JPH11318849A - Magnetic resonance imaging system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always catch a concerned part as an image by automatically varying the position of the tomographic plane of fluoroscopic image pickup corresponding to the movement of an examinee in a magnetic resonance imaging(MRI) system. SOLUTION: The MRI imaging system generates a static magnetic field in a space where the examinee 10 is arranged, generates a tilting magnetic field to be added to this static magnetic field, generates the high frequency pulse magnetic field of a frequency corresponding to a slice position to examine of the examinee 10 to irradiate and detects an NMR signal generated from the slice position of the examinee 10 by this irradiation to give fluoroscopic image pickup to the optional tomographic plane of the examinee 10. The MRI system refers to a detecting signal from a means 9 detecting the movement of the examinee 10 and estimates the position of the tomographic plane of fluoroscopic image pickup to automatically vary. Thus, the position of the tomographic plane of fluoroscopic image pickup is automatically varied corresponding to the movement of the examinee 10 to always catch the concerned as the image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to nuclear magnetic resonance (NM)
R) The present invention relates to a magnetic resonance imaging apparatus for performing fluoroscopic imaging of an arbitrary tomographic plane of a subject using a phenomenon and displaying the image, and in particular, automatically changes a tomographic plane position of the fluoroscopic imaging in response to movement of the subject, and always changes a region of interest. The present invention relates to a magnetic resonance imaging apparatus capable of capturing an image as an image.

[0002]

2. Description of the Related Art A magnetic resonance imaging apparatus uses a nuclear magnetic resonance (NMR) phenomenon to measure a nuclear spin density distribution and a relaxation time distribution at a desired examination site in a subject, and obtains a target based on the measured data. This is to display an image of an arbitrary tomographic plane of the sample. A conventional magnetic resonance imaging apparatus is configured to generate a static magnetic field in a space in which a subject is arranged, to generate a gradient magnetic field applied to the static magnetic field, and to correspond to a slice position of the subject to be examined. Means for generating and irradiating a high-frequency pulsed magnetic field having a frequency, and means for detecting an NMR signal generated from the slice position of the subject by the irradiation, so that an arbitrary tomographic plane of the subject can be perspectively imaged. I was

[0003] In the fluoroscopic imaging of an arbitrary tomographic plane of a subject by the magnetic resonance imaging apparatus, a puncture position and an approach direction when an operator such as a doctor advances a puncture needle or a biopsy needle to a lesion of the subject are determined in real time. It is used for confirming the dynamics of a subject or performing a dynamic test of a joint of a subject. In this case, the setting of the imaging tomographic plane in the fluoroscopic imaging may be fixed during the fluoroscopic imaging, or may be changed by moving the object table by moving the object table by the operation device, or by changing the imaging tomographic plane itself by the operation device. It was changed by translation or rotation.

[0004]

However, in such a conventional magnetic resonance imaging apparatus, the setting of the imaging tomographic plane is fixed, or the subject is changed by moving the subject by moving the subject table. Alternatively, since the imaging tomographic plane itself is changed by moving or rotating the imaging tomographic plane itself, it is possible to follow the setting of the imaging tomographic plane with respect to small changes such as the respiratory movement of the subject and the movement of the joint. Did not. That is, when the surgeon advances the puncture needle or biopsy needle to the lesion of the subject, or when performing a dynamic test of the joint of the subject, the imaging tomographic plane may be used to determine the respiratory motion of the subject or the movement of the joint. It was not possible to automatically follow small changes. Therefore, the image of the site of interest may or may not be seen depending on the movement of the subject. For this reason, the imaging tomographic plane may be set again during the fluoroscopic imaging, so that smooth imaging cannot be performed, examination time is required, and the burden on the subject is increased.

Accordingly, the present invention has been made to address the above-described problems, and to automatically change the position of a tomographic plane in fluoroscopic imaging in accordance with the movement of a subject, thereby enabling a region of interest to be always captured as an image. It is intended to provide a device.

[0006]

In order to achieve the above object, a magnetic resonance imaging apparatus according to the present invention generates a static magnetic field in a space where a subject is arranged, and generates a gradient magnetic field applied to the static magnetic field. Generates and irradiates a high-frequency pulsed magnetic field having a frequency corresponding to the slice position of the subject to be inspected, and detects an NMR signal generated from the slice position of the subject by this irradiation to detect the NMR signal. In the magnetic resonance imaging apparatus for performing fluoroscopic imaging of an arbitrary tomographic plane, a tomographic plane position of fluoroscopic imaging is estimated and automatically changed by referring to a detection signal from the means for detecting the movement of the subject. .

[0007]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment of a magnetic resonance imaging apparatus according to the present invention. The magnetic resonance imaging apparatus measures a nuclear spin density distribution and a relaxation time distribution at a desired inspection site in a subject by utilizing an NMR phenomenon, and displays an image of an arbitrary tomographic plane of the subject from the measurement data. As shown in FIG. 1, a static magnetic field generating magnet 1, a gradient magnetic field generating system 2, a sequencer 3, a transmitting system 4, a receiving system 5, a signal processing system 6, a central processing unit (CPU) 7 and an operation unit 8, and further includes a motion detection unit 9.

The static magnetic field generating magnet 1 serves as a means for generating a uniform static magnetic field around the subject 10 in the body axis direction or in a direction orthogonal to the body axis in the space where the subject 10 is arranged. A static magnetic field generating means of a permanent magnet type, a normal conduction type, or a superconducting type is arranged in a certain space around the subject 10.

The gradient magnetic field generating system 2 serves as a means for generating a gradient magnetic field applied to the static magnetic field generated by the static magnetic field generating magnet 1, and includes a gradient magnetic field coil 11 in three axes of X, Y, and Z directions. , 11,... And a gradient magnetic field power supply 12 for driving these gradient magnetic field coils 11. Then, by driving the gradient magnetic field power supplies 12 of the respective gradient magnetic field coils 11 in accordance with a command from the sequencer 3 described later,
Gradient magnetic fields Gs (slice magnetic field in the slice direction), Gp (gradient magnetic field in the phase encode direction), and Gf in three axes of X, Y, and Z directions.
(Frequency-encoding direction gradient magnetic field) is applied to the subject 10. The slice position and the tomographic plane with respect to the subject 10 can be set by these methods of applying the gradient magnetic field.

The sequencer 3 repeatedly applies a high-frequency pulse and a gradient magnetic field for causing NMR to the nuclei of the atoms constituting the living tissue of the subject 10 in a predetermined pulse sequence, and obtains measurement data for a region of interest of the subject 10. And operates under the control of the CPU 7 to send various commands necessary for collecting tomographic image data of the subject 10 to the gradient magnetic field generation system 2 and the transmission system 4 and reception It is sent to system 5.

The transmitting system 4 has a frequency corresponding to a slice position to be examined of the subject 10 in order to cause the nuclei of the atoms constituting the living tissue of the subject 10 to undergo NMR by a high frequency pulse commanded from the sequencer 3. And a means for generating and irradiating a high-frequency pulsed magnetic field, and includes a high-frequency oscillator 13, a modulator 14, a high-frequency amplifier 15, and an irradiation coil 16. Then, the high-frequency pulse output from the high-frequency oscillator 13 is amplitude-modulated by the modulator 14 in accordance with a command of the sequencer 3, and the high-frequency pulse subjected to the amplitude modulation is amplified by the high-frequency amplifier 15, and then placed close to the subject 10. The electromagnetic wave is applied to the subject 10 by supplying the applied irradiation coil 16.

The receiving system 5 includes the irradiation coil 1 of the transmitting system 4.
Irradiation of a high-frequency pulsed magnetic field from
And a means for detecting an echo signal (NMR signal) generated by NMR of the nucleus of the living tissue from the slice position of the living tissue. Become. Then, an electromagnetic wave (NMR signal) of the response of the subject 10 due to the electromagnetic wave radiated from the irradiation coil 16 is detected by the receiving coil 17 disposed close to the subject 10, and the amplifier 18 and the quadrature phase detector 19 are detected. Through two series of collected data,
The digital signal is input to the A / D converter 20 and converted into a digital signal. The digital signal is sent to the signal processing system 6 described later.

The signal processing system 6 serves as a means for inputting and processing the digital signal from the receiving system 5 to display an image, and includes a CPU 7, a magnetic disk 21 and an optical disk 2.
2 and a display 23 such as a CRT. The CPU 7 performs processes such as Fourier transform, correction coefficient calculation, and image reconstruction, and performs necessary calculations on the measured data of the nuclear spin density distribution and relaxation time distribution on an arbitrary tomographic plane of the subject 10. The distribution data is imaged and displayed on the display 23 as a tomographic image.

The CPU 7 controls the operation of each of the above components. Further, the operation unit 8 is for inputting control information for processing performed by the signal processing system 6 and includes a keyboard 8, a mouse, a trackball, and the like as input devices.

With the above device configuration, the subject 10
Is performed by repeatedly performing processing such as measurement of an NMR signal from the slice position of the subject 10, image reconstruction, and image display in a short time.

Here, in the present invention, the subject 1
A motion detecting means 9 for detecting a motion of 0 is provided, and a detection signal from the motion detecting means 9 is inputted to the CPU 7 via an A / D converter 25. Then, the movement of the subject 10 is quantitatively detected by the movement detecting means 9, and the analog detection signal is converted into a digital signal by the A / D converter 25 and input to the CPU 7.
U 7 estimates the tomographic plane position of the fluoroscopic imaging of the subject 10 with reference to the input digital detection signal, and sends the control signal to the sequencer 3. The sequencer 3 controls the gradient magnetic field power supply 12 in accordance with the control signal from the CPU 7 as described above, and operates to automatically change the tomographic plane with respect to the subject 10.

FIG. 2 is an explanatory plan view showing a specific example of the motion detecting means 9. This example is used for performing a dynamic test of, for example, the neck of the subject 10, and a plate-shaped head support 27 on which a head is placed is placed on one end of a table 26 on which the subject 10 is placed. The rotation shaft 28 and the pulley 29 provided on the motion detecting means 9 are connected by a belt 30 so as to be rotatable as indicated by arrows A and B by 28. As the motion detecting means 9, for example, a potentiometer is used. It was what was. When the head support 27 rotates around the rotation shaft 28 as shown by arrows A and B, the rotation is transmitted to the pulley 29 via the belt 30, and the rotation of the pulley 29 causes the potentiometer to rotate. After being rotated, the rotation of the head support 27 is quantitatively detected by the potentiometer. In this case, since the head of the subject 10 is placed on the head support 27, the movement of the neck of the subject 10 can be quantitatively detected by the rotation of the head support 27.

FIG. 3 is an explanatory view showing the subject 10 laid on the table 26 shown in FIG. 2 and a tomographic plane for fluoroscopic imaging set on the neck thereof. At this time, the head 31 of the subject 10 is placed on the head support 27 shown in FIG.
In FIG. 3, first, when the head 31 of the subject 10 is tilted together with the head support 27 as shown by a solid line, the neck 32 also tilts in the same direction. The image is measured at this position, and the tomographic plane Ia at the position is set as indicated by the solid line. Next, when the head 31 is tilted together with the head support 27 as shown by the broken line, the neck 32 also tilts in the same direction. The image is measured at this position, and the tomographic plane Ib at the position is set as indicated by the broken line. At this time, when the tomographic planes Ia and Ib are set, detection signals from the potentiometers (9) corresponding to these positions are used as information on the movement of the subject 10 as A / D signals.
It is input to the CPU 7 via the converter 25.

FIG. 4 is an explanatory side view showing another specific example of the motion detecting means 9. This example is used for advancing a puncture needle or a biopsy needle to, for example, a lesion in the abdomen of the subject 10. For example, a respiratory motion sensor is used as the motion detection unit 9 for detecting the motion of the lesion 33 due to respiration of the subject 10. Is attached to the abdomen. This respiratory movement sensor is
The movement of the internal lesion 33 as shown by a solid line position and a broken line position by the breathing of 0 is equivalently detected by the movement of the solid line position a and the broken line position b on the upper surface of the abdomen. The movement of the positions a and b is detected by a change in pressure or a change in resistance of a member wound around the abdomen.

FIG. 5 shows the subject 10 and the lesion 3 on the abdomen.
It is a plane explanatory view showing the tomographic plane of the perspective imaging set to 3. 4 and 5, first, when the subject 10 is breathing, the lesion 33 is at the position indicated by the solid line. As shown in FIG. 5, the image is measured at this position and the tomographic plane Ia at this position is indicated by the solid line. Set as shown. Here, the fault plane I
a is a cross section including a puncture point 34 and a lesion 33 indicated by a solid line. Next, in a state where the subject 10 fully inhales, the lesioned part 33 is at a position indicated by a broken line, and as shown in FIG. 5, an image is measured at this position and the tomographic plane Ib at the position is indicated by a broken line. Set. Here, the tomographic plane Ib is a cross section including the puncture point 34 and the lesion 33 shown by a broken line. At this time, when the tomographic planes Ia and Ib are set, detection signals from the respiratory movement sensor (9) corresponding to these positions are sent to the CPU 7 via the A / D converter 25 as movement information of the subject 10. Is entered.

Next, the operation of estimating and automatically changing the tomographic plane position of the fluoroscopic imaging in the magnetic resonance imaging apparatus thus configured will be described with reference to FIGS. These figures show the subject 1 shown in FIGS.
For example, an operation example of performing a dynamic test of the neck, such as 0, is shown.

First, in FIG. 2, the head 31 of the subject 10 (not shown) placed on the table 26 is placed on the head support 27, and the head support 27 is moved to the position indicated by an arrow A in FIG.
Tilt in the direction. At this time, the neck 32 of the subject 10 is tilted to a position where it can bend in the direction of arrow A. Then, the image was measured at this position to obtain a scan positioning image IM ₁ as shown in Figure 6 (a). Also, it sets the fault plane fluoroscopic imaging of the neck 32 of the subject 10 from the captured positioning image IM ₁ above as Ia. In this state, the tomographic plane Ia is at an angle θ between the X and Y orthogonal coordinate axes with respect to the Y axis.
a and the distance La from the imaging center. Further, the magnitude of the detection signal from the motion detecting means 9 (see FIG. 2) corresponding to the position at this time is defined as Sa.

Next, in FIG. 2, the head support 27 on which the head 31 of the subject 10 (not shown) is placed is tilted, for example, in the direction of arrow B. At this time, the neck 32 of the subject 10 is tilted to a position where it can bend in the direction of arrow B. Then, the image was measured at this position to obtain a scan positioning image IM ₂ as shown in Figure 6 (b). In addition, the above-described imaging positioning image I
The fault plane fluoroscopic imaging of the neck 32 of the subject 10 from M ₂ is set as Ib. In this state, the tomographic plane Ib is at an angle θb between the X and Y orthogonal coordinate axes with respect to the Y axis.
And the distance Lb from the imaging center. further,
At this time, the magnitude of the detection signal from the motion detection means 9 (see FIG. 2) corresponding to the position is Sb.

The detection signals Sa,
Sb is supplied to the CPU 7 via the A / D converter 25 shown in FIG.
Is input to As a result, the CPU 7 uses the information Sa, Sb, θa, θb, La, and Lb described above to
As shown in FIG. 7A, a graph capable of linearly estimating the angle θ corresponding to the magnitude S of the detection signal from the motion detecting means 9 is created, and as shown in FIG.
Create a graph that can linearly estimate the distance L corresponding to.

Using such graphs, FIG. 2 and FIG.
The tomographic plane position at the time of performing fluoroscopic imaging while moving the neck 32 of the subject 10 as shown by arrows A and B is referred to the detection signal S from the motion detection means 9 as shown in FIG. The angle θ corresponding to the position on the graph of (a), (b)
By linearly estimating the distance L and the distance L, it can be estimated as defined by the angle θ and the distance L as in FIG.

Thereafter, the control signal of the tomographic plane position of the fluoroscopic imaging estimated in this way is sent to the sequencer 3 shown in FIG. The sequencer 3 controls the gradient magnetic field power supply 12 according to the control signal from the CPU 7 as described above, and automatically changes the tomographic plane with respect to the subject 10. This allows
The position of the tomographic plane in the fluoroscopic imaging is automatically changed in accordance with the movement of the subject 10, and the region of interest can always be captured as an image.

When the graphs of FIGS. 7A and 7B are created, if the number of information Sa and Sb is increased to create the graph, it is possible to estimate the position of the tomographic plane with higher accuracy.
In FIG. 6, the positioning of the tomographic plane is defined as (a),
Although the measurement was performed using the two cross sections of (b), application to a three-dimensional image is also possible by using another cross section orthogonal to these two cross sections.

FIGS. 6 and 7 show an example of the operation of the subject 10 shown in FIGS. 2 and 3 when, for example, a dynamic test of the neck is performed. In the operation example of advancing a puncture needle or a biopsy needle to a diseased part of the abdomen, for example, an imaging positioning image is obtained in the same manner as described above, and an angle, What is necessary is just to create a graph that can linearly estimate the distance and the like.

[0029]

The present invention has been configured as described above.
With reference to the detection signal from the means for detecting the movement of the subject,
By automatically changing the position of the tomographic plane in fluoroscopic imaging by estimating the position, for example, when the operator advances a puncture needle or a biopsy needle to the lesion of the subject, or performs a dynamic test of the joint of the subject In this case, the imaging tomographic plane can automatically follow small changes such as the respiratory movement of the subject and the movement of the joint, and the tomographic plane position of the fluoroscopic imaging can be automatically adjusted in accordance with the movement of the subject. , And the region of interest can always be captured as an image. Therefore, the imaging tomographic plane is not reset during the fluoroscopic imaging as in the related art, so that the imaging can be performed smoothly, the examination time can be reduced, and the burden on the subject can be reduced.

[Brief description of the drawings]

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

FIG. 2 is an explanatory plan view showing a specific example of a motion detection unit.

FIG. 3 is an explanatory diagram showing a subject lying on a table and a tomographic plane for fluoroscopic imaging set on the neck of the subject.

FIG. 4 is an explanatory side view showing another specific example of the motion detecting means.

FIG. 5 is an explanatory plan view showing a subject and a tomographic plane for fluoroscopic imaging set on a lesion of the abdomen;

FIG. 6 is a view for explaining an operation of estimating a tomographic plane position of the fluoroscopic imaging and automatically changing the tomographic plane position, and shows a state in which an imaging positioning image is obtained.

FIG. 7 illustrates a state in which a graph that can linearly estimate an angle or a distance corresponding to the magnitude of a detection signal from a motion detection unit is created.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Static magnetic field generation magnet 2 ... Gradient magnetic field generation system 3 ... Sequencer 4 ... Transmission system 5 ... Reception system 6 ... Signal processing system 7 ... CPU 8 ... Operation part 9 ... Motion detection means 10 ... Subject 25 ... A / D conversion vessel 31 ... head 32 ... neck 33 ... lesion 34 ... puncture point Ia, Ib ... tomographic plane IM _1, IM ₂ ... scan positioning image

Claims (1)

[Claims] 1. A static magnetic field is generated in a space in which a subject is arranged, and a gradient magnetic field to be applied to the static magnetic field is generated, and a high-frequency pulsed magnetic field having a frequency corresponding to a slice position of the subject to be examined is generated. The magnetic resonance imaging apparatus generates and irradiates, irradiates, and detects the NMR signal generated from the slice position of the subject by this irradiation, and detects the movement of the subject in a magnetic resonance imaging apparatus for performing fluoroscopic imaging of an arbitrary tomographic plane of the subject. A magnetic resonance imaging apparatus characterized in that a position of a tomographic plane in fluoroscopic imaging is estimated and automatically changed by referring to a detection signal from the means.