JP4526107B2 - X-ray CT system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an X-ray CT apparatus that emits X-rays to a diagnostic site of a subject, detects a transmitted X-ray image thereof, reconstructs a tomographic image, and displays the image as an image. The present invention relates to an X-ray CT apparatus that is provided with means for supplying power from a power supply and can facilitate maintenance and inspection of the power supply means and improve reliability.
[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 X-ray tube and the detector are integrated to rotate around the subject by at least 180 degrees to detect transmitted X-rays of the subject at certain angles. .
[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 can be obtained in the body axis direction, thereby enabling generation of a three-dimensional image”. Rotational CT called helical scan or spiral scan has spread rapidly.
In this rotation CT, the time taken for multilayer imaging over a wide range is greatly reduced by actively moving the imaging position during imaging, and three-dimensional CT imaging is possible.
[0005]
The spiral CT having such a feature causes the X-ray tube to rotate relative to the subject by moving the bed in the body axis direction simultaneously with the fixed scanner body performing continuous rotation scanning. . 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.
[0006]
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 supply 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 for mounting is supplied, and the high voltage generator is supplied with electric power for generating required X-rays from the X-ray tube via the power supply mechanism. 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 device 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 device.
[0007]
However, since the conventional X-ray CT apparatus using the power supply mechanism using the slip ring and the brush is a power supply method by mechanical sliding contact between the slip ring and the brush, a large current is generated between the slip ring and the brush. As a result of flowing, wear and corrosion occurred at the contact area. That is, the high voltage transformer mounted on the scanner rotating unit generates a high voltage of hundreds of kV on the output side, and has a sufficient insulation distance inside for insulation from the input side. For this reason, there is a leakage inductance of several μH to several tens of μH. Further, the current flowing through the slip ring and the brush is about 400 A at the maximum. In this state, if a small gap is generated between the slip ring and the brush provided on the scanner fixing part when the scanner rotating part rotates, current tends to continue to flow due to the influence of the leakage inductance. In some cases, an arc is generated and the temperature is locally increased. Since the slip ring and brush may be worn or corroded by this high temperature, maintenance inspection such as polishing of the slip ring and replacement of the brush must be periodically performed. And cost. In addition, this problem is becoming more serious in recent years because there has been a demand for higher-speed scanning X-ray CT apparatuses from the market for the purpose of effectively diagnosing organs such as the heart that are moving rapidly. .
[0008]
Therefore, as a method for dealing with such problems, a method using electromagnetic induction that supplies power from the power source to the X-ray tube side in a non-contact manner without mechanical sliding contact is disclosed in Japanese Patent Laid-Open No. 7-204192. Has been. This is connected to the output side of the inverter circuit of the inverter type X-ray high-voltage device as a means for supplying power from the power source to the X-ray tube side provided in the scanner rotation unit, and around the fixed frame of the scanner rotation unit. A first winding is disposed on the second winding, and is disposed on the circumference of the rotating frame of the scanner rotating portion so as to face the first winding and connected to the input side of the high-voltage transformer. The electromagnetic induction power transmission means comprising a combination of windings is provided.
[0009]
An X-ray CT apparatus using non-contact transmission means using optical communication combining a light-emitting element and a light-receiving element as means for sending a detection signal from an X-ray detector to an image processing apparatus is disclosed in JP-A-9-313473. Has been.
As a result, a high voltage can be supplied to the X-ray tube in a non-contact manner, and an X-ray detection signal can be transmitted to the image processing apparatus. The power transmission means and the signal transmission means by mechanical sliding contact with a slip link and brush can be used. Wear and corrosion can be prevented, maintenance and inspection can be facilitated, and the reliability of the entire apparatus can be improved.
[0010]
[Problems to be solved by the invention]
However, the above-mentioned JP-A-7-204192 requires X-ray generation such as a filament heating circuit for heating the filament of the X-ray tube and an anode rotation driving circuit for the X-ray tube for rotating the anode of the X-ray tube. No mention is made of power supply to the various circuits other than the high voltage generating circuit.
For this reason, since it does not function as an X-ray CT apparatus without power supply to the various circuits, power supply to the various circuits is also a big problem.
[0011]
In this case, it is conceivable to use the same power supply method by mechanical sliding contact between the slip ring and the brush for power supply to the various circuits, but the power required for the various circuits is much higher than that of the high voltage generation circuit. Even though it is small, a current of several tens of amperes flows, and this method still has problems of wear and corrosion. Further, since the tube voltage of the X-ray CT apparatus disclosed in the above-mentioned JP-A-7-204192 is controlled by an inverter circuit on the fixed side of the scanner rotating unit, the output voltage of this inverter circuit, that is, the scanner Since the voltage supplied to the primary side of the high voltage transformer mounted on the rotating side of the rotating unit changes according to the tube voltage, it cannot be used as a power supply source for the various circuits. Therefore, it is necessary to provide electromagnetic induction power transmission means for each of the various circuits. Therefore, the entire system is further complicated, and the cost increase and size / weight increase become significant.
[0012]
Therefore, an object of the present invention is not only a high voltage generating circuit, but also a scanner rotating unit such as an X-ray tube filament heating circuit and an X-ray tube anode rotation driving circuit other than the high voltage generating circuit. An X-ray CT system that facilitates maintenance and inspection of the power supply means that supplies power to the scanner rotating unit from the power source without contact and improves the reliability of the entire system and supports high-speed scanning It is to provide.
[0013]
[Means for Solving the Problems]
The above object is achieved by the following means.
[0014]
(1) an X-ray tube that emits X-rays, an X-ray detector that detects a transmitted X-ray dose distribution in which the X-rays emitted from the X-ray tube pass through the subject, and amplifies the detection signal; A scanner rotation unit that rotates an X-ray tube and an X-ray detection unit facing each other and rotates around a subject, and an image processing apparatus that processes an output signal from the X-ray detection unit and reconstructs a tomographic image of a diagnostic site And an image display device for displaying a tomogram by inputting an output signal from the image processing device, a power source for generating a DC voltage, and a DC voltage from the power source to AC An inverter circuit to be converted, a first winding connected to the output side of the inverter circuit and disposed on the circumference of the fixed frame of the scanner rotation unit, and the first winding on the circumference of the rotation frame of the scanner rotation unit; A plurality of second windings arranged opposite one winding And a voltage to be applied to the X-ray tube by controlling at least the output voltage or frequency of one of the plurality of second windings of the electromagnetic induction power transmitting means. Tube voltage control means for controlling, a high voltage transformer for boosting the AC voltage controlled by the tube voltage control means, a high voltage rectifier for converting the output voltage of the high voltage transformer to a DC voltage, and the high voltage rectifier A capacitor for smoothing the output voltage, and a high DC voltage smoothed by the capacitor is applied to the X-ray tube to emit X-rays.
[0015]
(2) The tube voltage control means is composed of AC voltage control means or a cycloconverter using a bidirectional switch capable of voltage control.
[0016]
(3) The electromagnetic induction power transmission means has its first winding wound around a ring-shaped iron core disposed on the circumference of the fixed frame of the scanner rotating unit, and a plurality of second windings are rotated by the scanner rotating unit. It is configured by winding around a ring-shaped iron core arranged on the periphery of the frame, and the magnetic flux generated in the first winding is linked to a plurality of second windings via the respective iron cores.
[0017]
(4) An output voltage of an arbitrary winding of the plurality of second windings of the electromagnetic induction power transmission unit is input to the tube voltage control unit, and the remaining windings of the plurality of second windings The output voltage of the line is supplied to a circuit mounted on the scanner rotation unit.
[0018]
(5) An output voltage of an arbitrary winding of the plurality of second windings of the electromagnetic induction power transmission unit is input to the tube voltage control unit and insulated from the remaining windings of the second winding. Insulating transformers that generate a plurality of types of output voltages are supplied, and the output voltages of the insulating transformers are supplied to a circuit mounted on the scanner rotating unit.
[0019]
The X-ray CT apparatus configured as described above includes a first winding and a second winding as power supply means for supplying power from the power source to each circuit mounted on the scanner rotation unit in the scanner rotation unit. By providing the combined electromagnetic induction power transmission means, it is possible to supply the required power in a non-contact manner by electromagnetic induction action, without the conventional mechanical sliding contact between the slip ring and the brush. As a result, it is possible to prevent the conventional power supply portion from being worn and corroded, to facilitate maintenance and inspection of the power supply means and to improve the reliability. In addition to the above, in the present invention, by applying at least an AC voltage control means or a frequency control means using a bidirectional switch to a tube voltage control circuit that occupies most of the X-ray generation system, the number of components is reduced, and the circuit is reduced. Since the simplification is achieved, the weight of the mounted part of the rotating part can be reduced, and an X-ray CT apparatus with high diagnostic capability that can perform higher-speed scanning can be obtained.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
Example 1
FIG. 1 is a block diagram of an overall configuration showing a first embodiment of an X-ray CT apparatus according to the present invention. The outline is as follows. In other words, this X-ray CT apparatus emits X-rays to the diagnosis site of a subject, detects the transmitted X-ray dose distribution, reconstructs a tomographic image, and displays it as an image. As shown in FIG. Power supply 1, inverter circuit 2, high voltage generation circuit 520, anode drive circuit 510, heating circuit 530, control power supply circuit 540, X-ray tube 560, X-ray detector 550, and image processing device 9 And an image display device 10, the scanner rotating unit 5 is provided with electromagnetic induction power transmission means 4 as means for supplying electric power from the power source 1 to each circuit mounted on the scanner rotating unit 5, and an X-ray detecting unit As a means for sending a detection signal from 550 to the image processing device 9, a light emitting element 7c for converting an output signal from the X-ray detection unit 550 provided in the scanner rotation unit to light and a light provided in the scanner fixing unit are converted into an electrical signal. And a signal transmission means by the light receiving 8c.
[0021]
Hereinafter, the configuration of each part, its role, operation, etc. will be described in detail. The power source 1 generates a DC voltage. The commercial AC power source 101, a converter circuit 102 that converts the voltage of the AC power source into a desired DC voltage, and a capacitor 103 that smoothes the output voltage of the converter circuit 102. It consists of. The commercial power source as an input power source of the power source 1 is a single-phase AC power source as an example, but this may be a three-phase AC power source, and if the power source 1 generates a DC voltage, For example, a battery may be used.
[0022]
The inverter circuit 2 converts the DC voltage output from the power source 1 into high-frequency AC. The inverter circuit 2 is controlled by a high voltage generation circuit 520, an anode driving circuit 510, a heating circuit 530, and a control circuit mounted on the scanner rotating unit 5, although depending on the role of the output control means 580 described later. A constant voltage or a controlled voltage may be used as long as the AC voltage necessary for the power supply circuit 540 can be supplied. As will be described in detail later, the electromagnetic induction power transmission means 4 is means for transmitting electric power to each of the circuits mounted on the scanner rotating unit 5 in a non-contact manner using electromagnetic induction.
[0023]
The high voltage generation circuit 520 controls the DC voltage (tube voltage) applied to the X-ray tube 560 to the target value using the output of the electromagnetic induction power transmission means 4 as an input. Here, the high voltage generation circuit 520 is composed of bidirectional switches 581 and 582 capable of voltage control. The output control means 580 inputs an AC voltage, controls the AC voltage and outputs it, a high voltage transformer 524, and the like. And a high voltage rectifier 525 and a smoothing capacitor 526. The output control means 580 inputs the AC voltage output from the electromagnetic induction power transmission means 4 and is controlled so that the target tube voltage and the actual tube voltage coincide with each other, and inputs the AC voltage to the high voltage transformer 524. The high voltage transformer 524 boosts the AC voltage. The boosted AC voltage is converted into a DC high voltage by the high voltage rectifier 525, and the converted DC high voltage is smoothed by the smoothing capacitor 526. The smoothed DC high voltage is applied to the X-ray tube 560. The smoothing capacitor 526 may be a floating capacitance of a high-voltage cable connecting the high-voltage rectifier 526 and the X-ray tube 560. If this capacitance is insufficient, a capacitor may be added separately. .
[0024]
The anode drive circuit 510 includes a converter circuit 511, a smoothing capacitor 512, and an inverter circuit 513. The converter circuit 511 rectifies the AC voltage from the electromagnetic induction power transmission means 4 into a DC voltage, and smoothes the DC voltage. The smoothed DC voltage is smoothed by the capacitor 512 and converted into a three-phase AC voltage by the inverter circuit 513, which is supplied to the stator coil 561 of the anode rotation drive mechanism of the rotary anode X-ray tube 560. The anode of the rotary anode type X-ray tube 560 is rotated at a required rotational speed. The rotary anode type X-ray tube 560 has a structure that reduces the heat concentration of the anode target during X-ray emission by rotating the anode, and the anode drive circuit 510 is not a rotary anode type X-ray tube. In the case of, it is not necessary.
[0025]
The heating circuit 530 includes a converter circuit 531, a smoothing capacitor 532, and an inverter circuit 533. The AC voltage from the electromagnetic induction power transmission means 4 is converted into a DC voltage by the converter circuit 531, the converted DC voltage is smoothed by the smoothing capacitor 532, and the smoothed DC voltage is converted to a high-frequency AC voltage by the inverter circuit 533. Convert. The converted AC voltage is input to the heating transformer 535, and the output voltage of the heating transformer 535 is supplied to the filament of the X-ray tube 560 so that the tube current of the X-ray tube 560 becomes a target value. Control heating.
[0026]
The control power supply circuit 540 is a circuit that supplies a DC voltage (5 V, 15 V, etc.) to the control circuits of the high voltage generation circuit 520, the anode drive circuit 510, and the heating circuit 530, and the electromagnetic induction power transmission means. The AC voltage from 4 is converted into a DC voltage by the rectifier circuit 541.
[0027]
The X-ray tube 560 is supplied with the AC voltage output from the anode drive circuit 510 to rotate the anode, the filament is heated by the heating circuit 530, and the DC high voltage output from the high voltage generation circuit 520 is further increased. A voltage is supplied to emit X-rays toward the subject 6.
Then, the X-ray transmitted through the subject enters the X-ray detection unit 550.
[0028]
The X-ray detection unit 550 detects the dose distribution of transmitted X-rays emitted from the X-ray tube 560 and transmitted through the subject and amplifies the detection signal, and detects the dose distribution of the transmitted X-rays. And a preamplifier 552 that amplifies the detection signal from the detector 551.
[0029]
The detection signal amplified by the preamplifier 552 is converted into light by the light emitting element 7c provided in the scanner rotating unit, and the converted optical signal is converted into an electric signal by the light receiving element 8c provided in the scanner fixing unit. The X-ray detection signal is transmitted to the scanner fixing unit without contact.
[0030]
The image processing device 9 receives an X-ray detection signal transmitted in a non-contact manner by the light emitting element 7c and the light receiving element 8c, performs various correction processes on this signal, performs image processing, and performs diagnostic processing on the subject 6. The tomographic image is reconstructed. The image display device 10 receives an output signal from the image processing device 9 and displays a tomographic image, and is a television monitor, for example. In FIG. 1, reference numeral 3 is a resonance capacitor for causing the output voltage of the inverter circuit 2 to resonate with the leakage inductance of the high-voltage transformer 524 to obtain sufficient power, and can be inserted if necessary. Good.
[0031]
Thus, in addition to the high voltage generation circuit 520, the X-ray tube 560, and the X-ray detection unit 550, the scanner rotation unit 5 includes the anode drive circuit 510, the heating circuit 530, and the control power supply circuit 540. And the X-ray tube 560 and the X-ray detection unit 550 are rotated around the subject 6 with the subject 6 being opposed to each other. The scanner rotating unit 5 has a rotating frame in which an opening for inserting a subject is formed at the center, and the anode driving circuit 510 and the high voltage generating circuit 520 (heating transformer 535 are provided on one side of the rotating frame. A heating circuit 530, a control power circuit 540, an X-ray tube 560 (including a stator coil 561 of an anode rotation driving mechanism), and an X-ray detection unit 550, which are detected around the body of the rotating frame. A light-emitting element 7C for signal transmission is provided, a light-receiving element 8C is provided on the fixed frame of the scanner so as to face the light-emitting element, and an X-ray detection signal transmitted through the subject is transmitted to the image processing apparatus 9 by these.
[0032]
Next, the electromagnetic induction power transmission means 4 will be described in detail. FIG. 2 is a specific structural diagram of the electromagnetic induction power transmission means 4. (A) is a cross-sectional view showing the positional relationship between the fixed frame 55 and the rotating frame 52 of the scanner, and (b) is an enlarged view of a part of the electromagnetic induction power transmission means 4 surrounded by a broken line in FIG. 2 (a). It is a perspective view. First, the rotating frame 52 is rotatably held by bearings 403a and 403b provided at a certain distance in the axial direction inside the fixed frame 55. As shown in FIG. 2 (a), a first iron core 404 and a second iron core 405 are arranged on the inner peripheral surface of the fixed frame 55 and the outer peripheral surface of the rotary frame 52 so as to face each other. Each iron core may be integrated or divided into a plurality of pieces. Various methods described in JP-A-8-336521, such as a combination in which one iron core is integrated and the other iron core is divided, are also applicable here. The first winding 401 connected to the output side of the inverter circuit 2 is fitted and fixed in the groove provided in the first iron core 404 in this embodiment. In the grooves provided in the second iron core 405, the second windings 402a to 402d connected to the input side of the high voltage generating circuit 520 and the like are fitted and fixed, and are respectively fixed to the second windings 402a to 402d. It has an output terminal. By configuring the electromagnetic induction power transmission means 4 as described above, when the alternating current supplied from the inverter circuit 2 in FIG. 1 flows through the first winding 401, it faces each other as shown in FIG. 2 (b). The first winding 401 and the second windings 402a to 402d, the first iron core 404 having a circular U-shaped cross section and the second iron core 405 having a circular shape and a U-shaped cross section. A magnetic circuit is formed in the constructed outer iron type transformer, and a magnetic flux φ is generated. Then, a voltage is induced in the second windings 402a to 402d interlinked with the magnetic flux φ, and the anode driving circuit 510 (the corresponding second winding shown in FIG. 1) is generated from the second windings 402a to 402d. 402d), high voltage generation circuit 520 (corresponding second winding is 402c), heating circuit 530 (corresponding second winding is 402b), control power circuit 540 (corresponding second winding is 402a) ) Can be supplied with an alternating voltage.
[0033]
Next, an output for receiving (inputting) the output of the electromagnetic induction power transmission means 4 serving as the maximum key point for reducing the weight of the rotating part in the present invention and outputting an AC voltage to the high voltage transformer 524. The control means 580 will be described in detail. The output control means 580 includes a rectifier circuit (AC-DC conversion circuit), a capacitor that smoothes the output voltage, and an inverter circuit that converts the DC voltage smoothed by the smoothing circuit into a high-frequency AC voltage. However, it is not only expensive because the number of parts is very large, but the weight of the part is heavy and the size is unavoidable, which is disadvantageous for high-speed scanning. Therefore, in this embodiment, a voltage-controllable power semiconductor switching element, for example, a bidirectional switch in which insulated gate bipolar transistors (abbreviated as IGBT) 581 and 582 are connected in series in opposite directions, AC voltage control is performed by the bidirectional switch, the controlled voltage is boosted by the high voltage transformer 524, the boosted AC high voltage is converted to DC by the high voltage rectifier 525, and the converted voltage is smoothed. The voltage is smoothed by the capacitor 526 and a high DC voltage is applied to the X-ray tube 560. Therefore, the tube voltage is controlled so that the flow width of the bidirectional switch becomes the target tube voltage.
[0034]
FIG. 3 is a diagram for explaining the operation of the bidirectional switch. FIG. 4A is a circuit diagram including a bidirectional switch and an input side and an output side of the switch, and FIG. 4B is an operation explanatory diagram of the bidirectional switch. In FIG. 3 (a), the voltage Vin of the second winding 402c of the electromagnetic induction power transmission means 4 is used as the input voltage of the output control means 580, and the bidirectional switches IGBT581 (S1) and IGBT582 (S2) are connected to FIG. 3 (b). When the bidirectional switch is controlled by giving the control signals G1 and G2 shown in FIG. 3, the output voltage Vo of the output control means 580 (= the input voltage Vo of the high voltage transformer 4) is as shown by Vo in FIG. Controlled, the power delivered to the X-ray tube 560 can be controlled. The two control signals G1 and G2 are overvoltages (L × di / dt, where L is the inductance of the circuit, i is the current flowing through the circuit, As shown in the figure, the control signals G1 and G2 are provided with a predetermined overlap period so that t does not occur in the switching time of the bidirectional switch. The current is commutated without interruption.
[0035]
According to the first embodiment of the present invention, not only the high voltage generating circuit but also the scanner rotating unit such as the filament heating circuit of the X-ray tube and the anode rotation driving circuit of the X-ray tube other than the high voltage generating circuit. Electric power can be supplied to the mounted circuit in a non-contact manner, and there is no need to provide electromagnetic induction power transmission means for each of the various circuits. Further, unlike the conventional method, the power source of the various circuits is not affected by the tube voltage control, and the high voltage generation circuit can be simplified by adopting the output control means 580, which allows the scanner of the X-ray CT apparatus. The rotating part is reduced in size and weight, which is advantageous for high-speed scanning.
[0036]
(Example 2)
FIG. 4 shows a main part of the second embodiment of the present invention. This corresponds to the electromagnetic induction power transmission means 4 and the scanner rotating unit 5 in FIG. The electromagnetic induction power transmission means 4 in this embodiment follows the same principle as in the first embodiment. The second winding 402c is connected to the input side of the high voltage generating circuit 520 having the same configuration as that of the first embodiment, and the second winding 402b is connected to the input side of the anode driving circuit 510. The second winding 402a is input to the heating circuit 530 and the control power supply circuit 540 after the output voltage of the second winding 402a is insulated through the insulating transformer 571. In this embodiment, it is necessary to add an insulation transformer 571, but the power consumed by the heating circuit 530 and the control power supply circuit 540 is tens to one-hundred or less compared to the high voltage generation circuit 520. Therefore, an insulation transformer of such a large scale is not required, and the output voltage of the electromagnetic induction power transmission means 4 can be converted into a desired value, so that there is an advantage that the heating circuit 530 and the control power circuit 540 are easy to design.
The operation of the output control means 580 is the same as that in the first embodiment.
[0037]
(Example 3)
FIG. 5 shows an essential part of a third embodiment of the present invention. This corresponds to the electromagnetic induction power transmission means 4 and the scanner rotating unit 5 in FIG. The electromagnetic induction power transmission means 4 in this embodiment follows the same principle as in the first embodiment. In the embodiment shown in FIG. 5, the output voltage of the electromagnetic induction power transmission means 4 is input to the output control unit 580 of each high voltage generation circuit 520 in the first and second embodiments and applied to the X-ray tube together with the frequency thereof. A single-phase cycloconverter that controls the voltage to be applied is applied. Here, a center tap 590 is provided at the midpoint of the second winding 402c, and one end of the load, that is, one end of the primary winding of the high voltage transformer 524 is connected to the center tap 590, and the other end is connected to IGBT. A two-phase switch (583 and 584 and 585 and 586) connected in reverse parallel to the IGBT is combined as shown in the figure to form a single-phase cycloconverter. Since this single-phase cycloconverter can step down or step up the output frequency as described below, it is suitable for an X-ray high voltage apparatus with a very wide load range. That is, in a light load continuous operation (when the tube voltage is high and the tube current is small, that is, when X-rays are continuously exposed with a large load resistance RX), it is determined by the product of the load resistance RX and the high voltage smoothing capacitor 526. Since the time constant is large and the pulsation of the tube voltage does not become a problem and the power loss does not need to be large, the output frequency fo of the cycloconverter is kept low, and conversely, the frequency is stepped up under heavy loads, etc. The advantage is that the optimum operating frequency can be selected. The operation of this cycloconverter will be described with reference to FIGS. Of these, FIG. 6 shows the operation of a so-called step-down type cycloconverter in which the frequency is lower than the input frequency determined by the operating frequency of the inverter circuit 2 (shown in FIG. 1) on the primary side of the electromagnetic induction power transmission means 4 (FIG. 6). Shows an example in which the output frequency of the cycloconverter is 1/3 of the input frequency. FIG. 2A is a circuit diagram including a cycloconverter composed of two sets of bidirectional switches and an input side and an output side of the converter, and FIG. 2B is an operation explanatory diagram of the cycloconverter.
[0038]
Even if the sign of the input voltage Vin (the output of the second winding 402c) changes, the sign of the output voltage Vo applied to the load is maintained without changing by giving a control signal as shown in the figure. Therefore, the frequency fo of the output voltage Vo can be made smaller than the input frequency fin. In this method, the peak value Vp of the output voltage is half of the input voltage Vin, but the output is controlled by the frequency or pulse width of the control signal.
[0039]
FIG. 7 shows the operation of a step-up type cycloconverter that makes the frequency fo of the output voltage Vo higher than the input frequency, contrary to FIG. FIG. 2A is a circuit diagram including a cycloconverter composed of two sets of bidirectional switches and an input side and an output side of the converter, and FIG. 2B is an operation explanatory diagram of the cycloconverter.
[0040]
In this embodiment, the output frequency fo is three times the input frequency fin. In this case, when the input voltage Vin is positive, the control signal of S1 and the control signal of S3 are alternated, and the input voltage Vin is negative. In this case, the frequency fo of the output voltage Vo can be made higher than the frequency fin (determined by the operating frequency of the inverter 2) of the input voltage Vin by alternately turning on / off the control signal of S2 and the control signal of S4. Even in this method, the peak value Vp of the output voltage is half of the input voltage Vin, but the output is controlled by the frequency or pulse width of the control signal.
[0041]
Example 4
FIG. 8 shows an essential part of a fourth embodiment of the present invention. This corresponds to the electromagnetic induction power transmission means 4 and the scanner rotating unit 5 in FIG. The electromagnetic induction power transmission means 4 in this embodiment follows the same principle as in the first embodiment. The second winding 402c is connected to the input side of the high voltage generation circuit 520 having the same configuration as that of the third embodiment, and the second winding 402b is connected to the input side of the anode driving circuit 510. The second winding 402a is input to the heating circuit 530 and the control power supply circuit 540 after the output voltage of the second winding 402a is insulated via the insulating transformer 571. In this embodiment, it is necessary to add an insulation transformer 571, but the power consumed by the heating circuit 530 and the control power supply circuit 540 is tens to one-hundred or less compared to the high voltage generation circuit 520. Therefore, an insulation transformer of such a large scale is not required, and the output voltage of the electromagnetic induction power transmission means 4 can be converted into a desired value, so that there is an advantage that the heating circuit 530 and the control power circuit 540 are easy to design. The operation of the output control means 580 is the same as that in the third embodiment.
[0042]
(Other examples)
In the present invention, the following various embodiments can be considered by modifying or combining a part of the first to fourth embodiments.
[0043]
(1) In the embodiments of FIGS. 1, 4, 5, and 8, the bidirectional switch (including the bidirectional switch of the cycloconverter) applied to the output control means 580 has two voltage controllable switches. However, the present invention is not limited to this, and a configuration in which one switch and one diode are combined as shown in FIG. 9 may be used. In this case, the number of switches capable of voltage control is reduced, and the circuit can be simplified.
[0044]
(2) In the embodiments of FIGS. 1, 4, 5, and 8, the anode drive circuit 510 is controlled by a combination of a converter circuit and an inverter circuit, but is applied to the high voltage generation circuit 520. It is also possible to apply AC voltage control using a bidirectional switch and a cycloconverter.
[0045]
(3) In the embodiments of FIGS. 1, 4, 5, and 8 described above, an insulating transformer was not used in the previous stage of the anode drive circuit 510, but the second embodiment of FIG. 4 and the fourth embodiment of FIG. In the example, as with the heating circuit 530 and the control power supply circuit 540, an insulating transformer may be used on the output side of the electromagnetic induction power transmission means 4. In this case, the insulating transformer may be shared with the heating circuit 530 or the control power supply circuit 540.
[0046]
(4) In the above embodiment, the shape of the iron core of the electromagnetic induction power transmission means 4 is a U-shape, but the magnetic flux generated in the first winding 401a causes the first iron core 404 and the second iron core 405 to move. If the second winding 402b is linked to the second winding 402b, other shapes can be used regardless of the shape.
[0047]
(5) The first winding 401 and the second winding 402 of the electromagnetic induction power transmission means 4 may use a Litz wire to reduce eddy current loss generated in the winding. It is effective for improving efficiency.
[0048]
(6) In the embodiments of FIGS. 1, 4, 5, and 8, the high voltage generation circuit 520, the anode drive circuit 510, the heating circuit 530, and the control power supply circuit 540 are mounted on the scanner rotating unit 5. However, the present invention is not limited to this, and a part thereof can be provided in the scanner fixing portion.
[0049]
(7) The circuit configuration of the anode drive circuit 510 is not limited to the above embodiment, and any configuration may be used as long as the anode rotation drive of the X-ray tube is possible.
[0050]
(8) The circuit configuration of the heating circuit 530 is not limited to the above embodiment, and any circuit configuration may be used as long as filament heating control of the X-ray tube is possible.
[0051]
(9) In the above embodiment, the bidirectional switch IGBT is applied. However, the present invention is not limited to this, and the gist of the present invention can be achieved even if a Si thyristor, GTO, bipolar transistor, or the like is applied.
[0052]
(10) The high voltage generation circuit 520 has a capacitor inserted in series with the primary side winding of the high voltage transformer 524, and performs AC voltage control and frequency control using the resonance phenomenon with the leakage inductance of the high voltage transformer. Various variations are possible, such as performing.
[0053]
【The invention's effect】
As described above, not only the high voltage generation circuit but also the circuits mounted on the scanner such as the X-ray tube filament heating circuit and the X-ray tube anode rotation drive circuit other than the high voltage generation circuit are contactless. Since power is supplied, X-rays that facilitate maintenance and inspection of the power supply means that supplies power to each circuit of the scanner rotation unit from the power source, improve the reliability of the entire apparatus, and support high-speed scanning A CT apparatus can be provided.
[Brief description of the drawings]
FIG. 1 is a block diagram of an overall configuration showing a first embodiment of the present invention.
2 is a specific structural diagram of electromagnetic induction power transmitting means of the first embodiment of FIG.
FIG. 3 is an output control circuit using the bidirectional switch of the first embodiment of FIG. 1 and its operation explanatory diagram;
FIG. 4 is a circuit block diagram of an essential part of a second embodiment of the present invention.
FIG. 5 is a circuit block diagram of an essential part of a third embodiment of the present invention.
FIG. 6 is a diagram for explaining the operation of a cycloconverter according to a third embodiment of the present invention (example in which the frequency is stepped down).
FIG. 7 is an operation explanatory diagram of a cycloconverter according to a third embodiment of the present invention (an example of stepping up the frequency).
FIG. 8 is a circuit block diagram of the main part of a fourth embodiment of the present invention.
FIG. 9 is a bidirectional switch circuit diagram of a combination of one switch and four diodes.
[Explanation of symbols]
1 ... Power supply, 2,513,533 ... Inverter circuit, 3,103,512,526,532 ... Condenser, 4 ... Electromagnetic induction power transmission means, 5 ... Scanner rotating part, 51 ... Scanner opening, 52 ... Scanner rotating frame, 55 ... Scanner fixing frame, 101 ... AC power supply, 102,511,525,531,541 ... Rectifier, 401 ... First winding, 402 ... Second winding, 404 ... First iron core, 405 ... Second iron core, 403 ... Bearing, 510 ... Anode drive circuit, 524 ... High voltage transformer, 526 ... high voltage smoothing capacitor, 530 ... heating circuit, 535 ... heating transformer, 540 ... control power supply circuit, 550 ... X-ray detector, 560 ... X-ray tube, 561 ... stator coil of anode rotation mechanism of X-ray tube, 571 ... Insulation transformer, 580 ... Output control means, 581-586 ... Insulated gate bipolar transistor (IGBT), 590 ... Center tap

Claims (4)

An X-ray tube that emits X-rays, an X-ray detector that detects a transmitted X-ray dose distribution in which the X-rays emitted from the X-ray tube pass through the subject and amplifies the detection signal; and the X-ray tube A scanner rotation unit that rotates the X-ray detection unit to face each other, an image processing apparatus that processes an output signal from the X-ray detection unit and reconstructs a tomographic image of a diagnostic region, and An X-ray CT apparatus having an image display device that inputs an output signal from an image processing device and displays a tomogram,
A DC power source, an inverter circuit for converting a DC voltage from the DC power source into an AC voltage, and a first winding connected to the output side of the inverter circuit and disposed on the circumference of the fixed frame of the scanner rotating unit. Electromagnetic induction power transmission means comprising a combination of a wire and a plurality of second windings arranged opposite to the first winding on the circumference of the rotating frame of the scanner rotating unit,
AC voltage control means by a bidirectional switch capable of controlling the output voltage or frequency of one of the plurality of second windings, controlling the voltage applied to the X-ray tube, and controlling the voltage, or An X-ray CT apparatus comprising a tube voltage control means configured by a cycloconverter and disposed in the scanner rotation unit . Comprising a high-voltage transformer for boosting the voltage output from the tube voltage control means, a high-voltage rectifier which converts the output voltage of the high voltage transformer into a DC voltage, a capacitor for smoothing the output voltage of the high voltage rectifier, a 2. The X-ray CT apparatus according to claim 1, wherein a DC high voltage smoothed by the capacitor is applied to the X-ray tube. The output voltage of one of the plurality of second windings of the electromagnetic induction power transmission means is input to the tube voltage control means, and the output of the other winding of the plurality of second windings An anode driving circuit for supplying a voltage to an anode rotation driving mechanism provided in an X-ray tube mounted on the scanner rotating unit, a heating circuit for supplying a voltage to a filament provided in the X-ray tube, the anode driving circuit, The X-ray CT apparatus according to claim 2, wherein the X-ray CT apparatus is supplied to at least one of a control power supply circuit that supplies a voltage to a control circuit of the heating circuit . The output voltage of one of the plurality of second windings of the electromagnetic induction power transmission means is input to the tube voltage control means and insulated from the other windings of the second winding. An anode drive circuit for supplying an output voltage to an anode rotation drive mechanism provided in an X-ray tube mounted on the scanner rotation unit, and an X-ray A heating power circuit for supplying a voltage to a filament provided in a tube, a control power circuit for supplying a voltage to a control circuit for the heating circuit, the anode driving circuit, or the heating circuit. Item 3. The X-ray CT apparatus according to Item 2.

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