Electromagnetic field gradient coil arrangement for micro device positioning

Abstract

An apparatus for generating magnetic field gradients, comprising (a) a first planar electromagnetic coil set configured to generate a first magnetic field gradient with respect to a first axis, (b) a second planar electromagnetic coil set configured to generate a second magnetic field gradient with respect to a second axis orthogonal to the first axis, (c) a third planar electromagnetic coil set configured to generate a third magnetic field gradient with respect to a third axis orthogonal to the first and second axes, and (d) a controller configured to selectively power the first, second, and / or third electromagnetic coil sets to sequentially generate positioning magnetic field gradients with respect to each of the first, second, and third axes, at least a portion of each positioning magnetic field gradient having a magnetic field magnitude that monotonically varies along the respective axis.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Provisional Application No. 62 / 934763, filed November 13, 2019, entitled “Real-Time GI Tract Monitoring with High Precision in 3D Using ATOMS Microchips”, and U.S. Provisional Application No. 62 / 934767, filed November 13, 2019, entitled “Magnetic Gradient Coil Design For Micro-Device Localization”, which are incorporated herein by reference.

[0003] Statement on Federally Funded Research

[0004] This invention was completed with the support of the government, under grant number CBET1823036 from the National Science Foundation of China. The government has certain rights to this invention. Technical Field

[0005] This application generally relates to an apparatus for generating a magnetic field gradient along mutually orthogonal axes. Background Technology

[0006] A key research direction in contemporary science envisions introducing miniature devices into the human body for the diagnosis and treatment of localized diseases. Significant progress has been made towards this vision, but the practical realization of miniature biosensors and actuators in living biology and medicine remains largely absent. Meanwhile, the demand for such devices is increasing as there is a growing awareness that many prevalent diseases involve localized pathologies requiring localized diagnosis and treatment (e.g., neurodegeneration, cancer, mental illness, and atherosclerosis). Notably, the recently launched National Brain Initiative, which aims to map the functional functions of the mammalian brain, has generated a need for distributed miniature sensors capable of recording neural activity on a large scale.

[0007] Miniature sensors may require components that: (a) convert local (in vivo) physiological information into electrical signals, (b) transmit these signals to an external receiver (outside the body), and (c) be located at specific sites in the body and differentiated from each other. Significant progress has been made on the first two requirements. For example, miniaturized devices have been developed to measure action potentials and neurotransmitters, the release of tumor antigens, and the presence of viral pathogens. Furthermore, advancements in integrated circuits and antennas have led to the development of smaller, more energy-efficient devices capable of high-bandwidth data transmission. However, the requirement for effective localization and differentiation of transmitters remains poorly addressed due to the limited accuracy and scalability of existing receiver proximity-based localization schemes. This is a significant limitation for scenarios ranging from individual localization of implantable biosensors and intravascular guidewires to distributed implantable sensors that hoist neural activity and immune cell internalization reporter substances to diseased tissues. Indeed, in these and other applications, differentiating between different sensors is necessary, for example, to determine which region of the body's organs their readouts originate from.

[0008] In particular, there is currently no effective method to precisely locate and communicate with miniature devices deep within the body. Existing methods based on near-field radio frequency (RF) electromagnet interactions have only limited localization and communication capabilities with a single implant because the strong dependence of RF signals on tissue properties (specifically, body composition) greatly reduces their spatial resolution and makes it difficult to interface with multiple devices simultaneously. Furthermore, localization using imaging procedures (such as X-ray computed tomography) exposes the patient to ionizing radiation and only allows visualization of devices at specific locations within the body, without the ability to send or receive information from them. Summary of the Invention

[0009] The exemplary embodiments described herein are innovative in nature, none of which are indispensable or solely responsible for their desired properties. The following description and accompanying drawings illustrate certain illustrative embodiments of this disclosure, indicating several exemplary ways in which the various principles of this disclosure can be implemented. However, the illustrative examples are not exhaustive of the many possible embodiments of this disclosure. Some advantageous features will now be summarized without limiting the scope of the claims. Other objects, advantages, and novel features of this disclosure will be set forth in the following detailed description of this disclosure when considered in conjunction with the accompanying drawings, which are intended to illustrate and not limit the invention.

[0010] One aspect of the present invention relates to an apparatus for generating a magnetic field gradient, comprising: a first planar electromagnetic coil group configured to generate a first magnetic field gradient relative to a first axis; a second planar electromagnetic coil group configured to generate a second magnetic field gradient relative to a second axis orthogonal to the first axis; a third planar electromagnetic coil group configured to generate a third magnetic field gradient relative to a third axis orthogonal to the first and second axes, the first, second, and third planar electromagnetic coil groups being arranged perpendicularly to the third axis; and a controller configured to selectively supply power to the first, second, and / or third planar electromagnetic coil groups to sequentially generate positioning magnetic field gradients relative to each of the first, second, and third axes, at least a portion of each positioning magnetic field gradient having a magnetic field amplitude that monotonically varies along the respective axis.

[0011] In one or more embodiments, the first planar electromagnetic coil group, the second planar electromagnetic coil group, and the third planar electromagnetic coil group are stacked. In one or more embodiments, the first planar electromagnetic coil group includes clockwise and counterclockwise helical windings arranged adjacent to each other. In one or more embodiments, the clockwise and counterclockwise helical windings are each formed from their respective conductors. In one or more embodiments, the clockwise and counterclockwise helical windings each extend in a direction parallel to a second axis, and each clockwise and counterclockwise helical winding has an axis of symmetry parallel to a first axis, and the axis of symmetry of the clockwise and counterclockwise helical windings are aligned. In one or more embodiments, the first planar electromagnetic coil group has a width parallel to the first axis, and (a) at least a portion of the magnetic field gradient having a monotonically varying magnetic field amplitude along the first axis is in the range of about 1:2 to about 3:4 to (b) the width of the first planar electromagnetic coil group. In one or more embodiments, this ratio is about 2:3.

[0012] In one or more embodiments, the clockwise spiral winding is a first clockwise spiral winding, the counterclockwise spiral winding is a first counterclockwise spiral winding, and the second planar electromagnetic coil group includes a second clockwise spiral winding and a second counterclockwise spiral winding arranged adjacent to each other. In one or more embodiments, the first clockwise spiral winding, the second clockwise spiral winding, the first counterclockwise spiral winding, and the second counterclockwise spiral winding are all formed by corresponding conductors. In one or more embodiments, a first clockwise spiral winding and a first counterclockwise spiral winding each extend in a direction parallel to the second axis, each having an axis of symmetry parallel to the first axis, the axis of symmetry of the first clockwise spiral winding being aligned with the axis of symmetry of the first counterclockwise spiral winding; a second clockwise spiral winding and a second counterclockwise spiral winding each extend in a direction parallel to the first axis, each having an axis of symmetry parallel to the second axis, and the axis of symmetry of the second clockwise spiral winding being aligned with the axis of symmetry of the second counterclockwise spiral winding.

[0013] In one or more embodiments, a first planar electromagnetic coil group has a width parallel to a first axis, and a second planar electromagnetic coil group has a length parallel to a second axis. The ratio of (a) at least a portion of the magnetic field amplitude, which is monotonically varying along the first axis and which is the location of the magnetic field gradient, to (b) the width of the first planar electromagnetic coil group is in the range of about 1:2 to about 3:4, and the ratio of (c) at least a portion of the magnetic field amplitude, which is monotonically varying along the second axis and which is the length of the second planar electromagnetic coil group is in the range of about 1:2 to about 3:4. In one or more embodiments, the ratio of (a) at least a portion of the magnetic field amplitude, which is monotonically varying along the first axis and which is the location of the magnetic field gradient, to (b) the width of the first planar electromagnetic coil group is about 2:3, and the ratio of (c) at least a portion of the magnetic field amplitude, which is monotonically varying along the second axis and which is the length of the second planar electromagnetic coil group is about 2:3.

[0014] In one or more embodiments, the third planar electromagnetic coil assembly includes a helical winding in a ring-like form. In one or more embodiments, the ring has an outer diameter measured parallel to the first axis, and the ratio of (e) at least a portion of the magnetic field gradient, having a magnetic field amplitude that monotonically varies along the third axis, to (f) the outer diameter of the ring is in the range of about 1:4 to about 2:5. In one or more embodiments, the ratio of (e) at least a portion of the magnetic field gradient, having a magnetic field amplitude that monotonically varies along the third axis, to (f) the outer diameter of the ring is about 1:3.

[0015] In one or more embodiments, the controller is configured to power only the first and third planar electromagnetic coil groups simultaneously to generate a first positioning magnetic field gradient relative to a first axis. In one or more embodiments, the first positioning magnetic field gradient includes the total magnetic field generated by the first and third planar electromagnetic coil groups. In one or more embodiments, the controller is configured to power only the second and third planar electromagnetic coil groups simultaneously to generate a second positioning magnetic field gradient relative to a second axis. In one or more embodiments, the second positioning magnetic field gradient includes the total magnetic field generated by the second and third planar electromagnetic coil groups. In one or more embodiments, the controller is configured to power only the third planar electromagnetic coil group to generate a third positioning magnetic field gradient relative to a third axis. In one or more embodiments, the controller is configured to selectively power on each positioning magnetic field gradient according to a predetermined timing sequence.

[0016] Another aspect of the invention relates to a manufacturing method comprising: forming a first planar electromagnetic coil group configured to generate a first magnetic field gradient relative to a first axis; forming a second planar electromagnetic coil group configured to generate a second magnetic field gradient relative to a second axis orthogonal to the first axis; forming a third planar electromagnetic coil group configured to generate a third magnetic field gradient relative to a third axis orthogonal to the first and second axes; arranging the first, second, and third planar electromagnetic coil groups perpendicularly along the third axis; and electrically connecting a controller to the first, second, and third planar electromagnetic coil groups, the controller being configured to selectively supply power to the first, second, and / or third planar electromagnetic coil groups to generate a localized magnetic field gradient relative to each of the first, second, and third axes, at least a portion of each localized magnetic field gradient having a magnetic field amplitude that monotonically varies along the respective axis.

[0017] In one or more embodiments, forming a first planar electromagnetic coil group includes: forming a first clockwise spiral winding with a first conductor, the first clockwise spiral winding having an axis of symmetry parallel to a first axis; forming a first counterclockwise spiral winding with a second conductor, the first counterclockwise spiral winding having an axis of symmetry parallel to the first axis; placing the first clockwise spiral winding adjacent to the first counterclockwise spiral winding; and aligning the axis of symmetry of the first clockwise spiral winding with the axis of symmetry of the first counterclockwise spiral winding.

[0018] In one or more embodiments, forming a second planar electromagnetic coil group includes: forming a second clockwise spiral winding with a third conductor, the second clockwise spiral winding having an axis of symmetry parallel to a second axis orthogonal to a first axis; forming a second counterclockwise spiral winding with a fourth conductor, the second counterclockwise spiral winding having an axis of symmetry parallel to the second axis; placing the second clockwise spiral winding adjacent to the second counterclockwise spiral winding; and aligning the axis of symmetry of the second clockwise spiral winding with the axis of symmetry of the second counterclockwise spiral winding.

[0019] In one or more embodiments, forming a third planar electromagnetic coil group includes forming a helical winding with a fifth conductor having a ring shape, the helical winding having an axis of symmetry parallel to a third axis orthogonal to the first and second axes.

[0020] In one or more embodiments, the method further includes elongating a first clockwise helical winding and a first counterclockwise helical winding in a direction parallel to the second axis. In one or more embodiments, the method further includes elongating a second clockwise helical winding and a second counterclockwise helical winding in a direction parallel to the first axis. In one or more embodiments, the method further includes vertically stacking a first planar electromagnetic coil group, a second planar electromagnetic coil group, and a third planar electromagnetic coil group.

[0021] In one or more embodiments, the method further includes configuring a controller to have a first setting that supplies power only to a first planar electromagnetic coil group and a third planar electromagnetic coil group to generate a first positioning magnetic field gradient relative to a first axis, at least a portion of which has a magnetic field amplitude that monotonically varies along the first axis. In one or more embodiments, the method further includes configuring a controller to have a second setting that supplies power only to a second planar electromagnetic coil group and a third planar electromagnetic coil group to generate a second positioning magnetic field gradient relative to a second axis, at least a portion of which has a magnetic field amplitude that monotonically varies along the second axis. In one or more embodiments, the method further includes configuring a controller to have a third setting that supplies power only to a third planar electromagnetic coil group to generate a third positioning magnetic field gradient relative to a third axis, at least a portion of which has a magnetic field amplitude that monotonically varies along the third axis. In one or more embodiments, the method further includes configuring a controller to supply power in a predetermined timing sequence according to the first, second, and third settings to encode the corresponding first, second, and third positioning magnetic field gradients.

[0022] Another aspect of the present invention relates to a method for generating a magnetic field gradient, comprising: electrically connecting a controller to (a) a first planar electromagnetic coil group configured to generate a first magnetic field gradient relative to a first axis, (b) a second planar electromagnetic coil group configured to generate a second magnetic field gradient relative to a second axis, and (c) a third planar electromagnetic coil group configured to generate a third magnetic field gradient relative to a third axis, wherein the first axis, the second axis, and the third axis are orthogonal to each other, and wherein the first planar electromagnetic coil group, the second planar electromagnetic coil group, and the third planar electromagnetic coil group are arranged perpendicularly to the third axis; using the controller, supplying power to (a) and (c) simultaneously only at a first time; using the controller, supplying power to (b) and (c) simultaneously only at a second time different from the first time; and using the controller, supplying power to (c) only at a third time different from the first time and the second time.

[0023] In one or more embodiments, simultaneously supplying power to (a) and (c) only includes generating a first combined magnetic field gradient relative to a first axis, at least a portion of which has a magnetic field amplitude that varies monotonically along the first axis. In one or more embodiments, the first planar electromagnetic coil group has a width parallel to the first axis, and the ratio of (a) at least a portion of the first combined magnetic field gradient having a magnetic field amplitude that varies monotonically along the first axis to (b) the width of the first electromagnetic coil group is in the range of about 1:2 to about 3:4.

[0024] In one or more embodiments, simultaneously supplying power to (b) and (c) only includes generating a second combined magnetic field gradient relative to the second axis, the second combined magnetic field gradient having a monotonically varying amplitude over at least a portion of the second electromagnetic coil assembly. In one or more embodiments, the second planar electromagnetic coil assembly has a length parallel to the second axis, and the ratio of (a) at least a portion of the second combined magnetic field gradient having a monotonically varying magnetic field amplitude along the first axis to (b) the length of the second electromagnetic coil assembly is in the range of about 1:2 to about 3:4.

[0025] In one or more embodiments, supplying power only to (c) includes generating a third magnetic field gradient, at least a portion of which has a magnetic field amplitude that varies monotonically along a third axis. In one or more embodiments, the ring has an outer diameter measured parallel to the first axis, and the ratio of (e) at least a portion of the third magnetic field gradient having a magnetic field amplitude that varies monotonically along the third axis to (f) the outer diameter of the ring is in the range of about 1:4 to about 2:5.

[0026] In one or more embodiments, the method further includes repeating the following steps according to a predetermined timing sequence: supplying power to (a) and (c) simultaneously only at a first time, supplying power to (b) and (c) simultaneously only at a second time, and supplying power to (c) only at a third time.

[0027] Another aspect of the invention relates to a system comprising: a three-dimensional magnetic field generator configured to sequentially generate: a first magnetic field gradient along a first axis, at least a portion of which has a magnetic field amplitude that monotonically varies along the first axis; a second magnetic field gradient along a second axis orthogonal to the first axis, at least a portion of which has a magnetic field amplitude that monotonically varies along the second axis; and a third magnetic field gradient along a third axis orthogonal to the first and second axes, at least a portion of which has a magnetic field amplitude that monotonically varies along the third axis; and a magnetic sensor device comprising: a three-dimensional magnetic sensor whose outputs a first magnetic field, a second magnetic field, and a third magnetic field gradient respectively corresponding to the first magnetic field gradient, the second magnetic field gradient, and the third magnetic field gradient. The device includes: a measurement of a first magnetic field, a measurement of a third magnetic field; a controller electrically coupled to a three-dimensional magnetic sensor, the controller generating a magnetic sensor output signal encoding the measurements of the first, second, and third magnetic fields; a device antenna electrically coupled to the controller, the antenna broadcasting the magnetic sensor output signal; a power supply electrically coupled to the three-dimensional magnetic sensor and the controller; and a receiver, including: a microprocessor; a receiver antenna receiving the magnetic sensor output signal from the device antenna; and a microprocessor-accessible non-volatile memory including computer-readable instructions that, when executed by the processor, cause the microprocessor to use the measurements of the first, second, and third magnetic fields to determine the three-dimensional position of the magnetic sensor device.

[0028] In one or more embodiments, the non-volatile memory includes a lookup table that includes multiple measurements of a first magnetic field gradient, a second magnetic field gradient, and a third magnetic field gradient at a known three-dimensional location.

[0029] Another aspect of the present invention relates to a method for determining the relative position of an object using a magnetic field gradient, comprising: using a three-dimensional magnetic field generator to sequentially generate: a first magnetic field gradient along a first axis, at least a portion of which has a magnetic field amplitude that monotonically varies along the first axis, the first magnetic field gradient being generated at a first time; a second magnetic field gradient along a second axis orthogonal to the first axis, at least a portion of which has a magnetic field amplitude that monotonically varies along the second axis, the second magnetic field gradient being generated at a second time different from the first time; and a third magnetic field gradient along a third axis orthogonal to the first and second axes, at least a portion of which has a magnetic field amplitude that monotonically varies along the third axis, the third magnetic field gradient being generated at a second time different from the first and second times. A third time is generated; using a magnetic sensor device including a three-dimensional magnetic sensor and a device antenna, a first total magnetic field is measured at the three-dimensional position of the magnetic sensor device at a first time; a second total magnetic field is measured at the three-dimensional position of the magnetic sensor device at a second time; a third total magnetic field is measured at the three-dimensional position of the magnetic sensor device at a third time; and the measurements of the first, second, and third total magnetic fields are broadcast using the device antenna; and the measurements of the first, second, and third total magnetic fields are received using a receiver including a microprocessor and a receiver antenna; and the three-dimensional position of the magnetic sensor device is determined using the measurements of the first, second, and third total magnetic fields using the receiver antenna. Attached Figure Description

[0030] To gain a more comprehensive understanding of the nature and advantages of this concept, please refer to the detailed description and accompanying drawings of the preferred embodiments.

[0031] Figure 1 This is a block diagram of an apparatus for generating a magnetic field gradient according to an embodiment.

[0032] Figure 2A , 2B 2C is a simplified view of the total magnetic field gradient used to encode the device location.

[0033] Figure 3 This is a schematic top view of the first electromagnetic coil assembly according to an embodiment.

[0034] Figure 4 yes Figure 3 The side view of the first electromagnetic coil assembly shown.

[0035] Figure 5 This is a graph showing an example of the Z component of the magnetic field generated by the first electromagnetic coil group.

[0036] Figure 6 This shows the X component (B) of the magnetic field generated by the first electromagnetic coil group. Xx (The example is a graph.)

[0037] Figure 7 This illustrates the total magnetic field (||B) generated by the first electromagnetic coil group according to an embodiment of the present disclosure. X A graph of an example of ||).

[0038] Figure 8 This is a schematic top view of the second electromagnetic coil assembly according to an embodiment.

[0039] Figure 9 This shows the Z component (B) of the magnetic field generated by the second electromagnetic coil group. Yz (The example is a graph.)

[0040] Figure 10 This shows the Y component (B) of the magnetic field generated by the second electromagnetic coil group. Yy (The example is a graph.)

[0041] Figure 11 This shows the total magnetic field (||B) generated by the second electromagnetic coil group. Y A graph of the example of ||).

[0042] Figure 12 This is a schematic perspective view of the third electromagnetic coil assembly according to an embodiment.

[0043] Figure 13 This shows the Z component (B) of the magnetic field generated by the third electromagnetic coil group. Zz (The example is a graph.)

[0044] Figure 14 This shows the X component (B) of the magnetic field generated by the third electromagnetic coil group. Zx (The example is a graph.)

[0045] Figure 15 This shows the monotonically changing total magnetic field (||B) generated by the third electromagnetic coil group. Z A graph of the example of ||).

[0046] Figure 16 It is a graph showing the Z component of the combined magnetic field generated simultaneously by the first and third electromagnetic coil groups.

[0047] Figure 17 This illustrates the total magnetic field (||B) generated simultaneously by the first and third electromagnetic coil groups. X A graph of an example of ||).

[0048] Figure 18 This illustrates the total magnetic field (||B) simultaneously generated by the second and third electromagnetic coil groups. Y A graph of the example of ||).

[0049] Figure 19This shows the total magnetic field (||B) plotted for different Y values. X The curve of ||).

[0050] Figure 20 This shows the total magnetic field (||B) plotted for different Z values. X The curve of ||).

[0051] Figure 21 This shows the total magnetic field (||B) plotted for different x values. y The curve of ||).

[0052] Figure 22 This shows the total magnetic field (||B) plotted for different Z values. y The curve of ||).

[0053] Figure 23 It is a timing diagram of the current passing through the first electromagnetic coil group, the second electromagnetic coil group and the third electromagnetic coil group respectively according to the embodiment.

[0054] Figure 24 This is a block diagram of a system for positioning the relative position of a magnetic sensor device according to an embodiment.

[0055] Figure 25 This is a flowchart of a method for determining the relative three-dimensional position of a magnetic sensor device according to an embodiment.

[0056] Figure 26 This is a flowchart of a method for determining the relative three-dimensional position of a magnetic sensor device according to an embodiment.

[0057] Figure 27 An example of a lookup table that can be used to determine the relative three-dimensional position of a magnetic sensor device according to an embodiment is shown.

[0058] Figure 28 This is a flowchart of a method for manufacturing an apparatus for generating a monotonically changing magnetic field gradient, according to an embodiment.

[0059] Figure 29 This is a flowchart of a method for generating a magnetic field gradient according to an embodiment.

[0060] Figure 30 This is a flowchart of a method for determining the relative position of an object using a magnetic field gradient, according to an embodiment. Detailed Implementation

[0061] A device comprising first, second, and third electromagnetic coil groups is used to generate a three-dimensional magnetic field gradient relative to mutually orthogonal axes. The first electromagnetic coil group is configured to generate a first magnetic field gradient relative to a first axis. The second electromagnetic coil group is configured to generate a second magnetic field gradient relative to a second axis orthogonal to the first axis. The third electromagnetic coil group is configured to generate a third magnetic field gradient relative to a third axis orthogonal to the first and second axes.

[0062] The controller selectively supplies power to the first, second, and / or third sets of electromagnetic coils to generate a positioning magnetic field gradient relative to each axis, wherein at least a portion of each positioning magnetic field gradient has a monotonically varying magnetic field amplitude along the corresponding axis. The controller can generate the positioning magnetic field gradients in a predetermined timing sequence to encode the positioning magnetic field gradients. The portion of the positioning magnetic field gradient with a monotonically varying amplitude can represent the field of view (FOV) of the device. In the FOV, the monotonically varying amplitude of each magnetic field gradient can correspond to the relative position or coordinates of the device. The relative position of the magnetic sensor device can be determined based on the magnetic field corresponding to each positioning magnetic field gradient measured by the magnetic sensor device.

[0063] Microscale device positioning for high-precision surgery has the potential to replace X-ray fluorescence fluoroscopy, which is the current imaging standard during many of these surgeries, a typical example being orthopedic surgery.

[0064] Figure 1 This is a block diagram of an apparatus 10 for generating a magnetic field gradient according to an embodiment. The apparatus 10 includes a controller 100, a first electromagnetic coil group 110, a second electromagnetic coil group 120, and a third electromagnetic coil group 130. The first electromagnetic coil group 110 is configured to generate a first magnetic field gradient relative to a first axis (e.g., the X-axis in a Cartesian coordinate system). The second electromagnetic coil group 120 is configured to generate a second magnetic field gradient relative to a second axis orthogonal to the first axis (e.g., the Y-axis in a Cartesian coordinate system). The third electromagnetic coil group 130 is configured to generate a third magnetic field gradient relative to a third axis orthogonal to the first and second axes (e.g., the Z-axis in a Cartesian coordinate system).

[0065] Electromagnetic coil assemblies 110, 120, and 130 can be stacked together (e.g., arranged vertically relative to the lower surface). The electromagnetic coil assemblies 110, 120, and 130 are preferably aligned relative to a first axis and a second axis, and centered (e.g., concentrically centered) and / or aligned with each other. Furthermore, each of the electromagnetic coil assemblies 110, 120, and 130 has an upper planar surface and a lower planar surface (e.g., orthogonal to the Z-axis), which allows them to be stacked and integrated or embedded in flat devices, such as boards, walls, chair backs, conformal wearable straps, or other locations to minimize patient discomfort.

[0066] Controller 100 is electrically coupled to a first electromagnetic coil group 110, a second electromagnetic coil group 120, and a third electromagnetic coil group 130. Controller 100 is configured to selectively power the first electromagnetic coil group 110, the second electromagnetic coil group 120, and / or the third electromagnetic coil group 130. Selectively powering the electromagnetic coil groups 110, 120, and / or 130 can sequentially generate a total magnetic field gradient relative to each axis, which has a monotonically varying magnitude along some or all of the corresponding positioning magnetic field gradients. For example, electromagnetic coil groups 110, 120, and / or 130 can be selectively powered such that at least a portion of the total magnetic field gradient relative to the first axis has a monotonically varying magnitude. In another example, electromagnetic coil groups 110, 120, and / or 130 can be selectively powered such that at least a portion of the total magnetic field gradient relative to the second axis has a monotonically varying magnitude. In yet another example, electromagnetic coil groups 110, 120, and / or 130 can be selectively powered such that at least a portion of the total magnetic field gradient relative to the third axis has a monotonically varying magnitude. The relative position of the magnetic sensor device with respect to electromagnetic coil groups 110, 120, and / or 130 can be determined by measuring the total magnetic field while generating each positioning magnetic field gradient. The portion of the total magnetic field gradient relative to a given axis can be referred to as the field of view (FOV).

[0067] Figure 2A -C is a simplified view of the total magnetic field gradient used to encode the device location. Three example magnetic sensor devices D1, D2, and D3 are located in the FOV. To position devices D1, D2, and D3 along the X-axis (e.g., the first axis), a magnetic field B with a monotonically varying amplitude is generated relative to the X-axis. X ,like Figure 2A As shown. The monotonically changing amplitude has a gradient in the absolute value of the total magnetic field along the X-axis. The gradient ensures that no two points within the FOV have the same absolute total magnetic field value along the X-axis. For example, the total magnetic field B measured by devices D1, D2, and D3 can be described according to Equation 1. X Range:

[0068] ||B X1 ||<||B X2 ||<||B X3 || (1)

[0069] The total magnetic field B at the X position of each device X The magnetic field contribution from each orthogonal magnetic field at the corresponding X position can be used to describe this, as described in Equation 2. The magnetic field gradient relative to the X-axis can be described using Equation 3.

[0070]

[0071]

[0072] Similarly, in order to position devices D1, D2, and D3 along the Y-axis (e.g., the second axis), a magnetic field B with a monotonically varying amplitude is generated relative to the Y-axis. Y ,like Figure 2B As shown in the diagram, the monotonically changing amplitude has a gradient in the absolute value of the total magnetic field along the Y-axis. This gradient ensures that no two points within the FOV have the same absolute total magnetic field value along the Y-axis. For example, the amplitude of the total magnetic field measured by devices D1, D2, and D3 can be described according to Equation 4:

[0073] ||B Y2 ||<||B Y3 ||<||B Y1 || (4)

[0074] The total magnetic field B at the Y position of each device Y The magnetic field contribution from each orthogonal magnetic field at the corresponding Y position can be used to describe this, as described in Equation 5. The magnetic field gradient relative to the Y-axis can be described using Equation 6.

[0075]

[0076]

[0077] Similarly, in order to position devices D1, D2, and D3 along the Z-axis (e.g., the third axis), a magnetic field B with a monotonically varying amplitude is generated relative to the Z-axis. Z ,like Figure 2C As shown. The monotonically changing amplitude has a gradient in the absolute value of the total magnetic field along the Z-axis. The gradient ensures that no two points within the FOV have the same absolute total magnetic field value along the Z-axis. For example, the total magnetic field B measured by devices D1, D2, and D3 can be described according to Equation 7. Z Range:

[0078] ||B Z1 ||<||B Z2 ||<||B Z3 || (7)

[0079] The total magnetic field B at the Z position of each device Z The magnetic field contribution from each orthogonal magnetic field at the corresponding Z position can be used to describe this, as described in Equation 8. The magnetic field gradient relative to the Y-axis can be described according to Equation 9.

[0080]

[0081]

[0082] Using these magnetic field measurements along three orthogonal axes, the complete 3D position of each device, D1, D2, and D3, can be definitively decoded. Since the gradient is represented in both the total and absolute magnetic field values ​​along any axis, this positioning technique is unaffected by potential inaccuracies caused by device misalignment and orientation mismatch relative to any particular coordinate. Individual field components in Equations 2, 5, and 8 may change as device orientation changes, but the overall magnitude remains the same.

[0083] To generate the desired spatial gradient along the three axes in a magnetic field, electromagnetic coils (e.g., electromagnetic coil groups 110, 120, and / or 130) can be designed with one or more of the following design objectives: (i) high gradient strength G for high resolution; (ii) flat or substantially flat coils that can be placed close to the patient, such as under or within the patient's bed; (iii) enhanced FOV to allow sufficient space for navigation, observation, and / or alignment of medical procedures; (iv) high current efficiency to maximize the use of the current drawn by the gradient coils; and / or (v) low coil length for lower inductance (for rapid switching) and lower resistance (for lower heating). The gradient coil efficiency η is defined as the ratio of the magnetic field gradient (G) generated by the coils to the drawn current (I). The geometry of the coils and static magnetic field simulation can be performed in magnetostatic software such as Radia, available from the European Synchrotron Radiation Facility. The FOV can be 15cm × 15cm × 10cm (X × Y × Z), but other FOVs are also available.

[0084] The spatial positioning resolution (Δx) obtained by the system is given by Equation 10:

[0085] Δx=ΔB eff / G (10)

[0086] Where ΔB eff It is the effective resolution achievable by the magnetic sensor when performing magnetic field measurements. It is determined by the noise of the sensing and processing units, primarily quantization noise. G is the applied magnetic field gradient, determined by the current in the electromagnet and its geometry. There are two main noise sources that can cause G to vary from the desired ideal value: (a) a deviation due to changes in the power supply current, expressed as δG. S (a) and (b) the interpolation error caused during gradient characterization, denoted by δG. i This indicates that in order to obtain Δx < 100 μm with G = 30 mT / m, ΔB is required. eff <3μT. To keep G consistently at 30mT / m, δG S +δG i The target is <1%. In other embodiments, a lower resolution (e.g., Δx < 500 μm) may be provided.

[0087] Figure 3 This is a schematic top view of a first electromagnetic coil assembly 110 according to an embodiment. The first electromagnetic coil assembly 110 includes clockwise helical windings 112 and counterclockwise helical windings 114 arranged adjacent to or adjacent to each other. The helical windings 112, 114 may be mirror images of each other. Each helical winding 112, 114 has an axis of symmetry 312, 314 parallel to a first axis (e.g., the X-axis). The axes of symmetry 312, 314 are aligned in the helical windings 112, 114 to generate a uniform or substantially uniform magnetic field gradient (e.g., a first magnetic field gradient) relative to the first axis. The helical windings 112, 114 extend along a second axis (e.g., the Y-axis) to form an elliptical, track-shaped (e.g., stadium-shaped), rectangular, rounded rectangle, or other elongated shape. The helical windings 112, 114 may have an elongated length. This can maintain the X gradient substantially uniform across the Y FOV. The width 116 of the first electromagnetic coil assembly 110 is measured along or parallel to a first axis (e.g., the X-axis). As used herein, "about" means ±10% of the relevant value.

[0088] Helical windings 112 and 114 are formed by respective conductors 322 and 324 (e.g., first and second conductors). Alternatively, more than one conductor may be connected together to form a helical winding. Helical windings 112 and 114 have a thickness (e.g., profile) defined by the thickness of the respective conductors 322 and 324. Conductors 322 and 324 may be identical and therefore have the same thickness. Thus, helical windings 112 and 114 have a top flat surface and a bottom flat surface (or substantially flat surface (e.g., at least 95% flat)) parallel to the XY plane 300. The top flat surface and bottom flat surface of helical windings 112 and 114 are defined by the respective top and bottom surfaces of conductors 322 and 324. The thickness of helical windings 112 and 114 relative to a third axis (e.g., the Z-axis) is equal to the thickness of conductors 322 and 324. Conductors 322 and 324 may have an appropriate number of windings or turns to generate a first magnetic field gradient.

[0089] Conductors 322 and 324 can be configured to receive DC currents in the range of approximately 10A to approximately 50A, including approximately 20A, approximately 30A, and approximately 40A, or other currents. For example, conductors 322 and 324 can be copper wires, such as Litz 50 / 32AWG conductors, which represent 50 strands of 32 AWG wire bundled together. Conductors 322 and 324 have an insulating covering to prevent electrical short circuits between them.

[0090] Figure 4This is a side view of the first electromagnetic coil assembly 110 along the second axis. The side view further shows that the helical windings 112 and 114 have flat top surfaces 401 and 402 and flat bottom surfaces 411 and 412, respectively, which are parallel to the XY plane 300. The thickness 420 of the helical windings 112 and 114, measured relative to a third axis (e.g., the Z-axis), is equal to the thickness of the conductors 322 and 324. In some embodiments, the thickness 420 may be from about 0.5 mm to about 1.5 mm.

[0091] Figure 5 This is a graph 500 showing an example of the Z component of the magnetic field 510 generated by the first electromagnetic coil group 110. The magnetic field 510 generated by the clockwise spiral winding 112 is negative (e.g., between approximately -4.5 mT and 0), and the magnetic field 510 generated by the counterclockwise spiral winding 114 is positive (e.g., between 0 and approximately 4.5 mT). The magnetic field 510 is 0 between the clockwise spiral winding 112 and the counterclockwise spiral winding 114.

[0092] In other words, the clockwise current-carrying half (to the left of curve 500) generated by the clockwise helical winding 112 produces a Z component (B) pointing into a plane (e.g., plane 300). Xz ) magnetic field B X , represented by negative values. The counterclockwise current-carrying half (to the right of curve 500) generated by the counterclockwise helical winding 114 produces a "B" pointing outwards from the plane (e.g., plane 300). Xz ", represented by a positive value. This creates a monotonically varying Z-component (along the X-axis) of the magnetic field 510 between the centers of the two coils 112 and 114 in region 520 of Figure 500. The average gradient (B) of the magnetic field 510 Xz The value is approximately 52.5 mT / m.

[0093] Figure 6 This shows the X component (B) of the magnetic field 610 generated by the first electromagnetic coil group 110. Xx Example graph 600. The Y component (B) of the magnetic field generated by the first electromagnetic coil group 110. Xy The value is 0 at Y = 0 cm and Z = 7.5 cm.

[0094] Figure 7 This illustrates the total magnetic field 710 (||B) generated by the first electromagnetic coil group 110. X The example curve 700 shows that the total magnetic field 710 is highly nonlinear.

[0095] Figure 5 The Z component (B) of the magnetic field generated by the first electromagnetic coil group 110 is shown. XzIn the central region (e.g., region 520), it is highly monotonic and linear. Figure 6 The X component (B) of the magnetic field generated by the first electromagnetic coil group 110 is shown. Xx In the central region, it is neither monotonic nor nonlinear. As a result, when the amplitude of the total field... exist Figure 7 When plotted, a highly non-monotonic and nonlinear magnetic field distribution is obtained. The nonlinearity of the total magnetic field 710 can be attributed to: (a) the addition of non-zero and nonlinear X and Y components to the Z component of the magnetic field, and (b) the nonlinearity of the amplitude function, which flips the negative half of the total field to produce an even function centered at X = 15 cm (between coils 112 and 114).

[0096] In each curve 500, 600, 700, the corresponding magnetic fields 510, 610, 710 are generated using a 30A DC current passing through helical windings 112, 114 in the same direction. The corresponding magnetic fields 510, 610, 710 are measured at a relative Y position of 0cm, a relative Z position of 7.5cm, and a varying relative X position.

[0097] Figure 8 This is a schematic top view of a second electromagnetic coil assembly 120 according to an embodiment. The second electromagnetic coil assembly 120 includes clockwise helical windings 122 and counterclockwise helical windings 124 arranged adjacent to or adjacent to each other. The helical windings 122, 124 may be mirror images of each other. Each helical winding 122, 124 has an axis of symmetry 812, 814 parallel to a second axis (e.g., the Y-axis). The axes of symmetry 812, 814 are aligned in the helical windings 122, 124 to produce a uniform or substantially uniform magnetic field gradient (e.g., a second magnetic field gradient) relative to the second axis. The second electromagnetic coil assembly 120 is identical to the first electromagnetic coil assembly 110 except that it is rotated 90 degrees relative to the first electromagnetic coil assembly 110. In other embodiments, the second electromagnetic coil assembly 120 may have other configuration differences compared to the first electromagnetic coil assembly 110.

[0098] Helical windings 122, 124 are formed by corresponding conductors 822, 824 (e.g., third and fourth conductors). Alternatively, more than one conductor may be connected together to form a helical winding. Helical windings 122, 124 have a thickness (e.g., profile) defined by the thickness of the corresponding conductors 822, 824. Conductors 822, 824 may be identical and therefore have the same thickness. Thus, helical windings 122, 124 have a top flat surface and a bottom flat surface (or substantially flat surfaces (e.g., at least 95% flat)) parallel to the XY plane 800. The top flat surface and bottom flat surface of helical windings 122, 124 are defined by the corresponding top and bottom surfaces of conductors 822, 824. The thickness of helical windings 122, 124 relative to a third axis (e.g., the Z-axis) is equal to the thickness of conductors 822, 824. Conductors 822, 824 may have an appropriate number of windings or turns to generate a second magnetic field gradient. The length 126 of the second electromagnetic coil group 120 is measured along or parallel to the second axis (e.g., the Y-axis).

[0099] Conductors 822 and 824 can be configured to receive DC current in the range of approximately 10A to approximately 50A, including approximately 20A, approximately 30A, and approximately 40A, or other currents. For example, conductors 822 and 824 can be Litz 50 / 32AWG conductors. Conductors 822 and 824 can be the same as or different from the corresponding conductors 322 and 324.

[0100] Figure 9 Graph 900 shows an example of the Z-component of the magnetic field 910 generated by the second electromagnetic coil group 120. The magnetic field 910 generated by the clockwise spiral winding 122 is negative (e.g., between approximately -4.5 mT and 0), and the magnetic field 910 generated by the counterclockwise spiral winding 124 is positive (e.g., between 0 and approximately 4.5 mT). The magnetic field 910 is 0 between the clockwise spiral winding 122 and the counterclockwise spiral winding 124. Graphs 500 and 900 are identical with respect to the corresponding X and Y axes because, in this embodiment, the first coil group 110 and the second coil group 120 are identical (except for a 90° relative rotation).

[0101] In other words, the clockwise current-carrying half (to the left of curve 900) generated by the clockwise helical winding 122 produces a Z component (B) pointing into a plane (e.g., plane 800). Yz ) magnetic field B Y , represented by negative values. The counterclockwise current-carrying half (to the right of curve 900) generated by the counterclockwise helical winding 124 produces B pointing outwards from the plane (e.g., plane 800). YzThis is represented by a positive value. This creates a monotonically varying Z-component of the magnetic field 910 in region 920 of graph 900, between the centers of the two coils 122 and 124 (along the Y-axis). The average gradient (B) of the magnetic field 910... Yz The value is approximately 52.5 mT / m.

[0102] Figure 10 This shows the Y component (B) of the magnetic field 610 generated by the second electromagnetic coil group 120. Yy Example graph 1000. The X component (B) of the magnetic field generated by the second electromagnetic coil group 120 at X = 0 cm and Z = 7.5 cm. Xy The value is 0.

[0103] Figure 11 This illustrates the total magnetic field 1110(||B) generated by the second electromagnetic coil group 120. Y The example curve 1100 shows that the total magnetic field 1110 is highly nonlinear.

[0104] Figure 9 The Z component (B) of the magnetic field generated by the second electromagnetic coil group 120 is shown. Yz In the central region (e.g., region 920), it is highly monotonic and linear. Figure 10 The X component (B) of the magnetic field generated by the second electromagnetic coil group 120 is shown. Yy In the central region, it is non-monotonic and nonlinear. As a result, when the total field... The range is Figure 11 When plotted, a highly non-monotonic and nonlinear magnetic field distribution is obtained. The nonlinearity of the total magnetic field 1110 can be attributed to: (a) the addition of non-zero and nonlinear X and Y components to the Z component of the magnetic field, and (b) the nonlinearity of the modulus function, which flips the negative half of the total field to produce an even function centered at Y = 15 cm (between coils 122 and 124).

[0105] In each curve 900, 1000, and 1100, the corresponding magnetic fields 910, 1010, and 1110 are generated using a 30A DC current passing through helical windings 122 and 124 in the same direction. The corresponding magnetic fields 910, 1010, and 1110 are measured at a relative X position of 0cm, a relative Z position of 7.5cm, and a varying relative Y position.

[0106] Figure 12This is a schematic perspective view of a third electromagnetic coil assembly 130 according to an embodiment. The third electromagnetic coil assembly 130 includes a helical winding 132, which includes one or more wires 612 wound in a loop, disc, or ring 134 (typically a loop). In one embodiment, two or more wires 612 are wound adjacent to each other to form a ring 134. The wires 612 are wound counterclockwise, but in other embodiments, the wires 612 may be wound clockwise.

[0107] The annular ring 134 has an inner diameter 640 and an outer diameter 650, wherein the inner diameter 650 defines a hollow region or cavity 642 excluding the conductor 612. The ratio of the outer diameter 650 to the inner diameter 640 can be selected to allow an appropriate number of windings or turns of the conductor 612 to generate a third magnetic field gradient. In a specific embodiment, the outer diameter 650 may be about 28 cm and the inner diameter 640 may be about 10 cm. The conductors 612 have an insulating cover to prevent electrical short circuits between them. The inner diameter 640 and the outer diameter 650 can be measured relative to or parallel to a first axis (e.g., the X-axis) or a second axis (e.g., the Y-axis).

[0108] The helical winding 132 has an axis of symmetry 632 parallel to a third axis (e.g., the Z-axis). The helical winding 132 has a thickness (e.g., profile) defined by the thickness of the conductor 612. Therefore, the helical winding 132 has a top flat surface and a bottom flat surface (or substantially flat surfaces (e.g., at least 95% flat)) parallel to the XY plane 1200. The top flat surface and bottom flat surface of the helical winding 132 are defined by the corresponding top and bottom surfaces of the conductor 612. The thickness of the helical winding 132 relative to the third axis (e.g., the Z-axis) is equal to the thickness of the conductor 612. The conductor 612 may have an appropriate number of windings or turns to generate a third magnetic field gradient.

[0109] Conductor 612 can be configured to receive DC current in the range of about 10A to about 50A, including about 20A, about 30A, and about 40A, or other currents. For example, conductor 612 can be Litz 50 / 32AWG conductor. Conductor 612 can be the same as or different from conductors 322, 324, 822, and / or 824.

[0110] Figure 13 This is a graph 1300 showing an example of the Z component of the magnetic field 1310 generated by the third electromagnetic coil group 130. The magnetic field 1310 is positive at all X positions across the helical winding 132. Therefore, the magnetic field B... Z It has a Z component (B) pointing out of the plane (e.g., plane 1200). Zz The Z component (B) is represented by positive values. ZzThe magnetic field 1310 is highest at the center of the helical winding 132 (e.g., at X = 15 cm). The magnetic field 1310 on either side of the center of the helical winding exhibits a partially monotonically changing characteristic.

[0111] Figure 14 This is a graph 1400 showing an example of the X component of the magnetic field 1410 generated by the third electromagnetic coil assembly 130. The left side of the helical winding 132 (between X = 0 cm and X = 15 cm) generates a magnetic field (B). Z ), having an X component (B) pointing into a plane (e.g., plane 1200). Zx ), represented by negative values. A (B) is generated on the right side of the helical winding 132 (between X = 15cm and X = 30cm). Zz ) points out of the plane (e.g., plane 1200) and is represented by a positive value. B Zx The value is 0 at the center of the helical winding 132 (e.g., at X = 15 cm). Zx The value of X increases monotonically from 5cm to 25cm.

[0112] Since the helical winding 132 is symmetrical with respect to the X and Y axes, the Y component of the magnetic field generated by the third electromagnetic coil group 130 is the same as the X component of the magnetic field 1410 (e.g., at X = 0 cm and at varying Y positions).

[0113] In each curve 1300, 1400, a corresponding magnetic field 1310, 1410 is generated using a 30A DC current through the helical winding 132. The corresponding magnetic fields 1310, 1410 are measured at a relative Y position of 0cm, a relative Z position of 7.5cm, and at a varying relative X position (i.e., where X and Y switch in curve 1400).

[0114] Figure 15 This illustrates the monotonically changing total magnetic field 1510(||B) generated by the third electromagnetic coil group 130. Z The example curve 1500 is shown. The curve 1510 for each total magnetic field is measured using the corresponding relative X position as a function of the Z position. The curve 1510 for each total magnetic field is measured using a relative Y position of 0 cm. Additionally, the total magnetic field 1510 is measured at a distance of 10 cm from Z = 1 cm to Z = 11 cm, where the Z distance is the height from the top surface of the third electromagnetic coil group 130.

[0115] Typically, the total magnetic field 1510 is monotonically decreasing with increasing height (Z position) from the third electromagnetic coil group 130. Furthermore, the total magnetic field 1510 is linear at most heights (Z). It is believed that the cavity 642 enhances the linearity of the total magnetic field 1510 (which is more exponential in the absence of the cavity 642). The third electromagnetic coil group 130 has a monotonically decreasing ZFOV 1520 of approximately 10 cm, in which the amplitude of the total magnetic field 1510 varies monotonically (decreases).

[0116] Therefore, the ratio of the 10cm Z FOV 1520 to the outer diameter 650 of the third magnetic coil group 130 (30cm when generating the total magnetic field gradient 1510) is approximately 1:3, although in other embodiments this ratio may be in the range of approximately 1:4 to approximately 2:5 (e.g., less than or equal to and / or greater than or equal to 1:3). Additionally, the ratio of the 10cm Z FOV 1520 to the inner diameter 640 of the third magnetic coil group 130 (10cm when generating the total magnetic field gradient 1510) is approximately 1:1, but in other embodiments this ratio may be in the range of approximately 4:5 to approximately 6:5 (e.g., less than or equal to and / or greater than or equal to 1:1).

[0117] The gradient intensity G is 46 mT / m at X = 0 cm, reaches a maximum of 67 mT / m at X = ±5 cm, and decreases to 48 mT / m at X = ±10 cm, thus ensuring G > 30 mT / m over a length of 20 cm along the X-axis. A DC current of 12.5 A is used in the third electromagnetic coil group 130 to produce curve 1500, which results in an average magnetic field gradient efficiency η of 4.3 mT / m / A.

[0118] Since the helical winding 132 is symmetrical with respect to the X and Y axes, the total magnetic field is the same when measured at the relative X position of 0 cm, the relative Y positions of ±2.5 cm, ±5 cm, ±7.5 cm and ±10 cm, and from Z = 1 cm to Z = 11 cm (i.e., where X and Y switch in curve 1500).

[0119] As can be seen from graphs 700, 1100, and 1500, the total magnetic field generated by the third magnetic coil group 130 has a monotonically varying amplitude relative to the third axis (e.g., the Z-axis), while the total magnetic field generated by the first and second magnetic coil groups 110 and 120 does not have a monotonically varying amplitude relative to the first axis and the second axis (e.g., the X and Y axes), respectively.

[0120] The strictly positive and monotonic properties of any half of (Figure 1300) make it suitable for offsetting the negative half B of (Figure 500). Xz And (Figure 900) the negative half B Yz Appropriate candidates. Additionally, B Zx(Figure 1400) The height is linear from X = 5cm to X = 25cm, B Xx The main nonlinear region in (Figure 600) indicates that the superposition of the two will be more significant than B alone. Xx More linear. Similarly, B Zy (Same Figure 1400) The height is linear from Y = 5cm to Y = 25cm, B Yy The main nonlinear region in (Figure 1000) indicates that the superposition of the two will be more significant than B alone. Yy It is relatively more linear.

[0121] Therefore, the third electromagnetic coil group 130 can be located below (e.g., directly below) the first electromagnetic coil group 110, and both can be switched on simultaneously. The resulting magnetic field distribution along the X-axis is plotted on... Figure 16 and 17 The curves 1600 and 1700 are shown in the figures. Curve 1600 shows the Z component of the combined magnetic field 1610 generated simultaneously by the first electromagnetic coil group 110 and the third electromagnetic coil group 130. The combined magnetic field 1610 was measured at Y = 0 cm, Z = 7.5 cm, and at varying X positions. A DC current of 30 A was used in the first and third electromagnetic coil groups 110 and 130 to generate the combined magnetic field 1610. It can be seen that the combined magnetic field 1610 has a monotonic variation region 1620 of 18 cm from X = 3 cm to X = 21 cm, which corresponds to the FOV of the combined magnetic field 1610. The average gradient (B) of the magnetic field 1610 is shown in the figure. Xz The value is approximately 54 mT / m.

[0122] Graph 1700 illustrates an example of the total magnetic field 1710 simultaneously generated by the first and third electromagnetic coil groups 110 and 130. The total magnetic field 1710 has a large region 1720, in which the amplitude of the total magnetic field 1710 increases monotonically. Region 1720 is approximately 27 cm wide, ranging from X = -6 cm to X = 21 cm, where the negative X value corresponds to an equivalent distance away from the outer edge of the counterclockwise spiral 114. When the first electromagnetic coil group 110 and the third electromagnetic coil group 130 are switched on together, region 1720 is an X FOV. The 27 cm FOV (region 1720) is equal to 90% of the width (30 cm) of the first electromagnetic coil group 110.

[0123] Magnetic field 1710(||B) X The average gradient of ||) is approximately 30 mT / m. The combined magnetic field 1710 was measured at Y = 0 cm, Z = 7.5 cm and at varying X positions. A DC current of 30 A was used in the first and third electromagnetic coil groups 110 and 130 to generate the total magnetic field 1710.

[0124] Graph 1800 shows an example of the total magnetic field 1810 simultaneously generated by the second and third electromagnetic coil groups 120 and 130. The total magnetic field 1810 has a large region 1820, in which the amplitude of the total magnetic field 1810 increases monotonically. Region 1820 is approximately 27 cm wide, ranging from Y = -6 cm to Y = 21 cm, where the negative Y value corresponds to an equivalent distance away from the outer edge of the counterclockwise spiral 124. When the second electromagnetic coil group 120 and the third electromagnetic coil group 130 are switched on together, region 1820 is the Y FOV. The 27 cm FOV (region 1720) is equal to 90% of the width (30 cm) of the second electromagnetic coil group 120.

[0125] Magnetic field 1810(||B) Y The average gradient of || is approximately 30 mT / m. The combined magnetic field 1810 was measured at X = 0 cm, Z = 7.5 cm, and at varying Y positions. A 30 A DC current was used in the first electromagnetic coil group 120 and the third electromagnetic coil group 130 to generate the total magnetic field 1810. (The text abruptly ends here.) Figure 18 As shown, the total magnetic field 1710 and the total magnetic field 1810 are the same or substantially the same with respect to the X-axis and Y-axis (e.g., the first axis and the second axis), respectively.

[0126] For the off-center regions where Y≠0 (for the total magnetic field 1710), the Y components of the X and Z coils also exist and contribute to the generation of the total magnetic field 1710 by the two coils. Nevertheless, the qualitative properties of the field distribution are similar to those of Figure 1700 in all cases, as described below.

[0127] To evaluate the uniformity of the total magnetic field simultaneously generated by the first electromagnetic coil group 110 and the third electromagnetic coil group 130, the total magnetic field 1910(||B) can be plotted at various X values ​​for different Y values ​​from 0 to ±10 cm at intervals of ±2.5 cm, while keeping Z = 7.5 cm. X ||), such as Figure 19 The curve is shown in Figure 1900. Due to the non-uniform nature of the magnetic field of the Z coil along the X-axis as the Y-coordinate changes, the total gradient intensity monotonically decreases from 37 mT / m at Y = 0 to 24 mT / m at Y = ±10 cm. A DC current of 30 A is used in the first and third electromagnetic coil groups 110 and 130 to generate the total magnetic field 1910. When operating simultaneously at a DC power of 30 A, the first electromagnetic coil group 110 and the third electromagnetic coil group 130 have a monotonic X FOV 1920 of approximately 20 cm, in which the amplitude of the total magnetic field 1910 changes monotonically (increases). This 20 cm X FOV 1920 represents the total magnetic field 1910 with a monotonic amplitude (||B). X A significant portion of ||).

[0128] Similarly, to evaluate the uniformity of the total magnetic field simultaneously generated by the first electromagnetic coil group 110 and the third electromagnetic coil group 130, the total magnetic field 2010 can be plotted at various X values ​​with ±1cm intervals for different Z values ​​ranging from ±5cm to ±10cm, while keeping Y=0. Figure 20 The curve 2000 is shown in the figure. As expected, the gradient strength decreases monotonically from 57 mT / m. The gradient strength decreases monotonically from 57 mT / m at Z = 5 cm to 23 mT / m at Z = 10 cm. A DC current of 30 A is used in the first electromagnetic coil group 110 and the third electromagnetic coil group 130 to generate the total magnetic field 2010. When operating simultaneously at a DC power of 30 A, the first electromagnetic coil group 110 and the third electromagnetic coil group 130 have a monotonic X FOV 2020 of approximately 20 cm, in which the amplitude of the total magnetic field 2010 changes monotonically (increases).

[0129] Therefore, the ratio of 20cm x FOV 1920, 2020 to the width 116 of the first magnetic coil group 110 (30cm when the total magnetic field gradient 1910, 2010 is generated) is about 2:3, although in other embodiments this ratio may be in the range of 1:2 to about 3:4 (e.g., less than or equal to and / or greater than or equal to 2:3).

[0130] Figure 21 and Figure 22 The graphs 2100 and 2200 show the total magnetic fields 2110 and 2200 simultaneously generated by the second electromagnetic coil group 120 and the third electromagnetic coil group 130. In graph 2100, the total magnetic field 2110 is plotted at various Y values ​​at intervals of ±2.5 cm for different X values ​​from 0 to ±10 cm, while keeping Z = 7.5 cm. Due to the non-uniform nature of the magnetic field of the Z coil along the Y axis as the X coordinate changes, the total gradient intensity monotonically decreases from 37 mT / m at X = 0 to 24 mT / m at X = ±10 cm, similar to graph 1900. A DC current of 30 A is used in the second and third electromagnetic coil groups 120 and 130 to generate the total magnetic field 2110. When operating simultaneously at 30 A DC power, the second electromagnetic coil group 120 and the third electromagnetic coil group 130 have a monotonic Y FOV 2120 of approximately 20 cm, in which the amplitude of the total magnetic field 2110 changes monotonically (increases).

[0131] Similarly, to evaluate the uniformity of the total magnetic field simultaneously generated by the second and third electromagnetic coil groups 120 and 130, as shown in Figure 2200, the total magnetic field 2210 was plotted at different Y values ​​at ±1 cm intervals, for different Z values ​​from ±5 cm to ±10 cm, while keeping X = 0 cm. As expected, the gradient intensity monotonically decreased from 57 mT / m at Z = 5 cm to 23 mT / m at Z = 10 cm. A DC current of 30 A was used in the second electromagnetic coil group 120 and the third electromagnetic coil group 130 to generate the total magnetic field 2210. When operating simultaneously at 30 A DC power, the second electromagnetic coil group 120 and the third electromagnetic coil group 130 have a monotonically changing (increasing) Y FOV 2220 of approximately 20 cm, where the amplitude of the total magnetic field 2210 monotonically varies (increases).

[0132] Therefore, the ratio of the length 126 of the 20cm Y FOV 2120, 2220 to the length 126 of the second magnetic coil group 110 (30cm when the total magnetic field gradient 2110, 2210 is generated) is about 2:3, although in other embodiments this ratio may be in the range of 1:2 to about 3:4 (e.g., less than or equal to and / or greater than or equal to 2:3).

[0133] This means that for a given sensor resolution, a higher positional resolution will be obtained when the magnetic sensor device moves closer to the center of a 20cm × 20cm × 10cm field of view (FOV) in the X, Y, and Z directions, respectively. To improve the positional resolution obtained at the boundary plane of the FOV, the DC current in the coil should be increased (resulting in a higher gradient), or the sensor resolution should be higher. Keeping the maximum current at 30A, we employ the sensor in a low-noise mode toward the boundary plane, where the gradient intensity is <30mT / m. In low-noise mode, the sensor resolution is 1μT, requiring only 10mT / m to achieve a 100μm positional error. However, the current consumption is 2.2mA for 850μs in low-noise mode, compared to 1.5mA for 250μs in low-power mode (with a resolution of 3μT). Utilizing the additional power loss on the sensor side, the desired positional resolution can be achieved throughout the entire FOV. In some embodiments, the power management unit in the magnetic sensor device (e.g., in the controller chip) can be efficiently designed to wirelessly transmit relatively high power to the magnetic sensor device when the magnetic sensor device is operating in a low-noise mode.

[0134] Each point within the FOV corresponds to a unique set of magnetic field values ​​obtained from three orthogonal gradients. For applications requiring a larger FOV, the physical dimensions can be scaled accordingly for all coils. DC current is another parameter used for vertical scaling of the FOV. With a DC current value of 30A in both the X and Z coils, the average value of η for the X gradient is 588 μT / m / A.

[0135] Figure 23 This is a timing diagram 2300 showing the current flowing through the first electromagnetic coil group 110, the second electromagnetic coil group 120, and the third electromagnetic coil group 130 according to an embodiment. Current diagram 2310 shows the current flowing through the first electromagnetic coil group 110 as a function of time. Current diagram 2320 shows the current flowing through the second electromagnetic coil group 120 as a function of time. Current diagram 2330 shows the current flowing through the third electromagnetic coil group 130 as a function of time. The current is selectively controlled by the controller 100.

[0136] As can be seen, in the current curves 2310, 2320, and 2330, there are corresponding ramp-up time periods 2312, 2322, and 2332, corresponding steady-state "on" time periods 2315, 2325, and 2335, and corresponding descent time periods 2318, 2328, and 2338. Timing diagram 2300 shows the first electromagnetic coil group 110 and the third electromagnetic coil group 130 simultaneously turned on during ramp-up time periods 2312 and 2332. During the steady-state on-time period 2315, steady-state current flows through the first and third electromagnetic coil groups 110 and 130 to simultaneously generate the first and third magnetic fields. The first total magnetic field (e.g., the first positioning magnetic field) generated by the first and third electromagnetic coil groups 110 and 130 has a monotonically varying amplitude within the field of view (FOV) on the first axis (e.g., the X-axis). The steady-state on-time period 2315 is the measurement time period for the first total magnetic field (e.g., for a magnetic sensor device). The first total magnetic field can be the same as the total magnetic fields 1710, 1910 and / or 2010.

[0137] After the steady-state turn-on period 2315, the controller 100 simultaneously ramps down 2318 the current to the first electromagnetic coil group 110 to turn off the first electromagnetic coil group 110 and ramps up 2322 the current to the second electromagnetic coil group 120 to turn on the second electromagnetic coil group 120. Alternatively, the controller 100 may ramp down 2318 the current to the first electromagnetic coil group 110 and then ramp up 2322 the current to the second electromagnetic coil group 120. The controller 100 continues to allow current to flow through the third electromagnetic coil group 130 during the ramp-up period 2322. In the steady-state turn-on period 2325, steady-state current flows through the second electromagnetic coil group 120 and the third electromagnetic coil group 130 to simultaneously generate a second magnetic field and a third magnetic field. The second total magnetic field (e.g., a second positioning magnetic field) generated by the second and third electromagnetic coil groups 120, 130 has a monotonically varying amplitude on the second axis (e.g., the Y-axis) within the FOV. The steady-state turn-on period 2325 is the measurement period of the second total magnetic field (e.g., for a magnetic sensor device). The second total magnetic field can be the same as the total magnetic fields 1810, 2110, and / or 2210. The time period 2325 can be from 50 ms to 250 ms, including approximately 100 ms, approximately 150 ms, approximately 200 ms, and any time period or range between any two of the aforementioned time periods.

[0138] After the steady-state turn-on period 2315, the controller 100 ramps down the current to the second electromagnetic coil group 120 2328 to turn off the second electromagnetic coil group 120 while maintaining power to the third electromagnetic coil group 130. After the second electromagnetic coil group 120 is turned off, the steady-state current flows only through the third electromagnetic coil group 130 during the time period 2340 to generate only a third magnetic field (e.g., a third positioning magnetic field), which has a monotonically varying amplitude on a third axis (e.g., the Z-axis) within the FOV. The time period 2340 is the measurement time period of the third magnetic field (e.g., for a magnetic sensor device). The third magnetic field can be the same as the monotonically varying total magnetic field 1510. The time period 2340 can be from 50 ms to 250 ms, including approximately 100 ms, approximately 150 ms, approximately 200 ms, and any time period or range between any two of the aforementioned time periods.

[0139] The steady-state measurement time periods 2315, 2325, and 2340 can be from approximately 10 ms to approximately 25 ms, including approximately 15 ms, approximately 20 ms, and any time period or any range between the aforementioned time periods. The ramp-up time periods 2312, 2322, and 2332 and the ramp-down time periods 2318, 2328, and 2338 can be from approximately 50 ms to approximately 150 ms, including approximately 75 ms, approximately 100 ms, approximately 125 ms, and any time period or range between the aforementioned time periods. The lengths of the ramp-up time periods 2312, 2322, and 2332 and the ramp-down time periods 2318, 2328, and 2338 can be affected by the DC current supply in the controller 100.

[0140] For a given magnetic field resolution (ΔB) that a magnetic sensor device can measure, the gradient intensity (G) of the magnetic field gradient is determined by the required positioning resolution (ΔX), as given by the relationship ΔX = ΔB / G. In one embodiment, ΔB is 15 μT, and to obtain a 500 μm resolution for ΔX, the required G is 30 mT / m. When measuring and averaging 25 or more magnetic field samples, the measurement error of the absorbable magnetic sensor can be reduced from 15 μT for ΔB to 3 μT, which can improve the spatial resolution from 500 μm to 100 μm for a given magnetic field gradient intensity of 30 mT / m.

[0141] Figure 24 This is a block diagram of a system 2400 for locating the relative position of a magnetic sensor device according to an embodiment. The system 2400 includes a magnetic field gradient device 10 (e.g., as described herein), a magnetic sensor device 2410, and a receiver 2420.

[0142] The magnetic sensor device 2410 includes a capsule or housing 2411 and circuitry including a three-dimensional magnetic sensor 2412, a device controller 2414, an antenna 2416, and a power supply 2418. The capsule or housing 2411 may be an ingestible capsule containing polydimethylsiloxane (PDMS) or another biosafety material. Alternatively, the capsule or housing 2411 may include a biocompatible housing that allows the magnetic sensor device 2310 to be placed on or near an anatomical feature 2430 of a subject, such as a mammal (e.g., a human). In another embodiment, the capsule or housing 2411 does not include a biocompatible housing or an ingestible capsule. In any case, the capsule or housing 2411 preferably does not attenuate or affect external magnetic fields (such as those generated by device 10).

[0143] A three-dimensional magnetic sensor 2412 measures the magnetic field at the location of the absorbable magnetic sensor 2412 and outputs the magnetic field measurement to a device controller 2414. The magnetic field measurement includes measurements of each of the X, Y, and Z field values, each of which can be provided as a 16-bit data vector. The three-dimensional magnetic sensor 2412 can measure the magnetic field based on control signals received from the device controller 1414, which can be transmitted via a protocol such as I2C. In some embodiments, 25 or more measurements can be performed for each magnetic field gradient. The control signals can include timing for the three-dimensional magnetic sensor 2412 to perform the magnetic field measurements. The timing can correspond to a predetermined timing for locating the magnetic field gradient. Additionally, the control signals can include configuration settings for the power, noise, and / or measurement frequency (e.g., 1 to 5 magnetic field measurements per minute) of the three-dimensional magnetic sensor 2412. In an example embodiment, the three-dimensional magnetic sensor 2412 can include an AK09970N triaxial magnetic sensor IC with digital output, available from Asahi Kasei Microdevices Corporation, but other three-dimensional magnetic sensors can also be used. It should be understood that certain embodiments provided herein are for illustrative and explanatory purposes only, and these embodiments do not limit the invention. Substitutions of equivalent, similar, or other examples will be understood by those skilled in the art without departing from the scope of this disclosure or the invention.

[0144] Device controller 2414 includes a microprocessor, local memory (e.g., cache and RAM), and a transceiver that can support one or more wireless protocols such as Bluetooth (e.g., Bluetooth Low Energy (LE)), Near Field Communication (NFC), and / or another wireless protocol. Device controller 2414 may store magnetic field measurements in its local memory (e.g., cache or RAM) and then encode the magnetic field measurements in one or more magnetic sensor output signals. The magnetic sensor output signals are broadcast by antenna 2416 using a wireless protocol (e.g., Bluetooth LE) and transmitted to receiver 2420 (e.g., which receives the output signals using receiver antenna 2422). Antenna matching circuitry may be included between device controller 2414 and antenna 2416 to improve and / or maximize power transfer to antenna 2416 for radiation. In an example embodiment, device controller 2414 may include an NRF52832 Bluetooth 5.2 system-on-chip (SoC) available from Nordic Semiconductor, but other microprocessors or SoCs may also be used. In addition, antenna 2416 may include the 2450AT18B100 2.4GHz miniature antenna available from Johanson Technology, Inc.

[0145] Power supply 2418 supplies power to the three-dimensional magnetic sensor 2412 and the device controller 2414. Power supply 2418 may include a battery, such as one or more button cell rechargeable batteries (e.g., 3V, 11mAh), such as the MS 920SE available from Seiko Instruments, Inc. In another embodiment, power supply 2418 may include an inductor capable of wirelessly receiving energy via inductive coupling. In another embodiment, power supply 2418 may obtain power biochemically. Power supply 2418 may receive and / or obtain power from other external sources and / or from internal sources.

[0146] Receiver 2420 includes a microprocessor and an antenna that can receive magnetic sensor output signals from magnetic sensor device 2410 using a wireless protocol (e.g., Bluetooth LE). For example, receiver 2420 may include a smartphone, laptop computer, desktop computer, tablet computer, or other computer. Receiver 2420 can then use magnetic field measurements encoded in the magnetic sensor output signals to determine the three-dimensional spatial coordinates of magnetic sensor device 2410 relative to device 10. The relative three-dimensional spatial coordinates of magnetic sensor device 2410 may optionally be displayed on an internal display on receiver 2420 and / or coupled to an external display of receiver 2420. The relative three-dimensional spatial coordinates can be determined using lookup tables, mathematical models, or other relationships stored in receiver 2420. For example, a lookup table can be created by performing a series of measurements of the localized magnetic field gradient generated by device 10 at a series of known spatial coordinates near device 10 (such as every 100 μm, every 500 μm, or other distances in each dimension). The Earth's ambient magnetic field can be subtracted from the measured magnetic field measurements in the lookup table.

[0147] Additionally, receiver 2420 can send control signals and / or commands to device controller 2414. Control signals and / or commands (typically, control signals) from receiver 2420 can trigger magnetic field measurements, such as by causing device controller 2414 to send control signals to three-dimensional magnetic sensor 2412. Control signals from receiver 2420 may also include timing for the three-dimensional magnetic sensor 2412 to perform magnetic field measurements. Alternatively, timing can be created by causing receiver 2420 to send control signals that trigger magnetic field measurements according to a predetermined timing sequence. Control signals from receiver 2420 can also cause device controller 2414 to send magnetic sensor output signals to receiver 2420. Furthermore, receiver 2420 can send control signals to configure device controller 2414 and / or three-dimensional magnetic sensor 2412. For example, receiver 2420 can configure wireless communication settings for device controller 2414 (e.g., wireless protocol, encryption, etc.). Additionally, receiver 2420 can configure power, noise, and / or measurement frequency (e.g., 1 to 5 magnetic field measurements per minute) settings for three-dimensional magnetic sensor 2412.

[0148] In operation, the magnetic sensor device 2410 can be inhaled or placed within the internal volume 1440 of a mammal (e.g., a human patient). For example, the magnetic sensor 2410 can be inhaled into the gastrointestinal tract (GI) of a mammal (e.g., a human patient or other mammal). The device 10 is then positioned such that its field of view (FOV) is within the mammal's gastrointestinal tract. For example, the device 10 can be placed on or within a platform or bed (on which the mammal lies), a chair (on which the mammal sits). Alternatively, the device 10 can be arranged in a wearable device, such as one that can be wrapped around the stomach of a subject (e.g., a mammal). The receiver 2420 wirelessly communicates with the device controller 2414 in the magnetic sensor device 2410 to trigger magnetic field measurements and / or receive raw field data. The user interface on the receiver 2420 can display the three-dimensional position of the absorbable magnetic sensor 2410 relative to the device 10 (e.g., electromagnetic coils 110, 120, 130).

[0149] Receiver 2420 can receive and / or display the relative position of magnetic sensor device 2410 in real time (or substantially real time due to transmission time, etc.) or non-real time (e.g., at a later time). For example, magnetic sensor device 2410 can temporarily store multiple magnetic field measurements and send them as a group to receiver 2420. Additionally or alternatively, receiver 2420 can receive magnetic field measurements from magnetic sensor device 2410 for later display on receiver 2420's display or on another device (such as a computer).

[0150] Because the DC current used to locate the magnetic field gradient can be quite high (e.g., up to 50 A), heating of the electromagnetic coils 110, 120, and 130 could be problematic if they remain on for extended periods. To avoid this, the electromagnetic coils 110, 120, and 130 can be switched in a highly time-multiplexed manner, so that they are turned on only when a measurement is needed and turned off at all other times. For example, performing a measurement every 5 minutes could generate an average of approximately 13 W of heat. Thermal insulation material (e.g., a heat shield) can be placed between the surfaces of the electromagnetic coils 110, 120, and 130 and the patient's back to prevent any undesirable heating effects.

[0151] Two example embodiments of device 10 are listed in Table 1. One embodiment is designed for orthopedic surgery, while the other is designed for gastrointestinal monitoring; these embodiments can be used for other applications. As can be seen from Table 1, the number of turns for each electromagnetic coil 110, 120, 130 is different, depending on the application used and the desired field of view (FOV). The required DC current in the electromagnet is also based on the application and the desired magnetic field gradient in the FOV. For the DC current given in Table 1, a magnetic field gradient of ≥30 mT / m can be achieved. This gradient is much stronger towards the surface and center of electromagnetic coils 110, 120, 130, and decreases to 30 mT / m at the boundaries of the FOV. The intensity of the gradient is determined using the spatial positioning resolution available to system 2400.

[0152]

[0153] Table 1

[0154] Figure 25 This is a flowchart of a method 2500 for determining the relative three-dimensional position of a magnetic sensor device according to an embodiment. Method 2500 can be performed using system 2400. In step 2510, the magnetic sensor device 2410 measures a first magnetic field relative to a first axis (e.g., the X-axis), which has a monotonically varying amplitude within the field of view (FOV) of the device 10. The first magnetic field corresponds to a first magnetic field gradient simultaneously generated by a first electromagnetic coil group 110 and a third electromagnetic coil group 130.

[0155] In step 2520, the magnetic sensor device 2410 measures a second magnetic field relative to a second axis (e.g., the Y-axis), which has a monotonically varying amplitude within the field of view (FOV) of the device 10. The second magnetic field corresponds to a first-second field gradient simultaneously generated by the second electromagnetic coil group 120 and the third electromagnetic coil group 130.

[0156] In step 2530, the magnetic sensor device 2410 measures a third magnetic field relative to a third axis (e.g., the Z-axis), which has a monotonically varying amplitude within the field of view (FOV) of the device 10. This third magnetic field corresponds to a third second field gradient generated solely by the third electromagnetic coil group 130. Steps 2510, 2520, and 2530 occur sequentially, but not necessarily in the order shown in method 2500.

[0157] In step 2540, receiver 2420 may receive measurements of a first magnetic field, a second magnetic field, and a third magnetic field, and use these measurements to determine the relative three-dimensional position of magnetic sensor device 2410. Receiver 2420 may use lookup tables, mathematical models, or other stored relationships to determine the relative three-dimensional position of magnetic sensor device 2410. Receiver 2420 may output, display, and / or store the relative three-dimensional position of magnetic sensor device 2410 determined in step 2540.

[0158] In an alternative embodiment, the magnetic sensor device 2410 may use the first magnetic field, the second magnetic field, and the third magnetic field measurements to determine its relative three-dimensional position in the same manner as the receiver 2420.

[0159] Figure 26 This is a flowchart of a method 2600 for determining the relative three-dimensional position of a magnetic sensor device 2410 according to an embodiment. In this embodiment, step 2540 is performed according to method 2600.

[0160] In step 2610, receiver 2420 measures the first magnetic field B from magnetic sensor device 2410. xi The magnetic field measurement is compared with a first magnetic field measurement stored in a master lookup table. The master lookup table can be created by taking a series of measurements of the magnetic field gradient generated by device 10 at a series of known spatial coordinates near device 10 (such as every 100 μm, every 500 μm, or other distances in each dimension). The Earth's ambient magnetic field can be subtracted from the measured magnetic field measurements in the master lookup table. An error ±ΔB can be included in the first magnetic field measurement B. xi In this case, receiver 2420 will measure the first magnetic field range B. xi ±ΔB is compared to a first magnetic field measurement stored in the master lookup table. The error ΔB can be from about 50 μT to about 150 μT, including about 75 μT, about 100 μT, about 125 μT, and any value or range between any two of the aforementioned values. Figure 27 An example of this step is shown in the main lookup table 2710.

[0161] In step 2620, receiver 2420 dynamically creates a first lookup table, which includes the first magnetic field measurement B from the main lookup table. xi Or the first magnetic field measurement range B xi All rows of ±ΔB. Therefore, the first lookup table is a subset of the main lookup table. Figure 27 An example of the first lookup table 2720 is shown in the figure.

[0162] In step 2630, receiver 2420 measures the second magnetic field B from magnetic sensor device 2410. yi The value is compared with a second magnetic field measurement stored in a first lookup table. An error ±ΔB may be included in the second magnetic field measurement B. yi In this case, receiver 2420 will measure the second magnetic field range B. yi ±ΔB is compared with the second magnetic field measurement value stored in the first lookup table.

[0163] In step 2640, receiver 2420 dynamically creates a second lookup table, which includes the second magnetic field measurement B from the first lookup table. yi Or the second magnetic field measurement range B yi All rows of ±ΔB. Therefore, the second lookup table is a subset of the first lookup table. Figure 27 An example of the second lookup table 2730 is shown below. The value in the second lookup table 2730 corresponds to B. xi and B yi The intersection of the planes results in an array of points scattered on various planes parallel to the coil surface (e.g., the surface of device 10).

[0164] In step 2650 (via placeholder A), receiver 2450 measures the third magnetic field B from magnetic sensor device 2410. zi The value is compared with the third magnetic field measurement stored in the second lookup table. The error ±ΔB can be included in the third magnetic field measurement B. zi In this case, receiver 2420 will measure the third magnetic field range B. zi ±ΔB is compared with the third magnetic field measurement stored in the second lookup table.

[0165] In step 2660, receiver 2420 dynamically creates a third lookup table, which includes the third magnetic field measurement B from the second lookup table. zi Or the second magnetic field measurement range B zi All rows of ±ΔB. Therefore, the third lookup table is a subset of the second lookup table. Figure 27 An example of the third lookup table 2740 is shown. The value in the second lookup table 2730 corresponds to B. xi Byi and B zi The intersection of planes.

[0166] The third lookup table created in step 2660 may include a single row or multiple rows. A single row corresponds to the relative three-dimensional coordinates or position of the magnetic sensor device 2410. When the output of step 2650 includes multiple rows from the second lookup table, then in optional step 2670, the receiver determines that it has a position relative to B. xi B yi B zi The relative three-dimensional coordinates of the minimum Euclidean difference or distance. In the third lookup table 2740, the output coordinates correspond to the 567th entry in the main lookup table 2710 (i.e., x). 567 y 567 z 567 B x567 B y567 and B z567 ).

[0167] Figure 28 This is a flowchart of a method 2800 for manufacturing an apparatus (e.g., apparatus 10) for generating a monotonically changing magnetic field gradient according to an embodiment.

[0168] In step 2810, a first electromagnetic coil group is formed. The first electromagnetic coil group (e.g., first electromagnetic coil group 110) is configured to generate a first magnetic field gradient relative to a first axis (e.g., the X-axis). In some embodiments, step 1110 includes (a) forming a first clockwise spiral winding with a first conductor (e.g., conductor 322) and (b) forming a first counterclockwise spiral winding with a second conductor (e.g., conductor 324). The first clockwise spiral winding and the first counterclockwise spiral winding each have an axis of symmetry parallel to the first axis. The first clockwise spiral winding may be placed adjacent to or immediately next to the first counterclockwise spiral winding. For example, the first conductor 322 and the second conductor 324 may be in physical contact with each other, or there may be a small gap between them. The axis of symmetry of the first clockwise spiral winding may be aligned with the axis of symmetry of the first counterclockwise spiral winding, which can provide a uniform or substantially uniform magnetic field gradient relative to the first axis.

[0169] In some embodiments, forming the first electromagnetic coil group includes elongating first clockwise and counterclockwise helical windings in a direction parallel to a second axis (e.g., parallel to the Y-axis). For example, the first clockwise and counterclockwise helical windings may include an elliptical, racetrack-shaped (e.g., stadium-shaped), rectangular, rounded rectangle, or other elongated shape.

[0170] The first electromagnetic coil assembly is typically arranged in a plane defined by a first axis and a second axis (e.g., the X and Y axes). For example, the wires forming the first clockwise helical winding and the first counterclockwise helical winding have a thickness or height that defines the thickness or height of the first electromagnetic coil assembly. The top and bottom surfaces of the first electromagnetic coil assembly are flat and parallel to the XY plane.

[0171] In step 2820, a second electromagnetic coil group is formed. The second electromagnetic coil group (e.g., second electromagnetic coil group 120) is configured to generate a second magnetic field gradient relative to a second axis (e.g., Y-axis) orthogonal to a first axis (e.g., X-axis). In some embodiments, step 2820 includes (a) forming a second clockwise spiral winding with a third conductor (e.g., conductor 822) and (b) forming a second counterclockwise spiral winding with a fourth conductor (e.g., conductor 824). The second clockwise spiral winding and the second counterclockwise spiral winding each have an axis of symmetry parallel to the second axis. The second clockwise spiral winding may be placed adjacent to or immediately next to the second counterclockwise spiral winding. For example, the third conductor 822 and the fourth conductor 824 may be in physical contact with each other, or a small gap may exist between them. The axis of symmetry of the second clockwise spiral winding may be aligned with the axis of symmetry of the second counterclockwise spiral winding, which can provide a uniform or substantially uniform magnetic field gradient relative to the second axis.

[0172] In some embodiments, forming the second electromagnetic coil group includes extending second clockwise and counterclockwise helical windings in a direction parallel to the first axis (e.g., parallel to the X-axis). For example, the second clockwise and counterclockwise helical windings may include an elliptical, racetrack-shaped (e.g., stadium-shaped), rectangular, rounded rectangle, or other elongated shape.

[0173] The second electromagnetic coil assembly is typically arranged in a plane defined by a first axis and a second axis (e.g., the X-axis and the Y-axis). For example, the wires forming the second clockwise helical winding and the second counterclockwise helical winding have a thickness or height that defines the thickness or height of the second electromagnetic coil assembly. The top and bottom surfaces of the second electromagnetic coil assembly are flat and parallel to the XY plane.

[0174] In step 2830, a third electromagnetic coil group is formed. The third electromagnetic coil group (e.g., third electromagnetic coil group 130) is configured to generate a third magnetic field gradient relative to a third axis (e.g., the Z-axis) orthogonal to the first and second axes (e.g., the X-axis and Y-axis). In some embodiments, step 2830 includes forming a helical winding with a fifth conductor (e.g., conductor 612). The helical winding may be flat within the plane defined by the first and second axes (e.g., the X-axis and Y-axis). The helical winding may be in the form of a ring, loop, or disc, wherein the internal cavity does not include the helical winding. The helical winding may be symmetrical with respect to the first, second, and third axes.

[0175] The third electromagnetic coil assembly is typically arranged in a plane defined by the first and second axes (e.g., the X and Y axes). For example, the wire forming the helical winding has a thickness or height that defines the thickness or height of the third electromagnetic coil assembly. The top and bottom surfaces of the third electromagnetic coil assembly are flat and parallel to the XY plane.

[0176] In step 2840, the first, second, and third electromagnetic coil groups are arranged vertically and / or aligned relative to a third axis (e.g., the Z-axis). In some embodiments, the first, second, and third electromagnetic coil groups may be directly stacked on top of each other.

[0177] In step 2850, a controller (e.g., controller 100) is electrically connected to a first group of electromagnetic coils, a second group of electromagnetic coils, and a third group of electromagnetic coils. The controller is configured to selectively power the first, second, and / or third group of electromagnetic coils to generate a positioning magnetic field gradient with a monotonically varying amplitude (e.g., field of view) relative to at least a portion of each axis. For example, the controller may be configured to simultaneously (a) power only the first and third groups of electromagnetic coils, (b) power only the second and third groups of electromagnetic coils, and (c) power only the third group of electromagnetic coils. Power can be supplied in a predetermined order and / or at a predetermined timing, which can encode the magnetic field gradient. Power can be supplied in any order.

[0178] The controller can be configured and / or programmed to have a first setting to generate a first positioning magnetic field gradient relative to a first axis, wherein at least a portion of the first positioning magnetic field gradient has an amplitude that monotonically varies along the first axis (e.g., a first field of view (FOV) relative to the first axis). In the first setting, the controller supplies power to only the first and third electromagnetic coil groups simultaneously. The controller can also be configured and / or programmed to have a second setting to generate a second positioning magnetic field gradient relative to a second axis, wherein at least a portion of the second positioning magnetic field gradient has an amplitude that monotonically varies along the second axis (e.g., a second FOV relative to the second axis). In the second setting, the controller supplies power to only the second and third electromagnetic coil groups simultaneously. The controller can also be configured and / or programmed to have a third setting to generate a third positioning magnetic field gradient relative to a third axis, wherein at least a portion of the third positioning magnetic field gradient has an amplitude that monotonically varies along the third axis (e.g., a third FOV relative to the third axis). In the third setting, the controller supplies power to only the third electromagnetic coil group simultaneously. The controller can be configured to supply power sequentially and / or selectively in a predetermined timing according to a first setting, a second setting, and a third setting, both of which can encode the first positioning magnetic field gradient, the second positioning magnetic field gradient, and the third positioning magnetic field gradient.

[0179] In some embodiments, the controller or receiver may store data representing a series of measurements of the magnetic field at a known location relative to the set of electromagnetic coils for each magnetic field gradient, for example, as discussed herein. The data may be stored in a database, a lookup table, or in another form. Alternatively, the controller may store a mathematical model of the data that can be used to determine the relative position of the magnetic sensor for a given magnetic field measurement of the magnetic sensor device. In another embodiment, a computer or receiver for the magnetic sensor device may store the data and / or the mathematical model. The computer or receiver may communicate with the controller.Additional details regarding the use of magnetic field gradients to locate magnetic sensor devices are disclosed in the following patents: (a) U.S. Patent No. 9,915,641, published March 13, 2018, entitled "Sensing and Actuation of Biological Function Using Addressable Transmitters Operated as Magnetic Spins"; (b) U.S. Patent No. 10,466,227, published November 5, 2019, entitled "Sensing and Actuation of Biological Function Using Addressable Transmitters Operated as Magnetic Spins"; (c) U.S. Patent No. 2019 / 0388105, published December 26, 2019, entitled "Surgical Alignment by Magnetic Field Gradient Localization"; and (d) U.S. Patent No. 2012, published December 26, 2012, entitled "In-Vitro Monitoring Of An Internal Volume of Mammals Using Magnetic Field". This application claims priority to U.S. Patent No. 17 / 097,421 entitled "Gradients", U.S. Patent No. 62 / 934,763 entitled "Real-Time GI Tract Monitoring with High Precision in 3D Using Atoms Microchips" filed November 13, 2019, and U.S. Patent No. 62 / 934,767 entitled "Magnetic Gradient Coil Design For Micro-Device Localization" filed November 13, 2019, and U.S. Patent No. 63 / 075,980 entitled "Precision Surgery Using Smart Surgical Tags" filed September 9, 2020, each of which is incorporated herein by reference.

[0180] Figure 29This is a flowchart 2900 of a method for generating a magnetic field gradient according to an embodiment. In step 2910, a controller (e.g., controller 100) is electrically connected to (a) a first electromagnetic coil group configured to generate a first magnetic field, (b) a second electromagnetic coil group configured to generate a second magnetic field, and (c) a third electromagnetic coil group configured to generate a third magnetic field. The first, second, and third electromagnetic coil groups may be identical to the first electromagnetic coil group 110, the second electromagnetic coil group 120, and the third electromagnetic coil group 130, respectively.

[0181] In step 2920, the controller simultaneously supplies power only to (a) the first electromagnetic coil group and (c) the third electromagnetic coil group. During step 2920, the controller does not supply power to (b) the second electromagnetic coil group. Supplying power only to (a) the first electromagnetic coil group and (c) the third electromagnetic coil group simultaneously generates a first combined magnetic field gradient relative to the first axis. The first combined magnetic field gradient includes a first magnetic field generated by the first electromagnetic coil group and a third magnetic field generated by the third electromagnetic coil group. The third magnetic field can be used as an offset of the first magnetic field, such that the first combined magnetic field gradient has an amplitude that monotonically varies relative to the first axis along at least a portion of it (e.g., FOV) (such as along a portion of the first electromagnetic coil group).

[0182] In step 2930, the controller simultaneously supplies power only to (b) the second electromagnetic coil group and (c) the third electromagnetic coil group. During step 2930, the controller does not supply power to (a) the first electromagnetic coil group. Supplying power only to (b) the second electromagnetic coil group and (c) the third electromagnetic coil group simultaneously generates a second combined magnetic field gradient relative to the second axis. The second combined magnetic field gradient includes a second magnetic field generated by the second electromagnetic coil group and a third magnetic field generated by the third electromagnetic coil group. The third magnetic field can be used as an offset of the second magnetic field, such that the second combined magnetic field gradient has an amplitude that monotonically varies relative to the second axis along at least a portion of it (e.g., FOV) (such as along a portion of the second electromagnetic coil group).

[0183] In step 2940, the controller supplies power only to (c) the third electromagnetic coil group. Supplying power only to (c) the third electromagnetic coil group generates a third magnetic field gradient, which has an amplitude that varies monotonically relative to at least a portion (e.g., FOV) of the third axis.

[0184] In one embodiment, steps 2920, 2930, and 2940 can be repeated according to a predetermined timing sequence. The predetermined timing sequence can encode the magnetic field gradient based on time and / or sequence. Steps 2920, 2930, and 2940 do not need to be performed in the order shown in method 2900. However, it is preferable to perform steps 2920, 2930, and 2940 in the same order in each predetermined timing sequence to encode the magnetic field gradient. In an alternative embodiment, steps 2920, 2930, and 2940 can be performed in a different or random sequence order in each loop of method 2900 to encrypt the magnetic field gradient.

[0185] Figure 30 This is a flowchart of a method 3000 for determining the relative position of an object using a magnetic field gradient, according to an embodiment. In step 3010, a three-dimensional magnetic field generator (e.g., device 10) sequentially generates (a) a first magnetic field gradient along a first axis, the first magnetic field gradient having a monotonically varying magnitude along a portion of the first axis; (b) a second magnetic field gradient along a second axis orthogonal to the first axis, the second magnetic field gradient having a monotonically varying magnitude along a portion of the second axis; and (c) a third magnetic field gradient along a third axis orthogonal to both the first and second axes. The third magnetic field gradient has a monotonically varying magnitude along a portion of the third axis. The first magnetic field gradient is generated at a first time or time period. The second magnetic field gradient is generated at a second time or time period different from the first time or time period. The third magnetic field gradient is generated at a third time or time period different from the first time and the second time or time period.

[0186] In step 3020, a three-dimensional magnetic sensor (e.g., three-dimensional magnetic sensor 2412) in the magnetic sensor device (e.g., magnetic sensor device 2410) is used to measure a first total magnetic field (e.g., a first positioning magnetic field) at the three-dimensional position of the magnetic sensor device at a first time or time period. The first total magnetic field corresponds to the first magnetic field gradient generated in step 3010.

[0187] In step 3030, a three-dimensional magnetic sensor (e.g., three-dimensional magnetic sensor 2412) in the magnetic sensor device (e.g., magnetic sensor device 2410) is used to measure a second total magnetic field (e.g., a second positioning magnetic field) at the three-dimensional position of the magnetic sensor device at a second time or time period. The second total magnetic field corresponds to the second magnetic field gradient generated in step 3010.

[0188] In step 3040, a three-dimensional magnetic sensor (e.g., three-dimensional magnetic sensor 2412) in the magnetic sensor device (e.g., magnetic sensor device 2410) is used to measure a third total magnetic field (e.g., a third positioning magnetic field) at the three-dimensional position of the magnetic sensor device at a third time or time period. The third total magnetic field corresponds to the third magnetic field gradient generated in step 3010.

[0189] In step 3050, the magnetic sensor device broadcasts measurements of the first, second, and third total magnetic fields using a device antenna (e.g., antenna 2416). These measurements can be encoded in the output signal, for example, by a processor within the magnetic sensor device.

[0190] In step 3060, the measurements of the first total magnetic field, the second total magnetic field, and the third total magnetic field are received by a microprocessor-based receiver including a receiver antenna.

[0191] In step 3070, the receiver uses measurements of the first, second, and third total magnetic fields to determine the three-dimensional position of the magnetic sensor device. For example, the receiver may use a lookup table according to method 2600. Alternatively, the receiver may use a mathematical model, machine learning, or other methods to determine the three-dimensional position of the magnetic sensor device using measurements of the first, second, and third total magnetic fields. The receiver may then display, output, and / or store the three-dimensional position of the magnetic sensor device determined in step 3070.

[0192] This invention should not be considered limited to the specific embodiments described above. Various modifications, equivalent processes, and numerous structures applicable to this invention will be apparent to those skilled in the art upon reading this disclosure. The above embodiments can be implemented in a variety of ways. One or more aspects and embodiments relating to the execution of a process or method can be performed or controlled using program instructions executable by a device (e.g., a computer, processor, or other device).

[0193] In this regard, various inventive concepts can be embodied in a non-transitory computer-readable storage medium (or multiple non-transitory computer-readable storage media) (e.g., any suitable type of computer memory, including transient or non-transitory digital storage cells, circuit configurations in field-programmable gate arrays or other semiconductor devices, or other tangible computer storage media) encoding one or more programs, which, when executed on one or more computers or other processors, perform one or more methods implementing the various embodiments described above. When implemented as software (e.g., as an app), the software code can execute on any suitable processor or set of processors, whether provided in a single computer or distributed among multiple computers.

[0194] Furthermore, it should be understood that a computer can be implemented in any of a variety of forms, such as rack-mounted computers, desktop computers, laptop computers, or tablet computers, as non-limiting examples. Additionally, a computer can be embedded in a device that is not typically considered a computer but has suitable processing capabilities, including personal digital assistants (PDAs), smartphones, or any other suitable portable or fixed electronic device.

[0195] Furthermore, the computer may have one or more communication devices that can be used to interconnect the computer to one or more other devices and / or systems, such as one or more networks of any suitable form, including local area networks (LANs) or wide area networks (WANs), such as enterprise networks, intelligent networks (INs), or the Internet. Such networks may be based on any suitable technology and may operate according to any suitable protocol, and may include wireless or wired networks.

[0196] In addition, a computer may have one or more input devices and / or one or more output devices. These devices can be used, in particular, to present a user interface. Examples of output devices that can be used to provide a user interface include printers or displays for visual presentation of output and speakers or other sound-generating devices for auditory presentation of output. Examples of input devices that can be used for a user interface include keyboards and pointing devices such as mice, touchpads, and digitizing tablets. As another example, a computer may receive input information via speech recognition or in other audible formats.

[0197] One or more non-transitory computer-readable media may be transmissible, such that one or more programs stored thereon may be loaded onto one or more different computers or other processors to implement one or more of the various aspects described above. In some embodiments, the computer-readable medium may be a non-transitory medium.

[0198] The terms “program,” “app,” and “software” are used herein in a general sense to refer to any type of computer code or set of computer-executable instructions that can be used to program a computer or other processor to implement the various aspects described above. Furthermore, it should be understood that, according to one aspect, one or more computer programs that perform the methods of this application when executed do not need to reside on a single computer or processor, but can be distributed in a modular manner among multiple different computers or processors to implement the various aspects of this application.

[0199] Computer-executable instructions can take many forms, such as program modules that are executed by one or more computers or other devices. Typically, program modules include routines, programs, objects, components, data structures, etc., that perform specific tasks or implement specific abstract data types. In various embodiments, the functionality of program modules can be combined or distributed as needed.

[0200] Furthermore, data structures can be stored in any suitable form on a computer-readable medium. For simplicity, a data structure can be shown as having fields related by their position within the data structure. Such relationships can also be implemented by allocating storage for fields that convey the relationships between fields in a computer-readable medium. However, any suitable mechanism can be used to establish relationships between information in the fields of a data structure, including by using pointers, labels, or other mechanisms to establish relationships between data elements.

[0201] Therefore, this disclosure and claims include new and novel improvements to existing methods and techniques that were not previously known and were not implemented to achieve the aforementioned useful results. Users of this method and system will derive tangible benefits from the functionality now achievable due to the effects of the system and its output to the user resulting from the specific modifications described herein. Significantly improved operation is anticipated when implementing the claimed invention using the technical components described herein.

[0202] Furthermore, as described, some aspects can be embodied as one or more methods. Actions performed as part of a method can be ordered in any suitable manner. Therefore, embodiments in which actions are performed in a different order than that shown can be constructed, which may include performing several actions simultaneously, even if they are shown as sequential actions in the illustrative embodiments.

Claims

1. An apparatus for generating a magnetic field gradient, comprising: A first planar electromagnetic coil group is configured to generate a first magnetic field gradient relative to a first axis; The second planar electromagnetic coil group is configured to generate a second magnetic field gradient relative to a second axis orthogonal to the first axis; A third planar electromagnetic coil group is configured to generate a third magnetic field gradient relative to a third axis orthogonal to the first and second axes, wherein the first, second, and third planar electromagnetic coil groups are arranged perpendicularly to the third axis. as well as The controller is configured to selectively power the first planar electromagnetic coil group, the second planar electromagnetic coil group, and / or the third planar electromagnetic coil group to sequentially generate positioning magnetic field gradients relative to each of the first, second, and third axes, each positioning magnetic field gradient having at least a portion of a magnetic field amplitude that monotonically varies along the corresponding axis. The controller is configured to supply power to the first planar electromagnetic coil group and the third planar electromagnetic coil group only simultaneously, thereby generating a first positioning magnetic field gradient relative to the first axis.

2. The apparatus according to claim 1, wherein, The first planar electromagnetic coil group, the second planar electromagnetic coil group, and the third planar electromagnetic coil group are stacked.

3. The apparatus according to claim 1, wherein, The first planar electromagnetic coil group includes clockwise spiral windings and counterclockwise spiral windings arranged adjacent to each other.

4. The apparatus according to claim 3, wherein, The clockwise spiral winding and the counterclockwise spiral winding are each formed by their respective conductors.

5. The apparatus according to claim 3, wherein: The clockwise spiral winding and the counterclockwise spiral winding each extend in a direction parallel to the second axis. The clockwise spiral winding and the counterclockwise spiral winding each have an axis of symmetry parallel to the first axis, and The axis of symmetry of the clockwise spiral winding is aligned with the axis of symmetry of the counterclockwise spiral winding.

6. The apparatus according to claim 5, wherein: The first planar electromagnetic coil group has a width parallel to the first axis, and (a) The ratio of at least a portion of the positioning magnetic field gradient having a magnetic field amplitude that varies monotonically along the first axis to (b) the width of the first planar electromagnetic coil group is in the range of 1:2 to 3:

4.

7. The apparatus according to claim 6, wherein, The ratio is 2:

3.

8. The apparatus according to claim 3, wherein: The clockwise spiral winding is the first clockwise spiral winding. The counterclockwise spiral winding is the first counterclockwise spiral winding, and The second planar electromagnetic coil group includes a second clockwise spiral winding and a second counterclockwise spiral winding arranged adjacent to each other.

9. The apparatus according to claim 8, wherein, The first clockwise spiral winding, the second clockwise spiral winding, the first counterclockwise spiral winding, and the second counterclockwise spiral winding are each formed by corresponding wires.

10. The apparatus according to claim 8, wherein: The first clockwise spiral winding and the first counterclockwise spiral winding each extend in a direction parallel to the second axis. The first clockwise spiral winding and the first counterclockwise spiral winding each have an axis of symmetry parallel to the first axis. The axis of symmetry of the first clockwise spiral winding is aligned with the axis of symmetry of the first counterclockwise spiral winding. The second clockwise spiral winding and the second counterclockwise spiral winding each extend in a direction parallel to the first axis. The second clockwise helical winding and the second counterclockwise helical winding each have an axis of symmetry parallel to the second axis, and The axis of symmetry of the second clockwise spiral winding is aligned with the axis of symmetry of the second counterclockwise spiral winding.

11. The apparatus according to claim 10, wherein: The first planar electromagnetic coil group has a width parallel to the first axis. The second planar electromagnetic coil assembly has a length parallel to the second axis. (a) the ratio of at least a portion of the positioning magnetic field gradient, having a magnetic field amplitude that varies monotonically along the first axis, to (b) the width of the first planar electromagnetic coil group is greater than or equal to 1:2, and (c) The ratio of at least a portion of the positioning magnetic field gradient having a magnetic field amplitude that varies monotonically along the second axis to (d) the length of the second planar electromagnetic coil group is less than or equal to 1:

2.

12. The apparatus according to claim 11, wherein: (a) the ratio of at least a portion of the positioning magnetic field gradient, having a magnetic field amplitude that monotonically varies along the first axis, to (b) the width of the first planar electromagnetic coil group is in the range of 1:2 to 3:4, and (c) The ratio of at least a portion of the positioning magnetic field gradient having a magnetic field amplitude that varies monotonically along the second axis to (d) the length of the second planar electromagnetic coil group is in the range of 1:2 to 3:

4.

13. The apparatus according to claim 11, wherein, The third planar electromagnetic coil group includes a helical winding in a ring shape.

14. The apparatus according to claim 13, wherein: The ring has an outer diameter measured parallel to the first axis, and (e) The ratio of at least a portion of the positioning magnetic field gradient, having a magnetic field amplitude that varies monotonically along the third axis, to (f) the outer diameter of the annulus is in the range of 1:4 to 2:

5.

15. The apparatus according to claim 14, wherein, (e) The ratio of at least a portion of the positioning magnetic field gradient, having a magnetic field amplitude that varies monotonically along the third axis, to (f) the outer diameter of the annulus is 1:

3.

16. The apparatus according to claim 1, wherein, The first positioning magnetic field gradient includes the total magnetic field generated by the first planar electromagnetic coil group and the third planar electromagnetic coil group.

17. The apparatus according to claim 16, wherein, The controller is configured to supply power only to the second planar electromagnetic coil group and the third planar electromagnetic coil group simultaneously, thereby generating a second positioning magnetic field gradient relative to the second axis.

18. The apparatus according to claim 17, wherein, The second positioning magnetic field gradient includes the total magnetic field generated by the second planar electromagnetic coil group and the third planar electromagnetic coil group.

19. The apparatus according to claim 17, wherein, The controller is configured to supply power only to the third planar electromagnetic coil group, thereby generating a third positioning magnetic field gradient relative to the third axis.

20. The apparatus according to claim 17, wherein, The controller is configured to selectively supply power according to a predetermined timing sequence to encode each positioning magnetic field gradient.

21. A manufacturing method, comprising: A first planar electromagnetic coil group is formed, the first planar electromagnetic coil group being configured to generate a first magnetic field gradient relative to a first axis; A second planar electromagnetic coil group is formed, the second planar electromagnetic coil group being configured to generate a second magnetic field gradient relative to a second axis orthogonal to the first axis; A third planar electromagnetic coil group is formed, the third planar electromagnetic coil group being configured to generate a third magnetic field gradient relative to a third axis orthogonal to the first axis and the second axis; The first planar electromagnetic coil group, the second planar electromagnetic coil group, and the third planar electromagnetic coil group are arranged perpendicularly along the third axis. The controller is electrically connected to the first planar electromagnetic coil group, the second planar electromagnetic coil group, and the third planar electromagnetic coil group. The controller is configured to selectively supply power to the first planar electromagnetic coil group, the second planar electromagnetic coil group, and / or the third planar electromagnetic coil group to generate a positioning magnetic field gradient relative to each of the first axis, the second axis, and the third axis, wherein at least a portion of each positioning magnetic field gradient has a magnetic field amplitude that varies monotonically along the respective axis. as well as The controller is configured to have a first setting that supplies power only to the first planar electromagnetic coil group and the third planar electromagnetic coil group to generate a first positioning magnetic field gradient relative to the first axis, at least a portion of which has a magnetic field amplitude that varies monotonically along the first axis.

22. The method according to claim 21, wherein, Forming the first planar electromagnetic coil group includes: A first clockwise spiral winding is formed using a first conductor, the first clockwise spiral winding having an axis of symmetry parallel to the first axis; A first counterclockwise spiral winding is formed using a second conductor, the first counterclockwise spiral winding having an axis of symmetry parallel to the first axis; The first clockwise spiral winding is placed adjacent to the first counterclockwise spiral winding; and Align the axis of symmetry of the first clockwise spiral winding with the axis of symmetry of the first counterclockwise spiral winding.

23. The method according to claim 22, wherein, Forming the second planar electromagnetic coil group includes: A second clockwise spiral winding is formed using a third conductor, the second clockwise spiral winding having an axis of symmetry parallel to a second axis orthogonal to the first axis; A second counterclockwise spiral winding is formed using a fourth conductor, the second counterclockwise spiral winding having an axis of symmetry parallel to the second axis; The second clockwise spiral winding is placed adjacent to the second counterclockwise spiral winding; and Align the axis of symmetry of the second clockwise spiral winding with the axis of symmetry of the second counterclockwise spiral winding.

24. The method according to claim 23, wherein, Forming the third planar electromagnetic coil group includes forming a helical winding with a fifth wire in a ring shape, the helical winding having an axis of symmetry parallel to a third axis orthogonal to the first and second axes.

25. The method of claim 24, further comprising elongating the first clockwise spiral winding and the first counterclockwise spiral winding in a direction parallel to the second axis.

26. The method of claim 25, further comprising elongating the second clockwise spiral winding and the second counterclockwise spiral winding in a direction parallel to the first axis.

27. The method of claim 21, further comprising vertically stacking the first planar electromagnetic coil group, the second planar electromagnetic coil group, and the third planar electromagnetic coil group.

28. The method of claim 21, further comprising configuring the controller to have a second setting that supplies power only to the second planar electromagnetic coil group and the third planar electromagnetic coil group to generate a second positioning magnetic field gradient relative to the second axis, at least a portion of the second positioning magnetic field gradient having a magnetic field amplitude that varies monotonically along the second axis.

29. The method of claim 28, further comprising configuring the controller to have a third setting that supplies power only to the third planar electromagnetic coil group to generate a third positioning magnetic field gradient relative to the third axis, at least a portion of the third positioning magnetic field gradient having a magnetic field amplitude that varies monotonically along the third axis.

30. The method of claim 29, further comprising configuring the controller to supply power according to the first setting, the second setting and the third setting in a predetermined timing sequence to encode corresponding first positioning magnetic field gradient, second positioning magnetic field gradient and third positioning magnetic field gradient.

31. A method for generating a magnetic field gradient, comprising: The controller is electrically connected to (a) a first planar electromagnetic coil group configured to generate a first magnetic field gradient relative to a first axis, (b) a second planar electromagnetic coil group configured to generate a second magnetic field gradient relative to a second axis, and (c) a third planar electromagnetic coil group configured to generate a third magnetic field gradient relative to a third axis, wherein the first axis, the second axis, and the third axis are orthogonal to each other, and wherein the first planar electromagnetic coil group, the second planar electromagnetic coil group, and the third planar electromagnetic coil group are arranged perpendicular to the third axis; Using the controller, power is supplied to (a) and (c) only at the same time in the first moment; Using the controller, power is supplied to (b) and (c) simultaneously only at a second time, different from the first time. as well as Using a controller, power is supplied to (c) only at a third time, which is different from the first time and the second time.

32. The method according to claim 31, wherein, Simultaneously supplying power to (a) and (c) includes generating a first combined magnetic field gradient relative to the first axis, at least a portion of which has a magnetic field amplitude that varies monotonically along the first axis.

33. The method according to claim 32, wherein: The first planar electromagnetic coil group has a width parallel to the first axis, and (a) The ratio of at least a portion of the magnetic field gradient of the first combined magnetic field, having a magnetic field amplitude that varies monotonically along the first axis, to (b) the width of the first electromagnetic coil group is in the range of 1:2 to 3:

4.

34. The method according to claim 32, wherein, Simultaneous power supply to (b) and (c) includes generating a second combined magnetic field gradient relative to the second axis, the second combined magnetic field gradient having an amplitude that varies monotonically over at least a portion of the second electromagnetic coil assembly.

35. The method according to claim 34, wherein: The second planar electromagnetic coil assembly has a length parallel to the second axis, and (a) The ratio of at least a portion of the second combined magnetic field gradient having a magnetic field amplitude that varies monotonically along the first axis to (b) the length of the second electromagnetic coil group is in the range of 1:2 to 3:

4.

36. The method according to claim 31, wherein, Supplying power to (c) alone includes generating a third magnetic field gradient, at least a portion of which has a magnetic field amplitude that varies monotonically along the third axis.

37. The method of claim 36, wherein: The third planar electromagnetic coil group includes a helical winding in a ring shape. The ring has an outer diameter measured parallel to the first axis, and (e) The ratio of at least a portion of the third magnetic field gradient, having a magnetic field amplitude that varies monotonically along the third axis, to (f) the outer diameter of the annulus is in the range of 1:4 to 2:

5.

38. The method of claim 31, further comprising repeating the following steps according to a predetermined timing sequence: Power is supplied to (a) and (c) simultaneously at the first moment. In the second time, power is supplied to (b) and (c) simultaneously only, and Power is supplied only to (c) at the third time.

39. A system for generating a magnetic field gradient, comprising: A three-dimensional magnetic field generator, including: A first planar electromagnetic coil group is configured to generate a first magnetic field gradient along a first axis; The second planar electromagnetic coil group is configured to generate a second magnetic field gradient along a second axis orthogonal to the first axis; A third planar electromagnetic coil assembly is configured to generate a third magnetic field gradient along a third axis orthogonal to the first and second axes; and A controller is configured to selectively power the first planar electromagnetic coil group, the second planar electromagnetic coil group, and / or the third planar electromagnetic coil group to sequentially generate a positioning magnetic field gradient relative to each of the first axis, the second axis, and the third axis, each positioning magnetic field gradient having at least a portion having a magnetic field amplitude that varies monotonically along the respective axis, wherein the controller is configured to power only the first planar electromagnetic coil group and the third planar electromagnetic coil group simultaneously to generate a first positioning magnetic field gradient relative to the first axis; Magnetic sensor devices, including: A three-dimensional magnetic sensor outputs measurements of the magnetic field gradient for each positioning location; A controller, electrically coupled to the three-dimensional magnetic sensor, generates a magnetic sensor output signal that encodes the measurement of each positioning magnetic field gradient; A device antenna, electrically coupled to the controller, broadcasts the output signal of the magnetic sensor; and Power supply, electrically coupled to the three-dimensional magnetic sensor and the controller; and Receiver, including: microprocessor; The receiver antenna receives the output signal of the magnetic sensor from the device antenna; and The microprocessor-accessible non-volatile memory includes computer-readable instructions that, when executed by the processor, cause the microprocessor to use measurements of each positioning magnetic field gradient to determine the three-dimensional position of the magnetic sensor device.

40. The system according to claim 39, wherein, The non-volatile memory includes a lookup table that includes multiple measurements of each location magnetic field gradient at a known three-dimensional location.

41. A method for determining the relative position of an object using a magnetic field gradient, comprising: Using a three-dimensional magnetic field generator, the following are generated sequentially: A first positioning magnetic field gradient along a first axis, at least a portion of which has a magnetic field amplitude that varies monotonically along the first axis, the first positioning magnetic field gradient being generated in a first instant. A second positioning magnetic field gradient along a second axis orthogonal to the first axis, at least a portion of which has a magnetic field amplitude that varies monotonically along the second axis, the second positioning magnetic field gradient being generated at a second time different from the first time, and A third positioning magnetic field gradient along a third axis orthogonal to the first and second axes, at least a portion of which has a magnetic field amplitude that varies monotonically along the third axis, and which is generated at a third time different from the first and second times. The three-dimensional magnetic field generator mentioned above includes: A first planar electromagnetic coil group is configured to generate a first magnetic field gradient relative to a first axis; The second planar electromagnetic coil group is configured to generate a second magnetic field gradient relative to the second axis; The third planar electromagnetic coil group is configured to generate a third magnetic field gradient relative to a third axis, and the first planar electromagnetic coil group, the second planar electromagnetic coil group and the third planar electromagnetic coil group are arranged perpendicularly to the third axis. as well as The controller is configured to selectively supply power to the first planar electromagnetic coil group, the second planar electromagnetic coil group, and / or the third planar electromagnetic coil group to sequentially generate the first positioning magnetic field gradient, the second positioning magnetic field gradient, and the third positioning magnetic field gradient. The controller is configured to supply power to the first planar electromagnetic coil group and the third planar electromagnetic coil group only simultaneously, thereby generating the first positioning magnetic field gradient relative to the first axis. A magnetic sensor device that utilizes a three-dimensional magnetic sensor and a device antenna, The first total magnetic field at the three-dimensional position of the magnetic sensor device is measured at the first time. The second total magnetic field at the three-dimensional position of the magnetic sensor device is measured at the second time. The third total magnetic field at the three-dimensional position of the magnetic sensor device is measured at the third time; and The measurements of the first total magnetic field, the second total magnetic field, and the third total magnetic field are broadcast using the device antenna; and Utilizing a receiver that includes a microprocessor and a receiver antenna, The receiver antenna is used to receive measurements of the first total magnetic field, the second total magnetic field, and the third total magnetic field; and The three-dimensional position of the magnetic sensor device is determined by measuring the first total magnetic field, the second total magnetic field, and the third total magnetic field.

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