JP5572294B2 - Nuclear magnetic resonance imaging system - Google Patents

Description

  The present invention relates to a nuclear magnetic resonance imaging system.

  A nuclear magnetic resonance imaging (MRI) diagnostic apparatus irradiates a subject placed in a static magnetic field with a high-frequency pulse, thereby exciting nuclear spins of nuclei in the subject and generating a nuclear magnetic resonance signal. At this time, positional information is given to the nuclear magnetic resonance signal by applying a gradient magnetic field in a predetermined sequence, and a tomographic image in the subject is obtained by reconstructing the nuclear magnetic resonance signal into an image. Can do.

  In recent years, an open-type MRI diagnostic device in which magnets (superconducting magnets, permanent magnets, etc.) for generating a static magnetic field are arranged up and down is placed in the operating room, and surgery and treatment are performed while performing MRI diagnosis. A diagnosis has been made.

For example, in head surgery, an MRI diagnosis is performed in order to confirm the progress of surgery while fixing the head with a head stereotaxic instrument and performing an operation such as removing a tumor using an endoscope or a microscope. Is appropriately performed. At this time, a device has been developed that also serves as a head localization fixture as a part of the receiving coil (see, for example, Patent Document 1).
JP 2004-97431 A Patent Publication

However, it is expected to develop an open-type MRI apparatus for analyzing a deeper part of the brain with high resolution and a method for using the same.
Accordingly, an object of the present invention is to provide a more functional nuclear magnetic resonance imaging system having a new configuration.

  The inventor of the present invention has developed a hemispherical (helmet type) transmission / reception coil for covering a human head in order to analyze the deeper part of the brain with high resolution using an open MRI diagnostic apparatus. In this case, the sensitivity and resolution of the nuclear magnetic resonance image can be increased as the diameter of the hemisphere formed by the coil is smaller.

  On the other hand, at the time of MRI diagnosis, it is necessary to specify the position of the head of the subject in the imaging region of the subject for which image diagnosis is performed by the MRI diagnostic apparatus. Therefore, an MRI marker detected by the MRI apparatus is provided as an index for specifying the head position.

  This MRI marker is used by being affixed to a plurality of locations on the head of the subject because the magnetic field generated outside the coil is extremely weak and needs to be placed inside the coil when using a transmission / reception coil. However, if the radius of the coil is reduced in order to increase the sensitivity and resolution of the nuclear magnetic resonance image, there is no gap for attaching the MRI marker between the coil and the head. Therefore, the present inventor has developed a head position specifying marker that is useful in such a case and can provide stable position information while being used outside the coil.

  That is, one embodiment of the present invention is a head position specifying marker for specifying the position of the head of a subject in a nuclear magnetic resonance imaging system, which can be detected by a nuclear magnetic resonance imaging apparatus. A head position specifying marker comprising: an MRI marker including a substance; and a resonance circuit including a concentric coil and a capacitor centering on the MRI marker. The resonance circuit preferably has a sensitivity adjustment mechanism. The sensitivity adjustment mechanism may adjust the sensitivity by adjusting the angle of the coil or by adjusting the resonance frequency of the resonance circuit by adjusting the capacitance of the resonance circuit or adjusting the inductance of the coil. Good.

  A further embodiment of the present invention is a nuclear magnetic resonance diagnostic imaging system comprising a magnetic circuit, a bed, a head localization fixture for fixing the head of the subject on the bed, and the head of the subject A hemispherical transmission / reception coil for covering the head, and any one of the head position specifying markers described above. Here, the head position specifying marker is preferably attached to the head positioning fixture. It is preferable that a plurality of the head position specifying markers are provided.

  A further embodiment of the present invention includes a magnetic circuit, a bed, a head positioning fixture for fixing the head of the subject on the bed, and a hemispherical transmitting / receiving coil for covering the head of the subject. A method of using the head position specifying marker in a nuclear magnetic resonance imaging system having any one of the above head position specifying markers, wherein the head position specifying marker is placed outside the transmission / reception coil. It is the usage method characterized by making it position. Here, it is preferable that the head position specifying marker is attached to the head positioning fixture. Further, it is preferable to provide a plurality of the head position specifying markers.

  According to the present invention, a more sophisticated nuclear magnetic resonance imaging system can be provided.

  The objects, features, advantages, and ideas of the present invention will be apparent to those skilled in the art from the description of the present specification, and those skilled in the art can easily reproduce the present invention from the description of the present specification. The embodiments of the present invention described below show preferred embodiments of the present invention, and are shown for illustration or explanation, and the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications and variations can be made based on the description of the present specification within the spirit and scope of the present invention disclosed herein.

== Nuclear magnetic resonance imaging system ==
FIG. 1 shows the overall configuration of a nuclear magnetic resonance diagnostic imaging system 1. This nuclear magnetic resonance diagnostic imaging system 1 includes a magnetic circuit 2, an operating table 3 provided with a bed, a head positioning fixture 4 for fixing the head of the subject on the operating table, and a head of the subject. A hemispherical transmission / reception coil 5 and a head position specifying marker 6 for specifying the position of the head of the subject.

  The magnetic circuit 2 is not particularly limited, but is preferably an open type using a permanent magnet. The operating table 3 and other parts are not particularly limited, and those used in conventional MRI diagnostic apparatuses can be used.

  FIG. 2 shows a schematic diagram of the head localization fixture 4. The head localization fixture 4 is a device that fixes the subject's head while the subject is placed on the operating table 3. This head localization fixture 4 includes a semicircular base portion 7 that follows the shape of the subject's head, a holding portion 8 that holds the base portion at an arbitrary angle in the circumferential direction, and a holding portion that is covered. It is composed of a fixing portion 9 that is held so as to be movable in the specimen body axis direction and fixed to the operating table. The base portion 7 is provided with a plurality of screw holes at predetermined intervals, and the screw holes are provided with bolts 10 that are fixed in contact with the subject's head. The positions of the holding unit 8 and the base unit 7 are adjusted according to the contents of the operation, the position and orientation of the subject's head, and the positions and number of the bolts 10 to be fixed are appropriately adjusted.

  FIG. 3 shows a schematic diagram of the transmitting / receiving coil 5 at the time of detachment. The transmission / reception coil 5 functions as an antenna that transmits RF radio waves and receives high-frequency signals, and includes a hemispherical substrate 11 and a conductive wire 12 formed in a hemispherical spiral shape thereon. The transmitting / receiving coil 5 preferably has a vent hole in a portion not related to the protection of the electric circuit such as the lead wire 12 or the capacitor or the structure of the head positioning fixture 4. For example, a circular vent hole is formed in the top of the head. It may be provided. Due to this air permeability, the increase in the temperature of the subject due to the high frequency excitation magnetic field generated from the transmitting / receiving coil 5, that is, the SAR can be reduced as much as possible, and the feeling of pressure felt by the subject can be reduced. Examples of the material of the substrate 11 include polypropylene resin and acrylic resin, but are not particularly limited. When this transmission / reception coil 5 is put on the head 20 of the subject, a notch corresponding to the bolt 10 is provided so that the transmission / reception coil 5 covers the head localization fixture 4 so that the eyes and nose are hidden. 13 is provided on the substrate 11. In this notch 13 part, the conducting wire 12 runs along the notch 13 so as to escape the notch 13. At this time, in the vicinity of the end of the substrate 11 (that is, the free end of the hemisphere), the high-frequency magnetic field uniform region transmitted / received by the transmitting / receiving coil 5 is transmitted / received by narrowing the interval between the conductors or by doubling the conductors. The coil 5 can be spread from the inside to the outside. In addition, although the wire 12 and the flat plate which consist of oxygen-free copper and tough pitch copper are illustrated as the material of the conducting wire 12, it is not specifically limited.

  FIG. 4 shows an enlarged view of the head position specifying marker 6. The head position specifying marker 6 includes an MRI marker 14 containing a substance that can be detected by the MRI diagnostic apparatus, a concentric coil 18 and a capacitor 16 around the MRI marker 14, and sensitivity for adjusting sensitivity. It has a hinge 17 and a coil expansion device 19 which are adjustment mechanisms. Examples of the substance that can be detected by the MRI diagnostic apparatus include an aqueous nickel chloride solution, an aqueous copper sulfate solution, and baby oil. Then, polyethylene spheres, liver oil spheres, and the like injected with these substances can be used as the MRI marker 14. The NMR relaxation time of the MRI marker 14 is preferably adjusted within 0.5 seconds. The concentric coil 18 is formed in a spiral shape with a copper wire or the like having a diameter of about 5 mm to 10 mm, and constitutes an LC resonance circuit together with the capacitor 16. As the sensitivity adjustment mechanism, for example, as shown in FIG. 4A, in order to adjust the angle formed by the coil housing portion 15 that houses the coil 18 and the capacitor 16, the coil housing portion is interposed between the coil housing portion 15 and the capacitor 16. A hinge 17 that can tilt 15 may be provided. Moreover, you may add the coil expansion apparatus 19 for expanding the coil 18 three-dimensionally from planar shape like FIG. 4B.

== How to use the transmit / receive coil ==
The transmission / reception coil 5 as described above can be used for MRI diagnosis of the head, that is, the brain. In particular, since the shape is hemispherical, it is suitable for analyzing deep brain areas. With this shape, there is no loss in sensitivity at the top of the head, and a uniform magnetic field distribution can be obtained over the entire area of the coil, so that an image with uniform pixel intensity can be acquired.

  Further, the transmission / reception coil 5 can be suitably used for intraoperative MRI. This is because the board 11 has the notch 13 corresponding to the bolt 10, so that the transmitting / receiving coil 5 can be easily attached / detached to / from the patient while the head is held on the head stereotaxic fixture 4. It is.

== How to use the head position specifying marker ==
When the MRI diagnosis of the subject's brain is performed using the nuclear magnetic resonance imaging system 1 having the above-described configuration, the head position specifying marker 6 is disposed outside the transmission / reception coil 5. Conventionally, the MRI marker 14 has been used by being affixed to a plurality of locations on the head of the subject inside the transmission / reception coil. Thus, by using the head position specifying marker 6 of the present invention, The MRI marker 14 can be placed outside the transmission / reception coil 5.

  When the head position specifying marker 6 is arranged, the axis of the coil 18 is orthogonal to the direction of the static magnetic field of the magnet in the magnetic circuit 2 (for example, the vertical direction in FIG. 1), and the transmission / reception coil 5 is generated on the outside thereof. The maximum sensitivity can be obtained by adjusting so as to be parallel to the direction of the high-frequency magnetic field to be detected. When the marker 6 is irradiated, in many cases, the magnetic field in the vicinity of the head position specifying marker 6 is amplified to an excessive excitation intensity by a resonance circuit attached to the marker. Therefore, every time the magnetic field generated by the transmitting / receiving coil 5 is actually used by using the sensitivity adjustment mechanism so that an appropriate MRI signal can be obtained from the head position specifying marker 6 by appropriately applying the magnetic field to the MRI marker 14. It is preferable to find the optimum condition. In other words, the head position specifying marker 6 may be arranged in any direction as long as it has a sensitivity adjustment mechanism. However, as the initial state, the axis of the coil 18 can be obtained so that the maximum sensitivity can be obtained. Is arranged so that is perpendicular to the direction of the static magnetic field of the magnet in the magnetic circuit 2 and the transmission / reception coil 5 is parallel to the direction of the high-frequency magnetic field generated on the outside thereof, and then the sensitivity is adjusted by a sensitivity adjustment mechanism.

  Here, the sensitivity adjustment mechanism adjusts the sensitivity by, for example, adjusting the angle of the coil 18 and bringing the axis of the coil 18 of the head position specifying marker 6 closer to the direction of the static magnetic field of the magnet in the magnetic circuit 2. May be.

  Alternatively, the sensitivity adjustment mechanism may adjust the sensitivity by adjusting the resonance frequency by adjusting the capacitance of the capacitor 16 of the resonance circuit or adjusting the inductance of the coil 18. For example, in order to adjust the capacitance of the capacitor 16, the resonance frequency may be adjusted by using the capacitor 16 as a variable type. Further, in order to adjust the inductance of the coil 18, the resonance frequency may be adjusted by mechanically changing the pitch of the coil 18. Thus, the sensitivity can be adjusted by shifting the resonance frequency of the head position specifying marker 6 from the NMR frequency used in MRI imaging.

  It is preferable to use a plurality of head position specifying markers 6, preferably three or more so that the positions can be specified three-dimensionally. Although the attachment location is not particularly limited, it is preferable that they are arranged so as not to form a straight line but to form surfaces with each other. In the head stereotaxic fixture 4, the attachment location is not particularly limited, but it is preferable to dispose them at a linear distance of 5 cm from each other. Therefore, for example, an arrangement is possible in which two are installed at both ends of the semicircular shape and two are installed near the middle. In addition, you may use in combination with the other MRI marker inside the coil 5 for transmission / reception.

  In the case of the conventional transmission / reception separation coil, there is no need to use a marker having a resonance circuit such as the head position specifying marker 6, but as in the present invention, a hemisphere for covering the head 20 of the subject. In the nuclear magnetic resonance imaging system 1 using the transmission / reception coil 5, the MRI marker 14 is not easily placed inside the transmission / reception coil 5, so the head position specifying marker 6 functions particularly advantageously.

  Further, in the case where there is no gap between the head and the transmitting / receiving coil 5, the conventional MRI marker may not be attached to the head but may be punctured by making a hole in the head. there were. However, the head position specifying marker 6 of the present invention produces an advantageous effect in that it is used noninvasively.

  Further, the imaging region inside the transmission / reception coil 5 is highly likely to be deformed by surgery or the like, and when it is directly attached to the subject, the intensity of the transmission magnetic field generated from the transmission / reception coil 5 is extremely near the transmission / reception coil 5. The marker may not generate an NMR signal properly. Therefore, the head position specifying marker 6 of the present invention also has an advantageous effect in that a better marker image can be obtained at a place away from the imaging region, such as outside the transmission / reception coil 5.

1 is a diagram illustrating an overall configuration of a nuclear magnetic resonance imaging system in an embodiment of the present invention. In one embodiment of this invention, it is the schematic diagram observed from the head upper part at the time of mounting | wearing with the coil 5 for transmission / reception. In one embodiment of the present invention, it is a schematic diagram showing a transmission / reception coil 5 at the time of detachment (A: at the time of removal, B: at the time of attachment). In one embodiment of the present invention, it is a schematic diagram showing a head position specifying marker 6.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Nuclear magnetic resonance imaging system 2 Magnetic circuit 3 Operating table 4 Head localization fixture 5 Transmission / reception coil 6 Head position specifying marker 7 Base portion 8 Holding portion 9 Fixing portion 10 Bolt 11 Substrate 12 Conductor 13 Notch 14 MRI marker DESCRIPTION OF SYMBOLS 15 Coil accommodating part 16 Capacitor 17 Hinge 18 Coil 19 Coil expansion apparatus 20 Head of subject

Claims (10)

A nuclear magnetic resonance imaging system comprising:
Magnetic circuit,
bed,
A head positioning fixture for fixing the subject's head on the bed;
A hemispherical transmitting / receiving coil for covering the head of the subject;
A head position specifying marker having an MRI marker containing a substance detectable by a nuclear magnetic resonance imaging apparatus, and a resonance circuit comprising a concentric coil and a capacitor centering on the MRI marker,
Have a, wherein the head localization marker is located outside of the transceiver coil system. The system of claim 1, wherein the resonant circuit has a sensitivity adjustment mechanism. The sensitivity adjustment mechanism adjusts the sensitivity by adjusting an angle of the coil or by adjusting a resonance frequency of the resonance circuit by adjusting a capacitor capacity of the resonance circuit or adjusting an inductance of the coil. Item 3. The system according to Item 1 or 2. The system according to any one of claims 1 to 3, wherein the head position specifying marker is attached to the head localization fixture. The system according to claim 1, comprising a plurality of markers for specifying the head position. Magnetic circuit,
bed,
A head positioning fixture for fixing the subject's head on the bed;
A hemispherical transmitting / receiving coil for covering the head of the subject, and
A head position specifying marker having an MRI marker containing a substance detectable by a nuclear magnetic resonance imaging apparatus, and a resonance circuit comprising a concentric coil and a capacitor centered on the MRI marker;
A method for using the head position specifying marker in a nuclear magnetic resonance imaging system comprising:
A method of use, wherein the head position specifying marker is arranged outside the transmission / reception coil. The method for using the head position specifying marker according to claim 6, wherein the resonance circuit has a sensitivity adjustment mechanism. The sensitivity adjustment mechanism adjusts the sensitivity by adjusting an angle of the coil or by adjusting a resonance frequency of the resonance circuit by adjusting a capacitor capacity of the resonance circuit or adjusting an inductance of the coil. Item 8. A method of using the head position specifying marker according to Item 6 or 7. The method according to any one of claims 6 to 8, wherein the head position specifying marker is attached to the head positioning fixture. The method according to any one of claims 6 to 9 , wherein a plurality of the head position specifying markers are provided.

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