JP4177940B2 - MRI RF coil and method for adjusting resonance frequency thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an MRI RF coil and a resonance frequency adjusting method thereof. More specifically, the present invention relates to an MRI RF coil capable of reducing component costs, simplifying the operation process of adjusting the resonance frequency, and shortening the adjustment time. The present invention relates to a frequency adjustment method.
[0002]
[Prior art]
FIG. 5 is an explanatory view showing a conventional MRI RF coil and a resonance frequency adjusting method thereof.
The MRI RF coil 500 includes a coil conductor 1, a fixed capacitor 2, and a trimmer capacitor 53 which is a variable (semi-fixed) capacitor.
The fixed capacitor 2 shares the fixed resonance frequency, and the trimmer capacitor 53 shares the variable resonance frequency.
[0003]
The resonance frequency of the MRI RF coil 500 is adjusted such that the resonance frequency measuring device MX is connected to the MRI RF coil 500 so that the resonance frequency conforms to the strength of the magnet of the MRI apparatus using the MRI RF coil 500. The trimmer capacitor 53 is adjusted. The strength of the magnet is heard from the hospital where the MRI apparatus is installed or measured.
[0004]
[Problems to be solved by the invention]
The conventional MRI RF coil 500 requires the trimmer capacitor 53. However, since the non-magnetic and high withstand voltage trimmer capacitor is expensive, there is a problem that the cost is increased.
Further, in the conventional method for adjusting the resonance frequency of the MRI RF coil 500, the work process of connecting the resonance frequency measuring device MX, adjusting the trimmer capacitor 53, and then removing the resonance frequency measuring device MX is complicated. There is a problem that it takes a long adjustment time.
Accordingly, an object of the present invention is to provide an MRI RF coil and a resonance frequency adjusting method thereof that can reduce the cost of components, simplify the work process of adjusting the resonance frequency, and shorten the adjustment time.
[0005]
[Means for Solving the Problems]
In a first aspect, the present invention comprises an MRI comprising a coil conductor, a socket or connector attached to the coil conductor, and a capacitor board on which a capacitor is mounted and removable from the socket or connector. An RF coil is provided.
In the MRI RF coil according to the first aspect, a socket or a connector is attached to the coil conductor, and a capacitor board is attached to or detached from the socket or connector. Since this capacitor board can be manufactured at a lower cost than a trimmer capacitor, the component cost can be reduced.
In addition, although expressed as "socket or connector" in the above configuration, this broadly means a connection means that allows the coil conductor and the capacitor board to be attached and detached, and is not limited to the narrowly defined "socket or connector". Absent.
[0006]
In a second aspect, the present invention provides a plurality of capacitor boards according to claim 1 each having a capacitor having a different capacity, and the strength of the magnet of the MRI apparatus using the MRI RF coil according to claim 1. The present invention provides a method for adjusting the resonance frequency of an RF coil for MRI, comprising selecting a capacitor board having a capacitor having a capacity suitable for the capacitor and mounting the capacitor board.
In the resonance frequency adjusting method for the MRI RF coil according to the second aspect, the capacity of the capacitor board that is equipped with capacitors having different capacities is adapted to the strength of the magnet of the MRI apparatus that uses the MRI RF coil. A capacitor board with a capacitor was selected and installed in the socket or connector. According to this, it is only necessary to select and install the capacitor board, there is no need to connect or disconnect the resonance frequency measuring device, and there is no need to adjust the trimmer capacitor while looking at the resonance frequency measuring device. The process can be simplified and the adjustment time can be shortened.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the invention shown in the drawings will be described. Note that the present invention is not limited thereby.
FIG. 1 is a perspective view of an MRI RF coil according to an embodiment of the present invention.
The MRI RF coil 100 includes a coil conductor 1, a fixed capacitor 2, a socket 3 attached to the coil conductor 1, and a capacitor board 10 on which the fixed capacitor 11 is mounted and detachable from the socket 3. ing.
The fixed capacitor 2 shares a fixed part of the resonance frequency, and the fixed capacitor 11 shares a variable part of the resonance frequency.
[0008]
FIG. 2 is a perspective view of a principal part showing a state before the capacitor board 10 is mounted on the MRI RF coil 100.
Pins 5 are erected on the socket 3. When these pins 5 are inserted into the holes 15 of the capacitor board 10 and the coil conductor 1 and the capacitor 11 are electrically connected, the capacitor board 10 is mounted. It will be in the state.
[0009]
FIG. 3 is an illustration of resonance frequencies corresponding to the capacitances of the capacitors 11 mounted on the capacitor board 10 respectively.
First, the capacitance of the fixed capacitor 2 is determined so that the resonance frequency is 8,550 kHz when the capacitance of the capacitor 11 mounted on the capacitor board 10 is 100 pF.
And the capacity | capacitance of the capacitor | condenser 11 each mounted in the capacitor | condenser board 10 is made into the capacity | capacitance from which a resonant frequency changes in steps of 10 kHz. For example, when the capacitance of the capacitor 11 is C6, the resonance frequency is 8,560 kHz.
[0010]
FIG. 4 is a frequency characteristic diagram of S / N (signal noise ratio).
When the resonance frequency of the MRI RF coil 100 is 20 kHz away from the resonance frequency fo of the MRI apparatus, the S / N ratio is reduced by about 5%.
Therefore, when the capacitances of the capacitors 11 mounted on the capacitor board 10 are changed every 10 kHz of the resonance frequency, the deviation of the resonance frequency of the MRI RF coil 100 from the resonance frequency fo of the MRI apparatus is 5 kHz at the maximum. Therefore, from the characteristics shown in FIG. 4, the maximum S / N reduction is about 1.5%. However, this decrease in S / N is negligible.
[0011]
The resonance frequency of the MRI RF coil 100 is adjusted as follows.
(1) Ask the hospital where the MRI system is installed, or actually measure it to check the strength of the magnet.
(2) The resonance frequency fo is calculated from the strength of the magnet.
(3) The capacitor board 10 on which the capacitor 11 having a capacity such that the resonance frequency of the MRI RF coil 100 is closest to the calculated resonance frequency fo is selected and mounted.
[0012]
For example, if the resonance frequency fo calculated from the strength of the magnet is 8,558 kHz, the capacitor board 10 on which the capacitor 11 having the capacity C6 in FIG. 3 is mounted may be selected and mounted.
In this case, the deviation of the resonance frequency of the MRI RF coil 100 from the resonance frequency fo of the MRI apparatus is 2 kHz. Therefore, from the characteristics shown in FIG. 4, the S / N decrease is about 0.5%. This decrease in S / N is negligible.
[0013]
【The invention's effect】
According to the MRI RF coil and the resonance frequency adjusting method of the present invention, only the work of selecting and mounting a capacitor board on which a capacitor having a capacity suitable for the magnet strength of the MRI apparatus using the MRI RF coil is selected. Since the resonance frequency adjustment is completed, the work process can be simplified and the adjustment time can be shortened. Further, since an expensive trimmer capacitor is not required, the component cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a perspective view of an MRI RF coil according to an embodiment of the present invention.
FIG. 2 is a perspective view of an essential part of an MRI RF coil before mounting a capacitor board.
FIG. 3 is a graph showing the relationship between the capacitance of a capacitor mounted on a capacitor board and the resonance frequency.
FIG. 4 is a graph showing the relationship between the S / N and the difference between the resonance frequency of the MRI apparatus and the resonance frequency of the MRI RF coil.
FIG. 5 is an explanatory diagram of a conventional MRI RF coil and a resonance frequency adjusting method thereof.
[Explanation of symbols]
1 Coil conductor 2 Fixed capacitor 3 Socket 5 Pin 10 Capacitor board 11 Fixed capacitor 12 Hall

Claims (2)

An MRI RF coil comprising: a coil conductor; a socket or connector attached to the coil conductor; and a capacitor board on which a capacitor is mounted and detachable from the socket or connector. A plurality of capacitor boards according to claim 1 each equipped with capacitors having different capacities are mounted, and capacitors having a capacity suitable for the strength of the magnet of the MRI apparatus using the MRI RF coil according to claim 1 are mounted. A method for adjusting the resonance frequency of an RF coil for MRI, comprising selecting a capacitor board and mounting the capacitor board.

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