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Abstract
OBJECTIVE The purpose of this study was to investigate a new method-the portal vein enhancement curve-for quantifying portal vein blood flow immediately at transjugular intrahepatic portosystemic shunt (TIPS) creation using digital subtraction angiography images and its potential usefulness as a predictor of TIPS revision. CONCLUSION The portal vein flow time constant, Qτ, was significantly different (p = 0.002) between patients grouped by 12-month revision (TIPS angioplasty, TIPS reduction, no revision); Qτ was higher in patients who required TIPS reduction.
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Peach TW, Ventikos Y, Byrne JV, You Z. Porcine In Vivo Validation of a Virtual Contrast Model: The Influence of Contrast Agent Properties and Vessel Flow Rates. AJNR Am J Neuroradiol 2016; 37:2304-2309. [PMID: 27390316 DOI: 10.3174/ajnr.a4884] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Accepted: 06/02/2016] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND PURPOSE Accurately and efficiently modeling the transport of angiographic contrast currently offers the best method of verifying computational fluid dynamics simulations and, with it, progress toward the lofty goal of prediction of aneurysm treatment outcome a priori. This study specifically examines the influence of estimated flow rate and contrast properties on such in silico predictions of aneurysm contrast residence and decay. MATERIALS AND METHODS Four experimental sidewall aneurysms were created in swine, with aneurysm contrast flow patterns and decay rates observed under angiography. A simplified computational fluid dynamics model of the experimental aneurysm was constructed from 3D angiography and contrast residence predicted a priori. The relative influence of a number of estimated model parameters (contrast viscosity, contrast density, and blood flow rate) on contrast residence was then investigated with further simulations. RESULTS Contrast infiltration and washout pattern were accurately predicted by the a priori computational fluid dynamics model; however, the contrast decay rate was underestimated by ∼25%. This error was attributed to the estimated parent vessel flow rate alone, and the effects of contrast viscosity and density on the decay rate were found to be inconsequential. A linear correlation between the parent vessel flow rate and the corresponding contrast decay rate was observed. CONCLUSIONS In experimental sidewall aneurysms, contrast fluid properties (viscosity and density) were shown to have a negligible effect on variation in the modeled contrast decay rate. A strong linear correlation was observed between parent vessel flow rate and contrast decay over a physiologically reasonable range of flow rates.
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Affiliation(s)
- T W Peach
- From the Department of Mechanical Engineering (T.W.P., Y.V.), University College London, London, UK
| | - Y Ventikos
- From the Department of Mechanical Engineering (T.W.P., Y.V.), University College London, London, UK
| | - J V Byrne
- Department of Neuroradiology (J.V.B.), John Radcliffe Hospital, Oxford, UK
| | - Z You
- Department of Engineering Science (Z.Y.), University of Oxford, Oxford, UK
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Boegel M, Gehrisch S, Redel T, Rohkohl C, Hoelter P, Doerfler A, Maier A, Kowarschik M. Patient-individualized boundary conditions for CFD simulations using time-resolved 3D angiography. Int J Comput Assist Radiol Surg 2016; 11:1061-9. [DOI: 10.1007/s11548-016-1367-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Accepted: 02/25/2016] [Indexed: 11/28/2022]
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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] [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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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] [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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Karmonik C. Toward improving fidelity of computational fluid dynamics simulations: boundary conditions matter. AJNR Am J Neuroradiol 2014; 35:1549-50. [PMID: 24763411 DOI: 10.3174/ajnr.a3984] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Christof Karmonik
- Departments of Neurosurgery and Translational Imaging Houston Methodist Hospital Research Institute Houston, Texas Weill Medical College of Cornell University New York, New York
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Anderson JR, Diaz O, Klucznik R, Zhang YJ, Britz GW, Grossman RG, Lv N, Huang Q, Karmonik C. Validation of computational fluid dynamics methods with anatomically exact, 3D printed MRI phantoms and 4D pcMRI. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2014; 2014:6699-6701. [PMID: 25571533 DOI: 10.1109/embc.2014.6945165] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
A new concept of rapid 3D prototyping was implemented using cost-effective 3D printing for creating anatomically correct replica of cerebral aneurysms. With a dedicated flow loop set-up in a full body human MRI scanner, flow measurements were performed using 4D phase contrast magnetic resonance imaging to visualize and quantify intra-aneurysmal flow patterns. Ultrashort TE sequences were employed to obtain high-resolution 3D image data to visualize the lumen inside the plastic replica. In-vitro results were compared with retrospectively obtained in-vivo data and results from computational fluid dynamics simulations (CFD). Rapid prototyping of anatomically realistic 3D models may have future impact in treatment planning, design of image acquisition methods for MRI and angiographic systems and for the design and testing of advanced image post-processing technologies.
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