JP6923400B2 - High frequency amplifier and magnetic resonance imaging equipment - Google Patents

Description

Embodiments of the present invention relate to high frequency amplifiers and magnetic resonance imaging devices.

The magnetic resonance imaging device applies high-frequency energy from an RF (Radio Frequency) coil to a subject placed in a static magnetic field, and based on the magnetic resonance signal generated from the subject under the influence of the high-frequency energy, the inside of the subject It is a device that generates an image. Here, the high-frequency energy applied to the subject is such that a high-frequency pulse having a desired waveform and frequency is generated by a control circuit or the like, and the generated high-frequency pulse is power-amplified by a high-frequency amplifier arranged in front of the RF coil. Obtained at.

Special Table 2006-521949

An object to be solved by the present invention is to provide a high frequency amplifier and a magnetic resonance imaging apparatus capable of reducing the power required for applying high frequency energy.

The high frequency amplifier according to the embodiment supplies high frequency power to a plurality of substantially independent coil elements that apply high frequency energy to the subject. The high frequency amplifier includes at least one more amplification module than the number of coil elements. The high-frequency amplifier is provided for each coil element, and includes a synthesizer that synthesizes high-frequency power output from each of the amplification modules and outputs the high-frequency power to the corresponding coil element. The high frequency amplifier is configured so that the number of amplification modules connected to each of the synthesizers can be selected.

FIG. 1 is a diagram showing a configuration example of the magnetic resonance imaging apparatus according to the first embodiment. FIG. 2 is a diagram showing a configuration example of a high frequency amplifier according to a comparative example of the first embodiment. FIG. 3 is a diagram showing a configuration example of a high frequency amplifier according to a comparative example of the first embodiment. FIG. 4 is a diagram showing a configuration example of the high frequency amplifier according to the first embodiment. FIG. 5 is a diagram showing a configuration example of the high frequency amplifier according to the first embodiment. FIG. 6 is a diagram showing another configuration example of the synthesizer and the switch in the high frequency amplifier according to the first embodiment. FIG. 7 is a diagram showing a configuration example of the high frequency amplifier according to the second embodiment. FIG. 8 is a diagram showing a configuration example of the high frequency amplifier according to the second embodiment.

Hereinafter, the high frequency amplifier and the magnetic resonance imaging apparatus according to the embodiment will be described in detail with reference to the drawings.

(First Embodiment)
FIG. 1 is a diagram showing a configuration example of the magnetic resonance imaging apparatus according to the first embodiment.

For example, as shown in FIG. 1, the magnetic resonance imaging (MRI) device 100 according to the present embodiment includes a static magnetic field magnet 1, a gradient magnetic field coil 2, a gradient magnetic field power supply 3, a whole body RF coil 4, and a transmission. A circuit 5, a local RF coil 6, a receiving circuit 7, an RF shield 8, a gantry 9, a sleeper 10, an input interface 11, a display 12, a storage circuit 13, and first to fourth processing circuits 14 to 17 are provided.

The static magnetic field magnet 1 generates a static magnetic field in the imaging space in which the subject S is arranged. Specifically, the static magnetic field magnet 1 is formed in a hollow substantially cylindrical shape (including a magnet having an elliptical cross section orthogonal to the central axis of the cylinder), and a static magnetic field is applied to the space inside the cylinder. generate. For example, the static magnetic field magnet 1 has a cooling container formed in a substantially cylindrical shape, and a magnet such as a superconducting magnet immersed in a cooling material (for example, liquid helium or the like) filled in the cooling container. Here, for example, the static magnetic field magnet 1 may be one that generates a static magnetic field by using a permanent magnet.

The gradient magnetic field coil 2 is arranged inside the static magnetic field magnet 1, and applies a gradient magnetic field to the imaging space in which the subject S is arranged. Specifically, the gradient magnetic field coil 2 is formed in a hollow substantially cylindrical shape (including one having an elliptical cross section orthogonal to the central axis of the cylinder), and is orthogonal to each other in the space inside the cylinder. A gradient magnetic field is generated along each of the X-axis, Y-axis, and Z-axis. Here, the X-axis, the Y-axis, and the Z-axis form a device coordinate system unique to the MRI device 100. For example, the Z axis coincides with the axis of the cylinder of the gradient magnetic field coil 2 and is set along the magnetic flux of the static magnetic field generated by the static magnetic field magnet 1. Further, the X-axis is set along the horizontal direction orthogonal to the Z-axis, and the Y-axis is set along the vertical direction orthogonal to the Z-axis.

The gradient magnetic field power supply 3 supplies a current to the gradient magnetic field coil 2 to generate a gradient magnetic field along the X-axis, Y-axis, and Z-axis in the space inside the gradient magnetic field coil 2. In this way, the gradient magnetic field power supply 3 generates a gradient magnetic field along each of the X-axis, Y-axis, and Z-axis to generate a gradient magnetic field along each of the lead-out direction, the phase encoding direction, and the slice direction. Can be done. The axes along the lead-out direction, the phase encoding direction, and the slice direction each constitute a logical coordinate system for defining the slice region or volume region to be imaged. In the following, the gradient magnetic field along the lead-out direction is referred to as a lead-out gradient magnetic field, the gradient magnetic field along the phase-encoded direction is referred to as a phase-encoded gradient magnetic field, and the gradient magnetic field along the slice direction is referred to as a slice gradient magnetic field. ..

These gradient magnetic fields are superimposed on the static magnetic field generated by the static magnetic field magnet 1 and are used to impart spatial position information to the magnetic resonance (MR) signal. Specifically, the lead-out gradient magnetic field imparts position information along the lead-out direction to the MR signal by changing the frequency of the MR signal according to the position in the lead-out direction. Further, the phase-encoded gradient magnetic field imparts position information in the phase-encoded direction to the MR signal by changing the phase of the MR signal along the phase-encoded direction. The slice gradient magnetic field is used to determine the direction, thickness, and number of slice regions when the imaging region is a slice region, and depends on the position in the slice direction when the imaging region is a volume region. By changing the phase of the MR signal, position information along the slice direction is given to the MR signal.

The whole-body RF coil 4 is arranged inside the gradient magnetic field coil 2, and high-frequency energy (high-frequency magnetic field) is applied to the imaging space in which the subject S is arranged, and is generated from the subject S due to the influence of the high-frequency energy. Receives the MR signal. Specifically, the RF coil 4 for the whole body is formed in a hollow substantially cylindrical shape (including one having an elliptical cross section orthogonal to the central axis of the cylinder), and high frequency energy is generated in the space inside the cylinder. Is applied. Further, the whole body RF coil 4 receives the MR signal generated from the subject S and outputs the received MR signal to the receiving circuit 7.

The transmission circuit 5 outputs an RF pulse signal corresponding to the Larmor frequency to the whole body RF coil 4. Specifically, the transmission circuit 5 includes an oscillator, a phase selector, a frequency converter, an amplitude modulator, and a high frequency amplifier. The oscillator generates a high-frequency pulse with a resonance frequency specific to the target nucleus placed in a static magnetic field. The phase selector selects the phase of the high frequency pulse output from the oscillator. The frequency converter converts the frequency of the high frequency pulse output from the phase selector. The amplitude modulator modulates the amplitude of the high frequency pulse output from the frequency converter according to, for example, a sinc function. The high frequency amplifier power-amplifies the high frequency pulse output from the amplitude modulator and outputs it to the whole body RF coil 4.

The local RF coil 6 receives the MR signal generated from the subject S. Specifically, the local RF coil 6 is attached to the subject S arranged inside the whole body RF coil 4, and is generated from the subject S due to the influence of the high frequency energy applied by the whole body RF coil 4. The MR signal is received, and the received MR signal is output to the receiving circuit 7. For example, the local RF coil 6 is a receiving coil prepared for each part to be imaged, and is a receiving coil for the head, a receiving coil for the neck, a receiving coil for the shoulder, a receiving coil for the chest, and an abdomen. The receiving coil for the lower limbs, the receiving coil for the spine, and the like. The local RF coil 6 may further have a transmission function of applying high frequency energy. In that case, the local RF coil 6 is connected to the transmission circuit 5 and applies high frequency energy to the subject S based on the RF pulse signal output from the transmission circuit 5.

The receiving circuit 7 generates MR signal data based on the MR signal output from the whole body RF coil 4 or the local RF coil 6, and outputs the generated MR signal data to the second processing circuit 15. For example, the receiving circuit 7 includes a selector, a pre-stage amplifier, a phase detector, and an analog-to-digital converter. The selector selectively inputs the MR signal output from the whole body RF coil 4 or the local RF coil 6. The pre-stage amplifier amplifies the MR signal output from the selector. The phase detector detects the phase of the MR signal output from the pre-stage amplifier. The analog-digital converter generates MR signal data by converting the analog signal output from the phase detector into a digital signal, and outputs the generated MR signal data to the second processing circuit 15.

The RF shield 8 is arranged between the gradient magnetic field coil 2 and the whole body RF coil 4, and shields the high frequency energy generated by the whole body RF coil 4. Specifically, the RF shield 8 is formed in a hollow substantially cylindrical shape (including one having an elliptical cross section orthogonal to the central axis of the cylinder), and is formed on the inner peripheral side of the gradient magnetic field coil 2. It is arranged in the space so as to cover the outer peripheral surface of the RF coil 4 for the whole body.

The gantry 9 houses a static magnetic field magnet 1, a gradient magnetic field coil 2, a whole-body RF coil 4, and an RF shield 8. Specifically, the gantry 9 has a hollow bore B formed in a cylindrical shape, and has a static magnetic field magnet 1, a gradient magnetic field coil 2, a whole body RF coil 4, and an RF shield 8 so as to surround the bore B. Each is housed in the state where. Here, the space inside the bore B of the gantry 9 becomes an imaging space in which the subject S is arranged when the subject S is imaged.

The sleeper 10 includes a top plate 10a on which the subject S is placed, and when the subject S is imaged, the top plate 10a is inserted inside the bore B of the gantry 9. For example, the sleeper 10 is installed so that the longitudinal direction is parallel to the central axis of the static magnetic field magnet 1.

The input interface 11 receives various instructions and various information input operations from the operator. Specifically, the input interface 11 is connected to the fourth processing circuit 17, converts the input operation received from the operator into an electric signal, and outputs the input operation to the control circuit. For example, the input interface 11 includes a trackball for setting imaging conditions and a region of interest (ROI), a switch button, a mouse, a keyboard, a touch pad for performing input operations by touching an operation surface, and a display. It is realized by a touch screen in which a screen and a touch pad are integrated, a non-contact input interface using an optical sensor, a voice input interface, and the like. In the present specification, the input interface 11 is not limited to the one provided with physical operating parts such as a mouse and a keyboard. For example, an example of the input interface 11 includes an electric signal processing circuit that receives an electric signal corresponding to an input operation from an external input device provided separately from the device and outputs the electric signal to a control circuit.

The display 12 displays various information and various images. Specifically, the display 12 is connected to the fourth processing circuit 17, and converts various information and various image data sent from the fourth processing circuit 17 into electrical signals for display and outputs the data. For example, the display 12 is realized by a liquid crystal monitor, a CRT (Cathode Ray Tube) monitor, a touch panel, or the like.

The storage circuit 13 stores various data. Specifically, the storage circuit 13 stores MR signal data and image data. For example, the storage circuit 13 is realized by a semiconductor memory element such as a RAM (Random Access Memory) or a flash memory, a hard disk, an optical disk, or the like.

The first processing circuit 14 has a sleeper control function 14a. The sleeper control function 14a is connected to the sleeper 10 and outputs a control electric signal to the sleeper 10 to control the operation of the sleeper 10. For example, the sleeper control function 14a receives an instruction from the operator to move the top plate 10a in the longitudinal direction, the vertical direction, or the horizontal direction via the input interface 11, and moves the top plate 10a according to the received instruction. The drive mechanism of the top plate 10a included in the sleeper 10 is operated.

The second processing circuit 15 has an execution function 15a. The execution function 15a executes various pulse sequences by driving the gradient magnetic field power supply 3, the transmission circuit 5, and the reception circuit 7 based on the sequence execution data output from the fourth processing circuit 17. For example, the executive function 15a drives the gradient magnetic field power supply 3, the transmission circuit 5, and the reception circuit 7 by transmitting input signals to the gradient magnetic field power supply 3, the transmission circuit 5, and the reception circuit 7, respectively.

Here, the sequence execution data is information that defines a pulse sequence indicating a procedure for collecting MR signal data. Specifically, the sequence execution data includes the timing and strength of the current supplied by the gradient magnetic field power supply 3 to the gradient magnetic field coil 2, and the strength of the RF pulse signal supplied by the transmission circuit 5 to the whole-body RF coil 4. This is information that defines the sheath supply timing, the detection timing at which the receiving circuit 7 detects the MR signal, and the like.

Then, the execution function 15a receives MR signal data from the reception circuit 7 as a result of executing various pulse sequences, and stores the received MR signal data in the storage circuit 13. The set of MR signal data received by the execution function 15a is arranged two-dimensionally or three-dimensionally according to the position information given by the lead-out gradient magnetic field, the phase-encoded gradient magnetic field, and the slice gradient magnetic field described above. As a result, it is stored in the storage circuit 13 as data constituting the k space.

The third processing circuit 16 has an image generation function 16a. The image generation function 16a generates an image based on the MR signal data stored in the storage circuit 13. Specifically, the image generation function 16a reads the MR signal data stored in the storage circuit 13 by the execution function 15a, and performs post-processing, that is, reconstruction processing such as Fourier transform on the read MR signal data. Generate an image. Further, the image generation function 16a stores the image data of the generated image in the storage circuit 13.

The fourth processing circuit 17 has a main control function 17a. The main control function 17a controls the entire MRI apparatus 100 by controlling each component of the MRI apparatus 100. For example, the main control function 17a receives input of imaging conditions from the operator via the input interface 11. Then, the main control function 17a generates sequence execution data based on the received imaging conditions, and transmits the sequence execution data to the second processing circuit 15 to execute various pulse sequences. Further, for example, the main control function 17a reads out image data from the storage circuit 13 and outputs it to the display 12 in response to a request from the operator.

Here, for example, each of the above-mentioned processing circuits is realized by a processor. In that case, for example, the processing function of each processing circuit is stored in the storage circuit 13 in the form of a program that can be executed by a computer. Each processing circuit realizes a function corresponding to each program by reading each program from the storage circuit 13 and executing the program. In other words, each processing circuit in the state where each program is read has each function shown in each processing circuit of FIG.

Further, each processing circuit may be configured by combining a plurality of independent processors, and each processor may execute a program to realize each function. Further, the functions of each processing circuit may be appropriately distributed or integrated into a single processing circuit or a plurality of processing circuits. Further, the function of each processing circuit may be realized by mixing hardware such as a circuit and software.

The overall configuration of the MRI apparatus 100 according to the present embodiment has been described above. Under such a configuration, the MRI apparatus 100 according to the present embodiment applies high frequency energy from the whole body RF coil 4 to the subject S arranged in a static magnetic field, and the subject S is affected by the high frequency energy. An image in the subject S is generated based on the magnetic resonance signal generated from. Here, the high-frequency energy applied to the subject S is generated by generating a high-frequency pulse having a desired waveform and frequency in the transmission circuit 5 by an oscillator, a phase selector, a frequency converter, and an amplitude modulator, and generating the generated high-frequency pulse. It is obtained by amplifying the power with a high frequency amplifier.

In such an MRI apparatus 100, it is generally desirable that high-frequency energy be uniformly applied over a site to be imaged in a subject. On the other hand, in recent years, a static magnetic field having a higher intensity (for example, 3T (tesla) to 7T, etc.) has been used to increase the resonance frequency with the aim of increasing the signal-to-noise ratio (SNR). It's coming. When the static magnetic field strength is increased in this way, the macroscopic magnetization increases and the signal intensity increases in proportion to it, while the resonance frequency increases, so that the distribution of high-frequency energy in the region to be imaged is distributed. The problem of non-uniformity arises. It is known that this is due to electrical characteristics including the shape of the subject, such as the influence of high-frequency eddy current and dielectric constant generated on the subject when high-frequency energy is applied to the subject. ..

The MRI apparatus 100 according to the present embodiment has a function of imaging the subject S by using a technique called a parallel transmission as a means for eliminating such non-uniformity of high-frequency energy distribution in the subject S. Have.

Specifically, in the MRI apparatus 100 according to the present embodiment, the whole body RF coil 4 has a plurality of substantially independent coil elements. Then, the high-frequency amplifier included in the transmission circuit 5 applies high-frequency power to each coil element with an amplitude and phase determined in advance for each coil element so that the distribution of high-frequency energy is finally uniform in the subject S. Supply. Here, in the present embodiment, the high-frequency amplifier included in the transmission circuit 5 has a plurality of amplification modules for supplying high-frequency power to each coil element.

In such a parallel transmission, the magnitude of high-frequency power output to each coil element changes depending on the shape of the subject and the like. Therefore, for example, when the number of amplification modules that supply high-frequency power to each coil element is fixed for each coil element, the power required to apply high-frequency energy in the high-frequency amplifier increases as shown below. It is possible to do.

2 and 3 are diagrams showing a configuration example of the high frequency amplifier according to the comparative example of the first embodiment.

For example, as shown in FIGS. 2 and 3, it is assumed that the whole body RF coil 4 has two coil elements, and the high frequency amplifier 90 included in the transmission circuit 5 has four amplification modules.

Specifically, the whole body RF coil 4 has first and second coil elements 41 and 42. Further, the high frequency amplifier 90 has first to fourth amplification modules 911 to 914. Here, the first and second amplification modules 911 and 912 are connected to the first synthesizer 921 in parallel with each other. Further, the third and fourth amplification modules 913 and 914 are connected to the second synthesizer 922 in parallel with each other.

In such a configuration, for example, as shown in FIG. 2, when 2 kW of high frequency power is output to each of the first coil element 41 and the second coil element 42, each amplification module has a high frequency power of 1 kW. Is output.

As a result, 1 kW of high-frequency power is supplied to the first synthesizer 921 from each of the first and second amplification modules 911 and 912, and the first coil element 41 is synthesized by the first synthesizer 921. The high frequency power of 2 kW will be supplied. On the other hand, 1 kW of high frequency power is supplied to the second synthesizer 922 from each of the third and fourth amplification modules 913 and 914, and the second coil element 42 is synthesized by the second synthesizer 922. Only 2 kW of high frequency power will be supplied.

On the other hand, for example, as shown in FIG. 3, when a high frequency power of 3 kW is output to the first coil element 41 and a high frequency power of 1 kW is output to the second coil element 42, the first and second coils are used. The amplification modules 911 and 912 each output 1.5 kW of high frequency power, and the third and fourth amplification modules 913 and 914 each output 0.5 kW of high frequency power.

As a result, 1.5 kW of high-frequency power is supplied to the first synthesizer 921 from each of the first and second amplification modules 911 and 912, and the first coil element 41 is supplied with the first synthesizer 921. The 3 kW high frequency power synthesized by the above will be supplied. On the other hand, 0.5 kW of high frequency power is supplied to the second synthesizer 922 from each of the third and fourth amplification modules 913 and 914, and the second coil element 42 is supplied by the second synthesizer 922. The synthesized high frequency power of 1 kW will be supplied.

As described above, in the parallel transmission, the magnitude of the high-frequency power output to each coil element changes depending on the shape of the subject and the like. Therefore, contrary to the example shown in FIG. 3, the first coil element 41 In some cases, a high frequency power of 1 kW is output to the second coil element 42, and a high frequency power of 3 kW is output to the second coil element 42.

Therefore, in the configurations shown in FIGS. 2 and 3, each amplification module needs to have a maximum output of 1.5 kW, and the high frequency amplifier 90 has a total of 1.5 kW × 4 (amplification modules). A maximum output of = 6 kW is required. As a result, the power required to apply high-frequency energy in the high-frequency amplifier increases.

Therefore, in the MRI apparatus 100 according to the present embodiment, the high-frequency amplifier included in the transmission circuit 5 is configured to be able to reduce the required power required for applying high-frequency energy.

Specifically, in the present embodiment, the high-frequency amplifier included in the transmission circuit 5 includes at least one more amplification modules than the number of coil elements included in the whole-body RF coil 4. Further, the high frequency amplifier is provided for each coil element included in the whole body RF coil 4, and includes a synthesizer that synthesizes high frequency power output from each amplification module and outputs the high frequency power to the corresponding coil element. The high-frequency amplifier is configured so that the number of amplification modules connected to each synthesizer can be selected.

Here, in the present embodiment, the high-frequency amplifier is provided for each synthesizer, and further includes a switch arranged in front of the synthesizer. The switch is configured to be able to select the number of amplification modules connected to the corresponding synthesizer.

Further, in the present embodiment, each amplification module connected to the synthesizer has a high frequency power substantially equal to the value obtained by dividing the high frequency power required for the coil element corresponding to the synthesizer by the number of the amplification modules. Output to the synthesizer. Here, the amplitude and phase of the high frequency power synthesized by the synthesizer are substantially the same.

Further, in a transmission line in which high-frequency power is transmitted, it is considered that the ratio of voltage and current changes in various places in the transmission line, and as a result, the impedance is different in each place in the transmission line. Therefore, in the present embodiment, the line length of the transmission line between the amplification module and the switch is such that the impedance on the switch side as seen from the amplification module is also substantially open when the switch is opened. The length is set to be approximately the same as an integral multiple of 1/2 wavelength.

4 and 5 are diagrams showing a configuration example of the high frequency amplifier according to the first embodiment.

For example, as shown in FIGS. 4 and 5, in the present embodiment, the whole body RF coil 4 has two coil elements, and the high frequency amplifier 50 included in the transmission circuit 5 has four amplification modules and four amplification modules. It has two synthesizers and eight switches.

Specifically, the whole body RF coil 4 has first and second coil elements 41 and 42. Further, the high frequency amplifier 50 includes first to fourth amplification modules 511 to 514, first and second synthesizers 521 and 522, and first to eighth switches 531 to 538.

Here, the first to fourth amplification modules 511 to 514 are connected to the first synthesizer 521 in parallel with each other via the first to fourth switches 531 to 534. Further, the first to fourth amplification modules 511 to 514 are connected to the second synthesizer 522 in parallel with each other via the fifth to eighth switches 535 to 538.

Specifically, the first amplification module 511 is connected to the first synthesizer 521 via the first switch 531 and further connected to the second synthesizer 522 via the fifth switch 535. ing. Further, the second amplification module 512 is connected to the first synthesizer 521 via the second switch 532, and further connected to the second synthesizer 522 via the sixth switch 536. Further, the third amplification module 513 is connected to the first synthesizer 521 via the third switch 533, and further connected to the second synthesizer 522 via the seventh switch 537. Further, the fourth amplification module 514 is connected to the first synthesizer 521 via the fourth switch 534, and further connected to the second synthesizer 522 via the eighth switch 538.

In such a configuration, in the present embodiment, the execution function 15a of the second processing circuit 15 controls the magnitude of the high frequency power output from each amplification module. Further, in the present embodiment, the execution function 15a of the second processing circuit 15 controls the connection between each synthesizer and each amplification module in the high frequency amplifier 50 by switching the open / closed state of each switch.

Here, for example, the number and combination of amplification modules connected to each synthesizer are predetermined for each part to be imaged. For example, in the MRI apparatus 100, when information in which imaging conditions for each of a plurality of imaging parameters (also called protocols) performed in an inspection targeting one site are set is stored in the storage circuit 13 in advance for each inspection. Further stores setting information indicating the number and combination of amplification modules connected to each synthesizer in association with each inspection. In this case, the execution function 15a of the second processing circuit 15 switches the open / closed state of each switch with reference to the setting information stored in the storage circuit 13.

For example, as shown in FIG. 4, when the high frequency power of 2 kW is output to each of the first and second coil elements 41 and 42, the execution function 15a is the first and second synthesizers 521 and 522, respectively. Two amplification modules are connected to each of the amplifier modules, and each amplification module is controlled to output 1 kW of high frequency power.

Specifically, the execution function 15a sets the first and second switches 531 and 532 in the closed state and opens the third and fourth switches 533 and 534 in the first synthesizer 521. , 1st and 2nd amplification modules 511 and 512 are connected. Further, the executive function 15a opens the fifth and sixth switches 535 and 536 and closes the seventh and eighth switches 537 and 538, so that the second synthesizer 522 has the third and third switches. A fourth amplification module 513,514 is connected.

As a result, 1 kW of high-frequency power is supplied to the first synthesizer 521 from each of the first and second amplification modules 511 and 512, and the first coil element 41 is synthesized by the first synthesizer 521. The high frequency power of 2 kW will be supplied. On the other hand, 1 kW of high-frequency power is supplied to the second synthesizer 522 from each of the third and fourth amplification modules 513 and 514, and the second coil element 42 is synthesized by the second synthesizer 522. Only 2 kW of high frequency power will be supplied.

On the other hand, for example, as shown in FIG. 5, when a high frequency power of 3 kW is output to the first coil element 41 and a high frequency power of 1 kW is output to the second coil element 42, the execution function 15a is the first. Three amplification modules are connected to the synthesizer 521 of one, one amplification module is connected to the second synthesizer 522, and each amplification module is controlled to output 1 kW of high frequency power.

Specifically, the execution function 15a causes the first to third switches 513 to 533 to be in the closed state and the fourth switch 534 to be in the open state, thereby causing the first synthesizer 521 to be in the first to first to third positions. The amplification modules 511 to 513 of No. 3 are connected. Further, the executive function 15a causes the second synthesizer 522 to have the fourth amplification module 514 by opening the fifth to seventh switches 535-537 and closing the eighth switch 538. Connecting.

As a result, 1 kW of high-frequency power is supplied to the first synthesizer 521 from each of the first to third amplification modules 511 to 513, and the first coil element 41 is synthesized by the first synthesizer 521. The high frequency power of 3 kW will be supplied. On the other hand, 1 kW of high frequency power is supplied to the second synthesizer 522 from the fourth amplification module 514, and 1 kW of high frequency power synthesized by the second synthesizer 522 is supplied to the second coil element 42. It will be supplied.

As described above, in the present embodiment, in any of the examples shown in FIGS. 4 and 5, each amplification module may have a maximum output of 1 kW, and the high frequency amplifier 50 has a total of 1 kW × 4. (Individual amplification modules) = 4 kW maximum output is sufficient. Therefore, in the present embodiment, it is possible to supply the required high frequency power to each coil element by the combination of the amplification modules having a lower maximum output as compared with the examples shown in FIGS. 2 and 3.

Here, an example in which the whole-body RF coil 4 has two coil elements has been described, but the number of coil elements is not limited to this. The number of coil elements provided in the whole-body RF coil 4 may be two or more, as long as parallel transmission can be performed.

Further, although an example in which the high frequency amplifier 50 includes four amplification modules has been described here, the number of amplification modules is not limited to four. The number of amplification modules provided in the high-frequency amplifier 50 may be at least one more than the number of coil elements provided in the whole-body RF coil 4. This makes it possible to dynamically change the connection destination among a plurality of coil elements for at least one amplification module when changing the magnitude of high-frequency power output to each coil element in a parallel transmission. ..

As described above, in the first embodiment, the high frequency amplifier 50 includes at least one more amplification module than the number of coil elements. Further, the high frequency amplifier 50 is provided for each coil element, and includes a synthesizer that synthesizes high frequency power output from each amplification module and outputs the high frequency power to the corresponding coil element. The high frequency amplifier 50 is configured so that the number of amplification modules connected to each synthesizer can be selected. Thereby, in this embodiment, the maximum output of each amplification module provided in the high frequency amplifier 50 can be reduced.

Therefore, according to the first embodiment, the required power required for applying high frequency energy can be reduced. Further, by reducing the required power, it is possible to reduce the risk of damage to the elements mounted on the high frequency amplifier 50. As a result, the reliability of the high frequency amplifier 50 and the MRI apparatus 100 can be improved.

(Modified example of the first embodiment)
In the high frequency amplifier 50 described in the first embodiment described above, the configurations of the synthesizer and the switch are not limited to those shown in FIGS. 4 and 5.

FIG. 6 is a diagram showing another configuration example of the synthesizer and the switch in the high frequency amplifier according to the first embodiment.

Here, the example shown in FIG. 6 is an example in which the number of amplification modules included in the high frequency amplifier 50 is 5, and the coil element of the whole body RF coil 4 is 2. In this case, the high frequency amplifier 50 has two synthesizers provided for each coil element.

For example, as shown in FIG. 6, the first synthesizer 1521 is connected to the first amplification module (not shown) via the first input terminal IN1, and is connected to the second amplification module (not shown) via the second input terminal IN2. Is connected to the amplification module (not shown), and is connected to the third amplification module (not shown) via the third input terminal IN3.

Here, the first input terminal IN1 is connected to the first synthesis point CP1 via the inductor L1, and the transmission line between the first input terminal IN1 and the inductor L1 is grounded via the capacitor C1. Has been done. Further, the second input terminal IN2 is connected to the first synthesis point CP1 via the inductor L2, and the transmission line between the second input terminal IN2 and the inductor L2 is grounded via the capacitor C21. The transmission line between the inductor L2 and the first synthesis point CP1 is grounded via the capacitor C22. Further, the third input terminal IN3 is connected to the first synthesis point CP1 via the switch S1, the inductor L31, and the switch S2 connected in series, and is a transmission line between the switch S1 and the inductor L31. Is grounded via the capacitor C31. The first synthesis point CP1 is connected to the first coil element (not shown) via the first output terminal OUT1.

Further, between the first input terminal IN1 and the second input terminal IN2, a transmission line including two resistors R11 and R12 connected in series and two resistors R21 and R22 connected in series are included. It is connected via a transmission line. Then, the third input terminal IN3 is connected to the first input terminal IN1 and the second input terminal IN2 via a transmission path including the switch S3, the two resistors R31, R32, and the switch S4 connected in series. Is connected between two transmission paths (a transmission line including resistors R11 and R12 and a transmission line including resistors R21 and R22). Here, for example, the resistors R11, R12, R21, R22, R31, and R32 are each 50Ω.

On the other hand, the second synthesizer 1522 is connected to the third amplification module (not shown) via the third input terminal IN3, and the fourth amplification module (not shown) via the fourth input terminal IN4. It is connected to a fifth amplification module (not shown) via a fifth input terminal IN5.

Here, the third input terminal IN3 is connected to the second synthesis point CP2 via the switch S5, the inductor L32, and the switch S6 connected in series, and the transmission between the switch S5 and the inductor L32. The line is grounded via the capacitor C32. Further, the fourth input terminal IN4 is connected to the second synthesis point CP2 via the inductor L4, and the transmission line between the fourth input terminal IN4 and the inductor L4 is grounded via the capacitor C41. The transmission line between the inductor L4 and the second synthesis point CP2 is grounded via the capacitor C42. Further, the fifth input terminal IN5 is connected to the second synthesis point CP2 via the inductor L5, and the transmission line between the fifth input terminal IN5 and the inductor L5 is grounded via the capacitor C5. ing. Then, the second synthesis point CP2 is connected to the second coil element (not shown) via the second output terminal OUT2.

Further, between the fourth input terminal IN4 and the fifth input terminal IN5, a transmission line including two resistors R41 and R42 connected in series and two resistors R51 and R52 connected in series are included. It is connected via a transmission line. Then, the third input terminal IN3 is connected to the fourth input terminal IN4 and the fifth input terminal IN5 via a transmission path including the switch S7, the two resistors R33, R34, and the switch S8 connected in series. Is connected between two transmission paths (a transmission line including resistors R41 and R42 and a transmission line including resistors R51 and R52). Here, for example, the resistors R41, R42, R51, R52, R33, and R34 are each 50Ω.

In such a configuration, also in this modification, the execution function 15a of the second processing circuit 15 switches the open / closed state of each switch to connect between each synthesizer and each amplification module in the high frequency amplifier 50. Control.

For example, as shown in FIG. 6, the execution function 15a (second processing circuit 15) closes all the switches S1 to S4 provided on the first synthesizer 1521 side, while the second one. By opening all the switches S5 to S8 provided on the synthesizer 1522 side, the third input terminal IN3 and the first output terminal OUT1 are made conductive.

In this case, the high frequency power input from the first amplification module via the first input terminal IN1, the high frequency power input from the second amplification module via the second input terminal IN2, and the second The high frequency power input from the third amplification module via the input terminal IN3 of 3 is combined by the first synthesizer 1521 and supplied to the first coil element via the first output terminal OUT1. Will be. Further, in this case, the second coil element receives the high frequency power input from the fourth amplification module via the fourth input terminal IN4 and the fifth amplification via the fifth input terminal IN5. The high frequency power input from the module is combined by the second synthesizer 1522 and supplied via the second output terminal OUT2.

On the other hand, for example, contrary to the example shown in FIG. 6, the execution function 15a (second processing circuit 15) opens all the switches S1 to S4 provided on the first synthesizer 1521 side. On the other hand, by closing all the switches S5 to S8 provided on the side of the second synthesizer 1522, the third input terminal IN3 and the second output terminal OUT2 are made conductive.

In this case, the high frequency power input from the fourth amplification module via the fourth input terminal IN4, the high frequency power input from the fifth amplification module via the fifth input terminal IN5, and the fifth The high frequency power input from the third amplification module via the input terminal IN3 of 3 is combined by the second synthesizer 1522 and supplied to the second coil element via the second output terminal OUT2. Will be. Further, in this case, the first output terminal OUT1 receives the high frequency power input from the first amplification module via the first input terminal IN1 and the second output terminal IN2 via the second input terminal IN2. The high-frequency power input from the amplification module is combined by the first synthesizer 1521 and supplied via the first output terminal OUT1.

As described above, also in this modification, when changing the magnitude of the high frequency power output to each coil element in the parallel transmission, the connection destination of the third amplification module is dynamically changed between the two coil elements. It becomes possible to do.

Further, in the first embodiment described above, an example in which a switch is provided in front of each synthesizer in the high frequency amplifier 50 has been described, but the embodiment is not limited to this. For example, as another modification, each synthesizer may be configured so that the magnitude of the high frequency power output to the coil element can be adjusted. In that case, the synthesizer converts the high-frequency power input from the amplification module into the size required for the corresponding coil element and supplies it to the coil element. For example, a synthesizer has a plurality of coils and converts the magnitude of high-frequency power by changing the degree of magnetic coupling between the coils. For example, such a synthesizer is realized by a variable transformer.

Further, in the above-described first embodiment, an example in which the number and combination of amplification modules connected to each synthesizer are predetermined for each part to be imaged has been described, but the embodiment includes this. Not limited. For example, as another modification, the number and combination of amplification modules connected to each synthesizer may be changed for each subject. Also in this case, the same number and combination of amplification modules are used throughout the inspection within the same inspection.

(Second embodiment)
Further, in the first embodiment described above, an example in which a synthesizer is provided for each coil element in the high frequency amplifier 50 has been described, but the embodiment is not limited to this. Therefore, in the following, as a second embodiment, another configuration example of the high frequency amplifier will be described. In the second embodiment, the points different from those of the first embodiment will be mainly described, and the components having the same role as the components described in the first embodiment are designated by the same reference numerals. A detailed description will be omitted.

In this embodiment, the high frequency amplifier included in the transmission circuit 5 includes one or more amplification modules, a synthesizer, and a distributor. The synthesizer synthesizes the high frequency power output from the amplification module and outputs it to the distributor. The distributor distributes the high frequency power output from the synthesizer to each coil element of the whole body RF coil 4. The distributor is configured to be able to select the distribution of high-frequency power output to each coil element.

7 and 8 are diagrams showing a configuration example of the high frequency amplifier according to the second embodiment.

For example, as shown in FIGS. 7 and 8, in the present embodiment, the whole body RF coil 4 has two coil elements, and the high frequency amplifier 250 included in the transmission circuit 5 has four amplification modules and four amplification modules. It has one synthesizer and one distributor.

Specifically, the whole body RF coil 4 has first and second coil elements 41 and 42. Further, the high frequency amplifier 250 includes first to fourth amplification modules 511 to 514, a synthesizer 252, and a distributor 253.

Here, the first to fourth amplification modules 511 to 514 are connected to the synthesizer 252 in parallel with each other. The synthesizer 252 is connected to the distributor 253, synthesizes high-frequency power output from each of the first to fourth amplification modules 511 to 514, and outputs the high frequency power to the distributor 253. The distributor 253 is connected to each of the first and second coil elements 41 and 42, and distributes the high frequency power output from the synthesizer 252 to each coil element.

The distributor 253 is configured to be able to select the distribution of high-frequency power output to each of the first and second coil elements 41 and 42. For example, the distributor 253 has a plurality of coils, and by changing the degree of magnetic coupling between the coils, the amount of high-frequency power distributed to the first coil element 41 and the amount of high-frequency power output to the second coil element 42 are output. Controls the amount of high-frequency power distribution. For example, such a distributor 253 is realized by a variable transformer.

In this embodiment as well, the first to fourth amplification modules 511 to 514 connected to the synthesizer 252 receive high frequency power required for the coil element corresponding to the synthesizer 252, respectively. High-frequency power that is substantially equal to the value divided by the number is output to the synthesizer 252. Then, in the present embodiment, the execution function 15a of the second processing circuit 15 controls the distribution amount of the high-frequency power supplied to each coil element by controlling the distributor 253.

For example, as shown in FIG. 7, when a high frequency power of 2 kW is output to each of the first and second coil elements 41 and 42, the execution function 15a of the second processing circuit 15 is provided by each amplification module. It is controlled to output high frequency power of 1 kW. As a result, 1 kW of high-frequency power is supplied to the synthesizer 252 from each of the first to fourth amplification modules 511 to 514. Then, the executive function 15a controls the distributor 253 so that the high frequency power of 4 kW synthesized by the combiner 252 is distributed by 2 kW to each of the first and second coil elements 41 and 42, respectively. Controls the amount of high-frequency power distributed to the coil elements.

On the other hand, for example, as shown in FIG. 8, when a high frequency power of 3 kW is output to the first coil element 41 and a high frequency power of 1 kW is output to the second coil element 42, the second processing circuit 15 The execution function 15a controls each amplification module to output 1 kW of high-frequency power. As a result, 1 kW of high-frequency power is supplied to the synthesizer 252 from each of the first to fourth amplification modules 511 to 514. Then, the executive function 15a distributes 4 kW of high-frequency power synthesized by the combiner 252 to the first coil element 41 by 3 kW and to the second coil element 42 by 1 kW by controlling the distributor 253. The amount of high-frequency power distributed to each coil element is controlled so as to be performed.

As described above, in the present embodiment, in any of the examples shown in FIGS. 7 and 8, each amplification module may have a maximum output of 1 kW, and the high frequency amplifier 250 has a total of 1 kW × 4. (Individual amplification modules) = 4 kW maximum output is sufficient. Therefore, also in this embodiment, it is possible to supply the required high frequency power to each coil element by the combination of the amplification modules having a lower maximum output as compared with the examples shown in FIGS.

Here, an example in which the whole-body RF coil 4 has two coil elements has been described, but the number of coil elements is not limited to this. The number of coil elements provided in the whole-body RF coil 4 may be two or more, as long as parallel transmission can be performed.

Further, although an example in which the high frequency amplifier 250 includes four amplification modules has been described here, the number of amplification modules is not limited to this. The number of amplification modules provided in the high-frequency amplifier 250 may be one or a plurality of amplification modules other than four as long as a maximum output of 4 kW can be obtained in total. When the number of amplification modules is one, the high-frequency amplifier 250 may be configured such that the amplification module and the distributor 253 are directly connected without the synthesizer 252.

As mentioned above, in the second embodiment, the high frequency amplifier 250 comprises one or more amplification modules. Further, the high frequency amplifier 250 includes a synthesizer that synthesizes the high frequency power output from the amplification module and outputs it to the distributor. Further, the high frequency amplifier 250 includes a distributor that distributes the high frequency power output from the synthesizer to each coil element of the whole body RF coil 4. The distributor is configured to be able to select the distribution of high-frequency power output to each coil element. Thereby, also in this embodiment, the maximum output of each amplification module provided in the high frequency amplifier 250 can be reduced.

Therefore, according to the second embodiment, the power required for applying the high frequency energy can be reduced as in the first embodiment. Further, by reducing the required power, it is possible to reduce the risk of damage to the elements mounted on the high frequency amplifier 250. As a result, the reliability of the high frequency amplifier 250 and the MRI apparatus 100 can be improved.

In each of the above-described embodiments, an example in which a synthesizer, a switch, and a distributor are provided in the high-frequency amplifier has been described, but the embodiment is not limited to this. For example, in each embodiment, the synthesizer, the switch, and the distributor may be arranged in whole or in part on the gantry 9 side.

The word "processor" used in the description of each of the above-described embodiments is, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), or an integrated circuit for a specific application (Application Specific Integrated Circuit: ASIC). , Programmable logic devices (eg, Simple Programmable Logic Device (SPLD), Complex Programmable Logic Device (CPLD), and Field Programmable Gate Array (FPGA)). Means. Here, instead of storing the program in the storage circuit, the program may be configured to be directly embedded in the circuit of the processor. In this case, the processor realizes the function by reading and executing the program embedded in the circuit. Further, each processor of the present embodiment is not limited to the case where each processor is configured as a single circuit, and a plurality of independent circuits may be combined to be configured as one processor to realize its function. good.

Here, the program executed by the processor is provided by being incorporated in a ROM (Read Only Memory), a storage circuit, or the like in advance. This program is a file in a format that can be installed or executed on these devices, such as CD (Compact Disk) -ROM, FD (Flexible Disk), CD-R (Recordable), DVD (Digital Versatile Disk), etc. It may be recorded and provided on a computer-readable storage medium. Further, this program may be provided or distributed by being stored on a computer connected to a network such as the Internet and downloaded via the network. For example, this program is composed of modules including each of the above-mentioned functional parts. In actual hardware, the CPU reads a program from a storage medium such as a ROM and executes it, so that each module is loaded on the main storage device and generated on the main storage device.

According to at least one embodiment described above, it is possible to provide a high frequency amplifier and a magnetic resonance imaging apparatus capable of reducing the power required for applying high frequency energy.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, as well as in the scope of the invention described in the claims and the equivalent scope thereof.

100 Magnetic Resonance Imaging (MRI) Equipment 4 Whole Body RF Coil 41,42 Coil Element 5 Transmission Circuit 50 High Frequency Amplifier 511-514 Amplification Module 521,522 Combiner 531-538 Switch

Claims (6)

A high-frequency amplifier that supplies high-frequency power to a plurality of substantially independent coil elements that apply high-frequency energy to a subject.
With at least one more amplification module than the number of coil elements,
It is provided for each coil element, and includes a synthesizer that synthesizes high-frequency power output from each of the amplification modules and outputs the high-frequency power to the corresponding coil element.
The number of amplification modules connected to each of the synthesizers can be selected.
High frequency amplifier. Each of the amplification modules connected to the synthesizer outputs high-frequency power substantially equal to the value obtained by dividing the high-frequency power required for the coil element corresponding to the synthesizer by the number of the amplification modules. ,
The high frequency amplifier according to claim 1. A switch provided for each synthesizer and arranged in front of the synthesizer is further provided.
The switch is configured to select the number of amplification modules connected to the corresponding synthesizer.
The high frequency amplifier according to claim 1 or 2. The line length of the transmission line between the amplification module and the switch is 1 of the high frequency power so that the impedance on the switch side as seen from the amplification module is also substantially open when the switch is opened. / 2 The length is set to be approximately the same as an integral multiple of the wavelength.
The high frequency amplifier according to claim 3. The amplitude and phase of the high frequency power synthesized by the synthesizer are substantially the same.
The high frequency amplifier according to any one of claims 1 to 4. Multiple substantially independent coil elements that apply high frequency energy to the subject,
A high-frequency amplifier that supplies high-frequency power to the coil element is provided.
The high frequency amplifier
With at least one more amplification module than the number of coil elements,
It has a synthesizer that is provided for each coil element, synthesizes high-frequency power output from each of the amplification modules, and outputs the high-frequency power to the corresponding coil element.
The number of amplification modules connected to each of the synthesizers can be selected.
Magnetic resonance imaging device.

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