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Modeling of moving anatomic structures is complicated by the complexity of motion intrinsic and extrinsic to the structures. However when motion is cyclical, such as in heart, effective dynamic modeling can be approached using modern fast imaging techniques, which provide 3D structural data. Data may be acquired as a sequence of 3D volume images throughout the cardiac cycle. To model the intricate non- linear motion of the heart, we created a physics-based surface model which can realistically deform between successive time points in the cardiac cycle, yielding a dynamic 4D model of cardiac motion. Sequences of fifteen 3D volume images of intact canine beating hearts were acquired during compete cardiac cycles using the Dynamic Spatial Reconstructor and the Electron Beam CT. The chambers of the heart were segmented at successive time points, typically at 1/15-second intervals. The left ventricle of the first item point was reconstructed as an initial triangular mesh. A mass-spring physics-based deformable model, which can expand and shrink with local contraction and stretching forces distributed in an anatomically accurate simulation of cardiac motion, was applied to the initial mesh and allowed the initial mesh to deform to fit the left ventricle in successive time increments of the sequence. The resultant 4D model can be interactively transformed and displayed with associated regional electrical activity mapped onto the anatomic surfaces, producing a 5D mode, which faithfully exhibits regional cardiac contraction and relaxation patterns over the entire heart. For acquisition systems that may provide only limited 4D data, the model can provide interpolated anatomic shape between time points. This physics-based deformable model accurately represents dynamic cardiac structural changes throughout the cardiac cycle. Such models provides the framework for minimizing the number of time points required to usefully depict regional motion of myocardium and allowing quantitative assessment of regional myocardial dynamics. The electrical activation mapping provides spatial and temporal correlation within the cardiac cycle. In procedures such as intra-cardiac catheter ablation, visualization of the dynamic mole can be used to accurately localize the foci of myocardial arrhythmias and guide positioning of catheters for effective ablation.
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