatio-temporal map encoding CSF volumetric flow rates and pressure was created. Micro-anatomy induced fluid patterns were found responsible for the rapid caudo-cranial spread of an intrathecally administered drug. The speed of rostral drug dispersion is drastically accelerated through pulsatile flow around microanatomy induced vortices. Exploring massive parallelization on a supercomputer, the feasibility of computational drug transport studies was demonstrated. CNS-wide simulations of intrathecal drugs administration can become a practical tool for in silico design, interspecies scaling and optimization of experimental drug trials.
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893
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Fan J, Wang Y, Liu J, Jing L, Wang C, Li C, Yang X, Zhang Y. Morphological-Hemodynamic Characteristics of Intracranial Bifurcation Mirror Aneurysms. World Neurosurg 2015; 84:114-120.e2. [PMID: 25753233 DOI: 10.1016/j.wneu.2015.02.038] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 02/26/2015] [Accepted: 02/26/2015] [Indexed: 11/16/2022]
Abstract
BACKGROUND Many morphological and hemodynamic parameters have been proposed as promising aneurysm rupture status discriminators. Besides, a clear dichotomy between sidewall and bifurcation aneurysms was reported. In this study, we strove to evaluate the contribution of many reported morphological and hemodynamic parameters to retrospective rupture status determination in bifurcation aneurysms independent of patients' characteristics. METHODS Computational fluid dynamics were performed on 16 patients with bifurcation mirror aneurysms (MANs). Each pair was divided into ruptured and unruptured groups. The morphological and hemodynamic factors were analyzed and compared. Receiver operating characteristics (ROC) analysis was performed, and the area under the ROC curve (AUC) was calculated for all parameters to quantify the predictability of each index and identify the optimal threshold. RESULTS Morphological (size, aspect ratio, size ratio, and height-width ratio) and hemodynamic (time-averaged mean wall shear stress [WSSmean], low WSS area [LSA]) parameters reached statistical significance (P < 0.05). Aneurysm irregular shape, oscillatory shear index (OSI), flow stability, inflow concentration, and impingement zone did not achieve significantly statistical differences (P = 0.508, P = 0.319, P = 0.523, P = 0.227, and P = 1.000, respectively). After ROC analysis, only aspect ratio and LSA had excellent AUC values (0.840 and 0.824, respectively). Other key parameters, including size, size ratio, height-width ratio, and WSSmean, had AUC values between 0.7 and 0.8 (0.730, 0.715, 0.703, 0.727, respectively). CONCLUSIONS Higher aspect ratio and LSA are good indicators for bifurcation aneurysm rupture. MANs with different rupture status might be a useful disease model in which many factors are balanced to investigate possible features linked to aneurysm rupture.
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Affiliation(s)
- Jixing Fan
- Department of Interventional Neuroradiology, Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Yang Wang
- Department of Interventional Neuroradiology, Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Jian Liu
- Department of Interventional Neuroradiology, Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Linkai Jing
- Department of Interventional Neuroradiology, Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Chao Wang
- Department of Interventional Neuroradiology, Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Chuanhui Li
- Department of Interventional Neuroradiology, Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Xinjian Yang
- Department of Interventional Neuroradiology, Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical University, Beijing, China.
| | - Ying Zhang
- Department of Interventional Neuroradiology, Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical University, Beijing, China.
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894
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Martin D, Boyle F. Sequential Structural and Fluid Dynamics Analysis of Balloon-Expandable Coronary Stents: A Multivariable Statistical Analysis. Cardiovasc Eng Technol 2015; 6:314-28. [PMID: 26577363 DOI: 10.1007/s13239-015-0219-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Accepted: 02/21/2015] [Indexed: 12/21/2022]
Abstract
Several clinical studies have identified a strong correlation between neointimal hyperplasia following coronary stent deployment and both stent-induced arterial injury and altered vessel hemodynamics. As such, the sequential structural and fluid dynamics analysis of balloon-expandable stent deployment should provide a comprehensive indication of stent performance. Despite this observation, very few numerical studies of balloon-expandable coronary stents have considered both the mechanical and hemodynamic impact of stent deployment. Furthermore, in the few studies that have considered both phenomena, only a small number of stents have been considered. In this study, a sequential structural and fluid dynamics analysis methodology was employed to compare both the mechanical and hemodynamic impact of six balloon-expandable coronary stents. To investigate the relationship between stent design and performance, several common stent design properties were then identified and the dependence between these properties and both the mechanical and hemodynamic variables of interest was evaluated using statistical measures of correlation. Following the completion of the numerical analyses, stent strut thickness was identified as the only common design property that demonstrated a strong dependence with either the mean equivalent stress predicted in the artery wall or the mean relative residence time predicted on the luminal surface of the artery. These results corroborate the findings of the large-scale ISAR-STEREO clinical studies and highlight the crucial role of strut thickness in coronary stent design. The sequential structural and fluid dynamics analysis methodology and the multivariable statistical treatment of the results described in this study should prove useful in the design of future balloon-expandable coronary stents.
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895
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Andersson M, Lantz J, Ebbers T, Karlsson M. Quantitative Assessment of Turbulence and Flow Eccentricity in an Aortic Coarctation: Impact of Virtual Interventions. Cardiovasc Eng Technol 2015; 6:281-93. [PMID: 26577361 DOI: 10.1007/s13239-015-0218-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Accepted: 02/13/2015] [Indexed: 01/01/2023]
Abstract
Turbulence and flow eccentricity can be measured by magnetic resonance imaging (MRI) and may play an important role in the pathogenesis of numerous cardiovascular diseases. In the present study, we propose quantitative techniques to assess turbulent kinetic energy (TKE) and flow eccentricity that could assist in the evaluation and treatment of stenotic severities. These hemodynamic parameters were studied in a pre-treated aortic coarctation (CoA) and after several virtual interventions using computational fluid dynamics (CFD), to demonstrate the effect of different dilatation options on the flow field. Patient-specific geometry and flow conditions were derived from MRI data. The unsteady pulsatile flow was resolved by large eddy simulation including non-Newtonian blood rheology. Results showed an inverse asymptotic relationship between the total amount of TKE and degree of dilatation of the stenosis, where turbulent flow proximal the constriction limits the possible improvement by treating the CoA alone. Spatiotemporal maps of TKE and flow eccentricity could be linked to the characteristics of the jet, where improved flow conditions were favored by an eccentric dilatation of the CoA. By including these flow markers into a combined MRI-CFD intervention framework, CoA therapy has not only the possibility to produce predictions via simulation, but can also be validated pre- and immediate post treatment, as well as during follow-up studies.
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Affiliation(s)
- Magnus Andersson
- Department of Management and Engineering (IEI), Linköping University, 581 83, Linköping, Sweden. .,Swedish e-Science Research Center (SeRC), Stockholm, Sweden.
| | - Jonas Lantz
- Department of Science and Technology, Linköping University, Linköping, Sweden.,Swedish e-Science Research Center (SeRC), Stockholm, Sweden
| | - Tino Ebbers
- Department of Science and Technology, Linköping University, Linköping, Sweden.,Department of Medical and Health Sciences, Linköping University, Linköping, Sweden.,Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden.,Swedish e-Science Research Center (SeRC), Stockholm, Sweden
| | - Matts Karlsson
- Department of Management and Engineering (IEI), Linköping University, 581 83, Linköping, Sweden.,Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden.,Swedish e-Science Research Center (SeRC), Stockholm, Sweden
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896
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Etminan N, Macdonald RL. Computational Fluid Dynamics and Intracranial Aneurysms: Higher Mathematics Meets Complex Biology. World Neurosurg 2015; 83:1017-9. [PMID: 25731798 DOI: 10.1016/j.wneu.2015.02.015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Accepted: 02/20/2015] [Indexed: 10/23/2022]
Affiliation(s)
- Nima Etminan
- Department of Neurosurgery, Medical Faculty, Heinrich-Heine-University, Düsseldorf, Germany.
| | - R Loch Macdonald
- Division of Neurosurgery, St. Michael's Hospital, Keenan Research Centre for Biomedical Science and the Li Ka Shing Knowledge Institute of St. Michael's Hospital, Department of Surgery, University of Toronto, Ontario, Canada
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897
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Rmaile A, Carugo D, Capretto L, Wharton JA, Thurner PJ, Aspiras M, Ward M, De Jager M, Stoodley P. An experimental and computational study of the hydrodynamics of high-velocity water microdrops for interproximal tooth cleaning. J Mech Behav Biomed Mater 2015; 46:148-57. [PMID: 25792412 DOI: 10.1016/j.jmbbm.2015.02.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Revised: 01/28/2015] [Accepted: 02/01/2015] [Indexed: 10/24/2022]
Abstract
The flow field and local hydrodynamics of high-velocity water microdrops impacting the interproximal (IP) space of typodont teeth were studied experimentally and computationally. Fourteen-day old Streptococcus mutans biofilms in the IP space were treated by a prototype AirFloss delivering 115 µL of water at a maximum exit-velocity of 60 ms(-1) in a 33-ms burst. Using high-speed imaging, footage was generated showing the details of the burst, and demonstrating the removal mechanism of the biofilms. Footage was also generated to characterize the viscoelastic behavior of the biofilms when impacted by an air-only burst, which was compared to the water burst. Image analysis demonstrated the importance of fluid forces on the removal pattern of interdental biofilms. X-ray micro-Computed Tomography (µ-CT) was used to obtain 3D images of the typodont and the IP spaces. Computational Fluid Dynamics (CFD) simulations were performed to study the effect of changing the nozzle position and design on the hydrodynamics within the IP space. Results confirmed our previous data regarding the wall shear stress generated by high-velocity water drops which dictated the efficacy of biofilm detachment. Finally, we showed how CFD models could be used to optimize water drop or burst design towards a more effective biofilm removal performance.
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Affiliation(s)
- A Rmaile
- nCATS, Faculty of Engineering and the Environment (FEE), University of Southampton, UK.
| | - D Carugo
- Bioengineering Science Research Group, Faculty of Engineering and the Environment (FEE), University of Southampton, UK
| | - L Capretto
- Bioengineering Science Research Group, Faculty of Engineering and the Environment (FEE), University of Southampton, UK
| | - J A Wharton
- nCATS, Faculty of Engineering and the Environment (FEE), University of Southampton, UK
| | - P J Thurner
- Bioengineering Science Research Group, Faculty of Engineering and the Environment (FEE), University of Southampton, UK
| | - M Aspiras
- Philips Oral Healthcare Inc. (POH), Bothell, WA, USA
| | - M Ward
- Philips Oral Healthcare Inc. (POH), Bothell, WA, USA
| | - M De Jager
- Philips Research, Oral Healthcare Research, Eindhoven, The Netherlands
| | - P Stoodley
- nCATS, Faculty of Engineering and the Environment (FEE), University of Southampton, UK; Center for Microbial Interface Biology, Departments of Microbial Infection and Immunity, and Orthopaedics, The Ohio State University, Columbus, OH, USA
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898
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Fernández Tena A, Casan Clarà P. Use of computational fluid dynamics in respiratory medicine. Arch Bronconeumol 2015; 51:293-8. [PMID: 25618456 DOI: 10.1016/j.arbres.2014.09.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Revised: 09/08/2014] [Accepted: 09/10/2014] [Indexed: 11/19/2022]
Abstract
Computational Fluid Dynamics (CFD) is a computer-based tool for simulating fluid movement. The main advantages of CFD over other fluid mechanics studies include: substantial savings in time and cost, the analysis of systems or conditions that are very difficult to simulate experimentally (as is the case of the airways), and a practically unlimited level of detail. We used the Ansys-Fluent CFD program to develop a conducting airway model to simulate different inspiratory flow rates and the deposition of inhaled particles of varying diameters, obtaining results consistent with those reported in the literature using other procedures. We hope this approach will enable clinicians to further individualize the treatment of different respiratory diseases.
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Affiliation(s)
- Ana Fernández Tena
- Instituto Nacional de Silicosis, Hospital Universitario Central de Asturias, Facultad de Medicina, Universidad de Oviedo, Oviedo, España
| | - Pere Casan Clarà
- Instituto Nacional de Silicosis, Hospital Universitario Central de Asturias, Facultad de Medicina, Universidad de Oviedo, Oviedo, España.
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899
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Oakes JM, Marsden AL, Grandmont C, Darquenne C, Vignon-Clementel IE. Distribution of aerosolized particles in healthy and emphysematous rat lungs: comparison between experimental and numerical studies. J Biomech 2015; 48:1147-57. [PMID: 25682537 DOI: 10.1016/j.jbiomech.2015.01.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Revised: 12/17/2014] [Accepted: 01/13/2015] [Indexed: 01/17/2023]
Abstract
In silico models of airflow and particle deposition in the lungs are increasingly used to determine the therapeutic or toxic effects of inhaled aerosols. While computational methods have advanced significantly, relatively few studies have directly compared model predictions to experimental data. Furthermore, few prior studies have examined the influence of emphysema on particle deposition. In this work we performed airflow and particle simulations to compare numerical predictions to data from our previous aerosol exposure experiments. Employing an image-based 3D rat airway geometry, we first compared steady flow simulations to coupled 3D-0D unsteady simulations in the healthy rat lung. Then, in 3D-0D simulations, the influence of emphysema was investigated by matching disease location to the experimental study. In both the healthy unsteady and steady simulations, good agreement was found between numerical predictions of aerosol delivery and experimental deposition data. However, deposition patterns in the 3D geometry differed between the unsteady and steady cases. On the contrary, satisfactory agreement was not found between the numerical predictions and experimental data for the emphysematous lungs. This indicates that the deposition rate downstream of the 3D geometry is likely proportional to airflow delivery in the healthy lungs, but not in the emphysematous lungs. Including small airway collapse, variations in downstream airway size and tissue properties, and tracking particles throughout expiration may result in a more favorable agreement in future studies.
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Affiliation(s)
- Jessica M Oakes
- INRIA Paris-Rocquencourt, 78153 Le Chesnay Cedex, France; Sorbonne Universités UPMC Univ. Paris 6, Laboratoire Jacques-Louis Lions, 75005 Paris, France
| | - Alison L Marsden
- Mechanical and Aerospace Engineering Department, University of California San Diego, La Jolla, CA 92093, USA
| | - Céline Grandmont
- INRIA Paris-Rocquencourt, 78153 Le Chesnay Cedex, France; Sorbonne Universités UPMC Univ. Paris 6, Laboratoire Jacques-Louis Lions, 75005 Paris, France
| | - Chantal Darquenne
- Department of Medicine, Division of Physiology, University of California San Diego, La Jolla, CA 92093, USA
| | - Irene E Vignon-Clementel
- INRIA Paris-Rocquencourt, 78153 Le Chesnay Cedex, France; Sorbonne Universités UPMC Univ. Paris 6, Laboratoire Jacques-Louis Lions, 75005 Paris, France.
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900
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Thompson AG, Raju R, Blanke P, Yang TH, Mancini GBJ, Budoff MJ, Norgaard BL, Min JK, Leipsic JA. Diagnostic accuracy and discrimination of ischemia by fractional flow reserve CT using a clinical use rule: results from the Determination of Fractional Flow Reserve by Anatomic Computed Tomographic Angiography study. J Cardiovasc Comput Tomogr 2015; 9:120-8. [PMID: 25819194 DOI: 10.1016/j.jcct.2015.01.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Revised: 11/09/2014] [Accepted: 01/09/2015] [Indexed: 12/23/2022]
Abstract
BACKGROUND Fractional flow reserve (FFR) is the gold standard for determining lesion-specific ischemia. Computed FFRCT derived from coronary CT angiography (coronary CTA) correlates well with invasive FFR and accurately differentiates between ischemia-producing and nonischemic lesions. The diagnostic performance of FFRCT when applied in a clinically relevant way to all vessels ≥ 2 mm in diameter stratified by sex and age has not been previously examined. METHODS Two hundred fifty-two patients and 407 vessels underwent coronary CTA, FFRCT, invasive coronary angiography, and invasive FFR. FFRCT and FFR ≤ 0.80 were considered ischemic, whereas CT stenosis ≥ 50% was considered obstructive. The diagnostic performance of FFRCT was assessed following a prespecified clinical use rule which included all vessels ≥ 2 mm in diameter, not just those assessed by invasive FFR measurements. Stenoses <30% were assigned an FFR of 0.90, and stenoses >90% were assigned an FFR of 0.50. Diagnostic performance of FFRCT was stratified by vessel diameter, sex, and age. RESULTS By FFR, ischemia was identified in 129 of 252 patients (51%) and in 151 of 407 vessels (31%). Mean age (± standard deviation) was 62.9 ± 9 years, and women were older (65.5 vs 61.9 years; P = .003). Per-patient diagnostic accuracy (83% vs 72%; P < .005) and specificity (54% vs 82%, P < .001) improved significantly after application of the clinical use tool. These were significantly improved over standard coronary CTA values before application of the clinical use rule. Discriminatory power of FFRCT also increased compared with baseline (area under the receiver operating characteristics curve [AUC]: 0.93 vs 0.81, P < .001). Diagnostic performance improved in both sexes with no significant differences between the sexes (AUC: 0.93 vs 0.90, P = .43). There were no differences in the discrimination of FFRCT after application of the clinical use rule when stratified by age ≥ 65 or <65 years (AUC: 0.95 vs 0.90, P = .10). CONCLUSIONS The diagnostic accuracy and discriminatory power of FFRCT improve significantly after the application of a clinical use rule which includes all clinically relevant vessels >2 mm in diameter. FFRCT has similar diagnostic accuracy and discriminatory power for ischemia detection in men and women irrespective of age using a cut point of 65 years.
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Affiliation(s)
- Angus G Thompson
- Department of Radiology, St Paul's Hospital, University of British Columbia, 1081 Burrard Street, Vancouver, BC, V6Z 1Y6, Canada.
| | - Rekha Raju
- Department of Radiology, St Paul's Hospital, University of British Columbia, 1081 Burrard Street, Vancouver, BC, V6Z 1Y6, Canada
| | - Philipp Blanke
- Department of Radiology, St Paul's Hospital, University of British Columbia, 1081 Burrard Street, Vancouver, BC, V6Z 1Y6, Canada
| | - Tae-Hyun Yang
- Department of Radiology, St Paul's Hospital, University of British Columbia, 1081 Burrard Street, Vancouver, BC, V6Z 1Y6, Canada
| | | | - Matthew J Budoff
- Department of Medicine, Harbor UCLA Medical Center, Los Angeles, California
| | - Bjarne L Norgaard
- Department of Cardiology B, Aarhus University Hospital Skejby, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark
| | - James K Min
- Department of Radiology, New York-Presbyterian Hospital and the Weill Cornell Medical College, New York, NY, USA
| | - Jonathon A Leipsic
- Department of Radiology, St Paul's Hospital, University of British Columbia, 1081 Burrard Street, Vancouver, BC, V6Z 1Y6, Canada
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