Patent ID: 7147373

Claim:
A system for obtaining coordinate data of a source and detector instrument, the system comprising: a marker assembly having a plurality of markers with a particular three dimensional geometry, wherein the plurality of markers describe a first circle and a second circle that are parallel and lie on a cylinder; an energy source for targeting the plurality of markers with energy packets; a detector for detecting energy packets after the plurality of markers have interacted therewith; an image device for forming image data of the plurality of markers from the energy packets detected by the detector, wherein the image data correspond to a first ellipse associated with a first projection of the first circle onto the detector and a second ellipse associated with a second projection of the second circle onto the detector; a calibration module including at least one equation, for non-iteratively determining, from the particular geometry of the plurality of markers and the image data, in a world coordinate system, coordinate data that includes a pitch of the detector, when coordinate data for the detector is obtained, wherein the calibration module comprises: a projection module for obtaining first ellipse parameters that describe the first ellipse and second ellipse parameters that describe the second ellipse; and a marker assembly module for obtaining geometric parameters of the marker assembly, the calibration module determining the coordinate data from the first ellipse parameters, the second ellipse parameters and the geometric parameters of the marker assembly; wherein the calibration module further comprises: an intersection module for determining a location of an intersection point where lines connecting points on the first ellipse to opposite points on the second ellipse intersect; and a scale module for obtaining a scale factor corresponding to the image data, wherein the calibration module determines the coordinate data from the first ellipse parameters, the second ellipse parameters, the geometric parameters of the marker assembly, the intersection point and the scale factor.