JPH02195938A - Probe for nuclear magnetic resonance device - Google Patents

Abstract

PURPOSE:To obtain a probe structure with a fixed filling rate regardless of the resonance frequency by capacity-coupling wings and guard rings. CONSTITUTION:A bobbin 2 is formed with a cylindrical insulator into which a human body can be inserted, arms 3a and 3b are provided in the Z-axis direction, and arms 3c and 3d are provided at symmetrical positions. Wings 4a and 4c are connected to both ends of the arm 3a, wings 4b and 4d to the arm 3b, wings 4e and 4g to the arm 3c, and wings 4f and 4h to the arm 3d. Guard rings 1a and 1b each formed with a cylindrical face and a vertical conductor plate are provided near the wings 4a, 4b, 4e and 4f, and guard rings 1c and 1d are provided near the wings 4c, 4d, 4g and 4h. The guard ring 1a is capacity- coupled with the wings 4a and 4e, and other guard rings are capacity-coupled with multiple wings nearby. The guard rings 1a-1d can be easily moved in the A-axis direction, and the capacitance formed between the guard ring and the wing can be easily adjusted.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to nuclear magnetic resonance (N) from hydrogen and phosphorus in living organisms.
The present invention relates to a device that measures MR (MR) signals and visualizes nuclear density distribution, relaxation time distribution, etc., and particularly relates to a device suitable for effectively operating a probe used for generating or receiving a high-frequency magnetic field even in a high frequency region.

[Conventional technology]

2. Description of the Related Art Conventionally, X-ray CT and ultrasonic imaging devices have been used as devices for non-destructively inspecting internal structures such as the head and abdomen of a human body. In recent years, attempts to conduct similar tests using NMR phenomena have been successful, and it has become possible to obtain a wide variety of information that could not be obtained with X-ray CT or ultrasound imaging devices. In an inspection device that uses this NMR phenomenon, it is necessary to separate and identify signals from an object to be inspected in correspondence to each part of the object. There is a method of obtaining position information by varying the resonant frequency or phase encode amount of each part.

The basic principles of the above method can be found in the Journal of
Magnetic Resonance Magazine rJournalof M
agnetic Re5onance), Volume 18, No. 6
9-83'' or ``Physics in Mesocine
Physics in Me
dicine & Bio1gy) *Volume 25, No. 751
Since it is described in detail on pages 756 to 756, it will be omitted here.

By the way, since the S/N ratio in NMR theoretically increases in proportion to about the 1.5th power of the static magnetic field, attempts are being made to improve the S/N ratio by increasing the magnetic field strength even a little. The probes that have been used so far have been solenoid or saddle type, but as the magnetic field strength increases, the resonant frequency also increases, resulting in a situation where the self-resonant frequency of the probe and the nuclear magnetic resonance frequency approach or reverse. However, there has been a problem of decreased sensitivity during reception or decreased efficiency in generating high-frequency magnetic fields during transmission.

In response, Alderman et al. 5 announced a new type of probe called a slot resonator type. This is discussed in the Journal of Magnetic Resonance.
Magnetic Re5onanca) Magazine, No. 36
(1979), page 447. 19th
20 and 21 show slot resonator type probes, FIG. 19 is a bird's-eye diagram of the probe, and FIGS.
The B-BAIIIN plane view and FIG. 21 are cross-sectional views taken in the Z-axis direction of FIG. 19, respectively. This operating characteristic is described in Alderman's paper mentioned above, so it will not be discussed here.

Here, the direction of the static magnetic field is the Z-axis direction, and the distance between arms is the distance between arms facing each other in the X# force direction, as shown in FIG. 20(b). The shorter the distance between the arms, the closer they can get to the human body, which improves the transmission and reception efficiency. The relationship between the distance between the human body and the arm is called the filling rate, and the closer the distance between the human body and the arm, the higher the filling rate.

[Problem to be solved by the invention]

The above-mentioned conventional technology does not take into account the filling factor when the resonant frequency is set to a high value, and there is a problem in that the higher the resonant frequency is set, the lower the filling factor becomes. An object of the present invention is to provide a probe structure with a constant filling factor regardless of the resonant frequency.

[Means to solve the problem]

The above object can be achieved by creating a structure that does not reduce the filling factor when trying to increase the resonant frequency of the probe. Regarding the resonant frequency, it is sufficient to reduce the capacitance, and regarding the filling rate, the distance between the arms (second
This problem can be solved by making 0 (see figure (b)) as small as possible.

On the other hand, in order to reduce the capacitance between the wing and guard ring, it is possible to anchor the width of the wing and guard ring, but even with a linear wing guard ring, if the distance between the two is close to a certain extent, the capacitance will be considerable. . Furthermore, since such thin wings and guard rings cannot provide stable characteristics, the capacitance between them has to be lowered to a desired value by making them both plate-shaped and keeping a certain distance between them. but,
In the conventional configuration in which the guard ring is disposed inside the wing portion, the diameter of the guard ring must be made smaller than the distance between the arms in order to maintain the above-mentioned distance, resulting in a problem that the insertion portion of the human body becomes small. On the other hand, even in the case of wings, since the wings and arms are integrated, a problem arises in that as the wings are expanded outward, the distance between the arms increases and the filling rate decreases.

Therefore, the above problem can be solved if the capacitance reducing portion and the arm can be configured separately.

For example, the wing and the guard ring can be made perpendicular to the arm, and the capacitance can be reduced by moving only the guard ring (see FIGS. 1 to 3).

[Function] By configuring the guard ring and wing perpendicularly to the arm portion of the probe, a high resonant frequency can be obtained by moving only the guard ring while keeping the distance between the arms constant (first (See Figures 3 to 3).

Furthermore, if the desired resonant frequency is determined from the beginning, the capacitance is also determined, so the distance between the guard ring and the wing can be determined by the thickness of the insulator. In this case, by keeping the distance between the arms and the diameter of the guard ring always equal, a high resonant frequency can be obtained without reducing the filling factor (see FIGS. 9 to 11).

〔Example〕

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

FIG. 4 shows the configuration of an inspection device that is an embodiment of the present invention. The control device 5 outputs various commands to each device at constant timing. The output of the high frequency pulse generator 6 is amplified by an amplifier 7 and excites the probe 8. The signal component received by the probe 8 passes through the amplifier 9 and the detector lO
After detection, the signal is converted into an image by the signal processing device 11. The generation of gradient magnetic fields in the Z direction and in the direction perpendicular thereto is carried out by coils 12, 13.14, respectively, which are driven by amplifiers 15, 16.17, respectively. The static magnetic field is generated by a coil 18, and the coil 18 is driven by a power source 19. The coil 14 has the same configuration as the coil 13, and the coil 14 has a rotation angle of 9 around the Z axis relative to the coil 13.
The human body 20 to be examined is placed on a bed 21, and the bed 21 moves on a support base 22.

1, 2 and 3 depict the probe 8 in more detail.

FIG. 1 is a bird's eye diagram of an embodiment of the present invention, FIG. 2(a),
(b) and (c) are sectional views taken along lines AA, BB, and CC in FIG. 1, and FIG. 3 is a sectional view taken along the xZ plane in FIG. 1, respectively. In these figures, the bobbin 2 is made of a cylindrical insulator, such as glass epoxy, and has an inner diameter into which a human body to be inspected can be inserted. This bobbin 2 is arranged in the Z-axis direction, which is the direction of the static magnetic field. A plurality of electrodes made of conductive plates forming an Alderman coil are provided on the outer periphery of the bobbin. first.

Band-shaped arms 1z3a and 3b are provided along the central axis of the cylinder, that is, the Z-axis direction. Other arms 3a, 3d are also installed at positions symmetrical to these with respect to the ZY plane.
is provided. 3c and 3d do not appear in FIG. 1, but are shown in FIG. 2C. Note that the arms are separated along a line in the Z41111 direction as in 3a and 3b, and 23c and 3d, as shown in Japanese Patent Application Laid-Open No. 62-207446.
As mentioned in the above issue, this is to uniformize the sensitivity by determining the direction of the current, and 38 and 3b and 3c and 3d may be integrated without being separated. Wings 4a, 4c connected thereto are provided.

Similarly, wings 4b and 4d are connected to arm 3b, wings 4e and 4g are connected to 3G, and wings 4f and 4h are connected to 3d, respectively. A feature of the wing in this embodiment is that it consists of a cylindrical surface and a conductor plate erected in a perpendicular direction. That is, the wings 4a, 4b, 4e, and 4f are arranged so as to form a flange perpendicular to the cylindrical surface of the bobbin 2. Also, wings 4 b, 4c, 4g, 4.
h are similarly arranged so as to form a flange perpendicular to the cylindrical surface. Note that each arm and the wings connected to both ends thereof may be formed by press-molding a single conductor plate. Wing 4a.

In the vicinity of 4b, 4e, and 4f, a guard ring 1 made of a conductive plate perpendicular to the cylindrical surface is installed at a position slightly on the axial side of the flange surface formed by these wings to form another flange surface.
a and 1b are provided. Also wings 4c, 4d, 4
Gart rings lc and ld, which form flange surfaces perpendicular to the cylindrical surface, are also provided near ge 4h. The guard rings 1a and 1b may be ring-shaped without being separated, and the same applies to the guard rings lc and ld. With this configuration, the guard ring 1a is erected facing the wings 4a, 4e, so that capacitive coupling occurs between them. Other guard rings also form capacitive coupling with multiple adjacent wings,
3 a -4a -1a-4e-3cm4g-1
A current path that goes around cm4cm3a, and: 3b,
4b-1b-4f-4h-1d-4d-3b and another current path is formed. This makes it possible to detect high-frequency magnetic flux in the Y-axis direction, and conversely, generate a high-frequency magnetic field in the Y-axis direction by applying a high-frequency signal.

As described above, in this embodiment, the guard ring and the wing are configured perpendicularly to the direction of the static magnetic field (Z-axis direction) and face each other, so it is not necessary to make the inner diameter of the guard ring smaller than the inner diameter of the wing. Therefore, the filling factor can be made sufficiently high and the probe resonant frequency can be made high. Furthermore, by making the guard rings 1a to 1d into one configuration, the guard rings 1a to 1d can be
Since it can be easily moved in the ili1 direction, there is an effect that the capacitance formed between the guard ring and the wing can be easily adjusted. FIGS. 5(a) to 5(c) show an example of a mechanism for changing the distance between the wing and the guard ring of the above embodiment. Fig. 5(a) shows an enlarged view of the upper left view of Fig. 3, and Fig. 5(b) shows a view of Fig. 5(a) seen from above.
It is fixed with screws 20 and nuts 21. By shifting the fixed position, the distance between the wing 4c and the guard ring 1c can be easily adjusted. Other guard rings are also fixed in a similar configuration. Furthermore, since there is a space between the wing and the guard ring, it has the effect of greatly reducing loss.

FIG. 5(c) and FIG. 5(a) show another fixed guard ring holding structure. Insulator bolt 22 is guard ring 1
Nut 23.c is fixed to the wing 4c and holds the wing 4c.
By adjusting 24, the position of the guard ring 1c can be finely adjusted.

Fig. 6 is a bird's eye diagram showing another embodiment of the present invention, Fig. 7 (a) and (b) are cross-sectional views taken along lines A-A and B-B in Fig. 6, and Fig. 7 (Q) is In this embodiment, which is a cross-sectional view taken along the Z-axis direction in FIG. ~1d is provided. That is, the diameter of the guard ring is larger than the distance between the opposing arms and the diameter of the wing. Therefore, the recoil filling rate does not decrease due to the restriction of the gart ring inner diameter. Guard ring (la, lb
, lc, ld) is relatively easy to change, and this has the effect of easily changing the capacitance formed between the guard ring and the wing.

FIG. 8 shows an embodiment of a mechanism for changing the diameter of the guard ring of the above embodiment. A plurality of insulating bolts 30 are radially fixed to the bobbin 2, and the diameter of the guard ring can be easily changed by adjusting nuts 32 that sandwich the wings lc, J, and d. Further, similar effects can be obtained by adjusting the thickness of the insulator 2.

FIG. 9 is a bird's eye diagram showing another embodiment of the present invention;
Figures (a) and (b) are cross-sectional views taken along lines A-A and B-B in Figure 9, and Figure 11 is a cross-sectional view taken in two axial directions in Figure 9, respectively.

In this embodiment, arms 38 to 3d and wings 4a to
4h is formed on the outside of the bobbin, and guard rings 1a to 1d are formed on the inside of the bobbin. In this respect, the conventional configuration (19th
21), but differs from the conventional one in that the outer diameter of the bobbin 2 is smaller only at the arm portion, and the thickness of the bobbin is increased at the wing portion. In the conventional configuration, in order to increase the resonant frequency, the distance between the wing and the guard ring must be increased, and as a result, the arm also expands along with the wing, resulting in a larger distance between the arms, and as a result, the filling rate decreases. There was a problem. By adopting this configuration, the characteristics can be obtained in the same way as in the conventional case, and the filling factor can also be kept constant regardless of the resonance frequency. Regarding the guard ring,
Generally, the diameter is the same as the distance between the arms, but the diameter may be larger than the distance between the arms.

12 and 13 show the bobbin 2 used in the above embodiment, and FIG. 12 is a bird's eye diagram showing the embodiment.
13(a) and 13(b) are cross-sectional views taken along lines A-A and B-B in FIG. 12, and FIG. 13(c) is a cross-sectional view taken along the Y-axis direction in FIG. 12. By changing the thickness of the part where the wing is attached, it is possible to set various resonance frequencies. Further, by using the structure shown in FIG. 8 in combination, it is possible to expand the wings outward without changing the thickness of the insulator.

FIG. 14 is a bird's eye diagram showing another embodiment of the present invention.
5(a), (b), and (c) are A-A in FIG. 14.

B-B, C-cm cross section JsA, 161ii! H
In this embodiment, all electrodes (wings 4a to 4h, arm 3
a to 3d, guard rings 18 to ld) are formed on the outer cylindrical surface of the bobbin 2. This configuration has the effect of making the outer diameter of the probe smaller than that of conventional probes, and the resonant frequency can be easily adjusted by moving the guard ring in the Z# force direction.

Furthermore, with this configuration, the capacitance due to the facing of the wing and guard ring is small, so the resonance frequency can be made higher.

In FIG. 17(a), each electrode portion is formed on a single film-like substrate 35. In FIG. Simply wind it around the cylindrical bobbin 2 shown in Figure 17(b) and the first
You can make one with the same configuration as in Figure 4. Here, the effect of making the electrodes into a film is that the processing accuracy is greatly improved (11! pole dimensions, etc.), which makes it possible to obtain reproducibility in the characteristics of the probe and shorten the assembly time.

If a flexible material such as Teflon is used as the insulator (b), it can be wrapped around a human body, thereby improving the filling rate. Also, in the figure, it is composed of a single film-like substrate.

By using a plurality of substrates, for example, using only the guard ring portion as a separate film-like substrate, the position of the guard ring can be changed freely, resulting in the effect that the resonance frequency can be easily adjusted.

FIG. 18 is another embodiment of FIG. 17 (,), in which the material is the same but the arrangement and shape are different. The effect of FIGS. 18(a) and (b) is that the arm 3 portion, which is the signal detection section, is extended in the Y-axis direction,
This makes it possible to obtain a larger signal than in the embodiment shown in FIG.

As described above, according to the present invention, it is possible to construct a probe whose filling rate does not decrease even in a high magnetic field, that is, at high frequency.Although the present invention has been described only with respect to a slot resonator type probe, it is possible to construct a probe with a slot resonator type probe having the same configuration. It is clear that the present invention can also be applied to quadrature phase detection probes.

〔Effect of the invention〕

According to the present invention, the capacitance formed between the wing and the guard ring can be easily changed without changing the distance between the arms, that is, without changing the filling rate.
This has the effect of keeping the filling factor constant regardless of the resonant frequency of the probe. This is particularly effective in improving the transmission and reception efficiency of the probe at high frequencies (high magnetic fields).

[Brief explanation of the drawing]

Figures 1, 2 and 3 are diagrams showing the probe of the present invention, Figure 4 is a block diagram of an NMR imaging apparatus in which the present invention is used, and Figures 5 to 18 are diagrams showing other embodiments of the present invention. 19 to 21 show probes that have been used conventionally. 2'0-Fupa￥J 5 Diagram (somewhat (C) Death mode card) R's Finished 74 shift (-g) Abusive diagram (a-) Figure (a-ji3ζ (b) Tinef. Figure Figure Figure (b) 3 A4 4 Kui >2"

Claims (1)

[Claims] 1. A plurality of arms made of band-shaped conductor plates formed in the axial direction along a cylindrical surface, and a plurality of arms formed by being connected to both ends of each of the arms, and flange-shaped from the cylindrical surface. It has a plurality of wings made of conductor plates extending outward, and a plurality of guard rings made of conductor plates extending outward along the flange surface proximate to the flange surface formed by the wings, A probe for a nuclear magnetic resonance apparatus, characterized in that the guard ring is capacitively coupled to the guard ring. 2. The nuclear magnetism according to claim 1, wherein the guard ring is attached to the cylindrical bobbin having the cylindrical surface so that its axial position can be adjusted. Probe for resonator. 3. A bobbin made of a cylindrical insulator, a plurality of arms made of axial band-shaped conductor plates formed on the inner cylindrical surface of the bobbin, and a plurality of arms extending from both ends of each arm along the inner cylindrical surface of the bobbin. a plurality of wings extending in a circumferential direction; and a plurality of conductor-shaped guard rings formed along an outer cylindrical surface of the bobbin to face the wings, the wings and the guard ring; A nuclear magnetic resonance apparatus probe consisting of capacitively coupled. 4. The nuclear magnetic resonance probe according to claim 3, wherein the guard ring is attached to the outside of the bobbin via a bolt so that its diameter can be adjusted. 5. A plurality of arms made of band-shaped conductor plates formed in the axial direction along the first cylindrical surface, and a second arm connected to both ends of each of the arms and having a larger diameter than the first cylindrical surface. It has a plurality of wings made of conductor plates extending in the circumferential direction along the cylindrical surface, and a plurality of guard rings made of ring-shaped conductor plates formed inside the wings,
A probe for a nuclear magnetic resonance apparatus, wherein the wing and the guard ring are capacitively coupled. 6. The nuclear magnetic resonance apparatus according to claim 5, wherein the arm and the wing are formed on a bobbin made of a cylindrical insulator in which the inside of the arm has a smaller outer diameter than the wing. probe. 7. A plurality of arms consisting of band-shaped conductor plates formed in the axial direction along the cylindrical surface, and a plurality of wings consisting of conductor plates extending from both ends of each arm in the circumferential direction along the front cylindrical surface. and a plurality of guard rings formed in a ring shape along the cylindrical surface adjacent to the wings, the wings and the guard rings being capacitively coupled. 8. The arm, the wing, and the guard ring are made of a film-like conductor formed on a film-like insulating substrate, and the film-like insulating substrate is rolled into a cylindrical shape. The nuclear magnetic resonance probe described above. 9. The probe for a nuclear magnetic resonance apparatus according to claim 8, wherein the film-like insulating substrate is wound on a cylindrical bobbin.