JP4220589B2 - X-ray equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an X-ray imaging apparatus that images a subject using a plurality of X-rays having different X-ray energies.
[0002]
[Prior art]
In a treatment using a catheter or the like, there is a pulse fluoroscopy technique as a method for reducing the exposure dose to a patient. In the pulse fluoroscopy technique, X-ray irradiation is stopped during a period in which an image obtained by an X-ray image tube is read as an electrical signal by a CCD element or the like. Therefore, when this method is used, an X-ray generator that generates X-rays in pulses at certain time intervals is used.
[0003]
By the way, in the pulse fluoroscopy technique, in order to obtain a high contrast image, it is necessary to irradiate a large amount of X-rays having a low energy and a large absorbed dose. For this reason, there exists a problem that the exposure dose of a patient or an operator increases.
[0004]
Further, there is an energy subtraction technique as a method for obtaining an image of a lesion portion or the like with high contrast by reducing the exposure dose. This technique utilizes the property that the X-ray absorption coefficient differs depending on the X-ray energy. For example, CR screens are arranged above and below a metal plate, and images with different X-ray energies are projected onto each CR screen using the inherent filtration of the metal plate. Then, the image captured on the CR screen is processed to diagnose the lesion. However, when the energy subtraction technique is used, there is a problem that the image cannot be observed in real time because it takes time to process the image.
[0005]
In addition, when performing lung examination using CT or the like, the X-ray energy conditions for imaging the bronchi and ribs are different from the X-ray energy conditions for imaging the alveoli and blood vessels. For this reason, if imaging is performed with only one X-ray energy condition, sufficient image information may not be obtained, and early lung cancer may be overlooked or discovery may be delayed.
[0006]
[Problems to be solved by the invention]
As described above, when X-rays are generated under two or more X-ray energy conditions and a lesion portion is imaged, a larger amount of image information can be obtained than when imaged under one X-ray energy condition. If there is a lot of image information, the image quality of the pulse fluoroscopic image and the X-ray CT image can be improved by processing the image information.
[0007]
However, when X-rays are generated with two or more X-ray energies, the conventional X-ray imaging apparatus uses a method of switching the magnitude of the tube voltage applied between the anode and cathode of the X-ray tube. . At this time, since the high voltage cable connecting the X-ray tube and the power supply has stray capacitance, there is a problem that the voltage waveform is disturbed when the voltage of the power supply is switched.
[0008]
Here, how the voltage waveform is disturbed will be described with reference to FIG. In FIG. 5, the horizontal axis represents time (t), and the vertical axis represents tube voltage (kV). FIG. 5A shows a state where the high voltage A and the low voltage B are normally switched. However, if the stray capacitance of the high-voltage cable is affected, when switching from a high voltage to a low voltage, a spike is generated in the low voltage B portion as shown in FIG. S is generated.
[0009]
Therefore, when using a pulse fluoroscopy technique or the like, if the tube voltage applied to the X-ray tube is changed in order to switch the energy condition of the generated X-ray, the voltage waveform changes and a correct electron beam cannot be generated. is there.
[0010]
In order to prevent the disturbance of the voltage waveform, for example, there is a method using a switching tether. In this method, when switching from a high voltage to a low voltage, the charging current on the secondary side of the power supply is discharged, and then the voltage is applied to the X-ray tube. However, this method has a problem that energy loss increases.
[0011]
Therefore, the temperature of the power source increases when the interval for generating X-rays is shortened. For this reason, a mechanism for releasing heat is required, and as a result, the entire apparatus is increased in size and cost. This hinders the use of energy subtraction technology in pulse fluoroscopy technology and the like.
[0012]
An object of the present invention is to solve the above-described drawbacks, and to provide an X-ray imaging apparatus that can easily generate X-rays having two or more X-ray energy conditions.
[0013]
[Means for Solving the Problems]
The present invention, at least two first and second filament emits electronic convergence electrodes for converging the electron, an anode for generating X-rays by collision of the conductive element, the filament and the focusing electrode, An X-ray imaging apparatus comprising: an X-ray tube having a vacuum envelope in which each of the anodes is housed; and a DC power source for generating a voltage to be applied between the anode of the X-ray tube and the filament. The potential of the first filament when the first X-ray is generated from the anode by the electrons emitted from the first filament, and the potential of the second filament when the second X-ray is generated by the electrons emitted from the second filament. It connects the first bias power supply for the filament to be set higher or lower than the potential between the first filament and said DC power source, the first 1X line before X-ray energy at the 2X line is characterized in that so as to differ.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIG. In FIG. 1, a power source for heating the filament of the X-ray tube, a mechanism for rotating the anode, a cooling mechanism for the X-ray tube, and the like are omitted because they are not necessary for the description of the invention.
[0015]
Reference numeral 11 denotes a tube container, and an X-ray tube 12 is accommodated in the tube container 11. The X-ray tube 12 is entirely composed of a vacuum envelope 13, and a rotating anode 14 is disposed at one end in the vacuum envelope 13. At the other end in the vacuum envelope 13, first and second filaments 15 and 16 for generating an electron beam are disposed. A converging electrode 17 for converging the electron beam is disposed in front of the filaments 15 and 16.
[0016]
The filaments 15 and 16 and the focusing electrode 17 are integrally formed as a cathode structure. For example, grooves are formed in two places of the cathode structure, the grooves are used as focusing electrodes, and filaments 15 and 16 are disposed inside the grooves. In such a structure, the electron beams emitted from the filaments 15 and 16 are converged by the focusing electrode 17 to form an electron impact surface in the same region on the anode 14.
[0017]
A DC power supply 18 is disposed outside the tube container 11, and a midpoint P of the DC power supply 18 is grounded. The + terminal of the DC power supply 18 is connected to the anode 14 of the X-ray tube 12. The negative terminal of the DC power supply 18 is connected to the common connection point Q, and between the common connection point Q and the first filament 15, first and second bias power supplies 19 having positive and negative polarities in opposite directions, 20 are connected in parallel. The common connection point Q is directly connected to the second filament 16. Between the second filament 16 and the converging electrode 17, a third bias power source 21 having a negative converging electrode 17 side is connected.
[0018]
Note that the voltage applied to the anode 14 is (Ea), the voltage at the common connection point Q is (Eb), and the stray capacitance of the high-voltage cable with respect to ground is indicated by reference numerals 22 and 23. Moreover, the voltage between the output terminals of the first to third bias power supplies 19 to 21 is set to the same magnitude (Ec), and the + terminal and the − terminal are indicated by the signs + and −, respectively.
[0019]
Here, a method for generating X-rays having different X-ray energies from the two filaments 15 and 16 in the above configuration will be described with reference to FIG. The vertical axis in FIG. 2 represents voltage (−kV).
[0020]
First, the case where X-ray energy is generated from the filament 15 will be described. The second bias power source 20 is connected between the common connection point Q and the filament 15, and the first bias power source 19 is disconnected. Then, the third bias power source 21 is connected between the common connection point Q and the convergence electrode 17. At this time, as shown in FIG. 2A, the voltage (E1f) of the filament 15 and the voltage (Eg) of the convergence electrode 17 are lower than the voltage (Eb) of the common connection point Q, and the voltage (E2f) of the filament 16 ) Is equal to the voltage Eb at the common connection point Q.
[0021]
With the above setting, electrons are emitted from the filament 15 and the emitted electrons strike the anode 14. At this time, the energy of X-rays generated from the anode 14 is (Ea + Eb + Ec) obtained by adding the anode voltage (Ea), the voltage (Eb) of the common connection point Q, and the voltage (Ec) of the second bias power supply 20. Become. The filament 16 is cut off by the connection of the third bias power source 21 and no electron beam is emitted.
[0022]
Next, the case where X-ray energy is generated from the filament 16 will be described. The third bias power source 21 is disconnected from between the filament 16 and the focusing electrode 17, and the filament 16 and the focusing electrode 17 are short-circuited. Further, the first bias power source 19 is connected between the common connection point Q and the filament 15. At this time, as shown in FIG. 2B, the voltage (E2f) of the filament 16 and the voltage (Eg) of the focusing electrode 17 are equal to the voltage (Eb) of the common connection point Q, and the voltage (E1f) of the filament 15 Increases by the amount (Ec) of the first bias power source 19 .
[0023]
With the above setting, an electron beam is emitted from the filament 16, and the emitted electrons strike the anode 14. At this time, the energy of the X-ray generated from the anode 14 is (Ea + Eb) obtained by adding the anode voltage (Ea) and the voltage (Eb) of the filament 16. The filament 15 is cut off when the first bias power source 19 is connected, and no electron beam is emitted.
[0024]
Next, the case where the two filaments 15 and 16 are in the cut-off mode and the electron beam is not emitted will be described. The first and second bias power supplies 19 and 20 are disconnected from between the filament 15 and the common connection point Q, and the filament 15 and the common connection point Q are directly connected. Further, the third bias power source 21 is connected between the common connection point Q and the convergence electrode 17. At this time, as shown in FIG. 2 (c), the common connecting point Q of the voltage (Eb) and the filaments 15, 16 of the voltage (E1f), (E 2f) are equal, the voltage of the focusing electrode 17 (Eg) is The voltage is lower than the voltages (E 1f ) and ( E 2f ) of the filaments 15 and 16.
[0025]
With the above setting, both the filaments 15 and 16 are cut off and no electron beam is emitted.
[0026]
According to the configuration described above, X-rays having different X-ray energies can be generated from the two filaments 15 and 16 by connecting or disconnecting the first to third bias power sources without changing the voltage of the DC power source 18. In addition, the generation of X-rays can be stopped. If such an operation is repeated, generation of X-rays with high X-ray energy, generation of X-rays with low X-ray energy, and stop of X-rays are sequentially performed.
[0027]
The connection and disconnection of the first to third bias power sources can be controlled at high speed, and there is no disturbance in the voltage waveform. For this reason, the change or stop of the X-ray energy can be switched to a correct value at a high speed of 1 ms or less. Further, if the output voltage of the first to third bias power supplies can be varied within the range of 0V to several thousand volts, the generated X-ray energy can be arbitrarily set within the variable range.
[0028]
Next, another embodiment of the present invention will be described with reference to FIG. 3 taking a CT apparatus used for X-ray tomography as an example. Reference numeral 31 is an examination table, and a subject 32 is placed on the examination table 31. A rotary table 33 that rotates about the subject 32 is provided, and the two X-ray devices 34 and 35 are fixed to the rotary table 33 at a certain interval. In addition, X-ray detectors 36 and 37 are fixed to a rotary table 33 at a position facing the X-ray devices 34 and 35 with the subject 31 interposed therebetween. A DC power supply 38 is fixed between the two X-ray devices 34 and 35, and a driving voltage is supplied from the DC power supply 38 to the two X-ray devices 34 and 35 through the high-voltage cable 39.
[0029]
In the configuration described above, X-rays emitted from the X-ray device 34 and transmitted through the subject 32 are detected by the X-ray detector 36, and X-rays emitted from the X-ray device 35 and transmitted through the subject 32 are detected by the X-ray detector. 37 is detected.
[0030]
Here, a circuit configuration for supplying a drive voltage from the DC power supply 38 to the X-ray devices 34 and 35 will be described with reference to FIG. In FIG. 4, parts corresponding to those in FIG.
[0031]
Each of the X-ray devices 34 and 35 includes an X-ray tube 41 and the like, and an anode 42 is provided at one end in the X-ray tube 41 and a filament 43 and a focusing electrode 44 are provided at the other end. Each anode 42 is connected to the + terminal of the DC power supply 38, each filament 43 and the focusing electrode 44 are connected in common, and further connected to the − terminal of the DC power supply 38. In the X-ray device 34, a bias power supply 45 is connected between a common connection point of the filament 43 and the focusing electrode 44 and a negative terminal of the DC power supply 38.
[0032]
According to the above configuration, a voltage higher than the X-ray tube 41 of the X-ray device 35 by the bias power supply 45 is applied between the anode 42 and the filament 43 to the X-ray tube 41 of the X-ray device 34 . . Therefore, different X-ray energies having the same X-ray energy can be obtained from the two X-ray devices 34 and 35 .
[0033]
In this case, using one DC power source and two X-ray devices, a tomographic image of X-rays with different X-ray energies can be taken in one scan, and an image with little artifact due to the movement of the subject is obtained. Obtainable.
[0034]
As described above, according to the present invention, X-rays having different X-ray energies can be easily realized. For this reason, even when optimal energy conditions differ between soft tissues such as alveoli and blood vessels and relatively hard tissues such as ribs and bronchi, as in the case of diagnosing the chest using CT. Can be obtained reliably and a correct diagnosis can be made. Further, even when imaging is performed using X-rays having different X-ray energies, it is not necessary to divide into two times and diagnosis can be speeded up. In addition, the energy subtraction technology and the biplane system that captures images from two directions can be easily used, and the accuracy of group screening can be improved.
[0035]
For example, in the configuration of FIG. 3, the subject 32 is imaged using X-rays having different X-ray energies output from the X-ray apparatuses 34 and 35 . And the image which image | photographed the test subject 32 is detected with the X-ray detectors 36 and 37 , this is converted into the image of an electric signal using a television camera etc., and it is obtained with the X-ray from which X-ray energy differs after that. This is a method of subtracting images. According to this method, a difference component of an image obtained by X-rays having different X-ray energies is emphasized, and a lesion or the like can be easily detected.
[0036]
In this configuration, X-rays having different X-ray energies are obtained using a bias power source. Therefore, X-rays having different X-ray energies can be generated simultaneously or at a slight time interval, and a difference component of an image having substantially no time difference can be detected. As a result, the screening accuracy is improved. In addition, since the signal is processed in the form of an electrical signal or the like, it can be processed in real time, thereby speeding up the examination.
[0037]
In this method, when obtaining X-rays having different X-ray energies, not only the configuration shown in FIG. 3 but also the configuration shown in FIG. 1 can be used. When the configuration shown in FIG. 1 is used, X-rays having different X-ray energies are generated at predetermined time intervals. For this reason, when subtracting images obtained with X-rays having different X-ray energies, processing such as delaying one of the two images using a delay circuit or the like and making the times coincide with each other is required. .
[0038]
In the embodiment of FIG. 1, the case where two filaments are provided in one X-ray tube has been described. However, three or more filaments may be provided. In the embodiment of FIG. 3, the X-ray apparatus is described as two examples. However, also in this case, three or more X-ray apparatuses can be configured. Further, when three or more X-ray apparatuses are configured, if a bias power source having a different output voltage is incorporated in each X-ray apparatus, X-rays having many types of X-ray energy can be simultaneously transmitted from the X-ray apparatus. Can be generated.
[0039]
【The invention's effect】
According to the present invention, an X-ray imaging apparatus capable of easily generating X-rays having two or more X-ray energy conditions can be realized.
[Brief description of the drawings]
FIG. 1 is a circuit configuration diagram for explaining an embodiment of the present invention;
FIG. 2 is a diagram for explaining a bias voltage used in the embodiment of the present invention.
FIG. 3 is a schematic configuration diagram for explaining another embodiment of the present invention.
FIG. 4 is a circuit configuration diagram for explaining another embodiment of the present invention.
FIG. 5 is a diagram illustrating a bias voltage for explaining a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Tube container 12 ... X-ray tube 13 ... Vacuum envelope 14 ... Anode 15 ... 1st filament 16 ... 2nd filament 17 ... Converging electrode 18 ... DC power supply 19 ... 1st bias power supply 20 ... 2nd bias power supply 21 ... Third bias power source 22, 23 ... Stray capacitance of high voltage cable

Claims (7)

At least two first and second filaments, focusing electrode for focusing the electron, an anode for generating X-rays by collision of the conductive element, the filament and the focusing electrode, the anode, respectively to release the electronic An X-ray imaging apparatus comprising: an X-ray tube having a vacuum envelope housed therein; and a DC power source that generates a voltage to be applied between the anode and the filament of the X-ray tube . The potential of the first filament when the first X-ray is generated from the anode by electrons emitted from the filament is higher than the potential of the second filament when the second X-ray is generated by electrons emitted from the second filament. or a first bias power supply for filament set low connected between the first filament and said DC power supply, with the first 2X line and the second 1X line X-ray imaging apparatus, wherein a linear energy was so different. Before Symbol X-ray imaging apparatus according to claim 1, wherein the bias supply for the second filament is connected is provided between the second filament and the focusing electrode.   The X-ray imaging apparatus according to claim 1 or 2, wherein the first filament bias power source is composed of two power sources connected in parallel with opposite polarities. A bias power supply for the second filament, X-rays imaging apparatus polarity orientation connected in the same direction as which do that請 Motomeko 2 wherein the DC power source. Vacuum, each of the filaments, which emits electronic, housed focusing electrode for focusing the electron, an anode for generating X-rays by collision of the conductive element, the filament and the focusing electrode, the anode inside each An X-ray imaging apparatus comprising: at least two X-ray tubes having an envelope; and a DC power source for generating a voltage to be applied between the anode and the filament of each of the at least two X-ray tubes. An X-ray imaging apparatus, wherein a bias power source is connected between the filament and the DC power source of at least one of the X-ray tubes.   6. The X-ray imaging apparatus according to claim 5, wherein an X-ray detector is provided at a position facing at least two X-ray tubes. An output device for outputting, as an image signal, an image of a subject imaged by first and second X- rays having different X-ray energies generated by the X-ray imaging device according to claim 1 or 5, and the output device An X-ray imaging apparatus comprising: an arithmetic unit that obtains a difference between an image signal output from the first X-ray and an image signal output from the second X-ray.

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