JPH08140959A - Rf coil magnetic resonance imaging - Google Patents

Abstract

PURPOSE: To provide an RF coil which ideal for use in monitoring a lesion with an MRI apparatus during operation. CONSTITUTION: This RF coil is constituted by a primary coupling part having a loop part 201 for the transmission of an RF pulse and the detection of a magnetic resonance signal and an induction coupling part 204, and a secondary coupling part having end parts to be connected to an FR transmitting part and an RF receiving part and an induction coupling part 205, and the induction coupling part 204 of the primary coupling part and the induction coupling part 205 of the secondary coupling part are made free to contact closely and separate. The primary coupling part and the secondary coupling part have the perimeter thereof covered with an antibacterial material and the loop part 201 of the primary coupling part is allowed to mount an apparatus for operation such as forceps thereon. This constitution enables the arranging of the RF coil near a lesion without disturbing the surgery while facilitating the preventing of the worsening of hygienic condition of a patient.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to magnetic resonance imaging capable of measuring magnetic resonance (MR) signals of hydrogen, phosphorus, etc. in an object and imaging the density distribution and relaxation time distribution of nuclei. Regarding an RF coil for an (MRI) device, in particular, a static magnetic field generating magnet and a gradient magnetic field coil are divided so that a person other than the subject can contact and operate the subject during measurement, and can be used as a monitor during surgery. The present invention relates to an RF coil for MRI suitable for use in a simple MRI apparatus.

[0002]

2. Description of the Related Art In an MRI apparatus, a subject (for example, a person)
MR signals from nuclei (for example, hydrogen, phosphorus, and carbon) contained in the site of interest are detected by the resonance type RF coil. In recent years, an MRI apparatus has been developed in which a static magnetic field generating magnet and a gradient magnetic field coil are divided and a human (doctor or technician) other than the subject can contact and operate the subject during measurement. Along with this, it is possible to monitor the affected area at the same time during surgery, and new demands are made on the shape and method of the RF coil used.

[0003]

In the MRI apparatus,
In order to monitor the affected area with high sensitivity during the operation, it is preferable to dispose the RF coil in the vicinity of the affected area. However, if a surface coil as commonly used is applied, the operation and work of a doctor can be improved. Interfere. Further, it is expected that the hygiene condition of the subject is deteriorated by disposing the RF coil in the vicinity during the operation. An object of the present invention is to provide an RF coil capable of solving the above problems with a simple structure and method.

[0004]

[Means for Solving the Problems] The above-mentioned object is to realize an R for MRI.
The F coil is composed of a primary coupling part for transmitting an RF pulse and detecting a magnetic resonance signal, and a secondary coupling part connected to the RF transmitting part or the RF receiving part. The parts are separable and are achieved by configuring the two such that they can be connected by inductive coupling when in use.

It is preferable that the loop portion of the primary connecting portion has a structure to which a surgical instrument such as forceps can be attached.
It is preferable that the shape can be changed according to the incision of the subject during surgery. The entire RF coil is preferably covered with an antibacterial material such as polyurethane, and it is preferable that at least a part of the RF coil is disposable.

[0006]

With the primary coupling portion of the RF coil to which surgical instruments such as forceps can be attached and the shape thereof is variable, the doctor does not have to arrange and fix the RF coil separately from the surgical instrument. A surgical instrument can be used, and it becomes possible to perform surgery in a situation similar to that when performing normal surgery. Further, by covering the RF coil with an antibacterial material and disposing a part of the antibacterial material, it is possible to maintain good hygiene of the RF coil.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an example of the overall configuration of a magnetic resonance apparatus according to the present invention. This magnetic resonance device is
The R phenomenon is used to obtain a tomographic image of the subject 101. The static magnetic field generating magnet 102, the signal processing unit 103, the RF transmitting unit 104, the RF receiving unit 105, and the gradient magnetic field driving unit 10 are used.
6, display unit 107, and control unit 108 for controlling these
Consists of

The static magnetic field generating magnet 102 is used for the subject 10
A strong static magnetic field is generated in the space in which 1 is arranged, and the static magnetic field is divided into two and arranged in the space around the subject 101. The output of the RF transmitter 104 is sent to the transmitting / receiving coil 109 to generate an RF magnetic field. Gradient magnetic field drive unit 1
The output of 06 is sent to the gradient magnetic field coil 110, and X,
It generates gradient magnetic fields Gx, Gy, and Gz in three directions of Y and Z. A tomographic plane with respect to the subject 101 can be set depending on how to apply the RF magnetic field and the gradient magnetic field. The RF receiver 105 receives the signal from the transmission / reception coil 109.
The output of the RF receiving unit 105 is subjected to processing such as image reconstruction in the signal processing unit 103, and then displayed on the display unit 107. Here, the image reconstruction means a process of creating one image by performing a two-dimensional complex Fourier transform in the measurement space. Note that, in FIG. 1, the gradient magnetic field coil 110 is divided into two and arranged in the space around the subject 101.

FIG. 2 shows an example of the RF coil according to the present invention. The primary coupling portion is composed of a loop portion 201 and an inductive coupling portion 204 incorporated in the loop portion 201, and the secondary coupling portion is composed of a cable 208 and an inductive coupling portion 205 which are connected to the RF transmitting portion or the RF receiving portion. Become.
The primary connecting part and the secondary connecting part are covered with an antibacterial material such as polyurethane. The loop portion 201 includes a conductive loop and a resonance circuit therein, and its shape is variable according to the shape of the surgical opening or the like. A part of the forceps 202 can be fixed to an arbitrary place of the loop portion 201 with a screw 203, and the forceps 202 has a structure that can be freely attached and detached. If the loop portion 201 is provided with a ring-shaped member instead of the screw hole, it is also possible to fix the tweezers by passing the legs of the tweezers through the ring.

RF signal transmission and MR signal reception are performed via inductive coupling units 204 and 205. The inductive coupling portions 204 and 205 are used in close contact with each other during use, and are separated at other times. Further, the primary coupling portion including the inductive coupling portion 204 and the loop portion 201 incorporating the inductive coupling portion 204 can be disposable as the hygienic condition deteriorates. If the hygienic condition extends to the secondary joint, the secondary joint can also be disposable. In addition, if necessary, the
The secondary joint can be easily replaced.

FIG. 3 shows a state in which the inductive coupling portion 204 of the primary coupling portion and the inductive coupling portion 205 of the secondary coupling portion are separated. The inductive coupling portions 204 and 205 can be easily attached and detached by the Velcro 220.
As the contact means, an adhesive tape or the like can be used instead of the magic tape. FIG. 4 shows the inductive coupling section 20.
4 is a schematic diagram showing a specific example of coupling of a primary coupling part and a secondary coupling part by 4,205. The primary coupling part and the secondary coupling part are not directly connected to each other via the connector, but are connected to the loop part 20.
The loop 206 coupled to 1 and the loop 207 including the resonance circuit provided at the tip of the cable 208 from the RF receiver are connected by inductive coupling. However, in this figure, the resonance circuit included in the loop 207 and the loops 206 and 207 are
The antibacterial material that covers the periphery of is omitted.

By adopting the inductive coupling method as described above, unlike the case where the RF coil is directly connected by the connector, it becomes easy to completely cover the surroundings with the antibacterial material. FIG. 5 is a schematic diagram of an equivalent circuit showing the principle of inductive coupling. R
The primary coupling unit that transmits the F pulse and detects the magnetic resonance signal is the primary coil 240, and the secondary coupling unit that is connected to the RF transmitting unit and the RF receiving unit is the secondary coil 241 and the inductive coupling therebetween. Indicates. In this equivalent circuit, each is LC
It is shown by the R circuit and the two inductors are inductively coupled. The output impedance Z of the secondary coil 241 is
It is given by the following equation (1) using the symbols in the figure. Subscript 1
And 2 represent a primary coil and a secondary coil, respectively. ω is an angular frequency and has a relationship of ω = 2πf with the frequency f. Z = {1 / (R ₁ + Z _i ) + jωC} ⁻¹ (1)

Zi is an output impedance when an ideal secondary coil (that is, the conductor loss R ₂ and the stray capacitance C ₂ is 0) is used, and is given by the following equation (2). Z _i = jωL ₂ + jω ³ M ² / L ₁ (ω ₀ ² −ω ² + jωω ₀ / Q ₀ ) (2) Here, M is the mutual inductance between the secondary coil and the primary coil, and the coupling constant k is It is given by the following equation (3). ω ₀ is the parallel resonance frequency of the primary coil alone and is given by the following equation (4), and Q ₀ is the Q value of the primary coil and given by the following equation (5). The output voltage V is obtained by the following equation (6) using the impedance Z.

M = k (L ₁ L ₂ ) ^1/2 (3) ω ₀ = 1 / (L ₁ C ₁ ) ^1/2 (4) Q ₀ = ωL ₁ / R ₁ (5) V = i / Re (Z) (6) Here, Re (Z) represents the real part of Z. Further, i is a current flowing in the secondary coil when a unit voltage is generated in the primary coil in the equivalent circuit of FIG. 5, and can be calculated in the same manner as the impedance calculation of the above formula (1). The output P of the secondary coil is given by the following equation (7). The basic characteristics of the inductively coupled RF coil can be known by calculating the frequency characteristics of Z and P.

P = | i | ² / Re (Z) (7) FIG. 6 shows an example in which the RF coil primary coupling portion of FIG. 2 is applied to an incision portion of a subject during open surgery. Subject incision 3
The shape of 01 is different depending on the degree and site of disease. R
The loop portion 201 of the F-coil has a flexible shape, both the coil forming the loop and the polyurethane coated thereon, and can be adapted to various shapes of the subject incision. Yes, transmission / reception is performed via the coupling unit 204. In this figure, surgical instruments such as forceps and screw holes for fixing them are omitted.

FIG. 7 shows an example of the structure of the conductive loop and the resonance circuit of the primary coupling portion of the RF coil. The conductive loop 401 is a solenoid coil with 7 turns in series, and includes variable capacitors 404 and 405 as a resonance circuit.
It is possible to automatically tune to a specific resonance frequency and impedance. The conductors 402 and 403 are connected to the coupling loop 206 shown in FIG. 2, and RF pulse transmission or magnetic resonance signal reception is performed through the coupling portion. The automatic tuning is performed by, for example, JP-A-3-510.
It can be carried out using any known means such as those described in Japanese Patent Laid-Open No. 37-51038 and Japanese Patent Laid-Open No. 3-51038.

FIG. 8 shows another example of the structure of the conductive loop and the resonance circuit of the primary coupling portion of the RF coil. Conductive loop 5
Reference numeral 01 is a parallel 7-turn solenoid coil, which is provided with variable capacitors 504 and 505 as a resonance circuit, and can be automatically tuned to a specific resonance frequency. The conductors 502 and 503 are connected to the coupling loop 206 shown in FIG. 2, and RF pulse transmission or magnetic resonance signal reception is performed through the coupling portion.

FIG. 9 shows an example of a sequence (RF pulse and gradient magnetic field application procedure) capable of high-speed imaging of the inside of a surgical target site in order to realize the present invention. In this sequence, measurement is performed according to the following procedure to obtain one image. First, the RF pulse 601 and the slice selection gradient magnetic field 602 are simultaneously applied to determine the target slice of the subject, and the magnetization of the atomic nucleus in the slice is defeated.
Next, a rephase gradient magnetic field 603 for the slice selection gradient magnetic field 602, a dephase gradient magnetic field 605 for the encode gradient magnetic field for adding position information, and a dephase gradient magnetic field 607 for the readout gradient magnetic field for signal reading are applied. . Then, as shown in the figure, the readout gradient magnetic field 608 is reversed at high speed, and at the same time, the encoding gradient magnetic field 606 is applied. At this time, all echo signals necessary for creating one image are acquired. The series of procedures is completed in a time TR, typically several hundred milliseconds to several seconds, and as a result, a region of interest of a subject can be imaged in near real time, and real-time monitoring during surgery becomes possible. 604 is a spoiler gradient magnetic field for canceling the remaining magnetization.

[0019]

According to the present invention, the doctor can use the surgical instrument without disposing the RF coil separately from the surgical instrument and fixing the RF coil. Is possible. Further, the RF coil can prevent deterioration of the hygiene condition (of the affected part) of the subject.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the overall configuration of a magnetic resonance apparatus.

FIG. 2 is a diagram showing an example of a primary coupling portion of an RF coil according to the present invention.

FIG. 3 is a diagram showing a state in which a primary coupling part and a secondary coupling part are separated.

FIG. 4 is a diagram showing a coupling example of a primary coupling unit and a secondary coupling unit.

FIG. 5 is an equivalent circuit diagram showing the principle of inductive coupling.

FIG. 6 is a diagram showing an example in which a primary coupling part is applied to a subject incision part.

FIG. 7 is a diagram showing an example of structures of a conductive loop of a primary coupling portion and a resonance circuit.

FIG. 8 is a diagram showing another example of the structure of the conductive loop of the primary coupling portion and the resonance circuit.

FIG. 9 is a diagram showing an example of a pulse sequence.

[Explanation of symbols]

101 ... Subject, 102 ... Static magnetic field generating magnet, 103 ... Signal processing unit, 104 ... RF transmitting unit, 105 ... RF receiving unit,
109 ... Transceiver coil, 110 ... Gradient magnetic field coil, 20
1 ... Loop part, 202 ... Forceps, 203 ... Screw, 20
4, 205 ... Inductive coupling portion, 206, 207 ... Inductive coupling loop, 208 ... Cable, 220 ... Velcro, 3
01 ... Incision part, 401 ... Conductive loop, 402, 403 ...
Conductive wire, 404, 405 ... Variable capacitor, 501 ... Conductive loop, 502, 503 ... Conductive wire, 504, 505 ... Variable capacitor, 601 ... RF pulse, 602 ... Slice selection gradient magnetic field, 603 ... Rephase gradient magnetic field, 604 ... Spoiler gradient magnetic field , 605, 607 ... Dephasing gradient magnetic field, 606 ... Encoding gradient magnetic field, 608 ... Readout gradient magnetic field

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Hirata 1-280, Higashikoigakubo, Kokubunji, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd.

Claims (7)

[Claims] 1. A primary coupling part having a loop part for transmitting an RF pulse and detecting a magnetic resonance signal and an inductive coupling part, an end connected to the RF transmitting part and the RF receiving part, and an inductive coupling part. R for magnetic resonance imaging, characterized in that the inductive coupling section of the primary coupling section and the inductive coupling section of the secondary coupling section can be closely attached and detached.
F coil. 2. The RF coil for magnetic resonance imaging according to claim 1, wherein the loop portion of the primary coupling portion has a portion for attaching an instrument for fixing a specific portion of the subject. 3. The magnetic resonance imaging R according to claim 1, wherein at least a part of the R is disposable.
F coil. 4. The RF coil for magnetic resonance imaging according to claim 1, 2 or 3, wherein the primary coupling portion and the secondary coupling portion are coated with an antibacterial material on their peripheries. 5. The RF coil for magnetic resonance imaging according to claim 1, wherein the loop portion of the primary coupling portion has a variable shape. 6. The RF for magnetic resonance imaging according to claim 1, further comprising automatic adjusting means for adjusting the resonance frequency and the impedance so that the signal-to-noise ratio becomes substantially maximum. coil. 7. A static magnetic field generating magnet that generates a uniform static magnetic field, a gradient magnetic field coil that superimposes on the static magnetic field to generate a gradient magnetic field in a predetermined direction, and a gradient magnetic field drive for driving the gradient magnetic field coil. Section, an RF transmitter that outputs an RF pulse for exciting the subject in the static magnetic field, and a pulse signal output from the RF transmitter applied to the subject in the static magnetic field to generate from the subject. An RF coil that detects a magnetic resonance signal, an RF receiving unit that receives the signal detected by the RF coil, a control unit that controls the operation of each unit, and signal processing based on the signal received by the receiving unit. A signal processing unit,
A display unit for displaying a signal processed by the signal processing unit as an image, wherein the magnetic resonance imaging RF coil according to any one of claims 1 to 7 is used as the RF coil. Magnetic resonance imaging device.