| CPC A61B 5/062 (2013.01) [G01V 3/10 (2013.01); G01V 15/00 (2013.01)] | 17 Claims |
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1. A method for determining a magnetic tag location and a magnetic tag orientation of at least one magnetic tag of a plurality of magnetic tags the method comprising steps of:
providing the plurality of magnetic tags, each of the plurality of magnetic tags having an elongated shape with an aspect ratio between a first edge and a second edge of at least 1000:1;
providing a system having a single-sided coil arrangement with a plurality of planar coils that, when DC current is applied thereto, create a selection field and, when AC current is applied thereto, create an interrogation field, the system including
at least one first planar coil for controlling a field-free point (FFP) or a field-free line (FFL) and for generating a first interrogation field at a first frequency,
at least one second planar coil for controlling the FFP or the FFL and for generating a second interrogation field at a second frequency, wherein the at least one first planar coil and the at least one second planar coil are co-planar,
at least one third planar coil for generating a third interrogation field at a third frequency, wherein the single-sided coil arrangement is configured to generate the selection field and the interrogation field,
at least one processor for receiving and processing detection signals from a plurality of receiver coils to determine the magnetic tag location and the magnetic tag orientation of the at least one magnetic tag, and
a display in communication with the at least one processor, and for displaying an indication of the magnetic tag location and the magnetic tag orientation of the at least one magnetic tag;
applying, by the at least one processor of the system, the DC current with a varying magnitude to one or more of the plurality of planar coils arranged on a plane to create the selection field within a detection volume, wherein the selection field varies to move the FFP or the FFL to a position approximating the magnetic tag location for the at least one magnetic tag;
applying, by the at least one processor of the system, the AC current to the one or more of the plurality of planar coils to generate the interrogation field within the detection volume, wherein the first interrogation field is produced at the first frequency, the second interrogation field is produced at the second frequency, and the third interrogation field is produced at the third frequency, and wherein each of the first frequency, the second frequency, and the third frequency is distinct;
determining, by the at least one processor of the system, harmonic responses as a function of excitation field amplitude, for the at least one magnetic tag in three sweep axes by:
detecting first harmonics of the first interrogation field at one or more of the plurality of receiver coils,
detecting second harmonics of the second interrogation field at the one or more of the plurality of receiver coils, and
detecting third harmonics of the third interrogation field at the one or more of the plurality of receiver coils;
determining, by the at least one processor of the system, the magnetic tag location for the at least one magnetic tag based on the first harmonics, the second harmonics, and the third harmonics by:
generating, by each of the first interrogation field, the second interrogation field, and the third interrogation field, a first magnetic response at the at least one magnetic tag of the plurality of magnetic tags, wherein the first magnetic response comprises a first width and is associated with a first axis of the at least one magnetic tag;
generating, by each of the first interrogation field, the second interrogation field, and the third interrogation field, a second magnetic response at the at least one magnetic tag of the plurality of magnetic tags, wherein the second magnetic response comprises a second width and is associated with a second axis of the at least one magnetic tag, and
generating, by each of the first interrogation field, the second interrogation field, and the third interrogation field, a third magnetic response at the at least one magnetic tag of the plurality of magnetic tags, wherein the third magnetic response comprises a third width and is associated with a third axis of the at least one magnetic tag;
comparing, for the at least one magnetic tag, the first width, the second width, and the third width to determine a shortest width when the FFP or the FFL is at the magnetic tag location;
identifying, for the at least one magnetic tag, which of the first axis, the second axis, or the third axis is associated with the shortest width;
determining, for the at least one magnetic tag, a long axis of the at least one magnetic tag based on the identifying of which of the first axis, the second axis, or the third axis is associated with the shortest width;
identifying, for the at least one magnetic tag, which of the first axis, the second axis, and the third axis corresponds to the long axis;
determining, for the at least one magnetic tag, the magnetic tag orientation of the least one magnetic tag based on the identifying of which of the first axis, the second axis, and the third axis corresponds to the long axis; and
transmitting, by the at least one processor of the system, the indication of the magnetic tag location and the magnetic tag orientation of the at least one magnetic tag to the display.
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