Surgical repair of the mitral valve is preferred in most cases over valve replacement, but replacement is often performed
instead due to the technical difficulty of repair. A surgical planning system based on patient-specific medical images that
allows surgeons to simulate and compare potential repair strategies could greatly improve surgical outcomes. In such a
surgical simulator, the mathematical model of mechanics used to close the valve must be able to compute the closed state
quickly and to handle the complex boundary conditions imposed by the chords that tether the valve leaflets. We have
developed a system for generating a triangulated mesh of the valve surface from volumetric image data of the opened
valve. We then compute the closed position of the mesh using a mass-spring model of dynamics. The triangulated mesh
is produced by fitting an isosurface to the volumetric image data, and boundary conditions, including the valve annulus
and chord endpoints, are identified in the image data using a graphical user interface. In the mass-spring model, triangle
sides are treated as linear springs, and sides shared by two triangles are treated as bending springs. Chords are treated as
nonlinear springs, and self-collisions are detected and resolved. Equations of motion are solved using implicit numerical
integration. Accuracy was assessed by comparison of model results with an image of the same valve taken in the closed
state. The model exhibited rapid valve closure and was able to reproduce important features of the closed valve.
Catheter ablation has emerged as a highly effective treatment for arrhythmias that are constrained by known, easily located, anatomic landmarks. However, this treatment has enjoyed limited success for arrhythmias that are characterized by complex activation patterns or are not anatomically constrained. This class of arrhythmias, which includes atrial fibrillation and ventricular tachycardia resulting from ischemic heart disease, demands improved mapping tools. Current technology forces the cardiologist to view cardiac anatomy independently from the functional information contained in the electrical activation patterns. This leads to difficulties in interpreting the large volumes of data provided by high-density recording catheters and in mapping patients with abnormal anatomy (e.g., patients with congenital heart disease). The goal of this is work is development of new data processing and display algorithms that will permit the clinician to view activation sequences superimposed onto existing fluoroscopic images depicting the location of recording catheters within the heart. In cases where biplane fluoroscopic images and x-ray camera position data are available, the position of the catheters can be reconstructed in three-dimensions.
Clinical procedures that rely on biplane x-ray images for three-dimensional (3-D) information may be enhanced by three-dimensional reconstructions. However, the accuracy of reconstructed images is dependent on the uncertainty associated with the parameters that define the geometry of the camera system. In this paper, we use a numerical simulation to examine the effect of these uncertainties and to determine the limits required for adequate three-dimensional reconstruction. We then test our conclusions with images of a calibration phantom recorded using a clinical system. A set of reconstruction routines, developed for a cardiac mapping system, were used in this evaluation. The routines include procedures for correcting image distortion and for automatically locating catheter electrodes. Test images were created using a numerical simulation of a biplane x-ray projection system. The reconstruction routines were then applied using accurate and perturbed camera geometries and error maps were produced. Our results indicate that useful catheter reconstructions are possible with reasonable bounds on the uncertainty of camera geometry provided the locations of the camera isocenters are accurate. The results of this study provide a guide for the specification of camera geometry display systems and for researchers evaluating possible methodologies for determining camera geometry.