JPH1176194A - Rf probe for magnetic resonance imaging - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an RF probe for MRI, with which the part of a subject near its surface can be examined with high sensitivity and a wide area can be examined. SOLUTION: An RF probe includes: an approximately cylindrical multiple RF coil 405 in which a plurality of RF coils (elements 101-108) receiving magnetic resonance signals are arranged in the circumferential direction of a rough cylinder; a signal combining circuit (phase shifter 803 and signal adder 805) in which the signals received from the elements 101-108 are made in pairs and transmitted to a signal processing system 407, with each of the pairs of signals added together as they are deviated from each other by a predetermined phase; a selection means (signal bypass 811) for selecting the signals from a part of the elements 101-108 among the signals received by all the elements 101-108 and for transmitting the signals to the signal processing system; and connection means (switches 802, 806) for connecting the output of either the signal combining circuit or the selection means to the signal processing system 407. Therefore, one RF probe can deal with two measurement modes, and, for example, can examine both sides of the brain simultaneously and examine the part of the brain near the surface with high sensitivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an RF probe for magnetic resonance imaging (hereinafter referred to as "MRI"), and more particularly to a cylindrical multiple RF probe having a plurality of RF coils arranged on a cylinder.

[0002]

2. Description of the Related Art In an MRI apparatus, a magnetic resonance signal (hereinafter referred to as "M") generated when a subject is irradiated with a high-frequency magnetic field.
As an RF probe for receiving an "R" signal), a so-called multiple RF coil or a phased array coil comprising a plurality of RF surface coils (RF receiving coils) is known (Japanese Patent Application Laid-Open No. 2-500175).
This multiple RF coil arranges a plurality of small RF receiving coils with relatively high sensitivity and combines the signals received by each RF receiving coil to expand the field of view while maintaining the high sensitivity of the small RF receiving coil. And a receiving-only RF coil for high sensitivity.

For example, as a multiple RF coil for a horizontal magnetic field head, an Array Head Coil for Improved Functio
nal MRI (Christoph Leussler), 1996 ISMRM abstruct
p.249 is the Helmet and Cylindrical Shaped CP Array Coi as the QD multiple RF coil for the horizontal magnetic field head.
ls for Brain Imaging: A Comparison of Signal-to-No
ise Characteristics (HAStark, EMHaacke), 1996
ISMRM abstruct p.1412 is a Four Channel Wrap-Around C
oil with Inductive Decoupler for 1.5T Body Imaging
(T. Takahashi et al.), 1996 ISMRM abstruct p. 1418 is known.

When the multiple RF coils are used, if noise propagates through magnetic coupling between the RF receiving coils, the S / N ratio of the synthesized signal is reduced. Parts are superimposed on each other, or an auxiliary coil is used (Japanese Patent Laid-Open No. 6-343).
618, 1996 ISMRM abstruct p. 1418) to remove magnetic coupling.

[0005]

The brain function measurement includes a case where a portion close to the surface of the brain is inspected with high sensitivity and a case where both sides of the brain are inspected simultaneously.

However, when performing these brain function measurements using multiple RF coils, the conventional RF probe is designed to be suitable for one of the above-mentioned measurements, and a good result is obtained in any of the measurements. Therefore, it was necessary to increase the number of signal detection circuits. For this reason, it has been difficult to realize a multiple RF coil that satisfies both measurements within a limited range of device scale and cost, despite the high necessity of both types of measurements.

In the case of inspecting a portion close to the surface of a subject such as the brain with high sensitivity, it is particularly important to reduce the magnetic coupling between the respective RF receiving coils constituting the multiple RF coil. There is also a request. .

Accordingly, an object of the present invention is to provide an RF probe capable of selecting an operation mode according to measurement conditions. In particular, it is possible to select between a case of inspecting the vicinity of the surface of the subject with high sensitivity and a case of simultaneously inspecting a wide range.
It is intended to provide an F probe. Another object of the present invention is to reduce magnetic coupling in such an RF probe.

[0009]

According to the present invention, there is provided an RF probe comprising: a plurality of RF coils for receiving magnetic resonance signals arranged in a circumferential direction of a substantially cylindrical column; And a signal combining circuit that adds the signals in each group by shifting them by a predetermined phase and sends the signals to a signal processing system, and one of the signals received by each RF coil. And a connection unit for connecting one output of the signal synthesis circuit and the selection unit to the signal processing system.

In such an RF probe, when the output from the signal synthesizing circuit is connected to the signal processing system, the signals (n) from each of the RF coils are formed into a set of two, and the phases are mutually shifted by θ and added. Thereafter, the image is formed in a signal processing system, and each image (n / 2) corresponding to each set of signals is weighted and synthesized for each picture element (referred to as a phase shift mode). In this phase shift mode, signals from all RF coils arranged on the cylinder are used, so that a wide range of examinations on both sides of the brain can be performed simultaneously.

On the other hand, when the signals (m: n> m) selected by the selection means among the signals (n) from the respective RF coils are connected to the signal processing system, each signal (m ) Are weighted and synthesized for each picture element (m selections). In this selection mode,
Since the signals of only the selected RF coils are used, the surface on which the RF coils are located can be inspected with high sensitivity.

In the case of the phase shift mode, the RF probe of the present invention can be used as a QD coil by shifting the phase of each set of signals by 90 °. In this case, the signals of each set are added with their phases shifted from each other by 90 °.
Create an image. In the case of using a QD coil, the signal intensity is generally increased by √2 times, so that a good image can be obtained particularly in a region having a large sectional depth.

In a preferred embodiment of the RF probe of the present invention, the multiple RF coils are arranged such that a part of adjacent RF coils are overlapped with each other, and at least a non-adjacent RF coil is disposed.
A part between the coils is provided with magnetic coupling means having a different coupling coefficient depending on an estimated angle between the non-adjacent coils. Here, the estimated angle between the coils means an angle formed by a line connecting the center axis of the cylinder and the center of each coil.

By providing such a magnetic coupling means, a cylindrical multiple R which forms a complicated magnetic coupling with each other is provided.
In the F coil, magnetic coupling between the coils can be effectively removed, and a good S / N image can be obtained.

The magnetic coupling means is a pair of figure-eight coils connected in series to two RF coils, respectively, and a part of the figure-eight coils is arranged so as to overlap each other. Are preferred.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an RF probe for MRI of the present invention will be described in detail.

MRI using the RF probe of the present invention
FIG. 1 schematically shows the apparatus. This MRI apparatus has a subject 401
A static magnetic field generating magnet 402 that generates a static magnetic field around the periphery, a gradient magnetic field coil 403 that generates a superposed magnetic field in this space, and a transmission coil 404 that generates a high-frequency magnetic field in this region, R for detecting the generated MR signal
An F probe 405 is provided. The present invention relates to the RF probe 405.

The gradient magnetic field coil 403 is composed of gradient magnetic field coils in three directions of X, Y and Z, and is connected to a gradient magnetic field power supply 409 for supplying electric power to the gradient magnetic field coil 403. Further, the transmission coil 404 modulates and amplifies the high-frequency signal.
The RF probe 405 is connected to the
It is connected to a signal detector 406 that amplifies the R signal, performs quadrature phase detection, and performs A / D conversion. The signal detection unit 406 is connected to a signal processing unit 407 that converts the signal into an image signal.
07 is connected to the display unit 408 for displaying an image. further,
Gradient magnetic field power supply 409, RF transmission unit 410, and signal processing unit 407
Are connected to a control unit 411 that controls the timing of pulse generation and signal acquisition.

In such an MRI apparatus, the pulse generation timing is controlled by the control unit 411 and the RF transmission unit 410
, An RF pulse is generated, and a high-frequency magnetic field is emitted from the transmission coil 404 to the subject 401. As a result, an MR signal is generated from the subject placed in the static magnetic field, and the RF signal is generated.
The signal is received by the probe 405 and converted into a digital signal by the signal detection unit 406. This digital signal is sent to the control unit 41
The timing is controlled by 1 and acquired, and the signal processing unit 4
At 07, it is converted to image data. At this time, the timing is controlled by the control unit 411, and the gradient magnetic field generated from the gradient coil 403 via the gradient magnetic field power supply 409 includes X, Y,
Since positional information in the Z direction is included, image reconstruction can be performed by two-dimensional Fourier transform or the like.

The image data thus obtained is displayed on the display unit 408 as an MR image.

Next, the RF probe of the present invention applied to the above MRI apparatus will be described. FIG. 2 shows an RF probe 405 of the present invention, a signal detection unit 406, and a signal processing unit.
In the block diagram showing the 407 in more detail, as described above, the MR signal received by the RF probe 405 is amplified by the signal detection unit 406, quadrature phase detection, and the like, and is converted into an image signal by the signal processing unit 407. Is converted.

The RF probe 405 includes a plurality of (eight in the illustrated example) RF coils 10 each of which receives an MR signal.
It is a multiple RF coil consisting of 1 to 108. As an example, FIG. 3A shows a basic configuration of a head multiple RF coil for a horizontal magnetic field. This RF probe has eight RF coils (elements) 101 to 108 as shown in the figure, and adjacent elements, for example, element 101 and element 102, element 102 and element 103, etc. They are arranged so as to be appropriately overlapped with each other in the circumferential direction so as to remove magnetic coupling, and form a cylindrical shape as a whole. Although not shown, these elements 101
A resonance capacitor is inserted in each of .about.108 to form a parallel resonance loop that resonates at a resonance frequency of protons of 1.5 T (63.8 MHz), for example. Such R
The F probe can receive an MR signal generated on an XY plane perpendicular to the direction of the static magnetic field (Z axis) when the center axis of the cylinder is set as the direction of the static magnetic field (Z axis).

The RF probe of the present invention converts the MR signal received by each element after performing a predetermined phase shift.
It is characterized in that it is possible to select an operation mode (a phase shift mode) in which processing is performed as an individual set and an operation mode (a selection mode) in which a part of a signal received by each element is selected and processed. .

For this reason, the signal detection unit 406 includes a preamplifier 501 for amplifying the MR signal, a phase shifter 803 for shifting the phase of the MR reception signal as a signal synthesizing circuit, and a signal adder 805 for adding the two phase-shifted signals. A signal bypass 811 for transmitting a signal selected by an operator among signals from the respective RF coils, and one of an output from the signal adder 805 and an output from the signal bypass 811 as signal selection means. Switches 802 and 806 are provided as connection means for connecting to the unit 407.

The preamplifier 501 in the signal detection unit 406
There are 8 elements, the same as the number of elements.
To 108 are connected one by one. The switches 802 are all upward in the phase shift mode, and connect the output of the preamplifier 501 to a signal combining circuit. In the selection mode, only the output of the preamplifier 501 selected by turning the switch 802 downward is connected to the signal bypass 811. The switches 806 are all upward in the phase shift mode, and connect the output of the signal synthesis circuit to the signal processing unit 407. In selection mode, all are facing down and the selected preamplifier 501
Is connected to the signal processing unit 407 via the signal bypass 811.

In this embodiment, the signal synthesizing circuit shifts the phase of signals from two elements (for example, elements 101 and 103) of which the prospective angles are 90 degrees from each other among the eight elements by 90 degrees. to add.

A signal processing unit 407 performs image processing such as two-dimensional Fourier transform and the like.
An image synthesis processing unit 809 is provided for synthesizing the images into one image.

Next, the operation in such a configuration will be described.

When the switches 802 and 806 are connected upward, each amplified MR signal is sent to the phase shifter 803. In this embodiment, the phase shifter 803 includes a set of orthogonal elements, that is, an element 101 and an element 103, an element 102 and an element 104, an element 105 and an element 107, and an element 106 and an element 108.
The phases of signals corresponding to the elements 101 to 108 are shifted so that the phase difference becomes 90 °, and output signals 8041 to 8048 are output. Therefore, in this embodiment, the RF probe is QD
Will be used as Next, the set of output signals corresponding to the set of orthogonal elements is added by the signal adder 805 to form four added signals.

The four added signals are input to an image conversion processing unit 807 of an image processing unit 407, and are converted into four images 8081 to 8084 by, for example, a known two-dimensional Fourier transform. A single image 810 is obtained by the unit 809.

FIG. 4 shows a manner in which one image 810 is synthesized from such four images 8081 to 8084. The image before synthesis is composed of elements which output signals (1 in the phase shift mode). It has a sensitivity distribution (shown as light and dark in the figure) depending on the position of the set of coils. The synthesis of the image 810 is performed using the image data en (i, j) and the sensitivity distribution Wn (i, j) of the images 8081 to 8084 as shown in Expression (1).

[0032]

(Equation 1) Here, en (i, j) means an image of the n-th set of coils,
n (i, j) means the sensitivity distribution of the nth set of coils.

The sensitivity distribution Wn (i, j) can be obtained from each of the obtained images. The method is shown in FIG. First, an image en (i, j) obtained by each set of RF coils is subjected to Fourier transform (FT) to obtain k-space data pn (i ', j'). next,
A low-frequency pass filter (LPF) is applied to the k-space data pn (i ', j') to remove high-frequency components derived from the subject. Thereafter, Fourier transform (FT) is performed again to obtain a sensitivity distribution Wn (i, j). Such a series of calculations is performed for each of the n images.

The image 810 obtained in the phase shift mode in this manner utilizes MR signals from all elements, and is therefore suitable for simultaneously examining a wide area such as both sides of the brain. In addition, the signal adder 805 adds two signals whose phases are shifted by 90 °.
The signal strength becomes √2 times. Therefore, a good image can be obtained in a region having a large cross-sectional depth.

On the other hand, when the switches 802 and 806 are connected downward, for example, four M
Only the R signal passes through the signal bypass 811 and the four switches 8
It is transmitted to 06 respectively.

FIG. 6 shows an embodiment of the signal bypass (signal bus) 811 for performing such a selection mode. In this embodiment, the output signal of the preamplifier 501 is connected to the phase shifter 803 in the above-described phase shift mode, but is connected to the signal line 1204 when the switch 802 is connected downward (selection mode) in FIG. Is done. The signal line 1204 and the signal line 1205 connected to each switch 806 are connected by a diode switch 1201. Each diode switch 1201
Is a PIN diode, for example, and its on / off is controlled by a control current 1203 via a choke circuit 1202.
If the control current i ₁₁ is in the forward direction as shown, the signal line 1
204 is connected to the signal line 1205 and electrically, the control current i ₁₁ signal line 1204 if reverse is electrically disconnected from the signal line 1205. By flowing control current for each diode,
Select four from any signal on signal line 1204, and select signal line 1205
Can be connected to Note that the signal lines 1204 and 1205
Is preferably a coaxial cable in order to prevent noise contamination.

The four signals thus selected are:
The image is input to the image conversion processing unit 807 of the image processing unit 407, and is converted into four images 8081 by a known two-dimensional Fourier transform, for example.
To 8084, and a single image 810 is obtained by the image synthesis processing unit 809 in the same manner as described above.

Since the image obtained in this way uses signals from half the number of elements, for example, an image of only the hemisphere of the brain can be obtained, and analog signals are synthesized (added). Since the process is not included, a good image can be obtained in a shallow portion where a good image cannot be obtained in the QD mode. Therefore, it is suitable for a case where a site close to the surface of the brain is inspected with high sensitivity.

In the above embodiment, the case where the phase shift angle is 90 ° in the phase shift mode, that is, the case of QD has been described. However, the phase shift angle is not limited to this, The angle can be selected according to the expected angle of the element.

In the selection mode, a case has been described where the number of signals to be selected among the signals received by each element is four, but any number may be used as long as the number is smaller than the number of elements. In addition, the position of the element to be selected is not limited to the case where a plurality of consecutive elements are selected, and any element can be selected according to the region to be measured, for example, corresponding to the left and right temporal or frontal lobe and occipital lobe It is also possible to select two places to perform.

As described above, in the RF probe of the present invention, as shown in the above embodiment, one RF probe can be operated in different operation modes. It is also possible to inspect near the surface of the brain with high sensitivity.

In the above embodiment, the head multiple RF coil shown in FIG. 3A has been described as an example of the RF probe, but the shape and application of the RF probe are not limited to this. For example, the RF probe having the shape shown in FIG. 3A may be used for a part other than the head, for example, the abdomen.

Although the multiple RF coil has been described as being composed of eight elements, it is not generally limited to eight elements, and may be composed of any number of elements. However, in order to realize the phase shift mode, the number of elements is preferably an even number so that two elements constitute one set. Further, in order to enable the QD mode, a set of orthogonal elements is required. Therefore, a multiple of 4, for example, 4, 8, or 12 is preferable. In general, the width of an element substantially matches the depth at which good measurement is possible, so that the number of elements increases, and if the width per element decreases, the depth cannot be obtained. For this reason, the number of elements is most preferably eight.

As a modification of the shape, for example, when measuring the head, a shape in which one end of a cylinder is narrowed as shown in FIG. 3B is preferable. Such a shape
It can be made by providing a curved portion at one end of each of the eight elements and bending each element so that the open diameter becomes smaller at one end of the cylinder. By using the narrowed side of such an RF probe as the parietal side, the sensitivity of the parietal part can be significantly improved.

FIGS. 7 and 8 show more specific head-only RF probes. FIG. 7A is a side view of the external shape, and FIG. 7B is a front view. In this example, the diameter is 300m
A bobbin is formed by attaching an arc-shaped lid 202 having a radius of 170 mm to one side of an acrylic pipe 201 having a length of 220 mm, a length of 220 mm, and a thickness of 5 mm. The portion of the lid 202 corresponds to the top of the head. In addition, the bobbin has a top air hole 204 having a diameter of 60 mm for improving air permeability, and a leg 2 for installation on a bed for an MRI apparatus.
03 is provided.

The element portions (101 to 108) are shown in FIG.
As shown in the figure, the coil is made of a copper plate having a width of 10 mm, and has a linear portion of 215 mm, a curved portion of 100 mm, and a width of We. This element includes three resonance capacitors 301 at three locations, and forms a parallel resonance loop that resonates at a proton resonance frequency of 1.5 T (63.8 MHz). The elements are arcuately formed in the width direction of the elements so as to have a cylindrical shape as a whole, and a part of adjacent elements are overlapped and arranged in the circumferential direction.

FIG. 8A shows the relationship between adjacent elements.
(B) of FIG.
In this embodiment, for example, the width We of the element is 172 mm as an arc, the overlapping portion Wo is 54 mm,
The angle (estimated angle) θ formed by the line connecting the center line of each element and the center of the bobbin is 45 °. Here, in order to reduce the capacitive coupling between the copper plates, the angle of the overlapping portion with the adjacent element is set to 45 ° to minimize the area where the copper plates overlap, and to form a bridge so as to increase the distance between the copper plates. Is preferred.

By the way, as described in the above embodiment, R
Since the F probe is formed by arranging a plurality of RF coils,
Magnetic coupling occurs between the individual coils. If magnetic coupling exists, noise propagates between the elements, leading to a reduction in the S / N ratio, and good image quality cannot be obtained. Therefore, it is necessary to remove such magnetic coupling. As a method of removing the magnetic coupling, there are a method of adjusting the superposition so that the magnetic coupling between the adjacent coils is minimized, a method of providing a trap circuit using a preamplifier having a low input impedance, and the like. As shown in FIG. 9, a trap circuit using this preamplifier includes a preamplifier 501 having a low input impedance and an element output circuit 503, a λ / 2 coaxial cable.
The output circuit 503 is connected by a capacitor C
The mp 504 and the inductor 505 are configured by a circuit connected in parallel, and are connected to the output terminal of the element.

In the RF probe of the present invention, it is preferable to additionally provide auxiliary magnetic coupling removing means in addition to these known methods. Hereinafter, the magnetic coupling removing means according to the present invention will be described.

The magnetic coupling removing means according to the present invention is such that a pair of auxiliary coils having a coupling coefficient corresponding to the expected angle are connected in series between non-adjacent coils of a multiple RF coil arranged on the circumference. is there.

The prospect angle is an angle formed by a line connecting the axis of the cylinder of the multiple RF coil and the center of each coil as described above, and is an RF probe composed of eight elements as shown in FIG. In this case, the prospective angle θ of the elements adjacent to each other is 45 °. Therefore, for example, the estimated angle θ between the element 101 and the element 102 is 45 °, the estimated angle θ between the element 101 and the element 103 is 90 °, the estimated angle θ between the element 101 and the element 104 is 135 °, and the estimated angle θ between the element 101 and the element 105 is The angle θ is 180 °.

Taking an RF probe composed of eight elements as an example, Table 1 shows the relationship between the expected angle θ and the coupling coefficient k.

[0053]

[Table 1] In Table 1, the coupling coefficient k was obtained by setting a non-target six element out of the eight elements to an open state and determining a magnetic coupling constant k of the magnetic coupling between the two elements from an impedance characteristic at no load. In addition, the coupling constant k and the interval between the two resonance frequencies f1 and f2 when the resonance peak of the impedance is split into two are calculated based on the function of the coupling constant k.

As can be seen from Table 1, in the case of the cylindrical multiple RF coil, the strength of the magnetic coupling is different if the expected angle between the elements is different. In this example, when the expected angle θ is 90 °, the coupling coefficient k is the largest. Is big. In such a multiple RF coil, the expected angle θ is 90 ° and 135 °.
In the case of °, the conventional trap circuit does not sufficiently remove magnetic coupling. Therefore, in the present invention, such magnetic coupling is eliminated by providing magnetic coupling means having different coupling coefficients in accordance with the expected angle θ.

As the magnetic coupling means, FIG.
(B) a pair of auxiliary coils 601, 601 '(603,
603 ′) can be used. Such a pair of auxiliary coils 601 and 601 'are connected in series to each of two non-adjacent elements, and have a coupling coefficient of 2 for both auxiliary coils.
The elements are overlapped so as to have a coupling coefficient that cancels out magnetic coupling between the two elements. Further, it is preferable that the auxiliary coils are each a figure-shaped coil as shown in the figure. In this case, since the magnetic coupling generated by one of the figures 8 is canceled by the other magnetic coupling, there is an advantage that it is not coupled to the other elements.

The auxiliary coils 601, 6 shown in FIG.
01 ′ is for an element having an estimated angle θ of 90 °, and any auxiliary coil is used by connecting a resonance capacitor 602 or 602 ′ between the element and the auxiliary coil. The auxiliary coils 603 and 603 ′ shown in FIG. 3B are for the element between which the estimated angle θ is 135 °. In this case, the two elements having a relationship of 135 ° in the estimated angle θ are farther apart than those having a relationship of 90 °, so that each element and the auxiliary coil are connected to the coaxial cable 60.
4, 604 'so that the auxiliary coils can overlap each other. Resonant capacitor 60
5 and 605 'are connected in the same manner as the auxiliary coil shown in FIG.

When such an auxiliary coil is considered with respect to one element, there is an element having a relationship of 90 ° with the element (two elements), and an element having a relationship of 135 ° with the element (also two elements). , Respectively. Therefore, in one element, four auxiliary coils are connected as shown in FIG. still,
FIG. 11 shows a configuration in which an auxiliary coil is provided to the coil shown in FIG. 8, and in the figure, components having the same reference numerals as those in FIG. 8 indicate the same components.

FIGS. 7 and 8 show examples of such an auxiliary coil.
Specifically, when applied to the RF probe shown in FIG.
01 and 1101 'are figure-shaped coils each having a width of 30 mm and a length of 25 mm, and are used by being superposed by 20 mm in the length direction of the auxiliary coil. Auxiliary coils 1103 and 1103 'provided between elements having a prospective angle of θ135 ° are figure-eight coils having a width of 32 mm and a length of 11 mm, and are each connected to the elements by 55 mm of a 1.5D-2V coaxial cable. Both auxiliary coils are used by overlapping 11 mm in the length direction.

As described above, in the RF probe of the present invention, considering the coupling coefficient k between the elements, the coupling coefficient k ′ between the auxiliary coils is individually selected so as to remove the magnetic coupling. The magnetic coupling according to the angle θ can be removed, and the magnetic coupling that cannot be sufficiently removed by the conventional trap circuit can be removed.

The magnetic coupling removing means (auxiliary coil) according to the present invention may be used alone, but is preferably used in combination with a trap circuit using a preamplifier, whereby eight elements are simultaneously operated. Even if it does, magnetic coupling can be removed stably.

The RF probe having such magnetic coupling removing means can be applied to an RF probe having a function of switching between two operation modes described in the embodiment shown in FIG. It can also be applied to multiple RF coils.

[0062]

As described above, according to the RF probe of the present invention, processing can be performed in two measurement modes, the phase shift mode and the selection mode, using one RF probe. For example, the present invention can be applied to a case where a large area is inspected at the same time and a case where the vicinity of the surface of the subject is inspected with high sensitivity. As described above, since two performances can be satisfied with one RF probe, both measurements can be performed even within a limited range of the apparatus scale and cost.

Particularly, in the phase shift mode, the phase is set to 9
When the QD is shifted by 0 °, a good image can be obtained in a region having a large sectional depth.

Further, in the multiple RF coil,
By providing magnetic coupling means having different coupling coefficients according to the estimated angle between the non-adjacent coils in the non-adjacent RF coil unit (element), the magnetic coupling of each element is reduced, so that the stability of the element is improved. Is improved, and a composite image with good image quality is obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of an MRI apparatus to which an RF probe of the present invention is applied.

FIG. 2 is a block diagram showing an RF probe and a signal processing system of the present invention.

FIG. 3 is a view showing the shape of the RF probe of the present invention;
(A) is a figure showing a basic shape, (b) is a figure showing a modification.

FIG. 4 is a view for explaining signal processing and image reconstruction detected by the RF probe of the present invention.

FIG. 5 is a diagram illustrating a method for deriving a sensitivity distribution in the RF probe of the present invention.

FIG. 6 is a diagram showing an embodiment of a main part of the signal processing system of FIG. 2;

7A and 7B are external views showing one embodiment of the RF probe of the present invention, wherein FIG. 7A is a side view and FIG. 7B is a front view.

8A and 8B are views showing an element portion of the RF probe of FIG. 7, wherein FIG. 8A is a side view of the element, and FIG.
A 'sectional drawing.

FIG. 9 is a configuration diagram of a trap circuit using a conventional preamplifier.

FIG. 10 is a diagram showing magnetic coupling removing means according to the present invention;
(A) shows an auxiliary coil when the estimated angle between the elements is 90 °, and (b) shows an auxiliary coil when the estimated angle between the elements is 135 °.

FIG. 11 is a diagram showing a state in which an auxiliary coil is provided in the RF probe of FIG. 8;

[Explanation of symbols]

101 to 108: Element (RF receiving coil) 405: RF probe, multiple RF coil 802, 806: Switch (connection means) 803: Phase Shifter (signal synthesis circuit) 805: Signal adder (signal synthesis circuit) 811: Signal bypass (selection means) 601, 601 ', 603, 603': auxiliary Coil (magnetic coupling means)

Claims (2)

[Claims] 1. A substantially cylindrical multiple RF coil comprising a plurality of RF coils for receiving a magnetic resonance signal arranged in a circumferential direction of a substantially column, and two sets of signals received by each of the RF coils. And a signal synthesis circuit that adds the respective signals in each group by shifting them by a predetermined phase and sends the signals to a signal processing system, and selects a signal from some of the RF coils among the signals received by the RF coils. An RF probe for a magnetic resonance imaging apparatus, comprising: selecting means for transmitting the signal to a signal processing system; and connecting means for connecting one output of the signal synthesizing circuit and the selecting means to the signal processing system. . 2. The multiple RF coil, wherein a part of the adjacent RF coils is overlapped with each other, and at least a part between the non-adjacent RF coils is provided according to an estimated angle between the non-adjacent coils. 2. The RF probe according to claim 1, further comprising magnetic coupling means having different coupling coefficients.