Patent Description:
In a navigation system for various procedures, such as surgical procedures, assembling procedures, and the like, an instrument or object may be tracked by measuring an effect of a magnetic field on a sensor coil. The sensor coil may include a conductive material that is placed within a magnetic field where a current is induced on the coil. The measured induced current may be used to identify or determine a location of the instrument or object. Determining the location of a coil, however, may be desired to be enhanced in various aspects.

The electro-magnetic field or fields may be generated with a plurality of purposefully positioned and oriented transmit coils. Various transmitter or field generation systems include the AxiEM™ electro-magnetic navigation system sold by Medtronic Navigation, Inc. , having a place of business in Louisville, Colorado. The AxiEM™ electro-magnetic navigation system may include a plurality of transmit coils that are used to generate one or more electro-magnetic fields that are sensed by a tracking device, which may be sensor coil, to allow a navigation system, such as a StealthStation® surgical navigation system to be used to track and/or illustrate a tracked location of an instrument.

The transmit coils positioned and oriented about one another generally fill a volume smaller than a navigation volume generated by the transmitting coils. The volume including the transmitting coils, however, is generally positioned near the patient so that the navigation field or volume encompasses a region of the patient in which navigation would occur. Accordingly, the transmitter coil array may be near an individual, such as a surgeon, performing a procedure.

The present invention relates to a navigation system according to claim <NUM>. Further aspects of the navigation system is defined by the dependent claims. Moreover, the present invention also relates to a method of shaping a magnetic field for a navigation system according to claim <NUM>.

Disclosed is a localizer, which may include a transmitting assembly, particularly a transmitting coil array (TCA), and a field shaping assembly that is configured and is operable to transmit one or more diverse magnetic field or fields. Particularly, the localizer is configured to generate field vectors that are highly diverse relative to one another with a relatively orthogonal or near orthogonal distribution of measurable vectors relative to an origin or within a volume. The diversity of one or more fields is generated even though a plurality of coils of the TCA are positioned on a substantially flat plane. The accuracy, precision, and reliability of a determined location of a sensor, such as a coil, may be improved with additional measurements, particularly additional measurements of effects of one or more of the diverse magnetic fields on a sensor coil.

The localizer may be formed of a plurality of cooperative features including the transmitting/transmitter coil array (TCA) including one or more transmitting coils and a field shaping assembly. The field shaping assembly is provided to include a plurality of portions or members that separately interact with the magnetic field produced by one or more of the coils. For example, a plurality of coils may be formed as one or more trios or triplets of coils that are all powered to generate a field. A field shaping segment may be provided to interact substantially individually with the field. The TCA, therefore, may generate or form a generated navigation field in a navigable volume that may substantially mimic a field created by co-center positioned and orthogonally oriented coils. The TCA, therefore, may include a substantially low profile, or flat configuration, and be positioned near or adjacent a location without being intrusive in an operating theater. For example, the TCA may be positioned under a patient or between a patient and a support structure.

The field shaping assembly may be included with or fixed relative to the TCA. The TCA and field shaping assembly may also be referred to as a localizer. The field shaping assembly may be used to affect a generated field to create the second field configuration for ensuring a diversity of the field. The field shaping assembly may also acts to mitigate or eliminate effects of external conductive surfaces and materials, such as conductive metal, which may be present in a support structure or in other structures away from the localizer. For example, the TCA may be positioned on a surgical operating bed that may include metal or other conductive materials where the field shaping assembly ensures that the conductive materials do not affect or substantially affect the field produced by the localizer. In various embodiments, substantially affecting the field produced by the localizer may include where a conductive material may be present near the localizer, but no compensation (e.g. processing or algorithmic compensation) need occur to allow for an appropriate and accurate tracking of a selected tracking device.

A navigation system <NUM> (<FIG>), which may include a localizer assembly or system <NUM> as illustrated in <FIG>, may be used for various purposes or procedures. A navigation system may be used to determine or track a location of an instrument in a volume. Tracking a location of an instrument may assist a user in determining a location of the instrument, even if the instrument is not directly viewable by the user. A location may include at least one three-dimensional position (e.g. X, Y, or Z coordinates) and at least one orientation (e.g. yaw, pitch, and roll). In various embodiments, therefore, location may include six-degrees of freedom. Various procedures may block the view of the user, such as performing a repair or assembling an inanimate system, such as a robotic system, assembling portions of an airframe or an automobile, or the like. Various other procedures may include a surgical procedure, such as performing a spinal procedure, neurological procedure, positioning a deep brain simulation probe, or other surgical procedures on a living subject. In various embodiments, for example, the living subject may be a human subject and the procedure may be performed on a human patient.

Various components of a surgical navigation system may include an imaging system that is operable to image a patient, such as an O-arm® imaging system, magnetic resonance imaging (MRI) system, computed tomography system, etc. Images may either be acquired during a surgical procedure or acquired prior to a surgical procedure for displaying on a display device. An instrument may be tracked in a trackable volume or a navigational volume that is produced by a transmitter or transmitting coil array that is incorporated into a localizer <NUM>, as illustrated in <FIG>.

With reference to <FIG>, the localizer <NUM> may be an electro-magnetic (EM) localizer that is operable to generate electro-magnetic fields with a transmitting coil array <NUM>. The coil array <NUM> may include one or more coil groupings or arrays such as a first grouping <NUM>, a second grouping <NUM>, and a third grouping <NUM>, and a fourth grouping <NUM>. Each of the groupings may include three coils, also referred to as trios or triplets. For example, the first grouping <NUM> may include a first coil 34a, a second coil 34b, and a third coil 34c. Similarly, the second grouping <NUM> may include a first coil 36a, a second coil 36b, and a third coil 36c. The third grouping <NUM> may include first coil 38a, a second coil 38b, and a third coil 38c. A fourth grouping <NUM> may include a first coil 40a, a second coil 40b, and a third coil 40c. The coils may be powered to generate or form an electro-magnetic field by driving current through the coils of the coil groupings <NUM>, <NUM>, <NUM> and <NUM>. As the current is driven through the coils, the electro-magnetic fields generated will extend away from the coils <NUM>, <NUM>, <NUM>, and <NUM> and form a navigation domain or volume <NUM> (e.g. as illustrated in <FIG>).

The navigation domain or volume generally defines a navigation space or patient space. As is generally understood in the art, an object or instrument <NUM>, such as a dill, lead, etc., may be tracked in the navigation domain relative to a patient or subject with an instrument tracking device <NUM>. For example, the instrument <NUM> may be freely moveable, such as by a user, relative to a dynamic preference frame (DRF) or reference frame tracker <NUM> that is fixed relative to the subject. Both the tracking devices <NUM>, <NUM> may include sensing coils (e.g. formed as coiled conductive material sensors) that sense and are used to measure a magnetic field strength, etc. Due to the tracking device <NUM>, connected or associated with the instrument <NUM>, relative to the DRF <NUM> the navigation system <NUM> may be used to determine location of the instrument <NUM> relative to the DRF <NUM>. The navigation volume or patient space may be registered to an image space of the patient and an icon representing the instrument <NUM> may be superimposed on the image. Registration of the patient space to the image space and determining a location of a tracking device, such as the tracking device <NUM>, relative to a DRF, such as the DRF <NUM> may be performed as is generally known in the art.

With continuing reference to <FIG>, the localizer <NUM> may further include a printer circuit board (PCB) <NUM> that includes traces thereon from a cable connector <NUM> to which a communication or power cable <NUM> may be connected. The traces on the PCB <NUM> may connect the cable <NUM> with individual cable connectors <NUM>, <NUM>, <NUM>, and <NUM>. The connectors may include leads or wires that may be connected to each of the coils in coil groups <NUM>, <NUM>, <NUM>, and <NUM>. Accordingly, the coils in coil groups <NUM>, <NUM>, <NUM>, and <NUM> may be powered or driven by power provided through the traces on the PCB <NUM> to each of the coils in coil groups <NUM>, <NUM>, <NUM>, and <NUM>, from a navigation processor system <NUM>. The navigation processor system may include the commercially available StealthStation® or Fusion™ surgical navigation systems sold by Medtronic Navigation, Inc. having a place of business in Louisville, CO.

The localizer <NUM> further includes a field shaping assembly <NUM>. The field shaping assembly <NUM> may generally include a first magnetically permeable portion that is also substantially nonconductive <NUM>, a spacer <NUM> which may be substantially inert, and a substantially conductive portion <NUM>. The magnetically permeable magnetic portion <NUM> may include various properties, such as being generally highly magnetically permeable, substantially nonconductive, high magnetic saturation, low magnetic coercivity, as discussed further herein. The spacer member <NUM> is substantially inert relative to an electric current and a magnetic field and may include a polymer or plastic material such as a polycarbonate having a thickness of about <NUM> millimeters (mm) to about <NUM>, including about <NUM>. The thickness of the spacer <NUM> generally defines a distance between the magnetically permeable member <NUM> and the conductive member <NUM>. The magnetically permeable magnetic portion <NUM> may be provided as four individual portions or members 82a, 82b, 82c, and 82d, as discussed further herein. The individual members may be positioned near each of the coil groups <NUM>, <NUM>, <NUM>, and <NUM> and near corners of the conductive member <NUM>. The conductive member or portion <NUM> generally includes a highly conductive material such as a high purity copper or other appropriate highly conductive material. The conductive member <NUM> may allow generation of eddy currents formed by induced currents due to magnetic fields permeating into the conductive material <NUM>.

The localizer <NUM> may further include two shells or cover portions including a first cover portion <NUM> and a second cover portion <NUM>. The two cover portions enclose all of the coil array <NUM>, the field shaping assembly <NUM>, and a structural or holding component <NUM>. Further, various feet or non-skid elements <NUM> may be adhered or connected to the case portion <NUM> for selected operational uses. Moreover, the case, such as the first case portion <NUM> may include select ergonomic and carrying portions including a hand hole or region <NUM> and shaped ergonomic portions. Shaped portions may include a neck support region <NUM> having lower or indent portions <NUM> and <NUM> to assist in holding or positioning a head or neck region of a patient or subject for selected procedures. It is understood, however, that the shape and configuration of the cover <NUM> may be formed in any appropriate shape. Further, the localizer <NUM> may have selected dimensions of length 20a, width 20b, and height 20c. The length 20a may be about <NUM> to about <NUM>, including about <NUM> to about <NUM>, including about <NUM>. The width 20b may be about <NUM> to about <NUM>, including about <NUM> to about <NUM>, including about <NUM>. The height 20c may be about <NUM> to about <NUM>, including about <NUM> to about <NUM>, including about <NUM>. With continued reference to <FIG> and additional reference to <FIG>, the coil array <NUM> includes the plurality of individual coils, as discussed above. The plurality of coils may be formed into the coil groups <NUM>-<NUM>. Each of the coils include various features, as described herein. Further, each coil may include substantially identical or similar features, which will not be repeated for clarity. Thus, an exemplary discussion of coil 34a will be made and it is understood that the other individual coils will have the same or similar features unless otherwise stated.

The coil 34a may be formed substantially as an ellipsis having a major axis <NUM> and a minor axis <NUM>. The coil 34a may be formed on a mold or form and then removed as including substantially only the coiled with or conductive portions. The coil, however, may include the dimensions as discussed herein. The coil 34a may, alternatively or in combination, be formed or wound on a bobbin or wire holder. As illustrated in <FIG>, the wire may be wound on a bobbin or holder and the combination may be inserted in the structural component <NUM>.

The major axis <NUM> may include an internal major axis portion 150a having a dimension, such as a length, of about <NUM> millimeters (mm) to about <NUM>, including about <NUM> to about <NUM>, and further including a dimension of about <NUM>. The major axis <NUM> may further an external major axis 150b, which includes the internal dimension 150a, that may include a dimension of about <NUM> to about <NUM>, further about <NUM> to about <NUM>, and further including about <NUM>. Thus, along the external major axis 150b the coil 34a may be about <NUM> long.

The minor axis <NUM> may also include an internal dimension or length of 154a and an external dimension or length 154b, wherein the external dimension 154b includes the internal dimension 154a. The internal dimension 154a may be about <NUM> to about <NUM>, including about <NUM> to about <NUM>, and further including about <NUM>. The external dimension of 154b may be about <NUM> to about <NUM>, further including about <NUM> to about <NUM>, and further including about <NUM>. In various embodiments the coil 34a may include an external major axis dimension 150b of about <NUM> and an internal dimension of 150a of about <NUM>. Further, the coil 34a may include a minor axis interior dimension 154a of about <NUM> and an external dimension 154b of about <NUM>.

It is understood that each of the coils of the coil groups <NUM>, <NUM>, <NUM>, and <NUM> may be substantially identical. Accordingly, each of the coils of the coil groups <NUM>-<NUM> may include dimensions substantially identical to those discussed above.

Further, the coils, such as coil 34a, may be formed by winding selected connective material, such as <NUM> gage copper magnet wire wound around an outer dimension of the internal major and minor axes. The wire may generally conform to NEMA MW-136C standards. Further, generally the wire may have a single layer of bonded polyurethane nylon insulation. The coil 34a may be formed by winding a pair of leads of the wire. The wire may come to the coil 34a as a twisted pair lead <NUM>, but is not twisted when wrapped around the major and minor internal dimension of the coil as wraps or coil portions <NUM>. The number of windings may include about <NUM> to about <NUM> wraps per layer and about <NUM>-<NUM> layers. In various embodiments the coils may include <NUM> wraps per layer and <NUM> layers. As discussed above, the external dimensions of the external major and minor axes 150b, 154b may be equal to the external.

As discussed herein, the combination of the TCA <NUM> with the selected field shaping components <NUM> may be used to form a selected field geometry and diversity, as also discussed further herein. The field volume may include a navigable or navigation volume, the navigation volume may be about <NUM><NUM> to about <NUM><NUM>, including about <NUM><NUM>. The navigation field or volume may begin about <NUM> above the TCA <NUM>. It is understood by one skilled in the art that the coils, such as the coil 34a, may be altered depending upon the specifications (e.g. size, type, materials, etc.) of the remaining field shaping components. However, it is understood that the coil 34a may be substantially identical to each of the other coils in the coil array <NUM> when positioned in the localizer <NUM>.

Each of the coils of the coil groups may be positioned in or on the structural component <NUM>. The structural component <NUM> may be made of selected materials that generally are inert and do not interact with a magnetic field. Further, the structural component may be made of a non-conductive material. The structural component generally also includes a selected rigidity to provide structural support to the localizer <NUM>.

Accordingly, with continuing reference to <FIG>, and additional reference to <FIG>, the structural component <NUM> will be discussed in greater detail. The structural component <NUM> may include a plurality of coil holding regions or portions <NUM>, such as twelve coil holding regions 160a, 160b, 160c, 160d, 160e, 160f, <NUM>, <NUM>, 160i, 160j, <NUM>, and <NUM>. Again, each of the coil holding regions 160a-<NUM> may be configured to form or provide the coil groups <NUM>-<NUM>, as discussed above. Accordingly, each of the groupings may include three coils, as illustrated in <FIG>. For the following discussion, therefore, it is understood that the separate coil groupings may include similar features and components as those discussed below and illustrated in <FIG>, but are not repeated for clarity of the current discussion. The structural component may have a dimension to fit within the overall dimensions of the localizer <NUM>, including a length 110a of about <NUM> to about <NUM>, including about <NUM> and a width of about <NUM> to about <NUM>, including the width of about <NUM>. The dimensions of the portions containing the coil holding regions or portions <NUM> may be less than the overall dimensions of the structural component <NUM> and may be about <NUM> to about <NUM> by about <NUM> to about <NUM>, including about <NUM> by about <NUM>.

With reference to coil holding regions 160a, 160b, 160c, each of these may respectively hold the coils 34a, 34b and 34c. Each coil holding region, such as the coil holding region 160a, illustrated in <FIG> and <FIG>, may include a raised outer wall <NUM> that may substantially hold the respective coil 34a in place. Further, a central peg or projection <NUM> may pass through the central portion <NUM> of the coil, such as the coil 34a. The peg <NUM> extends from a floor or bottom surface <NUM> of the coil holding region 160a. As discussed above, the major internal axis 150a and minor internal axis 154a may define the opening <NUM> of the coil 34a or a bobbin holding the coiled portions. The projection <NUM> may pass into or through the opening <NUM> and the external wall <NUM> may be near an external surface <NUM> of the coil 34a or a bobbin holding the coiled portions. Again, it is understood that each coil holding region of the multiple coil holding regions <NUM> may include similar features.

The coil grouping, such as the first coil group <NUM>, may be positioned around a central point or region <NUM>. The center point or region <NUM> may be a center point around which each of the coils 34a, 34b, 34c are positioned. Generally, each of the coils 34a, 34b, 34c are radially spaced from the center <NUM>. The coils 34a, 34b, 34c, however, may not all be equally spaced from the center <NUM> and/or each other. The coils may each be specifically spaced from an edge of the magnetically permeable member over which the respective coil group is placed. In various embodiments, the respective holding regions 160a, 160b, and 160c may be positioned at a selected "clocking angle" relative to one another, such as about <NUM>° from one another around the center <NUM>. It is understood, however, that the respective holding regions 160a, 160b, and 160c need not be <NUM>°, or that all need not be <NUM>° apart.

In various embodiments, for example, the coil holding region 160b may be on an axis or line <NUM> extending through the center of the coil holding region 160b and the center <NUM>. Similarly, a second axis or line <NUM> may extend through the center point <NUM> and a center of the coil holding region 160c. An angle <NUM> between the two lines <NUM> and <NUM> and the angle may be about <NUM>°. It is understood, however, as noted above, that the positioning of the coil holding regions relative to one another may be selected to achieve a selected type of field, such as the appropriate diversity in a field, and, therefore, may be altered from the current illustration. Nevertheless, the coil regions of each of the coil groups <NUM>, <NUM>, <NUM>, and <NUM> may be formed to hold the respective coils at about <NUM>° from one another around the center point <NUM>. Further, as discussed above and herein, diversity may include diversity relative to time based on a transmitted field from the coil groups and an induced current field from the conductive member <NUM>. Diversity of the field(s) assists in ensuring accurate and/or precise tracking of a selected tracking device.

In various embodiments, the respective coils 34a, 34b, and 34c, in the holding regions 160a, 160b, and 160c may be spaced a selected distance from an edge of the respective magnetically permeable member <NUM> over which they are placed. The distance may be of an outside edge of the coil to a nearest edge of the magnetically permeable member. The distance may be about <NUM> to about <NUM>, including about <NUM> to about <NUM>, and further <NUM> to about <NUM>, and further including about <NUM> to about <NUM>. Another distance may be of an outside edge of the coil to a farthest edge of the magnetically permeable member. This distance may be about <NUM> to about <NUM>, including about <NUM> to about <NUM>.

In various embodiments, in additional to and/or in combination with those discussed above, the respective coils 34a, 34b, and 34c, in the holding regions 160a, 160b, and 160c may be spaced a selected distance from a corner and/or edges of the respective magnetically permeable member <NUM> over which they are placed. The respective coils 34a, 34b, and 34c and/or the holding regions 160a, 160b, and 160c may be positioned around the common center <NUM>. A center of the coils <NUM> and/or the center 166a of the coil holding regions <NUM> may be placed about <NUM> to <NUM> including about <NUM> to about <NUM> from the common center <NUM>. Further, the center of the coils <NUM> and/or the center 166a of the coil holding regions <NUM> may be spaced apart at a distance of about <NUM> to about <NUM> including about <NUM> to about <NUM> from each other. Also, the center of the coils <NUM> and/or the center 166a of the coil holding regions <NUM> may be a distance from a nearest boundary edge of the magnetically permeable member <NUM>, the distance may be about <NUM> to about <NUM> including about <NUM> to about <NUM> from the nearest boundary. The center of the coils <NUM> and/or the center 166a of the coil holding regions <NUM> may sit about <NUM> degrees to about <NUM> degrees including about <NUM> degrees around the common center <NUM>. One of the coil centers may sit about <NUM> degrees to about <NUM> degrees from a diagonal of the magnetically permeable member <NUM>. The long or major axis <NUM> axes of the coil 34a may vary from about <NUM> to about <NUM> degrees to the nearest boundary line or tangent line of the magnetically permeable member <NUM>. It is understood that each of the coils of the various coil groups <NUM>, <NUM>, <NUM>, and <NUM> may be configured as discussed above. Further, each may be varied to achieve a selected field geometry.

With continuing reference to <FIG> and with further reference to <FIG>, the coil holding regions may also include a geometry relative to a substantially flat plane184. As discussed further herein, the flat plane <NUM> may be any appropriate plane, such as one defined by a surface of the field shaping portion <NUM>, especially defined by a surface of the magnetically permeable portion <NUM>.

The coil holding region 160c may include a bottom surface <NUM>, as also illustrated in <FIG>, upon which the coil, such as the coil 34c, may rest when positioned in the structural component <NUM>. The bottom surface <NUM> of the coil holding portion 160c contacts or holds the coil 34a in a position and orientation, the bottom surface <NUM> may define a plane <NUM> that orients or positions the coil 34a relative to the plane <NUM>. The plane <NUM> may be parallel or at an angle that will intersect the plane <NUM>, such as about zero degrees (°) to about <NUM>°, including about <NUM>°, further including about <NUM>° to about <NUM>°. In various embodiments, the plane <NUM> defined by the bottom surface <NUM> may extend at an angle <NUM> relative to a line <NUM> that is normal to the bottom plane <NUM>. The angle <NUM> may be about zero degrees (°) to <NUM>°, including about <NUM>° and further including about <NUM>° to about <NUM>°, including about <NUM>°. In various embodiments, each of the coil holding regions 160a - <NUM> may include the angle <NUM> that is the same, in various embodiments, however, at least one of the holding regions 160a-<NUM> may include the angle <NUM> that is different from the others. Further, it is understood that the bottom surface <NUM> of the respective coil holding regions 160a-<NUM> may tilt along the major axis of the respective coil, the minor axis of the respective coil, or a combination thereof. In various embodiments, therefore, the coil 34a may be positioned relative to the plane <NUM> in any appropriate angle. Thus, the coil 34a may not have a top or bottom surface that is substantially parallel with the plane <NUM>. Rather, the coil 34a, may be tilted relative to the plane <NUM>. As discussed further herein, the positioning of the coil 34a relative to the plane <NUM> may be a position of the coil 34a relative to a plane defined by the magnetically permeable field shaping portion <NUM> to assist in forming or generating a selective field diversity. Again, as discussed above, each coil holding portion <NUM> may include similar or identical features and dimensions, as discussed above.

With additional reference to <FIG> and <FIG>, and continuing reference to <FIG>, the structural component <NUM> includes a field shaping assembly contact or holding side <NUM> that is opposite the coil holding side <NUM>. The field shaping assembly holding side <NUM> of the structural component <NUM> may include various features such as a main or expansive pocket <NUM> that has a main surface or base surface <NUM> and a wall <NUM> that extends from the main surface <NUM>. The wall <NUM> may assist in holding the conductive member <NUM> relative to the coil array <NUM>. The conductive member <NUM> is formed as or configured as a single (e.g. one) piece of material. In various embodiments, the conductive member <NUM> may be formed as a plurality of members that are electrically connected or electrically isolated over the entire surface of the expansive pocket <NUM>.

The coils of the coil array <NUM> are held in the coil holding portions 160a-160i while the main surface <NUM> and the upstanding wall <NUM> assist in holding the conductive member <NUM> relative to the coil array <NUM>. The upstanding wall <NUM> may have a dimension that is substantially equivalent to or has an interference fit with the conductive member <NUM>. Further, various adhesives or holding materials or members (e.g., rivets, screws, or the like) may be used to fix or hold the conductive member <NUM> relative to the structural component <NUM>.

The structural component <NUM> may further include a pocket <NUM>, which may be referred to as a small or coil group pocket <NUM>. The small pocket <NUM> may include a main surface <NUM> and an upstanding wall <NUM>. The upstanding wall may extend from the main surface <NUM> to the surface <NUM> of the conductive pocket <NUM>. The upstanding wall <NUM> may have a dimension that is substantially equivalent to an exterior dimension of the magnetically permeable component <NUM>. The spacer component <NUM> may have a dimension that is equal to or slightly larger than the upstanding wall <NUM>. Therefore, the conductive member <NUM> may press the spacer component <NUM> onto the magnetically permeable component <NUM> and the surface <NUM> of the conductive pocket <NUM> to assist in holding the spacer material <NUM> in place. Further, a force may be applied against the magnetically permeable component <NUM> as the conductive member <NUM> is pressed against the spacer component <NUM>, which, in turn presses against the magnetically permeable component <NUM> into the small pocket <NUM>.

It is understood that each of the coil groupings, including the coil grouping <NUM>, <NUM>, <NUM>, and <NUM> may each include a separate pocket. As illustrated in <FIG>, and discussed further herein, the magnetically permeable component <NUM> may be formed as an individual unit or member (or laminated members of the same perimeter dimensions) for each of the coil groups or trios <NUM>, <NUM>, <NUM>, and <NUM>. Accordingly, each magnetically permeable component <NUM> may be positioned in a separate one of the pocket <NUM>. The structural component <NUM> by defining or forming the pockets <NUM>, therefore, may provide a physical spacing between each of the magnetically permeable component <NUM>. Generally, the pockets <NUM> are formed to hold the magnetically permeable members <NUM> near the coil group <NUM>, but not in contact with another magnetically permeable member <NUM>. The magnetically permeable members <NUM> may be spaced a distance <NUM>', <NUM>" (<FIG>) apart. The distances <NUM>', <NUM>" may be about <NUM> to about <NUM> apart including about <NUM> to about <NUM> apart, including about <NUM> apart.

It is understood that each of the elements, including the TCA <NUM> the magnetically permeable component <NUM>, spacer <NUM>, and electrically conductive member <NUM> may be adhered or affixed to the structure component <NUM> in a selective manner. For example, an adhesive or epoxy, such as Locktite® brand adhesive or epoxy may be used to fix all or portions of the coils and field shaping components <NUM> to the structural component <NUM>. Accordingly, each coils of the TCA <NUM> and the field shaping components <NUM> may be substantially fixed in a three-dimensional space relative to one another when affixed to the structural component <NUM>.

The field shaping assembly members <NUM>, as illustrated in <FIG>, include various components and members and discussed further herein. As discussed above the TCA <NUM>, including the various individual coil members or portions, may be driven to generate an electro-magnetic field. The electro-magnetic field may extend from the TCA <NUM> as is generally understood by one skilled in the art. As discussed above, the electro-magnetic field may affect tracking devices, such as the instrument tracking device <NUM> and/or the DRF tracking device <NUM>. The electro-magnetic field is sensed by the tracking devices <NUM>, <NUM> and a position of the tracking devices <NUM>, <NUM> may be determined relative to one another. The shell or case components <NUM>, <NUM> may be substantially inert and/or not affect the electro-magnetic field. In various embodiments the shell portions <NUM>, <NUM> may be substantially electrically resistive as well.

With continued reference to <FIG> and additional reference to <FIG>, the field shaping assembly <NUM> may include the magnetic or magnetically permeable portion or portions <NUM>, the substantially inert spacer portions <NUM>, and the conductive member <NUM>. As illustrated in <FIG>, <FIG>, the conductive member <NUM> may include a first surface <NUM> that has a surface area. The surface area of the surface <NUM> may be substantially continuous and extend or be defined by the length of a first edge <NUM> and a second edge <NUM>. As is generally understood in geometry, the surface area of the surface <NUM> may be the two lengths <NUM>, <NUM> multiplied together.

The magnetically permeable member <NUM> may be provided as a plurality of magnetically permeable members 82a, 82b, 82c, and 82d. Each of the magnetically permeable members <NUM> may be substantially similar or identical in size and may include respective first surfaces 270a, 270b, 270c, and 270d. Each of the surfaces <NUM> may include substantially similar surface areas and be bounded by respective edges <NUM> and <NUM>. Again, as understood in geometry, the surface area of the respective surfaces <NUM>, would be the dimension of the edge <NUM> multiplied by the dimension of the edge <NUM>.

The magnetically permeable members <NUM> may be sized and dimensioned to be positioned relative to each of the coil groups <NUM>, <NUM>, <NUM>, <NUM>. For example, with reference to <FIG>, the coils 32a, 32b, and 32c (illustrated in phantom) may be positioned on the structural member <NUM> on the coil array side <NUM>. The structural member may separate the coil 34a, 34b, 34c physically from the magnetically permeable member 82a, but a magnetic field produced by the coil group <NUM> may be affected by the magnetically permeable member 82a and the conductive member <NUM>. Again, it is understood that the coils 34a, 34b, 34c may be positioned about <NUM> degrees apart, such that the axis <NUM> extending through a center of the coil 34b and the center <NUM> and the second axis <NUM> extending through the center <NUM> and the center of the coil 34a are positioned at the angle <NUM> from one another. The angle <NUM> allows each of the coils 34a, 34b, 34c to be positioned around the center <NUM> separated by about <NUM>°.

It is further understood that the spacers <NUM> may be positioned between the conductive member <NUM> and each of the magnetically permeable members 82a, 82b, 82c, and 82d. It is understood that the spacer <NUM> may be provided as a large single spacer member that has a surface area that covers an area equivalent to an exterior dimension defined by all of the magnetically permeable members <NUM> and/or the conductive member <NUM>, alternatively or in addition thereto an individual spacer member may be provided for each of the magnetically permeable members <NUM>. The spacer member <NUM> is substantially inert to both electrical current and magnetic fields. The spacer member <NUM>, therefore, may be formed in a manner for efficient assembly and manufacturing, thus one spacer member may be provided for each of the magnetically permeable members <NUM>, rather than a single large spacer member.

The conductive member <NUM>, with additional reference to <FIG>, may be selected of an appropriately electrically conductive material. The electrically conductive material may include a copper sheet of high purity, such as copper sheet C101A-<NUM> that meets material standards ASTN F-<NUM>. The conductive sheet <NUM> may be an appropriate thickness <NUM> such as about <NUM> to about <NUM>, including about <NUM> to about <NUM>, , and further including about <NUM>. The conductive member <NUM> may further have the side <NUM> having a length of about <NUM> to about <NUM>, further including about <NUM> to about <NUM>, further including about <NUM> to <NUM>, and further including about <NUM>. The edge or side <NUM> may have a dimension of about <NUM> to about <NUM>, further including about <NUM> to about <NUM>, further including about <NUM> to about <NUM>, and further including about <NUM>.

The magnetically permeable members <NUM> may be selected from any appropriate highly magnetically permeable material that is substantially nonconductive and has high magnetic saturation as well as low magnetic coercivity and low frequency dispersion. For example, the magnetically permeable members may be formed of Finemet® nanoparticle crystalline material sold by Hitachi Metals, Ltd. having a place of business in Tokyo, Japan and Novi, Michigan. The magnetically permeable member <NUM> may include the Finemet® material having a manufacturer number MS-FR code FIAH0535. Generally, each magnetically permeable member <NUM> may be formed of a plurality of layers of the Finemet® nanoparticle crystalline material laminated together and held together with a selected adhesive. It is understood that magnetic permeable materials may include appropriate or selected materials such as Finemet® nanoparticle crystalline material, METGLAS® magnetic permeable materials Magnetic 2605SA1 or 2605HB1M Alloy sold by MetGlas, Inc. a division of Hitachi Metals America, Ltd.

The magnetically permeable members <NUM> may have a selected dimension including a length on the sides <NUM> and <NUM>. For example, the dimension of the side <NUM> may be about <NUM> to about <NUM>, further including about <NUM> to about <NUM> millimeters, and further including about <NUM>. The side <NUM> may include a length of about <NUM> to about <NUM>, further including a length of about <NUM> to about <NUM> and further including a dimension of about <NUM>. As discussed above, each of the magnetically permeable members 82a, 82b, 82c, and 82d may have substantially identical dimensions.

The magnetically permeable members <NUM> may be formed as a plurality of layers of the Finemet® magnetically permeable material laminated to one another. The number of laminated layers may be about <NUM> layers to about <NUM> layers, including about <NUM> layers to about <NUM> layers, and further including about <NUM> layers. In various embodiments, the number of layers may further include about <NUM> layers. The layers may be laminated together with a selected piece of material including a substantially electrically and magnetically inert adhesive material. The magnetically permeable members <NUM>, as illustrated in <FIG>, may further include a thickness <NUM> of about <NUM> to about <NUM>, and further including a thickness <NUM> of about <NUM>.

With reference to <FIG>, a schematic illustration of magnetic field lines from two coils, for example, coil 34a and 34b are illustrated. The coil 34a is schematically illustrated to produce the solid field lines <NUM> and the coil 34b includes the dashed field lines <NUM>. The coils 34a and 34b are illustrated in position above or near the field shaping assembly <NUM> and in the structural component <NUM>. The field shaping assembly <NUM> includes the components discussed above including the individual magnetically permeable members, such as the magnetically permeable member 82a and the conductive member <NUM> separated by the spacer member <NUM>. As illustrated in <FIG>, the coil group <NUM> is positioned near the magnetically permeable member 82a and the coil group <NUM> is positioned near the magnetically permeable member 82b. Further, the magnetically permeable members are separated by a space <NUM>. As illustrated in <FIG>, therefore, the field line <NUM>, <NUM> may interact with both the magnetically permeable member 82a and the electrically conductive member <NUM>. This allows for a selected diversity of vectors (e.g. different angles between two vectors at a single location in space) defined by the field lines <NUM>, <NUM>, also referred to as field line vectors or field vectors. A diverse field may include a field that has vectors that are about <NUM> degrees to about <NUM> degrees relative to one another, including about <NUM> degrees to about <NUM> degrees apart, and further including about <NUM> degrees and about <NUM> degrees apart.

In various embodiments, a single point or location in space <NUM> may be defined by two vectors, a first vector <NUM> that relates to a field line 300a that is produced by the coil 34a and a second vector <NUM> that is defined by a field line 320a produced by the coil 34b. The two vectors <NUM>, <NUM> have an angle <NUM> between them. This angle may be equal to or greater than <NUM> degrees to less than or equal to <NUM> degrees. The two vectors <NUM>, <NUM> are linearly dependent if the angle is equal to <NUM> degrees or <NUM> degrees. The two vectors <NUM>, <NUM> are linearly independent if the angle is greater than <NUM> degrees to less than <NUM> degrees. The two vectors <NUM>, <NUM> are orthogonal if the angle is equal to <NUM> degrees. The angle <NUM> between the vectors <NUM>, <NUM> may be used in the calculation of the location <NUM> in a three-dimensional space. The calculation of a position of the point <NUM> in a three-dimensional space may be similar to that as understood by one skilled in the art and may be based upon a previously determined representation, such as a look-up table, determined and stored based on calibrated field measurements at a plurality of locations in the navigation space, such as defined by the field lines <NUM>, <NUM>.

The angle <NUM> between the two vectors <NUM>, <NUM> relative to the lines <NUM> and <NUM> may be different than an angle <NUM> between two vectors <NUM> defined by a field line 300b and a vector <NUM> defined by a field line 320b. The different angle <NUM> between the two vectors <NUM>, <NUM> may allow for different information regarding a location <NUM> at the origin of the two vectors <NUM>, <NUM>. Additionally, as illustrated in <FIG>, the field lines <NUM>, <NUM> allow for a great diversity of measurable vectors at different locations relative to the coils 34a and 34b in the navigation space <NUM>. With additional reference to <FIG>, fields may be considered diverse and/or have a selected diversity if, over a set of different locations, a majority of field vector pairs at those different locations are orthogonal or near orthogonal. As an example thereof and/or alternative example, fields may be considered diverse if a majority, including a selected number, of field vector pairs have angles equal to or greater than a selected angle of approximately <NUM>° to less than or equal to <NUM>°minus the selected angle or approximately <NUM>°. As another example, fields may be considered diverse if a majority of field vector pairs have angles equal to or greater than approximately <NUM>°to less than or equal to about <NUM>°. Without being bound by the theory, but noting the angle range of these examples center around orthogonality at about <NUM>°. Also, diverse fields may provide accurate, precise, and reliable navigation. Fields may be considered not diverse if, over a set of different locations, a majority of field vector pairs at those different locations are linearly dependent or nearly linearly dependent. As an example, fields may be considered not diverse if a majority of field vector pairs have angles equal to or greater than approximately <NUM>° to less than or equal approximately <NUM>° or equal to or greater than approximately <NUM>° to less than or equal approximately <NUM>°.

In various embodiments, the field lines <NUM>, <NUM> may be substantially diverse and generally extend away from the field shaping assembly <NUM>, such as in the direction of arrow <NUM>. Therefore, the field lines <NUM>, <NUM> that, along with field lines and fields produced by all of the coils in the TCA <NUM>, may define the navigation space or the navigable volume. Therefore, the navigable space may generally be away from the field shaping assembly <NUM>. The field shaping assembly <NUM>, thus also allows any magnetic field interfering objects positioned generally away from the TCA <NUM>, such as on a side opposite the field shaping assembly <NUM> from the TCA <NUM>, to not substantially affect the navigable space generated in the direction of arrow <NUM>.

The TCA <NUM> generally may be operated to transmit in a power range of about <NUM> nano-Watts (nW) to about <NUM> milli-Watts (mW), including about less than <NUM> mW. It is understood, however, that the TCA <NUM> may be operated to transmit at any appropriate selected power.

With continued reference to <FIG> and further reference to <FIG>, a graphical representation of possible field diversities is illustrated in <FIG>. The y-axis represents a percentage of sensed field vectors pair angles over a set of locations and the x-axis represents an angles between two vectors that are determined. The diversity is the difference between two vectors having the same original in space, where the vectors are defined by the field lines of the field generated by the TCA <NUM>.

As illustrated in <FIG>, if a plurality of transmit coils, such as conductive transmit coils, such as the coils discussed above, are laid substantially flat on a plane without any field shaping the percentage of vectors measured at specific angles is illustrated by the graphical area <NUM>. As illustrated, there is substantially no angular diversity as nearly all vectors have near <NUM>° angular difference or near <NUM>° angular difference. This is understood by one skilled in the art that the field lines are produced substantially in one direction relative to the flat coil array and do not generate a high degree of diversity between field lines. For a coil array positioned in an orthogonal configuration with co-center positioned and orthogonally oriented coil trios, such as a coil array in the AxiEM™ electro-magnetic navigation system, a diversity is illustrated by the graphical area <NUM> and includes a greater diversity of angle differences between measured field lines from the configured coils. Finally, in various embodiments, the localizer <NUM>, including the TCA <NUM> and the field shaping assembly <NUM>, has a diversity illustrated by graphical representation <NUM> as having a large diversity. In other words, the curve of measured angle differences between two vectors at different points is orthogonal or near orthogonal and spread out and not inclusive of only a few angle differences. For example, angles between vectors measured based upon field lines produced by the localizer <NUM> may have an angle difference between them over a larger broad range, such as about <NUM> degrees to about <NUM> degrees between vectors measured at different points. The greater diversity of angles between vectors measured at different points provides additional or greater information for navigation of a tracking device used to measure the fields produced by the coil array <NUM>.

The localizer <NUM>, including the field shaping components <NUM>, is configured to generate the diversity of field lines or angles between vectors defined by field lines as discussed above. In particular, the magnetically permeable members <NUM> may absorb and redirect a portion of the magnetic field. For example, each layer of the magnetically permeable members <NUM> may absorb and redirect a certain amount of the field before becoming saturated. Generally the magnetically permeable member <NUM> is able to absorb and redirect substantially all of the magnetic field that comes in contact with it, but some of the field is from the coil 34a and coil group <NUM>, may leak over and effect the conductive member <NUM>. However, as noted above, each of the coil groups <NUM>, <NUM>, <NUM>, and <NUM> includes an individual magnetically permeable portion having a space <NUM> therebetween. Therefore, at least a portion of the field produced by the coil groups <NUM>, <NUM>, <NUM>, and <NUM> may interact with the conductive member <NUM>. When a magnetic field interacts with conductive member <NUM> eddy currents may be generated. In various embodiments, an eddy current may form around the magnetically permeable member <NUM> on the conductive member <NUM>.

The eddy currents may then also produce electro-magnetic fields that are generally generated and formed in the navigation space. The induced magnetic field produced by the conductive member <NUM> may be proportional to the time derivative of the field produced by the TCA <NUM>. The induced field produced by the eddy currents in the conductive member <NUM> may generally be, in terms of complex function of time as is understood by one skilled in the art, out of phase and about <NUM>° out of phase from those produced with the TCA <NUM>. As such, the induced field is diverse (e.g. orthogonal or near orthogonal) to the field produced with the TCA <NUM>. The field produced by the conductive member <NUM> due to the eddy currents may also be incorporated into navigation space and used by the navigation system <NUM> to determine location of the tracked member and tracking device, as discussed above.

With reference to <FIG>, a flowchart <NUM> is illustrated. The flowchart <NUM> may be incorporated in an algorithm that includes instructions that may be stored on a storage or memory system, such as a memory system of the navigation system <NUM>, as discussed further herein. The instructions may be executed by the navigation processor <NUM> or other appropriate processor. The flowchart <NUM> may allow for determining or navigating based upon the fields formed by the TCA <NUM> and fields generated due to the eddy currents in the conductive member <NUM>.

In the flowchart <NUM>, in a first block 395a a drive current is used to generate a magnetic field as a complex function of time by driving current into the coils of the TCA <NUM>. Each of the coils of the TCA <NUM> may be driven in various multiplexing manners to allow distinguishing between each field generated by each coil. Multiplexing may include frequency multiplexing, time multiplexing, code multiplexing, and/or combinations of multiplexing. After driving current to generate the field with the TCA <NUM>, a tracking device, such as the tracking device <NUM> of the instrument <NUM> may sense the total magnetic field as a complex function of time in block 395b.

The sensed total magnetic field may then be transferred to a processor system, for example the navigation processor <NUM>, as discussed above, which may include or access instructions to separate real and imaginary field components sensed by the tracking device in block 395b. It is understood that any appropriate processor system or processor specifically designed or a general purpose processor executing code may be used for separation of the real and imaginary components of the magnetic field. The separation of real and imaginary magnetic field components in block 395c may be based upon generally known computations, as is generally understood by one skilled in the art. The separation of the real and imaginary magnetic field components, however, allows for the sensed total magnetic field to be analyzed in further detail to allow for a greater accuracy of tracking the tracking device <NUM>. Further, by accounting for the real and imaginary magnetic field components, the field generated due to the eddy currents in the conductive member <NUM> may be used to provide additional field diversity and tracking information for navigation of the instrument <NUM>.

Accordingly, navigation of the instrument <NUM> by sensing the field with the tracking device <NUM> may allow for navigation over the real and imaginary magnetic field components in block 395d. As discussed above, and further herein, the navigation system <NUM> may be used to navigate the location of the instrument <NUM> by sensing the field generated by the localizer <NUM> which may include fields generated by the TCA <NUM> and fields generated due to eddy currents in the conductive member <NUM>. Moreover, the eddy currents generated in the conductive member <NUM> may be based upon the shape, size, and location of the magnetically permeable members <NUM> relative to the conductive member <NUM>. Accordingly, as discussed above, the shape and position of the coils of the TCA <NUM> and of the field shaping components <NUM> may generate a field that allows for navigation of the instrument <NUM>.

With reference to <FIG>, the localizer <NUM> may be used in the navigation system <NUM>, as discussed above. The localizer <NUM> may be positioned relative to a subject, such as a patient <NUM>, while a user <NUM> operates or moves the instrument <NUM> having the tracking device <NUM> associated therewith. The DRF <NUM> may be connected to the subject <NUM>. The subject <NUM> may be positioned near or adjacent the localizer <NUM>. The localizer <NUM> may be held and supported on a support <NUM>, such as an operating room table. The navigation system <NUM> may also include a second localizer, such as an optical localizer <NUM>.

Tracking information, including magnetic fields sensed with the tracking devices <NUM>, <NUM> may be delivered via a communication system, such as a coil array and tracking device controller <NUM> to the navigation processor <NUM>. Navigation processor <NUM> may be a part of a work station or computer system <NUM> that includes a display <NUM> to display an image <NUM>. Further, a tracked location of the instrument <NUM> may be illustrated as an icon <NUM> relative to the image <NUM>. Various other memory and processing systems may also be provided such as a memory system <NUM> in communication with the navigation processor <NUM> and an imaging processing unit <NUM>. The image processing unit <NUM> may be incorporated into imaging system <NUM>, such as the O-arm® imaging system, as discussed above. The imaging system <NUM> may be a x-ray imaging system including a x-ray source <NUM> and a detector <NUM> that are moveable within a gantry <NUM>. The imaging system <NUM> may also be tracked with a tracking device <NUM>.

Information from all of the tracking devices may be communicated to the navigation processors <NUM> for determining a location of the tracked portions relative to each other and/or for localizing the instrument <NUM> relative to the image <NUM>. The imaging system <NUM> may be used to acquire image data to generate or produce the image <NUM> of the subject <NUM>. It is understood, however, that other appropriate imaging systems may also be used. The coil array controller <NUM> may be used to operate and power the TCA <NUM> and the localizer <NUM>, as discussed above.

The localizer <NUM>, as discussed above, may include a various components including the TCA <NUM> that includes one or more coils positioned relative to one another and other components, such as the field shaping assembly <NUM>. As discussed above, the field shaping assembly <NUM> may be positioned within a holding structure and include various other portions such as one or more cover portions <NUM>, <NUM> and holding portions such as the structural or holding component <NUM>. As illustrated above, the localizer <NUM> includes the TCA <NUM> positioned on the structural component or positioner <NUM> relative to the field shaping assembly <NUM>. The field shaping assembly <NUM>, as discussed above and illustrated in <FIG>, includes a plurality of or portions such as the magnetic permeable member <NUM> positioned relative to a coil group, such as the coil group <NUM>. A plurality of the magnetic permeable members <NUM> are positioned spaced apart from one another relative to the single conductive member <NUM>. Accordingly the localizer <NUM> may include a plurality of coil groups in the TCA <NUM> that are positioned relative to a plurality of the magnetically permeable members <NUM> all positioned relative to the single or one conductive member <NUM>. It is understood, according to various embodiments, that the localizer <NUM> may include different configurations including the coil groups in the TCA <NUM>, the magnetic permeable members or single member <NUM>, and the conductive member <NUM>.

According to various embodiments, with reference to <FIG>, the localizer <NUM>, or other appropriate localizer, including those discussed further herein may include components or portions similar to the localizer <NUM> illustrated in <FIG>. According to various embodiments, however, the localizer may include different shapes and/or configurations of the TCA <NUM>, and/or the field shaping assembly <NUM>. For example, the field shaping assembly <NUM> may include a coil or coil group that may include one or more coils, such as a coil <NUM>. It is understood, that the discussion here of the coil <NUM> may refer to a plurality of coils, such as a plurality of coils in the coil groups, such as the coil group <NUM>, discussed above. Accordingly, the discussion of the coil <NUM> as a single coil is merely exemplary and the coil <NUM> and the related assembly may be repeated and selectively shaped, similar to the coils of the coil groups discussed above, to generate a selectively shaped (e.g. diverse) field that includes a selected or appropriate diversity, such as that discussed above.

With continuing reference to <FIG>, the coil <NUM> may be positioned within a cup or well field shaping assembly <NUM>. The field shaping assembly <NUM> may include a conductive member <NUM> and one or more spacer member portions <NUM>, as discussed above. It is understood that the spacer <NUM>, however, may be optional and is not necessary between the conductive member <NUM> and a well or cup magnetic permeable member or layer <NUM>. The conductive member <NUM> may be formed of materials, including those discussed above. Further, the magnetic permeable member <NUM> may also be formed of the similar materials as discussed above. THE cupped shape magnetic permeable member may be provided to shape and direct the transmitted field form the coil <NUM>, such as away from the coil <NUM>, but within the outer wall <NUM>.

The cupped magnetic permeable member <NUM> may include various portions or assemblies, such as a wall or upturned sidewall <NUM>. The upturned sidewall may extend from a bottom wall <NUM> over which the coil <NUM> is positioned. The sidewall <NUM> may be positioned or formed to surround the coil <NUM>. In addition to the sidewall <NUM> and the bottom wall <NUM>, a punt or central wall or extension <NUM> may also extend from the bottom wall <NUM> up to and/or through the coil <NUM>. As specifically illustrated in <FIG>, the punt wall <NUM> extends through the coil <NUM>. It may be possible that the punt wall <NUM> acts as a core for the coil <NUM>. It is understood, however, that the punt wall portion <NUM> may only extend a portion through or into the coil <NUM> as illustrated in Fanta <NUM>'.

The magnetic permeable member <NUM> may interact with a field transmitted or generated by the coil <NUM> in a manner similar to that discussed above. Given the shape and/or position of the magnetic permeable member <NUM> the field or field lines formed by the coil <NUM> may be positioned or shaped relative to the conductive member <NUM>.

In addition, the coil <NUM> may be positioned substantially perpendicular to the conductive member <NUM>. In other words, a central axis 534a or axis around which the coil <NUM> is wound, may be formed at an angle or positioned at an angle 534θ relative to a surface of the conductive member <NUM>. In various embodiments, the axis 534a may be substantially perpendicular such as the angle 534θ is <NUM> degrees or may be a non-<NUM> degree angle. For example, the angle 534θ may be about <NUM> degrees to about <NUM> degrees. As discussed above, positioning the coil <NUM> within the magnetic permeable member <NUM> may position or move the field formed by the coil <NUM> relative to the conductive member. It is further understood that the coil <NUM> and the magnetic permeable member <NUM> may be formed as a unit such that the punt wall <NUM> may be positioned along the axis 534a and may also be moved at the selected angle or position of the selected angle 534θ relative to the conductive member <NUM>.

With continuing reference to <FIG> and additional reference to <FIG> the cupped or well-shaped magnetic permeable member <NUM> may be selectively sized and/or shaped relative to the coil <NUM>. As illustrated in <FIG>, the magnetic permeable cup <NUM> includes a cup <NUM>' that includes a side wall <NUM>' that has a height <NUM>' from a bottom surface or plane, such as the bottom wall <NUM>'. The height <NUM>' may also be relative to a surface of the conductive member <NUM> and from the bottom wall <NUM>' is merely exemplary. However, the height <NUM>' may be less than a height <NUM> of the magnetic permeable <NUM>, illustrated in <FIG>. Further the magnetic permeable member <NUM>', according to various embodiments, does not and need not include the punt wall <NUM>. It is further understood that the spacer <NUM>, according to various embodiments, may include an air gap or space between the magnetic permeable member <NUM>' or magnetic permeable member <NUM> or <NUM>, and the respective conductive member.

The coil <NUM> may be positioned relative to the magnetic permeable member <NUM>' in any appropriate manner, such as with a spacer <NUM> which may be formed of a substantially inert material (e.g. non-conductive and/or non-magnetically interfering or distorting such as non-conductive cloth or other textile material or polymer material). The coil <NUM>, therefore, may be positioned relative to the magnetic permeable member <NUM>' to form a field relative to the conductive member <NUM>, as discussed above. The shape and position of the magnetic permeable member <NUM>', however, may influence or shape a field formed or transmitted by the coil <NUM>. Again, the spacer <NUM> may be selected with the position between the magnetic permeable member <NUM>' and the conductive member <NUM> or may be selectively not positioned. Further, the transmitted field from the coil <NUM> may induce a current in the conductive member <NUM> which then generates an induced field, as discussed above. The induced field may be diverse or have diverse components relative to the transmitted field. Shaping and/or angling the magnetic permeable member <NUM>' relative to the conductive member <NUM> may further create the diverse field.

With continuing reference to <FIG> and additional reference to 10D, a magnetic permeable member <NUM>" is illustrated. The magnetic permeable member <NUM>" includes a sidewall <NUM>" that has a height <NUM>" relative to a bottom wall <NUM>". Again the height <NUM>" may be different, such as less than, the height <NUM>' and/or the height <NUM>. In various embodiments, the height <NUM>" may be such that the sidewall <NUM>" includes an upper or terminal surface or edge <NUM> that is below a portion, such as any portion, including at least a top portion, of the coil <NUM>. Accordingly, it is understood that the magnetic permeable member <NUM> may be shaped relative to the coil <NUM>, or any appropriate coil for forming or shaping the localizer <NUM> to shape a selected field.

In addition to, or alternatively to the above described embodiments of the TCA <NUM> and the various coils and coil groups thereof, the localizer <NUM> may include embodiments as discussed and illustrated herein. It is understood that while an exemplary coil or coil group may be discussed, a plurality of each may be included in a single localizer, such as the localizer <NUM> discussed above.

Turning reference to <FIG> field shaping components, according to various embodiments, are illustrated. The field shaping components may include a substantially circular geometry, including a field shaping component or assembly <NUM> as illustrated in <FIG>. As illustrated in <FIG> a field shaping component or assembly <NUM> may include an elongated or oval shape, as discussed further herein. Further, as illustrated in <FIG> a field shaping component or assembly <NUM> that may include various shapes, such as a rounded triangle, rounded corner triangle, or other complex shapes. Accordingly, the field shaping component or assembly, such as the circular field shaping component <NUM>, the oval field shaping component <NUM>, or the complex shape field shaping component <NUM> may be included with the localizer <NUM>, or any appropriate localizer. As discussed above, each field shaping component or assembly may have a coil positioned relative thereto.

With additional reference to <FIG>, the field shaping component <NUM> may have positioned relative thereto a coil such as a coil <NUM>. The coil <NUM> may be positioned at a center <NUM> of the field shaping component <NUM>. It is understood, however, that a central axis (e.g. an axis around which the coil <NUM> is wound) may be positioned off center or away from the center <NUM> of the field shaping component. Nevertheless the field shaping component <NUM> may include a magnetic permeable member or portion <NUM> that has a radius 682r. The field shaping component <NUM> may also include additional portions or members, such as those discussed above, including a conductive layer portion <NUM>. As discussed above one or more spacer portions may be positioned between the magnetic permeable member <NUM> and the conductive member <NUM>. The field shaping component <NUM>, according to various embodiments including those also as discussed above, may further include a second or auxiliary magnetic permeable member or portion <NUM>. Accordingly, the field shaping component <NUM> may include the conductive member <NUM> positioned between the first magnetic permeable member <NUM> and the second magnetic permeable member <NUM>. Thus, the first magnetic permeable member <NUM> and the second magnetic permeable member <NUM> are on opposite or opposed sides of the conductive member <NUM>. It is understood, that various shapes of field shaping components may also include this construction or arrangement.

In various embodiments, the magnetic permeable member positioned on a side of a conductive member away from a coil transmitting a field may assist in absorbing additional field from the coil that would extend beyond the conductive member. For example, the second magnetic permeable member <NUM> may absorb field form the coil <NUM> that extends beyond the conductive member <NUM>. Therefore, an interfering object or object on a side of the conductive member away from the coil <NUM> is less likely or will not influence or have induced therein a current. It is understood, the second or auxiliary magnetic permeable member of the field shaping assembly according to various embodiments may produce the same or similar effect.

Further each of the members or components may be positioned relative to one another. For example, the conductive member <NUM> may include an area or region 690a that extends beyond an outer edge of the first magnetic permeable member <NUM> and the second magnetic permeable member <NUM> includes an area or region 696a that extends beyond an edge of the conductive member <NUM>. It is understood that the second magnetic permeable member <NUM> may be selected to be optional and need not be required or included in the field shaping component <NUM>. Further, according to various embodiments, a second magnetic permeable member may be included in any appropriate field shaping component assembly, including the field shaping assembly <NUM> (as illustrated in <FIG>) and/or other field shaping assemblies including the field shaping assembly <NUM> discussed above.

Turning reference to <FIG>, the field shaping component <NUM> may include a first magnetic permeable member <NUM> positioned over or relative to a conductive member or component <NUM> and a second magnetic permeable member <NUM>. As discussed above each of the respective members, such as the conductive member <NUM> and the second magnetic permeable member <NUM> may have an edge that extends beyond an edge of the member or portion above it. Accordingly the field shaping assembly <NUM> may again include the first magnetic permeable member <NUM> and the second magnetic permeable member <NUM> with the conductive member <NUM> therebetween. It is further understood, however, that the second magnetic permeable member <NUM> may be optional.

The field shaping component <NUM> may include or have positioned relative thereto a coil <NUM>. A center of the coil 734c may be positioned or offset from a center or point 782c of the first magnetic permeable member <NUM>. The shape of the first magnetic permeable member <NUM> may include a first distance or radius 782r' and a second distance or radius 782r". The two radii 782r', 782r" may be different to provide or give a selected shape to the magnetic permeable member <NUM>. Further the coil <NUM> may be positioned that a center or central axis 784c may be positioned at the point 782c. Positioning the coil <NUM> relative to or at a different location on the magnetic permeable member <NUM> may be selected to achieve a selected shape of a field formed by the coil <NUM>, as discussed above, to include or create a selected field diversity.

Turning reference to <FIG>, the field shaping assembly <NUM> may include a first magnetic permeable member <NUM>, a conductive member <NUM>, and a second magnetic permeable member <NUM>. Again, the second magnetic permeable member <NUM> may be optional, but if selected the conductive member <NUM> may be positioned between the first magnetic permeable member <NUM> and the second magnetic permeable member <NUM>. The shape of the first magnetic permeable member <NUM> may be a selected shape such as a complex shape including a generally triangular portion 882t and a rectangular portion 882r. The first magnetic permeable member <NUM> may be formed as a single piece but including the selected shape as illustrated in <FIG>. It is understood, however, as discussed further herein, that the field shaping assembly may have an appropriate shape to achieve a selected diversity. Accordingly, a coil <NUM> may be positioned such that a center or central axis 834c is positioned in one of the regions of the magnetic permeable member <NUM>, such as in the triangular 882t. Further, the connective member <NUM> may extend beyond an external edge or parameter of the first magnetic permeable member <NUM> and the second permeable member <NUM> may extend beyond a parameter of the connective member <NUM>.

As illustrated in <FIG> the respective coils <NUM>, <NUM>, <NUM> include substantially round perimeters or cylindrical shapes. Accordingly distance from the respective centers to the outer perimeters of the respective coil <NUM>, <NUM>, <NUM> may be substantially uniform around the outer perimeters of the coil. It is understood, however, that the coils may include non-circular or cylindrical shapes, including oval or asymmetrical shapes, as discussed above. Further, as also illustrated in <FIG> and as exemplary described and discussed relative to <FIG> the respective coils may be positioned at asymmetrical or non-central locations of the respective field shaping assemblies.

With reference to <FIG> a field shaping component may include a single coil positioned relative thereto. In various embodiments, however, a plurality of coils may be positioned relative to the respective field shaping assemblies. Also, the plurality of coils may be placed asymmetrically, such as not equidistant apart or from edges, of the respective field shaping assemblies.

As illustrated in <FIG> selected field shaping assemblies may include a plurality of coil positioned relative thereto, as discussed above as illustrated in <FIG>. With additional reference to <FIG> a field shaping assembly <NUM> is illustrated. The field shaping assembly <NUM> may include a first magnetic permeable member <NUM> and a conductive member <NUM>. Again, the field shaping assembly <NUM> may include an optional second magnetic permeable member <NUM> wherein the conductive member <NUM> is positioned between the first magnetic permeable member <NUM> and the second magnetic permeable member <NUM>. The field shaping assembly <NUM> may have a selected shape, such as a substantially triangular shape. Further a coil group may include a first coil 934a, a second coil 934b, and the third coil 934c. Each of the coils 934a, 934b, and 934c may be positioned away from a center and/or near a corner of the triangle. Each of the coils 934a, 934b, 934c may have a respective center and may be substantially round or cylindrical shaped. The coils, however, may generate a field that is substantially diverse due to the field shaping assembly <NUM>, as discussed above.

Turning reference to <FIG> a field shaping assembly <NUM> is illustrated. The field shaping assembly <NUM> may be substantially rectangular and include a first magnetic permeable member <NUM> and a conductive member <NUM>. Again an optional second magnetic permeable member <NUM> may be positioned such that the conductive member <NUM> is between the first magnetic permeable member <NUM> and the second magnetic permeable member <NUM>. As discussed above each of the respective members <NUM> and second permeable member <NUM> may have an outer parameter that extends a selected distance or area beyond the adjacent or next layer. Further, selected spacers may be positioned between each of the respective layers <NUM>, <NUM>, <NUM> as discussed above.

Positioned relative to the first magnetic permeable member <NUM> may be a coil group including a first coil 1034a, 1034b, and 1034c. Each of the coils may be elongated or ellipsis or oval in shape rather than round. Accordingly, each of the coils 1034a, 1034b, and 1034c may generate or transmit a field relative to the field shaping assembly <NUM> that is different than a field generated by a cylindrical or round coil. Again the respective shape of the coils and the field shaping assembly <NUM> may affect or generate a selectively diverse field as discussed above.

As discussed and illustrated in <FIG>, <FIG>, and in various embodiments as discussed above, different portions of the field shaping assemblies may be substantially independent of other field shaping assembly portions. In various embodiments, as illustrated in <FIG>, a plurality of coil groups may be positioned relative to a plurality of separated magnetic permeable members <NUM> that are all positioned on a single or unitary conductive member <NUM> of the field shaping assembly <NUM>. It is understood that alternative embodiments and/or additional embodiments may be used either alone or in combination with the field shaping assembly <NUM> or as otherwise understood by one skilled in the art.

Turning reference to <FIG>, a field shaping assembly <NUM> is illustrated. The field shaping assembly <NUM> includes various portions such as a first magnetic permeable member <NUM>, a conductive member <NUM>, and a second magnetic permeable member <NUM>. The first magnetic permeable member <NUM> may be provided as one or more members that are formed as substantially single units or members that are spaced apart from one another, such as a first spacing <NUM> and a second spacing <NUM>, but positioned over or on the connective member <NUM>. Accordingly, as illustrated in <FIG> the conductive member <NUM> may have an external edge <NUM> that extends beyond an external edge of any one of the member <NUM>, which may include four magnetic permeable members 1182a, 1182b, 1182c, or 1182d. The conductive member <NUM> may be provided or formed as a single piece. As a single piece the conductive member <NUM> is conductive throughout its area.

The first magnetic permeable members <NUM> positioned on or over the conductive member <NUM> may be similar to the embodiment illustrated in <FIG>. It is understood, however, that various spacers may also be positioned between the magnetic permeable members <NUM> and the conductive member <NUM>. As illustrated in <FIG>, however, an alternative second magnetic permeable member <NUM> may be positioned on an opposite side of the conductive member <NUM> from the first magnetic permeable members <NUM>. An external or outer parameter <NUM> of the second magnetic permeable member <NUM> may extend beyond the outer parameter <NUM> of the conductive member <NUM>. It is understood, however, that the second magnetic permeable member <NUM> may be provided as a single member that extends as a single member or formed as a single member within the parameter <NUM> of the magnetic permeable member <NUM>.

It is further understood, however, that a second magnetic permeable member <NUM> may be optional and is not required. Further it is understood that the first magnetic permeable members <NUM> may be provided in any appropriate number and four is merely exemplary. Further the field shaping assembly <NUM> may be provided as a portion of the localizer <NUM>, as discussed above, including the TCA <NUM> and/or a TCA <NUM> as illustrated in <FIG>. The TCA <NUM> may include a plurality of coil groups such as a first coil group <NUM>, a second coil group <NUM>, a third coil group <NUM>, and a fourth coil group <NUM>. Each of the coil groups may include a selected number of coils, such as three coils illustrated in <FIG>, including the three coils 1134a, 1134b, and 1134c of the first coil group <NUM>; a first coil 1136a, a second coil 1136b, and a third coil 1136c of the second coil group <NUM>; a first coil 1138a, a second coil 1138b, and a third coil 1138c of the third coil group <NUM>; and a first coil 1140a, a second coil 1140b, and a third coil 1140c of the fourth coil group <NUM>. If less than four of the magnetic permeable members <NUM> are provided, less coil groups may also be provided. Nevertheless, each of the coils of the respective coil groups <NUM> - <NUM> may generate a field relative to the field shaping assembly <NUM>.

The field shaping assembly <NUM>, however, in combination with the TCA <NUM> may generate the selectively diverse field as discussed above. The field shaping assembly <NUM> may include various features such as shapes of the first conductive member <NUM>, including those discussed above, or any appropriate shape. Further, the field diversity may be achieved by positioning the coils of the TCA <NUM> relative to the first magnetic permeable members <NUM> in a selected or appropriate manner to achieve the selected diversity. For example, asymmetrically placing the coils relative to the first magnetic permeable members <NUM> may achieve the appropriate or selected diversity of the field. Also, as discussed above, a portion of the transmitted field that extends beyond the first magnetic permeable members <NUM> may induce a current in the conductive member <NUM>, which, in turn, will generate an induced field.

Accordingly, although rectangular members are illustrated in <FIG>, it is understood that the first conductive members <NUM> may be circular, trapezoidal, or other appropriate shape even if placed on the conductive member <NUM> that is substantially rectangular. Moreover, the conductive member <NUM> may be provided as individual separated members such as the conductive member <NUM> not being provided as a single unitary member, but as at least two members that are positioned between the first magnetic permeable members <NUM> and the first magnetic permeable members <NUM> with the one or more conductive members <NUM> therebetween. It is further understood, however, that the second magnetic permeable member <NUM> is optional and therefore two or more conductive members <NUM> may be positioned relative to the first magnetic permeable members <NUM> to form the field shaping assembly <NUM> with the TCA <NUM>.

Further the selected coils of the coil groups <NUM> - <NUM> of the TCA <NUM> may be selectively shaped, such as oval, round, cylindrical, or other appropriate shape relative to selected field shaping members of the field shaping assembly <NUM>. It is further understood that the TCA <NUM> may include the connections and controls, as discussed above, for driving and otherwise operating a localizer <NUM>. The coils of the TCA <NUM> are shown relative to the field shaping assembly <NUM> as merely exemplary and being shown without the other portions of the localizer assembly.

Accordingly, as discussed above, the TCA according to various embodiments, including those discussed above in combination and/or alternatively to one another, may be used to generate a field. A field shaping assembly, also according to various embodiments including those discussed above as alternatives or in addition to one another, may be used to shape the field selectively. The shaped field achieves a selected diversity, as also discussed above, to allow for tracking of a selected sensor within a navigation domain or volume. The diversity provides for or allows for a plurality of vectors that are orthogonal or substantially orthogonal to one another to assist in increased accuracy and/or speed in determining a location of the tracking device. In various embodiments, a transmitted field may be or is diverse relative to an induced field (i.e. generated from an induced current in a conductive member). Accordingly, the tracking coil or other sensor that has been tracking space with the navigation domain may be resolved substantially precisely or accurately in three-dimensional space including an X,Y,Z position and orientation, including at least one of yaw, pitch, or roll.

The field shaping assembly, such as the field shaping assembly <NUM>, or according to any appropriate embodiment including those discussed above, may include the magnetic permeable members of the materials discussed above and the conductive member of the materials discussed above. Accordingly, various embodiments are discussed that may be combined or provided as alternatives to one another. Nevertheless, the field shaping assemblies, as discussed herein, may operate to substantially reduce or eliminate distortion or interference that may be introduced by a conductive member other than the field shaping assembly. Therefore, tracking of the tracking device in the navigational domain may be substantially immune to various members or materials that may affect the field produced by the TCA.

Claim 1:
A navigation system having a localizer, comprising:
a transmitting coil array (<NUM>) including at least one coil of conductive material operable to generate a transmitted magnetic field; and
field shaping assembly (<NUM>), comprising:
a conductive member (<NUM>) having a first surface with a first area; and
a first magnetic permeable member (<NUM>) having a second surface (<NUM>) with a second surface area;
wherein the field shaping assembly and the transmitting coil array cooperate to generate a selectively diverse field; and characterized in that:
the field shaping assembly further comprises:
a second magnetic permeable member (<NUM>) having a third surface with a third surface area;
wherein the conductive member (<NUM>) is positioned between the first magnetic permeable member (<NUM>) and the second magnetic permeable member (<NUM>)