JP2001276013A - Rf coil and magnetic resonance imaging instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an RF coil without mutual interference between two groups of saddle type coils, and a magnetic resonance imaging instrument using the RF coil. SOLUTION: The two groups of saddle type coils 802, 804 and 812, 814 are provided with a quatrature configuration. The coil pairs of the respective groups are respectively connected by co-axial cables 806, 808 and 816, 818.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an RF coil (ra
The present invention relates to a radio frequency coil and a magnetic resonance imaging apparatus, and more particularly to an RF using a saddle type coil.
The present invention relates to a coil and a magnetic resonance imaging apparatus using such an RF coil.

[0002]

2. Description of the Related Art As a static magnetic field, for example, 3T (tesla)
In a magnetic resonance imaging apparatus using a high magnetic field of the order, the R is composed of a combination of two sets of saddle type coils.
Using the F coil, the R of the spin to be photographed
F-excitation and reception of a magnetic resonance signal generated by the excited spin are performed.

As shown schematically in FIG. 15, this type of RF coil has four saddle type coils 702, 704, 7
12,714. Saddle type coil 702, 70
4,712,714 are the same size and are assembled to form a cylinder as a whole.

The saddle type coils 702 and 704 are opposed to each other with the central axis of the cylinder therebetween, and constitute one set. The saddle-shaped coils 712 and 714 face each other with the center axis of the cylinder interposed therebetween, and constitute the other set. The opposing directions of the two sets of saddle coils 702, 704 and 712, 714 are orthogonal.

[0005] The two sets of saddle type coils 702, 704 and 712, 714 are provided with connecting conductors 706, 708 and 716, 718 as shown in FIGS.
, But are not shown in FIG.

In each set, the RF power is supplied to the saddle type coil, for example, as shown in the developed views in FIGS. 18 and 19, at the portions of the connection conductors 706, 708 and 716, 718 by the power supply portions 710 and 720, respectively. Done. The power supply by the power supply units 710 and 720 is 90
° phase difference, so-called quadrature drive (q
udrature drive).

Receiving units (not shown) are connected in parallel to the power supply units 710 and 720, and receive magnetic resonance signals sensed by the saddle type coils for each pair. The received signals of the two systems have a phase difference of 90 °. By adding these received signals, SNR (signal-to-no
A received signal with improved is ratio is obtained.

[0008]

In the above-described RF coil, since the connecting conductors cross each other's coil surfaces, mutual interference between the two sets of saddle-type coils occurs through electrostatic coupling due to stray capacitance. Occurs. This mutual interference is not negligible in an RF coil for a high magnetic field where the frequency of the RF signal is high, and deteriorates the quality of RF transmission and reception.

It is therefore an object of the present invention to realize an RF coil having no mutual interference between two sets of saddle coils and a magnetic resonance imaging apparatus using such an RF coil.

[0010]

Means for Solving the Problems (1) According to a first aspect of the present invention for solving the above-described problems, four saddle-type coils each having a substantially cylindrical shape as a whole, and four saddle-type coils are formed. A first coil connecting two coils facing each other in a first direction perpendicular to the central axis of the cylindrical shape;
And a second coaxial cable connecting two coils of the four saddle-shaped coils which are opposed to each other in a second direction substantially perpendicular to the cylindrical central axis and the first direction. An RF coil comprising a cable.

In the invention according to this aspect, since the coils constituting the set are connected to each other by the coaxial cable, mutual interference with the coils of another set does not occur through the stray capacitance. (2) According to another aspect of the invention for solving the above-mentioned problem, the saddle-type coil is characterized in that mutual induction between two adjacent coils is the same as mutual induction between the other two coils. An RF coil according to the above (1).

In the invention from this viewpoint, the mutual induction between two adjacent coils is made the same as the mutual induction between the other two coils, so that the quadrature operation can be performed correctly.

(3) According to another aspect of the invention for solving the above-mentioned problem, in the saddle type coil, the area of the overlapping portion between two adjacent coils is equal to the area of the overlapping portion between the other two coils. The RF coil according to (2), wherein the RF coil has the same area.

According to the invention from this viewpoint, the area of the overlapping portion between two adjacent coils is made equal to the area of the overlapping portion between the other two coils, and the mutual induction between the two adjacent coils is the other two. Since the mutual induction between the two coils is the same, the quadrature operation can be performed correctly.

(4) According to another aspect of the invention for solving the above-mentioned problem, the saddle-type coil is characterized in that the interval between two adjacent coils is the same as the interval between the other two coils. The RF coil according to (2).

In the invention according to this aspect, the interval between two adjacent coils is made equal to the interval between the other two coils, and the mutual induction between the two adjacent coils is the same as the mutual induction between the other two coils. , The quadrature operation can be performed correctly.

(5) According to another aspect of the present invention for solving the above-mentioned problem, the saddle-shaped coil is characterized in that an area of an overlapping portion between two coils adjacent in one direction is different from that of the other two coils. Is the same as the area of the overlapping portion of
The RF coil according to (2), wherein a distance between two coils adjacent to each other in one direction is the same as a distance between the other two coils.

According to the invention from this viewpoint, the area of the overlapping portion between two coils adjacent to each other in one direction is made equal to the area of the overlapping portion between the other two coils, and the area of the overlapping portion between two coils adjacent to each other in the opposite direction is determined. The spacing is the same as the spacing between the other two coils, and the mutual induction between the two coils is the same as the mutual induction between the other two coils, regardless of which one is adjacent, so that the quadrature operation is performed correctly. be able to.

(6) The invention according to another aspect for solving the above-mentioned problem is characterized in that the saddle type coil can be opened and closed between two adjacent coils at an interval (4). ) Or (5).

In the invention according to this aspect, since the space between two adjacent coils can be opened and closed, it is easy to put objects into and out of the internal space of the coils. (7) According to another aspect of the present invention, there is provided a first power supply unit provided at an end of the first coaxial cable opposite to a connection side of the coil; Any one of (1) to (6), including a second power supply unit provided at an end of the second coaxial cable opposite to a connection side of the coil. RF described in
Coil.

In the invention according to this aspect, the power supply unit is provided at the end opposite to the connection side of the coil of the coaxial cable, so that the degree of freedom in arranging the power supply unit is increased. (8) According to another aspect of the invention for solving the above-described problem, the first and second power supply units are separated from the saddle-type coil in an axial direction of the cylindrical shape. An RF coil according to 7).

In the invention according to this aspect, since the power supply unit is separated from the saddle type coil, interference with the other coil system through the power supply unit is eliminated. (9) According to another aspect of the invention for solving the above-described problems, a magnetic field forming an image based on a magnetic resonance signal acquired by applying a high-frequency magnetic field to an object to be imaged under a static magnetic field and a gradient magnetic field. A resonance imaging apparatus, comprising: four saddle coils each having a generally cylindrical shape as an RF coil for performing at least one of the application of the high-frequency magnetic field and the acquisition of the magnetic resonance signal; A first coaxial cable connecting the two coils facing each other in a first direction perpendicular to the central axis of the cylindrical shape among the coils, and the cylindrical central axis of the four saddle coils and the first coaxial cable; An RF coil having a second coaxial cable that connects two coils facing each other in a second direction substantially perpendicular to the first direction is used. A magnetic resonance imaging apparatus.

In the invention according to this aspect, since the coils constituting the set are connected to each other by the coaxial cable, mutual interference with the coils of another set does not occur through the stray capacitance. Thereby, high quality magnetic resonance imaging can be performed.

(10) According to another aspect of the invention for solving the above-mentioned problem, in the saddle type coil, the mutual induction between two adjacent coils is the same as the mutual induction between the other two coils. The magnetic resonance imaging apparatus according to (9), wherein:

In the invention from this viewpoint, the mutual induction between two adjacent coils is made the same as the mutual induction between the other two coils, so that the quadrature operation can be performed correctly. Thereby, high quality magnetic resonance imaging can be performed.

(11) According to another aspect of the invention for solving the above-mentioned problem, the saddle-type coil is characterized in that the area of the overlapping portion between two adjacent coils is equal to the area of the overlapping portion between the other two coils. The magnetic resonance imaging apparatus according to (10), wherein the magnetic resonance imaging apparatus has the same area.

According to the invention from this viewpoint, the area of the overlapping portion between two adjacent coils is made equal to the area of the overlapping portion between the other two coils, and the mutual induction between the two adjacent coils is the other. Since the mutual induction between the two coils is the same, the quadrature operation can be performed correctly. Thereby, high quality magnetic resonance imaging can be performed.

(12) According to another aspect of the invention for solving the above-mentioned problem, the saddle type coil is characterized in that the interval between two adjacent coils is the same as the interval between the other two coils. A magnetic resonance imaging apparatus according to (10).

In the invention according to this aspect, the interval between two adjacent coils is made equal to the interval between the other two coils, and the mutual induction between the two adjacent coils is the same as the mutual induction between the other two coils. , The quadrature operation can be performed correctly. Thereby, high quality magnetic resonance imaging can be performed.

(13) According to another aspect of the invention for solving the above-mentioned problem, the saddle-shaped coil is such that an area of an overlapping portion between two coils adjacent in one direction is the other.
(10) wherein the area of the two coils adjacent to each other in the direction opposite to the one direction is the same as the area of the overlapping portion of the two coils, and the distance between the two coils adjacent to each other is the same. It is a magnetic resonance imaging apparatus of the description.

According to the invention from this viewpoint, the area of the overlapping portion between two coils adjacent in one direction is made equal to the area of the overlapping portion between the other two coils, and the area of the overlapping portion between two coils adjacent to each other in the opposite direction is determined. The spacing is the same as the spacing between the other two coils, and the mutual induction between the two coils is the same as the mutual induction between the other two coils, regardless of which one is adjacent, so that the quadrature operation is performed correctly. be able to. Thereby, high quality magnetic resonance imaging can be performed.

(14) According to another aspect of the invention for solving the above-mentioned problem, the saddle type coil is characterized in that two coils adjacent to each other at a distance can be opened and closed. ) Or (13).

In the invention according to this aspect, two adjacent coils can be opened and closed with an interval therebetween, so that the object can be easily taken in and out of the internal space of the coils. (15) According to another aspect of the invention for solving the above-described problems, a first power supply unit provided at an end of the first coaxial cable opposite to a connection side of the coil; A second power supply unit provided at an end of the second coaxial cable opposite to the connection side of the coil, and any one of (9) to (14). 2. A magnetic resonance imaging apparatus according to item 1.

According to the invention from this viewpoint, the power supply section is provided at the end opposite to the connection side of the coil of the coaxial cable, so that the degree of freedom of arrangement of the power supply section is increased. (16) According to another aspect of the invention for solving the above-described problem, the first and second power supply units are separated from the saddle-shaped coil in the axial direction of the cylindrical shape. A magnetic resonance imaging apparatus according to 15).

In the invention according to this aspect, since the power supply unit is separated from the saddle type coil, interference with the other coil system through the power supply unit is eliminated.

[0036]

Embodiments of the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiment. FIG. 1 shows a block diagram of the magnetic resonance imaging apparatus. This device is an example of an embodiment of the present invention. The configuration of the present apparatus shows an example of an embodiment relating to the apparatus of the present invention.

As shown in FIG. 1, the present apparatus has a magnet system (magnet system) 100. The magnet system 100 includes a main magnetic field coil unit 102.
And a gradient coil unit 106. Each of these coil portions has a substantially cylindrical outer shape and is arranged coaxially.

In the internal space of the magnet system 100,
For example, an imaging target 300 whose body is wrapped by the RF coil unit 108 is mounted on a cradle 500 and carried in.

The RF coil section 108 also has a substantially cylindrical outer shape, and the main magnetic field coil section 102 and the gradient coil section 106
Are positioned so as to be coaxial with RF coil unit 10
8 is an example of an embodiment of the RF coil of the present invention.
The configuration of the present coil indicates the configuration related to the RF coil of the present invention. The RF coil unit 108 will be described later.

The main magnetic field coil section 102 forms a static magnetic field in the internal space of the magnet system 100. The direction of the static magnetic field is substantially parallel to the body axis direction of the object 300. 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. It is needless to say that not only the superconducting coil but also a normal conducting coil may be used.

The gradient coil section 106 generates a gradient magnetic field for giving a gradient to the static magnetic field strength. The generated gradient magnetic fields are a slice gradient magnetic field, a readout gradient magnetic field, and a phase encode gradient magnetic field. The gradient coil unit 1 corresponds to these three types of gradient magnetic fields.
Reference numeral 06 has three gradient coils (not shown).

The RF coil unit 108 generates a high-frequency magnetic field for exciting spins in the body of the subject 300. Less than,
Forming a high-frequency magnetic field is also referred to as transmitting an RF excitation signal. The RF coil unit 108 also receives an electromagnetic wave generated by the excited spin, that is, a magnetic resonance signal.

The gradient coil unit 106 includes a gradient driving unit 130
Is connected. The gradient driving unit 130 is a gradient coil unit 1
A drive signal is given to 06 to generate a gradient magnetic field. The gradient drive unit 130 has three drive circuits (not shown) corresponding to the three gradient coils in the gradient coil unit 106.

The RF coil section 108 includes the RF drive section 14
0 and the data collection unit 150 are connected. The RF driving unit 140 supplies a driving signal to the RF coil unit 108 to
An F excitation signal is transmitted to excite spins in the body of the subject 300. The data collection unit 150 captures the magnetic resonance signal received by the RF coil unit 108 and collects the magnetic resonance signal as digital data.

A control unit 160 is connected to the gradient driving unit 130, the RF driving unit 140, and the data collection unit 150. The control unit 160 controls the gradient driving unit 130 to the data collection unit 150, respectively.

The output side of the data collection unit 150 is connected to the data processing unit 170. The data processing unit 170 stores the data fetched from the data collection unit 150 in a memory (not shown). A data space is formed in the memory. The data space is a two-dimensional Fourier (Fo)
urier) space. The data processing unit 170
An image of the object 300 is reconstructed by performing a two-dimensional inverse Fourier transform on the data in the two-dimensional Fourier space.

The data processing section 170 is connected to the control section 160. The data processing unit 170 is at a higher level than the control unit 160 and controls it. The display section 180 and the operation section 190 are connected to the data processing section 170. The display unit 180 displays the reconstructed image output from the data processing unit 170 and various information. The operation unit 190 is operated by an operator, and inputs various commands and information to the data processing unit 170.

FIG. 2 shows a schematic configuration of the RF coil unit 108. The RF coil unit 108 is an RF coil having the same configuration as that shown in FIG. Describing again, as shown in FIG.
It has two saddle type coils 802, 804, 812, 814. Saddle type coils 802, 804, 812, 81
Numerals 4 have the same size and are supported by supporting means (not shown) so as to form a substantially cylindrical shape as a whole. The saddle type coils 802, 804, 812, 814 are an example of the embodiment of the saddle type coil in the present invention. Less than,
The saddle type coil is also simply called a coil.

The saddle type coils 802 and 804 oppose each other with the central axis of the cylinder interposed therebetween, and constitute one set. The saddle type coils 812 and 814 face each other with the central axis of the cylinder interposed therebetween, and form the other set. The facing direction of one set of saddle coils is orthogonal to the facing direction of the other set of saddle coils.

The two sets of saddle type coils 802, 804 and 812, 814 are provided with coaxial cables 806, 808 and 816, 818 as shown in FIGS. 3 and 4, for example.
Are connected respectively. Coaxial cable 806, 80
8 is an example of an embodiment of a first coaxial cable according to the present invention. The coaxial cables 816 and 818 are an example of an embodiment of the second coaxial cable in the present invention. In FIG. 2, illustration of these coaxial cables is omitted.

An example of the connection state of each set of coil pairs by a coaxial cable is schematically shown in a developed view in FIGS. 5 and 6, respectively. As shown in FIG. 5, one end and the other end of the loop of the coil 802 are provided with a center conductor and a shield (shield) on one end of the coaxial cable 806.
d) The conductors are respectively connected. The center conductor and the shield conductor on one end of the coaxial cable 808 are connected to one end and the other end of the loop of the coil 804, respectively.

At the other end of the coaxial cables 806 and 808, the shield conductor of the coaxial cable 806 and the center conductor of the coaxial cable 808 are connected, and a power supply section 810 is provided between the center conductor of the coaxial cable 806 and the shield conductor of the coaxial cable 808. Is connected. The power supply unit 810 is the RF drive unit 14
0 corresponds to the output terminal. With such a connection, the coils 802 and 804 are fed in series. The power supply unit 810
It is an example of embodiment of the 1st feeder in the present invention.

As shown in FIG. 6, a center conductor and a shield conductor at one end of a coaxial cable 816 are connected to one end and the other end of the loop of the coil 812, respectively. A coaxial cable 8 is connected to one end and the other end of the loop of the coil 814.
The center conductor and the shield conductor on one end side of 18 are respectively connected.

At the other ends of the coaxial cables 816 and 818, the shield conductor of the coaxial cable 816 and the center conductor of the coaxial cable 818 are connected, and a power supply section 820 is provided between the center conductor of the coaxial cable 816 and the shield conductor of the coaxial cable 818. Is connected. The power supply unit 820 is the RF drive unit 14
0 corresponds to the output terminal. With such a connection, the coils 812 and 814 are fed in series. The power supply unit 820
It is an example of embodiment of the 2nd feeder in the present invention.

The other ends of the coaxial cables 806 and 808 are connected as shown in FIG.
808 are connected between the center conductors and the shield conductors, respectively, and a power supply section 810 is provided between the center conductor and the shield conductors.
May be connected. With such a connection,
The coils 802 and 804 are fed in parallel.

Similarly, the other ends of the coaxial cables 816 and 818 are connected as shown in FIG.
6,818 are connected between the center conductors and between the shield conductors, respectively.
20 may be connected. With such a connection, the coils 802 and 804 are fed in parallel.

FIG. 9 is an exploded view of two sets of saddle type coils having such a coaxial cable and a power feeding section. Power supply by the power supply units 810 and 820 is performed with a phase difference of 90 °, and so-called quadrature drive is performed.

The input terminals of the data collection unit 150 are connected in parallel to the power supply units 810 and 820, and receive magnetic resonance signals sensed by the saddle type coils for each pair. The received signals of the two systems have a phase difference of 90 °. The data collection unit 150 adds these received signals and obtains a received signal with an improved SNR by vector synthesis.

As shown in FIG. 9, the coaxial cable 80
6,808 cross the coil surface of the coil 814, but the coaxial cable has a high degree of external signal shielding, so that the electrostatic or electromagnetic coupling with the coil 814 is independent of the spatial relationship between the two. Absent. Also, the coaxial cable 8
16, 818 cross the coil surface of the coil 802, but similarly there is no electrostatic or electromagnetic coupling with the coil 802.
For this reason, there is no interference with other sets of coils originating from the conductor connecting the paired coils. Therefore, quadrature transmission and reception can be performed correctly. In addition, the degree of freedom in the spatial arrangement of the coils and the spatial arrangement of the wiring connecting them is increased.

The coaxial cables 806, 808, 81
6,818, the length of the power supply unit 8 can be appropriately determined.
10, 820 can be installed at an appropriate place away from the RF coil unit 108, so that the power supply units 810, 820
The degree of freedom of arrangement increases.

Four saddle coils 802, 804, 8
The cross section of the cylinder constituted by 12, 814 may be an ellipse or a shape similar to the cross section of the body or the like of the object 300 instead of making it a perfect circle. By doing so, the distance between each coil and the object 300 is shortened, and the efficiency of RF transmission and reception can be further improved. In the present invention, a cylinder having an elliptical cross section is also included in the category of the cylinder.

If the cross section deviates from a perfect circle, the two sets of saddle type coils are liable to cause interference due to mutual induction. Therefore,
In order to cancel such interference, the two sets of saddle type coils are defined in a mutual relationship as shown in FIG. 10, for example. FIG. 10 is a schematic view of the RF coil unit 108 as viewed in the axial direction.

As shown in the drawing, two adjacent coils 812 and 804 of the four saddle coils are arranged so that the coil surfaces partially overlap. The same applies to the remaining two coils 814 and 802. The area of the overlapping portion is the same in both cases. Thereby, the coil 8
Mutual inductance between 12,804 (mutuali)
nductance) The mutual inductance Mcd between the Mab and the coils 814 and 802 becomes equal.

On the other hand, the ends of the adjacent coils 812 and 802 face each other at a predetermined distance, and the remaining coils 8
The ends of 14,804 also face each other at a predetermined distance. The facing distance is the same. Thereby, the mutual inductance M between the coils 812 and 802 is obtained.
M and the mutual inductance M between the coils 814 and 804
bc become equal.

By defining the mutual relationship in this manner, the electromagnetic induction to the coil 804 by the current flowing through the coil 812 and the coil 8 by the current flowing through the coil 814 are determined.
The electromagnetic induction to 02 is equal in magnitude and opposite in polarity.
Therefore, in the set of the coils 802 and 804, the two cancel each other out, so that no influence occurs. The same can be said for the induction from the coil 804 to the coil 812 and the induction from the coil 802 to the coil 814.

The electromagnetic induction to the coil 802 due to the current flowing through the coil 812 and the electromagnetic induction to the coil 804 due to the current flowing through the coil 814 are equal in magnitude and opposite in polarity.
It does not affect the set of 2,804. The same can be said for the induction from the coil 802 to the coil 812 and the induction from the coil 804 to the coil 814.

As described above, the two sets of saddle coils can be operated without mutual interference, and quadrature transmission and reception can be performed correctly. In addition, by configuring as described above, the opening area of each coil can be increased, so that RF can be extended to a deep portion of the body of the subject 300 with high sensitivity.
Can send and receive.

In order to easily put the object 300 in and out, the RF coil unit 108 is preferably configured so that the upper half is opened on both sides by quarters as shown in FIG. 11, for example. In this case, the joint 822 when the upper part is closed as shown by a dashed line is, for example, a portion where the coil 812 and the coil 802 face each other with an interval as shown in FIG. This eliminates the need to provide an electrical connector or the like at the joint.
It should be noted that hinge portions 824 and 82 on both sides are provided.
4 'is provided with a connector for maintaining the electrical connection of the coil loop.

The RF coil unit 108 may be configured so that the upper half is opened to one side as shown in FIG. 12, for example.
In this case, the joint 826 when the upper part is closed as shown by the one-dot chain line is, for example, a portion where the coil 812 and the coil 802 face each other with an interval as shown in FIG. This eliminates the need to provide an electrical connector or the like at the joint. Also, as shown in FIG. 10, the hinge portion 828 located at a position symmetrical to the seam is, for example, a portion where the coil 814 and the coil 804 face each other at an interval, so that it is necessary to provide an electrical connector or the like. Absent.

The photographing operation of the present apparatus will be described. In FIG.
Pulse sequence used for imaging
ence). This pulse sequence has a gradient echo (GRE).
This is a pulse sequence of the ho) method.

That is, (1) is the RF in the GRE method.
A sequence of α ° pulses for excitation, (2)
(3), (4) and (5) are the sequences of the slice gradient Gs, readout gradient Gr, phase encode gradient Gp and gradient echo MR, respectively. The α ° pulse is represented by the center signal.
The pulse sequence proceeds from left to right along the time axis t.

As shown in the figure, α ° excitation of spin is performed by an α ° pulse. Flip angle (flip
angle) α ° is 90 ° or less. At this time, a slice gradient Gs is applied, and selective excitation for a predetermined slice is performed.

After the α ° excitation, the phase encode gradient Gp
Performs phase encoding of the spin. next,
The spin is first dephased by the readout gradient Gr, and then the spin is rephased (r
ephase) to generate a gradient echo MR. The signal strength of the gradient echo MR is α °
It becomes maximum at the time point after the echo time (echo time) TE from the excitation. The gradient echo MR is collected by the data collection unit 150 as view data.

Such a pulse sequence has a period TR
(Repetition time) is repeated 64 to 512 times. The phase encoding gradient Gp is changed for each repetition, and a different phase encoding is performed each time. As a result, view data of 64 to 512 views filling the k space is obtained.

FIG. 14 shows another example of the pulse sequence for magnetic resonance imaging. This pulse sequence is a pulse sequence of a spin echo (SE: Spin Echo) method.

That is, (1) is a sequence of 90 ° and 180 ° pulses for RF excitation in the SE method, and (2), (3), (4) and (5) are slice gradients, respectively. Gs, readout gradient G
r, phase encoding gradient Gp and spin echo M
This is a sequence of R. Note that a 90 ° pulse and 18
Each 0 ° pulse is represented by a center signal. The pulse sequence proceeds from left to right along the time axis t.

As shown in the figure, 90 ° excitation of spin is performed by a 90 ° pulse. At this time, the slice gradient G
s is applied to perform selective excitation for a predetermined slice. After a predetermined time from the 90 ° excitation, 180 ° excitation by a 180 ° pulse, that is, spin inversion is performed. Also at this time, the slice gradient Gs is applied, and selective inversion is performed for the same slice.

During the period between the 90 ° excitation and the spin inversion, the readout gradient Gr and the phase encode gradient Gp
Is applied. The spin dephase is performed by the readout gradient Gr. The phase encoding of the spin is performed by the phase encoding gradient Gp.

After the spin inversion, the spin is rephased by the readout gradient Gr to generate a spin echo MR.
The signal intensity of the spin echo MR becomes maximum at a point after TE from the 90 ° excitation. The spin echo MR is collected by the data collection unit 150 as view data. Such a pulse sequence is repeated 64 to 512 times in the period TR. Phase encoding gradient Gp for each iteration
And perform different phase encoding each time. As a result, view data of 64 to 512 views filling the k space is obtained.

The pulse sequence used for photographing is G
The method is not limited to the RE method or the SE method.
E (Fast Spin Echo) method, Fast Recovery FSE (Fast Recovery Fast)
Spin Echo method, Echo Planar Imaging (EPI: Echo Planar Imaging)
g) or any other suitable technique.

The data processing unit 170 reconstructs a tomographic image of the object 300 by performing two-dimensional inverse Fourier transform on the view data in the k space. The reconstructed image is stored in the memory and displayed on the display unit 180. RF coil unit 108-2
There is no mutual interference between the sets of saddle coils and the quadrature operation is performed correctly, so that a high quality image can be obtained.

The above is an example in which the RF coil unit 108 is also used for transmitting and receiving RF signals.
Of course, it may be configured separately for transmission only and reception only of the RF signal.

The present invention is not limited to the saddle type coil having the quadrature structure, but also a so-called phased array coil (phased array coil) having a plurality of coil loops arranged in parallel.
In the case of oil, the mutual interference between a plurality of coil loops can be eliminated by wiring the individual coil loops with a coaxial cable.

[0084]

As described above in detail, according to the present invention, an RF coil having no mutual interference between two sets of saddle type coils and a magnetic resonance imaging apparatus using such an RF coil are realized. be able to.

[Brief description of the drawings]

FIG. 1 is a block diagram of a device according to an example of an embodiment of the present invention.

FIG. 2 is a schematic diagram of an RF coil unit in the device shown in FIG.

FIG. 3 is a schematic view of a saddle-type coil pair constituting the RF coil unit shown in FIG. 2;

FIG. 4 is a schematic view of a saddle-type coil pair constituting the RF coil unit shown in FIG. 2;

FIG. 5 is a development view of the saddle type coil pair shown in FIG. 3;

6 is a development view of the saddle type coil pair shown in FIG.

FIG. 9 is a development view of the RF coil unit shown in FIG. 2;

FIG. 10 is a diagram showing a mutual relationship between saddle-type coils constituting the RF coil unit shown in FIG. 2;

11 is a diagram showing an open / closed state of the RF coil unit shown in FIG. 2;

FIG. 12 is a diagram showing an open / closed state of the RF coil unit shown in FIG. 2;

FIG. 13 is a diagram illustrating an example of a pulse sequence executed by the device illustrated in FIG. 1;

FIG. 14 is a diagram illustrating an example of a pulse sequence executed by the device illustrated in FIG. 1;

FIG. 15 is a schematic diagram of an RF coil unit.

FIG. 16 is a schematic diagram of a saddle-type coil pair constituting the RF coil unit shown in FIG.

FIG. 17 is a schematic diagram of a saddle-type coil pair constituting the RF coil unit shown in FIG.

FIG. 18 is a development view of the saddle type coil pair shown in FIG.

FIG. 19 is a development view of the saddle-type coil pair shown in FIG. 17;

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 magnet system 102 main magnetic field coil section 106 gradient coil section 108 RF coil section 130 gradient drive section 140 RF drive section 150 data collection section 160 control section 170 data processing section 180 display section 190 operation section 300 target 500 cradle 802, 804, 812 814 Saddle type coil 806, 808, 816, 818 Coaxial cable 810, 820 Power supply unit

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] April 14, 2000 (2004.1.
4)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Change

[Correction contents]

[Brief description of the drawings]

FIG. 1 is a block diagram of a device according to an example of an embodiment of the present invention.

FIG. 2 is a schematic diagram of an RF coil unit in the device shown in FIG.

FIG. 3 is a schematic view of a saddle-type coil pair constituting the RF coil unit shown in FIG. 2;

FIG. 4 is a schematic view of a saddle-type coil pair constituting the RF coil unit shown in FIG. 2;

FIG. 5 is a development view of the saddle type coil pair shown in FIG. 3;

6 is a development view of the saddle type coil pair shown in FIG.

FIG. 7 is a development view of the saddle type coil pair shown in FIG. 3;
You.

8 is a development view of the saddle type coil pair shown in FIG.
You.

FIG. 9 is a development view of the RF coil unit shown in FIG. 2;

FIG. 10 is a diagram showing a mutual relationship between saddle-type coils constituting the RF coil unit shown in FIG. 2;

11 is a diagram showing an open / closed state of the RF coil unit shown in FIG. 2;

FIG. 12 is a diagram showing an open / closed state of the RF coil unit shown in FIG. 2;

FIG. 13 is a diagram illustrating an example of a pulse sequence executed by the device illustrated in FIG. 1;

FIG. 14 is a diagram illustrating an example of a pulse sequence executed by the device illustrated in FIG. 1;

FIG. 15 is a schematic diagram of an RF coil unit.

FIG. 16 is a schematic diagram of a saddle-type coil pair constituting the RF coil unit shown in FIG.

FIG. 17 is a schematic diagram of a saddle-type coil pair constituting the RF coil unit shown in FIG.

FIG. 18 is a development view of the saddle type coil pair shown in FIG.

FIG. 19 is a development view of the saddle-type coil pair shown in FIG. 17;

[Description of Signs] 100 Magnet system 102 Main magnetic field coil unit 106 Gradient coil unit 108 RF coil unit 130 Gradient drive unit 140 RF drive unit 150 Data collection unit 160 Control unit 170 Data processing unit 180 Display unit 190 Operation unit 300 Target 500 cradle 802, 804, 812, 814 Saddle type coil 806, 808, 816, 818 Coaxial cable 810, 820 Power supply unit

Claims (16)

[Claims] 1. Four saddle coils each having a substantially cylindrical shape as a whole, and two coils of the four saddle coils facing each other in a first direction perpendicular to a center axis of the cylindrical shape are connected to each other. A first coaxial cable that connects two coils of the four saddle coils that oppose each other in a second direction substantially perpendicular to the central axis of the cylindrical shape and the first direction; And a coaxial cable. 2. The RF coil according to claim 1, wherein in the saddle-shaped coil, mutual induction between two adjacent coils is the same as mutual induction between the other two coils. 3. The saddle-shaped coil according to claim 2, wherein an area of an overlapping portion between two adjacent coils is the same as an area of an overlapping portion between the other two coils. RF coil. 4. The saddle-shaped coil, wherein an interval between two adjacent coils is the same as an interval between the other two coils.
The RF coil according to claim 2, wherein: 5. The saddle-shaped coil according to claim 1, wherein an area of an overlapping portion between two coils adjacent in one direction is the same as an area of an overlapping portion between the other two coils.
The RF coil according to claim 2, wherein a distance between two coils adjacent to each other in one direction is the same as a distance between the other two coils. 6. The RF coil according to claim 4, wherein the saddle type coil can be opened and closed between two adjacent coils at an interval. 7. A first power supply unit provided at an end of the first coaxial cable opposite to a connection side of the coil, and a first power supply unit opposite to a connection side of the coil of the second coaxial cable. 7. The RF coil according to claim 1, further comprising: a second power supply unit provided at an end on the side of the RF coil. 8. 8. The RF coil according to claim 7, wherein the first and second power supply portions are separated from the saddle-shaped coil in the axial direction of the cylindrical shape. 9. A magnetic resonance imaging apparatus that forms an image based on a magnetic resonance signal obtained by applying a high-frequency magnetic field to an object to be imaged under a static magnetic field and a gradient magnetic field, As an RF coil for performing at least one of acquisition of a magnetic resonance signal, four saddle-shaped coils which are generally cylindrical as a whole, and a first of the four saddle-shaped coils which is perpendicular to a central axis of the cylindrical shape. A first coaxial cable connecting the two coils facing each other in the direction of, and a second direction substantially perpendicular to the central axis of the cylindrical shape and the first direction among the four saddle coils. And a second coaxial cable connecting the two coils facing each other. 10. The magnetic resonance imaging apparatus according to claim 9, wherein in the saddle type coil, mutual induction between two adjacent coils is the same as mutual induction between the other two coils. 11. The saddle-shaped coil according to claim 10, wherein an area of an overlapping portion between two adjacent coils is the same as an area of an overlapping portion between the other two coils. Magnetic resonance imaging device. 12. The magnetic resonance imaging apparatus according to claim 10, wherein, in the saddle type coil, an interval between two adjacent coils is the same as an interval between the other two coils. 13. The saddle type coil according to claim 1, wherein an area of an overlapping portion between two coils adjacent in one direction is the other.
11. The space between two coils adjacent to each other in the direction opposite to the one direction is the same as the area of the overlapping portion between the two coils, and the space between the other two coils is the same. 7. A magnetic resonance imaging apparatus according to item 1. 14. The magnetic resonance imaging apparatus according to claim 12, wherein the saddle type coil can be opened and closed between two adjacent coils at an interval. 15. A first power supply unit provided at an end of the first coaxial cable opposite to a connection side of the coil, and a first power supply unit opposite to a connection side of the coil of the second coaxial cable. The magnetic resonance imaging apparatus according to any one of claims 9 to 14, further comprising: a second power supply unit provided at an end on the side. 16. The magnetic resonance imaging apparatus according to claim 15, wherein the first and second power supply units are separated from the saddle-shaped coil in the cylindrical axial direction.