The present invention relates to a device and a method for determining the position of an instrument with respect to medical images of a body. The device comprises (1) a calibration support comprising a set of fiducial markers visible on medical images and fixed to the skin of a body, (2) at least one micro-camera providing video images and mounted on the calibration support in a known position, and (3) a processing unit connected to the micro-cameras and configured to process the video images from said micro-cameras to determine the position of the instrument with respect to medical images.
