JPH0433455B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a nuclear magnetic resonance (NMR) apparatus and its coil arrangement.

More particularly, the present invention relates to an NMR apparatus suitable for use in medical testing of patients, in which a selected quantity, for example the density or NMR spin relaxation of selected nucleons, such as protons of hydrogen, is used. It produces an image representing the distribution of time constants in selected areas of the patient.

(2) Description of the Prior Art Such devices have the ability to generate radio frequency (RF) excitation magnetic fields in the presence of other magnetic fields.
and by sensing and analyzing the resulting nuclear magnetic resonance within the body. An RF magnetic field is typically applied and the resulting signals sensed by various coils. However, the same coil can be used for both functions.

It has been found that it is desirable to position these coils, especially the coils used for sensing RF magnetic fields, as close to the body as possible during the examination, but the body under examination, which is a human body, is Since they have a regular shape and vary in size, this can cause many problems.

Conventional NMR devices have a circular RF coil structure in which the human body to be examined is placed. Therefore, during the examination, it is necessary to change the orientation of the body within the coil or move the coil relative to the body to obtain the required position. Therefore, it is necessary to make the coil large so that it does not become an obstacle when moving the human body or the coil. For example, when examining a patient's neck, the coil needs to be large enough to move without hitting the patient's head, making the coil too large for the area of the neck being examined. Since it is desirable to place the RF coil as close as possible to the human body to be examined, it is a major drawback that the RF coil cannot be placed as close to the examination area as in the neck examination described above. Furthermore, the coil may hit the patient's nose or the like, which may cause discomfort to some patients.

The present invention overcomes these drawbacks and allows the RF coil to be placed very close to the examination site in any part of the human body, allowing NMR to be used without causing discomfort to the patient even when moving the RF coil. It provides equipment.

(3) SUMMARY OF THE INVENTION It is an object of the present invention to provide an NMR apparatus with a coil arrangement for applying and/or sensing RF magnetic fields in a manner that alleviates this problem.

According to the present invention, in the NMR apparatus, the NMR apparatus includes a coil array for applying and/or sensing an RF magnetic field while examining a body, wherein the coil array is arranged around the body to be examined. It is comprised of at least two separable parts arranged and adapted to form said coil arrangement.

In a particular embodiment of the invention, said coil array has a tubular shape when installed, and each of said parts constitutes a semicircular part of said installed array.

In another particular embodiment of the invention, said coil arrangement comprises coupling means which are adjustable to adjust the volume surrounded by said coil arrangement when installed, whereby: The parts are positioned relative to each other.

In yet another embodiment according to the invention, said coil array is provided with said coupling means, by which a plurality of coils of the various said parts are electrically connected when said coil array is installed.

In yet another particular embodiment according to the invention suitable for use in patient head examinations, said coil arrangement comprises:
When installed, the coil arrangement supports a plurality of coils and includes a coil form with a window through which the head of the patient can see out of the coil arrangement.

In one such embodiment, the coil is in the form of a tube with a section punched out to provide the window.

In another such embodiment, said window is provided by said coil of at least partially transparent material.

The device according to the invention is described, for example, in British patent no.
Most are of conventional type, as described in No. 1578910 or No. 2056078.

(4) Description of a preferred embodiment Now, as an example, a certain device according to the present invention will be described with reference to the accompanying drawings.

The basic principle of the device according to the invention is as follows. That is, the device according to the invention comprises a first coil arrangement, by means of which the device has a gradient in one or more of the three orthogonal directions, namely the X, Y and Z directions. With this, a magnetic field can be applied in a predetermined direction (usually defined as the Z direction) to the body to be examined.

In Fig. 1, the first coil device includes a coil 1 that generates a steady uniform magnetic field B _p in the Z direction, a coil 3 that generates a magnetic field gradient G _x in the X direction, and a magnetic field gradient G _y in the Y direction. and a coil 7 that generates a magnetic field gradient _Gz in the Z direction.

Furthermore, the device according to the invention comprises a second RF coil arrangement, by means of which an RF magnetic field is applied to the body under examination in a plane perpendicular to the direction of the magnetic field generated by the first coil arrangement. , and thereby result in a nucleus in the body under examination being excited to nuclear magnetic resonance by a spin vector component other than the Z direction.
RF magnetic fields can be detected.

The second coil device includes a first coil array consisting of a pair of coils 9A and 9B that provides an RF magnetic field, and a pair of coils 10 that detects the RF magnetic field.
A and a second coil array consisting of 10B.

Various coils 1, 3, 5, 7, 9A and 9B
are B _p , G _x , G _y , G _z and the RF drive amplifier 1
1, 13, 15, 17 and 19, respectively, and B _p , G _xy , G _z and the RF control circuit 21,
23, 25 and 27, respectively.
These circuits may take a variety of forms well known to those skilled in the art of NMR equipment as well as other equipment using coil-induced magnetic fields.

The circuits 21, 23, 25 and 27 are controlled by a central processing controller 29 which includes input and other peripheral devices 31 for providing commands and instructions to the device, and a display device. 33 is related.

detected by coils 10A and 10B
The NMR signal is applied to a signal processing device 37 via an amplifier 35. The signal processing device is configured to perform any appropriate calibration and correction of the signal, but is primarily for transmitting the signal to the processing control device 29, where the signal is displayed. It is processed to be applied to the device to produce an image representing the distribution of NMR quantities in the body being examined.

Although shown separately for clarity of this description, it will be appreciated that the signal processing unit 37 may conveniently form part of the central processing control unit 29.

The device according to the invention receives signals via an amplifier 41 from magnetic field probes _{X 1} , X ₂ , Y 1 and Y ₂ placed in appropriate positions with respect to the body 43 being examined, as shown in FIG. It also includes a magnetic field measurement and error signal generation circuit 39 for monitoring the applied magnetic field.

The device according to the invention can be used in a known manner to produce an image representing the distribution of proton density or NMR spin relaxation time constant in a selected region of the body under examination. however,
Knowledge of such technology is not necessary to understand the present invention and therefore will not be described in further detail here.

In conventional NMR imaging devices, the RF coil device is attached to a tubular coil (not shown) and the body to be examined is inserted through one end of said coil, which , positioned within the first coil arrangement 1, 3, 5, 7 and adapted to receive the body to be examined.

In the device according to the invention, which is described by way of example, the coil arrangement consisting of coils 9A and 9B is attached to a tubular winding (not shown) positioned within the first coil arrangement, as in conventional devices. It is being

A coil array consisting of coils 10A and 10B is adapted to be closely positioned within coil arrays 9A, 9B about the body being examined. To facilitate this, in FIG. 3, the coil array making up coils 10A and 10B has two sections, each section having a separable winding in the form of a semicircular section of tube. The coils 10A and 1 attached to 51 or 53
It constitutes one side of 0B. The two winding shapes are
As shown in FIG. 3, the coupling means 55,
57, 59 and 61 are positioned relative to each other by interlocking them.

One of the coupling means 55 comprises a two-part electrical coupling, whereby when windings 51 and 53 are installed, i.e. coil 10A
and 10B are connected in parallel, both ends of the coil 10A are electrically connected to both ends of the coil 10B.

In FIG. 4, each electrical coupling part is composed of a plug part 63 having a rectangular cross section and a socket part 65 incorporating an elastic leaf part 67. When inserted into the socket, the plug portion 63 engages the wiping action to minimize RF resistance.

The two coils 10A and 10B are equipped with a common line 69 in the form of a balanced feeder shown connected to the plug portion of the electrical coupling, said common line being, of course, connected to the socket portion of these couplings. can also be combined in the same way.

The coupling means 55 to 61 are configured to allow some adjustment of the spacing between the coil turns 51 and 53 and thus the volume encompassed by the coil arrangement as a whole.

In using the device according to the invention, two coil turns 51 and 53 are placed around the part of the body to be examined, for example the head or neck of the patient. The adjustable spacing between coil turns allows the coil to fit tightly around the patient despite differences in patient size. Furthermore, by using a two-part coil arrangement, examination areas, such as the neck region, which cannot be accessed closely if the coil is mounted in a one-part tubular winding can also be very closely accessed. can be installed.

The coil windings 51 and 53 are arranged so that the patient can
the coil device and the coil arrays 9A, 9B.
properly placed around the patient before being placed in the patient. In this regard, it is to be understood that although it is usually desirable for the two parts to be separated about a vertical plane to facilitate positioning of the parts and for the patient to lie on a couch, this is not necessary.

In the particular embodiment of the invention described by way of example, the two coil turns 51 and 53 each have a semicircular shape, but this may not necessarily be the case and may vary depending on the body, i.e. the part of the body that is desired to be mapped. It may be of any suitable shape determined by the method.

Considering that the coil array of the device according to the invention is intended to be positioned as closely as possible to the body under examination, when said coil array is used for examining the head of a patient, said coil array is placed in very close proximity. This may cause the patient to feel claustrophobic, so it is desirable to minimize this as much as possible.

For this reason, the coil arrangement of the device according to the invention is
Preferably, the coil arrangement is designed to provide a window through which the patient's head can be seen.

A possible modification of the coil arrangement of FIGS. 3 and 4 is shown in FIG. A gap 71 is provided that extends axially along the length. gap 71
A window is provided to allow the patient to lie on his back with his head inside the coil, allowing him to see outside.
The possibility that the patient will feel claustrophobic is thus reduced.

In another such modification, illustrated in FIG. 6, a gap 73 is provided that extends only partially along the length of the coil array, and coil 10A is provided.
and 10B at each end.

It will be appreciated that in another modification it is possible to punch out a portion of only one of the rolls 51 and 53 and provide a window through which the patient can look out.

In yet another alternative, instead of providing a gap, at least a portion of at least one of the coils 51 and 53 is made of a transparent material, providing a window through which the patient can see out.

In the embodiment of the present invention described above by way of example, the plurality of coils are shown as having one turn, but in reality they may have one turn or more. I understand.

Furthermore, in the above embodiment, the coil arrays 10A, 1
Although OB has two separable parts, in other devices according to the invention the coil arrangement may be comprised of more than two separable parts.

By bringing the coil used to sense the RF magnetic field into close contact with the body during the examination, high detection sensitivity for NMR signals generated in the body can be obtained, but this may come at the expense of some spatial non-uniformity in detection sensitivity. It turns out that there is. However, such non-uniformity can be taken into account when processing the detected signal.

Generally, the multiple coils used to apply the RF magnetic field to the body during the examination are placed at a sufficient distance from the body during the examination to obtain good uniformity of the magnetic field throughout the body, as well as for safety. However, if for some reason it is necessary to use the plurality of coils in close contact to apply an RF magnetic field to the body, the present invention clearly facilitates this.

Thus, while in the particular embodiment of the invention described above by way of example, the coil arrangement according to the invention is used only for sensing RF magnetic fields, in other embodiments of the invention the coil arrangement according to the invention can also be used separately or additionally to apply the RF magnetic field.

[Brief explanation of drawings]

1 and 2 show a block diagram of an embodiment of the device according to the invention, and FIGS. 3 and 4 show the structure of a coil arrangement forming part of the device according to the invention. Further, FIGS. 5 and 6 illustrate modifications of the coil arrangement of FIGS. 3 and 4. In the figure, 1-9 is a coil, 11-19 and 35
is an RF drive amplifier, 21-27 is an RF control circuit, 2
9 is a central processing control unit, 31 is an input and other peripheral devices, 33 is a display device, 37 is a signal processing device, 39 is a magnetic field measurement and error signal generation circuit,
41 is a probe amplifier, 43 is a body, 51 and 53 are wound shapes, 55-61 are coupling means, 63 is a plug part, 65 is a socket part, 67 is a leaf part, 69
indicates a common line, and 71 and 73 indicate gaps, respectively.

Claims (1)

[Scope of Claims] 1. A nuclear magnetic resonance apparatus equipped with a coil array for applying and/or sensing an RF magnetic field while examining a body, wherein the coil array is arranged around the body to be examined, and the coil array is arranged around the body to be examined; It consists of at least two separable parts (10A, 51 and 10B, 53) configured to form a coil arrangement, said separable parts having coupling means for holding said separable parts separably from each other. 55,5
7, 59, 61,
Nuclear magnetic resonance apparatus. 2. A device according to claim 1, characterized in that the coil array has a tubular shape when installed, and each of the sections constitutes a semicircular part of the installed array. Magnetic resonance device. 3. The device according to claim 1, wherein the coil arrangement consists of a substantially semicircular section.
A nuclear magnetic resonance apparatus comprising two of the above-mentioned parts. 4. A nuclear magnetic resonance apparatus according to claim 1, characterized in that the coupling means is adjustable so that the volume surrounded by the coil arrangement can be adjusted. . 5. In the device according to claim 1, 2, 3, or 4, the coil array has a structure in which, when the coil array is installed, the coils of various parts are electrically connected to each other. A nuclear magnetic resonance apparatus characterized in that it includes electrical coupling means 63, 65, 67 connected to. 6. A nuclear magnetic resonance apparatus according to claim 5, wherein the electrical coupling means is in the form of a plug 63 and sockets 65, 67. 7. In the device according to claim 1, 2, 3, 4, 5, or 6, when installed, the coil array has a Each magnetic field is characterized in that it includes a coil form 51, 53 supporting a plurality of coils and having a window 71 or 73 through which a patient whose head is placed within the coil arrangement can look out. Resonator. 8. The nuclear magnetic resonance apparatus according to claim 7, wherein the wound shape has a tubular shape with a portion punched out to provide the window. 9. A nuclear magnetic resonance apparatus according to claim 7, wherein the window is provided by the winding, at least a portion of which is made of a transparent material.