Improved Non-Contact Heart Chamber Modeling Using Catheter Mediated Ultrasound Returns

Non-contact (inverse) techniques for mapping of cardiac electrical activity require the existence of an accurate surface representation, typically in the form of a triangulated mesh. One approach for surface mesh generation employs ultrasound reflected from the endocardium. Transmitted from a catheter within the heart chamber, localized reflections form a shell of points descriptive of the shape of the interior surface of the heart. The existence of significant variance in the position of ultrasound reflections discourages the use of conventional meshing techniques. A surface reconstruction technique which is robust in the presence of positional variance and sensitive to peripheral heart structures is required. A Poisson equation relating a 3-D scalar function to the normal of the (as yet) unknown surface yields an iso-surface as the desired anatomic boundary. Evaluation of the Poisson-based surface technique is accomplished by consideration of the mesh obtained from in-vitro acquisition of ultrasound from polymer left and right atrium targets. Error between the computed mesh vertices and the target surface was ~1.5 mm average, and the technique is sensitive to surface structures in all orientations.