Magnetic field probe for determining placement of implantable markers using two or more detection zones

Abstract

The present application provides a magnetic field probe for determining the angular arrangement of an implantable magnetic marker, the probe comprising: a first magnetic sensor near the distal end and a second magnetic sensor closer to the proximal end, the first magnetic sensor and the second magnetic sensor being configured to determine two or more magnetic field vectors of the marker; the probe being further configured to: define two or more marker detection zones extending from the distal end; determine the angular arrangement of the implantable marker; and determine whether the angular arrangement is substantially consistent with one of the two or more marker detection zones, thereby determining that the marker falls within one marker detection zone. By defining two or more marker detection zones and configuring the probe to determine whether a magnetic marker appears within one marker detection zone, a simplified and intuitive decision algorithm is provided to indicate the arrangement of the marker relative to the probe.

Description

Technical Field

[0001] The present disclosure relates to a magnetic field probe for determining the angular arrangement of an implanted marker, a detection unit comprising the probe and a method of detecting the angular arrangement of an implanted marker. Background Art

[0002] During invasive and non-invasive treatments and therapies, it is important that health professionals are able to accurately locate areas of concern. Professionals often rely on vision and manual manipulation to find and remember areas of concern, which typically results in marking the outer surface of the skin. In practice, imaging devices such as X-ray and / or ultrasound may also be used to assist with positioning, however, this relies on being able to distinguish the area of ​​concern from surrounding tissue using imaging techniques. Inaccuracies in the ability to locate the area of ​​concern may mean that not all areas are treated, or that treatment is incomplete. This is a problem for both therapeutic and cosmetic surgeries and treatments (including tumor removal, polyp removal, cosmetic surgery, removal and / or correction of tissue, positioning of implanted devices - for example, birth control devices such as Implanon may require positioning).

[0003] For example, if a lesion excision or removal is prescribed after a cancer screening, the surgeon needs to know the location and extent of the lesion. The current gold standard in clinical practice requires that a metal anchor wire be placed in the target immediately prior to surgery, which carries the risk of infection and dislodged wire. Newer solutions use radioactive markers, but the use of radioactive materials is strictly controlled and regulated. Electromagnetic and RFID (radio frequency identification) markers have been developed, but these are bulky and prone to malfunction. Any inaccuracy in locating the area of ​​concern can result in incomplete excision or removal of the lesion, leading to the need for additional treatment.

[0004] Additionally, improvements in screening procedures mean that smaller, early-stage lesions are being found in an increasing number of patients—and while this early detection is better for the patient, small lesions can be difficult for surgeons to identify and locate. They can also be difficult to reach. Intraoperative imaging is often cumbersome and expensive.

[0005] Recently, the use of implantable magnetic markers (seeds) has been proposed. These magnetic markers offer a higher degree of safety than radioactive markers, but still require considerable effort on the part of the medical professional to detect the placement (localization) of the marker. This becomes even more difficult when very small magnetic markers are used to mark very small areas of interest.

[0006] U.S. Patent No. 7,561,051 describes a device for locating a magnet and / or determining the orientation of the device relative to a magnet. In one embodiment, the device includes a multi-axis magnetic field sensor that moves in a reciprocating manner to obtain sensor readings at multiple spaced-apart locations. In another embodiment, the device includes multiple multi-axis magnetic field sensors arranged along a straight line. The device can be used for many medical and other applications, including tissue removal, tracking the movement of medical devices in a body cavity, and tracking the movement of internal organs.

[0007] PCT application WO 2018 / 045465 A1 describes systems and methods for marking the location and extent of an area of ​​anatomical interest, such as a tumor, using magnetic seeds whose location and orientation are measured or otherwise detected using a detection device including two or more magnetic sensors. One or more magnetic seeds are implanted to mark and define the center and extent of an area of ​​anatomical interest, and a magnetic sensor-based detector system is used to accurately identify the location of the magnetic seeds.

[0008] US patent application US2016 / 0051164A1 describes a probe comprising a first sensor having a first magnetometer and a first accelerometer and a second sensor having a second magnetometer and a second accelerometer, which is configured to determine the distance and direction to a marker. The marker can be magnetic and can be surgically inserted into a patient to mark a specific location. The probe can be used to locate the marker to identify the location. The probe may include a microprocessor that receives an output from the first sensor and an output from the second sensor and determines the distance and direction to the marker.

[0009] U.S. Patent US 6,129,668 describes a device for detecting the position of a magnet coupled to an indwelling medical device in a patient's body using three or more groups of magnetic sensors, each group of magnetic sensors having sensor elements arranged in a known manner. Each sensor element senses the magnetic field strength generated by the magnet and provides data indicating the orientation of the magnet in three-dimensional space. An initial estimate of the position and orientation of the magnet results in a predicted magnetic field value. Based on the difference between the predicted value and the measured value, the device estimates the new position of the magnet and calculates a new predicted magnetic field strength value. This iterative process continues until the predicted value matches the measured value within a desired tolerance range. A two-dimensional display provides an indication of the position of the magnet relative to the detector housing. A depth indicator portion of the display can be used to provide a relative or absolute indication of the depth of the magnet

[0010] In order to optimally support the surgeon it is important to provide both the distance and the direction to the marked location.It is an object of the present invention to provide improved directionality detection for magnetic markers or inductive magnetic beacons. Summary of the invention

[0011] According to a first aspect of the present disclosure, there is provided a magnetic field probe for determining the angular arrangement of an implantable marker, the marker being configured to generate a magnetic field when in use, the probe comprising: a distal end; a first magnetic sensor proximal to the distal end; a second magnetic sensor disposed between the first magnetic sensor and the proximal end, the first magnetic sensor and the second magnetic sensor being configured and arranged to determine one or more magnetic field vectors of the marker when in use; the probe being further configured to: define two or more marker detection zones extending from the distal end along the longitudinal axis of the probe; determine the angular arrangement with the implantable marker using the one or more magnetic field vectors; and determine whether the angular arrangement is substantially consistent with one of the two or more marker detection zones, thereby determining that the marker falls within one of the two or more marker detection zones.

[0012] By defining two or more marker detection zones and configuring the probe to determine whether a magnetic marker is present in one of the two or more marker detection zones, a simplified decision algorithm is provided to indicate the placement of the marker relative to the probe. For example, the probability of a marker being in one of the two or more marker detection zones can be determined. Alternatively, a determination is made whether the angular placement is substantially consistent with the first or second marker detection zone.

[0013] In addition, by modifying one or more parameters or aspects associated with two or more detection zones (such as, for example, range, shape, orientation, arrangement, scaling, resolution, angular boundaries, longitudinal extent, lateral extent, and any combination thereof), the search parameters can be modified in a manner that is intuitive to the user. In other words, the zone is configured to act as a software-controlled collimator. Another advantage over prior art probes is that there is no need to continuously move the probe to determine the angular arrangement of the magnetic markers.

[0014] It may be advantageous to configure and arrange the probe head so that the two or more marker detection zones are substantially symmetrical about the longitudinal axis.

[0015] Users may find this particularly intuitive as it allows the probe to be used as a handheld wand whose detection zone is not significantly affected by rotating the wand probe about its longitudinal axis.

[0016] Configurations that can improve intuitiveness of use can include further configuring and arranging the probe to: determine the angular placement of the marker relative to the distal end of the probe; determine the angular placement of the marker relative to the longitudinal axis of the probe; determine the longitudinal and / or lateral placement of the marker relative to the distal end of the probe; or any combination thereof.

[0017] It may be advantageous to configure and arrange two or more marker detection zones to have a generally circular, oval, elliptical, triangular, rectangular or square longitudinal section substantially perpendicular to the longitudinal axis of the probe. For example, if the longitudinal axis of the probe extends along the Y axis, the longitudinal section may be determined in the XY plane or the YZ plane.

[0018] Additionally or alternatively, two or more zones may be configured and arranged to have a generally arcuate, sector-shaped, cylindrical or conical shape. Additionally or alternatively, two or more zones may be configured and arranged to have a parabolic, linear or hyperbolic shape.

[0019] By providing two or more software configurable detection zones, a user can select a configuration that is particularly suitable for, for example, the expected location of the marker in the human or animal body, the expected proximity, the expected magnetic field strength, and the expected marker orientation. The user can also select a configuration that they personally think is particularly efficient for marker positioning. Since two or more detection zones can be configured in several dimensions, two or more of these shapes and cross-sectional shapes can be combined. Simple shapes and / or complex shapes can be used.

[0020] Depending on the (user) expected proximity and / or orientation to the marker, two or more marker detection zones may also be configured and arranged to adopt a specific configuration. This may also be automated to a certain extent, depending on the measured and / or estimated proximity and / or orientation (by the probe). Any combination of varying degrees is also possible.

[0021] Additionally or alternatively, two or more marker detection zones may differ in a parameter selected from the group consisting of: range, shape, orientation, arrangement, scaling, resolution, angular boundaries, longitudinal extent, lateral extent, or any combination thereof. Additionally or alternatively, two or more marker detection zones: share one or more boundaries, are continuous along one or more axes, are discontinuous along one or more axes, or any combination thereof.

[0022] Another advantage of providing software configurable detection zones is that the user can configure and arrange two or more marker detection zones. This can provide, for example, coarse / fine marker detection zone configurations - as the distal end of the probe gets closer to the magnetic marker, the marker detection zone with a smaller angle can further improve accuracy and sensitivity.

[0023] According to another aspect of the present disclosure, the probe is further configured to: define an additional marker detection zone extending from the distal end along the longitudinal axis of the probe; and determine whether the angular arrangement is substantially consistent with one of the three or more marker detection zones, thereby determining that the marker falls within one of the three or more marker detection zones.

[0024] Another advantage of providing software configurable detection zones is that the user can configure and arrange any number of marker detection zones.

[0025] Alternatively, wherein the probe is further configured to: define an additional marker detection zone extending from the distal end along the longitudinal axis of the probe; and determine whether the angular arrangement is substantially consistent with: the additional marker detection zone; both the first marker detection zone and the additional marker detection zone; both the second marker detection zone and the additional marker detection zone; neither the first marker detection zone nor the additional marker detection zone; neither the second marker detection zone nor the additional marker detection zone; or any combination thereof.

[0026] Another advantage of providing software configurable detection zones is that the user can configure and arrange additional marker detection zones with varying degrees of specific overlap. These may be substantially fixed, dynamic, or any combination thereof.

[0027] According to another aspect of the present disclosure, the probe may include a plurality of magnetic sensors included in one or more 1D, 2D, or 3D arrays.

[0028] This allows for increased density (or packaging density) of magnetic sensors. These additional magnetic sensors can be configured and arranged to improve parameters such as, for example, sensitivity, accuracy, and reliability. In general, increasing the sensitivity of the distal end can make the probe more intuitive to use.

[0029] According to yet another aspect of the present disclosure, the probe may further include one or more compensation sensors for measuring a background magnetic field; wherein: determining one or more angular arrangements of the markers when in use further takes the background magnetic field into account.

[0030] Advantageously, existing sensors or dedicated sensors may be configured to measure (or detect) background magnetic fields, such as the Earth's magnetic field. Background measurements may be used to compensate for placement determinations to further improve accuracy and sensitivity.

[0031] According to yet another aspect of the present disclosure, the probe is configured and arranged to determine an angular arrangement with a magnetic dipole and / or an induced magnetic dipole included in the marker.

[0032] By providing a software configurable detection zone, the user can select a configuration that is particularly suitable for, for example, the expected magnetic field strength and expected marker orientation.

[0033] According to another aspect of the present disclosure, the probe is further configured and arranged to provide audio feedback, and the audio characteristics depend on the proximity to the marker. Additionally or alternatively, the audio characteristics depend on whether the angular arrangement is substantially consistent with the first or second marker detection zone. Optionally, the audio characteristics are pitch, volume, loudness, amplitude, spatial position, duration, pause duration, tone, beep, pause duration between beeps, frequency, spectrum, or any combination thereof.

[0034] It may be advantageous for the probe to be further configured and arranged to provide coarse and fine marker detection zones. It may also be advantageous for the probe to be further configured and arranged to select marker detection zones with smaller angles as the distal end of the probe gets closer to the marker.

[0035] According to another aspect of the present disclosure, the probe is configured and arranged to determine one or more aspects of the two or more detection zones based on: one or more measurements from one or more sensors; one or more suitable parameters; one or more parameters provided by a user; user selection; or any combination thereof

[0036] Software configurable detection zones provide a high degree of configuration flexibility.

[0037] According to yet another aspect of the present disclosure, a detector unit for detecting an angular arrangement of an implantable marker may be provided, the detector unit comprising a magnetic probe according to the present disclosure.

[0038] Optionally, the detector unit further comprises a display, and the detector is configured and arranged to indicate the result of the determination to a user on the display. Optionally, the detector unit is further configured and arranged to indicate the first marker detection zone and the second marker detection zone on the display.

[0039] According to another aspect of the present disclosure, there is provided a method for determining an angular arrangement of an implantable marker, the marker being configured to generate a magnetic field when in use, the method comprising:

[0040] - providing a probe comprising a distal end, the probe further comprising: a first magnetic sensor proximal to the distal end; a second magnetic sensor disposed between the first magnetic sensor and the proximal end, the first magnetic sensor and the second magnetic sensor being configured and arranged to determine one or more magnetic field vectors of the marker when in use;

[0041] - configuring and arranging the probe to define two or more marker detection zones extending from the distal end along a longitudinal axis of the probe;

[0042] - using the one or more magnetic field vectors to determine an angular disposition with respect to the implantable marker; and

[0043] - determining whether the angular arrangement is substantially consistent with one of the two or more marker detection zones.

[0044] Optionally, the method further comprises determining whether the angular arrangement is substantially consistent with the first or second marker detection zone.

[0045] Additionally or alternatively, the method comprises configuring and arranging the probe to achieve an expected position, an expected proximity, an expected magnetic field strength or an expected marker orientation of the marker within the human or animal body. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Features and advantages of some embodiments of the present invention and the manner in which the same are achieved will become more apparent upon consideration of the following detailed description of the invention taken in conjunction with the accompanying drawings, which illustrate preferred and exemplary embodiments and are not necessarily drawn to scale, wherein:

[0047] Figure 1A and Figure 1B depicts a longitudinal section through an embodiment of a magnetic field probe according to the invention;

[0048] FIG. 2A to FIG. 2F depicts additional probe configurations that may be used with the present invention;

[0049] Figure 3A A simulated schematic diagram depicting approximately circular field lines representing a cross section of the magnetic field generated by a magnetic dipole;

[0050] Figure 3B a graph depicting probe tilt versus field tilt values ​​within the probe plane;

[0051] Figure 4A and Figure 4B depicts the measurements taken at each magnetic sensor when scanning the probe at a fixed tilt through different angular arrangements;

[0052] Figure 5A and Figure 5B The difference in B-field tilt measured at distances of 15.0 mm, 20.0 mm, and 25.0 mm compared to the magnetic sensor closest to the distal end (i.e., the sensor at 10.0 mm) is depicted;

[0053] Figure 6 Depicts examples of differential measurements and lateral displacement characteristics that can be used to convert LR signals from a sensor into lateral displacement;

[0054] Figure 7 depicts an example of the expected magnetic field components when the probe is pointed directly at a magnetic dipole; and

[0055] Fig. 8Aand Figure 8B Two examples with different ranges of detection zones are depicted. DETAILED DESCRIPTION

[0056] In the following detailed description, numerous non-limiting specific details are given to aid understanding of the present disclosure. It will be apparent to those skilled in the art that the computer processing portion of the method can be implemented on any type of stand-alone system or client-server compatible system including any type of client, network, server and database elements.

[0057] Figure 1A A longitudinal section through a magnetic field probe 100 for detecting the placement (positioning) of an implantable marker 200 is depicted. As depicted, a magnetic marker 200 is implanted below the outer surface of the skin 300 to mark an area of ​​interest - this may be a few millimeters or centimeters below the outer surface of the skin. This may also be referred to as depth. The marker 200 is configured to generate a magnetic field when in use - it may include, for example, a magnetic dipole.

[0058] The marker may be implanted in any convenient manner, such as by injection. For example, the injection may be into soft tissue or an organ, or delivered to a lung bronchi via a bronchoscope, or delivered to the colon via a colonoscope. The method of implantation may depend, for example, on the depth required, the subsequent procedures to be performed, the size of the area of ​​interest, the location of the area of ​​interest, the tissue types in the area, and the tissue types surrounding the area. It may be implanted immediately prior to detection, or at an earlier time.

[0059] Typically, a suitable marker 200 comprising a magnetic dipole is generally cylindrical in shape, wherein:

[0060] - 1.45 mm in diameter, 2.19 mm in length, and a residual magnetic field (Br) of 1.43 T (Nd N52), or

[0061] - Diameter 1.75 mm, length 5 mm, residual magnetic field (Br) 1.43 T (neodymium N52).

[0062] A marker with a diameter of 1.45 mm and a length of 4.7 mm may also be suitable.

[0063] As higher grades of neodymium become available, they may also be used to advantage with embodiments of the present invention.

[0064] Additionally or alternatively, the marker 200 may include an induced magnetic dipole. Since the magnetic field probe 100 determines the angular disposition of the marker 200 based on the properties of the dipole field, the configuration and arrangement of the marker 200 used to produce such a field is less important. Combinations of various techniques may also be used to produce multiple magnetic dipoles. In the context of the present disclosure, angular disposition may be considered the same as angular arrangement - it is the angular component in the relative position of the marker 200 relative to the probe.

[0065] The probe 100 includes a distal end 160. The magnetic field probe can extend along a probe longitudinal axis 150. To make it easier to compare different views of the same and different embodiments, axes are also defined - the plane of the drawing (paper) in X 600 and Y 700, substantially perpendicular to each other. The X axis 600 extends from bottom to top and the Y axis 700 extends from right to left. The Z axis 800 is substantially perpendicular to the X 600 and Y 700 and is out of the drawing plane (out of the paper). The longitudinal axis 150 is depicted here as being substantially parallel to the Y axis 700.

[0066] The probe 100 is further configured and arranged to determine an angular arrangement between the probe reference and the marker 200, as described below—the angular arrangement may include an angular arrangement 180 in XY (in Figure 1A ), angular arrangement 190 in YZ ( Figure 1B ), the angular arrangement in XZ (not shown in Figure 1A or Figure 1B The probe reference may be one or more points of the probe 100 along the longitudinal axis 150, the distal end 160, the proximal end 165, or any combination thereof.

[0067] Figure 1B Depicted is another longitudinal section through the magnetic field probe 100 for detecting the placement (positioning) of the implantable marker 200. The drawing plane (paper) is located in Y 700 and Z 800, which are substantially perpendicular to each other. The Z axis 800 extends from bottom to top and the Y axis 700 extends from right to left. The X axis 600 is substantially perpendicular to the Z 800 and Y 700 and enters the drawing plane (into the paper). The longitudinal axis 150 is also depicted as being substantially parallel to the Y axis 700. The probe 100 is further configured and arranged to determine the angular arrangement between the probe reference and the marker 200, which may include a YZ angle arrangement 190 as described below.

[0068] In this example, distal end 160 is configured and arranged to be disposed proximate an outer surface of skin ( 300 ).

[0069] Additionally or alternatively, the distal end 160 may be configured and arranged to:

[0070] - an outer surface in contact with the skin (300);

[0071] - inserted through the outer surface of the skin (300);

[0072] - inserted into a body cavity; or

[0073] - any combination thereof.

[0074] The user may be particularly interested in the indication of the angular arrangement between the probe longitudinal axis 150 and the marker 200 provided at the distal end 160. This is particularly advantageous when the probe 100 is configured and arranged to be hand-held extending along the longitudinal axis 150, thereby providing an intuitive configuration to determine the orientation of the marker 200 relative to the distal end 160 or tip.

[0075] The angular arrangement 180, 190 of the marker 200 may be defined and / or expressed in any convenient parameter, such as degrees or radians.

[0076] The probe 100 comprises at least a first magnetic sensor 110 and a second magnetic sensor 120 configured to measure at least the vector of the local magnetic field (Bx, By, Bz) generated by the marker 200. These properties are used to determine one or more angular arrangements 180, 190 using a software algorithm.

[0077] The distal end 160 may be disposed at a distance from the outer surface of the skin 300 - a spacer may be used to maintain a fixed distance, or the distance may be zero if the probe 100 is further configured and arranged to contact the outer surface of the skin 300. The probe 100 may be further configured and arranged to be pushed against the outer surface of the skin 300 to create an indentation that may further reduce the distance between the distal end 160 of the probe 100 and the marker 200. In general, the smaller the distance between the probe 100 and the marker, the greater the amplitude of any signal measured. For some treatments, the probe 100 may be further configured and arranged to be inserted through the outer surface of the skin 300 and / or into a body cavity to further reduce the distance between the probe 100 and the marker 200. For example, this may be via a surgical incision or via a natural orifice.

[0078] The probe 100 may be included in a detection unit or device (not shown). It will be clear to those skilled in the art that the functions for determining one or more arrangements may be implemented in the hardware and software of the magnetic probe 100, or they may be implemented in the hardware and software of the rest of the detector. These functions may also be divided between the magnetic probe 100 and the rest of the detector unit in any convenient manner.

[0079] The detection unit or device of the probe 100 may include one or more of the following:

[0080] - an optional electrical and / or mechanical connection, configured to attach to the proximal end 165 of the probe 100. It may be advantageous to make this attachment releasable. The connection may also be wireless, configured and arranged to allow at least data transfer between the probe 100 and the rest of the detector;

[0081] - A power supply to provide energy to the probe magnetic sensor;

[0082] - a processor configured to collect the magnetic sensor measurements and to determine one or more angular arrangements 180, 190 (angular inclinations) using appropriate software algorithms;

[0083] Optionally, a display may also be provided to indicate the result of the determination to the user. Preferably, one or more angular arrangements 180, 190 with the marker 200 are graphically displayed. Additionally or alternatively, one or more detection zones (as described below) are indicated, thereby providing intuitive feedback. Additionally or alternatively, a number may be displayed.

[0084] Additionally or alternatively, audio feedback may also be provided - this will be described in more detail below. For example, the distance (disposition) may be displayed as a relative value and / or an absolute value. For example, audio feedback may be provided, similar to the way a car parking sensor indicates the distance to an object with different tones.

[0085] Other examples of audio characteristics that may be configured to depend on proximity to the marker 200 include pitch, volume, loudness, amplitude, spatial location, duration, pause duration, tone, beeps, pause duration between beeps, frequency, spectrum, or any combination thereof.

[0086] If the probe is configured to define two or more detection zones, the indication and / or audio feedback may differ depending on whether the angular arrangement (180, 190) is substantially consistent with:

[0087] - a first marker detection zone;

[0088] - a second marker detection zone;

[0089] - both a first detection zone and a second detection zone;

[0090] - neither the first detection zone nor the second detection zone; or

[0091] - any combination thereof.

[0092] The probe 100 includes two or more magnetic sensors:

[0093] - 110: a first magnetic sensor close to the distal end 160 of the probe 100; and

[0094] − 120 : a second magnetic sensor disposed between the first magnetic sensor 110 and the proximal end 165 of the probe 100 . In other words, the second magnetic sensor is located farther from the distal end 160 than the first magnetic sensor 110 .

[0095] The sensors 110, 120 are configured and arranged to determine, in use, one or more B-field 3D vector measurements of the magnetic field of the marker 200. Typically, the sensor output is a 3D vector of the B-field - with two or more sensors, the angular arrangement can be derived.

[0096] The first and second measurements associated with the first and second sensors 110, 120 are used in a software algorithm to determine one or more angular placements 180, 190 of the marker 200. The angular placements 180, 190 are measurements (or estimates) of the orientation of the marker 200 associated with the entire probe 100.

[0097] Optionally, the probe may include a third magnetic sensor 130. It is advantageously located closer to the proximal end 165 of the probe 100 (in other words, farther from the distal end 160) than the first magnetic sensor 110 and the second magnetic sensor 120. It may be configured and arranged as a compensation sensor for detecting background magnetic fields, such as naturally occurring magnetic fields (from the earth), artificial magnetic fields present due to the environment in which the device is operating in which measurements and determinations are performed, and / or diamagnetic fields generated by tissue in or around the area of ​​interest.

[0098] Additionally or alternatively, the magnetic sensors 110, 120, such as 3-axis Hall sensors, use 3 magnetic detectors to measure the three field components Bx, By and Bz - typically such Hall sensor packages are ICs that include three (3D) substantially mutually perpendicular detectors, thereby providing three degrees of freedom measurements at approximately the same physical location in the probe. The sensors 110, 120 may be of the same type or of different types.

[0099] In this disclosure, sensors and detectors are sometimes used interchangeably. Typically, a sensor is a single sealed package that includes one or more detectors. A sensor with a single magnetic detector can be considered a sensor or a detector.

[0100] If the sensor package includes two detectors, where the physical separation between the detectors is large enough to measure significantly different values ​​of a particular B-vector of the magnetic field of the marker 200, then in the terminology of the present disclosure, such a package includes two sensors—each detector provides B-vector measurements of the magnetic field of the marker 200 associated with significantly different sensor locations (or arrangements) within the probe 100. If the physical separation between the detectors is too small (they measure substantially the same value for a particular B-vector), then in the terminology of the present disclosure, such a package includes one sensor—each detector provides vector measurements of the marker 200 associated with substantially the same location (or arrangement) within the probe 100.

[0101] Note that in some packages, two or more detectors may be configured to measure different orientations - for example, some Hall sensor packages include three detectors oriented substantially perpendicular to each other. When they measure the B vector associated with substantially the same position (or arrangement), they are considered to be included in the same (one) sensor.

[0102] like Figure 1A As shown, a 1D array of at least two magnetic sensors 110, 120 may be used. The sensors 110, 120 are depicted as being disposed along a longitudinal axis 150 of the probe 100 - this is not required, as their relative position (disposition) may be determined from measurement and / or design data and accounted for (taken into account) in the software algorithm. The probe 100 is configured and arranged to transform B-vector measurements from the sensors 110, 120 to any reference plane or reference axis of the probe 100. It is particularly advantageous to locate the sensors 110, 120 along the longitudinal axis 150 and use the longitudinal axis 150 as a reference for the angular measurements, as this simplifies the geometric transformation of the measurement data.

[0103] These magnetic detectors 110, 120 can be of any suitable type, such as magnetometers, fluxgate sensors, geomagnetic sensors, Lorentz force digital MEMS, magnetic induction sensors, magnetoresistive sensors, Hall sensors, magnetic tunnel junctions and any combination thereof. There are many small IC packages available that include 3-axis detection. Therefore, a 'multi-axis' solution can be provided with a simple PCB design and preferably a smaller probe diameter. The sensor packages proposed below are examples. They are digital, so the interface is relatively simple because less analog design is required. TIDRV425 Fluxgate Sensor (1D)

[0104]

[0105] NOTE: The offset can be reduced by using a calibration sensor with good zero field offset performance. For example, another type of sensor can be integrated into the probe 100 to provide a degree of offset and / or drift correction for the fluxgate. Preferably, such a calibration sensor is positioned close to or at the proximal end to reduce the effect of the magnetic field properties of the magnetic marker 200.

[0106] Bosch BMM150 3-axis digital geomagnetic sensor (3D)

[0107]

[0108]

[0109] ST LIS3MDL(1D)

[0110]

[0111] ST IIS2MDC(3D)

[0112]

[0113] Melexis MLX90393 micropower three-axis magnetometer (3D)

[0114]

[0115]

[0116] MEMSIC MMC3416xPJ(3D)

[0117]

[0118] AKM AK09970N(3D)

[0119]

[0120] PNIRM3100 Sensor System (3D)

[0121]

[0122] Note: The sensor system consists of 3 coils and a driver IC with a digital interface

[0123] A longitudinal sensor array length 400 of 40 mm to 50 mm is preferred.

[0124] Each sensor 110, 120 measures the B-field 3D vector of any local magnetic field, which may include any background magnetic field (such as the earth's magnetic field) and the magnetic field of the marker 200. These measurements are provided to a software algorithm that combines them with physical parameters such as orientation, sensitivity, sensor separation distance, etc. to determine the angular arrangement 180, 190 of the magnetic marker 200 relative to a predetermined reference position of the probe 100.

[0125] One of the insights on which the present invention is based is that when the inclination (angular arrangement) is zero (in other words, when the marker 200 is arranged along the longitudinal axis 150 of the probe 100, for example in the YZ plane 700-800), the magnetic field measured at all sensors 110, 120 arranged along the longitudinal axis is substantially in the same direction. When this point is detected with the handheld probe 100, the probe 100 will substantially "point" in the direction of the marker 200.

[0126] In handheld applications, the user can rotate the probe 100, for example in the YZ plane 700-800, to different inclinations so that the longitudinal axis 150 has multiple orientations relative to the skin 300. By continuously monitoring the magnetic field vector measurements and determining the degree of deviation (difference) in the magnetic field direction measured by each sensor 110, 120, an indication of the relative inclination (angular arrangement) to the marker 200 can be provided. When the degree of deviation is below a predetermined threshold, the probe 100 will be substantially "pointing" at the marker 200.

[0127] It may be advantageous to configure the probe 100 to minimize noise to improve the accuracy of the measurement, for example by:

[0128] - Use more sensitive sensors 110, 120;

[0129] - Use markers that provide a stronger magnetic field 200

[0130] By using a greater number of sensors 110 , 120 ;

[0131] By using one or more averaging filters;

[0132] and any combination thereof.

[0133] For a magnetic dipole included in marker 200 at the origin with dipole moment m pointing in the Z direction 800, the magnetic field in spherical polar coordinates is given by the following equation:

[0134] B r =2|m|cosθ / r 3

[0135] B θ =|m|sinθ / r 3

[0136]

[0137] Figure 3A A simulated schematic diagram of generally circular field lines 401, 402, 403, 404 is depicted, which represent a cross section in the YZ plane 700-800 of the magnetic field generated by the magnetic dipole 200 at the origin of Y-Z 700-800. The Z axis 800 represents nominal distance units, from -4 at the bottom to +4 at the top, passing through 0. The Y axis 700 also represents nominal distance units, from -1 on the right to +5 on the left, passing through 0. The dipole moment m is set along the Z axis 800. The X axis 600 enters the drawing plane (into the paper). The field lines 401, 402, 403, 404 all pass through the origin 0,0 of YZ 700-800, depicting the field lines radiating outward from the origin:

[0138] - The first field line 401 has a nominal diameter of 1 distance unit and passes approximately through the coordinates 0, 0 / 0.5, -0.5 / 1, 0 / 0.5, 0.5 of YZ 700-800

[0139] - The second field line 402 has a nominal diameter of 2 distance units and passes approximately through the coordinates 0,0 / 1,-1 / 2,0 / 1,1 of YZ 700-800

[0140] - The third field line 403 has a nominal diameter of 3 distance units and passes approximately through the coordinates 0, 0 / 1.5, -1.5 / 3, 0 / 1.5, 1.5 of XY 600-700

[0141] - The fourth field line 404 has a nominal diameter of 4 distance units and passes approximately through the coordinates 0,0 / 2,-2 / 4,0 / 2,2 of YZ 700-800

[0142] For clarity, only four field lines are shown - in practice, additional field lines will be present and measurable with suitably sensitive magnetic sensors 110 , 120 .

[0143] Also depicted are six orientations of the probe 100, each representing an inclination of 181 to 186 - the probe 100 having an extension of four nominal distance units along the longitudinal axis 150. In each position, the YZ angular arrangement 190 is approximately 0 degrees, because the distal end 160 is "pointing" at the dipole 200, and the deviation between the vector measurements measured by the sensors 110, 120 is very low or approximately zero:

[0144] - First tilt 181, probe 100 extends from 0,-4 to 0,0, distal end 160 coincides with origin 0,0 of YZ 700-800. For all sensors 110, 120, field lines 401, 402, 403, 404 intersect probe 100 at approximately 0 (or 180) degrees.

[0145] - A second tilt 182, the probe 100 extends from about 2,-3.3 to 0,0, the distal end 160 coincides with the origin 0,0 of YZ 700-800. The field lines 401, 402, 403, 404 intersect the probe 100 at about 50 degrees.

[0146] - A third tilt 183, the probe 100 extends from about 3.4,-2 to 0,0, the distal end 160 coincides with the origin 0,0 of YZ 700-800. The field lines 401, 402, 403, 404 intersect the probe 100 at about 70 degrees.

[0147] - A fourth inclination 184, the probe 100 extends from about 4,0 to 0,0, the distal end 160 coincides with the origin 0,0 of YZ 700-800. The field lines 401, 402, 403, 404 intersect the probe 100 at about 90 degrees.

[0148] - Fifth inclination 185, probe 100 extends from about 3.4,2 to 0,0, distal end 160 coincides with origin 0,0 of YZ 700-800. Field lines 401, 402, 403, 404 intersect probe 100 at about 110 degrees.

[0149] - Sixth inclination 185, the probe 100 extends from about 2,3.3 to 0,0, the distal end 160 coincides with the origin 0,0 of YZ 700-800. The field lines 401, 402, 403, 404 intersect the probe 100 at about 130 degrees.

[0150] Therefore, by utilizing this property of the magnetic field of the magnetic dipole generated by the marker 200, the orientation of the probe 100 having a YZ angle arrangement 190 of approximately zero can be determined by an orientation with very low or almost zero deviation in the field direction measured by the magnetic sensors 110, 120. Preferably, the deviation is less than about 15 degrees.

[0151] The field lines 401, 402, 403, 404 intersect the magnetic sensors 110, 120 of the probe 100 at substantially the same angle. The angles of the field lines 401, 402, 403, 404 depend largely on the angle formed by the probe 100 and the magnetic dipole generated by the marker 200. This is because the dipole field is self-similar, i.e., field lines far from the dipole 200 have substantially the same shape as field lines closer to the dipole 200.

[0152] This relationship is 500 Figure 3B Depicted in - the values ​​of probe tilt θ 550 are plotted from left to right along the horizontal axis from 0 to 180 degrees, and the values ​​of the tilt of the field in the probe plane 575 are plotted along the vertical axis from -90 degrees at the bottom to +90 degrees at the top. The relationship passes through the following points:

[0153]

[0154]

[0155] If the probe 100 is moved to different inclinations in a constant Z 800 arrangement, θ is related to the position of the sensors 110, 120 from the marker 200:

[0156] tan(θ)=Z sen / Y sen

[0157] tan(α)=tan(θ) / 2=(Z sen / Y sen) / 2

[0158] Figure 7 Depicted are the expected magnetic field components when the probe is pointed directly at the magnetic dipole.

[0159] The magnetic marker 200 extends longitudinally along a marker magnetic axis 900. The marker magnetic axis 900 is the axis of the dipole moment (vector) of the magnet. It is convenient to use a magnetic marker 200 that is substantially aligned with the dipole moment 900, but other shapes and other alignments of the marker 200 may also be used.

[0160] In the depicted situation, the probe longitudinal axis 150 points towards the magnetic marker 200 (the probe points towards the centre of the magnetic dipole of the magnetic marker 200 )—the probe longitudinal axis 150 intersects the marker magnetic axis 900 at an inclination θ.

[0161] In the case of spherical polar coordinates (r, θ, At a detection position 970 (r, theta, phi), a horizontal axis 950 is depicted that intersects the probe longitudinal axis 150 substantially perpendicularly. At the detection position 970, a magnetic field (B) 920 generated by the magnetic marker 200 is present and can be detected. At the detection position 970, a magnetic field vector 930B that is at an angle α (alpha) to the horizontal axis 950 can be detected.

[0162] Since the probe is pointed directly at the magnetic marker 200 in the depicted situation, the magnetic field vector 930B is in the azimuthal direction The component on can be considered to be approximately zero. It can be considered that the angle α (alpha) mainly corresponds to the inclination θ (theta) of the probe relative to the magnetic dipole of the magnetic marker 200.

[0163] Therefore, for the purpose of determining the angular placement of the magnetic marker 200, the magnetic field vector 930B can be considered to have two components:

[0164] |B|sinα=Br——along the longitudinal axis 150 of the probe, in the radial direction r

[0165] |B|cosα=B θ ——In the direction of inclination θ.

[0166] In prior art systems, a 1D sensor line can be used to provide both distance and direction measurements - however, accuracy can be poor when the probe is not pointing directly at the magnetic marker 200 .

[0167] from Figure 3A and Figure 3B A person skilled in the art will recognize that when two or more magnetic sensors arranged on a 1D line indicate approximately the same magnetic field angle α (alpha), the probe is pointing to a magnetic marker 200. From the amplitude of the measured field, the distance to the magnetic dipole 200 can be calculated.

[0168] When the multiple sensors indicate different angles α (alpha), the probe is pointing away from the magnetic marker 200. Any manual measurement of the angle deviation by the various sensors can be used as an indicator of the degree to which the probe is pointing away from the magnetic marker 200.

[0169] Figure 4A and Figure 4B Depicted are measurements taken at each magnetic sensor 110, 120 disposed along the longitudinal axis 150 as the probe 100 is scanned through different XY angular arrangements 190 at a fixed tilt θ 191, 192, 193, 194, 195, 196 of 30.0 degrees. By comparing the B-field vectors measured with each magnetic sensor 110, 120, it is possible to determine the XY angular arrangement 190 at which the probe is substantially “pointing directly” at the marker 200 (in other words, when the XY angular distribution 190 is substantially zero) by identifying the point at which the graph is truncated (also referred to as the zero intercept or “intercept=0” point).

[0170] Figure 4AThe measured values ​​of the B-field tilt at the sensor in degrees are depicted, with the field tilt plotted from -75 degrees to +90 degrees on the vertical axis and from -50 mm to +50 mm for the probe Z 800 arrangement on the horizontal axis. Four graphs are shown, one for each sensor 110, 120 disposed at the following distances along the longitudinal axis 150: 10.0 mm, 15.0 mm, 20.0 mm, and 25.0 mm from the distal end 160 along the Y-axis 700 (depicted sequentially from bottom to top on the left side of the figure). Each graph forms a flat S that passes through the same zero intercept (0 mm on the horizontal axis).

[0171] Figure 4B Depicted with Figure 4A The same data (four graphs, one for each sensor 110, 120 at the following distances along the vertical axis 150: 10.0 mm, 15.0 mm, 20.0 mm and 25.0 mm from the distal end 160 along the Y axis 700, plotted from bottom to top on the left side of the graph). Figure 4B and Figure 4A The difference is that the vertical axis used is the tan of the B-field slope from -4 to +6. The advantage of using the tan function is that the characteristics become approximately linear, making them easier to use to estimate and / or determine the location of the zero intercept (0 mm on the horizontal axis).

[0172] Similarly, the difference in B field tilt can be used to compare the values ​​measured at 15.0 mm, 20.0 mm, and 25.0 mm compared to the magnetic sensor closest to the distal end (i.e., the sensor at 10.0 mm). These graphs are Figure 5A In the figure, from bottom to top on the left side are 10.0mm (reference), 15.0mm, 20.0mm and 25.0mm. The difference between the B field tilt and the 10.0mm value is plotted on the vertical axis from -12 degrees to +55 degrees. The horizontal axis depicts the arrangement from -50mm to +50mm. Since the other values ​​are compared to the 10.0mm value, the 10.0mm value is depicted as a horizontal line with a zero difference line. Again, these graphs intercept each other at the zero intercept (0mm on the horizontal axis).

[0173] Figure 5B Depicted with Figure 5A The same data (10.0 mm (reference), 15.0 mm, 20.0 mm, and 25.0 mm from bottom to top on the left side of the graph) is plotted as a horizontal line with the zero difference line because the other values ​​are compared to the 10.0 mm value. Figure 5B and Figure 5AThe difference is that the vertical axis used is the tan of the B field tilt difference from -3 to +3. The advantage of using the tan function is that the characteristics become approximately linear, making them easier to use to estimate and / or determine the location of the zero intercept (0 mm on the horizontal axis).

[0174] Therefore, the deviation of the B-field tilt angle can be used as a measure of the angular placement of the marker: when the deviation is minimal, the probe is pointing directly at the marker. The deviation can be quantified, for example, using:

[0175] - Absolute average - in other words, the field angle is monitored relative to the field average. This is the preferred option - the field average as a reference puts more weight on the stronger fields, which may result in a higher SNR. It is also possible to use the field closest to the far end 160, but this may require additional measures to reduce noise.

[0176] - Figure 4B The average value of tan in field B is depicted in .

[0177] - Instead of using the means shown, the average tangent line can be used.

[0178] Figure 1A Further depicted are marker detection zones 170a, 170b extending from the distal end 160 along the longitudinal axis 150 of the probe. Although depicted as triangular cross-sections and substantially symmetrical in the XY plane 600-700, this is not required—any form of cross-section may be used. The marker detection zone may be primarily determined by two or more angular boundaries 170a, 170b as shown in dashed lines. Additionally and optionally, the distance between the two or more angular boundaries 170a, 170b near the distal end 160 of the probe 100 may be predetermined and / or controlled. Additionally and optionally, the extent to which the marker detection zone extends away from the distal end 160 of the probe 100 along the longitudinal axis 150 (depicted as a curved dashed line) may be predetermined or controlled.

[0179] Similarly, Figure 1B A further extent of a marker detection zone 170c, 170d is depicted extending from the distal end 160 along the probe longitudinal axis 150. Although depicted as a triangular cross section in the YZ plane 700-800 and substantially symmetrical, this is not required - any form of cross section may be used. The zone may have an extent in XY 600-700 and / or YZ 700-800.

[0180] The marker detection zone can be primarily defined by two or more angular boundaries 170c, 170d as shown in dashed lines. Additionally and optionally, the distance between the two or more angular boundaries 170c, 170d near the distal end 160 of the probe 100 can be predetermined and / or controlled. Additionally and optionally, the extent to which the marker detection zone extends away from the distal end 160 of the probe 100 along the longitudinal axis 150 (depicted as a curved dashed line) can be predetermined or controlled.

[0181] Although Figure 1A and Figure 1B The shapes of the cross sections depicted in the figure are substantially the same but with different ranges, but this is not necessary. For example, the marker detection zones 170a, 170b, 170c, 170d may optionally have a substantially circular, arc-shaped, fan-shaped, oval, elliptical, triangular, rectangular or square cross section substantially perpendicular to the longitudinal axis 150.

[0182] If the marker detection zones 170a, 170b, 170c, 170d are substantially symmetrical about the longitudinal axis 150, it can provide a more intuitive probe 100 for finding the marker 200, especially when the probe is configured to be handheld. For example, it can be defined as a cylindrical or conical shape. The conical marker detection zone can further have a parabolic, linear or hyperbolic shape.

[0183] Parabola = wider angle near the distal end 160 and narrower angle away from the distal end towards a more negative Y 700 arrangement

[0184] • Linear = approximately the same angle when close to the distal end 160 and when arranged away from the distal end 160 towards a more negative Y 700. This can also be described as a focused beam.

[0185] • Hyperbolic = angle is narrower near the distal end 160 and wider towards a more negative Y 700 arrangement away from the distal end.

[0186] Software can be used to define the marker detection zones 170a, 170b, 170c, 170d - for example, during the measurement of the B-field vector, angular arrangements 180, 190 that are estimated / measured to be outside the marker detection zones 170a, 170b, 170c, 170d can be suppressed. In other words, the software can be configured to consider these vector measurements in the angular arrangement calculations only when the vector measurements appear to indicate that the marker 200 falls within the marker detection zones 170a, 170b, 170c, 170d. In other words, the zone is configured to act as a software-controlled collimator. Additionally and optionally, the extent to which the marker detection zones extend along the longitudinal axis 150 can also be used to determine whether the marker 200 falls within the longitudinally restricted marker detection zone.

[0187] Defining the region in software means that simple shapes such as cylinders, slits, and cones can be used. Alternatively or additionally, complex shapes can also be used - for example, using a narrow cone near the distal end 160 of the probe 100 and fanning out further away from the distal end 160 or defining a straight (cylindrical) beam further away from the distal end 160.

[0188] This can be implemented as a simple goniometric test, implementing the required detection volume. If the marker 200 appears to be at the edge of the zones 170a, 170b, 170c, 170d, noise may cause the marker 200 to be sometimes suppressed and sometimes used. Solutions that may be implemented include:

[0189] 1) Hysteresis of measurement - for example, once it is deemed to be within region 170a, 170b, 170c, 170d, the B-field vector measurement should not be suppressed until a significant distance and / or angle movement has occurred.

[0190] 2) The 3D positioning output described in the earlier patent application NL 2022093 of the same applicant may also have a certain degree of uncertainty. If the position uncertainty is considered as a heat map in space, it can be multiplied by the zones 170a, 170b, 170c, 170d and then integrated over the volume. If the integral is above a threshold, these values ​​are used when determining the angular arrangement 180, 190.

[0191] 3) Shape the weights of zones 170a, 170b, 170c, 170d to decrease in sequence. For example, the probe 100 may be configured and arranged to evaluate the B-field vector and return a Jacobian that may be used to give an indication of the uncertainty of the estimated position of the marker 200. This is similar to the approach commonly used to mitigate uncertainty issues in GPS systems.

[0192] 4) To determine the distance-dependent audio pitch, a suggested embodiment is to multiply the estimated position by the shape of the zones 170a, 170b, 170c, 170d. Alternatively, the uncertainty region may be multiplied by the shape of the zones 170a, 170b, 170c, 170d. The integral indicating the confidence in the angular placement 180, 190 may be output as the volume of the tone, while the pitch of the tone may indicate the lateral and / or longitudinal placement (distance). For example, an inverse relationship may be used between the duration of the pauses between beeps - shorter pauses indicating a higher degree of proximity (or closeness).

[0193] The probe 100 may further be configured and arranged to determine the longitudinal and / or lateral placement of the marker 200 relative to an appropriate reference point on the probe 300 (eg, the distal end 160 of the probe 100 ).

[0194] If the probe 100 is first oriented so that it is pointing towards the marker 200 , the distance to the marker 200 (longitudinally and / or laterally arranged) can be estimated with high accuracy.

[0195] When the probe 100 points to the marker 200 , Br=−By (the Y axis 700 of the probe 100 points to the marker 200 , and r points from the marker 200 to the magnetic sensors 110 , 120 included in the probe 100 ).

[0196] because The square of the field amplitude is therefore given by:

[0197]

[0198] and

[0199]

[0200] According to the above B r and B θ The equation is:

[0201]

[0202] Insert the preceding Br and |B θ |, we get

[0203]

[0204] This gives a simpler expression for estimating r,

[0205]

[0206] The solution may be implemented with various sensor arrangements, including those depicted in FIGS. 1 and 2 .

[0207] FIG. 2A to FIG. 2F Additional probe configurations are depicted that may be used with the present invention.

[0208] For example:

[0209] Figure 2A - The magnetic field sensors 110, 120 are arranged substantially along the longitudinal or Y axis 700. In this example, they are arranged along the probe longitudinal axis 150. They are arranged on a suitable substrate, such as a PCB. The substrate lies in the XY plane 600-700. One or more additional sensors 130 may be provided at the proximal end 165, may be provided to compensate for any background fields, or may be configured and arranged at a larger sensor spacing from the sensors 1110, 120 closer to the distal end.

[0210] This can be thought of as a 1D geometry - the magnetic field sensors are essentially arranged along an axis.

[0211] If the background field is not uniform enough, or if the background field sensor detects the dipole field of a marker (not depicted) due to the proximity of the marker to the background field sensor, it may be advantageous to locally subtract the background field.

[0212] For example, by measuring the gradient of the B field (due to the spatial variation of the dipole field) and assuming that the background field is uniform (at least within the measurement range; e.g., the distance between two adjacent sensors), this approach can be used with 3D arrays that are sensitive to curvature in all three directions 600, 700, 800.

[0213] The 3D array comprises magnetic field sensors arranged substantially along a plane and further arranged along at least one axis substantially perpendicular to the plane. It may also comprise magnetic field sensors arranged substantially along a first plane and further along a second plane substantially perpendicular to the first plane.

[0214] Another method that can be used with a 2D array is described below. The 2D array includes magnetic field sensors arranged substantially along a plane. For a uniform field, and This can be implemented by taking the difference in field along the length of the probe (Y axis 700 and / or longitudinal axis 150). It will align with r when the probe is pointed at the magnet included in the marker. r is the -y direction and |Bθ| = √(B 2 x +B 2 z ).

[0215] For a dipole:

[0216] and

[0217] then:

[0218]

[0219] And r is given by:

[0220]

[0221] So the partial derivative can be approximated as:

[0222] and Among them B θ =B x +B z

[0223] Figure 2B- The sensors 110, 120, 130 are stacked so that they are generally placed along the longitudinal or Y axis 700. In this example, they are arranged along the probe longitudinal axis 150. Each sensor can be on its own small PCB (can have sensors on one or both sides) - each PCB is arranged in the XZ plane 600-800. This arrangement increases the packaging density of the sensors.

[0224] Figure 2C - The magnetic field sensors 110, 120, 130 are arranged substantially along the longitudinal or Y-axis 700. In this example, they are arranged along the longitudinal axis 150 of the probe, similar to Figure 2A . They are arranged on a suitable substrate, such as a PCB. The substrate is located in the XY plane 600-700. In this example, a 2D array is provided - another row of sensors (only partially visible) is arranged along the underside of the depicted substrate. In other words, the sensors 110, 120, 130 are arranged at different arrangements along the horizontal axis 800, but on both sides of the substrate. This arrangement increases the packaging density of the sensor 110 and also allows the magnetic field gradient to be inferred. For example, the magnetic field measurements of adjacent sensors 110, 120, 130 above and below can be averaged. This provides B-field vector measurements that are actually made along lines in the space between adjacent sensors 110, 120, 130.

[0225] Figure 2D - The magnetic field sensors 110, 120 are arranged substantially along the longitudinal or Y-axis 700 (only part of it is visible). In this example, they are arranged along the longitudinal axis 150 of the probe, similar to Figure 2C . They are arranged on a suitable substrate, such as a PCB. The substrate lies in the XY plane 600-700. In this example, a 3D array is provided - two further rows of sensors (only partially visible) are arranged along the underside of the depicted substrate. In other words, the sensors 110, 120 are arranged at different arrangements along the horizontal axis 800, but on both sides of the substrate. The sensors 110, 120 can also be considered to be divided into three groups in a triangular arrangement in the XZ plane 600-800 - only one group 110, 120 of sensors is visible.

[0226] Figure 2E ——Similar to Figure 2B , the sensors 110 , 120 , 130 are stacked so that they appear in groups of three in a triangular arrangement, with each group being disposed on a PCB located in an XZ plane 600 - 800 .

[0227] The PCBs are arranged substantially along the longitudinal or Y axis 700. In this example, they are arranged along the longitudinal axis 150 of the probe. Each sensor can be on its own small PCB (which can have sensors on one or both sides) - each PCB is arranged in the XZ plane 600-800. In other words, the sensors 110, 120, 130 are provided in a 3D array. This arrangement further increases the packaging density of the sensors 110, 120 and also allows the magnetic field gradient to be inferred.

[0228] Figure 2F - The sensors 110, 120, 130 are arranged on three substrate parts, each extending along a longitudinal or Y axis 700. The three substrate parts are attached to each other by their longitudinal edges, forming a hollow substrate arrangement with a triangular cross-section 600-800, arranged so that the cross-section in the XZ plane is triangular. In other words, a 3D array is provided using three 1D sensor arrays, each 1D array being arranged on a separate substrate part, and each 1D sensor array being arranged along a longitudinal axis 700 that is substantially parallel to the longitudinal axis 700 of the probe.

[0229] This arrangement greatly increases the packing density of sensors 110, 120 and also allows inference of magnetic field gradients. It also allows a large number of sensors to be packed into a relatively cylindrical package and also reduces the distance between the "front sensor" and the marker (not depicted).

[0230] Example 2: 3D sensor array and magnetic field strength gradient

[0231] For another embodiment of the probe 100, a 3D sensor grid 110, 120 may be used to measure the spatial gradient of magnetic field strength; e.g. Figure 2D or Figure 2E Layout depicted in . Square / cubic grids are possible.

[0232] The magnetic field strength gives an estimate of the distance, and the relative strength of the magnetic field between the left / right sensors (and similarly for up / down) gives an estimate of the direction: if the seed is on the left, the left sensor will see a stronger signal than the right sensor. This difference can be used as a (relative) measure of lateral displacement. If the difference between the left / right and up / down sensors is minimized, the rod is essentially pointing towards the marker.

[0233] Figure 6An example of a differential measurement and lateral displacement characteristic that can be used to convert the LR signal from the sensor into a lateral displacement is depicted. The magnitude of the magnetic field is measured from each sensor (L and R). The differential measurement is made by comparing the field strengths of adjacent sensors. For example, left vs. right; front vs. back, top vs. bottom. If the difference is zero, the marker 200 is set close to the midpoint between the sensors. If the difference is positive, the marker is set further to the right. If the difference is negative, the marker is set further to the left.

[0234] The x-axis shows the displacement X in centimeters (cm), from -3.0 to +3.0. The Y-axis shows the LR signal from -0.60 to 0.60. Using a cylindrical magnetic marker 200 made of NdFeB, 4 mm in length and 2 mm in diameter, the LR signal was measured at lateral arrangements of X = -2.0, -1.0, 0, +1.0 and +2.0 - these are plotted as points at those displacement values. These distances range from five to twenty times the size of the magnetic marker 200. At X = 0, the magnetic marker 200 is set on the longitudinal axis 150 of the probe. Based on these values, a characteristic has been fitted, namely a straight line from -2.5, -0.52775 to 2.5, 0.52775. In other words, the distance X can be calculated based on LR = 0.2111X. In this example, the correlation factor (R 2 ) is 0.9328.

[0235] Another advantage of providing a software configurable detection zone is that two or more marker detection zones with different ranges, different shapes, different angular boundaries, different longitudinal ranges, different lateral ranges, and any combination thereof can be configured. The two or more marker detection zones can share one or more boundaries, be continuous along one or more axes, be discontinuous along one or more axes, or any combination thereof.

[0236] For example, Fig. 8A and Figure 8B Two examples with more than one detection zone of different ranges are depicted. The views shown and the probe 101 depicted are similar to Figure 1B The probe 100 is depicted in FIG.

[0237] Fig. 8A Second marker detection zones 171c, 171d are depicted extending from distal end 160 along probe longitudinal axis 150. Although depicted as triangular cross-sections and substantially symmetrical in the YZ plane 700-800, this is not required - any form of cross-section may be used.

[0238] The second marker detection zone can be primarily defined by two or more angular boundaries 171c, 171d as shown by dashed lines—eg, + / - 22.5 degrees relative to the longitudinal axis 150. In other words, a 45 degree marker detection angle is provided substantially symmetrically about the probe longitudinal axis 150.

[0239] Additionally and optionally, the distance between the two or more angular boundaries 171c, 171d near the distal end 160 of the probe 101 can be predetermined and / or controlled—e.g., 18.5 mm. Additionally and optionally, the extent to which the second marker detection zone extends away from the distal end 160 of the probe 101 along the longitudinal axis 150 (depicted as a curved dashed line) can be predetermined or controlled—e.g., 29 mm.

[0240] Fig. 8A Further depicted are third marker detection zones 172c , 172d extending from the longitudinal extent of the second marker detection zones 171c , 171d and further away from the distal end 160 of the probe 101 .

[0241] Although depicted as arcuate cross-sections and substantially symmetrical in the YZ plane 700 - 800 , this is not required—any form of cross-section may be used.

[0242] The third marker detection zone can be primarily defined by two or more angular boundaries 172c, 172d as shown in dashed lines—eg, + / - 30 degrees relative to the longitudinal axis 150. In other words, a 60 degree marker detection angle is provided substantially symmetrically about the probe longitudinal axis 150.

[0243] Additionally and optionally, the distance between the two or more angular boundaries 172c, 172d near the longitudinal extent of the second marker detection zone 171c, 171d is, for example, 47mm. Additionally and optionally, the extent of the third marker detection zone 172c, 172d extending away from the longitudinal extent of the second marker detection zone 171c, 171d along the longitudinal axis 150 (depicted as a curved dashed line) is, for example, 20mm.

[0244] Figure 8B Fourth marker detection zones 173c, 173d are depicted extending from distal end 160 along probe longitudinal axis 150. Although depicted as triangular cross-sections and substantially symmetrical in the YZ plane 700-800, this is not required - any form of cross-section may be used.

[0245] The fourth marker detection zone can be primarily defined by two or more angular boundaries 173c, 173d as shown in dashed lines - for example, + / - 10 degrees relative to the longitudinal axis 150. In other words, a 20 degree marker detection angle is provided substantially symmetrically about the probe longitudinal axis 150.

[0246] Additionally and optionally, the distance between the two or more angular boundaries 173c, 173d near the distal end 160 of the probe 101 can be predetermined and / or controlled—e.g., 5 mm. Additionally and optionally, the extent to which the fourth marker detection zone extends away from the distal end 160 of the probe 101 along the longitudinal axis 150 (depicted as a curved dashed line) can be predetermined or controlled—e.g., 33 mm.

[0247] Figure 8B Further depicted are fifth marker detection zones 174c , 174d extending from the longitudinal extent of the fourth marker detection zones 173c , 173d and further away from the distal end 160 of the probe 101 .

[0248] Although depicted as arcuate cross-sections and substantially symmetrical in the YZ plane 700 - 800 , this is not required—any form of cross-section may be used.

[0249] The fifth marker detection zone can be primarily defined by two or more angular boundaries 174c, 174d as shown in dashed lines—eg, + / - 30 degrees relative to the longitudinal axis 150. In other words, a 60 degree marker detection angle is provided substantially symmetrically about the probe longitudinal axis 150.

[0250] Additionally and optionally, the distance between the two or more angular boundaries 174c, 174d near the longitudinal extent of the fourth marker detection zone 173c, 173d is, for example, 47 mm. Additionally and optionally, the extent of the fifth marker detection zone 174c, 174d extending away from the longitudinal extent of the fourth marker detection zone 173c, 173d along the longitudinal axis 150 (depicted as a curved dashed line) is, for example, 20 mm.

[0251] Additional marker detection zones with varying degrees of special overlap may also be configured and arranged. These may be substantially fixed, dynamic, or any combination thereof. This may provide a coarse / fine marker detection zone configuration—for example, as the distal end 160 of the probe 101 gets closer (e.g., less than 30 to 40 mm or less than about 35 mm) to the magnetic marker 200, a marker detection zone with a smaller angle may be automatically selected to further improve accuracy, selectivity, and sensitivity.

[0252] Another advantage of providing software configurable detection zones is that two or more marker detection zones may be defined, and the probe may be further configured and arranged to determine whether the angular arrangement 180, 190 is substantially consistent with:

[0253] - first marker detection zones 170abcd, 1710cdb, 1720cd, 1730cd, 174cd;

[0254] - Second marker detection zones 170abcd, 1710cdb, 1720cd, 1730cd, 174cd;

[0255] - Both the first and second detection zones 170abcd, 1710cdb, 1720cd, 1730cd, 174cd;

[0256] - Neither the first detection zone nor the second detection zone 170abcd, 1710cdb, 1720cd, 1730cd, 174cd; or

[0257] - any combination thereof.

[0258] By modifying one or more parameters or aspects associated with one or more detection zones (such as, for example, range, shape, orientation, placement, scaling, resolution, angular boundaries, longitudinal extent, lateral extent, and any combination thereof), search parameters may be modified in a manner that is intuitive to the user.

[0259] One or more configurable aspects of the detection zone may be automatically determined by the probe based on one or more measurements from one or more sensors and / or based on one or more suitable parameters. Additionally or alternatively, a user may provide one or more parameters to influence the determination.

[0260] Additionally or alternatively, the determination may be user selectable. Using different detection zones is particularly intuitive so that the user can modify their use of the probe - for example, a "further" detection zone may encourage larger and faster movements, while a "closer" detection zone may encourage smaller and slower movements.

[0261] Additionally or alternatively, the user selection may be based on treatment or therapy. Additionally or alternatively, the user selection may be based on invasive or non-invasive use. Additionally or alternatively, the user selection may be based on use as a handheld wand.

[0262] Additionally or alternatively, the user can select a configuration that is particularly suitable for, for example, the expected position, expected proximity, expected magnetic field strength, and expected marker orientation of the marker in the human or animal body. Depending on the expected proximity and / or orientation of the (user) with the marker, one or more marker detection zones may also be configured and arranged to adopt a specific configuration. This may also be automated to a certain extent, depending on the proximity and / or orientation measured and / or estimated (by the probe). Any combination of varying degrees is also possible.

[0263] Additionally or alternatively, the user may also select a configuration that they personally consider to be particularly efficient for marker positioning.

[0264] Since one or more detection zones can be configured in several dimensions, one or more of these shapes and cross-sectional shapes can be combined. Simple shapes and / or complex shapes can be used. Another advantage of providing software configurable detection zones is that the user can configure and arrange two or more marker detection zones. This can provide, for example, a coarse / fine marker detection zone configuration - as the distal end of the probe gets closer to the magnetic marker, the marker detection zone with a smaller angle can further improve accuracy and sensitivity.

[0265] In addition, the probe may include additional sensors to provide measurements of the probe's orientation. For example, the pitch, roll, and yaw angles of the probe from an IMU (inertial measurement unit) sensor, the orientation relative to the background magnetic field from a background field sensor, or other input. This orientation may also be considered when determining the placement of the magnetic markers 200 and / or when determining configurable aspects of the detection zone.

[0266] Any other input that gives position information may similarly be used - for example, an optical sensor similar to that used on an optical mouse may be used to determine the point of contact on the skin surface.

[0267] Although the present invention has been described in conjunction with specific exemplary embodiments, it should be understood that various changes, substitutions and alterations apparent to those skilled in the art may be made to the disclosed embodiments without departing from the spirit and scope of the invention as described in the appended claims.

[0268] Particularly advantageous embodiments can be summarized as follows:

[0269] A. A magnetic field probe (100, 101) for determining the angular arrangement (180, 190) of an implantable marker (200), the marker (200) being configured to generate a magnetic field when in use, the probe comprising:

[0270] - distal end (160);

[0271] - a first magnetic sensor (110) proximate the distal end (160);

[0272] - a second magnetic sensor (120) disposed between the first magnetic sensor (110) and the proximal end (165), the first magnetic sensor and the second magnetic sensor being configured and arranged to determine one or more magnetic field vectors of the marker (200) when in use;

[0273] The probe is further configured as:

[0274] - defining one or more marker detection zones (170abcd, 171cd, 172cd, 173cd, 174cd) extending from the distal end (160) along the longitudinal axis (150) of the probe;

[0275] - using the one or more magnetic field vectors to determine an angular disposition (180, 190) with respect to the implantable marker (200); and

[0276] -determining whether the angular arrangement (180, 190) is substantially consistent with the one or more marker detection zones (170abcd, 171cd, 172cd, 173cd, 174cd).

[0277] B. The probe of embodiment A, wherein the probe is further configured to determine whether the angular arrangement (180, 190) is substantially consistent with:

[0278] - first marker detection zone (170abcd, 1710cdb, 1720cd, 1730cd, 174cd);

[0279] - second marker detection zone (170abcd, 1710cdb, 1720cd, 1730cd, 174cd);

[0280] - both the first marker detection zone and the second marker detection zone (170abcd, 1710cdb, 1720cd, 1730cd, 174cd);

[0281] - neither the first marker detection zone nor the second marker detection zone (170abcd, 1710cdb, 1720cd, 1730cd, 174cd); or

[0282] - any combination thereof.

[0283] Q. A detector unit for detecting the angular arrangement of an implantable marker (200), the detector unit comprising a magnetic probe (100, 101) according to any one of embodiments A and B.

[0284] R. A method for determining an angular arrangement (180, 190) of an implantable marker (200), the marker (200) being configured to generate a magnetic field when in use, the method comprising:

[0285] - providing a probe (100, 101) having a distal end (160), the probe further comprising: a first magnetic sensor (110) proximal to the distal end (160); a second magnetic sensor (120) disposed between the first magnetic sensor (110) and the proximal end (165), the first magnetic sensor and the second magnetic sensor being configured and arranged to determine one or more magnetic field vectors of the marker (200) when in use;

[0286] - configuring and arranging the probe to define one or more marker detection zones (170abcd, 171cd, 172cd, 173cd, 174cd) extending from the distal end (160) along the longitudinal axis (150) of the probe;

[0287] - using the one or more magnetic field vectors to determine an angular disposition (180, 190) with respect to the implantable marker (200); and

[0288] -determining whether the angular arrangement (180, 190) is substantially consistent with the one or more marker detection zones (170abcd, 171cd, 172cd, 173cd, 174cd).

[0289] Reference symbols used in the drawings

[0290] 100 First embodiment of the magnetic field probe

[0291] 101 Second Embodiment of Magnetic Field Probe

[0292] 110 First Sensor

[0293] 120 Second sensor

[0294] 130 Third sensor

[0295] 150 Probe longitudinal axis

[0296] 160 Probe distal end

[0297] 165 Proximal end of probe

[0298] 170a, 170b Range of the marker detection zone in the XY plane

[0299] 170c, 170d Range of the marker detection area in the YZ plane

[0300] 171c, 171d Range of the second marker detection zone in the YZ plane

[0301] 172c, 172d Range of the third marker detection zone in the YZ plane

[0302] 173c, 173d Range of the fourth marker detection zone in the YZ plane

[0303] 174c, 174d Range of the fifth marker detection zone in the YZ plane

[0304] 180 XY angle arrangement

[0305] 190 YZ angle arrangement

[0306] 191 First inclination θ

[0307] 192 Second inclination θ

[0308] 193 The third inclination θ

[0309] 194 Fourth inclination θ

[0310] 195 Fifth inclination θ

[0311] 196 Sixth inclination θ

[0312] 200 Implantable magnetic markers or inductive magnetic markers

[0313] 300 Outer surface of the skin

[0314] 401 First Magnetic Field Line

[0315] 402 Second magnetic field line

[0316] 403 Third magnetic field line

[0317] 404 Fourth magnetic field line

[0318] 500 Tilt Relationship

[0319] 550 Probe Tilt

[0320] 575 Field tilt in the probe plane

[0321] 600 X-axis

[0322] 700 Y-axis

[0323] 800 Z axis

[0324] 900 Magnetic Marker Axis

[0325] 920 Magnetic Field

[0326] 930 Magnetic Vector

[0327] 950 Horizontal Axis

[0328] 970 Detection position

Claims

1. A magnetic field probe for determining the angular arrangement (180, 190) of a magnetic marker (200) comprising a magnetic dipole, the magnetic marker (200) being configured to generate a magnetic field when in use, the magnetic field probe comprising: - distal end (160); - a first magnetic sensor (110) proximate the distal end (160); - a second magnetic sensor (120) disposed between the first magnetic sensor (110) and the proximal end (165), the first magnetic sensor and the second magnetic sensor being configured and arranged to determine one or more magnetic field vectors of the magnetic marker (200) when in use; The magnetic field probe is further configured as: - defining two or more marker detection zones extending from the distal end (160) along the longitudinal axis (150) of the probe; - using the one or more magnetic field vectors to determine an angular arrangement (180, 190) with a magnetic dipole included in the magnetic marker (200); as well as - determining whether the angular arrangement (180, 190) is substantially consistent with one of the two or more marker detection zones, thereby determining that the magnetic marker (200) falls within one of the two or more marker detection zones.

2. The magnetic field probe according to claim 1, wherein: The magnetic field probe is further configured to determine whether the angular arrangement (180, 190) is substantially consistent with a first or second marker detection zone.

3. The magnetic field probe according to claim 1, wherein: The two or more marker detection zones are generally symmetrical about the longitudinal axis (150).

4. The magnetic field probe according to claim 2, wherein: The two or more marker detection zones are generally symmetrical about the longitudinal axis (150).

5. The magnetic field probe according to claim 1, wherein: The two or more marker detection zones have a substantially arc-shaped, sector-shaped, cylindrical or conical shape.

6. The magnetic field probe according to claim 1, wherein: The two or more marker detection zones share one or more boundaries.

7. The magnetic field probe according to claim 1, wherein: The two or more marker detection zones differ in a parameter selected from the group consisting of: - extent, shape, orientation, placement, scaling, resolution, angular boundaries, longitudinal extent, lateral extent, or any combination thereof.

8. The magnetic field probe according to any one of claims 1 to 7, wherein: The magnetic field probe is further configured to: - defining another marker detection zone extending from the distal end (160) along the longitudinal axis (150) of the probe; and - determining whether the angular arrangement (180, 190) is substantially consistent with one of three or more marker detection zones, thereby determining that the magnetic marker (200) falls within one of the three or more marker detection zones.

9. The magnetic field probe according to any one of claims 1 to 7, wherein: The magnetic field probe is further configured to: - defining another marker detection zone extending from the distal end (160) along the longitudinal axis (150) of the probe; and - Determine whether the angular arrangement (180, 190) is substantially consistent with: - the further marker detection zone; - both the first marker detection zone and the further marker detection zone; - both the second marker detection zone and the further marker detection zone; - neither the first marker detection zone nor the further marker detection zone; or - Neither the second marker detection zone nor the further marker detection zone.

10. The magnetic field probe according to any one of claims 1 to 7, wherein: The magnetic field probe is further configured and arranged to determine an angular position (180, 190) of the magnetic marker (200) relative to a distal end (160) of the magnetic field probe.

11. The magnetic field probe according to any one of claims 1 to 7, wherein: The magnetic field probe is further configured and arranged to determine an angular disposition (180, 190) of the magnetic marker (200) relative to a longitudinal axis (150) of the magnetic field probe.

12. A magnetic field probe according to any one of claims 1 to 7, comprising at least one further magnetic sensor, the magnetic sensors being comprised in one or more 1D, 2D or 3D arrays.

13. The magnetic field probe according to any one of claims 1 to 7, wherein: The magnetic field probe is further configured and arranged to provide audio feedback, and the audio characteristics differ depending on whether the angular arrangement (180, 190) is substantially coincident with the first or second marker detection zone.

14. The magnetic field probe according to any one of claims 1 to 7, wherein: The magnetic field probe is further configured and arranged to provide coarse and fine marker detection zones.

15. The magnetic field probe according to any one of claims 1 to 7, wherein: The magnetic field probe is further configured and arranged to select a marker detection zone having a smaller angle as the distal end (160) of the magnetic field probe gets closer to the magnetic marker (200).

16. A method for determining the angular arrangement (180, 190) of a magnetic marker (200) comprising a magnetic dipole, the magnetic marker (200) being configured to generate a magnetic field when in use, the method comprising: - providing a probe having a distal end (160), the probe further comprising: a first magnetic sensor (110) proximal to the distal end (160); a second magnetic sensor (120) disposed between the first magnetic sensor (110) and the proximal end (165), the first magnetic sensor and the second magnetic sensor being configured and arranged to determine one or more magnetic field vectors of the magnetic marker (200) when in use; - configuring and arranging the probe to define two or more marker detection zones extending from the distal end (160) along the longitudinal axis (150) of the probe; - using the one or more magnetic field vectors to determine an angular arrangement (180, 190) with a magnetic dipole included in the magnetic marker (200); - determining whether the angular arrangement (180, 190) is substantially consistent with one of the two or more marker detection zones; and - determining that the magnetic marker (200) falls within one of the two or more marker detection zones.

Images