Cobiveco: Consistent biventricular coordinates for precise and intuitive description of position in the heart -- with MATLAB implementation

Ventricular coordinates are widely used as a versatile tool for various applications that benefit from a description of local position within the heart. However, the practical usefulness of ventricular coordinates is determined by their ability to meet application-specific requirements. For regression-based estimation of biventricular position, for example, a consistent definition of coordinate directions in both ventricles is important. For the transfer of data between different hearts as another use case, the coordinate values are required to be consistent across different geometries. Existing ventricular coordinate systems do not meet these requirements. We first compare different approaches to compute coordinates and then present Cobiveco, a consistent and intuitive biventricular coordinate system to overcome these drawbacks. A novel one-way mapping error is introduced to assess the consistency of the coordinates. Evaluation of mapping and linearity errors on 36 patient geometries showed a more than 4-fold improvement compared to a state-of-the-art method. Finally, we show two application examples underlining the relevance for cardiac data processing. Cobiveco MATLAB code is available under a permissive open-source license.