NuMRI/presentation/pres03.tex

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\title[A new mathematical model for verifying the Navier-Stokes compatibility of 4D flow MRI data]{ A new mathematical model for verifying the Navier-Stokes compatibility of 4D flow MRI data}
%\author[Jeremías Garay Labra]
%{Jeremías Garay Labra}
\institute[University of Groningen]
{
Bernoulli Institute\\
Faculty of Sciences and Engineering\\
University of Groningen\\[0.5cm]
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\texttt{Jeremías Garay Labra \\ \ j.e.garay.labra@rug.nl}
}
\date{\today}
\begin{document}
\frame{\titlepage}
% \onslide<1->
\begin{frame}
\frametitle{Index}
\tableofcontents
\end{frame}
\section{4D flow MRI}
\begin{frame}
\frametitle{4D flow MRI}
\begin{columns}[c]
\column{.55\textwidth} % Left column and width
\footnotesize
4D flow MRI has been shown potential in the assesment of blood flow dynamics in heart and large arteries, allowing wide variety of options for visualization and quantification.
\column{.5\textwidth} % Right column and width
\end{columns}
\end{frame}
\begin{frame}
\frametitle{4D flow MRI}
\footnotesize
Main limitation for its clinical applicability is the long scan times involved. Therefore, multiple strategies emerged in order to make acquisition faster, such as:
\begin{itemize}
\item Navigator gating
\item modest spatial resolutions $ \sim (2.5 \times 2.5 \times 2.5 \ mm^3)$
\item partial data coverage
\end{itemize}
Typical quality estimators: SNR, VNR, peak flows/velocities, mass conservation (zero divergence)
We want to introduce a novel measure for quantify the quality of the 4D flow measurements, using the conservation of momentum of the flow (Navier-Stokes compatibility).
\end{frame}
\section{The corrector field}
\begin{frame}
\frametitle{The corrector field}
\footnotesize
We assume a perfect physical velocity field $\vec{u}$
\begin{eqnarray*}
\rho \frac{\partial \vec{u}}{\partial t} + \rho \big ( \vec{u} \cdot \nabla \big) \vec{u} - \mu \Delta \vec{u} + \nabla p = 0 \quad \text{in} \quad \Omega \label{eq:NSmom}
\end{eqnarray*}
And a corrector field $\vec{w}$ which satisfies:
\begin{align}
\vec{u} & \approx \vec{u}_{meas} + \vec{w} \quad \text{in} \quad \Omega \label{eq:corrector} \\
\nabla \cdot \vec w & = 0 \quad \text{in} \quad \Omega \label{eq:correctorDiv} \\
\vec w & = \vec 0 \quad \text{on} \quad \partial \Omega \label{eq:correctorBC}
\end{align}
$\vec{w}$ measures the level of agreedment of the 4D flow measures respect to the Navier-Stokes equations.
\end{frame}
\begin{frame}
\frametitle{Numerical tests}
\begin{columns}[c]
\column{.6\textwidth} % Left column and width
\footnotesize
We tested the corrector using CFD simulations as a measurements, in the following testcases:
\begin{itemize}
\item Womersley flow in a cilinder
\item Navier-Stokes simulations in an aortic mesh
\end{itemize}
Also perturbations were added into the measurements:
\begin{itemize}
\item velocity aliasing
\item additive noise
\item simulated k-space undersampling
\end{itemize}
\column{.5\textwidth} % Right column and width
\footnotesize
\begin{figure}[!hbtp]
\begin{center}
\includegraphics[height=\textwidth]{images/aorta_blender.png}
\caption{Aortic mesh }
\end{center}
\end{figure}
\end{columns}
\end{frame}
\begin{frame}
\frametitle{Experiments}
\footnotesize
\begin{itemize}
\item We performed 4D flow measurements in a silicon aortic phantom
\item 4 healthy volunteers were scanned using a clinical standard 4D flow protocol.
\end{itemize}
\end{frame}
\section{Results}
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\frametitle{Results}
\footnotesize
results for the synthetic data. Comparison againts the perfect correction field: du.
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\begin{frame}
\frametitle{Results}
\footnotesize
results for experimental phantom
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\frametitle{Results}
\footnotesize
results in healthy volunteers
\end{frame}
\section{Conclusions}
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\frametitle{Conclusions and future}
\footnotesize
potential of the new quality parameter:
\begin{itemize}
\item analize real data
\item use the specificity for label zones with strong disagreedment
\item Use the field for create new inverse problems which can be used for further accelerations
\end{itemize}
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\begin{frame}
\begin{center}
\huge{Thank you for your time!}
\end{center}
\end{frame}
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\end{document}