JP7345342B2 - X-ray generator and X-ray CT device - Google Patents

Description

Embodiments disclosed in this specification and the like relate to an X-ray generator and an X-ray CT device.

When an X-ray CT device (Computed Tomography) generates a discharge inside the X-ray tube while executing a scan plan for an object, it temporarily stops the X-ray output while continuing the scan plan and waits for the discharge to disappear. Some devices have a so-called automatic discharge recovery function, which restarts X-ray output after a certain amount of time has passed. In general, an X-ray CT device with this type of automatic discharge recovery function outputs X-rays only for a certain waiting time (for example, several tens of milliseconds) when a discharge occurs in the X-ray tube to prevent the discharge from continuing. Stop.

This fixed waiting time is set to be a sufficient time for the discharge to disappear before the X-rays are outputted again. However, the longer the fixed waiting time for stopping the X-ray output, the more the discharge can be reliably extinguished, but the negative effect that stopping the X-ray output has on the X-ray CT image becomes greater. may result in an abnormal image that cannot be used for diagnosis.

One possible method for suppressing the occurrence of abnormal images is to shorten the length of a certain waiting time, but it is difficult to employ this method. This is because the duration of discharge and the way the tube voltage and tube current fall differ depending on the mode of discharge.

For example, in a discharge mode in which a large discharge current flows, the tube voltage falls quickly, but the discharge may continue even after the tube voltage falls. On the other hand, in a discharge mode in which a large discharge current does not flow and the discharge quickly disappears, the tube voltage falls slowly. For this reason, if the fixed waiting time until the re-output of X-rays is shortened, in the case of the former discharge mode, the X-output may start before the discharge disappears. In addition, in the latter discharge mode, the re-output of X-rays starts before the tube voltage becomes sufficiently low, so the tube voltage and tube current at the time of X-ray rise may become unstable. There is.

Therefore, when the length of the standby time is set to a certain length, the length of the standby time must be set to a length with a margin in order to ensure that the discharge disappears regardless of the mode of discharge. . Therefore, if the waiting time is set to a constant length, it is difficult to avoid abnormal images caused by the waiting time.

Japanese Patent Application Publication No. 2001-145625

One of the problems to be solved by the embodiments disclosed in this specification and the like is to determine the re-output timing of X-rays based on information regarding the tube voltage value after the occurrence of discharge within the X-ray tube.

However, the problems solved by the embodiments disclosed in this specification and the like are not limited to the above problems. Problems corresponding to the effects of each configuration shown in the embodiments described later can also be positioned as other problems to be solved by the embodiments disclosed in this specification and the like.

The X-ray generation device according to the embodiment includes an X-ray tube, a discharge detection section, a high voltage generation section, an X-ray control section, a tube voltage detection section, and a determination section. X-ray tubes generate X-rays. The discharge detection section detects discharge in the X-ray tube. The high voltage generator generates a tube voltage to be applied to the X-ray tube. The X-ray control section controls the X-rays output from the X-ray tube by controlling the high voltage generation section, and controls the X-ray output to be stopped when discharge is detected. The tube voltage detection section detects tube voltage. The determining unit determines the timing for re-outputting the X-rays after the discharge occurs, based on information regarding the tube voltage detected by the tube voltage detecting unit.

FIG. 1 is a block diagram showing an example of the configuration of an X-ray CT apparatus according to an embodiment. FIG. 1 is a block diagram showing an example of the configuration of an X-ray generator according to an embodiment. 5 is a flowchart illustrating an example of a conventional restoration process procedure. FIG. 3 is an explanatory diagram showing the relationship among tube voltage, tube current, filament current, and X-ray output in conventional return processing. 5 is a flowchart illustrating an example of a procedure of automatic return control processing according to the first embodiment. 6 is a subroutine flowchart showing an example of the procedure of the first return control process executed in step S6 of FIG. 5. FIG. FIG. 6 is an explanatory diagram showing the relationship between tube voltage value, tube current value, filament current value, and X-ray output in the first return control process. 6 is a subroutine flowchart showing an example of the procedure of the second return control process executed in step S9 of FIG. 5. FIG. FIG. 7 is an explanatory diagram showing the relationship between tube voltage value, tube current value, filament current value, and X-ray output in the second return control process. FIG. 3 is an explanatory diagram showing an example of the relationship between the magnitude of the immediately preceding tube voltage value and the immediately preceding tube current value and a set of the tube voltage threshold and the tube current threshold. 6 is a subroutine flowchart showing an example of the procedure of the third return control process executed in step S11 of FIG. 5. FIG. FIG. 7 is an explanatory diagram showing the relationship between tube voltage value, tube current value, filament current value, and X-ray output in the third return control process. 7 is a flowchart illustrating an example of the procedure of automatic return control processing according to the second embodiment. 14 is a subroutine flowchart showing an example of the procedure of the fourth return control process executed in step S25 of FIG. 13. FIG. 7 is an explanatory diagram showing the relationship between the tube voltage value, its time differential, the tube current value, the filament current value, and the X-ray output in the fourth return control process. 14 is a subroutine flowchart showing an example of the procedure of the fifth return control process executed in step S27 of FIG. 13. FIG. 7 is an explanatory diagram showing the relationship between a tube voltage value, its time differential, a tube current value, a filament current value, and an X-ray output in a fifth return control process.

Hereinafter, embodiments of an X-ray generator and an X-ray CT apparatus will be described in detail with reference to the drawings.

(overall structure)
FIG. 1 is a block diagram showing an example of the configuration of an X-ray CT apparatus 1 according to an embodiment. Moreover, FIG. 2 is a block diagram showing an example of the configuration of the X-ray generator 20 according to one embodiment. Although the X-ray CT apparatus 1 shown in FIG. 1 has one gantry apparatus 10, for convenience of explanation, a plurality of two gantry apparatuses 10 are depicted in FIG.

As shown in FIG. 1, the X-ray CT apparatus 1 includes a gantry device 10, a bed device 30, and a console device 40. The gantry device 10 includes an X-ray generator 20. The X-ray generator 20 includes an X-ray tube 11 and an X-ray high voltage device 21 (see FIG. 2). Note that the X-ray generating device 20 can also be applied to a dental CT device.

As shown in FIG. 1, in this embodiment, the rotation axis of the rotation frame 13 in a non-tilted state or the longitudinal direction of the top plate 33 of the bed device 30 is in the z-axis direction, orthogonal to the z-axis direction, and relative to the floor surface. The axial direction that is horizontal is defined as perpendicular to the x-axis direction and the z-axis direction, and the axial direction that is perpendicular to the floor surface is defined as the y-axis direction.

The X-ray CT device 1 has a Rotate/Rotate-type (third generation CT) in which the X-ray tube and detector rotate around the subject as one unit, and a large number of X-ray detection elements arranged in a ring shape. There are various types such as Stationary/Rotate-Type (4th generation CT) in which the X-ray tube is fixed and only the X-ray tube rotates around the subject, and any type can be applied to this embodiment. In the following description, an example will be shown in which the third generation Rotate/Rotate-Type is adopted as the X-ray CT apparatus 1 according to the present embodiment.

The gantry device 10 includes an X-ray tube 11 and an X-ray high voltage device 21 included in the X-ray generator 20, as well as an X-ray detector 12, a rotating frame 13 having an opening 19 containing an imaging area, and a control device 15. , a wedge 16, a collimator 17, and a data acquisition circuit (DAS: Data Acquisition System) 18.

The X-ray tube 11 is a vacuum tube that generates X-rays by applying a high voltage from the X-ray high voltage device 21 to irradiate thermoelectrons from a filament (cathode) 11c toward a target (anode) 11a. FIG. 2 shows an example in which the X-ray tube 11 is a rotating anode type X-ray tube that generates X-rays by irradiating a rotating anode 11a with thermoelectrons. Note that this embodiment can be applied to both a single-tube type X-ray CT device and a so-called multi-tube type X-ray CT device in which multiple pairs of X-ray tubes and detectors are mounted on a rotating ring. Applicable.

The X-ray detector 12 detects the X-rays emitted from the X-ray tube 11 and passed through the subject P, and outputs an electrical signal corresponding to the amount of X-rays to the DAS 18. The X-ray detector 12 has a plurality of X-ray detection element rows in which a plurality of X-ray detection elements are arranged in the channel direction along one arc with the focal point of the X-ray tube 11 as the center. Further, the X-ray detector 12 has a structure in which a plurality of X-ray detection element rows in which a plurality of X-ray detection elements are arranged in the channel direction are arranged in the slice direction (column direction, row direction).

Further, the X-ray detector 12 is, for example, an indirect conversion type detector having a grid, a scintillator array, and a photosensor array. The scintillator array includes a plurality of scintillators, and each scintillator includes a scintillator crystal that outputs light in an amount of photons corresponding to the amount of incident X-rays. The grid is disposed on the X-ray incident side of the scintillator array and has an X-ray shielding plate that has a function of absorbing scattered X-rays. Note that the grid is sometimes called a collimator (one-dimensional collimator or two-dimensional collimator). The optical sensor array has a function of converting the amount of light from the scintillator into an electrical signal, and includes optical sensors such as photomultiplier tubes (PMTs).

Note that the X-ray detector 12 may be a direct conversion type detector having a semiconductor element that converts incident X-rays into electrical signals.

The rotating frame 13 is an annular frame that supports the X-ray tube 11 and the X-ray detector 12 facing each other, and rotates the X-ray tube 11 and the X-ray detector 12 by a control device 15, which will be described later. Note that, in addition to the X-ray tube 11 and the X-ray detector 12, the rotating frame 13 further includes and supports a high voltage device 14 and a DAS 18.

Note that the detection data generated by the DAS 18 is transmitted to a non-rotating portion (for example, a fixed frame, not shown) of the gantry device 10 by optical communication from a transmitter having a light emitting diode (LED) provided in the rotating frame 13. , to a receiver having a photodiode and forwarded to the console device 40. A fixed frame (not shown) is a frame that rotatably supports the rotating frame 13. Further, the method of transmitting the detection data from the rotating frame 13 to the non-rotating portion of the gantry device 10 is not limited to optical communication, and any method may be used as long as it is a non-contact data transmission method.

The control device 15 includes a processor provided on a control board, a memory circuit, and drive mechanisms such as a motor and an actuator. The control device 15 has a function of receiving an input signal from an input interface 43 attached to the console device 40 or the gantry device 10, which will be described later, and controlling the gantry device 10 and the bed device 30. For example, the control device 15 receives an input signal and performs control to rotate the rotating frame 13, control to tilt the gantry device 10, and control to operate the bed device 30 and the top plate 33. Note that the control for tilting the gantry device 10 is performed by the control device 15 tilting the rotating frame 13 about an axis parallel to the This is achieved by rotating the . Note that the control device 15 may be provided on the gantry device 10 or may be provided on the console device 40.

The wedge 16 is a filter for adjusting the amount of X-rays irradiated from the X-ray tube 11. Specifically, the wedge 16 transmits and attenuates the X-rays emitted from the X-ray tube 11 so that the X-rays emitted from the X-ray tube 11 to the subject P have a predetermined distribution. It's a filter. For example, the wedge 16 (wedge filter, bow-tie filter) is a filter made of aluminum processed to have a predetermined target angle and a predetermined thickness.

The collimator 17 is a lead plate or the like for narrowing down the irradiation range of the X-rays that have passed through the wedge 16, and forms a slit by combining a plurality of lead plates or the like. The collimator 17 is sometimes called an X-ray movable aperture.

The DAS 18 (Data Acquisition System) includes an amplifier that performs amplification processing on electrical signals output from each X-ray detection element of the X-ray detector 12, and an A/D conversion that performs analog-to-digital conversion (AD conversion) of the electrical signals. and generates detection data. The detection data generated by the DAS 18 is transferred to the console device 40.

As described above, the X-ray generator 20 includes the X-ray tube 11 and the X-ray high voltage device 21 (see FIG. 2). The X-ray high voltage device 21 may be provided on the rotating frame 13 or may be provided on the fixed frame side of the gantry device 10. Details of the configuration and operation of the X-ray generator 20 will be described later.

The bed device 30 is a device on which a subject P to be scanned is placed and moved, and includes a base 31, a bed driving device 32, a top plate 33, and a support frame 34.

The base 31 is a casing that supports the support frame 34 movably in the vertical direction (y direction). The bed driving device 32 is a motor or an actuator that moves the top plate 33 on which the subject P is placed in the longitudinal direction (z direction) of the top plate 33. The top plate 33 provided on the upper surface of the support frame 34 is a plate on which the subject P is placed.

In addition to the top plate 33, the bed driving device 32 may move the support frame 34 in the longitudinal direction (z direction) of the top plate 33. Further, the bed driving device 32 may move the base 31 of the bed device 30 together. If the present invention is applicable to standing CT, a method may be adopted in which a patient moving mechanism corresponding to the top plate 33 is moved.

The console device 40 includes a memory 41 , a display 42 , an input interface 43 , a network connection circuit 44 , and a processing circuit 45 . Although the console device 40 will be described as being separate from the gantry device 10, the gantry device 10 may include some or all of the components of the console device 40. Furthermore, although the following explanation will be given assuming that the console device 40 executes all functions with a single console, these functions may be executed by a plurality of consoles.

The memory 41 has a configuration including a recording medium readable by a processor, such as a RAM (Random Access Memory), a semiconductor memory element such as a flash memory, a hard disk, an optical disk, and the like. Further, the memory 41 stores, for example, projection data, reconstructed image data, volume data of the subject P acquired in advance, and the like.

The display 42 displays various information. For example, the display 42 outputs a medical image (CT image) generated by the processing circuit 45, a GUI (Graphical User Interface) for accepting various operations from the user, and the like. For example, the display 42 is a liquid crystal display, a CRT (Cathode Ray Tube) display, an OLED (Organic Light Emitting Diode) display, or the like. Further, the display 42 may be provided on the gantry device 10. Further, the display 42 may be of a desktop type, or may be configured with a tablet terminal or the like that can communicate wirelessly with the main body of the console device 40.

The input interface 43 accepts various input operations from the user, converts the received input operations into electrical signals, and outputs the electrical signals to the processing circuit 45 . For example, the input interface 43 receives from the user information such as acquisition conditions when acquiring projection data, reconstruction conditions when reconstructing a CT image, and image processing conditions when generating a post-processed image from a CT image. For example, the input interface 43 may include a mouse, a keyboard, a trackball, a switch, a button, a joystick, a touchpad that performs input operations by touching the operation surface, a touchscreen that integrates a display screen and a touchpad, and an optical sensor. This is realized by the non-contact input circuit and voice input circuit used. Further, the input interface 43 may be provided in the gantry device 10. Further, the input interface 43 may be configured with a tablet terminal or the like that can communicate wirelessly with the main body of the console device 40.

The network connection circuit 44 implements various information communication protocols depending on the network type. The network connection circuit 44 connects the X-ray CT apparatus 1 and other devices such as an image server according to these various protocols. For this connection, an electrical connection via an electronic network or the like can be applied. Here, electronic networks refer to information and communications networks in general that utilize telecommunications technology, including wireless/wired hospital backbone LANs (Local Area Networks) and Internet networks, as well as telephone communications networks, optical fiber communications networks, and cable networks. Includes communications networks and satellite communications networks.

The processing circuit 45 is a processor that controls the overall operation of the X-ray CT apparatus 1 by reading and executing programs stored in the memory 41.

(Configuration of X-ray generator)
Next, the configuration of the X-ray generator 20 will be explained.

As shown in FIG. 2, the X-ray high voltage device 21 of the X-ray generator 20 includes a high voltage generator 22, a tube voltage detection circuit 23, a tube current detection circuit 24, a filament heating power source 25, a filament current detection circuit 26, It has a memory circuit 27 and a processing circuit 28.

The high voltage generator 22 has an electric circuit such as a transformer and a rectifier, has a function of generating a high tube voltage to be applied between the poles of the X-ray tube 11, and outputs an output voltage to the processing circuit 28. is controlled. The high voltage generator 22 may be of a transformer type or an inverter type. In the following description, an example will be shown in which the high voltage generator 22 is of an inverter type. The high voltage generator 22 is an example of a high voltage generator.

The tube voltage detection circuit 23 detects the tube voltage kV of the X-ray tube 11, outputs a signal corresponding to the value of the detected tube voltage kV, and provides the signal to the processing circuit 28. The tube current detection circuit 24 detects the tube current mA of the X-ray tube 11, outputs a signal corresponding to the value of the detected tube current mA, and provides the signal to the processing circuit 28. The tube voltage detection circuit 23 is an example of a tube voltage detection section. Further, the tube current detection circuit 24 is an example of a tube current detection section.

The filament heating power supply 25 is a current source that supplies a filament current If to be applied to the cathode filament 11c of the X-ray tube 11, and its output current is controlled by the processing circuit 28.

The filament current detection circuit 26 detects the filament current If, outputs a signal corresponding to the value of the detected filament current If, and provides the signal to the processing circuit 28. The filament current detection circuit 26 is an example of a filament current detection section.

The storage circuit 27 has a configuration including a recording medium that can be read by a processor, such as a semiconductor memory element such as a RAM (Random Access Memory), a flash memory, a hard disk, or an optical disk, and stores programs and various data. . The storage circuit 27 stores in advance a table (hereinafter referred to as "If table") in which, for example, the value of the tube current mA is associated with the value of the filament current If. Part or all of the programs and data stored in the storage circuit 27 may be downloaded by communication via an electronic network, or may be provided to the storage circuit via a portable storage medium such as an optical disk.

The processing circuit 28 reads out and executes the automatic return control program stored in the storage circuit 27, detects the discharge within the X-ray tube 11, and then determines the re-output timing of X-rays based on the value of the tube voltage kV. This is a processor that executes processing to determine the

The processor of the processing circuit 28 implements a discharge detection function 281, an X-ray control function 282, a determination function 283, and a setting function 284, as shown in FIG. Each of these functions is stored in the storage circuit 27 in the form of a program. Note that some of the functions 281 to 284 of the processing circuit 28 are performed by other processors (for example, a processor of the processing circuit 45 of the console device 40 or a processor of the control device 15) connected to the X-ray high voltage device 21 so as to be able to transmit and receive data. , an external processor, etc.).

The discharge detection function 281 detects discharge in the X-ray tube 11. It is known that when a discharge occurs, the tube voltage decreases and the tube current increases rapidly. Therefore, the discharge detection function 281 is activated, for example, when the value of the tube voltage kV becomes equal to or less than a preset threshold voltage based on the output signal of the tube voltage detection circuit 23 and/or when the tube current detection circuit 24 It is preferable to detect that discharge has occurred in the X-ray tube 11 when the value of the tube current mA exceeds a preset threshold current based on the output signal. The discharge detection function 281 is an example of a discharge detection section.

The X-ray control function 282 controls the X-rays output from the X-ray tube 11 by controlling the high voltage generator 22 . Moreover, the X-ray control function 282 controls the high voltage generator 22 to stop outputting X-rays when discharge is detected. In this embodiment, an example will be shown in which the high voltage generator 22 is of an inverter type. In this case, when discharge is detected, the X-ray control function 282 stops the X-ray output by stopping the supply of alternating current to the inverter of the high voltage generator 22. The X-ray control function 282 is an example of an X-ray control section.

Further, the X-ray control function 282 controls the high voltage generator 22 to output X-rays based on the timing of re-outputting the X-rays determined by the determination function 283.

Furthermore, the X-ray control function 282 controls the filament current If applied to the filament 11c of the X-ray tube 11 by controlling the filament heating power supply 25.

The determination function 283 determines the timing for re-outputting the X-rays after the discharge occurs, based on information regarding the tube voltage kV detected by the tube voltage detection circuit 23. The information regarding the tube voltage kV includes the value of the tube voltage kV itself and the time differential ΔkV of the value of the tube voltage kV.

Furthermore, the determination function 283 may determine the timing of re-outputting the X-rays after the discharge occurs, further based on the value of the tube current mA detected by the tube current detection circuit 24. The decision function 283 is an example of a decision unit.

The setting function 284 sets the value of tube voltage kV immediately before detection of discharge (hereinafter referred to as "immediate tube voltage value") kV0, the value of tube current mA (hereinafter referred to as "immediate tube current value") mA0, and the value of filament current If (hereinafter referred to as "immediate tube current value"). Based on If0 (hereinafter referred to as the immediately preceding If value) and the timing of X-ray re-output determined by the determination function 283, the value of the tube voltage kV and the value of the tube current mA at the time of starting the re-output of X-rays, and the value of filament current If. The setting function 284 is an example of a setting section.

(Conventional recovery process)
Here, conventional processing (conventional return processing) of processing (hereinafter referred to as automatic return control processing) for continuing X-ray irradiation while continuing the scan plan when discharge occurs within the X-ray tube 11 will be explained. .

FIG. 3 is a flowchart illustrating an example of the procedure of the conventional restoration process. In the flowcharts below, including FIG. 3, the symbols with a numeral attached to S indicate each step of the flowchart. Moreover, FIG. 4 is an explanatory diagram showing the relationship among tube voltage kV, tube current mA, filament current If, and X-ray output in the conventional return process.

In the conventional automatic recovery control process, first, in step S1001, it is determined whether or not discharge is detected. If no discharge is detected, the determination in step S1001 is repeated. On the other hand, if discharge is detected (YES in step S1001), the X-ray output is stopped (step S1002, see time t=0 in FIG. 4).

Next, in step S1003, after the X-ray output is stopped, it is determined whether a preset constant waiting time tp (for example, several tens of ms) has elapsed in order to wait for the discharge to disappear.

The process waits until a certain waiting time tp has elapsed (NO in step S1003), and when the certain waiting time tp has elapsed (YES in step S1003), the process advances to step S1004. Generally, the constant waiting time tp is set to be a sufficient time for the tube voltage kV and tube current mA to become zero (see FIG. 4). This waiting time tp becomes the timing for re-outputting the X-rays.

Next, in step S1004, a post-return tube current value mAp and a post-return filament current value Ifp are acquired. Specifically, first, when X-rays are re-outputted at time t=tp, the rise time from the current tube voltage kV=0 to the original tube voltage kV is calculated. The tube current value mAp at the time obtained by adding the determined rise time to time t=tp is determined as the tube current value mAp after recovery.

Then, in step S1005, re-output of X-rays is started at time t=tp. At this time, the initial value of the tube voltage kV is set to zero, the initial value of the tube current mA is set to mAp, and the initial value of the filament current If is set to Ifp.

In the above-described conventional return processing procedure, the re-output of X-rays is started after a certain preset waiting time tp has elapsed after the occurrence of discharge. As described above, the constant waiting time tp is set to be a sufficient time for the discharge to disappear. For this reason, while the discharge can be reliably extinguished, linear artifacts (streak artifacts) occur in X-ray CT images due to the stop of X-ray output, making it difficult to use X-ray CT images for diagnosis. This may result in an abnormal image that cannot be corrected.

(First embodiment of automatic return control processing)
Next, automatic return control processing by the processing circuit 28 of the X-ray generator 20 according to the first embodiment will be described with reference to FIGS. 5 to 12.

FIG. 5 is a flowchart illustrating an example of the procedure of automatic return control processing according to the first embodiment.

First, in step S1, the discharge detection function 281 determines whether discharge is detected. If no discharge is detected, the determination in step S1 is repeated. On the other hand, if discharge is detected (YES in step S1), the discharge detection function 281 provides information to that effect to the X-ray control function 282.

Next, in step S2, the X-ray control function 282 stops the X-ray output by stopping the supply of alternating current to the inverter of the high voltage generator 22 (time t=0).

Next, in step S3, the determination function 283 determines the value of the tube voltage kV immediately before detection of discharge (immediate tube voltage value) kV0, the value of tube current mA (immediate tube current value) mA0, and the value of filament current If. (Immediate If value) If0 is acquired. Here, the immediately previous value may be a value a predetermined time before discharge detection, a value one value before the sampling interval, or a value a predetermined number (for example, five) before the previous value at the sampling interval. It may be an additive average value or a weighted average value up to the value. The actual measured values of the tube voltage kV, tube current mA, and filament current If are the most recent values, multiple values from the most recent to a predetermined period of time, or multiple values from the most recent to a predetermined number of samplings in the memory circuit. It is stored in a storage medium such as 27. The determination function 283 obtains the immediately preceding tube voltage value kV0, immediately preceding tube current value mA0, and immediately preceding If value If0 based on the measured values stored in this storage medium.

Next, in step S4, the determination function 283 determines whether the first predetermined time T1 has elapsed since the discharge was detected. The first predetermined time T1 is an example of another predetermined time.

If the first predetermined time T1 has elapsed (YES in step S4), in step S5, the determination function 283 determines that at t=T1, the actual value kV (t=T1) of the tube voltage kV is equal to or lower than the immediately preceding tube voltage value kV0. It is determined whether the actual value kV (t=T1) of the tube current is less than or equal to the immediately preceding tube current value mA0. If at t=T1, the actual measured value kV(T1) of the tube voltage kV is equal to or less than the immediately preceding tube voltage value kV0, and the actual measured value kV(T1) of the tube current is equal to or less than the immediately preceding tube current value mA0, the determination function is activated in step S6. 283 and the setting function 284 perform the first return control process, and the series of procedures ends. In the first return control process, the determination function 283 determines the timing of re-outputting the X-rays as t=T1.

On the other hand, when the actual value kV(T1) of the tube voltage kV is not equal to or less than the immediately preceding tube voltage value kV0 at t=T1, or the actual value kV(T1) of the tube current is not equal to or less than the immediately preceding tube current value mA0. (NO in step S5), in step S7, the determination function 283 determines whether or not the second predetermined time Tth has elapsed since the discharge detection. The second predetermined time Tth is an example of a predetermined time.

If the second predetermined time Tth has not elapsed (YES in step S7), and if the actual value kV(t) of the tube voltage kV is equal to or less than the tube voltage threshold kVth (YES in step S8), the determination function 283 The setting function 284 then performs the second return control process, and the series of procedures ends. In the second return control process, the determination function 283 determines the timing of re-outputting the X-rays to the timing (t=T2) determined as YES in step S8.

On the other hand, if the actual value kV(t) of the tube voltage kV is larger than the tube voltage threshold kVth (NO in step S8), the process returns to step S7. In addition, in step S8, the determination function 283 may further control the process to proceed to step S9 only when the tube current value mA(t) is less than or equal to the tube current threshold value mAth.

On the other hand, if the second predetermined time Tth has elapsed while the actual measured value kV(t) of the tube voltage kV remains larger than the tube voltage threshold kVth (YES in step S7), the process proceeds to step S10.

In step S10, the determination function 283 determines whether the actual measured value kV(t) of the current tube voltage kV is equal to or less than the immediately preceding tube voltage value kV0. If the actual measured value kV(t) of the current tube voltage kV is less than or equal to the immediately preceding tube voltage value kV0, the determination function 283 and the setting function 284 perform the third return control process in step S11, and the series of procedures ends. In the third return control process, the determination function 283 determines the timing of re-outputting the X-rays to the timing (t=T3) determined as YES in step S10.

On the other hand, if the actual value kV(t) of the tube voltage kV is larger than the tube voltage threshold kVth (NO in step S10), step S10 is repeated. In addition, in step S10, the determination function 283 may further control the process to proceed to step S11 only when the tube current value mA(t) is less than or equal to the immediately preceding tube current value mA0.

By the above procedure, after the discharge of the X-ray tube 11 is detected, the re-output timing of X-rays can be determined based on the tube voltage value kV(t).

(First return control process)
FIG. 6 is a subroutine flowchart showing an example of the procedure of the first return control process executed by the determination function 283 and the setting function 284 in step S6 of FIG. Moreover, FIG. 7 is an explanatory diagram showing the relationship between the tube voltage value kV(t), the tube current value mA(t), the filament current value If(t), and the X-ray output in the first return control process.

The first return control process is performed when the actual measurement value kV(T1) of the tube voltage kV is equal to or less than the immediately preceding tube voltage value kV0 and the actual measurement value kV(T1) of the tube current is equal to or less than the immediately preceding tube current value mA0 at time t=T1. executed. In the first return control process, the timing for re-outputting the X-rays is determined by the determination function 283 to be t=T1.

In step S61, the setting function 284 acquires the elapsed time t (=T1) from the stop of X-ray output (t=0) and the current tube voltage value kV (T1)=kV1 from the tube voltage detection circuit 23. do.

Next, in step S62, the setting function 284 determines whether the re-output of X-rays is started at the tube voltage value kV(T1)=kV1 at t=T1, which is the timing of re-output of X-rays. A rise time tr1 from the point in time to a return point at which the tube voltage value kV(t) reaches the previous tube voltage value kV0 from kV1 is determined.

Next, in step S63, the setting function 284 changes the X-ray output stop time t=0 to the current time t=T1, assuming that no discharge occurs and the X-ray output is not stopped. The predicted value of the tube current mA (T1+tr1) and the filament current If (T1+tr1) at time t=T1+tr1 after which the time obtained by adding the rise time tr1 has elapsed are obtained.

For example, when tube current modulation control is performed, the rise time tr is determined based on the tube current modulation information in tube current modulation control, assuming that no discharge occurs and X-ray output is not stopped. A predicted value of the tube current mA (T1+tr1) at time T1+tr, which is obtained by adding the current time T1 to the current time T1, is calculated.

Further, the value of the filament current If (T1+tr1) is determined based on the obtained value of the tube current mA (T1+tr1). For example, if a table that associates the values of tube current mA and filament current If is available, the value of filament current If corresponding to the obtained tube current mA is extracted from the table, and this extracted value is used to It is acquired as the value of current If (T1+tr1).

At this time, the setting function 284 further corrects the value extracted from the table based on the filament current value on the table corresponding to the immediately preceding tube current value mA0 and the immediately preceding If value If0. ) may be obtained as the value. For example, consider a case where the immediately preceding tube current value mA0 is 300 mA, the immediately preceding If value If0 is 4.13 A, and the obtained tube current mA (T1+tr1) is 305 mA. In this case, assume that on the table, a tube current value of 300 mA is associated with an If value of 4.10A, and a tube current value of 305 mA is associated with an If value of 4.12A. In this case, the If value corresponding to the immediately preceding tube current value mA0 of 300 mA on the table is 4.10 A, whereas the actual immediately preceding If value If0 is 4.13 A, the difference is 0.03 A, and the ratio is It is 4.13/4.10. Therefore, instead of using the If value 4.12A that corresponds to the obtained tube current mA (T1 + tr1) of 305mA on the table as it is, we added the above difference of 0.03A to this 4.12A to correct it to 4.15A. Alternatively, 4.15 A corrected by multiplying by the above ratio may be obtained as the value of the filament current If (T1+tr1).

Next, in step S64, re-output of X-rays is started at time t=T1. At this time, the initial value of the tube voltage kV(t) is set to kV1, the initial value mAset1 of the tube current mA(t) is set to mA(T1+tr1), and the initial value Ifset1 of the filament current If is set to If(T1+tr1).

Then, in step S65, the determination function 283 controls the X-ray control function 282 to restart the output of X-rays at each initial value set by the setting function 284.

According to the above procedure, when the actual value kV(T1) of the tube voltage kV is equal to or less than the immediately preceding tube voltage value kV0 and the actual measured value kV(T1) of the tube current is equal to or less than the immediately preceding tube current value mA0 at time t=T1, the time At t=T1, output of X-rays can be started with an appropriate initial value.

Note that the timing t=T1 at which it is determined to proceed to the first return control process in step S5 of FIG. 5 and the actual re-output timing are, strictly speaking, only the time required for the processes of steps S62 to S64 of FIG. Although it is thought that there is a difference, for the sake of simplicity, in this specification, etc., the explanation will be made assuming that the two coincide. In this respect, the 2-5 return control process is also similar.

According to the first return control process, when the first predetermined time T1 has elapsed from the stop of X-ray output, if the tube voltage value and the tube current value are equal to or less than the immediately preceding tube voltage value kV0 and below the immediately preceding tube current value mA0, respectively. By setting time t=T1 as the X-ray re-output timing, it is possible to immediately start outputting X-rays at an appropriate initial value. Therefore, compared to the case where the X-ray output is stopped for a certain standby time tp as in the conventional recovery process, the effect of stopping the X-ray output on the X-ray CT image can be significantly suppressed.

(Second return control process)
FIG. 8 is a subroutine flowchart showing an example of the procedure of the second return control process executed by the determination function 283 and the setting function 284 in step S9 of FIG. Moreover, FIG. 9 is an explanatory diagram showing the relationship between the tube voltage value kV(t), the tube current value mA(t), the filament current value If(t), and the X-ray output in the second return control process.

The second return control process is executed when the tube voltage value kV(t) is equal to or less than the tube voltage threshold kVth at a time t that is longer than the first predetermined time T1 and shorter than the second predetermined time Tth. In the second recovery control process, the timing for re-outputting the X-rays is determined by the determining function 283 to be the timing t=T2 when the tube voltage value kV(t) is determined to be equal to or lower than the tube voltage threshold kVth in step S8 of FIG. It has been decided. In addition, when the first return control process is omitted, the time when the tube voltage value kV(t) becomes equal to or less than the tube voltage threshold kVth during the period from the discharge detection time t=t0 until the second predetermined time Tth has elapsed. may be determined at the timing T2 of re-outputting the X-rays.

In step S91, the setting function 284 acquires the elapsed time t (=T2) from the stop of X-ray output (t=0) and the current tube voltage value kV (T2)=kV2 from the tube voltage detection circuit 23. do.

Next, in step S92, the setting function 284 sets the tube voltage value kV when re-outputting the X-rays is started at the tube voltage value kV(T2)=kV2 at t=T2, which is the timing of re-outputting the X-rays. The rise time tr2 from kV2 to the return point at which (t) reaches the immediately preceding tube voltage value kV0 is determined. Note that FIG. 9 shows an example where the tube voltage kV (T2) is equal to the tube voltage threshold kVth.

Next, in step S93, when it is assumed that no discharge occurs and the X-ray output is not stopped, the X-ray output stop time t=0 is changed to the current time t=T2 (<Tth). The value of the tube current mA (T2+tr2) and the filament current If (T2+tr2) at time t=T2+tr2 after which the time sum of the time tr2 has elapsed is obtained.

At this time, similarly to step S63 in FIG. 6, the setting function 284 further extracts the value extracted from the table based on the filament current value on the table corresponding to the immediately preceding tube current value mA0 and the immediately preceding If value If0. The corrected value may be determined as the value of the filament current If (T2+tr2).

Next, in step S94, re-output of X-rays is started at time t=T2. At this time, the initial value of the tube voltage kV(t) is set to kV2, the initial value mAset2 of the tube current mA(t) is set to mA(T2+tr2), and the initial value Ifset2 of the filament current If is set to If(T2+tr2).

Then, in step S95, the determination function 283 controls the X-ray control function 282 to restart the output of X-rays at each initial value set by the setting function 284.

Through the above procedure, if the tube voltage value kV (T2) is equal to or lower than the tube voltage threshold kVth at time t=T2 (<Tth), X-ray output can be started at an appropriate initial value at time t=T2. I can do it.

As shown in FIG. 10, the set of tube voltage threshold kVth and tube current threshold mAth used in the determination in step S8 of FIG. Multiple sets may be used as appropriate. FIG. 10 shows the immediately preceding tube voltage value kV0 and the immediately preceding tube current value mA0 in the case where the magnitudes are each classified into three levels and nine types of sets of tube voltage threshold kVth and tube current threshold mAth are available. An example of the relationship between the magnitude of the tube voltage value kV0 and the immediately preceding tube current value mA0 and the set of the tube voltage threshold kVth and the tube current threshold mAth is shown. For example, whether or not to determine the tube current value in step S8 of FIG. 5 may be determined depending on the value of the tube voltage threshold kVth.

According to the second recovery control process, the timing of re-outputting the X-rays after the occurrence of discharge is determined based on the tube voltage value kV(t) during the period from the stop of the X-ray output until the second predetermined time Tth has elapsed. can be determined, and output of X-rays can be immediately started at an appropriate initial value. Therefore, similar to the first return control process, the effect of stopping X-ray output on X-ray CT images is significantly reduced compared to the conventional return process in which X-ray output is stopped for a certain waiting time tp. can be suppressed to

(Third return control process)
FIG. 11 is a subroutine flowchart showing an example of the procedure of the third return control process executed by the determination function 283 and the setting function 284 in step S11 of FIG. Moreover, FIG. 12 is an explanatory diagram showing the relationship between the tube voltage value kV(t), the tube current value mA(t), the filament current value If(t), and the X-ray output in the third return control process.

In the third recovery control process, when the second predetermined time Tth has elapsed while the actual measured value kV(t) of the tube voltage kV is greater than the tube voltage threshold kVth, the actual measured value kV(t) of the tube voltage kV is This is executed when the value is less than or equal to the value kV0. In the third recovery control process, the timing for re-outputting the X-ray is determined by the determining function 283 to be the timing t= when the tube voltage value kV(t) is determined to be equal to or lower than the immediately preceding tube voltage value kV0 in step S10 of FIG. It has been decided to be T3. Note that since it is highly likely that the discharge has disappeared by the time the third recovery control process is reached, the determination of the tube current value in step S10 in FIG. 5 can be omitted.

In step S111, the setting function 284 acquires the elapsed time t (=T3) from the stop of X-ray output (t=0) and the current tube voltage value kV (T3)=kV3 from the tube voltage detection circuit 23. do.

Next, in step S112, the setting function 284 sets the tube voltage value kV when re-outputting the X-rays is started at the tube voltage value kV(T3)=kV3 at t=T3, which is the timing of re-outputting the X-rays. A rise time tr3 from kV3 to a return point at which (t) reaches the immediately preceding tube voltage value kV0 is determined.

Next, in step S113, assuming that no discharge occurs and the X-ray output is not stopped, the X-ray output stop time t=0 rises from the current time t=T3 (≧Tth). The value of the tube current mA (T3+tr3) and the filament current If (T3+tr3) at time t=T3+tr3 after which the sum of the time tr3 and the time tr3 have elapsed are obtained.

At this time, similarly to step S63 in FIG. 6, the setting function 284 further extracts the value extracted from the table based on the filament current value on the table corresponding to the immediately preceding tube current value mA0 and the immediately preceding If value If0. The corrected value may be determined as the value of the filament current If (T3+tr3).

Next, in step S114, re-output of X-rays is started at time t=T3. At this time, the initial value of the tube voltage kV(t) is set to kV3, the initial value mAset3 of the tube current mA(t) is set to mA(T3+tr3), and the initial value Ifset3 of the filament current If is set to If(T3+tr3).

Then, in step S115, the determination function 283 controls the X-ray control function 282 to restart the output of X-rays at each initial value set by the setting function 284.

According to the above procedure, when the second predetermined time Tth has elapsed while the actual measured value kV(t) of the tube voltage kV remains larger than the tube voltage threshold kVth, the actual measured value kV(t) of the tube voltage kV changes to the immediately preceding tube voltage value kV0. At time t=T3, when the time t=T3 becomes below, output of X-rays can be started with an appropriate initial value.

According to the third recovery control process, if the second predetermined time Tth has elapsed while the tube voltage value kV(t) is still larger than the tube voltage threshold kVth, the actual measured value kV(t) of the tube voltage kV is The timing when the value kV0 or less can be determined as the timing for re-outputting the X-rays after the discharge occurs, and the outputting of the X-rays can be promptly started at an appropriate initial value. Therefore, similar to the first return control process, the effect of stopping X-ray output on X-ray CT images is significantly reduced compared to the conventional return process in which X-ray output is stopped for a certain waiting time tp. can be suppressed to

If the second predetermined time Tth elapses while the tube voltage value kV(t) is larger than the tube voltage threshold kVth, the discharge will quickly disappear, and from then on, the tube voltage and tube voltage will change in the same way as when normal X-ray output is stopped. This includes cases where the current is slowly decreasing. In this case, if the second predetermined time Tth is not set and the wait continues until the tube voltage value kV(t) becomes equal to or less than the tube voltage threshold kVth, it may take a very long time. In this regard, according to the third recovery control process, if the second predetermined time Tth elapses while the tube voltage value kV(t) remains larger than the tube voltage threshold kVth, the actual measured value kV(t) of the tube voltage kV X-ray output can be promptly restarted if the immediately previous tube voltage value kV0 or less is reached.

According to the X-ray generator 20 and the X-ray CT apparatus 1 including the X-ray generator 20 according to the first embodiment, after detecting the discharge of the X-ray tube 11, the X-ray Re-output timing can be determined. Therefore, any one of the first to third return control processes can be executed appropriately depending on the discharge mode. Therefore, in the automatic return control process after detecting the discharge of the X-ray tube 11, it is possible to greatly shorten the X-ray stop time and start-up time while reliably extinguishing the discharge. The negative effects of output stoppage can be significantly suppressed.

(Second embodiment of automatic return control processing)
Next, automatic return control processing by the processing circuit 28 of the X-ray generator 20 according to the second embodiment will be described with reference to FIGS. 13 to 17.

The automatic return control process by the processing circuit 28 of the X-ray generator 20 according to the second embodiment is performed based on the time differential ΔkV(t) of the tube voltage value kV(t) after the discharge is detected. This differs from the automatic return control process according to the first embodiment in that the line re-output timing is determined. Since the configuration is the same as the X-ray generator 20 according to the first embodiment, a description of the configuration will be omitted.

FIG. 13 is a flowchart illustrating an example of the procedure of automatic return control processing according to the second embodiment.

First, in step S21, similarly to step S1 in FIG. 5, the discharge detection function 281 determines whether or not discharge has been detected. If no discharge is detected, the determination in step S1 is repeated. On the other hand, if discharge is detected (YES in step S21), the discharge detection function 281 provides information to that effect to the X-ray control function 282.

Next, in step S22, the X-ray control function 282 stops the X-ray output by stopping the supply of alternating current to the inverter of the high voltage generator 22 (time t=0 ).

Next, in step S23, similarly to step S3 in FIG. 5, the determination function 283 obtains the immediately preceding tube voltage value kV0, the immediately preceding tube current value mA0, and the immediately preceding If value If0.

Next, in step S24, the determination function 283 calculates the time differential ΔkV(t) of the tube voltage value kV(t) based on the output signal of the tube voltage detection circuit 23, and determines whether the time differential ΔkV(t) is equal to or greater than the threshold value ΔkVth. judge. Immediately after discharge, the time differential ΔkV(t) of the tube voltage value kV(t) crosses the threshold value ΔkVth in the negative direction, takes a negative maximum value, and then gradually moves toward zero. For this reason, specifically, the determination function 283 preferably determines whether or not this time differential ΔkV(t) has changed from a negative value smaller than the threshold value ΔkVth to the threshold value ΔkVth or more in step S24.

If the time differential ΔkV(t) of the tube voltage value kV(t) is equal to or greater than the threshold value ΔkVth (YES in step S24), the determination function 283 and the setting function 284 perform a fourth return control process in step S25, and a series of The procedure ends. In the fourth return control process, the determination function 283 determines the timing of re-outputting the X-rays to the timing (t=T4) determined as YES in step S24.

On the other hand, if the time differential ΔkV(t) of the tube voltage value kV(t) is smaller than the threshold value ΔkVth (NO in step S24), in step S26, the determination function 283 sets the actual value kV(t) of the tube voltage value kV. It is determined whether or not is less than or equal to the tube voltage threshold kVth2. If the tube voltage value kV(t) is less than or equal to the tube voltage threshold kVth2 (YES in step S26), the determination function 283 and the setting function 284 perform the fifth return control process in step S27, and the series of procedures ends. In the fifth return control process, the determination function 283 determines the timing of re-outputting the X-rays to the timing (t=T5) determined as YES in step S26.

On the other hand, if the tube voltage value kV(t) is larger than the tube voltage threshold kVth2 (NO in step S26), the process returns to step S24. In addition, in step S26, the determination function 283 may further control the process to proceed to step S9 only when the tube current value mA(t) is less than or equal to the tube current threshold value mAth2. Further, the tube voltage threshold kVth2 and the tube current threshold mAth2 may be the same as the tube voltage threshold kVth and the tube current threshold mAth used in step S8 of FIG. 6, respectively.

By the above procedure, after the discharge of the X-ray tube 11 is detected, the re-output timing of X-rays can be determined based on the time differential ΔkV(t) of the tube voltage value kV(t).

(Fourth return control process)
FIG. 14 is a subroutine flowchart showing an example of the procedure of the fourth return control process executed by the determination function 283 and the setting function 284 in step S25 of FIG. Further, FIG. 15 shows the relationship between the tube voltage value kV(t), its time differential ΔkV(t), the tube current value mA(t), the filament current value If(t), and the X-ray output in the fourth return control process. FIG. In addition, in FIG. 15, for the time differential ΔkV(t) of the tube voltage value kV(t), illustration of the graph after time t=t4 is omitted.

The fourth return control process is executed when the time differential ΔkV(t) of the tube voltage value kV(t) is equal to or greater than the threshold value ΔkVth. In the fourth recovery control process, the timing of re-outputting the X-rays is determined by the determination function 283 in step S24 of FIG. The timing t=T4 is determined.

In step S251, the setting function 284 acquires the elapsed time t (=T4) from the stop of X-ray output (t=0) and the current tube voltage value kV (T4)=kV4 from the tube voltage detection circuit 23. do.

Next, in step S252, the setting function 284 sets the tube voltage value kV when re-outputting the X-rays is started at the tube voltage value kV(T4)=kV4 at t=T4, which is the timing for re-outputting the X-rays. A rise time tr4 from kV4 to a return point at which (t) reaches the immediately preceding tube voltage value kV0 is determined.

Next, in step S253, the current time t=T4 and the rise time tr4 are calculated from the X-ray output stop time t=0, assuming that no discharge occurs and the X-ray output is not stopped. The value of the tube current mA (T4+tr4) and the filament current If (T4+tr4) at time t=T4+tr4 after the added time has passed are obtained.

At this time, similarly to step S63 in FIG. 6, the setting function 284 further extracts the value extracted from the table based on the filament current value on the table corresponding to the immediately preceding tube current value mA0 and the immediately preceding If value If0. The corrected value may be determined as the value of the filament current If (T4+tr4).

Next, in step S254, re-output of X-rays is started at time t=T4. At this time, the initial value of the tube voltage kV(t) is set to kV4, the initial value mAset4 of the tube current mA(t) is set to mA(T4+tr4), and the initial value Ifset4 of the filament current If is set to If(T4+tr4).

Then, in step S255, the determination function 283 controls the X-ray control function 282 to restart the output of X-rays at each initial value set by the setting function 284.

Through the above procedure, it is possible to start outputting X-rays at an appropriate initial value at time t=T4, when the time differential ΔkV(t) of the tube voltage value kV(t) is determined to be equal to or greater than the threshold value ΔkVth. .

According to the fourth recovery control process, the timing at which the time differential ΔkV(t) of the tube voltage value kV(t) becomes equal to or greater than the threshold value ΔkVth can be determined as the timing for re-outputting X-rays after the occurrence of discharge. , it is possible to immediately start outputting X-rays at appropriate initial values. Therefore, similar to the first return control process, the effect of stopping X-ray output on X-ray CT images is significantly reduced compared to the conventional return process in which X-ray output is stopped for a certain waiting time tp. can be suppressed to

(Fifth return control process)
FIG. 16 is a subroutine flowchart showing an example of the procedure of the fifth return control process executed by the determination function 283 and the setting function 284 in step S27 of FIG. Further, FIG. 17 shows the relationship between the tube voltage value kV(t), its time differential ΔkV(t), the tube current value mA(t), the filament current value If(t), and the X-ray output in the fifth return control process. FIG. Note that, similarly to FIG. 15, in FIG. 17, the illustration of the graph after time t=t4 regarding the time differential ΔkV(t) of the tube voltage value kV(t) is omitted.

The fifth return control process is executed when the tube voltage value kV(t) is less than or equal to the tube voltage threshold kVth2. In the fifth recovery control process, the timing for re-outputting the X-rays is determined by the determining function 283 to be the tube voltage value kV(t) equal to or lower than the tube voltage threshold kVth2 in step S26 of FIG. 13, at a timing t=T5. It has been decided.

In step S261, the setting function 284 acquires the elapsed time t (=T5) from the stop of X-ray output (t=0) and the current tube voltage value kV (T5)=kV5 from the tube voltage detection circuit 23. do.

Next, in step S262, the setting function 284 sets the tube voltage value kV when re-outputting the X-rays is started at the tube voltage value kV(T5)=kV5 at t=T5, which is the timing of re-outputting the X-rays. The rise time tr5 from kV5 to the return point at which (t) reaches the immediately preceding tube voltage value kV0 is determined. Note that FIG. 17 shows an example where the tube voltage kV (T5) is equal to the tube voltage threshold kVth2.

Next, in step S263, assuming that no discharge occurs and the X-ray output is not stopped, the current time t=T5 and the rise time tr5 are calculated from the X-ray output stop time t=0. The value of tube current mA (T5+tr5) and filament current If (T5+tr5) at time t=T5+tr5 after the elapse of the added time are obtained.

At this time, similarly to step S63 in FIG. 6, the setting function 284 further extracts the value extracted from the table based on the filament current value on the table corresponding to the immediately preceding tube current value mA0 and the immediately preceding If value If0. The corrected value may be determined as the value of the filament current If (T5+tr5).

Next, in step S264, re-output of X-rays is started at time t=T5. At this time, the initial value of the tube voltage kV(t) is set to kV5, the initial value mAset2 of the tube current mA(t) is set to mA(T5+tr5), and the initial value Ifset5 of the filament current If is set to If(T5+tr5).

Then, in step S265, the determination function 283 controls the X-ray control function 282 to restart the output of X-rays at each initial value set by the setting function 284.

According to the above procedure, when the tube voltage value kV (T5) is equal to or lower than the tube voltage threshold kVth2 at time t=T5, output of X-rays can be started at an appropriate initial value at time t=T5.

Note that, similarly to the second return control process, the set of tube voltage threshold kVth2 and tube current threshold mAth2 used in the determination in step S26 in FIG. A plurality of sets may be used as appropriate (see FIG. 10). Further, whether or not to determine the tube current value in step S26 of FIG. 13 may be determined depending on the value of the tube voltage threshold kVth2.

According to the fifth recovery control process, the timing for re-outputting the X-rays after the occurrence of discharge can be determined based on the tube voltage value kV(t), and the X-ray outputting can be promptly performed at an appropriate initial value. You can start. Therefore, similar to the first return control process, the effect of stopping X-ray output on X-ray CT images is significantly reduced compared to the conventional return process in which X-ray output is stopped for a certain waiting time tp. can be suppressed to

According to the X-ray generator 20 and the X-ray CT apparatus 1 including the X-ray generator 20 according to the second embodiment, X-rays are re-outputted based on the time differential ΔkV(t) of the tube voltage value kV(t). You can decide the timing. Specifically, any one of the 4th and 5th return control processes can be executed appropriately depending on the discharge mode. Therefore, the X-ray CT apparatus 1 including the X-ray generator 20 and the X-ray generator 20 according to the second embodiment also uses the X-ray generator 20 and the X-ray generator 20 according to the first embodiment. Similar to the CT apparatus 1, in the automatic return control process after detecting a discharge in the X-ray tube 11, the discharge can be reliably extinguished while the X-ray stop time and start-up time can be greatly shortened. It is possible to significantly suppress the adverse effects of stopping X-ray output on the In addition, the X-ray generating device 20 according to the second embodiment and the X-ray CT apparatus 1 including the X-ray generating device 20 have the following characteristics: Therefore, the automatic return control process can be executed more easily than in the first embodiment, in which the instantaneous tube voltage and tube current are continuously monitored at each sampling point.

Note that the second embodiment and the first embodiment may be combined. For example, in the procedure shown in FIG. 13 of the second embodiment, the fourth return control process is executed for a short time after discharge (for example, t<T1), and if it is longer than that, only the fifth return control process or the fourth return control process is executed. Either the control process or the fifth return control process may be executed. That is, in the second embodiment as well, the fourth return control process and the fifth return control process may be selectively used depending on the passage of time after discharge.

According to at least one embodiment described above, after the discharge occurs in the X-ray tube 11, the timing for re-outputting the X-rays can be determined based on information regarding the tube voltage value kV(t).

In the above embodiments, the term "processor" refers to, for example, a dedicated or general-purpose CPU (Central Processing Unit), GPU (Graphics Processing Unit), or Application Specific Integrated Circuit (ASIC). Circuits such as programmable logic devices (e.g., Simple Programmable Logic Devices (SPLDs), Complex Programmable Logic Devices (CPLDs), and Field Programmable Gate Arrays (FPGAs)) means. When the processor is, for example, a CPU, the processor implements various functions by reading and executing programs stored in a storage circuit. Further, when the processor is, for example, an ASIC, instead of storing the program in a storage circuit, the function corresponding to the program is directly incorporated into the processor circuit as a logic circuit. In this case, the processor implements various functions through hardware processing that reads and executes programs built into the circuit. Alternatively, the processor can also implement various functions by combining software processing and hardware processing.

Furthermore, in the above embodiment, an example is shown in which a single processor of the processing circuit realizes each function, but a processing circuit may be configured by combining multiple independent processors, and each processor realizes each function. Good too. Furthermore, when multiple processors are provided, a memory circuit for storing programs may be provided individually for each processor, or a single memory circuit may collectively store programs corresponding to the functions of all processors. Good too.

Although several embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, changes, and combinations of embodiments can be made without departing from the gist of the invention. These embodiments and their modifications are included within the scope and gist of the invention as well as within the scope of the invention described in the claims and its equivalents.

1 X-ray CT device 11 X-ray tube 11a Anode 11c Filament 12 X-ray detector 14 High voltage device 20 X-ray generator 21 X-ray high voltage device 281 Discharge detection function 282 X-ray control function 283 Decision function 284 Setting function If Filament Current value If0 Immediate filament current value Ifset1 Filament current initial value T1 First predetermined time (other predetermined time)
Tth Second predetermined time (predetermined time)
kV(t) Tube voltage value kV0 Immediate tube voltage value mA(t) Tube current value mA0 Immediate tube current value mAset Tube current initial value tp Conventional standby time tr Rise time ΔkV(t) Time differential

Claims (17)

an X-ray tube that generates X-rays;
a discharge detection unit that detects discharge in the X-ray tube;
a high voltage generator that generates a tube voltage to be applied to the X-ray tube;
an X-ray control unit that controls the X-rays output from the X-ray tube by controlling the high-voltage generating unit, and controls the output of the X-rays to be stopped when the discharge is detected;
a tube voltage detection section that detects the tube voltage;
a determining unit that determines the timing of re-outputting the X-rays after the discharge occurs, based on information regarding the tube voltage detected by the tube voltage detecting unit;
Equipped with
The determining unit is
The timing of re-outputting the X-rays is set at the time when the value of the tube voltage detected by the tube voltage detection unit becomes equal to or less than a threshold value during a predetermined time period from the time when the discharge is detected.
X-ray generator. The X-ray control section includes:
controlling the high voltage generator to output X-rays based on the determined timing of re-outputting the X-rays;
The X-ray generator according to claim 1. The determining unit is
When the predetermined time period elapses while the value of the tube voltage is greater than the threshold value, the time point when the value of the tube voltage becomes equal to or less than the value of the tube voltage immediately before the detection of the discharge is set as the timing for re-outputting the X-rays. and
The X-ray generator according to claim 1 or 2 . The determining unit is
determining the timing of re-outputting the X-rays after the occurrence of the discharge, based on a time differential value of the tube voltage value detected by the tube voltage detection unit;
The X-ray generator according to any one of claims 1 to 3 . The determining unit is
The time point at which the time differential value of the tube voltage becomes equal to or greater than a threshold value is set as the timing for re-outputting the X-rays;
The X-ray generator according to claim 4 . The X-ray control unit further controls a tube current applied to the X-ray tube,
a tube current detection unit that detects the tube current;
Furthermore,
The determining unit is
Further based on the value of the tube current detected by the tube current detection section, determining the timing of re-outputting the X-ray after the occurrence of the discharge;
The X-ray generator according to any one of claims 1 to 5 . The X-ray control unit further controls a tube current applied to the X-ray tube,
a tube current detection unit that detects the tube current;
Furthermore,
The determining unit is
The value of the tube voltage and the value of the tube current after another predetermined time shorter than the predetermined time from the time of detection of the discharge are the value of the tube voltage and the value of the tube current immediately before the detection of the discharge, respectively. If the value is less than or equal to the value, the time point at which the other predetermined time has elapsed is determined as the timing for re-outputting the X-rays;
The X-ray generator according to any one of claims 1 to 3 . The X-ray control unit further controls a filament current applied to the cathode of the X-ray tube,
a filament current detection section that detects the filament current;
Based on the value of the tube voltage, the value of the tube current, and the value of the filament current immediately before the detection of the discharge, and the timing of re-outputting the X-ray determined by the determining section, a setting unit that sets the value of the tube voltage, the value of the tube current, and the value of the filament current at the time of starting re-output;
The X-ray generation device according to claim 6 or 7 , further comprising: The setting section includes:
When the re-output of the X-rays is started at the value of the tube voltage at the timing of the re-output of the X-rays, the value of the tube voltage immediately before the detection of the discharge from the time of starting the re-output of the X-rays. setting the value of the tube current and the value of the filament current at the time of starting the re-output of the X-rays based on the rise time until the return point reached;
The X-ray generator according to claim 8 . The setting section includes:
Based on the value of the tube current immediately before the detection of the discharge and the rise time, calculate a predicted value of the tube current at the time of return assuming that the discharge does not occur, and calculate this predicted value. setting the tube current to a value at the time of starting the re-output of the X-rays;
The X-ray generator according to claim 9 . The setting section includes:
The value of the filament current corresponding to the predicted value of the tube current at the time of return is extracted from a table that associates the value of the tube current with the value of the filament current, and the value of the filament current corresponding to the predicted value of the tube current at the time of return is extracted, setting the value of the filament current;
The X-ray generator according to claim 10 . The setting section includes:
Extracted from the table based on the relationship between the value of the filament current on the table corresponding to the value of the tube current immediately before the detection of the discharge, and the value of the filament current immediately before the detection of the discharge. correcting the value of the filament current corresponding to the predicted value of the tube current at the time of return, and setting the corrected value of the filament current to the value of the filament current at the time of starting re-output of the X-rays; ,
The X-ray generator according to claim 11 . an X-ray tube that generates X-rays;
a discharge detection unit that detects discharge in the X-ray tube;
a high voltage generator that generates a tube voltage to be applied to the X-ray tube;
an X-ray control unit that controls the X-rays output from the X-ray tube by controlling the high-voltage generating unit, and controls the output of the X-rays to be stopped when the discharge is detected;
a tube voltage detection section that detects the tube voltage;
a determining unit that determines the timing of re-outputting the X-rays after the discharge occurs, based on information regarding the tube voltage detected by the tube voltage detecting unit;
Equipped with
The determining unit is
determining the timing of re-outputting the X-rays after the occurrence of the discharge, based on a time differential value of the tube voltage value detected by the tube voltage detection unit;
X-ray generator. an X-ray tube that generates X-rays;
a discharge detection unit that detects discharge in the X-ray tube;
a high voltage generator that generates a tube voltage to be applied to the X-ray tube;
an X-ray control unit that controls the X-rays output from the X-ray tube by controlling the high-voltage generating unit, and controls the output of the X-rays to be stopped when the discharge is detected;
a tube voltage detection section that detects the tube voltage;
a determining unit that determines the timing of re-outputting the X-rays after the discharge occurs, based on information regarding the tube voltage detected by the tube voltage detecting unit;
Equipped with
The determining unit is
determining the timing of re-outputting the X-rays after the occurrence of the discharge based on the time differential value of the tube voltage value detected by the tube voltage detection unit;
The X-ray control unit further controls a tube current applied to the X-ray tube,
a tube current detection unit that detects the tube current;
Furthermore,
The determining unit is
Further based on the value of the tube current detected by the tube current detection section, determining the timing of re-outputting the X-ray after the occurrence of the discharge;
X-ray generator. an X-ray tube that generates X-rays;
a discharge detection unit that detects discharge in the X-ray tube;
a high voltage generator that generates a tube voltage to be applied to the X-ray tube;
an X-ray control unit that controls the X-rays output from the X-ray tube by controlling the high-voltage generating unit, and controls the output of the X-rays to be stopped when the discharge is detected;
a tube voltage detection section that detects the tube voltage;
a determining unit that determines the timing of re-outputting the X-rays after the discharge occurs, based on information regarding the tube voltage detected by the tube voltage detecting unit;
an X-ray generator having
an X-ray detector that detects the X-rays that have passed through the subject;
Equipped with
The determining unit is
The timing of re-outputting the X-rays is set at the time when the value of the tube voltage detected by the tube voltage detection unit becomes equal to or less than a threshold value during a predetermined time period from the time when the discharge is detected.
X-ray CT device. an X-ray tube that generates X-rays;
a discharge detection unit that detects discharge in the X-ray tube;
a high voltage generator that generates a tube voltage to be applied to the X-ray tube;
an X-ray control unit that controls the X-rays output from the X-ray tube by controlling the high-voltage generating unit, and controls the output of the X-rays to be stopped when the discharge is detected;
a tube voltage detection section that detects the tube voltage;
a determining unit that determines the timing of re-outputting the X-rays after the discharge occurs, based on information regarding the tube voltage detected by the tube voltage detecting unit;
an X-ray generator having
an X-ray detector that detects the X-rays that have passed through the subject;
Equipped with
The determining unit is
determining the timing of re-outputting the X-rays after the occurrence of the discharge, based on a time differential value of the tube voltage value detected by the tube voltage detection unit;
X-ray CT device. an X-ray tube that generates X-rays;
a discharge detection unit that detects discharge in the X-ray tube;
a high voltage generator that generates a tube voltage to be applied to the X-ray tube;
an X-ray control unit that controls the X-rays output from the X-ray tube by controlling the high-voltage generating unit, and controls the output of the X-rays to be stopped when the discharge is detected;
a tube voltage detection section that detects the tube voltage;
a determining unit that determines the timing of re-outputting the X-rays after the discharge occurs, based on information regarding the tube voltage detected by the tube voltage detecting unit;
an X-ray generator having
an X-ray detector that detects the X-rays that have passed through the subject;
Equipped with
The determining unit is
determining the timing of re-outputting the X-rays after the occurrence of the discharge based on the time differential value of the tube voltage value detected by the tube voltage detection unit;
The X-ray control unit further controls a tube current applied to the X-ray tube,
a tube current detection unit that detects the tube current;
Furthermore,
The determining unit is
Further based on the value of the tube current detected by the tube current detection section, determining the timing of re-outputting the X-ray after the occurrence of the discharge;
X-ray CT device.

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