Method for 3D motion tracking in an MRI scanner using inductively coupled microcoils

A method for tracking the position and orientation of an object in a magnetic resonance (MR) imaging system, the method comprising:

• disposing three or more wireless markers on the object having predetermined and unvarying relative positions, whereby motion of the object causes rigid body motion of a configuration of the three or more wireless markers;
• wherein the wireless markers each include an MR-visible sample coupled to a resonant circuit, and wherein the resonant circuits of the wireless markers are inductively coupled to one or more receive coils of the MR imaging system;
• providing one or more navigator tracking pulses in an MR pulse sequence for motion tracking of the wireless markers on the object;
• receiving marker signals from the wireless markers via the one or more receive coils, wherein the marker signals are responsive to the one or more navigator tracking pulses;
• wherein the marker signals responsive to the one or more navigator tracking pulses include three 1-D projections along three orthogonal directions, wherein the 1-D projections include marker signal peaks from the wireless markers;
• determining a correspondence between the received marker signal peaks and the wireless markers such that the wireless marker responsible for each received marker signal peak in the three 1-D projections is determined, wherein determination of the correspondence relies on knowledge of the predetermined relative positions of the wireless markers, whereby position and orientation information of the object is obtained;
• and
• providing the position and orientation information of the object as an output or as an input for further processing;
• wherein the wireless markers are separated by distance from each other in each of three orthogonal directions;
• wherein the knowledge of the predetermined relative positions of the wireless markers is used to determine the correspondence from order of the marker signal peaks in the three 1-D projections;
• further comprising performing prospective motion correction of the navigator tracking pulses to keep a relative orientation of coordinates of the navigator tracking pulses and the tracking device within a predetermined range;
• wherein the prospective motion correction of the navigator tracking pulses ensures that orders of the wireless markers in the three 1-D projections do not change, whereby there is no limit to the range of motion that can be tracked.