Systems and methods for magnetic material imaging

1. A magnetic material imaging (MMI) system comprising:

first and second sets of field-generating coils, each of the field-generating coils of the first and second sets having an elongated segment that extends along an imaging axis of the imaging system, wherein the elongated segments of the first set of field-generating coils are positioned opposite from and spaced apart from the elongated segments of the second set of field-generating coils such that a region-of-interest (ROI) of an object is configured to be located between the first and second sets of field-generating coils;

one or more computer processors configured to control a flow of current through the first and second sets of field-generating coils to generate a selection field and to generate a drive field, the selection and drive fields combining to form a movable 1D field free region (FFR) that extends through the ROI; and

one or more recording coils, antennas, or magnetometers positioned relative to the ROI to detect changes in magnetization of magnetic material located proximate to the 1D FFR in the ROI,

wherein the drive field is a first drive field and the one or more computer processors are configured to control the flow of the current through the first and second sets of field-generating coils to generate a second drive field, each of the first and second drive fields being configured to move the 1D FFR in a different direction within the ROI, wherein the first drive field is configured to move the 1D FFR along a y-axis and the second drive field is configured to move the 1D FFR along a z-axis, the 1D FFR extending a length along an x-axis that is greater than a width of the 1D FFR along the y-axis and a height of the 1D FFR along the z-axis, the x-, y-, and z-axes being mutually perpendicular.

2. The MMI system of claim 1 , wherein the one or more computer processors are configured to control the flow of the current through the first and second sets of field-generating coils to move the 1D FFR back and forth through the ROI.

3. The MMI system of claim 1 , wherein the elongated segments for each of the first and second sets are positioned relative to each other to form multiple coil layers in which each coil layer includes a plurality of the elongated segments.

4. The MMI system of claim 1 , further comprising an image-processing module configured to receive image data from the one or more recording coils, antennas, or magnetometers, the image data being based on measurements of the changes in magnetization.

5. The MMI system of claim 4 , wherein the magnetic material is part of an instrument, the changes in magnetization within the ROI being caused by the magnetic material of the instrument, the image-processing module configured to generate a representation of the instrument within the ROI.

6. The MMI system of claim 1 , further comprising a table configured to be positioned generally between the first and second sets of field-generating coils such that the object is positioned between the first and second sets of field-generating coils, the drive field extending between the first and second sets of field-generating coils.

7. The MMI system of claim 1 , wherein a length for each of the elongated segments of the field-generating coils of the first and second sets is between 20 centimeters and 50 centimeters.

8. The MMI system of claim 7 , wherein the 1D FFR has a cross-section transverse to a length of the 1D FFR that contains a low field region of 0.5-5.0 mm 2 .

9. The MMI system of claim 1 , wherein the 1D FFR is linear and extends parallel to the elongated segments of the first and second sets of field-generating coils.

10. The MMI system of claim 1 , wherein the 1D FFR is linear and extends parallel to the elongated segments of the first and second sets of field-generating coils.

11. The MMI system of claim 1 , wherein a length for each of the elongated segments of the field-generating coils of the first and second sets is between 20 centimeters and 50 centimeters.

12. A magnetic material imaging (MMI) system comprising:

first and second sets of field-generating coils, each of the field-generating coils of the first and second sets having an elongated segment that extends along an imaging axis of the imaging system, the imaging axis extending through a region-of-interest (ROI) of an object, wherein the elongated segments of the first set of field-generating coils are positioned opposite the elongated segments of the second set of field-generating coils and the ROI is located between the first and second sets of field-generating coils;

one or more computer processors configured to control a flow of current through the first and second sets of field-generating coils to generate a selection field and to generate a drive field, the selection and drive fields combining to form a movable 1D field free region (FFR) that extends through the ROI; and

one or more recording coils, antennas, or magnetometers positioned relative to the ROI to detect changes in magnetization of magnetic material located proximate to the 1D FFR in the ROI;

wherein the selection field is configured to be generated by a plurality of the elongated segments from the first set of field-generating coils and a plurality of the elongated segments from the second set of field-generating coils, and wherein the drive field is configured to be generated by a plurality of the elongated segments from the first set of field-generating coils and a plurality of the elongated segments from the second set of field-generating coils,

wherein the drive field is a first drive field and the one or more computer processors are configured to control the flow of the current through the first and second sets of field-generating coils to generate a second drive field, each of the first and second drive fields being configured to move the 1D FFR within the ROI in a space between the first and second sets of field-generating coils, wherein the first drive field is configured to move the 1D FFR along a y-axis and the second drive field is configured to move the 1D FFR along a z-axis, the 1D FFR extending a length along an x-axis that is greater than a width of the 1D FFR along the y-axis and a height of the 1D FFR along the z-axis, the x-, y-, and z-axes being mutually perpendicular.