JP5292000B2 - MRI apparatus and high frequency coil unit for MRI apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an MRI apparatus capable of detecting MR signals from the imaging part of a subject with excellent sensitivity, and a high frequency coil unit for the MRI apparatus. <P>SOLUTION: The high frequency coil unit for the MRI apparatus includes: first and second coil units 71a and 71b for detecting magnetic resonance signals from the head part of the subject P lying on a bed 41; a frame 73 for holding the first and second coil units 71a and 71b turnably in an R1 direction; two arms 76a and 76b for holding the frame 73 turnably in an R2 direction; and a support 80 for holding the arms 76a and 76b tiltably in a height direction. The first and second coil units 71a and 71b are closely arranged at the head part of the subject P lying on the bed 41 in a comfortable posture. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an MRI apparatus and an MRI apparatus high-frequency coil unit, and more particularly to an MRI apparatus suitable for MRI imaging of a subject's head and an MRI apparatus high-frequency coil unit.

  An MRI (Magnetic Resonance Imaging) apparatus irradiates a subject placed in a static magnetic field with radio waves (RF waves) of a specific frequency to excite hydrogen nuclear spins, and RF waves emitted from the hydrogen nuclei after irradiation. Is an apparatus for reconstructing image data based on a magnetic resonance signal (MR signal) detected by receiving the signal. In this MRI apparatus, image data can be obtained without being invasive to a subject without being affected by bone or air, and therefore, it is indispensable in the field of diagnostic imaging today.

  By the way, when imaging with an MRI apparatus, there are an irradiation coil for irradiating a subject placed in a static magnetic field with an RF wave and a receiving coil for receiving an RF wave emitted from the subject. These coils are collectively referred to as a high frequency coil. This high-frequency coil includes a cross coil system that uses two coils, an irradiation coil and a reception coil, and a single coil system that uses a single coil that is used for both irradiation and reception.

  And if the receiving coil of a high frequency coil becomes large, it will have a wide detection area | region, but a noise area | region will also spread and SN ratio will fall relatively. Moreover, if it becomes small, a detection area | region will become narrow, but S / N ratio will improve. Therefore, in order to detect a weak MR signal from the imaging region of the subject, it is necessary to dispose the receiving coil close to the surface around the imaging region. For this reason, dedicated coils for the head, the neck, the shoulder, etc. are used in accordance with the imaging region of the subject.

In the case of the coil for the head, it is known to perform imaging by bringing the head coil arranged on the bed close to the head of the subject who is dressed on the bed for MRI imaging (for example, (See Patent Document 1).
JP-A-8-593

  However, when imaging the head of the subject using the head coil, it is small if the head coil is brought close to the head of the subject whose neck or waist is bent due to obstacles or aging. The coil for the head has a problem of forcing the subject to an unreasonable posture and causing pain. In addition, when photographing is performed using a large head coil, there is a problem in that the SN ratio is lowered and a portion that cannot be close to the head surface is generated, thereby degrading the image quality of the image data.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to provide an MRI apparatus and a high-frequency coil unit for an MRI apparatus that can detect MR signals from an imaging region of a subject with high sensitivity.

  In order to solve the above-described problem, a high-frequency coil unit for an MRI apparatus according to a first aspect of the present invention includes a magnetic field from the head arranged close to the head of a subject lying on a bed of the MRI apparatus. A coil unit for detecting a resonance signal, a frame that holds the coil unit around a virtual first straight line passing through the vicinity of the center of the coil unit, and a vicinity of the center of the coil unit. And is arranged perpendicular to a virtual second straight line that is orthogonal to the first straight line and parallel to the upper surface of the bed, and holds the frame about the second straight line so as to be rotatable. And an arm that is movably disposed on the bed and holds the arm so as to be tiltable in a height direction.

  According to a fourth aspect of the present invention, the MRI apparatus of the present invention performs MRI imaging using the high-frequency coil unit for an MRI apparatus according to the first aspect.

  According to the present invention, it is possible to detect MR signals with high sensitivity from a position close to the imaging region of the subject, and it is possible to generate high-quality image data.

  Embodiments of the present invention will be described below with reference to the drawings.

  Embodiments of the MRI apparatus according to the present invention will be described below with reference to FIGS. FIG. 1 is a block diagram showing a configuration of an MRI apparatus according to an embodiment of the present invention.

  The MRI apparatus 10 includes an MRI imaging unit 1 that performs MRI imaging of a subject P, an image processing unit 2 that generates image data based on MR signals detected by the MRI imaging unit 1, and an image processing unit 2. Display unit 3 that displays the image data, a bed unit 4 that moves the subject P to the MRI imaging unit 1, an operation unit 5 that operates the MRI imaging unit 1 and the bed unit 4, and operations from the operation unit 5 A system control unit 6 that controls the MRI imaging unit 1, the image processing unit 2, and the bed unit 4 based on the signal is provided.

  The MRI imaging unit 1 includes a gantry unit 11 that generates a magnetic field, a power source unit 12 that supplies power to the gantry unit 11 to generate a magnetic field, and irradiates the gantry unit 11 with an RF pulse on the subject P and the subject. And a transmission / reception unit 13 for processing MR signals from P.

  The gantry 11 has an opening 111 for imaging the subject P, the high-frequency coil unit 7 that can be arranged according to the position of the head of the subject P in the opening 111, and the outer periphery of the opening 111 A magnet 112 that generates a static magnetic field on the subject P disposed in the center, and a gradient magnetic field coil 113 that generates a gradient magnetic field disposed between the opening 111 and the magnet 112.

  The high-frequency coil unit 7 irradiates the subject P with an RF pulse for exciting the hydrogen nuclei, and receives an RF wave emitted from the subject P in response to the irradiation to detect an MR signal. Then, the detected MR signal is output to the transmission / reception unit 13.

  As the magnet 112, for example, a superconducting magnet is used, and a uniform static magnetic field is generated in the subject P located in the opening 111. The gradient coil 113 generates a gradient magnetic field in the static magnetic field generated by the magnet 112.

  The power supply unit 12 includes a static magnetic field power supply unit 121 that supplies power to the magnet 112 of the gantry unit 11 and a gradient magnetic field power supply unit 122 that supplies power to the gradient magnetic field coil 113. Then, the gradient magnetic field power supply unit 122 generates a gradient magnetic field that is distributed in an inclined manner in the direction in which the static magnetic field is set based on the control signal supplied from the system control unit 6.

  The transmission / reception unit 13 includes a transmission unit 131 that supplies an RF pulse for irradiation to the high-frequency coil unit 7 of the gantry unit 11 and a reception unit 132 that processes the MR signal from the high-frequency coil unit 7.

  The transmission unit 131 includes a reference signal oscillator, a modulator, a power amplifier (not shown) and the like, and outputs an RF pulse corresponding to the Larmor frequency to the high frequency coil unit 7 of the gantry unit 11.

  The receiving unit 132 includes an amplifier, an intermediate frequency converter, a phase detector, a filter, an A / D converter (not shown), and the like, which are detected by the high frequency coil unit 7 after outputting RF pulses to the high frequency coil unit 7. The processed MR signal is subjected to processing such as intermediate frequency conversion, phase detection, filtering, and A / D conversion, and then output to the image processing unit 2.

  The image processing unit 2 includes a calculation unit 21 and a storage unit 22. Then, the calculation unit 21 reconstructs the MR signal output from the reception unit 132 of the transmission / reception unit 13 to generate image data, and then outputs the image data to the display unit 3. Further, the generated image data is stored in the storage unit 22.

  The display unit 3 includes a monitor such as a CRT or a liquid crystal panel, and displays the image data output from the calculation unit 21 of the image processing unit 2.

  The bed part 4 is a bed 41 on which the subject P is placed, and the bed 41 is moved in the horizontal direction and the vertical direction so that an imaging part of the subject P is opened in the gantry part 11 in the MRI imaging unit 1. And a moving mechanism 42 that is set at the center of the gantry located inside.

  The operation unit 5 includes various input devices such as switches, a keyboard, and a mouse (not shown) and a display panel, and inputs imaging conditions for performing MRI imaging and sets the subject P in the opening 111 of the gantry unit 11. For input.

  The system control unit 6 includes a CPU, a storage circuit, and the like (not shown). Based on an input signal from the operation unit 5, the MRI imaging of the power supply unit 12 and the transmission / reception unit 13 of the MRI imaging unit 1 and the image processing unit 2. Control of the entire system is performed such as control related to generation of image data and control related to the movement operation of the bed unit 4.

  Next, the configuration of the high-frequency coil unit 7 used for imaging the head of the subject P will be described with reference to FIGS. FIG. 2 is a perspective view of the high-frequency coil unit 7. FIG. 3 is a side view of the high-frequency coil unit 7. FIG. 4 is a diagram showing directions in which the high-frequency coil unit 7 can be arranged.

  The high-frequency coil unit 7 shown in FIG. 2 is arranged close to the head of the subject P, irradiates the subject P with RF pulses, and detects first and second MR signals from the subject P. The coil units 71 a and 71 b, the hinge 71 c for holding the second coil unit 71 b so as to be openable and closable with respect to the first coil unit 71 a, the first and second coil units 71 a and 71 b, and the transceiver 13. And a cable 71d for electrically connecting the two.

  Further, the two first shafts 72a and 72b for holding the first and second coil units 71a and 71b and the first and second coil units 71a and 71b are arranged in the direction of the arrow R1 shown in FIG. A frame 73 that is rotatably held, two first stoppers 74a and 74b for fixing the first and second coil units 71a and 71b set at a desired angle in the R1 direction, and the frame 73 are held. And two second shafts 75a and 75b.

  Furthermore, two arms 76a and 76b that hold the frame 73 rotatably in the direction of the arrow R2, and two second stoppers 77a and 77b for fixing the frame 73 set at a desired angle in the R2 direction, A tilting shaft 78 for holding the arms 76a and 76b so as to be tiltable in the height direction, and two third stoppers 79a for fixing the arms 76a and 76b tilted and set to desired heights. 79b and a support 80 that holds the arms 76a and 76b so as to be tiltable.

  The first coil unit 71a has a bowl shape having an opening surface with an elliptical cross section, and as shown in FIG. 3, the inner surface is similar to the shape of the back of the subject P, that is, similar to the shape of the back of the head. It has an inner surface shape. In addition, an internal coil disposed in a predetermined direction for irradiating the subject P with an RF pulse and detecting an MR signal from the subject P is provided.

  The second coil unit 71b has a shape excluding a part of the bowl shape, and is held so as to be openable and closable with respect to the first coil unit 71a via a hinge 71c. Also, as shown in FIG. 3, when closed, the inner surface of the subject P can be approached from the top of the frontal region of the subject P to the vicinity of the nose of the frontal region, that is, the inner surface similar to the frontal shape. It has a shape. Further, a part of the end surface is engaged with the first coil unit 71a. In addition, an internal coil disposed in a predetermined direction for irradiating the subject P with an RF pulse and detecting an MR signal from the subject P is provided.

  One piece of the hinge 71c is joined to the end on the top side of the subject P in the first coil unit 71a, and the other piece is joined to the end on the top side of the subject P in the second coil unit 71b. ing. The RF pulse for irradiation from the transmission unit 131 of the transmission / reception unit 13 is transmitted to the internal coil of the second coil unit 71b inside the hinge 71c, and the MR signal detected by this internal coil is transmitted to the reception unit 132. A signal line for transmission is wired.

  One end of the cable 71d is connected to the signal line inside the hinge 71c and the internal coil of the first coil unit 71a, and the other end is connected to the transmitter 131 and the receiver 132. And while transmitting the RF pulse from the transmission part 131 to each internal coil of the 1st and 2nd coil units 71a and 71b, MR signal from each internal coil of the 1st and 2nd coil units 71a and 71b is sent. The data is transmitted to the receiving unit 132.

  Here, a point located on the first coil unit 71a side in the vicinity of the center of the egg shape formed by the first and second coil units 71a and 71b is defined as a virtual point 72c.

  Each of the first axes 72a and 72b passes through a virtual point 72c, and on a virtual first straight line 72d that is substantially parallel to an elliptical long axis that forms the opening surface of the first coil unit 71a, It arrange | positions facing through the coil unit 71a. Each end surface is joined to the outer surface of the first coil unit 71a.

  The frame 73 has an annular shape similar to the ellipse, and is disposed outside the first coil unit 71a and loosely passes through holes at two intersecting points intersecting the first straight line 72d. , 72b. The first and second coil units 71a are held so as to be rotatable in the R1 direction via the first shafts 72a and 72b.

  Each first stopper 74a, 74b is screwed to the other end of the first shaft 72a, 72b outside the frame 73. Then, the first and second coil units 71a and 71b are fixed to the frame 73 by fastening the first stoppers 74a and 74b in the direction of the first coil unit 71a.

  Thus, by rotating the 1st and 2nd coil units 71a and 71b, as shown in FIG. 4, the 1st and 2nd coil units 71a and 71b are set to the desired angle of R1 direction. And can be fixed at a set angle.

  Each of the second axes 75a and 75b passes the first coil unit 71a on a virtual second straight line 75c that passes through the virtual point 72c, is orthogonal to the first straight line 72d, and is parallel to the upper surface of the support 80. Are arranged opposite to each other. Each edge is joined to the outer surface of the frame 73.

  The arms 76a and 76b are arranged perpendicular to the second shafts 75a and 75b and opposed to each other with the first coil unit 71a and the frame 73 interposed therebetween. Two shafts 75a and 75b are provided. The frame 73 is held so as to be rotatable in the R2 direction via the second shafts 75a and 75b.

  The second stoppers 77a and 77b are screwed into the other end portions of the second shafts 75a and 75b outside the arms 76a and 76b. The frame 73 is fixed to the arms 76a and 76b by tightening the second stoppers 77a and 77b in the direction of the first coil unit 71a.

  Thus, by rotating the frame 73, as shown in FIG. 4, the first and second coil units 71a and 71b are set to desired angles in the R2 direction and fixed at the set angles. Can do.

  The tilting shaft 78 is disposed between the other end portions of the arms 76a and 76b perpendicularly to the arms 76a and 76b, and both end portions are loosely inserted into the holes at the other end portions of the arms 76a and 76b. .

  The third stoppers 79a and 79b are screwed to both ends of the tilt shaft 78 outside the arms 76a and 76b. Then, the arms 76 a and 76 b are fixed to the tilting shaft 78 by tightening the third stoppers 79 a and 79 b toward the center of the tilting shaft 78.

  The flat support 80 is movably disposed at an arbitrary position on the bed 41 of the bed 4, and a tilting shaft 78 is joined to the upper surface thereof. The arms 76a and 76b are held so as to be rotatable about the tilting shaft 78 in the R2 direction, that is, tiltable in the height direction.

  Note that the first and second coil units 71a and 71b may be replaced with first and second coil units dedicated to reception for detecting MR signals from the subject P.

  Thus, by tilting the arms 76a and 76b, as shown in FIG. 4, the first and second coil units 71a and 71b are set to a desired height in the height direction indicated by the arrow L1. , Can be fixed at the set height.

  Further, by moving the support 80, as shown in FIG. 4, the first and second coil units 71a and 71b are moved to a desired angle indicated by an arrow R3 with a vertical line passing through the virtual point 71c as a center, for example. Can be arranged.

  Hereinafter, the MRI imaging operation using the high-frequency coil unit 7 will be described with reference to FIGS. FIG. 5 is a flowchart showing a procedure of MRI imaging work using the high-frequency coil unit 7.

  First, input of patient information of the subject P and imaging conditions for performing MRI imaging are performed from the operation unit 5. After the subject P is introduced into the shield room for shielding the magnetism where the MRI imaging unit 1 of the MRI apparatus 10 is arranged, the subject with the back of the head placed on the first coil unit 71a of the high-frequency coil unit 7 is placed. The sample P is placed in the supine position on the bed 41 at the home position of the bed unit 4 (step S1).

  Next, the first stoppers 74a and 74b, the second stoppers 77a and 77b, and the third stoppers 79a and 79b are tightened to fix the first coil unit 71a, the frame 73, and the arms 76a and 76b (step). S2).

  After fixing, the second coil unit 71b is closed. By this operation, the head of the subject P leaning on the bed 41 in an easy posture is placed in a state where the inside of the high-frequency coil unit 7 including the first and second coil units 71a and 71b is fitted.

  Next, after the bed 41 is moved from the home position by the operation from the operation unit 5 and the head of the subject P is set at the imaging position of the opening 111 of the gantry unit 11, MRI imaging of the subject P is performed. (Step S3).

  After the photographing is finished, the bed 41 is moved from the photographing position of the opening 111 by the operation from the operation unit 5 and returned to the home position. Next, after opening the second coil unit 71b, the head of the subject P is lifted, and the high-frequency coil unit 7 is moved to a position away from the subject P (step S4).

  After moving the high-frequency coil unit 7, the subject P is lowered from the bed 41 (step S5), taken out of the shield room, and the MRI imaging operation is completed.

  According to the embodiment of the present invention described above, the first and second coil units 71a and 71b are set and fixed at desired angles and desired heights in the R1 and R2 directions, and angles in the R3 direction. Therefore, the first and second coil units 71a and 71b can be fitted and placed on the head of the subject P leaning in an easy posture on the bed 41.

  Thereby, MR signals from the head of the subject P can be detected with high sensitivity and uniformity, and high-quality image data can be generated.

The block diagram which shows the structure of the MRI apparatus which concerns on the Example of this invention. The perspective view of the high frequency coil unit which concerns on the Example of this invention. The side view of the high frequency coil unit which concerns on the Example of this invention. The figure which shows the direction which can arrange | position the high frequency coil unit which concerns on the Example of this invention. The flowchart which shows the procedure of the MRI imaging | photography operation | work using the high frequency coil unit which concerns on the Example of this invention.

Explanation of symbols

P subject 1 MRI imaging unit 2 image processing unit 3 display unit 4 bed unit 5 operation unit 6 system control unit 7 high-frequency coil unit 10 MRI apparatus 11 gantry unit 12 power supply unit 13 transmission / reception unit 21 calculation unit 22 storage unit 41 bed 42 movement Mechanism 71a First coil unit 71b Second coil unit 71c Hinge 71d Cables 72a, 72b First shaft 72c Virtual point 72d First straight line 73 Frames 74a, 74b First stoppers 75a, 75b Second shaft 75c Second shaft Two straight lines 76a and 76b Arms 77a and 77b Second stopper 78 Tilting shafts 79a and 79b Third stopper 80 Support 111 Opening 112 Magnet 113 Gradient magnetic field coil 121 Static magnetic field power supply unit 122 Gradient magnetic field power supply unit 131 Transmission unit 132 Receiver

Claims (4)

A coil unit for detecting a magnetic resonance signal from the head arranged close to the head of the subject lying on the bed of the MRI apparatus;
A frame that holds the coil unit around a virtual first straight line passing through the vicinity of the center of the coil unit,
The frame that passes through the vicinity of the center of the coil unit, is perpendicular to the first straight line and is perpendicular to a virtual second straight line that is parallel to the upper surface of the bed, and is centered on the second straight line An arm that holds the rotation of
A high-frequency coil unit for an MRI apparatus, comprising: a support body that is movably disposed on the bed and holds the arm so as to be tiltable in a height direction. The coil unit has a first coil unit rotatably held by the frame having an inner surface shape similar to the occipital shape of the subject, and an inner surface shape similar to the frontal shape of the subject. A second coil unit,
The high frequency coil unit for an MRI apparatus according to claim 1, wherein the second coil unit is held by the first coil unit so as to be openable and closable. First fixing means capable of fixing the coil unit to the frame;
Second fixing means capable of fixing the frame to the arm;
The high-frequency coil unit for an MRI apparatus according to claim 1, further comprising third fixing means capable of fixing the arm to the support.   An MRI apparatus that performs MRI imaging using the high-frequency coil unit for an MRI apparatus according to claim 1.

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