Stefano Buoso^{1}, Christian T Stoeck^{1}, Johanna Stimm^{1}, and Sebastian Kozerke^{1}

^{1}Institute for Biomedical Engineering, ETH Zurich, Zurich, Switzerland

We show the feasibility of embedding physiological coordinates and directions into a left ventricle anatomical shape model using Proper Orthogonal Decomposition. The volumetric anatomical mesh and the physiological parametrization can be personalized directly from the selection of control points on MR cardiac images. This approach provides a consistent way of augmenting low-resolution data using features from high-resolution datasets. Additionally, the physiological parametrization is automatically adapted to each specific case without any additional calculation steps. This simplifies the processing of clinical images and, particularly, strain calculations and microstructural analysis that require the definition of the physiological parametrization.

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Mean
left ventricular shape with physiological parametrization: longitudinal
position (a) and directions (b), circumferential position (c) and directions
(d), transmural position (e) and direction (f). Panel g) shows the position of
the control points resulting from the DEIM algorithm on the mean shape for the
first 11 modes.

Long-
and short-axis views of the POD basis of the shape model. Orange and blue
shapes represent the effect of maximum and minimum amplitudes of the POD modes
from the WACM dataset, respectively. Panels (a) to (f) show modes from 1 to 6.

Reconstruction
errors of the WACM dataset as a function of the number of modes for (a) anatomy, (b) transmural direction, (c) longitudinal
direction and (d) circumferential direction. Anatomical errors are defined
as the norm of the distance between the real and reconstructed points, while directions
errors are defined as the angle between the real and reconstructed directions. Scatter
points represent the average error for each anatomy in the dataset, while the
solid black line represents the mean.

(a)
– (g) Overlay of original MR image and LV myocardium masks (orange) obtained
from the shape model using 11 points. The amplitudes of the modes for
reconstruction are calculated from the boundary points of DEIM selected
directly on the image. (h) Reconstruction of circumferential (yellow) and
longitudinal (orange) directions directly on the image.