JPS63272337A - Magnetic resonance imaging apparatus - Google Patents

Abstract

PURPOSE:To transmit cardiac sound data in a sonic wave to a position imparting no mutual effect along with a magnetic field using a means imparting no mutual effect along with the magnetic field and to perform heart rate synchronous photographing by forming a heart rate synchronous signal on the basis of cardiac sound, by applying a synchronous signal to at least one of pulse sequence and signal processing as a data forming control signal. CONSTITUTION:A sound collecting part 12a is brought into contact with the heart area of an examinee P and the sound from the sound collecting part 12a, that is, cardiac sound is led out to the outside of a room, for example, to which a magnetic shield and a radioactive shield are applied by a transmission tube 12b. Herein, a main unit 1 is arranged in the heart area and a computer system 10 is arranged outside the room. The sound collecting part 12a and the transmission tube 12b constitutes a cardiac sound transmitting means 12 and constituted of a resin material which is not a high magnetic substance and a good conductor. Since acoustic cardiac sound data is obtained by the cardiac sound transmitting means 12 composed of material which is not the high magnetic substance and the good conductor, a magnetic field is not disturbed and the deterioration of image quality is not brought about.

Description

[Detailed Description of the Invention] [Purpose of the Invention (Industrial Application Field) The present invention is directed to producing a magnetic resonance phenomenon in a biological subject by the action of a magnetic field, detecting a signal based on this phenomenon,
In particular, with regard to magnetic resonance imaging equipment that obtains information such as the spin density and chemical shift of specific atomic nuclei present in the local region of the subject by subjecting this to signal processing,
The present invention relates to a magnetic resonance imaging apparatus with improved means for implementing a heartbeat synchronized imaging mode as an imaging mode.

(Prior Art) A complete example of the heartbeat synchronized imaging mode of a conventional magnetic resonance imaging apparatus will be explained with reference to FIG. That is, in FIG. 2, the main body 1 is formed of a substantially cylindrical body, and inside thereof there is a solenoid coil 2 as a static magnetic field generating device that generates a static magnetic field along the Z-axis direction, and a solenoid coil 2 that generates a static magnetic field along the Z-axis direction. It includes a gradient magnetic field generation coil 3 that generates a gradient magnetic field along a direction, and a probe coil 4 that generates a high frequency magnetic field and detects the induced magnetic resonance signal. At an axial position of the main body 1, a next bed 6 having a slideable top plate 5 is arranged. In addition, it is equipped with various magnetic field generation power supplies, a pulse sequencer, a computer system, etc. (not shown).

In the above configuration, the subject P is placed on the top plate 5, and the main body! Insert it into the body by a sliding motion, and
A static magnetic field, a gradient magnetic field, and a high-frequency magnetic field are applied according to a predetermined pulse sequence. Then, a specific atomic nucleus existing in a local region determined by the Noculus of the gradient magnetic field, the frequency of the pain frequency magnetic field, etc. exhibits a magnetic resonance phenomenon. A signal based on this phenomenon is detected by the globe coil 4 and subjected to signal processing to form, for example, a tomographic image.

The above-mentioned is a general magnetic resonance imaging device, and in the heart rate synchronized imaging mode, the electrocardiograph is 7f! :establish. That is, the electrode 7a is attached to the subject P, and the electrode 7a and the main body 7b are
The heart rate synchronization signal obtained from the main body 7b is guided to a pulse sequencer or computer system via the bed 6 or the like, for example. This heartbeat synchronized signal is used as a control signal for image generation during signal processing when a pulse sequence synchronized with the heartbeat is performed during imaging. This is useful when: In other words, in addition to this magnetic resonance imaging puffer fish device, in X-ray CT devices, etc., if the movement of the heart is not taken into account during multi-slice imaging or imaging of the heart region over time, image quality deterioration such as out-of-focus may occur. becomes. On the other hand, if the above-mentioned heartbeat-synchronized imaging is performed, information can be collected under the same state of heart movement, so the above-mentioned image quality deterioration does not occur.

However, the above configuration has the following problems. In other words, the high-frequency magnetic field (
fl p a4 rus), the electrode 7a acted as an antenna, and noise due to RF pulses was mixed into the electrocardiographic signal, causing an inaccurate heartbeat synchronization signal and eventually deterioration of image quality.

In addition, noise generated outside the main body is guided into the test subject placement space using the electrode 7a as an antenna, causing disturbance of the magnetic field, and M
Noise was mixed into the signal based on the R phenomenon, causing image quality deterioration.

Furthermore, in a high magnetic field type device, the above-mentioned problems of noise mixing into the electrocardiogram signal and disturbance of the magnetic field are further increased, and the following problems are also raised.

In other words, if the subject P moves during imaging, the subject P will be placed in a high magnetic field,
The bent cable 7C also moves, which causes a change in magnetic flux linkage, causing a large fluctuation in the electrocardiographic waveform. Further, in a high magnetic field type device, a large power RFz-1' pulse may be used, and the electrocardiogram waveform varies greatly due to this Rp/arm pulse. Furthermore, the flow of blood in a high magnetic field affects the electrocardiogram waveform.

(Problems to be Solved by the Invention) In this way, in the conventional technology, the magnetic field and the electrocardiogram detection system influence each other, leading to noise contamination and signal fluctuations in the electrocardiogram signal, resulting in inaccurate Unable to perform heart rate imaging,
Another problem is that it disturbs the magnetic field, leading to deterioration in image quality.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a magnetic resonance imaging apparatus that can perform accurate heartbeat-synchronized imaging without mutual influence between the magnetic field and the electrocardiogram detection system, and that does not disturb the magnetic field. do.

[Structure of the Invention] (Means for Solving the Problems) The magnetic resonance imaging apparatus according to the present invention uses a good conductor or a highly magnetic material that makes a musical sound of a subject's heart and propagates it to a position where it does not interact with the magnetic field. A heart sound propagation means made of a material other than at least one of the above, and a synchronization signal generation means for converting the heart sound propagated by the heart sound propagation means into an electrical signal and generating a synchronization signal synchronized with the operation of the heart based on the signal, A synchronizing signal is provided to at least one of the pulse sequence and the signal processing as an information generation control signal.

(Function) According to such a configuration, it is possible to transmit heart sound information based on sound waves to a position where there is no mutual influence with the magnetic field using a means that does not have mutual influence with the magnetic field, and here the heart sound information can be transmitted based on the heart sound. It becomes possible to generate a synchronization signal and perform heart rate synchronized imaging.

(Example) An example of a magnetic resonance imaging apparatus according to the present invention will be described below with reference to FIG.

In FIG. 1, as a static magnetic field generating device, for example, an electromagnetic coil 2 and a gradient magnetic field generating coil 3 constitute a main body 1,
Inside the main body 1, a space S is formed in which a subject P is placed and in which stray magnetic fields are generated. A probe coil 4 constituting a transmitting/receiving coil is applied to the subject P placed in this space S.

Here, the electromagnetic coil 2 is driven by a static magnetic field generating power source (not shown), the gradient magnetic field generating coil 3 is driven by a gradient magnetic field generating power source 8, and the probe coil 4 is driven to transmit by a transmitting/receiving circuit 9. There is. Further, the gradient magnetic field generation power supply 8 and the transmitting/receiving circuit 9 are driven and controlled by a pulse sequencer 11 under the control of a computer system 10 so as to execute a predetermined /4' pulse sequence.

The above-mentioned configuration is the same as the conventional one, and in this embodiment, the means for obtaining the heartbeat synchronization signal is configured as follows. That is, the sound collecting section 12m is applied to the heart region of the subject P, and the sound from the sound collecting section 12a, that is, the heart sound is transmitted to the transmission tube 12b.
For example, a magnetic shield (not shown) is led outside the wave shielded room. Here, a main body 1 is installed in this part, and a computer system 1 is installed.
The 0th grade is installed outside the room. The above-mentioned sound collecting section 12m
and the transmission tube 12b constitute the heart sound propagation means 12,
Both of these are made of a resin material that is neither highly magnetic nor a good conductor, and an ordinary stethoscope is an example thereof. The heart sound led out of the room by this heart sound propagation means 12 is converted into an electrical signal by a microphone Z3, and a heartbeat synchronized signal is generated by a signal processor 14 including an amplifier 141 and a comparator 14b. This heart rate synchronization signal is
It is given to the pulse sequencer 11 to execute a notarus sequence synchronized with the heartbeat, or it is given to the computer system 10 to collect the signal from the probe coil 4 and receive it in the transmitting/receiving circuit 9 to generate a signal based on the MR phenomenon. Execute signal processing in synchronization with heartbeat.

According to the apparatus of this embodiment configured as described above, the following effects are achieved. That is, since heart sound information is obtained by sound using the heart sound propagation means 12 made of a material that is not highly magnetic or a good conductor, the magnetic field is not disturbed and image quality is not degraded. In addition, this means 12
Since the heart sound information indicating the heart sound waveform is not affected by noise caused by the magnetic field, an accurate heartbeat synchronized signal can be obtained, and accurate heartbeat synchronized imaging can be performed. Needless to say, the above-mentioned advantages become more effective as the magnetic field increases, and heart sound information itself is not affected by blood flow in a high magnetic field, which is advantageous. Furthermore, since the configuration does not include a good conductor within the magnetic field space, there is no need to worry about the generation of eddy currents. Of course, since no electricity is applied to the subject PK, safety is improved in this respect as well.

The present invention is not limited to the embodiments described above, and various modifications can be made without departing from the gist thereof.

[Effects of the Invention] As described above, the magnetic resonance imaging apparatus according to the present invention is made of a material that is not at least one of a good conductor and a highly magnetic material, which collects the heart sound of a subject and propagates it to a position where it does not interact with the magnetic field. a heart sound propagation means, and a synchronization signal generation means for converting the heart sound propagated by the heart sound propagation means into an electrical signal and generating a synchronization signal synchronized with the operation of the heart based on the signal, By giving an information generation control signal to at least one of the pulse sequence and the signal processing, heart sound information generated by sound waves can be caused to interact with the magnetic field using a means that does not interact with the magnetic field. Here, a heart rate synchronized signal is generated based on the heart sounds, and heart rate synchronized imaging can be performed. This allows the magnetic field and the electrocardiogram detection system to accurately detect each other without affecting each other. Therefore, it is possible to provide a magnetic resonance imaging apparatus that can perform heartbeat-synchronized imaging without disturbing the magnetic field.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an embodiment of a magnetic resonance imaging apparatus according to the present invention, and FIG. 2 is a diagram showing the configuration of a conventional example. DESCRIPTION OF SYMBOLS 1... Main body, 2... Electromagnetic coil, 3... Gradient magnetic field generation coil, 4... Probe coil, 12... Heart sound propagation means, 13... Microphone, 14... Signal processor . Applicant's agent Patent attorney Takehiko Suzue Figure 1

Claims (1)

[Claims] By applying a high-frequency magnetic field and a gradient magnetic field to a subject placed in a static magnetic field according to a predetermined pulse sequence, a signal based on a magnetic resonance phenomenon is detected, and by signal processing the signal, the subject is In a magnetic resonance imaging apparatus that obtains information such as the spin density and chemical shift of a specific atomic nucleus existing in a local region of A heart sound propagation means made of a material other than at least one of the highly magnetic materials, and a synchronization signal generation means for converting the heart sound propagated by the heart sound propagation means into an electrical signal and generating a synchronization signal synchronized with the operation of the heart based on the signal. A magnetic resonance imaging apparatus, characterized in that the synchronization signal is given to at least one of the pulse sequence and the signal processing as an information generation control signal.