JP2005253816A - Rf coil and mri apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an RF coil whose g factor is small when photographed with the SI direction as the direction of phase-encoding, and to provide an MRI apparatus with the RF coil. <P>SOLUTION: The MRI apparatus comprises a first coil group (12-42) consisting of a plurality of unit coils disposed to surround a subject without overlapping each other and without coupling with each other, and a second coil group (52-82) consisting of a plurality of unit coils disposed at different positions from the unit coils of the first coil group in the direction of body axis of the subject to surround the subject without overlapping with each other, but partly overlapping with the plurality of unit coils of the first coil group, without coupling with each other. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an RF coil (radio frequency coil) and an MRI apparatus, and more particularly to an RF coil for performing parallel imaging and an MRI apparatus including such an RF coil.

  One method of magnetic resonance imaging (MRI: Magnetic Resonance Imaging) is parallel imaging. In parallel imaging, magnetic resonance signals are collected simultaneously through a plurality of receiving systems. The collection of magnetic resonance signals is performed by reducing the field of view (FOV) to 1 / n. By reducing the FOV to 1 / n, the signal acquisition speed is improved n times. Parallel imaging is also referred to as sense (SENSE: sensitivity encoding).

An RF coil for parallel imaging is composed of a plurality of unit coils that are not coupled to each other. As such an RF coil, one using eight unit coils whose loop shape is a right triangle is known. Two unit coils are paired so as to be adjacent to each other on the hypotenuse, and four pairs are arranged so as to surround a subject to be photographed. The unit coils are adjacent to each other so that the loops do not overlap (see Non-Patent Document 1, for example).
Seeber and others, New RF Coil Topology for High Performance Sense in 3D (New RF Coil Topology for High Performance SENSE in 3D) of Magnetic Resonance in Medicine Eventing and Exhibition) ”(USA), 2003, p. 465

  Since the RF coil as described above has a large g factor when the SI (superior-inferior) direction is taken as the phase encode direction, when the phase encode is performed in the SI direction, the SNR (signal) Too good ratio) cannot be taken.

  Accordingly, an object of the present invention is to realize an RF coil having a small g factor when photographing with the SI direction as the phase encoding direction, and an MRI apparatus including such an RF coil.

  (1) One aspect of the invention for solving the above problems is an RF coil that is used in close proximity to an imaging target to perform magnetic resonance imaging, and the target can be detected without overlapping each other. The first coil group composed of a plurality of unit coils that are arranged so as to surround each other and the first coil group are different in position in the body axis direction of the target, and the target is not overlapped with each other. And a second coil group comprising a plurality of unit coils that are not coupled to each other and are disposed so as to partially overlap each of the plurality of unit coils in the first coil. It is an RF coil.

  (2) An invention according to another aspect for solving the above-described problem is an MRI apparatus for reconstructing an image based on a magnetic resonance signal collected by applying a static magnetic field, a gradient magnetic field, and an RF magnetic field to an imaging target. An RF coil for receiving magnetic resonance signals, the RF coil being used in close proximity to the object to be imaged so as to surround the object without overlapping each other The first coil group composed of a plurality of unit coils that are not coupled to each other and the first coil group have different positions in the body axis direction of the object, and surround the object without overlapping each other and The first coil is composed of a plurality of unit coils which are arranged so as to partially overlap the plurality of unit coils in the first coil and which are not coupled to each other. And groups of coils, a MRI apparatus characterized by comprising.

  The loop of the unit coil preferably has four internal angles that are perpendicular to each other in terms of good space utilization. It is preferable that the number of unit coils in the first and second coil groups is four in terms of a four-quadrant arrangement.

  It is preferable that the plurality of unit coils surround the object in a cylindrical shape in terms of high signal reception efficiency. The arrangement of the unit coils is preferably symmetric with respect to the central axis of the cylinder in that the coil patterns are shared by the symmetrical ones. The cylinder is preferably a cylinder in that all unit coils are equidistant from the central axis.

  It is preferable that at least one end of the tube is squeezed in view of a good filling factor. It is preferable that the tip of the squeezed side protrudes in the body axis direction from the viewpoint of separating this portion from the subject to be photographed.

  In the invention in each aspect described above, the RF coil is arranged so as to surround the object without overlapping each other, the first coil group comprising a plurality of unit coils that are not coupled to each other, and the first coil group, Are different in position in the body axis direction, surround the object without overlapping each other, and are arranged so as to partially overlap with the plurality of unit coils in the first coil, respectively. Since the second coil group including the unit coils is included, the g factor when the SI direction is taken as the phase encoding direction is small.

  The best mode for carrying out the invention will be described below in detail with reference to the drawings. The present invention is not limited to the best mode for carrying out the invention. FIG. 1 shows a block diagram of the MRI apparatus. This apparatus is an example of the best mode for carrying out the invention. An example of the best mode for carrying out the present invention relating to the MRI apparatus is shown by the configuration of the apparatus.

  As shown in the figure, the apparatus has a magnet system 100. The magnet system 100 includes a main magnetic field coil unit 102, a gradient coil unit 106, and an RF coil unit 108. Each of these coil portions has a substantially cylindrical shape and is arranged coaxially with each other.

  The imaging target 1 is mounted on a cradle 500 in a generally cylindrical internal space (bore) of the magnet system 100 and is carried in and out by a conveying means (not shown). A receiving coil unit 110 is attached to the head of the subject 1. The receiving coil unit 110 will be described later.

  The main magnetic field coil unit 102 forms a static magnetic field in the internal space of the magnet system 100. The direction of the static magnetic field is generally parallel to the direction of the body axis of the object 1. That is, a so-called horizontal magnetic field is formed. The main magnetic field coil unit 102 is configured using, for example, a superconducting coil. In addition, you may comprise using not only a superconductive coil but a normal conductive coil.

  The gradient coil section 106 generates three gradient magnetic fields for giving gradients to the static magnetic field strength in the directions of three axes perpendicular to each other, that is, the slice axis, the phase axis, and the frequency axis.

  When the coordinate axes perpendicular to each other in the static magnetic field space are x, y, and z, any of the axes can be a slice axis. In that case, one of the remaining two axes is a phase axis, and the other is a frequency axis. In addition, the slice axis, the phase axis, and the frequency axis can have arbitrary inclinations with respect to the x, y, and z axes while maintaining the perpendicularity between them. In this apparatus, the body width direction of the object 1 is the x direction, the body thickness direction is the y direction, and the body axis direction is the z direction.

  The gradient magnetic field in the slice axis direction is also called a slice gradient magnetic field. The gradient magnetic field in the phase axis direction is also referred to as a phase encode gradient magnetic field or a phase encode gradient magnetic field. The gradient magnetic field in the frequency axis direction is also referred to as a read out gradient magnetic field. The readout gradient magnetic field is synonymous with the frequency encoding gradient magnetic field. In order to make it possible to generate such a gradient magnetic field, the gradient coil unit 106 has three gradient coils (not shown). Hereinafter, the gradient magnetic field is also simply referred to as a gradient.

  The RF coil unit 108 forms a high-frequency magnetic field for exciting spins in the body of the target 1 in the static magnetic field space. Hereinafter, the formation of a high-frequency magnetic field is also referred to as transmission of an RF excitation signal. The RF excitation signal is also referred to as an RF pulse.

  An electromagnetic wave generated by the excited spin, that is, a magnetic resonance signal is received by the receiving coil unit 110. The magnetic resonance signal can also be received by the RF coil unit 108. The magnetic resonance signal is a signal in the frequency domain (Fourier) space. Since the magnetic resonance signal is encoded in two axes by the gradient in the phase axis direction and the frequency axis direction, the magnetic resonance signal is obtained as a signal in a two-dimensional Fourier space.

  The phase encode gradient and readout gradient determine the sampling position of the signal in two-dimensional Fourier space. Hereinafter, the two-dimensional Fourier space is also referred to as k-space.

  A gradient driving unit 130 is connected to the gradient coil unit 106. The gradient driving unit 130 gives a driving signal to the gradient coil unit 106 to generate a gradient magnetic field. The gradient drive unit 130 has three systems of drive circuits (not shown) corresponding to the three systems of gradient coils in the gradient coil unit 106.

  An RF drive unit 140 is connected to the RF coil unit 108. The RF drive unit 140 gives a drive signal to the RF coil unit 108 to transmit an RF pulse, thereby exciting the spin in the body of the subject 1.

  A data collection unit 150 is connected to the reception coil unit 110. An RF coil unit 108 can also be connected to the data collection unit 150. The data collection unit 150 collects reception signals received by the reception coil unit 110 or the RF coil unit 108 as digital data.

  A sequence control unit 160 is connected to the gradient driving unit 130, the RF driving unit 140, and the data collecting unit 150. The sequence controller 160 controls the gradient driver 130 or the data collector 150 to collect magnetic resonance signals.

  The sequence control unit 160 is configured using, for example, a computer. The sequence control unit 160 has a memory (not shown). The memory stores a program for the sequence control unit 160 and various data. The function of the sequence control unit 160 is realized by the computer executing a program stored in the memory.

  The output side of the data collection unit 150 is connected to the data processing unit 170. Data collected by the data collection unit 150 is input to the data processing unit 170. The data processing unit 170 is configured using, for example, a computer. The data processing unit 170 has a memory (not shown). The memory stores a program for the data processing unit 170 and various data.

  The data processing unit 170 is connected to the sequence control unit 160. The data processing unit 170 is above the sequence control unit 160 and controls it. The function of this apparatus is realized by the data processing unit 170 executing a program stored in the memory.

  The data processing unit 170 stores the data collected by the data collection unit 150 in a memory. A data space is formed in the memory. This data space corresponds to k-space. The data processing unit 170 reconstructs an image by performing two-dimensional inverse Fourier transform on k-space data.

  A display unit 180 and an operation unit 190 are connected to the data processing unit 170. The display unit 180 is configured by a graphic display or the like. The operation unit 190 includes a keyboard having a pointing device.

  The display unit 180 displays the reconstructed image and various information output from the data processing unit 170. The operation unit 190 is operated by the user and inputs various commands and information to the data processing unit 170. The user operates the apparatus interactively through the display unit 180 and the operation unit 190.

  The receiving coil unit 110 will be described. The receiving coil unit 110 is an example of the best mode for carrying out the invention. An example of the best mode for carrying out the present invention related to the RF coil is shown by the configuration of the receiving coil unit 110. The receiving coil unit 110 is also an example of an RF coil in the present invention.

  FIG. 2 is a perspective view showing the outer shape of the receiving coil unit 110. As shown in the figure, the receiving coil section 110 has a substantially cylindrical outer shape. One end of the tube is recessed. The tip of the squeezed side protrudes in the axial direction of the cylinder. Hereinafter, such a shape is also referred to as a dome shape.

  The axial direction of the cylinder coincides with the body axis direction. By definition, the body axis direction is also the SI direction. The receiving coil unit 110 is attached to the head such that the side that is narrowed is the top of the head. Therefore, the side that is sunk is the S (superior) side, and the opposite side is the I (inferior) side.

  The two directions perpendicular to the SI direction and perpendicular to each other are, by definition, an AP (anterior-posteror) and an RL (right-left) direction. In the figure, the vertical direction of the cylinder is the AP direction, and the horizontal direction of the cylinder is the RL direction.

  Since the one end side of the tube is squeezed, a filling factor at the time of photographing is good. Since the tip of the narrowed side protrudes in the body axis direction, this portion can be separated from the object to be photographed.

  The receiving coil unit 110 having such an outer shape has a plurality of coils 12-82 as shown in FIG. Each of the coils 12-82 forms a closed loop. Each loop is a conductor loop having a capacitor in series.

  The coils 12-82 are configured not to electromagnetically couple to each other. Coils that are not coupled to each other can be realized by providing a neutralization circuit in the loop. Coil 12-82 is an example of an embodiment of a unit coil in the present invention.

  As shown in FIG. 4, the coil 12-82 is divided into two groups, a coil 12-42 and a coil 52-82. The coils 12-42 are an S-side coil group, and the coils 52-82 are an I-side coil group. These two groups of coils are combined so as to partially overlap in the SI direction to form a receiving coil unit 110 as shown in FIG.

  Hereinafter, the coil 12-42 is also referred to as an S group coil, and the coil 52-82 is also referred to as an I group coil. S group coil 12-42 is an example of the 1st coil group in the present invention. The I group coil 52-82 is an example of the second coil group in the present invention. Here, an example in which each of the S group coil 12-42 and the I group coil 52-82 includes four coils is shown, but the number is not limited to four, and may be an appropriate plural larger than two.

  FIG. 5 shows a state where the coil 12-82 is developed on a plane. As shown in the figure, the I group coil 52-82 is a rectangular or square loop. That is, the loop has four internal angles at right angles. The S group coil 12-42 is basically a rectangular or rectangular loop, but is deformed in accordance with the recess. The S group coil 12-42 also has four internal angles at right angles.

  The S group coils 12-42 are arranged along the circumferential surface of the cylinder without overlapping each other. The I group coils 52-82 are also arranged along the circumferential surface of the cylinder without overlapping each other. Corresponding elements between the S group and the I group, that is, the coils 12 and 52, the coils 22 and 62, the coils 32 and 72, and the coils 42 and 82 are arranged so as to partially overlap in the SI direction.

  Since the loop of the coil 12-82 has four internal angles at right angles, it is preferable in that the space utilization rate when positioned along the circumference is good. By setting the number of coils of the S group and the I group to four, a four-quadrant arrangement can be achieved. The number of coils in both groups is not limited to four.

  Since these coils surround the object in a cylindrical shape, the efficiency of signal reception is good. If these coils are arranged symmetrically with respect to the central axis of the cylinder, the symmetrical coil patterns can be shared. Moreover, by making the shape of the cylinder cylindrical, all the coil loops can be equidistant from the central axis. The shape of the cylinder is not limited to a cylinder. Moreover, it is not restricted to a dome shape.

  FIG. 6 shows the measurement result of the g factor, together with a comparative example, for the receiving coil unit 110 configured as described above. The comparative example is an RF coil of the aforementioned Siber et al., That is, an RF coil having a triangular loop. The measurement of the g factor was performed by setting the shape of the cylinder in which the coil is disposed as a simple cylinder and a dome, and the phase encoding direction as the SI direction and AP, respectively.

  As shown in the figure, when the phase encoding direction is set to the SI direction, the mean value mean_SI of the g factor is a rectangular coil, that is, a coil of this system is a triangular coil for both the cylinder and the dome. It is smaller than the coil of Seeber et al. Moreover, the dome has a smaller g factor than the cylinder. The maximum value max_SI of the g factor is equal to that of the rectangular coil and is considerably smaller than that of the dome-shaped triangular coil.

  When the phase encoding direction is the AP direction, the g factor of the rectangular coil is equivalent to that of the triangular coil for both the average value mean_AP and the maximum value max_AP. That is, performance equivalent to that of a triangular coil having a small g factor can be obtained.

  From this result, it is clear that the coil of this method is more advantageous than the coil of Seeber et al. Further, even when the phase encoding direction is set to the AP direction, the same performance as that of a triangular coil having a small g factor can be obtained, so that the coil of this system has a small g factor in both the SI and AP directions.

  FIG. 7 shows the effect of coil overlap. The figure shows the difference in g factor depending on the presence or absence of overlap. In the same figure, the separation is a state where no coils overlap, the SI overlap is a state overlapping in the SI direction, the RL overlap is a state overlapping in the circumferential direction of the cylinder, and all overlaps ( “all overlap” is a state of overlapping in the SI direction and the circumferential direction of the cylinder.

  As shown in the figure, the g factor in the SI overlap state is minimum regardless of whether the phase encoding direction is SI or AP, regardless of the average value or the maximum value. From this, the advantage of the present system overlapping in the SI direction is clear.

  Coils 12-82 that are not coupled to each other can independently receive magnetic resonance signals. As shown in FIG. 8, the reception signals of the coils 12-82 are input to the reception circuits 14-84 in the data collection unit 150, respectively. As a result, eight receiving systems 10-80 are configured. As described above, since the plurality of reception systems individually have coils, signal reception can be performed in parallel by the plurality of reception systems.

  FIG. 9 shows an example of a pulse sequence for photographing. This pulse sequence is a pulse sequence by EPI (echo planer imaging). The pulse sequence proceeds from left to right. The same applies hereinafter.

  In the figure, (1) shows an RF signal sequence. (2) to (4) are all gradient magnetic field sequences, (2) is a slice gradient, (3) is a frequency encoding gradient, and (4) is a phase encoding gradient. The static magnetic field is always applied with a constant magnetic field strength.

  First, spin excitation is performed by a 90 ° pulse. 180 ° excitation by a 180 ° pulse is performed after a predetermined time of 90 ° excitation. Both are selective excitations under the slice gradient Gslice.

  Next, a phase encode gradient Gphase and a frequency encode gradient Gfreq are applied in a predetermined sequence, and a plurality of echoes are sequentially read out. Multiple echoes have different phase encodings. The echo is represented by the center signal. The same applies hereinafter.

  Such a pulse sequence is repeated a predetermined number of times with a repetition time TR, and a plurality of echoes are read out each time. That is, a multi-shot scan is performed. The echo phase encoding is changed at each repetition, and an echo for one screen is acquired by repeating a predetermined number of times.

  By reading the echo by phase encoding and frequency encoding, k-space data is sampled. FIG. 10 is a conceptual diagram of the k space. As shown in the figure, the horizontal axis kx of the k space is the frequency axis, and the vertical axis ky is the phase axis.

  In the figure, each of a plurality of horizontally long rectangles represents a data sampling position on the phase axis. The number written in the rectangle represents the amount of phase encoding. The amount of phase encoding is normalized by π / N. N is the number of samplings in the phase direction.

  The phase encoding amount is 0 at the center of the phase axis ky. The phase encoding amount gradually increases from the center to both ends. The polarities of the increase are opposite to each other. The sampling interval, that is, the difference in phase encoding amount is π / N. The tomographic image is reconstructed by performing two-dimensional inverse Fourier transform on such k-space data. The reconstructed image becomes an image for a complete FOV. Hereinafter, a complete FOV is also referred to as a full FOV (full FOV).

  In parallel imaging, the sampling interval of the k space is increased to reduce the number of samplings in order to speed up imaging. That is, for example, as indicated by the hatched lines in FIG. 11, every other sampling in the direction of the phase axis ky is performed to reduce the number of samplings to 1/2. This shortens the shooting time by half and speeds up shooting.

  By having every other sampling, the sampling interval is doubled. By doubling the sampling interval, the FOV of the reconstructed image is reduced to ½ of the full FOV.

  The sampling interval in the phase encoding direction is doubled by setting the difference in phase encoding amount to 2π / N. As a result, the FOV is reduced to ½ in the phase encoding direction.

  In general, when the sampling interval, that is, the difference in phase encoding amount is increased by R times, the FOV is reduced to 1 / R. R is also called a reduction factor. In FIG. 11, R = 2. Hereinafter, the reduced FOV is also referred to as a reduced FOV.

  When the number of receiving systems is n, it is preferable that the reduction factor R satisfies the following relationship from the viewpoint of appropriately obtaining a full FOV output image described later.

here,
R: Reduction factor n: Number of receiving systems The operation of this apparatus by parallel imaging will be described. FIG. 12 shows a flow chart of the operation of this apparatus. As shown in the figure, at step 701, reception sensitivity distribution measurement is performed. Thereby, the spatial distribution of sensitivity of a plurality of receiving systems is measured.

  The spatial distribution of sensitivity of the receiving system is obtained as a sensitivity map (map) image. The sensitivity map image is obtained from images obtained by scanning the same slice of the target 1 using the RF coil unit 108 and the receiving coil unit 110, for example.

  That is, an image photographed using the RF coil unit 108 is used as a reference, an image photographed using each of the coils 12-82 is used as a measurement image, and a ratio between the measurement image and the reference image is obtained for each pixel. Created. The reference image and the measurement image are both taken by full FOV scanning. Thereby, a sensitivity map image is obtained at full FOV for each of the coils 12-82. Such a scan is also called a calibration scan.

  Next, in step 703, a sensitivity matrix is created. The sensitivity matrix is created based on a sensitivity map image for each coil. Hereinafter, the sensitivity map image is also simply referred to as a sensitivity map.

  The sensitivity matrix is an n × R matrix. Here, n is the number of receiving systems, and R is a reduction factor. When n = 8 and R = 2, the sensitivity matrix S is as follows.

  In the sensitivity matrix S, s11, s21,..., S81 are values of the same pixel in the sensitivity map image of the coils 12, 22,. The pixel values of each sensitivity map image at a distance of 1/2 FOV in the phase encoding direction from this pixel are s12, s22,. These are all complex numbers.

  Next, in step 707, scanning is performed. Scanning is performed by EPI. The EPI scan is performed on the reduced FOV by expanding the k-space sampling interval. The reduced FOV is, for example, 1/2 FOV. Note that the reduction factor is not limited to 1/2, and may be appropriate. Echo reception is performed in parallel through a plurality of reception systems 10-80.

  Next, in step 711, intermediate image generation is performed. The intermediate image generation is performed by two-dimensional inverse Fourier transform of echoes of a plurality of reception systems that have undergone phase correction. Since the intermediate image is a reduced FOV image, it includes an aliasing image.

  Next, in step 713, output image generation is performed. The output image is generated by calculation using the intermediate image and the sensitivity matrix. The following equation is used to generate the output image. The following equation is the same as that described in the above-mentioned document.

here,
V: Pixel value of full FOV image S: Sensitivity matrix S *: Adjoint matrix of S A: Pixel value of intermediate image As a result, a tomographic image of full FOV in which the aliasing image is rearranged at the original position is obtained. Can be obtained. Such tomographic images are displayed and stored at step 715. The display of the tomographic image is performed by the display unit 180, and the storage is performed in the memory in the data processing unit 170.

  The pulse sequence for parallel imaging is not limited to EPI, and may be another appropriate pulse sequence. As parallel imaging other than EPI, for example, there is imaging by a 3D gradient echo (3D gradient echo) method.

  FIG. 13 shows the pulse sequence. In both figures, (1) shows the pulse sequence of the RF signal. (2)-(4) each show a pulse sequence of a gradient magnetic field. (2) is the slice gradient and the phase encode gradient in the slice direction, (3) is the frequency encode gradient, and (4) is the phase encode gradient. The static magnetic field is always applied with a constant magnetic field strength.

  First, spin excitation by an α ° pulse is performed. α ° excitation is selective excitation under a slice gradient Gslice. After the α ° excitation, the phase encode gradient Gslice, the frequency encode gradient Gfreq, and the phase encode gradient Gphase in the slice direction are applied in a predetermined sequence, and the echo is read out.

  Such a pulse sequence is repeated a predetermined number of times with a repetition time TR, and an echo is read out each time. The echo phase encoding is changed each time it is repeated, and an echo for one screen is acquired by repeating a predetermined number of times.

  By reading the echoes by biaxial phase encoding and frequency encoding, three-dimensional k-space data is sampled. By increasing the sampling interval, data collection is performed on a three-dimensional reduced FOV.

  A 3D image is reconstructed by performing a three-dimensional inverse Fourier transform on this data. The 3D image is an intermediate image for the reduced FOV. From this intermediate image, a full FOV output image is generated using the sensitivity matrix S. However, a sensitivity matrix corresponding to 3D is used.

  Since the receiving coil unit 110 used for such imaging is configured as shown in FIG. 3, parallel imaging with good SNR can be performed even when phase encoding is performed in the SI direction, thereby improving the quality. A good image can be obtained.

  The present invention has been described above based on the preferred embodiments. However, those skilled in the art to which the present invention pertains have the technical scope of the present invention with respect to the above embodiments. Various changes and substitutions can be made without departing. Accordingly, the technical scope of the present invention includes not only the above-described embodiments but also all the embodiments belonging to the scope of the claims.

It is a block diagram of an example of the best mode for carrying out the present invention. It is a figure which shows the external shape of a receiving coil part. It is a figure which shows the coil of a receiving coil part. It is a figure which shows the coil of a receiving coil part. It is a figure which shows the plane expansion | deployment of the coil of a receiving coil part. It is a figure which shows g factor of a receiving coil part. It is a figure which shows g factor of a receiving coil part. It is a figure which shows a some receiving system. It is a figure which shows an example of the pulse sequence for magnetic resonance imaging. It is a figure which shows k space. It is a figure which shows k space. It is a flowchart of operation | movement of the apparatus of an example of embodiment of this invention. It is a figure which shows an example of the pulse sequence for magnetic resonance imaging.

Explanation of symbols

1 Target 100 Magnet system 102 Main magnetic field coil unit 106 Gradient coil unit 108 RF coil unit 110 Reception coil unit 130 Gradient drive unit 140 RF drive unit 150 Data collection unit 160 Sequence control unit 170 Data processing unit 180 Display unit 190 Operation unit 500 Cradle 12-82 coil 14-84 receiving circuit

Claims (16)

An RF coil that is used in proximity to an imaging target to perform magnetic resonance imaging,
A first coil group composed of a plurality of unit coils that are arranged so as to surround the object without overlapping each other and are not coupled to each other;
The position of the object in the body axis direction is different from that of the first coil group, and the object is disposed so as to surround the object without overlapping each other and partially overlap the plurality of unit coils in the first coil. A second coil group comprising a plurality of unit coils that are not coupled to each other;
An RF coil comprising: The unit coil loop has four internal angles at right angles,
The RF coil according to claim 1. The number of unit coils in the first and second coil groups is four.
The RF coil according to claim 1 or 2, wherein The plurality of unit coils surround the object in a cylindrical shape,
The RF coil according to any one of claims 1 to 3, wherein The arrangement of the unit coils is symmetric with respect to the central axis of the cylinder.
The RF coil according to claim 4. The cylinder is a cylinder;
The RF coil according to claim 4 or 5, wherein The cylinder has at least one end that is recessed,
The RF coil according to any one of claims 4 to 6, wherein: The tip side protrudes in the body axis direction,
The RF coil according to claim 7. An MRI apparatus for reconstructing an image based on a magnetic resonance signal collected by applying a static magnetic field, a gradient magnetic field, and an RF magnetic field to an imaging target,
An RF coil for receiving magnetic resonance signals;
This RF coil
An RF coil used in proximity to an imaging target,
A first coil group composed of a plurality of unit coils that are arranged so as to surround the object without overlapping each other and are not coupled to each other;
The position of the object in the body axis direction is different from that of the first coil group, and the object is disposed so as to surround the object without overlapping each other and partially overlap the plurality of unit coils in the first coil. A second coil group comprising a plurality of unit coils that are not coupled to each other;
An MRI apparatus characterized by comprising: The unit coil loop has four internal angles at right angles,
The MRI apparatus according to claim 9. The number of unit coils in the first and second coil groups is four.
The MRI apparatus according to claim 9 or 10, wherein the MRI apparatus is characterized. The plurality of unit coils surround the object in a cylindrical shape,
12. The MRI apparatus according to claim 9, wherein the MRI apparatus is any one of claims 9 to 11. The arrangement of the unit coils is symmetric with respect to the central axis of the cylinder.
The MRI apparatus according to claim 12, wherein: The cylinder is a cylinder;
The MRI apparatus according to claim 12 or 13, wherein the MRI apparatus is characterized in that The cylinder has at least one end that is recessed,
15. The MRI apparatus according to claim 12, wherein the MRI apparatus is any one of claims 12 to 14. The tip side protrudes in the body axis direction,
The MRI apparatus according to claim 15.

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