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; image guided surgery systems, namely, hardware and software and application tools and instruments and component parts therefor for tracking instrument location; computer assisted surgery systems consisting primarily of computer hardware and software for image guided surgery, spatial position sensors, tool interface units for tracking tools, universal handles, monitors and cart; 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 software for medical use; computer hardware for medical use; computer hardware; computer software computer assisted image guided surgery systems, all being computer systems for medical use; computer assisted image guided surgery system for guiding instruments using pre-operative and intra-operative images; computer assisted image guided surgery system for providing 3-dimensional visualization and navigation of instruments, all being computer systems for medical use; surgery planning software; computer assisted surgery system, all being computer systems for medical use; image guided surgery system, all being computer systems for medical use; surgery planning software for use in image guided surgery; tool identification software used for use in image guided surgery; navigation software for image guided surgery; mobile system cart for use in image guided surgery, all being computer systems for medical use; mobile system cart having electro-magnetic field generator, computer workstation and instrument connection unit, all being computer systems for medical use; image guided surgery cart having electromagnetic field generator, computer work station and connections for medical instruments and devices; image guided surgery workstation; tool offset calibrators; magnetic tool offset calibrators; distortion measurement devices; footswitches; input devices; metrological instruments and equipment; optical tool offset calibrators; input devices; medical devices; tracking devices for medical devices; trackers for use in image guided surgery; telemetry devices for medical applications; endoscopes; flexible endoscopes; bronchoscopes; tracked endoscopes; tracked flexible endoscopes; tracked bronchoscopes catheters; tracked catheters; needles; tracked needles; stylettes; tracked stylettes; bone screws; tracked bone screws; laparoscope ultrasound trackers; tracked laparoscope ultrasound; tracked ultrasound transducers; positioning aids for use in ultrasound imagery; transcutaneous ultrasound trackers; endorectal ultrasound trackers; ultrasound tracker calibrators; fluoroscope tracker and local calibrator therefor; tracked fluoroscope; fluoroscope tracker and integrated calibrator therefor; universal adaptor for medical devices; medical instrument adaptors; stylette pairs; cannula pairs; tracked cannula pairs; needle device introducers; tracked needle device introducers; needle introducers; tracked needle introducers; biopsy needle guns; tracked biopsy needle guns; tracked k-wires; k-wires; bone wires; tracked bone screws; tracked multisensor guidewires; guidewires; tracked single sensor guidewires; disposable button probes; tracked disposable button probes; reusable probes; tracked reusable probes; disposable dynamic reference patches; skin patches for referencing; locatable guides; tracked locatable guides; steerable catheters; tracked steerable catheters; reusable dynamic reference frames; positioning aids; vertebroplasty needles; tracked vertebroplasty needles; steerable locatable guides; tracked steerable locatable guides; tracked clamps; clamps; tracked cutting devices; cutters; scalpels; tracked scalpels; stents; tracked stents; cannulas; tracked cannulas; shunts and introducers; tracked shunts and introducers; needles; locatable guides; aspiration needles; tracked aspiration needles; tracked grasper; grasper; tracked brush; brush precision spatial measurement devices; ultrasound tracker calibrators; fluoroscope tracker and local calibrator therefor; tracked multisensor guidewires; tracked clamps; clamps; tracked cutting devices; cutters scalpels; stents; shunts and introducers; fluoroscope tracker and integrated calibrator therefor; medical instrument adaptors; tracked medical instrument adaptors; positioning aids; footswitches. Sale of precision spatial measurement devices; sale of metrological instruments; sale of metrological equipment; sale of metrological devices; sale of image guided surgery systems; sale of computer assisted surgery systems; sale of computer software and hardware for image guided surgery systems; sale of computer hardware and software for computer assisted surgery systems; sale of medical instruments and apparatuses; sale of medical devices; service of computer assisted surgery systems and tools; service of image guided surgery systems and tools; maintenance of computer assisted surgery systems and tools; maintenance of image guided surgery systems and tools