Magnetic field generator orientation for magnetic tracing in planar magnetic field generation components

Abstract

A magnetic tracking system includes a field generator assembly for generating a plurality of magnetic fields, wherein each magnetic field is generated by a corresponding magnetic field generator of the field generator assembly, at least one of the magnetic field generators having a first angular orientation, and at least another of the magnetic field generators having a second angular orientation different from the first angular orientation. The magnetic tracking system includes a magnetic sensor for measuring the plurality of magnetic fields, and a computing device configured to calculate the position and orientation of the magnetic sensor within the magnetic fields measured by the sensor. The first angular orientation is between one and fifteen degrees, and the second angular orientation is between one and fifteen degrees.

Description

[0001] Priority requirements

[0002] This application claims priority to U.S. Patent Application No. 63 / 321434, filed March 18, 2022, pursuant to 35 USC §119(e), the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to using magnetic fields to determine the position and orientation of an object. Background Technology

[0004] Magnetic tracking systems use magnetic fields to determine the position and orientation of an object within a given area. Sensors are positioned on an object (such as a piece of equipment or a person's body) to detect the magnetic field present in the given area. Based on the detected magnetic field information, a computer system can calculate the object's position and orientation relative to a reference coordinate system. These systems are useful, for example, in the medical field, for tracking instruments involved in medical procedures, thereby facilitating advanced methods in surgery and diagnosis. Summary of the Invention

[0005] Different magnetic fields can be generated by orienting the magnetic field generator at different angles. Some of the generated magnetic fields can be advantageous for tracking objects within a given area. Parallel magnetic fields close to the field generator assembly, for example, make it difficult to determine the sensor's position and orientation. When the magnetic fields are parallel, fewer field generators can provide useful information about the sensor's position and orientation at close range. Non-parallel magnetic fields are advantageous because the sensor can determine unique measurements from each magnetic field, even at very close range. Using thin, flat field generators with different angular orientations can, for example, lead to improved tracking.

[0006] In one aspect, the magnetic tracking system includes a field generator assembly for generating a plurality of magnetic fields, wherein each magnetic field is generated by a corresponding magnetic field generator of the field generator assembly, at least one of the magnetic field generators having a first angular orientation, and at least another of the magnetic field generators having a second angular orientation different from the first angular orientation. The first angular orientation is between one and fifteen degrees, and the second angular orientation is between one and fifteen degrees. The magnetic tracking system also includes a magnetic sensor for measuring the plurality of magnetic fields, and a computing device configured to calculate the position and orientation of the magnetic sensor within the magnetic field measured by the sensor.

[0007] In some implementations, the magnetic field generator includes at least one of a wound electromagnetic coil, a quaternary electromagnetic coil, or a planar helix.

[0008] In some implementations, the magnetic field generators are distributed on the field generator assembly such that at least two of the magnetic field generators are offset in position.

[0009] In some implementations, the computing device is configured to determine a first angular orientation and a second angular orientation.

[0010] In some implementations, the magnetic tracking system includes a conductive plate beneath the field generator assembly, the conductive plate comprising a permeable material.

[0011] In some implementations, the magnetic field generator has the same elevation angle and different azimuth angles.

[0012] In some implementations, the magnetic tracking system includes a third magnetic field generator having a third angular orientation that is different from the first and second angular orientations.

[0013] In some implementations, the first angular orientation is in the opposite direction to the second angular orientation.

[0014] In some implementations, the first angle orientation is the first elevation angle, while the second angle orientation is the second elevation angle, which is different from the first elevation angle.

[0015] In one aspect, an apparatus includes a structural surface for supporting a portion of a patient during a medical procedure, and a surface including a plurality of magnetic field generators comprising a field generator assembly for generating a magnetic field to form a measurement volume; wherein at least one magnetic field generator is angularly oriented relative to the surface, and wherein the angular orientation of the at least one magnetic field generator is between one and fifteen degrees relative to the surface.

[0016] In some implementations, the device includes a conductive plate beneath the surface.

[0017] In some implementations, at least two magnetic field generators are oriented at different angles relative to the surface.

[0018] In some implementations, at least two magnetic field generators are oriented at different angles relative to each other.

[0019] In some implementations, the at least two magnetic field generators are oriented at opposite angles to each other.

[0020] In some implementations, the at least two magnetic field generators are oriented at an angle between one and fifteen degrees from the surface.

[0021] In some implementations, the at least two magnetic field generators are oriented at an angle greater than 15 degrees from the surface.

[0022] In some implementations, the at least two magnetic field generators are oriented at an angle pointing towards the center of the surface.

[0023] In some implementations, the at least two magnetic field generators are oriented at an angle pointing away from the center of the surface.

[0024] In some implementations, the at least two magnetic field generators are oriented at the same angle relative to the surface.

[0025] In some implementations, the at least two magnetic field generators are oriented at different angles relative to the surface.

[0026] In some implementations, the plurality of magnetic field generators are distributed on the field generator assembly such that at least two of the magnetic field generators are offset in position.

[0027] The foregoing and other advantages and features will be partly apparent in the following detailed description and claims, together with the appended ones. Figure 1 Get up and take a look. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a magnetic tracking system.

[0029] Figure 2 This is a schematic top view of an example of a field generator component.

[0030] Figure 3 This is a schematic diagram of two field generators with the same angular orientation.

[0031] Figure 4 This is a schematic diagram of two field generators with different angular orientations.

[0032] Figure 5 This is a schematic diagram of an example of a field generator component.

[0033] Figure 6 This is a perspective view of an example of a magnetic field generator.

[0034] Figure 7 This is a schematic diagram illustrating an example of a magnetic field generated by a magnetic field generator.

[0035] Figure 8 This is an example of a frequency division multiplexing scheme that excites different magnetic field generators. Detailed Implementation

[0036] Different magnetic fields can be generated by orienting a magnetic field generator at different angles. Some of these generated magnetic fields are advantageous for tracking objects within a given area. (See reference...) Figure 1A schematic diagram of a magnetic tracking system 100 is shown and described. In short, system 100 includes a magnetic field generating component 102 configured to generate a magnetic field within a given three-dimensional region (e.g., volume 104). A sensor component 106, placed on an object 108 (e.g., a scalpel) within the given volume 104, detects and / or measures the magnetic field and transmits the measurement results to a computing device 110, for example, via a communication link 112 (e.g., a wired or wireless connection). Based on the measurements from the sensor component 106, the computing device 110 can calculate the position of the sensor component 106 (and therefore the object 108) relative to a coordinate system 114. This position calculation facilitates motion tracking of the sensor component 106 within region 104. This is useful in advanced surgical procedures where the sensor component 106 can be mounted on an object such as a scalpel to track the movement of the object as a medical procedure is performed (e.g., tracking the movement of the scalpel relative to a second sensor component, such as one attached to a patient's body).

[0037] In some implementations, the field generating component 102 is relatively thin in size (e.g., height) and can be mounted on a flat surface (such as an operating table 116). Such a field generating component can be referred to as a flat field generator. Although Figure 1 The field generating assembly 102 is depicted as being mounted on the operating table 116, but in some embodiments, the field generating assembly 102 may be integrated into the operating table 116 by embedding the field generating assembly 102 within the operating table 116. In this particular arrangement, the field generating assembly 102 includes a plurality of field generators 118 (e.g., one or more field generators), each of which may include one or more electromagnetic coils that generate a magnetic field (e.g., by passing current through each coil). For example, the electromagnetic coils may be formed by winding a conductor (such as an electrical wire) around a core of a magnetic or non-magnetic material (such as air). When current passes through the windings of the coil, a magnetic field is generated that extends along the longitudinal axis of the coil through the center of the coil and loops around the outer edge of the loop or coil. The magnetic field around each loop or winding combines with the field from other loops to generate a concentrated magnetic field at the center of the coil. The magnetic field strength of the coil can be controlled by controlling the current, the number of loops or windings of the coil, and other parameters and characteristics associated with the coil.

[0038] Other parameters can be changed to control the shape of the induced field. These include, for example, the level of current flowing through a single generator, the number of windings in a single generator, the physical dimensions of the generator, the materials used to construct the generator, and other similar parameters for shape control (also known as generator geometry). In some implementations, coils with adjustable taps can be used to control the number of windings in the field generator 118.

[0039] In some implementations, the presence of a specific type of material (e.g., a conductive material) near the induced magnetic field may help distort or alter the shape of the field. Even the shape of the field may be bent or altered due to the presence of a permeable material. Generally, the random presence of conductive and / or permeable objects generates parasitic eddy current fields, thereby distorting the shape of the induced field. While such random presence of conductive and / or permeable materials is generally undesirable, in some implementations, such objects can be used to control the shape of the induced magnetic field. For example, conductive plate 120 can be used to shield or shape the induced magnetic field. In some implementations, multiple plates can be used. For example, multiple conductive plates can be used around, above, below, etc., the magnetic field. In some implementations, all plates are conductive; however, this is not always the case. For example, only some plates may be conductive. In the example shown, it is undesirable for the induced magnetic field to be below the plane of the field generator assembly 102. In this case, the conductive plate or shielding layer 120 significantly attenuates the magnetic field located below the field generator assembly 102, making the system insensitive to objects (e.g., metals or permeable materials) positioned below the field generator assembly 102. In some implementations, the conductive plate 120 may include a permeable (e.g., ferromagnetic) material to further attenuate the magnetic field located beneath the field generator assembly 102, for example, to provide the system with additional insensitivity to objects.

[0040] In some embodiments, the field generator assembly 102 also includes a cover layer 122 that substantially encloses the field generator 118. The cover layer 122 provides an interface surface for the patient during the procedure (e.g., sitting or lying on it). The cover layer 122 can be constructed of various types of materials or combinations of materials; for example, non-conductive or non-magnetic materials (such as plastic) can be incorporated into the cover layer 122. In some embodiments, the cover layer 122 can be configured to provide mechanical support to the field generator 118. For example, the field generator 118 can be embedded within a solid cover layer 122. In some embodiments, the cover layer 122 can simply cover the field generator 118. In some embodiments, if the field generator 118 is movable, the cover layer 122 can be configured to accommodate possible movements (e.g., translation, rotation, etc.) or modular combinations of the field generator. For example, a channel or path for a movable field generator can be defined within the cover layer 122.

[0041] Sensor assembly 106 is used to detect the magnetic field induced in region 104. In some embodiments, sensor assembly 106 may include one or more sensors (e.g., a sensor array) that combine one or more types of sensing technologies. For example, sensor assembly 106 may include a simple coil, several coils, one or more Hall sensors, fluxgate sensors, or other types of sensors capable of measuring characteristics of an electromagnetic field (e.g., magnetic flux, magnetic field difference, etc.). In some embodiments, the magnetic field generated by one or more field generators 118 induces an electromotive force (EMF) in sensor assembly 106. The measured EMF represents a local value of the magnetic field measured at the location and orientation of sensor assembly 106 in three-dimensional space defining region 104. In some embodiments, sensor assembly 106 includes multiple sensors, such as two different sensor coils, thereby potentially doubling the number of individual magnetic field measurements that can be achieved by sensor assembly 106. In some embodiments, sensor assembly 106 may include additional components (e.g., circuitry, electronics, etc.) for transmitting the measured signal to computing device 110. For example, sensor assembly 106 may include a transceiver configured to communicate with computing device 110 (e.g., via communication link 112, which may include a simple wired or wireless connection, or may utilize a wired or wireless network).

[0042] The sensor assembly 106 outputs signals representing several measured magnetic fields, corresponding to a single field sensed by activating one or more field generators 118 (e.g., different generator groups, such as generator pairs). Measuring several fields sensed within region 104 allows the sensor assembly 106 to be tracked in multiple degrees of freedom. For example, at least five different magnetic fields can be used to determine five degrees of freedom. Where the coordinates (x, y, z) and angles The three-dimensional position and orientation of the sensor relative to a reference are specified separately. In some embodiments, a greater number of fields can improve the accuracy of calculating the position of the sensor assembly 106. For example, the field generator assembly 102 can be configured such that eight or twelve different field generators 118 are used to sense different magnetic fields. In this configuration, the sensor assembly 106 will measure the corresponding field generated by each of the eight or twelve field generators 118, resulting in eight different field measurement results.

[0043] In some embodiments, if sensor assembly 106 includes two sensor coils, each coil can independently measure the strength of the magnetic field generated by a single set of field generators. Therefore, if eight different magnetic field measurements are required, and sensor assembly 106 includes two sensor coils, only four sets of field generators 118 are needed, because each coil will independently measure the magnetic field generated by each of the four sets of field generators 118, resulting in eight different magnetic field measurements. In other embodiments, if sensor assembly 106 includes two or more sensor coils, the coils can be considered as a set. Such a set allows the sensor coils to be positioned and oriented to optimize the magnetic field measurements.

[0044] In some embodiments, the measured magnetic field value depends on one or more system-related parameters (e.g., the gain factor of sensor assembly 106) and the three-dimensional position and orientation of the sensor coils. The number of field generators 118 and the number of sensor coils in sensor assembly 106 can vary depending on factors including the specific measurement application (e.g., measurements taken in an operating room). In this particular arrangement, computing device 110 determines the gain factor of sensor assembly 106, as well as the position and orientation of sensor assembly 106. Since the position and orientation of sensor assembly 106 are described by specifying multiple degrees of freedom (e.g., up to six degrees of freedom, including X-axis position, Y-axis position, Z-axis position, roll, pitch, and yaw), the number of matching position factors (e.g., six) can be calculated by computing device 110. Therefore, computing device 110 generates a number of combinations (e.g., seven) of factors representing position and gain. In some embodiments, the number of different field measurements required to determine these factors is one more than the number of factors determined. Therefore, if the computing device 110 determines the system gain factor and six position factors (i.e., degrees of freedom), totaling seven calculated factors, then a total of eight different field measurement results may be required. As mentioned above, this can be achieved using a single sensor coil and eight field generators 118 in the sensor assembly 106. Alternatively, a sensor assembly with two sensor coils and four field generators 118, or other similar variations, can also be used. Similarly, if the computing device 110 determines the system gain factor plus five position factors (i.e., five degrees of freedom), then a total of six calculated factors need to be determined. Again, as mentioned above, this can be accomplished using various configurations of the field generator sets and sensor coils.

[0045] When different field generators 118 are excited within their respective time periods, the computing device 110 may need to know details about the field generator that senses the detected magnetic field. In one arrangement, the computing device 110 may identify the field generator 118 that senses the magnetic field detected by the sensor assembly 106 based on information conveyed to the computing device 110 from the field generator assembly 102. In other embodiments, the timing of the field generator and sensor assembly is derived from a synchronization signal derived from one of the following: the computing device, the field generator assembly, or the sensor assembly. In some embodiments, timing information associated with the sensed field is used to identify the field generator 118 that generates the measured field. For example, the field generator assembly 102 may provide time-multiplexed power to different field generators 118 and provide timing information for determining the location of the sensor assembly 106 (e.g., this information is provided to the computing device 110 via the sensor assembly 106 and communication link 112).

[0046] In some embodiments, field generators 118 may be distributed within a field generator assembly such that at least two of the field generators 118 are offset in position, for example, relative to the remaining field generators 118. The field generators 118 may be distributed in any pattern to achieve the desired magnetic field shape, as shown below. Figure 5 Further description. Additionally, one or more field generators 118 may have angular orientation, for example, relative to field generator assembly 102 at an elevation angle, an azimuth angle, or a combination thereof. In some embodiments, computing device 110 may determine the angular orientation of field generator 118 based on measurements of the corresponding magnetic field generated by field generator 118.

[0047] In some arrangements, the field generating assembly 102 may drive each field generator 118 at different frequencies. To identify the specific field generator responsible for the measured field, the computing device 110 may decompose the measured electromagnetic field from the sensor assembly 106 into frequency components. These frequency components of the measured field are then matched to individual field generators.

[0048] Sensor assembly 106 sends the measured magnetic field value to computing device 110, which uses the geodetic magnetic field value to determine the position / orientation of sensor assembly 106. In some embodiments, this determination is performed by comparing the measured magnetic field value with a magnetic field value from a physical model.

[0049] The physical model can be a set of physical equations that determine the value of the magnetic flux measured by sensor assembly 106 as a function of several parameters. Therefore, the physical model can describe the magnetic flux values ​​that can be expected at different points within the measurement volume (e.g., region 104) due to the magnetic field induced by a known source (e.g., a field generator) at a known location. These parameters can then be calculated from the actual measurement results by comparing them with the physical model. These parameters may include, but are not limited to: the position, orientation, and magnetic moment of field generator 118; and the position, orientation, and sensitivity of sensor assembly 106. (Vector (x, y, z) and a pair of angles) The three-dimensional position and orientation of the sensor coils in sensor assembly 106 can be specified. If sensor assembly 106 has multiple coils, the parameters can include additional angular parameters (Ψ) that define the relative orientation of the coils in sensor assembly 106. Such parameters (e.g., a sixth degree of freedom) can be calculated using sensor assembly 106 with second coils on different axes (because multiple coils operating on the same axis may not allow sensing of probe rotation about that axis). The physical model can describe each field generator 118 as a magnetic multipole, such that the field measured by sensor assembly 106 is the associated multipole field (e.g., dipole or quadrupole). The multipole field value can depend on the system gain and the position, orientation, and magnetic moment “m” of each individual field generator 118. The measured value of the magnetic flux may depend on the position, size, orientation, and gain of the sensor assembly relative to the field generator 118.

[0050] In some implementations, the physical model may also be based on one or more fundamental assumptions about the environment near region 104. The model may, for example, assume pre-selected values ​​for the position and orientation of each field generator 118 and the absence of other sources or field-distorting objects. The presence of field-distorting objects (e.g., conductors, other field sources) may require additional parameters for the model to correctly predict field values. In some implementations, sensor assembly 106 may measure time-varying magnetic fields. Alternatively, if a static magnetic field needs to be measured, a fluxgate sensor, Hall effect sensor, or similar type of sensor may be used in sensor assembly 106 to provide measurements of a static (or constant) magnetic field. In some implementations, once measured by sensor assembly 106, the magnetic field value is provided to computing device 110, which calculates the appropriate system gain factor and the position / orientation of sensor assembly 106. In some implementations, sensor assembly 106 measures a set of magnetic fluxes to obtain a set of measured magnetic field values ​​B1-Bn, where “n” is greater than or equal to the number of factors being calculated (i.e., position and system gain).

[0051] In some arrangements, the measured field values ​​B1-Bn may have a nonlinear dependence on the three-dimensional position / orientation of sensor assembly 106 and a linear dependence on the system gain factor. The position and orientation of sensor assembly 106 can be determined by vectors (x, y, z) and at least one azimuth and polar angle. Each is specified separately. A vector (x, y, z) can be specified relative to a coordinate system 114 with a known origin. Although Figure 1 Cartesian coordinate system 114 is shown, but other types of coordinate systems, such as polar coordinates, may also be used. Furthermore, the system gain factor of sensor assembly 106 may be defined by a gain coefficient (g). Using a physical model of the "measured" field dependencies, computing device 110 can determine the gain factor, position, and orientation of sensor assembly 106 from the associated measured field values ​​B1-Bn. In some embodiments, the gain factor, position, and orientation may be calculated by computing device 110 via an iterative process. Such an iterative process is described in U.S. Application 09 / 892153, filed June 26, 2001 (published as U.S. Patent 6,625,563), which is incorporated herein by reference in its entirety.

[0052] A physical model can describe a pre-selected magnetic environment in a region (e.g., region 104) of sensor assembly 106. The pre-selected magnetic environment may or may not include contributions from nearby objects. The actual environment may vary, for example, due to the presence of field-torsuring objects that support eddy currents (e.g., a pair of surgical scissors, ferromagnetic materials, and active magnetic field sources). If the pre-selected environment differs from the actual environment, the model may need to incorporate additional parameters to predict the correct magnetic field values. In some embodiments, computing device 110 can be configured to detect and alert the user to the presence of potential measurement distortion conditions (e.g., by flashing information on a video monitor or via an audio alarm signal). In some cases, the effects of field-torsuring objects that support eddy currents can be reduced by using these eddy current sources as additional generators. While object 108 is in Figure 1 The object 108 is shown as a scalpel, but this is for illustrative purposes only. The object 108 could be other devices or tools, such as catheters, endoscopes, biopsy needles, body-mounted position sensors, etc.

[0053] The computing device 110 can be any computer configured to perform the functions described herein, such as a laptop or desktop computer. In some embodiments, the computing device 110 is a mobile computing unit, such as a smartphone, personal digital assistant, or handheld computing unit. In some embodiments, the computing device is a specialized computing device designed specifically for the purpose of controlling the generation of a magnetic field and calculating the position and orientation of a sensor coil from measured signals. The computing device 110 is configured to run a computer program article tangibly embodied in an information carrier (e.g., in a machine-readable storage device) for execution by a programmable processor; and features can be performed by a programmable processor executing instructions to perform the functions of the embodiments by manipulating input data and producing outputs. In some embodiments, the sensor assembly 106 and the computing device 110 are configured to communicate with each other via a communication link (e.g., Universal Serial Bus (USB), Bluetooth, Wireless USB, etc.). The features can be implemented in one or more computer programs that can execute on a programmable system including at least one programmable processor coupled to receive and transmit data and instructions from a data storage system, at least one input device, and at least one output device. A computer program includes a set of instructions that can be used directly or indirectly in a computer to perform an activity or produce a result. A computer program can be written in any programming language, including compiled or interpreted languages, and can be deployed in any form, including as a standalone program or as a module, component, subroutine, or other unit suitable for use in a computing environment.

[0054] For example, a suitable processor for executing a program's instructions includes general-purpose and special-purpose microprocessors. Generally, the processor receives instructions and data from read-only memory or random access memory, or both. The computing device 110 may include a processor for executing instructions and one or more memories for storing instructions and data.

[0055] The computing device 110 can communicate with the sensor assembly 106 over a communication link 112. In some embodiments, the communication link 112 may include a direct wired or wireless connection between the sensor assembly 106 and the computing device 110. Such a connection may include USB, Bluetooth, Wireless USB, etc. In other cases, the communication link 112 may include a wired or wireless network, such as a local area network (LAN), a metropolitan area network (MAN), or a wide area network (WAN), such as the Internet.

[0056] While the above system utilizes a sensor array to track the tool and a field generator component to generate a magnetic field, it is equally clear that the reverse of this configuration is also possible, i.e., all magnetic sensors can be replaced by generators, and all generators can be replaced by sensors.

[0057] Reference Figure 2 The schematic diagram depicts a top view of an example field generator assembly 200, which includes a plurality of individual field generators 202 distributed on a layer 204 (similar to...). Figure 1 The field generator 118 shown). Although Figure 2 Sixteen field generators 202 are shown distributed in a specific manner, but this is for illustrative purposes only and should not be considered limiting. More or fewer field generators 202 can be placed in the field generator assembly 200 in various other distributions, including distribution in multiple planes (e.g., vertically distributed planes). The layer 204 can be composed of elements as described above. Figure 1 The covering layer 122 is made of substantially the same material. In some embodiments, the layer 204 may be a conductive plate or a shielding layer (e.g., Figure 1 The top surface of the conductive plate 120 shown. One or more field generators 202 are connected to each other and to a main power supply via wires (not shown). These connections can be configured according to which generators are arranged to start simultaneously. The field generator assembly 200 may also include a circuit board 206. In some embodiments, the circuit board houses electronic modules that control the excitation or ignition of the field generators 202. The circuit board 206 may also include a memory that communicates with the computing device 106 and stores configuration data associated with the field generator assembly 200. The circuit board 206 may also serve as an interface to a power supply that powers the field generator assembly 200. In some embodiments, the computing device 106 may be implemented as part of the circuit board 206.

[0058] Different magnetic fields can be generated by orienting a magnetic field generator at different angles. Some of these generated magnetic fields are advantageous for tracking objects within a given area. Parallel magnetic fields near the field generator components, for example, can make it difficult to determine the sensor's position and orientation. Generally, the coils in a field generator are naturally placed as flat as possible, e.g., all in the same plane. However, near the field generator, this results in all magnetic fields being generated in the same direction. When magnetic fields are oriented in the same direction, at close range, fewer field generators contribute useful information about the sensor's position and orientation. Magnetic fields not oriented in the same direction are advantageous because the sensor can determine unique measurements based on each magnetic field, even at close range. Even at close range, magnetic fields provide different information to the sensor.

[0059] Figure 3This view shows a portion of a generator assembly 300, which includes two magnetic field generators 302 and 304 with the same angular orientation. Magnetic field generator 302 is shown with a longitudinal axis 306 (e.g., extending through the center of the generator) indicating its angular orientation. Magnetic field generator 304 is shown with a longitudinal axis 308 (e.g., extending through the center of the generator) indicating its angular orientation. Both magnetic field generators 302 and 304 are aligned in a plane 310. Plane 310 may represent, for example, a section of a table, wall, etc. In the example shown, longitudinal axis 306 is perpendicular to plane 310. Longitudinal axis 308 is also perpendicular to plane 310. Plane 310 is also shown with axis 312 to indicate its angular orientation. The bottom of each generator 302 and 304 is below plane 310, so the lower half of each magnetic field generator 302 and 304 is shown with dashed lines. Axis 312 is perpendicular to plane 310. Because each longitudinal axis 306, 308 has the same angular orientation as axis 312 of plane 310 (e.g., relative to coordinate system 314), the two magnetic field generators have the same angular orientation as plane 310 and the same orientation as each other. The generated magnetic fields have the same orientation because magnetic field generators 302, 304 have the same angular orientation. As mentioned above, when the magnetic fields are oriented in the same direction, fewer field generators contribute useful information about the sensor's position and orientation at close range.

[0060] Magnetic fields that are not oriented in the same direction are advantageous because the sensor can determine unique measurements based on each magnetic field, even at close range. Even at close range, magnetic fields will, for example, provide different information to the sensor. Figure 4 This view shows a portion of a generator assembly 400, which includes two magnetic field generators 402 and 404 with different angular orientations. Magnetic field generator 402 is shown with a longitudinal axis 406 (e.g., extending through the center of the generator) indicating its angular orientation. Magnetic field generator 404 is shown with a longitudinal axis 408 (e.g., extending through the center of the generator) indicating its angular orientation. Both magnetic field generators 402 and 404 are aligned in a plane 410. Plane 410 may represent, for example, a section of a table, wall, etc. In the figure, plane 410 extends through the center of magnetic field generators 402 and 404. The lower half of each magnetic field generator 402 and 404 is positioned below plane 410 and is shown in dashed lines.

[0061] In the example shown, each longitudinal axis 406, 408 has a different angular orientation relative to plane 410. To demonstrate how magnetic field generators 402, 404 have different angular orientations relative to plane 410, plane 410 is also shown with axis 412 to illustrate the angular orientation of plane 410. Axis 412 is perpendicular to plane 410. Another axis 422 is perpendicular to plane 410 and extends through the center of magnetic field generator 402. The longitudinal axis 406 of generator 402 is tilted at an angle 414 from axis 422. Magnetic fields that are not oriented in the same direction (i.e., tilted) are advantageous because the sensor can determine unique measurements based on each magnetic field, even at close range.

[0062] Angular orientation and tilt can be represented in various ways. Angular orientation, for example, can be represented using a Cartesian coordinate system. Coordinate system 420 includes the X-axis, Y-axis, and Z-axis. Line 426 shows the azimuth angle (θ) in coordinate system 420. The azimuth angle of line 426 shows the rotation from the x-axis to the y-axis (i.e., around the z-axis). Another line 428 shows the elevation angle (i.e.,...) in coordinate system 420. Line 428 shows the deviation from the z-axis. Therefore, any point in coordinate system 420 can be defined by azimuth and elevation. Angular orientation can also be defined by azimuth and elevation. The angle 414 separating the longitudinal axis 406 from axis 422 can be defined by azimuth and elevation. The longitudinal axis 408 also has a different angular orientation than plane 410. Axis 424 is perpendicular to plane 410 and extends through the center of magnetic field generator 404. The longitudinal axis 408 of generator 404 is tilted at an angle 416 from axis 424. The angle 414 separating the longitudinal axis 406 from axis 422 can be defined by azimuth and elevation (e.g., relative to coordinate system 420).

[0063] Furthermore, magnetic field generator 402 is oriented at a different angle than magnetic field generator 404. The longitudinal axis 406 of magnetic field generator 402 is tilted to the left of axis 422. The longitudinal axis 406 has, for example, an azimuth angle corresponding to the left of axis 422. Simultaneously, the longitudinal axis 408 of magnetic field generator 404 is tilted to the right of axis 424. The longitudinal axis 408 has an azimuth angle corresponding to the right of axis 424. These different azimuth angles cause magnetic field generators 402 and 404 to tilt in different directions. The resulting magnetic fields are not parallel because magnetic field generators 402 and 404 have different angular orientations.

[0064] Magnetic field generators 402 and 404 are oriented at opposite angles to each other. Magnetic field generators 402 and 404 may have azimuth angles that cause the magnetic field generators to point away from each other. However, in some embodiments, magnetic field generators 402 and 404 are oriented at angles pointing towards each other. Magnetic field generator 402 may, for example, have an azimuth angle corresponding to the right of axis 422. Simultaneously, magnetic field generator 404 may have an azimuth angle corresponding to the left of axis 424. These exemplary azimuth angles will cause the magnetic field generators to point towards each other. In other embodiments, the magnetic field generators are tilted in a direction that is neither towards nor away from each other (e.g., the magnetic field generators may have various azimuth angles). Magnetic field generators can be oriented at any angle in any direction. Furthermore, the magnetic field generators may have a range of elevation angles. In some embodiments, the magnetic field generators may have different elevation angles and different azimuth angles. In other embodiments, the magnetic field generators may have the same azimuth angle and different elevation angles.

[0065] In the example shown, angle 414 can be a relatively small angle (e.g., 1 to 15 degrees). In some embodiments, a small elevation angle can be advantageous because the magnetic field generator is more aligned with the surface of the plane. A large angle 414 would, for example, cause the magnetic field generator to change further from the plane 410. A magnetic field generator that is more aligned with the surface of the plane is advantageous for thin magnetic components. A magnetic field generator with a large angle 414 that changes further from the plane increases the thickness of the magnetic component. In some embodiments, angle 414 can be a large angle (e.g., greater than 15 degrees).

[0066] Figure 5 Demonstrates field generator component 500. Field generator component 500 can be used in magnetic tracking systems (e.g., similar to...). Figure 1 The magnetic tracking system 100). The field generator assembly 500 includes a housing 502 whose shape can be adapted to the field generator 504 (e.g., as shown in the image). Figure 4 (Field generator). The housing 502 is generally flat, so the generator is laid on a flat surface. Various types of materials can be used to produce the housing 502; for example, non-metallic materials (e.g., plastic), metallic materials (e.g., steel), combinations of materials, etc., can be used. Different geometries, shapes, and sizes can also be utilized.

[0067] Furthermore, each generator is positioned in a single well (e.g., a groove) 506. In other embodiments, each well may use a different geometry (e.g., triangle, hexagon, octagon, etc.). In the illustrated embodiment, all individual wells have the same geometry. However, in other embodiments, different wells may have different geometries. Furthermore, in the illustrated embodiment, each generator is located in a single well 506. However, in other embodiments, multiple generators may be positioned in one well. In some embodiments, the wells may be positioned in a specific pattern (e.g., array, concentric circles, etc.). In other embodiments, the wells may not be positioned in a pattern. Parameters such as geometry, number of wells, number of generators in each well, and relative distance and orientation of the wells can be adjusted to produce a field with the desired shape.

[0068] Each field generator 504 is oriented at an angle relative to the housing and slightly different from each other (e.g., relative to the housing 502 and offset from each other by a small angle). Each field generator 504 may, for example, include different azimuth and different elevation angles. A first field generator may, for example, have a first angular orientation relative to coordinate system 508, a second field generator may have a second angular orientation relative to coordinate system 508, a third field generator may have a third angular orientation relative to coordinate system 508, and so on. In some embodiments, each field generator 504 may have an angular orientation pointing towards the center of component 500 (e.g., each field generator 504 may have an azimuth that tilts the field generator toward the center of the component). In other embodiments, each field generator 504 may have an angular orientation pointing away from the center of component 500 (e.g., each field generator 504 may have an azimuth that tilts the field generator away from the center of the component). In some embodiments, some field generators may have an angular orientation pointing towards the center of component 500, while others may have an angular orientation pointing away from the center of the component. Field generators located immediately adjacent to the center of component 500 may point towards the center of component 500, while field generators closer to the edge of component 500 may have an angular orientation pointing away from the center of the component (i.e., towards the edge of the component). In some embodiments, a subset of field generators 504 (e.g., one generator, two generators, three generators, etc.) have different angular orientations, while other field generators 504 have the same angular orientation. In other embodiments, each field generator 504 has a different angular orientation. The field generators 504 have different angular orientations to generate magnetic fields in different directions. Each field generator 504 has a connection line 510 leading to an external connector 512. The external connector 512 can, for example, connect the field generators 504 to a power source.

[0069] Reference Figure 6The image shows a top view of an example of a single field generator 600. The field generator 600 can be designed as a flat coil with an opening at its center. Figure 2 As shown, a thin generator 600 can be used to implement a flat field generator assembly 200. The flat field generator can be very thin. The field generator 600 includes, for example, a coil, the thickness of which can be, for example, about 2 mm to about 3 mm. The outer diameter 602 of the coil 600 can be, for example, about 84 mm. The inner diameter 604 of the coil 600 can be, for example, about 51 mm. In some embodiments, the field generator can be other shapes. The field generator can be, for example, a quaternary field generator (e.g., the shape of the field generator is parabolic). In another example, the field generator is planar spiral (e.g., the field generator is a spiral coil without plates).

[0070] Reference Figure 7 The diagram illustrates an example of a field induced by a pair of generators 702 and 704. In this particular example, the current applied to each of generators 702 and 704 flows in the same direction and produces magnetic flux lines (illustrated using corresponding lines 706 and 708). Generators 702 and 704 also have different angular orientations relative to each other. Magnetic field generator 702 is shown with a longitudinal axis 710 (e.g., extending through the center of the generator), which shows the angular orientation of magnetic field generator 702. Magnetic field generator 704 is shown with a longitudinal axis 712 (e.g., extending through the center of the generator), which shows the angular orientation of magnetic field generator 704. Parallel axes 714 and 722 illustrate how magnetic field generators 702 and 704 have different angular orientations. Axis 714 is perpendicular to the plane connecting the centers of magnetic field generators 702 and 704. The longitudinal axis 710 is tilted at an angle 716 relative to axis 714 (e.g., relative to coordinate system 720). Angle 716 can be defined by azimuth and elevation angles. The longitudinal axis 710 is tilted to the left of axis 714. Additionally, the longitudinal axis 712 is tilted at an angle 718 to axis 722. The longitudinal axis 712 is tilted to the right of axis 722. Therefore, the axes of generators 702 and 704 are not parallel, and the resulting magnetic field lines 706 and 708 are not parallel. This non-parallel magnetic field is advantageous; the sensor, for example, will determine the unique measurement from each magnetic field 706 and 708, regardless of position. Even very close to generators 702 and 704, the magnetic fields are not parallel because generators 702 and 704 are tilted. This allows the sensor to distinguish each magnetic field 706 and 708 from each corresponding generator 702 and 704.

[0071] In some arrangements, the field generation components can drive each field generator at different frequencies. To identify the specific field generator responsible for the measured field, the computing device can decompose the measured EMF from the sensor components into frequency components. These frequency components of the measured field are then matched to individual field generators. An example of this frequency division multiplexing excitation scheme is shown in... Figure 8 As shown in the figure. In this example, a given generator (e.g., field generator 1 shown in the figure) is excited by AC current 802 at a first frequency. Another field generator (e.g., pair 4) is also simultaneously excited by another AC current 804 having a second frequency different from the first frequency. Similarly, other generators can also be excited using AC current operating at other frequencies.

Claims

1. A magnetic tracking system, comprising: A field generator assembly defining a planar surface and including a magnetic field generator for generating a plurality of magnetic fields, wherein each magnetic field is generated by a corresponding magnetic field generator from the magnetic field generators of the field generator assembly, at least one of the magnetic field generators having a first angular orientation relative to the planar surface, and at least another of the magnetic field generators having a second angular orientation relative to the planar surface, the second angular orientation being different from the first angular orientation, wherein the first angular orientation includes a first azimuth angle and a first elevation angle, and the second angular orientation includes a second azimuth angle and a second elevation angle; Magnetic sensors for measuring the plurality of magnetic fields; and A computing device configured to calculate the position and orientation of a magnetic sensor within a magnetic field being measured by the magnetic sensor.

2. The magnetic tracking system according to claim 1, wherein, The magnetic field generator includes at least one of the following: (i) a wound electromagnetic coil, (ii) a quaternary electromagnetic coil, or (iii) a planar spiral.

3. The magnetic tracking system according to claim 1, wherein, The magnetic field generators are distributed on the field generator assembly, such that at least two of the magnetic field generators are offset in position.

4. The magnetic tracking system according to claim 1, wherein, The computing device is configured to determine a first angular orientation and a second angular orientation.

5. The magnetic tracking system according to claim 1, further comprising a conductive plate below the field generator assembly, wherein, The conductive plate contains a permeable material.

6. The magnetic tracking system according to claim 1, wherein, The magnetic field generators have the same elevation angle and different azimuth angles.

7. The magnetic tracking system according to claim 1, further comprising a third magnetic field generator having a third angular orientation different from the first angular orientation and the second angular orientation.

8. The magnetic tracking system according to claim 1, wherein, The first angle orientation is in the opposite direction to the second angle orientation.

9. The magnetic tracking system according to claim 1, wherein, The second elevation angle is different from the first elevation angle.

10. The magnetic tracking system according to claim 1, wherein, The first angular orientation is between 1 degree and 15 degrees relative to the planar surface, and the second angular orientation is between 1 degree and 15 degrees relative to the planar surface.

11. A magnetic tracking device, comprising: Structural surfaces used to support a part of the patient during medical procedures; as well as A field generator assembly that defines a planar surface and includes a magnetic field generator for generating a magnetic field to form a measurement volume; Wherein, at least one of the magnetic field generators is oriented at a first angle relative to the planar surface, and at least another of the magnetic field generators is oriented at a second angle relative to the planar surface, the second angle being different from the first angle; and The first angular orientation includes a first azimuth angle and a first elevation angle, and the second angular orientation includes a second azimuth angle and a second elevation angle.

12. The magnetic tracking device according to claim 11, further comprising a conductive plate below the planar surface.

13. The magnetic tracking device according to claim 11, wherein, At least two magnetic field generators are oriented at different angles relative to each other.

14. The magnetic tracking device according to claim 13, wherein, The at least two magnetic field generators are oriented at opposite angles to each other.

15. The magnetic tracking device according to claim 13, wherein, The at least two magnetic field generators are oriented at an angle greater than 15 degrees from the plane surface.

16. The magnetic tracking device according to claim 13, wherein, The at least two magnetic field generators are oriented at an angle pointing towards the center of the planar surface.

17. The magnetic tracking device according to claim 13, wherein, The at least two magnetic field generators are oriented at an angle away from the center of the planar surface.

18. The magnetic tracking device according to claim 13, wherein, The at least two magnetic field generators are oriented at the same angle relative to the planar surface.

19. The magnetic tracking device according to claim 13, wherein, The first angular orientation is between 1 degree and 15 degrees relative to the planar surface, and the second angular orientation is between 1 degree and 15 degrees relative to the planar surface.

20. The magnetic tracking device according to claim 11, wherein, Multiple magnetic field generators are distributed on the field generator assembly, such that at least two of the magnetic field generators are offset in position.

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