1. A system for measuring the true dimension and orientation of objects in a two dimensional(2D) medical image, said system comprising: a set of markers visible in the 2D medical images, which markers are located upon a surgical tool and have known spatial relationships between them; receiving circuitry adapted to receive a given 2D medical image, which given 2D medical image includes the surgical tool and an organ of a subject; image processing circuitry adapted to calculate distance within the given 2D image based on the appearance of said markers in the 2D image, characterized in that said processing circuitry include programs adapted to: (a) identify said markers in the given 2D medical image and determine their location; (b) calculate from the determined locations of the identified markers in the given medical image a three dimensional position and orientation of the surgical tool, in relation to the organ, thereby providing 3D positional information of the tool from the appearance of the markers in the given 2D medical image; and (c) calculate a dimension of a spatial relationship between the surgical tool, or a point on the surgical tool, and the organ, based on the locations of the identified markers in the given medical image and the calculated relative 3D position and orientation of the surgical tool.