Magnetic field probe for determining the arrangement of an embedded marker using two or more detection regions

Abstract

During both invasive and non-invasive treatments and therapies, medical professionals need to accurately locate areas of interest. Inaccuracy can mean that not all areas are treated or that treatment is incomplete. Electromagnetic and RFID (radio frequency identification) markers have been developed, but they are bulky and prone to malfunction. For example, inaccuracy can result in incomplete excision or removal of a lesion, requiring additional treatment. A magnetic field probe (100, 101) for determining an angular arrangement (180, 190) of an implantable marker (200) is provided, the probe comprising a first magnetic sensor (110) near a distal end (160) and a second magnetic sensor (120) nearer a proximal end (165) configured to determine two or more magnetic field vectors of the marker (200), the probe defining two or more marker detection areas (170, 171, 172, 173, 174) extending from the distal end (160), and the magnetic field probe (100, 101) is further configured to determine the angular arrangement (180, 190) relative to the implantable marker (200) and determine whether the angular arrangement (180, 190) substantially coincides with one of the two or more marker detection areas (170, 171, 172, 173, 174), thereby determining that the marker is within one of the marker detection areas. By defining two or more marker detection zones and configuring the probe to determine whether a magnetic marker appears to be within one marker detection zone, a simplified and intuitive decision algorithm is provided for indicating the placement of the marker relative to the probe.

Description

Technical Field

[0001] [Field] The present disclosure relates to a magnetic field probe for determining the angular arrangement of an embedded marker, a detection unit including the probe, and a method for detecting the angular arrangement of the embedded marker.

Background Art

[0002] [Background] During invasive and non-invasive treatments and therapies, it is important that medical professionals can accurately locate the area of interest. In many cases, professionals rely on vision and manual manipulation to find and remember the area of interest, often marking the outer surface of the skin. In practice, imaging devices such as X-rays and / or ultrasounds can also be used to assist in location. However, this relies on being able to distinguish the area of interest from surrounding tissues using imaging techniques. Inaccuracy in the locatability of the area of interest can mean that not all areas are treated or that treatment is incomplete. This is a problem for both treatment and cosmetic procedures and treatments, including tumor removal, polyp removal, cosmetic surgery, tissue removal and / or correction, and positioning of implanted devices (e.g., it may be necessary to position a contraceptive device such as Implanon).

[0003] For example, when resection or removal of a lesion is prescribed after cancer screening, the surgeon needs to know the location and extent of the lesion. The current gold standard in clinical practice requires placing a metallic anchor wire at the target immediately before a surgical procedure, which has a risk of infection and wire movement. A newer solution is to use radioactive markers, but the use of radioactive substances is strictly regulated. Electromagnetic and RFID (Radio Frequency Identification) markers have been developed, but these are bulky and prone to failure. Inaccuracy in locating the area of interest can result in incomplete resection or removal of the lesion, potentially requiring additional treatment.

[0004] Furthermore, the improvement of screening procedures means that smaller early lesions in patients will be more readily identified. While this early detection is more beneficial to the patient, it can be difficult for surgeons to identify and locate small lesions. They may also be highly unlikely to be palpable. Intraoperative imaging is often cumbersome and costly.

[0005] In recent years, the use of implanted magnetic markers (seeds) has been proposed. These offer higher safety compared to radioactive markers, yet medical experts still require a significant amount of effort to detect the placement (positioning) of the markers. This becomes even more difficult when using very small magnetic markers to mark very small regions of interest.

[0006] U.S. Patent No. 7,561,051 describes an apparatus for locating magnets and / or determining the orientation of a device relative to a magnet. In one embodiment, the apparatus includes a multi-axis magnetic field sensor that is reciprocally movable to enable sensor readings at a plurality of spaced positions. In another embodiment, the apparatus includes a plurality of multi-axis magnetic field sensors arranged along a straight line. This apparatus can be used in many medical and other applications, including tissue resection, tracking the movement of medical devices within body cavities, and tracking the movement of internal organs.

[0007] International Publication No. WO 2018 / 045465 describes a system and method for marking the location and extent of an anatomical region of interest, such as a tumor, using magnetic seeds whose position and orientation are measured or 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 the anatomical region of interest, and a magnetic sensor-based detector system is used to accurately identify the position of the magnetic seeds.

[0008] U.S. Patent Application Publication No. 2016 / 0051164A1 describes a probe including 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 may be magnetic and can be surgically inserted into a patient's body to mark a specific position. The probe can be used to locate the marker and thereby identify the position. The probe may include a microprocessor that receives the output from the first sensor and the output from the second sensor and determines the distance and direction to the marker.

[0009] U.S. Patent No. 6,129,668 describes a device for detecting the position of a magnet coupled to an implantable medical device within a patient, which uses three or more sets of magnetic sensors each having sensor elements arranged in a known pattern. Each sensor element senses the magnetic field strength generated by the magnet and provides data indicating the direction of the magnet in three-dimensional space. An initial estimate of the position and orientation of the magnet generates predicted magnetic field values. Based on the difference between the predicted values and the measured values, the device estimates the new position of the magnet and calculates new predicted magnetic field strength values. This iterative process continues until the predicted values match the measured values within a desired tolerance. A two-dimensional display provides an indication of the position of the magnet relative to the housing of the detector. The depth indicator portion of the display can be used to provide a relative or absolute indication of the depth of the magnet. [Summary of the Invention] [Problems to be Solved by the Invention]

[0010] To optimally support a surgeon, it is important to provide both the distance and direction to the marked position. The object of the present invention is to provide improved directional detection regarding a magnetic marker or an inductive magnetic beacon. [Means for Solving the Problems]

[0011] [General Statement] According to a first aspect of the present disclosure, a magnetic field probe for determining the angular arrangement of an implantable marker, wherein the marker is configured to generate a magnetic field during use, and the probe comprises a distal end, a first magnetic sensor close to the distal end, and a second magnetic sensor disposed between the first magnetic sensor and the proximal end. The first and second magnetic sensors are configured and arranged to determine one or more magnetic field vectors of the marker during use. The probe defines two or more marker detection regions extending from the distal end along the probe longitudinal axis, uses one or more magnetic field vectors to determine the angular arrangement with respect to the implantable marker, and determines whether the angular arrangement substantially coincides with one of the two or more marker detection regions, thereby further configured to determine that the marker is within one of the two or more marker detection regions. A magnetic field probe is provided.

[0012] By defining two or more marker detection regions and configuring the probe to determine whether the magnetic marker appears to be within one of the two or more marker detection regions, a simplified determination algorithm for indicating the arrangement of the marker with respect to the probe is provided. For example, the probability that the marker is within one of the two or more marker detection regions can be determined. Alternatively, it is determined whether the angular arrangement substantially coincides with the first or second marker detection region.

[0013] Furthermore, for example, by changing one or more parameters or aspects related to the two or more detection regions, such as range, shape, orientation, arrangement, scaling, resolution, angular boundaries, longitudinal range, lateral range, and any combination thereof, it becomes possible to change the search parameters in an intuitive way for the user. In other words, the regions are configured to act as software-controlled collimators. A further advantage over prior art probes is that it is not necessary to continuously move the probe to determine the angular arrangement of the magnetic marker.

[0014] It may be advantageous to configure and arrange the probe such that two or more marker detection regions are substantially symmetric with respect to the longitudinal axis.

[0015] Since the probe can be used as a handheld rod, the user can recognize it particularly intuitively, and the detection region is not significantly affected even when the rod-shaped probe is rotated around its longitudinal axis.

[0016] Configurations that can enhance the intuitiveness of use may include further configuring and arranging the probe to determine the angular arrangement of the markers with respect to the longitudinal axis of the probe, determine the angular arrangement of the markers with respect to the distal end of the probe, determine the longitudinal and / or transverse arrangement of the markers with respect 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 regions to have a longitudinal cross-section that is substantially circular, oval, elliptical, triangular, rectangular, or square and is substantially perpendicular to the probe longitudinal axis. For example, when the probe longitudinal axis extends along the Y-axis, the longitudinal cross-section may be determined in the X-Y plane or the Y-Z plane.

[0018] Additionally or alternatively, two or more regions may be configured and arranged to have a substantially arc, segment, cylindrical, or conical shape. Additionally or alternatively, two or more regions may be configured and arranged to have a parabolic, linear, or hyperbolic shape.

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

[0020] Two or more marker detection regions may be configured and arranged to adopt a specific configuration depending on the expected proximity and / or orientation (by the user) to the marker. This may also be automated to some extent depending on the proximity and / or orientation measured and / or estimated (by the probe). Any combination to various degrees is also possible.

[0021] Additionally or alternatively, two or more marker detection regions may differ with respect to parameters selected from the group consisting of range, shape, orientation, disposition, scaling, resolution, angular boundaries, longitudinal range, lateral range, and any combination thereof. Additionally or alternatively, two or more marker detection regions may share one or more boundaries, may be adjacent along one or more axes, may not be adjacent along one or more axes, or may be any combination thereof.

[0022] A further advantage of providing software-configurable detection regions is that a user can configure and arrange two or more marker detection regions. This can provide, for example, a coarse / fine marker detection region configuration. As the distal end of the probe approaches the magnetic marker, a marker detection region having a smaller angle can further enhance accuracy and sensitivity.

[0023] According to another aspect of the present disclosure, the probe defines a further marker detection area extending from the distal end along the probe longitudinal axis, and determines whether the angular arrangement substantially coincides with one of three or more marker detection areas, thereby further configured to determine that the marker is within one of the three or more marker detection areas.

[0024] A further advantage of providing a software-configurable detection area is that the user can configure and arrange any number of marker detection areas.

[0025] Alternatively, the probe defines a further marker detection area extending from the distal end along the probe longitudinal axis, and determines whether the angular arrangement substantially coincides with the further marker detection area, whether it substantially coincides with both the first marker detection area and the further marker detection area, whether it substantially coincides with both the second marker detection area and the further marker detection area, whether it does not coincide with either the first marker detection area or the further marker detection area, whether it does not coincide with either the second marker detection area or the further marker detection area, or any combination thereof.

[0026] Another advantage of providing a software-configurable detection area is that the user can configure and arrange further marker detection areas with various degrees of special overlap. These may be substantially fixed, dynamic, or any combination thereof.

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

[0028] Thereby, the concentration (or filling density) of the magnetic sensors can be increased. These additional magnetic sensors may be configured and arranged to increase parameters such as sensitivity, accuracy, and reliability. Generally, the increased sensitivity at the distal end makes the probe more intuitive to use.

[0029] According to yet another aspect of the present disclosure, the probe may further comprise one or more compensation sensors for measuring a background magnetic field, and the background magnetic field is further taken into account in determining one or more angular arrangements of the markers in use.

[0030] Advantageously, an existing sensor or a dedicated sensor may be configured to measure (or detect) a background magnetic field such as the Earth's magnetic field. The determination of the arrangement can be compensated using the background measurement to further enhance the accuracy and sensitivity.

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

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

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

[0034] It may be advantageous if the probe is further configured and arranged to provide coarse and fine marker detection areas. Also, it may be advantageous if the probe is further configured and arranged to select the marker detection area at a smaller angle as the distal end of the probe approaches the marker.

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

[0036] Software-configurable detection regions provide high flexibility in configuration.

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

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

[0039] According to another aspect of the present disclosure, a method for determining the angular arrangement of an embedded marker is provided, the marker being configured to generate a magnetic field in use, the method comprising providing a probe having a distal end, the probe further comprising a first magnetic sensor close to the distal end and a second magnetic sensor disposed between the first magnetic sensor and the proximal end, the first and second magnetic sensors being configured and arranged to determine one or more magnetic field vectors of the marker in use, configuring and arranging the probe to define two or more marker detection regions extending from the distal end along the longitudinal axis of the probe, using the one or more magnetic field vectors to determine the angular arrangement relative to the embedded marker, and determining whether the angular arrangement substantially coincides with one of the two or more marker detection regions is provided.

[0040] Optionally, the method further includes determining whether the angular arrangement substantially coincides with the first or second marker detection area.

[0041] Additionally or alternatively, the method includes configuring and arranging the probe in accordance with the expected position, expected proximity, expected magnetic field strength, and expected orientation of the marker within the body of a human or animal.

[0042] [Brief Description of the Drawings] The features and advantages of some embodiments of the present invention, and the manner in which they are achieved, will become more readily apparent by considering the following detailed description of the invention taken in conjunction with the accompanying drawings. The accompanying drawings illustrate preferred exemplary embodiments and are not necessarily drawn to scale.

Brief Description of the Drawings

[0043]

Figure 1A

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Embodiments for Carrying Out the Invention

[0044] [Detailed Description] In the following detailed description, many non - limiting specific details are provided to assist in the understanding of the present disclosure. It will be apparent to those skilled in the art that the computer processing part of the method can be implemented in any type of stand - alone system or client - server compatible system including any type of client, network, server, and database elements.

[0045] FIG. 1A shows a longitudinal cross-section through a magnetic field probe 100 for detecting the placement (positioning) of an implantable marker 200. As shown, the magnetic marker 200 is implanted under the outer surface of the skin 300 to mark the region of interest. This can be several millimeters or centimeters below the outer surface of the skin. This is sometimes referred to as the depth. The marker 200 is configured to generate a magnetic field during use and may, for example, comprise a magnetic dipole.

[0046] The marker can be easily implanted, for example, by injection. The injection can be, for example, an injection into soft tissue or an organ, or delivery via a bronchoscope to the pulmonary bronchi, or delivery via a colonoscope to the colon. The method of implantation may depend, for example, on the required depth, the subsequent procedure to be performed, the size of the region of interest, the position of the region of interest, the type of tissue within the region, and the type of tissue surrounding the region. The marker can be implanted immediately before or shortly before detection.

[0047] Typically, a suitable marker 200 with a magnetic dipole is generally cylindrical, - having a diameter of 1.45 mm, a length of 2.19 mm, and a residual magnetic field (Br) of 1.43 T (neodymium N52), or - having a diameter of 1.75 mm, a length of 5 mm, and a residual magnetic field (Br) of 1.43 T (neodymium N52) or.

[0048] Markers having a diameter of 1.45 mm and a length of 4.7 mm may also be suitable.

[0049] When higher grades of neodymium become available, they can also be advantageously used in embodiments of the present invention.

[0050] Additionally or alternatively, marker 200 may comprise an induced magnetic dipole. Since magnetic field probe 100 determines the angular orientation of marker 200 based on the characteristics of the dipole magnetic field, the configuration and arrangement of marker 200 for generating such a magnetic field are not that important. A combination of techniques can also be used to generate multiple magnetic dipoles. In the context of the present disclosure, angular orientation can be considered synonymous with angular arrangement and is the angular component of the relative position of marker 200 with respect to the probe.

[0051] Probe 100 comprises a distal end 160. The magnetic field probe may extend along probe longitudinal axis 150. An axis is also defined to facilitate comparison of different lines of sight in the same and different embodiments. The plane of the drawing (paper plane) is within X600 and Y700 that are 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 X600 and Y700 and exits the plane of the drawing (out of the paper). The longitudinal axis 150 is shown here as being substantially parallel to the Y-axis 700.

[0052] Probe 100 is further configured and arranged to determine the angular orientation between the probe reference and marker 200 as described below. This angular orientation may include the angular orientation 180 in XY (shown in FIG. 1A), the angular orientation 190 in YZ (shown in FIG. 1B), the angular orientation in XZ (not shown in FIG. 1A or 1B), and any combination thereof. The probe reference can be one or more points of probe 100 along longitudinal axis 150, distal end 160, proximal end 165, or any combination thereof.

[0053] Figure 1B shows a further longitudinal cross-section through the magnetic field probe 100 for detecting the arrangement (positioning) of the embedded marker 200. The plane of the drawing (paper) is in Y700 and Z800 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 Z800 and Y700 and enters the plane of the drawing (towards the paper). The longitudinal axis 150 is also shown here 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, and the angular arrangement may include a YZ angular arrangement 190 as described below.

[0054] In this example, the distal end 160 is configured and arranged to be disposed near the outer surface of the skin (300).

[0055] Additionally or alternatively, the distal end 160 can be configured and arranged as follows. - Contacting the outer surface of the skin (300); - Inserted through the outer surface of the skin (300); - Inserted into a body cavity; or - Any combination thereof.

[0056] The user may be particularly interested in being provided with an indication of the angular arrangement between the probe longitudinal axis 150 of the distal end 160 and the marker 200. This is particularly advantageous when the probe 100 is configured and arranged to be hand-held by being extended along the longitudinal axis 150, providing an intuitive configuration for determining the direction of the marker 200 relative to the distal end 160 or tip.

[0057] The angular arrangements 180, 190 of the marker 200 can be defined and / or expressed in any convenient parameter such as degrees or radians.

[0058] The probe 100 comprises at least a first magnetic sensor 110 and a second magnetic sensor 120 configured to at least measure the vector of the local magnetic field (Bx, By, Bz) generated by the marker 200. These characteristics are used to determine one or more angular arrangements 180, 190 using a software algorithm.

[0059] The distal end 160 can be arranged away from the outer surface of the skin 300. A spacer can be used to maintain a constant distance, or the distance can 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 pressed against the outer surface of the skin 300 to create a recess that further reduces the distance between the distal end 160 of the probe 100 and the marker 200. Generally, the smaller the distance between the probe 100 and the marker, the greater the amplitude of the measured signal. In 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. This may be, for example, via a surgical incision or a natural orifice.

[0060] The probe 100 may be included in a detection unit or device (not shown). It will be apparent to those skilled in the art that the function for determining one or more arrangements can be implemented as hardware and software of the magnetic probe 100, or as hardware and software of the remaining part of the detector. The function can also be conveniently divided between the magnetic probe 100 and the remaining part of the detector unit.

[0061] The detection unit or device for the probe 100 may comprise one or more of the following. - An optional electrical and / or mechanical connection configured to be attached to the proximal end 165 of the probe 100. It may be advantageous to make the attachment releasable. The connection may be wireless and may be configured and arranged to enable at least data transmission between the probe 100 and the rest of the detector; - A power source for supplying energy to the probe magnetic sensor; - A processor configured to collect magnetic sensor measurements and determine one or more angular arrangements 180, 190 (angular inclinations) using appropriate software algorithms; - Optionally, a display can also be provided to show the user the result of the determination. Preferably, one or more angular arrangements 180, 190 with respect to the marker 200 are graphically displayed. Additionally or alternatively, one or more detection areas (described below) are shown to provide intuitive feedback. Additionally or alternatively, numbers can also be displayed.

[0062] Additionally or alternatively, audio feedback can also be provided. This will be described in more detail below. The distance (arrangement) may be displayed, for example, as a relative value and / or an absolute value. The audio feedback may be provided, for example, in the same way as the distance to an object is indicated by different tones in a car's parking sensor.

[0063] Other examples of audio characteristics that may be configured to depend on the proximity to the marker 200 include pitch, volume, loudness, amplitude, spatial position, duration, pause period, tone, beep sound, pause period between beep sounds, frequency, frequency spectrum, or any combination thereof.

[0064] If the probe is configured to define two or more detection areas, the indication and / or audio feedback is based on whether the angular arrangement (180, 190) - Substantially coincides with the first marker detection area; - Substantially coincides with the second marker detection area; - Whether it substantially coincides with both the first and second detection regions; - Whether it does not substantially coincide with either the first or second detection region; or - Any combination thereof May vary accordingly.

[0065] The probe 100 comprises two or more magnetic sensors as follows. - 110: A first magnetic sensor close to the distal end 160 of the probe 100; and - 120: A second magnetic sensor disposed between the first magnetic sensor 110 and the proximal end 165 of the probe 100. In other words, it is further away from the distal end 160 than the first magnetic sensor 110.

[0066] The sensors 110, 120 are configured and arranged to determine one or more B-field 3D vector measurements of the magnetic field of the marker 200 during use. Typically, the sensor output is a 3D vector of the B-field. The angular arrangement can be derived using two or more sensors.

[0067] The first measurement value and the second measurement value associated with the first sensor 110 and the second sensor 120 are used in a software algorithm to determine one or more angular arrangements 180, 190 of the marker 200. The angular arrangements 180, 190 are measurements (or estimations) of the direction to the marker 200 related to the probe 100 as a whole.

[0068] Optionally, the probe may comprise a third magnetic sensor 130. The third magnetic sensor 130 is preferably closer to the proximal end 165 of the probe 100 than the first magnetic sensor 110 and the second magnetic sensor 120 (in other words, further away from the distal end 160). The third magnetic sensor 130 can be configured and arranged as a compensation sensor for detecting background magnetic fields such as the natural magnetic field (from the earth), the artificial magnetic field present due to the operation of equipment in the environment where the measurement and determination are performed, and / or the diamagnetic field generated by tissues in or around the region of interest.

[0069] Additionally or alternatively, magnetic sensors 110, 120, such as a three-axis Hall sensor that uses three magnetic detectors to measure three magnetic field components Bx, By, Bz. Typically, such a Hall sensor package is an IC with three (3D) substantially mutually perpendicular detectors, providing measurements of three degrees of freedom at approximately the same physical location within the probe. The sensors 110, 120 may be of the same type or different types.

[0070] In the present disclosure, sensors and detectors are sometimes used interchangeably. Generally, a sensor is a single encapsulated package that includes one or more detectors. A sensor with a single magnetic detector can be regarded as either a sensor or a detector.

[0071] If the sensor package includes two detectors having a physical separation distance between the detectors that is large enough to measure substantially different values for a particular B vector of the magnetic field of the marker 200, then, from the perspective of the present disclosure, such a package includes two sensors. Each detector provides a B vector measurement of the magnetic field of the marker 200 for a substantially different sensor position (or arrangement) within the probe 100. If the physical separation distance between the detectors is too small (the detectors measure substantially the same value for a particular B vector), then, from the perspective of the present disclosure, such a package includes one sensor. Each detector provides a vector measurement of the marker 200 for a substantially the same position (or arrangement) within the probe 100.

[0072] 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. Since those detectors measure B vectors associated with substantially the same position (or arrangement), they are considered to be included in the same (one) sensor.

[0073] As shown in FIG. 1A, a 1D array of at least two magnetic sensors 110, 120 can be used. The sensors 110, 120 are shown disposed along the longitudinal axis 150 of the probe 100, but their relative positions (dispositions) can be determined from measurement and / or design data and taken into account (considered) by a software algorithm, so this is not essential. The probe 100 is configured and arranged to convert the B vector measurements from the sensors 110, 120 to a reference plane or reference axis of any probe 100. Disposing the sensors 110, 120 along the longitudinal axis 150 and using this longitudinal axis 150 as a reference for angle measurement is particularly advantageous because it simplifies the geometric transformation of the measurement data.

[0074] 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. Many IC packages are available that are small and include triaxial detection. Thus, a simple PCB design and preferably a "multi-axis" solution with a smaller probe diameter can be provided. The sensor packages proposed below are an example. They are digital and thus the interface is relatively simple because less analog design is required.

[0075] TIDRV425 Fluxgate Sensor (1D) Technology: Fluxgate Size: 4×4×0.8 mm Range: ±2 mT (uniaxial) Resolution: (analog, by ADC) RMS noise: 0.42 μT @ 1000 Hz (0.2 μT @ 50 Hz) Offset: 8.3 μT + 1.4 μT hysteresis + 0.4 temperature drift Gain error: 0.3% Absolute maximum magnetic field: >2 T (in any direction) Note: By using a correction sensor with good zero magnetic field offset performance, the offset can be reduced. Another type of sensor may be integrated into the probe 100, for example, to provide some offset and / or drift correction regarding the fluxgate. Preferably, such a correction sensor is positioned near or at the proximal end to reduce the influence of the magnetic field characteristics of the magnetic marker 200.

[0076] Bosch BMM150 3-Axis Digital Geomagnetic Sensor (3D) Technology: FlipCore Size: 1.56×1.56×0.6 mm Range: ±1.2 mT (x, y); ±2 mT (z) Resolution: 3 μT (LSB) RMS Noise: 0.3 μT @ 20 samples / second Offset: 40 μT (without software compensation), 2 μT (after compensation, typically) Gain Error: 5% (after compensation) Absolute Maximum Magnetic Field: >7 T (in any direction)

[0077] ST LIS3MDL (1D) Technology: Lorentz Force Digital MEMS Size: 2×2×1 mm Range: ±1.6 mT (x, y, z) (user selectable: 0.4, 0.8, 1.2 mT) Resolution: 0.015 μT (LSB) (@ 0.4 mT range; 0.06 μT @ 1.6 mT range) RMS Noise: 0.3 μT (x, y); 0.4 μT (z) @ 1.2 mT range Offset: 100 μT; drift when magnetic field >5 mT (applied) Gain Error: 0.15% full scale (best fit straight line, non - linear) Absolute Maximum Magnetic Field: <0.1 T (in any direction)

[0078] ST IIS2MDC (3D) Technology: 3 - Axis Digital Output Magnetometer High Precision, Ultra - Low Output Noise: 0.3 μT (by using available low-pass filter or offset cancellation). 1 SD at 20 samples / second. Offset error: 6 μT; can be corrected to 1.2 μT over a 20 °C range. Hysteresis measured at 3 T is 53 μT and 13 μT in a 5 mT field Offset variation: 0.03 μT / °C with temperature Gain error: 1.5% (typical), 7% (maximum) Gain variation: 0.03% / °C with temperature

[0079] Melexis MLX90393 Micropower Triaxis Magnetometer (3D) Technology: Hall effect Size: 3 × 3 × 1 mm Range: ±5 - 50 mT (x, y, z) (user selectable) Resolution: 0.16 μT (x, y); 0.3 μT (z) (LSB) RMS noise: 0.7 μT (x, y); 0.9 μT (z) @ 50 samples / second Offset: 0 μT 2.7 μT / °C temperature drift (on-chip compensation available) Gain error: <1% cross-axis sensitivity + 3% temperature excess Absolute maximum magnetic field: -

[0080] MEMSIC MMC3416xPJ (3D) Technology: AMR Size: 1.6 × 1.6 × 0.6 mm Range: ±1.6 mT (x, y, z) (user selectable: 0.4, 0.8, 1.2 mT) Resolution: 0.015 μT (LSB) (@ 0.4 mT range; 0.06 μT @ 1.6 mT range) RMS noise: 0.15 μT @ 125 samples / second Offset: Repeatability error 0.1% full scale = 1.6 μT Gain error: - Absolute maximum magnetic field: 1 T

[0081] AKM AK09970N (3D) Technology: Hall effect Size: 3 × 3 × 0.6 mm Range: ±36 mT (x, y); ±102 mT (z) Resolution: 1.1 μT (LSB) RMS Noise: 5 μT @ 100 samples / second Offset: 743 μT (x, y), 1050 μT (z) Gain Error: 10% Absolute Maximum Magnetic Field: -

[0082] PNI RM3100 Sensor System (3D) Technology: Magnetic Induction Size: 15.24 × 12.8 × 3 × 10.5 mm Range: ±800 μT (z) Resolution: 13 nT (LSB) RMS Noise: 15 nT @ 100 samples / second Offset: Repeatability 8 nT, Hysteresis 15 nT Gain Error: Linear 0.5% Absolute Maximum Magnetic Field: - Note: The sensor system includes three coils and a driver IC with a digital interface.

[0083] The length 400 of the longitudinal sensor array of 40 mm to 50 mm is preferred.

[0084] Each sensor 110, 120 measures the B-field 3D vector of any local magnetic field that may include any background magnetic field such as the Earth's magnetic field and the magnetic field of the marker 200, respectively. These measurement values are provided to a software algorithm, which combines the measurement values with physical parameters such as orientation, sensitivity, and sensor separation distance to determine the angular arrangement 180, 190 of the magnetic marker 200 with respect to a predetermined reference position of the probe 100.

[0085] One of the insights underlying the present invention 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, within the Y-Z plane 700 - 800), the magnetic fields measured by all the sensors 110, 120 arranged along the longitudinal axis are in substantially the same direction. When this is detected by the handheld probe 100, the probe 100 is substantially "pointing" in the direction of the marker 200.

[0086] In a handheld application, the user can rotate the probe 100 to different inclinations, for example, within the Y-Z plane 700 - 800, whereby the longitudinal axis 150 has multiple orientations with respect to the skin 300. By continuously monitoring the magnetic field vector measurements and determining the degree (difference) of deviation of the magnetic field directions measured by each sensor 110, 120, it is possible to provide an indication of the relative inclination (angular arrangement) with respect to the marker 200. When the degree of deviation is lower than a predetermined threshold value, the probe 100 is substantially "pointing" at the marker 200.

[0087] To improve the accuracy of the measurement, it may be advantageous to configure the probe 100 to reduce noise as much as possible. This is done, for example, by the following. - Using more sensitive sensors 110, 120; - Using a marker 200 that provides a stronger magnetic field; By using a larger number of sensors 110, 120; By using one or more averaging filters; and Any combination thereof.

[0088] Taking the magnetic dipole in the marker 200 as the origin and assuming that the dipole moment m is directed in the Z direction 800, the magnetic field in spherical polar coordinates is given by the following equation. B r =2|m|cosθ / r 3 B θ =|m|sinθ / r 3 Bφ = 0 (Equation 1)

[0089] Figure 3A shows a simulated schematic of generally circular magnetic field lines 401, 402, 403, 404, representing a cross-section in the Y-Z 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. Also, the Y-axis 700 represents nominal distance units from -1 on the right to +5 on the left passing through 0. The dipole moment m is disposed along the Z-axis 800. The X-axis 600 enters the plane of the drawing (into the paper). All of the magnetic field lines 401, 402, 403, 404 pass through the origin (0, 0) of Y-Z 700 - 800 and show magnetic field lines radiating radially from the origin. - The first magnetic field line 401 has a nominal diameter of 1 distance unit and approximately passes through the Y-Z 700 - 800 coordinates (0, 0), (0.5, -0.5), (1, 0), (0.5, 0.5). - The second magnetic field line 402 has a nominal diameter of 2 distance units and passes through the Y-Z 700 - 800 coordinates (0, 0), (1, -1), (2, 0), (1, 1). - The third magnetic field line 403 has a nominal diameter of 3 distance units and approximately passes through the X-Y 600 - 700 coordinates (0, 0), (1.5, -1.5), (3, 0), (1.5, 1.5). - The fourth magnetic field line 404 has a nominal diameter of 4 distance units and approximately passes through the Y-Z 700 - 800 coordinates (0, 0), (2, -2), (4, 0), (2, 2).

[0090] For clarity, only four magnetic field lines are shown. In reality, there are additional magnetic field lines that can be measured using magnetic sensors 110, 120 with appropriate sensitivity.

[0091] Six orientations of the probe 100 are also shown, each representing inclinations 181-186. The probe 100 has an extension length of 4 nominal distance units along the longitudinal axis 150. At each position, since the distal end 160 is "facing" the dipole 200, the Y-Z angular arrangement 190 is approximately 0 degrees, and the deviation between the vector measurement values measured by the sensors 110, 120 is very low or approximately zero. - The first inclination 181. The probe 100 extends from (0, -4) to (0, 0), and the distal end 160 coincides with the origin (0, 0) of the Y-Z 700-800. The magnetic field lines 401, 402, 403, 404 intersect the probe 100 at approximately 0 (or 180) degrees with respect to all the sensors 110, 120. - The second inclination 182. The probe 100 extends from approximately (2, -3.3) to (0, 0), and the distal end 160 coincides with the origin (0, 0) of the Y-Z 700-800. The magnetic field lines 401, 402, 403, 404 intersect the probe 100 at approximately 50 degrees. - The third inclination 183. The probe 100 extends from approximately (3.4, -2) to (0, 0), and the distal end 160 coincides with the origin (0, 0) of the Y-Z 700-800. The magnetic field lines 401, 402, 403, 404 intersect the probe 100 at approximately 70 degrees. - The fourth inclination 184. The probe 100 extends from approximately (4, 0) to (0, 0), and the distal end 160 coincides with the origin (0, 0) of the Y-Z 700-800. The magnetic field lines 401, 402, 403, 404 intersect the probe 100 at approximately 90 degrees. - The fifth inclination 185. The probe 100 extends from approximately (3.4, 2) to (0, 0), and the distal end 160 coincides with the origin (0, 0) of the Y-Z 700-800. The magnetic field lines 401, 402, 403, 404 intersect the probe 100 at approximately 110 degrees. - The sixth inclination 18 6 6. The probe 100 extends from approximately (2, 3.3) to (0, 0), and the distal end 160 coincides with the origin (0, 0) of the Y-Z 700-800. The magnetic field lines 401, 402, 403, 404 intersect the probe 100 at approximately 130 degrees.

[0092] Therefore, by utilizing this characteristic of the magnetic field of the magnetic dipole generated by the marker 200, the orientation of the probe 100 having a substantially zero YZ angle arrangement 190 can be determined by the orientation in which the deviation of the magnetic field direction measured by the magnetic sensors 110 and 120 is very low or substantially zero. Preferably, the deviation is less than about 15 degrees.

[0093] The magnetic field lines 401, 402, 403, 404 intersect the magnetic sensors 110, 120 of the probe 100 at substantially the same angle. The angle of the magnetic field lines 401, 402, 403, 404 depends greatly on the angle formed by the probe 100 with the magnetic dipole generated by the marker 200. This is because the dipole magnetic field is self-similar. That is, the magnetic field lines far from the dipole 200 have substantially the same shape as the magnetic field lines close to the dipole 200.

[0094] This relationship 500 is shown in FIG. 3B. Along the horizontal axis, the values of the probe tilt θ550 are plotted from 0 to 180 degrees from left to right, and along the vertical axis, the values of the tilt of the magnetic field in the probe plane 575 are plotted from -90 degrees at the bottom to +90 degrees at the top. This relationship passes through the following points.

[0095]

Table 1

[0096] When the probe 100 is moved to different tilts with a fixed Z800 arrangement, θ is related to the positions of the sensors 110, 120 from the marker 200. tan(θ)=Z sen / Y sen tan(α)=tan(θ) / 2=(Z sen / Y sen ) / 2

[0097] FIG. 7 shows the expected magnetic field components when the probe is directly facing the magnetic dipole.

[0098] The magnetic marker 200 extends longitudinally along the 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 the magnetic marker 200 substantially aligned with the dipole moment 900, but other shapes and other alignments of the marker 200 can also be used.

[0099] As shown, the probe longitudinal axis 150 is directed towards the magnetic marker 200 (the probe is directed towards the center of the magnetic dipole of the magnetic marker 200). The longitudinal axis 150 of the probe intersects the marker magnetic axis 900 at an angle θ.

[0100] At the detection position 970 having spherical coordinates (r, θ, φ), a transverse axis 950 is shown that intersects substantially perpendicular to the probe longitudinal axis 150. At the detection position 970, there is a magnetic field (B) 920 generated by the magnetic marker 200 and it is detectable. At the detection position 970, the magnetic field vector 930B is detectable at an angle α with respect to the transverse axis 950.

[0101] As shown, since the probe is directly facing the magnetic marker 200, it can be considered that the component (Bφ) of the magnetic field vector 930B in the azimuthal direction is approximately zero. The angle α can be considered to mainly correspond to the tilt θ of the probe with respect to the magnetic dipole of the magnetic marker 200.

[0102] Therefore, in order to determine the angular arrangement of the magnetic marker 200, the magnetic field vector 930B can be considered to have the following two components. |B|sinα = Br (along the probe longitudinal axis 150 in the radial direction r) |B|cosα = B θ (along the direction of the tilt θ)

[0103] In prior art systems, a 1D line sensor can be used to provide both distance measurement values and direction measurement values. However, when the probe is not directly facing the magnetic marker 200, the accuracy may be reduced.

[0104] As can be understood by those skilled in the art, when two or more magnetic sensors arranged on the 1D line show substantially the same magnetic field angle α, the probe is facing the magnetic marker 200. The distance to the magnetic dipole 200 can be calculated from the measured amplitude of the magnetic field.

[0105] When multiple sensors show different angles α, the probe is facing in a direction deviated from the magnetic marker 200. As an indicator of how much the direction of the probe is deviated from the magnetic marker 200, any artificial scale regarding the angular deviation across various sensors can be used.

[0106] Figures 4A and 4B show the measurements obtained by each magnetic sensor 110, 120 arranged along the longitudinal axis 150 when the probe 100 is scanned through different XY angle arrangements 190 with fixed inclinations θ191, 192, 193, 194, 195, 196 of 30.0 degrees. By comparing the B - field vectors measured by each magnetic sensor 110, 120, the XY angle arrangement 190 where the probe is "facing" the marker 200 substantially directly (in other words, when the XY angle arrangement 190 is substantially zero) can be determined by identifying the point where the graph has an intercept (also called the zero intercept or "intercept = 0" point).

[0107] Figure 4A shows the measurement of the B - field inclination at the sensor (unit is degree), where the magnetic field inclination is plotted from - 75 degrees to + 90 degrees on the vertical axis and from - 50 mm to + 50 mm in the probe Z800 arrangement on the horizontal axis. Four graphs are shown, which are for each sensor 110, 120 arranged along the longitudinal axis 150 at distances of 10.0 mm, 15.0 mm, 20.0 mm, and 25.0 mm (shown in this order from bottom to top on the left side of the figure) along the Y - axis 700 from the distal end 160. Each graph forms a flattened S - shape and passes through the same zero intercept (0 mm on the horizontal axis).

[0108] Figure 4B shows the same data as Figure 4A (four graphs regarding each of sensors 110, 120 disposed along longitudinal axis 150 at distances of 10.0 mm, 15.0 mm, 20.0 mm, and 25.0 mm (shown in this order from bottom to top on the left side of the figure) along Y-axis 700 from distal end 160). Figure 4B is different from Figure 4A in that the vertical axis used is the tangent of the B-field slope from -4 to +6. The advantage of using the tangent function is that the characteristics become approximately linear and it can be used more easily to estimate and / or determine the position of the zero intercept (0 mm on the horizontal axis).

[0109] Similarly, by using the difference in the B-field slope, the values measured at 15.0 mm, 20.0 mm, and 25.0 mm can be compared with the magnetic sensor closest to the distal end, i.e., the sensor at 10.0 mm. These graphs are shown in Figure 5A in the order of 10.0 mm (reference), 15.0 mm, 20.0 mm, and 25.0 mm, from bottom to top on the left side of the figure. The difference in the B-field slope from the value at 10.0 mm is plotted on the vertical axis from -12 degrees to +55 degrees. The horizontal axis shows the arrangement from -50 mm to +50 mm. Since the other values are compared with the value at 10.0 mm, the value at 10.0 mm is shown as a horizontal line with a difference line of 0. Here too, all the graphs have an intercept at the zero intercept (0 mm on the horizontal axis).

[0110] Figure 5B shows the same data as Figure 5A (in the order of 10.0 mm (reference), 15.0 mm, 20.0 mm, 25.0 mm, in this order on the left side of the drawing). Since the other values are compared with the value at 10.0 mm, the value at 10.0 mm is shown as a horizontal line with a difference line of 0. Figure 5B is different from Figure 5A in that the vertical axis used is the tangent of the B-field slope from -3 to +3. The advantage of using the tangent function is that the characteristics become approximately linear and it can be used more easily to estimate and / or determine the position of the zero intercept (0 mm on the horizontal axis).

[0111] Therefore, the deviation of the B-field tilt angle can be used as a measure of the angular arrangement with respect to the marker. When the deviation is at a minimum, the probe is directly facing the marker. The deviation can be quantified, for example, using the following. - Absolute mean. In other words, the magnetic field angle with respect to the mean of the magnetic field is monitored. This is a preferred option. The mean of the magnetic field as a reference places a greater weight on stronger magnetic fields, thereby increasing the SNR. It is also possible to use the magnetic field closest to the distal end 160, but this may require additional means for noise reduction. - Figure 4 B The average of the B-field tangents shown in. - Instead of using the above average, the average tangent can be used.

[0112] FIG. 1A further shows marker detection regions 170a, 170b extending from the distal end 160 along the probe longitudinal axis 150. Although shown substantially symmetrically in a triangular cross-section in the XY plane 600 - 700, this is not essential. Any cross-sectional shape can be used. The marker detection region can be determined mainly by two or more angular boundaries 170a, 170b as shown by the dashed lines. Additionally and optionally, the distance between two or more angular boundaries 170a, 170b proximal to the distal end 160 of the probe 100 may be predetermined and / or controlled. Additionally and optionally, the range in which the marker detection region extends along the longitudinal axis 150 from the distal end 160 of the probe 100 (shown as a curved dashed line) may be predetermined or controlled.

[0113] Similarly, FIG. 1B shows a further extent of marker detection regions 170c, 170d extending from the distal end 160 along the probe longitudinal axis 150. Although shown substantially symmetrically in a triangular cross-section in the YZ plane 700 - 800, this is not essential. Any cross-sectional shape can be used. The region may have a range within XY 600 - 700 and / or YZ 700 - 800.

[0114] The marker detection area can be determined mainly by two or more angular boundaries 170c, 170d as shown by the dashed lines. Additionally and optionally, the distance between two or more angular boundaries 170c, 170d proximal to the distal end 160 of the probe 100 may be predetermined and / or controlled. Additionally and optionally, the range in which the marker detection area extends along the longitudinal axis 150 from the distal end 160 of the probe 100 (shown as a curved dashed line) may be predetermined or controlled.

[0115] The cross-sections shown in FIGS. 1A and 1B are substantially the same shape and have different ranges, but this is not essential. For example, the marker detection areas 170a, 170b, 170c, 170d may optionally have a transverse cross-section that is substantially circular, arcuate, segmental, oval, elliptical, triangular, rectangular, or square, substantially perpendicular to the longitudinal axis 150.

[0116] When the marker detection areas 170a, 170b, 170c, 170d are substantially symmetric with respect to the longitudinal axis 150, especially when the probe is configured to be hand-held, a more intuitive probe 100 for finding the marker 200 can be provided. For example, the marker detection area can be defined as cylindrical or conical. The conical marker detection area may further have a parabolic, linear, or hyperbolic shape. · Parabola = wider angle proximal to the distal end 160 and narrower angle as it moves away from the distal end towards the more negative Y700 arrangement. · Line = approximately the same angle both proximal to the distal end 160 and as it moves away from the distal end 160 towards the more negative Y700 arrangement. This is sometimes called a focused beam. · Hyperbola = narrower angle proximal to the distal end 160 and wider angle as it moves away from the distal end towards the more negative Y700 arrangement.

[0117] The marker detection regions 170a, 170b, 170c, 170d can be defined using software. For example, during the measurement of the B-field vector, the angular arrangements 180, 190 that are estimated / measured to be outside the marker detection regions 170a, 170b, 170c, 170d may be suppressed. In other words, the software can be configured to take into account the vector measurement values in the calculation of the angular arrangement only when the vector measurement values appear to indicate that the marker 200 is within the marker detection regions 170a, 170b, 170c, 170d. In other words, the regions are configured to act as software-controlled collimators. Additionally and optionally, the range in which the marker detection region extends along the longitudinal axis 150 can be used to determine whether the marker 200 is within the longitudinally restricted marker detection region.

[0118] Defining the regions with 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, a narrow cone near the distal end 160 of the probe 100 and a wider fan-shaped spread or a (cylindrical) beam that travels straight from the distal end 160 are defined.

[0119] This can be implemented as a simple gonometric test to achieve the desired detection volume. If the marker 200 appears to be at the edge of the regions 170a, 170b, 170c, 170d, due to noise, the marker 200 may be excluded sometimes and used sometimes. Solutions that can be implemented include the following. 1) Hysteresis regarding the measurement. For example, if it is considered to be inside the regions 170a, 170b, 170c, 170d, a significant distance and / or angular movement should occur before the B-field vector measurement is suppressed. 2) The 3D positioning output described in Dutch Patent No. 2022093, which is a prior patent application by the same applicant as the present application, may also have a certain degree of uncertainty. If the uncertainty of the position is considered to be a heat map in space, regions 170a, 170b, 170c, 170d can be multiplied by it and then integrated over the entire volume. If the integrated value exceeds a threshold, those values are used for the determination of the angular arrangements 180, 190. 3) Shape and taper the weights of regions 170a, 170b, 170c, 170d. For example, the probe 100 can be configured and arranged to evaluate the B-field vector and return the Jacobian, and the Jacobian can be used to give an indication of the uncertainty of the estimated position of the marker 200. This is similar to a technique commonly used to mitigate problems associated with uncertainty in GPS systems. 4) To determine a distance-dependent audio pitch, the proposed embodiment is to multiply the shape of regions 170a, 170b, 170c, 170d by the estimated position. Alternatively, the shape of regions 170a, 170b, 170c, 170d can be multiplied by the region of uncertainty. The integrated value indicating the reliability of the angular arrangements 180, 190 can be output as the volume of the sound, and the pitch of the sound may indicate the lateral and / or longitudinal arrangement (distance). For example, an inverse relationship can be used during the pause period between beep sounds. That is, a shorter pause indicates a higher proximity (or closeness).

[0120] The probe 100 can be further configured and arranged to determine the longitudinal and / or lateral arrangement of the marker 200 relative to a suitable reference point at the probe 1 00, such as the distal end 160 of the probe 100.

[0121] If the probe 100 is initially directed to face the marker 200, the distance (longitudinal and / or lateral arrangement) to the marker 200 can be estimated with high accuracy.

[0122] When the probe 100 is facing the marker 200, Br = -By (the Y-axis 700 of the probe 100 faces the marker 200, but r faces from the marker 200 to the magnetic sensors 110, 120 included in the probe 100).

[0123] Since Bφ = 0, the square of the magnitude of the magnetic field is given by the following equation.

Equation

[0124] From the above equation, the following equation holds for B r and B θ The following equation holds for.

Equation

Equation

Equation

[0125] This solution can be implemented in various sensor arrangements, including those shown in FIGS. 1 and 2.

[0126] Figs. 2A - 2F show further probe configurations that can be used in the present invention.

[0127] For example, it is as follows. Figure 2A. The magnetic field sensors 110, 120 are arranged substantially along the longitudinal axis or Y-axis 700. In this example, the magnetic field sensors are arranged along the probe longitudinal axis 150. The magnetic field sensors are arranged on a suitable substrate such as a PCB. The substrate is within the X-Y plane 600-700. One or more additional sensors 130 can be disposed at the proximal end 165, provided to compensate for any background magnetic field, or configured and arranged to be at a main sensor separation distance from the sensors 1110, 120 closer to the distal end.

[0128] This can be considered a 1D geometry. The magnetic field sensors are arranged substantially along the axis.

[0129] If the background magnetic field is not sufficiently uniform, or if the background magnetic field sensor senses the dipole magnetic field of a marker (not shown) (since the marker is close to the background magnetic field sensor), it may be advantageous to locally subtract the background magnetic field.

[0130] For example, assume that the dipole magnetic field varies over space so that the gradient of the B-field is measured and the background magnetic field is uniform (at least over the measurement range, e.g., the distance between two adjacent sensors). This technique can be used in a 3D array that has sensitivity to curvature in all three directions 600, 700, 800.

[0131] A 3D array comprises magnetic field sensors arranged substantially along a plane and further along at least one axis substantially perpendicular to the plane. A 3D array may also comprise magnetic field sensors arranged substantially along a first plane and further along a second plane substantially perpendicular to the first plane.

[0132] Additional techniques that can be used in a 2D array are described below. The 2D array comprises magnetic field sensors arranged substantially along a plane. For a uniform magnetic field, ∂Br / ∂r and ∂Bθ / ∂r = 0. This can be implemented by taking the difference in the magnetic field along the length of the probe (Y-axis 700 and / or longitudinal axis 150). The magnetic field is aligned with r when the probe is facing the magnet included in the marker. r is in the -y direction and |Bθ| = √(B x 2 + B z 2 ).

[0133] For a dipole,

Number

Number

Number

[0134] Here, the partial derivative terms can be approximated by the following equation.

Number

[0135] Figure 2B. Sensors 110, 120, 130 are stacked so as to be located substantially along the longitudinal axis or Y-axis 700. In this example, the sensors are arranged along the probe longitudinal axis 150. Each sensor can be on its own small PCB (which may have sensors on one or both sides). Each PCB is disposed within the XZ plane 600 - 800. This arrangement increases the filling density of the sensors.

[0136] Figure 2C. The magnetic field sensors 110, 120, 130 are arranged substantially along the longitudinal axis or Y-axis 700. In this example, the magnetic field sensors are arranged along the probe longitudinal axis 150, similar to Figure 2A. The magnetic field sensors are arranged on a suitable substrate such as a PCB. The substrate is within the X-Y plane 600-700. In this example, a 2D array is provided. Additional rows of sensors (only some are visible) are disposed along the lower surface of the illustrated substrate. In other words, the sensors 110, 120, 130 are arranged differently along the transverse axis 800, but are provided on both sides of the substrate. This arrangement increases the packing density of the sensors 110 and also enables the inference of the magnetic field gradient. The magnetic field measurements of the vertically adjacent sensors 110, 120, 130 can be averaged, for example. This provides a B-field vector measurement substantially along a line within the space between the adjacent sensors 110, 120, 130.

[0137] Figure 2D. The magnetic field sensors 110, 120 are arranged substantially along the longitudinal axis or Y-axis 700 (only some are visible). In this example, the magnetic field sensors are arranged along the probe longitudinal axis 150, similar to Figure 2C. The magnetic field sensors are arranged on a suitable substrate. The substrate is within the X-Y plane 600-700. In this example, a 3D array is provided. Additional two rows of sensors (only some are visible) are disposed along the lower surface of the illustrated substrate. In other words, the sensors 110, 120 are arranged differently along the transverse axis 800, but are provided on both sides of the substrate. The sensors 110, 120 can also be considered to be grouped in sets of three in a triangular arrangement in the X-Z plane 600-800. Only one group of the sensors 110, 120 is visible.

[0138] Figure 2E. Similar to Figure 2B, the sensors 110, 120, 130 are stacked, and the sensors exist in groups of three in a triangular arrangement, with each group disposed on a PCB within the X-Z plane 600-800.

[0139] The PCB is disposed substantially along the longitudinal axis or Y-axis 700. In this example, the PCB is arranged along the probe longitudinal axis 150. Each sensor can be on its own small PCB (which may have sensors on one or both sides). Each PCB is disposed within the XZ plane 600 - 800. In other words, sensors 110, 120, 130 are provided as a 3D array. This arrangement further increases the packing density of sensors 110, 120 and also enables the magnetic field gradient to be inferred.

[0140] Figure 2F. Sensors 110, 120, 130 are disposed in three substrate sections, each substrate section extending along the longitudinal axis or Y-axis 700. The three substrate sections are attached to each other by their longitudinal edges, forming a hollow substrate arrangement having a triangular cross-section in the X - Z plane with a triangular lateral cross-section 600 - 800 arranged such that the cross-section in the X-Z plane is triangular. In other words, the 3D array is provided using three 1D arrays of sensors, each 1D array being disposed on a separate substrate section, and each 1D array of sensors being arranged along the longitudinal axis 700, substantially parallel to the longitudinal axis 700 of the probe.

[0141] This arrangement significantly increases the packing density of sensors 110, 120 and also enables the magnetic field gradient to be inferred. This arrangement also allows a large number of sensors to be packed within a relatively cylindrical package and reduces the distance between the "front sensor" and a marker (not shown).

[0142] Embodiment 2: 3D Sensor Array and Magnetic Field Strength Gradient Regarding a further embodiment of probe 100, a 3D sensor grid 110, 120 can be used to measure the spatial gradient of the magnetic field strength (e.g., the layout shown in Figure 2D or Figure 2E). A square / cubic grid is possible.

[0143] The magnetic field strength provides an estimate of the distance, and the distance and relative strength of the magnetic field between the left / right sensors (similarly for the top / bottom) provide an estimate of the direction. When the seed is positioned facing left, the left sensor senses a stronger signal than the right sensor. This difference can be used as a (relative) measure of the lateral displacement. When the difference between the left / right sensors and the top / bottom sensors is minimized, the rod is essentially facing the marker.

[0144] Figure 6 shows an example of the differential measurement versus lateral displacement characteristic that can be used to convert the L-R signal from the sensors into lateral displacement. From each sensor (L and R), the magnitude of the magnetic field is measured. The differential measurement is performed by comparing the magnetic field strengths at adjacent sensors. Adjacent sensors are, for example, left and right, front and back, top and bottom. When the difference is zero, the marker 200 is disposed near the midpoint between the sensors. When the difference is positive, the marker is disposed more to the right. When the difference is negative, the marker is disposed more to the left.

[0145] The X-axis shows the displacement X in centimeters (cm) from -3.0 to +3.0. The Y-axis shows the L-R signal from -0.60 to 0.60. Using a cylindrical magnetic marker 200 made of NdFeB with a length of 4 mm and a diameter of 2 mm, the L-R signal was measured for lateral displacements at X = -2.0, -1.0, 0, +1.0, and +2.0. These are shown as dots at their displacement values. These distances are within the range of 5 to 20 times the dimensions of the magnetic marker 200. At X = 0, the magnetic marker 200 is disposed on the probe longitudinal axis 150. Based on these values, the characteristic has been fitted and is a straight line from (-2.5, -0.52775) to (2.5, 0.52775). In other words, the distance X can be calculated from L-R = 0.2111X. In this example, the correlation coefficient (R2) for the linear curve fit is 0.9328.

[0146] A further advantage of providing a software-configurable detection area is that two or more marker detection areas can be configured with different ranges, different shapes, different angular boundaries, different longitudinal ranges, different lateral ranges, and any combination thereof. These two or more marker detection areas may share one or more boundaries, may be adjacent along one or more axes, may not be adjacent along one or more axes, or may be any combination thereof.

[0147] For example, FIGS. 8A and 8B show two examples of detection areas having a plurality of different ranges. The illustrated line of sight and the probe 101 shown are similar to the probe 100 shown in FIG. 1B.

[0148] FIG. 8A shows second marker detection areas 171c, 171d extending from the distal end 160 along the probe longitudinal axis 150. Although shown substantially symmetrically in triangular cross-section in the YZ plane 700-800, this is not essential. Any cross-sectional shape can be used.

[0149] The second marker detection area can be mainly determined by two or more angular boundaries 171c, 171d as shown by the dashed lines. For example, it is ±22.5 degrees with respect to the longitudinal axis 150. In other words, at a marker detection angle of 45 degrees, it is disposed substantially symmetrically with respect to the probe longitudinal axis 150.

[0150] Additionally and optionally, the distance between two or more angular boundaries 171c, 171d proximal to the distal end 160 of the probe 101 may be predetermined and / or controlled, for example, 18.5 mm. Additionally and optionally, the range (shown as a curved dashed line) in which the second marker detection area extends along the longitudinal axis 150 from the distal end 160 of the probe 101 may be predetermined or controlled, for example, 29 mm.

[0151] FIG. 8A further shows third marker detection regions 172c, 172d that extend from the longitudinal range of the second marker detection regions 171c, 171d and extend further away from the distal end 160 of the probe 101.

[0152] Although shown substantially symmetrically in a circular arc cross-section in the YZ plane 700 - 800, this is not essential. Any cross-sectional shape can be used.

[0153] The third marker detection region can be mainly determined by two or more angular boundaries 172c, 172d as shown by the dashed lines. For example, it is ±30 degrees with respect to the longitudinal axis 150. In other words, at a marker detection angle of 60 degrees, it is arranged substantially symmetrically with respect to the probe longitudinal axis 150.

[0154] Additionally and optionally, the distance between two or more angular boundaries 172c, 172d proximal to the longitudinal range of the second marker detection regions 171c, 171d is, for example, 47 mm. Additionally and optionally, the range in which the third marker detection regions 172c, 172d extend further along the longitudinal axis 150 from the longitudinal range of the second marker detection regions 171c, 171d (shown as a curved dashed line) may be predetermined or controlled, for example, 20 mm.

[0155] FIG. 8B shows fourth marker detection regions 173c, 173d that extend from the distal end 160 along the probe longitudinal axis 150. Although shown substantially symmetrically in a triangular cross-section in the YZ plane 700 - 800, this is not essential. Any cross-sectional shape can be used.

[0156] The fourth marker detection region can be mainly determined by two or more angular boundaries 173c, 173d as shown by the dashed lines. For example, it is ±10 degrees with respect to the longitudinal axis 150. In other words, at a marker detection angle of 20 degrees, it is arranged substantially symmetrically with respect to the probe longitudinal axis 150.

[0157] Additionally and optionally, the distance between two or more angular boundaries 173c, 173d proximal to the distal end 160 of the probe 101 may be predetermined and / or controlled, for example, 5 mm. Additionally and optionally, a fourth marker detection area may be predetermined or controlled for a range extending along the longitudinal axis 150 from the distal end 160 of the probe 101 (shown as a curved dashed line), for example, 33 mm.

[0158] FIG. 8B further shows a fifth marker detection area 174c, 174d that extends from the longitudinal extent of the fourth marker detection areas 173c, 173d and extends further away from the distal end 160 of the probe 101.

[0159] Although shown substantially symmetrically in a circular arc cross-section in the YZ plane 700 - 800, this is not essential. Any cross-sectional shape can be used.

[0160] The fifth marker detection area can be mainly determined by two or more angular boundaries 174c, 174d as shown by the dashed lines. For example, it is ±30 degrees with respect to the longitudinal axis 150. In other words, with a 60-degree marker detection angle, it is disposed substantially symmetrically with respect to the probe longitudinal axis 150.

[0161] Additionally and optionally, the distance between two or more angular boundaries 174c, 174d proximal to the longitudinal extent of the fourth marker detection areas 173c, 173d is, for example, 47 mm. Additionally and optionally, a fifth marker detection area 174c, 174d may be predetermined or controlled for a range extending along the longitudinal axis 150 from the longitudinal extent of the fourth marker detection areas 173c, 173d (shown as a curved dashed line), for example, 20 mm.

[0162] Additional marker detection regions can also be configured and arranged with various degrees of special overlap. These may be substantially fixed, dynamic, or any combination thereof. This can provide a coarse / fine marker detection region configuration. For example, as the distal end 160 of the probe 101 approaches the magnetic marker 200 (e.g., less than 30 - 40 mm, or less than about 35 mm), a marker detection region with a smaller angle can be automatically selected to further enhance accuracy, selectivity, and sensitivity.

[0163] Another advantage of providing a software-configurable detection region is that two or more marker detection regions can be defined, and the angular arrangements 180, 190 are - whether it substantially coincides with the first marker detection region 170abcd, 17 1 cd 17 2c d, 17 3c d, 174cd; - whether it substantially coincides with the second marker detection region 170abcd, 17 1 cd 17 2c d, 17 3c d, 174cd; - whether it substantially coincides with both the first and second detection regions 170abcd, 17 1 cd 17 2c d, 17 3c d, 174cd; - whether it does not coincide with either the first or the second detection region 170abcd, 17 1 cd 17 2c d, 17 3c d, 174cd; or - any combination thereof The probe can be further configured and arranged to determine.

[0164] For example, by changing one or more parameters or aspects related to one or more detection regions, such as range, shape, orientation, disposition, scaling, resolution, angular boundaries, longitudinal range, lateral range, and any combination thereof, it becomes possible to change the search parameters in an intuitive way for the user.

[0165] One or more configurable aspects of the detection area can be automatically determined by the probe based on one or more measurements from one or more sensors and / or based on one or more appropriate parameters. Additionally or alternatively, the user can provide one or more parameters to influence the determination.

[0166] Additionally or alternatively, the determination can be selectable by the user. Using individual detection areas is particularly intuitive, whereby the user can change the use of the probe. For example, in a "farther" detection area, larger and faster movements may be encouraged, and in a "closer" detection area, smaller and slower movements may be encouraged.

[0167] Additionally or alternatively, the user selection can be based on a treatment or therapy. Additionally or alternatively, the user selection can be based on invasive or non-invasive use. Additionally or alternatively, the user selection can be based on use as a handheld wand.

[0168] Additionally or alternatively, the user can select a configuration that is particularly suitable for, for example, the expected position of the marker, the expected proximity, the expected magnetic field strength, and the expected orientation of the marker within the human or animal body. One or more marker detection areas may be configured and arranged to adopt a specific configuration depending on the expected proximity and / or orientation to the marker (by the user). This may also be automated to some extent depending on the proximity and / or orientation measured and / or estimated (by the probe). Any combination to various degrees is also possible.

[0169] Additionally or alternatively, the user can also select a configuration that the user personally determines to be particularly efficient for marker positioning.

[0170] Since one or more detection regions can be configured in multiple dimensions, one or more of these shapes and cross-sectional shapes can be combined. Simple shapes and / or complex shapes can be used. A further advantage of providing a software-configurable detection region is that the user can configure and arrange two or more marker detection regions. This can provide, for example, a coarse / fine marker detection region configuration. As the distal end of the probe approaches the magnetic marker, a marker detection region with a smaller angle can further enhance accuracy and sensitivity.

[0171] Furthermore, 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 with respect to the background magnetic field from a background magnetic field sensor, or other inputs. This orientation can also be considered when determining the arrangement of the magnetic marker 200 and / or when determining the configurable aspects of the detection region.

[0172] Any other input that provides position information can be used similarly. For example, an optical sensor similar to the sensor used in an optical mouse can be used to determine the contact point on the surface of the skin.

[0173] Although the invention has been described in connection with specific exemplary embodiments, it should be understood that various changes, substitutions, and alternatives apparent to those skilled in the art can be made to the disclosed embodiments without departing from the spirit and scope of the invention as set forth in the appended claims.

[0174] Particularly advantageous embodiments can be summarized as follows. A. A magnetic field probe (100, 101) for determining the angular arrangement (180, 190) of an embedded marker (200), wherein the marker (200) is configured to generate a magnetic field during use, and the probe has a distal end (160), and a first magnetic sensor (110) close to the distal end (160), and A magnetic field probe (100, 101) comprising a second magnetic sensor (120) disposed between the first magnetic sensor (110) and the proximal end (165), the first and second magnetic sensors being configured and arranged to determine one or more magnetic field vectors of a marker (200) during use, the probe being, defining one or more marker detection regions (170abcd, 171cd, 172cd, 173cd, 174cd) extending from the distal end (160) along the probe longitudinal axis (150), using the one or more magnetic field vectors to determine an angular arrangement (180, 190) relative to the implantable marker (200), and further configured to determine whether the angular arrangement (180, 190) substantially coincides with one or more of the marker detection regions (170abcd, 171cd, 172cd, 173cd, 174cd). A magnetic field probe (100, 101) further configured as described above.

[0175] B. Whether the angular arrangement (180, 190) substantially coincides with, a first marker detection region (170abcd, 17 1 cd 17 2c d, 17 3c d, 174cd), a second marker detection region (170abcd, 17 1 cd 17 2c d, 17 3c d, 174cd), both the first and second marker detection regions (170abcd, 17 1 cd 17 2c d, 17 3c d, 174cd), neither the first marker detection region nor the second marker detection region (170abcd, 17 1 cd 17 2c d, 17 3c d, 174cd), or any combination thereof is further configured to determine as described above for the probe according to Embodiment A. A probe according to Embodiment A further configured as described above.

[0176] Q. A detector unit for detecting the angular arrangement of an embedded marker (200), the detector unit comprising a magnetic probe (100, 101) according to any one of embodiments A - B.

[0177] R. A method for determining the angular arrangement (180, 190) of an embedded marker (200), the marker (200) being configured to generate a magnetic field during use, the method comprising: providing a probe (100, 101) having a distal end (160), the probe further comprising a first magnetic sensor (110) close to the distal end (160) and a second magnetic sensor (120) disposed between the first magnetic sensor (110) and the proximal end (165), the first and second magnetic sensors being configured and arranged to determine one or more magnetic field vectors of the marker (200) during use; configuring and arranging the probe to define one or more marker detection regions (170abcd, 171cd, 172cd, 173cd, 174cd) extending from the distal end (160) along the probe longitudinal axis (150); using the one or more magnetic field vectors to determine the angular arrangement (180, 190) with respect to the embedded marker (200); and determining whether the angular arrangement (180, 190) substantially coincides with the one or more marker detection regions (170abcd, 171cd, 172cd, 173cd, 174cd). A method comprising the above steps.

Description of Reference Numerals

[0178] Reference numerals used in the drawings 100 First embodiment of a magnetic field probe 101 Second embodiment of a magnetic field probe 110 First sensor 120 Second sensor 130 Third sensor 150 Probe longitudinal axis 160 Distal end of the probe 165 Proximal end of the probe The ranges of the marker detection areas in the X-Y plane of 170a and 170b The ranges of the marker detection areas in the Y-Z plane of 170c and 170d The ranges of the second marker detection areas in the Y-Z plane of 171c and 171d The ranges of the third marker detection areas in the Y-Z plane of 172c and 172d The ranges of the fourth marker detection areas in the Y-Z plane of 173c and 173d The ranges of the fifth marker detection areas in the Y-Z plane of 174c and 174d XY angular arrangement of 180 YZ angular arrangement of 190 The first inclination θ of 191 The second inclination θ of 192 The third inclination θ of 193 The fourth inclination θ of 194 The fifth inclination θ of 195 The sixth inclination θ of 196 Embedded magnetic marker or inductive magnetic marker of 200 The outer surface of the skin of 300 The first magnetic field line of 401 The second magnetic field line of 402 The third magnetic field line of 403 The fourth magnetic field line of 404 Inclination relationship of 500 The inclination of the probe of 550 The inclination of the magnetic field on the probe surface of 575 X-axis of 600 Y-axis of 700 Z-axis of 800 Magnetic marker axis of 900 Magnetic field of 920 Magnetic vector of 930 Lateral axis of 950 Detection position of 970

Claims

1. A magnetic field probe (100, 101) for determining the angular arrangement (180, 190) of an implanted marker (200), said marker comprising a magnetic dipole configured to generate a magnetic field during use, said probe (100, 101) comprising a distal end (160), and a first magnetic sensor (110) at the distal end (160) of said probe (100, 101), and a second magnetic sensor (120) disposed between said first magnetic sensor (110) and the proximal end (165) of said probe (100, 101), said first and second magnetic sensors being configured and arranged to determine one or more magnetic field vectors of said magnetic dipole during use, said probe (100, 101) comprising defining two or more marker detection regions (170abcd, 171cd, 172cd, 173cd, 174cd) extending from said distal end (160) along a probe longitudinal axis (150), using said one or more magnetic field vectors to determine said angular arrangement (180, 190) relative to said magnetic dipole, when said angular arrangement (180, 190) relative to said magnetic dipole coincides with one of said two or more marker detection regions (170abcd, 171cd, 172cd, 173cd, 174cd), determining that said implanted marker (200) is within one of said two or more marker detection regions, when said angular arrangement (180, 190) relative to said magnetic dipole does not coincide with said one of said two or more marker detection regions (170abcd, 171cd, 172cd, 173cd, 174cd), suppressing determining said angular arrangement using said one or more magnetic field vectors and further configured to be a magnetic field probe (100, 101).

2. The probe according to claim 1, wherein said two or more marker detection regions (170abcd, 171cd, 172cd, 173cd, 174cd) are symmetric with respect to said longitudinal axis (150).

3. The probe according to claim 1 or 2, wherein the two or more marker detection regions (170abcd, 171cd, 172cd, 173cd, 174cd) have an arc, segment, cylindrical, or conical shape.

4. The probe according to any one of claims 1 to 3, wherein the two or more marker detection regions (171cd, 172cd, 173cd, 174cd) share one or more boundaries.

5. The two or more marker detection regions (171cd, 172cd, 173cd, 174cd) differ with respect to parameters selected from the group consisting of range, shape, orientation, arrangement, scaling, resolution, angular boundary, longitudinal range, lateral range, or any combination thereof The probe according to any one of claims 1 to 4. Define a further marker detection region (170abcd, 171cd, 172cd, 173cd, 174cd) extending from the distal end (160) along the probe longitudinal axis (150), Determine whether the angular arrangement (180, 190) with respect to the magnetic dipole coincides with one of the three or more marker detection regions (170abcd, 171cd, 172cd, 173cd, 174cd), thereby determining that the marker (200) is within said one of the three or more marker detection regions (170abcd, 171cd, 172cd, 173cd, 174cd). The probe according to any one of claims 1 to 5, further configured as such.

7. The probe defines a first marker detection region, a second marker detection region, and a further marker detection region (170abcd, 171cd, 172cd, 173cd, 174cd) extending from the distal end (160) along the probe longitudinal axis (150), The angular arrangement (180, 190) with respect to the magnetic dipole is (1) Whether it coincides with the further marker detection area (170abcd, 171cd, 172cd, 173cd, 174cd), (2) Whether it coincides with both the first marker detection area and the further marker detection area (170abcd, 171cd, 172cd, 173cd, 174cd), (3) Whether it coincides with both the second marker detection area and the further marker detection area (170abcd, 171cd, 172cd, 173cd, 174cd), (4) Whether it does not coincide with any of the first marker detection area or the further marker detection area (170abcd, 171cd, 172cd, 173cd, 174cd), (5) Whether it does not coincide with any of the second marker detection area or the further marker detection area (170abcd, 171cd, 172cd, 173cd, 174cd), or (6) Whether it is any combination of the above (1) to (5), The probe according to any one of claims 1 to 6, further configured such that the probe determines the above.

8. The probe (100, 101) according to any one of claims 1 to 7, further configured and arranged to determine the angular arrangement (180, 190) of the magnetic dipole of the marker (200) with respect to the distal end (160) of the probe (100, 101).

9. The probe (100, 101) according to any one of claims 1 to 8, further configured and arranged to determine the angular arrangement (180, 190) of the magnetic dipole of the marker (200) with respect to the longitudinal axis (150) of the probe (100, 101).

10. The probe (100, 101) according to any one of claims 1 to 9, comprising at least one further magnetic sensor (130), wherein the magnetic sensors (110, 120) are included in one or more 1D, 2D, or 3D arrays. **Claim 11**: The two or more marker detection regions (170abcd, 171cd, 172cd, 173cd, 174cd) include a first marker detection region (170abcd, 171cd, 172cd, 173cd, 174cd) and a second marker detection region (170abcd, 171cd, 172cd, 173cd, 174cd), the probe (100, 101) is further configured and arranged to provide an audio feedback, and audio characteristics are different according to whether the angular arrangement (180, 190) with respect to the magnetic dipole coincides with the first or second marker detection region (170abcd, 171cd, 172cd, 173cd, 174cd). The probe according to any one of claims 1 to 10. **Claim 12** The two or more marker detection regions (170abcd, 171cd, 172cd, 173cd, 174cd) are further configured and arranged to provide a coarse and a fine marker detection region (170abcd, 171cd, 172cd, 173cd, 174cd). The probe according to any one of claims 1 to 11. **Claim 13**: As the distal end (160) of the probe (100, 101) approaches the marker (200), it is further configured and arranged to select a marker detection region (170abcd, 171cd, 172cd, 173cd, 174cd) having a smaller marker detection angle. The probe according to any one of claims 1 to 12. **Claim 14**: A method for determining the angular arrangement (180, 190) of a magnetic marker (200), the magnetic marker (200) comprises a magnetic dipole configured to generate a magnetic field during use, the method comprising A probe (100, 101) comprising a distal end (160) is provided, the probe further comprising a first magnetic sensor (110) at the distal end (160) and a second magnetic sensor (120) disposed between the first magnetic sensor (110) and the proximal end (165) of the probe (100, 101), the first and second magnetic sensors being configured and arranged to determine one or more magnetic field vectors of the magnetic dipole during use, The probe is configured and arranged to define two or more marker detection regions (170abcd, 171cd, 172cd, 173cd, 174cd) extending from the distal end (160) along the probe longitudinal axis (150), The probe uses the one or more magnetic field vectors to determine the angular arrangement (180, 190) relative to the magnetic dipole, When the angular arrangement (180, 190) relative to the magnetic dipole matches one of the two or more marker detection regions (170abcd, 171cd, 172cd, 173cd, 174cd), the probe determines that the magnetic marker (200) is within one of the two or more marker detection regions, and When the angular arrangement (180, 190) relative to the magnetic dipole does not match the one of the two or more marker detection regions (170abcd, 171cd, 172cd, 173cd, 174cd), the probe suppresses the determination of one or more magnetic field vectors, A method comprising.

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