JP2003010149A - Magnetic resonance imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic resonance imaging device capable of adjusting a slice position by an operator himself. SOLUTION: A display means 182 for displaying a tomographic image of a medical operation part, and an operation means 192 for allowing changing operation of the slice position of the tomographic image in imaging are arranged in the vicinity of an imaging space for performing magnetic resonance imaging parallel to medical operation by the operator 300 on an object 1 housed in the imaging space.

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 magnetic resonance imaging apparatus for performing magnetic resonance imaging on an object housed in an imaging space in parallel with an operation by an operator.

[0002]

2. Description of the Related Art Magnetic resonance imaging (MRI: Magneti)
c Resonance Imaging)
An object to be imaged is carried into an internal space of a magnet system, that is, an imaging space in which a static magnetic field is formed, and a gradient magnetic field and a high frequency magnetic field are applied to generate magnetic resonance signals from spins in the object. , Reconstruct an image based on the received signal.

A livestock (biopsy) about an object
When performing psy), magnetic resonance imaging is performed in parallel with that, and the operator performs a puncture while observing the state of entry of the living needle into the body on the displayed tomographic image.

[0004]

[Problems to be Solved by the Invention] When the puncture direction of the sausage needle does not exactly coincide with the slice direction of imaging, or when the sausage needle gradually bends as the needle enters, the needle tip May deviate from the slice thickness range. In that case, the image of the needle tip portion cannot be seen in the tomographic image, and the arrival position of the puncture cannot be known.

In such a case, the operator operating the magnetic resonance imaging apparatus in the operation room is instructed to adjust the slice position until the image of the needle tip becomes visible. It is not always easy to make smooth adjustments because it is a joint work of the operators.

Therefore, an object of the present invention is to realize a magnetic resonance imaging apparatus in which the operator can adjust the slice position himself.

[0007]

SUMMARY OF THE INVENTION The present invention for solving the above problems is a magnetic resonance imaging apparatus capable of performing magnetic resonance imaging on an object housed in an imaging space in parallel with an operation by an operator. A display means installed near the imaging space for displaying a tomographic image of a region being operated on by the operator, and a tomographic image being installed by the operator near the imaging space and being imaged by the operator. A magnetic resonance imaging apparatus comprising: an operation unit that enables an operation of changing a slice position of an image.

According to the present invention, since the operation means for changing the slice position of the tomographic image being photographed is provided near the photographing space, the operator can adjust the slice position himself.

It is preferable that the operating means is capable of parallel movement of the slice plane in order to track the lateral displacement of the needle tip. It is preferable that the operation means be capable of rotating the slice plane in order to tilt the slice according to the needle.

It is preferable that the operating means be capable of parallel movement and rotation of the slice plane in order to track the lateral displacement of the needle tip and to tilt the slice according to the needle. The operating means enables position-type operation,
This is preferable because the correspondence between the manipulated variable and the slice displacement is clear.

It is preferable that the operation means is capable of speed-type operation because the operation is easy. It is preferable that the operating means has a slider for manual operation in terms of intuitive operation.

It is preferable that the slider automatically returns to a predetermined position because the operation start position becomes constant.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiment. FIG. 1 shows a block diagram of the magnetic resonance imaging apparatus. This device is an example of an embodiment of the present invention. The configuration of this device shows an example of an embodiment relating to the device of the present invention.

As shown in the figure, the apparatus has a magnet system 100. The magnet system 100 includes a pair of main magnetic field coil units 102, a pair of gradient coil units 106, and an RF (radio frequency) coil unit 1.
08. Each of these coil portions has a substantially cylindrical shape and is arranged coaxially with each other.

The main magnetic field coil section 102 and the gradient coil section 106 are paired and are opposed to each other with a predetermined distance in the axial direction. A space is formed between the facing pairs. The center C of this space is the center of the magnet system 100, that is, the magnet center.
er). A three-dimensional area having a predetermined radius centered on the magnet center C is the imaging space. This shooting space is a space open to the outside.

In the shooting space of the magnet system 100,
The object 1 to be imaged is mounted on a cradle 500 and is carried in and out by a carrying unit (not shown). The imaging region (for example, abdomen) of the target 1 is the RF coil unit 1.
It is housed in 08.

The main magnetic field coil section 102 forms a static magnetic field in the imaging space. The direction of the static magnetic field is substantially parallel to the direction of the body axis of the target 1. That is, a so-called horizontal magnetic field is formed. The main magnetic field coil unit 102 is composed of, for example, a superconducting coil. Needless to say, a normal conductive coil or the like may be used instead of the superconductive coil.

The gradient coil section 106 produces three gradient magnetic fields for imparting gradients to the static magnetic field strength in the directions of three mutually perpendicular axes, ie, the slice axis, the phase axis and the frequency axis.

When the mutually perpendicular coordinate axes in the static magnetic field space are x, y, and z, any axis can be a slice axis. In that case, one of the remaining two axes is the phase axis and the other is the frequency axis. Further, the slice axis, the phase axis, and the frequency axis can be made to have arbitrary inclinations with respect to the x, y, and z axes while maintaining the verticality among them. In this apparatus, the direction of the body axis of the target 1 is the z-axis direction.

The gradient magnetic field in the slice axis direction is also called a slice gradient magnetic field. The gradient magnetic field in the phase axis direction is also referred to as a phase encode gradient magnetic field. Read out the gradient magnetic field in the frequency axis direction.
t) Also called a gradient magnetic field. In order to enable the generation of such a gradient magnetic field, the gradient coil unit 106 has three systems of gradient coils (not shown). Hereinafter, the gradient magnetic field is also simply referred to as a gradient.

The RF coil unit 108 is used for the object 1 in the static magnetic field space.
A high-frequency magnetic field is generated to excite spins in the human body. In the following, RF is used to form a high frequency magnetic field.
It is also called the transmission of an excitation signal. The RF excitation signal is also called an RF pulse. The RF coil unit 108 also receives an electromagnetic wave generated by the excited spin, that is, a magnetic resonance signal.

The gradient coil unit 106 includes a gradient drive unit 130.
Are connected. The gradient driving unit 130 is the gradient coil unit 1.
A drive signal is given to 06 to generate a gradient magnetic field. The gradient drive unit 130 has three-system drive circuits (not shown) corresponding to the three-system gradient coils in the gradient coil unit 106.

The RF coil unit 108 includes an RF drive unit 140.
Are connected. The RF driving unit 140 is the RF coil unit 1.
A drive signal is given to 08 to transmit an RF pulse to excite spins in the body of the subject 1.

The RF coil unit 108 stores data (dat
a) The collecting unit 150 is connected. Data collection unit 15
0 captures the reception signal received by the RF coil unit 108 by sampling and collects it as digital data.

A control unit 160 is connected to the gradient driving unit 130, the RF driving unit 140 and the data collecting unit 150. The controller 160 controls the gradient driver 130 and the data collector 150 to perform imaging.

The control unit 160 is, for example, a computer (c
computer) and the like. Control unit 160
Has a memory (not shown). The memory stores a program for the control unit 160 and various data. The function of the control unit 160 is realized by the computer executing the program stored in the memory.

The output side of the data collecting section 150 is connected to the data processing section 170. The data collected by the data collection unit 150 is input to the data processing unit 170. The data processing unit 170 is configured using, for example, a computer or the like. The data processing unit 170 has a memory (not shown). The memory stores programs for the data processing unit 170 and various data.

The data processing section 170 is connected to the control section 160. The data processing unit 170 is above the control unit 160 and controls it. The function of this apparatus is realized by the data processing unit 170 executing a program stored in the memory.

The data processing section 170 includes a data collection section 15
0 stores the collected data in memory. A data space is formed in the memory. This data space constitutes a two-dimensional Fourier space. Hereinafter, the Fourier space is also referred to as k-space. The data processing unit 170 performs a two-dimensional inverse flow on the k-space data.
The tomographic image of the target 1 is reconstructed by Rie conversion.

A display unit 180 and an operation unit 190 are connected to the data processing unit 170. The display unit 180 includes a graphic display.
ay) and the like. The operation unit 190 includes a keyboard having a pointing device and the like.

The display section 180 displays the reconstructed image and various information output from the data processing section 170. The operation unit 190 is operated by the user and inputs various commands and information to the data processing unit 170. A user interactively operates the apparatus through the display unit 180 and the operation unit 190.

The data processing section 170 also includes a display section 1.
82 and the operation unit 192 are connected. Display 18
2 and the operation unit 192 are provided as an accessory to the magnet system 100. The display unit 182 includes a graphic display or the like. Display unit 182
Displays the reconstructed image output from the data processing unit 170. The operation unit 192 includes an operation tool for adjusting the slice position for imaging. The display unit 182 is an example of an embodiment of the display unit in the present invention. Operation unit 19
2 is an example of an embodiment of the operating means in the present invention.

2 and 3, the magnet system 1 is shown.
00, the display unit 182, and the operation unit 192 are schematically shown. FIG. 2 is a side view, and FIG. 3 is A- regarding FIG.
FIG.

As shown in the figure, the magnet system 1
00 has a front structure 202 and a rear structure 204.
The front structure 202 and the rear structure 204 include one of the pair of main magnetic field coil units 102 and the pair of gradient coil units 10.
6 and one of the pair of main magnetic field coil sections 102 and the other of the pair of gradient coil sections 106 are respectively incorporated.

The front structure 202 and the rear structure 204 are
The upper portion is connected by a bridge 206, and the lower portion is integrated by a table 208. Cradle 5 on top of table 208
00, and the target 1 is mounted on it. Target 1
An RF coil unit 108 is attached to the.

The display unit 182 is attached to the bridge 206. As the display unit 182, for example, LCD (Li
Quid Crystal Display) or the like is used. The operation unit 192 includes a front structure 202 and a rear structure 2.
Between 04, the operation surface is attached to the upper part of the side surface of the table 208 such that the operation surface is substantially horizontal.

FIG. 4 shows an example of the arrangement of operation tools on such an operation surface. As shown in the figure, a slider 902 is provided as an operation tool. The slider 902 can be linearly displaced along the groove 912. The slider 902 is for moving the slice position in parallel in the slice axis direction. The slider 902 is an example of the embodiment of the slider in the present invention.

By moving slider 902 to the right or left from the neutral position, the slice can be moved, for example, right or left, respectively. The slice displacement amount is proportional to the displacement amount of the slider 902. That is, position-type slice adjustment can be performed. The position-type slice adjustment is preferable because the correspondence between the operation amount and the slice movement amount becomes clear and the intuition is good.

The slider 902 may return to the neutral position when the operator releases the hand. In that case, the slice position may remain at the same position regardless of the return of the slider 902, or
You may make it return to the original position with 2. Such a slider is preferable because the starting point of the operation is always constant.

The slice adjustment is not limited to the position type but may be performed by the velocity type. In that case, the operation tool is replaced by a slider, for example, a stick. When the stick is tilted right or left from the neutral position, the slice position moves toward the right or left only during that time, and the integrated value during that time becomes the slice movement amount. A speed type operation tool is preferable because it is easy to operate.

Two additional knobs (kno
b) 922 and 924 are provided. Knobs 922, 9
Reference numeral 24 represents the slice along the vertical axis (V: vertical) and the horizontal axis (H: horizontal) in the slice plane.
It is for rotating about the center.

By turning knobs 922 or 924 clockwise or counterclockwise from the neutral position, the slice can be rotated, eg clockwise or counterclockwise, respectively. The amount of rotation of the slice is proportional to the amount of rotation of the knob 922 or 924. That is, position-type slice adjustment can be performed.

Knobs 922 or 924 may be such that they return to the neutral position when the operator releases their hand. In that case, the slice position may remain in the same position regardless of the return of the knob 922 or 924, or may return to the original position together with the knob 922 or 924. Of course, the knobs 922 and 924 may also be speed type.

As described above, the means for moving the slice in parallel and the means for rotating the slice do not necessarily have to have both, and only one of them may be provided. Moreover, you may make it provide the operation tool which makes a slice surface the slice direction as needed.

Slider 902 and knobs 922, 924
The operation amount of is input to the data processing unit 170. The data processing section 170 gives a slice position change signal to the control section 160 based on this input signal. The control unit 160 controls the gradient drive unit 130 and the RF drive unit 140 based on the slice position change signal, and performs imaging for the slice designated by the operator.

The photographing operation of this apparatus will be described. FIG. 5 shows an example of a pulse sequence for acquiring a magnetic resonance signal executed by the present apparatus. This pulse sequence is a spin echo.
This is a pulse sequence for acquiring o), that is, a pulse sequence by the spin echo method.

(1) in the figure is an RF pulse, that is, 90 °
A sequence of pulses and 180 ° pulses,
(2), (3), (4) and (5) are sequences of the slice gradient Gs, the phase encode gradient Gp, the readout gradient Gr and the spin echo MR, respectively. The 90 ° pulse and the 180 ° pulse are represented by the central value. The pulse sequence progresses from left to right along the time axis t.

As shown in the figure, 90 ° pulse and 1
The 80 ° pulse provides 90 ° and 180 ° excitation of the spins, respectively. 90 ° excitation and 180 °
Upon excitation, slice gradients Gs1 and Gs3, respectively
Is applied and selective excitation is performed for a predetermined slice.

Between the 90 ° excitation and the 180 ° excitation, phase encoding in the phase axis direction by the phase encoding gradient Gp and dephasing in the frequency axis direction by the readout gradient Gr1 are performed.

After 180 ° excitation, the readout gradient Gr2
A spin echo MR is generated by the rephasing by the. The spin echo MR is an RF signal having a symmetrical waveform with respect to the echo center. The echo center occurs TE (echo time) after 90 ° excitation. The spin echo MR is collected by the data collection unit 150 as view data.

Such a pulse sequence has a period TR.
For example, 64 to 2 in (repetition time)
Repeated 56 times. The phase encode gradient Gp in the phase axis direction is changed each time it is repeated. The broken line conceptually represents the sequential change of the phase encode gradient Gp. by this,
View data of 64-256 views having different phase encoding in the phase axis direction can be obtained. The view data obtained in this way is collected in the k space of the memory of the data processing unit 170.

By performing the two-dimensional inverse Fourier transform on the k-space data, the two-dimensional image data in the real space, that is, the reconstructed image is obtained. This image is displayed on the display unit 180
Is displayed.

FIG. 6 shows another example of the pulse sequence for magnetic resonance signal acquisition executed by this apparatus. This pulse sequence has a gradient echo.
Echo) is a pulse sequence for obtaining an echo, that is, a pulse sequence by a gradient echo method.

(1) is a sequence of RF pulses, that is, 90 ° pulses, and (2), (3), (4) and (5) are slice gradient Gs, phase encode gradient Gp and readout, respectively. It is a sequence of gradient Gr and gradient echo MR. The 90 ° pulse is represented by the center value. The pulse sequence progresses from left to right along the time axis t.

As shown in the figure, 90 ° excitation of spin is performed by a 90 ° pulse. A slice gradient Gs1 is applied at the time of 90 ° excitation, and selective excitation is performed for a predetermined slice. After the 90 ° excitation, phase encoding in the phase axis direction is performed by the phase encoding gradient Gp.

After that, dephasing in the frequency axis direction is performed by the readout gradient Gr1, and then gradient echo MR is generated by rephasing by the readout gradient Gr2 that is performed next.

The gradient echo MR is an RF signal having a symmetrical waveform with respect to the echo center. The echo center occurs TE after 90 ° excitation. The gradient echo MR is collected by the data collection unit 150 as view data.

Such a pulse sequence has a period TR.
Is repeated 64 to 256 times, for example. The phase encode gradient Gp in the phase axis direction is changed each time it is repeated. The broken line conceptually represents the sequential change of the phase encode gradient Gp. As a result, view data of 64-256 views having different phase encoding in the phase axis direction can be obtained. The view data thus obtained is used as the data processing unit 17
Collected in k-space of 0 memory.

By performing the two-dimensional inverse Fourier transform on the k-space data, the two-dimensional image data in the real space, that is, the reconstructed image is obtained. This image is displayed on the display unit 180
Is displayed.

The photographing is not limited to the spin echo method or the gradient echo method, but the fast spin echo (Fas
t Spin Echo) method and echo planer (Ech)
Other suitable techniques such as the oPlanar method may be used.

When the subject 1 is to be lived in parallel with the radiography, the operator 300 puts himself in the space between the front structure 202 and the rear structure 204 to perform puncture, as shown in FIG. R
The F coil portion 108 is appropriately provided with an opening for puncturing, and puncturing is performed through the opening. The operator 300 advances the puncture while confirming the positions of the affected part and the needle 400 in the body of the target 1 by the image displayed on the display unit 182.

FIG. 8 shows an image displayed on the display unit 182 during the puncture together with the position of the slider 902 on the operation unit 192. As shown in (a) of FIG.
Displays a tomographic image 12 being taken. The tomographic image 12 includes the affected part image 14 and the image 400 ′ of the needle being punctured toward the affected part image 14. Since the needle 400 does not generate a magnetic resonance signal, its image is a black straight line. The tip of the straight line corresponds to the needle tip.

When the puncturing direction does not exactly coincide with the slice direction, or when the needle 400 gradually bends during the puncturing process, the needle tip may deviate from the slice thickness range. Then, the needle 400 is not drawn in the deviated portion, and the position of the needle tip does not change on the screen even if the needle is pushed forward.

In such a case, for example, as shown in (b) of the figure, the slider 902 is operated to move the slice position laterally in parallel. With this, the needle image 4 showing the tip portion
00 'can be visually recognized.

When the needle is advanced in this state and the movement of the needle tip is stopped again, the slice position is further shifted laterally by the slider 902 to reach the affected area as shown in FIG. You can check the needle point that is present.
In this way, it is possible to track the needle tip that is laterally displaced.

Knobs 922, 9 instead of slider 902
By operating 24, the inclination of the slice can be adjusted according to the inclination of the needle. This is convenient for imaging the needle 400 over its entire length.

[0067]

As described in detail above, according to the present invention, it is possible to realize a magnetic resonance imaging apparatus capable of adjusting the slice position by the operator himself.

[Brief description of drawings]

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

FIG. 2 is a schematic diagram showing the configuration of a magnet system.

FIG. 3 is a schematic diagram showing the configuration of a magnet system.

FIG. 4 is a schematic view showing an example of arrangement of operating tools.

FIG. 5 is a diagram showing an example of a pulse sequence for magnetic resonance imaging.

FIG. 6 is a diagram showing an example of a pulse sequence for magnetic resonance imaging.

FIG. 7 is a schematic view showing a state during puncturing.

FIG. 8 is a schematic diagram showing a slice position adjustment situation.

[Explanation of symbols]

100 magnet system 102 main magnetic field coil section 106 gradient coil section 108 RF coil section 130 Gradient drive 140 RF driver 150 Data Collection Department 160 control unit 170 Data processing unit 180,182 Display 190,192 Operation section 1 target 500 cradle 202 front structure 204 rear structure 206 bridge 208 table 902 slider 922, 924 knob

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tetsuji Tsukamoto             127, 4-7 Asahigaoka, Hino City, Tokyo             GE Yokogawa Medical System Co., Ltd.             Within F-term (reference) 4C096 AA01 AA20 AB36 AD07 AD15                       AD22 BB12 BB21 DD02 DD08

Claims (8)

[Claims] 1. A magnetic resonance imaging apparatus capable of performing magnetic resonance imaging on an object housed in an imaging space in parallel with an operation performed by an operator, the apparatus being installed in the vicinity of the imaging space and provided to the operator. On the other hand, a display unit for displaying a tomographic image of a site being treated, and an operating unit installed near the imaging space for enabling the operator to change the slice position of the tomographic image being imaged. A magnetic resonance imaging apparatus comprising: 2. The magnetic resonance imaging apparatus according to claim 1, wherein the operating unit enables parallel movement of a slice plane. 3. The magnetic resonance imaging apparatus according to claim 1, wherein the operating unit enables rotation of the slice plane. 4. The magnetic resonance imaging apparatus according to claim 1, wherein the operating unit enables parallel movement and rotation of the slice plane. 5. The magnetic resonance imaging apparatus according to claim 2, wherein the operation unit enables position-type operation. 6. The magnetic resonance imaging apparatus according to claim 2, wherein the operation unit enables a speed type operation. 7. The magnetic resonance imaging apparatus according to claim 2, wherein the operating unit has a slider for manual operation. 8. The magnetic resonance imaging apparatus according to claim 7, wherein the slider automatically returns to a predetermined position.