JP2006346234A - Magnetic resonance imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic resonance imaging apparatus capable of easily confirming whether or not followup ability to input signals of the output signals of a gradient magnetic field power source is in a normal range. <P>SOLUTION: In the gradient magnetic field power source 111, the input signals and output signals of an amplifier 124 are supplied to a difference calculation circuit 121, and the difference is calculated, supplied to a comparator circuit 122 and compared with a prescribed threshold. The output signals of the gradient magnetic field power source 111 has the followup ability to the input signals when the difference value is the prescribed threshold or smaller, the followup ability is lowered when it exceeds the threshold, and the output signals indicating the above are supplied to a display circuit 123 and a computer 107. The display circuit 123 lights a display lamp or the like in the case that the followup ability of the gradient magnetic field power source 111 is lowered. Both in the case that the gradient magnetic field power source has the followup ability and in the case that it is lowered, the computer 107 displays these facts on a display 114. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a magnetic resonance imaging apparatus, and more particularly to a technique for determining performance of output signals of a gradient magnetic field power source and a high-frequency amplifier.

  2. Description of the Related Art Magnetic resonance imaging (MRI) imaging methods that obtain tomographic images of human bodies and animals using nuclear magnetic resonance (NMR) phenomena and obtain internal information are widely used in the medical and research fields. .

  This MRI imaging method requires a magnet that generates a uniform magnetic field strength in the space in which the subject is arranged, a gradient magnetic field generating means for obtaining position information, and a receiving unit for obtaining an NMR signal obtained from the subject. is there.

  Among these, the gradient magnetic field generating means uses a gradient magnetic field coil for generating a gradient magnetic field and a gradient magnetic field power source for driving this coil in order to generate a gradient magnetic field for obtaining position information.

  The gradient magnetic field generating means desirably generates an ideal gradient magnetic field, and a technique for reducing an error magnetic field accompanying the generation of the gradient magnetic field is described in Patent Document 1.

JP 2005-34538 A

  Incidentally, the MRI apparatus is always required to shorten the imaging time. Therefore, a strong high-frequency magnetic field that realizes high-speed imaging, a gradient magnetic field that can be controlled at high speed, and a computer unit that can perform high-speed computation are required.

  In particular, higher voltage and higher speed of the gradient magnetic field power supply output have been demanded in recent years, and high followability to the input signal of the gradient magnetic field power supply is essential.

  The work to confirm the followability of this gradient magnetic field power supply is done by measuring the output signal of the gradient magnetic field power supply using a measuring instrument such as an oscilloscope, and the adjuster determines that it is within the specifications specified for the input signal. Because of this, it took time to do so.

  In addition, since measurement of the output signal of the gradient magnetic field power supply requires knowledge in the electrical field, the user of the MRI apparatus cannot easily obtain information on the output abnormality of the gradient magnetic field power supply.

  Moreover, even if an output abnormality of the gradient magnetic field power supply occurs during use of the MRI apparatus, the user cannot know the information on the output abnormality.

  As with the gradient magnetic field power supply, it is convenient if the high-frequency amplifier of the MRI apparatus can automatically determine whether or not the follow-up performance is deteriorated even during use of the MRI apparatus. The automatic determination of the followability with respect to is not considered.

  The present invention has been made with respect to the above-mentioned problem. The purpose of the present invention is to determine whether or not the followability of the output signal of the gradient magnetic field power supply and high-frequency amplifier of the magnetic resonance imaging apparatus is within the normal range. Is to realize a magnetic resonance imaging apparatus capable of easily confirming the above.

  The magnetic resonance imaging apparatus of the present invention detects a static magnetic field generation means, a gradient magnetic field generation means, a gradient magnetic field power supply means, a high frequency transmission means, a high frequency amplifier means for driving the high frequency transmission means, and a nuclear magnetic resonance signal. Receiving means, signal processing means for performing image reconstruction calculation using nuclear magnetic resonance signals, and control means for controlling the operation of the entire apparatus.

  The gradient magnetic field power supply means or the high-frequency amplifier means in the magnetic resonance imaging apparatus includes an amplifying means for amplifying a signal from the control means, and a difference calculating means for calculating a difference between the signal from the control means and the output signal of the amplifying means. And comparing the difference calculated by the difference calculating means with a predetermined threshold value, determining whether the difference is larger than the threshold value, and outputting a signal indicating this, and an output signal from the comparing means However, when the difference indicates that the difference is larger than the threshold, display means for displaying a warning is provided.

  According to the present invention, it is easily determined whether the followability of the output signal with respect to the input signal of the gradient magnetic field power supply or the high frequency amplifier is within an arbitrary range in a short time even while the MRI apparatus is in use. be able to.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is an overall schematic configuration diagram of an MRI apparatus to which the present invention is applied.
In FIG. 1, the MRI apparatus includes a static magnetic field generating magnet 102 disposed opposite to each other so as to sandwich a space in which a subject 101 is placed, and a gradient magnetic field coil 103 disposed inside the static magnetic field generating magnet 102. Furthermore, a high-frequency coil 104 disposed on the inside thereof and a detection coil 105 for detecting an NMR signal generated from the subject 101 are provided.

  The gradient magnetic field coil 103 and the high frequency coil 104 have a pair of upper and lower plate-like structures so as not to hinder the open shape in the MRI apparatus.

  The MRI apparatus further includes a sequencer 106 that controls the operation timing of each gradient magnetic field coil 103, a computer 107 that controls the MRI apparatus and processes an NMR signal to perform imaging, and a subject 101 of a static magnetic field generating magnet 102. And a transfer table 108 disposed in the central space. The sequencer 106 and the computer 107 constitute control means for controlling the operation of the entire MRI apparatus.

  The static magnetic field generating magnet 102, the gradient magnetic field coil 103, the high frequency coil 104, the detection coil 105, and the transfer table 108 are installed in a shield room 109 that is shielded from electromagnetic waves.

  The electromagnetic shielding by the shield room 109 is for the purpose of preventing external electromagnetic waves from being induced in the detection coil 105, and the resonance frequency (the magnetic field of the static magnetic field generating magnet 102) of the nuclei used for the inspection (usually hydrogen nuclei are used). (Corresponding to the intensity) has an attenuation factor of about 70 dB.

  The gradient coil 103, the high frequency coil 104, the detection coil 105, the static magnetic field generating magnet 102, the transfer table 108, and the power supply and control device outside the shield room 109 are shielded so that external noise is not drawn into the shield room 109. 109 is connected via a filter circuit 110 grounded. Alternatively, the outside is connected by a coaxial cable covered with a shield layer (a distinction between coaxial cables is not described in the figure).

  The gradient magnetic field coil 103 is composed of three sets of coils wound so as to change the magnetic east density in the three axial directions of x, y, and z orthogonal to each other, and each of them is connected to the gradient magnetic field power supply 111 and has a gradient. A magnetic field generating means is configured.

  Then, the gradient magnetic field power supply 111 is driven in accordance with a control signal from the sequencer 106 to be described later, and the value of the current flowing through the gradient coil 103 is changed, so that the gradient magnetic fields Gx, Gy, and Gz having three axes are changed. Superposed on the static magnetic field in the arrangement space.

  This gradient magnetic field is used to identify the spatial distribution of NMR signals obtained from the imaging region of the subject 101.

  The high-frequency coil 104 is connected to a high-frequency power amplifier 112 for causing a high-frequency current to flow through the high-frequency coil 104, and generates a high-frequency magnetic field for resonantly exciting hydrogen nuclei at the imaging region of the subject 101. The high-frequency power amplifier 112 is also controlled by a control signal from the sequencer 106.

  The detection coil 105 is connected to the receiver 113 and detects the NMR signal. The receiver 113 amplifies and detects the NMR signal detected by the detection coil 105 and converts it into a digital signal that can be processed by the computer 107. The operation timing of the receiver 113 is also controlled by the sequencer 106 in the same manner as the gradient magnetic field power supply 111 and the high frequency amplifier 112.

  The computer 107 performs operations such as image reconstruction and spectrum calculation using the NMR signals converted into digital quantities, and controls the operation of each unit of the MRI apparatus via the sequencer 106 at a predetermined timing. The computer 107, the display device 114 for displaying the processed data, and the console 115 for performing operation input constitute an arithmetic processing system.

  Next, the internal configuration of the gradient magnetic field power supply 111, which is a characteristic part of the present invention, will be described with reference to FIG.

  In FIG. 2, the gradient magnetic field power supply 111 supplies the input signal of the amplifier 124 and the output signal from the output terminal 125 of the amplifier 124 to the difference calculation circuit 121, and calculates the difference between these input signal and output signal. .

  The difference value calculated by the difference calculation circuit 121 is supplied to the comparison circuit 122 and compared with a predetermined threshold value.

  The comparison circuit 122 outputs a signal indicating whether or not the difference value is equal to or smaller than a predetermined threshold value. If the difference value is equal to or smaller than the predetermined threshold value, the output signal of the gradient magnetic field power supply 111 follows the input signal. If the threshold value is exceeded, it means that the follow-up performance is deteriorated (whether the amplification degree of the amplifier 111 satisfies an intended value).

  The output signal of the comparison circuit 122 is supplied to the display circuit 123 and also to the computer 107.

  If the output signal of the comparison circuit 122 means that the output signal of the gradient magnetic field power supply 111 is less trackable with respect to the input signal, the display circuit 123 indicates a display lamp or the like for indicating a decrease in trackability. Lights up and displays a warning.

  In addition, the computer 107 outputs the signal to the display 114 both when the output signal of the comparison circuit 122 means that the output signal of the gradient magnetic field power supply 111 has a follow-up characteristic with respect to the input signal and when the output signal decreases. Display.

  The gradient magnetic field power supply 111 is provided for each of the X axis, the Y axis, and the Z axis, and has a configuration shown in FIG.

  As described above, according to one embodiment of the present invention, the input signal and the output signal of the amplifier 111 of the gradient magnetic field power supply 111 are compared, and it is determined whether or not the followability to the input signal of the gradient magnetic field power supply 111 is appropriate. If it is not appropriate, it is configured to automatically display it, so that no special time is required for confirming the followability of the gradient magnetic field power supply.

  Further, even an MRI apparatus user who does not have knowledge in the electrical field can easily obtain information on output abnormality of the gradient magnetic field power supply.

  Furthermore, even when the MRI apparatus is in use, the user can know the output abnormality of the gradient magnetic field power supply.

  Note that the computer 107 is configured to display the information on the display 114 and stop the operation of the MRI apparatus when it is determined from the output signal of the comparison circuit 122 that the followability of the gradient magnetic field power supply is reduced. May be.

  Moreover, although the example mentioned above is about follow-up confirmation of the gradient magnetic field power supply 111, the same means as the difference calculation circuit 121, the comparison circuit 122, and the display circuit 123 shown in FIG. It is also possible to display whether or not the follow-up performance of the high-frequency amplifier 112 has decreased.

  The present invention can be realized not only by the MRI apparatus using the gradient magnetic field power supply and the high-frequency amplifier described above but also by each of the gradient magnetic field power supply apparatus and the high-frequency amplifier used in the MRI apparatus.

It is a figure which shows the whole schematic structure of the MRI apparatus with which this invention is applied. It is a figure which shows the internal structure of the gradient magnetic field power supply in one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Subject 102 Static magnetic field generating magnet 103 Gradient magnetic field coil 104 High frequency coil 105 Detection coil 106 Sequencer 107 Computer 108 Subject conveyance table 109 Shield room 110 Filter circuit 111 Gradient magnetic field power supply 112 High frequency power amplifier 113 Receiver 114 Display 115 Console 121 Difference derivation circuit 122 Comparison circuit 123 Display circuit 124 Amplifier 125 Output terminal

Claims (4)

A static magnetic field generating means for applying a static magnetic field to the subject, a gradient magnetic field generating means for applying a gradient magnetic field, a gradient magnetic field power supply means for driving the gradient magnetic field generating means, and a high frequency for causing nuclear magnetic resonance in the subject High-frequency transmission means for irradiating a magnetic field, high-frequency amplifier means for driving the high-frequency transmission means, reception means for detecting a nuclear magnetic resonance signal emitted from the subject, and a nuclear magnetic resonance signal detected by the reception means In a magnetic resonance imaging apparatus having a signal processing means for performing image reconstruction calculation using a control means and a control means for controlling the operation of the entire apparatus,
The gradient magnetic field power supply means includes:
Amplifying means for amplifying the signal from the control means;
Difference calculating means for calculating a difference between the signal from the control means and the output signal of the amplifying means;
A comparison unit that compares the difference calculated by the difference calculation unit with a predetermined threshold, determines whether the difference is larger than the threshold, and outputs a signal indicating the difference;
When the output signal from the comparison means indicates that the difference is greater than the threshold, display means for displaying a warning,
A magnetic resonance imaging apparatus comprising: A static magnetic field generating means for applying a static magnetic field to the subject, a gradient magnetic field generating means for applying a gradient magnetic field, a gradient magnetic field power supply means for driving the gradient magnetic field generating means, and a high frequency for causing nuclear magnetic resonance in the subject High-frequency transmission means for irradiating a magnetic field, high-frequency amplifier means for driving the high-frequency transmission means, reception means for detecting a nuclear magnetic resonance signal emitted from the subject, and a nuclear magnetic resonance signal detected by the reception means In a magnetic resonance imaging apparatus having a signal processing means for performing image reconstruction calculation using a control means and a control means for controlling the operation of the entire apparatus,
The high frequency amplifier means includes
Amplifying means for amplifying the signal from the control means;
Difference calculating means for calculating a difference between the signal from the control means and the output signal of the amplifying means;
A comparison unit that compares the difference calculated by the difference calculation unit with a predetermined threshold, determines whether the difference is larger than the threshold, and outputs a signal indicating the difference;
When the output signal from the comparison means indicates that the difference is greater than the threshold, display means for displaying a warning,
A magnetic resonance imaging apparatus comprising: A static magnetic field generating means for applying a static magnetic field to the subject, a gradient magnetic field generating means for applying a gradient magnetic field, a high frequency transmitting means for irradiating a high frequency magnetic field for causing nuclear magnetic resonance to the subject, and emission from the subject Receiving means for detecting the detected nuclear magnetic resonance signal, signal processing means for performing image reconstruction calculation using the nuclear magnetic resonance signal detected by the receiving means, and control means for controlling the operation of the entire apparatus In the gradient magnetic field power supply device for driving the gradient magnetic field generating means of the magnetic resonance imaging apparatus,
Amplifying means for amplifying the signal from the control means;
Difference calculating means for calculating a difference between the signal from the control means and the output signal of the amplifying means;
A comparison unit that compares the difference calculated by the difference calculation unit with a predetermined threshold, determines whether the difference is larger than the threshold, and outputs a signal indicating the difference;
When the output signal from the comparison means indicates that the difference is greater than the threshold, display means for displaying a warning,
A gradient magnetic field power supply device comprising: A static magnetic field generating means for applying a static magnetic field to the subject, a gradient magnetic field generating means for applying a gradient magnetic field, a high frequency transmitting means for irradiating a high frequency magnetic field for causing nuclear magnetic resonance to the subject, and emission from the subject Receiving means for detecting the detected nuclear magnetic resonance signal, signal processing means for performing image reconstruction calculation using the nuclear magnetic resonance signal detected by the receiving means, and control means for controlling the operation of the entire apparatus In the high frequency amplifier device that drives the high frequency transmission means of the magnetic resonance imaging apparatus,
Amplifying means for amplifying the signal from the control means;
Difference calculating means for calculating a difference between the signal from the control means and the output signal of the amplifying means;
A comparison unit that compares the difference calculated by the difference calculation unit with a predetermined threshold, determines whether the difference is larger than the threshold, and outputs a signal indicating the difference;
When the output signal from the comparison means indicates that the difference is greater than the threshold, display means for displaying a warning,
A high frequency amplifier device comprising:

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