Periodic structures and magnetic resonance imaging devices

Abstract

This invention improves receiver gain. The periodic structure of this embodiment includes a cylindrical conductor layer and a cylindrical laminate. The laminate is disposed on the inner periphery of the conductor layer and has multiple frequency selection plates stacked on it, the frequency selection plates having multiple elements periodically arranged thereon. At least a portion of the edge of each element opposite to an adjacent element within the layer is formed to face towards the center of the element.

Description

[0001] Cross-reference to related applications

[0002] This application is based on and claims priority to Japanese Patent Application No. 2021-076424, filed on April 28, 2021, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The embodiments described herein typically relate to periodic structures and magnetic resonance imaging devices. Background Technology

[0004] In existing magnetic resonance imaging (MRI) devices, insufficient receiving gain is encountered when attempting to receive MR (Magnetic Resonance) signals from a subject via a whole-body coil, which serves as the transceiver coil. One reason for this insufficient gain is the phase reversal of the signal reflected from the RF shield located around the periphery of the whole-body coil. This phase reversal cancels out the MR signal directly received from the subject via the receiving coil, resulting in a decrease in gain.

[0005] Therefore, a receiving coil needs to be installed on the subject. However, for engineers, setting up the receiving coil on the subject and connecting the cable to it is cumbersome and inefficient from a workflow perspective. Furthermore, having a receiving coil installed is uncomfortable for the patient, so ideally, it would be desirable to avoid using a receiving coil altogether.

[0006] Existing technical documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2009-183472

[0008] Patent Document 2: Japanese Patent Application Publication No. 1-242052 Summary of the Invention

[0009] The problem that the invention will solve

[0010] One of the problems to be solved by the embodiments disclosed in this specification and accompanying drawings is to improve receiver gain. However, the problems to be solved by the embodiments disclosed in this specification and accompanying drawings are not limited to the above-mentioned problems. The problems corresponding to the effects of the various configurations shown in the embodiments described later can also be identified as other problems.

[0011] The periodic structure of this embodiment includes a cylindrical conductor layer and a cylindrical laminate. The laminate is disposed on the inner periphery of the conductor layer and has multiple frequency selection plates stacked on it, the frequency selection plates having multiple elements periodically arranged thereon. At least a portion of the edge of each element that faces an adjacent element within the layer is formed to face towards the center of the element.

[0012] Invention Effects

[0013] The purpose of the invention is to improve the receiving gain. Attached Figure Description

[0014] Figure 1 This is a schematic diagram showing an MRI device including the periodic structure of this embodiment.

[0015] Figure 2 This is a perspective view showing the details of the periodic structure in this embodiment.

[0016] Figure 3 This is a cross-sectional view along the z-axis of the MRI apparatus gantry of this embodiment.

[0017] Figure 4 This is a cross-sectional view along the x-axis of the MRI apparatus gantry of this embodiment.

[0018] Figure 5 This is a schematic diagram illustrating an example of a design method for the elements of the laminated body in this embodiment.

[0019] Figure 6 This is a diagram showing a first example of the shape of the element in this embodiment.

[0020] Figure 7 This is a diagram showing a stack having the element shape of the first example of this embodiment.

[0021] Figure 8 This is a diagram showing a second example of the shape of the components in this embodiment.

[0022] Figure 9 This is a diagram showing a stack having the element shape of the second example of this embodiment.

[0023] Figure 10 This diagram illustrates an example of a laminate formed by combining the element shapes of the first and second examples of this embodiment.

[0024] Figure 11 This is a diagram showing the first example of a modified component configuration.

[0025] Figure 12 This is a diagram showing the second example of the component configuration in the modified example.

[0026] Figure 13 This is a diagram showing the third example of the component configuration in the modified example.

[0027] Figure 14 This is a diagram showing the fourth example of the component configuration in a modified example.

[0028] Figure 15 This is a diagram of the fifth example of a modified component configuration.

[0029] Figure 16 This is a diagram showing an example of the case where the components 1401 are arranged at an angle.

[0030] Figure 17 This is a diagram showing an example of the case where the components 1501 are arranged at an angle.

[0031] Explanation of reference numerals in the attached figures

[0032] 1 MRI device

[0033] 20-period structure

[0034] Components 31, 32, 51, 61, 71, 81, 91, 1101, 1401, 1501

[0035] 62 Offset section

[0036] 82, 83 sides

[0037] 101 Static magnetic field magnet

[0038] 103 Inclined magnetic field coil

[0039] 105 Inclined Magnetic Field Power Supply

[0040] 107 Examination Beds

[0041] 109 Examination Bed Control Circuit

[0042] 111 holes (bore)

[0043] 113 Transceiver Coil

[0044] 115 Transmitting Circuit

[0045] 119 Receiver Circuit

[0046] 121 Sequence Control Circuit

[0047] 123 bus

[0048] 125 interface

[0049] 127 monitor

[0050] 129 Storage devices

[0051] 131 Processing Circuit

[0052] 150 racks

[0053] 201 Conductor Layer

[0054] 202 Layered Body

[0055] 202-1 First Floor

[0056] 202-2 Second Floor

[0057] 1071 Top Plate

[0058] 1311 System Control Functions

[0059] 1313 Image generation function Detailed Implementation

[0060] Hereinafter, the periodic structure and magnetic resonance imaging apparatus (hereinafter referred to as MRI apparatus) of this embodiment will be described with reference to the accompanying drawings. In the following embodiments, parts marked with the same reference numerals as those in the accompanying drawings will be considered as parts that perform the same operations, and repeated descriptions will be omitted as appropriate.

[0061] Figure 1 This is a schematic diagram showing an MRI device including the periodic structure of this embodiment.

[0062] like Figure 1 As shown, the MRI apparatus 1 includes a periodic structure 20, a static magnetic field magnet 101, a tilted magnetic field coil 103, a tilted magnetic field power supply 105, an examination table 107, an examination table control circuit 109, a transceiver coil 113, a transmitting circuit 115, a receiving circuit 119, a sequence control circuit 121, a bus 123, an interface 125, a display 127, a storage device 129, and a processing circuit 131. The processing circuit 131 has system control functions 1311 and image generation functions 1313. The static magnetic field magnet 101, the tilted magnetic field coil, the periodic structure 20, and the transceiver coil 113 are arranged within a gantry 150. Alternatively, the MRI apparatus 1 may have a hollow cylindrical shimming coil between the static magnetic field magnet 101 and the tilted magnetic field coil 103.

[0063] The static magnetic field magnet 101 is a magnet formed in a hollow, generally cylindrical shape. However, the static magnetic field magnet 101 is not limited to a generally cylindrical shape and can also be configured in an open shape. The static magnetic field magnet 101 generates a uniform static magnetic field within its internal space. In this embodiment, the static magnetic field magnet 101 is assumed to be a superconducting magnet using a superconducting coil.

[0064] The tilted magnetic field coil 103 is a coil formed into a hollow cylindrical shape. The tilted magnetic field coil 103 is disposed inside the static magnetic field magnet 101. The tilted magnetic field coil 103 is formed by combining three coils corresponding to mutually orthogonal X, Y, and Z axes. The Z-axis direction is set to be the same as the direction of the static magnetic field. Furthermore, the Y-axis direction is set to be vertical, and the X-axis direction is set to be perpendicular to both the Z and Y axes. The three coils in the tilted magnetic field coil 103 receive current individually from the tilted magnetic field power supply 105, and generate a tilted magnetic field with magnetic field strength varying along the X, Y, and Z axes.

[0065] The tilted magnetic fields along the X, Y, and Z axes generated by the tilted magnetic field coil 103 form, for example, a tilted magnetic field for frequency encoding (also called a readout tilted magnetic field), a tilted magnetic field for phase encoding, and a tilted magnetic field for slice selection. The tilted magnetic field for frequency encoding is used to vary the frequency of the MR signal emitted from the subject P according to its spatial position. The tilted magnetic field for phase encoding is used to vary the phase of the MR signal according to its spatial position. The tilted magnetic field for slice selection is used to determine the imaging profile.

[0066] The tilted magnetic field power supply 105 is a power supply device that supplies current to the tilted magnetic field coil 103 under the control of the sequence control circuit 121.

[0067] The examination table 107 is a device having a top plate 1071 on which the subject P is placed. Under the control of the examination table control circuit 109, the top plate 1071 on which the subject P is placed is inserted into the insertion hole 111. The examination table 107 is, for example, arranged in the examination chamber where the MRI device 1 is located, with its long side parallel to the central axis of the static magnetic field magnet 101.

[0068] The examination bed control circuit 109 is a circuit that controls the examination bed 107. It drives the examination bed 107 by means of instructions from the operator via the interface 125, thereby causing the top plate 1071 to move along the long side and in the vertical direction.

[0069] Transceiver coil 113 is an RF coil, such as a whole-body coil, disposed inside tilted magnetic field coil 103. Transceiver coil 113 receives RF (Radio Frequency) pulses from transmitting circuit 115 and generates a transmitted RF wave equivalent to a high-frequency magnetic field. Transceiver coil 113 receives the MR signal emitted from subject P through the high-frequency magnetic field and outputs the received MR signal to receiving circuit 119.

[0070] A periodic structure 20 is positioned between the transceiver coil 113 and the tilted magnetic field coil 103 to improve the receiving gain of the MR signal. (Refer to...) Figure 2 The periodic structure 20 will be described later.

[0071] The transmitting circuit 115 supplies RF pulses corresponding to the Ramor frequency to the transceiver coil 113 under the control of the sequence control circuit 121.

[0072] The receiving circuit 119, under the control of the sequence control circuit 121, generates a digital MR signal as digitized complex data based on the MR signal output from the transceiver coil 113. Specifically, after performing various signal processing operations on the MR signal, the receiving circuit 119 performs analog-to-digital (A / D) conversion on the processed data. The receiving circuit 119 samples the A / D converted data. Thus, the receiving circuit 119 generates a digital MR signal (hereinafter referred to as MR data). The receiving circuit 119 outputs the generated MR data to the sequence control circuit 121.

[0073] The sequence control circuit 121 controls the tilted magnetic field power supply 105, the transmitting circuit 115, and the receiving circuit 119, etc., according to the inspection protocol output from the processing circuit 131, to perform imaging of the subject P. The inspection protocol has various pulse sequences (also called imaging sequences) corresponding to the inspection. The inspection protocol defines: the magnitude of the current supplied to the tilted magnetic field coil 103 through the tilted magnetic field power supply 105, the timing of the current being supplied to the tilted magnetic field coil 103 through the tilted magnetic field power supply 105, the magnitude of the RF pulse supplied to the transceiver coil 113 through the transmitting circuit 115, the timing of the RF pulse supplied to the transceiver coil 113 through the transmitting circuit 115, and the timing of the MR signal being received by the transceiver coil 113, etc.

[0074] Bus 123 is a data transmission path between interface 125, display 127, storage device 129, and processing circuit 131. Various biosignal detectors, external storage devices, and various medical devices (modality) can be appropriately connected to bus 123 via a network or other means. For example, an electrocardiogram scanner (not shown) is connected to the bus as a biosignal detector.

[0075] Interface 125 has circuitry for receiving various instructions and information inputs from the operator. Interface 125 may include circuitry related to pointing devices such as a mouse or input devices such as a keyboard. However, the circuitry of interface 125 is not limited to circuitry related to physical operating components such as a mouse or keyboard. For example, interface 125 may also have electrical signal processing circuitry that receives electrical signals corresponding to input operations from external input devices located separately from the MRI apparatus 1 and outputs the received electrical signals to various circuits.

[0076] Under the control of the system control function 1311 in the processing circuit 131, the display 127 displays various magnetic resonance images (MR images) generated by the image generation function 1313, as well as various information related to imaging and image processing. The display 127 is, for example, a CRT display, a liquid crystal display, an organic EL display, an LED display, a plasma display, or any other display, monitor, or other display device known in the art.

[0077] Storage device 129 stores MR data filled in the k-space by the image generation function 1313 in processing circuit 131, image data generated by the image generation function 1313, etc. Storage device 129 stores imaging conditions including various inspection protocols and multiple imaging parameters that define the inspection protocols. Storage device 129 stores programs corresponding to various functions executed by processing circuit 131. Storage device 129 can be, for example, a semiconductor memory element such as RAM (Random Access Memory), flash memory, a hard disk drive, a solid state drive, or an optical disc. Furthermore, storage device 129 can also be a drive device for reading and writing various information between portable storage media such as CD-ROM drives, DVD drives, and flash memory.

[0078] The processing circuit 131 has a processor (not shown), ROM (Read-Only Memory), RAM and other memory as hardware resources, and controls the MRI device 1 in a unified manner.

[0079] The various functions of the processing circuit 131 are stored in the storage device 129 as programs executable by a computer. The processing circuit 131 is a processor that implements the functions corresponding to each program by reading the programs corresponding to these various functions from the storage device 129 and executing them. In other words, the processing circuit 131, having read the state of each program, has... Figure 1 The processing circuit 131 shown contains multiple functions, etc.

[0080] In addition, Figure 1 In this paper, the various functions described above are implemented by a single processing circuit 131. However, multiple independent processors can also be combined to form the processing circuit 131, and each processor can execute a program to implement the functions. In other words, the various functions described above can be configured as programs and executed by a single processing circuit, or a specific function can be installed in a dedicated, independent program execution circuit.

[0081] Additionally, the term "processor" as used in the above description refers to circuits such as CPU (Central Processing Unit), GPU (Graphics Processing Unit), or Application Specific Integrated Circuit (ASIC), programmable logic device (e.g., Simple Programmable Logic Device (SPLD), Complex Programmable Logic Device (CPLD), and Field Programmable Gate Array (FPGA)).

[0082] The processor performs various functions by reading and executing the program stored in the storage device 129. Alternatively, instead of storing the program in the storage device 129, the program can be directly programmed into the processor's circuitry. In this case, the processor performs the functions by reading and executing the program programmed into the circuitry. Furthermore, the examination bed control circuit 109, the transmitting circuit 115, the receiving circuit 119, the sequence control circuit 121, etc., are also similarly composed of the aforementioned electronic circuitry, such as the processor.

[0083] Processing circuit 131 controls MRI device 1 via system control function 1311. Specifically, processing circuit 131 reads the system control program stored in storage device 129 and expands it in memory, controlling each circuit of MRI device 1 according to the expanded system control program. For example, processing circuit 131 reads the examination protocol from storage device 129 based on the imaging conditions input by the operator via interface 125 through system control function 1311. Alternatively, processing circuit 131 may also generate an examination protocol based on the imaging conditions. Processing circuit 131 sends the examination protocol to sequence control circuit 121 to control the imaging of the subject P.

[0084] The processing circuit 131 is controlled by the system control function 1311 to apply excitation pulses and a tilted magnetic field according to the excitation pulse sequence. After executing the excitation pulse sequence, the processing circuit 131 collects the MR signal from the subject P according to the data collection sequence of the pulse sequence used for various data collection, and generates MR data. The system control function 1311 can have the same processing function as the sensor control unit 21.

[0085] Processing circuit 131 fills MR data along the reading direction of k-space based on the strength of the read tilted magnetic field using image generation function 1313. Processing circuit 131 generates an MR image by performing a Fourier transform on the MR data filled in k-space. For example, processing circuit 131 can generate an absolute value (magnitude) image from complex MR data. Furthermore, processing circuit 131 can generate a phase image using the real and imaginary data in complex MR data. Processing circuit 131 outputs MR images, including the absolute value image and the phase image, to display 127 and storage device 129.

[0086] Next, refer to Figures 2-4 The details of the periodic structure 20 are explained below.

[0087] Figure 2 It is a three-dimensional diagram of the 20 parts of the periodic structure. Figure 3 This is a cross-sectional view of the gantry 150 of the MRI device 1 along the z-axis. Figure 4 This is a cross-sectional view of the gantry 150 of the MRI device 1 along the x-axis.

[0088] The periodic structure 20 is the inner periphery of the tilted magnetic field coil 103 and is disposed on the outer periphery of the transceiver coil 113. The periodic structure 20 includes a conductor layer 201 and a laminate 202.

[0089] Conductor layer 201 is a cylindrical conductor disposed inside rack 150. Conductor layer 201 may be an RF shield that blocks RF signals and is housed in rack 150.

[0090] The stack 202 is a cylindrical structure disposed on the inner periphery of the conductor layer 201, and is a so-called metasurface formed by stacking multiple frequency selective surfaces (FSS) with periodically arranged elements. Each frequency selective surface forming the metasurface has elements formed of metallic conductors periodically arranged on a cylindrical flexible substrate, for example. By changing the shape and arrangement of the elements, the frequency, amplitude, and phase of the electromagnetic waves reflected from the conductor layer 201 can be selectively changed and controlled. That is, when the periodic structure 20 is mounted on the MRI device 1, the phase of the MR signal emitted from the subject P and reflected by the conductor layer 201 can be controlled.

[0091] In this embodiment, an example is shown where two layers are stacked: a first frequency selection board (hereinafter referred to as first layer 202-1) and a second frequency selection board (hereinafter referred to as second layer 202-2) disposed on the inner periphery of the first layer 202-1. However, this is not a limitation, and more than two layers may be stacked. Furthermore, materials such as dielectrics may be inserted between the substrates or the layers.

[0092] In the first layer 202-1 and the second layer 202-2, elements arranged periodically act as so-called patches. The element 31 arranged in the first layer 202-1 and the element 32 arranged in the second layer 202-2 are configured such that, when viewed from the central axis of the cylinder in the outer circumferential direction, they are arranged to... Figure 3 or Figure 4 The centers of the concentric circles facing outwards are different from each other. For example, a portion of element 31 formed in the first layer and a portion of element 32 formed in the second layer are arranged to overlap. More specifically, when viewed from the central axis of the cylinder in the outward direction, the center of element 32 formed in the second layer is arranged to overlap the gaps between the elements 31 that are periodically formed in the first layer.

[0093] Next, refer to Figure 5 The schematic diagram illustrates an example of the design method for the components of the laminate 202.

[0094] Figure 5 (a) shows the case where the first layer 202-1 and the second layer 202-2 forming the laminate 202 are stacked on a plane. When the arrangement of the elements 51 on the plane is designed based on the usage frequency of the application that will become the periodic structure 20 (hereinafter, also referred to as planar design), the size (area) and the interval of the periodic arrangement of each element 51 are determined according to the usage frequency of the application. The shape of the elements 51 in the planar design is assumed to be rectangular.

[0095] The operating frequency of the application object refers, for example, to the resonant frequency of the electromagnetic wave corresponding to the magnetic field strength used in the MRI device. Furthermore, the capacitive and inductive components of the laminate 202 in the planar design are calculated. Specifically, the capacitance C along the length of the laminate 202 is calculated. V And the capacitance C in the circumferential direction H and the inductance L along the length of the laminate 202 V and the inductance L in the circumferential direction H .

[0096] Next, as Figure 5As shown in (b), it is assumed that the stack 202 is formed into a cylindrical shape with a desired curvature. The desired curvature, for example, refers to the curvature of the cylinder within the gantry 150 of the MRI apparatus 1, positioned further inward than the inclined magnetic field coil 103 and forming the outer periphery of the transceiver coil 113. When the stack 202 is formed from a planar shape into a cylindrical shape in this way, the circumferential lengths of the layers are different. Specifically, compared to the planar design, the spacing of the elements does not change in the longitudinal direction of the stack 202, but in the circumferential direction of the stack 202, such as... Figure 5 As shown in (b1), the outermost layers have longer circumferences, thus increasing the spacing between elements 51. Therefore, it can be considered that... Figure 5 (b1) to Figure 5 The deformation shown in (b3). Additionally, in Figure 5 (b1) to Figure 5 (b3) will be explained using the first floor 202-1 as an example.

[0097] If the circumferential spacing increases, the capacitance C between the components in the circumferential direction will increase. H It becomes smaller. Therefore, as Figure 5 As shown in (b2), if the size of the components in the circumferential direction is increased to return the spacing between components in the circumferential direction to the planar design, then the inductance L in the length direction... V On the other hand, the circumferential inductance L decreases. H It increases. Furthermore, the capacitance C along the length direction... V It gets bigger.

[0098] Therefore, as Figure 5 As shown in (b3), by increasing the size of the component in the length direction while maintaining the size of the component in the circumferential direction, it is possible to increase the inductance L in the length direction. V The inductance L increases in size and in the circumferential direction. H Adjustments are made by reducing the value. This allows the inductance L to return to its original value in the planar design. V and inductor L H However, by increasing the side length and decreasing the component spacing, the capacitance component (C)... V And C H )Increase.

[0099] Therefore, when the laminate 202 is ultimately designed as a cylindrical shape, such as Figure 5 As shown in (c), offsets can be set in each component, and the area and shape of each component in the first layer 202-1 and the second layer 202-2 can be adjusted based on curvature. Thus, even when the laminate 202 is cylindrical, it is possible to design it to have approximately the same values ​​for inductance and capacitance as in a planar design.

[0100] More specifically, refer to Figure 6 The first example of the shape of the component will be explained.

[0101] Figure 6 Let 61 be an example of a first element. Element 61 is a conductor formed in a planar shape, and at least a portion of its edge opposite to other adjacent elements 61 within the layer is shaped to be more towards the center of the element than the other portions of that edge. In other words, the center of the element is the center point of element 61, and when viewed from the top surface, element 61 is formed such that at least the midpoint portion of each side is concave towards the center point of element 61. Furthermore, element 61 can also be described as having an offset portion 62 at the center of each side, derived from a rectangular (quadrilateral) shape. By adjusting the size d1 of the offset portion 62 of element 61, i.e., the size d1 of the notch in the length direction, and the depth d2 towards the center of the offset portion 62, the capacitance component (C) can be adjusted. V And C H Adjustments can be made. Thus, even when the laminate 202 is set to a cylindrical shape, it can be designed to have approximately the same capacitance value as in a planar design.

[0102] Next, refer to Figure 7 The laminate 202 having the element shape of the first example will be described.

[0103] Figure 7 This is a partial view of the stacked body 202. The horizontal direction is the circumferential direction, and the vertical direction is the length direction (z-axis direction) orthogonal to the circumferential direction.

[0104] Figure 7 The left figure shows the component configuration of layer 202-1. Component 61 of layer 202-1 is... Figure 6 The shapes shown are arranged periodically with prescribed gaps. Offset portions 62 (notches) are formed at the center of each side of element 61.

[0105] Figure 7 The central diagram shows the component configuration of the first layer 202-1. Component 71 of the second layer 202-2 is formed in the same manner as the components of the first layer 202-1.

[0106] Figure 7The right figure shows the state of the stacked body 202 formed by stacking the first layer 202-1 and the second layer 202-2 in a cylindrical shape. Thus, when viewed from the outer periphery along the central axis of the cylinder in the stacking direction of the first layer 202-1 and the second layer 202-2 (in other words, in the case of a cylindrical shape), the element 71 of the second layer 202-2 is arranged such that the center of element 71 is located in the gap of the group of elements 61 of the first layer 202-1. More specifically, the center of element 71 of the second layer 202-2 is located in a gap formed by being surrounded by four elements from the group of elements 61 of the first layer 202-1. Furthermore, this is not limited to... Figure 7 As shown in the right figure, the positional relationship allows for appropriate control of the phase of the operating frequency, and the component configuration of each layer can be any configuration.

[0107] in addition, Figure 7 The design process of the laminate 202 shown in the right figure can be achieved analytically through simulation, for example, based on the design values ​​of the capacitance and inductance components on the plane. Thus, when the laminate 202 is cylindrical, the same inductance and capacitance components as in the planar design can be designed, thereby obtaining the desired phase characteristics for electromagnetic waves. That is, the reflected signal obtained by the MR signal being reflected by the conductor layer can be adjusted to be in phase with the MR signal received through the direct transceiver coil 113, thereby improving the receiving gain of the MR signal received through the transceiver coil 113. Furthermore, the adjustment of the phase characteristics also has the same effect when transmitting RF signals, thus increasing the signal strength of the RF signal when transmitting RF signals from the transceiver coil 113.

[0108] exist Figure 5 The design sequence of components is described, but for ease of explanation of the changes in inductive and capacitive components caused by changes in component shape, the order is not limited to the above. For example, without planar design, the cylindrical laminate 202 can be periodically configured. Figure 6 The components of the shape shown are designed by analytically adjusting the spacing between components in the circumferential and length directions, the offset of the components by magnitude d1, and the depth d2 through simulation.

[0109] Next, refer to Figure 8 The second example of the shape of the component will be explained.

[0110] Figure 8This represents a component 81 in the second example. Component 81 is formed of a ring-shaped conductor, and the width (thickness) of the side 82 (the long side of the rectangle) parallel to the circumferential direction is formed to be wider (thicker) than the width (thickness) of the side 83 (here, the short side of the rectangle) parallel to the length direction (z-axis direction) of the laminate 202. Figure 8 In the example, the ring conductor is assumed to be rectangular (quadrilateral).

[0111] Furthermore, the edge 82, which is parallel to the circumferential direction, is offset towards the center of the component. This reduces the capacitance component C along the length direction. V At this point, even with an offset of edge 82, the inductance component (L) V and L H ) and circumferential capacitance C H It also remains unchanged. By adjusting the width d3 of side 82, it is possible to adjust only the circumferential inductance L. H Adjustments were made. As a result, the inductive and capacitive components could be easily adjusted.

[0112] Next, refer to Figure 9 The laminate 202 having the element shape of the second example will be described.

[0113] Figure 9 and Figure 7 Similarly, this is also a partial view of the stack 202, with the horizontal direction being the circumferential direction and the vertical direction being the length direction (z-axis direction) orthogonal to the circumferential direction.

[0114] Figure 9 The left image shows the configuration of component 81 in layer 202-1. Figure 9 The central diagram shows the configuration of component 91 in layer 202-2. Aside from the different component shapes, Figure 7 Left image and Figure 7 The central image can be configured the same way.

[0115] Figure 9 The right figure and Figure 7 Similarly, the right figure shows the state of the stacked body 202 formed by stacking the first layer 202-1 and the second layer 202-2 into a cylindrical shape. In the second example of the element shape, when viewed from the outer periphery direction from the stacking direction of the first layer 202-1 and the second layer 202-2, in other words, from the central axis of the cylinder in the case of a cylindrical shape, the element 91 of the second layer 202-2 is arranged such that the center of the element 91 is located in the gap of the group of elements 81 of the first layer 202-1.

[0116] Alternatively, it can be to Figure 7 and Figure 9 The stacked body 202 is composed of components arranged in various shapes. (Refer to...) Figure 10An example of a laminate 202 formed by combining the first and second examples of element shapes will be described.

[0117] Figure 10 This indicates that the first layer, 202-1, is... Figure 6 The first example of the component structure is shown, and the second layer 202-2 is... Figure 8 The component structure shown in the second example. Alternatively, conversely, the first layer 202-1 could also be... Figure 8 The component structure shown in the second example, and the second layer is Figure 6 The component structure shown in the first example.

[0118] When designing a frequency selection board for the operating frequency, it is possible to achieve this by pre-designing the component configuration in a stacked state with layers having different component structures. Figure 10 The laminate 202 shown has different component structures.

[0119] Furthermore, not limited to the shape of the components mentioned above, when the laminate 202 is set to a cylindrical shape, it can be any shape and periodic configuration as long as the values ​​of the inductance and reactance components are approximately the same as those in the planar design.

[0120] (Modified Example)

[0121] The above-mentioned component shapes, as well as the first example of component shape 61 and the second example of component shape 81, are all assumed to be based on rectangles, but are not limited to this. Other polygons such as hexagons and octagons can also be used as the basis, as well as circles, or even complex shapes such as arcs for a part of the component.

[0122] The first example of the component configuration of the variant is shown in Figure 11 Additionally, in Figure 11 In the variations shown below, for ease of explanation, the first layer 202-1 and the second layer 202-2 are not distinguished. However, when they are stacked, similar to the above-described embodiment, when viewed from the outer periphery direction from the central axis of the cylinder in the case of a cylindrical shape, the center of the element 71 of the second layer 202-2 is located at the gap of the element group of the first layer 202-1.

[0123] exist Figure 11The example shown illustrates an element 1101 formed from a conductor based on a hexagon. Element 1101 has a shape in which the central portion of each side opposite to other elements 1101 adjacent to it within the layer is offset. Element 1101 can also be formed by offsetting the central portion of each side of the hexagonal conductor; it can also be formed such that the central portion is offset relative to the central portion by providing protrusions at each vertex of the hexagonal conductor.

[0124] The capacitance and inductance components can be adjusted by modifying the size of the apex (or protrusion if a protrusion is included) and the size of the offset portion. Furthermore, here, the offset portion, or in other words, the notch, is trapezoidal, but it is not limited to this; it can also be... Figure 6 The rectangular notch shown.

[0125] Next, a second example of the component configuration of the modified example will be shown. Figure 12 .

[0126] exist Figure 11 In the first example of the component configuration shown, it indicates that the edge portion (offset portion) of component 1101 is configured so that it is parallel to the length direction. Figure 12 In the second example of the component configuration shown, it is shown that the edge portion of component 1101 is arranged in a manner that is parallel to the circumferential direction.

[0127] Furthermore, a third example of the component configuration of the modified example is shown in Figure 13 . Figure 13 This indicates a configuration where the arrangement direction of element 1101 is tilted. In this way, element 1101 can also be arranged arbitrarily.

[0128] Next, a fourth example of the component configuration of the modified example will be shown. Figure 14 .

[0129] Figure 14 This is a first variation of the second example of the element shape of the ring conductor, where the ring conductor 1401 represents a hexagonal ring conductor. Element 1401 is configured such that its sides are parallel to the length direction. In element 1401, even the side opposite to the element 1401 in the length direction, i.e., the side extending in the approximately circumferential direction, is formed to be thicker than the side parallel to the length direction.

[0130] Furthermore, the edge extending in the approximate circumferential direction is offset towards the center of the component. By adjusting the size (depth) of the offset portion, the capacitance component between adjacent components 1401 in the longitudinal direction can be adjusted. Moreover, by adjusting the line width, the inductive component in the circumferential direction can be adjusted. In addition, by adjusting the length of the edge parallel to the longitudinal direction, the capacitance component in the circumferential direction can be adjusted.

[0131] Next, the fifth example of the component configuration of the modified example will be shown. Figure 15 .

[0132] Figure 15 This is a second variation of the ring-shaped conductor, which is the second example of the component shape. Component 1501 is an example in which the edges are arranged parallel to the circumferential direction.

[0133] Even the edge opposite the adjacent element 1501 in the length direction, the width of the edge extending parallel to the circumferential direction is made thicker than the edge that is approximately parallel to the length direction. Furthermore, the edge extending parallel to the circumferential direction is offset towards the center of the element. By adjusting the size (depth) of the offset portion, the capacitance component between adjacent elements 1501 in the length direction can be adjusted. Moreover, by adjusting the line width, the inductive component in the circumferential direction can be adjusted. Furthermore, by adjusting the lengths of the two edges that are approximately parallel to the length direction, the capacitance component in the circumferential direction can be adjusted.

[0134] Alternatively, components 1401 and 1501 can be arranged in an oblique orientation.

[0135] The cases in which the components 1401 are arranged at an angle are shown respectively. Figure 16 The arrangement of components 1501 at an angle is shown in the figure. Figure 17 .

[0136] According to the embodiments shown above, a cylindrical periodic structure is formed, comprising a conductor layer serving as an RF shield and multiple frequency selection plates designed for the operating frequency stacked together. The elements of each frequency selection plate are formed such that at least a portion of the edge opposite to an adjacent element within the layer faces the center of the element. This allows for adjustment of the phase characteristics of the operating frequency. In particular, for example, by arranging the periodic structure on the outer periphery of the transceiver coil (whole-body coil) in an MRI device, the reflected signal of the MR signal reflected by the conductor layer can be adjusted to be in phase with the MR signal received directly by the transceiver coil, thus improving the reception gain of the MR signal received by the transceiver coil. This facilitates a workflow where an examination can be performed without placing a receiving coil on the subject P.

[0137] According to at least one embodiment described above, the receiving gain can be improved.

[0138] Several embodiments have been described, but these embodiments are merely illustrative and not intended to limit the scope of the invention. These embodiments can be implemented in various other ways, and various omissions, substitutions, modifications, and combinations of embodiments are possible without departing from the spirit of the invention. These embodiments, and their variations, are included in the scope and spirit of the invention, and likewise in the scope of the claims and their equivalents.

[0139] Regarding the above-described embodiments, as one aspect of the invention and as a selective feature, the following notes are disclosed.

[0140] (Postscript 1)

[0141] A periodic structure, wherein:

[0142] A cylindrical conductor layer; and

[0143] A cylindrical laminate is disposed on the inner periphery of the conductor layer, and multiple frequency selection plates are stacked thereon, the frequency selection plates having multiple elements periodically arranged thereon.

[0144] At least a portion of the edge of the element that is opposite to an adjacent element in the layer is formed to face the center of the element.

[0145] (Postscript 2)

[0146] Alternatively, the element may be a conductor formed in a planar shape, with at least a portion of the edge formed offset toward the center of the element.

[0147] (Note 3)

[0148] Alternatively, the element may be a polygonal conductor, with a portion of each side formed to be offset toward the center of the element.

[0149] (Postscript 4)

[0150] Alternatively, the element may be a ring-shaped conductor, with an edge parallel to the circumferential direction offset toward the center of the element, and the width of this edge is greater than the width of the edge orthogonal to the circumferential direction.

[0151] (Note 5)

[0152] Alternatively, the annular conductor may be polygonal.

[0153] (Note 6)

[0154] The polygon can also be a quadrilateral or a hexagon.

[0155] (Note 7)

[0156] Alternatively, the center of the component can be the center point of the component.

[0157] Furthermore, each edge is formed such that at least the midpoint portion of each edge is concave towards the center point.

[0158] (Postscript 8)

[0159] Alternatively, the element may be configured such that the inductive and capacitive components, based on the planar arrangement of the laminate designed according to the frequency used, are approximately the same values ​​as when the laminate is formed in a cylindrical shape.

[0160] (Note 9)

[0161] Alternatively, the element may be formed and configured such that its area is adjusted based on the curvature of the cylinder formed by the laminate, thereby becoming approximately the same value as the inductive and capacitive components configured on the plane.

[0162] (Postscript 10)

[0163] Alternatively, the plurality of elements may be configured such that, when viewed from the central axis of the cylinder formed by the laminate, a portion of an element formed in the first layer of the laminate overlaps with a portion of an element formed in the second layer of the laminate.

[0164] (Postscript 11)

[0165] Alternatively, the plurality of elements may be configured such that, when viewed from the central axis of the cylinder formed by the laminate, the center of an element formed in a second layer that is located on the inner periphery side of the second layer, which is positioned relative to the first layer of the laminate, is located in the gap between the elements in the first layer.

[0166] (Postscript 12)

[0167] Alternatively, the element formed in the first layer of the laminate may be a quadrilateral conductor, with a portion of each side formed offset toward the center of the element.

[0168] Alternatively, the element formed in the second layer of the laminate may be a rectangular ring conductor, with its side, which is parallel to the circumferential direction, offset toward the center of the element and is thicker than the side orthogonal to the circumferential direction.

[0169] (Postscript 13)

[0170] A magnetic resonance imaging device, comprising:

[0171] Inclined magnetic field coil;

[0172] A cylindrical conductor layer is disposed on the inner periphery of the tilted magnetic field coil;

[0173] The periodic structure described in any one of (Appendix 1) to (Appendix 12) is disposed on the inner periphery of the conductor layer; and

[0174] Transceiver coils are configured on the inner periphery of the periodic structure to transmit and receive RF signals.

[0175] (Postscript 14)

[0176] Alternatively, the element may be a quadrilateral conductor, with a notch formed on a portion of each side at the center of the element.

[0177] (Postscript 15)

[0178] Alternatively, the plurality of elements may be configured such that, when viewed from the central axis of the cylinder formed by the laminate, the centers of the elements formed in the second layer, which is located on the inner periphery side of the second layer, which is more inner than the first layer of the laminate, overlap with a gap formed by four elements in the element group formed in the first layer of the laminate.

[0179] (Toshiba Framework) Several embodiments are described, but these embodiments are provided as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention.

Claims

1. A periodic structure, wherein, have: A cylindrical conductor layer; and A cylindrical laminate is disposed on the inner periphery of the conductor layer, and multiple frequency selection plates are stacked thereon, the frequency selection plates having multiple elements periodically arranged thereon. The element has at least a portion of its edge opposite to an adjacent element within the layer formed in a concave shape toward the center of the element. The layers of the frequency selection plate are formed only by elements having the concave shape.

2. The periodic structure according to claim 1, wherein, The element is a conductor formed in a planar shape, and at least a portion of the edge is formed to be offset toward the center of the element.

3. The periodic structure according to claim 1, wherein, The element is a polygonal conductor, with a portion of each side formed offset toward the center of the element.

4. The periodic structure according to claim 1, wherein, The element is a ring-shaped conductor, and is formed with an edge parallel to the circumferential direction of the laminate offset toward the center of the element, and the width of the edge is greater than the width of the edge orthogonal to the circumferential direction of the laminate.

5. The periodic structure according to claim 4, wherein, The annular conductor is polygonal.

6. The periodic structure according to claim 3 or 5, wherein, The polygon is a quadrilateral or a hexagon.

7. The periodic structure according to any one of claims 1 to 5, wherein, The center of the component is the center point of the component. Furthermore, each edge is formed such that at least the midpoint portion of each edge is concave towards the center point.

8. The periodic structure according to any one of claims 1 to 5, wherein, The element is formed and configured such that the inductive and capacitive components, based on the planar arrangement of the laminate designed according to the frequency used, are approximately the same values ​​as when the laminate is formed in a cylindrical shape.

9. The periodic structure according to claim 8, wherein, The element is formed and configured such that its area is adjusted based on the curvature of the cylinder formed by the laminate, thereby becoming approximately the same value as the inductive and capacitive components configured on the plane.

10. The periodic structure according to any one of claims 1 to 5, wherein, The plurality of elements are configured such that, when viewed from the central axis of the cylinder formed by the laminate, a portion of an element formed in the first layer of the laminate overlaps with a portion of an element formed in the second layer of the laminate.

11. The periodic structure according to any one of claims 1 to 5, wherein, The plurality of elements are configured such that, when viewed from the central axis of the cylinder formed by the laminate, the center of an element formed in a second layer that is located on the inner periphery side of the second layer, which is disposed in a layer that is more inner than the first layer of the laminate, is located in the gap between the elements formed in the first layer.

12. The periodic structure according to any one of claims 1 to 5, wherein, The elements formed in the first layer of the laminate are quadrilateral conductors, and a portion of each side is offset toward the center of the element. The element formed in the second layer of the laminate is a rectangular ring conductor, and is formed such that the edge parallel to the circumferential direction of the laminate is offset toward the center of the element, and the thickness of the edge is thicker than the edge orthogonal to the circumferential direction of the laminate.

13. A magnetic resonance imaging device, wherein, have: Inclined magnetic field coil; A cylindrical conductor layer is disposed on the inner periphery of the tilted magnetic field coil; The periodic structure according to any one of claims 1 to 12 is disposed on the inner periphery of the conductor layer; as well as Transceiver coils are configured on the inner periphery of the periodic structure to transmit and receive RF signals.

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