Software for use in image guided surgery; computer software for integrating views of a patient with the tracked position of tools or instruments for use in computer assisted surgery; computer software for integrating representations of application tools and instruments with images of patients obtained by imaging modalities including Computed Tomography (CT), Magnetic Resonant Imaging (MR), Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET); computer hard...