Magnetic resonance imaging system

Abstract

A magnetic resonance imaging system comprises: a magnetic resonance imaging device (100), comprising: a cylindrical gradient coil device (120), a radio frequency coil device (160) coaxially arranged around and adjacent to the inner diameter surface of the gradient coil device (120), the radio frequency coil device (160) being configured to transmit a radio frequency signal of a first frequency, and a first shielding device, the first shielding device comprising a first shielding layer (132) circumferentially arranged between the gradient coil device (120) and the radio frequency coil device (160); and a patient table (200) detachable from or attachable to the magnetic resonance imaging device (100), comprising: a bed board (210) configured for a patient to lie on, and a second shielding device arranged around at least a portion of the bed board (210); wherein, when the magnetic resonance imaging device (100) is attached to the patient table (200), the first shielding device is in conductive contact with the second shielding device to form a cutoff waveguide around the bed board, the cutoff waveguide being capable of cutting off radio frequency signals lower than a second frequency, the second frequency being greater than the first frequency.

Description

Technical Field

[0001] The present invention relates to the field of magnetic resonance imaging (MRI), and more particularly to magnetic resonance imaging systems. Background Art

[0002] The MRI system utilizes radiology-based MRI technology to digitally image at least a portion of the patient's internal structure and tissue by scanning the patient (or subject). In general, the MRI system includes: a superconducting magnet device for generating a strong and uniform static magnetic field (i.e., a "main magnetic field") during operation, which can polarize the nuclear spins associated with hydrogen nuclei in the patient's internal structure and tissue; a gradient coil device for generating a gradient magnetic field with a smaller amplitude and varying with the spatial position during operation, which can identify any position in the patient's internal structure and tissue; and a radio frequency (RF) coil device for emitting RF excitation pulses corresponding to the resonance frequency (also known as the Larmor frequency) of the hydrogen nuclei to increase energy to the nuclear spins of the hydrogen nuclei, and receiving or detecting magnetic resonance (MR) signals formed when the hydrogen nuclei release the increased energy, so as to digitally image based on the MR signals.

[0003] In order to prevent electromagnetic coupling between the gradient coil device and the RF coil device in the MRI system, an RF shielding layer can be inserted between the two to electromagnetically isolate the gradient coil device from the RF coil device. At the same time, in order to prevent the natural electromagnetic signals in the external environment or the electromagnetic signals generated by other nearby precision instruments from interfering with the MRI system, a special RF shielding room is required to place the MRI system, and the MRI system can only be operated in such a special RF shielding room. Summary of the invention

[0004] An object of the present invention is to provide an MRI system that achieves "local shielding" in a simple, easy to operate and cost-effective manner by utilizing existing RF shielding devices.

[0005] According to one aspect of the present invention, a magnetic resonance imaging system is provided, comprising: a magnetic resonance imaging device, comprising: a cylindrical gradient coil device, a radio frequency coil device coaxially arranged around and adjacent to the inner diameter surface of the gradient coil device, the radio frequency coil device configured to transmit a radio frequency signal of a first frequency, and a first shielding device, the first shielding device comprising a first shielding layer circumferentially arranged between the gradient coil device and the radio frequency coil device; and a patient table detachable from or engageable with the magnetic resonance imaging device, comprising: a bed board configured for a patient to lie on, and a second shielding device arranged around at least a portion of the bed board; wherein, when the magnetic resonance imaging device is engaged with the patient table, the first shielding device is in conductive contact with the second shielding device to form a cutoff waveguide surrounding the bed board, and the cutoff waveguide can cut off radio frequency signals lower than a second frequency, the second frequency being greater than the first frequency.

[0006] Optionally, the magnetic resonance imaging device is movable, and the first shielding device further comprises an anti-collision component conductively connected to the first shielding layer, the anti-collision component being configured to control the magnetic resonance imaging device to stop moving and conductively contact with the second shielding device when the magnetic resonance imaging device is moved to engage with the patient table.

[0007] Optionally, the anti-collision component includes an elastic anti-collision ring and a conductive rubber sleeve, the conductive rubber sleeve includes a first rubber sleeve part and a second rubber sleeve part which are sleeved on both ends of the anti-collision ring, wherein when the magnetic resonance imaging device is disengaged from the patient table, the first rubber sleeve part and the second rubber sleeve part are not in conductive contact, and wherein when the magnetic resonance imaging device is engaged with the patient table, the anti-collision ring is compressed and the first rubber sleeve part and the second rubber sleeve part are in conductive contact.

[0008] Optionally, the magnetic resonance imaging device defines a cylindrical scanning channel at the center, the scanning channel includes a service port away from the patient table when the magnetic resonance imaging device is engaged with the patient table, and wherein the first shielding device also includes a shielding door configured to openably close the service port, and when the shielding door closes the service port, the shielding door is in conductive contact with the first shielding layer.

[0009] Optionally, the second shielding device defines a transmission channel around the at least a portion of the bed board, the transmission channel comprising a foot port configured for a patient's foot to pass through, and the foot port is open.

[0010] Optionally, the second shielding device comprises a lower shielding part and an upper shielding part separable from the lower shielding part, and when the upper shielding part is placed above the lower shielding part, the upper shielding part is in conductive contact with the lower shielding part.

[0011] Optionally, the upper shielding component includes an arched body, which includes a first transparent layer, a second shielding layer, and a second transparent layer which are laminated, wherein the first transparent layer and the second transparent layer are insulating, and the second shielding layer is conductive and made of a wire mesh-like conductive material so that the arched body is transparent or translucent.

[0012] Optionally, the upper shielding component further comprises an upper conductive section extending longitudinally from the arched body and radially expanding to be aligned with the first shielding device, the upper conductive section comprising an upper conductive flange configured to be in conductive contact with the first shielding device.

[0013] Optionally, the lower shielding component includes a conveying plate, and the bed plate is movably connected to the top of the conveying plate relative to the conveying plate. An elastic conductive gasket is provided on the edge of the upper surface of the conveying plate. When the upper shielding component is placed above the lower shielding component, the upper shielding component and the lower shielding component are in conductive contact via the conductive gasket.

[0014] Optionally, the transfer plate comprises a lower end section extending longitudinally and radially deformed to be aligned with the first shielding device, and the lower end section is provided with a lower conductive flange configured to be in conductive contact with the first shielding device.

[0015] The MRI system provided by the present invention utilizes the first shielding device (RF shielding device) currently arranged in the MRI equipment and the second shielding device arranged around the bed board to form a cutoff waveguide to effectively cut off the natural electromagnetic signals in the external environment from interfering with the MRI system, or the electromagnetic signals generated by other nearby precision instruments and the radio frequency signals emitted by the RF coil device of the MRI system. Interference is mutually prevented, thereby achieving local shielding with the help of the first shielding device and the second shielding device, that is, there is no need to provide a special RF shielding room. The cost of local shielding is one tenth or less of the cost of providing a special RF shielding room. In addition, due to the cutoff frequency effect of the cutoff waveguide, the second shielding device can be open, that is, not completely closed, which makes the use and design of the MRI system more flexible and also brings a better diagnostic experience to patients.

[0016] Further features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments of the present invention with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which constitute a part of the specification, illustrate embodiments of the present invention and, together with the description, serve to explain the principles of the present invention.

[0018] Figure 1 is a schematic structural cross-sectional view of an MRI system according to an embodiment of the present invention, wherein a patient table is separated from the MRI device.

[0019] Figure 2 yes Figure 1 Another schematic structural cross-sectional view of an MRI system, wherein a patient table is aligned with and about to engage with the MRI device.

[0020] Figure 3 yes Figure 1 Another schematic structural cross-sectional view of an MRI system, wherein a patient table is coupled to the MRI device.

[0021] Figure 4 is a perspective view of a patient table of an MRI system according to an embodiment of the present invention.

[0022] Figure 5 yes Figure 4 Side view of the patient table.

[0023] Figure 6 yes Figure 4 Another perspective view of a patient table with the upper shielding part removed. DETAILED DESCRIPTION

[0024] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangement of parts and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention unless otherwise specifically stated.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] It should also be noted that in this document, "upper" refers to the direction away from the ground, "lower" refers to the direction toward the ground, and "longitudinal" refers to the direction of the MRI system along the direction in which the patient lies. However, unless otherwise specified, the use of "upper", "lower" and "longitudinal" is only for convenience of description and does not limit the specific orientation of the equipment, devices or components of the MRI system.

[0029] Reference Figures 1 to 3, the exemplary MRI system includes an MRI device 100 and a patient table 200, the MRI device 100 can be electrically or manually moved via a corresponding walking mechanism (not shown, for example, wheels or a track and pulley assembly, etc.), and therefore when the MRI system is not in operation, the MRI device 100 and the patient table 200 are separated from each other, and before the patient is prepared to be scanned using the MRI system, the MRI device 100 is coupled with the patient table 200. For example, the patient can lie on the patient table 200 separated from the MRI device 100 in advance, and then the movable MRI device 100 is brought close to the patient table 200, aligned with the patient table 200, and finally coupled with the patient table 200. How the MRI device 100 is coupled with the patient table 200 will be described in detail below.

[0030] The exemplary MRI apparatus 100 includes a superconducting magnet device 110, a gradient coil device 120, a first shielding layer 132, and an RF coil device 160 that are coaxially arranged from outside to inside in the radial direction. The exemplary MRI apparatus 100 also includes one or more control devices (not shown) that control the superconducting magnet device 110 and the gradient coil device 120 to generate a desired magnetic field and control the RF coil device 160 to generate a desired RF excitation pulse (or RF signal). It can be understood that the one or more control devices are electrically connected and / or communicated with the superconducting magnet device 110, the gradient coil device 120, the RF coil device 160, and their auxiliary electrical devices (e.g., various amplifiers and various sensors, etc.) through one or more electrical lines and / or data transmission lines to control the operation of the entire MRI apparatus 100.

[0031] The MRI apparatus 100, which is composed of the superconducting magnet device 110, the gradient coil device 120, the first shielding layer 132, and the RF coil device 160, defines a cylindrical scanning channel in the center, and the scanning channel has a longitudinal first central axis M, so the “coaxial arrangement” refers to the arrangement with the first central axis M as the common central axis of the superconducting magnet device 110, the gradient coil device 120, the first shielding layer 132, and the RF coil device 160. The scanning channel also has a “service port” and a “patient port” that are oppositely positioned along the first central axis M, wherein when the MRI apparatus 100 is fully engaged with the patient table 200, the service port is farther from the patient table 200 than the patient port.

[0032] The superconducting magnet device 110 is arranged at the outer periphery of the MRI apparatus 100 and is cylindrical relative to the gradient coil device 120, the first shielding layer 132, and the RF coil device 160. As is known, the superconducting magnet device 110 may include and be kept at low temperature via a helium storage container and thermally isolated from other devices. The gradient coil device 120 is coaxially arranged around and adjacent to the inner diameter surface of the superconducting magnet device 110 and is also cylindrical. Similarly, the RF coil device 160 is coaxially arranged around and adjacent to the inner diameter surface of the gradient coil device 120 and is also cylindrical. In order to prevent electromagnetic coupling between the gradient coil device 120 and the RF coil device 160, the first shielding layer 132 is circumferentially arranged between the gradient coil device 120 and the RF coil device 160 so that the outer diameter surface of the first shielding layer 132 is adjacent to the inner diameter surface of the gradient coil device 120, and the inner diameter surface of the first shielding layer 132 is adjacent to the outer diameter surface of the RF coil device 160. It is understood that "adjacent to" in this article means that there may be a radial gap between the devices, or they may abut against each other. It is also understood that for the sake of clarity, the description of other components of the MRI device 100 such as the housing, the support component and / or the suspension component, and the end cover is omitted in this article.

[0033] The control device may start the superconducting magnet device 110 to cause the superconducting magnet device 110 to generate a main magnetic field B0 distributed substantially along or parallel to the first central axis M in the scanning channel. The control device may also start the gradient coil device 120 to cause the X-axis gradient coil, the Y-axis gradient coil, and the Z-axis gradient coil in the gradient coil device 120 to generate a gradient magnetic field for spatially encoding the MR signal. The control device may also start the RF coil device 160, for example, a body coil for transmitting RF excitation pulses, to cause the RF coil to generate an RF magnetic field B1 for scanning the desired internal structure and tissue of the patient. + , RF magnetic field B1 + In the scanning channel, the control device is perpendicular to the main magnetic field B0; alternatively, the control device can also start the RF coil device 160, for example, a body coil for receiving MR signals, to cause the RF coil device 160 to receive the RF magnetic field B1 from the patient. + induced MR signal.

[0034] Optionally, the first shielding device includes a first shielding layer 132, which is cylindrical because it is circumferentially arranged between the gradient coil device 120 and the RF coil device 160, and the cylindrical first shielding layer 132 includes a first end 136 and a second end 134 that are oppositely positioned along the first central axis M and are both annular, and the first end 136 and the second end 134 are both extended or exposed from between the gradient coil device 120 and the RF coil device 160 to be respectively electrically connected to the anti-collision component of the first shielding device and to be able to be electrically connected to the shielding door 144 of the first shielding device. It can be understood that the "conductive connection" and "conductive contact" herein refer to the permanent electrical connection relationship or temporary electrical contact relationship formed between the various components, devices and equipment in the MRI system in order to achieve RF shielding, and do not mean that they need to be powered on when the MRI system is in operation.

[0035] For example, the first shielding layer 132 is made of a wire mesh or woven conductive material, and the conductive material includes, for example, copper, stainless steel, or any other conductive material, and may be mixed with other materials such as epoxy resin or glass fiber tape. The first shielding layer 132 is necessary. On the one hand, the first shielding layer 132 electromagnetically isolates the gradient coil device 120 from the RF coil device 160, thereby avoiding the adverse effect of the electromagnetic coupling between the gradient coil device 120 and the RF coil device 160 on the quality factor of the RF coil device 160. On the other hand, since the first shielding layer 132 is arranged radially inward relative to the gradient coil device 120, the electrical circuit and / or data transmission circuit connected to the gradient coil device 120 from the outside of the MRI device 100 does not need to be filtered. It should be pointed out that in the present invention, the cylindrical first shielding layer 132 and therefore the first shielding device are also used to form a first section of the cutoff waveguide, and the scanning channel is contained in the first section of the cutoff waveguide, which is used to effectively cut off the natural electromagnetic signals in the external environment from interfering with the MRI system, or the electromagnetic signals generated by other nearby precision instruments from interfering with the radio frequency signals emitted by the RF coil device 160 of the MRI system.

[0036] Additionally, the anti-collision assembly conductively connected to the extended or exposed first end 136 of the first shielding layer 132 helps prevent the movable MRI device, which may weigh up to 2 tons, from excessive movement and causing accidental injury to a patient.

[0037] For example, the anti-collision component includes an elastic and insulating anti-collision ring 138. Figure 1 When the MRI device 100 is separated from the patient table 200, the anti-collision ring 138 has a first longitudinal length L1, which is also the natural length of the anti-collision ring 138 when it is not loaded. Figure 2When the MRI apparatus 100 is aligned with the patient table 200 and is about to be engaged, the anti-collision ring 138 is deformed to have a second longitudinal length L2, which is equal to or less than the first length L1, wherein the anti-collision ring 138 is loaded and compressed by the longitudinal opposite squeezing forces from the patient table 200 and the MRI apparatus 100, respectively. Figure 3 When the MRI device 100 is fully engaged with the patient table 200, that is, when the MRI system is ready for operation, the anti-collision ring 138 is further deformed to have a third longitudinal length L3, which is smaller than the second length L2 and therefore smaller than the first length L1.

[0038] Reference Figure 2 and Figure 3 , the anti-collision assembly also includes a conductive rubber sleeve that is also elastic, and the conductive rubber sleeve includes a first rubber sleeve part 140A and a second rubber sleeve part 140B, which are respectively mounted on the two ends of the anti-collision ring 138 that are oppositely positioned along the first central axis M, wherein the first rubber sleeve part 140A is annular and conductively connected to the first end 136 of the first shielding layer 132 in a covering manner. The radial thickness of the first rubber sleeve part 140A is significantly greater than the radial thickness of the first shielding layer 132 to facilitate the conductive connection between the first rubber sleeve part 140A and the first end 136 of the first shielding layer 132. It can be understood that the radial thickness in this article refers to the distance from the outer diameter surface to the inner diameter surface. When the insulating anti-collision ring 138 has a first length L1 or a second length L2, the first rubber sleeve part 140A is not in conductive contact with the second rubber sleeve part 140B, so the anti-collision assembly is not conductive, and the MRI device 100 is aligned with the patient table 200 but has not yet completed the engagement. When the anti-collision ring 138 has a third length L3, the first rubber sleeve portion 140A and the second rubber sleeve portion 140B are in conductive contact, so the anti-collision assembly can be conductive, and the MRI device 100 is now fully engaged with the patient table 200. At the same time, the anti-collision ring 138 has a built-in relay (not shown), and the relay is connected to the running mechanism of the MRI device 100 via an electrical line. The relay is configured to control the running mechanism of the MRI device 100 to stop moving when the anti-collision ring 138 has the third length L3, that is, when the MRI device 100 is moved to fully engage with the patient table 200, to prevent accidental injury to the patient.

[0039] Optionally, the first shielding device further includes a filter 142 arranged on the extended second end 134 of the first shielding layer 132, the filter 142 is conductively connected to the first shielding layer 132, and the electrical lines and / or data transmission lines that need to be connected to the RF coil device 160 from the outside of the first shielding layer 132 and / or need to be led out from the RF coil device 160 to the outside of the first shielding layer 132 can enter and exit through the filter and be filtered, so that the filter 142 allows the electrical lines and / or data transmission lines to pass through the first shielding layer 132 without affecting the electromagnetic shielding effect of the first shielding layer 132. Moreover, when considering grounding the first shielding layer 132 to stabilize the performance of the RF coil device 160, a connector for grounding can be conveniently provided on the filter 142.

[0040] Optionally, the first shielding device further includes a shielding door 144 that can be opened to close the service port of the scanning channel, and the shielding door 144 is configured to be in conductive contact with the second end 134 of the first shielding layer 132 when the service port is closed. For example, the shielding door 144 is an engineering plastic plate with metal copper plated on the surface, so that the shielding door 144 is light in weight and low in cost.

[0041] Reference Figures 4 to 6 The patient table 200 includes: a bed plate 210 made of insulating material, the bed plate 210 is used for the patient to lie in a posture suitable for being scanned by the MRI device 100; and a support frame 220 for supporting the bed plate 210, the support frame 220 can be raised and lowered and includes a base 222. It can be understood that the base 222 can also be selectively installed with another walking mechanism (not shown, for example, wheels, etc.), so that the patient table 200 can be automatically or manually movable via the other walking mechanism.

[0042] The patient table 200 further includes a second shielding device, which includes a lower shielding component 230 and an upper shielding component 250 that is detachable and removable from the lower shielding component 230. The upper shielding component 250 is configured to surround at least a portion of the bed plate 210 when assembled or placed above the lower shielding component 230 to form an arched transmission channel, and when the arched transmission channel is assumed to be completed into a corresponding cylindrical shape, the transmission channel has a longitudinal second central axis H. When the patient table 200 is fully engaged with the MRI device 100, the transmission channel is aligned with the scanning channel and thus the second central axis H is aligned with the first central axis M, that is, the second central axis H is in a straight line with the first central axis M. The transmission channel also has a head port and a foot port that are oppositely positioned along the second central axis H to allow the patient's head and foot to pass through, respectively. Therefore, when the patient is scanned using the MRI system, a portion of the patient's body is accommodated in the transmission channel, and another portion of the patient's body is accommodated in the scanning channel.

[0043] Optionally, you can refer again to Figure 1 The upper shielding component 250 includes an arched body, which includes a first transparent layer 252, a second shielding layer 254, and a second transparent layer 256 arranged in sequence from the inside to the outside in the radial direction, that is, they are laminated together. The first transparent layer 252 and the second transparent layer 256 are made of an insulating material, such as glass or other transparent or translucent materials. The second shielding layer 254 is similar to or the same as the first shielding layer 132, that is, it can be made of a wire mesh or woven conductive material, so that the patient lying on the bed board 210 can be visually observed through the arched body of the upper shielding component 250. Optionally, the conductive material itself is also transparent or translucent. The second shielding layer 254 includes a third end 258 and a fourth end 260 that are oppositely positioned along the second central axis H and are both arched, wherein the third end 258 is close to the head port and the fourth end 260 is close to the foot port. The third end 258 extends or is exposed from between the first transparent layer 252 and the second transparent layer 256 so as to be able to be in conductive contact with the second rubber sleeve portion 140B of the anti-collision assembly after the MRI apparatus 100 is aligned with the patient table 200. The fourth end 260 may not extend or be exposed from between the first transparent layer 252 and the second transparent layer 256. In addition, the second shielding layer 254 further includes two side edges extending or being exposed from between the first transparent layer 252 and the second transparent layer 256 along two longitudinal edges of the arched body.

[0044] Alternatively, if the diameter of the arched body is designed to be smaller than the diameter of the second rubber sleeve part 140B due to the need, that is, the third end 258 cannot be matched with the second rubber sleeve part 140B and conductively contacted, the upper shielding component 250 can also include an upper conductive segment 257 made of a metal material, the upper conductive segment 257 extends from the arched body along the second central axis H and gradually expands radially to be able to match or align with the second rubber sleeve part 140B. For example, the upper conductive segment 257 includes an upper conductive flange 257A, and the upper conductive flange 257A is configured to be in conductive contact with the corresponding upper portion of the second rubber sleeve part 140B. Since the upper conductive segment 257 is already conductively connected to the third end 258 of the second shielding layer 254 when it is installed to the arched body, and the radial thickness of the upper conductive flange 257A is significantly greater than the radial thickness of the second shielding layer 254, the upper conductive segment 257 helps to achieve conductive contact between the upper shielding component 250 and the anti-collision component.

[0045] Optionally, refer to Figure 4 and Figure 5 A reinforcing member 233 is also provided on the outer contour of the arch body to strengthen the strength of the arch body. The reinforcing member 233 is made of metal material and can be integrally formed with the upper conductive section 257 to further ensure the electromagnetic shielding effect of the upper shielding component 250.

[0046] Optionally, the lower shielding component 230 is fixed on the support frame 220 and includes a conveying plate 232. For example, via a common electric conveying mechanism, the bed board 210 is movably connected above the conveying plate 232 relative to the conveying plate 232, so that the bed board 210 can move longitudinally relative to the conveying plate 232 via the electric control board 212 to move the patient's body to a suitable position in the scanning channel.

[0047] For example, the transmission plate 232 can be made of insulating material, and the insulating material can be engineering plastics to achieve magnetic field compatibility, and the insulating material has high strength and light weight. As a supplement or replacement for the insulating material, a more suitable material with magnetic resonance compatibility can also be used, such as a non-magnetic material or a material without crystal water.

[0048] In order to realize the magnetic shielding effect of the lower shielding member 230, at least a portion of the transmission plate 232 is plated with a suitable metal material (to form a plating layer that is not easy to fall off), coated with a conductive coating layer, or coated with a sheet-like conductive coating member. In the following, the plating layer, the conductive coating layer or the conductive coating member are collectively referred to as the third shielding layer 235 (refer to Figure 1 For example, the third shielding layer 235 is plated, coated, or covered on the lower surface of the transmission plate 232 and the side surface between the upper surface and the lower surface of the transmission plate 232. Due to the skin effect, the current flows only on the conductive surface of the lower shielding member 230, such as metal, and does not affect the magnetic field compatibility of the transmission plate 232.

[0049] Optionally, refer to Figure 6 , a conductive gasket 236 is provided on the edge 232A of the upper surface of the transfer plate 232. The conductive gasket 236 is conductively connected to the third shielding layer 235, and the width of the conductive gasket 236 is significantly greater than the radial thickness of the two side edges of the second shielding layer 254. When the upper shielding component 250 is placed above the lower shielding component 230, the two side edges of the second shielding layer 254 are in conductive contact with the edge 232A of the upper surface of the transfer plate 232. Here, the conductive gasket 236 helps to achieve conductive contact between the second shielding layer 254 and the third shielding layer 235. The conductive gasket 236 is also elastic, so as to play a buffering role when the upper shielding component 250 is placed on the lower shielding component 230 to avoid collision damage. The patient table 200 with the upper shielding component 250 removed can be used as an ordinary patient bed.

[0050] Most of the transmission plate 232 is generally flat, but the transmission plate 232 includes a lower end section 259, which protrudes along the second central axis H and gradually deforms radially to be able to cooperate or align with the corresponding lower portion of the annular second rubber sleeve portion 140B. The lower end section 259 is provided with a lower conductive flange 259A for conductively contacting the corresponding lower portion of the second rubber sleeve portion 140B. For example, the lower conductive flange 259A is conductively connected to the third shielding layer 235, and the radial thickness of the lower conductive flange 259A can be greater than the thickness of the third shielding layer 235, which helps to achieve conductive contact between the lower shielding component 230 and the anti-collision component. When the upper shielding component 250 is placed above the lower shielding component 230, the second shielding layer 254 and the third shielding layer 235 are conductively contacted to form the second section of the cutoff waveguide described above, and the transmission channel is contained in the second section of the cutoff waveguide. When the patient table 200 is completely joined with the MRI device 100, the arched body or the upper conductive section 257 and the lower end section 259 are assembled into a trumpet-shaped transition section, which, together with the anti-collision component, transitions the first section of the cutoff waveguide formed by the first shielding layer 132 to the second section of the cutoff waveguide formed by the second shielding layer 254 and the third shielding layer 235. Thus, the first shielding device and the second shielding device together form a complete cutoff waveguide.

[0051] It is known that for a cutoff waveguide, the following formula exists:

[0052] f c =c / 3.412r

[0053] Among them, f c is the cutoff frequency, higher than f c Frequencies below f can propagate freely through the cutoff waveguide, while frequencies below f c The frequency will be cut off by the cutoff waveguide when it passes through the cutoff waveguide; c is the speed of light 299792458m / s; r is the radius of the cutoff waveguide.

[0054] In order to effectively cut off below f c For frequencies of 100 MHz to 200 MHz, the length of the cutoff waveguide should be at least four times the diameter of the cutoff waveguide.

[0055] In one embodiment of the present invention, the exemplary MRI system is a 0.5T MRI system, or even an MRI system less than 0.35T. The effective length of the cutoff waveguide formed by the first shielding device of the MRI device 100 of the exemplary MRI system and the second shielding device of the patient table 200 is in the range of 2000mm-2500mm, preferably 2300mm. Among them, the effective length of the first segment of the cutoff waveguide formed by the first shielding device is based on the distance from the ISO center (optimal imaging area) to the patient port of the scanning channel, that is, it is about half of the longitudinal length of the first shielding device. The diameter of the cylindrical first shielding layer 132 of the exemplary MRI device 100 is in the range of 500mm-700mm, preferably 600mm, and the effective diameter of the cutoff waveguide is about 60%-70% of the diameter of the first shielding layer 132, for example, in the range of 300mm-490mm, preferably 420mm. Therefore, in the embodiment of the present invention, the effective length of the cutoff waveguide is greater than four times the effective diameter of the cutoff waveguide, and the cutoff waveguide can effectively cut off frequencies below about 400MHz.

[0056] The cutoff waveguide composed of the first shielding device and the second shielding device of the exemplary MRI system can effectively cut off the natural electromagnetic signals in the external environment from interfering with the MRI device 100, or the electromagnetic signals generated by other nearby precision instruments from interfering with the RF signals emitted by the RF coil device 160 of the MRI device 100. For example, the RF coil device 160 emits an RF signal of a first frequency, and the cutoff waveguide can cut off the radio frequency signal lower than the second frequency (as mentioned above, about 400 MHz), and the second frequency is significantly greater than the first frequency.

[0057] Therefore, there is no need to set an RF shielding end cover for the foot port of the transmission channel, that is, one end of the second shielding device is open and there is no end cover similar to a shielding door. This not only simplifies the structure and facilitates wiring, but also provides patients with a non-closed scanning environment, giving patients a better treatment experience.

[0058] It should be noted that when the exemplary MRI system is a high field strength (field strength greater than 0.5T, such as 1.0T) MRI system, in order to ensure that the MRI device operates in an optimal state, a shielding end cover can be provided at the foot port of the transmission channel. The shielding end cover can openably close the foot port, and when the shielding end cover closes the foot port, the shielding end cover is in conductive contact with the second shielding layer and selectively in conductive contact with the conductive pad. It is understood that when the foot port is closed, the wiring of the lower shielding component 230 accessed from the outside of the patient table 200 will be completed using an additional filter.

[0059] Optionally, when the support frame 220 is made of a metal material, an insulating member 237 may be sandwiched between the support frame 220 and the third shielding layer 235 (see Figure 1 ) to prevent the support frame 220 from affecting the electromagnetic shielding function of the second shielding device.

[0060] Although some specific embodiments of the present invention have been described in detail by way of example, it will be appreciated by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present invention. It will be appreciated by those skilled in the art that the above embodiments may be modified without departing from the scope and spirit of the present invention. The scope of the present invention is defined by the appended claims.

Claims

1. A magnetic resonance imaging system, comprising: A magnetic resonance imaging apparatus defining a first central axis and comprising: Cylindrical gradient coil device, a radio frequency coil arrangement coaxially disposed about and adjacent to an inner diameter surface of the gradient coil arrangement, the radio frequency coil arrangement being configured to transmit a radio frequency signal at a first frequency, and a first shielding arrangement comprising a first shielding layer circumferentially arranged between the gradient coil arrangement and the radio frequency coil arrangement; and A patient table detachable from or attachable to a magnetic resonance imaging device, comprising: a bed frame configured for a patient to lie on, and a second shielding device disposed around at least a portion of the bed board; When the magnetic resonance imaging device is engaged with the patient table, the first shielding device is in conductive contact with the second shielding device to form a cutoff waveguide surrounding the bed board, and the cutoff waveguide can cut off radio frequency signals lower than a second frequency, and the second frequency is greater than the first frequency. The signals carried by the electrical circuits and / or data transmission circuits connected to the gradient coil device from outside the magnetic resonance imaging device do not need to be filtered, and The first shielding layer includes a first end and a second end which are oppositely positioned along the first central axis and are both annular, and the first end and the second end both extend out or are exposed between the gradient coil device and the radio frequency coil device. The magnetic resonance imaging device is movable, and the first shielding device further comprises an anti-collision component conductively connected to the first end, the anti-collision component being configured to control the magnetic resonance imaging device to stop moving and conductively contact with the second shielding device when the magnetic resonance imaging device is moved to engage with the patient table. wherein the anti-collision assembly comprises an elastic anti-collision ring and a conductive rubber sleeve, the conductive rubber sleeve comprises a first rubber sleeve portion and a second rubber sleeve portion which are sleeved on two opposite ends of the anti-collision ring along a first central axis, wherein when the magnetic resonance imaging device is disengaged from the patient table, the first rubber sleeve portion and the second rubber sleeve portion are not in conductive contact, and wherein when the magnetic resonance imaging device is engaged with the patient table, the anti-collision ring is compressed and the first rubber sleeve portion and the second rubber sleeve portion are in conductive contact, and The filter is conductively connected to the second end, and the electrical line and / or data transmission line outside the first shielding layer is connected to the radio frequency coil device via the filter.

2. The magnetic resonance imaging system according to claim 1, wherein: The magnetic resonance imaging device defines a cylindrical scanning channel at the center, the scanning channel includes a service port remote from the patient table when the magnetic resonance imaging device is engaged with the patient table, and wherein the first shielding device also includes a shielding door configured to openably close the service port, and when the shielding door closes the service port, the shielding door is in conductive contact with the first shielding layer.

3. The magnetic resonance imaging system according to claim 1, wherein: The second shielding device defines a transmission channel around the at least a portion of the bed board, wherein the transmission channel includes a foot port configured for a patient's foot to pass through, and the foot port is open.

4. The magnetic resonance imaging system according to claim 1, wherein: The second shielding device includes a lower shielding member and an upper shielding member separable from the lower shielding member, and when the upper shielding member is placed over the lower shielding member, the upper shielding member is in conductive contact with the lower shielding member.

5. The magnetic resonance imaging system according to claim 4, wherein: The upper shielding component includes an arched body, which includes a first transparent layer, a second shielding layer, and a third transparent layer that are laminated, wherein the first transparent layer and the third transparent layer are insulating, and the second shielding layer is conductive and made of a wire mesh-like conductive material so that the arched body is transparent or translucent.

6. The magnetic resonance imaging system according to claim 5, wherein: The upper shielding member further includes an upper conductive section extending longitudinally from the arcuate body and radially expanding to be aligned with the first shielding device, the upper conductive section including an upper conductive flange configured to be in conductive contact with the first shielding device.

7. The magnetic resonance imaging system according to claim 4, wherein: The lower shielding component includes a conveying plate, and the bed plate is movably connected to the top of the conveying plate relative to the conveying plate. An elastic conductive gasket is provided on the edge of the upper surface of the conveying plate. When the upper shielding component is placed above the lower shielding component, the upper shielding component and the lower shielding component are in conductive contact via the conductive gasket.

8. The magnetic resonance imaging system according to claim 7, wherein: The transfer plate comprises a lower end section extending longitudinally and radially deformed to be aligned with the first shielding device, and a lower conductive flange configured to be in conductive contact with the first shielding device is disposed on the lower end section.

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