JPH06209916A - Rf coil unit for magnetic resonance imaging - Google Patents

Abstract

PURPOSE:To facilitate the tuning of an RF coil by permitting a load to be installed on an RF coil unit used in a magnetic resonance imaging (MRI) device. CONSTITUTION:As for an RF coil unit for MRI, an RF coil 1 is previously tuned in accordance with a prescribed load quantity (e.g. max. load quantity), and fixed. Further, each load having plural kinds of load quantity is previously manufactured. In photographing, the photographed part of a testee P is inserted into the RF coil 1. The photographed part is fixed by a fixing mat 2. At this time, a plurality of loads having a same load quantity which are previously manufactured according to the load quantity of the photographed part are inserted into a plurality of load insertion holes 3a, 3b, 3c, and 3d of the fixing mat 2 so that the load quantity considered from the RF coil 1 becomes equal to a prescribed load quantity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an RF coil unit used in a magnetic resonance imaging apparatus.

[0002]

2. Description of the Related Art Conventionally, magnetic resonance imaging (MRI)
When an image of a subject such as a patient is taken by the apparatus, an RF (radio frequency) pulse is efficiently transmitted to the subject, the predetermined portion of the subject is excited by this RF pulse, and a predetermined portion of the excited subject is determined. The RF coil used to efficiently receive magnetic resonance (MR) signals from the site is tuned (tuning and matching) according to the load on the subject.
Has been done.

In an RF coil (single coil) unit capable of transmitting and receiving MR signals, a vacuum capacitor or an air variable capacitor (air variable capacitor) is used as a variable capacitor for tuning the RF coil. A motor for driving the motor is attached to the RF coil unit.

[0004]

By the way, with respect to the local RF coil unit selected according to the imaged region of the subject, for example, the head RF coil unit, the knee RF coil unit, etc., each subject is to be examined. It is necessary to replace the unit each time. The operator replaces the RF coil unit.

However, in the case of a single coil unit,
Since the motor for driving the variable capacitor is attached to the unit, the total weight of the unit becomes considerable, and handling of such a unit becomes difficult. Particularly, in a quadrature (QD) coil, since four motors are attached, it becomes more difficult to handle the unit.

[0006] Further, the imaging region of the subject, for example, the abdomen,
Since there are large individual differences in the chest, feet, etc., the RF coil cannot be tuned to a predetermined subject, and therefore the subject cannot be imaged.
Alternatively, there may be a case where shooting cannot be performed under appropriate shooting conditions.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an RF coil unit for MRI in which the tuning of the RF coil is easy and the weight is reduced. .

[0008]

An RF coil unit for magnetic resonance imaging according to the present invention has an RF coil that is tuned and fixed in advance according to a predetermined load amount and a hole into which a plurality of loads can be inserted. A fixing means for fixing a predetermined part of the subject, and a plurality of loads having a predetermined load amount are inserted into the respective holes of the fixing means according to the load amount of the predetermined part of the subject. Characterize that.

[0009]

With the above construction, it is not necessary to attach a motor for driving a variable capacitor to the RF coil unit.
The weight of the entire F coil unit can be reduced. In addition, regardless of the load on the imaged part of the subject, by adjusting the load using the load produced in advance in the unit, the load seen from the RF coil becomes constant, so tuning of the RF coil is easy. Therefore, shooting can be performed under appropriate shooting conditions.

[0010]

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

For example, in a quadrature (QD) coil for knees, when an RF coil (single coil) type for both transmission and reception of magnetic resonance (MR) signals is adopted in order to improve the uniformity of sensitivity, at the time of photographing. The thigh of the subject as a load is inserted into this RF coil. In addition, there are considerable individual differences in the size of the thigh of the subject corresponding to the load amount.

Normally, when an RF coil is used, the coil is tuned according to the load on the imaged region of the subject.
Since the RF coil is used for both transmission and reception, it is not possible to use a varicap (a variable capacitance diode used in a reception-only RF coil) as a tuning capacitor, so an air variable capacitor (air variable capacitor) or a vacuum capacitor is used. , It is necessary to attach a motor for driving such a capacitor to the coil unit.

For example, the QD coil unit for knee has 2
Having a channel requires four drive motors for tuning the QD coil. This QD coil unit for the knee is incorporated in the magnetic resonance imaging (MRI) apparatus only when photographing the knee of the subject.
The heavier the coil unit, the heavier the load on the operator.

FIG. 1 is a perspective view showing the structure of an RF coil unit for magnetic resonance imaging which is an embodiment of the present invention. As shown in FIG. 1, the RF coil unit of the embodiment of the present invention has a QD coil 1 and a fixed mat 2 as a transmission / reception RF coil used for photographing a knee. The fixed mat 2 has four load insertion holes 3a, 3b, 3c, 3d for inserting a prefabricated load.

In this embodiment, the tuning of the QD coil 1 is performed and fixed according to a predetermined load amount, for example, the maximum load amount. Therefore, it is not necessary to attach a drive motor to the RF coil unit. Also, loads having various loads (for example, physiological saline, PVA (polyvinyl alcohol), etc. are used as materials) are manufactured. When the load amount of the imaging region of the subject P is smaller than the maximum load amount with which the QD coil 1 is synchronized, the maximum load amount is obtained,
The manufactured load is selected.

A table based on the relationship between the size of the imaged region of the subject P, the height and weight of the subject P and the load is created in advance, and the created table is referred to. A load selection is made.

As shown in FIG. 1, in the case of the QD coil 1, the load mating holes 3a, 3b, 3c, 3d are provided in the fixed mat 2 so that the loads can be arranged at four positions. There is. Several types of loads to be inserted into the load insertion holes 3a, 3b, 3c, 3d are manufactured in advance, and a predetermined load having the same load amount is inserted into each load insertion hole according to the load amount of the imaging region of the subject. To be done. That is, the load insertion hole 3a,
The loads inserted in 3b, 3c and 3d have the same load amount.

As a result, the same image quality as when the QD coil 1 is tuned by the drive motor can be obtained without the conventional tuning of the QD coil 1 according to the load amount of the subject's imaging region. It is possible to obtain an MR image having the same.

Further, as described above, since it is not necessary to attach the drive motor to the coil unit, the weight of the coil unit can be reduced, and the control line for the drive motor is also unnecessary, so that the operator is not required. This makes it easier to handle the coil unit.

The various loads used in this embodiment are not only manufactured by the load alone, but are also assembled in advance in a mat or band used to fix the imaging site of the subject and It is also possible to select and use such a mat or band according to the imaged part of the examiner.

Further, since it has been reported that the strength of the MR signal is increased by winding the PVA sheet around the subject, this PVA sheet can also be used as a load material.

Furthermore, since it is not necessary to tune the RF coil for each subject, the time required for tuning can be saved as in the conventional case, and therefore the time for the entire imaging can be shortened.

Although the RF coil for the knee has been described in the present embodiment, the RF coil for the knee, for example, the Q coil is used in the present invention.
The present invention is not limited to the D coil, but can be applied to, for example, a head RF coil and the like, and the same effect as that of the present embodiment can be obtained.

Even in an RF coil that needs to be tuned by a driving motor, the coil is tuned in advance in accordance with a large load amount, and at the time of photographing, the coil is appropriately tuned according to the load amount of the imaged region of the subject. By using the load, the coil can be tuned for almost all parts of the subject, so that the coil tuning range can be expanded. The embodiment of the present invention has been described above,
The present invention is not limited to the above embodiments, and various modifications can be made within the scope of the gist of the present invention.

[0025]

As described above, according to the present invention, since it is not necessary to attach a motor for driving a variable capacitor to the RF coil unit, it is possible to reduce the weight of the RF coil unit as a whole. In addition, regardless of the load on the imaged part of the subject, by adjusting the load using the load produced in advance in the unit, the load seen from the RF coil becomes constant, so tuning of the RF coil is easy. Therefore, shooting can be performed under appropriate shooting conditions.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of an RF coil unit for magnetic resonance imaging that is an embodiment of the present invention.

[Explanation of symbols]

P ... Subject, 1 ... QD coil, 2 ... Fixed mat, 3a,
3b, 3c, 3d ... Load insertion holes.

Claims (1)

[Claims] 1. Pre-tuned to a predetermined load amount,
The RF coil is fixed, and the fixing means has a hole into which a plurality of loads can be inserted and fixes a predetermined part of the subject. An RF coil unit for magnetic resonance imaging, characterized in that a plurality of loads having the same load amount are inserted into each hole of the fixing means.