Shimming method of polymorphic magnetic resonance imaging system

Abstract

The present application discloses an MRI system and a shimming method for an MRI system, the MRI system comprising: an MRI device defining a magnet scanning cavity and adapted to generate a main magnetic field passing through the magnet scanning cavity; an operating table; a displacement mechanism adapted to displace one of the MRI apparatus and the surgical table; a tracing device adapted to control the displacement mechanism to cause the one of the MRI apparatus and the operating table to be displaced between the first region and the second region in a preset path; at least one first shim sheet disposed at a preset position of the MRI apparatus to correct a first non-uniformity of the main magnetic field detected in a state where the MRI apparatus is located in the first region and the operating table is located in the second region; and at least one second shim sheet disposed at a preset position of the operating table to correct a second non-uniformity of the main magnetic field detected in a state in which the operating table is engaged with the MRI apparatus, where the at least one second shim sheet is different in size from the at least one first shim sheet.

Description

Technical Field

[0001] The present application relates to the technical field of magnetic resonance imaging (MRI), and more specifically, to an MRI system and a shimming method for the MRI system. Background Art

[0002] MRI technology plays an important role in medical diagnosis. MRI technology is generally implemented by an MRI device, which defines a magnet scanning cavity and is suitable for generating a main magnetic field passing through the magnet scanning cavity so as to align the magnetic nuclear spins of at least a portion of the patient located in the magnet scanning cavity. The main magnetic field strength is relatively high, and it is expected that the distribution of the main magnetic field within a certain volume range of the magnet scanning cavity has a uniformity that meets the requirements, that is, the number of magnetic flux lines passing through any unit area within the certain volume range is consistent. During the MRI process, if the main magnetic field is not uniform, it may cause the image generated for at least a portion of the patient to be blurred or artifacts to appear.

[0003] Due to the limitations of MRI equipment design and manufacturing process and the influence of the surrounding environment, the main magnetic field generated by the MRI equipment initially in an environment is basically unable to achieve the uniformity that meets the requirements. In order to improve the uniformity of the main magnetic field, the MRI equipment in this environment can be subjected to a shimming operation. Generally speaking, shimming operations include active shimming and passive shimming. Active shimming is also called active shimming, which refers to the change of the local magnetic field around it by appropriately adjusting the current intensity of each coil in the shimming coil array installed in the MRI equipment. Passive shimming is also called passive shimming, which refers to adding a special shimming sheet to the MRI equipment to deform / distort the main magnetic field. The shimming sheet can be a thin plate made of silicon steel or other soft magnetic materials, and the shape can be rectangular or other geometric shapes. The accurate addition of shimming sheets involves multiple field raising and lowering processes of the MRI equipment, which is time-consuming and labor-intensive. This is also one of the reasons why the MRI equipment is fixed and does not change the environment as much as possible after completing the shimming operation in an environment.

[0004] It can be seen that when the same MRI device needs to be used in different environments, even if the MRI device has completed the initial shimming operation in one environment, it is still necessary to perform subsequent shimming operations on the MRI device again in another environment. Therefore, how to conveniently and quickly perform subsequent shimming operations in another environment and ensure the relative independence of the results of the initial and subsequent shimming operations performed by the same MRI device in different environments has become a challenge. Summary of the invention

[0005] An object of the present application is to provide an MRI system and a shimming method for the MRI system, which can perform initial and subsequent shimming operations on the same MRI device in different environments / states in an improved manner and ensure the relative independence of the results of the initial and subsequent shimming operations.

[0006] According to one aspect of the present application, an MRI system is provided, comprising: an MRI device, which defines a magnet scanning cavity and is suitable for generating a main magnetic field passing through the magnet scanning cavity; an operating table, which is suitable for engaging with the MRI device so that at least a portion of a patient located on the operating table enters the magnet scanning cavity; a shifting mechanism, which is suitable for making one of the MRI device and the operating table shiftable; a tracking device, which is suitable for controlling the shifting mechanism to cause one of the MRI device and the operating table to shift between a first area and a second area along a preset path; at least one first shim, which is arranged at a preset position of the MRI device to correct a first inhomogeneity of the main magnetic field generated by the MRI device, which is detected when the MRI device is located in the first area and the operating table is located in the second area; and at least one second shim, which is arranged at a preset position of the operating table, which is detected when the operating table is engaged with the MRI device, which is detected when the operating table is engaged with the MRI device, wherein the at least one second shim is different in size from the at least one first shim.

[0007] Optionally, the first area is included in a diagnostic room with radio frequency shielding, the second area is included in an operating room with radio frequency shielding, and the shifting mechanism is installed to the MRI device, whereby the MRI device is suitable for shifting from a first position in the first area to a second position in the second area with the aid of a tracking device to engage with an operating table located in the second area; or the first area is included in a diagnostic room with radio frequency shielding, the second area is included in an operating room without radio frequency shielding, and the shifting mechanism is installed to the operating table, whereby the operating table is suitable for shifting from the second position in the second area toward the first position in the first area with the aid of a tracking device to engage with the MRI device located in the first area.

[0008] Optionally, the at least one second shim comprises a plurality of second shims, and the plurality of second shims are different in size from each other.

[0009] Optionally, the operating table includes a supporting table top and a flat plate detachably mounted on the supporting table top, the flat plate being suitable for a patient to lie on, wherein the preset position of the operating table is a plurality of action positions marked on the supporting table top, and when one of the at least one second shim plates is positioned at a corresponding one of the plurality of action positions, the main magnetic field will be deformed according to a predetermined deformation action, thereby correcting the second inhomogeneity.

[0010] Optionally, a slot for inserting a second shim piece is provided at at least one of the plurality of action positions, and the second shim piece is slidable in the slot.

[0011] Optionally, multiple slots are spaced apart along the width direction of the support table, and each slot extends along the length direction of the support table; or multiple slots are spaced apart along the length direction of the support table, and each slot extends along the width direction of the support table; or multiple slots are arranged along the length direction of the support table and / or multiple slots are arranged along the width direction of the support table to form a slot array; or at least one of the multiple slots extends at an angle to the length direction or width direction of the support table.

[0012] Optionally, the MRI system further comprises a shim strip, wherein the shim strip is provided with a plurality of second chambers spaced apart from each other along its length direction for placing the at least one second shim plate, and the support table is defined with a recess, and when the shim strip is placed in the recess, the plurality of second chambers respectively correspond to the plurality of action positions.

[0013] Optionally, the plate is made of a non-magnetic non-metal with low thermal conductivity and / or the support table is made of a non-magnetic metal with high thermal conductivity.

[0014] According to another aspect of the present application, a shimming method is provided, which is used in the MRI system as described above, and the shimming method includes the following steps: shifting one of the MRI device and the operating table to engage with the other of the MRI device and the operating table; detecting a second inhomogeneity of the main magnetic field generated by the MRI device when the operating table is engaged with the MRI device; and arranging the at least one second shim piece at a preset position of the operating table to correct the second inhomogeneity.

[0015] Optionally, the shimming method further includes the following steps: before shifting one of the MRI device and the operating table to engage with the other of the MRI device and the operating table, detecting a first inhomogeneity of a main magnetic field generated by the MRI device when the MRI device is located in the first area and the operating table is located in the second area; and arranging the at least one first shimming piece at a preset position of the MRI device to correct the first inhomogeneity.

[0016] In the MRI system and the shimming method for the MRI system provided in the present application, the one of the MRI device and the operating table can be shifted between the first area and the second area, so that the surrounding environment of the MRI device, especially the magnetic field influencing elements distributed in the surrounding environment, changes. The arrangement of the at least one first shimming piece at the preset position of the MRI device is an initial shimming operation performed on the MRI device for the surrounding environment / state before the change (that is, the MRI device is located in the first area and the operating table is located in the second area), and the arrangement of the at least one second shimming piece at the preset position of the operating table is a subsequent shimming operation performed on the MRI device for the surrounding environment / state after the change (that is, in the first area or the second area, the operating table is engaged with the MRI device). Compared with the initial shimming operation, the subsequent shimming operation can conveniently and quickly adjust the main magnetic field generated by the MRI device in particular in a slight amount in accordance with the changed surrounding environment, that is, to slightly shift the magnetic flux lines of the main magnetic field in a required direction.

[0017] Other features and advantages of the present application will become apparent from the following detailed description of exemplary embodiments of the present application with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which constitute a part of the specification, illustrate embodiments of the present application and, together with the description, serve to explain the principles of the present application.

[0019] Figure 1 is a schematic perspective view of an MRI system according to one embodiment of the present application.

[0020] Figure 2 yes Figure 1 Another schematic perspective view of an MRI system.

[0021] Figure 3 yes Figure 1 Schematic stereogram of the operating table of the MRI system.

[0022] Figure 4 yes Figure 1 A schematic perspective view of an MRI device of an MRI system.

[0023] Figure 5 is another schematic top view of an MRI system according to one embodiment of the present application.

[0024] Figure 6 is another schematic top view of an MRI system according to one embodiment of the present application.

[0025] Figure 7 It is a schematic perspective view showing that a first shim of an MRI system according to one embodiment of the present application is ready to be arranged at a preset position of the MRI device.

[0026] Figure 8 It is a schematic stereoscopic diagram showing that a second shim of an MRI system according to an embodiment of the present application is ready to be arranged at a preset position of an operating table.

[0027] Fig. 9 is a schematic cross-sectional view showing a second shim of an MRI system according to an embodiment of the present application being arranged at a preset position of an operating table.

[0028] Fig.10 is a schematic cross-sectional view showing a second shim of an MRI system according to another embodiment of the present application being arranged at a preset position of an operating table. DETAILED DESCRIPTION

[0029] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present application.

[0030] Techniques and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the techniques and equipment should be considered part of the specification.

[0031] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0032] It should be noted that like reference numerals and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0033] The MRI system 100 according to one embodiment of the present application includes an MRI device 10 and an operating table 30. Figure 1 As shown, the MRI system 100 is located in the diagnosis room A with radio frequency shielding, and the operating table 30 is located in the operating room B without radio frequency shielding. The diagnosis room A with radio frequency shielding means that the diagnosis room A is equipped with radio frequency shielding materials. The operating room B without radio frequency shielding means that the operating room B is not equipped with radio frequency shielding materials. In this embodiment of the present application, the operating table 30 is movable, such as Figure 2 As shown, the operating table 30 is moved to the diagnosis room A to be connected with the MRI device 10. When the operating table 30 is connected with the MRI device 10 in the diagnosis room A, the patient can be scanned by the MRI device 10 and undergo surgery at the same time in the diagnosis room A, so the diagnosis room A can also have at least the same cleanliness as the operating room B under certain conditions.

[0034] An isolation door C may be provided between the diagnosis room A and the operating room B, and the isolation door C isolates the diagnosis room A and the operating room B. When the isolation door C is opened, it is convenient for the operating table 30 to be shifted between the diagnosis room A and the operating room B. When the isolation door C is closed, the diagnosis room A is radio-frequency shielded, so that during the MRI process, interference caused by external radio frequency signals from outside the diagnosis room A can be effectively prevented, thereby improving the accuracy of the image generated by the MRI device 10.

[0035] from Figure 3 It can be clearly seen that the shifting mechanism is installed to the bottom of the operating table 30 so that the operating table 30 is shiftable. Specifically, the shifting mechanism includes a base 330 for supporting the operating table 30, a driven wheel 322, a driving wheel 321, a driving device for driving the driving wheel 321, and a power device for providing power to at least the driving device. For example, the driven wheel 322 can be configured as an omnidirectional wheel made of a non-magnetic material. For example, the driving device can be configured as a servo motor and contain a magnetic material. For example, the power device can be configured as a battery (such as Figure 6 ), or configured as a plug device with a retractable cable pair for electrical connection with a power source located in the diagnosis room A or the operating room B. Optionally, the power device can also provide power for other electrical components on the operating table 30.

[0036] The operating table 30 is provided with an operating bed 340, an adjusting device 350 for adjusting the height and angle of the operating bed 340, and a fixing device 370 for fixing the head of the patient undergoing the operation. For example, the operating bed 340 includes a support table 341 connected to the adjusting device 350 and a flat plate 342 detachably mounted on the support table 341, the flat plate 342 can be used for the patient to lie down and can be made of non-magnetic non-metal, for example, the non-magnetic non-metal has low thermal conductivity, for example, the non-magnetic non-metal is non-magnetic plastic, and the support table 341 is made of metal with very low magnetism or even non-magnetic metal, for example, the metal has high thermal conductivity, for example, the metal is steel.

[0037] In addition, the operating table 30 is also provided with a vital sign detection device 310, which is used to detect or maintain the vital signs of the patient undergoing surgery, such as detecting the heart rate, breathing and other vital signs of the surgical patient, so that the medical staff can monitor the patient's physical condition during the operation. The vital sign detection device 310 may include devices such as a ventilator, a monitor, and an injection pump. Optionally, the vital sign detection device may also include an anesthesia machine. Optionally, the operating table 30 may also be provided with other devices for assisting doctors in performing surgery. For example, the operating table 30 may also be provided with a control panel 360, and the control panel 360 includes an input interface for medical staff to input adjustment instructions to control the various controlled components of the operating table 30. In summary, the operating table 30 can basically be equivalent to a fully functional integrated system.

[0038] The MRI system 100 further includes a tracking device 40 for controlling the displacement mechanism. The tracking device 40 includes an identifier 410 disposed on the base 330, a track belt 420 extending straight on the floor of the operating room B and the floor of the diagnosis room A, and a controller. The identifier 410 can be configured as an optical camera. The track belt 420 is composed of, for example, a black and white strip. When the displacement mechanism drives the operating table 30 to shift between the diagnosis room A and the operating room B, the identifier 410 identifies the track belt 420 and transmits the identified color information, for example, to the controller, so that the controller can determine the position of the operating table 30 based on the identified color information, for example, and control the motion trajectory of the displacement mechanism based on the position of the operating table 30, that is, control the driving device of the displacement mechanism to ensure that the displacement mechanism shifts along the track belt 420. Thus, the tracking device 40 is used to control the displacement speed and displacement path of the displacement mechanism between the diagnosis room A and the operating room B, thereby realizing the displacement control of the operating table 30.

[0039] For example, return to Figure 1 and Figure 2 , the track belt 420 includes a first sub-track belt 421, a second sub-track belt 422 and a third sub-track belt 423, and the second sub-track belt 422 is located between the first sub-track belt 421 and the third sub-track belt 423. During the displacement process of the operating table 30, the speed of displacement from the operating room B to the diagnosis room A can be different to meet the needs of different stages and prevent accidents during the displacement process. Optionally, the displacement speed of the operating table 30 in the first sub-track belt 421 and the third sub-track belt 423 is less than the displacement speed of the operating table 30 in the second sub-track belt 422.

[0040] like Figure 4 As shown, the MRI device 10 defines a magnet scanning cavity 101 and is suitable for generating a main magnetic field B0 passing through the magnet scanning cavity 101. Specifically, the MRI device 10 includes a superconducting magnet device 102, and the magnetic field direction of the main magnetic field B0 generated by the superconducting magnet device 102 is substantially parallel to the central axis direction of the magnet scanning cavity 101 in the magnet scanning cavity 101. It is expected that the distribution of the main magnetic field B0 within a certain volume range of the magnet scanning cavity 101 has a uniformity that meets the requirements, that is, the number of magnetic flux lines passing through any unit area within the certain volume range is consistent.

[0041] In this embodiment of the present application, the MRI device 10 is fixed in the diagnosis room A, and the MRI device 10 has a first end M and a second end N that are relatively arranged along the central axis direction of the magnet scanning cavity 101. Optionally, the MRI device 10 also includes a diagnosis bed 50 integrated therewith. In this case, in the diagnosis room A, the patient to be diagnosed is suitable for entering the magnet scanning cavity 101 from the second end N by lying on the diagnosis bed 50, and when the operating table 30 is shifted to engage with the MRI device 10 in the diagnosis room A, the patient lying on the flat plate 342 of the operating bed 340 to be subjected to surgical operation is suitable for entering the magnet scanning cavity 101 from the first end M of the MRI device 10.

[0042] Back to Figure 1 and Figure 2 , the MRI device 10 also includes an imaging control system 20, which can be connected to the MRI device 10 for communication, so as to receive the detection signal generated by the MRI device 10 by scanning at least a part of the patient, and process the detection signal to generate an image. The imaging control system 20 can also be connected to the operating table 30 for communication, so as to send the generated image to the vital sign detection device 310, so that the medical staff can refer to the generated image in time for subsequent surgical operations. Generally speaking, the imaging control system 20 is located in another room different from the diagnosis room A and the operating room B to reduce the interference between it and the MRI device 10 and the vital sign detection device 310.

[0043] In another embodiment of the present application, Figure 5 and Figure 6 As shown, the MRI device 10 is located in a diagnosis room A with radio frequency shielding and is displaceable, while the operating table 30 is located in an operating room B with radio frequency shielding and is fixed in the operating room B. Therefore, a shifting mechanism is installed to the bottom of the MRI device 10 so that the MRI device 10 is displaceable. In patent application 202120809968.4 filed by the applicant on April 20, 2021 and patent application 202220150705.1 filed on January 20, 2022, how the MRI device 10 is shifted by the shifting mechanism is described in detail, and these two patent applications are incorporated herein by reference. In this case, when MRI is required for a patient undergoing surgery in operating room B, the MRI device 10 can be shifted to operating room B to engage with the operating table 30. As Figure 5 and Figure 6 As shown, the diagnostic bed 50 integrated with the MRI apparatus 10 will be shifted together with the MRI apparatus 10 so that a portion of the diagnostic bed 50 is located in the operating room B and another portion is located in the diagnostic room A, and thus the isolation door C may not be closed.

[0044] Regardless of whether the displacement mechanism is installed on the MRI device 10 or the operating table 30, the operating table 30 can be connected to the MRI device 10 to facilitate real-time MRI diagnosis of the patient undergoing surgery, while the patient does not need to be moved, thereby reducing unexpected situations caused by the movement of the patient during the surgery. Therefore, such an MRI system 100 is particularly suitable for interventional surgeries that require a large number of interventional instruments to be inserted into the patient's body.

[0045] It is understandable that, in the present application, whether it is movable or not, the MRI device 10 must face the changed surrounding environment, especially the change of the magnetic field influencing elements distributed in the surrounding environment. For example, when the MRI device 10 is moved from the diagnosis room A (i.e., the first area) to the operating room B (i.e., the second area), the area where the MRI device 10 is located changes, and the changed area has the changed magnetic field influencing elements. When the operating table 30 is moved from the operating room B to the diagnosis room A, the first area where the MRI device 10 is located will be added with new magnetic field influencing elements, such as the driving device and the vital sign detection device 310 in the operating table 30. In order to accurately locate the MRI device 10 and the operating table 30 relative to the magnetic field influencing elements, a first point and a second point are marked on the track tape 420, the first point is aligned with the first position of the first area and the second point is aligned with the second position of the second area, so as to ensure that the MRI device 10 or the operating table 30 is accurately shifted between the first position of the first area and the second position of the second area along a preset path by means of the tracking device 40.

[0046] When the MRI device 10 is initially positioned at the first position of the diagnosis room A and the operating table 30 is still in the operating room B, the main magnetic field B0 generated by the MRI device 10 or the superconducting magnet device 102 is basically unable to achieve the required uniformity. Therefore, it is necessary to perform a shimming operation on the MRI device 10 in this environment. Figure 7 As shown, at least one first shim 130 is arranged at a preset position of the MRI device 10 shown in a further simplified manner, so as to correct the detected first inhomogeneity of the main magnetic field B0 generated by the MRI device 10 through passive shimming. Optionally, the first inhomogeneity may also be corrected through active shimming, but for some MRI devices 10, since a shim coil array for high-order active shimming is not provided, it is more necessary to perform high-order passive shimming on the MRI device 10 through the first shim 130 to effectively correct the first inhomogeneity.

[0047] Continue to refer to Figure 7The first shim sheet 130 may be placed in the first shim strip 120, and the first shim strip 120 may be inserted into the insertion hole 110 on the MRI device 10 along a direction parallel to the central axis direction of the magnet scanning cavity 101. For example, the MRI device 10 is provided with a plurality of insertion holes 110 distributed around the central axis direction of the magnet scanning cavity 101. Figure 7 Only one first shim bar 120 is shown in the figure. It is understandable that the MRI system 100 may also include a plurality of first shim bars 120 . The plurality of first shim bars 120 may be respectively inserted into corresponding sockets 110 to perform passive shimming on the MRI device 10 .

[0048] The first shim strip 120 may be provided with a plurality of first chambers 120 spaced apart from each other along its length direction, and each first chamber 120 is used to accommodate a first shim piece 130. In the process of performing an initial shim operation on the MRI device 10, a first parameter related to the main magnetic field B0 generated by the MRI device 10 is first detected, and the detected first parameter can indicate a first inhomogeneity. According to the first parameter, the amount of the first shim piece 130 required to be added to each first chamber 120 can be calculated, and then the required amount of the first shim piece 130 is placed in the corresponding first chamber 120, and then the first shim strip 120 equipped with the first shim piece 130 is inserted into the corresponding jack 110, and installed and fixed to complete the passive shim operation. The first shim piece 130 may contain iron or silicon, for example, the shim piece 130 may be a silicon steel sheet, and the shape is a rectangle or other geometric shape. When the first shim bar 120 containing the first shim piece 130 is inserted into the insertion hole 110, the first shim piece 130 can attract the magnetic flux lines of the main magnetic field B0 to shift in a desired direction, thereby maintaining a uniform magnetic field distribution of the main magnetic field B0. Figure 7 Only one first shim 130 is shown in the figure. It can be understood that, as required, a plurality of first shims 130 can be placed in one first chamber 120 .

[0049] Since the first shim pieces 130 placed in the main magnetic field B0 will be affected by the magnetic force and thus have a tendency to move, the accurate addition of the first shim pieces 130 involves multiple field raising and lowering processes of the MRI device 10 to prevent danger to the staff performing the shim operation. Therefore, the initial shim operation generally consumes a long time.

[0050] In addition, in order to improve the efficiency of adding the first shims 130, the deformation effect of a certain number of first shims 130 when located in the corresponding first chambers 120 of the corresponding first shim strips 120 can be predetermined by various algorithms, simulations and actual test data, and the deformation effect indicates the direction and size / degree of deformation of the main magnetic field B0.

[0051] When the MRI device 10 is moved to the second position of the operating room B to engage with the operating table 30 fixed in the operating room B, or the operating table 30 is moved to the first position of the diagnosis room A to engage with the MRI device 10 fixed in the diagnosis room A, the surrounding environment of the MRI device 10 changes, so that the main magnetic field B0 generated by the MRI device 10 has a second inhomogeneity. For this reason, Figure 8 As shown, at least one second shim 150 may be arranged at a preset position of the operating table 30 to correct the detected second inhomogeneity of the main magnetic field B0 generated by the MRI apparatus 10 .

[0052] Generally speaking, excessive magnetic materials are avoided as much as possible during the manufacturing process of the operating table 30. Therefore, the second inhomogeneity of the main magnetic field B0 caused by the connection between the operating table 30 and the MRI device 10 may be very small compared to the first uniformity, and the second inhomogeneity can be corrected by providing at least one shim 150. The second shim 150 may be different in size from, for example, smaller than, the at least one first shim 130. Optionally, the main surface (i.e., the surface with the largest area) of the second shim 150 is significantly smaller than the main surface area of ​​the first shim 130. Optionally, the thickness of the second shim 150 is significantly smaller than the thickness of the first shim 130. Optionally, the second shim 150 may also be different in shape from the first shim 130.

[0053] Continue to refer to Figure 8 ,exist Figure 8 In the figure, the flat plate 342 is removed to clearly show that the preset positions of the operating table 30 are a plurality of action positions marked on the support table 341 by, for example, visually visible markings, and one of the at least one second shim 150, when positioned at a corresponding one of the plurality of action positions, will deform the main magnetic field B0 according to a predetermined deformation effect, thereby correcting the second inhomogeneity. That is, in order to improve the efficiency of adding the second shim 150, the deformation effect of the second shim 150 when located at a corresponding one of the action positions can be predetermined by various algorithms, simulations, and real test data, and the deformation effect indicates the direction and size / degree of deformation of the main magnetic field B0.

[0054] In addition, unlike the first shims 130 that implement the deformation effect of size change by stacking a certain number of shims, the second shims 150 implement the deformation effect of size change by different sizes. That is, the second shims 150 have multiple models, and the multiple models of the second shims 150 are different in size from each other, for example, the multiple models of the second shims 150 have main surfaces of different sizes, thicknesses, or have different shapes.

[0055] Thus, in the subsequent shimming operation of the MRI device 10, the second parameter related to the main magnetic field B0 generated by the MRI device 10 is first detected, and the detected second parameter can indicate the second inhomogeneity. According to the second parameter, whether the second shim piece 150 needs to be added to each action position and the type of the second shim piece 150 to be added can be calculated, and then the second shim piece 150 of the corresponding type is positioned at the corresponding action position.

[0056] In one example, the main surface of the second shim piece 150 can be attached to a corresponding action position, and optionally, the second shim piece 150 can be fixed at the corresponding position by, for example, a threaded connection from a connector. After the subsequent shim operation is completed, the platform is mounted on the support table 341. It can be understood that the platform can be at least disassembled by tools, so that it is possible to add, replace and / or remove the second shim piece 150 at any time in the future. In addition, since the flat plate 342 is made of a non-magnetic non-metallic material with low thermal conductivity, and the support table 341 is made of a metal with high thermal conductivity and very low magnetism, or even a non-magnetic metal, the heat generated by the operation of the second shim piece 150 can be prevented from being transferred to the patient lying on the flat plate 342.

[0057] Reference Figure 8 and Fig. 9 A slot 345 for inserting a second shim 150 may be provided at at least one of the plurality of marked action positions on the support table 341. Figure 8 and Fig. 9 Each slot 345 shown in the figure extends along the length direction of the operating bed 340 or the support table 341, and the plurality of slots 345 are spaced apart along the width direction of the operating bed 340 or the support table 341, but it is understandable that, as required, the plurality of slots 345 can be spaced apart along the length direction of the support table 341, and each slot 345 can extend along the width direction of the support table 341. Optionally, the second shim 150 is slidable in the slot 345, thereby marking multiple action positions in a flexible manner. Optionally, a plurality of slots 345 are arranged along the length direction of the support table 341, and / or a plurality of slots 345 are arranged along the width direction of the support table 341 to form a slot array. Optionally, at least one of the plurality of slots 345 extends at an angle to the length direction or the width direction of the support table 341. In summary, the extension direction of each slot 345 and the array formed by the plurality of slots 345 can be specifically designed according to the specific application. In addition, although Figure 8 Only one second shim 150 is shown in the figure, and it can be understood that a plurality of second shims 150 can be inserted into the slot 345 as needed.

[0058] Fig. 9 is a cross-sectional view of the support table 341 taken along the width direction of the support table 341. Fig. 9 In the figure, multiple models of second shim plates 150 have been inserted into the slot 345. The support table 341 includes a base 347 and an edge 348 protruding on the periphery of the base 347, the edge 348 is used to support the flat plate 342 mounted on the support table 341, and the base 347 is used to open a slot 345 therein. In one example, a plug-in card 351 made of an insulating material can be provided, for example, the plug-in card 351 includes an insertion portion 352 and a hand-held portion 353, the second shim plate 150 is at least embedded in the insertion portion 352 and the insertion portion 352 is suitable for being inserted into the slot 345, when the insertion portion 352 is inserted into the slot 345, the hand-held portion 353 protrudes relative to the slot 345 to facilitate the insertion, sliding and removal of the plug-in card 351. From Fig. 9 It can be seen that the models / sizes of the second shims 150 in each plug-in card 351 are different from each other. As mentioned above, the second shims 150 of corresponding models / sizes are selected according to the predetermined deformation effect and inserted into the corresponding slots 345 .

[0059] Alternatively, in Fig.10 In the embodiment, second shim pieces 150 of different sizes can be placed in, for example, a box-shaped second shim strip 160, and the three-dimensional shape of the second shim strip 160 can be similar to or the same as the first shim strip 120. The second shim strip 160 is provided with a plurality of second chambers 170 spaced apart from each other along its length direction, and each second chamber 170 can accommodate one or more second shim pieces 150, or no second shim piece 150. That is, the amount of second shim pieces 150 required to be added to each second chamber 170 is determined based on whether the calculated second shim pieces 150 are required to be added to each action position. After the required amount of second shim pieces 150 are placed in the corresponding second chamber 170, the second shim strip 160 equipped with the second shim pieces 150 is moved along the second chamber 170. Fig.10 The second chambers 170 are inserted into the recess 349 defined by the support table 341 in the direction indicated by the arrow in FIG. 34 . Specifically, the recess 349 is defined by the edge 348 of the base 347 , so that the plurality of second chambers 170 respectively correspond to the plurality of action positions.

[0060] It is understandable that other suitable methods may be used to find a suitable position in the operating table 30 to set the second shim 150 .

[0061] Because the deformation effect of the first shim 130 located at the preset position of the MRI device 10 on the main magnetic field B0 is independent of the deformation effect of the second shim 150 located at the preset position of the operating table 30 on the main magnetic field B0, the results of the initial and subsequent shimming operations are relatively independent. That is, when returning to the state where the MRI device 10 is located in the diagnosis room A and the operating table 30 is located in the operating room B, the second shim 150 that leaves with the operating table 30 will not affect the result of the initial shimming operation.

[0062] Accordingly, a shimming method for an MRI device 10 is provided, which may include the following steps: detecting a first inhomogeneity of a main magnetic field B0 generated by the MRI device 10 when the MRI device 10 is located in a first area and an operating table 30 is located in a second area; arranging the at least one first shim piece 130 at a preset position of the MRI device 10 to correct the first inhomogeneity; shifting the one of the MRI device 10 and the operating table 30 to engage with the other of the MRI device 10 and the operating table 30; detecting a second inhomogeneity of the main magnetic field B0 generated by the MRI device 10 when the operating table 30 is engaged with the MRI device 10; and arranging the at least one second shim piece 150 at a preset position of the operating table 30 to correct the second inhomogeneity.

[0063] Subsequent shimming operations can be performed by the second shimming sheet 150 to adjust / deform the main magnetic field B0 generated by the MRI device 10 in a micro-amount in response to changes in the surrounding environment caused by, for example, the operating table 30, that is, to shift the magnetic flux lines of the main magnetic field B0 in a desired direction. Compared with the initial shimming operation, the subsequent shimming operation is more convenient and faster.

[0064] Although some specific embodiments of the present application have been described in detail by way of example, it should be understood by those skilled in the art that the above examples are only for illustration and not for limiting the scope of the present application. It should be understood by those skilled in the art that the above embodiments may be modified without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims

1. A magnetic resonance imaging system (100), characterized in that: include: A magnetic resonance imaging apparatus (10) defining a magnet scanning cavity (101) and adapted to generate a main magnetic field passing through the magnet scanning cavity (101); An operating table (30) adapted to be coupled to a magnetic resonance imaging device (10) so that at least a portion of a patient located on the operating table (30) enters a magnet scanning cavity (101); a displacement mechanism adapted to enable one of the magnetic resonance imaging apparatus (10) and the operating table (30) to be displaceable; A tracking device (40) adapted to control the displacement mechanism to cause one of the magnetic resonance imaging apparatus (10) and the operating table (30) to be displaced between the first area and the second area along a preset path; At least one first shim (130) is arranged at a preset position of the magnetic resonance imaging device (10) to correct a first inhomogeneity of a main magnetic field generated by the magnetic resonance imaging device (10) detected when the magnetic resonance imaging device (10) is located in a first area and the operating table (30) is located in a second area; as well as At least one second shim (150) is arranged at a preset position of an operating table (30) to correct a second inhomogeneity of a main magnetic field generated by a magnetic resonance imaging device (10) detected when the operating table (30) is engaged with the magnetic resonance imaging device (10), wherein the at least one second shim (150) is different in size from the at least one first shim (130).

2. The magnetic resonance imaging system (100) according to claim 1, characterized in that: The first area is included in a diagnosis room with radio frequency shielding, the second area is included in an operating room with radio frequency shielding, and the displacement mechanism is mounted to the magnetic resonance imaging device (10), whereby the magnetic resonance imaging device (10) is adapted to be displaced from a first position in the first area to a second position in the second area by means of a tracking device (40) to engage with an operating table (30) located in the second area; or The first area is included in a diagnostic room with radio frequency shielding, the second area is included in an operating room without radio frequency shielding, and a shifting mechanism is mounted to an operating table (30), whereby the operating table (30) is adapted to be shifted from a second position in the second area toward a first position in the first area by means of a tracking device (40) to engage with a magnetic resonance imaging device (10) located in the first area.

3. The magnetic resonance imaging system (100) according to claim 1, characterized in that: The at least one second shim (150) comprises a plurality of second shims (150), and the plurality of second shims (150) are different in size from each other.

4. The magnetic resonance imaging system (100) according to any one of claims 1 to 3, characterized in that: The operating table (30) comprises a support table top (341) and a flat plate (342) detachably mounted on the support table top (341), wherein the flat plate (342) is suitable for a patient to lie on, wherein the preset position of the operating table (30) is a plurality of action positions marked on the support table top (341), and when one of the at least one second shim sheet (150) is positioned at a corresponding one of the plurality of action positions, the main magnetic field is deformed according to a predetermined deformation action, thereby correcting the second inhomogeneity.

5. The magnetic resonance imaging system (100) according to claim 4, characterized in that: A slot (345) for inserting a second shim piece (150) is provided at at least one of the plurality of action positions, and the second shim piece (150) is slidable in the slot (345).

6. The magnetic resonance imaging system (100) according to claim 5, characterized in that: A plurality of slots (345) are spaced apart along the width direction of the support table (341), and each slot (345) extends along the length direction of the support table (341); or A plurality of slots (345) are spaced apart along the length direction of the support table (341), and each slot (345) extends along the width direction of the support table (341); or A plurality of slots (345) are arranged along the length direction of the support table (341) and / or a plurality of slots (345) are arranged along the width direction of the support table (341) to form a slot array; or At least one of the plurality of slots (345) extends at an angle to a length direction or a width direction of the support table (341).

7. The magnetic resonance imaging system (100) according to claim 4, characterized in that: The invention also comprises a shim strip (160), wherein the shim strip (160) is provided with a plurality of second chambers (170) spaced apart from each other along its length direction for accommodating the at least one second shim plate (150), and the support table (341) is defined with a recess (349), and when the shim strip (160) is placed in the recess (349), the plurality of second chambers (170) respectively correspond to the plurality of action positions.

8. The magnetic resonance imaging system (100) according to claim 4, characterized in that: The flat plate (342) is made of a non-magnetic non-metal with low thermal conductivity and / or the supporting table (341) is made of a non-magnetic metal with high thermal conductivity.

9. A shimming method, used in a magnetic resonance imaging system (100) according to any one of claims 1 to 8, characterized in that: The shimming method comprises the following steps: shifting one of the magnetic resonance imaging device (10) and the operating table (30) to engage with the other of the magnetic resonance imaging device (10) and the operating table (30); Detecting a second inhomogeneity of a main magnetic field generated by the magnetic resonance imaging apparatus (10) in a state where the operating table (30) is engaged with the magnetic resonance imaging apparatus (10); and The at least one second shim (150) is arranged at a preset position of the operating table (30) to correct the second inhomogeneity.

10. The shimming method according to claim 9, characterized in that: The following steps are also included: Before shifting one of the magnetic resonance imaging apparatus (10) and the operating table (30) to engage with the other of the magnetic resonance imaging apparatus (10) and the operating table (30), detecting a first inhomogeneity of a main magnetic field generated by the magnetic resonance imaging apparatus (10) in a state where the magnetic resonance imaging apparatus (10) is located in a first area and the operating table (30) is located in a second area; as well as The at least one first shim (130) is arranged at a preset position of the magnetic resonance imaging device (10) to correct the first inhomogeneity.

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