JP4347957B2 - Magnetic resonance imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an RF coil (radio frequency coil), a magnetic resonance signal measuring apparatus, and a magnetic resonance imaging apparatus, and more particularly, an RF coil having a pair of coil loops facing each other, and a magnetic resonance signal measurement using such an RF coil. The present invention relates to an apparatus and a magnetic resonance imaging apparatus using such a magnetic resonance signal measuring apparatus.
[0002]
[Prior art]
In a magnetic resonance imaging apparatus, a magnetic resonance signal is received using a pair of coil loops facing each other with an imaging target interposed therebetween. A typical example of this type of coil is a saddle coil. A schematic diagram of the saddle coil and its use state is shown in FIG. As shown in the figure, a pair of coil loops 002 and 002 ′ are opposed to each other with the imaging target 004 interposed therebetween. The coil loops 002 and 002 ′ are connected in series, and the sum of signals received by both coil loops is extracted from signal extraction points (not shown) provided at appropriate locations.
[0003]
The distance between the coil loops 002 and 002 ′ is a fixed value according to the maximum image pickup target that can be accommodated, or a variable value that can be adjusted according to the physique of the image pickup target.
[0004]
[Problems to be solved by the invention]
If the distance between the coil loops is fixed, in the case of a small or thin imaging target, the distance from the coil loop to the imaging target increases, so the S / N (signal to noise ratio) of the received signal is reduced. there were.
[0005]
On the other hand, in the case where the distance between the coil loops is adjustable, the tuning condition for signal reception changes due to the change in the coupling state between the coil loops due to the change in the distance, and the S / N also decreases. There was a problem.
[0006]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an RF coil for receiving a signal having a good S / N while the interval between a pair of coil loops facing each other is adjustable. It is to realize a magnetic resonance signal measuring apparatus using such an RF coil and a magnetic resonance imaging apparatus using such a magnetic resonance signal measuring apparatus.
[0007]
[Means for Solving the Problems]
(1) The invention according to the first aspect for solving the above-described problem is that a pair of coil loops each having a substantial LC parallel circuit in a reception signal output unit and facing each other, and the pair of coils An RF coil comprising supporting means for supporting the loop so that a distance between them can be adjusted.
[0008]
(2) An invention according to a second aspect for solving the above-described problem is a magnetic resonance signal measuring apparatus having an RF coil and a magnetic resonance signal measuring means connected to the RF coil, A magnetic resonance signal measuring apparatus using the RF coil described in (1) as a coil.
[0009]
(3) According to a third aspect of the invention for solving the above-described problem, the magnetic resonance signal measuring means includes an adding means for adding the output signals of the pair of coil loops ( The magnetic resonance signal measuring apparatus according to 2).
[0010]
(4) In a fourth aspect of the invention for solving the above-described problem, the magnetic resonance signal measuring means includes adjusting means for adjusting the output signals of the pair of coil loops, respectively, before the adding means. (3) The magnetic resonance signal measuring apparatus according to (3).
[0011]
(5) The invention according to a fifth aspect for solving the above-described problem includes a static magnetic field forming unit that forms a static magnetic field in a space that accommodates an imaging target, a gradient magnetic field forming unit that forms a gradient magnetic field in the space, A magnetic resonance imaging apparatus comprising: a high-frequency magnetic field forming unit that forms a high-frequency magnetic field in the space; a measurement unit that measures a magnetic resonance signal from the space; and an image generation unit that generates an image based on the measured magnetic resonance signal A magnetic resonance imaging apparatus using the magnetic resonance signal measuring apparatus according to any one of (2) to (4) as the measuring means.
[0012]
(6) In a sixth aspect of the invention for solving the above-described problem, the image generation means generates images based on the output signals of the pair of coil loops and combines the images. The magnetic resonance imaging apparatus according to (5), which generates an image.
[0013]
(7) In another aspect of the invention for solving the above-described problem, the magnetic resonance signal measuring means includes storage means for storing the output signals of the pair of coil loops in a preceding stage of the adding means. (3) The magnetic resonance signal measuring apparatus according to (3).
[0014]
(8) In another aspect of the invention for solving the above problem, the magnetic resonance signal measuring means includes an adjusting means for adjusting read data of the storage means between the storage means and the adding means. (7) The magnetic resonance signal measuring apparatus according to (7).
[0015]
(9) In another aspect of the invention for solving the above problems, a static magnetic field is formed in a space accommodating an imaging target, a gradient magnetic field is formed in the space, a high-frequency magnetic field is formed in the space, A magnetic resonance imaging method for measuring a magnetic resonance signal from the space and generating an image based on the measured magnetic resonance signal, wherein the measurement is performed in (2), (3), (4), (7) or A magnetic resonance imaging method, which is performed using the magnetic resonance signal measuring apparatus according to (8).
[0016]
(10) In another aspect of the invention for solving the above-described problem, the image generation includes generating images based on output signals of the pair of coil loops, and combining the images. The magnetic resonance imaging method according to (9), wherein the magnetic resonance imaging method is generated.
[0017]
(Function)
In the present invention, the substantial LC parallel circuit of each of the pair of coil loops substantially decouples both with high impedance at the time of parallel resonance, so that the tuning condition does not change even if the distance between the two is changed. For this reason, it is possible to perform signal reception with good S / N by adjusting the distance between the coil loops according to the physique of the imaging target.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiment. FIG. 1 shows a block diagram of the magnetic resonance imaging apparatus. This apparatus is an example of an embodiment of the present invention. An example of an embodiment relating to the apparatus of the present invention is shown by the configuration of the apparatus.
[0019]
As shown in FIG. 1, the apparatus has a magnet system 100. The magnet system 100 includes a main magnetic field coil unit 102, a gradient coil unit 106 and an RF coil unit 108. Each of these coil portions has a substantially cylindrical outer shape and is arranged coaxially with each other. The imaging object 300 is mounted on a cradle 500 and carried into and out of the internal space of the magnet system 100 by a conveying means (not shown).
[0020]
The cradle 500 is provided with a receiving coil unit 110. The reception coil unit 110 has a pair of members facing each other. The imaging target 300 is mounted on the cradle 500 in a posture in which the body is sandwiched from the front and rear between a pair of members facing each other. The reception coil unit 110 is an example of an embodiment of the RF coil of the present invention. The receiving coil unit 110 will be described later.
[0021]
The main magnetic field coil unit 102 forms a static magnetic field in the internal space of the magnet system 100. The main magnetic field coil section 102 is an example of an embodiment of the static magnetic field forming means in the present invention. The direction of the static magnetic field is generally parallel to the body axis direction of the imaging target 300. That is, a so-called horizontal magnetic field is formed. The main magnetic field coil unit 102 is configured using, for example, a superconducting coil. Needless to say, the present invention may be configured using not only a superconducting coil but also a normal conducting coil.
[0022]
The gradient coil unit 106 generates a gradient magnetic field for giving a gradient to the static magnetic field strength. There are three types of gradient magnetic fields that are generated: a slice gradient magnetic field, a read out gradient magnetic field, and a phase encode gradient magnetic field. The gradient coil unit 106 corresponds to these three types of gradient magnetic fields. Has three gradient coils (not shown).
[0023]
The RF coil unit 108 forms a high-frequency magnetic field for exciting spins in the body of the imaging target 300. Hereinafter, the formation of a high-frequency magnetic field is referred to as transmission of an RF excitation signal. The receiving coil unit 110 receives an electromagnetic wave generated by excited spin, that is, a magnetic resonance signal.
[0024]
A gradient driving unit 130 is connected to the gradient coil unit 106. The gradient driving unit 130 gives a driving signal to the gradient coil unit 106 to generate a gradient magnetic field. The portion composed of the gradient coil section 106 and the gradient drive section 130 is an example of an embodiment of the gradient magnetic field forming means in the present invention. The gradient driving unit 130 includes three systems of driving circuits (not shown) corresponding to the three systems of gradient coils in the gradient coil unit 106.
[0025]
An RF drive unit 140 is connected to the RF coil unit 108. The RF drive unit 140 provides a drive signal to the RF coil unit 108 and transmits an RF excitation signal to excite spins in the body of the imaging target 300. The portion composed of the RF coil section 108 and the RF drive section 140 is an example of an embodiment of the high-frequency magnetic field forming means in the present invention.
[0026]
A data collection unit 150 is connected to the reception coil unit 110. The portion comprising the receiving coil unit 110 and the data collecting unit 150 is an example of an embodiment of the measuring means in the present invention. The data collection unit 150 is an example of an embodiment of the magnetic resonance signal measuring means in the present invention. The data collection unit 150 takes in the reception signal received by the reception coil unit 110 and collects it as digital data.
[0027]
A bias driving unit 120 is also connected to the receiving coil unit 110. The bias driving unit 120 supplies a bias signal to a diode (diode), which will be described later, included in the receiving coil unit 110, thereby switching the receiving coil between enable / disable (enable / disable).
[0028]
A control unit 160 is connected to the bias driving unit 120, the gradient driving unit 130, the RF driving unit 140, and the data collection unit 150. The controller 160 controls the bias driver 120 or the data collector 150, respectively.
[0029]
The output side of the data collection unit 150 is connected to the data processing unit 170. The data processing unit 170 stores the data fetched from the data collection unit 150 in a memory (not shown). A data space is formed in the memory. The data space constitutes a two-dimensional Fourier space. The data processing unit 170 reconstructs an image of the imaging target 300 by performing two-dimensional inverse Fourier transform on the data in the two-dimensional Fourier space. The data processing unit 170 is an example of an embodiment of image generation means in the present invention.
[0030]
The data processing unit 170 is connected to the control unit 160. The data processing unit 170 is above the control unit 160 and controls it. A display unit 180 and an operation unit 190 are connected to the data processing unit 170. The display unit 180 displays the reconstructed image and various information output from the data processing unit 170. The operation unit 190 is operated by an operator and inputs various commands and information to the data processing unit 170.
[0031]
Next, the receiving coil unit 110 will be described. In FIG. 2, the schematic diagram of the mutual relationship of the imaging target 300 and the receiving coil part 110 is shown. As shown in the figure, the receiving coil unit 110 includes a pair of members facing each other, that is, a pair of coil plates 210 and 220. Each of the coil plates 210 and 220 is provided with a coil loop. A coil loop is an example of an embodiment of a coil loop in the present invention. The electrical configuration of the coil loop will be described later.
[0032]
The coil plates 210 and 220 are opposedly supported by the support member 230 at a predetermined interval. The support member 230 is an example of an embodiment of the support means in the present invention. The support member 230 can be expanded and contracted in the length direction, whereby the distance between the coil plates 210 and 220 can be adjusted.
[0033]
For example, as shown in FIG. 3, the extendable support member 230 includes a column member 232 fixed to the coil plate 210 side and a sheath member 234 fixed to the coil plate 220 side, and the column member 232 is a sheath. The member 234 is fitted and slidable. There is friction between the two, and the stretched or shortened state to an arbitrary length can be maintained.
[0034]
The support portion 230 can be omitted. In this case, the coil plates 210 and 220 are configured to have flexibility, and the imaging target 300 is wrapped from the front and the back.
[0035]
FIG. 4 shows an electric circuit of the coil loop. As shown in the figure, the coil loop is constituted by a series connection of a capacitor 302 and a conductor 304. Capacitors and conductors are represented in one place. The number of capacitors 302 is not limited to four as shown, and may be appropriate.
[0036]
An input circuit of a preamplifier 306 that amplifies a magnetic resonance signal received by the coil loop is connected to both ends of one capacitor 302 through an inductor 308. As the preamplifier 306, an amplifier whose impedance of the input circuit is sufficiently low, that is, a low input impedance amplifier is used.
[0037]
A diode 310 is connected in parallel to the input circuit of the preamplifier 306. A forward bias voltage or a reverse bias voltage is applied to the diode 310 from the bias driver 120 via an RF choke circuit 312. The diode 310 is sufficiently turned on by the forward bias voltage to configure a parallel circuit of the inductor 308 and the capacitor 302.
[0038]
Since the resonance frequency of the LC parallel circuit is selected to match the frequency of the RF signal, the LC parallel resonance circuit is turned on by turning on the diode 310 when the RF coil unit 108 transmits the RF signal. Thus, the coil loop is substantially opened with high impedance, and decoupling with the RF coil unit 108 is performed. A state in which the diode 310 is on is referred to as a disabled state of the receiving coil unit 110.
[0039]
When receiving a magnetic resonance signal, the diode 310 is turned off by a reverse bias voltage. A state in which the diode 310 is off is referred to as an enable state of the reception coil unit 110. In this case, since the preamplifier 306 is a low input impedance amplifier, an LC parallel circuit composed of the capacitor 302 and the inductor 308 is substantially formed. For this reason, even when a magnetic resonance signal is received, the coil loop is substantially in an open loop state due to the high impedance due to the resonance of the LC parallel circuit.
[0040]
Even if the diode 310 and the input terminal of the preamplifier 306 are connected by a coaxial cable having an integral multiple of 1/2 (λ / 2) of the wavelength of the magnetic resonance signal, the above condition is satisfied. Therefore, this allows the preamplifier 306 to be provided at an appropriate position away from the coil loop.
[0041]
Coil loops having such a configuration are formed on the coil plates 210 and 220, respectively, and are mounted on the cradle 500 with the loop surfaces facing each other. An electric circuit of a pair of coil loops in the opposed state is shown in FIG. FIG. 5 is drawn from an angle at which the loop surface of each coil is viewed obliquely.
[0042]
Since the pair of coil loops are substantially open loops due to the high impedance of the LC circuit at the time of reception, there is substantially no coupling between them. For this reason, it becomes the same as that each coil loop exists independently, and can receive a magnetic resonance signal individually, without receiving the influence of the coil loop which opposes.
[0043]
Further, since they are not affected by each other, the tuning condition does not change even if the distance between the coil loops is changed by extending / contracting the support member 230. Therefore, it is possible to freely adjust the interval according to the physique of the imaging target 300 and to receive a signal with good S / N while always approaching the imaging target 300.
[0044]
Further, since there is no mutual influence, a plurality of pairs of other coil loops having the same configuration may be provided. Thereby, a wider range of the imaging target 300 can be imaged. Hereinafter, the case where there is one pair of coil loops will be described.
[0045]
FIG. 6 shows a block diagram of the magnetic resonance imaging apparatus. This apparatus is an example of an embodiment of the present invention. An example of an embodiment relating to the apparatus of the present invention is shown by the configuration of the apparatus.
[0046]
The apparatus shown in FIG. 6 includes a magnet system 100 ′ and a receiving coil section 110 ′ that are different from the apparatus shown in FIG. Other than that, the configuration is the same as that of the apparatus shown in FIG. 1, and the same reference numerals are given to the same parts, and the description is omitted.
[0047]
The magnet system 100 ′ includes a main magnetic field magnet unit 102 ′, a gradient coil unit 106 ′, and an RF coil unit 108 ′. Each of the main magnetic field magnet section 102 ′ and each coil section is composed of a pair of facing each other across a space. Moreover, all have a disk-shaped external shape and are arrange | positioned sharing a central axis. The imaging object 300 is mounted on the cradle 500 and carried into and out of the internal space of the magnet system 100 ′ by a conveying means (not shown).
[0048]
The cradle 500 is provided with a receiving coil section 110 ′. The reception coil unit 110 ′ has a pair of members facing each other. The imaging target 300 is mounted on the cradle 500 in a posture in which the body is sandwiched between a pair of members facing each other from the left and right. The reception coil unit 110 ′ is an example of an embodiment of the RF coil of the present invention. The receiving coil unit 110 ′ will be described later.
[0049]
The main magnetic field magnet unit 102 ′ forms a static magnetic field in the internal space of the magnet system 100 ′. The direction of the static magnetic field is substantially orthogonal to the body axis direction of the imaging target 300. That is, a so-called vertical magnetic field is formed. The main magnetic field magnet section 102 ′ is configured using, for example, a permanent magnet. Of course, not only permanent magnets but also superconducting electromagnets or normal conducting electromagnets may be used.
[0050]
The gradient coil section 106 ′ generates a gradient magnetic field for giving a gradient to the static magnetic field strength. There are three types of gradient magnetic fields to be generated: a slice gradient magnetic field, a readout gradient magnetic field, and a phase encode gradient magnetic field, and the gradient coil unit 106 'has three gradient coils (not shown) corresponding to these three types of gradient magnetic fields. .
[0051]
The RF coil unit 108 ′ transmits an RF excitation signal for exciting spins in the body of the imaging target 300. The reception coil unit 110 ′ receives a magnetic resonance signal in which excited spin occurs.
[0052]
Next, the receiving coil unit 110 ′ will be described. FIG. 7 shows a schematic diagram of the mutual relationship between the imaging target 300 and the receiving coil unit 110 ′. As shown in the figure, the receiving coil section 110 ′ has a pair of members facing each other, that is, a pair of coil plates 210 ′ and 220 ′. The coil plates 210 'and 220' are provided with coil loops, respectively. A coil loop is an example of an embodiment of a coil loop in the present invention. The electrical configuration of each coil loop is the same as that shown in FIG.
[0053]
The coil plates 210 ′ and 220 ′ are opposed and supported by a support member 230 ′ at a predetermined interval. Support member 230 'is an example of an embodiment of a support means in the present invention. The support member 230 ′ can be expanded and contracted in the length direction, and thereby the distance between the coil plates 210 ′ and 220 ′ can be adjusted. The extendable support member 230 'has a configuration similar to that shown in FIG.
[0054]
That is, the receiving coil unit 110 ′ has the same configuration as the receiving coil unit 110. However, the mutual relationship with the imaging target 300 is 90 ° different from the receiving coil unit 110 around the body axis.
[0055]
Also in the receiving coil section 110 ′, the coil loop provided in the coil plates 210 ′ and 220 ′ is an electric circuit similar to the coil loop provided in the coil plates 210 and 220 of the receiving coil section 110. The distance between the coil plates 210 ′ and 220 ′ can be freely adjusted according to the physique of the imaging target 300 without affecting the tuning conditions.
[0056]
The data collection unit 150 in the apparatus shown in FIG. 1 or FIG. 6 includes an adder 470 that adds the output signals of the preamplifiers 306 and 306 ′, as shown in FIG. Adder 470 is an example of an embodiment of the adding means in the present invention. By adding the two reception signals by the adder 470, a reception signal equivalent to that received by the saddle coil can be obtained.
[0057]
That is, if the sensitivity characteristics of the individual coil loops are given by, for example, the curves a and b shown in FIG. 9, a received signal equivalent to that received by the receiving coil having the sensitivity as the composite curve c is obtained. Can do. The composite curve c is equivalent to the sensitivity characteristic of the saddle coil.
[0058]
The reception signal may be added after being converted into a digital signal. The digital signal may be temporarily stored in a memory and performed on the read signal.
[0059]
In addition, as shown in FIG. 10, signal adjustment units (units) 472 and 472 ′ are provided in the subsequent stage of the preamplifiers 306 and 306 ′, and the output signals are adjusted to freely adjust the sensitivity characteristics of the synthesis. . That is, for example, by changing the gain or phase of the output signal of the preamplifier 306 ′ by the signal adjustment unit 472 ′, the sensitivity characteristic b is changed to b ′ as shown in FIG. The characteristic can be changed from c to c ′. The signal adjustment units 472 and 472 ′ are an example of an embodiment of the adjustment means in the present invention.
[0060]
Such signal adjustment may be performed after conversion to a digital signal. Alternatively, it may be performed on a signal once stored in the memory. Alternatively, the digital signals subjected to signal adjustment may be stored in a memory, and the read signals may be added.
[0061]
Alternatively, as shown in FIG. 12, based on the output signals of the preamplifiers 306 and 306 ′ stored in the memories 474 and 474 ′ as digital data, the images are reconstructed by the image reconstruction units 476 and 476 ′, respectively. The reconstructed images may be combined by the image combining unit 480 to obtain one image. Needless to say, appropriate image processing may be performed in advance when combining images.
[0062]
In this case, the image reconstruction units 476 and 476 ′ and the image composition unit 480 are realized by, for example, a computer program (computer program) provided in the data processing unit 170. Image processing is also performed by a computer program.
[0063]
The operation of this apparatus will be described. The operation is essentially the same between the apparatus shown in FIG. 1 and the apparatus shown in FIG. The operation of this apparatus proceeds under the control of the control unit 160.
[0064]
FIG. 13 shows an example of a pulse sequence used for magnetic resonance imaging. This pulse sequence is a pulse sequence of a spin echo (SE: Spin Echo) method.
[0065]
That is, (1) is a sequence of 90 ° pulses and 180 ° pulses for RF excitation in the SE method, and (2), (3), (4) and (5) are respectively the slice gradient Gs and the lead. This is a sequence of an out gradient Gr, a phase encode gradient Gp, and a spin echo MR. The 90 ° pulse and the 180 ° pulse are represented by center signals. The pulse sequence proceeds from left to right along the time axis t.
[0066]
As shown in the figure, 90 ° excitation of spin is performed by a 90 ° pulse. At this time, the slice gradient Gs is applied, and selective excitation for a predetermined slice is performed. After a predetermined time from the 90 ° excitation, 180 ° excitation by a 180 ° pulse, that is, spin inversion is performed. At this time, the slice gradient Gs is applied, and selective inversion is performed for the same slice.
[0067]
In the period between 90 ° excitation and spin reversal, a readout gradient Gr and a phase encode gradient Gp are applied. Spin dephase is performed by the lead-out gradient Gr. Spin phase encoding is performed by the phase encoding gradient Gp.
[0068]
After the spin inversion, the spin is rephased at the readout gradient Gr to generate the spin echo MR. The spin echo MR is an RF signal having a symmetrical waveform with respect to the echo center. The central echo occurs after TE (echo time) from 90 ° excitation. The spin echo MR is received by two coil loops on the coil plates 210 and 220, and the received signals are output from the preamplifiers 306 and 306 ′, respectively.
[0069]
The data collection unit 150 performs data collection by adding two output signals at the stage of an analog signal or a digital signal. In addition, both signals are simply added, or are adjusted after being adjusted appropriately. Alternatively, data is collected as two systems of received signals that are not added.
[0070]
Such a pulse sequence is repeated 128 to 256 times in a cycle TR (repetition time). The phase encoding gradient Gp is changed every time it is repeated, and a different phase encoding is performed each time. Thereby, view data of 128 to 256 views are obtained.
[0071]
Another example of the pulse sequence for magnetic resonance imaging is shown in FIG. This pulse sequence is a pulse sequence of a gradient echo (GRE) method.
[0072]
That is, (1) is a sequence of α ° pulses for RF excitation in the GRE method, and (2), (3), (4) and (5) are respectively slice gradient Gs, readout gradient Gr, It is a sequence of a phase encoding gradient Gp and a spin echo MR. The α ° pulse is represented by a center signal. The pulse sequence proceeds from left to right along the time axis t.
[0073]
As shown in the figure, the α ° excitation of the spin is performed by the α ° pulse. α is 90 or less. At this time, the slice gradient Gs is applied, and selective excitation for a predetermined slice is performed.
[0074]
After the α ° excitation, spin phase encoding is performed by the phase encoding gradient Gp. Next, the spin is first dephased by the readout gradient Gr, and then the spin is rephased to generate a gradient echo MR. The gradient echo MR is an RF signal having a symmetrical waveform with respect to the echo center. The central echo occurs after TE from α ° excitation.
[0075]
The gradient echo MR is collected as view data by the data collection unit 150 as described above. Such a pulse sequence is repeated 128 to 256 times with a period TR. The phase encoding gradient Gp is changed every time it is repeated, and a different phase encoding is performed each time. Thereby, view data of 128 to 256 views is obtained.
[0076]
View data obtained by the pulse sequence of FIG. 13 or FIG. 14 is collected in the memory of the data processing unit 170. Note that the pulse sequence is not limited to the SE method or the GRE method, and may be one of other appropriate techniques such as a Fast Spin Echo (FSE) method and Echo Planar Imaging (Echo Planar Imaging). Needless to say.
[0077]
The data processing unit 170 reconstructs a tomographic image of the imaging target 300 by performing two-dimensional inverse Fourier transform on the view data. Alternatively, when two systems of view data are collected, a set of view data is synthesized from each view data, and an image is reconstructed by two-dimensional inverse Fourier transform of the synthesized data. Alternatively, two images are reconstructed from the two systems of view data, and a tomographic image is generated by synthesis from these images.
[0078]
Since a signal with good S / N is received by adjusting the distance between the two coil loops according to the physique of the imaging object 300, the reconstructed image is of high quality. The reconstructed image is displayed as a visible image by the display unit 180. The display image is of high quality.
[0079]
【The invention's effect】
As described above in detail, according to the present invention, an RF coil that receives a signal having a good S / N while the interval between a pair of coil loops facing each other is adjustable, and a magnet that uses such an RF coil. A resonance signal measuring apparatus and a magnetic resonance imaging apparatus using such a magnetic resonance signal measuring apparatus can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram of an exemplary apparatus according to an embodiment of the present invention.
2 is a schematic diagram showing a mutual relationship between a receiving coil unit and an imaging target in the apparatus shown in FIG.
FIG. 3 is a schematic configuration diagram of a part of the receiving coil unit shown in FIG. 2;
FIG. 4 is an electric circuit diagram of a coil loop in a receiving coil section.
FIG. 5 is an electric circuit diagram of a pair of coil loops.
FIG. 6 is a block diagram of an exemplary apparatus according to an embodiment of the present invention.
7 is a schematic diagram showing a mutual relationship between a receiving coil unit and an imaging target in the apparatus shown in FIG. 6;
8 is a block diagram of a part of a data collection unit in the apparatus shown in FIG. 1 or FIG. 6;
FIG. 9 is a graph showing reception sensitivity characteristics;
10 is a block diagram of a part of a data collection unit in the apparatus shown in FIG. 1 or FIG. 6;
FIG. 11 is a graph showing a sensitivity characteristic of reception.
12 is a block diagram of a part of a data processing unit in the apparatus shown in FIG. 1 or FIG. 6;
13 is a diagram showing an example of a pulse sequence executed by the apparatus shown in FIG. 1 or FIG.
14 is a diagram showing an example of a pulse sequence executed by the apparatus shown in FIG. 1 or FIG. 6;
FIG. 15 is a schematic diagram showing a mutual relationship between a saddle coil and an imaging target.
[Explanation of symbols]
100, 100 ′ Magnet system 102 Main magnetic field coil unit 102 ′ Main magnetic field magnet unit 106, 106 ′ Gradient coil unit 108, 108 ′ RF coil unit 110, 110 ′ Reception coil unit 120 Bias driving unit 130 Gradient driving unit 140 RF driving unit 150 Data Collection Unit 160 Control Unit 170 Data Processing Unit 180 Display Unit 190 Operation Unit 300 Image Target 500 Cradle 210, 220, 210 ′, 220 ′ Coil Plate 230, 230 ′ Support Member 232 Column Member 234 Sheath Member 302, 302 ′ Capacitor 304, 304 'Conductors 306, 306' Preamplifier 308, 308 'Inductor 310, 310' Diode 312, 312 'Choke coil circuit 470 Adder 472, 472' Signal adjustment unit 474, 474 'Memory 476, 476' Image reconstruction unit Doo 480 image synthesis unit

Claims (3)

A static magnetic field forming means for forming a static magnetic field in a space containing an imaging target;
A gradient magnetic field forming means for forming a gradient magnetic field in the space;
High-frequency magnetic field forming means for forming a high-frequency magnetic field in the space;
Measuring means for measuring magnetic resonance signals from the space;
A magnetic resonance imaging apparatus comprising image generation means for generating an image based on the measured magnetic resonance signal,
The measuring means includes
A pair of coil loops in which two receiving coil loops face each other at a distance;
An RF coil comprising supporting means for supporting the pair of coil loops such that a distance between them can be adjusted;
Two terminals for receiving signal output in each of the coil loops are connected to a low input impedance amplifier,
A capacitor is connected between the two terminals for receiving signal output,
An inductor is connected between the reception signal output terminal and the low input impedance amplifier,
An RF coil in which an LC parallel circuit of the capacitor, the inductor and the low input impedance amplifier resonates when receiving a signal;
Adding means for adding the output signals of the two low input impedance amplifiers in the RF coil;
The reception sensitivity of the RF coil corresponding to the signal added by the adding means is high at the position where each coil loop is located in the distance direction where the pair of coil loops face each other. A magnetic resonance imaging apparatus, wherein reception sensitivity decreases as the distance from the coil loop increases. The magnetic resonance imaging apparatus according to claim 1,
The RF coil is
A diode is connected between the two input terminals of the low input impedance amplifier,
Comprising bias means for supplying a forward bias voltage to the diode;
The magnetic resonance imaging apparatus according to claim 1, wherein when a forward bias voltage is supplied from the bias means and the diode is turned on, an LC parallel circuit is formed by the capacitor, the inductor, and the diode. The magnetic resonance imaging apparatus according to claim 1 or 2,
The magnetic resonance imaging apparatus according to claim 1, wherein the measuring unit includes an adjusting unit that changes a gain or a phase of an output signal of each of the low input impedance amplifiers before the adding unit.

Images