JPH0919414A - Mri device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the structure of a blocking circuit stopping the action of a coil by providing an MRI device with a switching circuit for switching elements to the conductive state and the external output to the cutoff state at the time of transmission and switching the elements to the nonconductive state and the external output to the reception state at the time of reception. SOLUTION: At the time of transmission via a transmission/reception coil in an MRI device, a bias in the forward direction is applied to the diodes D1, D2 of a switching circuit 100 by an instruction from a CPU via a bias circuit 110 to set them to the conductive state. The coil element L is short-circuited, no potential difference is generated across both ends of the diode D1 at the time of large-power transmission, and the difference component is prevented from being transferred to a preamplifier 70 side. At the time of reception via the transmission reception coil, a bias in the backward direction is applied to the diodes D1, D2 to set them to the nonconductive state. The reception signal is fed to the input of the preamplifier 70 via an LC bridge circuit 101.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in the periphery of an MRI RF coil used in a magnetic resonance imaging (MRI) apparatus, and more particularly, to validating / invalidating the operation of the MRI RF coil during transmission and reception. T / R for switching between switching circuit, coil and transmitting / receiving circuit
The present invention relates to an MRI apparatus having a function of a switch and having an improved configuration for switching between transmission and reception.

[0002]

2. Description of the Related Art An MRI apparatus uses a nuclear magnetic resonance phenomenon to measure a nuclear spin density distribution, a relaxation time distribution, and the like at a desired inspection site in a subject, and uses the measured data to determine a cross section of the subject. An image is displayed.

A nuclear spin of a subject placed in a uniform and strong static magnetic field generator precesses around a direction of the static magnetic field at a frequency (Larmor frequency) determined by the strength of the static magnetic field. Therefore, when a high-frequency pulse having a frequency equal to the Larmor frequency is irradiated from the outside, spins are excited and transit to a high energy state. This is called a nuclear magnetic resonance phenomenon. When the irradiation of the high frequency pulse is terminated, the spin returns to the original low energy state with a time constant corresponding to each state, and at this time, the electromagnetic wave is irradiated to the outside. A high frequency receiver coil (M
It is detected by the RF coil for RI). At this time, a triaxial gradient magnetic field is applied to the static magnetic field space for the purpose of adding position information to the space. As a result, position information in space can be captured as frequency information.

In such an MRI apparatus, an MRI RF coil used for applying a high-frequency rotating magnetic field to a subject or for receiving an electromagnetic wave generated by the subject accommodates the subject therein, A high-frequency current is applied to the part of the wire (element) around the subject.

As such an MRI RF coil,
There are a transmission / reception coil used for both transmission and reception, a transmission dedicated coil used only for transmission, and a reception dedicated coil used only for reception.

In the case of this transmission-dedicated coil, the transmission-dedicated coil does not operate in order to prevent the pulse of the Larmor frequency from the subject from being absorbed by the transmission-dedicated coil after the transmission (irradiation of the high frequency pulse) is completed. Need to switch to. That is, the operation is stopped by cutting the loop of the coil so that the pulse from the subject is not absorbed.

Similarly, in the case of the receive-only coil, the receive-only coil is switched so as not to directly receive the high-frequency pulse from the transmit-only coil during transmission (irradiation of the high-frequency pulse). There is a need.

Further, in the case of a transmission / reception coil, T / R (Transmit / Transmit / Transmission / Transmission / Transmission) is performed to switch the transmission pulse from the transmitter to the coil and the reception signal from the coil to the receiver. Receive) switch is provided.

FIG. 9 is a block diagram showing an example of such a circuit. The CPU 20 is a control unit that controls the entire apparatus. The transmission circuit 30 generates a high frequency pulse necessary for MRI, amplifies the high frequency pulse by the power amplifier 40, and supplies the high frequency pulse to the transmission / reception coil 50 via the T / R switch 60. At the time of reception, the signal detected by the transmitting / receiving coil (body coil) 50 is switched to the preamplifier 70 side by the T / R switch 60, various processing is executed by the receiving circuit 80, and the result is displayed by the CPU 20 on the display 90. The image is displayed on. In order to perform reception by a reception-dedicated coil (not shown), a blocking circuit 61 for cutting the loop to stop the operation of the transmission / reception coil 50 is arranged in the element of the transmission / reception coil 50. Conducting / non-conducting switching is used. A bias circuit 62 that controls the blocking circuit 61 is provided.

[0010]

As described above, when the transmission / reception coil 50 is used, in order to switch the power supply to the coil at the time of transmission and the reception from the coil at the time of reception, the T
It was necessary to provide the / R switch 60. Also, in the case of performing reception using the receiving coil, the transmitting / receiving coil 5
The blocking circuit 61 was provided in the element of 0.
As described above, various switch means are required, and there is a problem that the configuration becomes complicated.

FIG. 10 is a circuit diagram showing an example of the periphery of such a blocking circuit 61. In such a circuit, MR
The inductor and the capacitor of the element of the RF coil for I are adjusted so as to be tuned to the Larmor frequency described above.

In the case of the MRI RF coil having the structure shown in FIG. 10, when the transmission-dedicated coil is transmitting and the reception-dedicated coil is receiving, a forward bias current is supplied from the bias circuit 62 to the diode D to conduct the diode D. Put in a state. As a result, the effect of the diode D is apparently eliminated, and the diode D is tuned to the Larmor frequency.

On the other hand, at the time of reception by the transmission-dedicated coil and at the time of transmission by the reception-dedicated coil, the bias current to the diode D is stopped and a reverse bias is applied to bring the diode D into a non-conducting state. As a result, the loop of the element is apparently broken, and the element does not operate as the MRI RF coil.

Further, as shown in FIG. 11, it is possible to use both the transmitting / receiving coil 50 composed of a body coil and the transmitting / receiving coil 51 composed of a surface coil for a local area to perform transmission and reception at both sides. Also in this case, the T / R switches 63 and 64 are required for the respective coils, and there is a problem that the configuration becomes complicated.

Therefore, in order to omit the T / R switch for switching between transmission and reception, a configuration as shown in FIG. 12 can be considered. That is, the transmission-only coil 5 using the body coil
By using 0 ′ and the reception-only coil 51 ′ by the surface coil, the T / R switch for switching the transmission / reception of the power feeding unit can be made unnecessary. Further, there is an advantage that the number of power amplifiers and preamplifiers can be reduced and the overall configuration can be simplified.

However, in such a case, since only the surface coil 51 'can receive, there is a problem that the sensitivity region becomes narrow. The present invention has been made in view of the above points, and an object thereof is to simplify the configuration of a blocking circuit that stops the operation of a T / R switch for switching between transmission and reception of a power supply unit and a coil. It is to realize an RF coil for MRI.

[0017]

DISCLOSURE OF THE INVENTION The inventor of the present application is keen to improve the problems relating to the configuration of a conventional T / R switch for switching transmission / reception around an RF coil for MRI and a blocking circuit for stopping the operation of the coil. As a result of research, the present invention has been completed by newly finding an optimal arrangement and configuration.

That is, the invention as means for solving the problems is as described below. A first invention comprises an MRI RF coil for both transmission and reception, and a switching circuit which is arranged between the elements of the MRI RF coil and which controls a conduction state between elements and an output state from the element to the outside, In the MRI apparatus, the switching circuit is set to the conduction state between elements and the external output cutoff state during transmission, and the switching circuit is set to the non-conduction state between elements and the external output enable state during reception.

In the MRI apparatus according to the first aspect of the present invention, the switching circuit is brought into a conduction state between the elements at the time of transmission, so that the MRI is performed.
The RF coil for use operates as a transmission coil, and the transmission signal does not leak to the reception circuit side because the external output is cut off.
In addition, since the switching circuit becomes non-conductive between the elements during reception and is ready for external output, the MRI RF coil operates as a reception coil, and the reception signal at this reception coil is output to the reception circuit side. become.

As a result, since the switching circuit can serve as both the T / R switch and the blocking circuit, it is possible to simplify the structure of the T / R switch and the blocking circuit.
As a second invention, in the switching circuit according to the first invention, a switching element is connected to an input end and an output end,
The input end is composed of an LC bridge circuit arranged between the elements of the RF coil for MRI, and when transmitting, each switching element is brought into a conducting state to make the LC bridge circuit in a shut-off state and a conducting state between elements and an external output shut-off state. And an LC bridge circuit is rendered conductive by setting each switching element to a non-conductive state at the time of reception to realize a non-conductive state between elements and an external output enabled state.

Incidentally, as the switching element in this case, for example, an element such as a PIN diode is preferable in that it performs switching. In the MRI apparatus of the second aspect of the present invention, at the time of transmission, both switching elements are in a conducting state, so that the MRI RF coil operates as a transmitting coil and the LC bridge circuit is in a cutoff state, so that a transmitting signal leaks to the receiving circuit side. There is no such thing. Since both switching elements are in a non-conducting state at the time of reception, the signal detected by the MRI RF coil is output to the receiving circuit side in a state of being balanced-unbalanced converted by the LC bridge circuit.

As a result, the switching circuit can be used as both the T / R switch and the blocking circuit, so that the configurations of the T / R switch and the blocking circuit can be simplified.
In addition, by using the switching element and the LC bridge circuit, reliable operation can be expected with a simple configuration. In addition, the LC bridge circuit can realize a cutoff state and a conduction state, and can further realize balanced-unbalanced conversion in the conduction state.

A third aspect of the invention is an RF for MRI that is used for both transmission and reception.
A coil, a switching circuit disposed between the elements of the MRI RF coil, and controlling a conduction state between the elements and an output state from the element to the outside, and an MRI dedicated to reception
RF coil for transmission, the switching circuit is made conductive between elements and the external output is cut off at the time of transmission, and the switching circuit is made non-conductive and output externally at the time of reception by the MRI RF coil for both transmission and reception. The MRI apparatus is characterized in that the switching circuit is brought into a non-conducting state between the elements when the MRI RF coil dedicated to reception is enabled and the switching circuit is in a non-conducting state.

In the MRI apparatus according to the third aspect of the invention, since the switching circuit becomes conductive between the elements during transmission, the MRI RF coil for both transmission and reception operates as a transmission coil.
Since the external output is cut off, the transmission signal does not leak to the receiving circuit side. Further, during reception by the MRI RF coil for both transmission and reception, the switching circuit becomes non-conducting between the elements and is ready for external output.
The RF coil for use operates as a receiving coil, and the signal received by this receiving coil is output to the receiving circuit side.
Furthermore, when receiving with the MRI RF coil dedicated to reception,
Since the switching circuit becomes non-conductive between the elements and the external output is cut off, the MRI RF coil for both transmission and reception does not operate as a receiving coil, but the MRI RF coil side dedicated to reception operates as a receiving coil. The reception signal is output from the RF coil for MRI dedicated to reception to the reception circuit side.

As a result, since the switching circuit can serve as both the T / R switch and the blocking circuit, the configurations of the T / R switch and the blocking circuit can be simplified.
Further, it is possible to reliably switch the operation of the MRI RF coil for both transmission and reception and the MRI RF coil for reception only at the time of reception.

As a fourth invention, the switching circuit in the third invention is an LC bridge circuit in which a switching element is connected to an input end and an output end, and the input end is arranged between the elements of the RF coil for MRI. And each switching element is turned on during transmission.
The C bridge circuit is cut off to realize the conduction between elements and the external output cutoff state, and when receiving by the MRI RF coil for both transmission and reception, each switching element is made non-conductive to make the LC bridge circuit conductive. State to realize the non-conduction state between elements and the state in which external output is possible.When receiving with the receive-only coil, the switching element at the input end is made non-conduction state and the switching element at the output end is made conductive state. The MRI apparatus is characterized by realizing a conductive state and an external output cutoff state.

Incidentally, as the switching element in this case, for example, an element such as a PIN diode is preferable in that it performs switching. In the MRI apparatus of the fourth aspect of the invention, since the switching element between the elements becomes conductive during transmission, the MRI RF coil for both transmission and reception operates as a transmission coil, and the switching element at the output end of the switching circuit becomes conductive. Therefore, the transmission signal does not leak to the receiving circuit side due to the external output cutoff state. Also, when receiving with the MRI RF coil for both transmission and reception, the switching element becomes non-conductive and ready for external output, so that the MRI RF coil for both transmission and reception operates as a reception coil, and reception by this reception coil is performed. The signal comes to be output to the receiving circuit side via the LC bridge circuit.
Furthermore, when receiving with the MRI RF coil dedicated to reception,
The switching elements bring the elements into a non-conductive state, the MRI RF coil for both transmission and reception does not operate as a reception coil, and the MRI RF coil for reception only operates as a reception coil.
The reception signal is output from the RF coil for use to the receiving circuit side, and the switching element at the output end of the LC bridge circuit becomes conductive so that the side of the MRI RF coil for both transmission and reception becomes in the external output cutoff state.

As a result, the switching circuit can serve as both the T / R switch and the blocking circuit, so that the configuration of the T / R switch, the blocking circuit, etc. can be simplified.
Further, it is possible to reliably switch the operation of the MRI RF coil for both transmission and reception and the MRI RF coil for reception only at the time of reception. In addition, the LC bridge circuit can realize a cutoff state and a conduction state, and can further realize balanced-unbalanced conversion in the conduction state.

A fifth aspect of the invention is an RF for MRI that is used for both transmission and reception.
A coil and a switching circuit that is arranged between the elements of the MRI RF coil and controls the conduction state between the elements;
A pickup coil arranged so as to be magnetically coupled to the MRI RF coil for both transmission and reception, and during transmission, the switching circuit is brought into a conduction state between the elements and the pickup coil is made inoperative, and an M for transmission and reception is provided.
The MRI apparatus is characterized in that, at the time of reception by the RF coil for RI, the switching circuit is brought into a conduction state between the elements, the external output is cut off, the pickup coil is put into an operating state, and a reception signal is outputted from the pickup coil. .

In the MRI apparatus according to the fifth aspect of the invention, since the switching circuit is brought into conduction between the elements during transmission, the MRI RF coil for both transmission and reception operates as a transmission coil.
Since the external output is cut off, the transmission signal does not leak to the receiving circuit side. Further, when the MRI RF coil for both transmission and reception is used, the switching circuit becomes conductive between the elements, so that reception is performed by the RF coil for MRI for both transmission and reception, and the switching circuit is cut off to the external output, so that the pickup coil is disconnected. The received signal comes to be output.

As a result, since the switching circuit can serve as both the T / R switch and the blocking circuit, the configurations of the T / R switch and the blocking circuit can be simplified.
Also, the output from the pickup coil during reception can be surely performed.

[0032]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration diagram showing a state around an MRI RF coil of a main part of an MRI apparatus in an example of an embodiment of the present invention, and FIG. 2 is a configuration showing a principle overall configuration of the MRI apparatus of the present invention. It is a figure.

First, the configuration and operation of the MRI apparatus in one example of the embodiment will be described with reference to FIG. CPU2
Reference numeral 0 is a control means for controlling the entire MRI apparatus as a whole, which gives an instruction to each section and processes a received signal to generate an image signal. At the time of transmission, the transmission circuit 30 makes the CPU 2
In response to the instruction from 0, a high frequency pulse required for MRI is generated, and the high frequency pulse is amplified by the power amplifier 40,
The signal is supplied to the transmitting / receiving coil 50 without passing through the T / R switch.

That is, the output of the power amplifier 40 is directly fed to the transmission / reception coil 50. It should be noted that the switching circuit 100 is assumed to have both the functions of a T / R switch for preventing a high-frequency, high-power pulse during transmission from being transmitted to the receiving side and a blocking circuit for performing reception by another surface coil. Are arranged in the elements of the transmission / reception coil 50, and the bias circuit 110 is configured to generate the bias current necessary for the switching operation of the switching circuit according to the instruction of the CPU 20.

At the time of reception, the signal detected by the transmission / reception coil 50 is transmitted to the preamplifier 70 via the switching circuit 100, various processing is executed by the receiving circuit 80, and the result is processed by the CPU 20 for display. The image is displayed on 90.

The operation of the MRI apparatus having such an overall structure will be described with reference to the detailed structure of the switching circuit 100 shown in FIG. The switching circuit 100 includes a transmission / reception coil 50.
A diode D1 as a switching element arranged between the elements L, an LC bridge circuit 101 arranged at both ends of the diode D, and a diode D2 as a switching element arranged at both ends of the output of the LC bridge circuit 101. It consists of The capacitors C1 and C2 are DC blocking capacitors for blocking the bias currents of the diodes D1 and D2.

The LC bridge circuit 101 is balanced between the MRI RF coil side and the input side of the preamplifier 70.
It is a circuit that performs unbalance conversion, and also L1-C3, L
The constants are selected to tune to the Larmor frequency in the 2-C4 LC circuit.

The bias circuit 110 is a switching control means for switching between conduction and non-conduction by supplying forward bias and reverse bias to the diode D1 and the diode D2, respectively.

PINs are used as the diodes D1 and D2.
It is preferable to use a diode or the like as the switching element. Consider a case where transmission and reception are performed by the transmission and reception coil 50 in the above circuit configuration. At this time, CP
The bias circuit 110 receives the diode D from the instruction from U20.
1 and diode D2 with forward bias applied,
The diodes D1 and D2 are turned on.

An equivalent circuit in this state is shown in FIG.
In this case, the element D of the coil is short-circuited by the conduction of the diode D1. As a result, even if transmission is performed with high power, there is no potential difference across the diode D1 and the differential component is not transmitted to the preamplifier 70 side. One of the inputs of the preamplifier 70 is GND
Installed in the L1 to C3 parallel resonant circuit and L2.
Since the parallel resonance circuit of −C4 has a high impedance, the in-phase component at both ends of the diode D1 does not flow to GND.

When the transmission / reception coil 50 performs reception, the bias circuit 110 applies a reverse bias to the diodes D1 and D2 according to an instruction from the CPU 20 to bring the diodes D1 and D2 into a non-conducting state.

An equivalent circuit in this state is shown in FIG.
In this case, the diode D2 becomes non-conducting, so that the state where the element L of the coil is short-circuited is released. As a result, the received signal is transmitted to the capacitors C1 and C2.
And is transmitted to the LC bridge circuit 101. Since the diode D2 is also non-conductive, the received signal is supplied to the input of the preamplifier 70. In this case,
The LC bridge circuit 101 operates as a balun for balanced-unbalanced conversion. That is, there is a matched state between the transmission / reception coil 50 in the balanced state and the input of the preamplifier 70 in the unbalanced state.

As described above, since the T / R switch and the blocking circuit can be used in common, it is possible to simplify the conventional circuit configurations of the T / R switch and the blocking circuit.

FIG. 4 is a block diagram showing the configuration of another example of the embodiment of the present invention. This configuration is configured such that, in addition to the case where transmission and reception are performed by the transmission / reception coil 50, only transmission is performed by the transmission / reception coil 50 and another reception-only coil 52 can be used. Also in this case, the operation as a conventional blocking circuit can be realized by performing the same switching control as in the above case at the time of transmission.

In this case as well, as in the case described above, the switching circuit 100 having both functions of the blocking circuit of the transmission / reception circuit 50 and the T / R switch can be used. Then, either the pickup coil 52 or the switching circuit 100 is guided to the preamplifier 70 by manually connecting the switch 63 or a cable.

In the MRI apparatus having the configuration shown in FIG. 4, since the switching circuit 100 becomes conductive between the elements during transmission, the MRI RF coil for both transmission and reception operates as a transmission coil, and the external output cutoff state causes the reception circuit. The transmission signal does not leak to the 80 side.

During reception by the transmission / reception coil 50, the switching circuit 100 becomes non-conductive between the elements and is ready for external output, so that the transmission / reception coil 50 operates as a reception coil and a reception signal at this reception coil is transmitted. The signal is output to the receiving circuit 80 side.

Further, at the time of reception by the reception-only coil 52, the switching circuit 100 becomes non-conductive between the elements,
Since the external output is cut off, the transmission / reception coil 50 does not operate as a reception coil, but the reception-dedicated coil 52 side operates as a reception coil.
The reception signal from 2 is output to the reception circuit 80 side.

As a result, since the switching circuit can serve as both the T / R switch and the blocking circuit, the configurations of the T / R switch and the blocking circuit can be simplified.
Further, it is possible to reliably switch the operation of the MRI RF coil for both transmission and reception and the MRI RF coil for reception only at the time of reception.

Further, the structure of FIG.
In addition to the case of performing transmission and reception at 0, the configuration in which a signal obtained by performing reception at the transmission / reception coil 50 is detected by the magnetically coupled pickup coil 52 ′ and guided to the reception circuit 80 is also shown.

In this case as well, as in the case described above, the switching circuit 100 having both functions of the blocking circuit of the transmission / reception circuit 50 and the T / R switch can be used. Then, either one of the pickup coil 52 'and the switching circuit 100 is guided to the preamplifier 70 by manually connecting the switch 63 or a cable.

As described above, in the MRI apparatus using the pickup coil 52 ', the transmitting / receiving coil 50 operates as a transmitting coil because the switching circuit 100 is in a conduction state between elements during transmission, and the receiving circuit is in an external output cutoff state. The transmission signal does not leak to the 80 side.

When the transmission / reception coil 50 receives the signal and outputs it from the pickup coil 52 ', the switching circuit 100 becomes conductive between the elements, so that the transmission / reception coil 50 performs the reception and the switching circuit 100.
Pick-up coil 5
The reception signal is output from 2 '.

In this case, since the signal received by the transmission / reception coil 50 is magnetically transmitted to the pickup 52 'when passing through the pickup coil 52', the sensitivity distribution is determined by the transmission / reception coil 50. Therefore, there is an effect that a sensitivity distribution in a wide range can be obtained.

Also in the case of this configuration, the T / R switch and the blocking circuit can be used in common, so that it is possible to simplify the circuit configurations of the T / R switch and the blocking circuit, which are separate in the past. Become.

As shown in each of the above embodiments,
5 to 8 for controlling the conduction / non-conduction state between the elements and the external output enable / shutdown state.
Modifications such as those shown in are also possible.

In FIG. 5, diodes D1, D3 and D4 are used as switching elements, and capacitors C1 for cutting off the direct current of the bias of each switching element.
C2.

Further, in FIG. 6, a capacitor C is provided between the elements.
0 is provided, and a π-type L is used instead of the LC bridge circuit described above.
A C circuit (L1, C3, C4) is provided, and a diode D2 is provided at the output end. In this case, the conduction / non-conduction of the diode D2 controls the enable / disable of the external output, and the operating state of the LC circuit changes to π type / parallel resonance according to the conduction / non-conduction of the diode D2. Can be used.

In FIG. 7, a capacitor C0 is provided between the elements, and diodes D3 and D4 are provided to enable / shut off external output. This switching circuit is suitable when the external output is controlled by the pickup coil 52 '.

In FIG. 8, a π-type LC circuit (L1, C3, C4) is provided instead of the above-mentioned LC bridge circuit, and diodes D1 and D2 are provided at the input / output ends. In this case, conduction / non-conduction of the diodes D1 and D2 controls conduction between elements and enabling / disabling of external output, and according to conduction / non-conduction of the diodes D1 and D2, LC
It can be used that the operating state of the circuit changes between π type / parallel resonance.

[0061]

According to the invention described in detail above, the following effects can be obtained. In the MRI apparatus of the first invention,
Since the switching circuit becomes conductive between elements during transmission, the MRI RF coil for both transmission and reception operates as a transmission coil, and the transmission signal does not leak to the reception circuit side due to the external output cutoff state. Further, the switching circuit during reception. Is in a non-conductive state between the elements and is ready for external output, the MRI RF coil for both transmission and reception operates as a reception coil, and the reception signal at this reception coil is output to the reception circuit side.

As a result, since the switching circuit can serve as both the T / R switch and the blocking circuit, the configurations of the T / R switch and the blocking circuit can be simplified.
In the MRI apparatus of the second invention, since both switching elements are in a conducting state at the time of transmission, the MR for both transmission and reception
Since the RF coil for I operates as a transmission coil and the LC bridge circuit is in the cutoff state, the transmission signal does not leak to the reception circuit side, and both switching elements are in the non-conduction state at the time of reception. The signal detected by the RF coil for output is output to the receiving circuit side in a state of being balanced-unbalanced converted by the LC bridge circuit.

As a result, since the switching circuit can serve as both the T / R switch and the blocking circuit, the configurations of the T / R switch and the blocking circuit can be simplified.
In addition, by using the switching element and the LC bridge circuit, reliable operation can be expected with a simple configuration. In addition, the LC bridge circuit can realize a cutoff state and a conduction state, and can further realize balanced-unbalanced conversion in the conduction state.

In the MRI apparatus of the third invention, since the switching circuit is in the conduction state between the elements during transmission, the MRI RF coil for both transmission and reception operates as a transmission coil, and since the external output is cut off, the transmission signal is transmitted to the reception circuit side. Does not leak, and when the MRI RF coil for both transmission and reception is used for reception, the switching circuit becomes non-conductive between elements and is ready for external output.
The coil operates as a receiving coil, and the signal received by this receiving coil is output to the receiving circuit side. Furthermore,
At the time of reception by the MRI RF coil dedicated to reception, the switching circuit is in a non-conducting state between elements and the external output is cut off, so that the MRI RF coil for both transmission and reception does not operate as a reception coil, and the MRI dedicated for reception The RF coil for use operates as a receiving coil, and the reception signal is output from the RF coil for MRI dedicated to reception to the receiving circuit side.

As a result, since the switching circuit can serve as both the T / R switch and the blocking circuit, it is possible to simplify the configuration of the T / R switch and the blocking circuit.
Further, it is possible to reliably switch the operation of the MRI RF coil for both transmission and reception and the MRI RF coil for reception only at the time of reception.

In the MRI apparatus of the fourth aspect of the invention, since the switching element between the elements becomes conductive during transmission, the MRI RF coil for both transmission and reception operates as a transmission coil, and the switching element at the output end of the switching circuit conducts. Since the external output is cut off, the transmission signal does not leak to the receiving circuit side.
When receiving with the I RF coil, the switching element is in a non-conducting state and is ready for external output, so that the MRI RF coil for both transmission and reception operates as a reception coil, and the reception signal at this reception coil is an LC bridge circuit. Will be output to the receiving circuit side via. Furthermore, during reception with the MRI RF coil dedicated to reception, the switching elements bring the elements into a non-conductive state, the MRI RF coil for both transmission and reception does not operate as a reception coil, and the MRI RF coil side dedicated to reception is the reception coil. As a result, the reception signal is output from the reception-only RF coil for MRI to the reception circuit side, and the switching element at the output end of the LC bridge circuit becomes conductive so that it can be used for both transmission and reception. The external output is cut off on the RF coil side.

As a result, since the switching circuit can serve as both the T / R switch and the blocking circuit, the configurations of the T / R switch and the blocking circuit can be simplified.
Further, it is possible to reliably switch the operation of the MRI RF coil for both transmission and reception and the MRI RF coil for reception only at the time of reception. In addition, the LC bridge circuit can realize a cutoff state and a conduction state, and can further realize balanced-unbalanced conversion in the conduction state.

In the MRI apparatus of the fifth invention, since the switching circuit becomes conductive between the elements during transmission, the MRI RF coil for both transmission and reception operates as a transmission coil, and since the external output is cut off, the transmission signal is sent to the reception circuit side. Does not leak, and since the switching circuit becomes conductive between elements during reception by the MRI RF coil for both transmission and reception,
Reception is carried out by the RF coil for MRI which is used for both transmission and reception, and the switching circuit is brought into the external output cutoff state, so that the reception signal is outputted from the pickup coil.

As a result, since the switching circuit can serve as both the T / R switch and the blocking circuit, it is possible to simplify the configuration of the T / R switch and the blocking circuit.
Also, the output from the pickup coil during reception can be surely performed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a configuration of a main part of an MRI apparatus of the present invention.

FIG. 2 is a circuit diagram showing an overall configuration of an MRI apparatus of the present invention.

FIG. 3 is a configuration diagram showing an equivalent circuit of a main part of the MRI apparatus of the present invention.

FIG. 4 is a circuit diagram showing another configuration of the MRI apparatus of the present invention.

FIG. 5 is a circuit diagram showing an example of a switching circuit used in the present invention.

FIG. 6 is a circuit diagram showing an example of a switching circuit used in the present invention.

FIG. 7 is a circuit diagram showing an example of a switching circuit used in the present invention.

FIG. 8 is a circuit diagram showing an example of a switching circuit used in the present invention.

FIG. 9 is a configuration diagram showing a configuration example of a conventional MRI apparatus.

FIG. 10 is a configuration diagram showing a configuration example of a conventional MRI apparatus.

FIG. 11 is a configuration diagram showing a configuration example of a conventional MRI apparatus.

FIG. 12 is a configuration diagram showing a configuration example of a conventional MRI apparatus.

[Explanation of symbols]

 D1, D2 diode 100 switching circuit 101 LC bridge circuit 110 bias circuit

Claims (5)

[Claims] 1. An MRI RF coil for both transmission and reception, and a switching circuit which is arranged between the elements of the MRI RF coil and controls an inter-element conduction state and an output state from the element to the outside. An MRI apparatus characterized in that the switching circuit is sometimes brought into a conduction state between elements and is in an external output cutoff state, and the reception circuit is in a non-conduction state between elements and is in an external output enable state at the time of reception. 2. The switching circuit comprises an LC bridge circuit in which a switching element is connected to an input end and an output end, and the input end is arranged between elements of an MRI RF coil. By setting the conduction state, the LC bridge circuit is cut off to realize the conduction state between elements and the external output cutoff state, and when receiving, each switching element is set to the non-conduction state to set the LC bridge circuit to the conduction state. The MRI apparatus according to claim 1, wherein a non-conductive state between elements and a state in which external output is possible are realized. 3. An MRI RF coil for both transmission and reception, a switching circuit arranged between the elements of the MRI RF coil for controlling a conduction state between elements and an output state from the element to the outside, and an MRI only for reception. RF coil for transmission, the switching circuit is set to the conduction state between the elements and the external output is cut off during transmission, and the switching circuit is set to the non-conduction state between the elements and external output during reception by the MRI RF coil for both transmission and reception. Enable and receive only MRI
An MRI apparatus characterized in that a switching circuit is set to a non-conducting state between elements and an external output is cut off at the time of reception by an RF coil for use. 4. The switching circuit comprises an LC bridge circuit in which a switching element is connected to an input end and an output end, and the input end is arranged between the elements of the MRI RF coil. By setting the conduction state, the LC bridge circuit is cut off to realize the conduction state between the elements and the external output cutoff state, and each switching element is set to the non-conduction state at the time of reception by the MRI RF coil for both transmission and reception. The LC bridge circuit is turned on to realize a non-conducting state between elements and a state in which external output is possible, and when receiving by the receiving coil, the switching element at the input end is made non-conducting and the switching element at the output end is made conducting. 4. A non-conductive state between elements and an external output cutoff state are realized by setting the state. Listed M
RI equipment. 5. An MRI RF coil for both transmission and reception, a switching circuit arranged between the elements of the MRI RF coil for controlling a conduction state between the elements, and magnetically coupled to the MRI RF coil for both transmission and reception. And a pickup coil arranged so as to make the switching circuit conductive between elements at the time of transmission and deactivate the pickup coil, and make the switching circuit conductive between elements at the time of reception by the MRI RF coil for both transmission and reception. The MRI apparatus is characterized in that the pickup coil is set to the state and the external output is cut off, the pickup coil is set to the operating state, and a reception signal is output from the pickup coil.