Rule Based Assignment of Myocardial Sheet Orientation

Ventricles consist of an ordered laminar arrangement of myocytes. This has influence on the electro-physiological and elasto-mechanical properties of the heart and cannot be neglected in realistic models. Main objective was to assign this sheet orientation into any given dataset of mammalian hearts. Sheet orientation is generally radial to ventricular surfaces inside the mid-myocardium and becomes roughly tangential to it near the epiand endocardium. The first step is to calculate wall normals, using the gradient of the Gaussian function as mask. These normals are verified through various criteria, such as the length and the direction of the normals and the distance towards boundaries of the area. Few relative sheet angles are assigned on these wall normals equidistantly, which are used as fulcra for a latter interpolation. Due to different patterns, the left and right ventricular free walls and the inter-ventricular septum are treated separately. Finally, all relative sheet angles are transformed into pairs of absolute angles. The tool was applied on the Visible Female dataset, which is part of the Visible Human project from the National Library of Medicine (USA). Together with the fibre orientation, a complete anatomical model of myocardial sheet orientation was created. Keywords— myocardial sheet orientation; anatomical model