A personalized mitral valve closure simulator

Interactive editing of virtual chordae tendineae for the simulation of the mitral valve in a decision support system

PURPOSE

Decision support systems for mitral valve disease are an important step toward personalized surgery planning. A simulation of the mitral valve apparatus is required for decision support. Building a model of the chordae tendineae is an essential component of a mitral valve simulation. Due to image quality and artifacts, the chordae tendineae cannot be reliably detected in medical imaging.

METHODS

Using the position-based dynamics framework, we are able to realistically simulate the opening and closing of the mitral valve. Here, we present a heuristic method for building an initial chordae model needed for a successful simulation. In addition to the heuristic, we present an interactive editor to refine the chordae model and to further improve pathology reproduction as well as geometric approximation of the closed valve.

RESULTS

For evaluation, five mitral valves were reconstructed based on image sequences of patients scheduled for mitral valve surgery. We evaluated the approximation of the closed valves using either just the heuristic chordae model or a manually refined model. Using the manually refined models, prolapse was correctly reproduced in four of the five cases compared to two of the five cases when using the heuristic. In addition, using the editor improved the approximation in four cases.

CONCLUSIONS

Our approach is suitable to create realistically parameterized mitral valve apparatus reconstructions for the simulation of normally and abnormally closing valves in a decision support system.

Mitral valve closure prediction with 3-D personalized anatomical models and anisotropic hyperelastic tissue assumptions

This study is concerned with the development of patient-specific simulations of the mitral valve that use personalized anatomical models derived from 3-D transesophageal echocardiography (3-D TEE). The proposed method predicts the closed configuration of the mitral valve by solving for an equilibrium solution that balances various forces including blood pressure, tissue collision, valve tethering, and tissue elasticity. The model also incorporates realistic hyperelastic and anisotropic properties for the valve leaflets. This study compares hyperelastic tissue laws with a quasi-elastic law under various physiological parameters, and provides insights into error sensitivity to chordal placement, allowing for a preliminary comparison of the influence of the two factors (chords and models) on error. Predictive errors show the promise of the method, yielding aggregate median errors of the order of 1 mm, and computed strains and stresses show good correspondence with those reported in prior studies.

Valvular closure prediction using anisotropic and hyperelastic tissue models and individualized anatomy derived from RT3DE

We describe a method for modeling the closure of the Mitral Valve (MV) and to compute realistic strain and stresses in MV tissues. This informs preoperative planning by allowing a surgeon to evaluate various MV repairs options. The modeling method exploits individualized (patient-specific) anatomical structure recovered from real-time 3D echocardiography (RT3DE). This study utilizes hyperelastic models of the MV tissues and employs patient specific leaflets, chordal length assessment and annulus shapes. We report experiments on ten intraoperative test cases, where we compute strain and stresses using several different tissue models from MV empirical studies by May-Newman and Holzapfel.