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A New MRI-Based Model of Heart Function with Coupled Hemodynamics and Application to Normal and Diseased Canine Left Ventricles.

Choi YJ, Constantino J, Vedula V, Trayanova N, Mittal R - Front Bioeng Biotechnol (2015)

Bottom Line: The time-dependent endocardial surfaces are registered using a diffeomorphic mapping algorithm, while the intraventricular blood flow patterns are simulated using a sharp-interface immersed boundary method-based flow solver.The utility of the combined heart-function model is demonstrated by comparing the hemodynamic characteristics of a normal canine heart beating in sinus rhythm against that of the dyssynchronously beating failing heart.We also discuss the potential of coupled CE and hemodynamics models for various clinical applications.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, Johns Hopkins University , Baltimore, MD , USA ; Institute for Computational Medicine, Johns Hopkins University , Baltimore, MD , USA.

ABSTRACT
A methodology for the simulation of heart function that combines an MRI-based model of cardiac electromechanics (CE) with a Navier-Stokes-based hemodynamics model is presented. The CE model consists of two coupled components that simulate the electrical and the mechanical functions of the heart. Accurate representations of ventricular geometry and fiber orientations are constructed from the structural magnetic resonance and the diffusion tensor MR images, respectively. The deformation of the ventricle obtained from the electromechanical model serves as input to the hemodynamics model in this one-way coupled approach via imposed kinematic wall velocity boundary conditions and at the same time, governs the blood flow into and out of the ventricular volume. The time-dependent endocardial surfaces are registered using a diffeomorphic mapping algorithm, while the intraventricular blood flow patterns are simulated using a sharp-interface immersed boundary method-based flow solver. The utility of the combined heart-function model is demonstrated by comparing the hemodynamic characteristics of a normal canine heart beating in sinus rhythm against that of the dyssynchronously beating failing heart. We also discuss the potential of coupled CE and hemodynamics models for various clinical applications.

No MeSH data available.


Template surfaces generated from MR images at the unloaded state. (A) MR image of the normal canine heart. (B) Triangulated template surface of the normal heart. (C) MR image of the failing canine heart. (D) Triangulated template surface of the failing heart.
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Figure 4: Template surfaces generated from MR images at the unloaded state. (A) MR image of the normal canine heart. (B) Triangulated template surface of the normal heart. (C) MR image of the failing canine heart. (D) Triangulated template surface of the failing heart.

Mentions: As mentioned above, the MRI-based electromechanical models described above consist of the left and right ventricles and exclude the atria, Ao and pulmonary arteries. However, since we are mainly interested in the blood flow patterns in the LV, for cardiac flow simulation, we need features, such as the LA and Ao, in order to simulate the blood flow into and out of the ventricle. To overcome this issue, we first create a template of the LV based on the MR image of the heart at the unloaded state and add to it simplified geometric representations of LA and Ao (Figure 4); For the segmentation step, the images are subjected to Gaussian filtering for noise reduction and a mask is extracted out of the images by thresholding the image intensities using Seg3D1 image processing software. A region growing-based segmentation is then performed on the mask using Mimics (Materialise Inc.2) to extract the ventricular lumen and a surface mesh is generated using the surface wrap tool and CAD module of Mimics (Materialise Inc.) software suite. While the electromechanical model employs hexahedral elements, the template lumen surface is represented with a mesh consisting of triangular elements that is compatible with the requirements of the hemodynamic solver (Mittal et al., 2008). Furthermore, a high mesh density with elements ranging from about 24,000 to 48,000 is employed so as to satisfy the resolution requirements of the hemodynamic solver.


A New MRI-Based Model of Heart Function with Coupled Hemodynamics and Application to Normal and Diseased Canine Left Ventricles.

Choi YJ, Constantino J, Vedula V, Trayanova N, Mittal R - Front Bioeng Biotechnol (2015)

Template surfaces generated from MR images at the unloaded state. (A) MR image of the normal canine heart. (B) Triangulated template surface of the normal heart. (C) MR image of the failing canine heart. (D) Triangulated template surface of the failing heart.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4585083&req=5

Figure 4: Template surfaces generated from MR images at the unloaded state. (A) MR image of the normal canine heart. (B) Triangulated template surface of the normal heart. (C) MR image of the failing canine heart. (D) Triangulated template surface of the failing heart.
Mentions: As mentioned above, the MRI-based electromechanical models described above consist of the left and right ventricles and exclude the atria, Ao and pulmonary arteries. However, since we are mainly interested in the blood flow patterns in the LV, for cardiac flow simulation, we need features, such as the LA and Ao, in order to simulate the blood flow into and out of the ventricle. To overcome this issue, we first create a template of the LV based on the MR image of the heart at the unloaded state and add to it simplified geometric representations of LA and Ao (Figure 4); For the segmentation step, the images are subjected to Gaussian filtering for noise reduction and a mask is extracted out of the images by thresholding the image intensities using Seg3D1 image processing software. A region growing-based segmentation is then performed on the mask using Mimics (Materialise Inc.2) to extract the ventricular lumen and a surface mesh is generated using the surface wrap tool and CAD module of Mimics (Materialise Inc.) software suite. While the electromechanical model employs hexahedral elements, the template lumen surface is represented with a mesh consisting of triangular elements that is compatible with the requirements of the hemodynamic solver (Mittal et al., 2008). Furthermore, a high mesh density with elements ranging from about 24,000 to 48,000 is employed so as to satisfy the resolution requirements of the hemodynamic solver.

Bottom Line: The time-dependent endocardial surfaces are registered using a diffeomorphic mapping algorithm, while the intraventricular blood flow patterns are simulated using a sharp-interface immersed boundary method-based flow solver.The utility of the combined heart-function model is demonstrated by comparing the hemodynamic characteristics of a normal canine heart beating in sinus rhythm against that of the dyssynchronously beating failing heart.We also discuss the potential of coupled CE and hemodynamics models for various clinical applications.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, Johns Hopkins University , Baltimore, MD , USA ; Institute for Computational Medicine, Johns Hopkins University , Baltimore, MD , USA.

ABSTRACT
A methodology for the simulation of heart function that combines an MRI-based model of cardiac electromechanics (CE) with a Navier-Stokes-based hemodynamics model is presented. The CE model consists of two coupled components that simulate the electrical and the mechanical functions of the heart. Accurate representations of ventricular geometry and fiber orientations are constructed from the structural magnetic resonance and the diffusion tensor MR images, respectively. The deformation of the ventricle obtained from the electromechanical model serves as input to the hemodynamics model in this one-way coupled approach via imposed kinematic wall velocity boundary conditions and at the same time, governs the blood flow into and out of the ventricular volume. The time-dependent endocardial surfaces are registered using a diffeomorphic mapping algorithm, while the intraventricular blood flow patterns are simulated using a sharp-interface immersed boundary method-based flow solver. The utility of the combined heart-function model is demonstrated by comparing the hemodynamic characteristics of a normal canine heart beating in sinus rhythm against that of the dyssynchronously beating failing heart. We also discuss the potential of coupled CE and hemodynamics models for various clinical applications.

No MeSH data available.