JPH05344960A - Magnetic resonance type inspection system - Google Patents

Abstract

(57) [Abstract] [Purpose] Magnetic resonance inspection that can perform high-precision inspection without being affected by electromagnetic noise even if the level of electromagnetic noise changes due to changes in the surrounding environment, even without high-frequency shielding. Realize the device. [Structure] A signal from a high-frequency coil for reception 4 is transmitted via a preamplifier 15 and a high-frequency amplifier 16 to a differential input amplifier 1
7 is supplied. An antenna 22 having the same frequency characteristics as the high frequency coil 4 is arranged on the end surface of the superconducting magnet 1, and the detection signal thereof is supplied to the differential input amplifier 17 via the high frequency amplifier 23 and the phase shifter 24. .. In this amplifier 17, the subtraction processing of the combined signal of the electromagnetic wave noise from the coil 4 and the nuclear magnetic resonance signal and the electromagnetic wave noise from the antenna 22 is performed, and only the nuclear magnetic resonance signal is extracted. With this, without applying high frequency shield,
High-precision inspection can be performed without being affected by electromagnetic noise.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention utilizes the nuclear magnetic resonance phenomenon to non-invasively determine the density distribution, relaxation time, movement, etc. of specific nuclei (for example, hydrogen nuclei and phosphorus nuclei) of each tissue in a living body. The present invention relates to a magnetic resonance examination apparatus that measures and obtains information for medical diagnosis.

[0002]

2. Description of the Related Art There is a magnetic resonance inspection apparatus for inspecting the inside of a human body by utilizing the nuclear magnetic resonance phenomenon. FIG. 9 is a schematic configuration diagram of the nuclear magnetic resonance inspection apparatus. In FIG. 9, the human body 5 to be inspected is carried into the superconducting magnet 1 that generates a uniform magnetic field. Then, the hydrogen nuclei constituting the tissue of the human body are oriented in the magnetic field direction and the demagnetizing field direction. And
When energy of a frequency (normally a high frequency of several MHz to several tens of MHz) corresponding to the difference between these two orientation energies is applied from the high frequency power amplifier 14 to the transmitting high frequency coil 3, a high frequency magnetic field is applied to the human body 5 to generate hydrogen. Nuclear nucleus causes nuclear magnetic resonance. The movement of the hydrogen nuclei after the application of the high-frequency magnetic field is stopped is detected by the receiving high-frequency coil 4 as a nuclear magnetic resonance signal.

However, as it is, the detected nuclear magnetic resonance signal cannot be applied to the diagnosis of a lesion. That is, it is not possible to specify from which part of the human body tissue the nuclear magnetic resonance signal originated. Therefore, the X axis and Y that are orthogonal to each other
By combining a gradient magnetic field capable of changing the magnetic field strength in the directions of the Z-axis and the Z-axis at the time of applying the high-frequency magnetic field and at the time of detecting the nuclear magnetic resonance signal, the X-axis and Y-axis of the nuclear magnetic resonance signal can be obtained.
It is possible to give positional information about the axes and the Z axis. For this reason,
Power from the X gradient magnetic field power source 9, the Y gradient magnetic field power source 10, and the Z gradient magnetic field power source 11 is supplied to the gradient magnetic field coil 2. Then, the nuclear magnetic resonance signal detected by the receiving high frequency coil 4 is supplied to the computer 7 through the preamplifier 15, the high frequency amplifier 16, the detector 18, the audio frequency amplifier 19, and the A / D converter 20. .. This calculator 7
Performs arithmetic processing such as Fourier transform on the supplied nuclear magnetic resonance signal, obtains a spectral distribution or a tomographic image of a specific part of human body tissue, and displays it on the display 21. Further, the computer 7 supplies a command signal to the control circuit 8 based on a key operation on the console 6. Then, the control circuit 8 controls the power supplies 9, 10, 11 and the reference signal generator 1 according to the supplied command signal.
2. The control signal is supplied to the modulator 13 and the high frequency amplifier 16.

Next, the operation of the nuclear magnetic resonance inspection apparatus will be described. FIG. 10 shows a pulse sequence of the spin echo method which is most often used when obtaining a tomographic image of a human body. 9 and 10, when the gradient magnetic field 31 in the Z direction is applied to the human body, the magnetic field strength changes along the body axis of the human body. A high-frequency magnetic field 29 of 90-degree pulse corresponding to the magnetic field strength of the region to be inspected is applied to the high-frequency coil for transmission 3. The high frequency magnetic field is amplitude-modulated by the SINC function so as to have a specific frequency band component. As a result, the thickness of the inspection cross section can be determined from the relationship between the strength of the gradient magnetic field 31 in the Z direction and the frequency bandwidth. Then Y
When the directional gradient magnetic field 32 is applied to the human body, the frequency phase of the spin motion of the hydrogen nuclei that have undergone the nuclear magnetic resonance phenomenon during the period A changes depending on the axial position of the Y directional gradient magnetic field. In the period C, the high frequency magnetic field 30 of 180 degree pulse is applied to the human body in order to reverse the direction of the motion of the nuclear spin. Next, a nuclear magnetic resonance signal is detected while the X-direction gradient magnetic field 33 is applied to the human body.

The detected signal is taken into the computer 7 as 256 discrete data 34. After the repetition time TR including the period E which is the waiting time has elapsed, the intensity of the Y-direction gradient magnetic field 32 for phase encoding is changed to detect a signal. By changing the strength of the Y-direction gradient magnetic field 32 by 256 steps, 256 × 256 matrix data can be obtained. Two-dimensional Fourier transform of this data gives X
A distribution map of the nuclear magnetic resonance signals developed in the two-dimensional direction and Y direction is obtained.

The detection level of the nuclear magnetic resonance signal detected by the receiving high-frequency coil 4 varies depending on the size of the region to be inspected, the strength of the static magnetic field, the efficiency of the high-frequency coil, and the inspection mode, but is usually in the range of 10 μV to 1 mV. .. Normally, as described above, the inspection region is decomposed into a matrix of 256 × 256, so that the signal intensity per pixel is 0.15 obtained by dividing the detection level by 65536 (256 × 256).
It is a weak voltage from nV to 0.015 μV. The frequency of the signal is 6MHz to 65M, which is proportional to the static magnetic field strength.
It is distributed in Hz. This frequency band matches the frequency band of short-wave broadcasting and amateur radio communication equipment. And,
Electromagnetic noise generated from various electric devices and automobile engines also contains components in this frequency band. If these electromagnetic waves are mixed in a weak nuclear magnetic resonance signal, not only the quality of the image of the inspection result, etc. will deteriorate, but also diagnosis failure or misdiagnosis may occur.

Therefore, as described on page 414 of "MRI Diagnosis" published by Asakura Shoten on November 25, 1988, the examination room in which the magnet for generating the static magnetic field is arranged is a copper plate. The electromagnetic wave noise from the outside is shielded by shielding the electromagnetic wave from the outside and transmitting / receiving an electric signal between the inside of the inspection chamber and the outside through a filter circuit. That is, as shown in FIG. 9, the high frequency shield 27 is provided, and the transmission and reception of signals between the inside of the high frequency shield 27 and the outside are performed.
This is performed via the filter circuit 28. Further, as described in U.S. Pat. No. 4,564,812, there is also a device in which a minimum necessary space including a high frequency coil and a subject is shielded from electromagnetic waves. Incidentally, as a configuration in which the magnetic field generating means and the like are arranged in the radio wave shielded room, there is an MRI apparatus described in JP-A-3-85145.

[0008]

However, in the above-mentioned conventional magnetic resonance inspection apparatus, a high-frequency shielded room for shielding electromagnetic wave noise is required. Therefore, an operator outside the shielded room and an examinee in the shielded room are required. It was not possible to directly communicate with the subject and monitor the subject under examination, and it was necessary to install a communication device using a microphone and a monitoring device using a monitor camera. For this reason, the equipment becomes large-scale and expensive. In addition, in order to maintain the performance of the high frequency shielded room, it was necessary to regularly perform troublesome maintenance and inspection. So, for example,
Comb-shaped metal (for example, phosphor bronze) is arranged on the peripheral portion of the shield room for electromagnetic shielding. In this comb-shaped metal, not only the resistance value increases due to dust and the like with time, but also metal pieces may be missing. Therefore, it takes a lot of time and labor for the maintenance and inspection.

Further, when the magnetic resonance inspection apparatus is introduced, even if the electromagnetic wave noise intensity of the surrounding environment is measured to determine the high frequency shielding capability of the high frequency shield, the ambient environment may change and the electromagnetic wave noise intensity may change. In this case, the shielded room had to be refurbished.

Therefore, the above-mentioned US Pat. No. 4,564,81 is used.
As described in Japanese Patent Laid-Open No. 2 (1994), it can be considered to shield the minimum necessary space including the high frequency coil and the subject from electromagnetic waves.
However, if the high-frequency shielded space is the minimum required,
There is a possibility that the subjects with claustrophobia and children may feel a sense of pressure and anxiety. If the subject is given a feeling of oppression and anxiety, the subject moves frequently during a long-term examination, and high-precision examination cannot be performed.

Further, as described in Japanese Patent Application Laid-Open No. 1-242057, there is also one which detects an external electromagnetic wave noise and corrects a nuclear magnetic resonance signal. This Japanese Patent Laid-Open No. 1-242057
According to the publication, only the electromagnetic wave noise is detected by the receiving high-frequency coil, and the detected electromagnetic wave noise is stored. Then, the nuclear magnetic resonance signal is measured from the examination region of the subject, and the stored electromagnetic wave noise is subtracted from the nuclear magnetic resonance signal in the process of data processing of the measured signal. In this case, the receiving high-frequency coil is
Since it is arranged in the magnet and the gradient magnetic field coil, the average addition processing of the electromagnetic wave noise is used to measure the external electromagnetic wave noise with high sensitivity. However, the phase of the external electromagnetic noise may not be constant, and it is difficult to measure it in synchronization with the timing at which the average addition processing is performed. For this reason, the average addition process could not achieve the intended effect. Further, since the stored electromagnetic wave noise is subtracted from the nuclear magnetic resonance signal obtained by the inspection, if the source of the electromagnetic wave noise changes during the inspection or the noise level changes, It is not possible to deal with it, and the noise component cannot be removed from the nuclear magnetic resonance signal.

In recent years, there has been a demand for clearly displaying an image of a fluid substance in a subject such as a blood vessel image. Therefore, it is desired to obtain a nuclear magnetic resonance signal in which electromagnetic noise is not mixed. An object of the present invention is to provide a high frequency shield,
It is another object of the present invention to realize a magnetic resonance inspection apparatus capable of performing highly accurate inspection without being affected by electromagnetic noise even if the level of electromagnetic noise changes due to changes in the surrounding environment.

[0013]

In order to achieve the above object, the present invention is configured as follows. Magnetic field generating means of static magnetic field, gradient magnetic field and high frequency magnetic field, signal detecting means for detecting a signal including a nuclear magnetic resonance signal from the examination target, and medical information of the examination subject based on the nuclear magnetic resonance signal In a magnetic resonance inspection apparatus having a computer for performing a calculation for outputting a calculation result of the computer, a noise receiving means for receiving electromagnetic wave noise in the vicinity of the inspection target, and an electromagnetic wave received by the noise receiving means. Amplitude and phase adjusting means for adjusting the amplitude and phase of noise, addition or subtraction processing of the signal detected by the signal detecting means and the electromagnetic noise signal output from the amplitude and phase adjusting means, and signal detecting means And a subtraction unit for extracting only the nuclear magnetic resonance signal by removing the electromagnetic noise component from the detection signal of the nuclear magnetic resonance signal output from the addition and subtraction unit. It constructed a signal corresponding to to supply to the computer. Preferably, the magnetic resonance inspection apparatus further includes an electromagnetic wave transmitting means for transmitting an electromagnetic wave having a predetermined frequency to the signal detecting means and the noise receiving means.

Further, each of the magnetic field generating means of the static magnetic field, the gradient magnetic field and the high frequency magnetic field, the signal receiving means for receiving the signal including the nuclear magnetic resonance signal from the inspection object, and the signal output from the signal receiving means are predetermined. Signal processing means for processing
In a magnetic resonance inspection apparatus having a computer that performs an operation for obtaining medical information of an inspection target based on a nuclear magnetic resonance signal, and an output unit that outputs an operation result of this computer, electromagnetic noise near the inspection object An output from the signal processing means, which comprises noise receiving means for receiving and noise signal processing means having a function equivalent to that of the signal processing means and performing predetermined processing on the noise signal output from the noise receiving means. The addition and subtraction processing of the signal and the output signal from the noise signal processing means is executed by the computer to remove the electromagnetic wave noise component and extract only the component corresponding to the nuclear magnetic resonance signal.

Preferably, in the magnetic resonance inspection apparatus, the computer includes a Fourier transform processing unit for performing two-dimensional Fourier transform on the output signal from the signal processing unit and the output signal from the noise signal processing unit, and the Fourier transform processing. Based on the output value from the absolute value calculation unit and the output value from this absolute value calculation unit, the inter-image calculation that removes the electromagnetic noise component and extracts only the component corresponding to the nuclear magnetic resonance signal And a processing unit. Further, preferably, in the magnetic resonance inspection apparatus, the signal receiving means and the noise receiving means are provided with an electromagnetic wave transmitting means for transmitting an electromagnetic wave of a predetermined frequency. Further, preferably, the static magnetic field generating means is covered with an outer cover, and the noise receiving means is arranged inside the outer cover.
In addition, preferably, an inspection target table for mounting the inspection target is provided, and the noise receiving means is arranged inside the inspection target table. Also, preferably,
Display means for monitoring and displaying the operation of removing the electromagnetic noise component is further provided.

[0016]

The signal including the nuclear magnetic resonance signal and the electromagnetic wave noise is detected by the signal detecting means. The noise receiving means receives only electromagnetic noise. The amplitude and the phase of the received electromagnetic wave noise are adjusted by the amplitude / phase adjusting means so as to correspond to the detection signal of the signal detecting means. The electromagnetic noise signal from the amplitude / phase adjusting means is added / subtracted from the detection signal of the signal detecting means by the adding / subtracting means, and only the nuclear magnetic resonance signal is extracted.

The signal received by the signal receiving means is
Predetermined signal processing is performed by the signal processing means. Then, the noise signal received by the noise receiving means is subjected to predetermined signal processing by the noise signal processing means. The computer performs addition / subtraction processing of the output signal of the signal processing means and the output signal of the noise signal processing means. As a result, only the component corresponding to the nuclear magnetic resonance signal is extracted.

[0018]

1 is a schematic configuration diagram of an embodiment of a magnetic resonance inspection apparatus according to the present invention. In FIG. 1, in a superconducting magnet 1 having a central magnetic field strength of 0.5 T, a gradient magnetic field coil 2 (X, Y, Z in the figure) that generates gradient magnetic fields in three directions of an X axis, a Y axis, and a Z axis orthogonal to each other. Is not shown), a transmitting high-frequency coil 3 for generating a high-frequency magnetic field of 21.13 MHz, and a receiving high-frequency coil 4 for detecting a nuclear magnetic resonance signal are provided. The person to be inspected 5 is carried into the magnet 1 so that the inspection site of the person to be inspected 5 coincides with the center of the superconducting magnet 1. Operator (not shown)
However, when a key on the console 6 is operated, the computer 7 supplies a command signal to the control circuit 8 according to a processing program input in advance.

The control circuit 8 activates the X gradient magnetic field power supply 9, the Y gradient magnetic field power supply 10 and the Z gradient magnetic field power supply 11 in accordance with the imaging sequence. The output currents of the gradient magnetic field power supplies 9, 10 and 11 are supplied to the gradient magnetic field coil 2 to generate a desired gradient magnetic field. Further, another command signal of the control circuit 8 is supplied to the reference signal generator 12 and the modulator 13, and a pulsed high-frequency signal of 21.13 MHz in which the hydrogen nuclei of the examination site of the subject 5 resonate is modulated. It is generated from 13. This high frequency signal is amplified to 1.6 kW by the high frequency power amplifier 14 and supplied to the transmitting high frequency coil 3. As a result, a high-frequency magnetic field is generated in the required space including the examination site, and a nuclear magnetic resonance phenomenon occurs.

The motion of the nuclear spins after the application of the high frequency magnetic field is induced in the receiving high frequency coil 4 as a high frequency current, and is transmitted from the preamplifier 15, the high frequency amplifier 16 and the input terminal 25 through the differential input amplifier 17 to the detector. 18 are supplied. Then, it is detected by the detector 18 and converted into an audible frequency band. The signal converted into the audio frequency band is amplified by the audio frequency amplifier 19 so that the peak value becomes about 10V. The total amplification degree of the preamplifier 15, the high frequency amplifier 16, and the audio frequency amplifier 17 is 80 to 120 dB, though it varies depending on the type of inspection site and the inspection range.

The signal amplified to about 10 V is supplied to the A / D converter 20 and converted into a digital signal by the A / D converter 20. The digital signal from the A / D converter 20 is supplied to the computer 7 and stored in the data memory of the computer 7. When a series of data is measured, the computer 7 arithmetically processes the signals in the data memory to display a tomographic image and a spectral distribution map of the examination site on the display 21.
To display. On the other hand, the end face of the superconducting magnet 1 has an antenna 22 having the same frequency characteristic as the receiving high-frequency coil 4.
Is provided, and the detection signal thereof is supplied to the input terminal 26 of the differential input amplifier 17 via the high frequency amplifier 23 and the phase shifter 24.

Before explaining the operation of the above-described magnetic resonance inspection apparatus, the outline of the principle of the present invention will be described. FIG. 2 is a schematic explanatory diagram of the principle of the present invention. In FIG. 2, the subject 3
The nuclear magnetic resonance signal from 5 is induced only in the high frequency coil 36 and detected as the high frequency signal A. On the other hand, electromagnetic wave noise from an external noise source (indicated by the noise source 37 and the transmitting antenna 38 in FIG. 2) is induced in both the high frequency coil 36 and the antenna element 39. High frequency coil 36
The electromagnetic wave noise B induced in the antenna element 39 and the electromagnetic wave noise C induced in the antenna element 39 are different in voltage and phase due to the difference in detection efficiency between the high frequency coil 36 and the antenna element 39 and the circuit configuration. When the combined signal of the high frequency signal A and the noise B is amplified by the high frequency amplifier 40 having the amplification degree G, the voltage of the combined signal becomes G (A + B). On the other hand, when the noise C passes through the high frequency amplifier 41 having the amplification degree H and the phase shifter 24, it becomes a noise signal represented by HC · sin θ.

The two high frequency amplifiers 40 and 41 are so constructed that their amplification degrees can be changed arbitrarily. As a result, the high frequency amplifiers 40 and 4 are set so that HC = GB.
The amplification factor of 1 is adjusted. Since the phase shifter 24 can also arbitrarily change the shift amount, if θ = 90 ° is adjusted, HC
The relationship of sin θ = GB holds. Next, the composite signal G
When (A + B) and the noise signal HC · sin θ are supplied to the differential input amplifier 17, the output voltage is only GA. That is, even if the electromagnetic wave noise from the noise source 37 is mixed in the nuclear magnetic resonance signal, the electromagnetic wave noise can be removed and the nuclear magnetic resonance signal without noise can be extracted.

Next, the operation of the embodiment shown in FIG. 1 will be described. (1) First, the operator carries the subject 5 into the center of the superconducting magnet 1 and then selects the pretreatment for inspection using the operation console 6. (2) In this preprocessing, the signal is measured without applying the gradient magnetic field and the high frequency magnetic field. A nuclear magnetic resonance signal is not induced in the receiving high-frequency coil 4, but an electromagnetic wave in the 21 MHz band near the receiving high-frequency coil 4 is induced. An electric signal corresponding to the intensity of the electromagnetic wave is transmitted from the high frequency coil 4 through the preamplifier 15 and the high frequency amplifier 16 to the differential input amplifier 17
Is input to the input terminal 25 of. (3) Since the antenna 22 is arranged on the end surface of the superconducting magnet 1, the distance from the receiving high-frequency coil 4 is within 1 m. This distance is within one wavelength of an electromagnetic wave of 21 MHz. Therefore, the receiving high-frequency coil 4 and the antenna 22 receive the same electromagnetic wave. The different points are the difference in reception efficiency and the phase of the signal. Antenna 2
The signal No. 2 is supplied to the input terminal 26 of the differential input amplifier 17 via the high frequency amplifier 23 and the phase shifter 24.

(4) The differential input amplifier 17 outputs a signal representing the component of the difference between the two signals. This output signal is detected by the wave detector 18, amplified by the audible amplifier 19, converted into a digital signal by the A / D converter 20, and supplied to the computer 7. (5) The computer 7 sets the amplification degree of the high frequency amplifier 23 and the phase shifter 2 so that the amplitude intensity of the supplied signal is minimized.
The phase amount of 4 is controlled via the control circuit 8. By performing the training operation (operations from (2) to (5)), the signals at the input terminal 25 and the input terminal 26 of the differential input amplifier 17 have the same amplitude but different phases by 180 °. Become. (6) Next, the operator starts the inspection by selecting a required inspection mode by operating the keys on the operation console 6. At this time, the amplification degree of the high frequency amplifier 16 changes according to the detection level of the nuclear magnetic resonance signal, but the amplification degree of the high frequency amplifier 23 is changed so that the same change amount is obtained. That is, depending on the inspection mode, the high frequency amplifiers 16 and 23
The degree of amplification is changed and electromagnetic noise is removed.

As described above, according to the embodiment of the present invention, the antenna 22 for receiving the same electromagnetic noise as the electromagnetic noise mixed in the receiving high-frequency coil 4 is installed, and the electromagnetic noise received by the antenna 22 is installed. Based on the above, the electromagnetic wave noise is removed from the signal from the receiving high-frequency coil 4. Therefore, it is possible to realize a magnetic resonance inspection apparatus that can perform a high-precision inspection without being affected by the electromagnetic wave noise even if the level of the electromagnetic wave noise changes due to a change in the surrounding environment without applying a high frequency shield. In addition, according to the inspection mode, the parameters of the circuit connected to the receiving high-frequency coil 4 and the antenna 22.
Since the parameter of the circuit connected to is changed, it is possible to perform highly accurate inspection regardless of the change of the inspection mode. Further, since the subject 5 is placed in the receiving high-frequency coil 4 and then the adjustment is performed, highly accurate inspection can be performed regardless of the individual difference of the subject.

FIG. 3 is a schematic configuration diagram of another embodiment of the magnetic resonance inspection apparatus according to the present invention, in which the same parts as those in the example of FIG. 1 are designated by the same reference numerals. In FIG. 3, the motion of the nuclear spins after applying the high-frequency magnetic field is represented by the high-frequency coil 4 for reception.
Is induced as a high-frequency current into the detector 18 and supplied to the detector 18 via the preamplifier 15 and the high-frequency amplifier 16. Then, it is detected by the detector 18 and converted into an audible frequency band. The signal converted into the audio frequency band is amplified by the audio frequency amplifier 19 so that the peak value becomes about 10V. The total amplification degree of the preamplifier 15, the high frequency amplifier 16, and the audio frequency amplifier 19 is 80 to 120 dB, although it varies depending on the type of inspection site and the inspection range.

The signal amplified to about 10 V is supplied to the A / D converter 20 and converted into a digital signal by the A / D converter 20. Then, the digital signal from the A / D converter 20 is supplied to the computer 7 and stored in one data memory 42 (shown in FIG. 4) of the computer 7.

On the other hand, on the end face of the superconducting magnet 1, an antenna 22 having the same frequency characteristic as the receiving high-frequency coil 4 is arranged, and its detection signal is detected by the preamplifier 15A and the high-frequency amplifier 16A. 18A. Then, it is detected by the detector 18A and converted into an audible frequency band. The signal converted into the audio frequency band is supplied to the audio frequency amplifier 19A and amplified.
The amplified signal is converted into a digital signal by the A / D converter 20A and stored in the other data memory 43 (shown in FIG. 4) of the computer 7.

FIG. 4 is a block diagram of the data processing section of the computer 7. The digital signals from the A / D converters 20 and 20A are processed by this data processing section. Next, the operation of another embodiment of the present invention will be described with reference to FIGS.

(1) The operator carries in the subject 5 so that the inspection site is at the center of the superconducting magnet 1, and the operator console 6
The inspection is started by pressing the key. (2) According to the program, the computer 7 causes the gradient magnetic field power supplies 9 to 11 and the reference signal generator 12 via the control circuit 8.
And the modulator 13 are operated. High frequency coil for reception 4
The nuclear magnetic resonance signal detected by the preamplifier 15, the high frequency amplifier 16, the detector 18, the audio frequency amplifier 19, A
It is supplied to the data memory 42 of the computer 7 via the / D converter 20. (3) At the same time as the detection of the nuclear magnetic resonance signal, the antenna 22
Like the nuclear magnetic resonance signal, the signal detected at is supplied to the data memory 43 of the computer 7 through the preamplifier 15A, the high frequency amplifier 16A, the detector 18A, the audio frequency amplifier 19A and the A / D converter 20A. ..

(4) The data stored in the data memory 42 is subjected to data correction such as offset amount by the data correction section 45 in the image processor 44. The data-corrected data is subjected to Fourier transform by the two-dimensional Fourier transform processing unit 46, and then the absolute value is calculated by the absolute value calculation unit 47. (5) The data stored in the data memory 43 is subjected to data correction such as offset amount by the data correction unit 45A in the image processor 44. Then, the data subjected to the data correction is processed by the two-dimensional Fourier transform processing unit 4
After the Fourier transform is performed by 6A, the absolute value is calculated by the absolute value calculator 47A.

(6) The two-dimensional data from the absolute value calculation units 47 and 47A is converted into the inter-image calculation processing unit 48.
Thus, the arithmetic processing is performed and the image data is temporarily stored in the image data memory 49. The inter-image calculation processing unit 48 also executes a weighting process of two two-dimensional data so that only the data by the nuclear magnetic resonance signal of the examination site of the subject 5 is extracted. (7) The final image is supplied to the image data disk memory 50, which is stored and managed for a long period of time, and also to the display memory 51. Then, the image supplied to the display memory 51 is displayed on the display unit 21.

As described above, according to another embodiment of the present invention, the same effect as that of the example shown in FIG. 1 can be obtained.
Further, according to another embodiment of the present invention, the circuit system connected to the receiving high-frequency coil 4 and the circuit system connected to the antenna 22 have the same configuration. Therefore, it is not necessary to perform the adjustment work between these circuit systems and the circuit systems before the inspection is performed, and the inspection can be promptly performed after the subject 5 is carried in.

FIG. 5 is a schematic view of the essential parts of a magnetic resonance inspection apparatus according to another embodiment of the present invention, in which parts equivalent to those in the example of FIG. 1 are designated by the same reference numerals. However, the configuration 53 shown by the alternate long and short dash line represents the entire example of FIG. 1. In FIG. 5, another transmitting antenna 38 is arranged at a distance of about 15 m from the superconducting magnet 1 (this is a distance longer than one wavelength of 21 MHz). A high frequency transmitter 52 is connected to the transmitting antenna 38, and is configured to radiate an electromagnetic wave having an arbitrary frequency into the air with an intensity of 1 mW.

Next, the operation of the example of FIG. 5 will be described. (1) First, prior to the inspection, 2 from the high frequency transmitter 52
A high frequency power of 1.14 MHz is supplied to the transmitting antenna 38. (2) The operator carries the subject 5 into the center of the superconducting magnet 1 and then selects the pretreatment for inspection by the console 6.

(3) The gradient magnetic field and the high-frequency magnetic field are not applied in this pretreatment for inspection. Therefore, a nuclear magnetic resonance signal is not induced in the receiving high-frequency coil 4, but an electromagnetic wave in the 21.14 MHz band near the receiving high-frequency coil 4 is induced. A signal corresponding to the intensity of this electromagnetic wave is transmitted through the preamplifier 15 and the high frequency amplifier 16 to the differential input amplifier 1
7 to the input terminal 25. (4) The antenna 22 is disposed on the end surface of the superconducting magnet 1 and the distance from the receiving high frequency coil 4 is within 1 m.
This distance is within one wavelength of an electromagnetic wave of 21 MHz.
Therefore, the receiving high-frequency coil 4 and the antenna 22 receive the same electromagnetic wave of 21.14 MHz. The different points are the difference in reception efficiency and the phase of the signal. The signal received by the antenna 22 is a high frequency amplifier 23 and a phase shifter 24.
Is supplied to the input terminal 26 of the differential input amplifier 17. (5) The output signal of the differential input amplifier 17 is detected by the wave detector 18, amplified by the audible amplifier 19, and supplied to the A / D converter 20. The A / D converter 20 produces a digital signal, which is supplied to the computer 7. (6) The computer 7 sets the amplification degree of the high frequency amplifier 23 and the phase shifter 2 so that the amplitude intensity of the supplied signal is minimized.
The phase amount of 4 is controlled via the control circuit 08. By performing the training operation (the operation from (3) to (6)),
The signals at the input terminal 25 and the input terminal 26 of the differential input amplifier 17 have the same amplitude but different phases by 180 °.

(7) Next, the operator starts the inspection by selecting a required inspection mode by operating the keys on the operation console 6. At this time, the amplification degree of the high frequency amplifier 16 changes according to the detection level of the nuclear magnetic resonance signal, but the amplification degree of the high frequency amplifier 23 is changed so that the same change amount is obtained. With this configuration, it is always 21.14MHz
The signal level of the electromagnetic wave is maintained at the minimum value at the input end of the computer 7.

As described above, according to the example shown in FIG.
An electromagnetic wave of 21.14 MHz is transmitted from a transmitting antenna 38 located approximately 15 m away from the superconducting magnet 1, and the high frequency amplifiers 16 and 23 and the phase shifter 24 are adjusted based on this electromagnetic wave. Therefore, in addition to the effect similar to the example of FIG. 1, the high frequency amplifiers 16 and 2 can be used even in a place where the electromagnetic field strength of the surrounding environment changes or a weak place.
3. The phase shifter 24 can be adjusted reliably.

FIG. 6 is a schematic view of the essential parts of a magnetic resonance inspection apparatus according to still another embodiment of the present invention, in which parts equivalent to those in the example of FIG. 3 are designated by the same reference numerals. However, the configuration 54 indicated by the alternate long and short dash line represents the entire example of FIG. In FIG. 6, another transmitting antenna 38 is arranged at a distance of about 15 m (which is a distance longer than one wavelength of 21 MHz) from the superconducting magnet 1. A high frequency transmitter 52 is connected to the transmitting antenna 38, and is configured to radiate an electromagnetic wave having an arbitrary frequency into the air with an intensity of 1 mW.

Next, the operation of the example shown in FIG. 6 will be described. (1) First, prior to the inspection, 2 from the high frequency transmitter 52
A high frequency power of 1.14 MHz is supplied to the transmitting antenna 38. (2) The operator carries in the inspection site of the subject 5 so that the inspection site becomes the center of the superconducting magnet 1, and then starts the inspection by operating the keys on the operation console 6. (3) According to the program, the computer 7 controls the gradient magnetic field power supplies 9 to 11 and the reference signal generator 12 via the control circuit 8.
And the modulator 13 are operated. High frequency coil for reception 4
The nuclear magnetic resonance signal detected by the preamplifier 15, the high frequency amplifier 16, the detector 18, the audio frequency amplifier 19, A
It is supplied to the data memory 42 of the computer 7 via the / D converter 20.

(4) At the same time as the detection of the nuclear magnetic resonance signal,
The signal detected by the antenna 22 is the preamplifier 15A,
It is supplied to the data memory 43 of the computer 7 through the high frequency amplifier 16A, the detector 18A, the audio frequency amplifier 19A, and the A / D converter 20A. (5) The data stored in the data memory 42 is subjected to data correction, two-dimensional Fourier transform processing, and absolute value calculation in the image processor 44. (6) The data stored in the data memory 43 is subjected to data correction, two-dimensional Fourier transform processing, and absolute value calculation in the image processor 44.

(7) Two-dimensional data is subjected to inter-image arithmetic processing and temporarily stored in the image data memory 49. This inter-image calculation processing also executes weighting processing of two two-dimensional data so that only the data based on the nuclear magnetic resonance signal from the examination region of the subject 5 is extracted. (8) The final image is supplied to the image data disk memory 50, which is stored and managed for a long period of time, and also the display memory 51.
And is displayed on the display 21.

As described above, according to the example shown in FIG.
An electromagnetic wave of 21.14 MHz is transmitted from the transmitting antenna 38 located approximately 15 m away from the superconducting magnet 1, and the electromagnetic wave is removed by using this electromagnetic wave. Therefore, in addition to the effect similar to the example of FIG. 3, since the reference signal is included in the external electromagnetic wave, the reference signal strength in the image data is determined from the relationship between the two-dimensional data and the reference signal. Then, the weighting process described in (7) can be automatically performed.

FIG. 7 shows an installation example of the antenna 22 in the examples of FIGS. 1, 3, 5, and 6. In FIG. 7, 5
Reference numeral 5 denotes a full-face cover of the outer case of the superconducting magnet 1, and the antenna 22 is embedded in the full-face cover 55. The front cover 55 is made of FRP (fiber reinforced plastic).
(Fiber Reinforced Plastic
s)) and has no shielding effect on 21 MHz electromagnetic waves. Therefore, even if the antenna 22 is embedded in the entire surface cover 55, the original functional characteristics of the antenna 22 are not affected. By thus embedding the antenna 22 in the entire surface cover 55, the antenna 22 can be brought close to the receiving high-frequency coil 4, so that the electromagnetic wave noise detected by the high-frequency coil 4 and the electromagnetic wave noise detected by the antenna 22 are detected. The correlation with is stronger. As a result, more accurate correction can be performed. Further, as compared with the case where the antenna 22 is arranged separately from the nuclear magnetic resonance inspection apparatus, it is not necessary to secure a new space for installing the antenna 22, and the appearance is also preferable. In the example of FIG. 7, reference numeral 56 is a patient table, and the antenna 22 may be incorporated in the patient table 56.

FIG. 8 is a schematic configuration diagram of still another embodiment of the present invention, in which parts equivalent to those in the example of FIG. 1 are designated by the same reference numerals. In the example of FIG. 8, a comparator 57 and a display 58 are added to the example of FIG. 1, and the other configurations are the same. Then, the control signal supplied from the control circuit 8 to the high frequency amplifier 23 and the phase shifter 24 is also supplied to the comparator 57. Comparator 5
In 7, the voltage levels of the two supplied control signals are compared, and it is determined whether or not the detection and correction of electromagnetic wave noise are normally executed. When the above detection and correction are normally executed, the comparator 57 drives the display 58 and displays a display indicating that the normal operation is in progress. With such a configuration, the operator who operates the nuclear magnetic resonance inspection apparatus can always grasp whether or not the detection and correction of electromagnetic noise are normally executed. Therefore, if the noise removing operation is defective, it is possible to grasp the fact and perform processing such as reinspection. The display means for displaying that the electromagnetic noise detection and correction operation is being executed is not limited to the example shown in FIG.
It can also be added to the examples of FIGS.

In the example of FIG. 8, the control signal supplied from the control circuit 8 to the high frequency amplifier 23 and the phase shifter 24 is used to indicate that the electromagnetic noise detection and correction operations are being executed. However, the processing steps of the calculator 7 may be displayed on a display to determine whether or not the detection and correction operations are being executed.

[0048]

Since the present invention is constructed as described above, it has the following effects. Magnetic field generating means, signal detecting means for detecting a signal containing a nuclear magnetic resonance signal, a computer for performing an operation based on the nuclear magnetic resonance signal,
In a magnetic resonance inspection apparatus having an output means for outputting a calculation result of a computer, a noise receiving means for receiving electromagnetic wave noise in the vicinity of an inspection target, and an amplitude and phase adjustment for adjusting the amplitude and phase of the received electromagnetic wave noise. Means for performing addition or subtraction processing of the signal detected by the nuclear magnetic resonance signal detection means and the output electromagnetic noise signal of the amplitude / phase adjustment means, removing the electromagnetic noise component, and extracting only the nuclear magnetic resonance signal; , And is configured to supply a signal corresponding to the nuclear magnetic resonance signal output from the adding / subtracting means to the computer. Therefore, it is possible to realize a magnetic resonance inspection apparatus that can perform a high-precision inspection without being affected by the electromagnetic wave noise even if the level of the electromagnetic wave noise changes due to a change in the surrounding environment without applying a high frequency shield.

Further, in the above magnetic resonance inspection apparatus, if the signal detecting means and the noise receiving means are further provided with an electromagnetic wave transmitting means for transmitting an electromagnetic wave of a predetermined frequency, the electromagnetic field strength of the surrounding environment changes. Even in an easy place or a weak place, the amplitude and phase adjusting means can be surely adjusted.

Further, the magnetic field generating means, the signal receiving means for receiving the nuclear magnetic resonance signal, the signal processing means for performing a predetermined process on the output signal from the signal receiving means, and the calculation based on the nuclear magnetic resonance signal. In a magnetic resonance inspection apparatus including a computer and an output unit that outputs a calculation result of the computer, a noise receiving unit that receives electromagnetic wave noise near an inspection target and a function that is equivalent to the signal processing unit and receives the noise. A noise signal processing means for performing a predetermined process on the output noise signal from the means, and an addition signal of the output signal from the signal processing means and the output signal from the noise signal processing means is executed by a computer, Remove the electromagnetic noise component,
It is configured to extract only the component corresponding to the nuclear magnetic resonance signal. Therefore, even if the high-frequency shield is not applied, even if the level of electromagnetic noise changes due to changes in the surrounding environment, high-precision inspection can be performed without being affected by electromagnetic noise. Furthermore, since the signal processing means and the noise signal processing means have the same configuration, it is not necessary to perform the adjustment work of the signal processing means and the noise signal processing means before performing the inspection, and after carrying in the subject, Can move to inspection promptly.

Further, in the above-mentioned magnetic resonance inspection apparatus, if the noise receiving means is arranged inside the outer cover of the magnetic field generating means so as to be closer to the signal receiving means, the noise receiving means and the noise receiving means can be received. The correlation of the electromagnetic noise detected by the means becomes large, and the accuracy of the electromagnetic noise removal processing is improved. Further, in the above magnetic resonance inspection apparatus, if the operator further has a display means for monitoring and displaying the removal operation of the electromagnetic noise component, the operator can constantly monitor the removal operation. In this case, it is possible to grasp it and perform processing such as re-inspection.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of a magnetic resonance inspection apparatus according to the present invention.

FIG. 2 is a diagram illustrating the principle of the present invention.

FIG. 3 is a schematic configuration diagram of another embodiment of the magnetic resonance inspection apparatus according to the present invention.

FIG. 4 is a block diagram of a data processing unit in the computer.

FIG. 5 is a schematic configuration diagram of a main part of still another embodiment of the magnetic resonance inspection apparatus according to the present invention.

FIG. 6 is a schematic configuration diagram of a main part of still another embodiment of the magnetic resonance inspection apparatus according to the present invention.

FIG. 7 is a schematic perspective view of a magnetic resonance apparatus showing an installation example of an antenna 22.

FIG. 8 is a schematic configuration diagram of a main part of still another embodiment of the magnetic resonance inspection apparatus according to the present invention.

FIG. 9 is a schematic configuration diagram of a conventional magnetic resonance inspection apparatus.

FIG. 10 is a pulse sequence diagram of the spin echo method.

[Explanation of symbols]

 1 superconducting magnet 2 gradient magnetic field coil 3 high frequency coil for transmission 4 high frequency coil for reception 5 subject 7 computer 9, 10, 11 gradient magnetic field power supply 15 preamplifier 16, 23 high frequency amplifier 17 differential input amplifier 18 detector 19 audible Frequency amplifier 20 A / D converter 21, 58 Display device 22 Antenna 24 Phase shifter 38 Transmission antenna 44 Image processor 45 Data correction means 46 Two-dimensional Fourier transform processing unit 47 Absolute value calculation unit 48 Inter-image operation processing unit 52 High frequency transmission Device 55 Full Cover 56 Patient Table 57 Comparator

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location 9118-2J G01N 24/02 N 8203-2G G01R 33/22 T

Claims (8)

[Claims] 1. A magnetic field generating means for each of a static magnetic field, a gradient magnetic field and a high frequency magnetic field, a signal detecting means for detecting a signal including a nuclear magnetic resonance signal from an inspection target, and an inspection target for the inspection target based on the nuclear magnetic resonance signal. A computer that performs an operation for obtaining medical information, and an output unit that outputs the operation result of this computer,
A magnetic resonance inspection apparatus having: a noise receiving means for receiving electromagnetic wave noise in the vicinity of an inspection object; an amplitude and phase adjusting means for adjusting the amplitude and phase of the electromagnetic wave noise received by the noise receiving means; and the signal detecting means. Addition / subtraction to remove the electromagnetic wave noise component from the detection signal of the signal detection means and extract only the nuclear magnetic resonance signal by performing addition or subtraction processing of the signal detected by the electromagnetic wave noise signal output from the amplitude phase adjustment means And a means for supplying a signal corresponding to the nuclear magnetic resonance signal output from the adding / subtracting means to the computer. 2. Magnetic field generating means for static magnetic field, gradient magnetic field and high frequency magnetic field, signal receiving means for receiving a signal including a nuclear magnetic resonance signal from an inspection target, and a signal output from the signal receiving means. Magnetic resonance examination apparatus having signal processing means for carrying out the above processing, a computer for performing an operation for obtaining medical information of an inspection object based on a nuclear magnetic resonance signal, and an output means for outputting the operation result of this computer. A noise receiving means for receiving electromagnetic noise near the inspection object, and a noise signal processing means having a function equivalent to that of the signal processing means and performing a predetermined process on the noise signal output from the noise receiving means. In addition, the addition signal and the subtraction process of the output signal from the signal processing unit and the output signal from the noise signal processing unit are executed by the computer to remove the electromagnetic wave noise component, and A nuclear magnetic resonance examination apparatus characterized in that only a component corresponding to a ringing signal is extracted. 3. The magnetic resonance inspection apparatus according to claim 1, wherein the signal detecting means and the noise receiving means are provided with an electromagnetic wave transmitting means for transmitting an electromagnetic wave of a predetermined frequency. 4. The magnetic resonance inspection apparatus according to claim 2, wherein the computer includes a Fourier transform processing unit that performs a two-dimensional Fourier transform on the output signal from the signal processing unit and the output signal from the noise signal processing unit. Based on the absolute value calculation unit that calculates the absolute value of the output data from this Fourier transform processing unit, and based on the output data from this absolute value calculation unit, the electromagnetic noise component is removed and only the component corresponding to the nuclear magnetic resonance signal is extracted. And a magnetic resonance inspection apparatus. 5. The magnetic resonance inspection apparatus according to claim 2, wherein the signal receiving means and the noise receiving means are provided with an electromagnetic wave transmitting means for transmitting an electromagnetic wave of a predetermined frequency. 6. The magnetic resonance inspection apparatus according to claim 1, wherein the static magnetic field generating means is covered by an outer cover, and the noise receiving means is the outer cover. A magnetic resonance inspection apparatus, which is arranged inside a cover. 7. The magnetic resonance inspection apparatus according to claim 1, further comprising an inspection object table for mounting the inspection object, wherein the noise receiving means includes the inspection object. A magnetic resonance inspection apparatus, which is arranged inside a target table. 8. The magnetic resonance inspection apparatus according to claim 1, further comprising display means for monitoring and displaying the removal operation of the electromagnetic noise component. Magnetic resonance inspection system.