The invention proposes a 3D reconstruction of a body and a body contour from transversally truncated projections using a polyhedral object model. Possible clinical applications arise in the field of guided biopsies on acquisition systems equipped with a flat panel detector, where truncated projections cannot be avoided in thorax and abdominal scan protocols. From, for example, a rotational run both a 3D volume reconstruction and a surface mesh reconstruction of a patient's shape is generated and then visualized simultaneously in order to help the physician guide the biopsy device and judge the distance from the patient's skin to the tissue of interest inside the reconstructed volume.