System and method to generate and calibrate a tracking field

Abstract

A method and system are disclosed for assisting in performing a procedure. The system and method may allow for a generation of a field with a field generation system. The field may be augmented to assist in determining a pose of a device in the field.

Description

A0011210SYSTEM AND METHOD TO GENERATE AND CALIBRATEA TRACKING FIELD

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 727,730, filed 4 December 2024 and U.S. Pat. App. No. 63 / 727,744 the entire content of which is incorporated herein by reference.FIELD

[0002] The present disclosure relates to a tracking field generation and calibration, and particularly to a surgical navigation localizer.BACKGROUND

[0003] This section provides background information related to the present disclosure which is not necessarily prior art.

[0004] A subject, such as a human patient, may undergo a procedure. The procedure may include a surgical procedure to correct or augment an anatomy of the subject. The augmentation of the anatomy can include various procedures, such as movement or augmentation of bone, insertion of an implant (i.e. an implantable device), or other appropriate procedures.

[0005] A surgeon can perform the procedure on the subject with images of the subject that are based on projections of the subject. The images may be generated with imaging systems such as a magnetic resonance imaging (MRI) system, computed tomography (CT) system, fluoroscopy (e.g., x-ray C-Arm imaging systems), or other appropriate imaging systems.A0011210

[0006] A surgical procedure may be performed with, such as assisting during, with a surgical navigation system. The surgical navigation system includes a localizer. The localizer generates a field within a region that may encompass only a small portion of the subject, thus possibly requiring it to be moved for a procedure.SUMMARY

[0007] This section provides a general summary of the disclosure and is not a comprehensive disclosure of its full scope or all of its features.

[0008] The subject disclosure relates to a system and method to generate a field relative to a subject. The field may be used for tracking one or more tracking devices relative to a subject in a tracking space or navigation space. The navigation system may determine the pose of the tracking device in the navigation space. The tracking device may be associated with an instrument and the navigation system may also determine a pose of the instrument based upon tracking the tracking device.

[0009] The tracking system included with the navigation system may include one or more conductive members. The conductive members may be provided in any appropriate configuration, such as flat or cylindrical coils or items that are effectively long wire segments, or sheets of current. Discussion herein of coils or conductive coils is understood to generally describe a conductive member appropriate for the respective portion, unless specifically disclosed otherwise. The conductive coils may be formed of a plurality of coils of conductive material, suchA0011210 as wire or other conductive material. The coils may be provided in any appropriate geometry relative to one another. The coils, however, may be positioned in a large region or volume relative to the subject. For example, one or more coils may be formed or positioned in a wall of a room in which the subject is positioned. The coils or conductive members may also be formed into a moveable wall or surface, such as a system that may resemble a moveable whiteboard or area divider.

[0010] The coils positioned in a wall of the room may be coils that define or form a substantially large surface area. The large surface area formed or defined by the coils may allow the coil to generate a large field in the room, such as relative to or encompassing the subject. Thus, the coils may generate a field within a room while being positioned entirely outside of a selected region in a room (e.g., a sterile field of a surgical or other procedure) or a floor space in the room. Further, the field that is generated may be substantially uniform through the room, as discussed further herein.

[0011] The generated field may be a magnetic field. The magnetic field may be generated as a component of an electromagnetic field cause by a current induced in the coils. Thus, the field generated may be a selected field and based on a parameter of the coil.

[0012] One or more field distorting objects may be positioned in the room. The distorting object may change or distort the field from the uniform field that may be generated by the coils in the room. A calibration device and related method may be used to then determine field parameters to allow for determination of variabilityA0011210 of sensed field strengths at different positions to determine a pose of the tracking device, such as relative to field distorting members.

[0013] A method of navigating a tracking device may be based upon the measured distortion in the field. The measured distortion may be based upon a real time measurement with a selected calibration device. The calibration device may include one or more sensors (e.g., magnetic field sensors or receivers) that sense of field within the room. The calibration device may include two or more receivers that are positioned at a fixed pose relative to one another to measure the field at two different poses that are known relative to one another. Thus, a determination (e.g., model) of a distortion of the field may be made to allow for a determination of a pose of a tracking device based upon a sensed field.

[0014] 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 DECSRIPTION OF THE DRAWINGS

[0015] The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

[0016] Fig. 1 is an environmental view of an imaging system in an operating theatre;A0011210

[0017] Fig. 2 is a detail schematic view of a portion of the operating theater with at least a first array, according to various embodiments;

[0018] Fig. 3 is a detail schematic view of a portion of the operating theater with at least the first and a second array, according to various embodiments;

[0019] Fig. 4 is a detail schematic view of a portion of the operating theater with at least a first array, according to various embodiments;

[0020] Fig. 5A is a detail schematic view of a portion of the operating theater with at least a first array and a distorting object, according to various embodiments;

[0021] Fig. 5B is a detail schematic view of a calibration system, according to various embodiments; and

[0022] Fig. 6 is a flowchart of a process to model a uniform field that has been distorted, according to various embodiments.

[0023] Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.DETAILED DESCRIPTION

[0024] Example embodiments will now be described more fully with reference to the accompanying drawings.

[0025] The subject disclosure is directed to an exemplary embodiment of a surgical procedure on a subject, such as a human patient. It is understood, however, that the system and methods described herein are merely exemplary and not intended to limit the scope of the claims included herein. In various embodiments, it is understood, that the systems and methods may be incorporatedA0011210 into and / or used on non-animate objects. The systems may be used to, for example, image and register coordinate systems between two systems for use on manufacturing systems, maintenance systems, and the like. For example, automotive assembly may use one or more robotic systems including individual coordinate systems that may be registered together for coordinated or consorted actions. Accordingly, the exemplary illustration of a surgical procedure herein is not intended to limit the scope of the appended claims.

[0026] Various members or portions thereof may also be tracked relative to the subject. For example, a tracking system may be incorporated into a navigation system to allow tracking and navigation of one or more instruments (which may be the members) that may be tracked relative to the subject. The subject may also be tracked. The navigation system may include one or more tracking systems that track various portions, such as tracking devices, associated with instruments. The tracking system may include a localizer that is configured to determine the pose of the tracking device in a navigation system coordinate system. The pose may include any number of degrees of freedom, such as a three-dimensional location (e.g., x, y, z) and an orientation (e.g., yaw, pitch, and roll). Techniques, systems, or processes to determine the navigation system coordinate system may include those described at various references including U.S. Pat. No. 8,737,708; U.S. Pat. No. 9,737,235; U.S. Pat. No. 8,503,745; U.S. Pat. No. 8,175,681 ; and U.S. Pat. No. 11 ,135,025; all incorporated herein by reference. In particular, a localizer may be able to track an object within a volume relative to the subject. The navigation volume, in which a device may be tracked, may include or be referred to as theA0011210 navigation coordinate system or navigation space. A determination or correlation between two coordinate systems may allow for or also be referred to as a registration between two coordinate systems.

[0027] Image data may be acquired for use and / or to generate images, which may also be referred to as image visualizations, of selected portions of a subject. The images may be displayed for viewing by a user, such as a surgeon. In various embodiments, superimposed on at least a portion of the image may be a graphical representation of a tracked portion or member, such as an instrument. The graphical representation may be generated (e.g., by a processor module executing instructions) entirely as a graphic that represents the instrument. According to various embodiments, the graphical representation may be superimposed on the image at an appropriate pose due to registration of an image space (also referred to as an image coordinate system) to a subject space. A method to register a subject space defined by a subject to an image space may include those disclosed in U.S. Pat. Nos. U.S. Pat. No. 8,737,708; U.S. Pat. No. 9,737,235; U.S. Pat. No. 8,503,745; and U.S. Pat. No. 8,175,681 ; all incorporated herein by reference.

[0028] During a selected procedure, a first coordinate system may be registered to a subject coordinate system (also referred to as a subject space) due to a selected procedure, such as imaging of the subject. In various embodiments, the first coordinate system may be registered to the subject by imaging the subject with a fiducial portion that is fixed relative to the first member or system, such as a robotic system or other instrument. The known position of the fiducial relative toA0011210 any portion, such as the robotic system or the subject, may be used to register the subject space relative to any coordinate system in which the fiducial may be determined (e.g., by imaging or detecting (e.g., touching)). A registration of a second coordinate system may allow for tracking of additional elements not fixed to a first portion, such as a robot that has a known coordinate system.

[0029] The tracking of an instrument during a procedure, such as a surgical or operative procedure, allows for navigation of a procedure. The navigation may be used to determine a pose of one or more portions, such as an instrument. The pose may include any number of degrees of freedom, such as a three-dimensional location (e.g., x, y, z) and an orientation (e.g., yaw, pitch, and roll). When image data is used to define an image space it can be correlated or registered to a physical space defined by a subject, such as a patient. According to various embodiments, therefore, the patient defines the patient space in which an instrument can be tracked and navigated. The image space defined by the image data can be registered to the patient space defined by the patient. The registration can occur with the use of fiducials that can be identified in the image data and in the patient space.

[0030] Fig. 1 is a diagrammatic view illustrating an overview of a procedure room or arena 18. In various embodiments, the procedure room may include a surgical suite in which may be placed a robotic system 20 and a navigation system 26 that can be used for various procedures. The robotic system 20 may include a MAZOR X® robotic guidance system, sold by Mazor Robotics Ltd. having a place of business in Israel and / or Medtronic, Inc. having a place of business inA0011210Minnesota, USA and / or as disclosed in U.S. Pat. No. 11 ,135,025, incorporated herein by reference. The robotic system 20 may be used to assist in guiding a selected instrument, such as drills, screws, be an ultrasound (US) probe 33, etc. relative to a subject 30.

[0031] The robotic system 20 may include a mount 34 that fixes a portion, such as a robotic base 38, relative to the subject 30. The robotic system 20 may include one or more arms 40 that are moveable or pivotable relative to the subject 30, such as including an end effector 44. The end effector 44 may be any appropriate portion, such as a tube, guide, or passage member. Affixed to and / or in place of the end effector may be the imaging system that may be the US probe 33. A robotic processor module 53 may be used to control (e.g., execute instructions) to move and determine a pose of the end effector, such as relative to the base 34. The pose of the base 34 may be known in a coordinate system, such as the patient space of the patient 30 and / or the image coordinate system due to a registration as discussed above and exemplary disclosed in U.S. Pat. No. 11 ,135,025, incorporated herein by reference.

[0032] The navigation system 26 can be used to navigate the various portions due to the tracked pose of one or more tracking devices, tracking devices may include a robot tracking device 54, a subject tracking device 58, an imaging system tracking device 62, a tool tracking device 66, and / or an US probe tracking device 81 . Each of the tracking devices may be used to track one or more portions, including those illustrated as being attached to the respective tracking devices.A0011210

[0033] An imaging device or system 80 may be an additional or alternative imaging system that may be used to acquire pre-, intra-, or post-operative or realtime image data of a subject, such as the subject 30, and may be tracked with the image system tracking device 62. It will be understood, however, that any appropriate subject can be imaged and any appropriate procedure may be performed relative to the subject. In the example shown, the imaging device 80 comprises an O-arm® imaging device sold by Medtronic Navigation, Inc. having a place of business in Louisville, Colorado, USA. The imaging device 80 may have a generally annular gantry housing 82 in which an image capturing portion is moveably placed. The imaging device 80 can include those disclosed in U.S. Pat. No. 7,188,998; U.S. Pat. No. 7,108,421 ; U.S. Pat. No. 7,106,825; U.S. Pat. No. 7,001 ,045; and U.S. Pat. No. 6,940,941 , all of which are incorporated herein by reference. It is further appreciated that the imaging device 80 may include additionally or alternatively a fluoroscopic C-arm. Other exemplary imaging devices may include fluoroscopes such as bi-plane fluoroscopic systems, ceiling mounted fluoroscopic systems, cath-lab fluoroscopic systems, fixed C-arm fluoroscopic systems, isocentric C-arm fluoroscopic systems, 3D fluoroscopic systems, etc. Other appropriate imaging devices can also include MRI, CT, ultrasound, etc. The various imaging systems may include or use one or more imaging modalities, such as x-ray, magnetic resonance, ultrasound, Positron emission tomography (PET) scans, combinations thereof, etc.

[0034] The position of the imaging system 33, 80, and / or portions therein such as the image capturing portion, can be precisely known relative to any otherA0011210 portion of the imaging device 33, 80. Also, the respective tracking devices may be used to track one or more portions of the respective imaging systems. The precise positioning and / or tracking can allow the imaging system 33, 80 and / or the navigation system 26 to know its position relative to the patient 30 or other references. In addition, as discussed herein, the precise knowledge of the position of the image capturing portion can be used in conjunction with a tracking system to determine the position of the image capturing portion and the image data relative to the tracked subject, such as the patient 30. The pose (e.g., distance from a selected portion of the US probe 33 and / or the tracking device 81) may be determined or predetermined and saved for recall with a calibration process and / or jig, such as that disclosed in U.S. Pat. No. 7,831 ,082; U.S. Pat. No. 8,320,653; and U.S. Pat. No. 9,138,204, all incorporated herein by reference.

[0035] The imaging device 80 may be controlled with a controller that may include one or more processor modules 97. Thus, the portions of the imaging system 80 relative to other portions, such as the gantry may be at known and / or controlled poses. Further, the imaging system 80 may be tracked with a tracking device 62. As discussed herein, this may allow the pose of one or more portions of the imaging system 80 to be known at a selected time, such as while acquiring image data of the subject 30 by the navigation system 26. Moreover, the pose of the imaging system or portion thereof may be planned and moved to a planned pose relative to the subject 30. Also, the tracking device 81 can be associated directly with the US probe 33. The US probe 33 may, therefore, be directly tracked with a navigation system as discussed herein. In addition or alternatively, the USA0011210 probe 33 may be positioned and tracked with the robotic system 20. Regardless, image data defining an image space acquired of the patient 30 can, according to various embodiments, be registered (e.g., manually, inherently, or automatically) relative to an object space. The object space can be the space defined by a patient 30 in the navigation system 26.

[0036] The patient 30 can also be tracked as the patient moves with a patient tracking device, DRF, or tracker 58. Alternatively, or in addition thereto, the patient 30 may be fixed within 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 subject space allows for navigation of the instrument 68 with the image data. When navigating the instrument 68, a position of the instrument 68 can be illustrated relative to image data acquired of the patient 30 on a display device 84. An additional and / or alternative display device 84’ may also be present to display an image. Various tracking systems, such as one including an optical localizer 88 or a different field generating localizer. A field generating localizer may include a small or portable electromagnetic (EM) localizer 94 (shown in phantom) and / or a large or “wall” EM localizer 94’. With the navigation system, the localizers may be used to track the instrument 68 alone or together. The EM localizer 94’ as a “wall” may be placed or formed into a moveable wall, such as resembling a moveable whiteboard or a moveable screen.

[0037] One or more tracking systems can be used to track the instrument 68, and / or any other tracking device, in the navigation system 26. According to various embodiments, these tracking systems can include an electromagneticA0011210 tracking (EM) system having the EM localizer 94, 94’, an optical tracking system having the optical localizer 88 and / or other appropriate tracking systems, not illustrated, such as an ultrasound tracking system, or other appropriate tracking systems. One or more of the tracking systems can be used to track selected tracking devices, as discussed herein, sequentially or simultaneously. It will be understood, unless discussed otherwise, that a tracking device can be a portion trackable with a selected tracking system. A tracking device need not refer to the entire member or structure to which the tracking device is affixed or associated.

[0038] Image data acquired from the imaging system 33, 80 or any appropriate imaging system, can be acquired at and / or forwarded from an image device controller 96, that may include the processor module 97, to a navigation computer and / or processor system 102 that can be a part of a controller or work station 98 having the display 84 and a user interface 106. The processor system 102 may be a processor module, as discussed herein, including integral memory or a communication system to access external memory for executing instructions and / or operated as a specific integrated circuit (e.g., ASIC). It will also be understood that the image data is not necessarily first retained in the controller 96, but may also be directly transmitted to the work station 98. The work station 98 can provide facilities for displaying the image data as an image 108 on the display 84, saving, digitally manipulating, or printing a hard copy image of the received image data. The image may be any appropriate type of image such as a two- dimensional image, three-dimensional image, a time changing image or cine, or combinations thereof. The user interface 106, which may be a keyboard, mouse,A0011210 touch pen, touch screen or other suitable device, allows the user 72 to provide inputs to control the imaging device 80, via the image device controller 96, or adjust the display settings of the display 84. The work station 98 may also direct the image device controller 96 to adjust the image capturing portion of the imaging device 80 to obtain various two-dimensional images along different planes in order to generate one or more representative two-dimensional and three-dimensional image data that may be used to generate two-dimensional, three-dimensional, or a more than of either or both images.

[0039] With continuing reference to FIG. 1 , the navigation system 26 can further include any one or more tracking systems, such as the tracking system including either or both of the electromagnetic (EM) localizer 94, 94’ and / or the optical localizer 88. The tracking systems may include a controller and interface portion 110. The controller 110 can be connected to the processor system or portion 102, which can include a processor included within a computer. The processor system 102 may include a processor module 102p and a memory module 102m. The EM tracking system may include the STEALTHSTATION® AXIEM™ Navigation System, sold by Medtronic Navigation, Inc. having a place of business in Colorado; or can be the EM tracking system described in U.S. Pat. No. 7,751 ,865; U.S. Pat. No. 5,983,126; U.S. Pat. No. 5,913,820; or U.S. Pat. No. 5,592,939; all of which are herein incorporated by reference. It will be understood that the navigation system 26 may also be or include any appropriate tracking system, including a STEALTHSTATION® TREON® or S7™ tracking systems having an optical localizer, which may be used as the optical localizer 88, and soldA0011210 by Medtronic Navigation, Inc. of Louisville, Colorado. Other tracking systems include an acoustic, radiation, radar, etc. The navigation system 26 and / or tracking system may be a hybrid system that includes components from multiple tracking systems. The tracking systems can be used according to generally known or described techniques in the above incorporated references. Details will not be included herein except when to clarify selected operation of the subject disclosure.

[0040] Various portions of the navigation system 26, such as the instrument 68, and others as will be described in detail below, can be equipped with at least one, and generally multiple, of the tracking devices 66. The instrument can also include more than one type or modality of tracking device 66, such as an EM tracking device and / or an optical tracking device. An EM tracking device may include one or more induction coils or any other kind of magnetometer. 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 with the tracking system, as discussed above. Image data of the patient 30, or an appropriate subject, can be used to assist the user 72 in guiding the instrument 68. The image data, which may include one or more image data or images, may be registered to the patient 30. The image data defines an image space that is registered to the patient space defined by the patient 30. The registration can be performed as discussed herein, automatically, manually, or combinations thereof.

[0041] Generally, registration allows a translation map to be generated of the physical location of the instrument 68 relative to the image space of the image data. The translation map allows the tracked position of the instrument 68 to beA0011210 displayed on the display device 84 relative to the image 108. A graphical representation 68i, also referred to as an icon, can be used to illustrate the location of the instrument 68 relative to the image 108 that may be generated with one or more types of image data.

[0042] With continuing reference to Fig. 1 , a subject registration system or method can use the tracking device 58. The tracking device 58 may include portions or members 120 that may be trackable, but may also act as or be operable as a fiducial assembly. A clamp or other fixation portion 124 may be connected to the imageable fiducial portions 120. The fiducial portions 120 may include one or more individual or discrete member (e.g., spheres) or may include an interconnected web of imageable portions (e.g., wires). It is understood, however, that the fiducial portions 120 may be separate from the tracking device 58. The fixation portion 124 can be provided to fix any appropriate portion, such as a portion of the anatomy. As illustrated in Fig. 1 , the fiducial portions 120 can be interconnected with a vertebra 126 and / or a portion of the vertebra 126 which may form a spine. In various embodiments, the connection may be to a spinous process. The fiducial portions 120, however, may be connected to any appropriate portion such as a skull, pelvis, etc.

[0043] In various embodiments, the imaging system 80 may move, as a whole or in part, relative to the subject 30. For example, within the gantry 82 may be a source and a detector that can move in a 360° motion around the patient 30. The movement of the source and the detector as a source / detector unit within the gantry 82 may allow the source to remain generally 180° opposed (such as with aA0011210 fixed inner gantry or rotor or moving system) to the detector. Thus, the detector may be referred to as moving around (e.g., in a circle or spiral) or about the subject 30 and it is understood that the source remains opposed thereto, unless disclosed otherwise. As discussed herein, however, the detector may move relative to the source in a small or minimal amount, such as an arc length of about one degree (°) to about 30°, 5° to about 20°, 5° to about 15°, etc., and increments therebetween.

[0044] Also, the gantry 82 can move isometrically (also referred to as “wag”) relative to the subject 30 generally in the direction of arrow 180 around an axis 181 , such as through a cart 160, as illustrated in Fig. 1. The gantry 82 can also tilt relative to a long axis 31 of the patient 30 illustrated by arrows 182. In tilting, a plane of the gantry 82 may tilt or form a non-orthogonal angle with the axis 181 of the subject 30.

[0045] The gantry 82 may also move longitudinally in the direction of arrows 184 along the line 181 relative to the subject 30 and / or the cart 160. Also, the cart 160 may move to move the gantry 82. Further, the gantry 82 can move up and down generally in the direction of arrows 186 relative to the cart 160 and / or the subject 30, generally transverse to the axis 181 and parallel with the axis 181.

[0046] The movement of the imaging system 80, in whole or in part is to allow for positioning of the source / detector unit (SDU) relative to the subject 30. The imaging device 80 can be precisely controlled to move the SDU relative to the subject 30 to generate precise image data of the subject 30.A0011210

[0047] The source, as discussed herein, may include one or more sources of x-rays for imaging the subject 30. In various embodiments, the source may include a single source that may be powered by more than one power source to generate and / or emit x-rays at different energy characteristics. In various embodiments, the source may emit x-rays in at least two different powers, such with varying voltages. Further, more than one x-ray source may be the source that may be powered to emit x-rays with differing energy characteristics at selected times.

[0048] With continuing reference to Fig. 1 and additional reference to Fig. 2, the localizer 94' is illustrated and discussed in greater detail. As discussed above the localizer 94, 94’ may generate a field in a room or volume (also referred to as a region), such as relative to the subject 30 and in in operating room or surgical theater 18. The localizer 94 may be a small or portable localizer, as illustrated in Fig. 1 . The localizer 94 may be positioned by the user 72 relative to the subject 30 to generate a field relative to the subject 30. The localizer 94 may generally be positioned relative to the subject 30 such that the electromagnetic field generated by the localizer 94 may allow for navigation of the instrument 68 relative to the subject 30. In various embodiments, for example, the localizer 94 is positioned relative to the subject 30 such that a field emitted by the localizer 94 is not distorted by any member relative to the subject 30. In various embodiments, for example, the subject support or table 104 may be positioned and / or formed of a material that does not to distort the field generated by the localizer 94. The localizer 94 may generate a field with one or more coils, such as a coil 99. The localizer 94 mayA0011210 include more than one of the coils 99 that are positioned at various geometries relative to one another, such as having different centers. The coils 99 may be formed of a conductive material, such as a wire, formed into a coil, such as wrapped in a cylinder, in a toroidal shape, or the like. Nevertheless, the localizer 94 is generally positioned to form a field and a volume that allows for navigation based upon a substantially undistorted field.

[0049] In various embodiments, however, the localizer 94’ may be formed relative to the subject 30 in the operating theatre 18. In various embodiments, for example, the localizer 94’ may be formed into or onto a wall 200. The wall 200 may be a wall of the operating room or theater 118. The wall 200 may be one wall of the room that extends between a floor 204, a ceiling 206, and other portions such as other walls of the room 18. The localizer 94’ may be formed in any wall of the room 18 and / or more than one of the walls, as discussed herein.

[0050] The localizer 94’ may include one or more conductive members through which a current may be driven to generate a field. In various embodiments, the conductive members may be formed as coils that may have a size or geometry that is substantially larger than the localizer 94. For example, the localizer 94’ may have a first coil element 210 that has a center 210c and a radius 210r. The radius 21 Or may be from several centimeters to several meters, including about 5 centimeters (cm) to about 10 meters (m), and further including about 5 cm to about 3 m, and further including about 5 cm to about 1.5 m, and further including about 10 cm to about 50 cm, and further including about 25 cm. The radius 21 Or of the coil 210 may be formed or defined by the geometry of the wall 200, the position ofA0011210 the localizer 94’ relative to the subject 30, or other considerations. Nevertheless, the coil 210 of the localizer 94’ may be formed to generate a substantially large field, as discussed further herein, relative to the subject 30. In various embodiments, the centers may be or referred to as central points rather than a center of a circle or round coil. Thus, the central point may be a point which may be identified relative to the conductive member. The central point may be a center of mass, a geometric center, or an arbitrary point that is referred to as the central point that is the same geometric position for different coils that may be used to reference the pose of each coil of the same shape.

[0051] For example, in various embodiments, the wall 200 or other material that may encapsulate and / or support for the localizer 94’, according to various embodiments, may be formed of an appropriate material. For example, the wall may be formed of non-interfering or non-reflecting material. These materials may, therefore, allow the field, such as a magnetic field, to pass through and not be reflected or interfered.

[0052] The coil 210 may be any appropriate geometry or shape. The coil 210 may be or may not be a circle, but maybe in an oval (e.g. including a variable radius), square, or other appropriate shape. The coil 210 may be a regular or irregular shape. The localizer coils may be formed as coils of conductive material or formed in any appropriate shape, as noted above. Further, the coils may be planar or non-planar as selected to form the selected field (e.g., a uniform magnetic field) in a navigation volume.A0011210

[0053] The localizer 94’ may include more than one coil. For example, the localizer 94’ may include a second coil 214 having a second center 214c. The localizer 94’ may further include 1 / third coil 218. The third coil 218 may extend in a substantially non-circular manner, such as around the boundary of the wall 200. Thus, the coil 218 may have a generally square or rectangle configuration, as illustrated in fig. 2.

[0054] Thus, the localizer 94’ may be formed relative to the subject 30 in the room 18. In various embodiments, for example, the localizer 94' may be formed into and / or with the wall 200 during construction of the wall 200. That is, the wall may be formed to form the room 18 and the localizer 94’ may be formed with the wall 200 during construction. The respective coils 210, 214, 218 may be embedded in the building materials, such as a wall or covering of a structural support of the wall 200. Alternatively or additionally the coils 210-218 may be formed by material that build the wall 200, such as the framing structure thereof.

[0055] The uniform field , as discussed herein, may fill or be formed in the entire room. Alternatively, the field may be formed in a selected region, such as where the subject 30 may be present. Generally, however, the uniform field may be generated in a navigation volume. The navigation volume may be a selected volume. For example, the navigation volume may be about one cubic meter to about 10 cubic meters, including about two cubic meters, three cubic meters, four cubic meters, or any appropriate value such as between one and 10 cubic meters.

[0056] As discussed herein, the uniform field may be a field that is able to be measured as uniform in a selected volume or within a selected range ofA0011210 variability. Thus, the uniform field may be or is a nearly uniform that is effectively uniform for the purposes of navigation, such as surgical navigation with tracking devices as discussed herein. The near-uniformity may be an effect due to a design of the transmitter of the localizer.

[0057] The localizer 94’ may be operated by a selected connection, such as a connection 222 that may be connected to the workstation 98 for operation of the localizer 94’. For example, power may be provided through the connection 222 to the localizer 94’. Controlling the field generated by the localizer 94’ may be provided through the connection 222. Also or alternatively, a signal may be received at the localizer 94’ and transmitted through the connection 222. Thus, the localizer 94’ may be formed into the wall and thereafter connected during a selected procedure, such as a procedure on the subject 30.

[0058] In turning to reference to Fig. 3, the localizer 94’ may include more than one localizer array, for example a first localizer array 94’a and a second localizer array 94’b. The two arrays 94'a and 94'b may be formed into opposing walls, including the wall 200 and a second wall 240. The operating room 18 may include the two walls 200, 240 and the patient 30 may be positioned within the room 18, such as on a patient support 104.

[0059] The localizer arrays 94'a, 94'b may be substantially opposed to one another, as illustrated in Fig. 3. For example, the two walls 200, 240 may be substantially opposed to one another across the room 18. The arrays 94'a, 94'b may operate in tandem or concert to generate the field within the room 18 relative to the subject 30. Thus, the localizer system for the tracking or navigation systemA001121026 may be provided with more than one localizer array, search is the first localizer array 94’a and the second localizer array 94'b.

[0060] The second localizer array 94'b may be formed substantially similar to the first array 94’a. Thus, the array 94’b may include one or more coils, such as coils that are generally analogous to the coils 210, 214, 218. In various embodiments, however, the coils may be formed larger or in a selected configuration. For example, more or less than three coils may be formed or used to define one or more of the localizer arrays 94'a, 94'b.

[0061] Nevertheless, turning reference to Fig. 4, the localizer array 94’ will be discussed in more detail. As discussed above, the localizer array 94’ may be formed into the wall 200 of the room 18. The localizer array 94’ may include one or more coils, such as the coils 210, 214, 218 as discussed above. The geometry of the coils of the localizer array 94’ may include a size, shape, or other parameter. Generally, the coils of the localizer array 94' may be formed and positioned in the wall 200 so as to form a substantially uniform field, such as exemplary illustrated by a field line 250 in the room 18. One skilled in the art will understand that the field may generally be understood to be similar to a far field such that it is generally uniform in the volume of the room 18. Thus, the volume of the room 18 may be defined as an entire navigation space or volume. As illustrated and discussed above, the subject 30 may be positioned within the room 18. Thus, the subject 18 may be positioned in the substantially uniform field when no distorting or conductive objects are positioned within the room 18.A0011210

[0062] In other words, when the room 18 is a substantially clean or empty room, the field generated by the localizer 94’ may be substantially uniform. That is that the field strength that is transmitted by the localizer 94’ may be substantially or nearly uniform at all points within the room 18. The substantially or nearly uniform field may be a field that is indistinguishable in strength, at least for navigation with selected or appropriate measuring instruments, within the room 18. Examples may include, for example, a strength of measurement of the earth's magnetic field or uniform field within a solenoid. Thus, the magnetic field strength measured at any point in the room 18 may be substantially constant and indistinguishable from any other point within the room 18 when no other object is present in the room and to the localizer array 94’ that is generating the field. As discussed above, the localizer array 94’ may include the one or more coils that generate the electromagnetic field, including the magnetic field illustrated by the magnetic field lines 250 in Fig. 4. This may also be referred to as a field with no diversity in the navigation space or volume.

[0063] In various embodiments, the localizer 94' including the coils 210-218 may generate a substantially uniform field, as discussed above. Particularly if each of the coils have a substantially similar diameter or size. Also, an infinitely long wire or effectively infinitely long wire will have a uniform field along its length. A positioning of the tracking device in the field may also effect and be accounted for in determining the pose of the tracking device, particularly in a uniform field. In various embodiments, however, the coils may have a plurality of different geometries or sizes which may allow for a diversity of field within the volume of theA0011210 room 18. For example, a field may be generated with a given current through the coil. A different current may generate a different field. Therefore, the connection 222 may allow for a separate connection to each of the coils of the localizer 94'. Thus, even if the first coil 210 is the substantially same size and geometry as the second coil 214, a varying current may be provided to vary the field generated by each of the coils. The two fields interacting may, therefore, create a diversity within the volume of the room 18.

[0064] Also, the field generated within the room 18 may be varied by providing different centers of the coils. For example, as illustrated Fig. 2, the center 210c of the coil 210 may be at a different position on the wall 200 than the center 214c of the second coil 214. Thus, even with a similar or identical current in the respective coil, the field generated within the room 18 by the two coils 210, 214 may differ and / or provide a diversity within the room 18. Thus, a diversity may be introduced into the room 18 of a magnetic field by providing a distinction or differentiation between coils of the localizer 94'.

[0065] Nevertheless, to provide a field that may substantially fill the room 18 the field may be substantially uniform, as illustrated in Fig. 4 with the field line 250. If the field generated by the localizer 94' is substantially uniform in the room 18, the ability to determine a pose of a tracking device based upon measuring magnetic field may be improbable or impossible given the uniformity of the field. With additional reference to Fig. 5, therefore, various items may cause distortion in the field in the room 18. For example, the patient support 104 may be formed of a conductive material. The conductive material in the patient’s support 104 mayA0011210 cause eddy currents that generate additional or alternative fields and / or cause a distortion in the field illustrated with the field lines 250. For example, as illustrated Fig. 5, undistorted field line 250 may be illustrated as substantially straight across the room 18 from the wall 200 to the wall 240. However, with the introduction or inclusion of the patient support 104 that is conductive, field lines may be curved or distorted as illustrated by the curved field lines 260 in Fig. 5. Thus, the field may be distorted or have variability or diversity within the room 18.

[0066] Due to the distortion or diversity of the field within the room 18, a distinction or differentiation of a first pose and a second pose of a tracking device may be made based upon a measuring of different field strengths, directions, and phases or determination of different field strengths directions, and phases at different poses within the room 18. As is understood by one skilled in the art, and discussed above, the magnetic field may induce a current in a conductive material. For example, the patient tracker or DRF 58 may include one or more coils that interact with the field, such as the field lines 260, in the room 18. For example, in the coil a current may be induced in the tracking device. The current may be measured to determine a field strength or other characteristic at a particular pose and allow for a determination of a pose of the tracking device due to the measured field or determined field strengths. The tracking device 58 may include a plurality of conductive portions, such as a plurality of conductive coil, to measure the field by an induced current in each coil at a more than one position in the tracking device 58. Thus, as discussed herein, the collection of the field measurements may include information regarding field strengths, directions, and phases. Thus,A0011210 discussion herein is understood that all of this information may be collected for determining a pose.

[0067] Thus, the diversity of the field may be required to determine a pose of the tracking device 58. It is understood that the tracking device or any portion may be used to measure the field strengths in the room 18, such as the tracking device 66 with the instrument 68. Further, any appropriate portion may cause a distortion in the field. As discussed above, and illustrated Fig. 1 , the imaging system 80, the robotic system 20, or other portions may be positioned within the room 18 to cause distortion in the field generated by the localizer 94'. Thus, the distorted field lines 260 may, after the introduction of a distorting item within the room 18, distort the field from the substantially uniform field 250 to the distorted field 260. The distorted field 260, however, may provide the diversity or differentiation of field strengths within the room 18 to allow for determination of pose.

[0068] While the distorted field 260 may be distorted by the distorting object, the type or amount of distortion may not be known due to the positioning of the distorting object within the room 18. For example, the object may be positioned at a substantially random position (e.g., by the user 72), be of a substantially random shape, or other generally random or provided differences. Further, during a selected procedure, the objects may move. For example, the user 72 may move the imaging system 80 from one position to another to acquire image data of the subject 30 at different points of a procedure. Thus, the distortion of the field that forms the distorted field 260 may change or alter during a procedure. However, itA0011210 may be selected to maintain navigation of the various portions, such as the instrument 68, during the procedure even during movement or after movement of the distorting object. A calibration assembly 300, therefore, may be provided to measure the distorted field and allow for a calibration or modeling of the distorted field during a procedure.

[0069] As discussed above, the calibration or distortion measurement system 300 may include one or more receivers or field sensors. Each of the sensors may be a magnetometer. The magnetometer may be any appropriate magnetometer such as an inductive coil, a flux gate, a superconducting quantum interference device, or a magneto resistive sensor . Each of the sensors may also be a combination or include more than one sensor type. The calibration system 300 may be provided in any appropriate shape such as a cube, a prismatic pyramid, a parallelepiped, tetrahedron, etc.

[0070] For example, the calibration system 300 may include eight receivers, one positioned at each vertex of a cube therefore the calibration system 300 may include sensors 310, 312, 314, 316, 318, 320, 322, and 324. Each of the field sensors 310-324 may also be referred to as field receivers or field sensors. The sensors 310-324 operate to sense the magnetic field at the pose at each of the sensors. This measurement may be a vector sum of the magnetic field at the pose of the senor. As discussed herein, each of the sensors may be referred to as a sensor or receiver and discussion of any one of the receivers, such as the receiver or sensor 310, may refer to each of them unless otherwise specifically indicated.A0011210

[0071] Accordingly, the receiver 310 may sense the field at a selected time. When the calibration system 300 is positioned within the room 18, for example when no other objects are present, the calibration system 300 may sense the substantially undistorted field. Therefore, the calibration system 300 may be used to identify or model the undistorted field when no object is present. The calibration system 300 assists in modeling the field by having each of the sensors positioned at known positions relative to one another. For example, as illustrated Fig. 5B, with the calibration system 300 may include a cube where each of the sensors are equidistant from one another at each vertex of the cube. The geometry of a cube is generally understood by one skilled in the art and the size of the cube 300 may be formed for any appropriate calibration or measurement system. For example, the first sensor 310 may be a selected distance 330 from the second sensor 312. The distance 330 may be any appropriate distance such as about one centimeter to about 20 centimeters apart. In various embodiments, the distance 330 is a selected or such as a significant fraction of the selected navigable volume, such as about 10% to about 200% including about 25%. In one example, a two cubic meter volume may include a cube with sides that are about 50 cm in length. It is understood, however, that the distance 330 may be in the appropriate distance.

[0072] The geometry of the calibration system 300, however, may also be formed in any appropriate geometry, including shape or size. For example, the calibration system 300 may be provided as a three-dimensional object including triangular faces, octagonal faces, or the like. The calibration system 300, however, maybe generally formed to have fixed or rigid distances between each of theA0011210 sensors and / or a configuration that may be made rigid for a selected period of time. The calibration system 300 may be used, therefore, to have a known pose of each of the sensors relative to one another to measure the field in a volume. Although the volume of the calibration system 300 is not the entire volume of the room 18, the field in the volume defined by the calibration system 300 may be measured at known poses relative to one another.

[0073] The calibration system 300 may be positioned within the room 18 with the distorting object, such as the operating or support table 104. The receivers 310-324 of the calibration system may sense the field at the eight poses. The eight poses may be known relative to one another, such as saved and recalled during a procedure. Thus, the navigation system 28 may measure and know a characteristic or selected characteristics of the field measured at the calibration system 300. The navigation system 26 would then execute instructions to determine parameters of the field in the room 18 due to the distorting object, such as the support 104. The navigation system 26, after the modeling or determination of the distorted field, may then determine poses of the tracked instruments based upon the sensing of the field that the tracking devices, such as the tracking device 66 or DRF 58.

[0074] The navigation system 26 may determine field parameters after the distortion or variability of the field due to the presence of the distorting object based upon a process 400 as illustrated in Fig. 6. The determination of the distorted or varied field for navigation of a tracking device may be performed according to theA0011210 process 400. The process 400 may begin in start block 410. Thereafter recalling or determining a uniform field, referred to as HTX is performed in block 414.

[0075] The uniform field may be determined such as measuring the field in the room 18 with the device 300 when the room is empty. Other calibrations of the uniform field may also be done such as after completion of building with the room, installation of the transmitter or localizer coils in the room, or the like. The uniform field may then be saved for later recall, such as being stored in the memory 102m of the navigation system 26. The uniform field may then be recalled for later modeling or transformation based upon the measured distortion, as discussed further herein.

[0076] The recalled or determined uniform field from block 414 may be determined based upon the initial construction or calibration, as discussed above. As further discussed above and illustrated in the figures such as Fig. 4, the field may be substantially uniform in the room or at least in an entire volume including the subject 30 when no distorting object is present in the room 18. As discussed above, the substantially uniform field may be a field that is uniform in vector intensity throughout the navigation volume, including the room 18, or the volume around the subject 30. The substantially uniform field may include a field that is immeasurably different based upon the measurements taken with selected instruments such as generally known magnetometers including an inductive coil, a flux gate, a superconducting quantum interference device (SQUID), or combinations thereof or the like. The magnetometers may measure the field toA0011210 substantially equal or equivalent throughout the volume thus defining a substantially uniform field.

[0077] The recalled uniform field may be recalled for various purposes such as those disclosed herein including fitting a model of distortion (Eq. 1 ) or navigating (Eq. 5).

[0078] The field may be distorted due to the presence of the distortion or distorting object, as discussed above. The distorting objects may be one that is required for a selected procedure such as the support of 104 or other objects positioned relative to the subject 30, such as a MAYFIELD® skull clamp, an instrument holding stand also referred to as a Mayo stand (e.g., a Mayo Stand sold by Universal Medical having a place of business in Oldsmar, FL.) , other surgical or procedure instrumentation, or the like. The distorting objects may cause a distortion in the field such that it is no longer uniform throughout the volume, such as the room or the navigation space. A process of modeling the distorting field may then occur in a modeling process or subprocess 420. The distorting field may be referred to or represented as HDIST which is meant to be just the distorting members addition to the total field in the volume. The field may be modeled due to the distortion at any selected position “x” within the field and may be modeled based on one or more number (e.g., P) of determined or measured parameters ©. Various parameters may be determined to model the distorting field, HDIST. Thus, the distorting field at the position x in the applied field and a set of parameters © may be used to model the field, as discussed herein. A further term HTX may be determined or recalled because the distortion in the uniform field may generallyA0011210 be a response to the transmitted field HTX and so is generally partially determined by the transmitted field HTX. Therefore, the model of the distorting field HDIST in the sub-process 420 may be represented by the general Eq. 1.

[0079] ffdist — Hdist(x', Htx, 0) Eq. 1

[0080] According, to various embodiments a dipole model may be generated. One skilled in the art will understand that a dipole model makes a nice example, other models may also be used such as a piecewise-continuous line current, a current loop, a truncated multipole expansion, an array of dipoles, the Biot-Savart law in general, a library of precomputed or empirical distortions, a finite element model, a boundary element model, or combinations thereof. The dipole model may be determined by evaluating an equation to allow the determination of P = six parameters 0 as represented and bolded in Eq. 2.

[0081] Hdist(x; Htx, 0) = (4TT)-1{3 (x - / ) [m ■ (x - / )] |x - r|5- m x - r|’3} Eq. 2

[0082] In Eq. 2, 0 = {r, m} where “r” is the dipole center and “m” is the moment vector. Eq. 2 may then be evaluated to determine the parameters for the dipole in block 424.

[0083] The model may then be determined by the positioning of the calibration system 300 having the selected number of magnetometers or sensors in the volume having the field that is distorted. The number of sensors may include eight, as discussed above, but may be provided in any appropriate number “M”. The sensors are at various positions or poses that may be in an arbitrary coordinate system yi where “i” refers to each of the sensors (i = 1 , 2, . . . M). The calibration system 300, including the one or more sensors may then measure theA0011210 magnetic field vector at the pose of each of the sensors. As discussed above, the pose of each of the sensors may be known relative to each other in the volume and may be recalled in block 428. The known relative pose of each of the sensors allows for a determination of the arbitrary coordinate system for the calibration system 300.

[0084] The calibration system may be used to measure the field in block 434 to measure or determine the magnetic field vector at each of these sensors. The vector may then be identified or referred to herein as Hmeas(yi). The measured vector may relate to the transmitted uniform field and the distorted field due to superpositioning and assuming that there is no other distortion, such as a moving or alternative distortion. The measurement of the vector relating to the field may be described by Eq. 3.

[0085] Hmeas(yi) ~ Hix + Hd si(yi', Hx, 0) Eq. 3

[0086] Due to the relationship of the measured vector and the field a determination of the parameter, as noted above, may be made. Thus the Eq. 1 , Eq. 2, and Eq. 3 may be solved for each of the various poses to solve for the parameters in block 438.

[0087] The solution of the parameters may be performed in an appropriate manner to determine or based upon the model of the dipole field. The equations for the model may be solved exactly or approximated based upon various root finding or optimization methods. The type of solution may be based upon the model and the required or desired accuracy of the determined solution.A0011210

[0088] Based upon the solution of the equations in block 438, the parameters may be known in the distorted field so that the distorted field may be related to the transmitted field based upon the parameters for any position x which is a position or pose that is attempted to be tracked or navigated, as discussed above. The relationship may be Eq. 4.

[0089] Hdist(x; Htx, 0) Eq. 4

[0090] The Eq. 4 may be used to calculate the distorted field for any pose x in block 442. As discussed above, the pose of an instrument or tracking device may be based upon a measured field, such as a vector thereof, at any pose. The determination of the parameters in the distorted field allow for the calculation that may be related to the undistorted field.

[0091] Once the parameters are determined for the distorted field, a navigation of the tracking device may occur by measuring the field, herein referred to as HMEAS and comparing it to an expected magnetic field as determined by Eq. 5.

[0092] Htx + Hdist(x; Htx, 0) Eq. 5

[0093] The calculation of the parameter in the distorted field may allow for a comparison of the measured field at the tracking device to an expected field in block 450. The comparison may be similar to the comparison in generally known navigation techniques where a table, such as a predetermined lookup table, of field measurements may be used to determine a current pose of a tracking device. For example, a volume may be calibrated with a selected device where field measurements are taken within the volume. During a procedure, theA0011210 measurements made with the tracking device may then be compared to the lookup table or database of calibration measurements to determine or output a current pose. Certain interpolation may also be used for measurements that do not exactly match a calibration measurement. Therefore, the comparison of the current measurement may be compared to the expected field measurement based upon the parameters of the distorted field, as modeled above. This allows a determination of a pose of the tracking device that may be based upon the comparison in block 450 and determined in block 454.

[0094] The determined pose may be a pose including all of the position and orientation factors, as discussed above. The pose may then be output in block 458. The output of the determined pose in block 458 may be any appropriate output such as a graphical illustration, a numerical output, or the like. According to various embodiments, as illustrated above, a pose of the instrument may be displayed as a geometric positioning of a graphical representation of the instrument. The navigation space may be registered to image space, as discussed above, such that a pose of the instrument may be displayed relative to an image as also discussed above.

[0095] The process may then end in block 460. The process 400, however, ending in block 460 may allow for navigation of the procedure. Therefore, the process 400 may not end a procedure on a subject, but may end the determination of a current pose of an instrument. It is understood that the process 400 may be repeated a selected number of times or at selected intervals to achieve an appropriate or selected navigated procedure. For example, the process 400 mayA0011210 be repeated at a selected rate, such as 10 times a second, 20 times a second, 100 times a second, or any other appropriate value. The recurring or selected rate may allow for the navigation to a selected preciseness and may alter based upon a speed of a procedure, type of procedure, or the like.

[0096] The system and method, as discussed above, may allow for the generation of a substantially uniform field in a volume. The uniform field may have introduced therein variability or field differences with a distorting system or member. The distorted field may allow for variability or diversity of the field to allow for determination of a tracked pose of a tracking device or instrument. The variability or diversity of the field may be modeled as discussed above to allow for the output of a tracked pose of a tracking device in a related instrument. The type of uniform field may be based upon the positioning and size and geometry of emitter coils, but the distortion generated with a such a distorting object may be modeled allow for the navigation as discussed above.

[0097] The techniques of this disclosure may also be described in the following examples

[0098] Example 1 - A surgical navigation system operable to navigate a procedure relative to subject, comprising: a first coil of a conductive material having a first coil center positioned relative to a volume and configured to generate a first magnetic field within the volume, wherein the magnetic field is substantially uniform within the volume; a calibration device including a first field sensor to sense a first magnetic field vector at a first pose in the volume based on the magnetic field; and a processor module configured to execute instructions to determine parameters ofA0011210 the field in the volume based on a distortion of the magnetic field by a distorting object and the sensed magnetic field vector by the calibration device.

[0099] Examples 2 - The system of Example 1 , further comprising: a navigation processor configured to execute instructions to (1) model the distorted field relative to the uniform field and (2) determine a pose of a tracking device in the distorted field based on the model.

[0100] Example 3 - The system of Example 2, wherein the instructions include determining a model of a dipole in the volume based on the first magnetic field vector.

[0101] Example 4 - The system of Example 2, further comprising: the distorting object configured to distort the uniform magnetic field to generate magnetic field diversity in the volume.

[0102] Example 5 - The system of Example 1 , wherein the first coil is fixed relative to the volume.

[0103] Example 6 - The system of Example 1 , wherein the calibration device includes a second field sensor to sense a second magnetic field vector at a second pose in the volume based on the magnetic field.

[0104] Example 7 - The system of Example 1 , wherein the first field sensor includes a plurality of field sensors; wherein the calibration device includes the plurality of field sensors at known poses relative to each other; wherein each field sensor of the plurality of field sensors is configured to sense a magnetic field vector at the respective pose of the magnetic field sensors.A0011210

[0105] Example 8 - The system of Example 7, wherein the calibration device defines a geometric shape; wherein at least the first field sensor and a second field sensor of the plurality of field sensors are spaced apart at a fixed pose relative to one another with the calibration device.

[0106] Example 9 - The system of Example 8, wherein the geometric shape is a three-dimensional shape and at least the first field sensor, the second field sensor, and a third field sensor are spaced apart to define a calibration volume.

[0107] Example 10 - The system of Example 9, wherein at least a single field sensor of the plurality of field sensors is fixed at each vertex of a cube.

[0108] Example 11 - The system of Example 1 , wherein the field sensor includes at least one of an inductive coil, a flux gate, a superconducting quantum interference device, magnetoresistive sensors, or combinations thereof.

[0109] Example 12 - A method of performing surgical navigation to navigate a procedure relative to subject, comprising: positioning a first coil of a conductive material having a first coil center fixed relative to a volume; providing the first coil to generate a first magnetic field within the volume, wherein the magnetic field is substantially uniform within the volume; sensing a first magnetic field vector at a first pose in the volume based on the magnetic field with a field sensor of a calibration device; and operating a processor module to receive the sensed first magnetic field vector at a first pose and executing instructions to determine parameters of the field in the volume based on a distortion of the magnetic field by a distorting object and the sensed magnetic field vector by the calibration device.A0011210

[0110] Example 13 - The method of Example 12, further comprising: operating the navigation processor to execute instructions to (1) model the distorted field relative to the uniform field and (2) determine a pose of a tracking device in the distorted field based on the model.

[0111] Example 14 - The method of Example 13, further comprising: positioning the distorting object to distort the uniform magnetic field to generate magnetic field diversity in the volume.

[0112] Example 15 - The method of Example 12, further comprising: providing the calibration device with a second field sensor to sense a second magnetic field vector at a second pose in the volume based on the magnetic field.

[0113] Example 16 - The method of Example 12, further comprising: providing the first field sensor as a plurality of field sensors; providing the calibration device to include the plurality of field sensors at known poses relative to each other; operating each field sensor of the plurality of field sensors to sense a magnetic field vector at the respective pose of the magnetic field sensors.

[0114] Example 17 - The method of Example 16, further comprising: providing the calibration device to define a shape; positioning at least the first field sensor and a second field sensor of the plurality of field sensors at a spaced apart and fixed pose relative to one another with the calibration device.

[0115] Example 18 - The method of Example 17, further comprising: providing the shape to be a three-dimensional shape; and positioning at least the first field sensor, the second field sensor, and a third field sensor are spaced apart to define a calibration volume.A0011210

[0116] Example 19 - The method of Example 18, wherein the three- dimensional shape is a cube; and positioning at least a single field sensor of the plurality of field sensors fixed at each vertex of the cube.

[0117] Example 20 - The method of Example 12, further comprising: providing the field sensor to include at least one of an inductive coil, a flux gate, a superconducting quantum interference device, magnetoresistive sensors, or combinations thereof.

[0118] Example embodiments are provided so that this disclosure will be thorough and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

[0119] Instructions may be executed by a processor and may include software, firmware, and / or microcode, and may refer to programs, routines, functions, classes, data structures, and / or objects. The term shared processor circuit encompasses a single processor circuit that executes some or all code from multiple modules. The term group processor circuit encompasses a processor circuit that, in combination with additional processor circuits, executes some or all code from one or more modules. References to multiple processor circuitsA0011210 encompass multiple processor circuits on discrete dies, multiple processor circuits on a single die, multiple cores of a single processor circuit, multiple threads of a single processor circuit, or a combination of the above. The term shared memory circuit encompasses a single memory circuit that stores some or all code from multiple modules. The term group memory circuit encompasses a memory circuit that, in combination with additional memories, stores some or all code from one or more modules.

[0120] The apparatuses and methods described in this application may be partially or fully implemented by a processor (also referred to as a processor module) that may include a special purpose computer (i.e. , created by configuring a processor) and / or a general purpose computer to execute one or more particular functions embodied in computer programs. The computer programs include processor-executable instructions that are stored on at least one non-transitory, tangible computer-readable medium. The computer programs may also include or rely on stored data. The computer programs may include a basic input / output system (BIOS) that interacts with hardware of the special purpose computer, device drivers that interact with particular devices of the special purpose computer, one or more operating systems, user applications, background services and applications, etc.

[0121] The computer programs may include: (i) assembly code; (ii) object code generated from source code by a compiler; (iii) source code for execution by an interpreter; (iv) source code for compilation and execution by a just-in-time compiler, (v) descriptive text for parsing, such as HTML (hypertext markupA0011210 language) or XML (extensible markup language), etc. As examples only, source code may be written in C, C++, C#, Objective-C, Haskell, Go, SQL, Lisp, Java®, ASP, Perl, Javascript®, HTML5, Ada, ASP (active server pages), Perl, Scala, Erlang, Ruby, Flash®, Visual Basic®, Lua, or Python®.

[0122] Communications may include wireless communications described in the present disclosure can be conducted in full or partial compliance with IEEE standard 802.11 -2012, IEEE standard 802.16-2009, and / or IEEE standard 802.20- 2008. In various implementations, IEEE 802.11 -2012 may be supplemented by draft IEEE standard 802.11ac, draft IEEE standard 802.11 ad, and / or draft IEEE standard 802.11 ah.

[0123] A processor, processor module, module or ‘controller’ may be used interchangeably herein (unless specifically noted otherwise) and each may be replaced with the term ‘circuit.’ Any of these terms may refer to, be part of, or include: an Application Specific Integrated Circuit (ASIC); a digital, analog, or mixed analog / digital discrete circuit; a digital, analog, or mixed analog / digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor circuit (shared, dedicated, or group) that executes code; a memory circuit (shared, dedicated, or group) that stores code executed by the processor circuit; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on- chip.

[0124] Instructions may be executed by one or more processors or processor modules, such as one or more digital signal processors (DSPs), generalA0011210 purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processor” or “processor module” as used herein may 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.

[0125] The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

Claims

A0011210CLAIMSWhat is claimed is:

1. A surgical navigation system operable to navigate a procedure relative to subject, comprising: a first coil of a conductive material having a first coil center positioned relative to a volume and configured to generate a first magnetic field within the volume, wherein the magnetic field is substantially uniform within the volume; a calibration device including a first field sensor to sense a first magnetic field vector at a first pose in the volume based on the magnetic field; and a processor module configured to execute instructions to determine parameters of the field in the volume based on a distortion of the magnetic field by a distorting object and the sensed magnetic field vector by the calibration device.

2. The system of Claim 1 , further comprising: a navigation processor configured to execute instructions to (1) model the distorted field relative to the uniform field and (2) determine a pose of a tracking device in the distorted field based on the model.

3. The system of Claim 2, wherein the instructions include determining a model of a dipole in the volume based on the first magnetic field vector.

4. The system of Claim 2, further comprising:A0011210 the distorting object configured to distort the uniform magnetic field to generate magnetic field diversity in the volume.

5. The system of Claim 1 , wherein the first coil is fixed relative to the volume.

6. The system of Claim 1 , wherein the calibration device includes a second field sensor to sense a second magnetic field vector at a second pose in the volume based on the magnetic field.

7. The system of Claim 1 , wherein the first field sensor includes a plurality of field sensors; wherein the calibration device includes the plurality of field sensors at known poses relative to each other; wherein each field sensor of the plurality of field sensors is configured to sense a magnetic field vector at the respective pose of the magnetic field sensors.

8. The system of Claim 7, wherein the calibration device defines a geometric shape; wherein at least the first field sensor and a second field sensor of the plurality of field sensors are spaced apart at a fixed pose relative to one another with the calibration device.A00112109. The system of claim 1 , wherein the field sensor includes at least one of an inductive coil, a flux gate, a superconducting quantum interference device, magnetoresistive sensors, or combinations thereof.

10. A method of performing surgical navigation to navigate a procedure relative to subject, comprising: positioning a first coil of a conductive material having a first coil center fixed relative to a volume; providing the first coil to generate a first magnetic field within the volume, wherein the magnetic field is substantially uniform within the volume; sensing a first magnetic field vector at a first pose in the volume based on the magnetic field with a field sensor of a calibration device; and operating a processor module to receive the sensed first magnetic field vector at a first pose and executing instructions to determine parameters of the field in the volume based on a distortion of the magnetic field by a distorting object and the sensed magnetic field vector by the calibration device.11 . The method of Claim 10, further comprising: operating the navigation processor to execute instructions to (1) model the distorted field relative to the uniform field and (2) determine a pose of a tracking device in the distorted field based on the model.

12. The method of Claim 10, further comprising:A0011210 providing the calibration device with a second field sensor to sense a second magnetic field vector at a second pose in the volume based on the magnetic field.

13. The method of Claim 10, further comprising: providing the first field sensor as a plurality of field sensors; providing the calibration device to include the plurality of field sensors at known poses relative to each other; operating each field sensor of the plurality of field sensors to sense a magnetic field vector at the respective pose of the magnetic field sensors.

14. The method of Claim 13, further comprising: providing the calibration device to define a shape; positioning at least the first field sensor and a second field sensor of the plurality of field sensors at a spaced apart and fixed pose relative to one another with the calibration device.

15. The method of Claim 10, further comprising: providing the field sensor to include at least one of an inductive coil, a flux gate, a superconducting quantum interference device, magnetoresistive sensors, or combinations thereof.

Images