JPH0947444A - Rf probe for magnetic resonance device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an RF probe for magnetic resonance device by which whole of head and cervical part can be well photographed. SOLUTION: This RF probe for magnetic resonance device is provided with a head part solenoid coil 1, a saddle solenoid coil 2, a cervical part solenoid coil 3, and an assisting part 10, and induced-coupling which is generated between the cervical part solenoid coil 3 and the head part solenoid coil 1 is canceled by an inversely induced-coupling which is generated in the assisting part 10, and signals are detected from respective coils at the same time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to magnetic resonance imaging for detecting magnetic resonance signals (hereinafter referred to as MR signals) from hydrogen, phosphorus, etc. in an object to visualize nuclear density distribution and relaxation time distribution. The present invention relates to a radio frequency (RF) probe for an apparatus (hereinafter referred to as an MRI apparatus).

[0002]

2. Description of the Related Art An MRI apparatus obtains a tomographic image of a subject by utilizing the MR phenomenon. By applying an RF magnetic field in pulses to the subject placed in a static magnetic field, A nuclear magnetic resonance (NMR) phenomenon is caused in nuclear spins such as protons that compose tissue, an MR signal that is an electromagnetic wave emitted by the nuclear spins is detected, and an image is reconstructed using this MR signal.

Here, an RF probe is used to apply an RF pulse and detect an MR signal. Among the RF probes, the receiving coil for receiving the MR signal is a solenoid coil, a saddle coil or a QD (Quadrature Detection;
(Eection) Various shapes such as coils are used, and further, an array coil formed by arranging a plurality of solenoid coils and a QD array coil formed by arranging a plurality of highly sensitive QD coils are also used. . The array coil is
Each unit coil that constitutes this is configured so that inductive coupling does not occur between adjacent unit coils, and the field of view can be substantially expanded. Regarding the array coil, for example, Japanese Patent Publication No. 2-500175 or Magnetic Resonance in Medicine (Magnetic Reson)
ance in Medicine) 16: 192 to 225 (1990). The QD array coil is described in JP-A-4-47020 or JP-A-6-343618.

[0004]

In the above-mentioned conventional array coil, since the size (shape) of each unit coil constituting the array coil is the same and the central axes of the unit coils are the same, the abdomen and the head are formed. It is good for imaging only the part where the shape is relatively unchanged, but when imaging a region where the shape changes significantly, such as the head and neck (up to the fifth thoracic vertebra), the unit coil used Depending on the size, problems arise with a narrow cervical field of view or poor cervical sensitivity. The present invention has been made in view of such problems,
R for MRI device that can satisfactorily image the entire area of multiple parts whose shape or size changes greatly like the head and neck
The purpose is to provide an F probe.

[0005]

In order to achieve the above-mentioned object, in the present invention, the NMs from the site where the size of the subject is different
Since the R signal is detected, the diameters of the coils for detecting the NMR signals from the respective parts are made different, and the ratio of the space occupied by the subject to the coils attached to the respective parts (referred to as filling factor) is increased. The first feature is that, and in consideration of the correspondence to a plurality of parts where the central axis of one part is inclined with respect to the other, such as the head and neck, the centers of the two coils are considered. The second feature is that the axes are arranged to intersect.

[0006]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram showing an embodiment in which the present invention is applied to a vertical magnetic field type head and neck coil, which includes a head solenoid coil 1, a saddle coil 2, a neck solenoid coil 3 and an auxiliary portion 10. There is. The head solenoid coil 1 and the saddle coil 2 are vertically (Z direction) 29
The head solenoid coil 1 has a width of 50 on an elliptic cylindrical acrylic bobbin (not shown) having a size of 5 mm and a width (X direction) of 225 mm.
mm, the saddle coil 2 is formed of a copper plate having a width of 30 mm, and each coil is arranged on the bobbin so as to share the central axis 21. The saddle coil 2 is a serial type having a parallel part gap G of 80 mm and a length (Y direction) of 245 mm. The neck solenoid coil 3 is smaller than the head coil, is formed of a copper plate having a width of 50 mm on a cylindrical acrylic bobbin (not shown) having a diameter of 200 mm, and has a central axis 22. Although not shown, each coil includes a resonance capacitance element and a matching capacitance element, and the coils resonate in parallel at a desired frequency to obtain a desired output impedance (for example, 200Ω). When the static magnetic field strength is 0.3 T and protons are detected, the resonance frequency is set to 12.7 MHz. In addition, each coil is a split type that can be split up and down by the connector 4 to facilitate mounting on a subject (not shown).

The head solenoid coil 1 forms an RF magnetic field in the Y direction and the saddle coil 2 forms an RF magnetic field in the X direction. That is, both coils detect the Y direction component and the X direction component of the MR signal rotating on the XY plane orthogonal to the static magnetic field direction (Z axis direction). Therefore, the head solenoid coil 1 and the saddle coil 2 form a QD coil. At this time, unless attention is paid to the arrangement of the two coils and 2, inductive coupling occurs between both coils, but by adjusting the relative positions of both coils in the Y direction, inductive coupling does not occur. On the other hand, the neck solenoid coil 3 forms an RF magnetic field in a direction (direction of the central axis 22) inclined by θ (for example, 16 degrees) from the Y direction. At this time, the neck solenoid coil 3 and the saddle coil 2
The inductive coupling between them is eliminated by making the central axes 21 and 22 of both coils exist on the same plane (YZ plane). Further, the inductive coupling generated between the neck solenoid coil 3 and the head solenoid coil 1 is canceled by the inductive coupling opposite to that generated in the auxiliary portion 10. with this,
It is possible to detect signals from each of the above coils simultaneously.

As shown in FIG. 2, the auxiliary portion 10 is an 8-shaped auxiliary coil 1 connected in series to the head solenoid coil 1.
1-1 connected to the neck solenoid coil 3 in series 8
It is composed of a square-shaped auxiliary coil 11-2 and a capacitive element 12 added to each auxiliary coil. Each auxiliary coil resonates in series at a desired frequency due to its own inductance component and the capacitive element 12. This resonance frequency is, for example, 1 when detecting a proton with a static magnetic field strength of 0.3T.
It is 2.7 MHz. The auxiliary coils 11-1 and 11-2 are
By overlapping each other by the length D, inductive coupling is generated between the auxiliary coils, and the inductive coupling between the head solenoid coil 1 and the neck solenoid coil 3 is canceled. For example, the center-to-center distance C between the copper plates of the head solenoid coil 1 and the neck solenoid coil 3 is 130 mm, and each auxiliary coil is made of copper wire having a diameter of 3 mm. The length (Y direction) is 30 mm and the width (X direction) is 70 mm. In this case, the overlap length D is 17 mm.

As described above, the head and neck coil from which the inductive coupling between the coils has been removed is an image obtained by the QD coil composed of the head solenoid coil 1 and the saddle coil 2 and an image obtained by the neck solenoid coil 3. By synthesizing the above, it becomes possible to satisfactorily image the entire head and neck. FIG.
FIG. 8 is a diagram showing another embodiment of the present invention. This embodiment is different from the embodiment of FIG. 1 in that the neck solenoid coil 3 is movable (saddle coil is not shown). The cervical solenoid coil 3 can be rotationally moved around the fixed point 23, and the angle θ at which the central axes 21 and 22 intersect is changed by the rotational movement. The reason why the cervical solenoid coil 3 is movable is to prevent the coil from touching the chin or the shoulder, and the wearability on the subject is improved. The cervical solenoid coil 3
The sensitivity decreases as the angle θ increases. This is because the MR signal to be detected is in the Y direction and the coil sensitivity is proportional to cos θ. It is desirable that the angle θ is as small as possible, but in consideration of the wearability to the subject, the angle θ always has a certain angle, and this angle is slightly different for each subject. Considering both wearability and sensitivity, the angle θ is 0-
The range of 45 degrees is preferable.

For example, when the cervical solenoid coil 3 is moved to increase the angle θ, the inductive coupling between the cervical solenoid coil 3 and the head solenoid coil 1 is reduced. At this time, in the auxiliary unit 10, the auxiliary coil 11-1 of FIG. 2 moves to the left side of the drawing in conjunction with the movement of the cervical solenoid coil 3, that is, the overlap length D becomes small, and Inductive coupling becomes smaller. As a result,
The inductive coupling generated between the neck solenoid coil 3 and the head solenoid coil 1 is canceled. Conversely, when the neck solenoid coil 3 is moved to decrease the angle θ, the overlap length D increases and the inductive coupling is canceled out. By this series of operations, even if the angle θ changes for each subject, the wearability is not impaired, signals can be simultaneously detected from the respective coils, and the entire head and neck can be imaged satisfactorily.

FIG. 4 is a diagram showing an example of the overall configuration of an MRI apparatus to which the RF probe of the present invention is applied. The MRI apparatus includes a static magnetic field generating magnet 30 that generates a strong and uniform static magnetic field around the subject 40, a high frequency transmitter 32 that transmits a high frequency signal to the subject 40, and an MR signal from the subject 40.
That is, a high-frequency receiving unit 34 that receives a high-frequency signal, a gradient magnetic field generating unit 36 that generates a gradient magnetic field in the three-axis directions to be superimposed on the static magnetic field, and an image reconstruction by performing processing such as Fourier transform and correction of the MR signal Signal processing unit 38, a display unit 39 such as a CRT that displays an image, and a control unit 31 that controls these.
The output of the high frequency transmission unit 32 is sent to the RF probe 33 for transmission, and the high frequency signal is transmitted to the subject 40. The output of the gradient magnetic field generator 36 is the gradient magnetic field coil 37.
And the gradient magnetic fields Gx, G in three axial directions orthogonal to each other.
y, Gz are generated. A tomographic plane with respect to the subject 40 can be set depending on how to apply these gradient magnetic fields. The high frequency receiver 34 receives the high frequency signal from the subject 40 through the RF probe 35 for reception. In FIG. 4, the transmitting RF probe 33, the receiving RF probe 35, and the gradient magnetic field coil 37 are arranged in the space around the subject 40, and between the RF probes 33, 35 and the gradient magnetic field coil 37. A high frequency shield (not shown) is provided to block high frequency noise from the outside.

The RF probe of the present invention has such an MRI.
It is applied to the receiving RF probe 35 of the device. The present invention can be modified within the scope not departing from the gist thereof, and in addition to the head and neck described in the above embodiment, the present invention can be used to change the shape or size between a plurality of parts such as the chest and the neck. Various probes that simultaneously image the site are possible.

[0013]

As described above, according to the present invention, it is possible to simultaneously image a plurality of regions having different sizes such as a head and a neck with high image quality. Moreover, the subject is not forced to have an unreasonable posture during imaging.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a main part of the embodiment shown in FIG.

FIG. 3 is a diagram showing another embodiment of the present invention.

FIG. 4 is a block diagram of an MRI apparatus to which the present invention is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Head solenoid coil 2 ... Saddle coil 3 ... Neck solenoid coil 4 ... Connector 10 ... Auxiliary part 11 ... Conductive loop 12 ... Capacitance element 21, 22 ... Central axis 23 ... Fixed point 30 ... Static magnetic field generating magnet 31 ... Control Part 32 ... High-frequency transmitter 33 ... Transmission RF probe 34 ... High-frequency receiver 35 ... Receiving RF probe 36 ... Gradient magnetic field generator 37 ... Gradient magnetic field coil 38 ... Signal processor 39 ... Display 40 ... Subject

Claims (5)

[Claims] 1. A first solenoid coil having a first diameter and a second solenoid coil having a diameter different from the first diameter are arranged in parallel, and the first solenoid coil and the second solenoid coil are arranged. An RF probe for a magnetic resonance apparatus, characterized in that an inductive coupling removing means for removing inductive coupling generated between the coils is provided between the RF probe and the solenoid. 2. A QD coil comprising a first solenoid coil having a first diameter, and a side coil combined with the first solenoid so that the detection direction is orthogonal to that of the first solenoid coil; A second solenoid coil having a diameter different from that of the first solenoid coil and arranged in parallel with the QD coil; and means for removing inductive coupling between the first solenoid coil and the second solenoid coil. An RF probe for a magnetic resonance apparatus, comprising: 3. The two coils are arranged in parallel so that the central axis of the first solenoid coil and the central axis of the second solenoid coil intersect at a predetermined angle. 2. An RF probe for a magnetic resonance apparatus. 4. The probe for a magnetic resonance apparatus according to claim 3, further comprising a mechanism for variably setting a crossing angle between the central axes of the two coils. 5. A probe for a magnetic resonance apparatus, wherein the RF probe according to any one of claims 1 to 4 is separable by a connector.