JPH04226637A - Mri device - Google Patents

Abstract

PURPOSE:To eliminate the artifacts by bodily motion, such as motion of the throat of a testee. CONSTITUTION:An air bag 51 and an air pipe 52 are mounted to the surface of the section to be inspected, such as the throat of the person 11 to be inspected and the vibrations (acoustic waves) by the motion in the section to be inspected are transmitted to an acoustic transmitting means where the acoustic waves introduced therein are converted to an electric signal. The presence or absence of the bodily motion can be decided from this electric signal. The data obtd. by the data collecting sequence of this time is nullified and is excluded if judgment is made that there is the bodily motion. Image reconstitution is then executed or the data is collected again by repeating this data collecting sequence.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] This invention relates to nuclear magnetic resonance (NMR).
) to perform imaging and spectroscopy
The present invention relates to an RI device, and particularly to an MRI device suitable for imaging the neck.

0002

2. Description of the Related Art In an MRI apparatus, a specific region of a subject is selectively excited, echo signals are received from the region, and spectroscopy is performed. The axial position information is converted into the frequency of the echo signal, and the other axial position information is converted into the phase of the echo signal.
Imaging is performed in which the received echo signals are encoded and subjected to two-dimensional Fourier transform to decode the position information in the two-axis directions and obtain a tomographic image on the slice plane.

Conventionally, when examining the vicinity of the neck, an RF coil with high reception sensitivity, such as an RF coil dedicated to the neck, is used to capture images.

0004

[Problem to be Solved by the Invention] However, when imaging the neck using such a highly sensitive RF coil, artifacts are likely to occur in the reconstructed image due to body movements such as the movement of the throat of the subject. There is a problem. It is necessary to keep the target area still for about 10 minutes for imaging, but the throat area often moves due to swallowing saliva, and it is difficult to keep that area still.

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide an MRI apparatus that is improved so that artifacts due to body movements such as movements of the throat of a subject do not occur.

[0006]

[Means for Solving the Problems] In order to achieve the above object, in the MRI apparatus according to the present invention, an acoustic transmitting means is attached to the surface of the examined part such as the throat, and vibrations (sound waves) due to movement inside the examined part are attached to the surface of the examined part such as the throat. ) is transmitted to this acoustic transmission means, and this sound wave is guided and converted into an electrical signal. Therefore, it is possible to determine the presence or absence of body movement from this electrical signal, and when it is determined that there has been body movement, the data obtained in the data collection sequence at that time can be invalidated, and image reconstruction can be performed by excluding it. The data collection sequence can be repeated to collect data again. As a result, it is possible to reconstruct an image from data that is not affected by body movement, so it is possible to obtain an image without body movement artifacts.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows an MRI apparatus according to an embodiment of the present invention. In this figure, a subject 11 is exposed to a static magnetic field formed by a main magnet 15 and a gradient coil 14, and a gradient magnetic field formed superimposed thereon. placed within. As shown in FIG. 2, a neck R is attached to the neck of the subject 11, which serves as a transmitting coil and a receiving coil.
F coil 12 is attached.

The gradient coils 14 are configured to be able to independently generate gradient magnetic fields whose magnetic field strengths are gradient in each direction of three orthogonal axes. The gradient magnetic fields of the three orthogonal axes are respectively a slice selection gradient magnetic field Gs, a readout (frequency encoding) gradient magnetic field Gr, and a phase encoding gradient magnetic field Gp. Current is supplied to the gradient coil 14 from respective power supplies 21, 22, and 23 for gradient magnetic fields Gs, Gr, and Gp, and gradient magnetic fields in each direction are formed. The waveforms of currents supplied by the gradient magnetic field power supplies 21 to 23 are controlled by a gradient magnetic field controller 24 so that the gradient coil 14 forms gradient magnetic field pulses with predetermined waveforms.

[0009] The RF coil 12 is supplied with RF pulses sent from a high frequency power source 33. This RF pulse is
In the frequency converter 32, R from the synthesizer 34
The RF waveform generator 3 uses the F sine wave signal as a carrier signal.
The sinc waveform from 1 is AM-modulated and amplified by the high-frequency power supply 33.

NMR generated after the subject 11 is irradiated with an RF pulse from the RF coil 12 to excite its nuclear spins.
The signal is received at RF coil 12. This received NMR signal is amplified by a preamplifier 35, then detected by a quadrature phase detector 36, and then converted into digital data by an A/D converter 37 and taken into the host computer 41. This quadrature phase detector 36 is a PSD (Phase S
This is a detection circuit based on an active detector method, and uses a circuit that mixes a reference signal sent from the synthesizer 34 and a received signal, and outputs the difference in frequency between the two signals.

Under the control of the host computer 41, the sequence controller 42 provides waveform information and generation timing information of each gradient magnetic field pulse to the gradient magnetic field control device 24.
The F waveform generator 31 is given sinc waveform information and generation timing information of the RF pulse, and the synthesizer 3
4 to control the sampling timing of the A/D converter 37, etc.

The host computer 41 includes a console 4 having a display device and an input device such as a keyboard device.
3 is connected. The data taken into the host computer 41 is subjected to two-dimensional Fourier transform to reconstruct an image, and the resulting image is displayed on the display device of the console 43.

As a pulse sequence for imaging, a normal spin echo method, saturation recovery method, inversion recovery method, etc. can be used.

An air bag 51 is attached to the throat of the subject 11 as shown in FIG.
The pressure is transmitted to the pressure sensor 58 of No. 3. This pressure sensor 58
An electrical signal corresponding to the sound wave obtained from the oscilloscope is sent to the host computer 41 via an amplifier 59.

[0015] The air bag 51 is illustrated in FIGS. 3 and 4, for example.
It is configured as shown in . That is, a disc-shaped air bag 55 also made of vinyl or the like is placed inside a flexible disc-shaped housing 54 made of vinyl or the like, and a disc-shaped sponge 56 is placed inside the air bag 55. Become. This sponge 56 maintains the cavity of the air bag 55 (prevents the air bag 55 from collapsing). An air pipe 52 such as a vinyl pipe is connected to this air bag 55. Adhesive tape 5 is attached to one side of the housing 54.
7 is provided so that it can be attached to the skin surface such as the throat.

As shown in FIG. 2, when the housing 54 of the air bag 51 is attached to the surface of the throat with an adhesive tape 57, vibrations (sound waves) inside the throat are transmitted into the air bag 55. This sound wave is transmitted through the air pipe 52 and is guided to the pressure sensor 58. Therefore, the electrical signal obtained by the pressure sensor 58 is a signal representing the sound inside the throat. Therefore, when a body movement occurs, such as by swallowing saliva, a signal representing the sound is obtained, and it is possible to determine whether a body movement has occurred based on the signal. This signal is amplified by an amplifier 59 and then sent to the host computer 41, where the presence or absence of body movement is determined by waveform analysis.

Therefore, when the host computer 41 determines that there has been a body movement, the data obtained from the pulse sequence of the view at that time is invalidated. And again,
controls to repeat the pulse sequence for that view,
A scan is completed in which data is collected in a state where there is no body movement, or data for image reconstruction is collected while the data is missing. In this way, an image without artifacts can be reconstructed from data without body movement, or data of a missing view can be interpolated from data of surrounding views, and image reconstruction can be performed to generate an image without artifacts. obtain.

Here, in order to detect body movements, vibrations (sound waves) inside the body of the subject 11 are sent to the pressure sensor 58 using the air bag 51 and the air pipe 52. Since it is an electrical signal for the first time, by placing the body movement detector 53 including the pressure sensor 58 in a place away from the subject 11, it is possible to
Body movements can be reliably detected without being affected by signals.

[0019]

Effects of the Invention As described above with respect to the embodiments, the MRI apparatus of the present invention can easily and reliably detect body movements without being affected by gradient magnetic fields or irradiated RF signals, and can eliminate body movement artifacts. It is possible to obtain a reconstructed image without any blemishes, and it is particularly effective for imaging the neck.

[Brief explanation of the drawing]

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

FIG. 2 is a schematic perspective view of the subject's neck.

FIG. 3 is a cross-sectional view of the airbag.

FIG. 4 is a vertical cross-sectional view of the airbag.

[Explanation of symbols]

Claims (1)

[Claims] 1. Means for generating a static magnetic field, means for generating gradient magnetic fields in each direction, and means for irradiating and exciting an RF signal to a subject placed in the static magnetic field and the gradient magnetic field. a means for receiving a resonance signal from a subject; an acoustic transmission means attached to the surface of the region to be examined; a means for converting the sound waves guided by the acoustic transmission means into electrical signals; and the gradient magnetic field generation described above. , comprising means for controlling a resonance signal data collection sequence consisting of a series of sequences regarding RF signal irradiation and signal reception, and for determining the collected data in accordance with the electrical signal representing the vibration. MRI equipment.