Slice2Mesh: 3D Surface Reconstruction From Sparse Slices of Images for the Left Ventricle.

Cine MRI is a widely used technique to evaluate left ventricular function and motion, as it captures temporal information. However, due to the limited spatial resolution, cine MRI only provides a few sparse scans at regular positions and orientations, which poses challenges for reconstructing dense 3D cardiac structures, which is essential for better understanding the cardiac structure and motion in a dynamic 3D manner. In this study, we propose a novel learning-based 3D cardiac surface reconstruction method, Slice2Mesh, which directly predicts accurate and high-fidelity 3D meshes from sparse slices of cine MRI images under partial supervision of sparse contour points. Slice2Mesh leverages a 2D UNet to extract image features and a graph convolutional network to predict deformations from an initial template to various 3D surfaces, which enables it to produce topology-consistent meshes that can better characterize and analyze cardiac movement. We also introduce As Rigid As Possible energy in the deformation loss to preserve the intrinsic structure of the predefined template and produce realistic left ventricular shapes. We evaluated our method on 150 clinical test samples and achieved an average chamfer distance of 3.621 mm, outperforming traditional methods by approximately 2.5 mm. We also applied our method to produce 4D surface meshes from cine MRI sequences and utilized a simple SVM model on these 4D heart meshes to identify subjects with myocardial infarction, and achieved a classification sensitivity of 91.8% on 99 test subjects, including 49 abnormal patients, which implies great potential of our method for clinical use.