The invention relates to a method for determining the position of a surgical tool relative to a target volume inside an animal body according to a pre-plan comprising the steps of i) obtaining a plurality of two-dimensional images of said target volume using imaging means, each 2D-image being represented by an image data slice I(x,y,z) ii) reconstructing from said plurality of image data slices I(x,y,z) a three-dimensional image of said target volume using transformation means, said 3D-image being represented by a volumetric image data array V(x,y,z) iii) displaying said three-dimensional image of said target volume to an user using displaying means.
