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WO2022133418A1 - Corrections de distorsion électromagnétique pour des dispositifs de distorsion connus - Google Patents

Corrections de distorsion électromagnétique pour des dispositifs de distorsion connus Download PDF

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Publication number
WO2022133418A1
WO2022133418A1 PCT/US2021/072879 US2021072879W WO2022133418A1 WO 2022133418 A1 WO2022133418 A1 WO 2022133418A1 US 2021072879 W US2021072879 W US 2021072879W WO 2022133418 A1 WO2022133418 A1 WO 2022133418A1
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WO
WIPO (PCT)
Prior art keywords
distorter
field
distortion
pose
experienced
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US2021/072879
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English (en)
Inventor
Bradley W. JACOBSEN
Victor D. SNYDER
Robert Pahl
Andrew J. WALD
Steven Hartmann
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Medtronic Navigation Inc
Original Assignee
Medtronic Navigation Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US17/454,921 external-priority patent/US12295666B2/en
Application filed by Medtronic Navigation Inc filed Critical Medtronic Navigation Inc
Priority to EP21859389.5A priority Critical patent/EP4262609A1/fr
Priority to CN202180084403.7A priority patent/CN116648209A/zh
Publication of WO2022133418A1 publication Critical patent/WO2022133418A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B34/00—Computer-aided surgery; Manipulators or robots specially adapted for use in surgery
    • A61B34/20—Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B90/00—Instruments, implements or accessories specially adapted for surgery or diagnosis and not covered by any of the groups A61B1/00 - A61B50/00, e.g. for luxation treatment or for protecting wound edges
    • A61B90/90—Identification means for patients or instruments, e.g. tags
    • A61B90/98—Identification means for patients or instruments, e.g. tags using electromagnetic means, e.g. transponders
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B17/00—Surgical instruments, devices or methods
    • A61B2017/00681—Aspects not otherwise provided for
    • A61B2017/00725—Calibration or performance testing
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B34/00—Computer-aided surgery; Manipulators or robots specially adapted for use in surgery
    • A61B34/20—Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis
    • A61B2034/2046—Tracking techniques
    • A61B2034/2051—Electromagnetic tracking systems
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B34/00—Computer-aided surgery; Manipulators or robots specially adapted for use in surgery
    • A61B34/20—Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis
    • A61B2034/2046—Tracking techniques
    • A61B2034/2055—Optical tracking systems
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B34/00—Computer-aided surgery; Manipulators or robots specially adapted for use in surgery
    • A61B34/20—Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis
    • A61B2034/2046—Tracking techniques
    • A61B2034/2059—Mechanical position encoders
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B34/00—Computer-aided surgery; Manipulators or robots specially adapted for use in surgery
    • A61B34/30—Surgical robots

Definitions

  • FIG. 2 illustrates the disposition of a tool near a spinal column of a patient incident to the performance of a surgical procedure, according to an embodiment.
  • FIG. 4 illustrates the disposition of the tool near a spinal column of a patient incident to the performance of a surgical procedure, when an EM emitter is transmitting an EM field, according to an embodiment.
  • FIG. 6 illustrates the disposition of a tool near a spinal column of the patient incident to the performance of a surgical procedure, with an optimized distortion field superimposed over a tip of the tool, according to an embodiment.
  • FIG. 9 illustrates a method of an EM tracking system, according to an embodiment.
  • Electromagnetic (EM) tracking systems may be used during a surgical procedure for tracking one or more anatomical structures that are being or may be moved (or for which pose information, including position and/or orientation, is otherwise relevant) during the surgical procedure.
  • EM tracking systems can also track one or more surgical tools during the surgical procedure.
  • an EM emitter transmits, emits, or generates one or more EM fields with one or more known characteristics.
  • One or more EM trackers attached to one or more of the anatomical structures and/or surgical tools measure and report their individually experienced EM fields back to the EM tracking system.
  • the pose(s) e.g., positions(s) and orientation(s)
  • the pose(s) e.g., positions(s) and orientation(s) of the one or more anatomical structures or surgical tools may be determined.
  • a corrective surgery may be performed on a patient to treat or correct an acute injury, a chronic injury, or a chronic disease (e.g., scoliosis) related to one or more anatomical structures (e.g., spinal vertebrae) of the patient.
  • a corrective spinal surgical procedure may be performed to align displaced or misaligned vertebrae while retention implants or hardware is secured to the vertebrae.
  • An EM tracking system may be used during the procedure to track a pose of a vertebra relative to an adjacent vertebra to facilitate determining the degree of displacement and/or the degree of alignment of the vertebrae. It is anticipated that other items could also be tracked using EM trackers. Such EM tracking may occur within a spatial volume defined by and for use with the EM tracking system.
  • One or more EM trackers are each attached (or coupled) to an anatomical structure of the patient.
  • the EM trackers detect field strengths, directions, and/or components of the EM field(s) received at their positions using one or more sensors (this disclosure describes the detected nature of a transmitted EM field acting on an EM tracker as an “experienced EM field” of the EM tracker).
  • EM trackers may also be capable of generating one or more EM fields in some embodiments, which may be received by, for example, other EM tracker(s) and/or an EM receiver within the system.
  • An EM receiver may have similar detection capabilities as an EM tracker, but may be a device within the EM tracking system that is not itself to be tracked (and in some cases may act as a known reference point within the spatial volume covered by the EM tracking system).
  • Data is transmitted from EM trackers and/or any EM receiver to, for example, one or more processors of the EM tracking system.
  • the processor processes the data to determine a pose of each of the EM trackers relative to adjacent EM trackers.
  • the pose of an EM tracker may be determined with reference to six degrees of freedom (including three position degrees of freedom and three orientation degrees of freedom).
  • the system may derive the pose of an object to which the EM tracker is attached (e.g., the pose of an anatomical structure or a tool to which the EM tracker is attached).
  • one or more transmitted EM fields detected at the EM trackers may be generated by an EM emitter that is separate from the EM trackers, such that the poses of the EM trackers can be determined with respect to the EM emitter.
  • one or more transmitted EM fields detected at any one of the EM trackers may be generated by another of the EM trackers, such that the poses of the EM trackers can be determined with respect to each other.
  • an EM receiver that is separate from the EM trackers may receive one or more transmitted EM fields from the one or more EM trackers, such that the poses of the EM trackers can be determined with respect to the EM receiver.
  • a distorter is introduced into a transmitted EM field.
  • the distorter can be, for example, a surgical tool (or part of a surgical tool) to be used during a surgical procedure during which the EM tracking system is being used. Due to interactions between the transmitted EM field and the distorter, a nonnegligible distortion field is present within the EM field and near the EM trackers, with the result that the EM field as reported by the EM trackers (and/or any EM receiver) is distorted by the distortion field.
  • the distortion field can vary based on the distorter's pose, magnetic permeability, its electrical conductivity, its size, and/or one or more of its physical dimensions (and/or combinations of these).
  • Experienced EM fields detected by EM trackers and/or EM receivers within the EM field may be different from an experienced EM field that would be detected by the same EM tracker without the influence of this distortion field.
  • the effects of such distortion fields may reduce accuracy in certain EM tracking systems that do not account for or compensate for the effects of these distortion fields (e.g., which make tracking determinations without modification to account for the effects of the distortion field on one or more EM trackers reporting the data used by the EM tracking system to make the described tracking determinations).
  • a distortion field generated by an interaction between a distorter and a transmitted EM field has aspects of: location, orientation, magnitude, and phase based on various properties of the distorter. For example, a pose (e.g., a position and orientation) of the distorter within the transmitted EM field and/or material characteristics of the distorter (such as shape, dimension, magnetic permeability and/or electrical conductivity) will determine the nature of the distortion field. Through measurements and/or modeling techniques described herein, these characteristics of such distortion fields can be determined or approximated.
  • embodiments herein may correct the experienced EM fields reported by the one or more EM trackers.
  • the one or more processors of the EM tracking system may perform these tasks in order to correct the experienced EM fields that are reported by the one or more EM trackers.
  • the one or more processors may then use the corrected experienced EM field data to generate more accurate poses of the one or more EM trackers.
  • FIG. 1 illustrates the use of an EM tracking system with a patient 102, according to an embodiment.
  • the patient 102 is disposed near an EM emitter 104.
  • the patient 102 may be, for example, within a surgical apparatus arranged such that, among other things, a portion of interest for a medical procedure to be performed on the patient 102 is proximate to the EM emitter 104.
  • the portion of interest is within range of one or more EM fields to be transmitted by the EM emitter 104.
  • the portion of interest for the medical procedure includes a portion of the spinal column 106 of the patient 102, corresponding to a medical procedure to be performed specifically on that portion of the spinal column 106. It is contemplated that in other embodiments, other portions of interest (corresponding to other medical procedures) may be used with embodiments disclosed herein.
  • the portion of interest may include one or more anatomical structures that are to be tracked by the EM tracking system. In the example of FIG. 1 the anatomical structures to be tracked may be the vertebrae 108a-108e of the spinal column 106.
  • one or more EM trackers may be attached to each anatomical structure that is to be tracked.
  • EM trackers 1 10a-1 10e have been attached or otherwise coupled to corresponding ones of the vertebrae 108a-108e.
  • the interaction between an EM field transmitted by the EM emitter 104 and each of the EM trackers 110a-110e is respectively measured by the EM trackers 1 10a- 1 10e and provided to the EM tracking system as experienced EM field information. This data allows the EM tracking system to track the vertebrae 108a-108e, in the manner described above.
  • any of the EM trackers 1 10a-110e may serve additional purposes beyond EM tracking.
  • the EM trackers 1 10a-110d are located entirely within the patient 102.
  • the EM tracker 110e extends externally from the patient 102. This may allow the EM tracker 1 10e to act as an optical tracker for use with an optical tracking system (which may be part of the EM tracking system) as well as an EM tracker for the EM tracking system.
  • FIG. 2 illustrates the disposition of a tool 202 near the spinal column 106 of the patient 102 incident to the performance of a surgical procedure, according to an embodiment.
  • the tool 202 may need to be disposed near the EM trackers 110a-1 10e (e.g., as illustrated) in order to be used to perform a part of the surgical procedure that uses the tool 202.
  • the tip 204 of the tool 202 may have properties such that the tip 204 (either alone or as part of the tool 202) acts as a distorter.
  • the interaction between an EM field transmitted by the EM emitter 104 and the tip 204 when the tool 202 is disposed at the illustrated pose may cause a distortion field at/around the position of the tip 204.
  • proximity of this (or any other) distortion field to any of the EM trackers 1 10a-1 10e may interfere with an experienced EM field measurement by the one or more of the EM trackers 1 10a-1 10e, in the manner described herein.
  • a distorter (such as the tip 204 or other portions of the tool 202) may be said to have a pose (including, for example, a position and an orientation) and characteristics (e.g., dimension, shape, magnetic permeability, and/or electrical conductivity, etc.) that are deterministic of certain properties (e.g., the location, orientation, magnitude, and phase) of a corresponding distortion field.
  • An EM tracking system leverages knowledge of the pose and characteristics of the distorter (whether measured or modeled) in order to estimate or approximate the properties (e.g., the location, orientation, magnitude, and phase) of a corresponding distortion field.
  • the pose of the distorter may include a position of the distorter within a transmitted EM field and an orientation of the distorter relative to one or both of the EM emitter 104 and/or one or more EM trackers 110a-1 10e.
  • the position of the distorter may be understood to be the position of the distorter within the EM field relative to a known point in the EM field.
  • the known point in the EM field may be, for example, a point on the EM emitter 104.
  • the orientation of the distorter may be understood to be the orientation of the distorter relative to one or more of the EM emitter 104 and/or one or more of the EM trackers 1 10a-1 10e.
  • the positioning and orientation elements of the pose of the distorter may be known to/determined by the EM tracking system in various ways.
  • the pose of the distorter within the EM field may be known to the system.
  • it may be that the distorter is in a pre-determined pose within the EM field (and therefore at a known position within the EM field) and does not move during the surgical procedure.
  • the EM tracking system may track the pose of the distorter. This may be done in various ways.
  • the distorter is tracked within the EM tracking system using an EM tracker on the tool 202.
  • the tip 204 of the tool 202 may be a distorter, as described, while the rest of the tool 202 does not act as a distorter.
  • the pose (e.g., the position and/or orientation) of the tip 204 may be tracked using an EM tracker that is attached to a portion of the tool 202 that does not exhibit a distortive effect within an EM field (and is far enough removed from the tip 204 that distortions from the tip 204 are negligible).
  • This EM tracker may report data regarding its interaction with a transmitted EM field from the EM emitter to the EM tracking system that is used to determine the pose of said EM tracker, from which the pose of the tool 202 (and thus the position of the tip 204 of the tool 202) may be derived.
  • a robotic posing system may (also) co-register to the spatial volume used by the EM tracking system for EM tracking, such that configuration data from the robotic posing system may be used relative to the EM tracking methods for the EM emitter of the tool 202 within that tracking volume.
  • the location of the distortion field may be based on the pose of the distorter. For example, in methods to be discussed, it may be that the distortion field is approximated about a point that represents the pose of the distorter.
  • any characteristics of the distorter may be provided to or otherwise known to the system. As will be further described below, these characteristic properties may exist as part of a general model corresponding to any given distorter and/or tool of a certain type, or as part of a specific model that is specific to a specific instance of that distorter and/or tool type.
  • the pose of the distorter (e.g., the position of the distorter and the orientation of the distorter) within a transmitted EM field may be deterministic of a corresponding distortion field.
  • the elements of the pose (e.g., the position and/or the orientation) of the distorter may be deterministic of the magnitude of the distortion field at its various points. For example, the distortion field may be approximated about a point that represents the position of the distorter.
  • the position of the distorter then affects the magnitude of the distortion field at the various points within the distortion field, in that, for a same point within the distortion field (relative to the approximated location of the distorter), the magnitude may vary (e.g., decrease or increase) as the distorter moves relative to an EM emitter (e.g., modifies its position relative to the EM emitter).
  • a magnitude of distortion field in a first direction may change as the orientation of a non-uniform distorter changes (as the locations of the non-uniformities relative to the first direction changes). Such non-uniformities may be in distorter shape, distorter material, etc.
  • the relationship between the elements of the pose (e.g., the position and/or the orientation) of the disorder relative to the EM emitter and the magnitude of the various points making up the distortion field corresponding to the distorter may be known to (via experimentation) or modeled by (using the physical attributes of the distorter) the EM tracking system.
  • the pose of the distorter may be deterministic of the orientation of the distortion field. As the distorter moves from a first pose to a second pose within an EM field, the direction of the EM field relative to the distorter may be different at the new location. Accordingly, the corresponding distortion field may have a different direction at the second location than the corresponding distortion field at the first location.
  • the characteristics of the distorter e.g., dimension, shape, magnetic permeability, and/or electrical conductivity
  • the characteristics of the distorter may be deterministic of a corresponding distortion field.
  • the magnitude at various points of the distortion field caused by the distorter may generally increase as the magnetic permeability of the distorter increases.
  • the relationship between a magnetic permeability of a distorter and the magnitude of the various points of the distortion field due to that magnetic permeability may be known to (via experimentation) or modeled by (based on mathematical estimations and/or experimentations on other distorters) the EM tracking system.
  • the electrical conductivity of the distorter may be deterministic of the magnitude and phase of the distortion field.
  • a distorter increases its effective inductance via magnetic flux concentration and its resistance via the induced current skin depth.
  • elements of the pose e.g., position and orientation
  • various characteristics dimension, shape, magnetic permeability, and/or electrical conductivity
  • a distorter may jointly together be deterministic of the nature of the distortion field. This means that multiple (including all) of these factors may be simultaneously used within the system to determine an appropriate model for a distortion field corresponding to the distorter, using the relevant principles discussed above related to each such factor.
  • FIG. 3 illustrates a dipole model 300, according to an embodiment.
  • the dipole model 300 may be used to conceptually represent a distortion field according to embodiments disclosed herein. While in the illustrated embodiment a dipole model 300 is used, in some embodiments, the distortion field may be modeled as one of a multiple dipole, a multipole, an effective charge, an effective current, a boundary element method model, a finite element analysis model, a measurement-based model or any other numerical approximation of the distortion field.
  • the dipole model 300 may also include an orientation 304, which may correspond to the direction of the EM field relative to the pose of the distorter for which the corresponding distortion field is being approximated by the dipole model 300.
  • the orientation 304 of the dipole model 300 may impute directional meaning to the distortion field lines 306 of the dipole model 300 representing the distortion field.
  • the distortion field lines 306 represent a portion of the magnetic field caused by the interaction between a transmitted EM field and the distorter. Note that one or more distortion field lines may be modeled within EM tracking systems described herein with much higher fidelity than is apparent in the dipole model 300 as illustrated in FIG. 3 (which is presented in a schematic form).
  • a distortion field could be represented using a multiple dipole model, a multipole model, a line, or a surface model such as an effective charge or current model, or an otherwise parameterized model such as a boundary element method or a measured and interpolated model.
  • the EM tracking system may include a lookup table (e.g., in a memory) that can be used in combination with current distorter pose information to determine a distortion field as a model of, e.g., distorter geometry, distorter conductivity, and/or distorter magnetic permeability.
  • the EM tracking system may then include in a memory a lookup table that can be used to determine a distortion field as a model of, e.g., distorter pose, distorter geometry, distorter conductivity, and/or distorter magnetic permeability.
  • a lookup table that can be used to determine a distortion field as a model of, e.g., distorter pose, distorter geometry, distorter conductivity, and/or distorter magnetic permeability.
  • FIG. 4 illustrates the disposition of the tool 202 near the spinal column 106 of the patient 102 incident to the performance of a surgical procedure, when the EM emitter 104 is transmitting an EM field, according to an embodiment.
  • the elements of FIG. 4 may be used to initialize an approximation (e.g., using a dipole model) of the distortion field generated by the interaction of the EM field with the tip 204 of the tool 202.
  • the center 402 of the tip 204 of the tool 202 may be a vector measured relative to, for example, the center of the EM emitter 104 using methods of, for example, an optical tracking system, a robotic posing system, and/or an EM tracker of the tool 202 for determining distorter poses, as described above.
  • the magnetic field portion of the EM field transmitted by the EM emitter 104 may be represented (at least in part) by one or more magnetic field lines.
  • One of these magnetic field lines is the magnetic field line 404, which illustrates the direction of B at each point on the magnetic field line 404, consistent with the magnetic field vector 406, which represents both the magnitude and the direction of B at the illustrated point (the center 402 of the tip 204).
  • An initial distorter magnetic moment 408 (referred to herein as Mi) for the tip 204 may be determined relative to the magnetic field vector 406 at the position of the tip 204 of the tool 202.
  • the initial distorter magnetic moment 408 may be calculated by :
  • Mi B f(p r , o, geometry), where p r is the (relative) magnetic permeability of the distorter; o is the electrical conductivity of the distorter; and f is a function corresponding to the geometry of the distorter.
  • f is equal to (4ira 3 /po)((pr-1)/(pr+2)).
  • Di may be said to be an approximation of the distortion field caused by the distorter.
  • FIG. 5 illustrates the disposition of the tool 202 near the spinal column 106 of the patient 102 incident to the performance of a surgical procedure, with an initial distortion field 502 superimposed over the tip 204 of the tool 202, according to an embodiment.
  • the tip 204 of the tool 202 acts as a distorter corresponding to the initial distortion field 502.
  • the initial distortion field 502 may conceptually represent Di (when using a dipole model).
  • the EM tracker 1 10c and the EM tracker 110d are near the tip 204. Accordingly, the system presumes some non-zero distortive effect on these EM trackers based on the initial distortion field 502.
  • a first distortion vector 504 and a second distortion vector 506 may be determined using Di(Mi , r), in the manner described above.
  • a first distortion vector 504 (corresponding to the position of the EM tracker 1 10c) and a second distortion vector 506 (corresponding to the position of the EM tracker 110d) may represent the presumed effect of the initial distortion field 502 at the positions of the first distortion vector 504 and the second distortion vector 506 and may be calculated accordingly.
  • the pose of and/or one or more characteristics of the distorter may be optimized or refined prior to their use in determining a distortion field approximation for use in the system.
  • This optimized pose and/or characteristics may be used in order to create an optimized distortion field Do.
  • D o rather than any Di, is used to calculate one or more distortion vectors.
  • the memory of an EM tracking system contains a general model for the distorter and/or the tool including the distorter that comprises one or more characteristics (e.g., geometry, magnetic permeability, electrical conductivity, etc.).
  • This general model may be based on what is pre-presumed (e.g., a pre-programmed parameterization) about the distorter and/or the tool including the distorter. It may alternatively be that this general model is based on prior experience by the EM tracking system with a distorter and/or a tool including the distorter that is the same type as the current distorter and/or tool including the distorter.
  • the EM tracking system may include a general model of the tool 202 and/or its tip 204.
  • the characteristics from a general model for a distorter and/or a tool including the distorter are used to calculate Di in the manner described above.
  • the general model for the distorter may have been pre-stored within the memory of the EM tracking system.
  • the EM tracking system may receive the general model for the distorter and/or the tool including the distorter from a memory that is found on the distorter and/or the tool including the distorter, and/or by receiving an identifier from the distorter and/or the tool including the distorter (e.g., a radio frequency identification (RFID) from the distorter and/or the tool including the distorter) and using this identifier to locate a general model for the distorter and/or the tool including the distorter from a server accessible over a network on which the EM tracking system communicates.
  • RFID radio frequency identification
  • the distorter and/or a tool including the distorter may not exactly match the general model corresponding to the distorter and/or a tool including the distorter.
  • a magnetic permeability of the tip 204 of the tool 202 may be slightly different than expected, based on slight material variations.
  • a size of the tool 202 may be slightly different than the general model corresponding to the tool 202.
  • the system is capable of using collected data (e.g., experienced EM field data) by one or more EM trackers taken while under the influence of a distortion field caused by the distorter to extrapolate relevant differences between the characteristics of the distorter and/or tool including the distorter (e.g., dimension, shape, magnetic permeability, and/or electrical conductivity, etc.) as recorded in the general model and the actual characteristics of the specific physical instance of distorter and/or the tool including the distorter based on these measured responses.
  • collected data e.g., experienced EM field data
  • EM trackers taken while under the influence of a distortion field caused by the distorter to extrapolate relevant differences between the characteristics of the distorter and/or tool including the distorter (e.g., dimension, shape, magnetic permeability, and/or electrical conductivity, etc.) as recorded in the general model and the actual characteristics of the specific physical instance of distorter and/or the tool including the distorter based on these measured responses.
  • Such differences may be determined by comparing the experienced EM field data to predicted experienced EM field data that is determined by using the current pose of the distorter and/or tool including the distorter with the characteristics of the general model (e.g., according to the initial distortion field Di, in the manner described above). Based on the delta between the experienced EM field data and the predicted experienced EM field data, differences between characteristics recorded in the general model and characteristics of the actual distorter and/or tool including the distorter can be extrapolated. These characteristic differences may then be applied to the general model corresponding to the distorter and/or the tool including the distorter, resulting in a specific model for the specific distorter and/or tool including the specific distorter.
  • a (previously optimized) specific model could be even further optimized by (repeating) an analogous process for the distorter and/or tool including the distorter as those described above for optimizing the general model. Accordingly, it is anticipated that the characteristics of a specific model for a distorter and/or a tool including the distorter may become more and more accurate the more the distorter and/or a tool including the distorter is used within the system for various purposes.
  • the specific model for the distorter may then be stored within the memory of the EM tracking system.
  • the EM tracking system may store the specific model for the distorter and/or the tool including the distorter to a memory that is found on the distorter and/or the tool including the distorter.
  • the EM tracking system may store the specific model to a server accessible over a network on which the EM tracking system communicates such that the specific model is associated an identifier (e.g., an RFID) reported by the tool.
  • This storage (in whatever case) may allow subsequent uses of the optimized characteristics for the distorter and/or the tool including the distorter in the EM tracking system without having to repeat the optimization process.
  • the specific model for the distorter and/or the tool including the distorter may also allow the specific model for the distorter and/or the tool including the distorter to be continuously improved through repeated optimization starting from the previous version of the specific model, corresponding with repetitious use of the distorter and/or the tool including the distorter as described above.
  • these values may be used to determine, for example, an optimized (more accurate) pose (e.g., position and/or orientation) of the distorter and/or the tool including the distorter. They may also and/or alternatively be used to determine an optimized distorter magnetic moment M o (e.g., by substituting in the optimized characteristics in the formula(s) for Mi described above) for the distorter. Then the optimized distortion field D o can be determined with D 0 (M 0 , r) in the manner described above (e.g., by substituting Mo and an optimized r into a formula for Di(Mi , r) as described above.
  • D o may be said to be an approximation of the distortion field caused by the distorter that has been optimized from Di, and that such optimization may be based (at least in part) on data representing one or more experienced EM fields as distorted by a second distortion field caused by the distorter as reported by one or more EM trackers.
  • Such optimizations may occur on a per EM sensor basis within a single EM tracker.
  • An EM tracker may have multiple EM sensors (such as multiple induction coils). Optimizations for these sensors may correct signal magnitudes and signal phases relative to an approximated distortion.
  • each sensor may experience a component magnitude and phase of each of a transmitted EM field and a distortion field.
  • An initial distortion field model may imply a different component magnitude and phase than what actually occurs.
  • the distortion field model may be adjusted appropriately.
  • a sensor may experience a component magnitude of 1 mV and a relative phase of 84 degrees.
  • An initial distortion field model may imply a component magnitude of 1 mV and a relative phase of 85 degrees. With this difference, a distorter resistance may be optimized.
  • optimizations may occur on a per EM tracker basis. For example, optimizations driven by one or more individual EM trackers may correct for tracking metrics relative to an approximated distortion. [0079] Such optimizations may occur across multiple EM trackers. For example, optimizations driven by a set of multiple EM trackers may correct for tracking metrics, relative poses, positions, orientations, and magnitudes of an approximated distortion.
  • FIG. 6 illustrates the disposition of the tool 202 near the spinal column 106 of the patient 102 incident to the performance of a surgical procedure, with an optimized distortion field 602 superimposed over the tip 204 of the tool 202, according to an embodiment.
  • the optimized distortion field 602 may conceptually represent Do (when using a dipole model).
  • the optimized distortion field 602 is slightly different (e.g., is different in one or more of position, orientation, magnitude, and/or phase) than the initial distortion field 502 due to the optimization process described herein.
  • the EM tracker 1 10c and the EM tracker 1 10d are near the initial optimized distortion field 602. Accordingly, the EM tracking system presumes some non-zero distortive effect due to the interaction of the EM field transmitted by the EM emitter 104 and the tip 204 on these EM trackers.
  • a first distortion vector 604 and a second distortion vector 606 (representing the presumed effect of the distortion field as represented by the optimized distortion field 602 at, respectively, the positions of the EM tracker 1 10c and the EM tracker 1 10d) may be calculated by the EM tracking system using Do(Mo, r) in the manner described herein.
  • the EM tracker 1 10c reports to the EM tracking system the first experienced EM field 608.
  • the first experienced EM field 608 is a raw reading taken by the EM tracker 1 10c that has not been corrected for the effects of the distortion field represented by the first distortion vector 604.
  • the EM tracker 1 10d reports to the EM tracking system the second experienced EM field 610.
  • the second experienced EM field 610 is a raw reading taken by the EM tracker 1 10d that has not been corrected for the effects of the distortion field represented by the second distortion vector 606.
  • the system uses the first corrected experienced EM field 702 and/or the second corrected experienced EM field 704 in tracking operations that use the experienced EM fields of the EM tracker 110c and/or the EM tracker 110d to determine, for example, the pose(s) of one or more of the vertebrae 108a-108e, as appropriate.
  • FIG. 8 illustrates the components of an EM tracking system 802 according to some embodiments.
  • the EM tracking system 802 includes a memory 804, one or more processor(s) 806, one or more I/O device(s) 808, one or more EM tracker(s) 810, an EM emitter 812, a robotic posing system 814, an optical tracking system 816, and a network interface 818.
  • a communication interface 820 may represent one or more internal communications interfaces (such as one or more traditional data busses between, e.g., the memory 804, the processor(s) 806, and the network interface 818) and/or one or more external communications interfaces (such as external data wiring to, e.g., I/O device(s) 808, EM tracker(s) 810, the robotic posing system 814, and/or the optical tracking system 816).
  • I/O device(s) 808, EM tracker(s) 810, the robotic posing system 814, and/or the optical tracking system 816 Other arrangements are contemplated. It is also contemplated that some EM tracking systems may also include and or use a lidar tracking system and/or visible light tracking system (among other possible tracking systems), as described above.
  • the memory 804 includes one or more general models 822, one or more specific models 824, and the engine instructions 826 that may be executed by the processor(s) 806.
  • the I/O device(s) 808 may provide a way for a local user to provide input/receive output from the system. Examples of such I/O device(s) 808 may include a keyboard, a mouse, a monitor, a speaker, etc. Any results determined by the EM tracking system 802 as described herein (e.g., positions of anatomical structures, corrected experienced EM fields, etc.) may be communicated to a user of the EM tracking system 802 via the one or more I/O device(s) 808.
  • the EM tracker(s) 810 may be connected to an anatomical structure of a patient and may each report a respective experienced EM field to the EM tracking system 802 generally, in the manner described above. Each of the EM tracker(s) 810 may be connected via, for example, a wire that carries such signaling from the EM tracker(s) 810 to, for example, the processor(s) 806 of the EM tracking system 802.
  • the EM emitter 812 may be disposed near the patient such that one or more EM fields transmitted by the EM emitter 812 will effectively cover the one or more EM tracker(s) 810 within an area of interest of the patient, as described above.
  • the optical tracking system 816 may optically track a distorter and/or a tool including the distorter within an EM field.
  • the optical tracking system 816 may accordingly be able to report to the EM tracking system 802 generally regarding the position and/or orientation of the distorter and/or tool including the distorter.
  • the robotic posing system 814 and the optical tracking system 816 may be co-registered 836 such that data from both can be used generally in EM tracking system 802 to determine a posing (e.g., a position and/or an orientation) of a distorter within the EM field. As described above, either or both of these may be further co-registered to a spatial volume for EM tracking used by the EM tracking system 802.
  • a posing e.g., a position and/or an orientation
  • the network interface 818 may transport data into and out of the EM tracking system 802. For example, any results determined by the EM tracking system 802 as described herein (e.g., positions of anatomical structures, corrected experienced EM fields, etc.) may be transported to another device via the network interface 818. Further, it is anticipated that in some embodiments, the robotic posing system 814 and the optical tracking system 816 may not directly be elements of the EM tracking system 802 as illustrated in FIG. 8, but rather may be separate entities that communicate with the EM tracking system 802 via the network interface 818. In this case, the EM tracking system 802 may communicate with and use either/both of the robotic posing system 814 and/or the optical tracking system 816 via the network interface 818, analogously as described herein.
  • the general models 822 may include one or more models for one or more distorters and/or tools including such distorters. These general models 822 may include (record) characteristics (e.g., geometry, magnetic permeability, electrical conductivity, etc.) regarding these distorters and/or the tools including the distorters. These general models 822 may be based on what is pre-presumed (e.g., a pre-programmed parameterization) about the distorters and/or the tools including the distorters. It may alternatively be that this general model is based on prior experience by the EM tracking system 802 with one or more of the distorters and/or tools including the distorters.
  • the engine instructions 826 may include instructions for one or more engines, including the distorter pose engine 828, the distortion field approximation engine 830, the experienced EM field correction engine 832, and the EM tracker pose engine 834. Various ones of these engines may be active within the EM tracking system 802 at different times, as the processor(s) 806 operate the relevant instructions thereof by using the engine instructions 826.
  • the distorter pose engine 828 may perform functionalities as described herein for determining a pose of a distorter within an EM field transmitted by the EM emitter 812.
  • the distorter pose engine 828 may operate/interface with the robotic posing system 814 and/or the optical tracking system 816 (and/or another tracking system) for the purposes of making distorter pose determinations.
  • the distorter pose engine 828 may make pose determinations using an EM tracker of, for example, a tool comprising the distorter, in the manner described herein.
  • the distortion field approximation engine 830 may perform functionalities described herein for approximating a distortion field (e.g., calculating either or both of Di and/or Do).
  • the experienced EM field correction engine 832 may perform functionalities described herein for generating one or more distortion vectors according to Di and/or Do. Further, the experienced EM field correction engine 832 may perform the correction on one or more experienced EM fields from the EM tracker(s) 810 using said distortion vectors, as described herein.
  • the EM tracker pose engine 834 may perform functionalities described herein for using the corrected experienced EM fields to locate one or more anatomical structures to which the EM tracker(s) 810 are attached within the area of interest of the patient.
  • FIG. 9 illustrates a method 900 of an EM tracking system, according to an embodiment.
  • the method 900 includes transmitting 902, via an EM emitter, an EM field, the EM field containing an EM tracker attached to an anatomical structure.
  • the method 900 further includes determining 904 a pose of a distorter within the EM field.
  • the method 900 further includes receiving 906, from the EM tracker, data representing an experienced EM field at the EM tracker, the experienced EM field distorted by a distortion field caused by the distorter.
  • the method 900 further includes receiving 908 a model comprising one or more characteristics of the distorter.
  • the method 900 further includes determining 912 the distortion field caused by the distorter within the EM field based on the pose of the distorter within the EM field and the model comprising the one or more characteristics of the distorter.
  • the method 900 further includes calculating 914 data representing a corrected experienced EM field for the EM tracker using the experienced EM field at the EM tracker and the distortion field.
  • FIGS. 1 -9 While the description of FIGS. 1 -9 has used an EM emitter and multiple EM trackers, it is contemplated that analogous principles could be applied in the case of EM trackers that provide EM fields to others of the EM trackers. It is also contemplated that analogous principles could be applied in the case of EM trackers that provide EM fields to an EM receiver.
  • FIGS. 2-7 describes the use of a tool 202 comprising a single distorter (the tip 204), it is contemplated that some tools may comprise multiple distorters. In these cases, the multiple disorders may each be individually tracked, modeled and accounted for, as described above. In these cases, multiple distortion vectors (one for each distorter in the tool) may be generated relative to an EM tracker, and may together be summed with the EM tracker's experienced EM field in order to generate a corrected experienced EM field for the EM tracker.
  • Any methods disclosed herein comprise one or more steps or actions for performing the described method.
  • the method steps and/or actions may be interchanged with one another.
  • the order and/or use of specific steps and/or actions may be modified.
  • At least one of the components set forth in one or more of the preceding figures may be configured to perform one or more operations, techniques, processes, and/or methods as set forth in the Example Section below.
  • Example 2 may include the method of Example 1 , further comprising optimizing the model of the distorter based on the data representing the experienced EM field.
  • Example 3 may include the method of Example 1 , wherein the distortion caused by the distorter within the EM field is a first distortion field and wherein the experienced EM field is a first experienced EM field, the method further comprising optimizing the model of the distorter based on data representing a second experienced EM field impacted by a second distortion field caused by the distorter.
  • Example 4 may include the method of Example 1 , wherein the distortion field is modeled as one of a dipole, a multiple dipole, a multipole, an effective charge, an effective current, a boundary element method model, a finite element analysis model, and a measurement-based model.
  • Example 5 may include the method of Example 1 , wherein the pose of the distorter includes one or more of a position of the distorter within the EM field and an orientation of the distorter relative to one of the EM emitter and the EM tracker.
  • Example 6 may include the method of Example 1 , wherein determining the distortion field caused by the distorter comprises determining one or more of a location, an orientation, a magnitude, and a phase of the distortion field.
  • Example 7 may include the method of Example 1 , wherein the model of the distorter comprises a relative magnetic permeability of the distorter.
  • Example 9 may include the method of Example 1 , wherein the model of the distorter comprises a physical dimension of the distorter.
  • Example 10 may include the method of Example 1 , wherein the pose of the distorter is determined using configuration tracking by a robotic posing system.
  • Example 12 may include the method of Example 1 , wherein the pose of the distorter is determined using configuration tracking by a robotic posing system and optical tracking by an optical tracking system.
  • Example 13 may include the method of Example 1 , wherein the pose of the distorter is determined using an EM tracker of a tool comprising the distorter.
  • Example 14 may include the method of Example 1 , wherein the pose of the distorter is determined using data from an EM tracker of a tool comprising the distorter and data from an optical tracking system.
  • Example 15 may include a computing apparatus comprising: a processor; and a memory storing instructions that, when executed by the processor, configure the apparatus to: determine a pose of a distorter within an electromagnetic (EM) field; receive, from an EM tracker in the EM field, data representing an experienced EM field at the EM tracker, the experienced EM field being distorted by a distortion field caused by the distorter within the EM field; determine the distortion field caused by the distorter within the EM field based on the determined pose of the distorter within the EM field and a model of the distorter comprising one or more characteristics of the distorter; and calculate a corrected experienced EM field for the EM tracker using the experienced EM field at the EM tracker and the determined distortion field.
  • EM electromagnetic
  • Example 16 may include the computing apparatus of Example 15, wherein the instructions, when executed by the processor, further configure the apparatus to optimize the model of the distorter based on the data representing the experienced EM field.
  • Example 17 may include the computing apparatus of Example 15, wherein the distortion caused by the distorter within the EM field is a first distortion field and wherein the experienced EM field is a first experienced EM field, and wherein the instructions, when executed by the processor, further configure the apparatus to optimize the model of the distorter based on data representing a second experienced EM field impacted by a second distortion field caused by the distorter.
  • Example 18 may include the computing apparatus of Example 15, wherein the distortion field is modeled as one of a dipole, a multiple dipole, a multipole, an effective charge, an effective current, a boundary element method model, a finite element analysis model, and a measurement-based model.
  • Example 19 may include the computing apparatus of Example 15, wherein the pose of the distorter includes one or more of a position of the distorter within the EM field and an orientation of the distorter relative to one of the EM emitter and the EM tracker.
  • Example 20 may include the computing apparatus of Example 15, wherein the instructions, when executed by the processor, configure the apparatus to determine the distortion field caused by the distorter by determining one or more of a location, an orientation, a magnitude, and a phase of the distortion field.
  • Example 21 may include the computing apparatus of Example 15, wherein the instructions, when executed by the processor, configure the apparatus to determine the distortion field based on a relative magnetic permeability of the distorter that is recorded in the model of the distorter.
  • Example 22 may include the computing apparatus of Example 15, wherein the instructions, when executed by the processor, configure the apparatus to determine the distortion field based on an electrical conductivity of the distorter that is recorded in the model of the distorter.
  • Example 23 may include the computing apparatus of Example 15, wherein the instructions, when executed by the processor, configure the apparatus to determine the distortion field based on a physical dimension of the distorter that is recorded in the model of the distorter.

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Abstract

Des systèmes et des procédés pour corriger des champs électromagnétiques rencontrés mesurés au niveau de chacun d'un ou de plusieurs dispositifs de suivi électromagnétiques d'un système de suivi électromagnétique, alors que de telles mesures sont influencées par un dispositif de distorsion connu, sont divulgués. Un émetteur électromagnétique peut transmettre un champ électromagnétique de telle sorte qu'il contient le ou les dispositif de suivi électromagnétiques. Le système détermine ensuite une pose d'un dispositif de distorsion dans le champ électromagnétique. Le système reçoit, en provenance de chaque dispositif de suivi électromagnétique, des données représentant des champs électromagnétiques rencontrés tels qu'ils sont déformés par un champ de distorsion provoqué par le dispositif de distorsion. Le système procède à la détermination du champ de distorsion à l'aide de la pose et d'un modèle comprenant une ou plusieurs caractéristiques du dispositif de distorsion. Le système peut optimiser le modèle dans un premier temps. Le système calcule des données représentant des champs électromagnétiques rencontrés corrigés correspondants sur la base de chaque champ électromagnétique rencontré respectif et du champ de distorsion déterminé au même emplacement.
PCT/US2021/072879 2020-12-15 2021-12-13 Corrections de distorsion électromagnétique pour des dispositifs de distorsion connus Ceased WO2022133418A1 (fr)

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CN202180084403.7A CN116648209A (zh) 2020-12-15 2021-12-13 对已知畸变器的电磁畸变校正

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US20050107687A1 (en) * 2003-11-14 2005-05-19 Anderson Peter T. System and method for distortion reduction in an electromagnetic tracker
US20060055712A1 (en) * 2004-08-24 2006-03-16 Anderson Peter T Method and system for field mapping using integral methodology
US20070225594A1 (en) * 2006-02-17 2007-09-27 General Electric Company Facilitation of In-Boundary Distortion Compensation
US20140354300A1 (en) * 2011-12-13 2014-12-04 Koninklijke Philips N.V. Distorsion fingerprinting for em tracking compensation, detection and error correction

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