Method and system for determining orientation and position of movable object relative to B0 field magnet

Abstract

The invention relates to a method for determining the orientation and position of a movable object relative to a B0 field magnet of a magnetic resonance tomography scanner in an X-Z coordinate plane of an X-Y-Z coordinate system based on the B0 field magnet, comprising at least the following steps: providing B0 reference data of the B0 field magnet having a magnetic field strength characterizing a plurality of X-Y-Z coordinates; providing at least three three-dimensional magnetic field intensity sensors which are arranged at the object at a fixed relative position; determining position data for the respective magnetic field strength sensor by evaluating a measured value component of the respective magnetic field strength sensor, the measured value component being independent of the respective orientation of the movable object in the X-Z coordinate plane; filtering the determined position data of the magnetic field strength sensor based on the relative position of the magnetic field strength sensor and providing filtered position data; based on the filtered position data, an orientation value and position of the movable object relative to the B0 field magnet is provided.

Description

Technical Field

[0001] The present invention relates to a method and system for determining the orientation and position of a movable object relative to a B0 field magnet of a magnetic resonance tomography scanner. Background Technology

[0002] A magnetic resonance imaging (MRI) scanner is an imaging device that aligns the nuclear spins of the object being examined with a strong external magnetic field in order to image the object. An alternating magnetic field is then used to excite the nuclear spins to precess around the alignment. The precession of the spins from the excited state or their return to a lower energy state generates another alternating magnetic field as a response, which is received by an antenna.

[0003] Spatial encoding is applied to the signal using a magnetic gradient field, which then allows the received signal to be correlated with volume elements. The received signal is then evaluated, providing a three-dimensional image of the object under examination.

[0004] Spatial encoding is typically based on the XYZ coordinate system. Here, the Z-axis is generally defined as the axis of symmetry of the B0 field magnet, which passes through the patient channel of the B0 field magnet along its preferred direction. In a common configuration of a magnetic resonance imaging (MRI) scanner, the Z-axis is horizontally oriented and centered through an opening in the winding of the B0 field magnet extending through the receiving area of ​​the B0 field magnet. The recording object is typically placed in the patient channel on the examination table parallel to the Z-axis. Together with the Z-axis, the X-axis and Y-axis form a space, wherein these axes are orthogonal to each other, with the X-axis oriented horizontally and the Y-axis vertically.

[0005] The mobile examination bed is typically moved manually by a person to approach the B0 field magnet, where it is then pulled into a predetermined position by an automated gripping device. Here, the examination bed, and thus the patient, is subjected to strong shaking motion because any inaccurate positioning or orientation of the examination bed must be corrected by the gripping device.

[0006] As demonstrated above, there is a need to provide a method and a system for providing the orientation and position of a movable object relative to the B0 field magnet of a magnetic resonance imaging (MRI) scanner. In particular, there is a need to simplify the movement of the examination table toward the B0 field magnet. Summary of the Invention

[0007] Therefore, the object of the present invention is to provide a solution by which the orientation and position of a movable object relative to the B0 field magnet of a magnetic resonance imaging (MRI) scanner can be provided. In particular, the object of the present invention is to simplify the approach movement of the examination table to the B0 field magnet.

[0008] These and other objectives, which may also be mentioned or recognized by those skilled in the art while reading the following text, are achieved through the subject matter of the embodiments. Embodiments of the invention improve the central concept of this application in a particularly advantageous manner.

[0009] According to the present invention, a method is provided for determining the orientation and position of a movable object relative to a B0 field magnet of a magnetic resonance imaging (MRI) scanner in the XZ coordinate plane of an XYZ coordinate system, wherein the XYZ coordinate system is referenced to the B0 field magnet, and the method includes at least the following steps:

[0010] Provide B0 reference data for a B0 field magnet, wherein the B0 reference data has a characterizing magnetic field strength for multiple XYZ coordinates;

[0011] Provide at least three three-dimensional magnetic field strength sensors, which are arranged at the object in a fixed relative position;

[0012] Position data for the corresponding magnetic field strength sensor is determined by evaluating the measured value components of the corresponding magnetic field strength sensor, which are independent of the corresponding orientation of the movable object in the XZ coordinate plane.

[0013] Based on the fixed relative position of the magnetic field strength sensor, the determined position data of the magnetic field strength sensor is filtered, and the filtered position data is provided.

[0014] Based on filtered position data, the orientation and position of a movable object relative to the B0 field magnet are provided.

[0015] In other words, the present invention proposes to determine the position data of the corresponding magnetic field strength sensor based on the measured value components of the magnetic field strength sensor in the first step, and the position data is independent of the orientation of the magnetic field strength sensor in the XZ coordinate plane.

[0016] The determined position data, in principle, does not yield explicit point coordinates, but rather point data with multiple possible point coordinates, also known as a point cloud. In another step, this determined position data is filtered based on the known, fixed relative positions of the magnetic field strength sensors relative to each other. In this context, filtering is understood as selecting points or point coordinates from the determined position data / point data that correspond to the known relative positions of the magnetic field strength sensors. In this regard, the determined position data can be filtered based on different conditions derived from the known relative positions of the magnetic field strength sensors relative to each other. The filtered position data can then be considered so that the orientation value of the object, for example, in the form of an angle relative to a B0 field magnet, and the position of the object, for example, in the form of XZ coordinates, can be determined with sufficiently high accuracy. The object's orientation value and position can then be considered, for example, to determine control data for navigation and motion devices for the object.

[0017] In principle, two XYZ coordinate systems or reference systems can be distinguished here. On one hand, the reference system is based on the B0 field magnet. In this reference system, the Z-axis corresponds to the axis of symmetry of the B0 field magnet along the preferred direction of the B0 field, wherein the coordinate axes are preferably orthogonal to each other, the X-axis is preferably horizontally oriented, and the Y-axis is preferably vertically oriented. This coordinate system based on the B0 field magnet is also referred to in practice as the so-called "Device Coordinate System" (DCS).

[0018] Another XYZ coordinate system can be referenced to the object. If the object is, for example, an examination bed, the zero point of the XYZ coordinate system can be centered on the front edge of the examination bed. The Z-axis is oriented, for example, along the longitudinal axis of the examination bed, the X-axis is preferably oriented horizontally, and the Y-axis is preferably oriented vertically, with the axes orthogonal to each other. This coordinate system based on the examination bed is also known in practice as a "table coordinate system" (TCS).

[0019] B0 reference data for a B0 field magnet is typically provided in the form of a 3D grid with a typical resolution of 1 mm, 5 mm, or 1 mm, ..., 10 mm. The B0 reference data here includes an explicit association between a point in space and the B vector at that point. The position of a point in space, such as a fixed point on a test bed, can be given in DCS coordinates as a vector p = (px, py, pz), where px, py, and pz are the coordinates of a point in the corresponding spatial direction, given, for example, in mm. The direction / orientation of the B0 field lines in the XZ plane, for example called angle α, can be calculated via the atan2 function as follows: α = atan2(hx, hz).

[0020] Preferably, at least three magnetic field strength sensors are arranged in the XZ coordinate plane, so that they have the same Y coordinate.

[0021] Preferably, in the XYZ coordinate system based on the object, at least two of the three magnetic field strength sensors have the same Z coordinate, and more preferably, at least two of the three magnetic field strength sensors also have the same X coordinate.

[0022] Preferably, the measurement components independent of the orientation of the movable object include: the magnitude of the B0 field vector (abs(h)), the Y field intensity component (hy), the Y field intensity component normalized to the magnitude of the B0 field vector (hy / abs(h)) and / or the magnitude of the vector in the XZ coordinate plane (abs(hx, hz)), thereby representing the length of the vector (hx, hz).

[0023] Preferably, the filtering step includes at least the following steps:

[0024] Point pairs are determined from the position data determined by the two magnetic field strength sensors, wherein the spacing between the points corresponds to the fixed relative positions of the two magnetic field strength sensors at the object.

[0025] Determine the orientation angles of the points used to determine the point pairs and determine the following point pairs in which the orientation angles of the points used in the point pairs are the same;

[0026] Determine point pair combinations in which the spacing and orientation of the point pairs correspond to the fixed relative positions of at least three magnetic field strength sensors.

[0027] Preferably, the movable object is an examination bed, wherein the magnetic field strength sensor is preferably located in the lower region of the lateral corner area of ​​the examination bed.

[0028] Preferably, the method further includes the following steps:

[0029] Control data is provided to a navigation and motion device based on the orientation and position of the movable object, the device being configured to move the movable object toward a target position relative to the B0 field magnet. Preferably, the control data is provided periodically, wherein at least one trajectory of the movable object and / or at least one direction vector and / or velocity vector of the movable object are also considered when providing the periodic control data. For example, the position and orientation of the examination bed relative to the B0 field magnet can be determined at a rate of 50 to 100 times per second and provided, for example, to a navigation controller, such that automatic navigation and motion of the examination bed can be performed, particularly until the examination bed docks at the B0 field magnet. Preferably, the position of the examination bed is given by a 2D vector having X and Z coordinates in the DCS reference system. The orientation of the examination bed is preferably given as an angle (yaw) between the Z-axis of the B0 field magnet and the longitudinal direction of the examination bed in a horizontal plane. Therefore, the navigation and motion device preferably transmits the X coordinate, Z coordinate, and angle (yaw) of the examination bed at a rate of approximately 50 to 100 times per second, so that the examination bed can reliably move in the B0 scattering field.

[0030] Preferably, the method further includes the following steps:

[0031] At least one collision sensor is provided, disposed at the object and configured to detect the area around the object and determine whether the object is within a planned movement path. Preferably, at least three collision sensors are disposed at the object, and the area with an angle of at least 90°, preferably at least 180°, and particularly preferably at least 270° is preferably detected by one or more collision sensors (160). It is feasible to use different collision sensors, for example, covering the area in front of the examination bed and the area to the side of the examination bed. For example, a LiDAR sensor can also be used here.

[0032] As already described, preferably, the B0 field magnet surrounds the patient channel of the magnetic resonance tomography scanner, wherein the Z-axis is defined by an axis of symmetry of the B0 field magnet along a preferred direction of the B0 field, wherein the coordinate axes are preferably orthogonal to each other and the X-axis is preferably horizontally oriented and the Y-axis is preferably vertically oriented.

[0033] Preferably, the magnetic field strength sensor is configured to detect the field strength of the three components of the B0 field along the three directions of the forming space.

[0034] The present invention also relates to a system for determining the orientation and position of a movable object relative to a B0 field magnet of a magnetic resonance computed tomography scanner in the XZ coordinate plane of an XYZ coordinate system based on the B0 field magnet, wherein the system comprises:

[0035] The first interface is set up to receive B0 reference data from a B0 field magnet, wherein the B0 reference data has a characterizing magnetic field strength for multiple XYZ coordinates.

[0036] The second interface is set up to receive measurements from at least three magnetic field strength sensors;

[0037] A computing unit, which is connected to an interface and configured to implement the methods described above.

[0038] Furthermore, the present invention relates to the application of a movable object having at least three three-dimensional magnetic field strength sensors in the method described above. The movable object is preferably the examination bed described above.

[0039] Furthermore, the present invention relates to a computer program element having instructions which, when executed on a data processing device in a data processing environment, are configured to implement the steps of the method described above in the system described above. Attached Figure Description

[0040] Unless otherwise expressly stated, all embodiments described herein can be combined with each other. Other features, advantages, and applications of the invention will become apparent from the following description, examples, and accompanying drawings. These illustrate:

[0041] Figure 1 A top view of the system according to the invention, in the form of a magnetic resonance tomography scanner, is shown;

[0042] Figure 2 Shown in Figure 1 The image shows a side view of a magnetic resonance imaging (MRI) scanner.

[0043] Figure 3 The preferred arrangement of the three magnetic field strength sensors relative to each other is shown;

[0044] Figure 4 A schematic diagram of a method according to the present invention for determining the orientation and position of a movable object relative to the B0 field magnet of a magnetic resonance tomography scanner in the XZ coordinate plane of an XYZ coordinate system with the B0 field magnet as a reference.

[0045] Figure 5 A schematic diagram showing the measurement components of a magnetic field strength sensor that are independent of its orientation;

[0046] Figure 6 A schematic diagram showing the point clouds of two magnetic field strength sensors; and

[0047] Figure 7 A schematic diagram of the point clouds from three magnetic field strength sensors is shown. Detailed Implementation

[0048] Figure 1 A top view of the system 100 according to the present invention is shown and Figure 2 A side view of a system 100 according to the invention is shown, the system being in the form of a magnetic resonance imaging (MRI) scanner 100. The MRI scanner 100 particularly includes a B0 field magnet 110 and an examination table 120.

[0049] As in Figure 1 and Figure 2 As shown, spatial encoding is based on the XYZ coordinate system of a reference B0 field magnet, the so-called DCS reference system. Here, the Z-axis 10 is defined, as commonly, as the axis of symmetry of the B0 field magnet 110, which passes through the patient channel 130 of the B0 field magnet 110 along a preferred direction of the B0 field. The Z-axis 10 is horizontally oriented in the commonly illustrated configuration of the magnetic resonance computed tomography scanner 100 and extends through the opening of the winding of the B0 field magnet 110 through the patient channel 130 of the B0 field magnet 110. The recording object is typically placed in the patient channel 130 on the examination table 120 parallel to the Z-axis 10. The X-axis 20 and Y-axis 30 form a space together with the Z-axis 10, wherein the XYZ coordinate axes are preferably orthogonal to each other and wherein the X-axis is horizontally oriented and the Y-axis is vertically oriented. The examination table 120 also includes a first magnetic field strength sensor unit 140, a second magnetic field strength sensor unit 150, a collision sensor unit 160, and an evaluation and navigation unit 170. As in Figure 3 As shown, in the illustrated embodiment, the first magnetic field strength sensor unit 140 includes two three-dimensional magnetic field strength sensors 145 and 146, and the second magnetic field strength sensor unit 150 includes a magnetic field strength sensor 147. The spacing and positioning of the magnetic field strength sensors 145, 146, and 147 relative to each other are known herein.

[0050] Figure 4 A schematic diagram of a method according to the invention for determining the orientation and position of a movable object 120 relative to the B0 field magnet 110 of a magnetic resonance tomography scanner 100 in the XZ coordinate plane of a DCS reference frame is shown.

[0051] In a first step 40, B0 reference data for the B0 field magnet 110 is provided, the B0 reference data having a characterizing magnetic field strength for multiple XYZ coordinates. In another step 41, at least three three-dimensional magnetic field strength sensors 145, 146, and 147 are provided, the magnetic field strength sensors being positioned at the object 120 in fixed relative positions. In another step 42, position data for the respective magnetic field strength sensors 145, 146, and 147 is provided by evaluating the measured value components of the respective magnetic field strength sensors 145, 146, and 147, the measured value components being independent of the corresponding orientation of the movable object 120 in the XZ coordinate plane. In another step 43, position data for the magnetic field strength sensors 145, 146, and 147 is determined based on the fixed relative positions of the magnetic field strength sensors 145, 146, and 147, and filtered position data is provided. Finally, in step 44, based on the filtered position data, the orientation value and position of the movable object 120 relative to the B0 field magnet 110 are provided.

[0052] The following describes a particularly preferred design of the method and system according to the invention. In a preferred design of the method according to the invention, the orientation value and position of the movable object 120 are used to provide control data for a navigation and motion device for the object 120 (here in the form of an autonomously moving examination bed 120).

[0053] In a preferred design, the examination bed 120 includes at least three three-dimensional magnetic field strength sensors 145, 146, and 147. Measurement data from the magnetic field strength sensors 145, 146, and 147 can be transmitted to an evaluation and navigation unit 170 and processed into control data. In the evaluation and navigation unit 170, the measurement data can be summarized, and the orientation and position of the examination bed 120 relative to the B0 field magnet 110 can be provided by applying the method according to the invention. Preferably, the X-coordinate, Z-coordinate, and angle (yaw) of the examination bed 120 are determined here at approximately 50 to 100 times per second. The evaluation and navigation unit 170 can then determine the next path point on the path for docking of the examination bed 120 at the B0 field magnet 110 and, for example, transmit corresponding control commands to servo motors for moving and steering the examination bed 120. Additionally, data from the collision unit 160 can be transmitted to the evaluation and navigation unit 170 to ensure that no object / person is in the travel path of the examination bed 120.

[0054] Preferably, the magnetic field strength sensor units 140 and 150, and thus the magnetic field strength sensors 145, 146, and 147 therein, are located in the lower region of the examination bed 120, as close to the ground as possible. The magnetic field strength sensor units 140 and 150 are preferably arranged laterally on the examination bed 120. This ensures that the B0 magnetic field measured by the magnetic field strength sensors 145, 146, and 147 is relatively small even in the immediate vicinity of the B0 field magnet 110, allowing the B0 magnetic field to be measured using cost-effective magnetic field strength sensors. Furthermore, the preferred arrangement of the magnetic field strength sensor units 140 and 150 ensures that no large metal components of the examination bed 120 are located near the magnetic field strength sensors 145, 146, and 147, and that the B0 magnetic field measured by the magnetic field strength sensors 145, 146, and 147 is not disturbed.

[0055] As described, position data for magnetic field strength sensors 145, 146, and 147 is first determined by evaluating the measured value components of the corresponding magnetic field strength sensors 145, 146, and 147, where the measured value components are independent of the corresponding orientation of the moving object in the XZ coordinate plane. The values ​​hx and hz, which are related to the orientation of magnetic field strength sensors 145, 146, and 147, are not used here. Figure 5 The corresponding measured value components are shown in the figure. The intersection of the measured value components is the position data / point cloud of magnetic field strength sensors 145, 146, and 147. In principle, the larger the point cloud, the farther the magnetic field strength sensors 145, 146, and 147 are from the B0 field magnet 110. The closer the magnetic field strength sensors 145, 146, and 147 are to the B0 field magnet 110, the smaller the point cloud becomes. The point cloud is decomposed into two or even four parts due to the rotational symmetry of the B0 field around the Z-coordinate axis.

[0056] In another step, the point clouds 200 and 210 of two of the magnetic field strength sensors 145, 146, and 147 are combined with each other. For example, in Figure 6 The diagram illustrates how point pairs are identified / filtered out, where the spacing d corresponds to the actual spacing between the two observed magnetic field strength sensors 145, 146, and 147. Corresponding point pairs are determined for two different combinations of magnetic field strength sensors 145, 146, and 147. It is important to note that point pairs are preferably identified that correspond to known spacing within a predetermined tolerance. For example, point pairs with tolerances of + / -3%, + / -2%, or + / -1% can be formed from the corresponding values ​​of the measured components. Alternatively, other tolerance limits / ranges can be considered.

[0057] In another step, the point pairs determined above for the two magnetic field strength sensors 145, 146, and 147 are filtered in terms of their orientation. Since the magnetic field strength sensors 145, 146, and 147 are fixedly mounted on the inspection bed 120, all magnetic field strength sensors 145, 146, and 147 have the same orientation, i.e., the same yaw angle. The orientation, expressed in yaw angle form, can be calculated for each determined point pair. This can be done, for example, by means of the atan2 function, where α = atan2(hx, hz). Therefore, point pairs are determined / filtered from the two point pairs for the two magnetic field strength sensors 145, 146, and 147 determined above, in which the magnetic field strength sensors 145, 146, and 147 have the same orientation. It is also preferable to determine point pairs with the same orientation within a preset tolerance. For example, point pairs with the same orientation within tolerances of + / -3%, + / -2%, or + / -1% can be filtered. Alternatively, other tolerance limits / ranges may be considered here.

[0058] In another step, the identified point pairs of magnetic field strength sensors 145, 146, and 147 with the same orientation are filtered again by determining the following point pairs of magnetic field strength sensors 145, 146, and 147, which in combination correspond to the actual geometry of at least three magnetic field strength sensors 145, 146, and 147. Figure 7 The diagram illustrates two solutions for these point pair combinations, which depict the actual geometry of at least three magnetic field strength sensors 145, 146, and 147. Therefore, in a preferred embodiment, the following point pairs of magnetic field strength sensors 145, 146, and 147 are determined, corresponding to... Figure 3 The diagram shows the triangular arrangement of the three magnetic field strength sensors 145, 146, and 147. It is also preferable to pre-set corresponding tolerances. For example, combinations can be filtered to correspond to the actual geometry of at least three magnetic field strength sensors 145, 146, and 147 with tolerances of + / -3%, + / -2%, or + / -1%. Alternatively, other tolerance limits / ranges can be considered.

[0059] The remaining point pairs of magnetic field strength sensors 145, 146, and 147 are used to determine the positions of magnetic field strength sensors 145, 146, and 147. These positions are then used to determine the X-coordinate, Z-coordinate, and angle values ​​of the examination bed 120, respectively. The corresponding intermediate values ​​of the thus determined X-coordinate, Z-coordinate, and angle values ​​can ultimately be used to provide control data for the navigation and motion mechanisms of the examination bed 120, so that the examination bed 120 moves towards a target position relative to the B0 field magnet 110. Preferably, the control data is provided periodically, wherein at least one motion trajectory of the examination bed 120 and / or at least one direction vector and / or velocity vector of the examination bed 120 are preferably also considered when providing the periodic control data. For example, the position and orientation of the examination bed 120 with respect to the B0 field magnet 110 can be determined at a rate of 50 to 100 times per second, and provided, for example, to a navigation controller, so that automatic navigation and movement of the examination bed 120 can be performed, especially until the examination bed 120 docks at the B0 field magnet 110.

[0060] Preferably, the position of the examination bed 120 is given by a 2D vector having X and Z coordinates in the DCS reference frame. The orientation of the examination bed is preferably given as an angle (yaw) between the Z-axis of the B0 field magnet 110 and the longitudinal direction of the examination bed 120 in a horizontal plane. Therefore, the navigation and motion device preferably transmits the X, Z coordinates, and angle (yaw) of the examination bed 120 at approximately 50 to 100 times per second, thereby enabling the examination bed 120 to reliably move within the B0 magnetic field.

[0061] Therefore, by means of the method or system according to the invention, the examination bed 120 can be automatically and smoothly aligned with the B0 field magnet 110, which significantly improves patient comfort. Automatic alignment can also be performed relatively quickly, especially compared to manual movement of the examination bed 120 by an operator. The method or system according to the invention can also be automatically used in other applications where the position and orientation of the object relative to the B0 field magnet need to be provided reliably, accurately, and quickly.

[0062] This invention is not limited to the foregoing embodiments, as long as they fall within the subject matter of the embodiments of this invention. In particular, this invention is not limited to the application of the three magnetic field strength sensors 145, 146, and 147. Using additional magnetic field strength sensors can provide advantageous redundancy, higher accuracy and reliability, and immunity to measurement noise. Preferably, each magnetic field strength sensor unit comprises up to 12 magnetic field strength sensors, so that a total of 36 magnetic field strength sensors can be used when using three magnetic field strength sensor units.

[0063] It should be further noted that the terms "comprising" and "having" do not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude multiple. It should also be noted that the features or steps described with reference to the embodiments above can also be used in combination with other features.

[0064] Furthermore, it should be noted that regardless of the grammatical gender of a particular term, people with either male or female gender identity are included.

Claims

1. A method for determining the orientation and position of a movable object (120) relative to a B0 field magnet (110) of a magnetic resonance computed tomography scanner (100) in the XZ coordinate plane of an XYZ coordinate system with the B0 field magnet (110) as a reference, wherein the method comprises at least the following steps: Provide (40) B0 reference data for the B0 field magnet (110), the B0 reference data having a characterizing magnetic field strength for multiple XYZ coordinates; Provide (41) at least three three-dimensional magnetic field strength sensors (145, 146, 147), said magnetic field strength sensors (145, 146, 147) being disposed at the object (120) in a fixed relative position; Position data for the respective magnetic field strength sensors (145, 146, 147) is determined by evaluating the measured value components of the respective magnetic field strength sensors (145, 146, 147), wherein the measured value components are independent of the corresponding orientation of the movable object (120) in the XZ coordinate plane. Based on the fixed relative positions of the magnetic field strength sensors (145, 146, 147), the determined position data of the magnetic field strength sensors (145, 146, 147) are filtered (43), and the filtered position data is provided. Based on the filtered position data, (44) the orientation value and position of the movable object (120) relative to the B0 field magnet (110) are provided.

2. The method according to claim 1, wherein at least three of the magnetic field strength sensors (145, 146, 147) are arranged in the XZ coordinate plane, thereby having the same Y coordinate.

3. The method according to claim 1 or claim 2, wherein in an XYZ coordinate system based on the movable object (120), at least two of the at least three magnetic field strength sensors (145, 146, 147) have the same Z coordinate and at least two of the three magnetic field strength sensors (145, 146, 147) have the same X coordinate.

4. The method according to any one of the preceding claims, wherein the measurement components independent of the orientation of the movable object (120) include: The magnitude (abs(h)) of the B0 field vector, the Y field intensity component (hy), the Y field intensity component normalized to the magnitude of the B0 field vector (hy / abs(h)) and / or the magnitude (abs(hx, hz)) of the vector in the XZ coordinate plane.

5. The method according to any one of the preceding claims, wherein the location data is provided as point data / point cloud.

6. The method according to any one of the preceding claims, wherein the filtering step comprises: Point pairs are determined from the position data determined by two magnetic field strength sensors (145, 146, 147), wherein the spacing (d) in the point pairs corresponds to the fixed relative positions of the two magnetic field strength sensors (145, 146, 147) at the object (120); Determine the orientation angles of the points used to determine the point pairs and determine the following point pairs in which the orientation angles of the points used in the point pairs are the same; A point pair combination is determined, wherein the spacing and orientation of the point pair combination correspond to the fixed relative positions of at least three of the magnetic field strength sensors (145, 146, 147).

7. The method according to any one of the preceding claims, wherein the movable object (120) is an examination bed (120), and wherein the magnetic field strength sensors (145, 146, 147) are disposed in the lower region of the lateral corner region of the examination bed (120).

8. The method according to any one of the preceding claims further comprises: Based on the orientation value and position provided by the movable object (120), control data is provided to the navigation and motion device (170), which is configured to move the movable object (120) toward a target position relative to the B0 field magnet (110).

9. The method according to any one of the preceding claims, wherein the control data is provided periodically and at least one motion trajectory of the movable object (120) and / or at least one direction vector and / or velocity vector of the movable object (120) are also considered when providing the periodic control data.

10. The method according to claim 8 or claim 9, further comprising: At least one collision sensor (160) is provided, said collision sensor (160) being disposed and positioned at said object (120) to detect the area around said object (120) and determine whether the object is in a planned motion path, wherein preferably at least three collision sensors (160) are disposed at said object (120), and wherein said collision sensors (160) preferably detect an area having an angle of at least 90°, preferably at least 180° and particularly preferably at least 270°.

11. The method according to any one of the preceding claims, wherein the B0 field magnet (110) surrounds the patient channel (130) of the magnetic resonance tomography scanner (100), wherein the Z coordinate axis (10) is defined by an axis of symmetry of the B0 field magnet (110) along a preferred direction of the B0 field, wherein the coordinate axes are preferably orthogonal to each other and the X coordinate axis (20) is preferably horizontally oriented and the Y coordinate axis (30) is preferably vertically oriented.

12. The method according to any one of the preceding claims, wherein the magnetic field strength sensor (145, 146, 147) is configured to detect the field strength of three components (B0.x-, B0.y-, B0.z) in three directions of the formation space of the B0 field.

13. A system for determining the orientation and position of a movable object (120) relative to a B0 field magnet (110) of a magnetic resonance computed tomography scanner (100) in the XZ coordinate plane of an XYZ coordinate system referenced to said B0 field magnet (110), wherein the system comprises: The first interface is set up to receive B0 reference data of the B0 field magnet (110), the B0 reference data having a characterizing magnetic field strength for multiple XYZ coordinates; The second interface is set up to receive measurements from at least three magnetic field strength sensors (145, 146, 147); A computing unit, which is connected to the interface and configured to implement the method according to any one of claims 1 to 12.

14. The use of a movable object (120) having at least three three-dimensional magnetic field strength sensors (145, 146, 147) in the method according to any one of claims 1 to 12, wherein the movable object (120) is preferably an examination bed (120).

15. A computer program element having instructions which, when implemented on a data processing device in a data processing environment, establish steps for implementing the method according to any one of claims 1 to 12 in a system according to claim 13.

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