JPH04279149A - Probe for magnetic resonance imaging apparatus - Google Patents

Abstract

PURPOSE:To provide a probe for an MRI apparatus which is allowed to be mounted at a desired position to match the shape of an object to be inspected. CONSTITUTION:This probe is made up of an opposed type coil in which a pair of loop coils comprising lower and upper coils 2 and 3 is arranged being separated at each loop with a holding strut 1 interposed. This is of an arm structure in which the holding support 1 is free to deform in a three-dimensional space.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

[Industrial Application Field] The present invention relates to the transmission of high frequency magnetic field signals (hereinafter referred to as "RE signals") and the transmission of magnetic resonance signals (hereinafter referred to as "RE signals").
A magnetic resonance imaging device probe (hereinafter referred to as "MR signal") used for receiving MR signals or exclusively used for receiving MR signals (hereinafter referred to as "MR signal")
The present invention relates to a probe for an MRI apparatus (referred to as "a probe for an MRI apparatus"), and particularly relates to an improvement of a probe for an MRI apparatus used for imaging the abdomen of a subject.

0002

[Prior Art] Conventionally, MRI is used to image the abdomen of a subject.
The saddle type coil shown in FIG. 5 and the opposing type coil shown in FIGS. 6 and 7 are used as the apparatus probe, and each of these coils generally has a functional configuration exclusively for receiving MR signals.

0003

[Problems to be Solved by the Invention] However, since the conventional saddle-type coil has a structure that does not change its shape, depending on the physique of the subject, the saddle pattern shown in FIG. 5 and the pattern shown in FIG. Due to the mismatch with the armpit width W of the subject, the subject may be forced into an unreasonable position when setting the subject P or during imaging, which may cause pain to the subject. was there.

Furthermore, in the case of the conventional opposed type coils shown in FIGS. 6 and 7, the shape of the holding column 103 that separates and arranges a pair of loop coils consisting of a lower coil 101 and an upper coil 102 for each loop is unchanged. Because of this structure, there was a problem in that the installation position on the subject's upper limb was restricted by the holding column.

[0005] The present invention has been made in view of the above-mentioned circumstances, and its purpose is to provide a probe for an MRI apparatus that can be attached to a desired position according to the body shape of the subject. . [Structure of the invention]

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an MRI apparatus constituted by a pair of opposed coils in which a pair of loop coils are arranged separately for each loop with a holding column interposed therebetween. The probe is characterized in that the holding column has an arm structure that can be freely deformed in three-dimensional space.

[0007]

[Function] With the configuration of the probe for an MRI apparatus according to the present invention, the holding column that separates and arranges a pair of loop coils for each loop has an arm structure that can be freely deformed in three-dimensional space. Deform the holding column according to the
It can be attached to a desired position on the subject.

[0008]

[Example] Figure 1 shows an MR of an example to which the present invention is applied.
FIG. 2 is a perspective view showing the outer shape of the I device probe.

[0009] The probe for the MRI apparatus according to this embodiment is as follows:
A lower coil 2 that forms a pair of loop coils using two holding columns 1 with a flexible arm structure made of non-magnetic material.
and upper coils 3 are arranged separately for each lube. Note that the lower coil 2 is installed on the top plate 4.

[0010] The lower coil 2 and the upper coil 3 are each wired with a wire (not shown) made of a material with high electrical conductivity such as a copper pipe or copper foil. It forms a loop. Here, the shape and size of the loops do not necessarily have to be the same for each of the lower coil 2 and the upper coil 3. Further, the lower coil 2 has a structure in which the outer shape of the cover can be fixed to the top plate 4, and the upper coil 3 is held by fixing, for example, two holding columns 1 each having a flexible arm structure to the cover. This is what we are doing. Note that the number of holding columns 1 having a flexible arm structure is not limited to two, and may be one.

[0011] The holding column 1 having a flexible arm structure has the following features:
The inside of the arm is hollow, and a conductor wire (not shown) with low loss and small line capacitance, such as a feeder line, is inserted into the hollow.
is passing through. This conductor wire electrically connects the loop coils of the lower coil 2 and the upper coil 3, and as shown in FIG. 2, two sets of passive resonators 5, 6 and a set of active resonators 7.

That is, in this embodiment, a pair of loop coils consisting of a lower coil 2 and an upper coil 3 are activated by actively controlling an active switching element such as a PIN diode from the outside. A set of active resonators 7 is provided in order to be detuned from the resonant frequency of the system. This active resonator 6 is, for example, shown in FIG.
This is a circuit that forms a parallel resonant circuit when the PIN diode is turned on by combining a PIN diode 8, an inductor 9, and a capacitor 10 as shown in FIG. In addition, in FIG. 3, 11 is PI
This is an N diode control line.

Further, each of the lower coil 2 and the upper coil 3 is provided with two sets of passive resonators 5 and 6, which serve as circuits exhibiting high impedance during RF transmission. As a result, even if induced electromotive force is generated in the loop coil during RF transmission, almost no induced current flows in the upper and lower loop coils due to the line capacitance of the conductor wires connecting the upper and lower loops, so the transmitted RF magnetic field is Spatial disturbances can be significantly suppressed. Note that two sets of passive resonators 5,
6, the static magnetic field B0 is generated by the active resonator 7.
The loop coil does not resonate at the resonant frequency corresponding to . However, due to the existence of line capacitance in the conductor wire that electrically connects the upper and lower coils, the upper and lower coils each form a high-frequency loop via this capacitance. Therefore, the spatial distribution of the transmitted RF magnetic field is disturbed. In other words, when a transmitting RF magnetic field passes through a pair of loop coils, this loop coil does not resonate, but an induced current flows in the high-frequency loop, resulting in a state of coupling between the lower coil 2 and the upper coil 3. The RF magnetic field inside this loop coil is thereby strengthened or weakened. In addition, if this passive switching high impedance circuit is implemented with active switching, a control line is required to control this active switching, and the lower coil 2 The performance of the pair of loop coils consisting of the upper coil 3 and the upper coil 3 deteriorates. From this point of view, in this embodiment, two sets of passive resonators 5 and 6 are provided as described above. These passive resonators 5 and 6 are
For example, as shown in FIG. 4, the circuit is a combination of a cross diode 12 and a parallel resonant circuit consisting of another resonant inductor 13 and capacitor 14. Note that the number of passive resonant circuits is not limited to two, but may be one or more.

With the mechanical and electrical configuration of this embodiment, the upper coil 3 can be freely arranged and fixed in a three-dimensional space by the holding column 1 having a flexible arm structure. It also serves as an upper coil that can be flipped up when setting a subject. Also, the passive resonator 5
, 6 and the active resonator 7 are provided on a substrate (not shown), and if this substrate is housed in the cover portion of the lower coil 2, no inconvenience will occur in handling. Furthermore, there is also an advantage that the upper coil 3 can be moved not only in the height direction but also in the left and right directions with respect to the static magnetic field B0.

[0015] The holding column 1 adopted in this embodiment is as follows:
Although it has a flexible arm structure made of non-magnetic material, the present invention is not limited to this. For example, by combining a small amount of non-magnetic metal or resin, a holding column having joint-like functions at several points and having a hollow structure may be employed.

[0016]

[Effects of the Invention] As explained above, according to the present invention, two
The pair of loop coils can be attached to the subject by appropriately deforming the holding column, which can be freely deformed in dimensional space, so that good imaging conditions can be ensured without forcing the subject into an unreasonable body position. become.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the outer shape of a probe for an MRI apparatus according to an embodiment of the present invention.

FIG. 2 is a connection diagram schematically showing the entire circuit of a probe for an MRI apparatus according to an embodiment of the present invention.

FIG. 3 is a circuit diagram showing an example of an active resonator.

FIG. 4 is a circuit diagram showing an example of a passive resonator.

FIG. 5 is a diagram showing an example of a saddle-type coil pattern.

FIG. 6 is a perspective view schematically showing an example of an opposed coil.

FIG. 7 is a perspective view schematically showing another example of the opposed coil.

FIG. 8 is a diagram schematically showing a subject.

[Explanation of symbols]

1 Holding post 2 Lower coil 3 Upper coil 4 Top plate 5, 6 Passive resonator 7 Active resonator 8 PIN diode 9 Inductor 10 Capacitor 11 PIN diode control line 12 Cross diode 13 Inductor 14 Capacitor

Claims (4)

[Claims] 1. A probe for magnetic resonance imaging comprising a pair of opposed coils each having a pair of loop coils arranged separately for each loop with a holding column interposed therebetween, the probe comprising:
A probe for a magnetic resonance imaging apparatus, wherein the holding column has an arm structure that can be freely deformed in three-dimensional space. 2. The probe for a magnetic resonance imaging apparatus according to claim 1, wherein the holding column is provided with wiring that electrically connects the pair of loop coils. 3. The probe for a magnetic resonance imaging apparatus according to claim 1, wherein the holding column has a flexible arm structure made of a non-magnetic material. 4. A portion of the pair of loop coils includes 1
The probe for a magnetic resonance imaging apparatus according to claim 1, comprising at least one set of passive resonators and one set of active resonators.