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Lp-norm regularization in volumetric imaging of cardiac current sources.

Rahimi A, Xu J, Wang L - Comput Math Methods Med (2013)

Bottom Line: Advances in computer vision have substantially improved our ability to analyze the structure and mechanics of the heart.In a set of phantom experiments, we demonstrate the superiority of the proposed Lp-norm method over its L1 and L2 counterparts in imaging cardiac current sources with increasing extents.This ability to preserve the spatial structure of source distribution is important for revealing the potential disruption to the normal heart excitation.

View Article: PubMed Central - PubMed

Affiliation: Rochester Institute of Technology, Rochester, NY 14623, USA.

ABSTRACT
Advances in computer vision have substantially improved our ability to analyze the structure and mechanics of the heart. In comparison, our ability to observe and analyze cardiac electrical activities is much limited. The progress to computationally reconstruct cardiac current sources from noninvasive voltage data sensed on the body surface has been hindered by the ill-posedness and the lack of a unique solution of the reconstruction problem. Common L2- and L1-norm regularizations tend to produce a solution that is either too diffused or too scattered to reflect the complex spatial structure of current source distribution in the heart. In this work, we propose a general regularization with Lp-norm (1 < p < 2) constraint to bridge the gap and balance between an overly smeared and overly focal solution in cardiac source reconstruction. In a set of phantom experiments, we demonstrate the superiority of the proposed Lp-norm method over its L1 and L2 counterparts in imaging cardiac current sources with increasing extents. Through computer-simulated and real-data experiments, we further demonstrate the feasibility of the proposed method in imaging the complex structure of excitation wavefront, as well as current sources distributed along the postinfarction scar border. This ability to preserve the spatial structure of source distribution is important for revealing the potential disruption to the normal heart excitation.

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Related in: MedlinePlus

Illustration of the spatial structure of ventricular current sources during a healthy (a) or pathological (b) cardiac cycle.
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fig1: Illustration of the spatial structure of ventricular current sources during a healthy (a) or pathological (b) cardiac cycle.

Mentions: In comparison, cardiac current source starts from a few focal sites but then propagates throughout the atrial and ventricular myocardium during the cardiac cycle. As a result, the structure of cardiac current sources undergoes a much more complex spatiotemporal change during the cardiac excitation, as illustrated by the two examples given in Figure 1. In a normal depolarization phase of the cardiac excitation, the current sources form an excitation wavefront between depolarized and resting cells (Figure 1(a)). After all the cells are depolarized, the heart goes through a stage without current flow (ST-segment in an ECG cycle). Afterwards, the repolarization phase starts and a similar repolarization wavefront can be observed to flow throughout the myocardium. In a diseased heart with an infarct, this normal excitation process will be disrupted. For example, during the ST-segment, there will be a voltage difference between healthy myocardium and the center of the infarct, and active current sources will be concentrated along the scar border (Figure 1(b)). This time-varying spatial structure of the current source is important because it reveals the potential disruption to a normal excitation of the heart.


Lp-norm regularization in volumetric imaging of cardiac current sources.

Rahimi A, Xu J, Wang L - Comput Math Methods Med (2013)

Illustration of the spatial structure of ventricular current sources during a healthy (a) or pathological (b) cardiac cycle.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3852818&req=5

fig1: Illustration of the spatial structure of ventricular current sources during a healthy (a) or pathological (b) cardiac cycle.
Mentions: In comparison, cardiac current source starts from a few focal sites but then propagates throughout the atrial and ventricular myocardium during the cardiac cycle. As a result, the structure of cardiac current sources undergoes a much more complex spatiotemporal change during the cardiac excitation, as illustrated by the two examples given in Figure 1. In a normal depolarization phase of the cardiac excitation, the current sources form an excitation wavefront between depolarized and resting cells (Figure 1(a)). After all the cells are depolarized, the heart goes through a stage without current flow (ST-segment in an ECG cycle). Afterwards, the repolarization phase starts and a similar repolarization wavefront can be observed to flow throughout the myocardium. In a diseased heart with an infarct, this normal excitation process will be disrupted. For example, during the ST-segment, there will be a voltage difference between healthy myocardium and the center of the infarct, and active current sources will be concentrated along the scar border (Figure 1(b)). This time-varying spatial structure of the current source is important because it reveals the potential disruption to a normal excitation of the heart.

Bottom Line: Advances in computer vision have substantially improved our ability to analyze the structure and mechanics of the heart.In a set of phantom experiments, we demonstrate the superiority of the proposed Lp-norm method over its L1 and L2 counterparts in imaging cardiac current sources with increasing extents.This ability to preserve the spatial structure of source distribution is important for revealing the potential disruption to the normal heart excitation.

View Article: PubMed Central - PubMed

Affiliation: Rochester Institute of Technology, Rochester, NY 14623, USA.

ABSTRACT
Advances in computer vision have substantially improved our ability to analyze the structure and mechanics of the heart. In comparison, our ability to observe and analyze cardiac electrical activities is much limited. The progress to computationally reconstruct cardiac current sources from noninvasive voltage data sensed on the body surface has been hindered by the ill-posedness and the lack of a unique solution of the reconstruction problem. Common L2- and L1-norm regularizations tend to produce a solution that is either too diffused or too scattered to reflect the complex spatial structure of current source distribution in the heart. In this work, we propose a general regularization with Lp-norm (1 < p < 2) constraint to bridge the gap and balance between an overly smeared and overly focal solution in cardiac source reconstruction. In a set of phantom experiments, we demonstrate the superiority of the proposed Lp-norm method over its L1 and L2 counterparts in imaging cardiac current sources with increasing extents. Through computer-simulated and real-data experiments, we further demonstrate the feasibility of the proposed method in imaging the complex structure of excitation wavefront, as well as current sources distributed along the postinfarction scar border. This ability to preserve the spatial structure of source distribution is important for revealing the potential disruption to the normal heart excitation.

Show MeSH
Related in: MedlinePlus