1. A method of rendering a medical image using a processor, comprising: providing a 3D voxel dataset of a heart, the 3D voxel dataset being generated from one of a Computer Tomography (CT) data of the heart and a Magnetic Resonance Imaging (MRI) data of the heart such that the 3D voxel data set is a spatial representation of the heart; generating, using the processor, a 3D vector representation of a selected part of the 3D voxel dataset of the heart; blending, using the processor, the 3D voxel dataset and the 3D vector representation to combine, in a common buffer, portions of the 3D voxel dataset that represent the selected part of the heart with the 3D vector representation replacing the portions of the 3D voxel dataset that represent the selected part of the heart with the 3D vector representation; and rendering, using the processor, the medical image, wherein said rendering is based on the blended 3D voxel dataset and the 3D vector representation, such that the selected part of the heart is shown as the 3D vector representation and another portion of the heart is shown as the 3D voxel representation.