SYSTEMS AND METHODS FOR WIRELESS LOCALIZATION INTEGRATION
20220361957 · 2022-11-17
Inventors
- Jason Hiltner (Eden Prairie, MN, US)
- Adam Fisher (Eden Prairie, MN, US)
- Bryan Dean (Eden Prairie, MN, US)
Cpc classification
A61B2090/365
HUMAN NECESSITIES
A61B2017/00221
HUMAN NECESSITIES
A61B34/20
HUMAN NECESSITIES
A61B2034/2072
HUMAN NECESSITIES
A61B2090/366
HUMAN NECESSITIES
A61B90/30
HUMAN NECESSITIES
International classification
A61B34/20
HUMAN NECESSITIES
Abstract
A wireless localization system including a pad with an exciter coil and a sensor coil, a tool or surgical robot including a wireless tag configured to generate a signal in response to a magnetic field generated by the exciter coil. The signal is detected by the sensor coil and a processor configured to determine the location of the tool.
Claims
1. A wireless localization system comprising: a pad including an exciter coil and a sensor coil; a tool including a wireless tag configured to generate a signal in response to a magnetic field generated by the exciter coil; wherein the signal is detected by the sensor coil; and a processor configured to determine the location of the tool based on the signal detected by the sensor coil.
2. The system of claim 1, wherein the tool is one of a camera, an ultrasound probe, an electric impedance probe, a light probe, a microforce probe, an electrocautery tool, a needle, a swallowable capsule, a keypad, a stapler, a clamp, and a sponge.
3. The system of claim 1, wherein the wireless tag is a first wireless tag and the signal is a first signal, and wherein the system further includes a second wireless tag coupled to a tissue of a patient and configured to generate a second signal in response to the magnetic field generated by the exciter coil.
4. The system of claim 3, wherein the processor is configured to determine the location of the tool relative to the second wireless tag.
5. The system of claim 3, wherein the tissue that the second wireless tag is coupled to is one of a lung tissue, a bone tissue, a soft tissue, and an artery.
6. The system of claim 1, wherein the processor is further configured to determine the orientation of the tool.
7. A wireless localization system comprising: a surgical robot assembly including a robotic arm, a camera, and a tool coupled to the robotic arm; a pad including an exciter coil and a sensor coil; a first wireless tag coupled to a portion of the surgical robot assembly, the first wireless tag configured to generate a first signal in response to a magnetic field generated by the exciter coil, wherein the first signal is detected by the sensor coil; a second wireless tag coupled to a tissue of a patient, the second wireless tag configured to generate a second signal in response to the magnetic field generated by the exciter coil, wherein the second signal is detected by the sensor coil a processor configured to determine the location of the first wireless tag and the second wireless tag based on the first signal and the second signal detected by the sensor coil.
8. The system of claim 7, wherein the first wireless tag is coupled to the camera.
9. The system of claim 7, wherein the first wireless tag is coupled to the robotic arm.
10. The system of claim 7, wherein the sensor coil is a first sensor coil and the system further includes a second sensor coil coupled to the robotic arm.
11. The system of claim 7, further including a movable object including a third wireless tag, wherein the movable object is moved to various positions and detected by the camera to register the field of view of the camera.
12. The system of claim 11, wherein the movable object includes an outer shell, an inner sphere movable with respect to the outer shell, wherein the third wireless tag is positioned within the inner sphere.
13. The system of claim 12, wherein the inner sphere includes a weighted portion to orient the sphere in a default orientation with respect to gravity.
14. The system of claim 7, wherein the surgical robot assembly includes a control console, and wherein the location of the first wireless tag and the location of the second wireless tag are displayed on the control console.
15-30. (canceled)
Description
BRIEF DESCRIPTION OF THE DRAWINGS
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[0070] Before any embodiments are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.
DETAILED DESCRIPTION
[0071] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, the present document, including definitions, will control. Preferred methods and materials are described below, although methods and materials similar or equivalent to those described herein can be used in practice or testing of the present disclosure. All publications, patent applications, patents and other references mentioned herein are incorporated by reference in their entirety. The materials, methods, and examples disclosed herein are illustrative only and not intended to be limiting.
[0072] The terms “comprise(s),” “include(s),” “having,” “has,” “can,” “contain(s),” and variants thereof, as used herein, are intended to be open-ended transitional phrases, terms, or words that do not preclude the possibility of additional acts or structures. The singular forms “a,” “an” and “the” include plural references unless the context clearly dictates otherwise. The present disclosure also contemplates other embodiments “comprising,” “consisting of” and “consisting essentially of,” the embodiments or elements presented herein, whether explicitly set forth or not.
[0073] For the recitation of numeric ranges herein, each intervening number there between with the same degree of precision is explicitly contemplated. For example, for the range of 6-9, the numbers 7 and 8 are contemplated in addition to 6 and 9, and for the range 6.0-7.0, the number 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, and 7.0 are explicitly contemplated.
[0074] In the foregoing description of preferred embodiments, specific terminology has been resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar technical purpose. Terms such as “top” and “bottom”, “front” and “rear”, “inner” and “outer”, “above”, “below”, “upper”, “lower”, “vertical”, “horizontal”, “upright” and the like are used as words of convenience to provide reference points.
[0075] Provided herein are systems, devices, assemblies, and methods for integrating a remotely located tag into medical procedures. While the specification focuses on medical uses in human tissues, it should be understood that the systems and methods find broader use, including non-human uses (e.g., use with non-human animals such as livestock companion animals, wild animals, or any veterinary settings). For example, the systems may be used in environmental settings, agricultural settings, industrial settings, or the like.
A. Wireless Tool Tracking Applications
[0076] In addition to being located within human tissue, the tags can be integrated into tools to wireless track the location and orientation of tools utilized in various medical procedures. With reference to
[0077] With continued reference to
[0078] A processor 120 (shown in
[0079] In the illustrated embodiment, the tool 112 includes two wireless tags 116 positioned along a longitudinal axis 113 of the tool 112 to determine the orientation of the tool 112 in addition to the position of the tool 112. In some embodiments, the tags 116 are positioned within an outer housing of the tool 112. In other embodiments, the tags 116 are positioned on an outer surface of the tool 112.
[0080] With continued reference to
[0081] In some embodiments, the tool 112 is a camera. For example, some medical procedures utilize a camera to visualize the treatment area, but wireless tags implanted in a patient are not typically visible in the camera view. A solution presented herein is a camera with an integrated wireless tag to track the location of the camera and a processor to determine a coordinate transformation from the implant tracker coordinates to the camera field of view coordinates. As such, the location of the implanted tag (e.g., tag 108) can be superimposed on the camera view that is presented to the user (e.g., the display 105)—thereby improving a user's identification of the tag from the camera's field of view.
[0082] To determine the coordinate transformation, an object of known geometry is simultaneously imaged with the camera and localized with the wireless localization system. To track the camera, a wireless tag (e.g., tag 116) is fixed to the camera and also tracked with the wireless localization system. To track roll of the camera, or if the wireless tag cannot be co-axial with the camera, two wireless tags are utilized. Registration of the camera can occur in two ways: either the camera remains stationary and a moving object is tracked (see
[0083] In some embodiments, the tool 112 is an ultrasound probe. Although ultrasound can be used to interrogate tissue and determine the position of target tissue, the imaging is two-dimensional and a separate probe must be used. A solution presented herein is to track the position and orientation of the ultrasound probe, simultaneously with the position of an implanted tag (e.g., tag 108). Ultrasound images at many positions and orientations may be acquired. Then, swap the ultrasound probe with a tool used to perform surgical excision, which is also tracked. Next, the ultrasound images are replayed according to the position of the electrosurgical tool, corrected by any relative shifts in implant position. Furthermore, ultrasound images can be segmented by tissue type, and a 3D model built up, registered to the implant position. After enough images are built up, the 3D model can be maintained relative to the implant position and used in live navigation.
[0084] In some embodiments, the tool 112 is an electrical impedance probe. It may be helpful to measure the 3D contours of the patient body including any external surfaces and internal organs (i.e., measure the geometry of excised tissue). A solution presented herein utilizes an electrical impedance probe to detect when the electrical impedance probe is in contact with the patient tissues. If the location of the probe tip is tracked the geometry of any part of the patient can be acquired by moving the probe tip around the skin.
[0085] In some embodiments, a tracked probe provides an ultrasound of patient tissue that is used to determine the location of a target with respect to tags positioned on the skin surface (e.g., embedded within an adhesive material adhered to a patient's skin). Once the ultrasound is segmented, direct feedback to the user can be provided on the needle placement, insertion orientation, and depth of insertion. In some embodiments, a motorized needle guide is tracked and adjusted to ensure proper needle insertion.
[0086] In some embodiments, the tool 112 is a light probe. Spectroscopy can be performed, for example, by illuminating tissue with broadband light and collecting reflected light but keeping track of the position of data collection must be performed manually. A solution presented herein collects the position and spectra data simultaneously, such that the location of anomalies or features of interest can be automatically collected and presented to the user.
[0087] Lung surgeons need the location of the tumor to be clearly visible during video-assisted thoracis surgery (VATS) and robot assisted thoracis surgery (RATS) procedures. Surgeon attempt position 2D or 3D cameras to define a point of view, and conventional video processing can overlay graphics and text on the video feed provided by the user. But video processing requires interconnections between systems, typically by cables, software, and site-specific configurations. A solution presented herein is projected light that overlays graphics and text on the tissue within the camera field of view. Alternatively, a tracked probe in the camera view can be equipped with one or more controlled light source(s).
[0088] A projected light implementation compatible with VATS and RATS procedures, in some embodiments, includes a robotically controlled laser pointer mounted near the camera, where two motor controlled axial degrees of freedom allow the system to always point the laser at the wireless tag, thereby illuminating the location on the tissue surface directly between the camera and the wireless tag. In some embodiments, the distance from the tissue surface to the wireless tag is determined by touching a wireless tracked probe to the tissue at the point of illumination, or by using the camera video feed to determine the location of the point of illumination. In such an embodiment, the camera is calibrated and tracked within the same reference frame as the wireless tag and light projector. In some embodiments, the projected light and machine vision processing is configured for structured light projection to determine tissue geometry more accurately. In some embodiments, rasterization is used to project other graphics and text. In some embodiments, the light projection technique has no moving parts. In some embodiments, a high-powered light is utilized to burn the tissue to create a durable mark on the tissue.
[0089] A tracked probe with a controlled light source compatible with VATS and RATS procedures, in some embodiments, includes a single light emitting diode (LED) attached to the tracked probe. In some embodiments, the LED brightness is controlled by the system based on the relative position and/or alignment of the probe to the wireless tag. For example, the user could manipulate the tracked probe until the user sees the illumination in the camera view, and when the brightness is maximized, the tracked probe is pointed directly at the wireless tag. In other embodiments, a tracked probe with a controlled light source compatible with VATS and RATS procedures includes multiple LEDs arranged in a pattern. In some embodiments, each LED brightness is controlled by the system based on the relative position and/or alignment of the probe to the wireless tag. For example, the user could observe the pattern that is configured to guide them to the wireless tag. In some embodiments, a set of LEDs arranged in a plane is lighted so that the location of the highest intensity corresponds to the position of the wireless tag.
[0090] In some embodiments, the tool 112 is a microforce probe. The clamping force of a robot may be easy to control, but there are advantages to also wirelessly monitoring the clamping force. In some instances, a robotic jaw is configured to grab an object, but there is no feedback on how much resistance the robotic jaws are experiencing. The solution presented herein is a wireless tag embedded into a small module with a wireless communications module and one or more sensors and mechanical interfaces to measure and transmit real time data such as force, temperature, pressure, etc. In some embodiments, the tool 112 is a specialized tracked tool that deflects in a way that is measurable via the angle between two wireless tags, and the deflection is related to the amount of force applied to what is captured within the jaws. Advantageously, no battery is required because the communications can be powered by the exciter via induction. In other words, the same exciter used for localization can also provide power to the microsensor. As such, size can be minimized. For example, communications chips can be as small as approximately 2.5 mm×approximately 2.5 mm without an antenna. The probe data can be utilized, for example, to generate haptic feedback to the user.
[0091] In some embodiments, the tool 112 is an electrocautery multi-tool. Conventional electrocautery tools include various cords or tubes that must be assembled by the user. A solution presented herein is a single device with smoke capture, illumination, electrocautery, and tip localization. The solution consolidates multiple cords into one and eliminates user assembly steps. It is beneficial for the localization and electrocautery system to be coordinated so that interference is mitigated. Advantageously, better cutting energy can be delivered by controlling the waveforms more precisely, and by using low energy to detect when the tip is in contact with tissue. In addition, low energy detection of the tip in contact with tissue can be used to build a 3D model of the patient.
[0092] In some embodiments, the tool 112 is an electrocautery tool accessory (e.g., a collar, a tip, etc.). Conventional electrocautery tools include a tip removable from the pen. A solution presented herein is an adaptor for an electrocautery tool (e.g., a bovie pen). In some embodiments, the adaptor is a small wireless device that attaches to the electrocautery tool like a collar. In other embodiments, a locatable tip (i.e., a tip with wireless tag embedded in the shaft) is provided such that the tip can be tracked wirelessly by the wireless localization system.
[0093] In some embodiments, the tool 112 is a stapler. In lung applications, a cut is optimally performed perpendicular to the lung plane. A solution presented herein is a stapler including at least one wireless tag configured to define the plane where the lung will be cut and the end of the stapler. In some embodiments, the wireless tag is oriented perpendicular to the plane of interest, which aligns an unknown roll coordinate of the wireless tag to be anywhere on the plane.
[0094] In some embodiments, the tool 112 is a tracked clamp configured to span the entire cut across a lung.
[0095] In some embodiments, the tool 112 is a needle that is utilized in a medical procedure. A solution presented herein includes a needle 200 with a wireless tag 202 (e.g., a SmartClip®) in the upper shaft that can be tracked. With reference to
[0096] In some embodiments, the tool 112 is a capsule or pill that is swallowed by a patient. For example, convention capsules are swallowed by a patient to diagnose GI issues. A solution presented herein is a capsule with integrated wireless tags to provide wireless tracking of the capsule to increase the utility of the devices. The capsule with an integrated wireless tag can be enabled to deliver medication based on a command given over wireless communication. Medication delivery could be protected by requiring a large pulse of energy from an exciter. The large pulse can physically change the capsule between a medication deliver prohibited configuration to a medication delivery allowed configuration. In addition, a capsule with an integrated tag could implant a wireless tag on demand to mark tissue of interest.
[0097] In some embodiments, the tool 112 is a keypad and stylus (i.e., a sterile surgical interface). In surgery, sterile users cannot touch non-sterile user input devices. Bringing additional wired devices to serve as input devices requires additional sterile field management. Conventional wireless input devices are typically expensive and require batteries. The solution presented herein provides a keypad without electronics or digital communications with an embedded wireless tag that can be localized (i.e., a low-cost keypad). A localized stylus or electrocautery tool can touch the localized keypad.
[0098] With reference to
[0099] With reference to
[0100] With continued reference to
B. Robotic Integration Applications
[0101] As disclosed herein, wireless tags are integrated into robots and robotic apparatuses utilized in various medical procedures. An example of such a robotic system is the Intuitive da Vinci System. An example of a computer-assisted tele-operated surgery system and methods disclosed in U.S. Pat. No. 11,207,143, the entire contents of which are incorporated herein by reference. Unique challenges arise when attempting to integrate a wireless located tag into a robotic environment.
[0102] For example, patient anatomy and pre-operating imaging is insufficient for many surgical interventions. Wired-only navigation systems depend on pre-operative imaging and other methods to register detected locations to patient anatomy. As mentioned, some medical procedures utilize a camera, but wireless tags implanted in a patient are not typically visible in the camera view. A solution presented herein provides wireless tag localization in a robotic application. Precise localization of an implanted tag, co-registered to the surgeon's visual frame of reference, along with localization of tools, can provide intuitive dimensional feedback essential for successful interventions like excision, ablation, drug delivery, etc.
[0103] With reference to
[0104] With continued reference to
[0105] With reference to
[0106] One challenge to integrating wireless tags into robotic applications is effectively using cameras to measure anatomical landmarks. Use of camera to measure landmarks has drawbacks such as, challenges with lighting, lack of clear reference marks, tissue changes compared to as-imaged, presence of fluids, etc. A solution presented herein allows for co-registration to be achieved by registering the camera location with respect to wireless tags mounted on the camera and by tracking an object that goes to specific points in the camera's field of view. A wireless tag mounted to the camera is not mounted directly on the lens, so the relative position of the wireless tag and the lens of the camera is registered to improve localization. In some embodiments, field of view registration is accomplished by moving a tracked object to the upper-right, lower-right, upper-left and lower-left corners of the field of view when the position of the camera is known. In some embodiments, the camera is calibrated by placing a first wireless tag at a known close distance from the camera (e.g., within approximately 50 mm) to get the camera position, and then the orientation of the camera is determined by imaging a second wireless tag with the camera while the second wireless tag is far away from the camera. The wireless localization system can locate the magnetic center and the direction of the longitudinal axis of the wireless tag, but not necessarily which end of the tag is which. In order to consistently co-register the camera view to the system coordinate system, an additional degree of freedom is required to be constrained.
[0107] With reference to
[0108] In some embodiments, the wireless tags are cylindrical and the roll about the longitudinal axis and the direction the tag is pointing are challenging to determine. A solution presented herein is to place a wireless tag within an asymmetrically weighted mount. The wireless tag in the mount creates an angle of approximately 20-70 degrees from a line extending between the mount's center of mass and the mount's axis of rotation. The asymmetric weight provides a constraint on the tag orientation sufficient to allow the determination of both the roll orientation and the pointing direction. In some embodiments, the mount is encased in an object having a known pattern (e.g., the plurality of sections 608). The known pattern is imaged with a camera, allowing the object to be simultaneously localized with a camera and the wireless localization system. Once simultaneously localized, the general transformation between the wireless localization system and the camera is determined.
[0109] If the position of the camera is not known, the four corners of the field of view can be measured at two different distances from the camera to determine the camera location. In some embodiments, the camera performs a set of pre-determined motions (e.g., spin, move forward, etc.). In other embodiments, the camera looks at the same point from different points of view. In some embodiments, configurations of the camera registration can be saved and loaded as a pre-set configuration.
[0110] With reference to
[0111] Another challenge to integrating wireless tags into a surgical robot application is that metal object should be kept away from detectors or sensor coils because they create distortions in the electromagnetic field. In other words, surgical robots often include metal components (e.g., a metallic arm) that can distort the electromagnetic field relied upon by the wireless localization system. A solution presented herein is to utilize various noise reduction and signal processing techniques. In some embodiment, the system utilizes a phase sensitive signal processing.
[0112] Another challenge to integrating wireless tags into a surgical robot application is attaching wireless tags directly to metal components (e.g., a robotic arm) can cause the signal transmitted by the wireless tag to degrade by induced eddy currents within the metal. A solution presented herein is to include a thin layer of high permeability material (e.g., iron, manganese, zinc, silicon, aluminum, nickel, electrical steel, cobalt-iron, etc.) positioned between the antenna winding of the wireless tag and the metal. In some embodiments, the layer of high permeability material is selected based on the frequency range of the signal transmitted by the wireless tag.
[0113] Another challenge to integrating wireless tags into a surgical robot application is that range is limited by the ability to measure and a feature of interest on a patient can often be positioned far away from the pad. The solution presented herein is to embed a high gain detector (e.g., 508 of
[0114] Another challenge to integrating tags into a surgical robot application is that small wireless tags respond to only one direction of the excited field, and in some embodiment the robotic applications would have a plurality of wireless localization tags (i.e., clips, SmartClips®) being tracked. A solution presented herein utilizes a pad that creates three orthogonal directions of an exciter field. With reference to
C. General Surgical Applications
[0115] The solutions provided herein also have general surgical applications including, but not limited to: preventing items being left within patients, bone modeling, and soft tissue modeling.
[0116] A general problem with surgery arises when items (e.g., surgical instruments, sponges, etc.) are left within a patient after surgery is completed. The solution presented herein embeds wireless tags into such items so that they can be tracked wirelessly. Conventional fielded wireless object tracking system are incompatible with the wireless tag localization system. As described herein, fielded wireless object tracking is integrated into the tag localization system to reduce the amount of equipment required and/or reduce the amount of wireless interference. Items tagged with a tag are detectable with high assurance with the EnVisio® system. A large number of tags can be supported if localization requirements are relaxed. In some embodiments, the system keeps an ongoing count and tracks the number of items introduced to the general fielded area and decrease the number when tagged items leave the general fielded area (i.e., keeps a running total of items in the environment).
[0117] Another challenge is conventional robot-guided orthopedic systems rely on optical tracking of bones, which requires optical trackers to be surgically implanted into bone and that the system maintains direct line of sight of the optical trackers. The solution presented herein embeds two or more wireless tags (i.e., SmartClips®) into a bone, use pre-operative imaging and image segmentation to establish the bone geometry within the coordinate system defined by two or more wireless tags. In some embodiments, at time of surgery the bone is mounted to motor driven actuators controlled by software (e.g., a robotic arm), and the bone interface includes the wireless tag excitation and sensing sub-systems.
[0118] Another challenge is that pre-operative imaging is collected with soft tissue in different positions, orientations, and shape than it is presented in the operating room for surgery. The solution presented herein is to implant two or more wireless tags within soft tissue and/or on the skin of the patient. Pre-operating imaging can be conducted with the tags in place, and imaging can be imported to observe the new locations and orientations of the tags. The 3D image is deformed according to a volume maintaining algorithm that aligns the imaged tags to the live observed tags. In some embodiments, the volume maintaining algorithm is physics and physiology-based that may incorporate tissue density, elasticity, deformation, etc.
D. Wireless Tag Deployment
[0119] Tags can be delivered into soft tissue through needles, catheters, etc. with a conventional plunger mechanism. In some embodiments, additional mechanical features are added to secure the wireless tag to surrounding tissue. Securing the wireless tag is especially important during tissue excision involving manipulation of the tissue. With reference to
[0120] With reference to
[0121] With reference to
[0122] With reference to
E. Targeted Radiation Delivery
[0123] When delivering high energy radiation to soft tissue of a patient, positioning the target tissue at the intended location is critical. Conventional techniques to determine the location to radiate include use of external landmarks (e.g., anatomy, tattoos) or x-ray-based imaging. Conventional techniques to detect patient movement after placement include monitoring an external tag, monitoring patient breaching via air flow.
[0124] A solution presented herein provides direct localization with a tag implanted at or near the site targeted for radiation. If a wireless tag is implanted at the site the radiation is intended to be delivered, the patient will necessarily be positioned such that the tag is at or near the focus of the targeted radiation systems. Therefore, the volume over which a wireless tag is placed is relatively small (e.g., 10 cm×10 cm×10 cm) compared to other procedures. The tag excitation and sensing elements should not overlap with the radiation to both prevent beam deflection and also prevent damage to the electronics. In some embodiments, it is advantageous to have the excitation and sensing elements in separate modules, such that the excitation field is much lower and electronic filters are sufficient to reject the excitation signal. In some embodiments, a Helmholtz coil configuration, with exciters at two locations with the wireless tag between the two, may also be advantageous. In other embodiments, a single pad with both exciter and sensors is placed alongside the patient during radiation treatment, instead of under the patient.
F. Perioperative Imaging
[0125] Radiopaque materials used in wireless tag signal excitation and sensing can obscure patient features when present between the imaging equipment source and detectors. In some procedures, a signal is provided when the wire, catheter, or similar device is at a certain location within the vessel relative to the implant.
[0126] A solution presented herein is a wireless tag positioned within a stent (e.g., a coronary vessel) when it is desired, for example, to retrieve the stent. A solution also includes a wired emitter is coupled to an outer wall of a catheter or similar device. The wired emitter provides enough magnetic field strength to power up the wireless tag. A sensor or set of sensors position outside the body listen for the wireless tag response (indicating the wired emitter is approaching the wireless tag). In some embodiments, the signal conditioning on the sensor signal includes a notch or low pass filter to block the exciter signal carried by the emitter. If the wireless tag is in range of the wired emitter, the frequency spectrum characteristic of the wireless can be sensed.
[0127] Alternatively, the implant includes a magnet, and the catheter includes a high-sensitivity magnetometer. This approach includes a “zeroing” procedure to reduce effect of variation in the local magnetic field due to the earth and nearby metallic components.
[0128] Alternatively, the tag includes a passive highly resonant LC circuit, and the reflected signal on the emitter is monitored. Changes in coupling between the wired emitter and implant alters the reflected signal, and a location where the reflected signal is affected the most would correspond to the position of maximum coupling, and the geometry of the emitter and tag are tailored such that the position of maximum coupling corresponds to a signal relative location of the catheter within the vessel.
G. Arterial Access
[0129] Gaining arterial access can be challenging especially for femoral access in either cardio or leg interventions. A solution presented herein is a wireless tag positioned along the artery at the location of intended access under ultrasound or imaging guidance. In some embodiments, the needle used for initial access is tracked with a wireless or wired beacon, then guided by the system for ideal placement and direction. High precision reduces bleeding and reduce the time required to gain access.
H. Different Environment
[0130] Changes in the complex magnetic permeability near the pad can influence the signals used to localize beacons. For example, metallic (high conductivity) materials force the magnetic field to zero by means of induced currents that act as signal source at the same frequency. Ferrous (high permeability) materials are much less common but also modify the fields. Pads positioned under the patient are placed as close as possible to beds with large metallic components. A mapping process is used to learn the influence of the bed on the fields, and remove the influence on localization. However, different environments range from including no metal to mounting a pad directly on metal. Solutions presented herein permit the pad to be used in these various environments.
[0131] A first challenge arises from large metal loops embedded in bed that can create an opposing magnetic field that effectively cancels the exciter field. A solution presented herein is to position an electrically conductive layer 1206 (e.g., conductive plate) on the bottom of the pad 1202. The conductive plate 1206 acts as a shield to changes in environment permeability below the pad 1202. With reference to
[0132] A second challenge arises from the conductive layer affecting the exciter field because of currents induced in the metal and the resulting opposing magnetic field. With reference to
[0133] In the illustrated embodiment, the first layer 1204 is positioned between a plurality of exciter coils 1212 and the second layer 1206. The electromagnetic field at second layer 1206 is lower and the corresponding currents induced lower. In the illustrated embodiment, the permeable layer 1202 is positioned between the exciter coil 1212 and the conductive layer 1206. As such, the pad 1202 includes a combination of materials that redirects and contains the magnetic flux on the bottom of the pad 1202, and the pad 1202 is configured to operate efficiently on various surgical beds (e.g., “bed agnostic”).
[0134] In some embodiments, the exciter coils 1212 are encapsulated with a high thermal conductivity encapsulating material 1214 (e.g., an epoxy). In some embodiments, the encapsulating material has a thermal conductivity greater than 1000 W/Kelvin. In some embodiments, the encapsulating material has a heat capacity greater than 1000 Joules per kg° C. In some embodiments, the encapsulating material 1214 has a dielectric strength of at least 400 Volts per mil. In some embodiments, ferrite material helps shape the magnetic field.
[0135] A third challenge arises because the presence of a high permeability material distorts the magnetic field directions. Distortion of the magnetic field directions creates challenges because it is desirable to position the sensors in a location and orientation where the sensor is orthogonal to the exciter field for each of the states of the exciter creating different field directions. The distortion is pronounced in multi-exciter systems where the phases of the current are varied to change the primary directionality of the induced magnetic field. This effect results in large changes in field direction, in the plane of the exciter, as the exciter is configured to create different field direction (e.g.,
[0136] With reference to
[0137] With continued reference to
[0138] In some embodiments, the exciter coil is circular. In other embodiments, the exciter coil is rectangular or another suitable shape. In some embodiment, the electronics utilized for monitoring and controls of the pad are positioned under the conductive shield (e.g., the conductive shield is positioned between the electronics and the exciter coils).
[0139] In the illustrated embodiment, the high permeability material tolerates high fields without becoming saturated. In some embodiments, the internal induced field the high permeability material can support is higher than the external applied field.
[0140] Various features and advantages are set forth in the following claims.