Apparatus and method for wide-range optical tracking during medical imaging

A method of determining a position and orientation of an object in a medical imaging device, the method comprising:

• rigidly attaching one one or more markers to the object, wherein each marker of the one or more markers comprises three or more feature points, wherein the three or more feature points of each marker of the one or more markers have known positions in a coordinate system of the corresponding marker;
• configuring two or more cameras to have partial or full views of at least one of the one or more markers;
• determining a camera calibration that provides transformation matrices Tij relating a coordinate system Ci of camera i to a coordinate system Cj of camera j, wherein i and j are index integers for the two or more cameras;
• forming two or more images of the one or more markers with the two or more cameras, wherein the known positions of the three or more feature points of each marker in the coordinate systems of the corresponding markers lead to image consistency conditions for images of the three or more feature points in the camera coordinate systems;
• wherein the image consistency conditions are relations that are true in images of the one or more markers because of known relative positions of the three or more feature points on each of the one or more markers;
• and
• solving the image consistency conditions to determine rigid-body transformation matrices Mk relating coordinate systems MCk of each marker k to the coordinate systems of the two or more cameras, wherein k is an index integer for the one or more markers, whereby the position and orientation of the object is provided;
• wherein the solving the image consistency conditions to determine each rigid-body transformation matrix Mk is performed with a least squares solution to an overdetermined system of linear equations;
• wherein the overdetermined system of linear equations for rigid-body transformation matrix Mk is a set of two equations for each feature point of marker k that is seen by each of the two or more cameras;
• and
• wherein the overdetermined system of linear equations for rigid-body transformation matrix Mk has coefficients of the rigid-body transformation matrix Mk as unknowns to be solved for.