JP3288806B2 - Magnetic resonance imaging equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved electrocardiogram synchronizer used in a magnetic resonance imaging apparatus which performs scanning in synchronization with an electrocardiogram waveform.

[0002]

2. Description of the Related Art The nuclear magnetic resonance phenomenon is a phenomenon in which a nucleus having a non-zero spin and a magnetic moment placed in a static magnetic field resonates and absorbs only a specific electromagnetic wave.
This atomic nucleus has an angular frequency ω ₀ (ω ₀ = 2πν)
₀ , ν ₀ ; Larmor frequency). ω ₀ = γ · H ₀ where γ is the gyromagnetic ratio specific to the type of nucleus,
H ₀ is the static magnetic field strength.

An apparatus for performing a living body diagnosis using the above principle receives an electromagnetic wave of the same frequency induced after the above-described resonance absorption by a receiving coil and processes the signal to obtain a nuclear density and a longitudinal relaxation time T. ₁ , diagnostic information reflecting information such as the lateral relaxation time T ₂ , flow, and chemical shift, for example, a slice image of a subject, etc., is obtained in a non-invasive manner. The collection of diagnostic information by nuclear magnetic resonance can excite all parts of the subject placed in a static magnetic field and collect signals. In view of the above requirements, an actual device performs excitation of a specific portion and collection of its signal. In this case, the specific part to be imaged is generally a slice part having a certain thickness, and an echo signal from this slice part and a nuclear magnetic resonance signal (NMR signal) of an FID signal are generally used many times. By executing the data encoding process described above, the data group is subjected to image reconstruction processing by, for example, a two-dimensional Fourier transform method, thereby generating an image of the specific slice portion. In the imaging of the heart with such a magnetic resonance imaging apparatus, when a scanning signal is output from a sequencer connected to a computer to a gradient magnetic field power source or a transmitter that emits an RF pulse to a transmission coil, the timing is synchronized with the waveform of the electrocardiogram. Sometimes do it. At that time, conventionally, as shown in FIG. 4, a plurality of electrodes 2 are arranged on the heart of a subject 1 lying on a bed (not shown) in a gantry, and a lead wire 3 is connected from each electrode 2. The waveform signal is taken into the electrocardiogram pickup unit 4 via the electrocardiogram pickup unit 4, amplified by the electrocardiogram pickup unit 4, and transmitted as it is. Then, the receiver 5 provided outside the gantry
The scan is performed in synchronization with the waveform of the electrocardiogram by transmitting the data to the sequencer on the control housing side.

[0004]

However, in this kind of conventional electrocardiogram synchronizing apparatus, the electrodes for the electrocardiogram are brought into contact with the heart of the subject using the leads, so that the leads form a closed loop. Then, the lead wire may become hot and cause a burn to the body of the subject, or the closed loop of the lead wire may be affected by the electromagnetic field and cause malfunction. In addition, since only the timing of the QRS waveform is necessary for imaging by the magnetic resonance imaging apparatus, since all the waveforms of the electrocardiogram are transferred, it becomes necessary to use radio waves or wires, and the waveform of the electrocardiogram waveform has to be used. The transfer is unnecessarily complicated, and the size of the transfer is limited. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electrocardiogram synchronizer that can easily and compactly transfer an electrocardiogram waveform and that does not cause a burn or malfunction of a subject's body. An object of the present invention is to provide a magnetic resonance imaging apparatus provided with:

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention makes it possible to reduce the size of an electrocardiogram synchronizing apparatus by configuring the magnetic resonance imaging apparatus as follows. That is, the apparatus includes means for irradiating the subject with electromagnetic waves in a static magnetic field in the gantry, and means for detecting a response to the electromagnetic waves. In the magnetic resonance imaging apparatus which is performed in synchronization with the
An electrode for detecting the RS waveform timing, an amplifier for amplifying a signal from the electrode, a circuit section such as a waveform shaping circuit connected to the amplifier, and a QRS waveform according to the signal from the waveform shaping circuit An infrared light emitting diode for transferring timing is integrated, an electrocardiogram pickup unit is formed by electromagnetically shielding the amplifier and a circuit unit such as a waveform shaping circuit, and a QRS waveform timing signal from the infrared light emitting diode of the electrocardiogram pickup unit is formed. Scanning is performed in synchronization with the waveform of the electrocardiogram by receiving the light by a light receiving unit provided outside the gantry and transmitting the light to the sequencer.

[0006]

According to the above arrangement, the detection of the electrocardiogram waveform of the electrocardiogram synchronizer detects only the required QRS waveform, and an electrode for detecting the QRS waveform timing without using a lead wire. An amplifier for amplifying the signal from the electrode, a circuit section such as a waveform shaping circuit connected to the amplifier, and an infrared light emitting diode for transferring the QRS waveform timing according to the signal from the waveform shaping circuit are integrated. Since the electrocardiogram pickup unit is configured by electromagnetically shielding the circuit unit such as the amplifier and the waveform shaping circuit, the device can be simplified and compacted, and the body of the subject does not suffer from burns or malfunction. .

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an embodiment of an electrocardiogram synchronizing device of a magnetic resonance imaging apparatus according to the present invention. In FIG. 1, electrodes 6 and 7 for detecting a QRS waveform of an electrocardiogram are connected to a differential amplifier 8. The electrode 6 is connected to the positive terminal of the differential amplifier 8 and the electrode 7 is connected to the negative terminal. The QRS waveform amplified by the differential amplifier 8 is shaped into a pulse signal by a waveform shaping circuit 10 through a differentiating circuit 9 to be converted into a pulse signal, and reaches the infrared light emitting diode 11 which is a light emitting element. When the signal reaches the infrared light emitting diode 11, the light emitting diode 11 emits infrared light and transmits that the QRS waveform of the electrocardiogram is detected. The electrodes 6 and 7, the differential amplifier 8, the differentiating circuit 9, the waveform shaping circuit 10 and the infrared light emitting diode 11 are integrally formed to form an electrocardiogram pickup unit 12. The differential amplifier 8, the differentiating circuit 9, and the waveform shaping circuit 10 are electromagnetically shielded. If the electrodes 6 and 7 are provided on one surface, the infrared light emitting diode 11 is provided on the other surface. There must be. A phototransistor 13 as a light receiving element is installed in the same electromagnetic shield room for the light emission of the infrared light emitting diode 11, and an optical signal received by the phototransistor 13 is used as an amplifier / waveform shaping circuit 1.
4 and transmitted to a control case outside the electromagnetically shielded room. The phototransistor 13 is formed by the phototransistor 13 and the amplifier / waveform shaping circuit 14. The ECG pickup unit 12 and the light receiving unit 15 constitute an ECG synchronizer. FIG.
Is an example of the electrocardiogram pickup unit 12. The electrocardiogram pickup unit 12 is formed to have a substantially cylindrical shape. Electrodes 6 and 7 are provided on one surface of the circular shape, and an infrared light emitting diode 11 is provided on the other surface. The substantially cylindrical surface of the electrocardiogram pickup section 12 is made of, for example, aluminum and is electromagnetically shielded. G in the figure is a ground electrode. The differential amplifier 8, the differentiating circuit 9, and the waveform shaping circuit 10 described in FIG. 1 are provided inside the substantially cylindrical shape. Naturally, a power supply for operating these circuits and the infrared light emitting diode 11 is provided. A circuit is provided. The battery for the power supply circuit is also included.

Next, a case where the electrocardiogram synchronizing apparatus is used will be described with reference to FIG. In the electromagnetic shield room, means for irradiating the subject 1 with an electromagnetic wave from a gradient coil or a transmission coil in a static magnetic field formed in a gantry, and a reception coil as means for detecting a response to the irradiation means Is installed. A scanning signal is emitted from a sequencer connected to a computer installed outside the electromagnetically shielded room to the gradient magnetic field coil and the transmission coil via a gradient magnetic field power supply and a transmitter to start scanning.

Electrodes 6, 7 and G are set at the heart of the subject 1 lying on a bed (not shown) in the gantry so that the QRS waveform of the electrocardiogram is detected, and the electrocardiogram pickup section 12 is installed. I do. Then, an infrared ray is emitted from the infrared light emitting diode 11 in response to the generation of the QRS waveform of the electrocardiogram. This infrared light is received by the phototransistor 13 in the light receiving unit 15 installed outside the gantry,
The received optical signal is optically transmitted, sent to a control case outside the electromagnetically shielded room, photoelectrically converted and transmitted to the computer, and a scanning signal is emitted from the sequencer to start scanning. As a result, in synchronism with the generation of the QRS waveform of the electrocardiogram, a gradient magnetic field is formed, an RF pulse is emitted from the transmission coil, and imaging of the heart is performed. When the electrodes 6, 7, and G are set on the heart of the subject 1 and the electrocardiogram pickup unit 12 is installed, the distance between the electrodes 6, 7, and G is accurately adjusted depending on the size of the subject 1. Although there is a possibility that the setting is not accurate, the present invention does not always detect the ECG waveform accurately, but only needs to obtain the detection timing of the QRS waveform of the electrocardiogram. Therefore, the setting may not be accurate. However, in the case of extreme differences, for example, in the case of an adult and a child, an ECG pickup unit 12 for an adult and a child may be created.

[0010]

As described above, according to the present invention, an electrocardiogram waveform is detected without using a lead wire.
Burns on the subject's body are completely eliminated, and malfunctions are hardly caused. Further, only the QRS waveform necessary for the detection of the ECG waveform of the ECG synchronizer is detected, and an electrode for detecting the QRS waveform timing, an amplifier for amplifying a signal from this electrode, and an amplifier connected to the amplifier. A circuit part such as a waveform shaping circuit and an infrared light emitting diode for transferring a QRS waveform timing according to a signal from the waveform shaping circuit are integrated, and the circuit part such as the amplifier and the waveform shaping circuit are electromagnetically shielded. Since the electrocardiogram pickup section is configured, the device can be simplified, inexpensively reduced in size, and the effects of improving the reliability of the device can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of an electrocardiogram synchronizer of a magnetic resonance imaging apparatus according to the present invention.

FIG. 2 is a diagram illustrating an example of an electrocardiogram pickup unit.

FIG. 3 is a diagram for explaining a case where an electrocardiogram synchronizer of the magnetic resonance imaging apparatus of the present invention is used.

FIG. 4 is a diagram for explaining a conventional technique.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 subject 2 electrode 3 lead wire 4 electrocardiogram pickup unit 5 receiver 6 electrode 7 electrode 8 differential amplifier 9 differentiation circuit 10 waveform shaping circuit 11 infrared light emitting diode 12 electrocardiogram pickup unit 13 phototransistor 14 amplifier and waveform shaping circuit 15 light receiving Department

Claims (1)

(57) [Claims] A means for irradiating the subject with an electromagnetic wave in a static magnetic field in a gantry; and a means for detecting a response to the electromagnetic wave. In a magnetic resonance imaging apparatus adapted to be performed in synchronization with a waveform of an electrocardiogram, an electrode for detecting a QRS waveform timing of an electrocardiogram of a subject, an amplifier for amplifying a signal from the electrode, and connection to the amplifier A circuit part including the shaped waveform shaping circuit, and an infrared light emitting diode for transferring the QRS waveform timing according to the signal from the waveform shaping circuit are integrated, and the circuit part including the amplifier and the waveform shaping circuit is electromagnetically shielded. An ECG pickup unit formed outside of the gantry for receiving a QRS waveform timing signal from an infrared light emitting diode of the ECG pickup unit And a sequencer for receiving a QRS waveform timing signal received by the light receiving unit and controlling the scanning timing in synchronization with the input signal. apparatus.