1. A system ( 300 ) for performing and visualizing a measurement of an object viewed in an image computed from image data, the system comprising: an image unit ( 310 ) for visualizing the image data in the image for displaying in a display; a deployment unit ( 320 ) for deploying a caliper ( 21 ; 22 ; 23 ; 24 ) in an image data space based on the location of the object in the images data space; and a caliper unit ( 330 ) for visualizing the caliper ( 21 ; 22 ; 23 ; 24 ) in the image; wherein the caliper ( 21 ; 22 ; 23 ; 24 ) comprises a first planar surface ( 211 ) and a second planar surface ( 212 ) substantially parallel to the first planar surface ( 211 ), and wherein the measurement of the object is determined based on the distance between the planes of the first and second planar surface.