JP4416217B2 - High voltage generator for X-ray high voltage apparatus and X-ray CT apparatus using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high-voltage generator for an X-ray high-voltage device that applies a high voltage to an X-ray tube, and in particular, houses a high-voltage transformer and a high-voltage rectifier that rectifies the output voltage of the high-voltage transformer. A high voltage generator for an X-ray high voltage device suitable for weight reduction and cooling of the container, and this high voltage generator is mounted on a scanner turntable, and a high voltage is applied to the X-ray tube from the high voltage generator. The present invention relates to an X-ray CT apparatus that obtains a tomographic image of a subject by irradiating the subject with X-rays and detecting transmitted X-rays of the subject.
[0002]
[Prior art]
The X-ray CT apparatus irradiates a subject with a fan-shaped X-ray beam from an X-ray tube, detects X-rays transmitted through the subject with an X-ray detector disposed at a position facing the X-ray tube, The detected data is image-processed to obtain a tomographic image of the subject.
[0003]
The X-ray detector is composed of hundreds of detection element groups arranged in an arc shape, and is arranged to face the X-ray tube with the subject interposed therebetween, corresponding to the number of detector elements. A plurality of radially distributed X-ray passages are formed, and the transmitted X-rays of the subject are detected at every predetermined angle when the X-ray tube and the detector are integrally rotated 360 degrees around the subject.
[0004]
In recent years, this X-ray CT apparatus has features such as “a wide range of scanning is possible in a short time” and “continuous data in the body axis direction can be obtained, thereby enabling generation of a three-dimensional image”. Rotational CT called helical scan or spiral scan has spread rapidly.
[0005]
In this CT, the time taken for multi-layer imaging from a wide range is greatly reduced by actively moving the imaging position during imaging, and three-dimensional CT imaging is possible.
[0006]
With this kind of spiral CT, the fixed scanner body performs continuous rotational scanning, and at the same time, the bed is continuously moved in the body axis direction, so that the X-ray tube performs a helical motion relative to the subject. Let In this way, the spiral scan changes the shooting position in parallel with the continuous rotation scan during shooting, so that the overall shooting time is shortened. Further, since continuous scanning is also performed in the body axis direction during photographing, three-dimensional data is collected.
[0007]
In order to realize this spiral scan, it is necessary to continuously rotate the scanner turntable. To that end, means for continuously supplying power to the X-ray tube mounted on the scanner turntable is required. Become. As this means, a power feeding mechanism comprising a slip ring and a brush is used, and a high voltage (hereinafter referred to as a tube voltage) is applied to the X-ray tube together with the X-ray tube on the scanner rotating disk. The high voltage generator is mounted, and the high voltage generator is supplied with power for generating required X-rays from the X-ray tube via the power supply mechanism.
[0008]
Thus, since the high voltage generator is mounted on the scanner turntable and rotated at a high speed, it is desirable that the weight be as light as possible. For this reason, an inverter type X-ray high voltage apparatus that can reduce the size and weight of the high voltage transformer of the high voltage generator and reduce the pulsation of the tube voltage is used for the X-ray high voltage apparatus.
[0009]
This inverter type X-ray high voltage device converts a commercial AC power source into a DC voltage with a converter circuit, converts this DC voltage into an AC voltage with a frequency higher than the commercial power source frequency with an inverter circuit, The AC voltage is boosted by a high voltage transformer, the boosted AC high voltage is rectified to a DC high voltage by a high voltage rectifier, and the DC high voltage is applied to an X-ray tube to generate X-rays. Composed. In the inverter type X-ray high voltage apparatus having such a configuration, the output voltage of the inverter circuit is boosted to generate a high voltage, and the high voltage is handled, that is, the high voltage transformer, high voltage rectifier, X-ray tube The heating transformer for heating the filament of the tube, the tube voltage detector for detecting the tube voltage applied to the X-ray tube, etc. are the high voltage insulation and the temperature caused by the heat generated from the high voltage transformer and the high voltage rectifier. For the purpose of cooling to suppress the rise, these are accommodated in a container (hereinafter, this container is referred to as a high voltage tank), and the high voltage tank is filled with insulating oil so as to fulfill the purpose of the insulation and cooling. It is configured. In order to reduce the size of the high voltage transformer and reduce the pulsation of the tube voltage waveform, the frequency of the inverter circuit is increased to 20 kHz or higher.
[0010]
As described above, the high-voltage generating part housed in the high-voltage tank mainly consists of a high-voltage transformer and a high-voltage rectifier, and iron loss, copper loss, and eddy current loss in the high-voltage transformer. Or generate heat due to loss such as switching loss of the high-voltage rectifier.
[0011]
Conventionally, this high-voltage tank has been mainly made of an iron container. The high-voltage transformer, high-voltage rectifier, etc. are housed in this container and immersed in insulating oil, and the high-voltage tank is made by natural air cooling or forced air cooling with a cooling fan. The heat generated in the voltage tank was cooled by a method of releasing the heat through the insulating oil and the high voltage tank. The temperature of the insulating oil inside the high voltage tank is about 60 ° C. on average, and the ambient temperature of the high voltage tank is about 45 ° C. This high voltage tank is disclosed in Japanese Patent Application Laid-Open No. 5-55956 and has a substantially rectangular parallelepiped box shape.
[0012]
[Problems to be solved by the invention]
In recent years, in an X-ray CT apparatus, it has been desired to shorten an imaging time in order to improve the throughput of the apparatus. Therefore, in order to increase the speed, it is necessary to increase the rotation speed of the scanner turntable. Therefore, the same X-ray conditions (the tube voltage and the X-ray tube anode and the cathode) In order to take a picture with the current flowing between them (hereinafter referred to as the tube current), the tube current is increased by the amount that the rotation speed of the scanner rotating plate has increased and the shooting time has been shortened. There must be. Further, in order to increase the rotation speed of the scanner turntable, it is essential to reduce the weight of the load on the scanner turntable. One of the weight reductions is to reduce the weight of the high voltage generator.
[0013]
In particular, it is most effective to reduce the weight of the high-voltage transformer that occupies most of the volume and weight of the high-voltage generator. As described above, the X-ray high-voltage apparatus for increasing the speed of the X-ray CT apparatus includes a high output accompanying an increase in tube current and a high-voltage generator mounted on the scanner turntable, that is, a small high-voltage transformer. It is necessary to reduce the weight. In order to reduce the size and weight of the high voltage transformer, it is necessary to increase the frequency of the inverter circuit. If this frequency is increased, heat generation due to the above-described loss of the high voltage transformer, the high voltage rectifier, and the like increases. In addition, the loss further increases due to the increase in output due to the increase in tube current. As described above, the speeding up of the X-ray CT apparatus increases the temperature in the high-voltage tank due to heat generation due to increased loss in the high-voltage generator, and the conventional cooling method, that is, a high-voltage tank made of a lot of iron. In order to fill the insulating oil and reduce it to the predetermined temperature or less by an air cooling method using a cooling fan from the outside of the tank, it is necessary to enlarge the high voltage tank and increase the insulating oil, which is contrary to downsizing and weight reduction. It will be. Therefore, since there is a limit to the air cooling method using the insulating oil and the cooling fan, it is necessary to consider dissipating the heat of the high voltage tank itself to the outside of the tank. JP-A-5-56856 discloses how to efficiently blow air from the cooling fan over the entire high-voltage tank, but does not describe heat dissipation of the high-voltage tank itself. High voltage tank of a conventional substantially rectangular parallelepiped box shape, its surface area is limited and 0.5m ² ~1.0m ^2, or the component mounted inside the high-voltage tank large, the insulation of the internal high voltage tank Measures such as increasing the amount of oil or dividing the high-voltage transformer into multiple parts and providing tanks for each of them are necessary, and the high-voltage tank must be increased in size and weight. Therefore, this is in conflict with the reduction in weight of the scanner turntable required for rotating the scanner turntable at high speed to shorten the photographing time. Furthermore, in the conventional method, the merit of increasing the inverter operating frequency (small size and weight of the high voltage transformer and low pulsation of the tube voltage waveform) cannot be fully utilized.
[0014]
Therefore, an object of the present invention is to suppress the temperature rise inside the high voltage tank of the high voltage generator for the X-ray high voltage device, and to reduce the temperature rise in the high voltage device for the X-ray high voltage device having a small and light high voltage tank with high cooling efficiency. An object of the present invention is to provide a voltage generator and an X-ray CT apparatus capable of shortening an imaging time by mounting the high voltage generator on a scanner turntable of an X-ray CT apparatus and rotating the scanner turntable at a high speed.
[0015]
[Means for Solving the Problems]
The above object is to provide a high voltage transformer that boosts an alternating voltage, a high voltage rectifier that rectifies the output voltage of the high voltage transformer to convert it into a direct high voltage, and at least these high voltage transformer and high voltage rectifier. were housed in a case, before the X-ray high voltage generator for the high voltage device having a radiating fin in close contact with the mute over scan, power is supplied from the high voltage generator for the X-ray high voltage unit X A rotating disk equipped with an X-ray tube for generating a line, an X-ray detector disposed at a position facing the X-ray tube, and an amplifier for amplifying the output of the X-ray detector is placed around the subject. In an X-ray CT apparatus that generates a tomographic image of the subject by rotating the X-ray CT apparatus, a cooling fan is provided in a stationary housing of the X-ray CT apparatus, and the cooling fan uses the cooling fan when the scanner rotating disk is stationary. This is accomplished by cooling the case .
[0016]
By housing the high-voltage transformer and high-voltage rectifier in a case made of aluminum or an alloy containing aluminum as a main component, the case can be reduced in weight, and heat radiation fins are provided in close contact with the case. The generated heat can be efficiently dissipated outside the case.
[0017]
Further, according to the present invention, since the high-voltage generator having a reduced weight and high heat dissipation effect is mounted on the scanner turntable of the X-ray CT apparatus, the speed of the scanner turntable can be increased. Can meet the demands of a wide range of scans.
[0018]
Further, a cooling fan is provided in the stationary side casing of the X-ray CT apparatus so that the direction of the groove of the radiating fin matches the rotating direction of the rotating disk, and when the rotating disk is stationary, By cooling the case, the cooling effect of the high voltage generator is increased, and an X-ray CT apparatus contributing to improvement of throughput can be provided.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS.
[0020]
FIG. 1 is a diagram showing an embodiment of a high voltage tank of a high voltage generator for an X-ray high voltage device according to the present invention. As described above, in order to reduce the size and weight of the high voltage transformer and reduce the pulsation of the tube voltage waveform, it is common to use an inverter type X-ray high voltage device for the X-ray high voltage device.
[0021]
This inverter type X-ray high voltage device converts a commercial AC power source into a DC voltage with a converter circuit, converts this DC voltage into an AC voltage with a frequency higher than the commercial power source frequency with an inverter circuit, The AC voltage is boosted by a high voltage transformer, the boosted AC high voltage is rectified to a DC high voltage by a high voltage rectifier, and the DC high voltage is applied to the X-ray tube.
[0022]
In the inverter type X-ray high voltage apparatus having such a configuration, a high voltage transformer that boosts the output voltage of the inverter circuit, a high voltage rectifier that rectifies the output voltage of the high voltage transformer to a DC voltage, and the X-ray tube 1 is housed in a case 3 shown in FIG. 1 including a heating transformer for heating the filament of the tube and a tube voltage detector for detecting an actual tube voltage used for tube voltage feedback control for stabilizing the tube voltage applied to the X-ray tube. The case 3 is filled with insulating oil so as to achieve the purpose of the insulation and cooling. The case 3 includes a high-frequency AC voltage input unit 4 that inputs an output voltage of the inverter circuit to a high-voltage transformer, and a high-voltage bushing 5 that is an output voltage terminal of the high-voltage rectifier. The case 3 and the case 3 The high-voltage tank 1 is constituted by the radiation fins 2 for radiating the heat generated inside.
[0023]
The high voltage tank 1 having such a configuration has a DC high voltage converted by a high voltage transformer and a high voltage rectifier housed in the case 3 by connecting the output terminal of the inverter circuit to a high frequency AC voltage input unit 4. Is connected to a high voltage bushing 5, a high voltage cable (not shown) is connected to the high voltage bushing 5, and the DC high voltage is applied to the X-ray tube to emit X-rays.
[0024]
In order to reduce the size of the high voltage transformer and reduce the pulsation of the tube voltage waveform, the frequency of the inverter circuit is increased to 20 kHz or higher.
[0025]
As the material of the case 3 of the high voltage tank 1, aluminum or an alloy mainly composed of aluminum is used. Its thermal conductivity is very large, about 5 to 10 times that of iron used as the material of the conventional case, so that the heat inside the case can be more effectively released to the outside of the case. Can do. Furthermore, the total weight of the high voltage tank using the conventional iron case (including the high voltage generating portion and the insulating oil) is 40 kg, and the weight of the case portion of the high voltage tank is 12 kg corresponding to 30% of the weight. When aluminum is used for the case portion of the high-voltage tank having the same shape, the weight density of aluminum is about 1/3 that of iron, so that the weight can be reduced by about 8 kg. This corresponds to 20% of the total weight of the high voltage tank. In this case, if the purpose is only to reduce the weight, a means of forming the case 3 with a resin may be considered. However, the thermal conductivity of this resin is one order of magnitude smaller than that of aluminum, so that it is also intended for cooling. Not suitable for. Note that the case 3 may not be entirely made of aluminum or an alloy containing aluminum as a main component, but a part of the case 3 may be made of iron if the temperature in the case 3 can be within an allowable value.
[0026]
As described above, in the present invention, the high-voltage tank 1 is configured by providing the radiation fins 2 on a part or the entire surface of the case 3. For example, if the heat dissipating fins 2 are provided with heat dissipating fins having a height of 50 mm at intervals of 20 mm, the surface area is five times that of a flat surface. The heat radiating fin 2 may be a method of attaching a ready-made heat sink of an appropriate size to the case 3 or using a cast that is integrated with the case 3, but according to the required shape of the heat radiating fin 2. Any method may be selected and used.
[0027]
FIGS. 2 and 3 show an example in which the high voltage tank 1 (high voltage generator) having features of both weight reduction and high cooling is mounted on the scanner turntable of the X-ray CT apparatus with the above configuration.
[0028]
FIG. 2 is a configuration diagram of the scanner rotating disk in which the high voltage tank 1 according to the present invention is mounted on the scanner rotating disk of the X-ray CT apparatus, and FIG. 3 is a detailed view of a portion A in FIG.
[0029]
In FIG. 2, a scanner turntable 10 includes an X-ray tube 7, an X-ray detector 8 disposed at a position facing the X-ray tube 7, an amplifier 9 for amplifying the output of the X-ray detector, and the X-ray. An X-ray tube cooling device 11 for cooling the tube, a high voltage tank 1 for supplying a high voltage to the X-ray tube, heating power for the filament, and the like, and other mounted objects 12 are mounted. The high voltage rectifier output DC high voltage is applied to the X-ray tube 7 to irradiate the subject with a fan-shaped X-ray beam radiated from the X-ray tube, and the X-ray transmitted through the subject is converted into the X-ray. The detection signal is detected by the detector 8, the detection signal is amplified by the amplifier 9, transmitted to the image processing apparatus, and image processing is performed to obtain a tomographic image of the subject.
[0030]
The heat generated in the case 3 of the high-voltage tank 1 is radiated to the outside of the case 3 by heat radiation fins attached in close contact with the case 3 to cool the high-voltage transformer, high-voltage rectifier and the like in the case. .
[0031]
Further, in the present invention, in order to efficiently cool the case 3 of the high-voltage tank 1, wind generated by the flow of air generated when the rotating disk 10 of the X-ray CT apparatus rotates is used.
[0032]
In this case, when the high voltage tank 1 is mounted on the turntable 10, the high voltage tank 1 is mounted as shown in FIG. 3 rotated 90 degrees counterclockwise from the state of FIG. That is, the high-voltage tank 1 is mounted on the turntable 10 so that the direction of the grooves of the radiating fins 2 provided on the high-voltage tank 1 matches the flow direction of air generated in the direction opposite to the rotation direction of the turntable 10. In the case of FIG. 1, an example in which the radiating fins 2 are provided only on the upper portion of the high voltage tank 1 is shown, but this may be provided on the entire surface of the high voltage tank 1 or on some other surface. In that case, when the high-voltage tank 1 is mounted on the turntable 10, the radiation fins 2 are provided on a plane (plane c in FIG. 2) perpendicular to the rotation radius direction of the turntable 10, and the rotation of the turntable 1. 2 and the rotation radius direction, the groove direction of the heat dissipating fin 2 and the rotation direction of the rotating disk 10 coincide with each other, and the heat dissipating fin 2 Is provided on a surface perpendicular to the rotation direction of the turntable 10 (surface b in FIG. 2), the high-voltage tank 1 so that the groove direction of the radiating fin 2 and the rotation radius direction of the turntable 10 coincide with each other. Is mounted on the turntable 10. The direction of the grooves of the radiating fins 2 provided in the high voltage tank 1 is a direction that does not interfere with the air flow generated in the direction opposite to the rotating direction of the rotating disk, even if it has a slight angle from the above direction. I do not care. In this way, by making the direction of the grooves of the radiating fins 2 provided in the high voltage tank 1 coincide with the direction of rotation of the turntable 10, the wind caused by the flow of air generated in the direction opposite to the direction of rotation of the turntable 10 is generated. By utilizing this, the high voltage tank 1 can be cooled more effectively. For example, at the position where the rotation radius of the turntable 10 is 0.8 m, the wind due to the air flow caused by the rotation of the turntable 10 has a cooling fan with a maximum wind speed of about 5 m / s when the rotation speed is 1 second / rotation. The same cooling effect as when attached to the high voltage tank 1 is obtained. This is because the maximum wind speed obtained with a commercially available 120 mm × 120 mm standard cooling fan is about 3.5 m / s, so that a cooling effect similar to that provided with a very powerful cooling fan can be obtained.
[0033]
When the turntable 10 is stationary, as shown in FIG. 3, the heat dissipating fins 2 of the high voltage tank 1 are cooled by the cooling fan 14 provided in the stationary casing 13. The cooling by the cooling fan 14 may be operated only when the turntable 10 of the X-ray CT apparatus is stopped. However, the turntable 10 may be rotated if necessary.
[0034]
The example of FIG. 2 is an example in which the high voltage tank 1 of the high voltage generator is configured as one, but the present invention is not limited to this, and the high voltage generator is limited to two or more. These may be divided and mounted at any position on the turntable 10. In this case, the degree of freedom in weight balance is increased, and optimal mounting on the rotating disk is possible.
[0035]
In the embodiment of FIG. 2, the high voltage generator (high voltage tank 1) is mounted on the turntable 10, but if it does not hinder the speedup of the turntable 10, a converter circuit and an inverter circuit are provided. The structure to mount may be sufficient.
[0036]
The high-voltage tank 1 of the high-voltage generator according to the present invention is not applied only to the X-ray CT apparatus, and suppression of temperature rise and weight reduction in the high-voltage tank are also desired for the X-ray apparatus. However, it goes without saying that it can be used for these effects.
[0037]
【The invention's effect】
As described above, according to the present invention, circuit components such as a high voltage transformer and a high voltage rectifier constituting a high voltage generator for an X-ray high voltage device are accommodated in a case made of aluminum or an alloy mainly composed of aluminum. Since the heat radiation fin is provided in close contact with the case, the high voltage generator can be reduced in weight, and the heat generated in the case can be efficiently radiated outside the case by the heat radiation fin. The effect that temperature rise can be suppressed is obtained. Further, according to the present invention, since the high-voltage generator having a reduced weight and high heat dissipation effect is mounted on the scanner turntable of the X-ray CT apparatus, the speed of the scanner turntable can be increased. It is possible to provide an X-ray CT apparatus capable of obtaining effects such as “scanning over a wide range in time” and “improvement of throughput by shortening imaging time”. In the X-ray CT apparatus equipped with the high-voltage generator, a cooling fan is provided in the stationary casing of the X-ray CT apparatus such that the direction of the groove of the heat dissipating fins coincides with the rotation direction of the rotating disk. The cooling effect of the high voltage generator is further increased by cooling the case with the cooling fan when the rotating disk is stationary.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of the present invention of a high-voltage tank that houses circuit components constituting a high-voltage generator for an X-ray high-voltage device.
FIG. 2 is a diagram showing an embodiment in which a high voltage generator using the high voltage tank of FIG. 1 is mounted on a scanner turntable of an X-ray CT apparatus.
FIG. 3 is a detailed view of part A in FIG. 2;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 High voltage tank 2 Radiation fin 3 Case 4 High frequency alternating voltage input part 5 High voltage bushing 7 X-ray tube 8 X-ray detector 9 Amplifier 10 Scanner turntable 13 Stationary side case 14 Cooling fan

Claims (2)

A high voltage transformer that boosts the AC voltage, a high voltage rectifier that rectifies the output voltage of the high voltage transformer and converts it to a DC high voltage, and at least these high voltage transformer and high voltage rectifier are made of aluminum or aluminum. And a high voltage generator for an X-ray high-voltage device in which a heat radiation fin is provided in close contact with the case, and the high-voltage generator for the X-ray high-voltage device receives electric power. A turntable equipped with an X-ray tube that is supplied to generate X-rays, an X-ray detector disposed at a position facing the X-ray tube, and an amplifier that amplifies the output of the X-ray detector. In an X-ray CT apparatus that generates a tomographic image of a subject by rotating around the subject,
An X-ray CT apparatus, wherein a cooling fan is provided in a stationary casing of the X-ray CT apparatus, and the case is cooled by the cooling fan when the rotating disk is stationary. The X-ray CT apparatus according to claim 1, wherein the direction of the groove of the heat dissipating fin is made to coincide with the direction of rotation of the rotating disk.

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