Many bio-medical simulations involve structures of complicated shape. Frequently, the geometry information is given by radiological images. A particular challenge for model discretization in this context is generating appropriate computational meshes. One efficient approach for Finite Element simulations avoiding meshing is the Composite Finite Element (CFE) approach that has been developed and implemented for image-based simulations during the past decade. In the present paper, we provide an overview of previous own work in this field, summarizing the method and showing selected applications: simulation of radio-frequency ablation including vaporization, simulation of elastic deformation of trabecular bone, and numerical homogenization of material properties for the latter.