JP4519331B2 - Noise interference control apparatus, MRI apparatus using the same, and noise interference control method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention, noise generated by a switching regulator (switching power supply) that supplies power to an apparatus such as an MRI apparatus does not affect a signal frequency band such as a resonance frequency band used inside the apparatus such as an MRI apparatus. The present invention relates to a noise interference control device to be controlled, an MRI apparatus using the same, and a noise interference control method.
[0002]
[Prior art]
Conventionally, an MRI apparatus has a characteristic that is extremely sensitive to electromagnetic noise because it includes a highly sensitive receiving coil that receives a signal having a resonance frequency determined by the main magnetic field strength of the magnet. Further, the MRI apparatus is generally used in a hospital or the like, and peripheral devices such as a table on which a human body is placed on the MRI apparatus are required to have good operability. In this peripheral device, a device that improves operability is incorporated, and a switching power source is being used as a power source of the peripheral device. Although this switching power supply uses several hundred kHz as its switching frequency, in principle, noise is radiated with high power at the switching frequency and its harmonics.
[0003]
Therefore, when the magnet of the MRI apparatus is arranged in an electromagnetic shield room and power is supplied from the outside to the inside of the shield room, a filter is arranged in the power cable on the shield room wall, and this Noise prevention measures such as winding the power cable around the ferrite core are taken.
[0004]
However, it is difficult to completely eliminate noise at the switching frequency and its harmonics. As a result, noise that enters the shield room may be received by the receiving coil of the MRI apparatus.
[0005]
[Problems to be solved by the invention]
However, it is difficult to completely eliminate noise at the switching frequency and its harmonics. As a result, noise that enters the shield room may be received by the receiving coil of the MRI apparatus.
[0006]
In this case, the signal received by the receiving coil is a resonance frequency band centered on the resonance center frequency, and when a harmonic component of the switching frequency exists in this resonance frequency band, the MRI image is deteriorated. There was a problem of end.
[0007]
The present invention has been made in view of the above, and a noise interference control apparatus capable of eliminating the influence of a harmonic component of a switching frequency in a switching power supply on an MRI image with a simple configuration, and an MRI using the noise interference control apparatus An object is to provide an apparatus and a noise interference control method.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a noise interference control device according to a first aspect of the present invention is a noise interference control device for controlling interference due to a noise frequency of a switching power source generated in a device frequency band used by a predetermined device as a power supply destination. A control device for detecting a noise frequency generated in the device frequency band; a temperature control unit for controlling a temperature of the switching power supply; and a noise frequency detected by the detection unit in the device frequency band. If present, the temperature control means changes the temperature of the switching power supply to shift the noise frequency out of the device frequency band.
[0009]
According to the noise interference control device of the first aspect of the invention, the detection means detects the noise frequency generated in the device frequency band, and the temperature control means excludes the noise frequency from the device frequency band. The temperature of the switching power supply is changed, and the noise frequency is shifted outside the device frequency band so that the noise frequency does not interfere with the device frequency band.
[0010]
The noise interference control apparatus according to the invention of the second aspect is characterized in that, in the above invention, the temperature control means changes the temperature of the switching power supply using a variable airflow fan.
[0011]
According to the noise interference control apparatus of the second aspect of the present invention, the variable airflow fan is used as the temperature control means, and the control means changes the airflow to the switching power supply by changing the rotation speed of the variable airflow fan. This controls the temperature of the switching power supply and excludes the noise frequency from the frequency band for the device.
[0012]
The noise interference control apparatus according to the invention of a third aspect is characterized in that, in the above invention, the temperature control means changes the temperature of the switching power supply using a water-cooled heat exchange means.
[0013]
According to the noise interference control apparatus according to the invention of the third aspect, a water-cooled heat exchange means is used as the temperature control means, and the control means changes the flow rate of the cooling water in the heat exchange means to change the flow rate of the switching power supply. The air volume is controlled, thereby controlling the temperature of the switching power supply, and the noise frequency is shifted outside the device frequency band.
[0014]
A noise interference control device according to a fourth aspect of the invention is characterized in that, in the above invention, the oscillator of the switching power supply is cooled.
[0015]
According to the noise interference control device of the fourth aspect of the invention, the noise of the switching power supply, which is the generation source of the noise frequency, is specifically cooled, so that the noise frequency is quickly and reliably shifted out of the device frequency band. I try to let them.
[0016]
An MRI apparatus according to a fifth aspect of the invention uses the noise interference control apparatus according to any one of the first to fourth aspects of the invention to resonate a noise frequency existing in a resonance frequency band. It is characterized by shifting outside the frequency band.
[0017]
The MRI apparatus according to the fifth aspect of the invention uses the noise interference control apparatus according to any one of the first to fourth aspects of the invention described above, and converts the noise frequency existing in the resonance frequency band of the MRI apparatus to the resonance frequency. The shift is made outside the frequency band.
[0018]
A noise interference control method according to a sixth aspect of the invention is a noise interference control method for controlling interference due to a noise frequency of a switching power supply generated in a device frequency band used by a predetermined device as a power supply destination. When detecting the noise frequency generated in the frequency band for use, determining whether the detected noise frequency exists in the frequency band for the device, and determining that the determined noise frequency exists in the frequency band for the device, The temperature of the switching power supply is changed, and the noise frequency is shifted outside the device frequency band.
[0019]
According to the noise interference control method of the sixth aspect of the invention, first, a noise frequency generated in the device frequency band is detected, and whether or not the detected noise frequency exists in the device frequency band is determined. If it is determined that the noise frequency is present in the device frequency band, the temperature of the switching power supply is changed to shift the noise frequency out of the device frequency band. This prevents the noise frequency from interfering with the device frequency band.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of a noise interference control apparatus according to the present invention, an MRI apparatus using the same, and a noise interference control method will be described below with reference to the accompanying drawings.
[0021]
(Embodiment 1)
First, a first embodiment according to the present invention will be described. FIG. 1 is a diagram showing the overall configuration of the MRI apparatus. In FIG. 1, this MRI apparatus has a magnet unit 100 and a table unit 200 inside a shield room 300, and a cabinet unit 4 and an operator console unit 5 outside the shield room 300. The shield room 300 electromagnetically shields the internal magnet unit 100 and the table unit 200 from the external cabinet unit 4 and the operator console unit 5.
[0022]
The magnet unit 100 and the table unit 200 of the MRI apparatus are provided inside the shield room 300, and are configured so that external RF electromagnetic noise does not enter the inside.
[0023]
The cabinet unit 4 has a built-in control system for controlling the magnet unit 100 and the table unit 200, and a signal is transmitted between the magnet unit 100 and the table unit 200 via the cable 3a outside the shield room 300 and the cable 2a inside. And send and receive power. Here, the cable 3a and the cable 2a are connected to each other through a penetration panel 6 of the shield room 300, and are configured to maintain an electromagnetic shielding effect. The operator console section 5 is connected to the cabinet section 4 via the cable 3b outside the shield room 300.
[0024]
FIG. 2 is a block diagram showing a schematic configuration of a switching power supply control apparatus which is applied to the MRI apparatus shown in FIG. 1 and is Embodiment 1 of the present invention. In FIG. 2, it has the power supply part 4a which supplies electric power into the shield room 300 inside. In FIG. 2, the computer 14 of the operator console unit 5 causes the scan controller unit 17 of the cabinet unit 4 to download a pulse sequence that is control software of the MRI apparatus based on an instruction input from the operation unit 16. Similarly, the scan controller unit 17 controls various driving of the magnet unit 100 and the table unit 200 via the drive control unit 18 in the cabinet unit 4. In this case, signal exchange between the drive control unit 18, the magnet unit 100, and the table unit 200 is performed via the filter 21 of the penetration panel 6.
[0025]
On the other hand, the switching power supply 13 of the power supply unit 4a is connected to the load 301 of the table unit 200 and the magnet unit 100 via the cable 3c, the filter 20 of the penetration panel 6, and the cable 2b. The power supply unit 4 a includes a switching power supply 13, a variable airflow fan 12 that cools the switching power supply 13, a fan power supply 11 that supplies a variable power supply to the variable airflow fan 12, and a harmonic of a switching frequency generated from the switching power supply 13. A detection coil 30 for detecting a frequency component of the resonance frequency band, that is, a noise frequency component, a noise monitor circuit 31 for monitoring a noise frequency component detected by the detection coil 30, and detection by the noise monitor circuit 31 The controller 32 variably controls the fan power supply 11 based on the noise frequency component information thus obtained and the resonance frequency band information of the MRI apparatus acquired from the computer 14. The filter 20 removes the high frequency component of the power supply noise. If the removal by the filter 20 is not sufficient, a ferrite core 19 is connected on the cable 2b as shown in FIG.
[0026]
The switching power supply 13 includes components whose noise frequency changes sensitively with respect to temperature changes. FIG. 3 is a diagram showing a detailed configuration of the switching power supply 13 realized by the series switching power supply. In FIG. 3, in the switching power supply 13, the transformer unit 13a converts the voltage of the AC power source into a desired AC voltage, and the rectifying / smoothing unit 13b rectifies the AC voltage into a DC voltage and smoothes it to the switch unit 13c. Output. The switch unit 13c energizes a desired DC current by switching of the control unit 13d, and the filter unit 13e filters the DC current output from the switch unit 13c and supplies DC power to the load 301. Here, the output of the filter unit 13e is fed back to the switch unit 13c via the control unit 13d and outputs stable power to the load 301.
[0027]
The control unit 13d includes an oscillator and the like, and includes an active element that determines a switching frequency for the switch unit 13c. This oscillator is easily affected by temperature, and the oscillation frequency changes as the temperature changes, and the switching frequency also changes. That is, in the case of the switching power supply 13, the component whose noise frequency is sensitively changed as described above is the control unit 13 d having an oscillator. Therefore, when the temperature of the switching frequency, that is, the noise frequency is controlled, the temperature of the control unit 13d, particularly the oscillator, may be controlled.
[0028]
Here, the noise control processing procedure by the control device 32 will be described with reference to the flowchart shown in FIG. In FIG. 4, first, the control device 32 reads information on the resonance frequency band of the MRI apparatus from the computer 14 (step S101). Thereafter, the control device 32 reads information on the noise frequency component monitored by the noise monitor circuit 31 (step S102). As described above, the frequency band monitored by the noise monitor circuit 31 is a frequency band including the resonance frequency band.
[0029]
Thereafter, the control device 32 determines whether or not the monitored noise frequency component is within the resonance frequency band (step S103). When the noise frequency component is within the resonance frequency band (step S103 / Yes), the power supply voltage of the fan power supply 11 is changed to control the rotational speed of the variable airflow fan 12. As a result, the air volume by the variable air volume fan 12 changes, and the cooling amount of the switching power supply 13 is controlled (step S104). As a result, the frequency of the noise frequency component that is a harmonic component of the switching frequency generated by the switching power supply 13 is shifted out of the resonance frequency band. Then, it transfers to step S102 and repeats the process mentioned above. On the other hand, if the noise frequency component is not within the resonance frequency band (step S103 / No), the process proceeds to step S102 as it is and the above-described processing is repeated.
[0030]
Here, the relationship between the resonance frequency band and the noise frequency will be described with reference to FIG. FIG. 5A shows a state in which the noise frequency 50 exists in the resonance frequency band 40. In this state, the noise frequency 50 is received together with the resonance frequency received by the receiving coil 1 (see FIG. 1) of the magnet unit 100, affects the MRI apparatus, and degrades the MRI image.
[0031]
Such an electromagnetic interference state can be easily determined by comparing the noise frequency component monitored by the noise monitor circuit 31 with the resonance frequency band 40 read from the computer 14 by the control device 32. Thereafter, the control device 32 increases the air volume by, for example, increasing the power supply voltage of the fan power supply 11 and increasing the rotational speed of the variable airflow fan 12 to cool the switching power supply 13. As a result, the oscillator of the switching power supply 13 is cooled, and the noise frequency 50 shifts on the frequency axis.
[0032]
The shift amount and direction of the noise frequency 50 on the frequency axis depend on the temperature characteristics of the oscillation frequency (noise frequency) of the oscillator of the switching power supply 13. For example, when the frequency characteristic of the oscillator is proportional to temperature, the noise frequency 50 is shifted to the lower side as a whole. Further, when the frequency characteristic of the oscillator is inversely proportional to the temperature, the noise frequency 50 is shifted to the higher side as a whole.
[0033]
Thus, by cooling the oscillator of the switching power supply 13, the noise frequency 50 shifts from the resonance frequency band 40 and does not exist on the resonance frequency band 40 as shown in FIG. As a result, the noise frequency 50 has no influence on the MRI image. Such processing is always repeated, and control is performed so that the noise frequency 50 does not always exist on the resonance frequency band 40.
[0034]
The noise frequency 50 can also be shifted from the resonance frequency band 40 by heating the oscillator of the switching power supply 13. However, heating the switching power supply 13 itself, which is a heat source, is not limited to the oscillator. In general, it is preferable to cool the other elements constituting 13 because there is a possibility of thermal destruction.
[0035]
Further, when controlling the temperature of the noise frequency, as described above, it is only necessary to control the temperature of the oscillator, which is a component in which the noise frequency reacts and changes sensitively. May be. In short, it is only necessary to specify a noise frequency transmission element and perform temperature control on the specified element.
[0036]
(Embodiment 2)
Next, a second embodiment according to the present invention will be described. In the first embodiment described above, the variable airflow fan 12 is used to change the temperature of the switching power supply 13. However, in this second embodiment, the temperature of the switching power supply 13 is controlled by water-cooling heat exchange means. As a result, the noise frequency is shifted.
[0037]
FIG. 6 is a block diagram showing a schematic configuration of an MRI apparatus including a switching power supply control apparatus according to the second embodiment of the present invention. In FIG. 6, a power supply unit 4 b corresponds to the power supply unit 4 a of the first embodiment shown in FIG. 2, and includes a switching power supply 13, a heat exchanger 60 that cools the switching power supply 13, and the heat exchanger 60. A pipe 61 through which cooling water for cooling the switching power supply 13 circulates, a pump 62 that circulates the cooling water in the pipe 61, a pump power supply 63 that variably drives the pump 62, and a higher harmonic of the switching frequency generated from the switching power supply 13 A detection coil 30 for detecting a frequency component in the resonance frequency band, that is, a noise frequency component, a noise monitor circuit 31 for monitoring a noise frequency component detected by the detection coil 30, and the noise monitor circuit 31 Based on the noise frequency component information detected by the and the resonance frequency band information acquired from the computer 14. Having a control unit 64 for variably controlling the pump power 63 Te. Other configurations are the same as those shown in FIG. 2, and the same reference numerals are given to the same components, and the description thereof is omitted.
[0038]
Here, the noise control processing procedure by the control device 64 will be described with reference to the flowchart shown in FIG. In FIG. 7, first, the control device 64 reads resonance frequency band information from the computer 14 (step S <b> 201). Thereafter, the control device 64 reads information on the noise frequency component monitored by the noise monitor circuit 31 (step S202). As described above, the frequency band monitored by the noise monitor circuit 31 is a frequency band including the resonance frequency band.
[0039]
Thereafter, the control device 64 determines whether or not the monitored noise frequency component is within the resonance frequency band (step S203). When the noise frequency component is within the resonance frequency band (step S203 / Yes), the power supply voltage of the pump power supply 63 is changed, the flow rate of the cooling water circulated by the pump 62 is controlled, and the cooling amount for the switching power supply 13 is determined. Is changed (step S204). As a result, the frequency of the noise frequency component that is a harmonic component of the switching frequency generated by the switching power supply 13 is shifted from the resonance frequency band of the MRI apparatus. Thereafter, the process proceeds to step S202, and the above-described processing is repeated. On the other hand, if the noise frequency component is not within the resonance frequency band (step S203 / No), the process proceeds to step S202 as it is and the above-described processing is repeated.
[0040]
Accordingly, as shown in FIG. 5, the noise frequency 50 shifts from the resonance frequency band 40 and does not exist on the resonance frequency band 40. As a result, the noise frequency 50 does not affect the MRI image. Such processing is always repeated, and control is performed so that the noise frequency 50 does not always exist on the resonance frequency band 40.
[0041]
As described in the first embodiment, if a transmission source of noise frequency 50, for example, an oscillator can be specified, it is efficient to cool only this transmission source in a concentrated manner. In particular, in the water-cooling system shown in the second embodiment, since the piping of the pipe 61 is accompanied, it is preferable to install the piping of the pipe 61 as close as possible to the transmission source. Further, as in the first embodiment, the temperature of the transmission source may be controlled by heating.
[0042]
【The invention's effect】
As described above, according to the noise interference control apparatus according to the first aspect of the invention, when the noise frequency detected by the detection means exists in the frequency band for the apparatus, the temperature control means changes the temperature of the switching power supply. The noise frequency is shifted outside the device frequency band. As a result, the noise frequency does not interfere with the device frequency band, so that the predetermined device can always obtain a high-quality signal using the device frequency band.
[0043]
According to the noise interference control device of the second aspect of the invention, the variable airflow fan is used as the temperature control means, and the rotation speed of the variable airflow fan is changed by the control means to change the airflow with respect to the switching power supply. As a result, the temperature of the switching power supply is controlled, and the noise frequency is shifted outside the device frequency band. As a result, it is possible to always obtain a high-quality signal using the device frequency band with a simple configuration.
[0044]
Moreover, according to the noise interference control apparatus according to the invention of the third aspect, a water-cooled heat exchange means is used as the temperature control means, the flow rate of the heat exchange means is changed by the control means, and the heat exchange rate with respect to the switching power supply To change. As a result, the temperature of the switching power supply is controlled, and the noise frequency is shifted outside the device frequency band. As a result, it is possible to always obtain a high-quality signal using the device frequency band with a simple configuration.
[0045]
Further, according to the noise interference control device of the fourth aspect of the invention, the noise of the switching power supply, which is the generation source of the noise frequency, is particularly cooled, so that the noise frequency can be quickly and surely out of the device frequency band. Since the shift is performed, it is possible to efficiently obtain a high-quality signal in the device frequency band.
[0046]
According to the MRI apparatus of the fifth aspect of the invention, the noise interference control apparatus according to any one of the first to fourth aspects of the invention described above is used, and the noise frequency existing in the resonance frequency band of the MRI apparatus. Is shifted out of the resonance frequency band, so that it is possible to always obtain a high-quality MRI image.
[0047]
According to the noise interference control method of the sixth aspect of the invention, first, a noise frequency generated in the device frequency band is detected, and whether or not the detected noise frequency exists in the device frequency band. If it is determined that the noise frequency is present in the device frequency band, the temperature of the switching power supply is changed to shift the noise frequency out of the device frequency band. As a result, the noise frequency is prevented from interfering with the device frequency band, so that the predetermined device can always obtain a high-quality signal using the device frequency band.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall configuration of an MRI apparatus.
FIG. 2 is a block diagram showing a schematic configuration of a switching power supply control apparatus which is applied to the MRI apparatus shown in FIG. 1 and is Embodiment 1 of the present invention;
FIG. 3 is a block diagram showing a configuration of a switching power supply shown in FIG.
4 is a flowchart showing a temperature control processing procedure by the switching power supply control device shown in FIG. 2; FIG.
FIG. 5 is a diagram illustrating a relationship between a noise frequency and a resonance frequency band.
FIG. 6 is a block diagram showing a schematic configuration of an MRI apparatus including a switching power supply control apparatus according to a second embodiment of the present invention.
7 is a flowchart showing a temperature control processing procedure performed by the switching power supply control device shown in FIG. 6;
[Explanation of symbols]
2a, 2b, 3a, 3b, 3c Cable 4 Cabinet section 5 Operator console section 4a, 4b Power supply section 6 Penetration panel 11 Fan power supply 12 Variable air volume fan 13 Switching power supply 14 Computer 19 Ferrite core 20, 21 Filter 30 Detection coil 31 Noise Monitor circuit 32, 64 Control device 40 Resonance frequency band 50 Noise frequency 60 Heat exchanger 61 Pipe 62 Pump 63 Power supply for pump 100 Magnet part 200 Table part 300 Shield room 301 Load

Claims (6)

A noise interference control device for controlling interference due to a noise frequency of a switching power supply generated in a device frequency band used by a predetermined device to which a power supply is provided,
Detecting means for detecting a noise frequency generated in the device frequency band;
Temperature control means for controlling the temperature of the switching power supply;
When the noise frequency detected by the detection means is present in the device frequency band, the temperature control means changes the temperature of the switching power supply to shift the noise frequency outside the device frequency band; and
A noise interference control device comprising: 2. The noise interference control apparatus according to claim 1, wherein the temperature control means changes the temperature of the switching power supply using a variable airflow fan. The noise interference control apparatus according to claim 1, wherein the temperature control unit changes the temperature of the switching power supply using a water-cooled heat exchange unit. The noise interference control device according to any one of claims 1 to 3, wherein an oscillator of the switching power supply is cooled. An MRI apparatus, wherein the noise interference control apparatus according to any one of claims 1 to 4 is used to shift a noise frequency existing in a resonance frequency band to the outside of the resonance frequency band. A noise interference control method for controlling interference due to a noise frequency of a switching power supply generated in a device frequency band used by a predetermined device as a power supply destination,
Detect the noise frequency generated in the device frequency band,
Determining whether the detected noise frequency is present in the device frequency band;
When it is determined that the determined noise frequency is present in the device frequency band, the temperature of the switching power supply is changed, and the noise frequency is shifted outside the device frequency band.

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