System and method for navigation

Abstract

A surgical navigation system includes a controller operable to generate a signal, a localizer coil formed of an electrically conductive material, an H-bridge switching system interconnecting the controller and the localizer coil, wherein the localizer coil is operable to emit a tracking signal from the controller when connected via the H-bridge.

Description

[0001] Cross Reference to Related Applications

[0002] This application includes subject matter similar to that disclosed in concurrently filed U.S. Patent Application No. 16 / 855,487 (Attorney Docket No. 5074A-000191-US) and U.S. Patent Application No. 16 / 855,573 (Attorney Docket No. 5074A-000226-US). The entire disclosures of the above applications are incorporated herein by reference. TECHNICAL FIELD

[0003] The present disclosure relates to data communication in a navigation system. BACKGROUND

[0004] This section provides background information relating to the present disclosure and is not necessarily prior art.

[0005] A surgical procedure can be performed on a subject, such as a human subject. The surgical procedure can require an incision into the subject to gain access to tissue or organs covered by the dermal layer of the subject. Visual access or visual acuity in these areas can be limited due to being covered by opaque tissue. Accordingly, determining a pose of an instrument within the subject can be selected. SUMMARY

[0006] This section provides a general summary of the disclosure and is not a comprehensive disclosure of its full scope or all of its features.

[0007] A navigation system can be used to track and determine a pose, which can include at least some coordinates of a position and / or orientation of an instrument over time. In various embodiments, a pose of an instrument is understood to include at least some tracked or navigated position coordinates (e.g., x, y, z) and / or orientation coordinates (e.g., roll, pitch, yaw). The navigation system can track position and / or orientation, including six degrees of freedom motion (e.g., three-dimensional position and multiple (e.g., pitch, roll, and yaw) orientations). Accordingly, a pose or position and / or orientation of a tracked instrument can be determined over time. In various embodiments, a visual representation of the instrument can be shown relative to a portion of a subject by a display device.

[0008] Accordingly, a navigation system can be used to determine a position and / or orientation and / or combination (as a pose), including multiple positions and / or orientations and / or poses of an instrument over time. In various embodiments, a pose of a tracked instrument can be determined relative to a subject. The subject can be any appropriate subject, such as a living or non-living subject. In various embodiments, a non-living subject can include a hollow or enclosed shell or other appropriate inanimate object. The inanimate object can have an opaque outer covering. Accordingly, a navigation or tracking system can be used to track an instrument relative to the inanimate object during use.

[0009] In various embodiments, the subject can include a living subject, such as a human subject. The procedure can include a surgical procedure in which an instrument is placed within the subject over a selected period of time to perform the procedure, such as stent placement, deep brain stimulation probe placement, or placement or implantation of other implantable components. Further, the selected procedure can include resection, hole formation, etc. relative to a bone of the subject. Regardless, the pose of the instrument can be determined by the navigation system.

[0010] The navigation system can operate by transmitting data between various elements or portions of the tracking system. For example, in various embodiments, the navigation system can include a tracking device connected with the instrument (e.g., fixed or incorporated into the instrument) that wirelessly transmits a signal to an array. The array can include an antenna array, as discussed further herein. Similarly or alternatively, the array can wirelessly transmit a signal to be received by the tracking device.

[0011] Spread spectrum, which can include various techniques as discussed herein, can be used to transmit signals, determine distorted signals, and ignore and / or correct for distorted signals. Spread spectrum systems, such as frequency hopping, can include modulation and demodulation of selected signals, as well as selected signal transformations for identifying or eliminating distortion or distorted signals within the system. Accordingly, the navigation system can incorporate spread spectrum systems to identify or determine signals for the tracking devices.

[0012] Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0013] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure.

[0014] Figure 1 is a diagrammatic view showing an overview of a navigation system according to various embodiments;

[0015] Figure 2 is a flowchart of a registration method according to various embodiments;

[0016] Figure 3 is a schematic view of a localizer and a tracker according to various embodiments;

[0017] Figure 4A is a flowchart of equalization in a spread spectrum navigation system according to various embodiments;

[0018] Figure 4B is Figure 4A a schematic view of a navigation system calibration and equalization method of

[0019] Figure 5A is a flowchart of equalization in a spread spectrum navigation system according to various embodiments;

[0020] Figure 5B is Figure 5A is a schematic of a navigation system calibration and equalization method of

[0021] Figure 6A is a flowchart of equalization in a spread spectrum navigation system according to various embodiments;

[0022] Figure 6B is Figure 6A is a schematic of a navigation system calibration and equalization method of

[0023] Figure 7 is a plot of a magnitude response of a non-equalized received navigation signal according to various embodiments;

[0024] Figure 8 is a plot of a magnitude response of a non-equalized received navigation signal with and without a distorting article according to various embodiments;

[0025] Figure 9 is a flowchart of a code multiplexed spread spectrum navigation system with distortion detection and correction according to various embodiments; and

[0026] Figure 10 is a plot of a magnitude response of an equalized received navigation signal in the presence of a distorting article according to various embodiments.

[0027] Corresponding reference numerals in the several figures indicate corresponding parts throughout the figures. DETAILED DESCRIPTION

[0028] Exemplary embodiments will now be described more fully with reference to the accompanying drawings.

[0029] Exemplary embodiments are disclosed herein, as further discussed herein. Generally, various embodiments can be disclosed with respect to a human subject. However, it should be understood that various disclosed systems, such as navigation or tracking systems, can be used with respect to any subject or system that can have an outer shell or housing that can encompass internal components or operations. For example, a body or a car frame can shield internal components that can be selected to operate in a selected procedure. The selected procedure can include removal, replacement, etc. of various components of any non-living or inanimate system. Thus, it should be understood that the discussion herein with respect to a subject, such as a human subject, is merely exemplary.

[0030] Further, as discussed herein, a navigation system can include tracking various components (such as instruments) relative to a coordinate system or frame of reference within a space. In various embodiments, the coordinate space can include an object coordinate space or a real space defined relative to a real space of an object. Additional coordinate spaces can include an image space having an image coordinate space that defines an image of an object. As discussed above, a pose of an instrument, which can include a position and orientation of the instrument, can be shown (e.g., superimposed on) relative to an image having a graphical representation for a user to view. Such a graphical illustration can require or use a registration between the object space or object coordinate space and the image coordinate space or image space.

[0031] Methods for registering an object space defined by an object to an image space can include those disclosed in U.S. Patent No. 8,737,708; U.S. Patent No. 9,737,235; U.S. Patent No. 8,503,745; and U.S. Patent No. 8,175,681; all of which are incorporated by reference herein.

[0032] According to various embodiments, Figure 1 is a diagrammatic view showing an overview of an operating room or surgical environment. In various embodiments, the operating room can include a surgical suite. The surgical suite can include a navigation system 26, which can be used for various procedures, such as procedures relative to an object 30.

[0033] The navigation system 26 can be used to track the pose of one or more tracking devices, and the tracking devices can include an object tracking device or dynamic reference frame (DRF) 58, an imaging system tracking device 62, and / or a tool tracking device 66. It should be appreciated that other tracking devices can also be included, such as a user or clinician tracking device, either alone or in combination with other systems (e.g., an augmented reality system). The tool 68 can be any suitable tool, such as a drill bit, a forceps, or other tool operated by a user 72. The tool 68 can also include an implant, such as a spinal implant or an orthopedic implant. It should be further noted that the navigation system 26 can be used to navigate any type of instrument, implant, or delivery system, including: a guidewire, an arthroscopic system, an orthopedic implant, a spinal implant, a deep brain stimulation (DBS) probe, etc. Further, these instruments can be used to navigate or map any region of the body. The navigation system 26 and various instruments can be used in any appropriate procedure, such as a generally minimally invasive procedure or an open procedure.

[0034] The imaging device 80 can be used to acquire pre-operative, intra-operative, or post-operative or real-time image data of an object, such as the object 30. However, it should be appreciated that any appropriate object can be imaged, and any appropriate procedure can be performed relative to the object. In the illustrated example, the imaging system 80 includes an O-Arm® sold by Medtronic Navigation, Inc., having a place of business in Louisville, Colorado, USA. Imaging device. The imaging device 80 can have a generally annular gantry housing 82 in which image capture portions are movably placed. The image capture portions can include x-ray sources or emitting portions, and x-ray receiving portions or image receiving portions are positioned generally or actually as close to 180 degrees from each other as possible, and mounted on a rotor relative to a track or rail. The image capture portions can be used to rotate 360 degrees during image acquisition. The image capture portions can rotate about a center point or axis, allowing image data of the object 30 to be acquired from multiple directions or in multiple planes. The imaging device 80 can include those disclosed in U.S. Patent Nos. 7,188,998; 7,108,421; 7,106,825; 7,001,045; and 6,940,941; all of which are incorporated herein by reference, or any appropriate portions thereof. In one example, the imaging device 80 can utilize flat panel technology having a 1,720 x 1,024 pixel viewable area.

[0035] The position of the imaging device 80 and / or portions therein, such as the image capture portions, can be known precisely relative to any other portions of the imaging device 80. According to various embodiments, the imaging device 80 can know and recall precise coordinates relative to a fixed or selected coordinate system. This can allow the imaging system 80 to know its position relative to the patient 30 or other reference. Additionally, as discussed herein, the precise knowledge of the position of the image capture portions can be used in conjunction with a tracking system to determine the position of the image capture portions and image data relative to a tracked object, such as the patient 30, etc.

[0036] The imaging device 80 can also be tracked with the image tracking device 62. According to various embodiments, image data defining an acquired image space of the patient 30 can be registered inherently or automatically relative to a target space. The target space can be a space defined by the patient 30 in the navigation system 26. The automatic registration can be achieved by including the tracking device 62 and / or determinable precise pose of the image capture portions on the imaging device 80. According to various embodiments, as discussed herein, imageable portions, virtual fiducials, and other features can also be used to allow automatic or otherwise registration. It will be understood, however, that image data of any object defining an object space can be acquired. The patient space is an exemplary object space. The registration allows mapping between the patient space and the image space.

[0037] The patient 30 can also be tracked using a patient tracking device, a DRF, or a tracker 58 while the patient is moving. Alternatively or additionally, the patient 30 can be immobilized within a navigation space defined by the navigation system 26 to allow for registration. As discussed further herein, registration of the image space to the patient space or object space allows for the use of image data to navigate an instrument 68. Various tracking systems, including at least one of an optical localizer 88 or an electromagnetic (EM) localizer 94, can be used to track the instrument 68. As discussed herein, in various embodiments, the localizer 94 can emit signals that are received by the tracking device 66 or other appropriate tracking device. Further, appropriate antennas (e.g., coils) can also be disposed to receive. For example, a calibration receiver 95 (e.g., coil) can be disposed to receive signals from the localizer 94. The calibration receiver 95 can be included in any appropriate portion of the navigation system 26, such as the controller 110, as discussed further herein. It will be appreciated by those skilled in the art that the calibration receiver 95 need not be incorporated into the navigation system 26 during use, but can be disposed or used during initial (e.g., factory) production or calibration of the navigation system 26. In various embodiments, the calibration receiver 95 can receive signals from the localizer 94 in a similar manner as the tracking device 66 and for various purposes, as discussed herein.

[0038] More than one tracking system can be used to track the instrument 68 in the navigation system 26. According to various embodiments, the tracking system can include an EM system with an electromagnetic tracking (EM) localizer 94 and / or an optical tracking system with an optical localizer 88. As discussed herein, either or both of the tracking systems can be used to track selected tracking devices. It will be appreciated that, unless otherwise discussed, a tracking device can be a trackable portion with the selected tracking system. The tracking device need not refer to the entire member or structure to which the tracking device is attached or associated.

[0039] It will also be appreciated that the imaging device 80 can be an imaging device other than an imaging device of the imaging device, and can additionally or alternatively include a fluoroscopic C-arm. Other exemplary imaging devices can include fluoroscopic machines, such as bi-plane fluoroscopic systems, ceiling mounted fluoroscopic systems, catheter lab fluoroscopic systems, fixed C-arm fluoroscopic systems, isocentric C-arm fluoroscopic systems, 3D fluoroscopic systems, etc. Other suitable imaging devices can also include MRI, CT, ultrasound, etc.

[0040] In various embodiments, the imaging device controller 96 can control the imaging device 80 and can receive image data generated at the image capture portion and store the images for later use. The controller 96 can also control rotation of the image capture portion of the imaging device 80. It should be appreciated that the controller 96 need not be integral with the gantry housing 82, but can be separate therefrom. For example, the controller can be part of the navigation system 26, which can include a processing system and / or control system 98 that includes a processing unit or processing portion 102. However, the controller 96 can be integrated with the gantry 82 and can include a second processor and separate processor, for example, in a laptop computer.

[0041] The patient 30 can be positioned, including immobilized, on a surgical table 104. According to one example, the surgical table 104 can be an Axis® surgical table sold by OSI, a division of Mizuho Ikakogyo Co., Ltd., having a place of business in Tokyo, Japan, or by Orthopedic Systems, Inc., having a place of business in California, USA. The surgical table. Patient positioning devices can be used with the surgical table and include clamps or those set forth in U.S. Patent Application Publication No. 2004 / 0199072, entitled "An Integrated Electromagnetic Navigation And Patient Positioning Device," published October 7, 2004 (U.S. Patent Application No. 10 / 405,068), which is hereby incorporated by reference.

[0042] Accordingly, the position of the patient 30 relative to the imaging system 80 can be determined by the navigation system 26. The tracking device 62 can be used to track at least a portion of the imaging device 80, such as the gantry or housing 82, and determine its pose. As discussed further herein, the patient 30 can be tracked with the dynamic reference frame 58. Accordingly, the position of the patient 30 relative to the imaging system 80 can be determined. Moreover, due to the precise position of the imaging portion on the rail within the housing 82, the substantially inflexible rotor, etc., the pose of the imaging portion can be determined relative to the housing 82. If the imaging device 80 is an O-Arm® imaging device sold by Medtronic Navigation, Inc., having a place of business in Louisville, Colorado, the imaging device 80 can include a precision of within 10 microns, for example. Precise positioning of the imaging portion is further described in U.S. Patent Nos. 7,188,998; 7,108,421; 7,106,825; 7,001,045; and 6,940,941; all of which are incorporated herein by reference.

[0043] ​According to various embodiments, the imaging device 80 can generate and / or emit x-rays from an x-ray source that propagate through the patient 30 and are received by an x-ray imaging receiving portion. An image capture portion generates image data representative of the received x-ray intensity. Typically, the image capture portion can include an image intensifier that first converts the x-rays to visible light and a camera (e.g., charge-coupled device) that converts the visible light to digital image data. The image capture portion can also be a digital device that converts the x-rays directly to digital image data to form an image, potentially avoiding distortions due to first conversion to visible light.

[0044] Two-dimensional and / or three-dimensional fluoroscopic image data that can be taken by the imaging device 80 can be captured and stored in the imaging device controller 96. Multiple image data acquired by the imaging device 80 can also be captured and combined to provide a greater view or image of an entire region of the patient 30, rather than just a portion of the patient 30. For example, multiple image data of the spine of the patient 30 can be appended together to provide a complete view or complete set of image data of the spine.

[0045] The image data can then be forwarded from the image device controller 96 to the navigation computer and / or processor system 102, which can be part of the controller or workstation 98 having the display 84 and user interface 106. It is also understood that the image data need not be first saved in the controller 96, but can be transferred directly to the workstation 98. The workstation 98 can provide facilities for displaying the image data as images 108 on the display 84 and for saving, digitally processing, or printing hard copy images of the received image data. The user interface 106, which can be a keyboard, mouse, touch pen, touch screen, or other suitable input device, allows the user 72 to provide input to control the imaging device 80 via the image device controller 96 or to adjust the image settings of the display 84. The workstation 98 can also instruct the image device controller 96 to adjust the image capture portion of the imaging device 80 to obtain various two-dimensional images along different planes to generate representative two-dimensional image data and three-dimensional image data.

[0046] With continued reference to Figure 1 , the navigation system 26 can also include a tracking system that includes one or both of an electromagnetic (EM) locator 94 and / or an optical locator 88. The tracking system can include a controller and interface portion 110. The controller 110 can be connected to a processor portion 102, which can include a processor contained within a computer. The EM tracking system can include an AXIEM® system sold by Medtronic Navigation, Inc., having a place of business in Louisville, Colorado. The optical tracking system can include a POLARIS® system sold by Northern Digital, Inc., having a place of business in Waterloo, Ontario, Canada. AXIEM TMThe navigation system; or can be an EM tracking system as described in U.S. Patent Application Serial No. 10 / 941,782, filed September 15, 2004, and entitled "METHOD AND APPARATUS FOR SURGICAL NAVIGATION"; U.S. Patent No. 5,913,820, issued June 22, 1999, and entitled "POSITION LOCATION SYSTEM"; and U.S. Patent No. 5,592,939, issued January 14, 1997, and entitled "METHOD AND SYSTEM FOR NAVIGATING A CATHETER PROBE"; each of which is incorporated herein by reference. It will be appreciated that the navigation system 26 can also be or include any appropriate tracking system, including optical localizers having or S7 TM A tracking system, which can be used as the optical localizer 88, and is sold by Medtronic Navigation, Inc. of Louisville, Colorado. Other tracking systems include acoustic systems, radiological systems, radar systems, etc. The tracking system can be used in accordance with generally known or described techniques in the references incorporated above. Unless selected operations of the subject disclosure are elucidated, details will not be included herein.

[0047] Wired or physical connections can interconnect the tracking system, imaging device 80, etc. Alternatively, rather than being directly coupled to the controller 110, individual portions such as the instrument 68 can employ wireless communication channels, such as disclosed in U.S. Patent No. 6,474,341, issued November 5, 2002, and entitled "SURGICAL COMMUNICATION POWER SYSTEM", which is incorporated herein by reference. Further, the tracking devices 62, 66 can generate fields and / or signals that are sensed by the localizers 88, 94. In various embodiments, the instrument tracking devices 66 and / or other appropriate tracking devices can communicate with the controller 110 and / or the array 94 by wireless signals 113 as discussed herein. In various embodiments, the array 94 can operate by a spread spectrum signal to communicate with the tracking devices 66.

[0048] Various portions of the navigation system 26, such as the instrument 68, and others described in detail below, can be equipped with at least one and typically a plurality of tracking devices 66. The instrument can also include more than one type or modality of tracking devices 66, such as EM tracking devices and / or optical tracking devices. The instrument 68 can include a graspable or steerable portion at a proximal end, and the tracking devices can be secured near the steerable portion of the instrument 68. However, it will be appreciated that the tracking devices can also be placed at a distal or intervention end of the instrument 68.

[0049] Another representative or alternative positioning and tracking system is set forth in U.S. Patent No. 5,983,126, issued November 9, 1999, entitled "Catheter Location System and Method," which is hereby incorporated by reference herein. The navigation system 26 can be a hybrid system that includes components from various tracking systems.

[0050] According to various embodiments, the navigation system 26 can be used to track the instrument 68 relative to the patient 30. The instrument 68 can be tracked by the tracking system, as discussed herein, such as by tracking and determining the pose of the tracking devices 66. Image data of the patient 30 or a suitable subject can be used to assist the user 72 in guiding the instrument 68. However, the image data is registered to the patient 30. The image data defines an image space that is registered to a patient space defined by the patient 30. The registration can be performed automatically, manually, or a combination thereof, as discussed herein.

[0051] In general, the registration allows for generation of a mapping of the physical pose of the instrument 68 relative to the image space of the image data (also referred to as a registration mapping). The mapping allows for display of the tracked pose of the instrument 68 relative to the image data 108 on the display device 84. It will be appreciated that the display device 84 can be any suitable display device, or include more than a single display device, such as including an augmented reality viewer, a head mounted display, etc. A graphical representation 68i (also referred to as an icon) can be used to illustrate the pose of the instrument 68 (e.g., a three-dimensional coordinate position and one or more degrees of freedom orientation) relative to the image 108.

[0052] With continuing reference to Figure 1 and with further reference to Figure 2 , the subject registration system or method can use a subject tracking device 58. The tracking device 58 can include a trackable portion or member 120, but can also function as or be operable as a fiducial assembly. The fiducial assembly 120 can include a fixture or other fixed portion 124 and an imageable fiducial body 120. However, it will be appreciated that the member 120 can be separate from the tracking device 58. The fixed portion 124 can be provided to fix any suitable portion, such as a portion of an anatomical structure. As discussed herein, the imageable fiducial body 120 can be imaged to determine a pose of the member 120 relative to the image data 108. The pose of the member 120 can be determined by the navigation system 26, such as by the tracking system 28. Figure 1As shown, fiducial assembly 120 can be interconnected with a portion of the spinal column, such as a spinous process of subject 30.

[0053] Fixed portion 124 can be interconnected with the spinous process in any suitable manner. For example, a pin or screw can be driven into the spinous process. Alternatively or additionally, a clamp portion 124 can be provided to interconnect the spinous process. Fiducial portion 120 can be imaged with imaging device 80. However, it should be appreciated that various portions of a subject, such as a spinous process, can also be used as fiducial portions.

[0054] In various implementations, when fiducial portion 120 is imaged with imaging device 80, image data is generated that includes or identifies fiducial portion 120. Fiducial portion 120 can be identified in the image data automatically (e.g., by a processor executing a program), manually (e.g., by a selection of an identification of user 72), or a combination thereof (e.g., by a selection of a seed point by user 72 and segmentation performed by a processor executing a program). Methods of automatic imaged portion identification include those disclosed in U.S. Patent No. 8,150,494, issued April 3, 2012, which is incorporated by reference herein. Manual identification can include a selection of an element (e.g., a pixel) or region in the image data in which an imaged portion has been imaged. Regardless, fiducial portion 120 identified in the image data can be used as a fiducial or fiducial location that can be used to register image data or an image space of image data to a patient space.

[0055] In various implementations, to register an image space or coordinate system to another space or coordinate system, such as a navigation space, fiducial portion 120 identified in image 108 can then be identified in a subject space defined by subject 30 in an appropriate manner. For example, if the fiducial portion was attached to subject 30 in the same location during acquisition of image data to generate image 108, user 72 can move instrument 68 relative to subject 30 to contact fiducial portion 120. It should be appreciated that, as discussed above in various implementations, fiducial portion 120 can be attached to subject 30 and / or can include an anatomical portion of subject 30. Additionally, tracking devices can be incorporated into fiducial portion 120 and they can remain with subject 30 after image acquisition. In this case, registration or identification of fiducial portion 120 can be performed in the subject space. However, according to various implementations, user 72 can move instrument 68 to contact fiducial portion 120.

[0056] According to various embodiments, the tracking system can track the pose of the instrument 68 due to the tracking device 66 attached to the instrument. This allows the user 72 to identify the pose (including, for example, six degrees of freedom information, which includes positioning and orientation) of the fiducial portion 120 identified in the image 108 in the navigation space (which can include or be part of the object space). After identifying the location of the fiducial portion 120 in the navigation space, a mapping can be made between the subject space defined by the object 30 in the navigation space and the image space defined by the image 108. Thus, the same or known locations allow for registration, as discussed further herein.

[0057] During registration, a mapping is determined between the image data coordinate system of the image data, such as the image 108, and the patient space defined by the patient 30. Once registration occurs, the instrument 68 can be tracked with the tracking system registered to the image data to allow the pose of the tracked instrument 68 to be identified and illustrated as an icon overlaid on the image data. Registration of the image 108 (or any selected image data) to the object 30 can occur at any appropriate time.

[0058] In various embodiments, the image space 108 and the object space defined by the object 30 can be registered according to the method 150. As discussed above, the image to patient registration can include acquiring and / or accessing image data of an object having fiducials, such as the object 30, in block 152 (e.g., from a memory system having the image data stored thereon). The image data of the object 30 can be any appropriate image data, such as image data acquired with the imaging system 80. Further, as described above, the fiducials can include the fiducial portions 120 and / or appropriate anatomical portions of the object 30. For example, the fiducial portions can include portions of anatomical structures, such as the spinous processes of the object 30. However, the acquired image data can include the fiducials therein. Once the image data of the object having the fiducials is acquired, identification of the fiducials in the image space can occur in block 154.

[0059] As also discussed above, the identification of the fiducials in the image space in block 154 can occur. For example, automatic identification of the fiducials can be made in the image data defining the image space, such as through automatic segmentation of the fiducial portions within the image. Manual identification and / or a combination of manual and automatic identification can also be used to determine the fiducials in the image space. The combination can include the user 72 identifying one or more pixels as seed pixels and the processor performing a segmentation procedure based on the seed pixels.

[0060] Identification of fiducial points in the object space and / or navigation space occurs in block 156. The object space can be coextensive with the navigation space and / or can overlap. Generally, the navigation space is a volume that can be tracked with a tracking system such as the localizer 94, and can contain all or a portion of the object or patient 30. Identification of fiducial points in the navigation space can occur in various ways, such as with respect to the fiducial portion 120 (which can also be a tracking device) and / or a spinous process movable trackable instrument such as the instrument 68. The tracking system of the navigation system 26 can track the instrument 68, and the navigation system 26 can include an input for inputting the portion of the fiducial portion 120 in the navigation space. The determination or identification of the pose of the fiducial points in the navigation space (e.g., including selected degree of freedom information including three-dimensional position and orientation) can then be used to form a mapping between the two or more coordinate systems in block 160.

[0061] The determination of the mapping determined in block 160 can be a coordinate system of the image space relative to the object and / or a correlation or registration with the coordinate system of the navigation space including the object 30. The mapping allows the determined pose of the tracked portion in the navigation space to be mapped to an equivalent or identical pose in the image. Once the mapping pose is determined, the pose can be illustrated or displayed with a display relative to the image 108, such as by superimposing the icon 68i on the image 108 or by superimposition of the icon relative to the image.

[0062] The image to patient registration allows tracked instruments or items to be illustrated relative to the image 108. However, without registration, any element that is not trackable or registered to the image 108 can not be properly or accurately illustrated at a real world pose relative to the image 108. Thus, the registration can allow the determined pose of the instrument 68 relative to the object 30 to be shown, such as by the icon 68i.

[0063] After the image space is registered to the patient space, the instrument 68 can be tracked relative to the image 108. As shown, an icon 68i representing the pose of the instrument 68 (which can include a 6 degree of freedom pose including a 3 dimensional position and a 3 degree of freedom orientation) can be displayed relative to the image 108 on the display 84. Due to the registration of the image space to the patient space, the pose of the icon 68i relative to the image 108 can substantially identify or mimic the pose of the instrument 68 relative to the patient 30 in the patient space. As noted above, this can allow the navigation process to occur. Figure 1

[0064] Additionally referring to Figure 2 and Figure 3 , and with continued reference to Figure 1 , the localizer 94 (which can also be referred to as an array or antenna array) can be set up in any physical configuration for a selected or appropriate procedure. For example, as shown in Figure 1 ​As shown, the positioner 94 is configured or formed to include a selected geometry, such as a petal shape. In various embodiments, such as Figure 3 As shown, the locator 94 may be planar or more elongated. The locator 94 may include multiple coils (such as any suitable number) to generate a navigation field or domain. The navigation field or domain may include volume 180. The navigation volume 180 is typically sized or moved or positioned relative to object 30 to allow navigation of one or more instruments (such as instrument 68) relative to object 30. Instrument 68 may include one or more tracking devices (such as tool tracking device 66). As discussed further herein, array 94 may transmit signals that can be received by tracking device 66 or other suitable tracking devices (such as object tracker 58 and / or imaging device tracker 62).

[0065] In various embodiments, array 94 may be incorporated into bed or support 104. Alternatively or otherwise, array 94 may be configured in a shape or size such that array 94 can be placed below object 30 and object 30 is positioned on top of at least a portion of array 94. In various embodiments, for example, array 94 may be placed (e.g., fixed) near the lumbar vertebrae and / or head of object 30 to allow navigation field 180 to be centered and / or cover selected areas of object 30 for navigation.

[0066] Navigation system 26 can operate in selected environments, such as in an operating room that includes various other components besides instrument 68. For example, navigation system 26 can operate in an operating room that includes imaging system 80, operating table 104, and / or other components. Furthermore, multiple instruments can be configured for selected procedures, such as instrument 68 and additional or alternative instruments (such as drill motor 69, which may be placed in storage or holding area 71). Holding area 71 may include conductive and / or magnetic materials, such as a metal tray or a conductive polymer tray. Tray 71 may be formed of various or selected metals or metal alloys (such as aluminum or stainless steel). In various embodiments, signals emitted by array 94 may be interfered with or distorted due to interactions from various metallic materials (such as tray 71, drill 69, imaging system 80, or other metallic components in the operating room where navigation system 26 is housed). Objects or items that can distort fields or signals may be referred to as distorting objects.

[0067] As discussed further herein, the array 94 can be operated to emit a signal or field. The field emitted by the localizer 94 can be sensed by one or more of the tracking devices, such as the instrument tracking device 66. Thus, the field emitted by the array 94 can be distorted due to metallic objects in or near the navigation volume 180. Thus, the signal received by the tracking device 66 or other tracking devices in the navigation system 26 can include both the emitted signal and the distortion. The distortion can be generated by eddy currents in conductive items or magnetization in magnetic items, which can be referred to herein as "distorting items." The signal received by the tracking device 66 can be transmitted to an appropriate processing system, such as the controller 110 and / or one or more processors in the processing unit 102. If an object is near the navigation volume 180 causing the distortion, the received signal can include the distortion. Thus, a distortion detection and correction (DDC) module 190, which can include equalization, can be incorporated or performed by the processing unit 102. As discussed further herein, the DDC module 190 can be used to assist in removing the distortion from the signal received by the tracking device 66. Once the distortion is removed in the DDC module 190, a navigation module 198 can also be incorporated into and / or performed by the processing unit 102. The navigation module 198 navigates through the corrected signal to determine the pose of the tracking device 66 in the navigation volume 180. Thus, a tracking signal can be emitted by a localizer and received by a tracking device 66. The received tracking signal can include distortion. As discussed above, navigation of an instrument 68 included in the tracking device 66 can allow a graphical representation 68i of the instrument 68 to be shown relative to the image 108 of the object 30.

[0068] Thus, due to the navigation registration, the user 72 can view the pose of the instrument 68 relative to the object 30 through the monitor 84. Those skilled in the art will appreciate that the tracking device 66 can also emit a signal that is received by the localizer 94. The emitted signal can be received by the localizer 94 and similar equalizers and navigation modules can be used to determine the pose of the tracking device 66 relative to the object 30 in a similar manner, but with the signal being received by the localizer 94 instead of being emitted by the localizer 94. Further, those skilled in the art will appreciate that when multiple instruments are tracked relative to the object 30 in the navigation volume 180 at substantially the same time, the multiple instruments can be navigated at substantially the same time to allow the multiple instruments to be shown relative to the image 108 at the same time.

[0069] Regardless of its configuration or external geometry, the localizer 94 can include one or more coils 200. The localizer can include an appropriate number of coils 200, such as sufficient to emit signals to be resolved at the tracking device 66 to navigate the tracking device 66. Thus, the localizer 94 can include one or more coils 200, including nine or more coils, 12 or more coils 200, or up to 36 coils, or an appropriate number of coils 200. The coils 200 can be provided in any appropriate number and the numbers discussed herein are merely exemplary. For example, the localizer 94 can include three coils that are oriented substantially orthogonally and placed about a single center or origin relative to one another. Alternatively or additionally, one or more coils can be placed and oriented at selected angles relative to one another within the localizer 94. Regardless of the configuration, the one or more coils generate a navigation field through electromagnetic (EM) signals that can be sensed by a corresponding tracking device, including the tracking device 66, to allow determination of a pose of the tracking device 66 in space.

[0070] With continued reference to Figure 1 and additional reference to Figure 3 , the localizer 94 can be configured in any appropriate manner, including those discussed herein. Figure 3 The example shown is a rectangular localizer assembly. The localizer assembly 94 can include one or more coils 200, such as a first coil 200a. The coil 200a can be included in the localizer 94 along with one or more other coils, such as a second coil 200b. It should be understood that any appropriate number of coils can be provided and the two coils 200a, 200b are merely exemplary. Additionally, the localizer 94 can be controlled by a controller 110 and / or have an on-board controller, such as a controller or control module 110'. Additionally, in various embodiments, a local power source or power converter can be provided at the localizer 94. For example, a power converter or battery can be provided to provide power to the controller 110' and / or the coils 200 to emit tracking signals. In various embodiments, an external power source can transmit power to the controller 110, 110' and / or the coils 200 from a location remote from the localizer 94, as an alternative and / or in addition to a local power source.

[0071] Regardless of the number or configuration, the respective coils, including coil 200, can be driven to emit signals that can be received by the tracking device 66. In various embodiments, for example, the respective coils 200a, 200b can be placed or incorporated into an "H" bridge configuration or switching system. With reference to coil 200a, and understanding that the second coil 200b can be incorporated into a similar configuration, the coil 200a can be interconnected between a drive source and ground through a plurality of switches. In various embodiments, for example, the coil 200a can be integrated into an "H" bridge assembly 220. The "H" bridge assembly 220 can include a plurality of switches, including a first switch 222, a second switch 224, a third switch 226, and a fourth switch 228. The switches 222-228 can selectively allow current to be driven through the coil 200a from a source or voltage source 230 to ground or an outlet 234.

[0072] For example, the first switch 222 and the second switch 224 can be closed to allow a voltage to be formed across the coil 220a and to allow current to flow through the coil 200a in a first direction. Similarly, the third switch 226 and the fourth switch 228 can be closed (with the respective first switch 222 and second switch 224 open) to allow current to be driven through the coil 200a in a second direction. As discussed above, the controller 110 can be used to control the selected switches to pass current through the coil 200a. The current through the coil 200a to cause a signal to be emitted by the coil 200a and received by the tracking device 66.

[0073] Similarly, the "H" bridge 220b can be connected to the coil 200b and operate in a similar manner. The controller 110 and / or the controller 110' can operate both of the "H" bridge assemblies 220a, 220b to power or emit signals through the respective coils 200a, 200b. It should be understood that the "H" bridge assemblies can be provided in any appropriate manner with respect to the respective coils, such as through manual or physical switches, transistor switches, or any appropriate switches. Further, as discussed above, any appropriate number of coils can be provided to the localizer 94 to generate a navigation field that is selected to generate or provide the navigation volume 180. Figure 3 The schematic or diagram of FIG. 1 is merely an example for the current discussion.

[0074] A coil, such as coil 200a, can be powered via an "H" bridge assembly 220a to provide a signal for navigation of instrument 68. The "H" bridge assembly 220a can be provided in the localizer 94 to allow the coil 200a to be driven while maintaining selected energy or field emission and heat generation of the coil 200a and the localizer 94. Thus, the localizer 94 can include an appropriate number of coils, such as between 1 and 36 coils, including three coils to 15 coils, while still maintaining the selected field emission and heat generation. As discussed herein, the multiple coils can be driven by the controller 110, 110' in an appropriate manner to generate the navigation field 180.

[0075] The tracking system can include a localizer 94, as discussed above. The localizer 94 can be controlled by the controller 110. The localizer 94 can emit a field or emit a field 113 that can be sensed by the tracking device 66 of the instrument 68. It should be understood that other appropriate tracking or receiving devices, such as the calibration receiver 95, can also sense the field 113 of the localizer 94. The field 113 can be generated in an appropriate manner, such as including or having a spread spectrum. Additionally or alternatively, the field 113 can also have a modulation that can be sensed by the tracking device 66. As discussed further herein, the field 113 can assist in reducing or eliminating distortion or interference of the field sensed by the tracking device 66 due to interfering, also referred to as distorting, objects.

[0076] As discussed above, the localizer 94 can be controlled by the controller 110, 110', according to an appropriate emission system (discussion herein related to the controller 110 is intended to encompass all appropriate controllers, including those discussed above, and reference to only the controller 110 is only for ease of the current discussion). As discussed above, a coil, such as coil 200a (discussion herein of the single coil 200a is also merely exemplary and for ease of the current discussion), can be powered or connected through an "H" bridge configuration 220a. The "H" bridge configuration 220 can be provided in any appropriate manner, including switches (e.g., physical or manual) and / or transistors that can be operated by the controller 110. Regardless, the coil or coils of the localizer 94 can be operated to emit through a binary emission system or scheme, including a binary near orthogonal (BNO) emission system or scheme. The coil or coils of the localizer 94 can be operated to emit a signal as a set of binary near orthogonal (BNO) sequences for efficient recovery of the emitted signal in the navigation field and the impulse response of the system and the impulse response of a distorting object, also referred to as a distorting article.

[0077] Under the BNO scheme, a pseudo-random binary (PRB) sequence (also known as a pseudo-noise binary (PRB) sequence, one such type being a maximum length (ML) sequence) can be generated by the controller 110 for transmission by the localizer 94 as the tracking signal 113. The transmission of the tracking signal 113 can also be a spread spectrum transmission such that it is spread across or over a large or wide spectrum, which can also be partitioned by time.

[0078] The PN sequences can be arranged in a substantially orthogonal or near-orthogonal manner to provide for suitable transmission for reception by the tracking device 66 or other suitable tracking device. The tracking signal 113 can be used for navigation of the tracking device 66. In addition, the discussion of a single tracking device 66 or any suitable or single portion of the navigation system 26 herein is exemplary only and is intended to simplify the current discussion, unless otherwise specifically indicated.

[0079] Thus, in various embodiments, cyclic shifts or offsets of the same repeating PN sequence are transmitted, one on each transmit coil. Statistically, the autocorrelation function of the PN sequence equals 1 at the offset zero and equals 0 at all other offsets where the sequence length equals 2 n -1 and the number of sequence generator bits equals n, where n = 14 can be used in various embodiments. The cyclic shifts or offsets of the PN sequence can be understood to be nearly orthogonal to each other in the sense that the correlation for any sufficiently large value "n" is poor from any different offset of the sequence. A system demodulating all cyclic shifts magnitudes in a repeating PN frame can recover the associated coil signal magnitudes by multiplying by the inverse of the PN leakage matrix, which has 1 on the diagonal and 0 elsewhere Further, when the PN offsets of the transmit coils have a separation greater than the distorter response duration (i.e., the time to receive a distortion from a distortion object), the method can recover the distorter impulse response for each transmitter coil. In various embodiments, the offset can be 10 sequence generator bits. The method of selection can be used to perform the calculations discussed above, including the Walsh-Hadamard transform via the fast Walsh transform described in Jens Hee, "Impulse response measurements using MLS," http: / / www.jenshee.dk / signalprocessing / mls.pdf (2003). The method can be used to perform the demodulation (multiplication by the PN sequence at all offsets) and leakage inversion directly.

[0080] As discussed above, the controller 110 can power the coil 200a to emit a signal that can be received by the tracking device 66. It should be appreciated that, as discussed above, the tracking device 66 can also emit a signal in a similar manner as discussed herein that is received by one or more coils of the localizer 94. The tracking device 66 can also include multiple coils, such as coils that are oriented substantially orthogonally to each other and / or separated from each other about a central point. In various examples, the tracking device 66 can include multiple coils, such as three coils 66a, 66b, and 66c. However, the tracking device 66 or any appropriate receiving coil device (e.g., the calibration receiver 95) can include a selected number of coils, for example, one coil, more than one coil, at least three coils, or more than three coils, such as six coils. The number of receiving coils can be appropriate for navigating the tracking device 66. Each of the coils can be formed of a selected electrically conductive material to induce a current therein by a signal from the localizer. In various embodiments, the coils can include wire wrapped around a center and / or traces formed on a printed circuit board (PCB). However, as discussed herein, the tracking device 66 can receive signals from the localizer 94, but one skilled in the art will appreciate that the localizer can receive signals from the tracking device, and vice versa.

[0081] In various embodiments, as discussed above, the controller 100 can cause or signal one or more coils of the localizer 94, such as the coil 200a, to emit a signal, which can also be referred to as a tracking signal, as discussed herein. The coil 200 can be formed of a selected electrically conductive material, such as a coil of metal or metal alloy wire. The impulse response is calculated from a set of successive emitted BNO signals received from the emitting coil. The tracking signal is a set of BNO signals that includes the same binary PN signal delayed by a different amount for each coil of the localizer. The inter-coil offset can include a selected time delay interval that is greater than a length of a metal distorter impulse response length. The signal delay or interval can include a selected duration, such as about 1 to 20 milliseconds, including 5 to 10 milliseconds, with an equivalent or greater interval between the signals from each coil.

[0082] The emitted tracking signals can be at any appropriate frequency range, such as in a frequency range of about 5 Hertz (Hz) to about 30 Megahertz (MHz), including about 10 Hz to about 3 MHz, and further including about 10 Hz to about 400 kilohertz (kHz). The frequency or frequencies can be selected or the signal can be emitted in a spread spectrum fashion through a range of frequencies. For example, a spread spectrum signal can emit a signal across a spectrum of about 1 Hz to 30 MHz, including about 10 Hz to about 400 kHz emitted at a sample rate equal to or about 375 kHz. In various embodiments, the control of the signal is the sample rate and waveform, which can include a binary drive waveform. From direct current (D.C.) to the sample rate, the spectrum can be flat. Thus, in various embodiments, the spectrum is flat when navigating the instrument, as discussed above. A controller configured via an H-bridge can select a frequency or a spread spectrum of frequencies across a selected frequency.

[0083] As discussed above, the localizer 94 can emit a signal from the controller 110 through one or more of the coils, such as the coil 200a. As further discussed above, the H-bridge configuration 220a can be set in any appropriate configuration, such as including transistors at the switches 222-228. Thus, the controller 100 can cause the coil 200a to emit a signal (e.g., an electromagnetic signal) that will be received by the tracking device 66. However, the navigation system 26 can use any appropriate way to emit the magnetic signal, including but not limited to an H-bridge circuit and a closed loop analog circuit.

[0084] Referring to Figure 4A and Figure 4B , a transmission to a receive calibration and / or equalization (C / E) procedure 300 and its associated schematic is shown. As discussed herein, reference is made to Figure 5A and Figure 5B and Figure 6A and Figure 6B Various additional and / or alternative C / E methods and systems can be used. In various embodiments, the C / E can include or be performed as a system-wide C / E and / or as various sub-channels or components.

[0085] Referring first to Figure 4A and Figure 4BC / E procedure 300 can be a full system C / E (also referred to as an end-to-end C / E) including various procedure steps such as starting in start block 310. After starting in start block 310, in block 311 (shown schematically as 311') a calibration or equalization signal can be generated from controller 110 and sent to localizer 94 (which can also be referred to as a transmitter). Then, in block 314 (shown schematically as 314') a calibration signal can be transmitted from localizer 94 which will be received such as at calibration receiving coil 95 and / or other appropriate receivers such as tracking device 66. The transmission of the calibration signal in block 314 can include transmitting the calibration signal according to a spread spectrum scheme as discussed above. In addition, the transmission can include PN signals from coil 200a and other coils 200 of localizer 94.

[0086] As discussed above, the signals sent by the coils can be generated as PN sequences. The PN sequences can include a selected length such as a length of 1023 to 16383 in the sequence. The various coils can be offset from one another by an appropriate amount such as about 1023 lengths to achieve differentiation between the coils 200 of localizer 94. The PN sequences can be generated and transmitted by controller 110. As discussed above, the transmitted signals at the selected frequency or spread spectrum will be received by tracking device 66 and / or other appropriate receivers such as calibration receiver 95 (even if only one receiver coil is referenced herein). Thus, the coils 200 can generate or transmit the signals at appropriate times such as in sequence or substantially simultaneously for receipt by tracking device 66. The PN sequences can be generated according to any appropriate technique. In various embodiments, for example, the PN sequences can be generated by an irreducible polynomial.

[0087] In block 318 (shown schematically as 318'), tracking device 66 can receive the transmitted calibration signals and transmit the received signals to controller 110. The received calibration signals in block 318 can then be sampled and various calculations can be performed by controller 120 (or any appropriate processor system) to perform calibration in block 322. The calibration in block 322 can include calibration based on various parameters such as a transmission distance, a field strength at a known pose, or other appropriate calibration parameters.

[0088] Calibration in block 322 can be performed according to appropriate techniques, as discussed below. In various embodiments, calibration in block 322 can include impulse response normalization, which places the tracking device 66 (e.g., including coils) in a fixed pose via the localizer 94 including one or more of the coils 200. Transmit calibration can include measurements of the transmitted magnetic field via an external or separate magnetometer and / or as previously characterized at the tracking device 66 (e.g., sensing coils). Receiver coil calibration can include measurements of the received voltage via an external multimeter at or near the tracking device and / or as previously characterized by the tracking device 66 (e.g., sensing coils).

[0089] Calibration in block 322 can include ensuring a known or clean room field strength at a selected pose. Calibration can include placing the localizer 94 at a selected position (which can also be referred to as an origin) and moving the tracking device 66 or appropriate receiving tracking device in a plurality of known poses (i.e., positions and orientations) relative to the origin. The signals received by the tracking device 66 can then be used in the calibration 322. For example, as the signal begins and travels through the transmitter (e.g., localizer 94) circuitry and filters, the transmitter coils, the air, the tracking device 66 coils, the circuitry and filters associated with or included with the tracking device 66, and then as the signal is received back at the controller, calibration can include or account for possible distortions or noise in the signal.

[0090] Calibration can then be equalized in an equalization step in block 324, regardless of how determined (including as discussed above). In the equalization in block 324, an equalization between each of the coils 200 of the localizer 94 and the tracking device 66 is determined. Each transmitting coil 200 and the tracking device 66 can be equalized for impulse response recovery and normalization of the signal. It should be understood that the discussion of the tracking device 66 can include a discussion of multiple coils in the tracking device 66, such as three coils, as discussed above. Thus, the equalization can be between each of the coils 200 of the localizer 94 and each of the coils of the tracking device 66. For example, between the coil 200a and each of the coils 66a, 66b, and 66c.

[0091] Equalization includes removing distortion and / or accounting for noise of the system (including from the controller 110 as well as various circuitry of the localizer 94 and receiver 66) to allow recovery of the discrete-time binary signal from an interference-free system. Generally, equalization is performed by removing distortion of the driver and receive hardware, and will only leave the signal and noise from any external distortion response. Specifically, a binary single-valued pseudo-noise signal can be measured (as it is measured as a voltage at the receive coil of the tracking device 66) and its inverse calculated. The equalization then convolves the determined inverse with the signal received at the tracking device 66 (i.e., the coil in the tracking device 66) to remove the effects of the localizer 94 and tracking device 66 and hardware associated therewith, leaving the drive signal from the controller 110 and noise or external distortion in the field.

[0092] Equalization is performed by determining coefficients. Specifically, an algorithm can be used to determine the coefficients in a test or calibration equalization determination. Equalization can be performed in any suitable manner, including those generally understood by those of skill in the art. For example, optimized and combined finite impulse response (FIR) filters and bi-directional infinite impulse response (IIR) filters can be used to equalize the channel. The determined coefficients can be used to remove hardware distortion in the equalization between the localizer coil 200 and any coil of the tracking device 66.

[0093] Accordingly, the equalization block 324 can be used to generate or determine a signal that is free of distortion due to the hardware of the localizer 94 transmitting via the coil 200 and being received at the tracking device 66 and coil included therein. Accordingly, the equalized signal can be used to determine the pose of the tracking device in the field generated by the localizer 94. As discussed above, the localizer 94 can transmit signals according to a BNO scheme, where each coil 200 is offset from another coil by about 1023 bits in a PN sequence.

[0094] In various embodiments, as briefly described above, selected sub-channels or sub-portions of the navigation system 26 can be calibrated and equalized. For example, with reference to Figure 5A and Figure 5B the respective sub-channels in and / or to each of the transmitter or localizer 94 and / or the receiver or tracking device 66 can be individually calibrated and equalized. This can be in addition to and / or instead of calibrating and equalizing the entire system, as discussed above and shown in Figure 4A and Figure 4B .

[0095] Reference is first made to Figure 5AFIG. 3a shows a method 300a for calibration and equalization. The method 300a can include similar parts as those discussed above in method 300, and like reference numerals will be augmented with a lower case letter "a". Thus, the method 300a can begin at block 310a. The process 300a can then move to block 311a to generate a signal by a controller, such as controller 110. The generated signal can include a PN sequence, as discussed above. Thus, the generation of the signal in block 311a at the controller is similar to the generation of the signal in block 311 as discussed above. The generation of the signal and controller 311a can then be sent through and / or to various components of the navigation system 26, including those as discussed above.

[0096] The calibration signal can be sent to the localizer in block 326 (shown schematically as line 326'). The signal can be sent to various components from the controller 110 to the localizer 94, including various circuitry and filters, the transmitter coil (e.g., coil 200), and other components between the controller 110 and the localizer 94 and / or including the localizer 94. The signal sent to the localizer 94 can then be transmitted back to the controller 110 after passing through all of the components of the localizer portion of the navigation system 26. Thus, the controller 110 can receive the signal returned from the localizer components, such as transmitted from the coil and / or returned to the controller 110 through the return line (after passing through all of the components of the localizer 94 portion).

[0097] The controller 110 can also transmit the signal to the receiver coil, such as the tracking device 66 and / or the calibration receiver 95 (also referred to herein as the receiver). The signal transmitted to the receiver 66 can be substantially the same as the signal transmitted to the localizer 94. Further, the signals can be transmitted substantially simultaneously and / or sequentially. Thus, the signal generated from the controller 110 can also be transmitted to the receiver 66, such as through all of its components, including receiver circuitry and / or filters, the sensor receiver coil (including all of its selected or appropriate components) of the tracking device 66. The signal can then be returned to the controller 110 after having passed through all of the components, such as the controller 110 receiving the returned signal from the receiver 66.

[0098] Thus, both blocks 326 and 328 can include two components, including transmitted and returned signals from respective components including the localizer and the receiver. In other words, the signal can be sent from and returned to the controller 110 for calibration and equalization. Thus, rather than only or requiring the signal to be transmitted to the localizer 94, then transmitted and received by the receiver 66, and then transmitted back to the controller 110, the signal can be sent and returned from each of the separate components as separate sub-channel calibration and equalization.

[0099] The return signals can then be further processed by the controller 110 or appropriate processor system as discussed above. Calibration can be performed in block 322a in a manner similar to that discussed above. Calibration can include various calibration techniques or measurements similar to those discussed above. For example, calibration can include measurements such as by selected magnetometers and / or fields as previously characterized by corresponding coils in the localizer 94 and / or receiver 66. The calibration signals and / or information can then be used in equalization in block 324a. Again, equalization in block 324a can include equalization as discussed above for equalization of signals in the navigation system 26.

[0100] Accordingly, calibration and equalization of the navigation system 26 can include separate or sub-channel calibration and equalization portions and / or steps as exemplarily shown in Figure 5A and Figure 5B as discussed above and as exemplarily shown in

[0101] Additionally and / or alternatively, sub-channel calibration and equalization can include methods as shown in Figure 6A and Figure 6B Method 300b can initially include similar steps or portions as method 300 and method 300a as discussed above. Similar portions will be referenced by similar numbers enhanced with a “b”. Accordingly, method 300b can begin in start block 310b and include generation of signals at the controller in block 311b. Generation of signals at the controller can be similar or the same as generation of signals at the controller 100 as discussed above.

[0102] The signals can be PN sequences and can then be transmitted or sent to various components of the navigation system 26. For example, the signals can be sent through various components of the localizer system including circuitry, filters, transmitter coils, etc. to the localizer 94. Sending the signals to the localizer 94 and the return of the signals to the controller in block 326b can be similar to that discussed above in block 326. The signals sent to the localizer 94 can be sent from the controller 110 to the localizer 94 through various circuitry of the localizer. As discussed above and further herein, the return signals returned to the controller 110 for various calibration and equalization can be returned in various selected manners. As discussed above, the signals can be sent or returned to the controller through various return paths from the localizer 94 to the controller 110. Additionally or alternatively, various external components can receive the transmitted signals from the localizer 94 such as magnetometers, etc. and the signals from the external components can be returned to the controller. However, the signals need not be transmitted wirelessly. The signals having passed through various components such as circuitry, filters, and coils of the localizer 94 can have signals that are then returned to the controller 110.

[0103] Additionally, the generated signals can be transmitted to various circuitry and components of the receiver 66 channels as Figure 6BThe receive coil circuitry 66' / 95' can include various circuitry, cabling, filters, etc. associated with the tracking devices 66 and / or the calibration coils 95. The receive coil circuitry 66' / 95' can include various hardware or components that are generally understood to be fixed with the navigation system 26. For example, as discussed above, the controller 110 can be connected to various tracking devices and / or receive tracking device information from various selected tracking devices, such as the tracking device 66. Additionally or alternatively, various other tracking devices, such as the tracking device 62, can also be connected to the controller 110.

[0104] During a selected procedure, for example, the tracking device coils or components 66, 95 can be interchanged with the receiver electronics 66' / 95' and thus connected to the controller 110. Further, as understood by those skilled in the art, more than one instrument can be tracked separately and independently during a selected procedure or multiple procedures. Thus, multiple tracking devices 66 can be tracked separately and independently. Accordingly, at a selected time, the identity of the selected and attached tracking device 66 can be input. Thus, the system, such as the controller 110, can call the characterization of the selected and input tracking device 66 from a storage system. Accordingly, the sub-component calibration and equalization of the receive circuitry 66' / 95' can allow for calibration of the navigation system 26 independent of the individual components being tracked therein, such as by the tracking device 66.

[0105] In view of the above, in block 330, the generated signal from block 311b can be transmitted to the receive circuitry. The signal received from the receive circuitry 66' / 95' can be received in any appropriate manner, such as in a return signal and / or from an external component, including a voltage measurement from an external multimeter, or other appropriate sensor.

[0106] Accordingly, the calibration and equalization of the navigation system 26 can also thus include calling the characterization of the selected receiver, also referred to as the receiver coil or component. For example, as discussed above, various components can be interconnected with the navigation system 26 for navigation of the selected components. Accordingly, the navigation system 26 can be calibrated and equalized without a particular and selected tracking device 66. During a selected time, such as during a procedure, when a particular tracking device is selected, the identity of the selected tracking device can be input (e.g., manually input by the user 72, automatically input by sensing or receiving a signal from the tracking device, or other appropriate mechanism). The navigation system 26 can call the previously made and predetermined characterization (including equalization) of the selected tracking device. Accordingly, the characterization of the tracking device can be completed at any previous time. The characterization can include calibration and equalization information that can be previously determined and stored in a selected memory, such as in a database and / or in a memory of the navigation system 26 including the workstation 98 or processor system 98.

[0107] The previously determined characterization, such as manually and / or automatically and / or a combination thereof, can be invoked to complete the calibration and equalization of the entire navigation system 26, including the selected particular receiver coil 66 / 95. Thus, when a selected receiver is selected, the invoked characterization can be incorporated and / or used with the received signal from the receive circuit in block 330 and the received signal from the localizer in block 326b for calibration and equalization. Thus, with the invoked characterization from block 322, calibration can be performed in block 322b. Following calibration in block 322b, equalization can be performed in block 324b. Calibration and equalization can include such procedures as discussed above.

[0108] Thus, calibration and equalization of the navigation system 26 can be performed in an appropriate manner, including those discussed above, such as Figures 4A to 6B The above and shown. It should be understood that calibration and equalization of the navigation system 26 can be performed in any appropriate manner and can include any of the above systems or methods and / or combinations thereof. For example, end-to-end completion of calibration and equalization can be performed in accordance with the method 300. Additionally, during a selected procedure, the calibration method 300b can be used to enhance and / or update the calibration and equalization of the navigation system 26 as tracking devices are added and / or changed during and / or between procedures. Thus, it should be understood that calibration and equalization can be performed in any appropriate manner and need not be limited to only a single method of the methods as discussed above, but can include multiple methods and / or combinations thereof, such as end-to-end calibration and equalization in accordance with the method 300, which can be supplemented and / or re-performed in accordance with the sub-channel procedure (in accordance with either and / or both of the methods 300a and 300b).

[0109] In accordance with various embodiments, including those discussed above, in step 324, the signal received at the tracking device 66 can be equalized by the equalizer 190 in accordance with the equalization process discussed above. Referring to Figure 7 , the unequalized impulse response can include a causal portion 340 and an anti-causal portion 344. The anti-causal portion can be used to compensate for various components of the navigation system 26 and can vary in view thereof. Thus, various different components can be used in the navigation system 26 and allow or cause the causal portion 340 to vary. The causal portion 340 can be used to compensate for variations and phase in the passband of the system and also in various components of the circuit of the localizer 94. Thus, the equalized signal in block 324 can use a pre-equalization impulse response as shown in Figure 7 to calibrate and equalize the signal.

[0110] The localizer 94 can transmit a signal to generate an electromagnetic field. The signal can be a spread spectrum signal transmitted according to a BNO scheme. The signal, including the BNO scheme, can be referred to as a tracking signal that includes a binary signal. The binary signal can be measured at the tracking device 66 that is involved in transmitting the signal. As discussed further herein, the received signal can include various components due to various distortions as discussed above and further herein. Equalization can assist in ensuring recovery of the impulse response transmitted by the localizer 94.

[0111] Turning to reference Figure 8 and Figure 9 , the pre-equalized signal is shown as being received by the tracking device 66 in Figure 8 . Figure 8 The pre-equalized signal in Figure 8 shows different received signals due to system distortions and including a distortion of material in the field or near the path of the tracking device 66. For example, the plot line 350 is related to a value of the pre-equalized signal received by the tracking device 66 over time without a distorting item. The second plot line 354 shows the received signal over time when a portion of aluminum is placed or positioned near the received signal or causes a distortion in the received signal. The third plot line 358 shows the received signal when a selected steel material is positioned near the tracking device 66. As shown by the plot lines 350-358 in Figure 8 , the signal received by the tracking device 66 can vary depending on the material positioned near the tracking device 66 and / or that will distort the signal transmitted by the localizer 94. As discussed further herein, the distortion caused by the selected material can be removed by analyzing the received signal to determine if there is a distortion and removing the distortion if there is. As discussed herein, the distortion can be determined whether or not there is. If it is determined that there is a distortion, the distortion can be removed to allow recovery of the undistorted tracking signal including the impulse response.

[0112] Referring to Figure 9 , a method or process of navigation 370 is shown. The navigation process can begin at start block 374 and include transmitting one or more signals in block 378. As discussed above, the transmitted signal can include a spread spectrum signal according to a BNO scheme as discussed above. The signal transmitted by the localizer 94 can be transmitted into the navigation volume 180. As discussed above, the transmitted signal can generate a near field magnetic field with a wavelength greater than or equal to 10 meters. The navigation volume 180 can depend on various factors such as the size of the coil 200, the overall size of the localizer 94, power transfer, and other factors. However, the navigation volume 180 can be a volume of about 0.001 m 3 to about 1 m 3 , including about 0.01 m 3 to about 0.5 m 3 .

[0113] In block 382, the tracking device 66 can receive one or more transmitted signals. The received signals in block 382 can be received by the tracking device 66 and / or transmitted to the navigation processor 102. It should be understood that the method or process 370 can be executed by the processor 102, where the transmitted signals 378 can be the signals to the localizer 94 to transmit the signals, and the received signals in block 382 can be the signals received from the tracking device 66 and transmitted to the navigation processor 102. The method 370 can include transmitting the signals by the localizer 94 and receiving the signals by the tracking device 66, or vice versa, and the navigation processor 102 can execute instructions to conduct the determination of the navigation in the method 370.

[0114] After receiving one or more signals in block 382, the signals can be processed in block 386, such as de-multiplexing and equalization. As discussed above, the received signals are received by the BNO scheme, and thus each cyclically shifted or offset code (corresponding to each transmitting coil) can be de-multiplexed from the received signals for further analysis. The equalization in block 386 can be similar to the equalization block 324, as discussed above. Generally, as discussed above, the localizer 94 can include the coil 200a and the tracking device 66 can include the coil 66a. It should be understood that the discussion herein of the coil 66a can include or be similar to a discussion of multiple coils at the tracking device 66, and the discussion herein of the single coil 66a is merely exemplary. The equalization between the coil 66a and the coil 200a can allow for a recovery of the impulse response of the transmitted signals.

[0115] After equalizing the signals in block 386, such as by the equalizer 190 as discussed above, the equalized signals can be evaluated to allow for a determination of whether distortion is present in block 390. The determination of whether distortion is present can be made based on the received signals, for example as shown by Figure 10 As shown by Figure 10 The received signals can include a determination or evaluation of an initial impulse, as shown by the black dot 394 in the plot of Figure 10 The impulse response can be the equalized impulse response from the received signals as equalized in block 386. The impulse response can also include a residual or tail, which is a non-impulsive or distorted portion that can include one or more tail signals or points 398. The tail points 398 can include a plurality of tail points in a tail portion 402. The presence of the tail portion 402 or tail portion can be used to determine whether distortion is present. Thus, if the signal including the impulse response as shown by Figure 10 is substantially free of a tail (as plotted over time), then a determination of no distortion is made and the no distortion path 410 is followed. As discussed above according to one or more of the various methods, the calibration and equalization can include a characterization of the system including a floor noise and a distortion limit. The absence of a tail (i.e., distortion) can be defined as being within these previously determined limits.

[0116] If no distortion is found in the received signal after equalization, such as determining that no tail 402 is present in the signal, and following a distortion free path 410, navigation of the tracking device 66 can be performed without correcting for distortion. As discussed above, distortion can be present or found in the received signal due to various distortion items in the signal path, such as affecting the signal emitted by the localizer 94. Distortion can be caused by various items, such as items in or near the navigation system 26, including the imaging device 80, the instrument 68, the surgical table or patient support table 104, or other items, as discussed above. Additionally, distortion can occur due to other items actively emitting a field, such as an electric field from a motorized drill bit, other coils in the localizer 94 other than the pair being resolved or evaluated at the time, or other items. Equalization can be performed on a pair basis (e.g., a single coil 200a of the localizer 94 and a single coil 66a of the tracking device 66). Thus, determination of the pose of the tracking device 66 can be performed by determining the pose of each of the coils 66a-c of the tracking device 66 for each of the coils 200a-n of the localizer 94. However, it should be understood that tracking of the instrument 68 by the tracking device 66 can include navigation between a selected number of coils of the localizer and the tracking device 66. Thus, for example, navigation can be performed by one tracking device and using nine or twelve transmit coils in the localizer 94. Other examples can include combinations of one receive coil using five transmit coils to three receive coils using three transmit coils to twelve receive coils using one transmit coil.

[0117] After determining that there is no distortion, an evaluation of whether certain metrics are accepted can be performed in block 414. Metrics can include signal metrics or any other appropriate metrics. Additional predetermined acceptable ranges or thresholds of the metrics can be generated and saved for access by the navigation processor 102. In various examples, a predetermined signal strength value above or below a threshold can be determined. Thus, if the received signal is above the threshold, the tracking device can be determined to be too close to the localizer, and if the received signal is below the threshold, the tracking device can be too far away from the localizer. However, the threshold can relate to the localizer size and / or power, the tracking device configuration, etc. Thus, the metrics can be analyzed and determined in block 414.

[0118] If the metric is determined to be unacceptable in block 414, a return or loop path 418 can be followed for transmitting the signal in block 378 and / or receiving the signal again in block 382. In various embodiments, the transmission can be repeated automatically, so looping to the transmission can not be necessary or desired, and looping to the reception in block 382 can be appropriate. By receiving the signal again at the tracking device 66, the signal can be re-analyzed. The transmitted signal can be transmitted for a selected time span, such as a millisecond, including a sequence of 1 to 100 milliseconds, including about 30 milliseconds with or without a break or pause in the transmission that follows. Thus, determining whether the metric is acceptable in block 414, if not found to be acceptable, can allow the signal to be received again in block 382, but without interfering with navigation of the navigation system 26 for a time acceptable to the user 72. However, if the metric is not found to be acceptable within a reasonable time period, such as about 30 to 500 milliseconds, the navigation system 26 can provide an output, such as through the display device 84, that can identify to the user 72 that an error has occurred and must be resolved.

[0119] If the metric is acceptable in block 414, a "yes" or resolution path 422 can be followed. The resolution path 422 can lead to a navigation resolution or pose determination in block 428. The navigation resolution in block 428 can allow the representation 68i to be shown on the display device relative to the image data 108 on the display device 84. The navigation resolution allows the pose of the tracking device 66 relative to the object 30 to be shown and / or determined. Thus, navigation of the instrument 68 relative to the object 30 can be performed.

[0120] Continuing with reference to Figure 9 If a distortion is found to exist in block 390, the navigation method 370 can also follow a distortion determination or distortion finding path 440. The "yes" distortion path 440 can lead to or enter a distortion correction (also referred to as removal) subroutine 460. As discussed herein, the subroutine 460 can include various procedures or processes for identifying and correcting selected distortions. In the subroutine, it will be appreciated by those skilled in the art that the processes described herein can be performed sequentially and / or simultaneously, as discussed herein. Thus, while the processes are shown in a selected order, the processes in the subroutine 460 can be performed substantially simultaneously. Figure 9 The processes in the subroutine 460 can be performed substantially simultaneously.

[0121] The distortion cause can be any distortion cause, including those discussed above. For example, a conductive metal object can be in the path of the field generated by the localizer 94. For example, as Figure 1 shown, an aluminum object, such as a tray 71 that can be formed therefrom, can be in the path of the signal from the localizer 94 to the tracking device 66. The aluminum tray 71 can cause a tail 402, as Figure 10 shown. The tail 402 can include a signal loss as along the Figure 10The x-axis in the graph shows multiple response data points separated by time. For example... Figure 10 As exemplified, time can be separated in microsecond increments, but it can also be any suitable time division. However, the determination and identification of the tail 402 can be used to ensure or determine the appropriate magnitude of the initial pulse 394.

[0122] Typically, when a signal is received in block 382, ​​the initial pulse 394 occurs at time “zero.” Specifically, a signal is transmitted in block 378 and received in block 382, ​​and the reception of the signal in block 382 will be at time zero, which is also understood as the start of a PN code or a PN code signal or shift. Any tail or residual received signal after this may be due to distortion objects (such as tray 71) in the field along the signal path. Therefore, the initial pulse 394 may be distorted (e.g., in terms of magnitude) and this distortion is indicated by the distortion tail 402.

[0123] Continue to refer to Figure 10 The initial pulse 394 can be plotted on a graph for discussion and calculation, as discussed herein. The initial pulse 394 is shown as a zero-time response to exemplarily show the initial pulse at time zero on the X-axis. Additionally, the initial pulse is shown as a zero magnitude value to better illustrate the value of the residual or tail response received in block 382 (if distortion is present). The corrected or undistorted size of the initial pulse 394 can be determined by calculating the tail 402 entering the initial pulse 394. The initial pulse and tail can typically be causal responses, where the tail 402 can be used to determine the expected or undistorted pulse magnitude value.

[0124] Distortion path 440 may first proceed to the residual or tail separation in block 444. Residual separation may include the determination of all tail portions. As discussed above, the initial pulse at time zero may be determined, for example, based on a determined or selected amount of time between the transmitted and received signals in blocks 378 and 382, ​​respectively. For example, it may be determined that the time between transmitting a signal from locator 94 and receiving a signal at tracking device 66 may be much less than microseconds. Thus, navigation system 26 may determine that the received signal at a selected amount of time after the transmission of the signal in block 378 may be zero time and the initial pulse. After this, any recovered pulse response may be determined as tail 402. However, tail 402 may be determined in any suitable manner, such as any recovered signal after the identified initial pulse. In any case, tail 402, which may be determined or detected in block 390 when determining the presence of distortion, may be separated from the initial pulse or first pulse 394. Residual separation provides separation of tail size or magnitude for further reconstruction.

[0125] Following the separation of the tail in block 444, reconstruction can be performed in block 448. The reconstruction block 448 can include reconstruction of the distorted impulse response. As discussed above, the initial or zero time impulse 394 can be distorted, and this distortion can be determined by the tail 402, if present. Thus, once the tail is separated in block 444, the separated tail can be reconstructed into a distorted initial impulse to determine the actual or corrected impulse. The reconstruction can be of any appropriate type of reconstruction.

[0126] For example, the direct reconstruction can include an addition reconstruction by adding the values of the tail 402 for a selected amount of time, such as about 1 to 10 milliseconds, including 5 milliseconds, to the values of the distorted initial or zero time impulse. The direct reconstruction can allow for a fast reconstruction of the distorted impulse and can be suitable for selected materials, such as conductive materials, such as certain plastics or polymers, metal alloys, etc.

[0127] The reconstruction can also include a modeled reconstruction of the impulse response, which can be based on weighting certain portions of the tail, adding or canceling certain portions of the tail 402, or other appropriate modeling techniques. In various embodiments, the reconstruction can not include first removing the tail in block 444, but can include simultaneous separation and modeling. In various embodiments, the tail can be summed and added to the impulse, particularly for conductive distortion materials. In other words, as a function of the residual, in a direct calculation, the residual is summed to determine the distorted initial impulse. In a modeled or indirect calculation, the tail can be broken down into separate functions and then fit for determining the distortion effect. For example, the broken down functions can be fit to a predetermined or measured distortion material or article. In other words, the residual can be modeled by parameterizing a combination of impulse responses (with conductive as well as conductive and magnetic contributions) and / or by measuring a combination of impulse responses (including expected conductive as well as conductive and magnetic contributions).

[0128] The reconstruction in block 448 can be performed to determine the corrected or undistorted impulse response in block 454. Following the reconstruction of the distorted impulse response in block 448, removal or deconvolution of the impulse response is performed in block 454. The removal or deconvolution of the impulse response in block 454 can include separating the distorted impulse response from the full impulse response via removal or deconvolution to determine the corrected or undistorted impulse response and impulse.

[0129] Following the removal or deconvolution in block 454, the navigation method 370 can then enter the determination of whether the selected metric is acceptable in block 414. Similar to as discussed above, the determination of whether the metric is acceptable in block 414 can allow for receiving additional signals in loop path 418 and / or performing navigation resolution in block 428.

[0130] Accordingly, the method 370 can follow the undistorted path 410 and / or the distorted path 440 to resolve navigation and determine the pose of the tracking device 66 in space relative to the object 30. The method 370 can include the undistorted path 410 and the distorted path 440, which can include the distortion correction subroutine 460. The distortion correction subroutine 460 can be executed by the controller 110 or the navigation processor 102 to allow removal or correction of distortions from a distorting object in order to determine the true or correct pose of the tracking device 66. Distortions can be detected in block 390 and removed in the distortion correction subroutine 460, as discussed above.

[0131] As briefly discussed above, the subroutine 460 can be substantially sequential, as discussed above. Accordingly, the various calculations (such as instructions executed by a processor) can be processed in the order directly shown in FIG. 4B, as discussed above. Figure 9 However, in various embodiments, all of the processes in the subroutine 460 can be performed simultaneously, or a selected plurality of processes can be performed simultaneously. In other words, the subroutine 460 can proceed via simultaneous separation 444, reconstruction 448, and removal or deconvolution 454. However, the subroutine 460 can still follow the decision in block 390 of whether the recovered impulse response includes a distortion tail. The subroutine 460 can then include simultaneous separation and deconvolution of the reconstructed distorted impulse response from the recovered impulse response to discover a corrected impulse response and impulse. The corrected impulse response and impulse can be determined by fitting the residue to a combination of measured or modeled impulse responses, including expected conductive as well as conductive and magnetic contributions.

[0132] Accordingly, as discussed above, the navigation system 26 can be used to determine the pose of a tracking device 66 associated with (such as connected to) an instrument 68. Accordingly, the navigation system 26 can track this tracking device 66 and navigate the instrument 68, such as by displaying the instrument 68 as a representation 68i on the display device 84. The use of spread spectrum transmissions can allow for low power and high fidelity signal transmissions through selected electronics (such as the "H" bridge configuration discussed above). Additionally, selected schemes (such as the BNO scheme) can allow for transmission of signals that are substantially free of distortions or confusions caused by external signals relative to the tracking device 66. Additionally, received signals can be analyzed or reconstructed to determine whether distortions are present or have been caused by a distorting object, and if so, the distortions can be removed. Accordingly, due to the received signals at the tracking device 66, the pose of the tracking device 66 can be determined with selected accuracy and correctness.

[0133] The foregoing description of implementations has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the application to the precise form disclosed. Individual elements or features of a particular implementation are generally not limited to that particular implementation, but, where applicable, are interchangeable and can be used in a selected implementation, even if not specifically shown or described. The same element or feature can be varied from implementation to implementation. Such variations are not to be regarded as a departure from the application, and all such modifications are intended to be included within the scope of the application.

[0134] It should be understood that various aspects disclosed herein can be combined in different combinations than the combinations specifically presented in the description and accompanying drawings. It should also be understood that certain actions or events can be performed in a different order than described within this specification, that certain actions or events can be performed concurrently, that some actions or events can be omitted, or that additional actions or events can be performed. Additionally, although a particular aspect can be described as being performed by a single module or unit for purposes of clarity, it should be understood that the techniques of this disclosure can be performed by a combination of units or modules associated with, for example, a medical device.

[0135] In one or more examples, the described techniques can be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions can be stored as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media can include non-transitory computer-readable media, which corresponds to a tangible medium such as data storage media (e.g., RAM, ROM, EEPROM, flash memory, or any other medium that can be used to

[0136] Instructions can be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, graphics processing units (GPUs), application-specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term "processor" as used herein can refer to any of the foregoing structure or any other physical structure suitable for implementation of the described techniques. Also, the techniques could be fully implemented in one or more circuits or logic elements.

Claims

1. A procedure navigation system comprising: a controller operable to generate signals; a localizer coil formed of an electrically conductive material; an H-bridge switching system interconnecting the controller and the localizer coil; wherein the localizer coil is operable to emit tracking signals from the controller when connected via the H-bridge, wherein the controller is configured to generate spread spectrum symbols operable to include a binary pseudo-noise signal as the tracking signals, and the tracking signals are operable to be emitted by the localizer coil as a set of binary near-orthogonal signals.

2. The system of claim 1, further comprising: a tracking device configured to receive the tracking signals.

3. The system of claim 2, wherein the controller is operable to receive tracking device signals based on the received tracking signals and determine a pose of the tracking device that can include at least some coordinates of a position and / or orientation.

4. The system of any of claims 1-3, wherein the localizer coil comprises a plurality of localizer coils; wherein H-bridge switching system comprises a plurality of H-bridge switching systems; wherein each of the plurality of localizer coils is interconnected with the controller by one of the plurality of H-bridge switching systems.

5. The system of claim 4, further comprising: a local power system operable to power the plurality of localizer coils.

6. The system of claim 4, wherein the plurality of localizer coils comprises up to 36 localizer coils.

7. The system of claim 6, further comprising: a tracking device configured to receive the tracking signals, wherein the tracking device comprises a plurality of tracking coils; wherein the controller is configured to resolve tracking device signals for each of the plurality of tracking coils of the tracking device and each of the plurality of localizer coils.

8. The system of claim 4, further comprising: a tracking device configured to receive the tracking signals, wherein the tracking device comprises a plurality of tracking coils; wherein the controller is configured to resolve tracking device signals for each of the plurality of tracking coils of the tracking device and each of the plurality of localizer coils.

9. The system of claim 2, further comprising: a display device operable to display an image and a graphical representation of an instrument associated with the tracking device.

10. The system of claim 2, further comprising: a processor configured to de-multiplex and equalize the tracking signals to determine an impulse response.

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