Perspective-translucent high-current electromagnetic planar emitter

Abstract

Systems including planar electromagnetic (EM) transmitters that are negligible in interference to other devices and methods of generating the same are disclosed.

Description

Related applications

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 428,584, filed on November 29, 2022, the contents of which are incorporated herein by reference in their entirety. Background Art

[0002] Some embodiments of the present invention relate to flat electromagnetic (EM) transmitters, and more particularly, but not exclusively, to flat electromagnetic transmitters that cause negligible interference with other devices.

[0003] In traditional EM systems, sensors are typically made of coils. The sensors sense the transmitted field based on Faraday's law of induction. Because the induced voltage on the coil is proportional to the transmit frequency, it is advantageous to use higher frequencies (e.g., >1 kHz) in these systems to amplify the pickup on the sensor coil. In this case, the amplitude of the transmitted field does not need to be excessively high, as the pickup amplification is primarily achieved by increasing the transmit frequency. However, increasing the frequency also increases the eddy currents induced in the surrounding metal of the system, such as by the metal rods in the patient's bed.

[0004] An EM transmitter can generate multiple different EM fields. For example, each EM field can be modulated using a different frequency, such as in the range of 1-40 kHz. The different fields can be used to track the position and / or orientation of an EM sensor (typically a coil-based sensor). The sensor can sense the superposition of the different EM fields, for example, based on Faraday's law of induction. The sensed signal can then be decomposed into multiple amplitudes by a processor using a frequency decomposition method, such as a discrete Fourier transform (DFT), correlation methods, or any other suitable method.

[0005] Additional background information includes: U.S. Patent 6,833,814 discloses a system and method for tracking the position and orientation of a probe, such as a catheter, having a maximum lateral internal dimension of approximately 2 mm. Three at least partially overlapping planar antennas are used to simultaneously transmit electromagnetic radiation, with the radiation emitted by each antenna having its own spectrum. In the case of a single spectrum, the antennas are provided with a mechanism for decoupling from each other. A receiver within the probe includes sensors for three components of the transmitted field, wherein the sensors for at least two of the three components are paired sensors (such as coils) symmetrically arranged relative to a common reference point. In one embodiment of the receiver, the coils are collinear and wound around paired cores symmetrically arranged in radially opposed holes in the probe housing. In another embodiment of the receiver-catheter combination, the catheter is configured with an inner sleeve and an outer sleeve connected at their ends by one or more flexible elements, on which the coils are mounted. Each element of the paired coils, sensing the same component of the transmitted field, is connected to a different input of a differential amplifier. The position and orientation of the receiver relative to the antenna are determined non-iteratively by formulating an overdetermined system of linear equations relating the received signal to the transmitter-receiver amplitudes, solving for the amplitudes, and deriving the position coordinates and orientation angle of the receiver relative to the transmitter from these amplitudes.

[0006] U.S. Patent 10,615,500 discloses a computer-implemented method for designing an antenna structure for radiating an electromagnetic field for electromagnetic navigation. Based on a seed rectangle having a plurality of vertices, a plurality of diagonals are calculated relative to a coordinate system of a substrate having a boundary. Each diagonal bisects a corresponding vertex of the seed rectangle and extends from the vertex to the boundary. For each diagonal, the distance between adjacent pairs of planar antenna vertices located along the corresponding diagonal is determined, and the planar antenna vertices are located along the corresponding diagonal based on the determined distance. The distance increases in a direction from the corresponding vertex of the seed rectangle to the boundary. The planar antenna layout is generated by interconnecting the planar antenna vertices through the respective straight line portions to form a plurality of loops that sequentially traverse each diagonal. Summary of the Invention

[0007] The following is a non-exclusive list of some examples of embodiments of the invention. The invention also includes embodiments in which less than all of the features of an embodiment are included, as well as embodiments that utilize features from multiple embodiments, even if not explicitly listed below.

[0008] Embodiment 1. An electromagnetic (EM) transmitter comprising a plurality of stacked EM transmitting coils; each of the plurality of EM transmitting coils having at least one conductive trace; and the EM transmitter defining a planar surface.

[0009] wherein a calculated amount of conductive trace material in a cross section along an axis perpendicular to a planar surface of the EM emitter is uniform or quasi-uniform compared to all other cross sections in the EM emitter.

[0010] Embodiment 2. The EM transmitter of embodiment 1, wherein the plurality of EM transmit coils are positioned offset relative to one another to generate the uniform or quasi-uniform amount of conductive trace material.

[0011] Embodiment 3. The EM transmitter of embodiment 1 or embodiment 2, further comprising at least one additional layer; the additional layer comprising one or more regions; the regions having one or more of at least one conductive trace or copper configured to provide the material required to achieve the uniform or quasi-uniform amount of conductive material.

[0012] Embodiment 4. The EM transmitter of any one of embodiments 1 to 3, wherein one or more of the plurality of EM transmit coils further comprises one or more regions having one or more of at least one conductive trace or copper configured to provide the material required to achieve the uniform or quasi-uniform amount of conductive material.

[0013] Embodiment 5. The EM transmitter of any one of embodiments 1 to 4, wherein the plurality of EM transmit coils are configured to use low frequency and high current with low power dissipation.

[0014] Embodiment 6. The EM transmitter of any one of embodiments 1 to 5, wherein: a. The low frequency is less than 1kHz; and b. The high current is higher than 0.3 amperes or higher than 1 ampere.

[0015] Embodiment 7. The EM transmitter of any one of embodiments 1 to 6, wherein the plurality of EM transmit coils are configured to use a combination of: a. low frequency and high current; and b. High frequency and low current.

[0016] Embodiment 8. The EM transmitter of any one of embodiments 1 to 7, wherein: a. The low frequency is lower than 1kHz; b. The high current is higher than 0.3 amperes or higher than 1 ampere; c. The high frequency is 1kHz to 40kHz; and d. The low current is less than 1 ampere.

[0017] Embodiment 9. The EM transmitter of any one of embodiments 1 to 8, wherein the conductive trace material is one or more of copper, silver, or any other compatible material.

[0018] Embodiment 10. The EM transmitter of any one of Embodiments 1 to 9, wherein the spacing between portions of the at least one trace is from about 1 mil to about 5 mils.

[0019] Embodiment 11. The EM transmitter of any one of Embodiments 1 to 10, wherein the spacing between portions of the at least one trace is greater than 5 mils.

[0020] Embodiment 12. The EM transmitter of any one of Embodiments 1 to 11, wherein the at least one conductive trace weighs from about 0.5 ounces to about 20 ounces.

[0021] Embodiment 13 The EM transmitter of any one of Embodiments 1 to 12, each EM transmit coil of the plurality of EM transmit coils comprising a geometric shape of the at least one conductive trace.

[0022] Embodiment 14. The EM transmitter of any one of Embodiments 1 to 13, wherein the geometric shape is one or more of a square, a rectangle, a triangle, a diagonal, a circle, or any other geometric form.

[0023] Embodiment 15. The EM transmitter of any one of Embodiments 1 to 14, wherein each EM transmit coil of the plurality of EM transmit coils is made of a plurality of sub-transmit coils.

[0024] Embodiment 16 The EM transmitter of any one of Embodiments 1 to 15, further comprising an isolation layer between each of the plurality of transmit sub-coils.

[0025] Embodiment 17. The EM transmitter of any one of Embodiments 1 to 16, wherein the offset is characterized by a direction and a size.

[0026] Embodiment 18. The EM transmitter of any one of Embodiments 1 to 17, wherein the direction is one or more of up, down, left, and right.

[0027] Embodiment 19. The EM transmitter of any one of Embodiments 1 to 18, wherein the direction is one or more of the X-axis and / or the Y-axis.

[0028] Embodiment 20. The EM transmitter of any one of Embodiments 1 to 19, wherein the dimension is from about 0.01 mm to about 10 mm.

[0029] Embodiment 21. The EM transmitter of any one of Embodiments 1 to 20, wherein the at least one additional layer is an inversion layer or a copper region comprising inversion copper used as another layer.

[0030] Embodiment 22. A tracking system comprising: a. The EM transmitter according to embodiment 1, b. Fluoroscope.

[0031] Embodiment 23. A method of generating a uniform or quasi-uniform distribution of copper over an area of ​​an EM emitter by offset positioning, comprising: a. Identify trace locations and spacing on multiple EM coil layers; b. positioning the first EM coil layer at a fixed position, thereby generating a reference layer for the offset; c. Providing each of the remaining EM coil layers with a unique offset in at least one direction and at least one dimension relative to the fixed position of the first EM coil layer.

[0032] Embodiment 24. The method of embodiment 23, further comprising providing a plurality of EM coils, each EM coil having a plurality of EM coil layers to be used in the same orientation.

[0033] Embodiment 25. The method of embodiment 23 or 24, further comprising providing a geometric shape of each of the EM coils.

[0034] Embodiment 26. The method of any one of Embodiments 23 to 25, wherein said identifying the position and spacing of traces on said EM coil is performed based on said geometric shape.

[0035] Embodiment 27. The method of any one of embodiments 23 to 26, further comprising providing a number of EM coil layers for each EM coil.

[0036] Embodiment 28 The method of any one of Embodiments 23 to 27, further comprising positioning each EM coil layer above or below the first layer according to the provided unique offset.

[0037] Embodiment 29. The method of any one of embodiments 23 to 28, further comprising evaluating the overall distribution of copper across the surface of the EM emitter to identify areas that may have uneven amounts of copper.

[0038] Embodiment 30. The method of any one of Embodiments 23 to 29, wherein when an area having a non-uniform copper amount has been identified, the method includes repeatedly providing a unique offset until no area having a non-uniform copper amount is identified.

[0039] Embodiment 31. A method of generating a uniform or quasi-uniform distribution of copper over an area of ​​an EM emitter by providing an inverse layer mask, comprising: a. Providing several EM coils to be used in the same orientation; b. Evaluating the amount of copper in the overall area of ​​the EM emitter; c. Identify areas with higher copper content; d. setting the higher copper amount as the threshold; e. Identify areas with lower copper content; f. generating one or more layers including copper traces in the identified regions having lower copper content, thereby generating a reverse layer mask; g. Positioning the generated one or more layers above or below the EM coil to generate an EM emitter having uniform or quasi-uniform copper over the entire surface of the EM emitter.

[0040] Embodiment 32. A method of creating a uniform or quasi-uniform distribution of copper over an area of ​​an EM emitter, comprising fabricating a PCB having the EM emitters spaced less than 3 mils apart.

[0041] Embodiment 33. A tracking system comprising:

[0042] a plurality of EM emitters, each EM emitter of the plurality of EM emitters configured to generate one or more unique EM fields;

[0043] Wherein, each of the plurality of EM emitters is uniformly translucent under visualization; and wherein superimposed EM emitters of the plurality of EM emitters are also uniformly translucent under visualization.

[0044] Embodiment 34. An electromagnetic (EM) transmitter comprising a plurality of EM transmitting coils stacked one above the other; each of the plurality of EM transmitting coils having at least one conductive trace; the EM transmitter defining a planar surface;

[0045] Wherein, the EM emitters are visually uniform or quasi-uniform when visualized by visualization means.

[0046] Embodiment 35. The EM transmitter of embodiment 34, wherein a calculated amount of conductive trace material in a cross section along an axis perpendicular to the planar surface of the EM transmitter is uniform or quasi-uniform compared to all other cross sections in the EM transmitter.

[0047] Embodiment 36 The EM transmitter of Embodiment 34 or 35, wherein the plurality of EM transmit coils are positioned offset relative to one another to generate the uniform or quasi-uniform amount of conductive trace material.

[0048] Embodiment 37. The EM transmitter of any one of Embodiments 34 to 36, further comprising at least one additional layer; said additional layer comprising one or more regions; said regions having one or more of at least one conductive trace or copper configured to provide the material required to achieve said uniform or quasi-uniform amount of conductive material.

[0049] Embodiment 38. The EM transmitter of any one of Embodiments 34 to 37, wherein one or more of the plurality of EM transmit coils further comprises one or more regions having one or more of at least one conductive trace or copper configured to provide the material required to achieve the uniform or quasi-uniform amount of conductive material.

[0050] Embodiment 39. The EM transmitter of any one of Embodiments 34 to 38, wherein the plurality of EM transmit coils are configured to use low frequency and high current with less power dissipation.

[0051] Embodiment 40. The EM transmitter of any one of Embodiments 34 to 39, wherein: a. The low frequency is less than 1kHz; and b. The high current is higher than 0.3 amperes or higher than 1 ampere.

[0052] Embodiment 41. The EM transmitter of any one of Embodiments 34 to 40, wherein the plurality of EM transmit coils are configured to use a combination of: a. low frequency and high current; and b. High frequency and low current.

[0053] Embodiment 42. The EM transmitter of any one of Embodiments 34 to 41, wherein: a. The low frequency is lower than 1kHz; b. The high current is higher than 0.3 amperes or higher than 1 ampere; c. The high frequency is 1kHz to 40kHz; and d. The low current is less than 1 ampere.

[0054] Embodiment 43. The EM transmitter of any one of Embodiments 34 to 41, wherein the conductive trace material is one or more of copper, silver, or any other compatible material.

[0055] Embodiment 44. The EM transmitter of any one of Embodiments 34 to 43, wherein the spacing between portions of the at least one trace is from about 1 mil to about 5 mils.

[0056] Embodiment 45 The EM transmitter of any one of Embodiments 34 to 44, wherein the spacing between portions of the at least one trace is greater than 5 mils.

[0057] Embodiment 46. The EM transmitter of any one of Embodiments 34 to 45, wherein the at least one conductive trace weighs from about 0.5 ounces to about 20 ounces.

[0058] Embodiment 47 The EM transmitter of any one of Embodiments 34 to 46, each EM transmit coil of the plurality of EM transmit coils comprising a geometric shape of the at least one conductive trace.

[0059] Embodiment 48. The EM transmitter of any one of Embodiments 34 to 47, wherein the geometric shape is one or more of a square, a rectangle, a triangle, a diagonal, a circle, or any other geometric form.

[0060] Embodiment 49 The EM transmitter of any one of Embodiments 34 to 48, wherein each EM transmit coil of the plurality of EM transmit coils is made of a plurality of sub-transmit coils.

[0061] Embodiment 50 The EM transmitter of any one of Embodiments 34 to 49, further comprising an isolation layer between each of the plurality of transmit sub-coils.

[0062] Embodiment 51. The EM transmitter of any one of Embodiments 34 to 50, wherein the offset is characterized by a direction and a size.

[0063] Embodiment 52. The EM transmitter of any one of Embodiments 34 to 51, wherein the direction is one or more of up, down, left, and right.

[0064] Embodiment 53. The EM transmitter of any one of Embodiments 34 to 52, wherein the direction is one or more of the X-axis and / or the Y-axis.

[0065] Embodiment 54. The EM emitter of any one of Embodiments 34 to 53, wherein the dimension is from about 0.01 mm to about 10 mm.

[0066] Embodiment 55. The EM transmitter of any one of Embodiments 34 to 54, wherein the at least one additional layer is an inversion layer or a copper region comprising inversion copper used as another layer.

[0067] Embodiment 56. A tracking system comprising: a. The EM transmitter of embodiment 34, and b. Fluoroscope.

[0068] Unless otherwise defined, all technical terms and / or scientific terms used herein have the same meaning as those of ordinary skill in the art to which the present invention pertains. Although methods and materials similar or equivalent to the methods and materials described herein can be used in the practice or testing of embodiments of the present invention, exemplary methods and / or materials are described below. In the event of a conflict, the patent specification (including definitions) shall prevail. In addition, materials, methods, and embodiments are merely illustrative and are not intended to be necessarily limited to this.

[0069] As will be appreciated by those skilled in the art, some embodiments of the present invention can be implemented as a system, method or computer program product. Therefore, some embodiments of the present invention can take the form of a pure hardware embodiment (entirelyhardware embodiment), a pure software embodiment (including firmware, embedded software, microcode etc.) or a combination of software and hardware, which can generally be referred to as "circuit", "module" or "system" in this article. In addition, some embodiments of the present invention can take the form of a computer program product embodied in one or more computer-readable media, with the computer-readable program code implemented thereon on the computer-readable medium. The implementation of the method of some embodiments of the present invention and / or the system can relate to manual, automatic or its combination execution and / or completion of selected tasks. In addition, according to the actual instruments and equipment of some embodiments of the method of the present invention and / or system, several selected tasks, for example, using an operating system, can be realized by hardware, software or firmware and / or its combination.

[0070] For example, according to some embodiments of the present invention, the hardware for performing the selected task can be implemented as a chip or circuit. As software, the selected task according to some embodiments of the present invention can be implemented as a plurality of software instructions executed by a computer using any suitable operating system. In an exemplary embodiment of the present invention, one or more tasks according to some exemplary embodiments of the method and / or system described herein are performed by a data processor, such as a computing platform for performing multiple instructions. Optionally, the data processor includes a volatile memory for storing instructions and / or data and / or a non-volatile memory for storing instructions and / or data, such as a magnetic hard disk and / or a removable medium. Optionally, a network connection is also provided. A display and / or a user input device, such as a keyboard or a mouse, are also optionally provided.

[0071] For some embodiments of the present invention, any combination of one or more computer-readable media can be utilized. The computer-readable medium can be a computer-readable signal medium or a computer-readable storage medium. A computer-readable storage medium can be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared or semiconductor system, device or equipment, or any suitable combination thereof. A more specific example (non-exhaustive listing) of a computer-readable storage medium will include the following: an electrical connector with one or more wires, a portable computer floppy disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable read-only compact disc (CD-ROM), an optical storage device, a magnetic storage device or any suitable combination thereof. In the context of this article, a computer-readable storage medium can be any tangible medium that can contain or store a program for use by an instruction execution system, a device or equipment or used in combination with it.

[0072] A computer-readable signal medium may include a propagated data signal having computer-readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including but not limited to electromagnetic, optical, or any suitable combination thereof. A computer-readable signal medium may be any computer-readable medium that is not a computer-readable storage medium and is capable of communicating, propagating, or transporting a program for use by or in connection with an instruction execution system, apparatus, or device.

[0073] Program code embodied on a computer-readable medium and / or data used by it may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, radio frequency, etc., or any suitable combination of the foregoing.

[0074] The computer program code for performing the operations of some embodiments of the present invention can be written in any combination of one or more programming languages, including object-oriented programming languages ​​(such as Java, Smalltalk, C++, etc.) and traditional procedural programming languages ​​(such as "C" programming language or similar programming languages). The program code can be executed entirely on the user's computer, or partially on the user's computer as a stand-alone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the latter case, the remote computer can be connected to the user's computer through any type of network (including a local area network (LAN) or a wide area network (WAN)), or can be connected to an external computer (e.g., by using the Internet through an Internet service provider).

[0075] Some embodiments of the present invention may be described below with reference to flowchart illustrations and / or block diagrams of methods, devices (systems) and computer program products according to embodiments of the present invention. It should be understood that each block of the flowchart illustrations and / or block diagrams and the combination of blocks in the flowchart illustrations and / or block diagrams may be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device to produce a machine so that instructions executed via the processor of the computer or other programmable data processing device create a means for implementing the function / action specified in one or more blocks of the flowchart and / or block diagram.

[0076] These computer program instructions can also be stored in a computer-readable medium (the computer-readable medium can boot a computer), other programmable data processing devices, or other devices and executed in a specific manner, so that the instructions stored in the computer-readable medium produce an article of manufacture including instructions for implementing the functions / actions specified in one or more boxes of the flowchart and / or block diagram.

[0077] The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to perform a series of operational steps on the computer, other programmable apparatus, or other devices to produce a computer-implemented process, such that the instructions executed on the computer or other programmable apparatus provide a process for implementing the functions / actions specified in one or more blocks of the flowchart and / or block diagram.

[0078] Some of the methods described herein are generally designed only for use by computers and may not be feasible or practical for a human expert to perform purely manually. A human expert who wishes to perform a similar task manually may need to use an entirely different approach, such as leveraging expert knowledge and / or the pattern recognition capabilities of the human brain, which may be much more efficient than manually performing the method steps described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] Some embodiments of the present invention are described by way of example only and with reference to the accompanying drawings. With specific reference now to the drawings in detail, it should be emphasized that the details shown are merely exemplary and are provided for purposes of illustrative discussion of embodiments of the present invention. In this regard, the description taken in conjunction with the drawings clearly demonstrates to those skilled in the art how embodiments of the present invention may be practiced.

[0080] In the attached figure:

[0081] Figure 1a - b is a schematic diagram of an exemplary tracking system according to some embodiments of the present invention;

[0082] Figure 1c is a schematic diagram of an exemplary planar electromagnetic transmitter according to some embodiments of the present invention;

[0083] Figure 2a -c is a schematic diagram of an exemplary geometry of an exemplary electromagnetic transmitter coil according to some embodiments of the present invention;

[0084] Figure 3 is a schematic enlarged partial top view of a coil according to some embodiments of the present invention;

[0085] Figure 4a -e is a visibility image of a printed circuit board (PCB) emitter under standard perspective in three different situations according to some embodiments of the present invention;

[0086] Figure 5a -b are respectively a partial top view and a schematic cross-sectional view of a multi-layer electromagnetic coil transmitter with an offset according to some embodiments of the present invention;

[0087] Figure 5c is a schematic cross-sectional view of an exemplary multilayer emitter according to some embodiments of the present invention;

[0088] Figure 6a is a schematic diagram of the reverse layer concept according to some embodiments of the present invention;

[0089] Figure 6b -c is a schematic diagram of an exemplary reverse layer according to some embodiments of the present invention;

[0090] Figure 6d -e is a schematic diagram of an exemplary "perfect" inversion layer according to some embodiments of the present invention;

[0091] Figure 7 is a flow chart of an exemplary method for generating a uniform or quasi-uniform distribution of copper over an electromagnetic emitter area by offset positioning according to some embodiments of the present invention;

[0092] Figure 8 is a flow chart of an exemplary method for generating a uniform or quasi-uniform distribution of copper over an electromagnetic emitter area by providing an inverse layer mask according to some embodiments of the present invention; and

[0093] Figure 9 is a flow chart of an exemplary method for generating a uniform or quasi-uniform distribution of copper over an electromagnetic emitter area by fabricating a printed circuit board (PCB) with a smaller pitch, according to some embodiments of the present invention. DETAILED DESCRIPTION

[0094] The present invention, in certain embodiments, relates to planar electromagnetic (EM) transmitters and, more particularly, but not exclusively, to planar electromagnetic (EM) transmitters that cause negligible interference with other devices. Overview

[0095] Some embodiments of the present invention relate to an EM transmitter that does not interfere with a user reading an image containing the EM transmitter within the field of view (FOV) of a visualization device. In some embodiments, the EM transmitter includes one or more EM coils, for example, the EM transmitter includes three or more EM coils. In some embodiments, each coil includes a PCB having traces with a specific geometry. In some embodiments, the EM transmitter includes traces with a high copper content, which allows the EM transmitter to use low frequencies and relatively high currents with low power dissipation. In some embodiments, each coil includes multiple layers. In some embodiments, the EM transmitter is a planar EM transmitter having a square or rectangular shape. In some embodiments, the EM transmitter includes the same or quasi-identical amount of copper in any and / or each cross-section of the EM transmitter, where the area is the area measured perpendicular to the surface of the planar EM transmitter—for example, the area of ​​the multiple coils stacked one on top of the other when the EM transmitter is viewed from above. In some embodiments, each of the multiple coils is arranged with a calculated offset from one another to provide the same or quasi-identical amount of copper. In some embodiments, the calculated offset takes into account areas within each coil that contain traces and areas that do not contain traces to produce an overall homogeneous or quasi-homogeneous distribution of copper in the traces across the entire surface of the EM transmitter when viewed from above. The terms "homogenous" and "quasi-homogeneous" as used herein refer to the EM transmitter being homogeneous from a subjective viewpoint under fluoroscopic imaging (or other visualization means) when viewed under conventional conditions with a general, non-specific fluoroscopy apparatus. In some embodiments, the EM transmitter includes an additional masking layer configured to fill gaps throughout the entire area with copper traces to achieve the same or quasi-homogeneous amount of copper. In some embodiments, the EM transmitter includes an electrically disconnected (floating) coil within the same transmitter coil that is configured to fill gaps throughout the entire area with copper traces in a pattern similar to that of the transmitter coil to achieve the same or quasi-homogeneous amount of copper. In some embodiments, continuing to wind the coil to fill areas of the transmitter with copper has the advantage of maintaining the same copper pattern while filling the gaps with copper. In some embodiments, the same or quasi-identical amount of copper is achieved by manufacturing the PCB with very small spacing between traces, thereby achieving an overall uniform or quasi-uniform distribution of copper in the traces across the entire surface of the EM transmitter when viewed from above. In some embodiments, the EM coils can be positioned in different orientations to provide different EM fields. In some embodiments, each EM coil transmits at a unique frequency that is different from the frequency used by other EM coils within the same EM transmitter.

[0096] Before explaining at least one embodiment of the present invention in detail, it should be understood that the invention is not limited in its application to the details of construction, arrangement of components, and / or methods described in the following description and / or illustrated in the drawings and / or examples. The invention may have other embodiments or may be practiced or implemented in various ways. Problem Introduction

[0097] Known tracking systems utilize electromagnetic transmitters and receivers to track medical devices within a patient's body during endovascular procedures. These systems typically employ electromagnetic tracking of the medical device in combination with visual monitoring, such as using fluoroscopy. Exemplary systems include Figure 1a shown.

[0098] refer to Figure 1a 2-b, illustrates an exemplary tracking system according to some embodiments of the present invention. In some embodiments, exemplary tracking system 100 includes a bed or mattress 102 on which a patient 104 is positioned. In some embodiments, tracking system 100 includes a fluoroscopy device 106 and a planar transmitter 108 positioned below patient 104 (e.g., below mattress 102). Figure 1a shows a schematic side view of the tracking system, and Figure 1b A schematic top view of a couch 102 is shown with a patient 104 positioned on the couch 102 and a planar emitter 108 positioned below the patient 104 .

[0099] For power and signal-to-noise ratio (SNR) considerations, known tracking systems typically employ high frequencies (e.g., 1-40 kHz) and relatively low currents (e.g., less than 1 amp) during tracking. For example, coil-based sensors sense alternating magnetic fields according to Faraday's law. For example, an alternating field of strength I0sin(ωt) in the transmitter will generate an electromotive force (EMF) in the receiver that is proportional to I0ω·cos(ωt), and therefore, the transmitted amplitude I0 generates a pickup voltage amplitude in the sensing coil that is proportional to I0ω according to Faraday's law of induction. Therefore, it is advantageous to increase ω (the transmit frequency) to increase the pickup in the sensor. Increasing I0 will also increase the pickup in the sensor, but at a greater cost. The power dissipated by the current I0 through the transmitter coil with resistance R is Therefore, it increases with increasing I0. However, it does not generally increase with ω (for very high ω, the skin effect can effectively increase R, thereby increasing power dissipation). Therefore, it is advantageous to use high frequencies (e.g., 1-40 kHz) and fairly small currents (e.g., 0.1 amps) to increase the pickup in the sensor while keeping the power dissipation in the transmitter fairly small. Furthermore, in medical applications, planar electromagnetic (EM) transmitters are used because they generally do not generate structural interference with other equipment. For example, a planar EM transmitter can be placed on the patient's bed, e.g., under the patient's mattress, as described above and in Figure 1a and 1b An exemplary planar EM emitter 108 is shown schematically in FIG. Figure 1c shown.

[0100] In contrast to some known tracking systems, the tracking system of the present invention uses low frequencies and relatively high currents in the process. A potential advantage of using low frequencies is that eddy currents induced in the metal surrounding the system are negligible.

[0101] In some embodiments, the system of the present invention employs a DC magnetic sensor configured to sense a DC magnetic field, for example by using the Hall effect, magnetoresistance, magnetoinductance or other suitable DC magnetic field sensing technology, while in some embodiments, the system may optionally employ a coil-based sensor that can only sense an AC magnetic field due to Faraday's law (i.e., the change of the magnetic field over time). In order to increase the sensor's pickup of low frequencies, it is necessary to increase the amplitude of the transmitted field. The same is true for a DC magnetometer, where increasing the frequency does not increase the sensor's pickup, and one way to increase the pickup may be to increase the amplitude of the transmitted field. In some embodiments, the term "DC magnetometer" herein refers to a sensor that senses DC fields (constant fields) as well as low and medium frequency fields. For example, a magnetic sensor with a sampling rate of 1000 Hz senses a magnetic field with a frequency of 0-500 Hz (Nyquist). It should be understood that although its basic sensing is for a "DC magnetic field", for the purpose of protection, it is also intended to cover any "magnetic field".

[0102] To achieve this, high current EM emitters are used (eg, above 0.3 amps, above 1 amp), since the amplitude of the emission field is proportional to the electrical emission current.

[0103] This is why, in some embodiments, the tracking system of the present invention employs low frequencies and relatively high currents during operation.

[0104] As previously mentioned, it is advantageous to use planar EM transmitters in medical applications, for example, for placement under the mattress of a patient's bed. In some embodiments, the planar transmitter comprises a printed circuit board (PCB) that includes conductive (e.g., copper or silver) traces describing EM transmit coils for emitting EM fields. In some embodiments, in order for these coils to carry high currents (e.g., greater than 0.3 amps or 1 amp), it is advantageous for the traces to be wide (e.g., wider than 1 mm) and / or thick (e.g., copper weight greater than 3 ounces). In some embodiments, a potential advantage of increasing the width and / or thickness of the copper is that it potentially reduces the resistance of the PCB traces (inversely proportional to the increase in the cross-sectional area of ​​the traces), which in turn reduces the power dissipated by the transmitter at the desired transmit current (according to Watt's law: P = I 2 R), thereby enabling high currents with high efficiency (preventing the emitter from overheating during operation at the specific required current I).

[0105] It should be understood that while the present disclosure primarily relates to copper traces, it should be understood that traces of other suitable metals or conductive materials may be used in some embodiments, with corresponding structural and / or quantitative changes as desired.

[0106] However, by increasing the copper (particularly the thickness), the PCB traces can become visible in standard fluoroscopy (e.g., in a standard fluoroscopy device such as a C-arm at 80 kVp projection) according to the Beer-Lambert attenuation law. Copper has a 0.76 cm attenuation at 80 kVp. 2 / g of mass attenuation coefficient, which makes copper highly visible (an absorber of X-ray energy) according to the Beer-Lambert attenuation law. On the other hand, reducing the copper width / thickness results in increased power dissipation of the required emission current, which can lead to increased heating of the emitter in the process. In addition, manufacturers typically require significantly larger spacing between heavier copper traces. For example, a 5-ounce layer of copper may require 14 mils of spacing between traces, while a 1-ounce layer of copper may require 3 mils of spacing between traces. This makes the 5-ounce traces more visible on images generated by standard fluoroscopy due to the increased spacing between traces. In summary, wider / thicker traces with larger inter-trace spacing will produce very visible EM emitters on images generated by standard fluoroscopy, but manufacturing narrower / thinner traces is not desirable, and current manufacturers cannot or will not manufacture PCBs with heavy copper and shorter spacing.

[0107] This presents a unique problem with the present system. On the one hand, the present system seeks to use low-frequency and / or DC magnetometers, which necessitates the use of higher currents. Higher currents require increased copper in PCB traces to reduce power dissipation. Increased copper in PCB traces results in EM emitters being visible, for example, during fluoroscopy, which can cause interference during visualization of the tracked medical device.

[0108] Thus, aspects of some embodiments of the present invention relate to an EM emitter having increased copper width / thickness while still maintaining negligible effects under standard perspectives. Exemplary Tracking System

[0109] In some embodiments, an exemplary tracking system such as Figures 1a-1c As shown, one major difference from known tracking systems is the dedicated EM emitter. In some embodiments, as described above, the EM emitter is characterized by having an increased copper width / thickness while still maintaining a negligible visual effect under standard fluoroscopy. In some embodiments, as described above, the EM emitter is used in electromagnetic tracking and / or navigation procedures. In some embodiments, the "transparency" of the EM emitter to fluoroscopy allows the use of a fluoroscopy instrument during an EM navigation procedure without distorting the resulting image. As used herein, "transparency" or "transparency" or "translucency" or "semi-transparency" of the EM emitter means "negligible effect on fluoroscopy and / or other equipment." It should be emphasized that when the fluoroscopy instrument is activated, the EM emitter is not actually transparent, but as will be further explained below, its presence in the field of view (FOV) of the fluoroscopy instrument is negligible for the tracking process.

[0110] In some embodiments, a fluoroscopy device can project an anteroposterior (AP) image through the emitter such that the emitter does not add any significant artifacts to the fluoroscopic image. For example, the trace of the emitter is not noticeable on the image or is sufficiently eliminated to not interfere with the medical professional's reading of the image. In some embodiments, similarly, the emitter can be used with a computed tomography (CT) system (e.g., cone beam CT (CBCT)) to provide three-dimensional (3D) imaging, for example, during a procedure, without adding significant artifacts to the 3D imaging. Exemplary EM Emitters

[0111] In some embodiments, the exemplary EM transmitter is a planar EM transmitter that includes a PCB having a plurality of EM transmit coils for transmitting corresponding different EM fields and different frequencies.

[0112] In some embodiments, the EM emitter includes an increased amount or thickness of copper. In some embodiments, the increased amount of copper may be due to one or more of the following:

[0113] 1. Allows high current to be carried with less power dissipation: In some embodiments, increasing the amount of copper reduces coil resistance and allows high current to be carried, for example, greater than 0.3 amps, or greater than 1 amp (amplitude, peak-to-peak, or RMS), with less power dissipation. In some embodiments, a potential advantage of using high current is that it allows the use of a low frequency EM tracking system with less power dissipation; and

[0114] 2. Increasing the number of transmitter EM fields: In some embodiments, for example, instead of 3 fields, the transmitter transmits 6 or more fields using 6 or more transmit coils to support "single sensor" (5-DOF) EM tracking.

[0115] In some embodiments, increasing the copper width (rather than the thickness) does not add more noise to the fluoroscopic image, as each X-ray will still pass through the same amount of copper (e.g., through 1 ounce of copper). However, as the trace width increases, the coil cannot be wound as densely in the PCB, so the PCB coil will have to contain fewer windings, and power dissipation will increase. On the other hand, increasing the copper thickness (rather than the width) does add more noise to the fluoroscopic image, but each coil can contain more windings (because the traces are narrower), and power dissipation is reduced. Example EM Transmitter Coil Geometry

[0116] refer to Figure 2a -c, shows a schematic representation of an exemplary geometry of an exemplary EM transmitter coil according to some embodiments of the present invention. In some embodiments, regardless of the mechanism by which the exemplary EM transmitter achieves "transparency" under imaging equipment, the exemplary EM transmitter includes a coil having a specific geometry. In some embodiments, the planar EM transmitter includes a PCB that includes metal traces that constitute a plurality of EM transmitting coils for emitting corresponding different EM fields. In some embodiments, each of the plurality of coils included in the EM transmitter is configured to emit a different EM field. For example, Figure 2a The coil 1 schematically shown in FIG. 1 comprises two vertically aligned sub-coils connected in series: a sub-coil X1 wound around a first half of the PCB in a first layer, and a sub-coil X2 wound around a second half of the PCB in a second layer. Similarly, Figure 2b The coil 2 schematically shown in FIG. 1 includes two horizontally aligned sub-coils Y1 and Y2 connected in series. Figure 2c The coil 3 schematically shown in FIG can be wrapped around the periphery of the PCB to provide a third EM field. In some embodiments, the coil can have Figure 2aAny of the geometric shapes disclosed in -c, for example, a coil includes more than two sub-coils (e.g., 3, 4, 5, 6, or more sub-coils). The geometric shape is not square or rectangular; it can be triangular, diagonal, circular, or characterized by any other geometric form. In the following description, rectangular and square geometric shapes will be used for convenience of description, and it should be understood that these geometric shapes are not intended to limit the scope of the present invention.

[0117] refer to Figure 3 , shows a schematic enlarged partial top view of a coil according to some embodiments of the present invention. In some embodiments, the exemplary coil 300 includes multiple traces, such as Figure 3 , wherein traces 302, 304, and 306 are shown, which constitute the three windings of the coil 300. In some embodiments, each of the traces 302, 304, and 306 is, for example, 1 mm wide (possibly with a negligible error margin). In some embodiments, the total height (thickness) of each of the traces 302, 304, and 306 can be a 5 oz PCB layer, which is equal to 175 microns (possibly with a negligible error margin). In some embodiments, the exemplary coil 300 includes spacing 308 between the traces. In general, manufacturers typically require a spacing of approximately 14 mils between traces of a 5 oz layer. In some embodiments, the traces of the 5 oz PCB layer are highly visible in a standard perspective, particularly when spaced 14 mils apart, such as Figure 4a shown (see below). Exemplary Multilayer Coil

[0118] In some embodiments, an exemplary coil of any geometry comprises a single coil layer. In some embodiments, each exemplary coil of any geometry comprises multiple coil layers (referred to herein as multi-layer coils). In some embodiments, within a coil of a particular geometry type, each layer comprises conductive traces that optionally have the same geometry. In some embodiments, a multi-layer coil optionally comprises adjacent coils having different geometries. In some embodiments, in this case, the complete coil comprises a single known geometry, and the sub-layers are arranged so that the result is see-through "transparent" (see below).

[0119] In some embodiments, for example, instead of using a single 5-ounce copper coil layer with, for example, 1 mm wide traces and 14 mil spacing, the 5-ounce copper layer is divided into, for example, five aligned 1-ounce layers, or into ten aligned 0.5-ounce layers, each with, for example, 1 mm wide traces and 3 mil spacing. In some embodiments, a potential advantage of dividing the coil into multiple layers is that it potentially reduces the spacing between traces, and as described above, reducing the spacing increases the level of "transparency" of the EM transmitter by making the separation between traces less noticeable in perspective. Reducing the spacing also allows for more windings of the EM coil to be included on a single layer, since the coil can be wound more densely. Including more windings increases the inductance of the coil and improves power dissipation.

[0120] In some embodiments, due to the alignment of traces between multiple layers, the EM transmit coil remains visible in fluoroscopy due to the effective high copper weight (since, according to the Beer-Lambert attenuation law, the final attenuation is the product of all differential attenuations of the total amount of copper in space that a single X-ray passes through). In some embodiments, a solution as explained below addresses this issue.

[0121] In some embodiments, the resulting coils (each of which may be composed of multiple PCB layers connected in parallel) can have similar inductance (possibly with negligible error margins) relative to a single coil made from a single (thick) PCB layer. In some embodiments, this is achieved because each coil comprises multiple parallel coils of identical geometry that are nearly perfectly aligned (see below). In some embodiments, the inductance of the parallel-connected aligned coils is relatively similar to the inductance of a single coil due to the perfect mutual inductance between the aligned coils. In addition, the parallel-connected aligned coils may introduce mutual capacitance between the coils. However, this capacitance may be negligible, especially in the case of low-frequency EM transmitters. Principle of the exemplary solution

[0122] In some embodiments, to overcome the problems caused by increasing the amount of copper in a single EM transmit coil or in multiple layers of transmit coils, the inventors have developed several potential solutions, all of which follow the same principle: the EM transmit coil has a similar amount of copper at every point or sub-area over the entire area of ​​the transmitter when viewed from above (or from some limited range of angles around a top view, such as a 45-degree range).

[0123] refer to Figure 4a -e, images showing the visibility of a PCB emitter under standard perspective in three different situations according to some embodiments of the present invention.

[0124] Figure 4aThe visibility of a transmitter with a single 5 oz layer per coil and 14 mil spacing between traces is shown. As can be seen, the traces are very visible and may interfere with the usability of the fluoroscopic image, for example in a manner that may impair the practitioner's ability to obtain information from the image.

[0125] Figure 4b The visibility of a transmitter with five 1 oz alignment layers per coil and 3 mil spacing between traces is shown. As can be seen, the visibility of the traces is reduced, but they are still very noticeable and can interfere with the usability of the see-through image.

[0126] Figure 4c The visibility of a transmitter with five 1 oz layers per coil and 3 mil spacing between traces is shown. As can be seen, the traces are barely visible and the transmitter is essentially see-through "transparent" or "translucent" in this case. Figure 4c The principle of an exemplary solution is shown, whereby every point over the entire area of ​​the emitter has a substantially similar amount of copper when viewed from above or from a range of angles above (e.g., a range of angles tilted 45 degrees from a top view), thereby producing a uniform or quasi-uniform copper surface that does not interfere with the usability of the see-through image.

[0127] Figure 4d -e shows a perspective image of the visual uniformity of an exemplary emitter according to some embodiments of the present invention. Figure 4d shows a clear visualization of the plastic lung model 402 on a uniform background 404 of the emitter, while Figure 4e The boundary 406 of the emitter is shown, where the difference between the area 404 where the emitter is present and the area 408 where the emitter is not present can be clearly seen, as well as how the emitter appears uniform in perspective.

[0128] In the following paragraphs, possible solutions for achieving a substantially see-through "transparent" emitter will be provided. Example solutions

[0129] Reduce spacing in PCBs

[0130] In some embodiments, an exemplary method of generating a uniform or quasi-uniform copper surface that does not interfere with the usability of the fluoroscopic image is by reducing the spacing between traces. For example, by producing 1 ounce / 0.5 ounce layers with very small spacing (1 mil, 2 mils, 3 mils), the resulting PCB will be effectively "transparent". In some embodiments, the quality of the fluoroscopy instrument also affects the image. For example, the better the fluoroscopy instrument resolution, the smaller the spacing should be. In some embodiments, for standard systems, a 3 mil spacing is sufficient as long as the number of such 3 mil spacings that are aligned with each other between different layers is small. In some embodiments, even in cases where alignment is required, a 1 mil spacing may be sufficient to meet the requirements.

[0131] Overlapping EM transmit coils with offset

[0132] refer to Figure 5a -b, shows a schematic representation of a partial top view and cross-sectional view of a multi-layer EM coil transmitter with offset according to some embodiments of the present invention.

[0133] As about Figure 3 As mentioned, manufacturers typically require approximately 14 mil spacing between traces in a 5-ounce layer. Traces in a 5-ounce PCB layer are highly visible in standard fluoroscopy, particularly when separated by a 14-mil spacing. In some embodiments, as described above, each 5-ounce layer is divided into multiple 1-ounce layers or 0.5-ounce layers, each having, for example, 1 mm wide traces and 3 mil spacing, with the coil layers in each EM transmit coil aligned at an offset relative to the other coil layers. Thus, for example, the offset traces overlap the spacing between each other's traces, and the traces become less noticeable in fluoroscopic images. In some embodiments, the offset is characterized by a direction and a size. In some embodiments, the direction is one or more of up, down, left, and right. In some embodiments, the direction is defined as movement in the X-axis and / or Y-axis. In some embodiments, the size is approximately 0.01 mm to approximately 10 mm.

[0134] refer to Figure 5a, shows a schematic representation of traces of different EM coils with offsets being overlapped, according to some embodiments of the present invention. In some embodiments, the multi-layer coil 500 may include multiple coil windings, including windings 502 and 504, with spacing 506 between them. In some embodiments, winding 502, representing any winding of coil 500, may include multiple layers, for example, five layers 502, 502a, 502b, 502c, and 502d. Similarly, for example, winding 504 includes multiple layers 504 and 504a to 504d (not shown). In some embodiments, each layer may be, for example, 1 ounce or 0.5 ounce (possibly with a negligible error tolerance). In some embodiments, the spacing 506 may be 3 mils (possibly with a negligible error tolerance). In some embodiments, optionally, the copper layers are separated by a thin insulating layer (see below) Figure 5c ) to prevent short circuits between different layers, as in standard PCB manufacturing processes.

[0135] In some embodiments, each layer is positioned at a unique offset relative to the other layers, e.g., in different orientations and / or different magnitudes (sizes) relative to the other layers, as described above. In some embodiments, the offsets are calculated for all coils and layers of the transmitter 108 so that X-rays passing through the transmitter 108 pass through relatively similar amounts of copper (or any other suitable trace metal) at various locations on the transmitter 108, and in some embodiments, pass through relatively similar amounts of copper (or any other suitable trace metal) at various angles of the X-rays (e.g., depending on the position and orientation of the C-arm). In some embodiments, for example, in the case of three EM coils, each with five layers, the PCB can have 15 layers, each with a different offset. In some embodiments, the offsets are used to blend the layers in a hybrid manner so that the resulting PCB is effectively "transparent" under standard fluoroscopy. For example, in the case of 1 mm wide traces with 3 mil spacing between traces, the offset magnitude can be less than 1.08 mm (which is the sum of the trace width plus the trace spacing). In some embodiments, the reason for this is that the period of the winding coil may be 1.08 mm, so a deviation beyond 1.08 mm will cycle back to a modulus deviation of 1.08 mm period.

[0136] In some embodiments, the ideal offset is found in a fluoroscopy simulation according to the Beer-Lambert attenuation law, for example based on the assumption that according to the Beer-Lambert attenuation law, there is an exponential relationship between the amount of copper an X-ray passes through and the radiation intensity lost by the X-ray in its path.

[0137] In some embodiments, the calculation of the required offsets is done manually by the user, who can freely "move" the various layers within a simulation program designing the EM emitter.

[0138] In some embodiments, the calculation of the required offset is done automatically by dedicated software with instructions to generate n possible combinations of shifts of the layer until a uniform or quasi-uniform distribution of copper over the EM emitter area is achieved.

[0139] In some embodiments, the calculation of the required offsets is automated by specialized software with instructions for converging to a uniform or quasi-uniform distribution of copper over the EM emitter area using a nonlinear optimization method (e.g., Gradient Descent, Levenberg-Marquardt, or any other suitable method). In some embodiments, the software can start with some initial guess (e.g., a random guess or a random offset value) and use the nonlinear optimization method to converge locally or globally to minimize an energy function that describes the inhomogeneity of the simulated fluoroscopic image based on the currently parameterized coil layer offsets.

[0140] refer to Figure 5c , showing a schematic cross-sectional view of an exemplary multilayer emitter according to some embodiments of the present invention. Figure 5c An exemplary multilayer emitter is shown (layers are not to scale), where copper layers are separated by layers of insulating material. For example, odd numbers (1, 3, 5, 7, etc.) are insulating layers, while even numbers (2, 4, 6, 8, etc.) are copper traces. Exemplary dimensions are, for example, approximately 0.09 mm for the insulating layer and approximately 0.035 mm for the 1 oz copper layer.

[0141] Provides a reverse layer

[0142] refer to Figure 6a , shows a schematic representation of the invert layer concept according to some embodiments of the present invention. In some embodiments, another option for making the PCB traces of a planar EM transmitter invisible in a fluoroscopic image includes providing an invert layer for each PCB coil layer, for example, a PCB layer comprising copper in all areas where the coil layer does not have copper, thereby making the traces invisible in the resulting fluoroscopic image. This concept is described in Figure 6a , where PCB 602 is covered in copper except at a location in the center 604. A reverse layer 606 includes copper traces 608 at locations 604 where copper is missing from PCB 602. Once installed, the two layers provide a uniform copper layer 610. In some embodiments, this can be achieved, for example, by utilizing each PCB core (a rigid substrate with copper laminated on one or both sides) by etching a transmit coil on one side (e.g., the top side) and a companion reverse layer on the other side (e.g., the bottom side). In this way, each reverse layer is always closest to its forward layer, achieving maximum transparency in the resulting see-through image.

[0143] In some embodiments, a reverse layer may contain copper that is missing only from its coil layer counterpart. In some embodiments, a reverse layer may contain copper that is missing from more than a single layer of a PCB. For example, multiple coil layers may contain spacing and other portions with missing copper. In some embodiments, a single reverse layer may contain the total copper content of those multiple coil layers in a single reverse layer.

[0144] Now refer to Figure 6b -c, which shows a schematic diagram of an exemplary inversion layer according to some embodiments of the present invention. Figure 6b A schematic upper partial view of the transmitter is shown, which shows the Figure 6c The two layers and the complementary coverage of copper, best observed in the cross-sectional view of , in fact provide an overall uniform or quasi-uniform distribution of copper on the emitter.

[0145] refer to Figure 6d Figure 5-e shows a schematic representation of an exemplary "perfect" return layer according to some embodiments of the present invention. In some embodiments, adding a return layer can provide see-through "translucency" but increases the overall copper content of the PCB. In some embodiments, the return layer can be used as a transmit coil layer, or two transmit coil layers can be designed as return layers for each other. Figure 6d A schematic upper partial view of the transmitter is shown, which shows the Figure 6e The two layers, best seen in the cross-sectional view of FIG, and the complementary coverage of the copper, actually provide an overall uniform or quasi-uniform distribution of copper across the transmitter. For example, a PCB coil may include 1 mm traces with 1 mm spacing between the traces. In some embodiments, as long as the coils are wound regularly, they may be "offset" by just 1 mm so that the copper and spacing will switch positions. In this embodiment, one layer may contain coils, while the other layer may contain coils offset by 1 mm, so that each coil trace covers the spacing between the traces of the other layer. In this embodiment, the two layers serve as counter layers, but they also both serve as transmit coil layers, so that all copper is transmit copper, rather than electrically isolated (floating) copper placed solely to balance visual non-uniformity in the perspective image. In some embodiments, these complementary coils can be connected in parallel or series and be part of a single transmit coil, or they can belong to separate transmit coils.

[0146] Low-high frequency hybrid transmitter

[0147] As mentioned above, low-frequency transmitters require relatively high currents to increase pickup in the sensor. However, the same transmitter can be used to transmit low-frequency and high-frequency fields in parallel. In some embodiments, this is achieved, for example, by driving a low-frequency, high-current sine wave into the transmit coil, superimposed with a high-frequency, low-current sine wave into the same coil. For example, a low-frequency transmitter comprising three transmit coils can transmit the following currents through its three coils: I0sin(1ω0t), I0sin(2ω0t), I0sin(3ω0t), where ω0=2πf0 and f0 is some basic low-frequency transmit frequency (e.g., f0=30 Hz). Sometimes both ω and f are referred to as "frequency," although ω can also be referred to as angular velocity. In a low-to-high-frequency transmitter, high frequency can be added to each transmitter coil, for example, transmitting the following currents through its three coils: I0sin(1ω0t)+I1sin(100·1ω0t) I0sin(2ω0t)+I1sin(100·2ω0t) I0sin(3ω0t)+I1sin(100·3ω0t)

[0148] For example, I0=1 Ampere, I1=0.1 Ampere, f0=30 Hz, so that the transmitted low frequencies are: 30 Hz, 60 Hz, 90 Hz, and the superimposed transmitted high frequencies are: 3 kHz, 6 kHz, 9 kHz.

[0149] The large amount of copper described in this article supports low-frequency, high-current signals by reducing the resistance of each transmitting coil, not to mention that it also supports high-frequency, low-current signals, making it easy for the superimposed high-frequency signal to be transmitted together with the low-frequency signal.

[0150] In some embodiments, a low-to-high frequency transmitter can be used to support both a low-frequency EM tracking system (e.g., utilizing a DC magnetometer) and a high-frequency "conventional" coil-based EM tracking system. The same low-to-high frequency transmitter can track both sensors in the same process: a low-frequency sensor (e.g., based on a DC magnetometer) and a high-frequency sensor (e.g., based on an EM coil and Faraday's law of induction, having a high frequency of, for example, 1 kHz to 40 kHz).

[0151] In some embodiments, the receivers may be independent, each using its own frequency range, such that low frequency receivers are not disturbed by EM fields emitted by high frequencies because they only receive specific low frequencies and ignore the high frequencies, and high frequency receivers are not disturbed by EM fields emitted by low frequencies because they only receive specific high frequencies and ignore the low frequencies.

[0152] In some embodiments, supporting both types of EM sensors can be advantageous for adding functionality to existing coil-based EM systems where existing coil-based devices are already in use, such as in clinical settings. A hybrid low-high frequency transmitter can then support existing devices while adding functionality to new low-frequency-based devices.

[0153] Using low-frequency electromagnetic tracking has the advantage of providing cost-effective shape and position tracking, as well as reducing electromagnetic metal distortion effects. Adding these capabilities to existing high-frequency tracking platforms, rather than completely replacing them with low-frequency platforms, allows for compatibility with existing products and a smooth transition to new low-frequency-based devices. Furthermore, by supporting both low-frequency and high-frequency electromagnetic tracking technologies, each tracked device can use the technology that best suits its needs within the same tracking platform.

[0154] The low-high frequency transmitter can provide a single platform that supports low-frequency and high-frequency EM tracking for various applications.

[0155] Example Use of Multiple Transmitters

[0156] In some embodiments, multiple fluoroscopic transmitters can be placed at different locations and / or orientations within the clinical environment to generate a greater number of different transmitted electromagnetic fields (e.g., more than three fields). In some embodiments, the transmitters are synchronized and configured to use different frequencies. For example, two 3-coil transmitters can be placed perpendicularly, parallel, one above the other, one next to the other, or in any other suitable configuration, so that they can each transmit a total of six different electromagnetic fields at six different frequencies. For example, in one embodiment, two 3-coil transmitters are positioned one above the other and rotated 45 degrees. Because each transmitter is "transparent" to fluoroscopy, the combined configuration is also "transparent." In some embodiments, a potential benefit of this is that multiple "simple" transmitters (e.g., 3-coil transmitters) can be used to generate a greater number of electromagnetic fields (e.g., six or more fields) to support 5-DOF sensor tracking. In some embodiments, the mechanical configuration of the transmitters is calibrated using electromagnetic calibration methods before the procedure begins. Exemplary Methods

[0157] refer to Figure 7 , a flow chart illustrating an exemplary method for generating a uniform or quasi-uniform distribution of copper over an area of ​​an EM emitter by offset positioning, according to some embodiments of the present invention.

[0158] In some embodiments, the method includes one or more of the following actions:

[0159] 702 provides several EM coils to be used on the transmitter board.

[0160] 704 provides the geometry of each EM coil.

[0161] 706 Several layers are provided for each EM coil.

[0162] 708 Identify the trace locations and spacing on the EM coil according to the specific geometry.

[0163] Position the first layer of the first EM coil at a fixed position 710. The fixed position is used as a reference for the offset of the remaining layers.

[0164] 712 provides each of the remaining layers with a unique offset in at least one direction and at least one dimension relative to the position of the first layer.

[0165] 714 positions each layer above or below the first layer according to the unique offset provided.

[0166] The overall distribution of copper across the surface of the EM emitter is evaluated 716 to identify areas that may have uneven amounts of copper.

[0167] 718 When an area with uneven copper content has been identified, actions 712, 714, and 716 are repeated until no area with uneven copper content is identified.

[0168] The method ends when no areas with non-uniform copper amounts are identified.

[0169] In some embodiments, the method is performed for any and all EM transmitters and / or EM transmitter coils that may be deployed, such as additional EM transmitters that are stacked with the first EM transmitter and / or additional EM transmitters that are positioned at different angles relative to the first EM transmitter.

[0170] In some embodiments, assessing the overall distribution of copper across the surface can be accomplished by calculating an energy function that measures the non-uniformity of the copper, for example, by generating a simulated perspective image of the current offset configuration (according to the Beer-Lambert law) and calculating the 2D standard deviation of the simulated image.

[0171] In some embodiments, reducing the overall non-uniformity of the copper distribution can be achieved by striving to minimize the above energy function, thereby bringing the 2D standard deviation of the simulated fluoroscopic images closer to zero.

[0172] In some embodiments, the above actions are performed manually by a user. In some embodiments, the above actions are performed automatically by dedicated software.

[0173] refer to Figure 8 , shows a flow chart of an exemplary method for generating a uniform or quasi-uniform distribution of copper over an area of ​​an EM emitter by providing an inverse layer mask, according to some embodiments of the present invention.

[0174] In some embodiments, the method includes one or more of the following actions:

[0175] 802 provides multiple EM coils to be used in the same orientation.

[0176] 804 assesses the amount of copper in the overall area of ​​the EM emitter.

[0177] 806 identifies areas with higher copper content.

[0178] 808 sets those higher copper amounts as thresholds.

[0179] 810 identifies areas with lower copper content.

[0180] One or more layers including copper traces are generated 812 in the identified locations having lower copper amounts, thereby generating a reverse layer mask.

[0181] One or more resulting layers are positioned above or below the EM coil 814, thereby generating an EM emitter having uniform or quasi-uniform copper across the surface of the EM emitter when viewed from above.

[0182] In some embodiments, the above actions are performed manually by a user. In some embodiments, the above actions are performed automatically by dedicated software.

[0183] In some embodiments, the method of generating a uniform or quasi-uniform distribution of copper over the area of ​​the EM emitter by providing an inverse layer mask is performed in addition to or instead of the method of generating a uniform or quasi-uniform distribution of copper over the area of ​​the EM emitter by offset positioning.

[0184] refer to Figure 9 , shows a flow chart of an exemplary method for generating a uniform or quasi-uniform distribution of copper over the area of ​​an EM emitter by fabricating a PCB with a smaller pitch, according to some embodiments of the present invention.

[0185] In some embodiments, a method for creating a uniform or quasi-uniform distribution of copper over the area of ​​the EM emitter is accomplished by calculating the desired geometry of the traces in PCB 902 and then manufacturing PCB 902 with a smaller pitch based on the calculations. In some embodiments, the smaller the pitch, the less impact the pitch has on the resulting fluoroscopic image. In some embodiments, the pitch is less than 3 mils. In some embodiments, the pitch is between about 3 mils and about 1 mil.

[0186] It is expected that during the life of the patent maturing from this application, many related PCB manufacturing technologies will be developed; the scope of this invention is intended to include all such a priori new technologies.

[0187] As used herein, with respect to quantities or values, the term "about" means "within ±10%."

[0188] The terms "comprises," "comprising," "includes," "including," "has," "having" and the like mean "including but not limited to."

[0189] The term "consisting of" means "including and limited to."

[0190] The term "consisting essentially of" means that the composition, method or structure may include additional ingredients, steps and / or parts, but only if the additional ingredients, steps and / or parts do not materially change the basic and novel characteristics of the claimed composition, method or structure.

[0191] As used herein, the singular forms "a," "an," and "the" include plural references unless the context clearly indicates otherwise. For example, the term "a compound" or "at least one compound" may include a plurality of compounds, including mixtures thereof.

[0192] Throughout this application, embodiments of the present invention may be presented in a range format. It should be understood that descriptions in range format are merely for convenience and brevity and should not be construed as immutable limitations on the scope of the invention. Therefore, descriptions of ranges should be considered to have specifically disclosed all possible subranges and individual numerical values ​​within that range. For example, descriptions of a range "from 1 to 6" should be considered to have specifically disclosed subranges such as "from 1 to 3," "from 1 to 4," "from 1 to 5," "from 2 to 4," "from 2 to 6," "from 3 to 6," etc.; as well as individual numbers within that range, such as 1, 2, 3, 4, 5, and 6. This applies to the breadth of the range.

[0193] Whenever a numerical range is indicated herein (e.g., "10-15," "10 to 15," or any pair of numbers linked by these or other such range indicators), it is intended to include any number (fractional or integer) within the indicated range, including range limits, unless the context clearly indicates otherwise. The phrases "a range between a first indicated number and a second indicated number" and "from a first indicated number to," "up to," "up to," or "through" (or another such range-indicating term) the second indicated number are used interchangeably herein and are intended to include the first indicated number and the second indicated number and all fractions and integers therebetween.

[0194] Unless otherwise indicated, the numbers used herein and any numerical ranges based thereon are approximations that are understood by those skilled in the art to be within reasonable precision of measurement and rounding error.

[0195] It should be understood that certain features of the present invention that are described in the context of separate embodiments for the sake of clarity may also be provided in combination in a single embodiment. Conversely, various features of the present invention that are described in the context of a single embodiment for the sake of brevity may also be provided individually or in any suitable subcombination or as applicable to any other described embodiment of the present invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperable without those elements.

[0196] Although the present invention has been described in conjunction with its specific embodiments, it is apparent that many alternatives, modifications and variations will be apparent to those skilled in the art. It is therefore intended to encompass all alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

[0197] It is the applicant's intention that all publications, patents, and patent applications mentioned in this specification are incorporated herein by reference, as if each individual publication, patent, or patent application were specifically and individually indicated as being incorporated herein by reference. Furthermore, citation or identification of any reference in this application should not be construed as an admission that such reference is prior art to the present invention. Where section headings are used, they should not be construed as necessarily limiting. Furthermore, any priority documents claimed in this application are incorporated herein by reference in their entirety.

Claims

1. An electromagnetic (EM) transmitter comprising a plurality of EM transmitting coils stacked one above the other; each of the plurality of EM transmitting coils having at least one conductive trace; the EM transmitter defining a planar surface; in, A calculated amount of conductive trace material in a cross section along an axis perpendicular to the planar surface of the EM emitter is uniform or quasi-uniform compared to all other cross sections in the EM emitter.

2. The EM transmitter of claim 1, wherein: The plurality of EM transmit coils are positioned offset relative to one another to generate the uniform or quasi-uniform amount of conductive trace material.

3. The EM transmitter of claim 1 , further comprising at least one additional layer; said additional layer comprising one or more regions; said regions having one or more of at least one conductive trace or copper configured to provide the material required to achieve said uniform or quasi-uniform amount of conductive material.

4. The EM transmitter of claim 1 , wherein: One or more of the plurality of EM transmit coils further include one or more regions having one or more of at least one conductive trace or copper configured to provide material required to achieve the uniform or quasi-uniform amount of conductive material.

5. The EM transmitter of claim 1 , wherein: The plurality of EM transmit coils are configured to use low frequency and high current with less power dissipation.

6. The EM transmitter of claim 5, wherein: a. The low frequency is less than 1kHz; and b. The high current is higher than 0.3 amperes or higher than 1 ampere.

7. The EM transmitter of claim 1 , wherein: The plurality of EM transmit coils are configured to use the following combinations: a. low frequency and high current; and b. High frequency and low current.

8. The EM transmitter of claim 7, wherein: a. The low frequency is lower than 1kHz; b. The high current is higher than 0.3 amperes or higher than 1 ampere; c. The high frequency is 1kHz to 40kHz; and d. The low current is less than 1 ampere.

9. The EM transmitter of claim 1 , wherein: The conductive trace material is one or more of copper, silver or any other compatible material.

10. The EM transmitter of claim 1, wherein: The spacing between portions of the at least one trace is from about 1 mil to about 5 mils.

11. The EM transmitter of claim 1 , wherein: The spacing between portions of the at least one trace is greater than 5 mils.

12. The EM transmitter of claim 1, wherein: The at least one conductive trace comprises a weight of about 0.5 ounces to about 20 ounces.

13. The EM transmitter of claim 1, each EM transmit coil of the plurality of EM transmit coils comprising a geometry of the at least one conductive trace.

14. The EM transmitter of claim 13, wherein: The geometric shape is one or more of a square, a rectangle, a triangle, a diagonal line, a circle or any other geometric form.

15. The EM transmitter of claim 1, wherein: Each EM transmitting coil of the plurality of EM transmitting coils is made of a plurality of sub-transmitting coils.

16. The EM transmitter of claim 15, further comprising an isolation layer between each of the plurality of sub-transmit coils.

17. The EM transmitter of claim 2, wherein: The offset is characterized by direction and size.

18. The EM transmitter of claim 17, wherein: The direction is one or more of up, down, left and right.

19. The EM transmitter of claim 17, wherein: The direction is one or more of the X axis and / or the Y axis.

20. The EM transmitter of claim 17, wherein: The size is from about 0.01 mm to about 10 mm.

21. The EM transmitter of claim 3, wherein: The at least one additional layer is an inverted layer or contains copper regions that serve as inverted copper for other layers.

22. A tracking system comprising: a. The EM transmitter according to claim 1, b. Fluoroscope.

23. A method of generating a uniform or quasi-uniform distribution of copper over an area of ​​an EM emitter by offset positioning, comprising: a. Identify trace locations and spacing on multiple EM coil layers; b. positioning the first EM coil layer at a fixed position, thereby generating a reference layer for the offset; c. Providing each of the remaining EM coil layers with a unique offset in at least one direction and at least one dimension relative to the fixed position of the first EM coil layer.

24. The method of claim 23, further comprising providing a plurality of EM coils, each EM coil having a plurality of EM coil layers to be used in the same orientation.

25. The method of claim 24, further comprising providing a geometry of each of the EM coils.

26. The method according to claim 25, wherein The position and spacing of the identification traces on the EM coil are based on the geometry.

27. The method of claim 23, further comprising providing a plurality of EM coil layers for each EM coil.

28. The method of claim 23, further comprising positioning each EM coil layer above or below the first layer according to the provided unique offset.

29. The method of claim 23, further comprising evaluating the overall distribution of copper across the surface of the EM emitter to identify areas that may have uneven amounts of copper.

30. The method according to claim 29, wherein When a region having a non-uniform copper amount has been identified, the method includes repeating the providing of a unique offset until no region having a non-uniform copper amount is identified.

31. A method of generating a uniform or quasi-uniform distribution of copper over an area of ​​an EM emitter by providing an inverse layer mask, comprising: a. Providing several EM coils to be used in the same orientation; b. Evaluating the amount of copper in the overall area of ​​the EM emitter; c. Identify areas with higher copper content; d. setting the higher copper amount as the threshold; e. Identify areas with lower copper content; f. generating one or more layers including copper traces in the identified regions having lower copper content, thereby generating a reverse layer mask; g. Positioning the generated one or more layers above or below the EM coil to generate an EM emitter having uniform or quasi-uniform copper along the entire surface of the EM emitter.

32. A method of creating a uniform or quasi-uniform distribution of copper over the area of ​​an EM emitter, comprising fabricating the EM emitter with a PCB having a pitch less than 3 mils.

33. A tracking system comprising: a plurality of EM emitters, each EM emitter of the plurality of EM emitters configured to generate one or more unique EM fields; Wherein, each of the plurality of EM emitters is uniformly translucent under visualization; and wherein superimposed EM emitters of the plurality of EM emitters are also uniformly translucent under visualization.

34. An electromagnetic (EM) transmitter comprising a plurality of EM transmitting coils stacked one above the other; each of the plurality of EM transmitting coils having at least one conductive trace; the EM transmitter defining a planar surface; in, The EM emitters are visually uniform or quasi-uniform when visualized by visualization means.

35. The EM transmitter of claim 34, wherein: A calculated amount of conductive trace material in a cross section along an axis perpendicular to the planar surface of the EM emitter is uniform or quasi-uniform compared to all other cross sections in the EM emitter.

36. The EM transmitter of claim 35, wherein: The plurality of EM transmit coils are positioned offset relative to one another to generate the uniform or quasi-uniform amount of conductive trace material.

37. The EM transmitter of claim 35, further comprising at least one additional layer; said additional layer comprising one or more regions; said regions having one or more of at least one conductive trace or copper configured to provide the material required to achieve said uniform or quasi-uniform amount of conductive material.

38. The EM transmitter of claim 35, wherein: One or more of the plurality of EM transmit coils further include one or more regions having one or more of at least one conductive trace or copper configured to provide material required to achieve the uniform or quasi-uniform amount of conductive material.

39. The EM transmitter of claim 34, wherein: The plurality of EM transmit coils are configured to use low frequency and high current with less power dissipation.

40. The EM transmitter of claim 39, wherein: a. The low frequency is less than 1kHz; and b. The high current is higher than 0.3 amperes or higher than 1 ampere.

41. The EM transmitter of claim 34, wherein: The plurality of EM transmit coils are configured to use the following combinations: a. low frequency and high current; and b. High frequency and low current.

42. The EM transmitter of claim 41 , wherein: a. The low frequency is lower than 1kHz; b. The high current is higher than 0.3 amperes or higher than 1 ampere; c. The high frequency is 1kHz to 40kHz; and d. The low current is less than 1 ampere.

43. The EM transmitter of claim 34, wherein: The conductive trace material is one or more of copper, silver or any other compatible material.

44. The EM transmitter of claim 34, wherein: The spacing between portions of the at least one trace is from about 1 mil to about 5 mils.

45. The EM transmitter of claim 34, wherein: The spacing between portions of the at least one trace is greater than 5 mils.

46. ​​The EM transmitter of claim 34, wherein: The at least one conductive trace has a weight of about 0.5 ounces to about 20 ounces.

47. The EM transmitter of claim 34, each EM transmit coil of said plurality of EM transmit coils comprising a geometry of said at least one conductive trace.

48. The EM transmitter of claim 47, wherein The geometric shape is one or more of a square, a rectangle, a triangle, a diagonal line, a circle or any other geometric form.

49. The EM transmitter of claim 34, wherein: Each EM transmitting coil of the plurality of EM transmitting coils is made of a plurality of sub-transmitting coils.

50. The EM transmitter of claim 49, further comprising an isolation layer between each of the plurality of sub-transmit coils.

51. The EM transmitter of claim 36, wherein: The offset is characterized by direction and size.

52. The EM transmitter of claim 51, wherein The direction is one or more of up, down, left and right.

53. The EM transmitter of claim 51 , wherein: The direction is one or more of the X axis and / or the Y axis.

54. The EM transmitter of claim 17, wherein: The size is from about 0.01 mm to about 10 mm.

55. The EM transmitter of claim 37, wherein: The at least one additional layer is an inverted layer or contains copper regions that serve as inverted copper for other layers.

56. A tracking system comprising: a. The EM transmitter according to claim 34, b. Fluoroscope.

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