1. An apparatus for visualizing the position of an object, comprising: a first imaging modality capable of producing projection images from at least two orientations with respect to the object; a second imaging modality capable of producing three-dimensional images of a volume including the object; identifying a distinguishing feature on the object in the projection images taken from different orientations; and a processor configured to compute the location of the distinguishing feature in a three dimensional coordinate system using the identified distinguishing feature.