JPH04371138A - Magnetic resonance imaging apparatus - Google Patents

Abstract

PURPOSE:To provide images of good S/N ratio and also to reduce the required number of surface coils by alternately disposing a receiving coil of one-turn structure and a pair of opposite coils so connected together that magnetic fields generated there are extended in opposite directions. CONSTITUTION:A magnetostatic field, a gradient magnetic field and a high-frequency magnetic field are applied to a subject 5 from a static magnet 1, an inclined coil 3 and a uniform coil 9, respectively. Magnetic resonance signals from the subject 5 are received by the uniform coil 9 and a multi-surface coil 10. Signals received at the uniform coil 9 are guided to a receiving portion 11 via a duplexer 8 and those received at the multi-surface 10 are guided directly to the receiving portion 11. After amplification and detection the magnetic resonance signals are transferred to an electronic computer 13 via a data collecting portion 12. Then the magnetic resonance signals are subjected to image reconfiguring process and image data from the multi-surface coil 10 are weighted and added together and synthesized into one image data.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention uses a surface coil to achieve high S.
The present invention relates to a magnetic resonance imaging apparatus equipped with means for obtaining /N images.

0002

[Prior Art] As is well known, a magnetic resonance imaging apparatus uses a high-frequency magnetic field that rotates at a specific frequency when a group of nuclei with a unique magnetic moment is placed in a uniform static magnetic field. This is a method of imaging chemical and physical microscopic information of substances by using the phenomenon of resonant absorption of energy. Regarding 1H (protons), it is useful for imaging stationary or slow-moving parts. On the other hand, it provides images of clinically good quality.

[0003] However, in recent years, parts that move rapidly (such as the heart)
Ultra-high-speed imaging (imaging time ~50ms) that enables imaging of nuclides other than 1H (31P, 19F)
, 13C, 23Na, etc.). In these imaging techniques, S
/N improvement is an important issue. For example, in the case of ultra-high-speed imaging, there is a decrease in S/N due to a decrease in the flip angle during real-time scanning and a decrease in S/N due to an increase in the gradient magnetic field. An example of this is a decrease in S/N due to the extremely small amount of about 10 to the -4th power.

[0004] As one means of improving the S/N ratio, imaging has been conventionally performed using a surface coil as a receiving coil. The surface coil is placed in close contact with the region of interest of the subject, and detects signals around the region of close contact with a high S/N ratio. However, this method has the disadvantage that only images around the contact area can be obtained, and it is not possible to obtain high S/N images over the entire desired area of the subject. There is also a method of obtaining an image of the entire desired area of the subject by sequentially changing the arrangement of a single surface coil and composing the respective images obtained, but each time the arrangement of the surface coil is changed, the equipment needs to be adjusted. Adjustments are required, which makes the work complicated and time-consuming.

In order to solve such problems, for example, US Pat. coils) are placed, magnetic resonance signals from the subject are detected through these multiple surface coils, and image processing is performed on each of the detected magnetic resonance signals to generate multiple series of image data. , create data for each pixel by multiplying pixel data corresponding to the same spatial position by a weighting function predetermined based on the distribution of the high-frequency magnetic field generated by each surface coil, and then combining them. A technique has been disclosed for obtaining a high S/N image of the entire desired region of a subject by doing so.

Furthermore, in this known technique, in order to avoid the influence of coupling between adjacent surface coils, adjacent surface coils are overlapped to decouple them. However, in this known technique, because adjacent surface coils are overlapped, the correlation between noises is lower due to the closer distance between the surface coils than in the case of obtaining an image of a desired area of the subject without overlapping. This increases noise in the combined reconstructed image. If superposition is used for decoupling between adjacent surface coils in this way, the S/N will decrease. Moreover, a large number of coils are required to cover the desired area of the subject. On the other hand, Figs. 18 and 19 show a method of decoupling without overlapping adjacent surface coils.
There is a method using a bridge circuit as shown in Figure 1, but it needs to be added between all adjacent surface coils, making the circuit complicated.

[0007]

[Problems to be Solved by the Invention] As mentioned above, in order to obtain an image of a desired area of a subject using a plurality of surface coils, a means for preventing coupling between the surface coils is required. If superposition is used to decouple the surface coils between the two, the noise in the synthesized reconstructed image will increase because the surface coils are close to each other.
The S/N is lower than when the surface coils are not overlapped. Furthermore, a large number of surface coils are required to cover a desired area of the subject. On the other hand, when a bridge circuit is used to decouple adjacent surface coils without using superposition, there is a problem that the circuit becomes complicated.

[0008] According to the present invention, it is possible to increase the distance between the surface coils to a certain extent, and it is possible to obtain an image with a better S/N ratio than before, and also to reduce the number of necessary surface coils. The purpose of the present invention is to provide a magnetic resonance imaging apparatus that is highly economical.

[0009]

[Means for Solving the Problems] The present invention includes means for applying a static magnetic field to a subject, means for applying a predetermined gradient magnetic field to the subject, and arranged outside the subject,
a transmitting and receiving coil that applies a high frequency magnetic field to the subject;
A receiving coil arranged inside the transmitting/receiving coil with the subject as a reference and detecting a magnetic resonance signal generated from the subject, and means for performing image processing based on the detected magnetic resonance signal. In the magnetic resonance imaging apparatus, the receiving coil includes a first coil having a one-turn structure and a pair of opposing coils having a wiring structure such that the magnetic fields generated by each of the opposing coils are in opposite directions. and a second coil constituted by opposing coils, and the first and second coils are arranged alternately.

0010

[Operation] In the present invention, by alternately arranging one-turn coils and differential type coils as shown in FIGS. 4(a) and 4(b) as surface coils, it is possible to use coil overlapping or a bridge circuit. Instead, it attempts to decouple adjacent surface coils. Due to its shape, a differential type coil generates equal opposite polarity positive electromotive force when both opposite coils in a pair are linked with equal magnetic flux in the same direction. If placed on the center plane of the coil, the two will be decoupled. According to the configuration of the present invention,
Decoupling of surface coils between adjacent ones eliminates the need for bridge circuits or superposition. Therefore, the circuit does not become more complicated than necessary. Furthermore, the distance between the coils can be increased to some extent compared to the case where the coils are overlapped. This reduces the noise correlation between the surface coils, making it possible to obtain high S/N images, and also reducing the number of surface coils required to cover the desired area of the subject, making it highly economical. .

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the magnetic resonance imaging apparatus of the present invention will be described below with reference to the drawings. (Example 1)

FIG. 1 is a schematic diagram showing the structure and arrangement of the uniform coil 9 and multi-surface coil 10 in FIG. 2. The uniform coil 9 can apply a uniform high-frequency magnetic field to a desired region of the subject 5 to be imaged, and also receives magnetic resonance signals from the subject. As the uniform coil 9, for example, a saddle type coil, a distributed constant type coil, or a quadrature coil configured using these coils is used. The multi-surface coil 10 is installed inside the uniform coil 9, and in the embodiment shown in FIG. 1, is arranged so as to surround the subject, and includes one-turn coils 10a to 10c as shown in FIG. Figure 4(b) from 10d to 10f
It consists of a differential coil as shown in .

Regarding the S/N when a differential coil is used as a surface coil, see the document: Magn. Reason.
Med. 3, 590-603 (1986). In other words, the S/N of a differential type surface coil is equivalent to that of a normal surface coil consisting of a one-turn coil if noise from the object is dominant, but the high frequency loss of the coil itself cannot be ignored. In such a situation, the S/N is inferior to that of a normal surface coil, so when actually manufacturing a surface coil, the distance to the subject and the distance between the two opposing coils 51 and 52 shown in FIG. 4(b) must be adjusted. need to be carefully considered. FIG. 2 is a block diagram showing the configuration of a magnetic resonance imaging apparatus according to an embodiment of the present invention.

In FIG. 2, a static magnetic field magnet 1 is excited by an excitation power source 2, and applies a uniform static magnetic field to a subject 5. The gradient coil 3 is driven by a drive circuit 4 controlled by a system controller 16, and the magnetic field strength is set to the X, Y, which are orthogonal to each other, with respect to the subject 5 on the bed 6.
, gradient magnetic fields Gx, Gy, Gz that vary linearly in the Z direction
Apply. Further, under the control of the system controller 16, the subject 5 is applied with a high-frequency magnetic field generated by applying a high-frequency signal from the transmitting section 7 via the duplexer 8 to the uniform coil 9, which is a coil for both transmitting and receiving purposes. Ru.

A multi-surface coil 10, which is a signal detection coil, is arranged inside the uniform coil 9 and close to the subject 5. and uniform coil 9 and multi-surface coil 10
The magnetic resonance signal from the subject 5 is received by the subject 5. The signal received by the uniform coil 9 is guided to the receiving section 11 via the duplexer 8. On the other hand, multi-surface coil 10
The received signal is directly guided to the receiving section 11. The duplexer 8 is for switching the uniform coil 9 between transmission and reception, and transmits the high frequency signal from the transmitter 7 to the uniform coil 9 during transmission, and transmits the high frequency signal from the uniform coil 9 to the uniform coil 9 during reception.
It functions to guide the received signal from the receiver to the receiver 11. The magnetic resonance signal guided to the receiving section 11 is amplified and detected, and then sent to the data collecting section 12 under the control of the system controller 16. The data collection unit 12 collects the input magnetic resonance signals under the control of the system controller 16, performs A/D conversion, and sends them to the computer 13. The electronic computer 13 is controlled by the console 14, performs image reconstruction processing of the magnetic resonance signals input from the data acquisition unit 12, weights and adds the image data obtained from each of the multi-surface coils 10, and generates a single image. Synthesize data. It also performs image reconstruction of the uniform coil 9 and control of the system controller 16. The image data obtained by the electronic computer 13 is transmitted to the image display 15 and the image is displayed.

FIG. 3 shows details of the receiving section 11 and data collecting section 12 in FIG. 2. Preamplifiers 21, 31a to 31f and detection circuits (DET) 22, 32 correspond to the uniform coil 9 and multi-surface coils 10a to 10f, respectively.
a to 32f and low pass filters (LPF) 23, 33
A signal detection means consisting of a to 33f is provided. In the data acquisition section 12 , the detected signal of the magnetic resonance signal inputted from the reception section 11 is converted into a digital signal by an A/D converter 41 , and then input into the electronic computer 13 via the interface 42 . At this time, since the uniform coil 9 and the multi-surface coils 10a to 10f are arranged close to each other, decoupling between both coils is required. Here, the principle of the decoupling method between the differential coils 10d to 10f and the uniform coil 9 used in the present invention will be explained using FIG. 4.

The differential type coils 10d to 10f are shown in FIG. 4(b).
As shown in the figure, it has a structure in which a pair of coils 51 and 52 of the same type are placed opposite each other and are connected so that currents flow in spatially opposite directions to each other. Conventionally, this coil is used as a differential type coil in a SQUID magnetometer. It is similar to what you have. Therefore, when the spatially uniform high-frequency magnetic fields generated by the uniform coil 9 are interlinked, equal electromotive force is generated in the opposing coils 51 and 52, but they cancel each other out, and the high-frequency current flows in the differential coil. does not flow.

Therefore, if the uniform coil 9 generates a uniform high frequency magnetic field in the space where the differential coil is placed, the current induced in the differential coil by the high frequency magnetic field from the uniform coil is canceled out, and the cup The ring doesn't happen.

On the other hand, when an electromotive force is generated in a uniform coil by the magnetic field generated by the differential coil, currents in opposite rotational directions flow through the opposing coil portions of the differential coil, so that the currents are equal in magnitude and have the same direction. A magnetic flux in the opposite direction is generated, and the electromotive force generated in the uniform coil is also canceled. In other words, between the adjacent uniform coil and differential coil,
This means that no coupling occurs between them.

Next, a method of decoupling the one-turn coils 10a to 10c and the uniform coil 9 will be explained. In the case of 1-turn coils 10a to 10c, differential coil 10d
10f, it is structurally difficult to decouple with the uniform coil 9. Therefore, in order to decouple both when transmitting from the uniform coil 9 and when receiving from the one-turn coils 10a to 10c,
A decoupling circuit as shown below is added to each of the uniform coil 9 and the one-turn coils 10a to 10c.

A tuning/matching circuit including a decoupling circuit as shown in FIGS. 5 and 6 is used for the one-turn coils 10a to 10c. Figure 5 is an example using a trap circuit,

[0022]

The values of L1, C1, and C2 are determined so as to satisfy [Formula 1]. L is 1
This is the inductance of the turn coil. When receiving a signal, turn off the PIN diode 61 and connect L-C1-C.
Make it resonate with the second circuit. Uniform coil 9 that does not receive a signal
When transmitting, the PIN diode 61 is turned on. At this time, since the L1-C2 circuit also resonates, both ends of C2 become in a high impedance state, and as a result, L-C1
- It becomes difficult for high frequency current to flow through the circuit C2, resulting in a decoupled state. FIG. 6 is an example in which a cross diode 62 is used instead of the PIN diode 61 in FIG. Decoupled.

On the other hand, a decoupling circuit shown in FIGS. 7(a) and 7(b) is added to the uniform coil 9. Figure 7
(a) and FIG. 7(b) show the case where a saddle-shaped coil is used as the uniform coil 9. In FIG. 7(a), when the uniform coil 9 is transmitting, the PIN diode 63 is turned on,
When receiving data from the one-turn coils 10a to 10c, the PIN diode 63 is turned off. FIG. 7(b) performs decoupling based on the same principle as FIG. 5.

Next, a method of decoupling between adjacent surface coils will be described when the multi-surface coil 10 includes one-turn coils 10a to 10c and differential coils 10d to 10f arranged alternately as in this embodiment. As shown in FIG. 8, the magnetic flux generated by the one-turn coil 10a interlinks with the differential coil 10b as shown by the arrow. As a result, the opposing coils 51, which constitute the differential coil 10b,
51, an induced electromotive force is generated respectively. When the one-turn coil 10a is placed at the same distance from the opposing coils 51 and 52 (it is placed on the midpoint plane of the coils 51 and 52), the induced electromotive force generated in the coils 51 and 52 is equal. Become. On the other hand, the coils 51 and 52 are shown in FIG. 4(b).
Since the wires are connected so that the current flows in spatially opposite directions as shown in FIG. The mold coil 10b is decoupled. By alternately arranging the one-turn coils 10a and the differential coils 10b in this way, adjacent surface coils are structurally decoupled, and no circuit or the like for decoupling is required.

Next, a method of decoupling between non-adjacent surface coils will be explained. Since the coupling between non-adjacent surface coils is smaller than the coupling between adjacent surface coils, the effect of coupling can be suppressed by lowering the apparent Q without using precise decoupling methods. It is sufficient to perform decoupling by focusing on Specifically, a Q-dump circuit described below may be added to each surface coil. FIG. 10 shows a specific example of the Q dump circuit. In FIG. 10, a coil 71 has an inductance L and a capacitance C at a specific frequency f.
Suppose that it resonates at 0. The parallel resistance RP indicates the impedance of the coil 71 in a resonant state, and is expressed as follows using the Q value. Rp=2πf0 LQ...Equation 3 The inverting input terminal and non-inverting input terminal of an amplifier 72 with a gain of K times are connected to both ends of this coil 71, and the amplifier 7
A feedback resistor 73 (resistance value Rf) is connected between the output terminal of the amplifier 72 and the inverting input terminal, and the output terminal and the non-inverting input terminal of the amplifier 72 are used as external connection terminals. As the amplifier 72, the preamplifiers 31a to 31f shown in FIG. 3 are actually used. The Q dump circuit consisting of the coil 71, amplifier 72, and feedback resistor (resistance value=Rf) 73 shown in FIG. 10 is represented by an equivalent circuit shown in FIG. 11. The resistance Rd in FIG. 11 is Rd=Rf/
(K+1)...Given by equation 4. Therefore, if the gain K of the amplifier 72 is made sufficiently large, Rp>>Rd, and the impedance at both ends becomes low. This reduces the apparent Q and enables decoupling.

Next, the imaging procedure in this embodiment will be specifically explained. Imaging methods using multi-surface coils are disclosed in US Pat. No. 4,825,162 and Japanese Patent Application Laid-Open No. 2-47814. As an example, Figure 1 shows the imaging sequence when obtaining a two-dimensional image.
Shown in 2.

[0027] This imaging sequence is a pulse sequence for obtaining a two-dimensional image by the known spin echo method using a 90° pulse - 180° pulse as a high frequency magnetic field (high frequency pulse), and Gs is a gradient in the slice direction. In the magnetic field, Gr indicates the gradient magnetic field in the read direction, and Ge indicates the application timing of the gradient magnetic field in the encode direction.

As shown in FIG. 12, magnetic resonance signals are collected while changing the amplitude of the encoding gradient magnetic field Ge. The uniform coil 9 is used to apply high frequency pulses, and the magnetic resonance signals are received using the uniform coil 9 and all the multi-surface coils 10a to 10f. The magnetic resonance signals detected by the receiving unit 11 via the uniform coil 9 and the multi-surface coils 10a to 10f are taken into the computer 13 as data for image reconstruction via the data acquisition unit 12, and are stored in the computer 13. The image is reconstructed by performing two-dimensional Fourier transformation.

In this embodiment, in the process of image reconstruction, the multi-surface coils 10a to 10f simultaneously detect magnetic resonance signals and undergo imaging processing. Unlike this embodiment, if the number of circuits configuring the receiving section is limited and is less than the number of multi-surface coils, imaging can be performed multiple times by switching the multi-surface coils using control signals from the system controller 16. You may also use a method such as performing the following. Through this image reconstruction, one channel of image data obtained via the uniform coil 9 and multiple channels (of the image data obtained via each surface coil 10a to 10f)
In this embodiment, image data of 6 channels) can be obtained. Then, the image data of one image is synthesized by weighting the six channels of image data obtained through the multi-surface coils 10a to 10f using a predetermined weighting function so as to maximize the S/N. Ru.

As shown in the prior art described above, the weighting function is expressed as a function of the high frequency magnetic field distribution of each surface coil, so it is necessary to find the high frequency magnetic field distribution of each surface coil 10a to 10b. The method for determining this will be explained below.

First, the uniform coil 9 and the surface coil 10a
~10b, phase correction is performed on the image data obtained respectively. Assume that an image as shown in FIG. 13 is obtained using the uniform coil 9.

In FIG. 13, the thick line indicates the position of the uniform coil 9, and the broken line indicates the position of the surface coil 10a. A histogram of the image along line A is shown in FIG. 14(a), and a histogram corresponding to the same position of the image obtained by the surface coil 10a is shown in FIG. 14(b). Figure 14(a),(b)
), the horizontal axis represents the position, and the vertical axis represents the signal strength St, Ss in each image. According to FIG. 14(b), it can be seen that the sensitivity of the image obtained by the surface coil 10a decreases as the distance from the surface coil 10a increases. If the S/N of the image is poor, it is desirable to perform smoothing processing such as moving average as appropriate.

Next, the signal intensity ratio ha(
=Ss/St). FIG. 14(c) shows the result of calculating this signal strength ratio ha from the histogram of the image along line A shown in FIGS. 14(a) and 14(b). Since data is missing at points where there is no signal source or where no signal appears due to relaxation time, etc., processing such as interpolation is performed. Since the high-frequency magnetic field distribution generated by the surface coil 10a can be expanded by orthogonal functions, a method may be used in which the obtained image data is used to determine the coefficients of each term of the orthogonal function system by the method of least squares or the like. By these methods, the entire imaging area of the surface coil 10a, FIG.
The high frequency magnetic field distribution shown as a histogram in 4(d) can be obtained. Note that, as the high-frequency magnetic field distribution, the histogram shown in FIG. 14(c) may be simply obtained by taking the signal intensity ratio ha (=Ss/St) of the part of the subject 5.

On the other hand, in the image obtained through the uniform coil 9, if the high frequency magnetic field distribution of the uniform coil 9 becomes non-uniform due to the influence of the subject 5, the high frequency magnetic field distribution of the uniform coil 9 can be adjusted in advance. You need to ask for it. In this way, coupling between adjacent surface coils that adversely affects image processing can be eliminated, and image diagnostic information with a good S/N ratio can be obtained. (Example 2)

In the previous embodiment, magnetic resonance signals were received using a squirrel-cage coil, but in order to obtain a local image of a subject, signals may be received using a planar coil. In this case as well, the same problem as in the previous embodiment may occur, so in order to solve this problem, an embodiment will be described in which one-turn coils and differential coils are arranged alternately in a plane.

FIG. 9 is a modification of the one shown in FIG.
This is a case where the one-turn coil and the differential type coil are arranged parallel to each other without being curved. In this example as well, the one-turn coil 10a is arranged at a position equidistant from the opposing coils 51 and 52 of the differential coil 10b, as in FIG. According to this arrangement, coupling does not occur between the adjacent one-turn coil and the differential type coil for the above-mentioned reason. In the conventional type, the coupling between adjacent coils is strong, and reducing this has been an issue. According to the present invention, there is no need to consider the influence of coupling between adjacent coils, so correlated noise can be reduced and image information with a good S/N ratio can be obtained. Furthermore, since the number of coils required per unit area can be reduced compared to the method of stacking adjacent coils, it is also economically effective. (Example 3) Next, another example of the present invention will be briefly described.

FIG. 15 shows a plurality of the arrangement shown in FIG. 9 arranged in parallel in another dimension. When a coordinate system is set up as shown in Fig. 15, uniform coils and differential coils are arranged alternately in the X direction, which eliminates the influence of coupling between adjacent coils in the X direction. can. Further, in the Y direction, by overlapping uniform coils or differential coils at predetermined positions, it is possible to eliminate the influence of coupling between overlapping coils.

By using such a two-dimensional coil arrangement, the influence of coupling between two-dimensionally adjacent coils can be removed, making it possible to perform even higher quality image processing. Become.

Regarding the arrangement in the Y direction, overlapping is used in this example for decoupling between adjacent surface coils, but decoupling as shown in FIGS. 18 and 19 is possible without using overlapping. Using circuits etc., Y
It is also possible to eliminate coupling between directionally adjacent coils. FIG. 16 shows a modification of the arrangement shown in FIG. 15, in which each coil is curved and arranged in a circumferential manner.

Further, in FIG. 16, the one-turn coil and the differential type coil are arranged alternately in the axial direction, but it is also possible to arrange the one-turn coil and the differential type coil in the circumferential direction (as shown in FIG. 17). Furthermore, although rectangular coils are used as the one-turn coil and the differential coil in the above embodiments, circular or elliptical coils may also be used. In summary, the present invention provides a magnetic resonance imaging apparatus that applies a static magnetic field to a subject and detects magnetic resonance signals from the subject by applying a predetermined gradient magnetic field. a transmitting/receiving coil and a plurality of receiving coils; the transmitting/receiving coil is arranged outside the plurality of receiving coils; a means for applying a high frequency magnetic field to the subject; means for detecting magnetic resonance signals from the subject via a coil; means for simultaneously detecting magnetic resonance signals from the subject from at least two of the plurality of receiving coils; and detection by the signal detection means. means for performing imaging processing on the obtained magnetic resonance signals to generate image data of a plurality of channels; and means for obtaining an image of a desired region of the subject using the image data of the plurality of channels; The receiving coil is composed of two types of coils with different shapes, one of which is called a one-turn coil, which is usually used as a surface coil, and the other is a pair of opposing coils that generate the signal. The present invention provides a magnetic resonance imaging apparatus characterized in that the coils are connected so that the directions of magnetic fields are opposite to each other.

[0041]

[Effects of the Invention] According to the present invention, it is no longer necessary to superimpose or use a bridge circuit for all surface coils in order to eliminate the influence of mutual coupling between adjacent surface coils. Noise in the reconstructed image can be reduced, and the number of surface coils required to cover the subject can also be reduced.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the configuration and arrangement of a uniform coil and a multi-surface coil for a subject.

FIG. 2 is a block diagram showing the configuration of a magnetic resonance imaging apparatus according to an embodiment of the present invention.

FIG. 3 is a diagram showing details of the receiving section in FIG. 2.

FIG. 4 is a diagram showing the structure of a one-turn coil and a differential coil.

FIG. 5 is a diagram showing an example of a decoupling circuit between a surface coil and a uniform coil.

FIG. 6 is a diagram showing an example of a decoupling circuit between a surface coil and a uniform coil.

FIG. 7 is a diagram showing an example of a decoupling circuit between a surface coil and a uniform coil.

8 is a diagram for explaining the principle of decoupling between the one-turn coil and the differential coil in FIG. 1. FIG.

FIG. 9 is a diagram showing a modification of FIG. 10.

FIG. 10 is a diagram showing an example of a Q dump circuit for decoupling.

FIG. 11 is a diagram showing an equivalent circuit of FIG. 12.

FIG. 12 is a diagram showing an example of a pulse sequence for imaging in the same embodiment.

FIG. 13 is a diagram showing an example of an image obtained through a uniform coil in the same example.

FIG. 14 is a diagram for explaining how to obtain the high-frequency magnetic field distribution generated by the surface coil in the same example.

FIG. 15 is a diagram showing other embodiments.

FIG. 16 is a diagram showing other embodiments.

FIG. 17 is a diagram showing other embodiments.

[Figure 18] 1 using a capacitor and inductor
The figure which shows an example of the other decoupling method between turn coils.

FIG. 19 is a diagram showing an example of another decoupling method between differential coils using a capacitor and an inductor.

[Explanation of symbols]

1 Static magnetic field magnet 2 Excitation power source 3 Gradient magnetic field generation coil 4 Drive circuit 5 Subject 6 Bed 7 Transmitter 8 Duplexer 9 Uniform coil 10 Multi-surface coils 10a to 10c Surface coil (1-turn coil) 10
d to 10f Surface coil (differential type coil) 11 Receiving section 12 Data collecting section 13 Electronic computer 14 Console 15 Image display 16 System controller 21, 31a to 31f Preamplifier 22, 32a to 32f Detection circuit 23, 33a to 33c Low pass filter 41 A
/D converter 42 Interfaces 51, 52 Differential coil configuration coils 61, 63,
64 Pin diode 62 Cross diode 71 Coil 72 Q dump coil 73 Feedback resistor

Claims (5)

[Claims] 1. A means for applying a static magnetic field to a subject, a means for applying a predetermined gradient magnetic field to the subject, and a transmitting/receiving device disposed outside the subject for applying a high-frequency magnetic field to the subject. a coil, a receiving coil disposed inside the transmitting/receiving coil with the subject as a reference and detecting a magnetic resonance signal generated from the subject, and means for performing image processing based on the detected magnetic resonance signal. In the magnetic resonance imaging apparatus, the receiving coil is composed of a first coil having a one-turn structure and a pair of opposing coils having a wire connection structure such that the generated magnetic fields are in opposite directions. a second coil, and the first and second coils are arranged alternately. 2. The magnetic resonance imaging apparatus according to claim 1, wherein the receiving coil includes at least one means for preventing mutual coupling between adjacent coils. 3. The magnetic resonance imaging apparatus according to claim 1, wherein the receiving coil includes at least one means for preventing mutual coupling with the transmitting and receiving coil. 4. The magnetic resonance imaging apparatus according to claim 1, wherein the transmitting and receiving coil is constituted by a wire-shaped, pipe-shaped, or plate-shaped conductor. 5. The magnetic resonance imaging apparatus according to claim 1, wherein the receiving coil is constituted by a wire-shaped, pipe-shaped, or plate-shaped conductor.