Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
  • A61B8/08—Clinical applications
  • A61B8/0833—Clinical applications involving detecting or locating foreign bodies or organic structures
  • A61B8/0841—Clinical applications involving detecting or locating foreign bodies or organic structures for locating instruments
• • 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
  • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
  • A61B8/42—Details of probe positioning or probe attachment to the patient
  • A61B8/4245—Details of probe positioning or probe attachment to the patient involving determining the position of the probe, e.g. with respect to an external reference frame or to the patient
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
  • A61B8/42—Details of probe positioning or probe attachment to the patient
  • A61B8/4245—Details of probe positioning or probe attachment to the patient involving determining the position of the probe, e.g. with respect to an external reference frame or to the patient
  • A61B8/4263—Details of probe positioning or probe attachment to the patient involving determining the position of the probe, e.g. with respect to an external reference frame or to the patient using sensors not mounted on the probe, e.g. mounted on an external reference frame
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
  • A61B8/58—Testing, adjusting or calibrating the diagnostic device
• • 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
  • A61B90/36—Image-producing devices or illumination devices not otherwise provided for
  • A61B90/37—Surgical systems with images on a monitor during operation
  • A61B2090/378—Surgical systems with images on a monitor during operation using ultrasound
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
  • A61B8/48—Diagnostic techniques
  • A61B8/483—Diagnostic techniques involving the acquisition of a 3D volume of data
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
  • A61B8/52—Devices using data or image processing specially adapted for diagnosis using ultrasonic, sonic or infrasonic waves
  • A61B8/5215—Devices using data or image processing specially adapted for diagnosis using ultrasonic, sonic or infrasonic waves involving processing of medical diagnostic data
  • A61B8/5238—Devices using data or image processing specially adapted for diagnosis using ultrasonic, sonic or infrasonic waves involving processing of medical diagnostic data for combining image data of patient, e.g. merging several images from different acquisition modes into one image
  • A61B8/5246—Devices using data or image processing specially adapted for diagnosis using ultrasonic, sonic or infrasonic waves involving processing of medical diagnostic data for combining image data of patient, e.g. merging several images from different acquisition modes into one image combining images from the same or different imaging techniques, e.g. color Doppler and B-mode

Definitions

• the present invention generally relates to accurate image guidance for surgical and interventional applications involving intra- operative ultrasound imaging.
• the present invention specifically relates to a calibration of a tracked ultrasound probe derived from an ultrasound image, two-dimensional ("2D US") or three-dimensional ("3D US"), of a calibration marker (e.g., a distal tip of a needle) within a global spatial coordinate system.
• 2D US two-dimensional
• 3D US three-dimensional
• Tracking an ultrasound probe with a spatial localizer has applications in surgical and interventional navigation, such as, for example, for live 3D ultrasound images of an anatomical region or for fusion of live 2D or 3D ultrasound images of the anatomical region with other image modalities (e.g., a magnetic resonance imaging ("MRI") scan or a computed tomography (“CT”) scan).
• Calibration of the tracked ultrasound probe is necessary to these applications and involves a determination of a fixed transform (i.e., fixed spatial relationship) between the ultrasound images and a local spatial tracker attached to the ultrasound probe.
• the calibration of the tracked ultrasound probe is a time consuming one-time procedure performed prior to a first clinical use of the ultrasound probe, and then applied identically for each clinical use thereafter.
• this approach ignores the case-specific distortions experienced by the spatial tracking system, which may render the a priori calibration inaccurate.
• the present invention provides new and unique methods for ultrasound calibration based on a registration whereby image coordinates P / of a calibration marker illustrated within ultrasound images, 2D or 3D, are registered to corresponding tracking coordinates Pt of the calibration marker within a global spatial coordinate system.
• One form of the present invention is a registration system employing a calibration tool, an ultrasound probe, a calibration spatial tracker attached to the calibration tool, and an image spatial tracker attached to the ultrasound probe.
• the calibration tool facilitates movement of the calibration marker within a global spatial coordinate system
• the ultrasound probe generates ultrasound image data representative of one or more ultrasound images illustrating the calibration marker within an ultrasound image coordinate system
• the calibration spatial tracker generates calibration tool tracking data representative of a spatial tracking of the calibration marker within a global spatial coordinate system
• the image spatial tracker generates ultrasound probe tracking data representative of a tracking of the ultrasound probe within the global spatial coordinate system.
• the registration system further employs an ultrasound probe calibrator to process the ultrasound image data and the tracking data for determining an ultrasound image transform matrix between the ultrasound image(s) and the image spatial tracker.
• a processing of the ultrasound image data and the tracking data by the ultrasound probe calibrator includes, for each ultrasound image, a mapping of an image coordinate of the calibration marker within the ultrasound image coordinate system to a corresponding tracking coordinate of the calibration marker within the global spatial coordinate system.
• a second form of the present invention is a registration method involving an operation of an ultrasound probe to generate ultrasound image data representative of one or more ultrasound images illustrating a calibration marker within an ultrasound image coordinate system, an operation of a calibration spatial tracker attached to a calibration tool to generate calibration tool tracking data representative of a spatial tracking of the calibration marker within a global spatial coordinate system, and an operation of an image spatial tracker attached to the ultrasound probe to generate ultrasound probe tracking data representative of a spatial tracking of the ultrasound probe within the global spatial coordinate system.
• the registration method further involves a processing of the ultrasound image data and the tracking data to determine a ultrasound image transform matrix between the ultrasound image(s) and the image spatial tracker, wherein the processing of the ultrasound image data and the tracking data includes, for each ultrasound image, mapping an image coordinate of the calibration marker within the ultrasound image coordinate system to a corresponding tracking coordinate of the calibration marker within the global spatial coordinate system.
• FIG. 1 illustrates an exemplary embodiment of an image-guided interventional system in accordance with present invention.
• FIG. 2 illustrates an exemplary embodiment of a flowchart representative of an image-guided interventional method in accordance with the present invention.
• FIG. 3 illustrates an exemplary implementation of the image-guided interventional method of FIG. 2 by the image-guided interventional system of FIG. 1.
• FIG. 4 illustrates an exemplary embodiment of a flowchart representative of an ultrasound calibration method in accordance with the present invention.
• FIGS. 5 and 6 illustrate an exemplary generation of ultrasound images of a calibration marker in accordance with the flowchart illustrated in FIG. 4.
• the present invention provides various methods for an ultrasound calibration based on a registration whereby image coordinates Pi of a calibration marker illustrated within ultrasound images, 2D or 3D, are registered to corresponding tracking coordinates P L of the calibration marker within a global spatial coordinate system.
• these ultrasound calibration methods are implemented by an ultrasound probe calibrator 50 of the present invention for determining a ultrasound image transform matrix between the ultrasound images and an image spatial tracker attached to an ultrasound probe generating the ultrasound images.
• ultrasound probe calibrator 41 will be described herein as one of the components of an image- guided interventional system.
• FIG. 1 illustrates an image-guided interventional system employing a calibration tool 10, a spatial tracking system 20, an ultrasound image system 30 and a surgical navigating system 40.
• calibration tool 10 is broadly defined herein as any tool associated with one or more calibration markers capable of image detection and extraction as illustrated within an ultrasound image 32.
• the calibration marker(s) may be directly associated with calibration tool 10 (e.g., a part of calibration tool 10) or indirectly associated with calibration tool 10 (e.g., controlled by calibration tool 10).
• calibration tool 10 is a needle and a distal tip 11 of the needle is the calibration marker.
• multiple points extracted at known distances from distal tip 11 along shaft of needle 10 may serve as a set of calibration markers capable of image detection and extraction as illustrated within ultrasound image 32.
• spatial tracking system 20 is broadly defined herein as any system including a calibration spatial tracker 22 and an image spatial tracker 23 respectively attached to calibration tool 10 and an ultrasound probe 31 and structurally configured for tracking movements of calibration tool 10 and ultrasound probe 31 within a global spatial coordinate system 21.
• Examples of spatial tracking system 20 include, but are not limited to, electromagnetic ("EM") tracking devices having spatial trackers in the form of EM sensors and optical tracking devices having spatial trackers in the form of optical sensors.
• EM electromagnetic
• the AuroraTM EM Tracking System offered by Northern Digital Inc. of Waterloo, Canada or a modified form thereof may be utilized as spatial tracking system 20.
• a PercNav system offered by Philips Medical Systems or a modified form thereof may be utilized as spatial tracking system 20.
• ultrasound imaging system 30 is broadly defined herein as any system structurally configured for controlling an operation of ultrasound probe in generating a 2D ultrasound image (not shown) or 3D ultrasound image 32 as shown.
• Examples of the ultrasound imaging system 30 include, but are not limited to, any type of ultrasound imaging system utilizing a 3D ultrasound probe 31 as shown.
• the iU22 xMATRIX Ultrasound System with X6-1 probe offered by Philips Healthcare or a modified form thereof may be utilized as ultrasound imaging system 30.
• surgical navigating system 40 is broadly defined herein as any system structurally configured for displaying a tracking of calibration tools in real time in both intra-operative and/or pre-operative images.
• surgical navigator 40 include, but are not limited to, systems tracking and displaying tools in real time in intra-operative ultrasound 3D images only or in intra-operative ultrasound 2D images fused with a pre-operative MRI scan or a pre-operative CT scan.
• PercNav system offered by Philips Healthcare or a modified form thereof may be utilized as surgical navigating system 40.
• ultrasound probe calibrator 41 is broadly defined herein as any module structurally configured with hardware, software and/or firmware for determining a ultrasound image transform matrix between ultrasound image 32 and image spatial tracker 23 attached to ultrasound probe 31 based on a registration whereby image coordinates Pi (x,y,z) of the calibration marker(s) (e.g., calibration marker 11) illustrated within an ultrasound image coordinate system 33 of ultrasound image 32 are mapped to corresponding tracking coordinates ⁇ ⁇ ) of the calibration marker(s) within global spatial coordinate system 21.
• image coordinates Pi (x,y,z) of the calibration marker(s) e.g., calibration marker 11
• ⁇ ⁇ tracking coordinates
• ultrasound probe calibrator 41 processes calibration tool tracking data (“CTTD”) 24 representative of a spatial tracking of calibration tool 10 via calibration spatial tracker 22 within global spatial coordinate system 21 and ultrasound probe tracking data (“UPTD”) 25 representative of a spatial tracking of ultrasound probe 31 via ultrasound spatial tracker 23 within global spatial coordinate system 21.
• CTTD calibration tool tracking data
• UPTD ultrasound probe tracking data
• ultrasound probe calibrator 41 process ultrasound image data (“UID”) representative of a 2D ultrasound image (not shown) or 3D ultrasound image 32 as shown.
• ultrasound probe calibrator 41 may be installed or integrated within surgical navigator 40 as shown, or alternatively installed or integrated within spatial tracking system 20 or ultrasound imaging system 30.
• FIG. 1 A description of exemplary ultrasound calibration methods of the present invention will now be provided herein as implemented by image-guided interventional system shown in FIG. 1. Specifically, a flowchart 50 representative of an image-guided interventional method of the present invention as shown in FIG. 2 is implemented by image-guided interventional system shown in FIG. 1 for an intra- operative calibration of one or more ultrasound images 32 to the image spatial tracker 23 attached to ultrasound probe 31.
• a stage S51 of flowchart 50 encompasses a pre-operative planning of a particular interventional procedure involving ultrasound probe 31.
• the interventional procedure involves ultrasound probe 31 as the exclusive imaging source.
• a pre-operative scan e.g., a MRI scan or a CT scan
• stage S51 may encompass a 3D pre-procedural scan 70 of a cardiac region 61 of a patient 60 and a storage of 3D pre- procedural scan 70 within a database 71.
• a stage S52 of flowchart 50 encompasses a setup of a working environment for the pre-planned interventional procedure including, as exemplary shown in FIG. 3, a positioning of spatial tracking system 20, ultrasound imaging system 30, surgical navigator 40 represented including ultrasound probe calibrator 41 and any additional imaging systems and/or equipment.
• the imaging systems and/or other equipment may create distortions of spatial tracking system 20 and such tracking distortions may alter a calibration transformation of ultrasound images 32 to image spatial tracker 23 that was determined prior to or during stage S51.
• an intra-operative ultrasound probe calibration performed during a stage S53 of flowchart 50 is thus desirable whereby the tracked probe 31 is exposed to the same distortions during calibration as experienced during the subsequent interventional procedure during stage S54 of flowchart 50.
• stage S53 encompasses an intra-operative ultrasound probe calibration based on a registration whereby image coordinates Pi (x,y,z) of calibration marker 11 illustrated within ultrasound image coordinate system 33 associated with one or more ultrasound images 32 are registered to corresponding tracking coordinates ⁇ ⁇ ⁇ ) of calibration marker 11 within global spatial coordinate system 21.
• calibration tool 10 is inserted in an imaginable medium (e.g., an imaging phantom) or in the patient in the same general location where the interventional procedure will be performed.
• the relative position between calibration tool 10 and ultrasound probe 31 may be fixed to obtain an ultrasound image of calibration tool 10 within the medium or patient, or may be changed to obtain two or more different ultrasound images 32 of calibration tool 10 within the medium or patient calibration tool 10 and ultrasound probe 31 are tracked within global spatial coordinate system 21.
• calibration tool 10 is inserted in patient 60 in the cardiac region 61 where the interventional procedure will be performed.
• the relative position between calibration tool 10 and ultrasound probe 31 may be fixed to obtain an ultrasound image of calibration tool 10 within patient 60, or may be changed to obtain two or more different ultrasound images 32 of calibration tool 10 within patient 60 as calibration tool 10 and ultrasound probe 31 are tracked within global spatial coordinate system 21.
• ultrasound images 32 may be acquired and processed continuously, or individual ultrasound images 32 may selected by the operator for processing.
• the ultrasound probe calibration of the present invention is based on a registration whereby image coordinates Pi (x,y,z) of calibration marker 11 illustrated within ultrasound image coordinate system 33 associated with one or more ultrasound images 32 are registered to corresponding tracking coordinates PL(X Z) of calibration marker 11 within global spatial coordinate system 21. More particularly, for each ultrasound image 32 of calibration marker 11, a ultrasound image transform matrix Fi between image spatial tracker 23 and ultrasound image 32 is determined in accordance with the following equation [1] :
• FIG. 4 illustrates a flowchart 80 representative of one embodiment of stage S53 and FIG. 4 will be described herein in reference to FIGS. 5 and 6 of various relative positioning of calibration tool 10 and ultrasound probe 31
• stage S81 of flowchart 80 encompasses an initial relative positioning of calibration tool 10(1) and ultrasound probe 31(1) as shown in FIGS. 5 and 6.
• a stage S82 of flowchart 80 encompasses a generation by spatial tracking system 20 of calibration tool tracking data ("CTTD") 24 representative of a spatial tracking of calibration tool 10(1) via calibration spatial tracker 22(1) within global spatial coordinate system 21 and ultrasound probe tracking data
• CTTD calibration tool tracking data
• UPTD 25 representative of a spatial tracking of ultrasound probe 31(1) via ultrasound spatial tracker 23(1) within global spatial coordinate system 21.
• Stage S82 also encompasses a generation by ultrasound imaging system 30 of ultrasound image data ("UID") 34 representative of the 3D ultrasound image 32(1).
• UID ultrasound image data
• a stage S83 of flowchart 80 encompasses ultrasound probe calibrator 41 executing an image extraction of calibration marker 11 from ultrasound image 32(1) via known techniques and adding a current entry CE in an image data set of an ultrasound coordinate Pi (x,y,z) of calibration marker 11 within ultrasound image coordinate system 33.
• a stage S84 of flowchart 80 encompasses ultrasound probe calibrator 41 adding a current entry CE within a tool data set of tracking coordinate ⁇ ⁇ ) of calibration marker 11 within global spatial coordinate system 21 and adding a current entry CE within a probe data set of ultrasound tracking transform matrix L F T( x z ) of ultrasound probe 31 within global spatial coordinate system 21.
• Stage S84 further includes ultrasound probe calibrator 41 mapping ultrasound coordinate Pi (X ,z) to tracking coordinate ⁇ ⁇ ) ⁇
• An N number of ultrasound images 32 of calibration marker 11 is pre-set whereby ultrasound probe calibrator 41 determines at a stage S85 of flowchart 80 whether to proceed to a stage S86 of flowchart 80 or to repeat stages S81-S84 if the current entry CE ⁇ N as a means of adding further entries to the data sets.
• N is ⁇ 1 and is preferably ⁇ 3.
• stage S86 encompasses ultrasound probe calibrator 41 calculating ultrasound image transform matrix Fi between image spatial tracker 23 and ultrasound image in accordance with equation [1] :
• stage S86 encompasses ultrasound probe calibrator 41 executing a singular value decomposition (SVD) of a transformation data set of calculated ultrasound image transform matrix Fi between image spatial tracker 23 and ultrasound images 32 in accordance with equation [1].
• SVD singular value decomposition
• stage S81 may involve a repositioning of calibration tool 22(2) as shown in FIG. 5 and/or a repositioning of ultrasound probe 31(2) as shown in FIG. 6.
• stages S82-S84 result in updated data sets and a mapping of current entries CE of ultrasound coordinate Pi (x,y,z) and tracking coordinate PL ⁇ X, Y,Z)-
• a final repeat of stage S81 may involve a repositioning of calibration tool 22(3) as shown in FIG. 5 and/or a repositioning of ultrasound probe 31(3) as shown in FIG. 6.
• stages S82-S84 again result in updated data sets and a mapping of current entries CE of ultrasound coordinate Pi (x,y,z) and tracking coordinate ⁇ ⁇ ⁇ ) ⁇
• ultrasound probe calibrator 41 executes a singular value decomposition of a transformation data set of calculated ultrasound image transform matrix Fi between image spatial tracker 23 and ultrasound images 32 in accordance with equation [1] .
• Flowchart 80 as described herein may be modified or enhanced in practice including, but not limited to, the following examples.
• ultrasound probe calibrator 41 may be structurally configured to indicate when a sufficient number of ultrasound images 32 with sufficiently spaced calibration marker positions have been acquired, and/or when a calibration with acceptable accuracy has been established.
• stage S82 may utilize an a priori calibration to determine the approximate position where calibration marker 11 is expected to appear in an ultrasound image 32, based on a tracking location of calibration tool 10. Knowing the approximate position of calibration marker 11 in ultrasound image 32 may speed up the automatic point detection, and/or make it more robust.
• flowchart 80 may be used to intra-procedurally update a priori (or a previous intra-procedural) ultrasound calibration.
• image guidance including tracking with a priori calibration may be used to guide the first part of calibration tool insertion in the patient or medium.
• Ultrasound imaging of calibration tool 10 in the patient or medium may then be used to update the previous calibration, providing more accurate tool guidance, fusion imaging etc. for the completion of the tool positioning and procedure.
• the calibration marker may be identified in one initial frame, and may then be tracked frame -by-frame providing accurate and fast calibration marker identification in a large number of frames as long as the calibration tool is moved sufficiently slowly relative to the ultrasound probe whereby frame-to-frame differences in calibration marker positions are sufficiently small.
• multiple calibration markers may be used as input points to the SVD decomposition algorithm.
• corresponding points in the global spatial coordinate system along the calibration tool may be generated to thereby allowing calculation of a calibration transform with a minimum of only 2 non-coplanar tool poses.
• higher-dimensional object(s) may serve as calibration marker(s) (e.g., straight lines, curved lines, surfaces, volumes, etc.) in lieu of individual point pairs being matched in ultrasound images and corresponding tracking data calibration markers.
• a curved line may for example be represented by a catheter which is imaged with ultrasound in the patient, and whose entire length is tracked.
• the desired calibration transform is determined by finding the transformation that minimizes the distance D between the ultrasound-imaged shape and the corresponding tracked shape, using some appropriate distance measure D (e.g., the mean absolute distance).
• a stage S54 of flowchart 50 encompasses a tracking of an interventional tool within ultrasound images or a pre-procedural scan based on the calibration transformation.
• surgical navigator 40 displays ultrasound image or pre-scan image 42 with a tracking overlay 43 of the interventional tool projected within image 42.
• flowchart 50 may be terminated upon completion of the procedure or stages S53-S54 may be repeated as necessary in view a repositioning of the equipment in the working environment.

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Cited By (11)

Citations (2)

• 2013
  • 2013-03-14 WO PCT/IB2013/052017 patent/WO2013140315A1/fr not_active Ceased

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