Browsing NTNU Open by Author "Hellevik, Leif Rune"
Now showing items 21-40 of 40
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Informed machine learning models to predict blood pressure curves of hypertensive individuals after cumulative physical activity
Dalheim, Kari Anne; Ahlsand, Anine (Master thesis, 2021)Denne oppgaven impementerer og analyserer modeller som predikerer blodtrykkskurver for hypertensive personer etter en periode med en gitt trening. Målet med studien var å vurdere anvendelsen av informert maskinlæring (IML) ... -
Machine learning augmented reduced-order models for FFR-prediction
Fossan, Fredrik Eikeland; Müller, Lucas O.; Sturdy, Jacob; Bråten, Anders Tjellaug; Jørgensen, Arve; Wiseth, Rune; Hellevik, Leif Rune (Peer reviewed; Journal article, 2021)Computational predictions in cardiovascular medicine have largely relied on explicit models derived from physical and physiological principles. Recently, the application of artificial intelligence in cardiovascular medicine ... -
Monitoring variability in parameter estimates for lumped parameter models of the systemic circulation using longitudinal hemodynamic measurements
Bjørdalsbakke, Nikolai Lid; Sturdy, Jacob Trent; Ingeström, Emma Maria Lovisa; Hellevik, Leif Rune (Journal article; Peer reviewed, 2023)Background Physics-based cardiovascular models are only recently being considered for disease diagnosis or prognosis in clinical settings. These models depend on parameters representing the physical and physiological ... -
Numerical Investigation of the Hemodynamics in the Human Fetal Umbilical Vein/ Ductus Venosus Bifurcation
Meland, Elisabeth (Master thesis, 2012)The transport of oxygenated blood from the placenta to the human fetus has received great attention in clinical Doppler velocimetry studies, especially the ductus venosus. The ductus venosus is connecting the intra abdominal ... -
Numeriske beregninger av blodstrømning for diagnostisering av koronarsykdom - En evaluering av én- og tredimensjonal modellering
Nilsen, Stig Marsteng (Master thesis, 2016)Hovedmålet med oppgaven har vært å undersøke metoder for ikke-invasiv diagnostisering av koronarsykdom. Numeriske strømningsberegninger har blitt gjort i én og tre dimensjoner, på geometri funnet i litteraturen og på ... -
Optimization of topological complexity for one-dimensional arterial blood flow models
Fossan, Fredrik Eikeland; Mariscal-Harana, Jorge; Alastruey, Jordi; Hellevik, Leif Rune (Journal article; Peer reviewed, 2018)As computational models of the cardiovascular system are applied in modern personalized medicine, maximizing certainty of model input becomes crucial. A model with a high number of arterial segments results in a more ... -
Parameter estimation for closed-loop lumped parameter models of the systemic circulation using synthetic data
Bjørdalsbakke, Nikolai Lid; Sturdy, Jacob; Hose, David Rodney; Hellevik, Leif Rune (Peer reviewed; Journal article, 2022)Physics-based models can be applied to describe mechanisms in both health and disease, which has the potential to accelerate the development of personalized medicine. The aim of this study was to investigate the feasibility ... -
Physics-based and data-driven reduced order models: applications to coronary artery disease diagnostics
Fossan, Fredrik Eikeland (Doctoral theses at NTNU;2020:362, Doctoral thesis, 2020)In this thesis we have developed reduced-order models for the prediction of pressure and flow in the arterial system and for the diagnosis of coronary artery disease. By reduced-order model we refer to a reduction of ... -
Physics-Informed Statistical Machine Learning and Methods for Digital Twins
Spitieris, Michail (Doctoral theses at NTNU;2023:177, Doctoral thesis, 2023) -
Repeatability in a multiphase pipe flow case study
Strand, Andreas; Brekken, Christian; Leinan, Paul Roger; Steinsland, Ingelin; Hellevik, Leif Rune (Peer reviewed; Journal article, 2021)A high degree of repeatability is most often an underlying assumption for research and development based on multiphase flow experiments. In this paper repeatability in multiphase flow experiments are studied through an ... -
Robust Cardiovascular Models for Prediction of Hypertension Using Minimal Data Sets
Bjørdalsbakke, Nikolai Lid (Doctoral theses at NTNU;2023:225, Doctoral thesis, 2023)Cardiovascular disease is the leading cause of death worldwide. Such diseases are multifaceted, but can manifest as acute events such as cardiac infactions, strokes and aortic dissections which can lead directly to death ... -
The Time Varying Elastance Model used as a Boundary Condition in Arterial Network Simulations
Maråk, Knut Petter (Master thesis, 2013)Vascular1Dflow is a program for simulating blood flow in vascular networks. It uses hyperbolic one-dimensional partial differential equations with ordinary differential equations as boundary conditions. The focus of this ... -
Uncertainty propagation through a point model for steady-state two-phase pipe flow
Strand, Andreas; Smith, Ivar Eskerud; Unander, Tor Erling; Steinsland, Ingelin; Hellevik, Leif Rune (Peer reviewed; Journal article, 2020)Uncertainty propagation is used to quantify the uncertainty in model predictions in the presence of uncertain input variables. In this study, we analyze a steady-state point-model for two-phase gas-liquid flow. We present ... -
Uncertainty quantification and sensitivity analysis for cardiovascular models
Eck, Vinzenz Gregor (Doctoral thesis at NTNU;2016:234, Doctoral thesis, 2016)The major challenge for applying cardiovascular models in personalized medicine is as follows: How certain are the predictions of a cardiovascular model, taking the natural variations and measurement uncertainty of model ... -
Uncertainty quantification and sensitivity analysis for computational FFR estimation in stable coronary artery disease
Fossan, Fredrik Eikeland; Sturdy, Jacob; Muller, Lucas Omar; Strand, Andreas; Bråten, Anders Tjellaug; Jørgensen, Arve; Wiseth, Rune; Hellevik, Leif Rune (Journal article; Peer reviewed, 2018)Purpose The main objectives of this study are to validate a reduced-order model for the estimation of the fractional flow reserve (FFR) index based on blood flow simulations that incorporate clinical imaging and ... -
Uncertainty quantification and sensitivity analysis informed modeling of physical systems
Sturdy, Jacob (Doctoral theses at NTNU;2019:115, Doctoral thesis, 2019) -
Uncertainty quantification and sensitivity analysis of material parameters in crystal plasticity finite element models
Khadyko, Mikhail; Sturdy, Jacob; Dumoulin, Stephane; Hellevik, Leif Rune; Hopperstad, Odd Sture (Journal article, 2018)A number of studies have directly compared measurements of polycrystals’ deformation to the solution of a crystal plasticity model of the same polycrystal. An accurate representation of the full 3D microstructure and the ... -
Uncertainty quantification and sensitivity analysis of vascular hemodynamics. Application to the common carotid artery
Schäfer, Friederike (Doctoral theses at NTNU;2024:235, Doctoral thesis, 2024)Cardiovascular diseases have been the leading cause of death globally for the past decades. Many cardiovascular diseases are a result of structural changes in the arterial wall, which modify its stiffness. Thus, arterial ... -
Uncertainty quantification for multiphase flow
Strand, Andreas (Doctoral theses at NTNU;2021:410, Doctoral thesis, 2021)The purview of this thesis is insight into, and development of, methods for uncertainty quantification in multiphase flow. The work is directed towards commercial simulators for transport of gas and liquid in pipelines and ... -
Uncertainty quantification of computational coronary stenosis assessment and model based mitigation of image resolution limitations
Sturdy, Jacob; Kjernlie, Johannes Kløve; Nydal, Hallvard Moian; Eck, Vinzenz Gregor; Hellevik, Leif Rune (Journal article; Peer reviewed, 2019)Coronary artery disease is one of the leading causes of death globally. The hallmark of this disease is the occurrence of stenosed coronary arteries which reduce blood flow to the myocardium. Severely stenosed arteries can ...