EDDY CURRENT BRAKE FOR PATIENT TABLE OF MRI

Abstract

The present invention relates to a patient support. In order to improve safety for MRI scanning protocols, a patient support is provided for an MRI scanner. The patient support comprises a braking device for deaccelerating the patient support when being transferred relative to the MRI scanner. The braking device comprises at least one non-magnetic electrically conductive element. The at least one non-magnetic electrically conductive element is configured to adjust one or more eddy currents induced in response to motion in a magnetic field of the MRI scanner to provide a counter force against an attractive force between the patient support and the MRI scanner, thereby creating an adjustable braking effect.

Claims

1. A patient support for a magnetic resonance imaging (MRI) scanner, the patient support comprising: a braking device for deaccelerating the patient support when being transferred relative to the MRI scanner; wherein the braking device comprises at least one non-magnetic electrically conductive element; and wherein the at least one non-magnetic electrically conductive element is configured to adjust one or more eddy currents induced in response to motion in a magnetic field of the MRI scanner to provide an adjustable counter force against an attractive force between the patient support and the MRI scanner, thereby creating an adjustable braking effect.

2. The patient support according to claim 1, wherein the braking device comprises a plurality of non-magnetic electrically conductive elements; and wherein the plurality of non-magnetic electrically conductive elements is configured and arranged to adjust the induced eddy currents in response to the magnetic field such that the counter force is adjustable against the attractive force during a transfer of the patient support relative to the MRI scanner.

3. The patient support according to claim 1, wherein the at least one non-magnetic electrically conductive element comprises a closed loop of conductive wire.

4. The patient support according to claim 3, wherein at least one of the closed loops of conductive wire is provided with a switch configured for switching the eddy currents on and off; wherein the switch comprises at least one of the following: a software controlled switch; and a user controlled switch.

5. The patient support according to claim 3, wherein at least one of the closed loops of conductive wire is configured to have low loop impedance in a passive state such that in an event of power outage the braking effect is present.

6. The patient support according to claim 1, wherein the at least one non-magnetic electrically conductive element comprises a non-magnetic metal block.

7. The patient support according to claim 5, wherein each non-magnetic metal block has a cross sectional area perpendicular to a primary magnetic field direction of the magnetic field; wherein the non-magnetic metal blocks are provided with: an element joining device configured for moving the non-magnetic metal blocks from electrically isolated positions to electrically contacting positions to increase the cross sectional area perpendicular to the primary magnetic field direction during a transfer of the patent support towards the magnetic field of the MRI scanner, thereby increasing the braking effect; and/or an element separating device configured for moving the non-magnetic metal blocks from electrically contacting positions to electrically isolated positions to decrease the cross sectional area perpendicular to the primary magnetic field direction during a transfer of the patient support away from the magnetic field of the MRI scanner, thereby decreasing the braking effect.

8. The patient support according to claim 7, wherein the element joining device comprises: a plurality of magnetic components, each arranged on a respective non-magnetic metal block; wherein each magnetic component has a dimension that is large enough to cause the attached non-magnetic metal block to move; and/or a guiding mechanism along the length of the patient support; wherein the guiding mechanism comprises a plurality of stoppers along the guiding mechanism for keeping the non-magnetic metal blocks in electrically isolated positions; and wherein the plurality of stoppers is configured to allow the non-magnetic metal blocks to move from electrically isolated positions to electrically contacting positions under the guidance of the guiding mechanism if the attractive force exceeds a certain measure; and wherein the element joining device the element separating device comprises at least one actuator.

9. The patient support according to claim 2, wherein at least one of the non-magnetic electrically conductive elements comprises a braking force controller for modulating the counter force in response to a control signal, thereby assisting with the braking effect and/or an alignment of the patient support with respect to a bore of the MRI scanner.

10. The patient support according to claim 9, wherein the braking force controller is configured to control the eddy currents independently at least on two parts of the patient support, thereby modulating the counter forces at least on the two parts of the patient support independently for steering the patient support.

11. The patient support according to claim 9, wherein the control signal is at least one of the following: a user input control signal; and a generated control signal based on a position and/or an orientation of the patient support detected by a position and orientation tracking device.

12. The patient support according to claim 2, wherein the number of non-magnetic electrically conductive elements per unit length increases along a length of the patient support.

13. The patient support according to claim 2, wherein the plurality of non-magnetic electrically conductive elements is arranged in predefined positions such that the combination of the predefined positions of the non-magnetic electrically conductive elements as a brake and the magnetic field of the MRI scanner allows the guidance of the patient support to a predefined position with respect to the MRI scanner.

14. The patient support according to claim 2, wherein the braking device comprises an orientation guiding mechanism; wherein each non-magnetic electrically conductive element has a maximal cross sectional area, wherein the orientation guiding mechanism is configured to rotate the orientation of each non-magnetic electrically conductive element into one of the following positions: the maximal cross sectional area of each non-magnetic electrically conductive element is perpendicular to a supporting plane of the patient support if the MRI scanner is a closed MRI scanner; or the maximal cross sectional area of each non-magnetic electrically conductive element is in or parallel to the supporting plane of the patient support if the MRI scanner is an open MRI scanner.

15. A magnetic resonance imaging (MRI) system, comprising: a patient support according to claim 1; and an MRI scanner; wherein the patient support is configured to provide a support for a patient and to facilitate a transfer of the patient in and out of the MRI scanner; and wherein the MRI scanner is configured to generate medical imaging data of the patient.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Exemplary embodiments of the invention will be described in the following with reference to the following drawings:

[0073] FIG. 1 shows a schematic diagram of a patient support according to an embodiment of the invention.

[0074] FIG. 2 shows a schematic diagram of a patient support according to a further embodiment of the invention.

[0075] FIG. 3A to 3C show a schematic diagram of non-magnetic electrically conductive elements according to a further embodiment of the invention.

[0076] FIGS. 4A and 4B show a schematic diagram of an element joining device and an element separating device according to an embodiment of the invention.

[0077] FIGS. 5A and 5B show a schematic diagram of the element joining device according to a further embodiment of the invention.

[0078] FIG. 6 shows a schematic diagram of a patient support according to a further embodiment of the invention.

[0079] FIGS. 7A and 7B show a schematic diagram of a patient support according to a further embodiment of the invention in different perspectives.

[0080] FIGS. 8A and 8B show a schematic diagram of a patient support according to a further embodiment of the invention in different perspectives.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0081] FIG. 1 shows a patient support 10 for an MRI scanner according to an embodiment of the invention. The patient support 10 comprises a braking device 12 for deaccelerating the patient support when being transferred relative to the MRI scanner 50 (shown in FIGS. 7A and 7B). The braking device 12 comprises at least one non-magnetic electrically conductive element 14 (shown in FIGS. 2 to 8). The at least one non-magnetic electrically conductive element 14 is configured to adjust one or more eddy currents induced in response to motion in a magnetic field of the MRI scanner 50 to provide an adjustable counter force against an attractive force between the patient support 10 and the MRI scanner 50, thereby creating an adjustable braking effect. A patient support 10 may be e.g. a bed, a transport unit, a scan table. The patient support 10 has a supporting plane 20 on which a patient can lie. The at least one non-magnetic electrically conductive element 14 may be built into or attached to the patient support 10.

[0082] In this way, the braking forces are induced by interaction with an external magnetic field and one or more non-magnetic electrically conductive elements built into or attached to the patient support. Thus, the patient support may be deaccelerated automatically when moving in/towards an external magnetic field, i.e. the field of an MRI scanner 50. This may advantageously provide a safety feature for regular MRI scanning protocols.

[0083] In one embodiment, the braking device 12 comprises a plurality of non-magnetic electrically conductive elements 14. The plurality of non-magnetic electrically conductive elements 14 is configured and arranged to adjust the induced eddy currents in response to the magnetic field such that the counter force is adjustable against the attractive force during a transfer of the patient support 10 relative to the MRI scanner 50. Examples of the arrangements and configurations are described in FIGS. 2 to 8.

[0084] FIG. 2 shows a schematic diagram of a patient support 10 according to a further embodiment of the invention. In FIG. 2, the at least one non-magnetic electrically conductive elements 14 comprises a closed loops of conductive wire 16, which may comprise Aluminum or Copper. The closed loops of conductive wire 16 may be arranged in the patient support 10 such that their effective loop cross-sections are perpendicular to a primary magnetic field direction 18, i.e. BO-field direction, to maximize the braking force. The plurality of non-magnetic electrically conductive elements 14 may also be arranged to encompass the complete cross-section of the patient support 10 to maximize the braking effect.

[0085] It is noted that the arrangement of the closed loops of conductive wires 16 in FIG. 2 is effective for the bore of a conventional closed MRI scanner 50 as here the primary magnetic field direction 18 is along a length axis of the scanner 60 (shown in FIG. 7B), i.e. in or parallel to the supporting plane 20 of the patient support 10.

[0086] In case of an open MRI scanner 50 (not shown), the closed loops of conductive wire 16 may have an effective loop cross-section parallel to the supporting plane 20 of the patient support 10, since the primary magnetic field direction of an open MRI scanner is perpendicular to the supporting plane 20 of the patient support 10.

[0087] In one embodiment, at least one of the closed loops of conductive wire 16 is provided with at least one switch 22 configured for switching the eddy currents on and off. The switch 22 comprises at least one of the following: a software controlled switch, and a user controlled switch. For example, a user may control the user controlled switch directly, for example, via a device wired to the patient support. In a further example, a user may control the user controlled switch indirectly via a software, such as wireless remote control, apps, etc. With the switch, the braking force can be switched off completely, e.g. when the patient support moves out of the bore of the MRI scanner.

[0088] In one embodiment, at least one of the non-magnetic electrically conductive elements comprises a braking force controller 24 for modulating the counter force to assist with the braking effect and/or alignment of the patient support with respect to a bore of the MRI scanner in response to a control signal.

[0089] For example, as shown in FIG. 2, the braking force controller 24 for the closed loops of conductive wire is a feedback controller. The feedback controller may use the input from a position or acceleration sensor to automatically adjust impedances. The feedback controller may comprise one or more software-controlled resistors configured to adjust eddy currents in response to a control signal. The software-controlled resistor may have a short response time and thus may be adapted in milliseconds. The software-controlled resistors may be used to continuously modulate the braking force.

[0090] For example (not shown), the braking force controller 24 comprises one or more actuators configured for joining/disjoining two or more non-magnetic metal blocks to modulate the counter force in response to the control signal.

[0091] In one embodiment, the braking force controller 24 is configured to control the eddy currents independently at least on two parts of the patient support, thereby modulating the counter forces at least on the two parts of the patient support independently for steering the patient support.

[0092] For example, as shown in FIG. 2, the braking force controller in form of a feedback controller may be configured to control the closed loops of conductive wire independently at least on two parts (e.g. left and right sides, four corners, etc.) of the patient support, thereby modulating the counter forces at least on the two parts of the patient support independently for steering the patient support.

[0093] For example, the braking force controller in form of an actuator may be configured to join/disjoin non-magnetic metal blocks independently at least on two parts (e.g. left and right sides, four corners, etc.) of the patient support.

[0094] In one embodiment, the control signal is at least one of the following: a user input control signal, and a generated control signal based on a position and/or an orientation of the patient support detected by a position and orientation tracking device.

[0095] A user may input the control signal directly via a device wired to the patient support (e.g. a button, a touch screen, etc.), or indirectly via a network (e.g. software, apps, etc.).

[0096] The position and orientation tracking device may be a camera system or an accelerometer or other localization device for detecting the position and/or the orientation of the patient support. A control signal is then generated based on the detected position and/or orientation of the patient support, which then controls the eddy current braking system in order to automatically assist with proper braking or even alignment of the bed with respect to the bore.

[0097] In one embodiment, the feedback controller 24 is configured to control the closed loops of conductive wire 16 independently at least on two parts of the patient support 10, thereby modulating the counter forces at least on the two parts of the patient support 10 independently for steering the patient support 10. For example, as shown in FIG. 2, the feedback controller 24 is configured to control the closed loops of conductive wire 16 independently at least on the left and right sides of the patient support 10, thereby modulating the counter forces at least on the left and right sides of the patient support 10 independently for steering the patient support 10. The feedback controller 24 may be configured to control the closed loops of conductive wire 16 independently on more parts of the patient support. In an example, the feedback controller 24 is configured to control the closed loops of conductive wire 16 independently on four corners of the patient support.

[0098] This may advantageously enable assisting with the alignment of the patient support with respect to the bore of the MRI scanner.

[0099] In one embodiment, at least one of the closed loops of conductive wire 16 is configured to have low loop impedance in a passive state such that in an event of power outage the braking effect is present.

[0100] FIG. 3A to 3C show a schematic diagram of non-magnetic electrically conductive elements 14 according to a further embodiment of the invention. In FIG. 3A to 3C, the at least one non-magnetic electrically conductive elements 14 comprises a non-magnetic metal block 26, which may be made of Aluminium or Copper.

[0101] The non-magnetic metal blocks 26 may have various designs:

[0102] In FIG. 3A, the non-magnetic metal blocks 26 are in form of a set of non-magnetic metal blocks without any interruption of the area of the conducting material.

[0103] In FIG. 3B, the non-magnetic metal block 26 are in form of a comb and a rectangular block.

[0104] In FIG. 3C, the non-magnetic metal block 26 are in form of two interdigitated combs.

[0105] In one embodiment, each non-magnetic metal block 26 has a cross sectional area perpendicular to a primary magnetic field direction 18, i.e. BO-field direction, of the magnetic field. The non-magnetic metal blocks 26 are provided with an element joining device 28 configured for moving the non-magnetic metal blocks 26 from electrically isolated positions to electrically contacting positions to increase the cross sectional area perpendicular to the primary magnetic field direction 18 during a transfer of the patent support towards the magnetic field of the MRI scanner 50, thereby increasing the braking effect. Alternatively or additionally, the non-magnetic metal blocks are provided with an element separating device 30 configured for moving the non-magnetic metal blocks from electrically contacting positions to electrically isolated positions to decrease the cross sectional area perpendicular to the primary magnetic field direction 18 during a transfer of the patient support away from the magnetic field of the MRI scanner 50, thereby decreasing the braking effect.

[0106] In FIG. 3A, for example, in the situation that only a regular braking is required, the non-magnetic metal blocks 26 are kept separate in electrically isolated positions. In a situation where a higher braking is required, for example if the velocity or acceleration of the patient support exceeds a certain value, the non-magnetic metal blocks 26 are joined together such that the eddy currents can circulate over a larger area and the braking force increases. The more non-magnetic metal blocks 26 are joined, the higher the braking force.

[0107] A similar situation can be realized with a non-magnetic metal block comprising slots, such as the non-magnetic metal blocks in FIGS. 3B and 3C. In this case, the braking force is dynamically increased by selectively closing one or more of the slots. The more slots that are closed, the higher the braking force.

[0108] It is also noted that the increased/decreased cross sectional area should be perpendicular to the primary magnetic field in order to effectively increase/decrease the braking force. Examples of the element joining device 28 and the element separating device 30 are describe in FIGS. 4 and 5.

[0109] FIGS. 4A and 4B show a schematic diagram of the element joining device 28 and the element separating device 30 according to an embodiment of the invention.

[0110] In FIG. 4A, the element joining device 28 comprises a plurality of magnetic components 32, each arranged on a respective non-magnetic metal block 26. Each magnetic component 32 has a dimension that is large enough to cause the attached non-magnetic metal block to move. The magnetic component 32 may have a dimension that is small enough not to cause the patient support 10 to move.

[0111] When the magnetic component 32 senses the magnetic force 34, as shown in FIG. 4B, it moves the non-magnetic metal block 26 in a direction to join a second (stationary) non-magnetic metal block. The joined non-magnetic metal blocks will produce a higher braking force, thereby retarding the motion of the entire patient support 10.

[0112] Optionally, a rail 36 may be provided to limit the degrees of freedoms of motion, which allows the non-magnetic metal blocks 26 to come closer together as they approach the MRI scanner 50 and experience the differing magnetic force as the gradients change.

[0113] With the magnetic components, as the magnetic force increases, the force on the patient support from the magnetic components also increases, thus resulting in an increasing braking force.

[0114] Optionally, the element separating device 30 is provided, which may comprise at least one actuator. The actuator can separate any joined non-magnetic metal blocks in order to minimize the force required to transfer the patient from the MRI scanner 50.

[0115] FIGS. 5A and 5B show a schematic diagram of the element joining device 28 according to a further embodiment of the invention. As an alternative concept, the element joining device 28 comprises a guiding mechanism 38 along the length of the patient support 10. The guiding mechanism 38 comprises a plurality of stoppers 40 along the guiding mechanism for keeping the non-magnetic metal blocks 26 in electrically isolated positions. The plurality of stoppers 40 is configured to allow the non-magnetic metal blocks 26 to move from electrically isolated positions to electrically contacting positions under the guidance of the guiding mechanism 38 if the attractive force exceeds a certain measure. For example, as shown in FIGS. 5A and 5B, the guiding mechanism 38 is provided as rails.

[0116] As shown in FIG. 5A, the separated non-magnetic metal blocks 26 can be installed on the guiding mechanism 38 and kept in place by stoppers 40. If the patient support 10 is moved too fast towards the MRI scanner 50 in a direction 42, the induced magnetic forces 44 in the first non-magnetic metal block 26 can be strong enough to overcome the force of the stopper 40 and join with the second non-magnetic metal block 26 to form a larger block 46. If the induced magnetic forces 44 in this joined non-magnetic metal block 46 exceed the force of the second stopper 40, the non-magnetic metal block can join with the third block and so on.

[0117] The guiding mechanism 38 and the stoppers 40 may thus be used as a safety feature during manual operation, i.e. when the patient support is moved by an operator of the MRI scanner 50. Especially when moving heavy patients, it can be challenging for the operator to stop the patient support before the MRI scanner 50 so that a patient support often collides with the MRI scanner 50 itself or the patient table of the MRI scanner 50.

[0118] FIG. 6 shows a schematic diagram of a patient support 10 according to a further embodiment of the invention. The number of non-magnetic electrically conductive elements 14 per unit length increases along a length of the patient support 10. The non-magnetic electrically conductive elements 14 may be closed loops of conductive wire, non-magnetic metal blocks or a mixed of both. In this way, the braking force increases as the patient support enters the bore of the MRI scanner 50 in the direction 42, thereby countering against the increased attractive force.

[0119] FIGS. 7A and 7B show a schematic diagram of a patient support 10 according to a further embodiment of the invention in different perspectives. The plurality of non-magnetic electrically conductive elements 14 (e.g. closed loops of conductive wire and/or non-magnetic metal blocks) is arranged in predefined positions 48 such that the combination of the predefined positions 48 of the non-magnetic electrically conductive elements 14 as a brake and the magnetic field of the MRI scanner 50 allows the guidance of the patient support 10 to a predefined position with respect to the MRI scanner 50. For example, as shown in FIGS. 7A and 7B, the non-magnetic electrically conductive elements are arranged in predefined positions 48, e.g. on four corners of the patient support 10.

[0120] In case of a non-symmetrical movement direction 52 towards the center position of the MRI scanner 50, as shown in FIG. 7B, an unsymmetrical force due to the symmetrically mounted non-magnetic electrically conductive elements 14 appears. The force would bring the patient support 10 back into a symmetrical direct movement direction 54 to the center scanner position in case the patient support 10 is moved with a regular speed.

[0121] This may advantageously allow for a very simple guiding functionality that can bring the patient support into a well predefined position e.g. to dock in an autonomous way to the scanner table and link to the patient transfer system from patient support to scanner table. Additionally, the exact geometry and combination of the non-magnetic electrically conductive elements allow for defined trajectories and in combination with the aforementioned examples to combine and separate non-magnetic electrically conductive elements, a programmable movement direction can be realized without any external guiding structure.

[0122] FIGS. 8A and 8B show a schematic diagram of a patient support 10 according to a further embodiment of the invention in different perspectives. The braking device 12 comprises an orientation guiding mechanism 56. Each non-magnetic electrically conductive element has a maximal cross sectional area 62. The orientation guiding mechanism 56 is configured to rotate the orientation of each non-magnetic electrically conductive element into one of the following positions: the maximal cross sectional area 62 of each non-magnetic electrically conductive element is perpendicular to a supporting plane 20 of the patient support if the MRI scanner is a closed MRI scanner, or the maximal cross sectional area 62 of each non-magnetic electrically conductive element is in or parallel to the supporting plane of the patient support if the MRI scanner is an open MRI scanner. The non-magnetic electrically conductive elements may be closed loops of conductive wire and/or non-magnetic metal blocks. In an example, as shown in FIG. 8, the orientation guiding mechanism is provided as rails, which direct the non-magnetic electrically conductive elements out of the plane of the patient support.

[0123] It is noted that the arrangement of non-magnetic electrically conductive element in the examples in FIGS. 4 to 6 are effective for an open MRI scanner as the primary magnetic field direction is perpendicular to the supporting plane of the patient support.

[0124] To function effective in a closed MRI scanner, it is required to realize a large cross section perpendicular to the supporting plane 20 of the patient support (i.e. length axis of the scanner 60). This can be realized by using the orientation guiding mechanism 56 (e.g. rails) to rotate the orientation of the non-magnetic electrically conductive elements in the embodiments in FIGS. 4 to 6 by 90 degrees such they lie perpendicular to the length axis of the scanner 60. Furthermore, the non-magnetic electrically conductive elements 14 are combined in a defined direction 58 such that their cross sectional area in the plane perpendicular to the length axis of the scanner 60 increases, as shown in FIG. 8B.

[0125] According to an embodiment of the invention, as shown in FIGS. 7A and 7B, an MRI system 100 is provided. The MRI system 100 comprises the patient support 10 according to any one of the embodiments described above and the MRI scanner 50. The patient support 10 is configured to provide a support for a patient and to facilitate a transfer of the patient in and out of the MRI scanner 50. The MRI scanner is configured to generate medical imaging data of the patient.

[0126] In some implementations, the MRI system may be an autonomous MRI system with the patient support and an autonomous MRI scanner. The patient support may further comprise a motor configured to drive the patient support to transfer the patient in and out of the MRI scanner and to position the patient support at a desired location for medical imaging. The autonomous MRI scanner may be configured to have an MRI scan of the patient when the patient support is positioned at the desired location.

[0127] A method may be provided for collision protection between a patient support and an MRI scanner. The method may comprise the following steps: i) providing a braking device to the patient support for deaccelerating the patient support when being transferred relative to the MRI scanner, wherein the braking device comprises at least one non-magnetic electrically conductive element; and ii) inducing one or more eddy currents in response to a magnetic field of the MRI scanner to provide a counter force against an attractive force between the patient support and the MRI scanner, thereby creating a braking effect.

[0128] It has to be noted that embodiments of the invention are described with reference to different subject matters. In particular, some embodiments are described with reference to method type claims whereas other embodiments are described with reference to the device type claims. However, a person skilled in the art will gather from the above and the following description that, unless otherwise notified, in addition to any combination of features belonging to one type of subject matter also any combination between features relating to different subject matters is considered to be disclosed with this application. However, all features can be combined providing synergetic effects that are more than the simple summation of the features.

[0129] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing a claimed invention, from a study of the drawings, the disclosure, and the dependent claims.

[0130] In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. A single processor or other unit may fulfil the functions of several items re-cited in the claims. The mere fact that certain measures are re-cited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.