@misc {43190,
	title = {The effects of cerebrospinal fluid and hyperelastic model on aneurysm wall vibration using high-fidelity fluid-structure interaction simulations},
	howpublished = {Summer Biomechanics, Bioengineering, and Biotransport Conference},
	year = {2023},
	author = {Yamamoto, Kei and Bruneau, David and Steinman, David and Valen-Sendstad, Kristian}
}
@article {43033,
	title = {On The Importance of Fundamental Computational Fluid Dynamics Towards a Robust and Reliable Model of Left Atrial Flows: Is There More Than Meets the Eye?},
	journal = {International journal of numerical methods in biomedical engineering},
	year = {2023},
	publisher = { John Wiley \& Sons},
	author = {Khalili, Ehsan and Daversin-Catty, C{\'e}cile and Andy L. {Olivares} and Mill, Jordi and Camara, Oscar and Valen-Sendstad, Kristian}
}
@article {kjeldsberg2023verified,
	title = {A verified and validated moving domain computational fluid dynamics solver with applications to cardiovascular flows},
	journal = {International journal for numerical methods in biomedical engineering},
	volume = {39},
	number = {6},
	year = {2023},
	pages = {e3703},
	publisher = { Wiley},
	author = {Kjeldsberg, Henrik and Sundnes, Joakim and Valen-Sendstad, Kristian}
}
@inproceedings {43017,
	title = {Characterization of Vessel Wall Vibrations of an Arteriovenous Fistula Over the Maturation Period},
	journal = {7th International Conference on Computational and Mathematical Biomedical Engineering (CMBE2022)},
	year = {2022},
	month = {06/2022},
	pages = {504-507},
	publisher = { CMBE Proceedings},
	abstract = {Arteriovenous fistula (AVF) is the preferred vascular access for hemodialysis, but is still associated with a high failure rate. This study aims at characterizing AVF changes in vessel wall vibrations during the maturation period. Three-dimensional AVF models were generated from MR images acquired 3 days and 6 weeks after surgery in a 72-year-old male patient. Blood velocities obtained from Ultrasound were imposed as boundary conditions for high-fidelity fluid-structure interaction simulations. Results showed predominant wall vibrations between anastomosis and perianastomotic vein, the typical areas where the stenosis develops, highlighting their potential role in the mechanobiological process responsible for AVF failure.},
	issn = {ISSN 2227-3085},
	author = {Soliveri, Luca and Bozzetto, Michela and Redaelli, Alberto and Remuzzi, Andrea and Valen-Sendstad, Kristian}
}
@inproceedings {43032,
	title = {A Comparative Study of Normal and High-Fidelity Approaches to Predict Flow Physics of Left Atrium},
	journal = {Computing in Cardiology, CinC 2022},
	year = {2022},
	publisher = {IEEE},
	url = {https://cinc.org/2022/Program/accepted/28.pdf},
	author = {Khalili, Ehsan and Daversin-Catty, C{\'e}cile and Valen-Sendstad, Kristian}
}
@misc {43030,
	title = {A Comparative Study of  Normal and High-Fidelity Computational Fluid Dynamics Approaches to  Predict Flow Physics of Left Atrium},
	howpublished = {Computing in Cardiology, Tampere, Finland},
	year = {2022},
	url = {https://cinc.org/2022/Program/accepted/28.pdf},
	author = {Khalili, Ehsan and Daversin-Catty, C{\'e}cile and Valen-Sendstad, Kristian}
}
@misc {43022,
	title = {Computational Fluid Dynamics Approaches to Predict Flow Physics of Left Atrium},
	howpublished = {Universitat Pompeu Fabra - Barcelona, Spain},
	year = {2022},
	author = {Khalili, Ehsan and Kjeldsberg, Henrik and Sergio Nabil {Gadur} and Daversin-Catty, C{\'e}cile and Valen-Sendstad, Kristian}
}
@article {28448,
	title = {High-Fidelity Fluid Structure Interaction Simulations of Turbulent-Like Aneurysm Flows Reveals High-Frequency Narrowband Wall Vibrations: A Stimulus of Mechanobiological Relevance?},
	journal = {Journal of Biomechanics},
	volume = {145},
	year = {2022},
	pages = {111369},
	publisher = {Elsevier},
	doi = {10.1016/j.jbiomech.2022.111369},
	url = {https://www.sciencedirect.com/science/article/pii/S0021929022004109},
	author = {Souche, Alban and Valen-Sendstad, Kristian}
}
@inproceedings {28451,
	title = {Impact of Flow Rate on Wall Vibration in Intracranial Aneurysms},
	journal = {8th European Congress on Computational Methods in Applied Sciences and Engineer- ing},
	year = {2022},
	address = {Oslo, Norway},
	author = {David A. {Bruneau} and Valen-Sendstad, Kristian and David A. {Steinman}}
}
@misc {43021,
	title = {Impact of Rigid Versus Dynamic Boundaries on Computational Fluid Dynamics Predictor of Left Atrial Appendage Thrombus Formation},
	year = {2022},
	address = {Computing in Cardiology},
	author = {Kjeldsberg, Henrik},
	editor = {Mill, Jordi and Carlos A. {Lucas} and David V. {Medel} and Camara, Oscar and Sundnes, Joakim and Valen-Sendstad, Kristian}
}
@misc {43023,
	title = {A mechanistic approach towards personalized treatment in patients with atrial fibrillation },
	howpublished = {University Heart \& Vascular Center Hamburg - UKE},
	year = {2022},
	author = {Kjeldsberg, Henrik and Sundnes, Joakim and Valen-Sendstad, Kristian}
}
@misc {42960,
	title = {SimCardioTest Open Source Software {\textendash} Demo on OASIS: Computational fluid dynamics solver \& SOFA: Simulation Open Framework Architecture},
	howpublished = {VPH2022, Porto, Portugal},
	year = {2022},
	publisher = {VPH2022 Porto},
	abstract = {SimCardioTest is a collaborative project between 10 organizations from 6 European countries and United States funded by the European Commission (EU H2020). The aim of the project is to provide new insight into designing predictive tools in cardiac pathologies and to accelerate the uptake of computer simulations for testing medicines and medical devices.The aim of the workshop is\&nbsp; hands on/demonstration of the open source OASIS and SOFA software.},
	url = {https://vph-conference.org/call-for-proposals/},
	author = {Yamamoto, Kei and Valen-Sendstad, Kristian}
}
@inproceedings {28450,
	title = {Turbulent-like arteriovenous fistula flows cause wall vibrations: a specific stimulus for stenosis formation?},
	journal = {9th World Congress of Biomechanics,},
	year = {2022},
	author = {Bozzetto, Michela and Ring, Johannes and Remuzzi, Andrea and Valen-Sendstad, Kristian}
}
@misc {42961,
	title = {Turbulent-like flow as a cause of cerebral aneurysm initiation: Can flow instability promote pathophysiological wall remodeling?},
	year = {2022},
	publisher = {Blood-Tissue Interface conference},
	address = {Blood-Tissue Interface conference, Montpellier, France},
	url = {https://bti.sciencesconf.org},
	author = {Yamamoto, Kei and Valen-Sendstad, Kristian}
}
@misc {42959,
	title = {Under-resolved DNS of turbulent flow in straight and helically coiled pipes},
	howpublished = {FEniCS 2022, San Diego, USA},
	year = {2022},
	publisher = {FEniCS2022},
	abstract = {Oasis\&nbsp;is an open-source Navier-Stokes solver built on FEniCS entirely written in Python. There are other open-source Navier-Stokes solvers available, such as openFOAM, but it is written in low-level programming language C++. One of the advantages of using Oasis over openFOAM is the usage of high-level Python code that enables users to flexibly control the implementation of problems. In addition, Oasis utilizes MPI to ensure high-performance and scalability on parallel clusters. Oasis has been previously verified and validated, but verification and validation is a continuous process that can establish the reliability of the solver when applied to new problems.\&nbsp;\&nbsp;Here, we present two turbulent flow problems that can illustrate flexible implementation of Oasis with fast and accurate performance. First, direct numerical simulation (DNS) of turbulent flow in a straight pipe was carried out for numerical validation, and the results were compared against published DNS data-set. Second, we examined turbulent flow in helically coiled pipes using fully developed turbulent flow from straight pipes as an inlet velocity profile.\&nbsp;In the straight pipe, our quantitative results showed convergence towards the DNS reference data, as the mesh was refined. In the helically coiled pipe, reported for the first time for a numerical model, stabilization of the turbulent flow was observed towards the outlet. Due to the curved path and the centrifugal force, two counter-rotating vortices referred to as Dean vortices were formed on the cross-section of the pipe. These vortices rapidly intensified the dissipation by creating smaller eddies in the flow and hence contributing to stabilizing the flow.\&nbsp;},
	url = {https://fenicsproject.org/fenics-2022/},
	author = {Yamamoto, Kei and Valen-Sendstad, Kristian}
}
@inproceedings {27727,
	title = {ARTERIOVENOUS FISTULA FOR HEMODIALYSIS: CAN TURBULENT-LIKE FLOW PHENOTYPE INDUCE WALL VIBRATIONS?},
	journal = {21st CONGRESS OF THE VASCULAR ACCESS SOCIETY},
	year = {2021},
	author = {Bozzetto, Michela and Souche, Alban and Remuzzi, Andrea and Valen-Sendstad, Kristian and , }
}
@article {kjeldsberg2021automated,
	title = {Automated landmarking of bends in vascular structures: a comparative study with application to the internal carotid artery},
	journal = {BioMedical Engineering OnLine},
	volume = {20},
	year = {2021},
	month = {11/2021},
	pages = {120},
	publisher = {Springer Nature BMC},
	doi = {10.1186/s12938-021-00957-6},
	url = {https://biomedical-engineering-online.biomedcentral.com/articles/10.1186/s12938-021-00957-6},
	author = {Kjeldsberg, Henrik and Bergersen, Aslak and Valen-Sendstad, Kristian}
}
@article {28446,
	title = {On delayed transition to turbulence in an eccentric stenosis model for clean vs. noisy high-fidelity CFD},
	journal = {Journal of Biomechanics},
	volume = {125},
	year = {2021},
	month = {Jan-08-2021},
	pages = {110588},
	publisher = {Elsevier},
	abstract = {Recent comparisons between experiments and computational fluid dynamics (CFD) simulations of flow in the Food and Drug Administration (FDA) standardized nozzle geometry have highlighted the potential sensitivity of axisymmetric CFD models to small perturbations induced by mesh and inlet velocity, particularly for Reynolds numbers (Re) in the transitional regime. This evokes the classic experiment of Reynolds on transition to turbulence in a straight pipe, which can be delayed, apparently indefinitely, if special care is taken to control for external influences. Such idealized experiments are, however, extremely difficult to perform and, in the context of cardiovascular modeling, belie the "noise" inherent in typical experimental and physiological systems. Previous high-fidelity CFD of a canonical eccentric (i.e., non-axisymmetric) stenosis model showed transition occurring for steady flow at Re ~ 700-800, with modest delay caused by the introduction of shear-thinning rheology. On the other hand, recent experimental measurements of steady flowing blood and blood-mimicking fluids in this same stenosis model report transition for Re ~ 400-500. Taking a cue from the FDA nozzle controversy, the present study demonstrates that the addition of small-magnitude random noise at the inlet brings the eccentric-stenosis CFD results more in-line with experiments, and reveals a more gradual transition towards turbulence. This highlights that, even in non-axisymmetric idealized geometries, unnaturally "clean" high-fidelity CFD may impede not only good agreement with experiments, but also understanding of the onset and character of blood flow instabilities as they may exist, naturally, in the vasculature.},
	issn = {00219290},
	doi = {10.1016/j.jbiomech.2021.110588},
	url = {https://www.sciencedirect.com/science/article/abs/pii/S0021929021003675?via\%3Dihub},
	author = {Haley, A.L. and Valen-Sendstad, Kristian and Steinman, D.A.}
}
@inproceedings {27726,
	title = {IMPACT OF FLOW RATE ON HIGH FREQUENCY FLOW INSTABILITIES IN INTRACRANIAL ANEURYSMS, WITH IMPLICATIONS FOR WALL VIBRATION},
	journal = {SB3C2021 Summer Biomechanics, Bioengineering and Biotransport Conference},
	year = {2021},
	author = {David A. {Bruneau} and Najafi, Mehdi and Natarajan, Thangam and Valen-Sendstad, Kristian and David A. {Steinman}},
	editor = {, }
}
@article {28447,
	title = {On the prevalence of flow instabilities from high-fidelity computational fluid dynamics of intracranial bifurcation aneurysms},
	journal = {Journal of Biomechanics},
	volume = {127},
	year = {2021},
	month = {Jan-10-2021},
	pages = {110683},
	publisher = {Elsevier},
	issn = {00219290},
	doi = {10.1016/j.jbiomech.2021.110683},
	url = {https://www.sciencedirect.com/science/article/abs/pii/S0021929021004528?via\%3Dihub},
	author = {Khan, M.O. and Arana, Toro and Najafi, M. and MacDonald, D.E. and Natarajan, T. and Valen-Sendstad, Kristian and Steinman, D.A.}
}
@inproceedings {28449,
	title = {Turbulent-like arteriovenous fistula flows cause wall vibrations: a specific stimulus for stenosis formation?},
	journal = {47th Congress of the European Society of Artificial Organs},
	year = {2021},
	publisher = {European Society for Artificial Organs},
	address = {London, England},
	author = {Bozzetto, Michela and Souche, Alban and Remuzzi, Andrea and Valen-Sendstad, Kristian}
}
@article {26774,
	title = {Computed Post-Stenotic Flow Instabilities Correlate Phenotypically with Vibrations Measured Using Laser Doppler Vibrometry: Perspectives for a Promising In-Vivo Device for Early Detection of Moderate and Severe Carotid  Stenosis},
	journal = {Journal of Biomechanical Engineering},
	volume = {142},
	year = {2020},
	month = {04/2020},
	pages = {091007},
	publisher = {American Society of Mechanical Engineers Digital Collection},
	author = {Mancini, Viviana and Bergersen, Aslak and Valen-Sendstad, Kristian and Segers, Patrick}
}
@article {bergersen2020framework,
	title = {A framework for automated and objective modification of tubular structures: Application to the internal carotid artery},
	journal = {International journal for numerical methods in biomedical engineering},
	volume = {36},
	number = {5},
	year = {2020},
	pages = {e3330},
	publisher = {Wiley Online Library},
	author = {Bergersen, Aslak and Kjeldsberg, Henrik and Valen-Sendstad, Kristian}
}
@inproceedings {27725,
	title = {Turbulent-Like Aneurysm Flows Trigger Distinct Highfrequent Wall Vibrations},
	journal = {14th World Congress in Computational Mechanics (WCCM)},
	volume = {Online},
	year = {2020},
	month = {2020},
	publisher = {European Community on Computational Methods in Applied Sciences},
	address = {Paris, France},
	author = {Souche, Alban and Valen-Sendstad, Kristian},
	editor = {, }
}
@article {27724,
	title = {turtleFSI: A Robust and Monolithic FEniCS-based Fluid-Structure Interaction Solver},
	journal = {Journal of Open Source Software},
	volume = {5},
	year = {2020},
	month = {Jan-06-2020},
	pages = {2089},
	publisher = {The Open Journal},
	doi = {10.21105/joss10.21105/joss.02089},
	url = {https://joss.theoj.orghttps://joss.theoj.org/papers/10.21105/joss.02089http://www.theoj.org/joss-papers/joss.02089/10.21105.joss.02089.pdf},
	author = {Bergersen, Aslak and Slyngstad, Andreas and Gjertsen, Sebastian and Souche, Alban and Valen-Sendstad, Kristian}
}
@misc {26550,
	title = {Are High-Frequency Aneurysm Wall Vibrations of Importance?},
	howpublished = {6th International Conference on Computational and Mathematical Biomedical Engineering {\textendash} CMBE2019, Sendai, Japan },
	year = {2019},
	abstract = {We present a preliminary study on aneurysm wall vibrations associated with turbulent-like hemodynamics in intracranial vascular sections. The specificity of our numerical model is to explore the fluid/structure coupling of the arterial flow and the wall mechanics to relatively high frequencies (100-500 Hz). Despite the computational cost of the couple FSI problem and its direct impact on the resolutions of the model presented here, our findings highlight an important mechanical interplay resulting in a complex, but characteristic, deformation of the arterial wall. We hope to stimulate discussions and further work towards this physiological process, which can potentially have important implications for cell signaling mechanisms.},
	keywords = {fluid-structure interaction, Intracranial aneurysm, wall vibrations},
	author = {Souche, Alban and Valen-Sendstad, Kristian}
}
@article {26490,
	title = {Automated and Objective Removal of Bifurcation Aneurysms: Incremental Improvements, and Validation Against Healthy Controls},
	journal = {Journal of Biomechanics},
	volume = {96},
	year = {2019},
	pages = {109342},
	publisher = {Elsevier},
	doi = {https://doi.org/10.1016/j.jbiomech.2019.109342},
	url = {https://www.sciencedirect.com/science/article/abs/pii/S0021929019305640},
	author = {Bergersen, Aslak and Chnafa, Christophe and Gallo, Diego and Piccinelli, Marina and David A. {Steinman} and Valen-Sendstad, Kristian}
}
@inproceedings {26548,
	title = {Automated and objective segmentation of medical image using machine learning techniques: all models are wrong, but some are useful},
	journal = {Computational and Mathematical Biomedical Engineering},
	year = {2019},
	publisher = {CMBE},
	address = {Sendai, Japan},
	abstract = {Medical images are the basis of {\textquotedblright}patient-specific{\textquotedblright} simulations but come with severe limitations, most notably through operator dependencies like image segmentation. The aim was to develop an open- source pipeline for automated and objective segmentation. Combining latest advances from machine learning and signal processing, we demonstrate that the pipeline preserve all major characteristic features of a test image and identify minor branches, which can be further modified by the user. In conclusion, the default pipeline will in the majority of cases offer labor free automated and objective segmentation, or at worst provide an optimal starting point for manual segmentation.},
	author = {Per Magne {Florvaag} and Naumova, Valeriya and Valen-Sendstad, Kristian}
}
@misc {26335,
	title = {Autonomic Modelling of Interaction between Coronary Perfusion Flow and Myocardium Mechanics using Computational Poroelasticity},
	howpublished = {International Society of Autonomic Neuroscience, Los Angeles, CA, USA},
	year = {2019},
	publisher = {International Society of Autonomic Neuroscience, 2019.},
	abstract = {Autonomic control and modelling the cross-talk between blood flow in coronary vessels and ventricular wall mechanical deformations are central problems in mechanocardiac physiology. In this study, we use a multi-scale approach that includes multi-physics modules of the heart with autonomic control, to accurately model this complex interaction between coronary perfusion and myocardium mechanics. In particular, we implement a 3D finite element numerical scheme to account for this coupling using a reconstructed and geometrically-accurate anatomical model of a porcine subject, Figure 1(A). A mathematical model using statistical measurements and space filling topology is used to specify the coronary tree networks in the finite element computational model, Figure 1(B). A multi-compartment poroelastic governing equations of the blood-soft tissue interactions are derived. The evolution equations for both blood and soft tissue phases are described in the Lagrangian frame of reference. The complex network of blood vessel that surround the myocardium tissue are integrated using a reduced order modelling of Darcy law with a heterogeneous permeability tensor along with the finite deformation elasticity of the myocardium. The derived methodology approach is tested on simplified 2D and 3D myocardium poroelastic geometries with customized modules and well-posed prescribed traction boundary conditions at a finite set of coronary compartments, Figure 1(C-D). Results are given for\&nbsp;the perfusion of the left ventricle deformation under passive inflation that show in particular wall compliance remodelling associated with perfusion dysfunction.},
	author = {Aboelkassem, Yasser and Alexandra K. {Diem} and Valen-Sendstad, Kristian and Andrew D. {McCulloch}}
}
@misc {26364,
	title = {Can turbulent-like flow cause high frequency vibrations of intracranial aneurysm walls ?},
	year = {2019},
	address = {Biomechanics in Vascular Biology and Cardiovascular Disease (14th international symposium), London, United Kingdom},
	abstract = {The presence of wall vibrations of relatively high frequencies (several hundreds of Hz) on the top of intracranial aneurysms have been reported in the 70{\textquoteright}s from open brain surgery measurements [1]. Later study [2], based on non-invasive recordings, provided additional evidences for charateristic high frequencie intracranial blood flow sounds associated with the presence of aneurysms. It is only recently that computational and experimental in-vitro studies modelled turbulent-like blood flow environments within intracranial vasculature, with characteristic fluctuations in the order of 100-300 Hz ([3, 4]). However, the link between unstable blood flow and arterial wall vibrations within intracranial aneurysms still remains speculative and is the focus of the present work.},
	author = {Souche, Alban and Valen-Sendstad, Kristian}
}
@inproceedings {26544,
	title = {Comparing apples to oranges; Measured skin vibrations correlate phenotypically with computed post-stenotic flow instabilities. A pragmatic but robust tool for early detection of carotid stenoses?},
	journal = {Computer Methods in Biomechanics and Biomedical Engineering},
	year = {2019},
	publisher = {Computer Methods in Biomechanics and Biomedical Engineering},
	address = {Sendai, Japan},
	author = {Mancini, Viviana and Bergersen, Aslak and Valen-Sendstad, Kristian and Segers, Patrick}
}
@article {26230,
	title = {High-Frequency Fluctuations in Post-Stenotic Patient Specific Carotid Stenosis Fluid Dynamics: a Computational Fluid Dynamics Strategy Study},
	journal = {Cardiovascular Engineering and Technology},
	volume = {10},
	year = {2019},
	pages = {277-298},
	publisher = {Springer},
	doi = {https://doi.org/10.1007/s13239-019-00410-9},
	author = {Mancini, Viviana and Bergersen, Aslak and Vierendeels, Jan and Segers, Patrick and Valen-Sendstad, Kristian}
}
@inproceedings {26339,
	title = {Intensity of Stenosis-Indused Flow Instabilities of the Internal Carotid Artery: A Computational Approach},
	journal = {Summer Biomechanics, Bioengineering, and Biotransport Conference},
	year = {2019},
	publisher = {SB3C Foundation},
	address = {Seven Springs, PA},
	author = {Mancini, Viviana and Bergersen, Aslak and Valen-Sendstad, Kristian and Segers, Patrick}
}
@misc {27137,
	title = {Modeling of {\textquoteleft}patient-specific{\textquoteright} blood flow in the brain: Are we there yet?},
	howpublished = {American Physical Society, Seattle, WA, USA},
	year = {2019},
	type = {Invited},
	author = {Valen-Sendstad, Kristian}
}
@article {26203,
	title = {morphMan: Automated manipulation of vascular geometries},
	journal = {Journal of Open Source Software},
	volume = {35},
	year = {2019},
	pages = {1065},
	publisher = {JOSS},
	doi = {https://doi.org/10.21105/joss.01065},
	author = {Kjeldsberg, Henrik and Bergersen, Aslak and Valen-Sendstad, Kristian}
}
@article {26227,
	title = {Multiple Aneurysms AnaTomy CHallenge 2018 (MATCH) - Phase II: Rupture Risk Assessment},
	journal = {International Journal of Computer Assisted Radiology and Surgery},
	volume = {14},
	number = {10},
	year = {2019},
	month = {05/2019},
	pages = {1795-1804},
	publisher = {British Medical Journal Publishing Group},
	doi = {https://doi.org/10.1007/s11548-019-01986-2},
	url = {https://link.springer.com/article/10.1007/s11548-019-01986-2},
	author = {Berg, Philipp and Vo{\ss}, Samuel and Saalfeld, Sylvia and Janiga, G{\'a}bor and Bergersen, Aslak and Valen-Sendstad, Kristian and Bruening, Jan and Goubergrits, Leonid and Spuler, Andreas and Nicole M. {Cancelliere} and David A. {Steinman} and Vitor M. {Pereira} and Tin Lok {Chiu} and Anderson Chun On {Tsang} and Bong Jae {Chung} and Juan R. {Cebral} and Cito, Salvatore and Pallares, Jordi and Copelli, Gabriele and Csippa, Benjamin and Pa{\'a}l, Gy{\"o}rgy and Fujimura, Soichiro and Takao, Hiroyuki and Hodis, Simona and Hille, Georg and Karmonik, Christof and Elias, Saba and Kellermann, Kerstin and Muhammad Owais {Khan} and Alison L. {Marsden} and Hern{\'a}n G. {Morales} and Piskin, Senol and Ender A. {Finol} and Pravdivtseva, Mariya and Rajabzadeh-Oghaz, Hamidreza and Paliwal, Nikhil and Meng, Hui and Seshadhri, Santhosh and Howard, Matthew and Shojima, Masaaki and Sugiyama, Shin-ichiro and Niizuma, Kuniyasu and Sindeev, Sergey and Frolov, Sergey and Wagner, Thomas and Brawanski, Alexander and Qian, Yi and Wu, Yu-An and Kent D. {Carlson} and Dragomir-Daescu, Dan and Beuing, Oliver}
}
@misc {26552,
	title = {Porous modelling of cardiac perfusion to optimise targeted drug delivery},
	year = {2019},
	month = {09/2019},
	address = {Computing in Cardiology, Singapore},
	abstract = {Delivery of therapy-loaded nanoparticles (NP) via inhalation is an innovative technology shown to successfully reduce heart failure in mice, improving the efficiency of drug delivery, and reducing adverse side effects. However, how exactly therapeutic NP are distributed and absorbed by heart tissue remains poorly understood, and accelerating this technology to humans is a major challenge. To overcome this problem we developed an open-source finite element model of myocardial perfusion based on porous media, where perfused tissue is treated as a sponge-like continuum material, driven by a continuum model of cardiac contraction to simulate perfusion patterns. We use our novel particle-tracking based method that remains numerically stable under high Peclet number flow to study NP distribution.},
	author = {Alexandra K. {Diem} and Valen-Sendstad, Kristian}
}
@inproceedings {27032,
	title = {Porous Modelling of Cardiac Perfusion under Contraction to Demonstrate the Distribution of Therapeutic Nanoparticles},
	journal = { International Conference in Computing in Cardiology, Singapore,  2019},
	year = {2019},
	publisher = {IEEE},
	abstract = {Delivery of therapy-loaded nanoparticles (NP) via inhalation is an innovative technology shown to successfully reduce heart failure in mice, improving the efficiency ofdrug delivery, and reducing adverse side effects. However, how exactly therapeutic NP are distributed and absorbed by heart tissue remains poorly understood, and accelerating this technology to humans is a major challenge. Working towards overcoming this problem we developed an open-source finite element model of myocardial per-fusion based on porous media, where perfused tissue is treated as a sponge-like continuum material, driven by a continuum model of cardiac contraction to simulate perfusion patterns. We use our novel particle-tracking based method that remains numerically stable under high Peclet number flow to enable the study of NP distribution.},
	author = {Alexandra K. {Diem} and Valen-Sendstad, Kristian}
}
@article {26491,
	title = {Time-Lapsing Perfusion: Proof of Concept of a Novel Method to Study Drug Delivery in Whole Organs},
	journal = {Biophysical Journal},
	volume = {117},
	year = {2019},
	pages = {2316-2323},
	publisher = {Cell Press},
	abstract = {Perfusion is one of the most important processes maintaining organ health. From a computational perspective, however, perfusion is amongst the least studied physiological processes of the heart. The recent development of novel nanoparticle-based targeted cardiac therapy calls for novel simulation methods that can provide insights into the distribution patterns of therapeutic agents within the heart tissue. Additionally, resolving the distribution patterns of perfusion is crucial for gaining a full understanding of the long-term impacts of cardiovascular diseases that can lead to adverse remodelling, such as myocardial ischemia and heart failure. In this study we have developed and used a novel particle tracking-based method to simulate the perfusion-mediated distribution of nanoparticles or other solutes. To model blood flow through perfused tissue we follow the approach of others and treat the tissue as a porous medium in a continuum model. Classically, solutes are modelled\&nbsp;using reaction-advection-diffusion kinetics. However, due to the discrepancy between advection and diffusion in blood vessels, this method becomes numerically unstable. Instead, we track a bolus of solutes or nanoparticles using particle tracking based purely on advection in arteries. In capillaries we employ diffusion kinetics, using an effective diffusion coefficient to mimic capillary blood flow. We first demonstrate the numerical validity and computational efficiency of this method on a 2D benchmark problem. Finally, we demonstrate how the method is used to visualise perfusion patterns of a human left ventricle geometry. The efficiency of the method allows for nanoparticle tracking over multiple cardiac cycles using a conventional laptop, providing a framework for the simulation of experimentally relevant time frames to advance pre-clinical research.},
	author = {Alexandra K. {Diem} and Valen-Sendstad, Kristian}
}
@article {26202,
	title = {Artery.FE: An implementation of the 1D blood flow equations in FEniCS},
	journal = {Journal of Open Source Software},
	volume = {3},
	number = {1107},
	year = {2018},
	publisher = {The Journal of Open Source Software, Open Source Initiative},
	keywords = {blood flow, FEniCS, Numerical models, PDE, Software},
	doi = {10.21105/joss.01107},
	url = {http://joss.theoj.org/papers/10.21105/joss.01107},
	author = {Syver D. {Agdestein} and Valen-Sendstad, Kristian and Alexandra K. {Diem}}
}
@inproceedings {mancini8th,
	title = {Can We Detect Carotid Artery Stenosis From Skin Vibrations: A Computational Investigation of High-Frequent Flow Under Physiological Varying Flow Conditions.},
	journal = {8th World Congress of Biomechanics},
	year = {2018},
	month = {06/2018},
	author = {Mancini, Viviana and Bergersen, Aslak and Vierendeels, Jan and Segers, Patrick and Valen-Sendstad, Kristian}
}
@misc {26231,
	title = {Data for "High-Frequency Fluctuations in Post-Stenotic Patient Specific Carotid Stenosis Fluid Dynamics: A Computational Fluid Dynamics Strategy Study"},
	year = {2018},
	publisher = {FigShare},
	address = {FigShare},
	doi = {10.6084/m9.figshare.7300496.v2},
	url = {https://doi.org/10.6084/m9.figshare.7300496.v2},
	author = {Mancini, Viviana and Bergersen, Aslak and Vierendeels, Jan and Segers, Patrick and Valen-Sendstad, Kristian}
}
@misc {26232,
	title = {Data for "The 2015 International Aneurysm CFD Challenge"},
	year = {2018},
	publisher = {FigShare},
	address = {FigShare},
	doi = {https://doi.org/10.6084/m9.figshare.6383516.v2},
	url = {10.6084/m9.figshare.6383516.v2},
	author = {Valen-Sendstad, Kristian and Bergersen, Aslak and Kono, Kenichi and David A. {Steinmam}}
}
@article {26193,
	title = {The FDA nozzle benchmark: {\textquotedblleft}In theory there is no difference between theory and practice, but in practice there is{\textquotedblright}},
	journal = {International Journal for Numerical Methods in Biomedical Engineering},
	volume = {35},
	year = {2018},
	month = {09/2019},
	pages = {e3150},
	publisher = { Wiley},
	abstract = {The utility of flow simulations relies on the robustness of computational fluid dynamics (CFD) solvers and reproducibility of results. The aim of this study was to validate the Oasis CFD solver against in vitro experimental measurements of jet breakdown location from the FDA nozzle benchmark at Reynolds number 3500, which is in the particularly challenging transitional regime. Simulations were performed on meshes consisting of 5, 10, 17, and 28 million (M) tetrahedra, with Δt = 10-5\&nbsp;seconds. The 5M and 10M simulation jets broke down in reasonable agreement with the experiments. However, the 17M and 28M simulation jets broke down further downstream. But which of our simulations are {\textquotedblleft}correct{\textquotedblright}? From a theoretical point of view, they are all wrong because the jet should not break down in the absence of disturbances. The geometry is axisymmetric with no geometrical features that can generate angular velocities. A stable flow was supported by linear stability analysis. From a physical point of view, a finite amount of {\textquotedblleft}noise{\textquotedblright} will always be present in experiments, which lowers transition point. To replicate noise numerically, we prescribed minor random angular velocities (approximately 0.31\%), much smaller than the reported flow asymmetry (approximately 3\%) and model accuracy (approximately 1\%), at the inlet of the 17M simulation, which shifted the jet breakdown location closer to the measurements. Hence, the high-resolution simulations and {\textquotedblleft}noise{\textquotedblright} experiment can potentially explain discrepancies in transition between sometimes {\textquotedblleft}sterile{\textquotedblright} CFD and inherently noisy {\textquotedblleft}ground truth{\textquotedblright} experiments. Thus, we have shown that numerical simulations can agree with experiments, but for the wrong reasons.},
	doi = {10.1002/cnm.3150},
	url = {http://doi.wiley.com/10.1002/cnm.3150http://onlinelibrary.wiley.com/wol1/doi/10.1002/cnm.3150/fullpdfhttps://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002\%2Fcnm.3150},
	author = {Bergersen, Aslak and Mortensen, Mikael and Valen-Sendstad, Kristian}
}
@misc {26066,
	title = {Modelling drug delivery via nanoparticle deposition in the myocardium of the left ventricle},
	year = {2018},
	publisher = {The Heart by Numbers: Integrating Theory, Computation, and Experiment to Advance Cardiology},
	address = {Berlin},
	abstract = {The use of nanoparticles (NP) target drug delivery directly to the heart for treatment of diseases via nanoparticles (NP) has been a major goal of cardiovascular research since the early 2000s. The benefits of such a NP drug delivery system would include the reduction of side effects by the administration of smaller dosages, cost reduction and reducing the need for invasive treatments. However, the development of a NP-based drug delivery system also poses a number of challenges, such as the optimisation of physico-chemical parameters of the NP, in order to achieve efficient distribution throughout the tissue. We address this challenge by presenting a finite-element model of NP delivery via perfusion through the myocardium in the left ventricle (LV). Perfusion is represented by the three compartment porous media equations based on Darcy{\textquoteright}s law. A 0D lumped parameter model is used to represent the inflow boundary condition to the perfusing blood vessels. NP transport is modelled via the scalar transport equations based on reaction-advection-diffusion kinetics, where deposition via endocytosis follows zero order reaction kinetics. The model is solved on a human LV geometry with randomly set arterial entry points throughout the outer surface of the myocardium. Efficiency of NP endocytosis is tested based on varied kinetic rates, initial NP concentration, NP inflow rate, chemical properties of NP, and perfusion pressure. These simulations provide a framework to virtually prototype physico-chemical properties of the NP and predict their distribution within the tissue.},
	keywords = {blood flow, cardiac perfusion, darcy flow, nanoparticles},
	author = {Alexandra K. {Diem} and Valen-Sendstad, Kristian}
}
@article {26195,
	title = {Multiple Aneurysms AnaTomy CHallenge 2018 (MATCH): Phase I: Segmentation},
	journal = {Cardiovascular Engineering and Technology},
	volume = {9},
	year = {2018},
	month = {09/2018},
	pages = {565{\textendash}581},
	publisher = {Springer US},
	issn = {1869-408X},
	doi = {10.1007/s13239-018-00376-0},
	url = {http://link.springer.com/10.1007/s13239-018-00376-0},
	author = {Berg, Philipp and Vo{\ss}, Samuel and Saalfeld, Sylvia and Janiga, G{\'a}bor and Bergersen, Aslak and Valen-Sendstad, Kristian and Bruening, Jan and Goubergrits, Leonid and Spuler, Andreas and Nicole M. {Cancelliere} and David A. {Steinman} and Vitor M. {Pereira} and Tin Lok {Chiu} and Anderson Chun On {Tsang} and Bong Jae {Chung} and Juan R. {Cebral} and Cito, Salvatore and Pallares, Jordi and Copelli, Gabriele and Csippa, Benjamin and Pa{\'a}l, Gy{\"o}rgy and Fujimura, Soichiro and Takao, Hiroyuki and Hodis, Simona and Hille, Georg and Karmonik, Christof and Elias, Saba and Kellermann, Kerstin and Owais Mohammad {Khan} and Alison L. {Marsden} and Hern{\'a}n G. {Morales} and Piskin, Senol and Ender A. {Finol} and Pravdivtseva, Mariya and Rajabzadeh-Oghaz, Hamidreza and Paliwal, Nikhil and Meng, Hui and Seshadhri, Santhosh and Howard, Matthew and Shojima, Masaaki and Sugiyama, Shin-ichiro and Niizuma, Kuniyasu and Sindeev, Sergey and Frolov, Sergey and Wagner, Thomas and Brawanski, Alexander and Qian, Yi and Wu, Yu-An and Kent D. {Carlson} and Dragomir-Daescu, Dan and Beuing, Oliver}
}
@article {26192,
	title = {Real-World Variability in the Prediction of Intracranial Aneurysm Wall Shear Stress: The 2015 International Aneurysm CFD Challenge},
	journal = {Cardiovascular Engineering and Technology},
	volume = {9},
	year = {2018},
	month = {10/2018},
	pages = {544{\textendash}564},
	publisher = {Springer},
	address = {US},
	abstract = {PurposeImage-based computational fluid dynamics (CFD) is widely used to predict intracranial aneurysm wall shear stress (WSS), particularly with the goal of improving rupture risk assessment. Nevertheless, concern has been expressed over the variability of predicted WSS and inconsistent associations with rupture. Previous challenges, and studies from individual\&nbsp;groups,\&nbsp;have focused on individual aspects of the image-based CFD pipeline. The aim of this Challenge was to quantify the total variability of the whole pipeline.Methods3D rotational angiography image volumes of five middle cerebral artery aneurysms were provided to participants, who were free to choose their segmentation methods, boundary conditions, and CFD solver and settings. Participants were asked to fill out a questionnaire about their solution strategies and experience with aneurysm CFD, and provide surface distributions of WSS magnitude, from which we objectively derived a variety of hemodynamic parameters.ResultsA total of 28 datasets were submitted, from 26 teams with varying levels of self-assessed experience.\&nbsp;Wide\&nbsp;variability of segmentations, CFD model extents, and inflow rates resulted in interquartile ranges of sac average WSS up to 56\%, which reduced to \&lt; 30\% after normalizing by parent artery WSS. Sac-maximum WSS and low shear area were more variable, while rank-ordering of cases by low or high shear showed\&nbsp;only\&nbsp;modest consensus among teams.\&nbsp;Experience\&nbsp;was not a significant predictor of variability.ConclusionsWide variability exists in the prediction of intracranial aneurysm WSS. While segmentation and CFD solver techniques may be difficult to standardize across groups, our findings suggest that some of the variability in image-based CFD could be reduced by establishing guidelines for model extents, inflow rates, and blood properties, and by encouraging the reporting of normalized hemodynamic parameters.},
	keywords = {Intracranial aneurysm, Patient-specific modeling, Rupture risk, Uncertainty quantification, Wall shear stress},
	issn = {1869-408X},
	doi = {10.1007/s13239-018-00374-2},
	url = {https://goo.gl/mG9u9t},
	author = {Valen-Sendstad, Kristian and Bergersen, Aslak and Shimogonya, Yuji and Goubergrits, Leonid and Bruening, Jan and Pallares, Jordi and Cito, Salvatore and Piskin, Senol and Pekkan, Kerem and Arjan J. {Geers} and Larrabide, Ignacio and Rapaka, Saikiran and Mihalef, Viorel and Fu, Wenyu and Qiao, Aike and Jain, Kartik and Roller, Sabine and Mardal, Kent-Andre and Kamakoti, Ramji and Spirka, Thomas and Ashton, Neil and Revell, Alistair and Aristokleous, Nicolas and Houston, Graeme and Tsuji, Masanori and Ishida, Fujimaro and Prahlad G. {Menon} and Leonard D. {Browne} and Broderick, Stephen and Shojima, Masaaki and Koizumi, Satoshi and Barbour, Michael and Aliseda, Alberto and Hern{\'a}n G. {Morales} and Lef{\`e}vre, Thierry and Hodis, Simona and Yahia M. {Al-Smadi} and Justin S. {Tran} and Alison L. {Marsden} and Vaippummadhom, Sreeja and Einstein, Albert and Alistair G. {Brown} and Debus, Kristian and Niizuma, Kuniyasu and Rashad, Sherif and Sugiyama, Shin-ichiro and Owais Mohammad {Khan} and Adam R. {Updegrove} and Shawn C. {Shadden} and Bart M. W. {Cornelissen} and Charles B. L. M. {Majoie} and Ber, Philipp and Saalfield, Sylvia and Kono, Kenichi and David A. {Steinmam}}
}
@article {25537,
	title = {Cerebral aneurysm blood flow simulations: There{\textquoteright}s solver settings and then there{\textquoteright}s solver settings},
	journal = {Journal of Biomechanics},
	volume = {61},
	year = {2017},
	pages = {280-280},
	publisher = {Journal of Biomechanics},
	doi = {10.1016/j.jbiomech.2017.04.039},
	author = {Owais Mohammad {Khan} and Valen-Sendstad, Kristian and David A. {Steinman}}
}
@inproceedings {25808,
	title = {Investigating the Numerical Parameter Space for a Stenosed Patient-Specific Internal Carotid Artery Model},
	journal = {Progress in Applied CFD. Selected papers from 10th International Conference on Computational Fluid Dynamics in the Oil \& Gas, Metallurgical and Process Industries},
	year = {2017},
	publisher = {SINTEF Academic Press},
	isbn = {978-82-536-1544-8},
	issn = {2387-4295},
	author = {Bergersen, Aslak and Mancini, Viviana and Segers, Patrick and Valen-Sendstad, Kristian}
}
@inproceedings {25807,
	title = {Prediction of Post Stenotic Flow Instabilities in a Patient Specific Common Carotid Artery Model?},
	journal = {Summer Biomechanics, Bioengineering, and Biotransport Conference},
	year = {2017},
	author = {Bergersen, Aslak and Mancini, Viviana and Segers, Patrick and Valen-Sendstad, Kristian}
}
@misc {25804,
	title = {Verification and Validation in Image-Based Biomedical Computing},
	howpublished = {International Conference on Computational Science and Engineering, Oslo, Norway},
	year = {2017},
	author = {Valen-Sendstad, Kristian and Bergersen, Aslak}
}
@inproceedings {25806,
	title = {A Virtual Inter Laboratory Comparison of Predicted Hemodynamic Indices in Intracranial Aneurysms: Consistent or Not?},
	journal = {Summer Biomechanics, Bioengineering, and Biotransport Conference},
	year = {2017},
	author = {Bergersen, Aslak and Valen-Sendstad, Kristian}
}
@inproceedings {25058,
	title = {A Benchmark Standard Model of a Generic Medical Device; All Models Are Wrong, but Some Are Useful.},
	journal = {11th International Symposium on Biomechanics in Vascular Biology and Cardiovascular Disease},
	year = {2016},
	author = {Bergersen, Aslak and Mortensen, Mikael and Valen-Sendstad, Kristian}
}
@inproceedings {25057,
	title = {Can Manipulation of Arterial Morphology Shed Light on the Mechanobiological Stimuli Behind Aneurysm Initiation?},
	journal = {11th International Symposium on Biomechanics in Vascular Biology and Cardiovascular Disease},
	year = {2016},
	author = {Bergersen, Aslak and Jimenez, Juan and Valen-Sendstad, Kristian}
}
@inproceedings {25054,
	title = {The FDA Nozzle Benchmark: In Theory There Is No Difference Between Theory and Practice, but in Practice There Is.},
	journal = {American Society of Mechanical Engineers Summer Biomechanics, Bioengineering and Biotransport Conference},
	year = {2016},
	author = {Bergersen, Aslak and Mortensen, Mikael and Valen-Sendstad, Kristian}
}
@inproceedings {25051,
	title = {Freezing   Turbulence   in   Brain   Aneurysm   Flow   Visualizations:   An   Applied   Art-Science   Collaboration.},
	journal = {Special Interest Group on GRAPHics and Interactive Techniques},
	year = {2016},
	author = {Coppin, Peter and Julian, Maxwell and Harvey, John and Valen-Sendstad, Kristian and David A. {Steinman}}
}
@inproceedings {25050,
	title = {Impact of Outflow Boundary Conditions on Flow Rates in Cerebrovascular CFD Models.},
	journal = {22nd Congress of the European Society of Biomechanics},
	year = {2016},
	author = {Chnafa, Christophe and Valen-Sendstad, Kristian and Brina, Olivier and Pereira, Vitor and David A. {Steinman}}
}
@article {25037,
	title = {Improved Reduced-Order Modelling of Cerebrovascular Flow Distribution by Accounting for Arterial Bifurcation Pressure Drops.},
	journal = {Journal of Biomechanics},
	volume = {51},
	year = {2016},
	pages = {83-88},
	publisher = {Journal of Biomechanics},
	author = {Chnafa, Christophe and Valen-Sendstad, Kristian and Brina, Olivier and Pereira, Vitor and David A. {Steinman}}
}
@inproceedings {25056,
	title = {Inconsistency Is the Only Thing in Which Men Are Consistent: Can Subtle Flow Rate Assumptions Have Large Implications?},
	journal = {11th International Symposium on Biomechanics in Vascular Biology and Cardiovascular Disease},
	year = {2016},
	author = {Bergersen, Aslak and Valen-Sendstad, Kristian}
}
@article {25036,
	title = {Non-Newtonian versus Numerical Rheology: Practical Impact Of Shear-thinning On The Prediction  Of Stable And Unstable Flows In Intracranial Aneurysms.},
	journal = {International Journal for Numerical Methods in Biomedical Engineering},
	volume = {33},
	number = {7},
	year = {2016},
	month = {10/16},
	publisher = {Int J Numer Method Biomed Eng},
	author = {Owais Mohammad {Khan} and David A. {Steinman} and Valen-Sendstad, Kristian}
}
@inproceedings {25053,
	title = {Non-Newtonian versus Numerical Rheology: Practical Impact Of Shear-thinning On The Prediction         Of Stable And Unstable Flows In Intracranial Aneurysms.},
	journal = {American Society of Mechanical Engineers Summer Biomechanics, Bioengineering and Biotransport Conference},
	year = {2016},
	author = {Owais Mohammad {Khan} and David A. {Steinman} and Valen-Sendstad, Kristian}
}
@inproceedings {25049,
	title = {The Oasis Navier-Stokes Solver: Theory, Accuracy, Applications, and High-Performance Computing Capabilities.},
	journal = {FEniCS 16},
	year = {2016},
	author = {Bergersen, Aslak and Valen-Sendstad, Kristian and Mortensen, Mikael}
}
@inproceedings {25055,
	title = {An Objective Framework for Digital Removal of Bifurcation Aneurysms - Incremental Improvements?},
	journal = {11th International Symposium on Biomechanics in Vascular Biology and Cardiovascular Disease},
	year = {2016},
	author = {Bergersen, Aslak and Chnafa, Christophe and Gallo, Diego and Piccinelli, Marina and Valen-Sendstad, Kristian}
}
@inproceedings {25048,
	title = {Proper Orthogonal Decomposition  Analyses of High-Frequency Transient Flow Instabilities in Intracranial Aneurysms},
	journal = {American Physical Society Division of Fluid Dynamics},
	year = {2016},
	author = {Owais Mohammad {Khan} and Chnafa, Christophe and Valen-Sendstad, Kristian and David A. {Steinman}}
}
@article {25038,
	title = {On the Quantification and Visualization of Transient Periodic Instabilities in Pulsatile Flows},
	journal = {Journal of Biomechanics},
	number = {52},
	year = {2016},
	month = {12/2016},
	pages = {179-182},
	publisher = {Journal of Biomechanics},
	author = {Owais Mohammad {Khan} and Chnafa, Christophe and Gallo, Diego and Molinari, Filippo and Morbiducci, Umberto and David A. {Steinman} and Valen-Sendstad, Kristian}
}
@inproceedings {25052,
	title = {A Simple and Rational Approach to Outflow Conditions in Cerebrovascular CFD Models.},
	journal = {American Society of Mechanical Engineers Summer Biomechanics, Bioengineering and Biotransport Conference},
	year = {2016},
	author = {Chnafa, Christophe and Valen-Sendstad, Kristian and Brina, Olivier and Pereira, Vitor and David A. {Steinman}}
}
@misc {23991,
	title = {The 2015 Aneurysm CFD Challenge: Are we there yet?},
	howpublished = {American Society of Mechanical Engineers Validation and Verification meeting, New York, USA.},
	year = {2015},
	author = {Valen-Sendstad, Kristian}
}
@misc {23994,
	title = {The 2015 Aneurysm CFD Challenge: Variability of Segmentations, Hemodynamics, and Hemodynamic Indices: Qualitative and Preliminary Results},
	howpublished = {Summer Biomechanics, Bioengineering \& Biotransport Conference, Utah, USA},
	year = {2015},
	author = {Valen-Sendstad, Kristian}
}
@misc {23992,
	title = {The 2015 Aneurysm CFD Challenge: Variability of Segmentations, Hemodynamics, and Hemodynamic Indices: Qualitative and Preliminary Results - Incremental updates},
	howpublished = {Computational Fluid Dynamics (CFD) in Medicine and Biology II, An Engineering Conferences International (ECI) Conference series. Albufeira, Portugal},
	year = {2015},
	author = {Valen-Sendstad, Kristian}
}
@misc {23989,
	title = {Are computer simulations misleading us about the nature of blood flow in the brain?},
	howpublished = {NSCM-28 - 28th Nordic Seminar on Computational Mechanics},
	year = {2015},
	author = {Valen-Sendstad, Kristian}
}
@inproceedings {23984,
	title = {Are computer simulations misleading us about the nature of blood  flow in the brain?},
	journal = {NSCM-28 - 28th Nordic Seminar on Computational Mechanics},
	year = {2015},
	month = {10/2015},
	author = {Valen-Sendstad, Kristian}
}
@inproceedings {23983,
	title = {On the assumption of laminar flow in the cerebrovasculature: Implications for CFD insights into aneurysm initiation and rupture?},
	journal = {Computational Fluid Dynamics (CFD) in Medicine and Biology II, An Engineering Conferences International (ECI) Conference Series.},
	year = {2015},
	month = {09/2015},
	author = {Valen-Sendstad, Kristian}
}
@misc {23988,
	title = {On the assumption of laminar  ow in the cerebrovas- culature: Implications for CFD insights into aneurysm initiation and rupture?},
	howpublished = {Computational Fluid Dynamics (CFD) in Medicine and Biology II, An Engineering Conferences International (ECI) Conference series. Albufeira, Portugal},
	year = {2015},
	author = {Valen-Sendstad, Kristian}
}
@inproceedings {23976,
	title = {Can Highly Resolved Computational Fluid Dynam- ics Simulations Shed New Light on Aneurysm Initiation?},
	journal = {4th International Conference on Computational and Mathematical Biomedical Engineering},
	year = {2015},
	month = {06/2015},
	author = {Valen-Sendstad, Kristian}
}
@misc {23993,
	title = {Can Highly Resolved Computational Fluid Dynamics Simulations Shed New Light on Aneurysm Initiation?},
	howpublished = {Accounting for complexity in blood flow modelling, Uncertainty Quantification in Predictive Computational Vascular Mechanics, Computational and Mathematical Biomedical Engineering, Paris, France.},
	year = {2015},
	author = {Valen-Sendstad, Kristian}
}
@inproceedings {23967,
	title = {CFD Simulation of Transition to Turbulence for Newtonian vs. Non-Newtonian Flow Through a Stenosis},
	journal = {The Summer Biomechanics, Bioengineering \& Biotransport Conference},
	year = {2015},
	note = {\&nbsp;Winner of the Best PhD Student Paper\&nbsp; competition},
	month = {06/2015},
	author = {Owais Mohammad {Khan} and Valen-Sendstad, Kristian and Biswas, D. and Casey, D. and Loth, F. and David A. {Steinman}}
}
@inproceedings {23970,
	title = {Characterization of Transition to Turbulence for Blood in a S-Shaped Pipe Under Steady Flow Conditions},
	journal = {The Summer Biomechanics, Bioengineering \& Biotransport Conference},
	year = {2015},
	month = {06/2015},
	author = {Biswas, D. and Casey, D. and D. C. {Crowder} and Valen-Sendstad, Kristian and David A. {Steinman} and Y. H. {Yun} and Loth, F.}
}
@article {berg2015computational,
	title = {The Computational Fluid Dynamics Rupture Challenge 2013{\textemdash}Phase II: variability of hemodynamic simulations in two intracranial aneurysms},
	journal = {Journal of Biomechanical Engineering},
	volume = {137},
	year = {2015},
	month = {2015},
	pages = {121008/1-121008/13},
	publisher = {American Society of Mechanical Engineers},
	author = {Berg, Philipp and Roloff, Christoph and Beuing, Oliver and Voss, Samuel and Sugiyama, Shin-Ichiro and Aristokleous, Nicolas and Andreas S. {Anayiotos} and Ashton, Neil and Revell, Alistair and Neil W. {Bressloff} and Alistair G. {Brown} and Bong Jae {Chung} and Juan R. {Cebral} and Copelli, Gabriele and Fu, Wenyu and Qiao, Aike and Arjan J. {Geers} and Hodis, Simona and Dragomir-Daescu, Dan and Nordahl, Emily and Yildirim Bora {Suzen} and Owais Mohammad {Khan} and Valen-Sendstad, Kristian and Kono, Kenichi and Prahlad G. {Menon} and Priti G. {Albal} and Mierka, Otto and M{\"u}nster, Raphael and Hern{\'a}n G. {Morales} and Bonnefous, Odile and Osman, Jan and Goubergrits, Leonid and Pallares, Jordi and Cito, Salvatore and Passalacqua, Alberto and Piskin, Senol and Pekkan, Kerem and Ramalho, Susana and Marques, Nelson and Sanchi, St{\'e}phane and Kristopher R. {Schumacher} and Sturgeon, Jess and Svihlov{\'a}, Helena and Hron, Jaroslav and Usera, Gabriel and Mendina, Mariana and Xiang, Jianping and David A. {Steinman} and Janiga, G{\'a}bor}
}
@inproceedings {23977,
	title = {Effects of non-Newtonian rheology on transition to turbulence},
	journal = {The 2015 AMMCS-CAIMS Congress},
	year = {2015},
	month = {06/2015},
	author = {Owais Mohammad {Khan} and Valen-Sendstad, Kristian and David A. {Steinman}}
}
@article {23408,
	title = {Estimation of Inlet Flow Rates for Image-Based Aneurysm CFD Models: Where and How to Begin?},
	journal = {Annals of Biomedical Engineering},
	volume = {43},
	year = {2015},
	pages = {1422-1431},
	publisher = {Springer},
	author = {Valen-Sendstad, Kristian and Piccinelli, Marina and Krishnankuttyrema, Resmi and David A. {Steinman}}
}
@inproceedings {23982,
	title = {Flow Instabilities in Volume-Matched Sidewall ICA Aneurysms: A Possible Association with Rupture Status?},
	journal = {Congress of Neurological Surgeons},
	year = {2015},
	month = {09/2015},
	author = {Valen-Sendstad, Kristian and Lauric, Alexandra and David A. {Steinman} and Adel M. {Malek}}
}
@inproceedings {23975,
	title = {Impact of Non-Newtonian Rheology in Transition to Turbulence in Artery Models.},
	journal = {4th International Conference on Computational and Mathematical Biomedical Engineering},
	year = {2015},
	month = {06/2015},
	author = {David A. {Steinman} and Owais Mohammad {Khan} and Valen-Sendstad, Kristian and Biswas, D. and Casey, D. and Loth, F.}
}
@misc {23995,
	title = {Implementation, verification and validation of large eddy simulation models in Oasis},
	howpublished = {MekIT - Conference on Computational Mechanics - NTNU, Trondheim, Norway},
	year = {2015},
	author = {B{\o}, Joakim and Bergersen, Aslak and Valen-Sendstad, Kristian and Mortensen, Mikael}
}
@inproceedings {23905,
	title = {Implementation, verification and validation of large eddy simulation models in Oasis},
	journal = {MekIT{\textquoteright}15 8th National Conference on Computational Mechanics},
	year = {2015},
	month = {11/2015},
	pages = {99-122},
	publisher = {International Center for Numerical Methods in Engineering (CIMNE)},
	address = {Barcelona, Spain},
	isbn = {978-84-944244-9-6},
	author = {B{\o}, Joakim and Bergersen, Aslak and Valen-Sendstad, Kristian and Mortensen, Mikael}
}
@inproceedings {23968,
	title = {Inlet Flow Rate Variation and Onset of Flow Instabilities in the Carotid Siphon},
	journal = {The Summer Biomechanics, Bioengineering \& Biotransport Conference},
	year = {2015},
	month = {06/2015},
	author = {Krishnankuttyrema, Resmi and Valen-Sendstad, Kristian and David A. {Steinman}}
}
@misc {23990,
	title = {Lessons learned from simulating blood flow in the brain: Preaching to the converted?},
	howpublished = {MPNS COST Action MP1404 Simulation and pharmaceutical technologies for advanced patient-tailored inhaled medicines, Parma, Italy},
	year = {2015},
	author = {Valen-Sendstad, Kristian}
}
@article {23444,
	title = {Narrowing the Expertise Gap for Predicting Intracranial Aneurysm Hemodynamics: Impact of Solver Numerics versus Mesh and Time-Step Resolution},
	journal = {American Journal of Neuroradiology},
	volume = {36},
	number = {7},
	year = {2015},
	publisher = {American Society of Neuroradiology},
	abstract = {BACKGROUND AND PURPOSE:\&nbsp;Recent high-resolution computational fluid dynamics studies have uncovered the presence of laminar flow instabilities and possible transitional or turbulent flow in some intracranial aneurysms. The purpose of this study was to elucidate requirements for computational fluid dynamics to detect these complex flows, and, in particular, to discriminate the impact of solver numerics versus mesh and time-step resolution.MATERIALS AND METHODS:\&nbsp;We focused on 3 MCA aneurysms, exemplifying highly unstable, mildly unstable, or stable flow phenotypes, respectively. For each, the number of mesh elements was varied by 320\&times; and the number of time-steps by 25\&times;. Computational fluid dynamics simulations were performed by using an optimized second-order, minimally dissipative solver, and a more typical first-order, stabilized solver.RESULTS:\&nbsp;With the optimized solver and settings, qualitative differences in flow and wall shear stress patterns were negligible for models down to \&sim;800,000 tetrahedra and \&sim;5000 time-steps per cardiac cycle and could be solved within clinically acceptable timeframes. At the same model resolutions, however, the stabilized solver had poorer accuracy and completely suppressed flow instabilities for the 2 unstable flow cases. These findings were verified by using the popular commercial computational fluid dynamics solver, Fluent.CONCLUSIONS:\&nbsp;Solver numerics must be considered at least as important as mesh and time-step resolution in determining the quality of aneurysm computational fluid dynamics simulations. Proper computational fluid dynamics verification studies, and not just superficial grid refinements, are therefore required to avoid overlooking potentially clinically and biologically relevant flow features.},
	author = {Owais Mohammad {Khan} and Valen-Sendstad, Kristian and David A. {Steinman}}
}
@article {23333,
	title = {Oasis: A high-level/high-performance open source Navier{\textendash}Stokes solver},
	journal = {Computer Physics Communications},
	volume = {188},
	year = {2015},
	pages = {177 - 188},
	publisher = {Elsevier},
	abstract = {Abstract Oasis is a high-level/high-performance finite element Navier{\textendash}Stokes solver written from scratch in Python using building blocks from the \{FEniCS\} project (fenicsproject.org). The solver is unstructured and targets large-scale applications in complex geometries on massively parallel clusters. Oasis utilizes \{MPI\} and interfaces, through FEniCS, to the linear algebra backend PETSc. Oasis advocates a high-level, programmable user interface through the creation of highly flexible Python modules for new problems. Through the high-level Python interface the user is placed in complete control of every aspect of the solver. A version of the solver, that is using piecewise linear elements for both velocity and pressure, is shown to reproduce very well the classical, spectral, turbulent channel simulations of Moser et al. (1999). The computational speed is strongly dominated by the iterative solvers provided by the linear algebra backend, which is arguably the best performance any similar implicit solver using \{PETSc\} may hope for. Higher order accuracy is also demonstrated and new solvers may be easily added within the same framework. Program summary Program title: Oasis Catalogue identifier: AEUW_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEUW_v1_0.html Program obtainable from: \{CPC\} Program Library, Queen{\textquoteright}s University, Belfast, N. Ireland Licensing provisions: \{GNU\} Lesser \{GPL\} version 3 or any later version No. of lines in distributed program, including test data, etc.: 3491 No. of bytes in distributed program, including test data, etc.: 266924 Distribution format: tar.gz Programming language: Python/C++. Computer: Any single laptop computer or cluster. Operating system: Any (Linux, OSX, Windows). RAM: a few Megabytes to several hundred Gigabytes Classification: 12. External routines: \{FEniCS\} 1.3.0 (www.fenicsproject.org, that in turn depends on a number of external libraries like MPI, PETSc, Epetra, Boost and ParMetis) Nature of problem: Incompressible, Newtonian fluid flow. Solution method: The finite element method. Unusual features: \{FEniCS\} automatically generates and compiles low-level C++ code based on high-level Python code. Running time: The example provided takes a couple of minutes on a single processor.},
	keywords = {Navier{\textendash}Stokes},
	issn = {0010-4655},
	doi = {http://dx.doi.org/10.1016/j.cpc.2014.10.026},
	url = {http://www.sciencedirect.com/science/article/pii/S0010465514003786},
	author = {Mortensen, Mikael and Valen-Sendstad, Kristian}
}
@article {mynard2015unified,
	title = {A unified method for estimating pressure losses at vascular junctions},
	journal = {International Journal for Numerical Methods in Biomedical Engineering},
	volume = {Jul;31(7):e02717},
	year = {2015},
	month = {2015},
	publisher = {Wiley Online Library},
	author = {Jonathan P. {Mynard} and Valen-Sendstad, Kristian}
}
@misc {Simula.simula.2588,
	title = {CFD Modelling of Cerebrovascular Hemodynamics: Breaking News},
	howpublished = {9th international symposium on Biomechanics in Vascular Biology and Cardiovascular Disease, Montreal, Canada, April, 2014},
	year = {2014},
	month = {04/2014},
	keywords = {Conference},
	author = {Valen-Sendstad, Kristian and Owais Mohammad {Khan} and Piccinelli, Marina and David A. {Steinman}}
}
@misc {Simula.simula.2592,
	title = {Flow Instabilities in Sidewall Aneurysms: a Possible Association With Rupture Status?},
	howpublished = {World Congress of Biomechanics},
	year = {2014},
	author = {Valen-Sendstad, Kristian and Lauric, Alexandra and Malek, Adel and David A. {Steinman}}
}
@article {Simula.simula.2594,
	title = {High-Resolution CFD Detects Flow Instabilities in the Carotid Siphon: Implications for Aneurysm Initiation and Rupture?},
	journal = {Journal of Biomechanics},
	number = {47},
	year = {2014},
	pages = {3210-3216},
	publisher = {Elsevier},
	author = {Valen-Sendstad, Kristian and Piccinelli, Marina and David A. {Steinman}}
}
@inproceedings {Simula.simula.2896,
	title = {Illustration-Inspired Visualization of Blood Flow Dynamics},
	journal = {World Congress of Biomechanics Proceedings},
	year = {2014},
	publisher = {JBioMech},
	type = {Conference},
	abstract = {Image-based computational fluid dynamics (CFD) has emerged as a central tool in the evaluation of hemodynamic factors in cardiovascular disease development and treatment planning, to the point where major vendors are now seeking to deploy CFD solvers on their medical imaging platforms. Detailed hemodynamic data available from CFD reveal complicated flows that are difficult to render clearly - and thus communicate to clinical stakeholders - using conventional engineering flow visualization techniques. This is especially challenging considering the four-dimensional nature of the flow patterns (i.e., varying in space and time), as well as the clinical need for generating static reports rather than cumbersome digital animations. Taking a cue from the rich history of biomedical illustration, the goal of our multi-disciplinary collaboration between the University of Toronto and the Ontario College of Art and Design University is to develop new data-driven paradigms for visualizing blood flow, based on the principles of illustration, sequential art and caricature, and informed by the visual vocabularies and conventions of radiology and vascular surgery. Our first investigations have involved the depiction of transitional flows in cerebral aneurysms. The top row of the included figure shows selected frames from an animation of vortex cores (i.e., positive and negative Q-criterion), created using the open-source scientific visualization package, Paraview. Note how difficult it is to infer the dynamics from these static images. For the bottom row, vortex cores were outlined in black to better discriminate them from each other. Surface shading was enhanced, and colouring was used to highlight selected cores, the dynamic motion of which can be followed easily across the individual frames. The original translucent lumen surface rendering was also replaced by a simple outline drawing that nevertheless retains, and perhaps even heightens, the impression of a 3D aneurysm. Although this example was composed by a professional biomedical illustrator (JH) using graphics editing tools applied to the individual static frames, we are presently working towards automating these steps in collaboration with Toronto-based Side Effects Software, developers of the Houdini 3D Animation suite widely used in the motion picture industry.},
	keywords = {Conference},
	author = {Coppin, Peter and Harvey, John and Valen-Sendstad, Kristian and David A. {Steinman}},
	editor = {Jay D. {Humphrey}}
}
@inproceedings {Simula.simula.2892,
	title = {Inlet Flow Rates for Image-Based Aneurysm CFD Models: Where (and How) to Begin?},
	journal = {World Congress of Biomechanics Proceedings},
	year = {2014},
	publisher = {JBioMech},
	type = {Conference},
	author = {Valen-Sendstad, Kristian and Piccinelli, Marina and Krishnankuttyrema, Resmi and David A. {Steinman}},
	editor = {Jay D. {Humphrey}}
}
@misc {23407,
	title = {It{\textquoteright}s not the size, but what you do with it: CFD solver settings trump model resolution.},
	howpublished = {Zurich},
	year = {2014},
	publisher = {Interdisciplinary Cerebrovascular Symposium / Intracranial Stent Meeting},
	author = {Valen-Sendstad, Kristian and Owais Mohammad {Khan} and Piccinelli, Marina and David A. {Steinman}}
}
@article {Simula.simula.1978,
	title = {Mind the Gap: Impact of Computational Fluid Dynamics Solution Strategy on Prediction of Intracranial Aneurysm Hemodynamics and Rupture Status Indicators},
	journal = {American Journal of Neuroradiology},
	volume = {35},
	number = {3},
	year = {2014},
	note = {Commentary:AJNR, 2014 Mar;35(3):544-5},
	month = {March},
	pages = {536-543},
	publisher = {American Journal of Neuroradiology},
	author = {Valen-Sendstad, Kristian and David A. {Steinman}}
}
@inproceedings {Simula.simula.2894,
	title = {A Novel Framework for Classifying Wall Shear Stress Phenotypes in Arterial Disturbed Blood Flow},
	journal = {World Congress of Biomechanics Proceedings},
	year = {2014},
	publisher = {JBioMech},
	type = {Conference},
	abstract = {Background and Purpose: Recent high-resolution (HR) computational fluid dynamics (CFD) simulations have revealed that flow instabilities with high-frequency fluctuations can occur at relatively low Reynolds numbers (Valen-Sendstad and Steinman, 2014). We have assumed that the highly disturbed wall shear stress (WSS) caused by such flow instabilities impact the (dys)functional nature of arterial endothelial cells, believed to initiate arterial diseases. Current indices designed to quantify the disturbed WSS, such as oscillatory shear index (OSI) and transverse wall shear stress (transWSS), however, sometimes fail to distinguish different types of highly disturbed WSS. We propose a method for quantifying and distinguishing the WSS disturbances adequately and demonstrate its capability. Materials and Methods: We used an anatomically realistic carotid siphon derived from the open-source Aneurisk data-set. The aneurysm was removed with previously developed and verified tools. Pulsatile flow was simulated using 30,000 time-steps per cycle and the equivalent of 24M linear tetrahedrons. Changes in instantaneous WSS were decomposed into magnitude and angle variations, respectively, with the angle defined relative to the cycle-averaged WSS vector direction. The proposed classification of WSS phenotypes therefore consists of a permutation (from low to high values) of WSS, WSS magnitude change, and WSS angle change; a total of 9. Results: The attached figure shows the distributions of OSI, transWSS, and the currently proposed phenotypes. Despite highly different stimuli at the wall (shown in the polar plots, where the WSS magnitude is plotted on a common logarithmic scale), both OSI and transWSS calculations return the same numerical value for large regions. E.g., the WSS phenotype in polar plots OSI=.211},
	author = {Shimogonya, Yuji and Valen-Sendstad, Kristian and David A. {Steinman}},
	editor = {Jay D. {Humphrey}}
}
@misc {Simula.simula.2920,
	title = {On Numerical Methods for Transitional Flow - Application to Blood Flow in Aneurysms},
	howpublished = {Quality and Validation of Computational Cardio-vascular Biomechanics, WCCM-ECCM-ECCOM},
	year = {2014},
	author = {Mardal, Kent-Andre and Owais Mohammad {Khan} and Valen-Sendstad, Kristian}
}
@inproceedings {Simula.simula.2890,
	title = {Numerical Resolution Requirements for Converging Wall Shear Stresses in Intracranial Aneurysms},
	journal = {World Congress of Biomechanics Proceedings},
	year = {2014},
	publisher = {JBioMech},
	type = {Conference},
	abstract = {Abstract: Background: CFD can simulate the hemodynamics forces like wall shear stress (WSS) that are known to play an important role in rupture of intracranial aneurysms. Every stone has been turned striving for more {{\textquoteleft}}patient-specific\&$\#$39; simulations, except for numerical accuracy itself. The purpose of this study is to quantify such errors, particularly for WSS. Methods: Five refinement levels were simulated for three previously reported cases based on flow phenotype (Valen-Sendstad and Steinman, 2014): stable-sidewall (case 8), quasi-unstable- bifurcation (case 9), and unstable-bifurcation (case 16). Pulsatile simulations were performed using second-order-accurate P2-P1 (Taylor-Hood) tetrahedral elements. Finest meshes had a sac resolution of 0.055mm, 0.061mm, and 0.10mm for cases 8, 9 and 16, respectively, resulting in 4-million elements (\~32M linear tetrahedra). These finest meshes were successively coarsened by a factor of sqrt(2) with respect to side length, resulting in coarsest meshes having \~100,000 elements (\~800,000 linear tetrahedra). All meshes had four boundary layers. We used 35,000 time- steps/cycle and second-order time-stepping scheme for three reasons: 1) to avoid adding artificial numerical viscosity to stabilize the solution, 2) to eliminate temporal discretization errors, and 3) to isolate and quantify spatial discretization errors alone. Results: In contrast to conventional mesh refinement studies, we show a 3-fold decrease in effective node spacing, not simply mesh size. As a consequence, mesh sizes grew cubically. In the figure, we show normalized L2 errors for domain-averaged velocity and dome-averaged WSS at peak systole relative to the finest mesh. Although the velocity errors, a standard metric for monitoring grid convergence, appear to be within 2\% error for the second-finest mesh (equivalent to \~13M linear tetrahedra), the WSS errors are an order of magnitude away from convergence. Having said this, patterns of WSS were qualitatively similar. Conclusions: High spatial resolution is required to converge WSS, even when velocity appears to be well-converged: on average, an effective mesh resolution of \~0.05mm is needed to converge WSS below \~10\%. Work to be presented will also include temporal refinement study with high spatial resolution to clarify the requirements on temporal resolution, as well as the impact on popular scalar hemodynamic indices.},
	author = {Owais Mohammad {Khan} and Valen-Sendstad, Kristian and David A. {Steinman}},
	editor = {Jay D. {Humphrey}}
}
@misc {Simula.simula.2590,
	title = {Unstable Flow in the Carotid Siphon: Implications for Aneurysm Initiation and Rupture},
	howpublished = {World Congress of Biomechanics},
	year = {2014},
	keywords = {Conference},
	author = {Valen-Sendstad, Kristian and Piccinelli, Marina and David A. {Steinman}}
}
@misc {Simula.simula.2254,
	title = {{{\textquoteleft}}Freezing Time{\textquoteright} to Show 4D Evolution of Transitional Vortex Cores in an Aneurysm That Is Undergoing Highly Unstable Flow},
	year = {2013},
	author = {Coppin, Peter and Harvey, John and Valen-Sendstad, Kristian and David A. {Steinman}}
}
@article {Simula.simula.1698,
	title = {High-Resolution Computational Fluid Dynamics Detects High-Frequency Velocity Fluctuations in Bifurcation, But Not Sidewall, Aneurysms of the Middle Cerebral Artery},
	journal = {Journal of Biomechanics},
	volume = {46},
	year = {2013},
	pages = {402-407},
	publisher = {Elsevier},
	abstract = {High-frequency flow fluctuations in intracranial aneurysms have previously been reported in vitro and in vivo. On the other hand, the vast majority of image-based computational fluid dynamics (CFD) studies of cerebral aneurysms report periodic, laminar flow. We have previously demonstrated that transitional flow, consistent with in vivo reports, can occur in a middle cerebral artery (MCA) bifurcation aneurysm when ultra-high-resolution direct numerical simulation methods are applied. The object of the present study was to investigate if such high-frequency flow fluctuations might be more widespread in adequately-resolved CFD models. A sample of N=12 anatomically realistic MCA aneurysms (five unruptured, seven ruptured), was digitally segmented from CT angiograms. Four were classified as sidewall aneurysms, the other eight as bifurcation aneurysms. Transient CFD simulations were carried out assuming a steady inflow velocity of 0.5 m/s, corresponding to typical peak systolic conditions at the MCA. To allow for detection of clinically-reported high-frequency flow fluctuations and resulting flow structures, temporal and spatial resolutions of the CFD simulations were in the order of 0.1 ms and 0.1 mm, respectively. A transient flow response to the stationary inflow conditions was found in five of the 12 aneurysms, with energetic fluctuations up to 100 Hz, and in one case up to 900 Hz. Incidentally, all five were ruptured bifurcation aneurysms, whereas all four sidewall aneurysms, including one ruptured case, quickly reached a stable, steady state solution. Energetic, rapid fluctuations may be overlooked in CFD models of bifurcation aneurysms unless adequate temporal and spatial resolutions are used. Such fluctuations may be relevant to the mechanobiology of aneurysm rupture, and to a recently reported dichotomy between predictors of rupture likelihood for bifurcation vs. sidewall aneurysms.},
	author = {Valen-Sendstad, Kristian and Mardal, Kent-Andre and David A. {Steinman}}
}
@misc {Simula.simula.1982,
	title = {Impact of CFD Solution Strategy on Predicted Aneurysm Hemodynamics: Good News and Bad News},
	howpublished = {8th International Symposium on Biomechanics in Vascular Biology and Cardiovascular Disease, Rotterdam},
	year = {2013},
	month = {April},
	keywords = {Conference},
	author = {Valen-Sendstad, Kristian and David A. {Steinman}}
}
@inproceedings {Simula.simula.1980,
	title = {Impact of CFD Solution Strategy on Predicted Aneurysm Hemodynamics: Good News and Bad News},
	journal = {Proceedings of 8th international symposium on Biomechanics in Vascular Biology and Cardiovascular Disease},
	year = {2013},
	publisher = {Proceedings},
	type = {Conference},
	abstract = {Last year at this meeting we demonstrated that high-resolution (HR) CFD simulations could detect a highly transient response to steady inflow conditions in 5 of 12 MCA aneurysm cases [1]. We also showed preliminary results suggesting that normal resolution (NR) simulations, representative of those from the clinical literature (e.g, [2,3]), might be misleading about the nature of aneurysm flow patterns and wall shear stress (WSS), and hence derived predictors of rupture risk. We now test this hypothesis in a controlled manner, by comparing NR vs. HR simulations of physiologically pulsatile flow in the 12 MCA aneurysm cases from [1].},
	author = {Valen-Sendstad, Kristian and David A. {Steinman}},
	editor = {Gijsen et {al.}}
}
@misc {Simula.simula.2528,
	title = {Impact of CFD Solution Strategy on Predicted Aneurysm Hemodynamics: Good News and Bad News},
	howpublished = {CBC seminar series},
	year = {2013},
	month = {April},
	author = {Valen-Sendstad, Kristian}
}
@inproceedings {Simula.simula.2256,
	title = {A Quasi-Analytical Method for Calculating Junction Pressure Losses in 1D Vascular Network Models: Validation With High-Resolution CFD},
	journal = {3rd International Conference on Computational and Mathematical Biomedical Engineering - CMBE2013},
	year = {2013},
	publisher = {Proceedings},
	type = {Conference},
	author = {Valen-Sendstad, Kristian and Jonathan P. {Mynard}},
	editor = {Perumal Nithiarasu {al}}
}
@article {Simula.simula.1796,
	title = {A Study of Wall Shear Stress in 12 Aneurysms With Respect to Different Viscosity Models and Flow Conditions},
	journal = {Journal of Biomechanics},
	volume = {46},
	number = {16},
	year = {2013},
	month = {November},
	pages = {2802-2808},
	abstract = {Recent computational fluid dynamics (CFD) studies relate abnormal blood flow to rupture of cerebral aneurysms. However, it is still debated how to model blood flow with sufficient accuracy. Common assumptions made include Newtonian behavior of blood, traction free outlet boundary conditions and inlet boundary conditions based on available literature. These assumptions are often required since the available patient specific data is usually restricted to the geometry of the aneurysm and the surrounding vasculature. However, the consequences of these assumptions have so far been inadequately addressed. This study investigates the effects of 4 different viscosity models, 2 different inflow conditions and 2 different outflow conditions in 12 middle cerebral artery aneurysms. The differences are quantified in terms of 3 different wall shear stress (WSS) metrics, involving maximal WSS, average WSS, and proportion of aneurysm sac area with low WSS. The results were compared with common geometrical metrics such as volume, aspect ratio, size ratio and parent vessel diameter and classifications in terms of sex and aneurysm type. The results demonstrate strong correlations between the different viscosity models and boundary conditions. The correlation between the different WSS metrics range from weak to medium. No strong correlations were found between the different WSS metrics and the geometrical metrics or classifications.},
	author = {Evju, {\O}yvind and Valen-Sendstad, Kristian and Mardal, Kent-Andre}
}
@article {Simula.simula.1746,
	title = {Variability of Computational Fluid Dynamics Solutions for Pressure and Flow in a Giant Aneurysm: the ASME 2012 Summer Bioengineering Conference CFD Challenge},
	journal = {Journal of Biomedical Engineering},
	volume = {135},
	number = {2},
	year = {2013},
	publisher = {J Biomech Eng},
	author = {David A. {Steinman} and Hoi, Yiemeng and Fahy, P. and Morris, L. and Walsh, MT and Aristokleous, N. and Anayiotos, AS and Papaharilaou, Y. and Arzani, A. and Shadden, SC and Berg, Philipp and Janiga, G. and Bols, Joris and Segers, Patrick and Neil W. {Bressloff} and Cibis, M. and Gijsen, FH and Cito, S. and Pallareacutes, J. and Joan Heller {Brown} and Costelloe, JA and Lynch, AG and Degroote, Joris and Vierendeels, Jan and Fu, Wenyu and Qiao, Aike and Hodis, S. and Kallmes, DF and Kalsi, H. and Long, Quan and Kheyfets, VO and Fino, EA and Kono, K. and Malek, AM and Lauric, Alexandra and Prahlad G. {Menon} and Pekkan, K. and Moghadam, Esmaily and Marsden, AL and Oshima, M. and Katagiri, K. and Peiffer, V. and Mohamied, Y. and Sherwin, SJ and Schaller, J. and Goubergrits, L. and Usera, G. and Mendina, M. and Habets, DF and Valen-Sendstad, Kristian and Xiang, Jianping and Meng, Hui and Karniadakis, GE and Shaffer, N. and Loth, F.}
}
@inproceedings {Simula.simula.1292,
	title = {CFD CHALLENGE: SOLUTIONS USING an IN-HOUSE FINITE ELEMENT METHOD FLOW SOLVER IMPLEMENTED in FEniCS},
	journal = {ASME 2012 Summer Bioengineering Conference, Fajardo, Puerto Rico},
	year = {2012},
	type = {Conference},
	abstract = {FEniCS is a finite element library for {{\textquoteleft}}automated, efficient solution of differential equations\&$\#$39; (www.fenicsproject.org). The focus has been to develop high level software interface that allows the user to type in the equations nearly as they are read. Recent development has involved extensions for parallell computing and building efficient pipeline for patient specific geometries based on Vascular Modelling Toolkit (VMTK, www.vmtk.org) meshes. The aim is therefore to evaluate the accuracy and efficiency of one of the developed computational fluid mechanics (CFD) solvers. The simulations were perfored according to the given instructions and information is not repeated. This abstract is therefore not complete and must be seen in the light of the Challenge.},
	author = {Valen-Sendstad, Kristian and David A. {Steinman}}
}
@inproceedings {Simula.simula.1290,
	title = {Is CFD Misleading Us About the Nature of Wall Shear Stresses in Cerebral Aneurysms?},
	journal = {The 7th International Symposium on Biomechanics in Vascular Biology \& Cardiovascular Disease, Atlanta, Georgia, USA},
	year = {2012},
	publisher = {Internal},
	type = {Conference},
	abstract = {Computational fluid dynamics (CFD) simulations are increasingly being used to model cerebral aneurysm hemodynamics and wall shear stress (WSS) in order to infer aneurysm wall strength and therefore risk of rupture. Numerous recent computational studies have been successful in retrospectively classifying aneurysms according to their rupture status, but the link between the proposed hemodynamic indices and the precise mechanisms leading to rupture remains unclear. One presumption common to virtually all of these CFD studies is that blood flow inside an aneurysm is laminar and stable, even though it is well known that many aneurysms produce sounds or bruits with energy peaks at hundreds of Hz. Clinicians have reported this invasively and non-invasively, and turbulence has been shown to occur in intracranial aneurysms in several experiments. These phenomena seem have raised little interest in the computational biomechanics community, and there is therefore a gap between the clinically reported frequencies and the resolution at which the simulations are performed. We have previously shown, using direct numerical simulation of pulsatile flow in two patient-specific middle cerebral artery (MCA) aneurysms, that transitional flow was present, leading to strong wall shear stress gradients. More recently, we have demonstrated the presence of unstable flow patterns in 5 of 12 MCA aneurysm cases simulated under high resolution, transient steady flow conditions. These findings would suggest that in many cases the aneurysmal wall may be subject to more violent forces than have been predicted by the vast majority of CFD model studies. To illustrate this, we carried out transient steady flow simulations for the two MCA cases we had previously simulated with DNS, using a first order accurate solver with roughly 600,000 linear tetrahedral and boundary layer elements and 10 msec temporal resolution, and a second order solver with the same number of elements (i.e. more than double the spatial resolution) and 0.03 msec temporal resolution. The latter simulations exhibited strong velocity and WSS fluctuations, as anticipated from the previous DNS studies, whereas the first order simulations stabilized quickly. These preliminary head-to-head comparisons are currently being extended to more cases, and under pulsatile flow conditions. In summary, the presumption of laminar, stable flow underlying most CFD models of cerebral aneurysms may be a self-fulfilling prophecy that leads to a misinterpretation of the biomechanical forces at play in aneurysm progression and rupture.},
	author = {Valen-Sendstad, Kristian and David A. {Steinman}},
	editor = {Oshinski, John}
}
@misc {Simula.simula.1286,
	title = {Is CFD Misleading Us About the Nature of Wall Shear Stresses in Cerebral Aneurysms?},
	howpublished = {The 7th International Symposium on Biomechanics in Vascular Biology \& Cardiovascular Disease, Atlanta, Georgia, USA},
	year = {2012},
	abstract = {Computational fluid dynamics (CFD) simulations are increasingly being used to model cerebral aneurysm hemodynamics and wall shear stress (WSS) in order to infer aneurysm wall strength and therefore risk of rupture. Numerous recent computational studies have been successful in retrospectively classifying aneurysms according to their rupture status, but the link between the proposed hemodynamic indices and the precise mechanisms leading to rupture remains unclear. One presumption common to virtually all of these CFD studies is that blood flow inside an aneurysm is laminar and stable, even though it is well known that many aneurysms produce sounds or bruits with energy peaks at hundreds of Hz. Clinicians have reported this invasively and non-invasively, and turbulence has been shown to occur in intracranial aneurysms in several experiments. These phenomena seem have raised little interest in the computational biomechanics community, and there is therefore a gap between the clinically reported frequencies and the resolution at which the simulations are performed. We have previously shown, using direct numerical simulation of pulsatile flow in two patient-specific middle cerebral artery (MCA) aneurysms, that transitional flow was present, leading to strong wall shear stress gradients. More recently, we have demonstrated the presence of unstable flow patterns in 5 of 12 MCA aneurysm cases simulated under high resolution, transient steady flow conditions. These findings would suggest that in many cases the aneurysmal wall may be subject to more violent forces than have been predicted by the vast majority of CFD model studies. To illustrate this, we carried out transient steady flow simulations for the two MCA cases we had previously simulated with DNS, using a first order accurate solver with roughly 600,000 linear tetrahedral and boundary layer elements and 10 msec temporal resolution, and a second order solver with the same number of elements (i.e. more than double the spatial resolution) and 0.03 msec temporal resolution. The latter simulations exhibited strong velocity and WSS fluctuations, as anticipated from the previous DNS studies, whereas the first order simulations stabilized quickly. These preliminary head-to-head comparisons are currently being extended to more cases, and under pulsatile flow conditions. In summary, the presumption of laminar, stable flow underlying most CFD models of cerebral aneurysms may be a self-fulfilling prophecy that leads to a misinterpretation of the biomechanical forces at play in aneurysm progression and rupture.},
	author = {Valen-Sendstad, Kristian and David A. {Steinman}}
}
@inbook {Simula.acdc.38,
	title = {A Comparison of Some Common Finite Element Schemes for the Incompressible Navier-Stokes Equations},
	booktitle = {Automated Solution of Differential Equations by the Finite Element Method},
	series = {Lecture Notes in Computational Science and Engineering},
	volume = {84},
	year = {2012},
	pages = {395-418},
	publisher = {Springer},
	organization = {Springer},
	chapter = {21},
	isbn = {978-3-642-23098-1},
	author = {Valen-Sendstad, Kristian and Logg, Anders and Mardal, Kent-Andre and Narayanan, Harish and Mortensen, Mikael},
	editor = {Logg, Anders and Mardal, Kent-Andre and Garth N. {Wells}}
}
@inbook {Simula.acdc.40,
	title = {Computational Hemodynamics},
	booktitle = {Automated Solution of Differential Equations by the Finite Element Method},
	series = {Lecture Notes in Computational Science and Engineering},
	volume = {84},
	year = {2012},
	pages = {439-454},
	publisher = {Springer},
	organization = {Springer},
	chapter = {23},
	isbn = {978-3-642-23098-1},
	author = {Valen-Sendstad, Kristian and Mardal, Kent-Andre and Logg, Anders},
	editor = {Logg, Anders and Mardal, Kent-Andre and Garth N. {Wells}}
}
@misc {Simula.simula.1890,
	title = {Non-Newtonian Effects in Cerebral Aneurysms. a Computational Study on 12 Patient Specific Aneurysms},
	howpublished = {ICS {\textquoteright}12},
	year = {2012},
	author = {Evju, {\O}yvind and Valen-Sendstad, Kristian and Mardal, Kent-Andre}
}
@misc {Simula.simula.1816,
	title = {On Non-Newtonian Effects in Cerebral Aneurysms: a Computational Study on 12 Patient Specific Aneurysms},
	year = {2012},
	author = {Evju, {\O}yvind and Mardal, Kent-Andre and Valen-Sendstad, Kristian}
}
@misc {Simula.simula.1288,
	title = {Revisiting {\textquoteright}Turbulence{\textquoteright} in Cerebral Aneurysms},
	year = {2012},
	abstract = {One of the commonly made assumptions in Computational Fluid Dynamics (CFD) is that cerebral blood flow is laminar, i.e., viscous forces are dominating and the flow is smooth. The numerical methods that are used, are chosen or tailored accordingly, i.e., to converge to such a laminar flow solution with the minimal amount of work1-2. The flow is modeled with a temporal resolution far below the clinically reported frequencies3 and thus any potential flow disturbances, if physically present, are being numerically suppressed. Since no potential disturbances are resolved, no disturbances are observed and the assumption of laminar flow is therefore a self-fulfilling prophecy. Even though recent laminar CFD studies can discriminate between ruptured and unruptured aneurysms better than, e.g. aneurysm size, the link between the proposed hemodynamic agonists and the mechanisms of rupture is unclear. However, the literature contains much evidence which supports that certain aneurysms exhibit energetic high frequency flow fluctuations. For example, high frequency flow fluctuations are known to produce sound, and clinicians have reported such sound or {\textquoteright}bruits{\textquoteright} from aneurysms during craniotomy.3 The predominant frequencies were at 460 Hz, which is consistent with the energy peaks at higher frequencies recorded acoustically on the eyes in patients with aneurysms.4 Unstable flow has also been reported in glass model studies of aneurysms.5 This evidence seems to have been ignored, or at least has not received much attention in computational modeling studies. The goal of the present study was to investigate if such high-frequency flow fluctuations in intracranial aneurysms might be a common occurrence, by using thousands of time steps in contrast to, e.g., one hundred2.},
	keywords = {Conference},
	author = {Valen-Sendstad, Kristian and Mardal, Kent-Andre and David A. {Steinman}}
}
@inproceedings {Simula.simula.638,
	title = {On the Complexity of Stationary Flow in Patient-Specific Aneurysms},
	journal = {MekIT{\textquoteright}11 Sixth national conference on Computational Mechanics},
	year = {2011},
	pages = {379-392},
	publisher = {tapir academic press},
	type = {Conference},
	abstract = {Summary Sound or bruits in the vasculatory system at the range of 1Hz-1kHz is known to occur, and frequency peaks at high frequencies are associated with sick blood vessels. The exact reason for these sounds are not known, but the sound may be generated by turbulence. Turbulence generated sound is typically associated with high frequencies but also with low energy levels. Unfortunately, most blood flow simulations are performed with space and time resolutions where rapid fluctuations typ- ically associated with non-laminar flow cannot be captured. Complex non-laminar flow and the subsequent oscillatory wall stresses can po- tentially be of importance in understanding aneurysm rupture through the local arterial wall response. To investigate the possible presence of complex non-laminar blood flow in intracranial aneurysms, we per- formed high resolution computational fluid dynamics (CFD) simulations for patient specific middle cerebral artery (MCA) aneurysms with sta- tionary inflow conditions. The current study confirms, through high resolution simulations, that complex oscillatory flow may occur in in- tracranial aneurysms. CFD practitioners should therefore be aware of the potentially strong demands to space-time computational resolution in blood flow simulations.},
	isbn = {978-82-519-2798-7},
	author = {Valen-Sendstad, Kristian and Mardal, Kent-Andre and Mortensen, Mikael and Bj{\o}rn Anders Petterson {Reif} and Hans Petter {Langtangen}},
	editor = {Bj{\o}rn H. {Skallerud} and Helge I. {Andersson}}
}
@misc {Simula.simula.408,
	title = {Computational Cerebral Hemodynamics},
	howpublished = {The Norwegian Defence Research Establishment},
	year = {2011},
	month = {March},
	author = {Valen-Sendstad, Kristian and Mardal, Kent-Andre and Mortensen, Mikael and Bj{\o}rn Anders Petterson {Reif} and Hans Petter {Langtangen}}
}
@phdthesis {Simula.simula.632,
	title = {Computational Cerebral Hemodynamics},
	year = {2011},
	month = {May},
	school = {University of Oslo},
	type = {phd},
	abstract = {Stroke is the third most common reason for death in the Western world. One type of stroke is caused by the rupture of an out-pouch of a blood vessel, called an aneurysm. As much as six per cent of us can develop aneurysms during our life time, and the number of incidences of stroke is on the rise. Understanding the underlying processes of initiation, growth and rupture of aneurysms is of great importance to both a patient and society in general. Therefore, one has to gain detailed knowledge of blood flow and its effects on the blood vessel wall. Blood flow inside aneurysms has previously been believed to be stable and smooth. However, in Valen-Sendstad{\textquoteright}s thesis, it is proven through very high-resolution computational fluid dynamics that the flow can be complex and turbulent. This means that the cells inside the blood vessels, or aneurysms, might experience forces much stronger than previously assumed.},
	isbn = {ISSN 1501-7710 No. 1067},
	author = {Valen-Sendstad, Kristian}
}
@article {Simula.simula.636,
	title = {Direct Numerical Simulation of Transitional Flow in a Patient-Specific Intracranial Aneurysm},
	journal = {Journal of Biomechanics},
	volume = {44},
	number = {16},
	year = {2011},
	pages = {2826-2832},
	abstract = {In experiments turbulence has previously been shown to occur in intracranial aneurysms, but the turbulent effects on the arterial wall have not been investigated. The effects of turbulence induced oscillatory wall stresses could be of great importance in understanding aneurysm rupture due to the local arterial wall response to such hemodynamical forces. To investigate the effects of turbulence on blood flow in an intracranial aneurysm, we performed a high resolution computational fluid dynamics (CFD) simulations in a patient specific middle cerebral artery (MCA) aneurysm using a realistic, pulsatile inflow velocity. The flow showed transition to turbulence just after peak systole, and the turbulent fluctuations increased in intensity until mid deceleration, before relaminarization occurred during diastole. The flow impinged with an angle nearly normal onto the aneurysm dome, and the turbulence structures greatly affected both the frequency of change of wall shear stress (WSS) direction and WSS magnitude, which reached a maximum value of 41.5 Pa. The recorded frequencies were predominantly in the range of 1-500 Hz. The current study confirms, through properly resolved CFD simulations, that turbulence can occur in intracranial aneurysms. Because of the local arterial wall response to hemodynamical forces, the effects of oscillatory WSS caused by turbulence, could be correlated with aneurysm rupture, and should be investigated experimentally. Keywords: Computational fluid dynamics, Blood flow, Direct Numerical Simulation, Turbulence, Middle cerebral artery aneurysm},
	doi = {doi:10.1016/j.jbiomech.2011.08.015},
	author = {Valen-Sendstad, Kristian and Mardal, Kent-Andre and Mortensen, Mikael and Bj{\o}rn Anders Petterson {Reif} and Hans Petter {Langtangen}}
}
@misc {Simula.simula.826,
	title = {Direct Numerical Simulation of Transitional Flow in Patient-Specific Intracranial Aneurysms},
	howpublished = {ASME 2011 Summer Bioengineering Conference},
	year = {2011},
	month = {June},
	author = {Valen-Sendstad, Kristian and Mardal, Kent-Andre and Mortensen, Mikael and Bj{\o}rn Anders Petterson {Reif} and Hans Petter {Langtangen}}
}
@misc {Simula.simula.782,
	title = {The Finite Element Library FEniCS and Simulation of Blood Flow in Cerebral Aneurysms},
	howpublished = {Talk at CSB Seminar, University of Stuttgart},
	year = {2011},
	author = {Mardal, Kent-Andre and Valen-Sendstad, Kristian and Martin Sandve {Aln{\ae}s} and Mortensen, Mikael and Hans Petter {Langtangen} and Bj{\o}rn Anders Petterson {Reif}}
}
@article {Simula.bioflows.2,
	title = {Flow Characteristics in a Canine Aneurysm Model: A Comparison of 4-D Accelerated Phase-Contrast MR Measurements and Computational Fluid Dynamics Simulations},
	journal = {Medical Physics},
	volume = {38},
	number = {11},
	year = {2011},
	pages = {6300-6313},
	publisher = {Med Phys},
	author = {Jiang, Jingfeng and Johnson, Kevin and Valen-Sendstad, Kristian and Mardal, Kent-Andre and Wieben, Oliver and Strother, Charles}
}
@inproceedings {Simula.simula.646,
	title = {Investigations of Transistional Flows Using Image Based Hemodynamics},
	journal = {8th International Conference on CFD in Oil \& Gas, Metallurgical and Process Industries},
	year = {2011},
	month = {June},
	type = {Conference},
	abstract = {We investigated the complexity of blood flow in intracranial aneurysms in terms of the frequency spectrum of pointwise velocity and pressure fluctuations. The investigations were performed using high-resolution computational fluid dynamics (CFD) simulations for patient-specific middle cerebral artery (MCA) aneurysms, using realistic inflow profile. Through these simulations, the study confirmed that complex transitional flow can occur in intracranial aneurysms. In particular, we found fluctuations of the order of 500- 1000 Hz.},
	author = {Valen-Sendstad, Kristian and Mortensen, Mikael and Mardal, Kent-Andre and Bj{\o}rn Anders Petterson {Reif} and Hans Petter {Langtangen}}
}
@article {Simula.simula.634,
	title = {A Quantitative Characterization of Differences in Flow Patterns in Ruptured Versus Unruptured MCA Aneurysms},
	journal = {journal},
	year = {2011},
	abstract = {The rupture of an intracranial aneurysm is often associated with death or severe neurological deficits. When detected, the physician has to evaluate the risk of rupture and determine the optimal treatment. Risk estimation based on computational fluid dynamics (CFD) and wall shear stress (WSS) has recently been the focus of many studies. Here, we introduce new indicators for assessing risk of aneurysm rupture based on fluid mechanical properties such as the kinetic energy, vorticity and pressure drop over the aneurysm.},
	author = {Valen-Sendstad, Kristian and Mardal, Kent-Andre and Isaksen, J{\o}rgen and Mortensen, Mikael}
}
@misc {Simula.simula.770,
	title = {Simulating Blood Flow in Cerebral Aneurysm},
	howpublished = {Minisymposium Numerical Methods for Biomedical Problems on Enumath},
	year = {2011},
	author = {Mardal, Kent-Andre and Valen-Sendstad, Kristian and Evju, {\O}yvind}
}
@misc {Simula.simula.406,
	title = {Simulation Methodology for Cerebral Blood Flow},
	howpublished = {Biomedical Simulation Lab, Institute of Biomaterials and Biomedical Engineering at the University of Toronto},
	year = {2011},
	month = {March},
	abstract = {In experiments turbulence has previously been shown to occur in intracranial aneurysms, but the turbulent effects on the arterial wall have not been investigated. The effects of turbulence induced oscillatory wall stresses could be of great importance in understanding aneurysm rupture due to the local arterial wall response to such hemodynamical forces. To investigate the effects of turbulence on blood flow in an intracranial aneurysm, we performed a high resolution computational fluid dynamics (CFD) simulations in a patient specific middle cerebral artery (MCA) aneurysm using a realistic, pulsatile inflow velocity. The flow showed transition to turbulence just after peak systole, and the turbulent fluctuations increased in intensity until mid deceleration, before relaminarization occurred during diastole. The flow impinged with an angle nearly normal onto the aneurysm dome, and the turbulence structures greatly affected both the frequency of change of wall shear stress (WSS) direction and WSS magnitude, which reached a maximum value of 41.5 Pa. The recorded frequencies were predominantly in the range of 1-500 Hz. The current study confirms, through properly resolved CFD simulations, that turbulence can occur in intracranial aneurysms. Because of the local arterial wall response to hemodynamical forces, the effects of oscillatory WSS caused by turbulence, could be correlated with aneurysm rupture, and should be investigated experimentally.},
	author = {Valen-Sendstad, Kristian and Mardal, Kent-Andre and Mortensen, Mikael and Bj{\o}rn Anders Petterson {Reif} and Hans Petter {Langtangen}}
}
@misc {Simula.simula.846,
	title = {{\textquoteright}Turbulence{\textquoteright} in Cerebral Aneurysms},
	howpublished = {CBC Workshop on Biomechanics, 17-18 November},
	year = {2011},
	author = {Valen-Sendstad, Kristian and Mardal, Kent-Andre and Mortensen, Mikael and Hans Petter {Langtangen} and Bj{\o}rn Anders Petterson {Reif} and David A. {Steinman}}
}
@misc {Simula.simula.828,
	title = {Why Blood Flow in the Vicinity of Aneurysms Is Difficult to Compute},
	howpublished = {Talk at CBC Workshop on CBC Key Topics},
	year = {2011},
	month = {August},
	author = {Valen-Sendstad, Kristian and Mardal, Kent-Andre and Mortensen, Mikael and Bj{\o}rn Anders Petterson {Reif} and Hans Petter {Langtangen}}
}
@inproceedings {Simula.simula.830,
	title = {Comparison of Aneurismal Hemodynamics Between 4D Accelerated Phase-Contrast MR Angiography and Computational Fluid Dynamics Simulations: Initial Experience in a Canine Aneurysm Model},
	journal = {Proceedings of the ASME 2010 Summer Bioengineering Conference},
	year = {2010},
	month = {June},
	pages = {SBC2010-19455 223},
	publisher = {American Society of Mechanical Engineers},
	type = {Conference},
	author = {Jiang, Jingfeng and Johnson, Kevin and Valen-Sendstad, Kristian and Mardal, Kent-Andre and Consigny, Dan and Wieben, Oliver and Strother, Charles}
}
@misc {Simula.simula.302,
	title = {A Note on the Efficiency and Accuracy of Some Common Finite Element Schemes for the Incompressible Navier-Stokes Equations},
	howpublished = {AC/DC seminar series},
	year = {2010},
	author = {Valen-Sendstad, Kristian}
}
@misc {Simula.simula.300,
	title = {Presence of Turbulence in Intracranial MCA Aneurysms},
	howpublished = {CBC Workshop on Aerosols: Dispersion, Transport and Effects, Simula, November 10},
	year = {2010},
	author = {Valen-Sendstad, Kristian}
}
@article {Simula.sc.772,
	title = {Sex Differences in Intracranial Arterial Bifurcations},
	journal = {Gender Medicine},
	volume = {7},
	number = {2},
	year = {2010},
	publisher = {Gend Med},
	abstract = {Background: Subarachnoid hemorrhage (SAH) is a serious condition, occurring 50-70\% more frequently in females than males. SAH is mainly caused by rupture of an intracranial aneurysm. An intracranial aneurysm is formed by localized dilation of the intracranial arterial vessel wall, usually at the apex of the arterial bifurcation. The female preponderance is usually explained by systemical factors (hormonal influences and intrinsic wall weakness). Objective: To explore any sex variation in the bifurcation anatomy of the MCA and ICA, and the subsequent hemodynamic impact. Methods: We measured vessel radii and bifurcation angles in 47 middle cerebral artery (MCA) and 52 internal carotid artery (ICA) bifurcations in 49 patients (32 females and 17 males). The measurements were used to create idealized, averaged bifurcations of the MCA and ICA for females and males. Computational fluid dynamics simulations were performed to calculate hemodynamic forces in the models. Results: The measurements showed statistically significant sex differences in vessel diameter (men larger than females), but not in bifurcation angles. Computational fluid dynamics simulations showed higher wall shear stress in the female MCA bifurcation (19 \%) and ICA bifurcation (50 \%) compared with the male bifurcations. Conclusions: The present study suggests that sex differences in vessel size and blood flow velocity result in higher hemodynamic forces acting upon the female vessel wall. This is a new hypothesis that may partially explain why intracranial aneurysms and SAH are more likely to occur in females than males.},
	author = {Haakon {Lindekle, iv} and Valen-Sendstad, Kristian and Michael K. {Morgan} and Mardal, Kent-Andre and Faulder, Kenneth and Magnus, Jeanette and Waterloo, Knut and Romner, Bertil and Ingebrigtsen, Tor}
}
@misc {Simula.sc.784,
	title = {Cerebral Blood Flow},
	howpublished = {Invited talk at Telemark College, Engineering Faculty, Porsgrunn, Norway, 2009},
	year = {2009},
	author = {Mardal, Kent-Andre and Hentschel, Susanne and Logg, Anders and Valen-Sendstad, Kristian}
}
@misc {Simula.sc.782,
	title = {CSF Flow Modelling},
	howpublished = {Invited talk at CSR Flow Research Conference at University of Wisconsin, Nov 9},
	year = {2009},
	author = {Mardal, Kent-Andre and Haughton, Victor and Hentschel, Susanne and Hans Petter {Langtangen} and Linge, Svein and Alf Emil {L{\o}vgren} and Valen-Sendstad, Kristian}
}
@misc {Simula.sc.1154,
	title = {Implementing a K-E Turbulence Model in the FEniCS Finite Element Programming Environment},
	howpublished = {Talk at MekIT{\textquoteright}09: Fifth National Conference on Computational Mechanics, Trondheim, May 26-27},
	year = {2009},
	author = {Valen-Sendstad, Kristian and Mortensen, Mikael and Hans Petter {Langtangen} and Bj{\o}rn Anders Petterson {Reif} and Mardal, Kent-Andre}
}
@inproceedings {Simula.SC.584,
	title = {Implementing a K-E Turbulence Model in the FEniCS Finite Element Programming Environment},
	journal = {MekIT{\textquoteright}09.~~Fifth~~national~~conference~~on~~Computational~~Mechanics},
	year = {2009},
	publisher = {Tapir},
	type = {Conference},
	isbn = {9788251924214},
	author = {Valen-Sendstad, Kristian and Mortensen, Mikael and Hans Petter {Langtangen} and Bj{\o}rn Anders Petterson {Reif} and Mardal, Kent-Andre},
	editor = {Bj{\o}rn H. {Skallerud} and Andersson, Helge}
}
@misc {Simula.sc.778,
	title = {Patient-Specific Hemodynamics in FEniCS},
	howpublished = {Presentation at the FEniCS 09 Workshop},
	year = {2009},
	author = {Mardal, Kent-Andre and Logg, Anders and Hentschel, Susanne and Oddrun Christin {Myklebust} and Valen-Sendstad, Kristian}
}
@misc {Simula.sc.786,
	title = {Patient-Specific Hemodynamics in FEniCS},
	howpublished = {Invited talk at the minisymposium on Computational Vascular and Cardiovascular Mechanics at USNCCM 2009},
	year = {2009},
	author = {Mardal, Kent-Andre and Hentschel, Susanne and Logg, Anders and Valen-Sendstad, Kristian}
}
@misc {Simula.sc.780,
	title = {Patient-Specific Simulations of Stroke and Syringomyelia},
	howpublished = {Talk : Advisory commitee meeting FFI project P1112 Aerosols: Dispersion, Transport and Consequences, Nov 03},
	year = {2009},
	author = {Mardal, Kent-Andre and Hentschel, Susanne and Helgeland, Anders and Hans Petter {Langtangen} and Linge, Svein and Alf Emil {L{\o}vgren} and Logg, Anders and Valen-Sendstad, Kristian}
}
@misc {Simula.sc.842,
	title = {Sex Differences in Intracranial Bifurcation Geometry and Blood Flow Velocity Result in Stronger Hemodynamic Forces Upon the Female Vessel Wall},
	howpublished = {Talk: Received award for best young presenter at the Nordic Society of Neuroradiology Meeting in 2009},
	year = {2009},
	month = {September},
	author = {Haakon {Lindekle, iv} and Valen-Sendstad, Kristian}
}
@misc {Simula.sc.774,
	title = {Simulation Methodology for Bioflows},
	howpublished = {Talk : Advisory commitee meeting FFI project P1112 Aerosols: Dispersion, Transport and Consequences, May 05},
	year = {2009},
	author = {Valen-Sendstad, Kristian and Mardal, Kent-Andre and Logg, Anders}
}
@misc {Simula.SC.636,
	title = {Some Biomedical Applications at Simula},
	howpublished = {Talk at the CBC Workshop on Computational Biology with UMB},
	year = {2009},
	author = {Mardal, Kent-Andre and Helgeland, Anders and Hentschel, Susanne and Hans Petter {Langtangen} and Logg, Anders and Linge, Svein and Alf Emil {L{\o}vgren} and Valen-Sendstad, Kristian}
}
@misc {Simula.SC.252,
	title = {Blood Flow Computations at Simula},
	howpublished = {Invited talk at Medical Physics, University of Wisconsin, March 11.},
	year = {2008},
	author = {Mardal, Kent-Andre and Valen-Sendstad, Kristian and Oddrun Christin {Myklebust} and Hentschel, Susanne}
}
@misc {Simula.SC.348,
	title = {Developing Flow Solver Methodology for Patientspecific Simulation of Hemodynamics},
	howpublished = {Talk at Workshop on Finite Element Methods for Fluids and Fluid-Structure Interaction, June 5},
	year = {2008},
	author = {Valen-Sendstad, Kristian and Logg, Anders and Mardal, Kent-Andre}
}
@misc {Simula.SC.248,
	title = {Scientific Computing at Simula},
	howpublished = {Invited Talk at Workshop on Cerebral Aneurysms and Subarachnoidal Hemorrhage, Troms{\o} Jan 24-26},
	year = {2008},
	author = {Mardal, Kent-Andre and Valen-Sendstad, Kristian and Oddrun Christin {Myklebust} and Hentschel, Susanne}
}
@article {Simula.SC.344,
	title = {Simulation of Hemodynamics in the Aneurysm Neck After Coiling},
	journal = {Neuroradiology},
	year = {2008},
	author = {Isaksen, J{\o}rgen and Valen-Sendstad, Kristian and Mardal, Kent-Andre and Ingebrigtsen, Tor}
}
