JPH05103770A - Magnetic resonance imaging device - Google Patents

Abstract

PURPOSE:To remove a burden from an operater totally with regard to the continuous instructions of respiration stop to an inspected body and prevent totally the instructions of respiration stop from becoming a burden to the patient (the inspected body). CONSTITUTION:A respiration sensor 41 to detect the inspiration and expiration of an inspected body and means (a voice generation circuit 43, a speaker 44) by which respiration stops whose timings (a timing signal generation circuit 42) are planned by the output of the respiration sensor 41, are informed to the inspected body and an operater in order, are equipped, and constitute the above device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic resonance imaging apparatus, and more particularly to a so-called two-dimensional Time-of-
The present invention relates to a magnetic resonance imaging apparatus suitable when the flight method is adopted.

[0002]

2. Description of the Related Art A magnetic resonance imaging apparatus uses a nuclear magnetic resonance (NMR) phenomenon to measure the density distribution, relaxation time distribution, etc. of nuclear spins at a desired examination site in a subject, and the measured data is used to measure the distribution. The cross-sectional image of the inspection site of the sample is displayed. Then, two-dimensional Time-of-flig in the magnetic resonance imaging apparatus
The ht method is used as a blood flow drawing method, and is briefly described below.

In a magnetic resonance imaging apparatus, when the same region is continuously excited by a high-frequency magnetic field for a short time (for example, several tens of ms), spins contained in the tissue of the region are saturated and emitted. The resulting signal will be low. However, on the other hand, the spins contained in the blood flow flow out of the region at any time, and new unsaturated spins flow in, so that a relatively high signal is emitted from other tissues. Utilizing this fact, imaging is performed on a plurality of slices, and images obtained thereby are superimposed and projected to perform drawing of blood flow. Such a two-dimensional Time-of-f
For the light method, for example, "Magnetic"
Resonance Imaging. StarkD
Det al. edited, The C. V. Mos
by Company ”.

When the blood flow is drawn by this method, the imaging of the abdominal region is usually performed while breathing is stopped so that a thin blood vessel can be drawn. For this reason, in the past, the operator issued a breath stop instruction to the subject by voice every measurement of one slice.

[0005]

However, the instruction to stop breathing by the operator reaches the number of times of imaging each slice according to the number of slices, and the operator's burden is large when the number of slices is several tens. It was a thing. In addition, the patient (subject) may not be able to properly adjust the timing of respiratory arrest in response to dozens of respiratory arrest instructions, which may cause distress.

The present invention has been made under such circumstances, and its purpose is to place no burden on the operator in regard to the instruction to the subject to continuously stop breathing. Another object of the present invention is to provide a magnetic resonance imaging apparatus. Further, another object of the present invention is to
An object of the present invention is to provide a magnetic resonance imaging apparatus in which the instruction to stop breathing does not impose any burden on the patient (subject).

[0007]

In order to achieve such an object, the present invention basically aims at timing by a respiratory sensor for detecting inspiration and expiration of a subject and the output of this respiratory sensor. It further comprises means for sequentially informing the subject and the operator of the stop of breathing.

[0008]

The magnetic resonance imaging apparatus constructed as described above is firstly provided with a means for informing of successive respiratory arrest. As this means, for example, it is configured to notify the patient visually or audibly. With this configuration, it is not necessary for the operator to give an instruction to stop breathing as in the conventional case, so that it is possible to prevent the operator from being burdened at all.

Further, the means for notifying the respiratory stop is designed to be driven from the output of the respiratory sensor for detecting inspiration and expiration of the subject. Therefore, the patient (subject) does not feel that the timing of the respiratory stop does not meet, and therefore the instruction of the respiratory stop does not feel pain.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a magnetic resonance imaging apparatus according to the present invention will be described below with reference to the drawings.

First, FIG. 4 is a block diagram showing the overall construction of a magnetic resonance imaging apparatus according to the present invention. This magnetic resonance imaging apparatus roughly includes a central processing unit (CPU) 1, a sequencer 2, a transmission system 3, a static magnetic field generating magnet 4, a reception system 5, and a signal processing system 6. Has been done.

The central processing unit (CPU) 1 controls each of the sequencer 2, the transmission system 3, the reception system 5 and the signal processing system 6 according to a predetermined program. The sequencer 2 operates based on a control command from the central processing unit 1 and sends various commands necessary for collecting data of a tomographic image of the subject 7 to the transmission system 3 and the magnetic field gradient generation system 21 of the static magnetic field generation magnet 4. It is sent to the receiving system 5. The sequencer 2 will be described later in detail.

The transmission system 3 has a high frequency oscillator 8, a modulator 9 and an irradiation coil 11 as a high frequency coil, and a modulator 9 amplitude-modulates a high frequency pulse from the high frequency oscillator 8 in accordance with a command from the sequencer 2. The amplitude-modulated high-frequency pulse is amplified through the high-frequency amplifier 10 and the irradiation coil 11
Is supplied to the subject 7 so that the subject 7 is irradiated with a predetermined pulsed electromagnetic wave.

The static magnetic field generating magnet 4 is for generating a uniform static magnetic field around the subject 7 in an arbitrary direction. Inside the static magnetic field generating magnet, in addition to the irradiation coil 11, a gradient magnetic field coil 13 for generating a gradient magnetic field and a receiving coil 14 of the receiving system 5 are installed. The gradient magnetic field generation system 21 has a configuration capable of independently applying a gradient magnetic field in Cartesian coordinate axis directions orthogonal to each other, that is, in the X axis direction, the Y axis direction, and the Z axis direction.
3 and gradient magnetic field power supply 12 for supplying electric current to the gradient coil
And a sequencer 2 for controlling the gradient magnetic field power supply 12.

The receiving system 5 has a receiving coil 14 as a high frequency coil, an amplifier 15 connected to the receiving coil 14, a quadrature detector 16 and an A / D converter 17, and an NMR signal from the subject 7 is received. When the receiving coil 14 detects the signal, the signal is converted into a digital amount through the amplifier 15, the quadrature detector 16, and the A / D converter 17, and the quadrature detector 16 is supplied at the timing instructed by the sequencer 2.
The data is converted into two series of collected data sampled by and sent to the central processing unit 1.

The signal processing system 6 has an external storage device such as a magnetic disk 20 and a magnetic tape 19 and a display 18 such as a CRT. When data from the receiving system 5 is input to the central processing unit 1. , The central processing unit 1 executes processing such as signal processing and image reconstruction, and the subject 7
The desired cross-sectional image is displayed on the display 18 and stored in the magnetic disk 20 or the like of the external storage device.

The pulse sequence in the pulse sequencer 2 is, as shown in FIG.
After applying 0, when the echo time is Te, Te / 2
After 180 hours, the 180 ° pulse 31 is applied. After the 90 ° pulse 30 is applied, each spin starts rotating in the XY plane at its own velocity, so that a phase difference occurs between the spins over time. 18 here
When the 0 ° pulse 31 is applied, each spin is inverted symmetrically with respect to the X ′ axis, and after that, in order to continue rotating at the same speed, time T
At e, the spins refocus and form an echo signal 36.

In this case, in order to construct a tomographic image, the spatial distribution of signals must be obtained. For this purpose, a linear gradient magnetic field is used. A spatial magnetic field gradient can be created by superimposing a gradient magnetic field on a uniform static magnetic field. As described above, since the spin rotation frequency is proportional to the magnetic field strength, the spin rotation frequencies are spatially different in the state where a gradient magnetic field is applied. Therefore, the position of each spin can be known by examining this frequency. For this purpose, a slice direction gradient magnetic field 32, a phase encode gradient magnetic field 33, and frequency encode gradient magnetic fields 34 and 35 are used.

Using the pulse sequence described above as a basic unit, the intensity of the phase-encoding gradient magnetic field is changed every time, and a predetermined number of times, for example, 256 times are repeated at a constant repetition time (TR). The spatial distribution of macroscopic magnetization can be obtained by subjecting the measurement signal thus obtained to two-dimensional inverse Fourier transform. Regarding the basic principles of MRI above,
"NMR studies" (basic and clinical) (Nuclear Magnetic Resonance Medicine),
Maruzen Co., Ltd., issued January 20, 1984).

FIG. 1 is an explanatory view showing a configuration especially provided in this embodiment. In the figure, first, the respiratory sensor 4
There is one. The respiratory sensor 41 is used in the vicinity of or in contact with the body of the subject in the magnetic resonance imaging apparatus, and is designed to detect inspiration and expiration of the subject. The detection signal from the breath sensor 41 is input to the timing signal generation circuit 42. In addition to the detection signal from the respiration sensor 41, the timing signal generating circuit 42 is also supplied with a Start signal and a time t setting signal. The Start signal and the time t setting signal can be input by the operator.

The operation performed by the timing signal generating circuit 42 will be described with reference to FIG. In the figure, the signal of the sin curve shows the signal from the respiratory sensor 41, and the signal value is adapted to correspond to the inspiration and expiration of the subject. That is, when the gradient is positive, it is during inspiration, and when the gradient is negative, it is during expiration. Then, when the signal value is a value v slightly larger than 0, the output to the voice generation circuit 43 described later can be sent.

When a plurality of slices are measured, the Start signal is input each time a slice image is picked up when preparation is completed, and a timer (not shown) is provided in the timing signal generation circuit 42 for this Start signal.
The measurement starts from the time when the t signal is input. This measurement is based on t of the time t setting signal that is input in advance.
It will continue until the time has passed. It should be noted that this time t can be set with reference to the time during which the operator can concentrate his or her nerve for the measurement in the stage before the slice measurement time.

Then, after a lapse of time t, when the signal value from the breathing sensor 41 first becomes v, the voice generating circuit 4
A signal for driving 3 will be output. Accordingly, the voice generation circuit 43 gives a subject an instruction to stop breathing through the speaker 44. If the subject who received the instruction to stop breathing tries to stop breathing due to this, since inhalation has ended and it is about to enter the exhalation stage, it is possible to perform breathing stop without experiencing any pain. Become.

Such an operation is repeated n times (for example, 60 times) in the order shown in FIG.
Each slice image is obtained, and they are superimposed and projected to draw the blood flow.

According to the embodiment described above, since the voice generating circuit 43 and the speaker 44 are provided with means for sequentially informing of the respiratory stop, the operator himself / herself issues an instruction of the respiratory stop as in the conventional case. It is not necessary to give something, and it is possible to avoid burdening the operator.

The voice circuit 43 and the speaker 44 are also provided.
The means for notifying the respiratory stop is designed to be driven by the timing signal generation circuit 42 with timing from the output of the respiratory sensor 41 which detects the inspiration and expiration of the subject. Therefore, the patient (subject) does not feel that the timing of the respiratory stop does not meet, and therefore the instruction of the respiratory stop does not feel pain.

In the above-mentioned embodiment, the means for notifying the respiratory stop is by the voice through the speaker 44, but the same is done by lighting the lighting lamp (which is arranged in the visual field of the patient). It goes without saying that the effect may be achieved.

[0028]

As is clear from the above description,
According to the magnetic resonance imaging apparatus of the present invention, it is possible to prevent the operator from being burdened with the instruction of continuous respiratory arrest to the subject. Further, it is possible to prevent the instruction of the respiratory stop from being a burden on the patient (subject) at all.

[Brief description of drawings]

FIG. 1 is a block configuration diagram showing an example of a configuration provided in a magnetic resonance imaging apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing an operation of the timing signal generating circuit shown in FIG.

FIG. 3 is an explanatory diagram showing a relationship between each slice measurement and a subject's respiration in the magnetic resonance imaging apparatus according to the present invention.

FIG. 4 is an overall schematic configuration diagram showing an embodiment of a magnetic resonance imaging apparatus according to the present invention.

FIG. 5 is an explanatory diagram showing an example of a pulse sequence of the magnetic resonance imaging apparatus according to the present invention.

[Explanation of symbols]

 41 breathing sensor 42 timing signal generating circuit 43 voice generating circuit 44 speaker

Claims (1)

[Claims] 1. A respiration sensor for detecting inspiration and expiration of a subject, and means for sequentially informing the subject and an operator of the timing of breathing stop by the output of the respiration sensor. Magnetic resonance imaging device.