Reduction of magnetic field (B0) artifacts through active shimming

Abstract

An electronic device (10) includes an electronic component (14); at least one conductive loop or winding (18) disposed around the electronic component; and an electronic controller (24) configured to: obtain (102) a magnetic field direction from a received ambient magnetic field measurement signal; determine (104) at least one magnetic field shim current based on the obtained magnetic field direction; and energize (106) the at least one conductive loop or winding to cause the determined at least one magnetic field shim current to flow.

Description

Technical Field

[0001] The following content generally relates to imaging technology, magnetic resonance imaging technology, magnetic resonance image quality technology, magnetic field shim current technology and related technologies. Background Art

[0002] Magnetic resonance imaging (MRI) scanners increasingly incorporate electronic components located within the bore of the magnet. These components utilize integrated circuit (IC) chips, such as field programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), microprocessors, memory chips, system-on-chip (SoC) chips, system-in-package (SiP) chips, and the like. These IC chips include magnetic materials along with packaging or shielding materials, such as nickel used as a diffusion barrier in gold plating for wire bonding bumps and flip-chip bonding bumps. Substituting non-magnetic materials is often not possible or requires purchasing custom IC chips, which may not be cost-effective. The magnetic materials of the IC chips locally distort the static (B0) magnetic field, which can lead to imaging artifacts. Because these can be large chips (e.g., an FPGA can be 1.7 cm x 1.7 cm square), the amount of image distortion introduced by the IC chips can be considerable.

[0003] Electronic components within the magnet bore also require power. Power cables can couple to magnetic field gradients and / or radio frequency (RF) signals, and cable routing issues can arise. Battery power is an attractive alternative. However, batteries also typically contain magnetic materials that can introduce image distortion.

[0004] Certain improvements that overcome these and other problems are disclosed below. Summary of the Invention

[0005] In one aspect, an electronic device includes: an electronic component; at least one conductive loop or winding arranged around the electronic component; and an electronic controller, which is configured to: obtain a magnetic field direction from a received ambient magnetic field measurement signal; determine at least one magnetic field shim current based on the obtained magnetic field direction; and excite the at least one conductive loop or winding to cause the determined at least one magnetic field shim current to flow.

[0006] In another aspect, an electronic device includes: an IC chip; a magnetic field sensor configured to measure an ambient magnetic field measurement signal; a plurality of conductive loops or windings arranged around the IC chip; and an electronic controller configured to: obtain a magnetic field direction from the ambient magnetic field measurement signal measured by the magnetic field sensor; determine at least one magnetic field shim current based on the obtained magnetic field direction; and excite the plurality of conductive loops or windings to cause the determined at least one magnetic field shim current to flow.

[0007] In another aspect, a method for determining a magnetic field shim current includes: obtaining a magnetic field direction from a received ambient magnetic field measurement signal; determining at least one magnetic field shim current based on the obtained magnetic field direction; and exciting at least one conductive loop or winding to cause the determined at least one magnetic field shim current to flow.

[0008] One advantage resides in eliminating artifacts in images caused by one or more magnetic components.

[0009] Another advantage resides in generating active shim currents to eliminate magnetic artifacts in the image.

[0010] Another advantage is that equal but opposite magnetizations are produced to eliminate magnetic artifacts in the image.

[0011] Another advantage is that the influence of magnetic components on the image can be hidden by generating corresponding shim currents.

[0012] A given embodiment may provide none, one, two, more, or all of the aforementioned advantages, and / or may provide other advantages that will become apparent to one of ordinary skill in the art upon reading and understanding this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present disclosure may take the form of various components and arrangements of components, and various steps and arrangements of steps. The drawings are only intended to illustrate preferred embodiments and are not to be construed as limiting the present disclosure.

[0014] Figure 1 An exemplary embodiment of an electronic device for an MRI system according to one aspect is shown.

[0015] Figure 2 Another exemplary embodiment of an electronic device for an MRI system according to one aspect is shown.

[0016] Figure 3 Shown Figure 1 and Figure 2 An exemplary flow chart of the operation of the apparatus. DETAILED DESCRIPTION

[0017] The systems and methods disclosed herein utilize the insight that the effect of an IC chip (or other magnetic object) in the B0 field can be modeled as bound currents flowing on the surface of the IC chip, which produce a concentrated magnetic moment M. In one exemplary embodiment, conductive wires or loops are wrapped around the outside of the IC chip, and current is passed through these conductors to cancel the magnetic moment M.

[0018] In some embodiments disclosed herein, the ambient magnetic field (i.e., the magnetic field in which the IC chip is embedded) is measured using a three-axis Hall sensor or other magnetic field sensor that is mounted on or together with a magnetic object and is capable of measuring a three-dimensional (3D) magnetic field. However, in order to remove image artifacts, it is not appropriate to simply disable the measured magnetic field. The goal is not to remove the magnetic field, but to restore B0 to its undistorted value. Compared with the measurement of the B0 magnetic field, the distorted magnetic moment M introduced by the magnetic material in the IC chip is generally small, that is, |M|<<|B0|. In addition, B0 and M are both vectors, which may be oriented in different directions. Therefore, it is difficult to determine the magnetic moment M vector to be removed by magnetic field measurement.

[0019] To remedy these issues, in some embodiments disclosed herein, the current applied by the conductive wire or loop to compensate for B0 distortion is pre-calibrated for various spatial orientations of the IC chip relative to the B0 vector using simulation or experimentation. For example, the IC chip can be placed in the aperture at a given orientation, an image acquired, and the compensation loop current adjusted until image artifacts are minimized. A similar approach can be accomplished using an electromagnetic simulator, where the goal is to adjust the compensation loop current until the distortion is eliminated. This calibration is performed at multiple different orientations.

[0020] Afterwards, the IC chip is placed together with the 3D Hall effect sensor. The Hall effect sensor is used only to determine the IC chip's orientation relative to the B0 field; the applied compensation loop current is the compensation loop current for that orientation calibration. (If there are several different discrete orientation calibrations, interpolation can be used.)

[0021] Advantageously, the Hall sensor does not need to be mounted on the IC chip, or even close to it. Instead, the Hall sensor must only be mounted in a fixed orientation relative to the IC chip. Typically, this is easiest when the Hall sensor is mounted on the same PCB as the IC chip. Furthermore, because the magnetic field measurement is used only to determine the direction of the B0 field, any magnetic field distortion at the Hall sensor due to the magnetic moment M generated by the IC chip (if it is close to the Hall sensor) typically has a negligible effect on the determined B0 direction due to the difference in magnitude, i.e., |B0| >> |M|.

[0022] In some embodiments disclosed herein, the IC chip is a programmable IC chip, such as an FPGA or a microprocessor. In these cases, the controller for driving the loop compensation current can be implemented on the IC chip itself. The conductive loops can be added to existing IC chips because they are external to the IC chip. In addition, the compensation loop current is a DC current, which in some embodiments can be drawn from a digital power rail (e.g., V CCTherefore, by adding the necessary onboard control program and the surrounding conductive ring, as well as a single 3D Hall sensor (or other 3D magnetic field sensor) mounted on the circuit board, all IC chips on the circuit board can be effectively "self-enclosed" in terms of distorting the B0 field.

[0023] The proposed design can also be easily deployed in MRI scanners using different B0 intensities. In this case, in addition to determining B0 orientation, the Hall sensor also determines its measurement |B0|. It is expected that the calibration compensation loop current should scale linearly with |B0|. Alternatively, the compensation current can be calibrated for several different standard field strengths (e.g., 1.5 Tesla, 3.0 Tesla).

[0024] In some embodiments disclosed herein, when the device is not performing imaging, the compensation loop current can be turned off to save power.

[0025] In some embodiments disclosed herein, the disclosed method can be used to compensate for magnetic field gradients by measuring ambient magnetic field measurements in real time and compensating for changes in the measurements as a function of time. Another contemplated variation requires measuring the derivative, d|B0| / dt, which is proportional to the induced eddy currents within the ground plane of the PCB. In this case, experimental or simulated calibration would be performed for the IC chip on the PCB, and the eddy current compensation would be calibrated as a function of d|B0| / dt by applying different magnetic field cycling patterns expected to be encountered during MRI imaging.

[0026] In other embodiments disclosed herein, the disclosed methods can be used to compensate for magnetic field gradients caused by the influence of a magnetic component that moves in time. This movement causes the spatial gradient dB / dx(t) of the magnetic moment M to vary over time, which induces a varying field in the IC chip.

[0027] While the exemplary illustrative embodiments provide artifact reduction for IC chips, the disclosed methods may also be applicable to other devices containing magnetic materials placed within an MRI bore, such as onboard batteries, large capacitors or inductors, shielding and / or packaging materials, etc.

[0028] As used herein, the term "ambient magnetic field" (and its variants) refers to the magnetic field in the surrounding area or environment surrounding the circuit on which the electronic components are mounted. Said another way, the ambient magnetic field is the magnetic field in which the circuit is embedded. In the context of MRI, the ambient magnetic field is typically a static B0 magnetic field generated by a (typically superconducting) magnet disposed in the MRI scanner, or a B0 magnetic field adjusted by the magnetic field gradient superimposed by the magnetic field gradient coils of the MRI scanner. It should be noted that, as used herein, "ambient magnetic field" does not typically refer to the earth's magnetic field. Any effect of the earth's magnetic field on the ambient magnetic field within the MRI bore is completely negligible. For example, the magnetic field on the surface of the earth is typically around 25-65 microteslas; and some standard B0 magnetic fields of some commercial MRI scanners have values of 0.23 tesla, 1.5 tesla, 3.0 tesla, or even higher.

[0029] As used herein, a conductive loop (and variants thereof) is a single conductor turn; whereas a conductive winding (and variants thereof) comprises two or more conductor turns whose induced magnetic fields combine in an additive manner, such as a solenoid (although more generally, the two or more conductor turns need not have the same radius, as is typically the case in a solenoid).

[0030] Figure 1 An exemplary embodiment of an electronic device 10 for use with an associated medical imaging device (e.g., an MRI scanner) 12 is shown. The electronic device 10 includes an electronic component 14. In some embodiments, the electronic component 14 may be a battery 15, such as the illustrative flat cylindrical button cell. In other embodiments, the electronic component 14 may be an IC chip 16, such as an FPGA, a microprocessor chip, or the like.

[0031] The electronic device 10 further includes at least one conductive loop or winding 18 disposed around the electronic component 14. The at least one conductive loop or winding 18 is configured to cause a magnetic field shim current to flow therethrough. Figure 1 As shown, the at least one conductive loop or winding 18 includes three conductive loops or windings 18 disposed about the electronic component 14; however, any suitable number of loops or windings may be used. Figure 1The three loops 18 shown in FIG have mutually orthogonal loop normals (e.g., the corresponding normal vectors of the corresponding planes in which the corresponding loops are arranged are mutually orthogonal). This arrangement of three mutually orthogonal loops enables compensation regardless of the orientation of the electronic device 10 relative to the direction of the ambient magnetic field. However, it is contemplated that fewer than three loops may be used—for example, if the approximate orientation of the electronic device relative to the B0 magnetic field is known in advance, then only two, or possibly even only one, conductive loop may be sufficient. As an example of this, a head coil designed to be used with a patient in a prone or supine position may have a roughly predetermined orientation relative to B0, and thus an IC chip mounted on the head coil may also have a roughly predetermined orientation relative to B0.

[0032] Continue to refer Figure 1 And refer to Figure 2 , the electronic device 10 also includes a magnetic field sensor 20, which is configured to generate an ambient magnetic field signal that indicates the magnitude and direction (3D) of the ambient magnetic field. In some examples, the magnetic field sensor 20 includes a three-axis Hall effect sensor, but other types of magnetometers are also contemplated as magnetic field sensors 20, such as magnetoresistive sensors, fluxgate magnetometers, etc. The electronic device 10 also includes (or, alternatively, is considered to be provided with) a printed circuit board (PCB) 22, on which the electronic components 14 are mounted. Figure 2 As shown, the electronic component 14 and the magnetic field sensor 20 are mounted on the (same) PCB 22, with three conductive loops 18 surrounding the electronic component. However, in some embodiments, the magnetic field sensor 20 need not be mounted on the PCB 22, but only needs to be mounted in a fixed orientation relative to the electronic component 14. (This fixed orientation is achieved when the electronic component 14 and the magnetic field sensor 20 are mounted on the same PCB 22, assuming that the PCB 22 is not a flexible PCB).

[0033] The electronic device 10 also includes an electronic controller 24 (also referred to as a processor or control unit) that is configured to determine and transmit a shim current to each conductive loop or winding 18. The electronic controller is electrically connected to at least one conductive loop or winding 18 and, in some embodiments, to the magnetic field sensor 20.

[0034] Conductive loop or winding 18 can be manufactured in a variety of ways. In one method, conductive loop or winding 18 comprises one or more turns of wire wrapped around electronic component 14. This method facilitates retroactive addition of conductive loop or winding 18 to existing electronic components. In another method, conductive loop or winding 18 comprises an electrical trace or set of traces deposited on the housing of electronic component 14, for example, using vacuum evaporation or a similar method, with an appropriate mask used during evaporation or photolithography to define the trace. In another method, conductive loop or winding 18 is formed as a PCB trace of PCB 22, arranged to surround the location where electronic component 14 is mounted on PCB 22. (This method is generally only suitable for conductive loops or windings 18 whose plane is parallel to the plane of PCB 22.) In another method, conductive loop or winding 18 is formed as an electrical trace fabricated on the silicon wafer of the IC chip during manufacture of the IC chip 14. (This assumes that the electronic component 14 is an IC chip and will generally only work with conductive loops or windings 18 whose plane is parallel to the plane of the silicon wafer and will not work with retrofitting existing IC chips.) In another approach, the electronic component 14 may be housed within an external housing (not shown) that includes the conductive loops or windings 18. This approach, for example, Figure 1 The battery 15 of the embodiment of the present invention may be suitable, wherein the housing can be a battery housing or a container in which the battery 15 is installed. In this way, off-the-shelf batteries can be used. These are only some non-limiting illustrative methods of providing the conductive loop or winding 18.

[0035] Each conductive loop or winding 18 should be arranged relative to the electronic component 14 so that the induced magnetic field generated by the current flowing through the conductive loop or winding 18 passes through the electronic component 14. This is easily achieved when the conductive loop or winding 18 is wrapped around the electronic component 14. However, it can also be achieved in other ways. For example, in the aforementioned embodiment, the conductive loop or winding 18 is formed as a conductive PCB trace on the PCB 22 that surrounds the mounting position of the electronic component 14, and the plane of the conductive PCB trace is spatially offset from the electronic component 14, but the magnetic field generated by the current flowing through the surrounding PCB trace will still pass through the electronic component 14. Generally speaking, it is expected that the conductive loop or winding 18 is wrapped around the electronic component 14 or is otherwise closely coupled thereto; therefore, although in Figure 2 In the example of FIG, the PCB traces surrounding the outer perimeter of the PCB 22 will generate a magnetic field that passes through the electronic component 14, but only a small portion of this magnetic field will actually pass through the electronic component, making the distortion compensation very inefficient.

[0036] The operative electrical connection of the electronic controller 24 to the conductive loop or winding 18 can be achieved in a variety of ways. If the electronic controller 24 is mounted on a PCB 22, then conductive PCB traces of the PCB 22 can be provided (during the manufacture of the PCB 22) to connect wire bonds or surface mount contact pads of the electronic controller 24 to pads to which the conductive loop or winding 18 is soldered. In embodiments where the electronic controller 24 is integrally implemented on an IC chip 14, for example, by programming an appropriate controller implemented in the IC chip 14 including an FPGA or microprocessor, then surface mount pads (not shown) of the IC chip 14 (to which the IC chip is programmed to direct drive current) are connected to the conductive loop or winding 18. In embodiments where a digital power rail (e.g., V CC In embodiments where the power for driving the conductive loop or winding 18 is provided by a single-source (-GND potential difference) power rail, no additional power supply is required to provide the driving power for the conductive loop or winding 18. Since the magnetization M caused by the magnetic material or other mostly non-magnetic components in the IC chip is expected to be small, a digital power rail is expected to be sufficient in many specific applications. If additional power is required, a separate power supply is provided. In this case, the operative electrical connection between the electronic controller 24 and the conductive loop or winding 18 can be appropriately controlled through a power control circuit, thereby controlling the amount of power delivered to the conductive loop or winding 18, and the electronic controller 24 controls the power control circuit. Again, these are some non-limiting, illustrative examples.

[0037] Continue to refer Figure 1 and Figure 2 , and further reference Figure 3 , the electronic controller 24 is configured to perform a method or process 100 for determining a magnetic field shim current. To this end, the electronic controller 24 is configured to: obtain 102 a magnetic field direction from a received ambient magnetic field measurement signal; determine 104 at least one magnetic field shim current based on the obtained magnetic field direction; and energize 106 at least one conductive loop or winding 18 to cause the determined at least one magnetic field shim current to flow.

[0038] In some embodiments, the obtaining operation 102 includes measuring or determining the direction of the magnetic field using the magnetic field sensor 20. In other embodiments, the obtaining operation 102 includes measuring or determining the magnetic field strength of the ambient magnetic field using the magnetic field sensor 20. In this example, the determining operation 104 includes determining at least one magnetic field shim current using the magnetic field direction (and optionally the magnetic field strength). If the measurement of the ambient magnetic field is known in advance (e.g., the electronic device 10 will be used with a standard 3 Tesla magnet), then the only variable is the orientation of the B0 field. Figure 3 A suitable shim current calibration 105 is shown in FIG, where each row of the calibration table stores a tuple of the form:

[0039] (DX,I1X,I2X,I3X)

[0040] Where "DX" represents the orientation of the (ambient) B0 magnetic field, and I1X, I2X, I3X represent the shim currents for each of the (illustrative) three conductive loops or windings 18 appropriate for the "DX" orientation. If the measured B0 orientation does not align exactly with any table entry, the closest entry can be selected, or interpolated between the two closest entries. If the ambient magnetic field strength is not known in advance, it can be obtained from the magnetic field measurement, and the shim current calibration can be modified to:

[0041] (DX,MY,I1XY,I2XY,I3XY)

[0042] Where "MY" represents the ambient magnetic field strength, and the appropriate shim current for each loop or winding is parameterized by both direction (X) and amplitude (Y). As previously described, the shim current calibration 105 is suitably generated offline by experimentation (e.g., placing the device in an MRI at different orientations and adjusting the shim current for each orientation until image distortion is minimized) or by simulation (by simulating the above process in an electromagnetic simulator). In another embodiment, the obtaining operation 102 includes determining the time derivative of the magnetic field strength of the ambient magnetic field, and using this time derivative (along with the direction) to determine at least one magnetic field shim current at operation 104. The time derivative of the magnetic field induces eddy currents in the ground plane of the PCB 22, which in turn induce magnetic moments that distort the image, and these are all shimmed.

[0043] In other embodiments, the energizing operation 106 includes energizing the at least one conductive loop or winding 18 only when the MRI scanner 12 is acquiring imaging data. This requires providing information to the electronic controller 24 regarding when imaging is in progress. For example, this information may be provided by an MRI imaging controller (not shown) of the MRI scanner 12. In another approach, detection of a time-varying magnetic field by the magnetic field sensor 20 provides an indication of when imaging is in progress. When not imaging, no magnetic field gradients should be applied, so the ambient magnetic field should be static. Conversely, during imaging, applied magnetic field gradients will dynamically alter the ambient magnetic field, and this can be detected by the magnetic field sensor 20 to determine when imaging is in progress. Because some portions of an MRI sequence may not involve magnetic field gradients, this approach preferably turns on the shim currents immediately upon detection of a dynamically varying ambient magnetic field, and turns off the shim currents only after a certain time interval has passed since the ambient magnetic field has become static (e.g., waiting one or two seconds after the magnetic field becomes static before turning off the shim currents).

[0044] In some embodiments, IC chip 14 includes an electronic processor or control unit, such as a microprocessor, microcontroller, or FPGA. For example, IC chip 14 itself is programmed to perform acquisition operation 102, determination operation 104, and stimulus operation 106. In this embodiment, microprocessor or microcontroller or FPGA 14 does not receive power except through a power pin of the microprocessor or microcontroller or FPGA that provides operating power to the microprocessor or microcontroller or FPGA.

[0045] At least one magnetic field shim current is a DC current, which in some embodiments may be supplied from a digital power rail (e.g., V CC Thus, by adding the necessary onboard control program and the surrounding conductive ring, as well as a single magnetic field sensor 20 mounted on the PCB 22, all electronic components 14 mounted on the PCB 22 can be effectively "self-enclosed" in terms of distorting the ambient magnetic field.

[0046] In other embodiments, the electronic component 14 includes a plurality of electronic components (e.g., a plurality of batteries, a plurality of IC chips, a combination of one or more batteries and one or more IC chips, etc.), each of which is mounted on the PCB 22. Each electronic component 14 has at least one conductive loop or winding 18 disposed therearound. The electronic controller 24 is configured to perform the acquisition operation 102, the determination operation 104, and the stimulation operation 106 for each electronic component 14.

[0047] In determining the at least one magnetic field shim current at operation 104 , the value of the at least one magnetic field shim current should restore the ambient magnetic field to an undistorted value, rather than removing the ambient magnetic field. However, based on the measurements of the magnetic field sensor 20 , it is not obvious what such an undistorted value would be.

[0048] To address this issue, the electronic device 10 can be calibrated for various orientations of the electronic component 14 relative to the ambient magnetic field (e.g., by placing the electronic component in the bore of an MRI scanner 12, acquiring an image, and adjusting the current of at least one conductive loop or winding 18 until the artifact is minimized or eliminated). Thereafter, when the magnetic field sensor 20 determines the orientation of the device relative to the ambient magnetic field, the compensation loop current applied is the compensation loop current calibrated for that orientation.

[0049] The present disclosure has been described with reference to preferred embodiments. Modifications and alterations may occur to others upon reading and understanding the foregoing detailed description. It is intended that the exemplary embodiments be interpreted as including all such modifications and alterations as come within the scope of the appended claims or their equivalents.

Claims

1. An electronic device (10) configured to be embedded in a static magnetic field of a magnetic resonance imaging scanner, the electronic device (10) comprising: Electronic components (14); a magnetic field sensor (20) mounted in a fixed orientation relative to the electronic component (14); three mutually orthogonal conductive loops or windings (18) disposed around the electronic component (14); and An electronic controller (24) configured to: obtaining (102) a measurement signal from the magnetic field sensor (20) when the electronic device (10) is embedded in the static magnetic field, the measurement signal comprising the direction and intensity of the static magnetic field or the direction of the static magnetic field if the measure of the static magnetic field is known in advance; determining (104) a magnetic field shim current for each of the conductive loops or windings (18) based on the obtained measurement signals; and The conductive loop or winding (18) is excited (106) to cause the determined magnetic field shim current to flow.

2. The electronic device (10) according to claim 1, wherein The electronic component (14) is an integrated circuit IC chip (16).

3. The electronic device (10) according to claim 2, wherein: The IC chip (16) is a microprocessor, a microcontroller, or a field programmable gate array (FPGA); and The electronic controller (24) includes the microprocessor or the microcontroller or the FPGA.

4. The electronic device (10) according to claim 3, wherein: The microprocessor or the microcontroller or the FPGA does not receive power except through power pins of the microprocessor or the microcontroller or the FPGA that provide operating power to the microprocessor or the microcontroller or the FPGA.

5. The electronic device (10) according to claim 1, wherein The electronic component (14) is a battery (15).

6. The electronic device (10) according to any one of claims 1 to 5, wherein: The electronic device further comprises: A printed circuit board PCB (22) on which the electronic component (14) and the magnetic field sensor (20) are mounted.

7. The electronic device (10) according to claim 6, wherein: The magnetic field sensor (20) comprises a Hall effect sensor.

8. The electronic device (10) according to claim 7, wherein: The electronic device (10) includes a plurality of electronic components, each of which is mounted on the PCB (22).

9. The electronic device (10) according to claim 7, wherein: Each of the conductive loops or windings (18) comprises a conductive loop or winding comprising a printed circuit of the PCB (22) surrounding the electronic components mounted on the PCB.

10. The electronic device (10) according to any one of claims 1 to 5, wherein: The electronic controller (24) is configured to energize the conductive loop or winding (18) to cause the determined magnetic field shim current to flow only when the magnetic resonance imaging scanner (12) is acquiring imaging data.

11. An electronic device (10) configured to be embedded in a static magnetic field of a magnetic resonance imaging scanner, the electronic device (10) comprising: Electronic components (14); a magnetic field sensor (20) mounted in a fixed orientation relative to the electronic component (14); at least one electrically conductive loop or winding (18) disposed around the electronic component (14), wherein the orientation of the electronic component (14) relative to the static magnetic field is known in advance; and An electronic controller (24) configured to: obtaining (102) a measurement signal from the magnetic field sensor (20) when the electronic device (10) is embedded in the static magnetic field, the measurement signal comprising the direction and intensity of the static magnetic field or the direction of the static magnetic field if the measure of the static magnetic field is known in advance; determining (104) a magnetic field shim current for each of the at least one conductive loop or winding (18) based on the obtained measurement signal; as well as The at least one conductive loop or winding (18) is excited (106) to cause the determined magnetic field shim current to flow.

12. The electronic device (10) according to claim 11, wherein The electronic component (14) is an integrated circuit IC chip (16), which is a microprocessor or microcontroller or field programmable gate array FPGA programmed to perform acquisition, determination and stimulation operations.

13. The electronic device (10) according to claim 11, wherein The electronic device further comprises: A printed circuit board (PCB) (22) on which at least one of the electronic component (14) and the magnetic field sensor (20) is mounted.

14. The electronic device (10) according to claim 13, wherein: The at least one conductive loop or winding (18) comprises a printed circuit of the PCB (22) surrounding the electronic component (14).

15. The electronic device (10) according to any one of claims 11 to 14, wherein The magnetic field sensor (20) comprises a Hall effect sensor.

16. The electronic device (10) according to any one of claims 1 to 5, wherein: In the case where the measurement signal comprises the direction and intensity of the static magnetic field, the electronic controller (24) is further configured to: obtaining a time derivative of the intensity of the static magnetic field from the measurement signal; and The magnetic field shim current is determined based on the obtained direction of the static magnetic field and the obtained time derivative of the intensity of the static magnetic field.

17. A method (100) for determining a magnetic field shim current, the method comprising: embedding an electronic component (14) and a magnetic field sensor (20) in a static magnetic field of a magnetic resonance imaging scanner, wherein the magnetic field sensor (20) is mounted in a fixed orientation relative to the electronic component (14) and three mutually orthogonal conductive loops or windings (18) are disposed around the electronic component (14); obtaining (102) a measurement signal from the magnetic field sensor (20), the measurement signal comprising the direction and strength of the static magnetic field or the direction of the static magnetic field if the measure of the static magnetic field is known in advance; determining (104) a magnetic field shim current for each of the conductive loops and windings (18) based on the obtained measurement signals; as well as The conductive loop or winding (18) is excited (106) to cause the determined magnetic field shim current to flow.

18. A method (100) for determining a magnetic field shim current, the method comprising: embedding an electronic component (14) and a magnetic field sensor (20) in a static magnetic field of a magnetic resonance imaging scanner, wherein the magnetic field sensor (20) is mounted in a fixed orientation relative to the electronic component (14) and at least one conductive loop or winding (18) is disposed around the electronic component (14), the orientation of the electronic component (14) relative to the static magnetic field being known in advance; obtaining (102) a measurement signal from the magnetic field sensor (20), the measurement signal comprising the direction and strength of the static magnetic field or the direction of the static magnetic field if the measure of the static magnetic field is known in advance; determining (104) a magnetic field shim current for each of the at least one conductive loop and the winding (18) based on the obtained measurement signal; as well as The at least one conductive loop or winding (18) is excited (106) to cause the determined magnetic field shim current to flow.

Images