Method for displaying a representation of the tip of a medical device located within a body region of interest of the body of a patient, on an image of the body region of interest, the image being acquired by an image detector of a moving imager at a selected physical zoom setting, the method comprising: acquiring at least one medical positioning system sensor image of an MPS sensor, by said image detector, at one or more physical zoom settings of said image detector respective of said image, and at a selected image detector region of interest setting of said image detector, said MPS sensor being associated with an MPS, said at least one MPS sensor (112, 114, 116) responding to an electromagnetic field generated by a plurality of electromagnetic field generators, that are firmly coupled with a moving portion of said moving imager; determining a set of intrinsic and extrinsic parameters at the selected physical zoom setting, according to sensor image coordinates of each of the MPS sensor images, in a two-dimensional optical coordinate system respective of said image detector, and according to non-real-time MPS coordinates of said MPS sensor (112, 114, 116), in an MPS coordinate system respective of said MPS, wherein each set of intrinsic parameters comprises optical characteristics of said image detector and each set of extrinsic parameters comprises rotation and translation parameters of the MPS coordinate system relative to the optical coordinate system; determining two-dimensional coordinates of said tip of said medical device, according to said selected physical zoom setting, according to said set of intrinsic and extrinsic parameters, according to said selected image detector region of interest setting, and according to real-time MPS coordinates of an MPS sensor located at said tip of said medical device; superimposing said representation of said tip of said medical device, on said image of said body region of interest, according to said two-dimensional coordinates; and displaying said representation of said tip of said medical device superimposed on said image of said body region of interest, wherein the method is characterised in that said step of determining said set of intrinsic and extrinsic parameters is performed with respect to a plurality of physical zoom settings of said image detector, by interpolating between intrinsic and extrinsic parameters associated with two adjacent ones of said physical zoom settings or by extrapolating beyond intrinsic and extrinsic parameters associated with two adjacent ones of said physical zoom settings. acquiring at least one medical positioning system sensor image of an MPS sensor, by said image detector, at one or more physical zoom settings of said image detector respective of said image, and at a selected image detector region of interest setting of said image detector, said MPS sensor being associated with an MPS, said at least one MPS sensor (112, 114, 116) responding to an electromagnetic field generated by a plurality of electromagnetic field generators, that are firmly coupled with a moving portion of said moving imager; determining a set of intrinsic and extrinsic parameters at the selected physical zoom setting, according to sensor image coordinates of each of the MPS sensor images, in a two-dimensional optical coordinate system respective of said image detector, and according to non-real-time MPS coordinates of said MPS sensor (112, 114, 116), in an MPS coordinate system respective of said MPS, wherein each set of intrinsic parameters comprises optical characteristics of said image detector and each set of extrinsic parameters comprises rotation and translation parameters of the MPS coordinate system relative to the optical coordinate system; determining two-dimensional coordinates of said tip of said medical device, according to said selected physical zoom setting, according to said set of intrinsic and extrinsic parameters, according to said selected image detector region of interest setting, and according to real-time MPS coordinates of an MPS sensor located at said tip of said medical device; superimposing said representation of said tip of said medical device, on said image of said body region of interest, according to said two-dimensional coordinates; and displaying said representation of said tip of said medical device superimposed on said image of said body region of interest, wherein the method is characterised in that