JP2591400B2 - MR device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an MR apparatus for performing imaging, spectroscopy, etc., utilizing an NMR (nuclear magnetic resonance) phenomenon, and more particularly to an MR apparatus for acquiring data in synchronization with a pulse of a living body.

[0002]

2. Description of the Related Art Conventionally, an MR apparatus detects a pulse of a living body, obtains a trigger signal synchronized with the pulse, and executes an imaging sequence and the like in synchronization with the trigger signal. A sensor for detecting the pulse is attached to the subject, and a pulse detection signal is extracted by a cable or the like.

[0003]

However, conventionally, it is difficult to accurately detect a pulse due to a malfunction of a pulse sensor or the like, and as a result, there is a problem that an MR image or the like is deteriorated.

[0004] That is, the subject is placed in the examination space where the static magnetic field and the gradient magnetic field are superimposed, and the pulse sensor is also placed in this space. In this space, a gradient magnetic field is applied in a pulsed manner, and an RF wave is emitted from the RF coil toward the subject. Therefore, these high-frequency magnetic fields and RF waves cause RF currents to be induced in conductors and the like constituting a cable connected to the pulse sensor, which prevents noise and malfunction of the pulse sensor and the like. Because there is no.

SUMMARY OF THE INVENTION In view of the above, the present invention provides a pulse detection system comprising:
It is an object of the present invention to provide an MR apparatus which is improved so as not to malfunction due to noise due to F-waves, thereby enabling accurate data acquisition in synchronization with a pulse, and improving the image quality and the like of an MR image.

[0006]

To achieve the above object, an MR apparatus according to the present invention comprises: a main magnet for applying a static magnetic field to an examination space in which a subject is arranged;
A gradient magnetic field applying device that applies a gradient magnetic field to the examination space, an RF irradiator that irradiates the subject with an RF signal, a receiver that receives an NMR signal from the subject, and a light emitting diode attached to the subject. A pulse sensor that obtains a pulse signal corresponding to the pulse by a phototransistor that receives the light, and a pulse signal that is disposed outside the examination space, and the pulse signal from the pulse sensor is transmitted via a conductor cable and synchronized with the pulse signal. A pulse detection circuit that outputs a triggered signal, and a control device that controls the gradient magnetic field applying device and the RF irradiator according to the trigger signal are provided. In the pulse sensor, an inductor is connected in series to the end of the conductor cable. In addition to the connection, the pulse detection circuit has an inductor connected in series to an end of the conductor cable. Therefore, when RF noise is induced in a pulse sensor or a conductor cable by a gradient magnetic field applied in a pulse form or an RF signal applied to the subject, the RF noise is output from the pulse sensor, It is possible to prevent RF noise induced in the conductor cable from being input to a pulse sensor or a pulse detection circuit. In addition, in the pulse sensor, since a capacitor is connected in parallel to the phototransistor, R
By preventing the F current from flowing through the phototransistor, a malfunction of the phototransistor can be prevented.
As a result, the pulse detection circuit can output a trigger signal accurately synchronized with the pulse, and data can be accurately synchronized with the pulse, so that an MR image with excellent image quality can be obtained.

[0007]

An embodiment of the present invention will be described below in detail with reference to the drawings. In FIG. 1, a main magnet 1 is for generating a static magnetic field, and a gradient magnetic field is applied by a gradient magnetic field coil 2 so as to overlap the static magnetic field. The space to which the static magnetic field and the gradient magnetic field are applied is an examination space in which the subject 3 is arranged. The subject 3 irradiates the subject 3 with an excitation RF pulse and receives an NMR signal generated by the subject 3 for receiving an NMR signal.
The F coil 4 is attached.

A gradient magnetic field power supply 5 is connected to the gradient magnetic field coil 2 to supply power for generating a gradient magnetic field. A transmission power amplifier 7 and a preamplifier 10 are connected to the RF coil 4 via a switch 6. The switch 6 is switched to the transmission power amplifier 7 at the time of excitation, and is switched to the preamplifier 10 at the time of reception. An RF signal obtained by modulating a carrier signal from a signal generator 9 with a modulation signal having a predetermined waveform in a transmission circuit 8 is sent to a transmission power amplifier 7. A receiving circuit 11 is connected to the preamplifier 10, and performs phase detection of the received signal using the signal from the signal generator 9 as a reference signal. The detected signal is sampled by an A / D converter 12, converted into digital data, and taken into a computer 13.

The computer 13 controls the modulation signal waveform of the excitation RF pulse in the transmission circuit 8 and controls the signal generator 9.
And the sampling timing of the A / D converter 12 is determined. Also, the gradient magnetic field power supply 5 is controlled to arbitrarily program the timing, waveform, intensity, etc. of the gradient magnetic field pulse. Further, processing such as reconstructing an image from the collected digital data is performed. The display device 14 displays a reconstructed image and the like.

On the other hand, a pulse sensor 21 is attached to the subject 3 so that a pulse detection circuit 22 generates a trigger signal corresponding to the pulse. This trigger signal is sent to the computer 13 to determine the start timing of the imaging sequence.

The pulse sensor 21 and the pulse detection circuit 22 are connected via a cable 23 as shown in FIG.
The pulse sensor 21 is a light emitting diode 31 in this embodiment.
And a phototransistor 32. A current flows through the light emitting diode 31 through the cable 23, and the light emitting diode 31 emits light. The light from the light emitting diode 31 is applied to the capillaries of the subject 3, and the reflected light is incident on the phototransistor 32. The wavelength of the reflected light deviates due to the blood flow in the capillaries, and the phototransistor 32 responds to the reflected light having the deviated wavelength. The output current of the phototransistor 32 is sent to the pulse detection circuit 22 through the cable 23. Pulse detection circuit 22
Is a buffer circuit 33, an amplification circuit 34, and a trigger generation circuit 3.
5 is provided.

The pulse detection circuit 22 is arranged outside the examination space to which a gradient magnetic field or the like is applied. On the other hand, the pulse sensor 21 is attached to the subject 3 and arranged in an examination space to which a gradient magnetic field or the like is applied. Therefore, it is inevitable that RF noise is mixed into the pulse sensor 21 and the cable 23 connected thereto. Therefore, in this embodiment, three inductors 41, 42, 4
3 are connected to the pulse detection circuit 22 by three inductors 44, 4
5 and 46 are connected to each other, and a capacitor 47 is connected in parallel to the phototransistor 32.

The inductors 41 to 46 have high impedance with respect to the high-frequency signal, and the high-frequency signal is output from the pulse sensor 21 or the RF current induced in the cable 23 is supplied to the pulse sensor 21 or the pulse detection circuit 22.
To prevent it from being entered.

A capacitor 47 is connected in parallel to the phototransistor 32, and the RF current is supplied to the capacitor 47.
Therefore, the RF current induced in the phototransistor 32 is prevented from flowing through itself, so that the operation does not become unstable.

As a result, the RF noise mixed into the cable 23 is prevented from flowing to the light emitting diode 31, so that the operation of the light emitting diode 31 is stabilized and the operation of the phototransistor 32 is stabilized as described above. Therefore, malfunction does not occur in pulse detection. As described above, the high-frequency signal is suppressed on the input side of the pulse detection circuit 22. That is, the high-frequency signal can be suppressed to such an extent that the trigger generation circuit 35 including the buffer circuit 33 and the amplifier circuit 34 does not malfunction due to the high-frequency signal. Therefore, the trigger generation circuit 35 operates only with a low frequency signal corresponding to the pulse from the pulse sensor 21, and the trigger generation circuit 35 can generate a trigger signal accurately corresponding to the pulse.

The above is a description of one embodiment, and the specific configuration and the like can be variously changed without departing from the spirit of the present invention.

[0017]

According to the MR apparatus of the present invention, it is possible to suppress RF noise inevitable to be guided to a cable conductor or the like, prevent a malfunction in pulse detection, and obtain MR data accurately synchronized with the pulse. , And a good MR image or the like can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of an MR apparatus according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing only a pulse sensor and a pulse detection circuit of the embodiment in detail;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main magnet 2 Gradient magnetic field coil 3 Subject 4 RF coil 5 Gradient magnetic field power supply 6 Switching device 7 Transmission power amplifier 8 Transmission circuit 9 Signal generator 10 Preamplifier 11 Receiving circuit 12 A / D converter 13 Computer 14 Display device 21 Pulse sensor 22 pulse detection circuit 23 cable 31 light emitting diode 32 phototransistor 33 buffer circuit 34 amplifier circuit 35 trigger generation circuit 41-46 inductor 47 capacitor

Claims (1)

(57) [Claims] 1. A static magnetic field in an examination space in which a subject is arranged.
And a gradient magnetic field in the examination space.
Applied gradient magnetic field application device and irradiates RF signal to subject
RF irradiator to receive NMR signal from subject
The receiver and the light emitting diode and its attached to the subject
Responds to the pulse with a phototransistor that receives the light
Pulse sensor that obtains a pulse signal, and placed outside the test space
The pulse signal from the pulse sensor
Output a trigger signal synchronized with the pulse signal
A pulse detection circuit which performs the above-described gradient magnetic field according to the trigger signal.
A field application device and a control device for controlling the RF irradiator.
In the above pulse sensor, the capacitor
Are connected in parallel and an inductor is
Are connected in series and the pulse detection circuit
Inductor connected in series at the end of the cable
MR device characterized by the following .