JPH0994234A - Mri apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an MRI apparatus to allow the working space for an operator to be widened and to enable all sorts of endoscopic operations to be applied by forming local static magnetic field. SOLUTION: This MRI apparatus comprises magnets 1a and 1b for forming static magnetic field and obtains a magnetic resonance image of a living body S by giving high-frequency magnetic field of a given frequency to the living body S laid in the magnetic field generated by the magnets 1a and 1b and by receiving magnetic resonance signal from the body of a subject, and also comprises a means 3, 4, 5, 6, 7 and 8 for moving the position and the direction of at least one of magnets 1a and 1b, so as to form a local static magnetic field at a desired site of the living body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an MRI apparatus for receiving a magnetic resonance signal in the body to obtain a magnetic resonance image (MR image) in the body of a patient.

[0002]

2. Description of the Related Art An endoscope is inserted into the body of the esophagus, large intestine, stomach or the like for observation or treatment, or percutaneous insertion of the endoscope into the abdominal cavity or thoracic cavity for surgical operation. Is widely practiced. This has made it possible to perform observation, treatment, surgery, etc. with minimally invasiveness.

On the other hand, a minimally invasive method for diagnosing a human body utilizing a nuclear magnetic resonance (hereinafter referred to as MR) phenomenon has been developed.
The MR phenomenon refers to a phenomenon in which a certain atomic nucleus resonates and absorbs electromagnetic wave energy of a specific wavelength in a magnetic field, and then emits this as an electromagnetic wave. In an MR imaging (hereinafter referred to as MRI) apparatus using this MR phenomenon, The human body is placed in a static magnetic field, a high-frequency magnetic field of a predetermined frequency is applied to the human body to excite nuclei with spin in the human body, and the MR signal of a predetermined frequency generated while the excited nucleus returns to its original state is detected. Then, it is processed by a computer to obtain a tomographic image of the human body.

Generally, such an MRI apparatus applies a single cylindrical magnet for covering almost the entire human body to generate a uniform static magnetic field, and a high-frequency magnetic field of a predetermined frequency for the human body placed in the static magnetic field. An RF coil for giving, an MR signal detecting coil for detecting an MR signal of a predetermined frequency emitted from an excited nucleus having a spin in the human body, and a control for processing a detection signal from the MR signal detecting coil to obtain a tomographic image of the human body Mainly composed of departments.

Recently, in order to reduce the burden on patients such as phobia of closure, an open type in which the above-mentioned single cylindrical magnet (closed type) that covers almost the entire human body is divided into two parts has become widespread. ing. This open type allows the doctor to directly approach the patient through the gap (space) between the two divided magnets, so that simultaneous treatment can be performed while observing the MR tomographic image in real time.

[0006]

With the widespread use of the open type MRI apparatus capable of performing treatment through the gap (space) between the magnets as described above, a minimally invasive endoscopic treatment (surgery) and an MRI apparatus have been developed. The combination of has come to be noticed. That is, an attempt has been made to perform endoscopic treatment (surgery) on a patient from between the divided magnets of the MRI apparatus. Further, not only endoscopic surgery but also various treatments have been attempted in combination with an MRI apparatus (US Pat. No. 5,368,032).

By the way, the image obtained by the endoscope is a real image, and therefore the back side of the observation target portion of the endoscope cannot be seen by the endoscope. On the other hand, the image obtained by the MRI apparatus is a cross-sectional image, and the surface of the target tissue or the like cannot be observed.
Therefore, it goes without saying that if the endoscopic treatment (surgery) and the MRI apparatus are combined, the advantages of both can be fully utilized while compensating for the disadvantages of each other. For example,
When incising an affected tissue, information on the running state of blood vessels on the back side (inside) of the tissue cannot be obtained by observation with an endoscope, but can be obtained by a tomographic image of an MRI apparatus. On the other hand, the condition of the surface of the affected tissue to be incised can be observed only by the endoscope. Therefore, an endoscopic treatment (surgery) is performed by simultaneously performing observation with an endoscope while obtaining a tomographic image with the MRI apparatus.
If you can do this, you will have a wide range of treatments and you can safely perform surgery.

Although the endoscopic image is a two-dimensional image, M
The RI apparatus can obtain a stereoscopic image by taking many sectional images. Two-dimensional image of such an endoscope and MR
The operator can stereoscopically image the treatment target site while observing the endoscopic image and the MR tomographic image by combining the three-dimensional image of 3).

In addition, the MRI apparatus can easily obtain an image of a portion of the brain, nasal cavity, joints, etc. that is difficult to see with the naked eye or an endoscope, and can display an image in consideration of changes in temperature. It is also effective in treatments such as cauterization. Therefore, there is no doubt that the safety and efficiency of surgery will be dramatically improved if endoscopic surgery is performed by effectively utilizing the advantages of the MRI apparatus.

However, the magnet for generating the static magnetic field in the conventional MRI apparatus is large in size and the distance between the magnets is fixed because importance is attached to the uniformity and stability of the static magnetic field. Moreover, the gap between the magnets is only large enough for one operator to insert. Therefore, the working space for the surgeons is limited, and the number of surgeons is limited due to the problem of the installation space. Further, due to such restrictions, the types of endoscopic surgery that can be simultaneously performed while obtaining a tomographic image by the MRI apparatus are also limited.

When performing surgery, particularly endoscopic treatment or surgery, it is sufficient to obtain a tomographic image of only a necessary portion. Of course, even in the conventional MRI apparatus, a tomographic image of only a necessary portion can be obtained, but from the viewpoint of securing a large working space, the magnet is large enough to generate a static magnetic field only in the observation target portion. The size is enough, and the size that limits the working space and the number of operators is not necessary. That is, when performing endoscopic surgery at the same time while obtaining a tomographic image by the MRI apparatus, the conventional open type MRI apparatus is too large.

The present invention has been made in view of the above circumstances, and an object thereof is to ensure a wide working space for an operator and locally generate a static magnetic field to perform any endoscopic surgery. It is to provide an MRI apparatus applicable to the.

[0013]

In order to solve the above problems, the present invention comprises a magnet for generating a static magnetic field,
In an MRI apparatus that applies a high-frequency magnetic field of a predetermined frequency to a living body placed in a static magnetic field generated by these magnets and receives a magnetic resonance signal in the body emitted at that time to obtain a magnetic resonance image in the body A drive means for changing at least one of the position and the direction of the magnet is provided so that a local static magnetic field can be formed at a desired portion of the living body.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. 1 and 2 show a first embodiment of the present invention. As shown in FIG.
The MRI apparatus of this embodiment is of a portable type that can be independently and easily moved, and is provided with a counter-pole static magnetic field generating magnet 1 including a pair of facing magnets 1a and 1b. The static magnetic field generating magnet 1 is composed of a permanent magnet (a superconducting magnet or a normal conducting magnet may be used), and an RF for applying a high frequency magnetic field of a predetermined frequency to the human body S placed in the static magnetic field. Coil (hereinafter,
It is called an RF transmission coil. ), And M for detecting an MR signal of a predetermined frequency emitted by an excited nucleus having a spin in the human body.
R signal detection coil (hereinafter referred to as RF reception coil)
And a gradient magnetic field generating coil for generating a minute gradient magnetic field for imparting spatial information to the MR signal.
It is provided inside the casings a and 1b.

As shown, the magnets 1a and 1b are
It is formed as a small one, preferably a small one, which can generate a local static magnetic field only to a predetermined site of the patient S lying on the operating table 2, and its position and direction, and mutual The separation distance can be changed.

The drive mechanism for driving the magnets 1a, 1b includes magnet gap changing parts 3, 4 for changing the gap between the magnets 1a, 1b, and the magnet 1.
Slide drive unit 6 for changing the directions of the opposing shafts a and 1b
And a horizontal support beam 7 for horizontally moving the magnets 1a, 1b, and a vertical moving portion 8 for vertically moving the magnets 1a, 1b.

The magnet gap varying portions 3 and 4 are adapted to move the magnets 1a and 1b forward and backward along their opposing axes to change the distance between the magnets 1a and 1b. These gap changing parts 3 and 4 are provided at both ends of a support beam 5 which is a C-shaped arm member.

The support beam 5 is movably supported by the slide drive unit 6. The slide driving unit 6 can slide the support beam 5 in an arc shape as indicated by an arrow in the figure, and can fix the support beam 5 at a predetermined slide position. When the support beam 5 is slid by the slide driving unit 6, the magnets 1a and 1b rotate around the midpoint on the facing axis between the magnets 1a and 1b while maintaining the facing state.

The slide drive unit 6 is provided on the horizontal support beam 7 and is slidable in the longitudinal direction of the horizontal support beam 7 by a linear moving means (not shown) built in the horizontal support beam 7. Further, the horizontal support beam 7 is connected to a vertical moving portion 8 capable of moving and fixing the horizontal support beam 7 in the vertical direction.

Further, as shown in FIG. 2, the MRI apparatus of this embodiment is equipped with a control system for performing MR signal processing and overall control. This control system is connected to an RF transmitting coil provided in the static magnetic field generating magnet 1 and an RF transmitter 16 for forming a high frequency magnetic field of a predetermined frequency, and an RF receiving coil provided in the static magnetic field generating magnet 1. And an RF receiver 15 connected to the RF receiver coil for receiving the MR signal detected by the RF receiving coil, and a tuning connected to the RF receiver 15 and the RF transmitter 16 and adjusting the transmission / reception band of these devices 15, 16. The circuit 13, the gradient magnetic field amplifier 17 connected to the gradient magnetic field generating coil provided in the static magnetic field generating magnet 1, the control circuit 14 for controlling the gradient magnetic field amplifier 17 to adjust the gradient magnetic field strength, the magnet 1a,
A magnet movement control circuit 18 that controls the drive of the gap varying units 3 and 4 that changes the gap of 1b, an arm control circuit 19 that controls the operation of the drive mechanism excluding the gap varying units 3 and 4, and an overall control of the control system. CPU 10 to
A console 11 as an operating means and a sequencer 12 are provided. A console 11, a sequencer 12, control circuits 14, 18, 19 and a tuning circuit 13 are respectively connected to the CPU 10, and an RF transmitter 16 and a gradient magnetic field amplifier 17 are connected to the sequencer 12.

Next, the operation of the MRI apparatus having the above configuration will be described. When performing endoscopic surgery at the same time while obtaining a tomographic image of the affected area using the MRI apparatus of the present embodiment, first, the magnet 1a is attached to the affected area of the patient to be diagnosed and treated.
Move 1b. For this, the operator inputs predetermined operation information through the console 11. Based on this operation information, the drive units 5, 6, 7, and 8 of the drive mechanism are driven via the CPU 10 and the arm control circuit 19, and the magnet 1
The a and 1b move to the affected area, and the affected area is located between the magnets 1a and 1b. As a result, a predetermined static magnetic field locally acts on the affected area.

When the affected area is located between the magnets 1a and 1b, the gap between the magnets 1a and 1b is adjusted this time. This means that it may be necessary to widen the MR tomographic image depending on the region to be treated, and conversely, for example, in a region such as the knee, the magnets 1a and 1b should be brought into contact with the region. This is because there is a case in which the MR tomographic image corresponding to the treatment target site needs to be obtained.

In this gap adjusting operation, the operator inputs, for example, a target gap through the console 11.
Based on this input information, the gap varying units 3 and 4 are driven via the CPU 10 and the magnet movement control unit 18,
The distance between the magnets 1a and 1b is set to a predetermined interval.

When the distance between the magnets 1a and 1b is changed in this way, the static magnetic field strength also changes according to the distance. This also changes the magnetic resonance frequency,
It becomes necessary to perform RF transmission / reception according to the changing magnetic resonance frequency. Therefore, in the present embodiment, the CPU 10 calculates the static magnetic field strength and the magnetic resonance frequency at that time based on the data indicating the magnet spacing output from the magnet movement control circuit 18, and the tuning circuit 13 calculates based on the calculated value. RF receiver 15 and RF transmitter 1
The transmission / reception band of 6 is adjusted. That is, the magnet 1
The strength of the static magnetic field that changes depending on the gap between a and 1b can be automatically accommodated.

Similarly, it is necessary to adjust the intensity of the gradient magnetic field required for performing the frequency encoding and the phase encoding required for the image construction according to the magnet spacing (static magnetic field intensity). The adjustment of the gradient magnetic field strength is performed by the control circuit 14 controlling the gradient magnetic field amplifier 17 based on the static magnetic field strength calculated by the CPU 10 and the magnetic resonance frequency at that time.

As described above, when the distance between the magnets 1a and 1b is set to a predetermined interval and the measurement state corresponding to the interval is secured, the human body S placed in the static magnetic field by the RF transmission coil is A high-frequency magnetic field of a predetermined frequency is applied and the MR signal of a predetermined frequency emitted from the body is RF.
An MR tomographic image is obtained by detecting with a receiving coil. Although not shown, this tomographic image is obtained by analyzing the MR signal obtained by the RF receiving coil by the CPU 10 and displayed on a display device (not shown).

As described above, the MRI of this embodiment
Since the device can change the positions and directions of the magnets 1a and 1b and the gap between the magnets 1a and 1b, the magnets 1a and 1b can be formed in a small size, and the entire device can be made compact. Becomes Therefore, it is possible to secure a large working space for the operator and locally apply a static magnetic field to apply the endoscopic surgery. That is, the magnet 1
Since the space occupied by a and 1b can be reduced as much as possible and the target site can be easily accessed, the operator can move the static magnetic field to the target site of the patient. It becomes possible to perform it under MR guide while imaging. In particular, it is very suitable for performing endoscopic treatments and treatments, and the degree of freedom in the treatment procedure and installation of the equipment used is greatly improved.

Further, by changing the positions and directions of the magnets 1a and 1b and the gap between the magnets 1a and 1b, it is possible to obtain a desired MR tomographic image according to the treatment target region.

Further, the transmission / reception band of the RF receiver 15 and the RF transmitter 16 and the gradient magnetic field strength are automatically adjusted according to the strength of the static magnetic field which changes depending on the gap between the magnets 1a and 1b. Therefore, a good MR tomographic image corresponding to the gap between the magnets 1a and 1b can be obtained.

In this embodiment, the magnets 1a,
Although the gap between 1b is variable, if it is fixed, substantially the same effect can be obtained and the structure can be simplified.

FIG. 3 shows a second embodiment of the present invention. In this embodiment, a shim coil (correction coil) not shown is built in the magnet 1a (1b) of the static magnetic field generating magnet 1. This shim coil generates a minute magnetic field for canceling out a very small nonuniform component (error magnetic field) included in the magnetic field generated by the static magnetic field generating magnet 1, and corrects the static magnetic field intensity distribution in the imaging target region.

The shim coil is connected to the CPU 10 via a shim coil amplifier 20, and the strength of the magnetic field generated by the shim coil can be adjusted through these devices. The other configuration is the same as that of the first embodiment.

As described above, according to the MRI apparatus of this embodiment, the uniformity of the static magnetic field can be increased by the shim coil, and a better MR image can be obtained. FIG. 4 shows a third embodiment of the present invention. In the present embodiment, the magnets 1a and 1b are provided with the opening 22 and formed into a ring shape, so that the treatment instrument can be accessed from the opening 22 to the treatment site (the head 24 in the figure) of the patient S. It has become. Other configurations are the first
This is the same as the embodiment.

According to this structure, the treatment tool can be accessed through the opening 22 of the magnet in the axial direction of the magnets 1a and 1b to treat the affected area, and the MR imaging region can be treated. .

FIG. 5 shows a fourth embodiment of the present invention. In the first embodiment, the RF receiving coil is provided in the magnet 1a (1b), but in the present embodiment, the RF receiving coil is used as the body surface coil 30 attached to the body surface of the patient. , Magnet 1a (1b)
It is provided separately from. In particular, the body surface coil 30 is attached to the patient during abdominal surgery.

The body surface coil 30 is composed of a multi-layer flexible substrate 31 and is provided with a loop coil (not shown) wound n times according to the number n of laminated layers. The output part 32 of the coil includes a matching circuit and a connector, and has a plug 3
3 and a cable 34 to be connected to the RF receiver 15 (see FIG. 2). In addition, the multilayer flexible substrate 3
1 has an opening 35 and an adhesive film 36 for covering the opening 35 and fixing the entire coil to the patient's body surface. The other MRI configuration is the same as that of the first embodiment.

According to the receiving coil 30 having such a structure, an MR image can be obtained by being attached to the body surface of a patient, and treatment or treatment can be performed through the opening 35. Further, unlike the conventional loop coil, the receiving coil 30 is formed as a flexible coil having n turns, so that the receiving coil 30 can be closely attached to the body surface of the patient, and the S / N ratio of the received signal can be increased. it can.

FIG. 6 shows a fifth embodiment of the present invention. In this embodiment, the RF transmitting coil, the RF receiving coil, and the gradient magnetic field generating coil are provided in the coil frame 40 installed on the operating table 2. The coil frame 40 is formed as a substantially cubic frame body having openings in five directions when installed on the operating table. In addition,
The other configuration is the same as that of the first embodiment.

As described above, in the present embodiment, various coils can be built in the coil frame 40 and the coils can be uniquely positioned with respect to the body axis of the patient, so that a better MR image can be obtained. Further, since the opening of the coil frame 40 exists in five directions, the treatment can be performed through this opening.

If the coil frame 40 is slidably installed on the operating table 2, combined with the sliding movement of the operating table 2, a better treatment under the MR image can be performed on the entire patient. it can.

FIG. 7 shows a structure in which the MRI apparatus is unitized with the endoscope system. In the figure, 100 is a magnet, 101 is a coil frame containing various coils C, 102 is an MR drive unit, and 103 is a CP.
U unit, 105 is an endoscope system unit including a light source device, a video processor, laser treatment tools, a control device, etc., 106 is an operator console, and 104 is a liquid crystal monitor. As shown, the system is shown as a stationary image, but it can be combined with a portable MRI apparatus as shown in FIG.

According to the system having such a configuration, the MR
All the procedures and operations using the I device can be performed by one, which is very convenient. In each of the above-described embodiments, the magnets of the MRI apparatus are of the opposite pole type, but the present invention is not limited to this, and as long as the drive mechanism is capable of changing the position and direction of the magnets,
It may have any form.

The configurations described above can provide various configurations shown in the following sections. Further, the various configurations shown in the following sections may be arbitrarily combined. 1. In a therapeutic MRI apparatus for performing treatment and treatment under diagnosis or guidance by MR images, a magnet that generates a static magnetic field is provided in a movable arm, and a local static magnetic field is formed at a desired patient site to be guided by the MR guide. A therapeutic MRI apparatus characterized by performing a treatment.

2. In an MRI-guided endoscopic system for performing endoscopic treatment and treatment under a diagnosis or guide based on an MR image and an endoscopic image, a magnet for generating a static magnetic field is provided in an endoscope system unit,
An MRI guided endoscopy system, which is characterized by performing guided endoscopic treatment.

3. 3. The apparatus or system according to item 1 or 2, wherein the magnet is a counter pole type magnet. 4. 4. The device or system according to item 3, wherein the counter-pole magnet is a permanent magnet.

5. 4. The apparatus or system according to item 3, wherein the counter-pole magnet is a normal conduction electromagnet. 6. 4. The device or system according to item 3, wherein the counter pole magnet is a superconducting electromagnet.

7. A first feature in which the movable arm is a movable arm that holds a counter electrode magnet at both ends.
The apparatus or system according to Item 2 or Item 2. 8. 8. The device or system according to item 7, wherein the movable arm is a C-shaped arm.

9. 8. The apparatus or system according to claim 7, wherein the movable arm has advancing / retreating driving means for adjusting the distance between the counter magnets. 10. 10. The device according to claim 9, wherein the drive portion of the advancing / retreating drive means for directly driving the counter magnet is a non-electromagnetic drive / non-magnetic drive means by hydraulic or pneumatic pressure, mechanical interlocking, or the like. system.

11. 8. The apparatus or system according to claim 7, wherein the movable arm has means for rotationally driving the counter-pole magnet about an arbitrary axis in the body axis direction of the patient.

12. 3. The apparatus or system according to item 1 or 2, wherein a gradient magnetic field coil and a transmission coil are provided in the magnet. 13. 3. The apparatus or system according to item 1 or 2, wherein a magnetic field correction coil for correcting the static magnetic field intensity distribution in the imaging target region is provided in the magnet.

14. 3. The apparatus or system according to claim 1 or 2, wherein the magnet is provided with an opening through which a therapeutic instrument can be accessed at an imaging / treatment site.

15. 15. The device or system according to item 14, wherein the shape of the opening is circular. 16. 15. The device or system according to item 14, wherein the shape of the opening is rectangular.

[0053]

As described above, according to the MRI apparatus of the present invention, it is possible to secure a wide working space for the operator, and to apply a static magnetic field locally to all endoscopic surgery. it can.

[Brief description of drawings]

FIG. 1 is an overall view of an MRI apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a control system of the MRI apparatus of FIG.

FIG. 3 is a block diagram showing a control system of an MRI apparatus according to a second embodiment of the present invention.

FIG. 4 is a perspective view showing a main part of an MRI apparatus according to a third embodiment of the present invention.

FIG. 5A is an MRI according to a fourth embodiment of the present invention.
A perspective view of the RF receiver coil of the device, (b) RF of (a)
It is sectional drawing which follows the AA line of a receiving coil.

FIG. 6 is an overall view of an MRI apparatus according to a fifth embodiment of the present invention.

FIG. 7 is a perspective view in which the MRI apparatus and the endoscope system are unitized.

[Explanation of symbols]

1 ... Magnet for generating static magnetic field, 1a, 1b ... Magnet, 3,
4 ... Magnet gap variable part (driving means), 5 ... Support beam (driving means), 6 ... Slide driving part (driving means), 7
... horizontal support beams (driving means), 8 ... vertical moving parts (driving means).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Takahashi 2-43-2 Hatagaya, Shibuya-ku, Tokyo Inside Olympus Optical Co., Ltd. (72) Ryoji Masuchibuchi 2-43-2 Hatagaya, Shibuya-ku, Tokyo Olympus Optical Co., Ltd. (72) Inventor Katsuya Suzuki 2-43-2 Hatagaya, Shibuya-ku, Tokyo Olympus Optical Co., Ltd.

Claims (1)

[Claims] 1. A magnet for generating a static magnetic field is provided,
In an MRI apparatus that applies a high-frequency magnetic field of a predetermined frequency to a living body placed in a static magnetic field generated by these magnets and receives a magnetic resonance signal in the body emitted at that time to obtain a magnetic resonance image in the body A therapeutic MRI characterized by comprising a driving means for changing at least one of a position and a direction of the magnet, and capable of forming a local static magnetic field at a desired portion of a living body.
apparatus.