JP2024008863A - Reception coil, magnetic resonance imaging device, and deformation dipole - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a gain of a reception coil by combining a loop coil with a reception element other than the loop coil.

SOLUTION: A reception coil includes a plurality of coil elements. At least one of the coil elements is configured by including a loop coil and a deformation dipole disposed inside the loop coil. The deformation dipole is configured by including a main dipole for supplying a high frequency signal to the outside, and a parasitic element that does not supply a high frequency signal to the outside, the parasitic element having a split ring with a gap in a part of the ring.

SELECTED DRAWING: Figure 4

COPYRIGHT: (C)2024,JPO&INPIT

Description

Embodiments disclosed herein and in the drawings relate to receive coils, magnetic resonance imaging devices, and modified dipoles.

A magnetic resonance imaging device excites the nuclear spins of a subject placed in a static magnetic field with a radio frequency (RF) signal at the Larmor frequency, and generates a magnetic resonance signal (MR) generated from the subject as a result of the excitation. This is an imaging device that generates an image by reconstructing the resonance signal.

Many magnetic resonance imaging (MRI) devices have a configuration called a gantry, and a cylindrical space (this space is called a bore) is formed in the gantry. An image of a subject (for example, a patient) lying on a tabletop is carried out into a cylindrical space. Inside the gantry, a cylindrical static magnetic field magnet, a cylindrical gradient magnetic field coil, and a cylindrical transmitting/receiving coil (ie, WB (Whole Body) coil) are housed.

When an RF pulse is transmitted from the transmitting/receiving coil toward the subject, a magnetic resonance signal is emitted from the subject due to the excitation of hydrogen nuclei within the subject. On the other hand, a receiving coil for receiving magnetic resonance signals is placed in a position close to the subject, for example, close to the chest, head, lower limbs, etc. of the subject.

Many receiving coils for receiving magnetic resonance signals are configured as a so-called array coil, and the array coil has a plurality of loop coils arranged in an array.

In order to increase the gain of the receiving coil, the number of loop coils included in the receiving coil may be increased. On the other hand, the dimensions of the receiving coil cannot be made that large because they are limited by the size of the subject. For this reason, if an attempt is made to increase the number of loop coils included in a receiving coil under limited dimensions, the diameter of each loop coil becomes smaller.

However, as the diameter of the loop coil becomes smaller, the strength of the magnetic field generated from the loop coil becomes weaker. For this reason, even if the coil diameter is made smaller and the number of loop coils is increased, there is a limit to improving the gain of the receiving coil.

Special Publication No. 2017-530825

One of the problems to be solved by the embodiments disclosed in this specification and the drawings is to improve the gain of the receiving coil by combining a loop coil and a receiving element other than the loop coil. However, the problems to be solved by the embodiments disclosed in this specification and the drawings are not limited to the above problems. Issues corresponding to each effect of each configuration shown in the embodiments described later can also be positioned as other issues.

The receiving coil of one embodiment is a receiving coil comprising a plurality of coil elements, at least one of the coil elements comprising a loop coil and a deformed dipole disposed inside the loop coil, The modified dipole includes a main dipole that feeds the received high-frequency signal to the outside, and a parasitic element that does not feed the high-frequency signal to the outside and has a split ring with a gap in a part of the ring. configured.

FIG. 1 is a block diagram showing the overall configuration of a magnetic resonance imaging apparatus including a receiving coil according to an embodiment. FIG. 3 is a diagram showing an example of arrangement of receiving coils according to the embodiment. FIG. 2 is a diagram showing a configuration example of a receiving coil 20. FIG. FIG. 3 is a diagram illustrating a configuration example of a modified dipole according to the first embodiment. FIG. 3 is a diagram showing an equivalent circuit of the modified dipole according to the first embodiment. The 1st figure showing the example of composition of the modification dipole of the 1st modification of a 1st embodiment. FIG. 3 is a second diagram illustrating a configuration example of a modified dipole according to a first modified example of the first embodiment. The 1st figure showing the example of composition of the modified dipole of the 2nd modification of a 1st embodiment. FIG. 3 is a second diagram showing a configuration example of a modified dipole according to a second modified example of the first embodiment. The first diagram showing a modification when the main dipole and parasitic elements are formed into plate shapes. The second diagram showing a modification when the main dipole and parasitic elements are formed into plate shapes. FIG. 7 is a diagram illustrating an example of the configuration of a modified dipole according to the second embodiment. FIG. 7 is a diagram showing an equivalent circuit of a modified dipole according to the second embodiment. FIG. 6 is a diagram illustrating a configuration example in which a modified dipole according to the second embodiment is generated on a substrate. FIG. 7 is a diagram showing a configuration example of a modified dipole according to a first modified example of the second embodiment. The figure which shows the example of a structure of the modified dipole based on the 2nd modification of 2nd Embodiment. FIG. 7 is a diagram illustrating a configuration example of a modified dipole according to a third modification of the second embodiment. The first diagram showing a configuration example of a coil element that combines a modified dipole and a loop coil. The second diagram showing a configuration example of a coil element that combines a modified dipole and a loop coil. The figure which shows the example of a structure of the receiving coil based on the 1st modification. The figure which shows the example of a structure of the receiving coil based on the 2nd modification. The figure which shows the example of a structure of the receiving coil based on the 3rd modification. The figure which shows the example of a structure of the receiving coil based on the 4th modification. FIG. 7 is a diagram illustrating a configuration example of a receiving coil according to a fifth modification. FIG. 7 is a diagram illustrating a configuration example of a receiving coil according to a sixth modification.

Embodiments of the present invention will be described below based on the accompanying drawings.

(Magnetic resonance imaging device)
FIG. 1 is a block diagram showing the overall configuration of a magnetic resonance imaging apparatus 1 including a receiving coil 20 according to an embodiment. The magnetic resonance imaging apparatus 1 includes a magnet mount 100, a control cabinet 300, a console 400, a bed 500, and the like.

The magnet mount 100 includes a static magnetic field magnet 10, a gradient magnetic field coil 11, a WB (Whole Body) coil 12, and the like, and these components are housed in a cylindrical housing. The bed 500 has a bed main body 50 and a top plate 51. The magnetic resonance imaging apparatus 1 also includes a receiving coil 20 disposed close to the subject.

The control cabinet 300 includes a gradient magnetic field power supply 31 (X-axis 31x, Y-axis 31y, Z-axis 31z), an RF receiver 32, an RF transmitter 33, and a sequence controller 34.

The static magnetic field magnet 10 of the magnet mount 100 has a generally cylindrical shape, and generates a static magnetic field within the bore (i.e., the space inside the cylinder of the static magnetic field magnet 10), which is the imaging area of the subject (for example, a patient). let The static field magnet 10 has a built-in superconducting coil, and the superconducting coil is cooled to an extremely low temperature by liquid helium. The static magnetic field magnet 10 generates a static magnetic field by applying a current supplied from a static magnetic field power supply (not shown) to the superconducting coil in the excitation mode, and then, when it shifts to the persistent current mode, the static magnetic field power supply (not shown) generates a static magnetic field. is separated. Once in the persistent current mode, the static magnetic field magnet 10 continues to generate a large static magnetic field for a long time, for example over a year. Note that the static magnetic field magnet 10 may be configured as a permanent magnet.

The gradient magnetic field coil 11 also has a generally cylindrical shape and is fixed inside the static magnetic field magnet 10. The gradient magnetic field coil 11 applies gradient magnetic fields to the subject in the X-axis, Y-axis, and Z-axis directions using currents supplied from gradient magnetic field power supplies (31x, 31y, 31z).

The bed main body 50 of the bed 500 can move the top plate 51 in the vertical direction, and moves the subject placed on the top plate 51 to a predetermined height before imaging. Thereafter, when photographing, the top plate 51 is moved horizontally to move the subject into the bore.

The WB coil 12 is fixed in a generally cylindrical shape inside the gradient magnetic field coil 11 so as to surround the subject. The WB coil 12 transmits RF pulses transmitted from the RF transmitter 33 toward the subject, and receives magnetic resonance signals emitted from the subject due to excitation of hydrogen nuclei.

The receiving coil 20 is an RF coil that receives magnetic resonance signals emitted from the subject at a position close to the subject. The receiving coil 20 is composed of, for example, a plurality of coil elements 200 (see FIG. 3, etc.). There are various types of receiving coils 20, such as those for the head, thorax, spine, lower limbs, or whole body, depending on the part of the subject to be imaged. In FIG. 1, the receiving coil 20 for the thorax is shown as an example. ing.

The RF transmitter 33 transmits RF pulses to the WB coil 12 based on instructions from the sequence controller 34. On the other hand, the RF receiver 32 detects the magnetic resonance signals received by the WB coil 12 and the receiving coil 20, digitizes the detected magnetic resonance signals, and sends raw data obtained by digitizing the detected magnetic resonance signals to the sequence controller 34.

The sequence controller 34 scans the object by driving the gradient magnetic field power supply 31, the RF transmitter 33, and the RF receiver 32, respectively, under the control of the console 400. Then, upon scanning and receiving raw data from the RF receiver 32, the sequence controller 34 sends the raw data to the console 400.

The sequence controller 34 includes a processing circuit (not shown). This processing circuit is composed of hardware such as a processor that executes a predetermined program, an FPGA (Field Programmable Gate Array), and an ASIC (Application Specific Integrated Circuit).
The console 400 is configured as a computer having a processing circuit 40, a storage circuit 41, a display 42, and an input I/F 43 (input interface 43).

The storage circuit 41 is a storage medium including ROM (Read Only Memory), RAM (Random Access Memory), and external storage devices such as HDD (Hard Disk Drive) and optical disk devices. The storage circuit 41 stores various types of information and data, as well as various programs executed by a processor included in the processing circuit 40.

The input I/F 43 is, for example, a mouse, keyboard, trackball, touch panel, etc., and includes various devices for inputting various information and data by the operator. The display 42 is a display device such as a liquid crystal display panel, a plasma display panel, or an organic EL panel.

The processing circuit 40 is, for example, a circuit including a CPU or a dedicated or general-purpose processor. The processor implements various functions described below by executing various programs stored in the storage circuit 41. The processing circuit 40 may be configured with hardware such as an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit). Various functions described below can also be realized by these hardware. Further, the processing circuit 40 can also realize various functions by combining software processing using a processor and a program, and hardware processing.

(receiving coil)
FIG. 2 is a diagram showing an example of arrangement of the receiving coil 20 according to the embodiment. The receiving coil 20 may be configured as a chest coil placed on the chest of the subject as illustrated in FIG. 2(a), or may be configured as a chest coil placed on the subject's chest as illustrated in FIG. It may be configured as a spine coil disposed between.

FIG. 3 is a diagram showing an example of the configuration of the receiving coil 20. As described above, the receiving coil 20 in recent years is generally configured as an array coil in which a plurality of coil elements 200 are arranged in an array. It is. In the example shown in FIG. 3, 16 coil elements 200 are arranged in a planar array of 4 columns and 4 rows.

In particular, in the receiving coil 20 of the embodiment, as shown in FIG. 3, each of the plurality of coil elements 200 included in the receiving coil 20 is configured to include a loop coil 210 and a modified dipole 300, and, The modified dipole 300 is arranged inside the loop coil 210.

Here, the modified dipole 300 of the embodiment is a special dipole antenna modified based on a dipole antenna, and the specific configuration and structure will be described later. Further, the main reason for arranging the modified dipole 300 inside the loop coil 210 is to improve the antenna gain of the coil element 200, as described above.

That is, in order to increase the gain of the receiving coil 20, the number of loop coils included in the receiving coil 20 may be increased. On the other hand, the external dimensions of the receiving coil 20 cannot be made that large because they are limited by the size of the subject. Therefore, when trying to increase the number of loop coils included in the receiving coil 20 under limited dimensions, the diameter of each loop coil becomes smaller. As the diameter of the loop coil becomes smaller, the strength of the magnetic field generated from the loop coil becomes weaker. Therefore, even if the coil diameter is reduced and the number of loop coils is increased, there is a limit to improving the antenna gain of the receiving coil 20. occurs. In other words, if the coil element 200 of the receiving coil 20 is composed of only loop coils, there will be a limit to the improvement of the antenna gain of the receiving coil 20.

Therefore, in each coil element 200 of the receiving coil 20 of the embodiment, the modified dipole 300 is arranged inside the loop coil 210, and the outputs of the loop coil 210 and the modified dipole 300 are combined to form the antenna of the receiving coil 20. Improving gains.

However, the length of the radiating element of a typical half-wavelength dipole antenna is literally about λ/2 (λ is the wavelength of the frequency used). On the other hand, the loop length of the loop coil 210 is usually one wavelength, and when the shape of the loop coil 210 is square, the inner dimension of the loop coil 210 (the distance between two opposing sides) is λ/4. be. Further, when the shape of the loop coil 210 is a circle, the inner dimension is λ/π (about λ/3).

Therefore, in order to place a dipole antenna inside the loop coil 210, it is necessary to shorten the length of the radiating element of the dipole antenna by a considerable amount, for example, by a large reduction rate of 33% or more with respect to λ/2. There is.

Conventionally, a matching circuit for a dipole antenna uses a coil (inductor) and a capacitor as lumped constant elements. However, when the shortening ratio of the dipole antenna increases, the matching circuit requires a very large value of inductance (L) and capacitance (C) of the capacitor. As the inductance (L) and capacitance (C) of the capacitor increase, the loss in these lumped constant elements increases, resulting in a decrease in the reception sensitivity of the dipole antenna.

Therefore, the modified dipole 300 of the embodiment has a configuration that allows matching of a dipole antenna in which the length of the radiating element is shorter than λ/2 without using a coil (inductor) and a capacitor as lumped constant elements. As a result, the loss of the dipole antenna is suppressed and the gain of the receiving coil 20 is improved.

(Modified dipole of the first embodiment)
FIG. 4 is a diagram showing a configuration example of the modified dipole 300 of the first embodiment. FIG. 4(a) shows one coil element 200 in the receiving coil 20. As described above, the coil element 200 includes a loop coil 210 and a modified dipole 300 disposed inside the loop coil 210.

FIG. 4(b) is a schematic perspective view showing a configuration and a structural example of the modified dipole 300. The modified dipole 300 includes a main dipole 310 that feeds the received high-frequency signal to the outside (for example, to the RF receiver 32), and a parasitic element 320 that does not feed the received high-frequency signal to the outside.

FIG. 4C is a schematic plan view showing the configuration of only the main dipole 310, and FIG. 4D is a schematic plan view showing the configuration of only the parasitic element 320.

As shown in FIG. 4C, the main dipole 310 includes a ring-shaped power feeding section 311 and a radiating element 313 extending from two opposing points on the power feeding section 311 in mutually opposite directions. Furthermore, a power feeding point 312 for supplying a high frequency signal to the outside (for example, to the RF receiver 32) is provided at one location of the ring-shaped power feeding section 311. In the example shown in FIG. 4C, the shape of the ring-shaped power supply section 311 is circular, but the shape of the power supply section 311 is not limited to the circle, and may be, for example, square or oval.

As described above, the length of the radiating element 313 of the main dipole 310 is configured to be shorter than a half wavelength so as to fit inside the loop coil 210. Conventionally, such dipole antennas shorter than a half wavelength have been matched by a matching circuit using a large inductance (L) or a large capacitance (C) capacitor. On the other hand, in the modified dipole 300 of this embodiment, a parasitic element 320 is provided instead of the matching circuit using such a lumped constant element, and this parasitic element 320 is made to function as a matching circuit for the main dipole 310. I have to.

Here, the parasitic element 320 is a parasitic element placed close to the main dipole 310, and is an element that produces some kind of electromagnetic effect on the main dipole 310.

As shown in FIG. 4(d), the parasitic element 320 includes a split ring 321 having a gap 322 in a part of the ring, and a parasitic element 320 that extends from the split ring 321 in opposite directions and parallel to the radiating element of the main dipole. It has a linear element 323 provided. Note that, as described later, the parasitic element 320 may have a configuration in which the linear element 323 is not provided and only the split ring 321 is provided.

In the example shown in FIG. 4(d), the shape of the split ring 321 is circular, but the shape of the split ring 321 is not limited to the circle, and may be, for example, square or oval.

The main dipole 310 and the parasitic element 320 are configured such that the ring-shaped power feeding section 311 and the split ring 321 are overlapped with each other at a predetermined interval, and the ring-shaped feeding section 311 and the split ring 321 are coaxial with each other. Placed. With this arrangement, the power feeding section 311 of the main dipole 310 and the split ring 321 of the parasitic element 320 are coupled to each other by electromagnetic induction.

In addition, from the viewpoint of making the ring-shaped power feeding section 311 and the split ring 321 resonate and strengthening the coupling between them, the position of the feeding point 312 in the feeding section 311 and the position of the gap 322 of the split ring 321 are It is preferable to provide them at positions rotated approximately 180 degrees with respect to the central axes of the portion 311 and the split ring 321, respectively.

The size of the split ring 321 may be the same as the size of the ring-shaped power feeding section 311 of the main dipole 310, or may be slightly smaller than that. Due to this size relationship between the two, it is possible to limit the electromagnetic coupling of the split ring 312 to only the feed section 311, and the radiating element 313 of the main dipole 310 is able to couple the split ring 312 with the feed section 311 and the split ring 312. can be prevented from interfering with

In the deformed dipole 300 described above, the parasitic element 320 and the main dipole 310 are arranged perpendicular to the same plane, and the parasitic element 320 and the main dipole 310 have a symmetrical structure with respect to their respective center positions. are doing.

In addition, in the above-described modified dipole 300, the main dipole 310 and the parasitic element 320 are perpendicular to the same plane and perpendicular to the same straight line on the same plane, and the main dipole 310 is on the same straight line. It can be said that the parasitic element 320 is point symmetrical with respect to a first point on this same straight line, and the parasitic element 320 is point symmetrical with respect to a second point different from the first point.

FIG. 5(b) is a diagram showing an equivalent circuit of the modified dipole 300 described above. Note that FIG. 5(a) is the same diagram as FIG. 4(b).

In FIG. 5(b), _Zr is the radiation resistance, _LD is the reactance specific to the radiating element 313 of the main dipole 310, _LL is the reactance specific to the linear element 323 of the parasitic element 320, and _CDL is the reactance specific to the linear element 323 of the parasitic element 320. , the capacitance between the radiating element 313 and the linear element 323, L _S is the inductance of the split ring 321, and C _G is the capacitance due to the gap between the split rings.

As can be understood from FIG. 5(b), the split ring 321 itself constitutes an LC parallel resonant circuit with the capacitance _CG due to the gap between the split rings and the inductance _LS of the split ring 321. ). As a result, even if the structure is small, the parasitic element 320 can be forcibly coupled to the main dipole 310, and the parasitic element 320 can function as a matching circuit.

(Modified example of the first embodiment)
6 and 7 are diagrams showing a configuration example of a modified dipole 300 according to a first modified example of the first embodiment.

As shown in FIG. 6(a), the parasitic element 320 may have only a split ring 321 and no linear element 323. Furthermore, as shown in FIG. 6B, the entire length of the linear element 323 included in the parasitic element 320 can be made shorter than the entire length of the radiating element 313 of the main dipole 310.

As shown in FIG. 7, by making the entire length of the linear elements 323 of the parasitic element 320 shorter than the entire length of the radiating elements 313 of the main dipole 310, the parasitic element 320 can be connected to the main dipole 310. It can be made to function as a waveguide.

FIG. 7(a) is the same diagram as FIG. 6(b). As shown in FIGS. 7(b) and 7(c), in this modified dipole 300, the parasitic element 320 functions as a waveguide, thereby increasing the directivity in the direction from the main dipole 310 to the parasitic element 320. It will be done.

Taking advantage of this property, for example, the receiving coil 20 may be arranged such that the surface closer to the parasitic element 320 of both surfaces of the receiving coil 20, that is, the surface in the direction in which the directivity is enhanced, faces the subject. By installing it above the subject, magnetic resonance signals emitted from the subject can be received with higher sensitivity.

8 and 9 are diagrams showing a configuration example of a modified dipole 300 according to a second modified example of the first embodiment.

The modified dipole 300 of the second modified example of the first embodiment is configured as a plate-shaped dipole antenna formed on a substrate 340. In this modified dipole 300, as shown in FIG. 8, the main dipole 310 is formed on one surface of the substrate 340, and the parasitic element 320 is formed on the opposite surface to the conductor of the main dipole 310. is formed insulated.

In the modified dipole 300 of the second modified example, the conductor constituting the radiating element 313 of the main dipole 310 may have a solid surface, or the radiating element 313 of the main dipole 310 may have a meandering surface as shown in FIG. 8(c). It may be formed into a shape.

By forming the radiating element 313 into a meandering shape, the entire length of the radiating element 313 (that is, the distance between both ends of the radiating element 313) can be shortened.

Note that the meander shape is a shape in which a thin conductor whose width is sufficiently narrower than the width of the planar main dipole 310 in the lateral direction is bent multiple times into a crank shape.

On the other hand, the parasitic elements 320 of the modified dipole 300 of the second modified example extend in opposite directions from the split ring 321 and parallel to the radiating element 313 of the main dipole 310, as shown in FIG. 8(b). It has a linear element 323 provided. The length of the linear element 323 in the longitudinal direction is not particularly limited, but in the example shown in FIG. It is formed.

Note that, as shown in FIG. 8B, the shape of the split ring 321 in the parasitic element 320 of the modified dipole 300 of the second modified example is not circular but rectangular. Correspondingly, the shape of the power feeding section 311 of the main dipole 310 is also square rather than circular (see FIG. 8(c)).

FIG. 9 is a diagram illustrating a preferable example and an unpreferable example regarding the length of the linear element 323 in the longitudinal direction.

Specifically, as shown in FIG. 9(a), the linear element 323 is connected to the outer edge and inner edge of each of the plurality of thin conductors parallel to the width direction of the main dipole 310. It is preferable that the position of the outer edge and the position of the end of the linear element 323 substantially coincide with each other. This is because by setting the length of the linear element 323 in this manner, it becomes easier to predict the effect of the inductance (L) of the parasitic element 320.

On the other hand, as shown in FIG. 9(b), a linear element 323 in which the position of the end of the linear element 323 does not match the outer edge of the thin conductor is not preferable. For example, as shown in FIG. 9(b), when the end of the linear element 323 is located between the outer edge and the inner edge of the thin conductor, the effect of the inductance (L) of the parasitic element 320 is This is not desirable because it becomes difficult to predict.

Note that, as described above, the parasitic element 320 functions as a matching circuit for the main dipole 310. In this case, the size of the capacitance C of the matching circuit is adjusted by the width of the linear element 323 of the parasitic element 320 and the size of the gap 322 of the split ring 321, and the size of the inductance L of the matching circuit is adjusted by the width of the linear element 323 of the parasitic element 320 and the size of the gap 322 of the split ring 321. It is adjusted by the length of the shaped element 323.

10 and 11 are diagrams illustrating several variations when the main dipole 310 and the parasitic element 320 of the modified dipole 300 are formed into plate shapes.

Up to this point, embodiments have been described in which the shapes of the main dipole 310 and the parasitic elements 320 are both linear or rectangular, but the shapes of the main dipole 310 and the parasitic elements 320 are not limited to linear or rectangular shapes.

For example, the surface on which the main dipole 310 is arranged and the surface on which the parasitic element 320 is arranged are arranged so as to be parallel to each other, and then the shape of the main dipole 310 is adjusted so that the surface on which the main dipole 310 is arranged is parallel to each other. The main dipole 310 can have a shape that is line symmetrical with respect to the intersection line between the plane and the plane that is perpendicular to the plane where the main dipole 310 is arranged and includes the feeding point. Further, the shape of the parasitic element 320 is made to be axisymmetric with respect to the intersection line between the plane on which the parasitic element 320 is arranged and the plane that is perpendicular to the plane on which the parasitic element 320 is arranged and includes the feeding point. be able to. If the shapes of the main dipole 310 and the parasitic element 320 are asymmetrical on the left and right sides, the symmetry of the antenna will be lost and, for example, it will be difficult to match the characteristic impedance of the transmission line (typically 50 ohms). This is because it becomes difficult.

FIG. 10 is a diagram illustrating some examples of embodiments in which the shapes of the main dipole 310 and the parasitic element 320 are axisymmetric as described above. In FIG. 10, the meander-shaped conductor pattern is omitted. FIG. 10A shows a shape corresponding to the second modification of the first embodiment described above.

FIG. 10B shows an embodiment in which the main dipole 310 is configured as a so-called bowtie antenna, and the shape of the parasitic element 320 is also similar to the shape of the main dipole 310. On the other hand, FIG. 10C shows an embodiment in which the shape of the main dipole 310 is inverted from that of the bowtie antenna, and the base side of the isosceles triangle is used as the feeding point.

On the other hand, the shapes of the main dipole 310 and the parasitic element 320 can also be made into planar antennas that are symmetrical with respect to the feeding point. More specifically, the surface on which the main dipole 310 is arranged and the surface on which the parasitic element 320 is arranged are arranged so as to be parallel to each other, and then the shape of the main dipole 310 is adjusted to match the main dipole 310. The main dipole 310 can have a shape that is symmetrical about the intersection of the plane where the main dipole 310 is arranged and a straight line that is perpendicular to the plane where the main dipole 310 is arranged and includes the feeding point. Further, the shape of the parasitic element 320 is made to be point-symmetrical with respect to the intersection of the plane on which the parasitic element 320 is arranged and a straight line that is perpendicular to the plane on which the parasitic element 320 is arranged and includes the feeding point. Can be done.

FIG. 11 is a diagram illustrating some examples of embodiments in which the shapes of the main dipole 310 and the parasitic element 320 are point-symmetric with respect to the feeding point. Also in FIG. 11, the meander-shaped conductor pattern is omitted. FIG. 11A shows an embodiment in which the left and right radiating elements of a rectangular planar main dipole 310 are arranged in a stepwise manner, and have a point-symmetrical shape with respect to the feeding point. The parasitic element 320 is arranged near the feeding point so as to cover the feeding point, and is arranged so as to overlap the areas near the feeding point of the left and right radiating elements. FIG. 11B shows an embodiment in which left and right radiating elements each having an isosceles triangular shape are arranged in a stepped manner, and the left and right radiating elements are arranged point-symmetrically with respect to the feeding point.

(Modified dipole of second embodiment)
FIG. 12A is a schematic perspective view showing a configuration example and a structure example of a modified dipole 300 according to the second embodiment. In the modified dipole 300 of the second embodiment, the main dipole 310 is configured as a folded dipole antenna.

As shown in FIGS. 12(a) and 12(c), the main dipole 310 of the second embodiment has a ring-shaped power feeding section 311 similarly to the first embodiment. On the other hand, regarding the radiating element, it has a first radiating element 313 extending in both directions from the power feeding part 311, and a second radiating element 314 which is folded back at both ends of the first radiating element 313. The two second radiating elements 314, which are folded back at both ends, are generally parallel to the first radiating element 313 and face toward the feeding section 311, and near the feeding section 311, the ends of the second radiating element 314 face each other with a predetermined gap 315.

On the other hand, in the modified dipole 300 of the second embodiment, as shown in FIGS. 12(a) and 12(b), the first radiating element 313 and the second radiating element 314 are It includes a parasitic element 320 and a second parasitic element 330. The first parasitic element 320 has a first split ring 321 and linear elements 323 extending from the first split ring 321 on both sides. The first split ring 321 has a first gap 322 where a portion of the ring is missing.

Similarly, the second parasitic element 330 has a second split ring 331 and a linear element 333 extending from the second split ring 331 on both sides. It has a second gap 332 that is partially missing.

Here, the first split ring 321 of the first parasitic element 320 is arranged to face the power feeding section 311 of the main dipole 310. On the other hand, the second split ring 331 of the second parasitic element 330 is arranged opposite to the gap 315 where the ends of the second radiating element 314 face each other.

FIG. 13(b) is a diagram showing an equivalent circuit of the modified dipole 300 according to the second embodiment described above. Note that FIG. 13(a) is the same diagram as FIG. 12(a).

In the equivalent circuit of FIG. 13(b), _Zr is the radiation resistance, _LD is the reactance specific to the first and second radiating elements 313 and 314 of the main dipole 310, and _LL is the first parasitic element. 320 linear element 323, reactance specific to the linear element 333 of the second parasitic element 330, _CDL is between the first radiating element 313 and the first linear element 323, 314 and the first linear element 333, L _S is the inductance of the first and second split rings 321 and 331, and C _G is the gap 322 and 332 between the first and second split rings. capacitance, due to

As shown in FIG. 13(b), the equivalent circuit 320 of the first parasitic element 320 is connected in parallel to the equivalent circuit 310 of the main dipole 310. The first parasitic element 320 functions as a matching circuit for the main dipole 310, as in the first embodiment.

On the other hand, the equivalent circuit 330 of the second parasitic element 330 is connected in series to the equivalent circuit 310 of the main dipole 310. The second parasitic element 330 mainly functions as a frequency adjustment circuit for the main dipole 310.

As described above, since the first parasitic element 320 and the second parasitic element 330 have different functions, the sizes of the split rings 321, 331 and the linear elements 323, 333 of the two parasitic elements 320, 330 are do not have to be the same.

FIG. 14 shows an example in which the modified dipole 300 of the second embodiment is mounted on a substrate 340 by processing the conductor by etching or the like to generate a main dipole 310 and parasitic elements 320 and 330. FIG.

In the modified dipole 300 of the second embodiment, as shown in FIG. It is formed on a surface opposite to one surface (for example, the upper surface of the substrate 340) so as to be insulated from the conductor of the main dipole 310.

In the modified dipole 300 of the second embodiment, the conductors forming the radiating elements 313 and 314 of the main dipole 310 are formed as meander lines, similarly to the second modified example of the first embodiment. For example, as shown in FIG. 14(c), a meander line in which a thin conductor is bent into a crank shape multiple times from the power feeding part 311 to the folding position and from the folding position to the gap 315 where the ends face each other. As a result, the lengths of the radiating elements 313 and 314 of the main dipole 310 can be shortened.

(Modified example of second embodiment)
15(a) and 15(b) are diagrams showing a first modified example of the modified dipole 300 according to the second embodiment. In the first modification of the second embodiment, similarly to the embodiment shown in FIG. A dipole 310 is formed. On the other surface of the substrate 340 (for example, the upper surface of the substrate 340), a first parasitic element 320 and a second parasitic element 330 are formed to be insulated from the conductor of the main dipole 310.

The radiating element 351 of the main dipole 310 is formed as a meander line in which a thin conductor is bent into a crank shape multiple times from the power feeding part 350 to both folding positions 352 and from both folding positions 352 to both ends 353 facing each other. has been done.

On the other hand, the first and second parasitic elements 320 and 330 are both formed as meander lines, unlike the embodiment shown in FIG. Specifically, the first parasitic element 320 has a split ring 354 at a position corresponding to the power feeding section 350 of the main dipole 310, and extends from the split ring 354 to both folding positions 356 and from both folding positions 356 to the center. The entire range up to a predetermined position towards the end is formed as a meander line 355. The second parasitic element 330 has a split ring 357 at a position corresponding to both ends 353 of the main dipole 310, and a meander line 358 extends from the split ring 357 in both directions.

In the first modification of the second embodiment, not only the main dipole 310 but also the first and second parasitic elements 320 and 330 are formed as meander lines. Therefore, the capacitance between the main dipole 310 and the first and second parasitic elements 320 and 330 can be increased, and as a result, the deformed dipole 300 can be made smaller, or the deformed dipole can be reduced in size. It is possible to realize a frequency reduction of 300 degrees.

16(a) and 16(b) are diagrams showing a second modification example of the modified dipole 300 according to the second embodiment. In the second modification of the second embodiment, similarly to the first modification described above, the main dipole 310 is formed on one surface of the substrate, and the parasitic element 320 is formed on the surface opposite to the one surface. It is formed insulated from the conductor of the main dipole 310.

On the other hand, in the second modification, the radiating element of the main dipole 310 is formed as a first linear element 361 having a predetermined width from the power feeding section 360 to the first intermediate position P1 on the way to the both folding positions 363. , from the first intermediate position P1 to both folding positions 363, and from both folding positions 363 to both ends 364 facing each other, are formed as a meander line in which a thin conductor is bent into a crank shape a plurality of times.

Further, the parasitic element 320 is formed in a shape substantially similar to the shape of the radiating element of the main dipole 310. Specifically, the parasitic elements 320 extend from the split ring 365 in opposite directions and are folded back at a folded position 368 to face each other near the split ring 365. The parasitic element 320 is formed as a second linear element 366 having a predetermined width from the split ring 365 to the second intermediate position P2 on the way to the double folding position 368, and from the second intermediate position P2 to the double folding position 368. From the folding positions 368 to the positions facing each other, the thin conductor is formed as a meander line that is bent multiple times into a crank shape.

In the second modification described above, the line from the power feeding part 360 of the main dipole 310 to the first intermediate position P1 is not formed as a meander line but as a linear element 361 having a predetermined width, and similarly, the split ring of the parasitic element 320 is formed as a linear element 361 having a predetermined width. 365 to the second intermediate position P2 are formed not as a meander line but as a linear element 366 having a predetermined width. As a result, the second modified example can further increase the capacitance between the main dipole 310 and the parasitic element 320 compared to the first modified example, and can further reduce the size of the modified dipole 300. Alternatively, it is possible to further reduce the frequency of the modified dipole 300.

Note that the length L1 of the first linear element 361 of the main dipole 310 is made longer than the length L2 of the second linear element 366 of the parasitic element 320, and then the second linear element 361 of the parasitic element 320 By adjusting the length L2 of 366, it is possible to finely adjust the frequency.

FIGS. 17(a) and 17(b) are diagrams showing a third modified example of the modified dipole 300 according to the second embodiment. The third modification is an embodiment that combines the first modification and the second modification.

FIGS. 18 and 19 are diagrams showing several configuration examples of a coil element 200 in which a modified dipole 300 according to each of the above-described embodiments and modified examples is combined with a loop coil 210.

FIG. 18(a) is a diagram showing a first configuration example of the coil element 200. The first configuration example includes an output circuit 220 that combines and outputs the output of the loop coil 210 and the output of the modified dipole 300. For the reception coil 20 as a whole, the outputs from the plurality of coil elements 200 may be further combined and used, or the outputs from the plurality of coil elements 200 may be selected and used as necessary. Such a configuration allows the receiving coil 20 to function as a composite diversity coil.

FIG. 18(b) is a diagram showing a second configuration example of the coil element 200. The second configuration example includes an output circuit 220 that outputs the output of the loop coil 210 and the output of the modified dipole 300 as signals in different frequency bands. For example, the output circuit 220 outputs a signal in the first frequency band f0 from the loop coil 210, and outputs a signal in the second frequency band f1 from the modified dipole 300. The receiving coil 20 as a whole may be used by combining outputs from a plurality of coil elements 200 for each frequency band, or by combining outputs from a plurality of coil elements 200 for each frequency band as necessary. You may select and use them. Such a configuration allows the receiving coil 20 to function as a frequency diversity coil.

This receiving coil 20 can be used, for example, as a receiving coil for magnetic resonance signals from different types of nuclides. Further, it can be used as a receiving coil of an open magnetic resonance imaging apparatus in which the static magnetic field strength varies depending on the imaging position.

FIG. 19(a) is a diagram showing a third configuration example of the coil element 200. The third configuration example includes an output circuit 220 that outputs the output of the loop coil 210 and the output of the modified dipole 300 as signals from different regions.

Generally, loop coils function as parallel resonant circuits and are more sensitive to signals from the near field than from the far field. Conversely, a dipole antenna functions as a series resonant circuit and is more sensitive to signals from the far field than from the near field. Utilizing such properties, the output circuit 220 of the third configuration example outputs the signal from the modified dipole 300 as a signal from the far field, and outputs the signal from the loop coil 210 as a signal from the near field. do.

The receiving coil 20 as a whole may be used by combining outputs from a plurality of coil elements 200 for each far field or near field region, or may be used by combining outputs from a plurality of coil elements 200 for each far field or near field region. The outputs from 200 may be selected and used as needed. Such a configuration allows the receiving coil 20 to function as a region diversity coil.

For example, as shown in FIG. 19(b), when this receiving coil 20 is used as a chest coil or an abdominal coil, the output signal from the loop coil 210 is mainly transmitted to the front side (i.e., the ventral side) of the subject. The output signal from the modified dipole 300 is mainly a signal from the region on the back side (or posterior) of the subject.

On the other hand, as shown in FIG. 19(c), when this receiving coil 20 is used as a spine coil, the output signal from the loop coil 210 is mainly transmitted to the rear side of the subject (i.e., the back side or posterior side of the subject). ), and the output signal from the modified dipole 300 is mainly a signal from the region on the anterior side (i.e., ventral side, or anterior) of the subject.

In addition, the modified dipole 300 according to each embodiment or each modified example can be used alone without being combined with the loop coil 210. As described above, the modified dipole 300 according to each embodiment or each modification can provide a matching circuit that is required when the length of the radiating element is made shorter than half a wavelength, without using a lumped constant element with large loss. , can be realized by the parasitic element 320 with small loss.

Therefore, the modified dipole 300 according to each embodiment or each modification can be used independently as a small and low-loss dipole antenna.

(Modified example of receiving coil)
Up to this point, an example has been described in which the modified dipole 300 included in the receiving coil 20 is arranged inside the loop coil 210, as illustrated in FIG. That is, an example of the receiving coil 20 configured such that the length of the modified dipole 300 in the longitudinal direction is shorter than the distance between the two opposing sides of the loop coil 210 has been described.

However, by devising the configuration of the coil element 200 in the receiving coil 20, it is also possible to make the length of the modified dipole 300 in the longitudinal direction longer than the distance between the two opposing sides of the loop coil 210. In this case as well, the length of the deformed dipole 300 in the longitudinal direction is shorter than the conventional half wavelength due to the provision of the above-described parasitic element 320.

FIG. 20 is a diagram showing a first modified example of the receiving coil 20. In the first modification, by shifting the vertical positions of two coil elements 200 that are adjacent in the horizontal direction in FIG. Even if they are longer than the interval, they do not interfere with each other.

FIG. 21 is a diagram showing a second modified example of the receiving coil 20. In the second modification, the longitudinal directions of the modified dipole 300 are set to differ by 90 degrees between two coil elements 200 that are adjacent to each other in the horizontal and vertical directions.

FIG. 22 is a diagram showing a third modified example of the receiving coil 20. In the third modification, between two coil elements 200 adjacent to each other in the horizontal and vertical directions, coil elements 200 with deformed dipoles 300 and coil elements 200 without deformed dipoles 300 are alternately arranged.

FIG. 23 is a diagram showing a fourth modification of the receiving coil 20. In the fourth modification, rows of coil elements 200 with modified dipoles 300 and rows of coil elements 200 without modified dipoles 300 are arranged alternately.

FIG. 24 is a diagram showing a fifth modification example of the receiving coil 20. In the fifth modification, some of the coil elements 200 in the receiving coil 20 are configured to include a dipole antenna different from the modified dipole 300 described above, that is, a dipole antenna 600 for non-contact biological monitoring. There is. Here, the dipole antenna 600 for non-contact biological monitoring is, for example, an antenna configured to non-contact monitor a person's heartbeat and respiratory motion, as described in Japanese Patent Application Laid-Open No. 2021-159310. . The receiving coil 20 of the fifth modification has a configuration in which the modified dipole 300 of the two coil elements 200 in the receiving coil 20 illustrated in FIG. 3 is replaced with a dipole antenna 600 for non-contact biological monitoring. .

FIG. 25 is a diagram showing a sixth modification example of the receiving coil 20. The receiving coil 20 of the sixth modification has a configuration in which the modified dipole 300 of the two coil elements 200 in the receiving coil 20 illustrated in FIG. 20 is replaced with a dipole antenna 600 for non-contact biological monitoring. .

According to the receiving coil of each embodiment described above, the gain of the receiving coil can be improved by combining the loop coil and a receiving element other than the loop coil.

Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, changes, and combinations of embodiments can be made without departing from the gist of the invention. These embodiments and their modifications are included within the scope and gist of the invention as well as within the scope of the invention described in the claims and its equivalents.

Regarding the above embodiments, the following additional notes are disclosed as one aspect and optional features of the invention.

(Additional note 1)
A receiver coil comprising a plurality of coil elements, the receiver coil comprising:
The coil element includes a loop coil and a deformed dipole disposed inside the loop coil,
The modified dipole is configured to include a main dipole that feeds a high frequency signal to the outside, and a parasitic element that does not feed a high frequency signal to the outside and has a split ring with a gap in a part of the ring. ,
receiving coil.

(Additional note 2)
The length of the radiating element of the main dipole is configured to be shorter than a half wavelength;
The parasitic element functions as a matching circuit for the main dipole.

(Additional note 3)
The main dipole has a ring-shaped power feeding part,
The ring-shaped power feeding section and the split ring are coupled by electromagnetic induction.

(Additional note 4)
The main dipole and the parasitic element are arranged such that the ring-shaped power supply part and the split ring are spaced apart from each other at a predetermined interval and the ring-shaped power supply part and the split ring overlap coaxially with each other. may be done.

(Appendix 5)
The position of the power feeding point in the ring-shaped power feeding part and the position of the gap between the split rings may be provided at positions rotated approximately 180 degrees with respect to central axes of the power feeding part and the split ring, respectively. good.

(Appendix 6)
The size of the split ring may be the same as or smaller than the size of the ring-shaped power feeding section.

(Appendix 7)
The parasitic element may include a linear element extending in opposite directions from the split ring and provided parallel to the radiating element of the main dipole.

(Appendix 8)
The total length of the linear element may be shorter than the total length of the radiating element.

(Appendix 9)
the parasitic element functions as a waveguide with respect to the main dipole;
The modified dipole has enhanced directivity in a direction from the main dipole toward the parasitic element.

(Appendix 10)
The parasitic element and the main dipole may be arranged perpendicular to the same plane, and the parasitic element and the main dipole may have structures that are symmetrical with respect to their respective center positions.

(Appendix 11)
The main dipole and the parasitic element are perpendicular to the same plane and perpendicular to the same straight line on the same plane, and the main dipole is perpendicular to the first point on the same straight line. The parasitic element may be point symmetrical with respect to a second point different from the first point on the same straight line.

(Appendix 12)
The main dipole may be formed on one surface of the substrate, and the parasitic element may be formed on a surface opposite to the one surface so as to be insulated from the conductor of the main dipole.

(Appendix 13)
The radiating element extending from the power feeding part of the main dipole may be formed in a meander shape.

(Appendix 14)
The main dipole includes a power feeding part and a radiating element, and is formed as a meander line in which a thin conductor is bent into a crank shape multiple times from the power feeding part to both ends of the radiating element,
The parasitic element is a linear element that extends from the split ring in opposite directions and is provided parallel to the radiating element of the main dipole, and is formed as a linear element shorter than the length of the radiating element. ,
The linear element is arranged such that the position of the outer edge of the thin conductor among the outer edges and inner edges of each of the plurality of thin conductors parallel to the width direction of the main dipole and the end of the linear element are determined. The positions may be formed so that the positions substantially coincide with each other.

(Appendix 15)
The parasitic element has a linear element extending in opposite directions from the split ring and provided parallel to the radiating element of the main dipole,
The parasitic element functions as a matching circuit for the main dipole,
The C component of the matching circuit may be adjusted by the width of the linear element and the size of the gap of the split ring, and the L component of the matching circuit may be adjusted by the length of the linear element. .

(Appendix 16)
The main dipole has a ring-shaped feeding part that feeds a high-frequency signal to the outside, and a radiating element extending in both directions from the feeding part, and the radiating element is folded back so that both ends of the radiating element are connected to the The antennas are configured as folded dipole antennas that face each other near the feeder.
The parasitic element includes a first parasitic element and a second parasitic element,
A first split ring included in the first parasitic element is arranged opposite to the power feeding section,
A second split ring included in the second parasitic element may be placed opposite to a position where both ends of the radiating element face each other.

(Appendix 17)
The radiating element of the main dipole may be formed as a meander line in which a thin conductor is bent into a crank shape a plurality of times from the feeding part to the folding position and from the folding position to both ends facing each other. good.

(Appendix 18)
The receiving coil may further include an output circuit that outputs a signal obtained by combining the output of the loop coil and the output of the modified dipole, and causes the receiving coil to function as a composite diversity coil.

(Appendix 19)
An output circuit that independently outputs the output of the loop coil and the output of the modified dipole, and that causes the receiving coil to function as a region diversity coil that has different sensitivities in the far field and the near field. Further provision may be made.

(Additional note 20)
The receiving coil may further include an output circuit that outputs the output of the loop coil and the output of the modified dipole as signals with different center frequencies, and causes the receiving coil to function as a frequency diversity coil.

1 Magnetic resonance imaging apparatus 20 Receiving coil 200 Coil element 210 Loop coil 220 Output circuit 300 Modified dipole 310 Main dipole 311 Feeding section 312 Feeding points 313, 314 Radiating elements 320, 330 Parasitic elements 321, 331 Split rings 322, 332 Gap 323, 333 Linear element

Claims (25)

A receiver coil comprising a plurality of coil elements, the receiver coil comprising:
at least one of the coil elements comprises a loop coil and a deformed dipole disposed inside the loop coil;
The modified dipole includes a main dipole that feeds the received high-frequency signal to the outside, and a parasitic element that does not feed the high-frequency signal to the outside and has a split ring with a gap in a part of the ring. composed of,
receiving coil. The length of the radiating element of the main dipole is configured to be shorter than a half wavelength;
the parasitic element functions as a matching circuit for the main dipole;
The receiving coil according to claim 1. The main dipole has a ring-shaped power feeding part,
The ring-shaped power feeding section and the split ring are coupled by electromagnetic induction,
The receiving coil according to claim 1. The main dipole has a ring-shaped power feeding part,
The main dipole and the parasitic element are arranged such that the ring-shaped power feeding section and the split ring overlap each other coaxially with a predetermined interval,
The receiving coil according to claim 1. The main dipole has a ring-shaped power feeding part,
The position of the power feeding point in the ring-shaped power feeding part and the position of the gap between the split rings are located at positions rotated approximately 180 degrees with respect to the central axes of the power feeding part and the split ring, respectively. ,
The receiving coil according to claim 1. The main dipole has a ring-shaped power feeding part,
The size of the split ring is the same as or smaller than the size of the ring-shaped power feeding part,
The receiving coil according to claim 1. The parasitic element has a linear element extending from the split ring in mutually opposite directions and provided parallel to the radiating element of the main dipole.
The receiving coil according to claim 1. the total length of the linear element is shorter than the total length of the radiating element;
The receiving coil according to claim 7. the parasitic element functions as a waveguide with respect to the main dipole;
The deformed dipole has enhanced directivity in a direction from the main dipole toward the parasitic element.
The receiving coil according to claim 8. The parasitic element and the main dipole are arranged perpendicular to the same plane, and the parasitic element and the main dipole have a structure that is symmetrical with respect to their respective center positions.
The receiving coil according to claim 1. The main dipole and the parasitic element are perpendicular to the same plane and perpendicular to the same straight line on the same plane, and the main dipole is perpendicular to the first point on the same straight line. point symmetrical, and the parasitic element is point symmetrical with respect to a second point different from the first point on the same straight line;
The receiving coil according to claim 1. The main dipole is formed on one surface of the substrate, and the parasitic element is formed on a surface opposite to the one surface, insulated from the conductor of the main dipole.
The receiving coil according to claim 1. At least a portion of the radiating element extending from the power feeding part of the main dipole is formed as a meander line in which a thin conductor is bent multiple times into a crank shape.
The receiving coil according to claim 1. The main dipole includes a power feeding part and a radiating element, and is formed as a meander line in which a thin conductor is bent into a crank shape multiple times from the power feeding part to both ends of the radiating element,
The parasitic element is a linear element that extends from the split ring in opposite directions and is provided parallel to the radiating element of the main dipole, and is formed as a linear element shorter than the length of the radiating element. ,
The linear element is arranged such that the position of the outer edge of the thin conductor among the outer edges and inner edges of each of the plurality of thin conductors parallel to the width direction of the main dipole and the end of the linear element are determined. formed so that the position substantially coincides with the
The receiving coil according to claim 1. The parasitic element has a linear element extending in opposite directions from the split ring and provided parallel to the radiating element of the main dipole,
The parasitic element functions as a matching circuit for the main dipole,
The C component of the matching circuit is adjusted by the width of the linear element and the size of the gap of the split ring, and the L component of the matching circuit is adjusted by the length of the linear element.
The receiving coil according to claim 1. The main dipole has a ring-shaped feeding part that feeds the high-frequency signal to the outside, and a radiating element extending in both directions from the feeding part, and the radiating element is folded back so that both ends of the radiating element are connected to each other. configured as folded dipole antennas with structures facing each other near the feed section;
The receiving coil according to claim 1. The parasitic element includes a first parasitic element and a second parasitic element,
A first split ring included in the first parasitic element is arranged opposite to the power feeding section,
A second split ring included in the second parasitic element is arranged opposite to a position where both ends of the radiating element face each other.
The receiving coil according to claim 16. The radiating element of the main dipole is formed as a meander line in which a thin conductor is bent into a crank shape a plurality of times from the feeding part to both folded positions and from both folded positions to both ends facing each other. ing,
The receiving coil according to claim 16. The main dipole is formed on one surface of the substrate, and the parasitic element is formed on a surface opposite to the one surface and insulated from the conductor of the main dipole,
The radiating element of the main dipole is formed as a first linear element having a predetermined width from the power feeding section to a first intermediate position toward the both folding positions, and from the first intermediate position to the both folding positions. , and a thin conductor is formed as a meander line in which the thin conductor is bent into a crank shape a plurality of times from the both folded positions to the two ends facing each other,
The parasitic elements extend in opposite directions from the split ring, are folded back at positions corresponding to folded positions of the radiating element, and have a shape substantially similar to the radiating element, facing each other near the split ring. formed,
The parasitic element is formed as a second linear element having a predetermined width from the split ring to a second intermediate position toward both folding positions, and from the second intermediate position to both folding positions, From both folding positions to positions facing each other, the thin conductor is formed as a meander line that is bent multiple times into a crank shape.
The receiving coil according to claim 16. The length of the second linear element is adjusted according to the frequency used.
The receiving coil according to claim 19. (a) an output circuit that outputs a signal obtained by combining the output of the loop coil and the output of the modified dipole, the output circuit causing the receiving coil to function as a composite diversity coil;
(b) An output circuit that independently outputs the output of the loop coil and the output of the modified dipole, the output circuit causing the receiving coil to function as a region diversity coil that has different sensitivities in the far field and in the near field. circuit, or
(c) further comprising: an output circuit that outputs the output of the loop coil and the output of the modified dipole as signals with different center frequencies, and causes the receiving coil to function as a frequency diversity coil;
The receiving coil according to claim 1. comprising the receiving coil according to any one of claims 1 to 20;
Magnetic resonance imaging device. A main dipole that feeds the received high frequency signal to the outside,
a parasitic element that does not feed the high-frequency signal to the outside and has a split ring having a gap in a part of the ring;
A modified dipole with a The length of the radiating element of the main dipole is configured to be shorter than a half wavelength;
the parasitic element functions as a matching circuit for the main dipole;
A modified dipole according to claim 23. The main dipole has a ring-shaped power feeding part,
The ring-shaped power feeding section and the split ring are coupled by electromagnetic induction,
A modified dipole according to claim 23.

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