JPH0642877B2 - Probe coil device and MRI device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention utilizes a magnetic resonance (MR) phenomenon to obtain morphological information such as a slice image of a subject (living body) and spectroscopic information. The present invention relates to a probe coil device of an MRI device that obtains functional information such as scanning.

(Prior Art) A magnetic resonance phenomenon is a phenomenon in which an atomic nucleus having a non-zero spin and magnetic moment placed in a static magnetic field resonates and emits only an electromagnetic wave of a specific frequency. Angular frequency ω ₀ (ω ₀ = 2πν ₀ , ν ₀ ;
Resonance at Larmor frequency).

ω ₀ = γH ₀ where γ is the gyromagnetic ratio peculiar to the type of nucleus,
H ₀ is the static magnetic field strength.

The apparatus for performing biomedical diagnosis using the above principle performs signal processing on the electromagnetic wave of the same frequency as that induced after the above-mentioned resonance absorption to obtain nuclear density, longitudinal relaxation time T1, transverse relaxation time T2, flow, Diagnostic information reflecting information such as chemical shift, for example, a slice image of a subject is obtained non-invasively.

Further, the collection of diagnostic information by magnetic resonance is capable of exciting all the parts of the subject placed in a static magnetic field and collecting signals, but there are restrictions on the device configuration and clinical demands for imaging images. Therefore, in an actual device, excitation and signal acquisition of a specific site are performed.

In this case, the specific region to be imaged is generally a sliced region having a certain thickness,
Echo signals from this sliced part and magnetic resonance signals (MR signals) of FID signals are collected by executing a number of data encoding processes, and these data groups are subjected to image reconstruction processing by, for example, a two-dimensional Fourier transform method. Thus, the image of the specific slice region is generated.

(Problems to be Solved by the Invention) There is a multi-slice method as an imaging method for biological diagnosis by the magnetic resonance imaging technique as described above. This multi-slice method excites a plurality of sites with one encoding and collects data from the excitation site, and when all encoding is completed, that is, when one imaging procedure is completed, A group of reconstructed data is obtained, and slice images of a plurality of parts can be obtained from them.

Generally, when multi-slicing a plurality of parts in a relatively wide area such as a body, a whole body coil is used as a receiving coil in order to cope with the large area. However, if the whole-body coil is used as the receiving coil, improvement in image quality characteristics such as S / N cannot be expected so much. Therefore, the image obtained by this method is used for high-accuracy diagnosis. It may be used for position confirmation or general diagnosis, and thereafter, high-sensitivity imaging of a certain area may be performed by using a surface coil as a receiving coil close to the imaging site and having good sensitivity characteristics. However, since the surface coil is for high-sensitivity imaging of a local area, the imaging area is naturally narrow due to the shape and other restrictions. The slicing method cannot be carried out.

Therefore, it is an object of the present invention to provide a probe coil device for an MRI apparatus that enables implementation of a high-sensitivity multi-slice method over a wide range.

[Structure of the Invention] (Means for Solving the Problems) The present invention has a structure in which the following means are provided in order to solve the above problems and achieve the object. That is, the invention according to claim 1 is a probe coil device used for performing at least one of transmission of an excitation magnetic field based on magnetic resonance and reception of an induced magnetic resonance signal with respect to a subject placed under a static magnetic field. In the above, a plurality of unit coils arranged two-dimensionally, a linear phantom arranged on a two-dimensional surface in which the plurality of unit coils are arranged side by side, and corresponding to a slice region when performing the multi-slice method And a control means for selecting one or a combination of the unit coils.

In the invention according to claim 2, a static magnetic field generating means for generating a static magnetic field applied to the subject, a gradient magnetic field generating means for generating a gradient magnetic field applied to the subject, and an excitation applied to the subject Excitation magnetic field generating means for generating a magnetic field for use, and a sequential drive control of the gradient magnetic field generating means and the exciting magnetic field generating means by executing a pulse sequence according to a predetermined multi-slice imaging method for performing multi-slice imaging of the subject. Controller, a plurality of unit coils arranged in close proximity to the subject, and a plurality of unit coils arranged two-dimensionally, and the plurality of unit coils serving as at least one coil unit for receiving an induced magnetic resonance signal. A selector for selecting at least one of the unit coils in conjunction with a pulse sequence according to the multi-slice imaging method. A probe coil device including a step, a collecting device that collects a magnetic resonance signal obtained from at least one of the plurality of unit coils selected by the selecting device of the probe coil device, and a collecting device that collects the magnetic resonance signal. And a means for generating a magnetic resonance image of the subject based on the magnetic resonance signal.

Further, the invention according to claim 3 is a static magnetic field generating means for generating a static magnetic field to be applied to the subject, a gradient magnetic field generating means for generating a gradient magnetic field to be applied to the subject, and an excitation applied to the subject. Excitation magnetic field generating means for generating a magnetic field for use, and a sequential drive control of the gradient magnetic field generating means and the exciting magnetic field generating means by executing a pulse sequence according to a predetermined multi-slice imaging method for performing multi-slice imaging of the subject. And a plurality of unit coils arranged in a two-dimensional array and a two-dimensional surface in which the plurality of unit coils are arranged in parallel. When performing a multi-slice imaging method with a linear phantom, one or a combination of the unit coils corresponding to the slice region A probe coil device comprising selection means for selecting in conjunction with a pulse sequence according to the slice imaging method, and the subject and the subject obtained from one or a combination of the unit coils selected by the selection means of the probe coil device. MRI comprising: collecting means for collecting magnetic resonance signals from the linear phantom; and means for generating magnetic resonance images of the subject and the linear phantom based on the magnetic resonance signals collected by the collecting means. Device.

(Operation) According to the invention of claim 1 having such a configuration,
Since one or a combination of unit coils can be selected corresponding to the slice site, a wide range of highly sensitive multi-slice methods can be performed, and since the linear phantom appears as a marker on the image, With this position marker, one or a combination of the imaging region and the unit coil to be selected can be associated. As a result, a suitable multi-slice imaging method can be realized.

According to the invention of claim 2 having the above-mentioned configuration, at least one of the unit coils corresponding to the slice region is selected in association with the execution of the multi-slice imaging method, so that the coil in the right place in the right place can be selected over a wide range. A highly sensitive multi-slice method is realized by means.

According to the third aspect of the invention having the above-mentioned configuration, at least one of the unit coils corresponding to the slice region is selected in conjunction with the execution of the multi-slice imaging method. A highly sensitive multi-slice method was realized by means of
Since the linear phantom appears as a marker on the image, the position marker can be associated with one or a combination of the imaging site and the unit coil to be selected. This allows
The preferred multi-slice imaging method can be realized.

(Example) A probe coil device according to the present invention will be described below with reference to FIGS. 1 to 3.

As shown in FIG. 1, the MRI apparatus according to the present embodiment includes a coil and an amplifier for generating a linear gradient magnetic field along the X, Y, and Z axis directions in order to provide positional information on the induction site of a magnetic resonance signal. Gradient magnetic field generation system 1 and this gradient magnetic field generation system 1
(Not shown) as a main element of a magnet assembly capable of accommodating a subject P (not shown) therein, a static magnetic field coil (not shown) of a normal conducting or superconducting type (a permanent magnet may be used). And a transmission system 2 including an implantable whole body coil (not shown) for transmitting an excitation magnetic field (RF pulse). This implantable whole-body coil is capable of not only transmitting RF pulses but also receiving induced magnetic resonance signals, but in the present embodiment, the coil is used for excitation over a wide area. Used as a credit coil.

Further, it has a receiver 3 for controlling reception of the induced MR signal,
The receiver 3 is connected to the receiving coil 4. The receiving coil 4 includes a plurality of small unit coils 4a1, 4a2, 4
a2 and the large coil 4b are arranged two-dimensionally, that is, in a plane, and the switches 4c1 and 4c are provided between the coils.
2, 4c3, 4c4 are placed, and one of the small unit coils or a combination thereof or the selection of the large coil is selected by the switch 4c.
It can be performed by controlling (4c1, 4c2, 4c3, 4c4) by the switching controller 5.
In this case, as shown in FIG. 1, the large coil 4b surrounds the outer side of the plurality of small unit coils 4a1, 4a2, 4a3, 4a4 and the plurality of small unit coils 4a1, 4a2, 4a4.
It is arranged on the same two-dimensional surface as a3, 4a4.

FIG. 2 is a diagram showing the details of the switching device 4c, which comprises a PIN diode 4c1, capacitors 4c2, 4c3, choke coils 4c4, 4c5, a power supply 4c6, and a switch 4c7, and is configured to switch between terminals in a high frequency signal band. It is a thing.

The receiving coil 4 is preferably formed in a mat shape so that it can be easily installed under the top plate on which the subject is placed, which may be suitable for photographing the waist.

The controller 6 can control the gradient magnetic field generation system 1, the transmission system 2, and the receiver 3 to execute a pulse sequence for excitation / data collection, and gives a command to the switching controller 5. , Switch 4c (4c1, 4c2, 4
c3, 4c4) switching control, small unit coil 4a
1, 4a2, 4a2, a combination of medium unit coils 4a1, 4a2, a combination of medium unit coils 4a2, 4a3, a combination of medium unit coils 4a1, 4a3, a large coil 4b To be able to do. This selection operation is configured to interlock with the pulse sequence so that the coil at the position corresponding to the slice region is selected when the multi-slice method is executed.

The host computer 7 functions as a higher-order controller of the controller and has a built-in reconstruction device, performs Fourier transform processing on the data group collected by the receiver 3 to generate a slice image, and displays it on the display 8. It is designed to let you.

Next, the operation of this embodiment configured as described above will be described with reference to FIG. That is, the receiving coil 4 is placed under the waist of the subject P (between the subject and the top plate), and in this state, the receiving coil 4 is placed in the diagnosable magnetic field space in the magnet assembly.

Then, the controller 6 is driven to execute the pulse sequence for data collection. As a result, a gradient magnetic field is generated from the gradient magnetic field generation system 1 and an excitation RF pulse is generated from the implantable whole-body coil, and the magnetic resonance signal induced along with this is collected by the receiving coil 4. This sequence is repeated a predetermined number of times to obtain a data group, and an image is generated from this data group. In this case, the slice positions P1, P2, P3, P4, P5 of the subject P and one of the small unit coils (C1, C2) which are close to the slice positions and which function as a surface coil having high sensitivity characteristics in the depth direction. , C3, C
4, C5) or a combination thereof, or a large coil is selected, a wide range of highly sensitive multi-slice method using a surface coil is realized. Further, since it is possible to observe an image by normal imaging over a wide range using the large coil 4b, it is possible to realize a suitable multi-slice method using an appropriate small unit coil placed at an appropriate position.

In the above embodiment, the operator needs to recognize the correspondence between the slice position and the coil to be selected prior to imaging, and set the imaging condition so that the slice position corresponds to the coil to be selected. But in this case
A reception coil incorporating a linear phantom can be used so that the position of the slice on the reception coil 4 can be known.

FIG. 4 is a view showing the structure of a receiving coil 9 incorporating a linear phantom, in which the pipes 9a, 9b, 9 containing the phantom solution are formed on the surface formed by the unit coils C1 to Cn.
As shown in the drawing, c shows two pipes 9 arranged in the coil juxtaposition direction.
a, 9b, 9c are placed, and the pipe 9b is connected to the pipes 9a, 9c.
They are arranged in a Z shape as a whole so as to be bridged between them.

FIG. 5 is a display example when slice imaging is performed using the receiving coil 9 incorporating the linear phantom shown in FIG. 4, and a slice image P ′ at a position of the subject P on the screen 8A is displayed. , The pipes 9a, 9 at the sliced portion
Cross-sectional images 9a ', 9b', 9c 'of b and 9c appear. Here, since the image can be measured and the vertical dimension H and the horizontal dimension L of the receiving coil 9 are known, as shown in FIG. 6A, h can be obtained by H × / L. Where h
Indicates the position of the receiving coil 9, so this h
Based on the above, the correspondence between the slice position and the coil to be selected can be set. In this case, the slice plane is a plane orthogonal to the direction in which the coils are arranged side by side. However, in the case of skewing, h indicating the coil position is calculated in the equivalent diagram shown in FIG. 6 (b). be able to.

Next, a clinical application using the receiving coils 4 and 9 capable of implementing the wide-range high-sensitivity multi-slice method according to the present embodiment will be specifically described with reference to FIGS. 7 and 8. That is, in the sequence according to this clinical application, the echo time T _E is set so that the proton spin of water is 180 ° with respect to the proton spin of fat, that is, both spins face in opposite directions (for example, static magnetic field H ₀ = 0.
The resonance frequency of the proton is 21.3MH when it is set to 5T.
If z and the echo time T _E is 20.1 msec, the magnetization of water and that of fat are oriented by 180 °. However, the echo time T _E is set to an allowable range of 20.1 ± 1.0 msec. ) Sequence, as shown in FIG.
A magnetic resonance signal (spin echo signal) is collected by a field echo method in which a 180 ° pulse of the spin echo method, which is a sequence of a ° -180 ° pulse sequence, that is, a magnetic field for converging the magnetization is replaced with a gradient magnetic field inversion. Is.

The slice thickness is relatively thick, for example, 15 to
The echo time T _E is set to about 40 mm, the echo time T _E is set to 15 to 30 msec or 4 to 10 msec, and the pulse repetition interval T _R is set to 100 to 500 msec as the time to recover the proton spins of the water. Angle α ° is 10 ° -40 ° to emphasize the protons of water.
And the gradient magnetic field in the shaded area is added to make the phase shift due to the flow zero.

Note that G _S is a slice gradient magnetic field in this case, a Z gradient magnetic field, G _R is a read gradient magnetic field in this case, an X axis gradient magnetic field, and G _E is an encoding gradient magnetic field. In the case, the gradient magnetic field is in the Y-axis direction.

Under such a condition setting, the implantable whole-body coil transmits an α ° pulse, the gradient magnetic field G _S for slice is applied from the gradient magnetic field generation system 1, and then the inverted read gradient magnetic field G _R and the variable strength are applied. The phase-encoding gradient magnetic field G _E is applied to collect an echo signal from the slice region by one or a combination of the unit coils of the receiving coil 4 at the echo time T _E. By repeating this a predetermined number of times, a data group is given to the host computer 7, an image is generated from this data group, and a display such as that shown in FIG. The displayed image will appear.

According to the above image sequence, the echo signal obtained from the slice region S having a relatively thick slice thickness of about 15 to 40 mm is 100 to 500.
With the pulse repetition interval T _R set to msec, the water will recover significantly during that T _R , so the signal strength obtained is large. Further, as described above, the magnetization of water and the magnetization of fat are 18
The signal from fat is suppressed by the echo time T _E set to face 0 °. Further, since the sliced part is placed in the center of the magnetic field and the unit coil or the combination of the receiving coil 4 is placed directly under the part, the receiving sensitivity is high.

According to the above, the signal is obtained from the water from the sliced part of the waist, but the signal from the fat is suppressed. Therefore, as shown in FIG. 9, the running form of the nerve root is well drawn on one image.

Further, since the gradient magnetic field in the hatched portion shown in the figure is applied so as to compensate the signal phase shift due to the flow, the cerebrospinal fluid (C
The artifact due to the flow of SF) will not occur. Therefore, the nerve roots can be clearly distinguished from other tissues for observation.

In the above case, since the repetition interval T _R is using field echo method can be made shorter than the other pulse sequences such as spin echo sequence, the time required for data collection requires only a short time.

Next, another example will be described. That is, since the sequence used in this example is mainly the one in which the fat signal is suppressed, as shown in FIG. 8 in addition to the above-described sequence, in the STIR (Short TI Invertion Recovery) sequence, the signal from fat is It is possible to apply a TI selected to be zero. Also, the echo time T is extremely
_E long SE method, for example, _T R = _{1500~3000msec,}
The one having T _E = 150 to 400 msec can be applied. Of course, the arrangement of sliced portions, the arrangement of transmission / reception coils, and the like can be appropriately selected.

In addition, the receiving coils 4 and 9 according to the present embodiment, which have the characteristic of being able to carry out a wide range of highly sensitive multi-slice method, can be used for various clinical applications.

Further, in the above example, the case where the coil shown in FIGS. 1 and 4 is used as the receiving coil is explained.
Of course, it can be used as a transmission coil.

Besides, various modifications can be made without departing from the scope of the present invention.

[Advantages of the Invention] As described above, according to the invention according to claim 1, 2 or 3, it is possible to provide a probe coil device and an MRI device capable of performing the high-sensitivity multi-slice imaging method.

[Brief description of drawings]

FIG. 1 is a diagram showing a probe coil device of an MRI apparatus according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing details of a switching device in the same embodiment, and FIG. 3 is a diagram showing an operation of the same embodiment. FIG. 4 is a view showing another embodiment of the present invention, FIGS. 5 and 6 are views showing the operation of the configuration shown in FIG. 4, and FIGS. 7 and 8 are probe coil devices of the present invention. FIG. 9 is a diagram showing a clinical application of the above, and FIG. 9 is a diagram showing a generated image in the clinical application. 1 ... gradient magnetic field generation system, 2 ... transmission system, 3 ... reception system,
4, 9 ... Receiving coil, 5 ... Switching controller, 6 ... Controller, 7 ... Host computer, 8 ... Display.

Claims (3)

[Claims] 1. A two-dimensional probe coil device used for performing at least one of transmitting an excitation magnetic field based on magnetic resonance and receiving an induced magnetic resonance signal with respect to a subject placed under a static magnetic field. A plurality of unit coils arranged in parallel with each other, a linear phantom arranged on a two-dimensional surface in which the plurality of unit coils are arranged in parallel, A probe coil device for an MRI apparatus, comprising: a control means for selecting one or a combination. 2. A static magnetic field generating means for generating a static magnetic field to be applied to a subject, a gradient magnetic field generating means for generating a gradient magnetic field to be applied to the subject, and an exciting magnetic field to be applied to the subject. Excitation magnetic field generating means, a controller for sequentially driving and controlling the gradient magnetic field generating means and the exciting magnetic field generating means by executing a pulse sequence according to a predetermined multi-slice imaging method for performing multi-slice imaging of the subject, At least one of the plurality of unit coils, which are arranged close to the subject and are two-dimensionally arranged side by side, and at least one of the unit coils as at least one coil means to be used for receiving the induced magnetic resonance signal. A selection means for selecting one in conjunction with a pulse sequence according to the multi-slice imaging method. Probe coil device, collecting means for collecting a magnetic resonance signal obtained from at least one of the plurality of unit coils selected by the selecting means of the probe coil device, and the magnetic resonance signal collected by the collecting means And a unit for generating a magnetic resonance image of the subject based on the above. 3. A static magnetic field generating means for generating a static magnetic field to be applied to the subject, a gradient magnetic field generating means for generating a gradient magnetic field to be applied to the subject, and an exciting magnetic field to be applied to the subject. Excitation magnetic field generating means, a controller for sequentially driving and controlling the gradient magnetic field generating means and the excitation magnetic field generating means by executing a pulse sequence according to a predetermined multi-slice imaging method for performing multi-slice imaging of the subject, A plurality of unit coils arranged in a two-dimensional array, and a linear phantom arranged on a two-dimensional surface in which the plurality of unit coils are arranged in parallel, When executing the multi-slice imaging method, one or a combination of the unit coils is used in association with the slice region. Probe coil device comprising a selection means for selecting in conjunction with a pulse sequence according to the method of scanning, and the subject and the line obtained from one or a combination of the unit coils selected by the selection means of the probe coil device. Apparatus for collecting magnetic resonance signals from a linear phantom, and means for generating magnetic resonance images of the subject and the linear phantom based on the magnetic resonance signals collected by the collecting means. .