Registering a magnetic tracking system using an interferometric system

Abstract

The present invention provides a registration device, which includes a rod, a light guide passing through the rod, and an orientation sensor fixed to the rod. The light source outputs a modulated light beam into the proximal end of the light guide so that the light is emitted from the distal end of the light guide toward a surface close to the distal end of the rod. The detector receives the light reflected from the surface into the distal end of the light guide from the proximal end of the light guide, and outputs a signal indicating the intensity of the reflected light. The processor calculates the distance from the distal end of the rod to the surface by extracting the phase difference between the output light beam and the reflected light from the signal, and calculates the orientation of the surface in the sensor reference system in response to the calculated distance and the position of the distal end found from the orientation sensor.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 892,105, filed on August 27, 2019, which is incorporated herein by reference. Technical Field

[0003] The present invention relates generally to surgical tools, and in particular to tools that can be used for ENT (ear, nose and throat) examinations. Background Art

[0004] When performing an ENT procedure, such as examining a patient's sinuses, the operating physician may need to track the tools used for the procedure. Although tracking can be performed using fluoroscopy, fluoroscopy uses ionizing radiation that can harm both the patient and the physician.

[0005] Rather than using ionizing radiation, it is preferred to use a tracking system for ENT tools that does not contain such radiation. Such systems are well known in the art and include, for example, tracking systems that use magnetic and / or electric fields. However, in order for the tracking system to provide results that are compatible with images of the patient (such images may be produced by fluoroscopic or non-fluoroscopic means), the reference frames of the tracking system and the images need to be registered.

[0006] Methods for registration are known in the art. For example, if the patient image is a computed tomography (CT) image, voxels corresponding to the patient's skin can be extracted from the CT image. Easily identifiable elements of the skin, such as points between the eyes or the tip of the nose, can then be used for registration by positioning sensors operating in the tracking system over these points and using the signals from the sensors for registration. Summary of the invention

[0007] An embodiment of the present invention provides a registration device, which is composed of the following items:

[0008] a rod having a distal tip;

[0009] a light guide extending through the rod and having a distal end at the distal end of the rod and a proximal end extending proximally from the rod;

[0010] a position sensor secured to the wand and configured to output a first signal indicative of a position of the distal tip in a sensor reference frame;

[0011] a light source coupled to output a light beam having an intensity temporally modulated at a predetermined carrier frequency into the proximal end of the light guide, whereby light is emitted from the distal end of the light guide toward a surface proximate the distal tip of the rod;

[0012] a detector configured to receive light from the proximal end of the light guide that has been reflected from the surface into the distal end of the light guide and to output a second signal indicative of an intensity of the reflected light; and

[0013] a processor configured to calculate a distance from the distal end of the rod to the surface by extracting a phase difference between the output light beam and the reflected light from the second signal, and to calculate an orientation of the surface in the sensor reference frame in response to the calculated distance and a position of the distal end indicated by the first signal.

[0014] In one embodiment disclosed in the present invention, there is a modulator coupled to the light source, the modulator being configured to amplitude modulate the light beam. Typically, the amplitude modulation frequency of the light beam is set so that the interval between adjacent modulation peaks of the modulated light is between 1 cm and 4 cm.

[0015] In another disclosed embodiment, the first signal indicates an orientation of the distal tip in a sensor reference frame.

[0016] In yet another embodiment disclosed herein, the processor is configured to determine a maximum and a minimum of the second signal in response to moving the distal end of the rod relative to the surface. The processor may be configured to acquire a given signal from the detector when the surface is a certain distance from the distal end of the rod, and calculate the distance in response to the maximum, the minimum, and the given signal.

[0017] In an alternative embodiment, the light source comprises a laser that generates light.

[0018] In another alternative embodiment, the processor is configured to determine the distance at which the distal tip of the rod does not contact the surface.

[0019] In yet another alternative embodiment, the processor is configured to determine an initial value of the orientation of the surface using the sensor while the distal end of the stick is in contact with the surface, and to update the initial value to a final value of the orientation using the distance without the distal end of the stick contacting the surface.

[0020] According to one embodiment of the present invention, there is also provided a device, the device comprising:

[0021] a catheter comprised of an elongated member having a member distal end and an axis of symmetry, the member distal end being configured to be inserted into an orifice of a body of a living subject;

[0022] a first camera located on an outer surface of a distal end of the member and a second camera located on an outer surface of the distal end of the member, the cameras being oriented so that their respective fields of view are away from the axis of symmetry and include overlapping portions; and

[0023] A processor is configured to acquire corresponding optical images of tissue of a body in overlapping portions from the cameras to identify common elements of the tissue in the corresponding optical images, analyze a computed tomography (CT) image of the body to identify the common elements in the CT image, and overlay the corresponding optical images of the common elements on the common elements of the CT image to produce an enhanced CT image having the common elements.

[0024] In one embodiment disclosed in the present invention, the device includes a first magnetic sensor and a second magnetic sensor positioned in the distal end of the component close to the first camera and the second camera, respectively, and the processor is configured to acquire signals from the sensors so as to determine the position of the distal end of the component in a reference frame of the sensors, and to align the reference frame of the sensors with the reference frame of the CT image.

[0025] In another disclosed embodiment, the device includes a wire fixed to the member distal end at the wire distal end, and pulling the wire deflects the member distal end from the symmetry axis to change the respective optical images acquired by the first camera and the second camera.

[0026] According to one embodiment of the present invention, there is also provided a device, the device comprising:

[0027] a catheter comprised of an elongated member having a member distal end and an axis of symmetry, the member distal end being configured to be inserted into an orifice of a body of a living subject;

[0028] a motor secured to a distal terminal end of the member distal end such that a motor shaft is aligned with the axis of symmetry;

[0029] a rotatable base attached to the motor shaft;

[0030] a camera secured to an outer surface of the rotatable base such that a field of view of the camera is directed away from the axis of symmetry; and

[0031] A processor configured to rotate the camera on a motor shaft to acquire a pair of optical images of tissue of a body from the camera as the camera rotates, to identify common elements of the tissue in the pair of optical images, to analyze a computed tomography (CT) image of the body to identify the common elements in the CT image, and to overlay corresponding optical images of the common elements on the common elements of the CT image to produce an enhanced CT image including the common elements.

[0032] The processor may be configured to rotate the camera by swinging about a selected direction and acquire a pair of optical images at respective ends of the swing.

[0033] According to one embodiment of the present invention, there is also provided a device, the device comprising:

[0034] a catheter comprised of an elongated member having a member distal end and an axis of symmetry, the member distal end being configured to be inserted into an orifice of a body of a living subject;

[0035] a camera secured to a distal terminal end of the member distal end such that the camera field of view is aligned with the axis and faces away from the member distal end; and

[0036] A biopsy needle is attached to the member distal end so as to extend from the distal terminal end and is oriented parallel to the axis of symmetry.

[0037] Typically, the device includes a control attached to the proximal end of the elongated member, the control coupled to the biopsy needle so that when the control is operated, the biopsy needle retrieves a biopsy of tissue of the body. Prior to operating the control, the tissue may be in the camera field of view.

[0038] According to one embodiment of the present invention, there is also provided a device, the device comprising:

[0039] a catheter comprised of an elongated member having a member distal end and an axis of symmetry, the member distal end being configured to be inserted into an orifice of a body of a living subject;

[0040] a magnetic sensor located in the distal end of the member;

[0041] an electrode fixedly attached to and encapsulating a distal terminal end of the member distal end, the electrode being configured to deliver radio frequency (RF) energy to tissue of the body in contact with the electrode so as to ablate the tissue;

[0042] an optical fiber (FO), the FO being located on the axis of symmetry such that the FO distal end penetrates the electrode, the FO having a FO proximal end;

[0043] a laser coupled to the proximal end of the FO and configured to input light energy to the tissue via the optical fiber to ablate the tissue; and

[0044] A processor is coupled to actuate the laser and supply RF energy to the electrode.

[0045] In one disclosed embodiment, the processor is configured to activate the laser when the impedance of the tissue is above a predetermined value.

[0046] In another disclosed embodiment of the present invention, the processor is configured to supply RF energy when the impedance of the tissue is below a predetermined value.

[0047] According to one embodiment of the present invention, there is also provided a method, the method comprising:

[0048] providing a rod having a distal tip;

[0049] passing a light guide through the rod, the light guide having a distal end located at a distal end of the rod and a proximal end extending proximally from the rod;

[0050] securing a position sensor to the wand, the sensor configured to output a first signal indicative of a position of the distal tip in a reference frame of the sensor;

[0051] coupling a light source to output a light beam having an intensity temporally modulated at a predetermined carrier frequency into the proximal end of the light guide, whereby light is emitted from the distal end of the light guide toward a surface proximate the distal tip of the rod;

[0052] receiving with a detector from the proximal end of the light guide light that has been reflected from the surface into the distal end of the light guide and outputting a second signal indicative of the intensity of the reflected light; and

[0053] The distance from the distal end of the rod to the surface is calculated by extracting the phase difference between the output beam and the reflected light from the second signal, and the orientation of the surface in the sensor reference frame is calculated in response to the calculated distance and the position of the distal end indicated by the first signal.

[0054] According to one embodiment of the present invention, there is also provided a method, the method comprising:

[0055] providing a catheter comprising an elongated member having a member distal end and an axis of symmetry, the member distal end being configured to be inserted into an orifice of a body of a living subject;

[0056] positioning a first camera on an outer surface of a distal end of the member and positioning a second camera on an outer surface of the distal end of the member, the cameras being oriented so that their respective fields of view are away from the axis of symmetry and include overlapping portions;

[0057] acquiring corresponding optical images of tissue of the body in the overlapping portions from the cameras;

[0058] identifying common elements of tissues in corresponding optical images;

[0059] Analyzing computed tomography (CT) images of the body to identify common elements in the CT images; and

[0060] The corresponding optical images of the common elements are superimposed on the common elements of the CT image to produce an enhanced CT image including the common elements.

[0061] According to one embodiment of the present invention, there is also provided a method, the method comprising:

[0062] providing a catheter comprised of an elongated member having a member distal end and an axis of symmetry, the member distal end being configured to be inserted into an orifice of a body of a living subject;

[0063] securing a motor to a distal terminal end of the member distal end such that the motor shaft is aligned with the axis of symmetry;

[0064] attaching a rotatable base to the motor shaft;

[0065] securing a camera to an outer surface of the rotatable base such that a field of view of the camera is directed away from the axis of symmetry;

[0066] Rotate the camera on the motor shaft;

[0067] acquiring a pair of optical images of tissue of the body from the camera as the camera rotates;

[0068] identifying common elements of tissue in a pair of optical images;

[0069] Analyzing computed tomography (CT) images of the body to identify common elements in the CT images; and

[0070] The corresponding optical images of the common elements are superimposed on the common elements of the CT image to produce an enhanced CT image including the common elements.

[0071] According to one embodiment of the present invention, there is also provided a method, the method comprising:

[0072] providing a catheter comprised of an elongated member having a member distal end and an axis of symmetry, the member distal end being configured to be inserted into an orifice of a body of a living subject;

[0073] affix a camera to a distal terminal end of the distal end of the member such that the camera field of view is aligned with the axis and faces away from the distal end of the member;

[0074] attaching a biopsy needle to the distal end of the member so as to extend from the distal terminal end; and

[0075] The needle was oriented parallel to the axis of symmetry.

[0076] According to one embodiment of the present invention, there is also provided a method, the method comprising:

[0077] providing a catheter comprised of an elongated member having a member distal end and an axis of symmetry, the member distal end being configured to be inserted into an orifice of a body of a living subject;

[0078] positioning a magnetic sensor in the distal end of the member;

[0079] fixedly attaching an electrode to a distal terminal end of the member distal end so as to enclose the distal end, the electrode being configured to deliver radio frequency (RF) energy to tissue of the body in contact with the electrode so as to ablate the tissue;

[0080] Positioning an optical fiber (FO) on the axis of symmetry so that the distal end of the FO penetrates the electrode;

[0081] coupling a laser to the proximal end of the FO, the laser being configured to input optical energy into tissue via the optical fiber to ablate the tissue; and

[0082] Actuate the laser or supply RF energy to the electrodes.

[0083] The present disclosure will be more fully understood through the following detailed description of the embodiments of the present disclosure in conjunction with the accompanying drawings, in which: BRIEF DESCRIPTION OF THE DRAWINGS

[0084] Figure 1 is a schematic diagram of an ENT (ear, nose and throat) system for ENT surgery according to an embodiment of the present invention;

[0085] Figure 2A is a schematic diagram of an interferometric system for registering a tracking system with a computed tomography image according to an embodiment of the present invention, and Figure 2B is a flow chart of the steps used for registration;

[0086] Figure 3A is a schematic diagram showing a distal end portion of a guide catheter according to an embodiment of the present invention, and Figure 3B A flowchart of the steps to follow for using the catheter;

[0087] Figure 4A is a schematic cross-section of a distal end portion of a catheter according to an embodiment of the present invention, and Figure 4B is a schematic diagram of a catheter along the symmetry axis of the catheter;

[0088] Figure 5 is a schematic cross-section of a distal end of a biopsy catheter according to an embodiment of the present invention; and

[0089] Figure 6 is a schematic cross-section of the distal end of an ablation catheter according to an embodiment of the present invention. DETAILED DESCRIPTION

[0090] Overview

[0091] Embodiments of the present invention provide a plurality of different tools configured for ENT (ear, nose and throat) surgery. During surgery, the tools are inserted into the patient and tracked within the patient using magnetic sensors located in different tools, respectively. Each magnetic sensor provides the position and orientation of its corresponding tool, as measured in a reference frame (FOR) defined by a magnetic field radiation system.

[0092] In order to make the tracking correct, embodiments of the present invention register the magnetic field radiation system FOR with a previously acquired computed tomography (CT) image FOR of the patient. Compared to other registration systems, the registration system of the present invention does not rely on contact with the patient and therefore does not make errors (due to, for example, concavity of the patient's skin in a contact system).

[0093] The non-contact registration system projects a coherent beam of light from a "wand" to the patient and interferometrically measures the distance from the wand to the patient's skin area. The wand is also tracked in the magnetic system so that the measured distance provides the position for the skin area as measured in the magnetic system FOR. The processor correlates the magnetic system FOR skin area position with a segment of the image of the skin derived from the CT image and uses this correlation to register the two systems FOR.

[0094] Embodiments of the present invention also provide an ENT catheter tracked in a registered magnetic system. The catheter includes: a catheter configured to generate three-dimensional images during an ENT procedure, a catheter configured to retrieve a biopsy from a patient, and a catheter configured to ablate patient tissue using optical radiation or radiofrequency energy. DETAILED DESCRIPTION

[0096] Hereinafter, all directional references (e.g., upper, lower, upward, downward, left, right, top, bottom, above, below, vertical, and horizontal) are used only for identification purposes to help the reader understand the present invention and do not create limitations, especially with respect to the position, orientation, or use of the embodiments of the present invention.

[0097] Reference now Figure 1 , which is a schematic diagram of an ENT (ear, nose and throat) system 20 for ENT surgery according to an embodiment of the present invention. In the following description, by way of example, it is assumed that a physician 54 examines a patient 22 using a plurality of tools during surgery. Figure 1 A guide catheter 21 is shown being used as one of the tools, and a physician 54 may use a catheter handle 52 to insert the catheter 21 into a patient 22. The handle 52 is also assumed to be used with other tools described herein.

[0098] The operation and function of the guide catheter 21 is described in more detail below, and this disclosure also describes the operation and function of other tools used in the procedure.As also described below, a magnetic tracking system 23 is used to track the position and orientation of a number of tools.

[0099] The magnetic tracking system 23 includes a magnetic radiator assembly 24 positioned below the patient's head. Assembly 24 includes magnetic field radiators 26 that are fixed in an appropriate orientation and emit an alternating sinusoidal magnetic field into a region 30 where the patient's 22 head is located. By way of example, the radiators 26 of assembly 24 are arranged in a general horseshoe shape around the patient's 22 head. Other configurations of radiators 26 to implement this embodiment are also considered to be within the scope of the present invention. Produced by Biosense Webster (33 Technology Drive, Irvine, CA 92618 USA) The system uses a tracking system similar to that described herein to find the position and orientation of the coil in an area irradiated by a magnetic field.

[0100] In order for the tracking system 23 to track any particular tool, a magnetic orientation sensor 28A is incorporated into the tool. The sensor 28A is typically a three-axis sensor formed by three coils oriented orthogonally to each other. In the following description, tools other than the guide catheter 21 are described, and unless otherwise specified, these tools may have magnetic sensors that are generally similar to the sensor 28A. Such sensors are labeled 28B, 28C, ..., and are generally referred to as sensors 28 herein. The elements of the system 20 (including the radiator 26 of the tracking system 23) are controlled by the system processor 40 and one or more modules described further below and are stored in the memory 42.

[0101] Thus, for the tracking system 23, the processor and tracking module 60 are also configured to receive signals originating from the magnetic sensor 28 of a given tool, and analyze and process the signals to derive position and orientation values ​​of the sensor (and thus the tool) in the reference frame defined by the radiator assembly 24. The processor 40 may be mounted in a console 50 that includes operating controls 58 that typically include a keypad and / or a pointing device, such as a mouse or trackball. The console 50 is connected to the radiator 26 via a cable and / or wirelessly. The physician 54 uses the operating controls 58 to interact with the processor while performing the surgery described herein using the system 20. While performing the surgery, the processor may present the results of the surgery on a screen 56.

[0102] Processor 40 operates system 20 using software stored in memory 42. The software may be downloaded to processor 40 in electronic form, such as over a network, or alternatively or additionally, the software may be provided and / or stored on non-transitory tangible media such as magnetic, optical or electronic memory.

[0103] Tracking module 60 is stored in software module library 32 in memory 42. Library 32 also includes interferometry module 62 and radiofrequency ablation module 68. Tracking module 60 communicates with processor 40 to provide the functionality described above for component 24. The functionality of the other modules in library 32 is explained in detail below.

[0104] Furthermore, the memory 42 stores a computed tomography (CT) image 64 of the patient 22. It is assumed herein that the CT image 64 is generated by fluoroscopy.

[0105] As described above, in the procedures described herein, the tracking system 23 is used to track the ENT tools used in the procedure. In order to make the tracking accurate, the reference system of the system 23 (also referred to herein as the reference system of the component 24) is registered with the reference system of the CT image 64, and such registration is usually performed before the ENT tool is inserted into the patient 22. The method for registration is described below.

[0106] Registration of the magnetic tracking system 23 with the CT image 64

[0107] Figure 2A is a schematic diagram of an interferometric system 100 for registering a tracking system 23 with a CT image 64 according to an embodiment of the present invention, and Figure 2B Flowchart of the steps for registration. As described in more detail below, system 100 is used to track the process of fine registration of the system with the CT image after an initial process of coarse registration of the system with the image has been performed.

[0108] System 100 includes a coherent light interferometer 104 typically located in console 50, the elements of the interferometer being controlled by processor 40. For clarity and simplicity, focusing elements such as lenses and / or mirrors used in the operation of interferometer 104 are not shown.

[0109] Interferometer 104 includes a light source 108, which is assumed to be a laser by way of example herein, and is referred to as laser 108, which is selected to transmit a beam in the visible or near-visible region of the electromagnetic spectrum. In one embodiment, laser 108 emits at about 600nm. Laser 108 is modulated in time by modulator 112, and the frequency of the amplitude modulation is set so that in one embodiment, the distance between adjacent modulation peaks of the laser output by laser 108 in air is about 1cm. In order to achieve a spacing of 1cm, the modulation is at about 30GHz. Other embodiments of the present invention have a spacing between adjacent modulation peaks of up to about 4cm, so that modulator 112 can operate at a frequency between about 7.5GHz and about 30GHz. In the following description, the distance between adjacent modulation peaks is represented by the symbol λ, and it is assumed that λ is 2cm.

[0110] Other methods for modulating laser 108, such as using an external modulator placed in the laser beam emitted by laser 108 (instead of modulator 112), are also considered to be within the scope of the present invention.

[0111] The amplitude modulated light from the laser 108 is transmitted to the semi-reflective mirror 116 so that approximately 50% of the light is transmitted through the mirror and approximately 50% is reflected from the mirror. The reflected light is delivered to the mirror 120, which returns the light to the semi-reflective mirror 116. Approximately 50% of the returned light is transmitted through the semi-reflective mirror to the light detector 124 as the first detector beam 122.

[0112] The transmitted light from the semi-reflective mirror 116 is delivered to the entrance port (ie, the proximal end) of a fiber optic (FO) light guide 128. The FO light guide 128 exits the interferometer 104 and is wrapped in a flexible protective sheath 132 in the portion external to the interferometer.

[0113] At their distal ends, the sheath 132 and FO 128 are attached to the proximal end of the non-flexible rod 136, and during operation of the interferometric system 100, the physician 54 grasps the rod 136 by the rod handle 140. The rod 136 includes a rod housing 144 in which is a FO light guide 148 optically coupled at its proximal end to the distal end of the FO light guide 128 so that the two light guides act as one light guide. The FO 148 terminates at the distal end or tip of the rod 136 at the distal end port 152 of the optical fiber.

[0114] Also incorporated into the distal end of wand 136 is a magnetic sensor 28B, which is generally configured as described above for sensor 28 A. The functionality of sensor 28B within tracking system 23 is described in more detail below.

[0115] When the system 100 is in operation, the amplitude modulated light from the semi-reflective mirror 116 is transmitted via the FO 128 and the FO 148, and is emitted from the distal end port 152. The direction of the emitted light corresponds to the direction of the FO 148, and therefore corresponds to the orientation of the rod 136. Therefore, the direction of the light emitted from the port 152 can be found from the signal acquired by the sensor 28B.

[0116] The outgoing light strikes a surface 156 of the patient 22 and a portion is reflected back toward the port 152 and from there to the semi-reflective mirror 116. The mirror 116 reflects approximately 50% of the light received from the port 152 to the detector 124 as a second detector beam 158.

[0117] Detector beams 122 and 158 interfere at detector 124, and the interference may be constructive, destructive, or an intermediate type of interference between constructive and destructive. The actual interference depends on the different path lengths followed by the two beams from their starting point at mirror 116 to their end point at detector 124, because the different path lengths introduce a phase difference φ between the beams.

[0118] The path length followed by the beam 158 from its origin on the mirror 116 includes forward and reverse traversals between the distal end port 152 and the surface 156, and the distance between these two points is referred to herein as "d".

[0119] It should be understood that the phase difference φ and the distance d are related, so that as long as d ≤ 0.5λ, we can write formula (1):

[0120] d=f(φ) (1)

[0121] where f is a monotonic function that depends on φ and d.

[0122] The signal S generated at the detector and provided to the processor 40 is the maximum value S for constructive interference when φ=0. 最大 , is the minimum value S for destructive interference when φ = π 最小 , and is a value between the minimum and maximum values, referred to in this article as S b , used for intermediate interference types when 0<φ<π.

[0123] If S 最大 , S 最小 , and S b If all are known, then formula (2) can be used to calculate the value suitable for generating S b The value of φ:

[0124] φ=g(S 最大 , S 最小 , S b ) (2)

[0125] where g is a function.

[0126] Substituting formula (2) into formula (1) yields:

[0127] d=h(S 最大 , S 最小 , S b ) (3)

[0128] where h is the function f×g.

[0129] The numerical relationship between the variables of formula (3) corresponding to the function h can be determined by calibration. In calibration, rod 136 is positioned so that distal end port 152 is located at a measured distance from the reflective surface. Processor 40 records the distance value and the detector signal, including S 最大 , S 最小 and S b .

[0130] Figure 2B The flow chart of describes how the system 100 is used to estimate the distance d.

[0131] Figure 2B Flow chart of the steps for registering the reference frame of the magnetic tracking system 23 with the reference frame of the CT image 64. As described above, the registration consists of an initial coarse registration process and a subsequent fine registration process. The fine registration uses the interferometry system 100.

[0132] In an initial step 180 of the coarse registration process, processor 40 accesses CT image 94 and calculates and stores three-dimensional (3D) coordinates of the skin of patient 22 .

[0133] In positioning step 182, the head of patient 22 is positioned over magnetic radiator assembly 24 and tracking system 23 is activated. Activation enables processor 40 to track the position and orientation of sensor 28B. At this stage of the procedure, activation of system 23 does not require activation of interferometry system 100.

[0134] In a rough registration step 184, the physician touches the distal end of the stick 136 on predetermined landmarks of the patient's head. The landmarks are typically easily identifiable areas, such as the tip of the nose, the area between the eyes, the center of the patient's forehead, and the areas on either side of the eyes. As each landmark is touched, the physician uses controls 58 to cause the processor to record a signal from sensor 28B and analyze the recorded signal to provide the location of the touched landmark (in the reference frame of tracking system 23). The processor then stores the location of the corresponding landmark in memory 42.

[0135] Step 184 is repeated for a preset number of different landmarks, such as four landmarks.

[0136] Once a preset number of landmarks have been contacted and their respective positions recorded and stored, the processor 40 correlates the patient's 3D skin coordinates found in step 180 with the stored landmark positions. Correlation is finding the best fit between the two sets of data, and an algorithm such as an iterative closest point (ICP) algorithm is typically used to find the best fit. The correlation found provides a rough registration between the CT image 64 and the magnetic tracking system 23, so that step 184 ends the rough registration process.

[0137] The coarse registration provided by steps 108-184 is somewhat inaccurate because the requirement to contact the patient typically results in a depression of the skin at the contacted location. Inaccuracies also exist due to the relatively small number of landmarks used for correlation. The following fine registration process corrects for both of these inaccuracies.

[0138] In an initial step 200 of the fine registration process, the interferometric system 100 is activated. Activation includes calibrating the system so as to determine the function h(S) of equation (3) 最大 , S 最小 , S b ). It will be appreciated that calibration may be performed by positioning a target at a known distance d (d≤0.5λ) from port 152 while recording the signal S acquired by detector 124 using processor 40. b .

[0139] In operation step 204, physician 54 grasps wand 136 by the wand handle and positions the wand so that light exiting distal end port 152 strikes a segment of skin on the head of patient 22. In the following description, the segment of skin is assumed to be surface 156 unless otherwise specified.

[0140] The physician positions the wand so that the distal end port 152 does not contact the patient's skin. More specifically, the physician moves the wand so that the distal end port is within 0.5λ of the skin.

[0141] Before moving the port to within 0.5λ of the skin, the physician moves the rod back and forth relative to the patient's skin so that the processor 40 captures the signal S acquired by the detector 124. 最大 and S 最小 The following description explains how the system 100 checks whether these moves have been performed correctly.

[0142] In the signal acquisition step 208, the processor 40 records the signal from the detector 124 and checks whether the signal has passed through the maximum and minimum values. When the signal has passed through these values, the processor stores it as S 最大 and S 最小, and a notification may then be provided to the physician on screen 56 to move the distal end port closer to the patient's skin.

[0143] Also in the signal acquisition step 208, once S 最大 and S 最小 The value of x has been stored, the processor 40 and the tracking module 60 obtain the signal generated in the sensor 28B and analyze the signal to find the position of the distal end port 152 (x d ,y d ,z d ). The processor and module also use the signal to calculate the orientation of the port. It should be understood that the values ​​of the position and orientation of the port are used in the reference system of the component 24.

[0144] The processor uses the rough registration found in step 184 to check the position (x d ,y d ,z d ) is less than or equal to 0.5λ from the skin of the patient 22. d ,y d ,z d ) is greater than 0.5λ from the patient's skin, the physician is requested to move port 152 closer to the patient, typically by providing a notification on screen 56.

[0145] When the position (x d ,y d ,z d ) is less than or equal to 0.5λ from the patient's skin, the processor together with the interferometric measurement module 62 acquires the signal S generated in the detector 124 b The processor uses the acquired signal S b and the stored signal S 最大 and S 最小 The value of the distance d is determined in formula (3).

[0146] In process step 212, processor 40 uses the value of d, the position of port 152 (x d ,y d ,z d ) and the orientation of the port to calculate the three-dimensional coordinates (x p ,y p ,z p The processor calculates (x p ,y p ,z p ) is stored in the memory 42. d ,y d ,z d ), position(x p ,yp ,z p ) is in the reference frame of component 24.

[0147] As indicated by arrow 216, steps 204-212 are iterated a preset number of times, e.g., 10 times, and at each iteration, the physician 54 grasps the wand so that light exiting the distal end port 152 strikes a different segment of the skin of the head of the patient 22. At each iteration, the physician grasps the wand so that the port 152 does not contact the patient's skin, while ensuring (as described above) that the distance from the distal end port to the patient's skin is less than or equal to 0.5λ.

[0148] In conditional step 220 , processor 40 checks whether a preset number of iterations has been exceeded. If not, iterations continue. If step 200 returns positive, control continues to registration step 224 .

[0149] In the final fine registration step 224, the processor 40 converts (x p ,y p ,z p ) are compared with the three-dimensional values ​​of the skin of the patient 22 obtained from the CT image 64 (as described in more detail below) to find the best fit between the two sets of values. The processor 40 typically uses the same algorithm as used for the coarse registration to perform the comparison, such as an iterative closest point (ICP) algorithm, but any other convenient algorithm that provides the best fit may be used. The fit determined in step 224 provides a translation and / or rotation vector that registers the reference frame of the magnetic tracking system with the reference frame of the CT image.

[0150] Other methods for registering the two reference frames using processor 40 include Figure 2B ) to implement the present embodiment are also considered to be within the scope of the present invention. For example, processor 40 may perform registration step 224 after each pass through steps 204-212, and iterate steps 204-212 until the fit calculated in step 224 is equal to or better than a predetermined threshold, rather than performing a preset number of iterations of steps 204-212.

[0151] Typically, once processor 40 has registered the two reference frames, an indication of successful registration may be provided to physician 54 , such as by displaying a notification on screen 56 .

[0152] The reference frame registration system described above relates the three-dimensional coordinates of the patient's skin measured in two modes, one measurement mode is a magnetic tracking system and the other measurement mode is a fluoroscopic CT imaging system. However, compared to other methods that align the two modes by finding the coordinates of the patient's skin, the interferometric measurement system 100 measures the coordinates in a non-contact manner, thereby avoiding the errors that occur in methods that use contact with the patient's skin. In addition, compared to other methods that can be used to measure the coordinates of the patient's skin, the resolution of the interferometric measurement system 100 can be adjusted by adjusting the modulation frequency of the modulator 112. Therefore, the resolution of the system 100 can be adjusted according to the resolution of the CT image 64 to provide the most appropriate best fit in step 224.

[0153] The registration described above may be used in the tracking tool described below for use in the ENT procedures mentioned herein.

[0154] Guide catheter 21

[0155] Figure 3A is a schematic diagram showing a distal end portion 250 of a guide catheter 21 according to an embodiment of the present invention, and Figure 3B Flow chart of the steps followed to use the catheter. Physician 54 uses catheter 21 to provide images of internal elements of patient 22. As explained below, the images formed by the catheter can be used to present physician 54 with enhanced images of internal elements of the patient.

[0156] Although the following description of the distal end 250 assumes that the distal end is flexible, if the distal end is non-flexible, modifications to the description will be apparent mutatis mutandis such that the scope of the present invention includes both flexible and non-flexible distal ends of the catheter 21.

[0157] The distal end 250 is formed of a biocompatible plastic, such as polyamide, and in one embodiment, includes a cylindrical tube 254 having a diameter of approximately 2 mm. The tube 254 is generally straight, having an axis of symmetry 258. However, the tube can be bent from the axis by the physician 54 pulling on the proximal end of the wire 262, which is attached to the distal portion of the tube 254 at its distal end. The physician 54 typically pulls the wire 262 ( Figure 1 ), and if the physician stops pulling, the controls can also be used to return the tube 254 to its straight configuration.

[0158] Two substantially similar cameras 266, 270 are fixedly attached to the outer surface 256 of the tube 254, which are generally separated by a preset distance. In one embodiment, the preset distance is 10 mm, but other embodiments generally have a preset distance in the range of about 3 mm to about 30 mm. The two cameras are located on the surface of the tube 254 so that the line segment connecting the cameras is parallel to the axis of symmetry 258, and the cameras are oriented so that their fields of view are away from the axis of symmetry. In addition, as shown in the figure, there is a portion of the field of view that overlaps, and the overlap depends on the size of the field of view and the distance from the camera. In one embodiment, the field of view of each camera in the camera is 90 °, and the overlap begins at a distance of 5 mm from the camera.

[0159] Magnetic sensors 28A, 28C are fixedly attached to tube 254 and are respectively located proximate cameras 266, 270. Processor 40 uses the signals from the magnetic sensors to provide position and orientation values ​​for each of the cameras, typically after a calibration process.

[0160] As described above, the physician 54 uses the catheter 21 during an ENT procedure so that the distal end 250 can be exposed to air and the cameras 266, 270 can acquire images of internal elements of the patient 22, such as the patient's sinuses. Although the camera may be obstructed by mucus or blood during the procedure, embodiments of the present invention generally include methods for cleaning the camera, such as providing irrigation to the camera lens. For simplicity, in Figure 3A Not shown are irrigation channels that may be present in distal end 250 .

[0161] Figure 3B Flow chart of the steps followed to use the catheter 21. In an initial step 300, after registration as described above, the physician 54 inserts the catheter into the nostril of the patient 22, and the processor 40 and tracking module 60 use the signals from the sensors 28A, 28C to track the distal end 250. The tracking is typically presented as an overlay on the CT image 64 presented on the screen 56.

[0162] In an image acquisition step 304, at an orientation selected by the physician (which may be at initial insertion or posterior), the cameras 266, 270 are activated and the processor stores the optical images acquired by the cameras in the memory 42. The acquired optical images are images of elements of the patient 22 that appear at the patient's air / solid interface, i.e., at the patient's external skin and / or at the surface of internal patient surfaces such as the patient's sinuses. Such elements may also be identified in the CT image 64 by the processor 40 due to changes in Hounsfield Unit (HU) values ​​at the interface.

[0163] In image recognition step 308, processor 40 identifies the boundary from air to the surface of patient 22 in image 64, taking advantage of the fact that the HU value of air is -1000, since surfaces such as the patient's skin have HU values ​​significantly different from -1000. (The methods described herein for identification may also be used in registration step 224 described above).

[0164] In the initial 3D image processing step 312, since the position and orientation of the cameras 266, 270 relative to the element being imaged are known from their respective sensor signals, the processor 40 applies the image acquired in step 304 to the boundary identified in step 308 by means of the reference frame registration that has been performed. The application typically uses projective texture mapping to overlap the image acquired in step 304 on the boundary, thereby producing two 3D images (because of the two different fields of view). The processor typically displays the two 3D images on the screen 56 as a combined 3D image.

[0165] In an enhanced 3D image processing step 316, processor 40 determines common elements in the two optical images formed by cameras 266, 270, corresponding to the area where the two fields of view overlap. The determination may be made by image analysis, but any other convenient method for common element determination may also be used. Once the common elements have been determined, processor 40 may apply the common elements to enhance the combined 3D image formed in step 312. The enhancement improves the three-dimensional representation on screen 56, for example by allowing the physician to rotate the combined image so that different aspects of the common elements that are not visible in only one image become visible.

[0166] As described above, the catheter 21 uses two images formed by separate cameras in the distal end 250 of the catheter to produce an enhanced 3D image. Alternatively or in addition, the physician 54 may use the following reference Figure 4A and Figure 4B Rotating catheter 400 is described to produce enhanced 3D images.

[0167] Rotating Catheter 400

[0168] Figure 4A is a schematic cross-section of a distal end portion 404 of a catheter 400 according to an embodiment of the present invention, and Figure 4B Schematic diagram of the catheter along the catheter's axis of symmetry. Except for the differences described below, the operation of the distal end 404 is similar to that of the distal end 250 ( Figure 3A and Figure 3B) are substantially similar in operation, and elements indicated by the same reference numerals in both distal ends are substantially similar in construction and operation. Thus, similar to distal end 250, distal end 404 is configured to acquire multiple optical images of elements of identifiable segments of patient 22, and these multiple images are substantially as described above in Figure 3B is processed as described in the flowchart of FIG.

[0169] However, in contrast to the distal end 250, the distal end 404 includes only one camera 408, substantially similar to the cameras 266, 270. Furthermore, the camera 408 is not fixedly attached to the surface 256 of the distal end 404. Instead, a motor 412 is fixed to the distal terminal end of the tube 254, and a rotatable cylindrical base 416 is attached to the motor via a shaft 420 lying along the axis 258. The diameter of the base 416 is substantially the same as the diameter of the tube 254.

[0170] Camera 408 is fixedly attached to outer surface 424 of base 416 and is oriented so that its field of view is away from axis 258. Magnetic sensor 28D is fixedly attached to base 416 near camera 408. For catheter 21, processor 40 typically uses signals from sensor 28D to provide position and orientation values ​​for camera 408 after a calibration process.

[0171] As physician 54 inserts catheter 400 into patient 22, camera 408 is able to acquire optical images of the interior surface of patient 22. To acquire the type of images that provide an enhanced 3D image, similar to the images acquired by distal end 254, physician 54 activates motor 412 to rotate base 416.

[0172] The camera 408 acquires images while the base 416 rotates, and Figure 4B The camera acquiring two such images is schematically shown.During rotation of the base, the processor 40 uses the signals from the sensor 28D to determine the position and orientation of the camera 408 at each image acquisition point.

[0173] In one embodiment, the motor 412 rotates the base 416 so that 180 images are acquired in one rotation of the camera 408. In this case, the orientation of the camera between adjacent images differs by 2°. In an alternative embodiment, before the motor 412 rotates the base 416, the physician 54 observes the images generated by the camera 408 and selects the direction of the image to be generated. Upon selection, the motor 412 swings the base 416 around the selected direction through an angle selected by the physician 54 (e.g., ±30°), and the camera 408 acquires images at the endpoints of the swing.

[0174] Processor 40 uses substantially the same Figure 3BThe adjacent image pairs acquired by rotating base 416 are described in the steps of the flowchart to generate a 3D image and an enhanced 3D image of patient 22 displayed to the physician on screen 56.

[0175] Typically, once physician 54 has viewed the images generated by catheter 21 and / or catheter 400, the physician may continue the procedure using biopsy catheter 500 and ablation catheter 600. Biopsy catheter 500 and ablation catheter 600 are described as follows.

[0176] Biopsy Catheter 500

[0177] Figure 5 5 is a schematic cross-section of a distal end 504 of a biopsy catheter 500 according to an embodiment of the present invention. The structure of the distal end 504 is similar to the distal end 250 ( Figure 3A ) are generally similar in structure, and elements indicated by the same reference numerals in the two distal ends are generally similar in construction and operation.

[0178] The distal end 504 is used to obtain a biopsy of a portion of the patient 22 selected by the physician 54. Thus, in contrast to the distal end 250, the distal end 504 includes a camera 508 fixedly attached to the terminal end of the distal end so that its field of view is aligned with the axis 258 and facing away from the distal end. The camera is used to view and enable the physician to select a segment of the patient 22 from which the biopsy is to be retrieved. The magnetic sensor 28E is fixedly connected to the distal end and is proximate to the camera 508. The sensor provides the physician with position and orientation information of the camera and also enables the processor 40 to display the position and orientation information of the distal end on the screen 56 as an overlay on the CT image 64.

[0179] The distal end also includes a biopsy needle 512 that is attached so as to extend from a terminal end of the distal end and is oriented parallel to the axis 258. Operation of the needle 512 is typically performed via a control in the handle 52 that is attached to a needle guide, but for simplicity, such a guide is not shown in the figure. Once the needle 512 has been used to perform a biopsy, the catheter 500 can be removed from the patient 22 to retrieve the biopsy.

[0180] For example, the distal end 504 includes two wires 516, 520 that are generally similar in function and structure to the wire 262 and are attached at their distal ends to the distal portion of the tube 254. In other embodiments, more than two wires are attached to the distal portion of the tube 254. Using controls for the wires in the handle 52, the physician is able to deflect the tube in multiple directions from the axis 258, thus facilitating more precise positioning of the needle 512 prior to performing a biopsy.

[0181] The distal end 504 also includes an irrigation channel 524 configured to deliver an irrigation fluid, typically a saline solution. The fluid, typically operated by a control in the handle 52, can be deflected by a deflector 528 attached to the terminal end of the tube 254 so that the deflected fluid passes through and cleans the lens of the camera 508.

[0182] Ablation Catheter 600

[0183] Figure 6 604 is a schematic cross-section of a distal end portion 604 of an ablation catheter 600 according to an embodiment of the present invention. The structure of the distal end portion 604 is similar to the distal end portion 250 ( Figure 3A ) are generally similar in structure, and elements indicated by the same reference numerals in the two distal ends are generally similar in construction and operation.

[0184] The distal tip 604 is used to ablate a portion of the patient 22 selected by the physician 54 using optical radiation or radio frequency (RF) energy, and in contrast to the distal tip 250, the distal tip 604 typically does not include a camera. To navigate the distal tip 604, the distal tip includes a magnetic sensor 28F fixedly attached to the tube 254. The processor 40 uses the signals from the sensor to calculate the position and orientation of the distal tip, and these can be used to track an image of the distal tip displayed on the screen 56 (typically an overlay on the CT image 64).

[0185] The distal end 604 includes an optical fiber (FO) 612, which is generally aligned along the axis 258 and is coupled to a laser 608 at the proximal end of the FO. In one embodiment, the laser 608 includes a Nd:YAG laser. The laser 608 is generally mounted in the console 50, and controls for operating the laser may be located in the handle 52 and / or the console.

[0186] When operating, the laser 608 directs optical power into the FO 612 such that the power emitted from the distal end 616 of the optical fiber is sufficient to ablate the segment of the patient 22 to which the power is irradiated.

[0187] The distal end 604 also includes an electrode 620, which is assumed herein to be a cup-shaped electrode fixedly attached to the terminal end of the distal end. The electrode 620 is configured to be ablated by the processor 40 and the ablation module 68 ( Figure 1 ) generates RF energy which is delivered to tissue of the patient 22 in contact with the electrodes.

[0188] It should be understood that the physician 54 can use the catheter 600 for RF ablation of tissue or for optical radiation ablation of tissue. The selected mode may depend on the impedance of the tissue; for example, if the tissue is bone with high impedance, RF ablation may be ineffective, and in this case, the physician may choose to ablate using the laser 608. Conversely, if the tissue is fat with relatively low impedance, it may be more effective to use RF ablation.

[0189] The distal end 604 typically includes one or more other electrodes 624 that can be used for signal acquisition and / or for pacing. Typically, when not used for ablation, the electrodes 620 can also be used for signal acquisition and / or for pacing.

[0190] It should be understood that the above embodiments are cited by way of example, and the present invention is not limited to what is specifically shown and described above. On the contrary, the scope of the present invention includes combinations and sub-combinations of the various features described above, as well as variations and modifications thereof, which should occur to those skilled in the art when reading the above description, and which are not disclosed in the prior art.

Claims

1. A registration device, comprising: a rod having a distal tip; a light guide passing through the rod and having a distal end located at the distal end of the rod and a proximal end extending proximally from the rod; a position sensor secured to the wand and configured to output a first signal indicative of a position of the distal tip in a sensor reference frame; a light source coupled to output a light beam having an intensity temporally modulated at a predetermined carrier frequency to a semi-reflective mirror such that a first portion is reflected to the mirror and a second portion is transmitted into the proximal end of the light guide, whereby the second portion of the light beam is emitted from the distal end of the light guide toward a surface proximate the distal tip of the rod; a detector configured to: receive a first detector beam comprising the first portion of the light beam that has been reflected from the mirror; and receive from the proximal end of the light guide a second detector beam comprising the second portion of the light beam that has been reflected from the surface into the distal end of the light guide, and wherein the first detector beam and the second detector beam interfere at the detector and wherein the detector is further configured to output a second signal indicative of the intensity of the interfered beams; as well as A processor configured to: determining and storing maximum and minimum values ​​of the second signal in response to moving the distal tip relative to the surface; acquiring a given signal from the detector when the surface is located at a distance from the distal end; calculating the distance from the distal end of the rod to the surface in response to the stored maximum and minimum values ​​and the given signal, and The orientation of the surface in the sensor reference system is calculated in response to the calculated distance and the position of the distal tip indicated by the first signal.

2. The apparatus of claim 1, and comprising a modulator coupled to the light source, the modulator being configured to amplitude modulate the light beam.

3. The device according to claim 2, wherein: The amplitude modulation frequency of the light beam is set so that the interval between adjacent modulation peaks of the modulated light beam is between 1 cm and 4 cm.

4. The device according to claim 1, wherein: The first signal is indicative of an orientation of the distal tip in the sensor reference frame.

5. The device according to claim 1, wherein: The light source includes a laser that generates the light beam.

6. The device according to claim 1, wherein: The processor is configured to determine the distance when the rod distal tip is not in contact with the surface.

7. The device according to claim 1, wherein: The processor is configured to determine an initial value of the position of the surface using the sensor while the wand distal end is in contact with the surface, and to update the initial value to a final value of the position using the distance without the wand distal end contacting the surface.

8. A method comprising: providing a rod having a distal tip; passing a light guide through the rod, the light guide having a distal end located at the distal end of the rod and a proximal end extending proximally from the rod; securing a position sensor to the wand, the sensor configured to output a first signal indicative of a position of the distal tip in a sensor reference frame; coupling a light source to output a light beam having an intensity temporally modulated at a predetermined carrier frequency to a semi-reflective mirror such that a first portion is reflected to the mirror and a second portion is transmitted into the proximal end of the light guide, whereby the second portion of the light beam is emitted from the distal end of the light guide toward a surface proximate the distal tip of the rod; receiving with a detector a first detector beam comprising the first portion of the beam that has been reflected from the mirror; as well as receiving from the proximal end of the light guide a second detector beam comprising the second portion of the light beam that has been reflected from the surface into the distal end of the light guide, wherein the first detector beam and the second detector beam interfere at a detector; outputting a second signal indicative of the intensity of the interfered light beam; as well as determining and storing maximum and minimum values ​​of the second signal in response to moving the distal tip relative to the surface; acquiring a given signal from the detector when the surface is located at a distance from the distal tip; calculating a distance from the distal end of the rod to the surface in response to the stored maximum and minimum values ​​and the given signal, and The orientation of the surface in the sensor reference system is calculated in response to the calculated distance and the position of the distal tip indicated by the first signal.

9. A method according to claim 8, and coupling a modulator configured to amplitude modulate the light beam to the light source.

10. The method according to claim 9, wherein: The amplitude modulation frequency of the light beam is set so that the interval between adjacent modulation peaks of the modulated light beam is between 1 cm and 4 cm.

11. The method according to claim 8, wherein: The first signal is indicative of an orientation of the distal tip in the sensor reference frame.

12. The method of claim 8, and comprising determining the distance when the rod distal tip is not in contact with the surface.

13. The method of claim 8, and comprising determining an initial value of the orientation of the surface using the sensor while the distal end of the stick is in contact with the surface, and updating the initial value to a final value of the orientation using the distance without the distal end of the stick in contact with the surface.

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