JP4601933B2 - Magnetic resonance imaging apparatus and high-frequency receiving coil - Google Patents

Description

  The present invention relates to a magnetic resonance imaging apparatus and a high frequency coil having means effective for setting a high frequency coil (RF coil) on a subject.

  A Magnetic Resonance Imaging (MRI) device resonates the energy of a high-frequency magnetic field that rotates at a specific frequency when a population of nuclei with inherent magnetic moments is placed in a uniform static magnetic field. It is a device that visualizes chemical and physical microscopic information of a substance or observes a chemical shift spectrum by utilizing a phenomenon of absorption.

  8, 9, and 10 are views showing the imaging settings of the conventional magnetic resonance imaging apparatus 70, respectively. As shown in FIG. 8, the magnetic resonance imaging apparatus 70 has a port 71 for connecting the high-frequency coil 73 and the main body of the apparatus 70 on the bed 73 side of the gantry 72. In order to connect the port 71 and the high-frequency coil 73 in the direction of the subject shown in the drawing, it is necessary to pass the subject side and draw out the cable 74 of the coil 73 to the port 71. In the conventional apparatus, in order to prevent contact between the subject and the cable due to the drawer, the cable is pulled out under the bed mat, or a spacer such as a towel is provided between the cable and the subject. We are aiming for safety in shooting.

  However, it is troublesome to pull out the cable from the bottom of the bed mat, set the spacer, and the like as described above every time shooting is performed, which is a heavy burden on the operator. In particular, in the setting shown in FIG. 9 in which the subject is fed from the foot to the pedestal 72, the cable comes out in the direction of the arm, so the subject may touch the cable from the coil to the mat. (Part a), there is a risk of changing the shooting environment.

In addition, since it takes time and labor to set the shooting, it is a burden for the photographed person.

  Furthermore, when photographing the shoulder with the surface coil, the surface coil is passed through the arm, and in order to prevent the cable from coming into contact with the subject, the cable outlet should be set to the head side as shown in FIG. Is natural. In this case, once the port 71 is on the front side of the pedestal 72, the cable once goes out to the head side and returns to the foot side, and passes through the side of the coil (part b). The passage of the high frequency coil cable through the high frequency coil body in this manner may affect the reception sensitivity of the high frequency coil due to the electromagnetic influence from the cable. Further, when the coil has a preamplifier, there is a risk of oscillation. Therefore, in order to realize accurate shooting, the shooting setting is not desirable.

  The present invention has been made in view of the above circumstances. A magnetic resonance imaging apparatus and a high-frequency coil that can easily perform imaging settings and can realize accurate imaging without affecting the reception sensitivity of the high-frequency coil. The purpose is to provide.

  In order to achieve the above object, the present invention takes the following measures.

The invention according to claim 1 is a magnetic resonance imaging apparatus for receiving a magnetic resonance signal generated from a subject arranged in a static magnetic field generated by a cylindrical magnet and generating a magnetic resonance image, wherein the cylinder A bed provided on one opening side of the shape magnet and moving the top plate carrying the subject into the cylindrical magnet to place the subject in the static magnetic field; and the magnetic resonance A high-frequency coil that receives a signal; an image generating unit that generates the magnetic resonance image based on the magnetic resonance signal; and the magnetic resonance signal that is connected to the high-frequency coil and received by the receiving coil. a port for transferring the generating means, and the bed side provided on the end face of the first of the high-frequency coil connectable port of the cylindrical magnet, and the bed of the cylindrical magnet anti A second port provided on the end face of the side connectable to the high frequency coil, and presenting means for presenting whether the high-frequency coil is connected to one of the first port or the second port to the operator a magnetic resonance imaging apparatus characterized by comprising a.
The invention according to claim 5 is used in a magnetic resonance imaging apparatus that receives a magnetic resonance signal generated from a subject arranged in a static magnetic field generated by a cylindrical magnet and generates a magnetic resonance image, and the cylinder A high frequency that can be connected to either the first port provided on the end surface of the shape magnet on the bed side on which the subject is mounted and the end surface of the cylindrical magnet on the opposite side of the bed. a coil, a first coil, and the first of the second coil disposed geometrically rotated 90 ° with respect to the body axis of the subject relative to the coil, the high frequency coil is the first Determining means for determining which of the first port and the second port is connected, and depending on the determination of the determining means, the first signal received by the first coil or the second port By coil Controls either phase of the second signal received Te, a high-frequency coil which is characterized by comprising a signal combining means for combining both the.

  As described above, according to the present invention, it is possible to realize a magnetic resonance imaging apparatus and a high-frequency coil that can easily perform imaging settings and can perform accurate imaging without affecting the reception sensitivity of the high-frequency coil.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, components having substantially the same function and configuration are denoted by the same reference numerals, and redundant description will be provided only when necessary.

  FIG. 1 is a block diagram showing a configuration of a magnetic resonance imaging apparatus according to the present embodiment. In the figure, a magnetic resonance imaging apparatus 10 includes a static magnetic field magnet 11, a cooling system controller 12, a shim coil (not shown), a gradient magnetic field coil 13, a high frequency transmission coil 14, a high frequency reception coil 15, a first port 16a, A second port 16b, a gradient magnetic field coil device power supply 17, a transmission unit 18, a reception unit 19, a data collection unit 20, a sequence control unit 21, a computer system 22, an input unit 23, and a display 24 are provided.

  The static magnetic field magnet 11 is a magnet that generates a static magnetic field, and generates a uniform static magnetic field. For example, a permanent magnet or a superconducting magnet is used as the static magnetic field magnet 11.

  A shim coil (not shown) is provided inside the static magnetic field magnet 11 and is a coil for actively enhancing the uniformity of the magnetic field. This shim coil is driven by a shim coil power supply (not shown). The shim coil and the gradient magnetic field coil 13 apply a uniform static magnetic field to a subject (not shown) and a gradient magnetic field having a linear gradient magnetic field distribution in three directions X, Y, and Z orthogonal to each other. In this embodiment, the Z-axis direction is the same as the direction of the static magnetic field.

  The cooling system control unit 12 controls the cooling mechanism of the static magnetic field magnet 11.

  The gradient magnetic field coil 13 is provided inside the static magnetic field magnet 11 and has a shorter axis than the static magnetic field magnet 11, and converts the pulse current supplied from the gradient magnetic field coil device power supply 17 into a gradient magnetic field. The signal generation site (position) is specified by the gradient magnetic field generated by the gradient magnetic field coil 13.

  In the present embodiment, it is assumed that the gradient magnetic field coil 13 and the static magnetic field magnet 11 are cylindrical. The gradient coil 13 is disposed in a vacuum by a predetermined support mechanism. This is because the vibration of the gradient magnetic field coil 13 generated by applying the pulse current is not propagated to the outside as a sound wave from the viewpoint of noise reduction.

  The high frequency transmission coil (RF transmission coil) 14 is a coil for applying a high frequency pulse for generating a magnetic resonance signal to the imaging region of the subject.

  The high-frequency receiving coil (RF receiving coil) 15 is a coil for receiving magnetic resonance from the subject, which is installed so as to sandwich the subject in the vicinity of the subject, preferably in a close contact state. The high-frequency receiving coil 15 generally has a dedicated shape for each part.

  1 illustrates a cross coil system in which a high-frequency transmission coil and a high-frequency reception coil are separated from each other, but a configuration using a single coil system in which these coils are shared by one coil may be employed.

  The first port 16 a and the second port 16 supply power to the connected high-frequency receiving coil 15, and transfer a reception signal received by the high-frequency receiving coil 15 to the receiving unit 19. The first port 16a and the second port 16 may be located at any location as long as they are allocated to the respective openings of the static magnetic field magnet 11 and the like.

  The transmission unit 18 includes an oscillation unit, a phase selection unit, a frequency conversion unit, an amplitude modulation unit, and a high frequency power amplification unit (each not shown), and transmits a high frequency pulse corresponding to the Larmor frequency to the transmission high frequency coil. To do. Due to the high frequency generated from the high frequency transmission coil 14 by the transmission, the magnetization of the predetermined atomic nucleus of the subject is excited.

  The receiver 19 has an amplifier, an intermediate frequency converter, a phase detector, a filter, and an A / D converter (each not shown). The receiving unit 19 amplifies the magnetic resonance signal (high frequency signal) received from the high frequency coil 14 and releases when the nuclear magnetization relaxes from the excited state to the ground state, and intermediate frequency conversion processing using the transmission frequency. , Phase detection processing, filter processing, and A / D conversion processing are performed.

  The receiving unit 19 includes a connection port determining unit 190 and a QD composition switching unit 191. The connection port determining unit 190 determines to which port the high frequency receiving coil 15 is connected. The QD synthesis switching unit 191 controls the phase shift of the QD coil based on the determination of the connection port determination unit 190 when performing a bi-directional measurement to be described later using a QD (Quadrature) coil as the high-frequency receiving coil 15. Perform signal synthesis.

FIG. 2 is a diagram illustrating a configuration of the QD synthesis switching unit 191. In the figure, when used the first port in the measurement, the tap of the coil A side a _1, the tap of the coil B side is connected to the b _1, 90 of the signal B received by the coil B A phase shift is executed, synthesized by the hybrid circuit (HYB), and output as a synthesized signal (STN). On the other hand, when used the second port in the measurement, the tap of the coil A side a _2, tap coil B side is connected to the b _2, a signal B received by the coil A 90 ° phase The shift is executed, synthesized by the hybrid circuit (HYB), and outputted as a synthesized signal (STN).

  The data collecting unit 20 collects the digital signal sampled by the receiving unit 19.

  The sequence control unit 21 controls the gradient coil device power source 17, the reception unit 19, and the data collection unit 20.

  The computer system 22 controls the sequence control unit 21 based on a command input from the input unit 23. In addition, the computer system 22 performs post-processing on the magnetic resonance signal input from the data collection unit 20, that is, reconstruction such as Fourier transform, and the like, and obtains spectrum data or image data of a desired nuclear spin in the subject. .

  The input unit 23 has an input device (mouse, trackball, mode changeover switch, keyboard, etc.) for capturing various instructions / commands / information from the operator.

  The display 24 is output means for displaying spectrum data or image data input from the computer system 22.

(Reverse shooting function)
The magnetic resonance imaging apparatus 10 has a reversal imaging function capable of imaging even if the high-frequency receiving coil 15 is arranged upside down with respect to the body axis (that is, arranged rotated 180 degrees in the z direction). Yes. Hereinafter, with reference to the drawings, the function will be described by taking as an example a case where a QD type abdominal flexible coil is used as the high frequency receiving coil 15 and a case where a linear type surface circular coil is used for shoulder imaging. .

  First, the case where an abdominal flexible coil is used is demonstrated. FIG. 3 is a top view of the static magnetic field magnet 11 portion of the magnetic resonance imaging apparatus 10 (except for the upper half of the static magnetic field magnet 11 and the like). FIG. 4 is a side view of the static magnetic field magnet 11 portion of the magnetic resonance imaging apparatus 10 (however, the front half of the static magnetic field magnet 11 etc. is excluded).

  As shown in FIGS. 3 and 4, when an abdominal flexible coil is used and the lower abdomen is imaged, the subject is inserted into the center of the static magnetic field magnet 11 from the foot side direction. The coil is placed on the lower abdomen of the subject arranged at the center of the static magnetic field magnet 11. Therefore, it is preferable that the cable of the abdominal flexible coil is drawn from the foot side of the subject because contact with the subject can be avoided. Since the viewpoint and the subject are inserted into the static magnetic field magnet 11 or the like from the foot side, the abdominal flexible coil cable is connected to the first port 16a in the examples of FIGS. .

The connection coil determination unit 191 determines that the abdominal flexible coil is connected to the first port 16a. Based on this determination, the QD combination switching unit 191 changes to the first port connection mode (in FIG. 2, the coil A side tap is connected to a ₁ and the coil B side tap is connected to b ₁ ). Switch taps.

  When an abdominal flexible coil is used and the upper abdomen is imaged, the subject is inserted into the center of the static magnetic field magnet 11 from the direction of the head as shown in FIG. Also in this case, since the cable of the abdomen flexible coil is preferably routed to the foot side, it is now connected to the second port 16b.

When connected to the second port 16b, the QD combination switching unit 191 determines the connection configuration for the second port (in FIG. 2, the coil A side) based on the determination of the connection coil determination unit 191. the tap into a _2, switches the tap-tap of the coil B side form) connected to b _2.

In this way, the phase of the received signal is controlled by the QD synthesis switching unit 191 in accordance with the direction of the high-frequency receiving coil 15 for the following reason. That is, the QD coil has two sets of coils arranged geometrically rotated by 90 ° with respect to the Z axis, and the signal received in each set has a phase of exactly 90 °. It will be shifted. Thus, the measurements from the normal point of view V _1, for example, a signal B received by the coil B as shown in FIG. 6 (a) + 90 ° phase shifted, by combining the signal A received in the coil A In order to enhance the signal. However, in the measurement from the viewpoint V ₂ obtained by inverting the direction of the high-frequency reception coil 15, when combined with the pre-inversion (i.e. FIG. 6 (a)) + 90 ° phase shift in the same manner as signal B and then signal A, FIG. 6 ( As shown in b), the two signals are subtracted, and the signal cannot be enhanced. Accordingly, when the measurement is performed with the direction of the high-frequency receiving coil 15 reversed, the phase control by the post-inversion QD synthesis switching unit 191 is required as in the magnetic resonance imaging apparatus 10.

  Next, a case where a surface circular coil is used as the high-frequency receiving coil 15 and a shoulder is photographed will be described. FIG. 7 is a side view of the static magnetic field magnet 11 portion of the magnetic resonance imaging apparatus 10 (except the front half of the static magnetic field magnet 11 and the like).

  As shown in FIG. 7, the surface circular coil is used in a state where the arm of the subject is passed through the surface circular coil, and is arranged at the center of the static magnetic field magnet 11. Therefore, it is preferable that the cable of the surface circular coil is pulled out from the head side of the subject because the contact with the subject can be avoided. Since the viewpoint and the subject are inserted into the static magnetic field magnet 11 and the like from the head side, the surface circular coil cable is connected to the first port 16a in the example of FIG.

  The connection coil determination unit 191 recognizes that the surface circular coil is connected to the first port 16a.

  According to the configuration described above, the following effects can be obtained.

  The magnetic resonance imaging apparatus 10 has ports for connecting cables of high-frequency receiving coils to both openings of the static magnetic field magnet 11 and the like. Therefore, since the cable of the high frequency receiving coil can be pulled out in any direction along the body axis, interference between the cable and the subject can be prevented.

  Even when the direction of the high-frequency receiving coil is reversed, the direction can be automatically recognized based on the port to be used, and appropriate signal synthesis can be performed. Therefore, the operator can perform accurate photographing without worrying about which direction the high-frequency receiving coil is used and which port is connected. As a result, it is possible to prevent photographing errors and reduce the work burden on the operator.

  Further, since the cable can be pulled out without passing through the side of the high-frequency receiving coil, it is possible to prevent the reception sensitivity of the coil from being lowered. This situation will be described in comparison with a system having only one port as follows. That is, unlike the present system, for example, in the case of a system having only one port 71 as shown in FIG. 10, the cable of the surface circular coil needs to go out to the head side and then to the folded leg side. In such a case, the cable passes beside the surface circular coil, and the reception efficiency of the surface circular coil may decrease due to the influence of the cable. In addition, when the surface circular coil has a preamplifier, there is a possibility of oscillation by a cable passing through the side.

  On the other hand, according to the magnetic resonance imaging apparatus 10, the cable can be pulled out without causing interference with the subject and passing through the side of the high-frequency receiving coil. Therefore, it is possible to prevent an adverse effect of the cable on the coil and to realize highly accurate signal measurement.

  Next, some modified examples of this embodiment will be shown.

(Modification 1)
In the magnetic resonance imaging apparatus 10, the connection port determining unit 190 determines whether the high-frequency receiving coil 15 is connected to the first port 16 a or the second port 16. In addition to this, not only the system but also the operator himself can quickly determine the connection port, so that the determination result of the connection port determination unit 190 is displayed on the display 24 or corresponds to the port in use according to the determination result The structure which has a function of blinking the lamp to perform may be sufficient.

  Thereby, the operator can grasp | ascertain rapidly the connection form of a high frequency receiving coil.

(Modification 2)
Moreover, the structure which has the connection port judgment part 190 and the QD synthetic | combination switching part 191 in the high frequency receiving coil 15 side may be sufficient.

(Modification 3)
In the above embodiment, the QD coil has been described as an example. Naturally, the magnetic resonance imaging apparatus 10 can use not only a QD coil but also a normal linear coil or the like.

  Although the present invention has been described based on the embodiments, those skilled in the art can come up with various changes and modifications within the scope of the idea of the present invention. It is understood that it belongs to the scope of the present invention, and various modifications can be made without departing from the scope of the invention.

  The above-described embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent requirements. For example, even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effect described in the column of the effect of the invention If at least one of the following is obtained, a configuration in which this configuration requirement is deleted can be extracted as an invention.

  As described above, according to the present invention, it is possible to realize a magnetic resonance imaging apparatus and a high-frequency coil that can easily perform imaging settings and can perform accurate imaging without affecting the reception sensitivity of the high-frequency coil.

FIG. 1 is a block diagram showing a configuration of a magnetic resonance imaging apparatus according to the present embodiment. FIG. 2 is a diagram illustrating a configuration of the QD synthesis switching unit 191. FIG. 3 is a top view of the static magnetic field magnet 11 portion of the magnetic resonance imaging apparatus 10. FIG. 4 is a side view of the static magnetic field magnet 11 portion of the magnetic resonance imaging apparatus 10. FIG. 5 is a side view of the static magnetic field magnet 11 portion of the magnetic resonance imaging apparatus 10. FIG. 6A and FIG. 6B are diagrams for explaining the phase of the received signal when the high-frequency receiving coil 15 is turned upside down along the subject body axis. FIG. 7 is a side view of the static magnetic field magnet 11 portion of the magnetic resonance imaging apparatus 10. FIG. 8 is a view showing a state of imaging settings of a conventional magnetic resonance imaging apparatus. FIG. 9 is a view showing a state of imaging settings of a conventional magnetic resonance imaging apparatus. FIG. 10 is a diagram showing a state of imaging settings of a conventional magnetic resonance imaging apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Magnetic resonance imaging apparatus 11 ... Static magnetic field magnet 13 ... Gradient magnetic field coil 14 ... High frequency transmission coil 15 ... High frequency reception coil 16a ... 1st port 16b ... 2nd port 17 ... Gradient magnetic field coil apparatus power supply 18 ... Transmission part 19 Receiving unit 20 Data collecting unit 21 Sequence control unit 22 Computer system 23 Input unit 24 Display

Claims (5)

A magnetic resonance imaging apparatus for receiving a magnetic resonance signal generated from a subject arranged in a static magnetic field generated by a cylindrical magnet and generating a magnetic resonance image,
A couch provided on one opening side of the cylindrical magnet and moving the top plate on which the subject is mounted to the inside of the cylindrical magnet to place the subject in the static magnetic field;
A high-frequency coil for receiving the magnetic resonance signal;
Image generating means for generating the magnetic resonance image based on the magnetic resonance signal;
A port connected to the high-frequency coil for transferring the magnetic resonance signal received by the receiving coil to the image generating means, provided on the end surface of the cylindrical magnet on the bed side, and the high-frequency coil A first port that can be connected, and a second port that is provided on the end surface of the cylindrical magnet opposite to the bed and to which the high-frequency coil can be connected ,
Presenting means for presenting to an operator whether the high-frequency coil is connected to the first port or the second port;
A magnetic resonance imaging apparatus comprising: The high-frequency coil is a QD coil having a first coil and a second coil that is geometrically rotated by 90 ° with respect to the body axis direction of the subject with respect to the first coil,
Determining means for determining whether the high-frequency coil is connected to the first port or the second port;
A signal for controlling the phase of either the first signal received by the first coil or the second signal received by the second coil in accordance with the determination by the determination means, and combining both Combining means;
The magnetic resonance imaging apparatus according to claim 1, further comprising:   The magnetic resonance imaging apparatus according to claim 1, wherein the high-frequency coil is a linear coil. The direction of the first port relative to the central axis of the cylindrical magnet viewed from the bed side and the direction of the second port relative to the central axis of the cylindrical magnet viewed from the side opposite to the bed the magnetic resonance imaging apparatus as claimed in any one of claims 1 to 3, wherein the at least. Used in a magnetic resonance imaging apparatus for receiving a magnetic resonance signal generated from a subject arranged in a static magnetic field generated by a cylindrical magnet and generating a magnetic resonance image, and mounting the subject of the cylindrical magnet A first port provided on an end surface on the bed side and a high frequency coil provided on an end surface opposite to the bed of the cylindrical magnet and connectable to both of the second ports ,
A first coil;
A second coil disposed by being rotated 90 ° geometrically with respect to the body axis direction of the subject with respect to the first coil;
Determination means for determining whether the high-frequency coil is connected to the first port or the second port ;
A signal for controlling the phase of either the first signal received by the first coil or the second signal received by the second coil in accordance with the determination by the determination means, and combining both Combining means;
A high frequency coil comprising:

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