CN1901835A - System and method for distortion reduction in an electromagnetic tracker - Google Patents
System and method for distortion reduction in an electromagnetic tracker Download PDFInfo
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- CN1901835A CN1901835A CNA2004800403577A CN200480040357A CN1901835A CN 1901835 A CN1901835 A CN 1901835A CN A2004800403577 A CNA2004800403577 A CN A2004800403577A CN 200480040357 A CN200480040357 A CN 200480040357A CN 1901835 A CN1901835 A CN 1901835A
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Abstract
The present invention provides a system (100) and method (200) for distortion analysis and reduction in an electromagnetic (EM) tracker. The EM tracker may employ coils as receivers and transmitters. Certain embodiments of the system (100) include a tracking analysis unit (120) for analyzing a tracking behavior of an instrument (110) and a tracking modification unit (130) for compensating for the tracking behavior of the instrument (110). Such an instrument (110) is, for example, a medical instrument, such as a drill, a catheter, a scalpel or a scope. These instruments and their surroundings often include metal components. Positioning an EM navigation device, such as a receiver or a transmitter, on the instrument (110) may cause a distortion in the magnetic field which affects the tracking and tracking accuracy. Uses outside medical applications are foreseen, as are tracking systems other than EM tracking systems, such as ultrasound or inertial position.
Description
Related application
The present invention relates to and require submit on November 12nd, 2003, and name is called the U.S. Provisional Application No.60/520 of " Systemand Method for Distortion Reduction in an ElectromagneticTracker ", the priority of 138 (agent's document number 1333165NV).
Background of invention
The present invention relates generally to electromagnetic tracking system.Especially, the present invention relates to reduce the system and method for the distortion that causes by the instrument in the electromagnetic tracking system and other element.
Practitioner as doctor, surgeon and other medical workers, often depends on technology when carrying out as medical procedures such as image guiding operation or inspections.For example, tracking system can provide the locating information of Medical Instruments with respect to patient or reference frame.When Medical Instruments was not in the sight line of practitioner, practitioner can be determined the position of Medical Instruments with reference to tracking system.Tracking system also helps to work out in advance operation plan.
Tracking or navigation system make practitioner can observe the position and the orientation of patient's anatomical structure and tracked instrument.Practitioner can adopt tracking system to determine when that instrument is placed into desired location.Practitioner can be located on required or affected area or operate, thereby avoids in other structural location or operation.The increase of positioning accuracy can provide wound less medical procedure to reduce its bump to the patient by the control that helps improving less instrument in Medical Instruments patient's body.Improvement control and accuracy less, more refining instrument also can reduce with as the relevant danger of the bigger process of the wound of open operation and so on.
Tracking system also can be used to follow the tracks of other article except that Medical Instruments in various application.That is to say that tracking system can be used for being difficult to accurately be determined by visual inspection other occasion of instrument position in object or the environment.For example, tracking technique can be used for court or Secure Application.Retail shop can adopt tracking technique to prevent theft of merchandise.In this case, can on commodity, place passive balise.In retailing facility, have and place emitter tactfully.This emitter is launched pumping signal with certain frequency, and this Frequency Design becomes from responder to produce response.When the commodity that have responder were positioned at the transmitting boundary of emitter, responder produces can be by the detected response signal of receptor.Then, receptor is based on the position of the feature definite response device of response signal.
Tracking system is also through being usually used in virtual reality system or simulator.Tracking system can be used for monitoring the position of the people in the simulated environment.One or more responders can be positioned on people or the object.Emitter emission pumping signal, and responder produces response signal.Receptor detects this response signal.Then, can be used for monitoring the position of people in the simulated environment or object by the signal of responder emission.
Tracking system can for example be ultrasonic, inertial position or electromagnetic tracking system.Electromagnetic tracking system can adopt coil as receptor and emitter.Typically, electromagnetic tracking system is configured to industry-standard coil architecture (ISCA).ISCA adopts three juxtaposed (colocated) quadrature accurate dipole emission device coils and three juxtaposed accurate dipole receiver coils.Other system can adopt three bigger non-dipoles non-and put emitter coil and three and put accurate dipole receiver coil.Another tracking system architecture adopts six or more a plurality of transmitter coil array and one or more accurate dipole receiver coil of spatial distribution.Selectively, can adopt six or more a plurality of receiver array of single accurate dipole emission device coil and spatial distribution.
ISCA follows the tracks of architecture and adopts three dipole emission devices and three dipole receiver.Each three emitter or receptor are configured to make three coils to present identical effective area, orthogonal thereto direction and be the center with the same point each other.If it is enough little that coil is compared with the distance between emitter and the receptor, then coil can present the dipole performance.Can detect by ternary receiver coil by the magnetic field that ternary emitter coil produces.For example, adopt the emitter coil of three approximate concentric locatings and the receiver coil of three approximate concentric locatings, can obtain nine parameter measurements.By these nine parameter measurements and known location or orientation parameter, position and orientation calculation can determine that each emitter coil is with respect to ternary position of receiver coil and orientation information with three degree of freedom.
Many medical procedures relate to Medical Instruments, as drilling equipment, conduit, surgical knife, diverter and other instrument.Many instruments that are used for curative activity comprise metal parts.In addition, can comprise metal in Medical Instruments or the tracking system surrounding.Metal or other this class material can make the field distortion in the electromagnetic tracking system.Distortion in the electromagnetic tracking system can cause tracking system inaccurate.
For example, practitioner depends on the operation that electromagnetic tracker is carried out the image guiding.When guiding the intravital precision instrument of patient under the situation that is not having direct sight line, the accuracy of position measurement is important.The distortion meeting produces inaccurate position measurement and to patient's potential danger.Therefore, the utmost point needs a kind of system that can reduce the tracking measurement inaccuracy.The utmost point needs a kind of minimized system of distortion effect that makes in the position measurement.
Therefore, need a kind of system and method that is used to reduce the distortion that causes by the instrument in the electromagnetic tracking system or other element.
Summary of the invention
Some embodiment of the present invention provides a kind of system and method that is used for carrying out distortion analysis in electromagnetic tracker and reduces distortion.Certain embodiment of improved electromagnetic tracking system comprises and is used to the distortion processing system of following the tracks of the emitter and the receptor of object and being used for the object analysis distortion characteristic.Emitter transmits, and receptor receives the signal from emitter.
In one embodiment, the distortion processing system is analyzed the signal that receives from receptor determining tracking accuracy, and the distortion processing system can comprise and is used for the virtual electromagnetic tracker of analog distortion feature to the influence followed the tracks of.Distortion characteristic can be magnetic field.The distortion processing system can be adjusted the tracking performance of object.
Certain embodiment of distortion processing system comprises the trace analysis unit that is used for the analytical tool tracking performance and is used for the tracking amending unit of compensation apparatus tracking performance.Follow the tracks of the tracking performance that amending unit can come compensation apparatus by the tracking performance of adjusting instrument.Follow the tracks of the tracking performance that amending unit also can come compensation apparatus by the tracking system of adjusting tracked instrument.Adjusted instrument tracking performance can be tested in the trace analysis unit.In one embodiment, the trace analysis unit generates the drawing (map) and/or the model of instrument distortion characteristic.This distortion characteristic can be magnetic field.In one embodiment, distortion processing system is the computer simulated distortion processing system.
Certain embodiment of virtual tracking system comprises the simulation toolset that is used to simulate the object simulation module of object to be tracked and is used to analyze at least one object distortion characteristic.Simulation toolset can generate the distortion information of object based on distortion characteristic.In one embodiment, simulation toolset comprises the accuracy module of the accuracy that is used for definite analogies volume tracing.Simulation toolset can comprise and be used for determining from the distortion of the object distortion detection module to the influence of tracking accuracy.Simulation toolset also can comprise the distortion modeling module, is used to produce the electromagnetic model of evaluation object to the distortion effect of tracker environment.In addition, simulation toolset can comprise the distortion compensation module that is used to improve the electromagnetic tracker distortion tolerance.
Certain embodiment of distortion analysis method in the electromagnetic tracking system comprises that the tracking performance of the tracking performance of Measuring Object and object analysis is to determine distortion effect.This analysis also can comprise and produces magnetic chart and/or object model is determined distortion effect with the tracking performance of object analysis.This method can comprise that also the tracking of simulating object is to determine distortion effect.In addition, this method can be included in and set up the electromagnetic field model in the electromagnetism tracking environmental to analyze distortion effect.This method also can comprise based on distortion effect improves distortion tolerance in the electromagnetic tracking system.
In one embodiment, this method comprises that the tracking performance of adjusting instrument is to reduce distortion effect.This method also comprises the distortion effect that test instrunment reduces with checking.In one embodiment, this method comprises that adjusting electromagnetic tracker influences with compensating distortion.This method also can comprise the distortion effect that this instrument of test reduces with checking.
Description of drawings
Fig. 1 illustrates the distortion processing system that is used to improve position measurement accuracy in the electromagnetic tracker that adopts according to the embodiment of the invention.
Fig. 2 illustrates the method flow diagram that carries out the distortion processing in electromagnetic tracking system that adopts according to the embodiment of the invention.
Fig. 3 illustrates and according to the embodiment of the invention instrument is carried out the method flow diagram of electromagnetic assessment.
Fig. 4 illustrates the virtual tracker that is used for the EM tracker development that adopts according to the embodiment of the invention.
When reading in conjunction with the accompanying drawings, the detailed description of aforementioned general introduction and following certain embodiments of the invention will be better understood.For the present invention that explains, some embodiment is shown in the drawings.Yet should be appreciated that the present invention is not subject to layout shown in the accompanying drawing and means.
The specific embodiment
Only be the purpose of explaining, following detailed is with reference to the embodiment of the electromagnetic tracking system that uses with image guiding surgery systems.Should be appreciated that the present invention can use use with other imaging system and other.
Fig. 1 illustrates the distortion processing system 100 that is used to improve position measurement accuracy in electromagnetism (EM) tracker according to of the present invention.System 100 comprises instrument 110, trace analysis unit 120 and follows the tracks of amending unit 130.The tracking performance of trace analysis unit 120 optical viewers 110.Following the tracks of amending unit 130 attempts based on improving from the information of trace analysis unit 120 or the tracking performance of compensation apparatus 110.Trace analysis unit 120 and tracking amending unit 130 can be separate unit or individual unit by hardware and/or software implementation.It maybe can be an autonomous system that trace analysis unit 120 and/or tracking amending unit 130 can integrate with the EM tracker.
Instrument 110 can be any instrument that is used for curative activity, as shaping tool (for example, electric drill or air drill), conduit, surgical knife, optical viewer, support or other instrument.Instrument 110 can produce or influence the magnetic field that causes EM tracker distortion in readings.With the EM guider,, be placed on the instrument 110 and can exert an influence to the effect on following the tracks of distortion and/or distortion as receptor or emitter.
The tracking performance and the influence of trace analysis unit 120 analytical tool 110.120 pairs of instruments in trace analysis unit 110 are carried out actual and/or mimic EM and are followed the tracks of to determine the distortion effect of 110 pairs of positions of instrument and/or orientation calculation.Trace analysis unit 120 can be from the computer of the influence of instrument 110 in the simulation tracing system.Receptor is placed on the instrument 110, and receptor and/or other pick off can be used for collecting the information about instrument 110.Trace analysis unit 120 obtains the magnetic field data of instrument 110.Trace analysis unit 120 generates position and the orientation data of instrument 110 in following the tracks of coordinate system.Can measure and/or simulation by trace analysis unit 120 other influence that instrument 110 is followed the tracks of.Trace analysis unit 120 also can generate drawing and/or the model about instrument 110 surrounding magnetic fields and distortion effect.
Follow the tracks of the tracking performance of amending unit 130 adjustment or compensation apparatus 110.Following the tracks of amending unit 130 adopts drawing, model and/or other data from trace analysis unit 120 that the distortion effect from instrument 110 is minimized.But different receptors on tracking amending unit 130 test instrunments 110 and/or transmitter configuration are to improve the tracking performance of instrument 110.Follow the tracks of that amending unit 130 can be made amendment to the EM tracker, recalibration or reprogramming be with the distortion effect of payment from instrument 110.
The tracking performance of instrument 110 can be adjusted or compensate in every way.For example, but the mathematical model of improved instruments 110 and/or system's 100 parts with correcting distortion.For example, can improve with the magnetic field for correcting model to reduce the error in the tracked instrument 110.In addition, can set up model to distortion, as the doughnut model of employing instrument 110 distortions, and can be in tracking measurement post-compensation error.In addition, maskable instrument 110 or other system 100 parts are to produce the known distortion that can compensate before or after tracking measurement.Distortion during follow the tracks of with compensation or minimizing adjustable EM tracker and/or adjustable transmitter or the receptor position on instrument 110.
In another embodiment, near the distorter of instrument 110, as comprising this distortion and compensate by instrument is characterized by near the distortion of three-winding emitter on the instrument or receptor.Selectively, for example, adopt a coil transmitter and receiver array to allow to follow the tracks of the emitter gain, rather than accurately characterize emitter.The distortion effect that can help to reduce in instrument 110 tracking is followed the tracks of in gain.
In one embodiment, the EM tracker comprises the emitter that is used to transmit, is used to receive from the receptor of the signal of emitter and is used to analyze the tracker electronics of the signal that is received by receptor.Tracker electronics is based on the position and/or the orientation of determining to follow the tracks of instrument 110 in the coordinate system from the signal of receptor and/or emitter.In one embodiment, receptor is placed on the instrument 110 to determine position and/or the orientation of instrument 110 with respect to emitter.Can select among the embodiment, emitter can be placed on the instrument 110 to determine position and/or the orientation of instrument 110 with respect to receptor.The EM navigator that is used in the EM tracker can for example be wired and/or wireless device (for example wireless transmitter).Can adopt from what the information of distortion processing system 100 was adjusted the EM tracker and be configured to compensate distortion effect from instrument and operating environment.
In operation, adopt EM tracker or other EM navigator tracked instrument 110.Can be in physical EM tracker tracked instrument 110 or can be in virtual tracking system the simulation of tracked instrument 110.Trace analysis unit 120 is measured and is related to the parameter that instrument 110 is followed the tracks of, as field, position and orientation data.Trace analysis unit 120 generates the distortion model and/or the field pattern of instrument 110.Then, following the tracks of amending unit 130 adopts these models and/or this figure and from other data of trace analysis unit 120 distortion effect from instrument 110 is minimized.Follow the tracks of amending unit 130 and can test various receptors configurations and/or the placement on instrument 110 so that the distortion minimization in the EM tracker.For example, certain point that receiver assembly is placed on drilling equipment is gone up the distortion minimization that causes can make by from drilling equipment.Tracking amending unit 130 is also reconfigurable or recalibrate the EM tracker to solve the distortion effect from instrument 110.For example, the EM tracker can be programmed to predict certain distortion that is caused by tracked drilling equipment.In addition, following the tracks of amending unit 130 can programme to ignore the distortion effect from surrounding, as metal, light and/or the room unit of patient's seating surface to the EM tracker.The interior instrument 110 of EM tracker then can be tested with the checking position accuracy in trace analysis unit 120.If test is satisfied, then instrument 110 can be adopted and be followed the tracks of in the EM tracker by practitioner.
Fig. 2 illustrates the flow chart that is used for carrying out at electromagnetic tracking system the method 200 of distortion processing that adopts according to embodiments of the invention.At first, in step 210, acquisition instrument 110.In one embodiment, but physics or (for example, image or electronic representation) acquisition instrument 110 virtually.
Then, in step 220, the tracking performance of gauge 110.For example, if physics acquisition instrument 110 is then measured magnetic field, position, orientation and/or other data.If the virtual representation instrument then for example can analog meter 110 influences on computer or virtual tracker.Can observe and/or simulate electromagnetism follow the tracks of during the distortion and/or the further feature of instrument 110.Can generate drawing and/or model with magnetic field and distortion effect around the analytical tool 110.
Next, in step 230, the tracking performance of adjusting instrument 110 or tracker with reduce or compensation from the distortion effect of instrument 110.Analyze the error in the tracked instrument 110.Can test different instruments 110 and receiving unit and be configured to determine which kind of configuration can make distortion effect and other error minimize.Can test the calibration of tracker or be configured to determine which kind of configuration can maximum compensating distortion and other influence.
In addition, can analyze behind adjusted instrument 110 or the tracker remaining residual error.Can analyze residual error to determine whether residual error is lower than a certain threshold value.For example, if residual error is enough little, can ignore residual error.Further, analyze the stability of residual error.For example, under given noise and other factors situation, can analyze residual error to determine whether residual error reliably is lower than a certain threshold value.In one embodiment, if residual error reliably is not lower than a certain threshold value, then further adjust instrument 110 or tracker to reduce residual error.
Then, in step 240, test adjusted instrument 110 and/or tracker with the checking tracking accuracy.In one embodiment, adopt the drawing and/or the model that during above-mentioned steps 220, generate to obtain position measurements again.If the tracking data of instrument 110 satisfies some standard or improvement level, then instrument 110 can use with electromagnetic tracker.
Can adopt many methods to assess the electromagnetic performance of instrument 110.Fig. 3 illustrates the flow chart of method 300 that is used to carry out instrument 110 electromagnetic assessment according to the embodiment of the invention.At first, in step 310, practicable preliminary test is placed with respect to the best of tested instrument 110 to estimate receiver assembly.Then, in step 320, by the placement of the assessment of the accuracy studies on numerical value working range receptor.Next, in step 330, the execution work flow testing is to solve workflow issues.The level of detail execution work flow testing that can adopt variation is to determine the interaction between instrument 110 and the surgical workflow.Will be further described below the example of the method for illustrating 300 steps.
For example, adopt preliminary blank or estimate EM receptor bag based on the test of robot and place with respect to the best of the instrument 110 that is considered.For example, can carry out the analysis of receptor placement appropriate degree by analyzing tracking system with the good degree of the fitting data of instrument position.In addition, can position and the orientation data stability analysis in retest to fixed EM receptor and emitter position implementation.
Can assess the placement of EM receptor bag by robot and hand form block (manual phantom) analysis of the accuracy.EM receptor bag can be fixed on the instrument 110 and/or robot assessment fixture that is under the test.Robot and/or hand form block can be used for being evaluated at the correlated error on the EM tracker working range under the given most advanced and sophisticated compensating length.For example, can analyze maximum, root-mean-square (rms) value, standard value and histogram of error to a plurality of measured values.In addition, can obtain the working range that to accept accuracy.But the influence that also analytical work motor on instrument 110 performances produce.Further, but analysis of Electromagnetic integrity detector (FID) detects the ability of the site error that the metal distortion by instrument 110 produces.
Can adopt various workflow tests to solve the problem of the workflow aspect in electromagnetic tracker and the distortion processing system 100.Influence based on range position output and FID warning measurement moving range and patient's surrounding.In one embodiment, instrument 110 is represented by rough approximation.For example, the surgical drill aperture apparatus can be represented by ejector.For example, drill guide can be represented by wood dowel, and wherein receptor wraps in correct position and knocks in wherein.Adopt the test of rough approximation to be intended to initially indicate for various application provide the interaction between instrument and the surgical workflow.
In another embodiment, adopt the more approaching approximate implementation test of instrument 110.Adopt suitable material to come recognition and tracking and FID error.For example, be inserted in corrosion resistant plate on the wooden testboard and/or rod as the succedaneum of operating room and fracture table, the surrounding that test can simulated patient by employing.
In another embodiment, can adopt prototype tool to be similar to the imitated instrument 110 that is in the clinical trial.For example, concept instrument models can be used in patient's surrounding, as has the hospital operating room of corpse or tested object.Can adopt test to come recognition and tracking and FID error.
In addition, can adopt simulation toolset to come development﹠ testing EM tracker system.For example, the tracking performance of the detectable different coil architecture of simulation toolset, metal tolerance and/or distortion detection.Can adjust tool group with the ability of development﹠ testing instrument 110 and/or the application of instrument 110.
Can adopt simulation tool to check the not accuracy limitations of distortion tracker.Virtual tracker (VT) with simulation toolset provides controlled system for checking the accuracy limitations that causes owing to signal to noise ratio, foozle, calibration error and other factors.Also can study each tracker parameters to obtain the single and/or combined effect on the tracker system accuracy.
Simulation tool also can be used for distortion modeling.In one embodiment, VT comprises the Electromagnetic Modeling of object environment.This model can be used for analyzing in the tracker swept volume or near the distortion effect of object.The distortion object can comprise for example operation tool, room unit (for example, reinforcing bar floor and/or plumbous wall), operating room platform or lamp.At first, estimate the distorted characteristic of object for given coil architecture.In one embodiment, estimate distorted characteristic not adopting under the situation of compensation technique.Adopt VT to derive the sensor body architecture that metal distortion is had improved tolerance limit, comprise fixed (for example tracked surgical unit) and sporadic (for example platform bed or clip) distortion.
VT also can be used for improving distortion compensation or distortion tolerance is followed the tracks of.Can adopt the distortion modeling data to help improving the interior distortion tolerance of EM tracking system.For example, passive and/or active shielding technology can integrate pick off with the distortion instrument.For example, the distortion drawing technique is as position and orientation (P﹠amp; O) draw in drawing or EM field, can merge into the basis with measurement data, analog data or data.Degree of freedom (DOF) the parametrization mould that extraction reduces from measurement and/or analog data certainly (for example, a plurality of dipole modules) can improve distortion tolerance or compensation.In one embodiment, multisensor " drafting room " and/or robot data acquisition can be used for drawing distortion data.
In addition, can improve distortion detection.Can improve the FID algorithm.For example, can improve single position sensor FID, Collection and analysis characterizes FID algorithm weaknesses and model fit procedure from the method for multi-sensor information.
Fig. 4 illustrates the virtual tracker (VT) 400 that is used for the exploitation of EM tracker that adopts according to the embodiment of the invention.VT 400 comprises object simulation module 410 and simulation toolset 420.For example, VT 400 may be embodied as software or application specific processor or the circuit on the general purpose computer.VT 400 can integrate with above-mentioned distortion processing system 100.
Object simulation module 410 simulations object or instrument 110 to be tracked.The data characteristics of instrument 110 is generated by object simulation module 410.Feature and tracking performance that simulation toolset 420 adopts from instrument 110 in the analog data analyzing virtual tracking system of object simulation module 410.In one embodiment, simulation toolset 420 comprises accuracy module 430, distortion detection module 440, distortion modeling module 450 and distortion compensation module 460.
The virtual sign of accuracy module 430 analytical tool 110 or instrument 110 is to determine to simulate the accuracy of EM tracker and the influence of 110 pairs of EM trackers of instrument accuracy.Accuracy module 430 is checked signal to noise ratio, error, as the foozle and the calibration error of instrument 110, and other factors, thereby definite single and/or combined effect to the tracker test accuracy.
Distortion detection module 440 is determined the influence of distortion to tracking accuracy.Distortion detection simulation 440 a utilization integrity detection (FID), distortion and instrument models and sensor information are determined the distortion field from instrument 110.Can be used for adjusting tracker and tracker software to improve tracking accuracy from the distortion information of distortion detection module 440.
Distortion modeling module 450 generates the electromagnetic model of EM tracker environment.This model be used to estimate object in the tracker swept volume or near distortion effect.Distortion modeling module 450 is set up the distortion field of various objects, as the working environment of instrument 110 and tracker (wall, floor, patient bed etc.).Information from distortion modeling module 450 can be used for changing the configuration of instrument 110 and/or development has improved tolerance limit to fixing and/or sporadic metal distortion tracker sensor body architecture.
Distortion compensation module 460 is used to improve the distortion tolerance of EM tracker and related system.For example, distortion compensation module 460 can be used for analog sensor shield technology (for example, passive and/or active), distortion drawing technique, the parametrization object model extracts and/or a drawing.Model configuration and data can be used for the EM tracker is programmed and/or improved the distortion tolerance of EM tracker.
In a certain embodiment, VT 400 can be used for helping to provide for the sane tracking system of incidental distorters.Can help to make pick off and operation tool closely or integrate from the information of VT 400 with meeting human engineering.Information from VT 400 can help configuration and calibration instrument, instrument guides and tracking system.The module of VT 400 helps to provide reliably to causing the detection of the inaccurate tracking of object.Some embodiment of VT 400 also can help operating in the tracking system (for example, the systematic error of minimizing) under the tracking accuracy that is subject to SNR.
According to some embodiment of the present invention, various systems, method and object can be used for distortion detection, compensation and tolerance limit.The example of several purposes that are used to explain is described below.
In one embodiment, if distortion object (distorter) is fixed with respect to the EM emitter, then can adopt the whole bag of tricks to draw from the distortion of distorter.For each emitter coil in the emitter, can be at the normal component of on the border surface of distorter, measuring magnetic field.Can from measured value, deduct distortion field value not to determine on the border field from distorter.In one embodiment, adopt Laplace's equation and finite element analysis to come the outer distortion field of computation bound.In another embodiment, distorter is created as the dipole array of for example all places, orientation and/or intensity in the border.Adjust dipolar position, orientation and/or intensity with boundary the field match.Then, add transmitter dipole to distorter dipole array.Dipole forms the analytical model of tested border external transmitter and distorter.Adopt this model, can place, the arbitrfary point on border calculating magnetic field,, magnetic field amplitude quadratic sum magnetic field gradient.
For transmitter coil field magnitudes, for example, can calculate one group of eight function from ternary transmitter field amplitude square.For example, can be the merging amount that each x, y and z divide quantity symbol and determine a function.For example, can adopt signal-matrix-symbol (Raab ' s signal-matfix-sign) function of table look-up interpolation method and/or Raab to determine these functions.In one embodiment, do not having under the situation of distortion, eight functions equate.The inversion of function can produce distortion and draw.In addition, rotatable function is to produce required drafting.Can adopt the method for least square best fit of field and gradient modules calculated distortion to separate.
Selectively, can be from distorter field measurement signal matrix.Then, calculate transmitter coil field magnitudes.Determine the not apparent position of distortion emitter coil (for example, adopting the Raab algorithm).Select the symbol of emission and choose candidate solution.If this is separated near axle, then rotatable matrix function is away from axle.Can obtain and separate.Select symbol.Then matrix is gone back to the home position.This separates proximate undistorted the separating of expression.Then adopting the not distortion transmitter dipole of being calculated to calculate the method for least square best fit separates.This is separated and comprises distortion.Employing comprises that the field of distortion and second method of least square best fit of gradient modules calculating separate.Repeat the distortion least square fitting and can improve the result who produces by the secondary influence.
In one embodiment, ISCA distortion drawing process can be used for distorter is created as the model of dipole array.The dipole that distortion produces is subjected to exciting from the dipole field of emitter.Distorter dipole gain is a distorter dipole moment and the ratio of the not distortion transmitter field of distorter dipole position.Distorter dipole is towards the direction opposite with transmitter field.Yet distorter dipole may be not parallel to the launching site.Therefore, distorter response is for can being different at x, y with distortion transmitter field component on the z direction.In one embodiment, gain matrix or tensor do not rely on transmitter field.If mobile transmitter, distortion gain remains unchanged.Can adopt the new transmitter field value of distorter position to recomputate distortion field.Therefore, distortion compensation can be undertaken tuning to proofread and correct mobile emitter by parameter.
For example, receptor can be installed on the debrider blade.This blade is installed on the axle that has controlled roll angle not in the remover housing.This housing causes distortion.This housing is asymmetric, so distortion changes with the rolling of housing with respect to receptor.Have distortion map as the tracking time adjustable parameter of distortion map roll value and so on and can adapt to distortion from the remover housing.Gather other data point can calculated distortion figure roll value to adapt to distorter with respect to emitter or receptor or any fixed-site.If there is more than one distorter, iterative analysis can draw the influence of distorter to producing each other.That is to say that for example, each distorter can be subjected to the field that produced by emitter and the influence of the field that produced by another distorter.
In one embodiment, can in distortion processing system 100, simulate the distortion of conducting ring.Determine the position and the orientation of this ring with respect to emitter.Also determine the shape of this ring.The cross section of conductor is compared less with the size of ring.Therefore, when the mutual inductance between ring and the emitter coil, this conductor can be counted as infinitely small.In addition, when the self-induction of ring, can ignore the self-induction of conductor.Then, can be by the self-induction of the shape ring of encircling.For example, the mutual inductance between ring and the emitter coil can be calculated by taking graceful mutual inductance double integral.The emitter model of emitter coil can be used for determining a certain position (x, y, the magnetic field of every coil current z), its unit is every ampere of a tesla.Then can be by the field model of the magnetic field calculation distorter ring of current value and every current value.
In one embodiment, can adopt the transmitter line girth sheets that comprises greater number minor spiral coil to carry out field distortion draws.Drive plate drives in the coil on this plate at every turn.In one embodiment, time-multiplexed (time-muliiplexed) coil on frequency drives coil board.The component side of plate is towards volume inside.The weld side of plate is towards volumetrical outside.Tested device is placed in the volume.The component side of plate makes the weld side of plate and tested device electrostatic screen is opened and provide return path for driver current.
Each coil on the plate is connected to a switch.Coil and corresponding switch are connected in series.Unselected coil connects and exchanges ground.The electric current of selected coil flows to current measuring device.Switch can be for example photo-coupler, diode or series diode, and/or audion.Y line on the component side is driven by alternating current source.Every Y line is by the ground trace electrostatic screen on the component side.The X line is positioned at component side and connects and exchanges ground or virtually.The X line is connected to current measuring device.Coil and switch are connected in series at the intersection point place of X and Y line.In one embodiment, plate comprises a plurality of coil and switches that are connected in series at the intersection point place of X and Y line.Coil board or drive plate can comprise time-multiplexed logic circuit so that be coil power supply.Time-multiplexed coil and current measuring device are used to set up device being tested field distortion on every side and draw.
In one embodiment, the fluoroscopic image system adopts a pair of ISCA receptor that is installed on the fluoro camera calibration fixture.Fluoro camera calibration fixture for example can be installed on the image intensifier tube.Image amplifier comprises various metals and makes field distortion depart from electromagnetic tracker.Robot system can be used for drawing distortion and generates tracker correction table.Then this table can be used for proofreading and correct the tracking error that is produced by distortion.The different images booster of same shape number presents different slightly field distortions.Therefore each booster can adopt different distortion correction table.
The distortion jar can be used for the camera calibration fixing device.In one embodiment, jar comprises that the monolithic height leads metal, as copper, silver or aluminum.Jar surrounds image amplifier as much as possible, and is consistent with mechanical constraints and can form transparent region in the image amplifier front.Jar also produces the field distortion of tracker.Therefore, the distortion of drawing jar and use the tracker correction table that is generated to proofread and correct.In one embodiment, the thickness of jar metal is greater than the depth of penetration (skindepth) of metal, thereby magnetic field at all can penetrating metal and the volume of metal back.Jar shields most of magnetic field and image amplifier, thereby booster does not almost have field distortion.Therefore, adopt this jar, change image amplifier and can not produce significantly influence field distortion.A distortion correction table can be used for all image amplifiers of given model.In another embodiment, distortion correction table can be used for the image amplifier of different model.
In addition, cryptoscope or other X wire system can comprise X line scatter filter.In one embodiment, but X line scatter filter comprises the alternating layer of plumbous and nonopaque material, but nonopaque material for example is plastics or aluminum.The perforate of X line can be provided, and this perforate can be conducted electricity, thereby stops magnetic field.Light filter can charge into the conductive shell that hides the fluoroscopic image booster to the perforate of X line.This shell makes tracker magnetic field and image amplifier keep separating, thereby change image amplifier tracker is had minimum influence.
In one embodiment, passive conducting ring can be placed in the fluoroscopic systems near the receptor place.Passive conducting ring for example can be with respect to the asymmetric placement of ISCA.Passive conducting ring has been eliminated the hemisphere of tracker and has not been needed large-scale wound coil.Selectively, ferromagnetic rod can be placed to the close ISCA emitter of one end to eliminate hemisphere.In addition, reciprocity make the ring or rod can be placed close to receptor but not emitter with clear one's mind of doubt.
In one embodiment, can draw existing ISCA seed routine (seed routine) to allow to calculate seed with respect to the fixed distorter of emitter in the system 100.For example, for each emitter, by three receiver coil mutual inductances and square calculate coil position component square (x
2, y
2, z
2).In one embodiment, inductance square does not rely on the receptor orientation.If distorter is fixed with respect to emitter, can calculate drawing and separate with the parsing dipole that replaces distorter.For distorter, inductance squares can still not rely on the receptor orientation.In addition, reciprocity can exchange receptor and emitter and definite position and orientation information with respect to the fixed distorter of receptor.
In one embodiment, after determining the magnetic field mapping data message, can adopt the plurality of data method for simplifying.For example can on the field pattern boundary point, adopt Laplace's equation and Finite Element Method.Can adopt internal point to check accuracy.Then can some kinds of forms represent the distorter model.For example this model can be to adopt the parametrization of interpolation method, function match and/or reference function and the look-up table that draws.Can be according to mathematics convenience and/or Electro Magnetic Compatibility selection reference function.Reference function is set up in the field that for example, can form about distortion ring, rod and/or the sheet by the parametrization size.Distortion model can be expressed as the functional form of convenience of calculation.Other reference function can comprise the dipole of for example various intensity and orientation and Green's function (Green ' s function).In one embodiment, the electro permanent magnetic sensible basis causes parameter value to provide satisfying separating of Laplace's equation.In addition, produce " good " model with less parameters.Can produce figure family by model.Figure family can provide the distortion with fewer strong point to draw.
In one embodiment, can be small-sized conductive loop distorter and set up simple dipole model.This distorter is fixed with respect to electromagnetic launcher.Suppose that this distorter has excellent electric conductivity.Field from emitter forms the magnetic flux that passes loop.This loop comprises that making the total magnetic flux of passing loop is zero eddy current.By the measurement of this eddy current, can calculate the distortion field that produces by loop.For large-scale loop, can adopt the integral and calculating distortion field.For small loop, this loop can be by dipole approximation, and can determine the field that produced by eddy current.For example, eddy current in the loop area, loop and the magnetic flux of wearing loop can be used for determining to come the distortion field of self loop.In one embodiment, distortion field can cause the variation in the transmitter currents, but these variations are measured and proofreaied and correct by tracker electronics.
In another embodiment, can be small-sized conductor distorter and set up simple dipole model.This distorter is fixed with respect to electromagnetic launcher.Suppose that distorter electric conductivity is splendid and can not produce magnetic flux in distorter inside.The distortion field of object distorter can by with the Normal plane of incident transmitter field in determine that the big cross section of object is similar to.The area of this cross section can be used for as mentioned above as small-sized conductive loop distorter calculated distortion field.In one embodiment, the distorter effective area is different for the incident transmitter field of different directions.
In another embodiment, can analyze near the non-conductive ferrite of small infinite-permeability of emitter.This object is preferably fixed with respect to emitter.This object for example makes the incident flux of interior of articles be increased to twice or three times.The object distortion field can be approximated to the aforesaid small-sized conductor distorter that is similar to.Then, distortion field can multiply by flux factor, as-2 or-3, to draw the incident flux of interior of articles.
Can and/or adopt the various instruments of VT 400 tests with the distortion effect of definite tracking system with based on distortion effect calibration tracking system in distortion processing system 100.For example, can check that air drill or electric drill are to determine that drilling equipment is to the position of tracking system and the influence of orientation accuracy.In addition, distortion processing system 100 can be used for estimating the suitable attachment distance between EM receptor bag and the drilling equipment.Suitable receiver attachment distance can be improved instrument 110, as the tracking of drilling equipment.Adopt FID can improve to by instrument 110, as drilling equipment, the detection that the error tracking that the field distortion of generation causes carries out.
For checking drilling equipment, pick off is placed apart with emitter and parallel with the x axle of following the tracks of coordinate system.Emitter and receptor bag are attached on the plate.Collection position and orientation data are to obtain calibration and reference data under the situation that does not have drilling equipment to exist.Then, drilling equipment is placed on apart from the position of a plurality of distances of receptor bag.The receptor bag is a plurality of apart from keeping parallelism with this to the orientation of drilling equipment top surface.A plurality of to this apart from collection position and orientation.Also can well spend (GOF) data in the record tracker match of a plurality of positions.Next, but the position data of calculated example such as drilling equipment tip.Adopt a plurality of test conditions to determine error in the apical location.Adopt navigation algorithm and threshold calculations FID data.Because the orientation and the tip offset of receptor bag all are parallel to the x axle of following the tracks of coordinate system, can come estimation theory drilling equipment guide pipe trajectory error by the x component of getting the tip error.
Like this, some embodiment of the present invention provides tracking system and method sane to the occasionality distortion and that allow.Some embodiment provide EM position sensor and operation tool or Other Instruments human engineering and effectively combine.Some embodiment provides the reliable detection to the situation that causes inaccurate tracking.Some embodiment minimizes the systematic error of the tracking accuracy with the signal to noise ratio of being subject to.Can analyze the tracking error that produces by metal distortion and adopt electromagnetic tracking system and the distortion processor compensates.
Virtual tracking system and modular environment, instrument direction device and/or tracking system that some embodiment is provided for measuring distortion and other influence and adjusts tracked instrument configuration.Some embodiment is provided for making the system and method for the distortion minimization in the tracking system.Some embodiment is provided for developing the system and method for allowing instrument and tracking system with test distortion.
Though the present invention is described with reference to some embodiment, it will be appreciated by those skilled in the art that under the situation that does not depart from the scope of the invention, can carry out various changes and available equivalents substitutes.In addition, under the situation that does not depart from the scope of the invention, can carry out many modifications to adapt to concrete condition or material according to instruction of the present invention.Therefore, the present invention will be subject to disclosed specific embodiment, but the present invention will comprise the whole embodiment that fall in the appended claims scope.
Claims (11)
1, a kind of improved electromagnetic tracking system, this system comprises:
The emitter that is used to transmit;
Be used to receive the receptor from the signal of emitter, described emitter and receptor are used to follow the tracks of object; With
The distortion processing system (100) that is used for the object analysis distortion characteristic.
2, system according to claim 1, wherein distortion processing system (100) comprise and are used for the virtual electromagnetic tracker (400) of analog distortion feature to the influence followed the tracks of.
3, a kind of distortion processing system (100), this system (100) comprising:
The trace analysis unit (120) that is used for the tracking performance of analytical tool (110); With
The tracking amending unit (130) that is used for the tracking performance of compensation apparatus (110).
4, system according to claim 3 (100), wherein trace analysis unit (120) generate the drawing of instrument (110) distortion characteristic and at least one in the model.
5, a kind of virtual tracking system (400), this system (400) comprising:
Be used to simulate the object simulation module (410) of tracked object; With
The simulation toolset (420) that is used at least one distortion characteristic of object analysis, this simulation toolset (420) can generate the distortion information of object based on this at least one distortion characteristic.
6, system according to claim 5 (400), wherein simulation toolset (420) also comprises the accuracy module (430) of the accuracy that is used to determine the object tracking that simulated.
7, system according to claim 5 (400), wherein simulation toolset (420) also comprises and is used for determining the distortion detection module (440) of object distortion to the influence of tracking accuracy.
8, system according to claim 5 (400), wherein simulation toolset (420) also comprises distortion modeling module (450), is used to generate the electromagnetic model of assessment object to the distortion effect of tracker environment.
9, system according to claim 5 (400), wherein simulation toolset (420) also comprises the distortion compensation module (460) of the distortion tolerance that is used to improve electromagnetic tracker.
10, a kind of method (200) that is used for carrying out distortion analysis at electromagnetic tracking system, this method (200) comprising:
The tracking performance of Measuring Object (220); With
The tracking performance of object analysis is to determine distortion effect.
11, method according to claim 10 (200), wherein analytical procedure also comprises at least one tracking performance with object analysis that generates in field pattern and the model, thereby determines distortion effect.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US52013803P | 2003-11-14 | 2003-11-14 | |
| US60/520,138 | 2003-11-14 | ||
| US10/869,594 | 2004-06-16 |
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| CN1901835A true CN1901835A (en) | 2007-01-24 |
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| Application Number | Title | Priority Date | Filing Date |
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| CNA2004800403577A Pending CN1901835A (en) | 2003-11-14 | 2004-11-04 | System and method for distortion reduction in an electromagnetic tracker |
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| CN103987337A (en) * | 2011-12-13 | 2014-08-13 | 皇家飞利浦有限公司 | Distorsion fingerprinting for EM tracking compensation, detection and error correction |
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| CN104665833A (en) * | 2010-12-22 | 2015-06-03 | 韦伯斯特生物官能(以色列)有限公司 | Compensation for magnetic disturbance due to fluoroscope |
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- 2004-11-04 CN CNA2004800403577A patent/CN1901835A/en active Pending
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| US10561371B2 (en) | 2010-12-29 | 2020-02-18 | St. Jude Medical, Atrial Fibrillation Division, Inc. | Dynamic adaptive respiration compensation with automatic gain control |
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| CN103987337A (en) * | 2011-12-13 | 2014-08-13 | 皇家飞利浦有限公司 | Distorsion fingerprinting for EM tracking compensation, detection and error correction |
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| CN112545648A (en) * | 2019-09-26 | 2021-03-26 | 阿森松技术公司 | Configurable transmitter array for electromagnetic tracking system |
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| CN113804093A (en) * | 2020-06-11 | 2021-12-17 | 阿森松技术公司 | Electromagnetic position measurement system with sensor parasitic loop compensation |
| CN113804093B (en) * | 2020-06-11 | 2024-05-31 | 北方数字化技术公司 | Electromagnetic position measurement system with sensor parasitic loop compensation |
| CN113796958A (en) * | 2020-06-12 | 2021-12-17 | 阿森松技术公司 | Electromagnetic field distortion correction using inside-out tracking |
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