X-ray tube control device, x-ray diagnosis device, and x-ray tube control method

Abstract

To improve a second output accuracy in double energy imaging.SOLUTION: An X-ray tube control device according to the embodiment includes a control part for controlling a supply of filament current for generating an X-ray of a first X-ray energy and an X-ray of a second X-ray energy which is different from the first X-ray energy in a filament of the X-ray tube. After completing the first X-ray irradiation corresponding to the first X-ray energy, the control part stops the supply of the filament current in a period until start of the second X-ray irradiation corresponding to the second X-ray energy.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The embodiments disclosed in this specification and the drawings relate to an X-ray tube control device, an X-ray diagnostic apparatus, and an X-ray tube control method. [Background technology]

[0002] An X-ray diagnostic device is a device that generates image data using X-rays generated from an X-ray tube. For example, an X-ray diagnostic device generates a desired dose of X-rays by passing a filament current through the cathode (filament) of the X-ray tube to heat it, and then controlling the filament temperature to maintain it at a target temperature, generating electrons that collide with an anode (target).

[0003] Furthermore, X-ray diagnostic equipment can measure indices that represent bone conditions, such as bone mineral density (BMD) and bone mineral content (BMC), using, for example, the dual-energy X-ray absorptiometry (DEXA) method. The DEXA method distinguishes between bone and soft tissue using image data of the subject corresponding to X-rays of two different energies, thereby calculating bone density and bone mineral content.

[0004] In DEXA, dual-energy X-rays are emitted in succession over a short period of time (pulse irradiation). Because the filament temperature changes slowly during this process, simply setting the filament current to match the X-ray conditions for the second output after the first output may result in a response that is too slow and the second output may not be in line with the X-ray conditions. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-79540 Summary of the Invention [Problem to be solved by the invention]

[0006] One of the problems to be solved by the embodiments disclosed in this specification and the drawings is to improve the accuracy of the second output in dual-energy imaging. However, the problems to be solved by the embodiments disclosed in this specification and the drawings are not limited to the above problem. Problems corresponding to the effects of each configuration shown in the embodiments described below can also be considered as other problems. [Means for solving the problem]

[0007] An X-ray tube control device according to an embodiment includes a control unit that controls the supply of a filament current to a filament of an X-ray tube to generate X-rays of a first X-ray energy and X-rays of a second X-ray energy different from the first X-ray energy. The control unit stops the supply of the filament current during a period from the end of a first X-ray irradiation corresponding to the first X-ray energy to the start of a second X-ray irradiation corresponding to the second X-ray energy. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram showing an example of the configuration of an X-ray diagnostic apparatus according to the first embodiment. [Figure 2] FIG. 2 is a configuration diagram showing an example of the X-ray high voltage device according to the first embodiment. [Figure 3] FIG. 3 is a diagram showing an example of a waveform of a tube current in dual-energy imaging according to a comparative example. [Figure 4] FIG. 4 is a diagram showing an example of processing in the X-ray tube control device according to the first embodiment. [Figure 5] FIG. 5 is a diagram showing an example of control of a filament current by the X-ray tube control device according to the first embodiment. [Figure 6] FIG. 6 is a diagram for explaining processing by the setting function according to the first embodiment. [Figure 7]FIG. 7 is a diagram showing an example of actual measurement values ​​according to the first embodiment. [Figure 8A] FIG. 8A is a diagram showing an example of a controllable period during which the supply of filament current is stopped according to the first embodiment. [Figure 8B] FIG. 8B is a diagram showing an example of a controllable period during which the supply of filament current is stopped according to the first embodiment. [Figure 9A] FIG. 9A is a diagram showing an example of a controllable period during which the supply of filament current is stopped according to the first embodiment. [Figure 9B] FIG. 9B is a diagram showing an example of a controllable period during which the supply of filament current is stopped according to the first embodiment. [Figure 10] FIG. 10 is a flowchart showing an example of a processing procedure for filament current control by the X-ray tube control device according to the first embodiment. [Figure 11] FIG. 11 is a flowchart illustrating an example of a procedure for adjusting a supply stop time by the X-ray tube control device according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of an X-ray tube control device, an X-ray diagnostic apparatus, and an X-ray tube control method will be described in detail with reference to the drawings. Note that, in the following, a general-purpose X-ray diagnostic apparatus capable of general radiography (an X-ray diagnostic apparatus having an X-ray tube capable of generating X-rays corresponding to general radiography) will be described as an example, but the present embodiment is not limited to this and may also be applied to a dedicated X-ray diagnostic apparatus that measures indices representing bone conditions.

[0010] (First embodiment) Fig. 1 is a block diagram showing an example of the configuration of an X-ray diagnostic apparatus 1 according to the first embodiment. As shown in Fig. 1, the X-ray diagnostic apparatus 1 according to the first embodiment includes an X-ray high-voltage device 10, an X-ray tube 11, an X-ray aperture 12, a tabletop 13, a grid 14, an X-ray detector 15, an input interface 16, a display 17, a memory 18, a communication interface 19, and a processing circuit 20.

[0011] The X-ray high voltage device 10 has electrical circuits such as a transformer and a rectifier, and supplies a high voltage used to generate X-rays to the X-ray tube 11. For example, the X-ray high voltage device 10 includes a high voltage generator that generates a high voltage. Here, the high voltage generator may be of a transformer type or an inverter type. In the following, a case where the high voltage generator is of an inverter type will be described as an example.

[0012] The X-ray high voltage device 10 also includes an X-ray tube controller 100 that controls the generation of X-rays by the X-ray tube 11. The X-ray tube controller 100 controls the generation of X-rays by the X-ray tube 11 by controlling the current (filament current) supplied to the filament 111 of the X-ray tube 11. The X-ray tube controller 100 will be described in detail later.

[0013] The X-ray tube 11 is a vacuum tube having a filament 111 that generates thermoelectrons and an anode 112 that generates X-rays upon impact of the thermoelectrons. The X-ray tube 11 generates X-rays by irradiating the thermoelectrons from the heated filament 111 toward the anode 112 using a high voltage supplied from the X-ray high voltage device 10. For example, the filament 111 is a metal wire made of tungsten. In addition, the anode 112 rotates under the control of a processing circuit 30, which will be described later, to avoid melting due to local heating.

[0014] The X-ray aperture 12 has aperture blades made of an X-ray shielding material such as lead or tungsten, and a filter. The aperture blades are slidably disposed to narrow down the X-rays generated by the X-ray tube 11. The X-rays generated by the X-ray tube 11 are narrowed down by an opening formed by, for example, four aperture blades. The filter changes the radiation quality of the transmitted X-rays depending on its material and thickness, with the aim of reducing the radiation dose to the subject P and improving the quality of the X-ray image. The filter reduces soft ray components that are easily absorbed by the subject P and high-energy components that cause a decrease in the contrast of the X-ray image. The filter also changes the X-ray dose and irradiation range depending on its material, thickness, position, etc., and attenuates the X-rays so that the X-rays irradiated from the X-ray tube 11 to the subject P have a predetermined distribution.

[0015] The top board 13 is a bed on which the subject P is placed. A bed having the top board 13 has a drive mechanism such as a motor, an actuator, etc., and the top board 13 can be moved horizontally and vertically by the drive mechanism, and can also be tilted.

[0016] The grid 14 removes scattered rays (secondary X-rays) generated when the subject P is irradiated with X-rays, and is detachably provided at a position between the top board 13 and the X-ray detector 15. The grid 14 is made of an X-ray shielding material such as lead or tungsten, and is formed in a lattice shape.

[0017] The X-ray detector 15 is, for example, an X-ray flat panel detector (FPD) having detection elements arranged in a matrix. The X-ray detector 15 detects X-rays irradiated from the X-ray tube 11 and transmitted through the subject P, and outputs a detection signal corresponding to the detected X-ray dose to the processing circuitry 20. The X-ray detector 15 may be an indirect conversion type detector having a grid, a scintillator array, and a photosensor array, or may be a direct conversion type detector having semiconductor elements that convert incident X-rays into electrical signals.

[0018] The input interface 16 is realized by a trackball, switches, buttons, a mouse, a keyboard, and other devices for entering various instructions and settings, a touchpad for performing input operations by touching the operation surface, a touchscreen in which the display screen and touchpad are integrated, a non-contact input circuit using an optical sensor, a voice input circuit, and the like. The input interface 16 converts input operations received from an operator into electrical signals and outputs the signals to the processing circuitry 20. Note that the input interface 16 is not limited to those having physical operation components such as a mouse and a keyboard. For example, an electrical signal processing circuit that receives electrical signals corresponding to input operations from an external input device provided separately from the X-ray diagnostic apparatus 1 and outputs the electrical signals to the processing circuitry 20 is also included as an example of the input interface 16.

[0019] The display 17 displays various types of information. For example, the display 17 displays a GUI (Graphical User Interface) for receiving instructions from an operator and various types of X-ray image data generated by the processing circuitry 20. For example, the display 17 is a liquid crystal display or a CRT (Cathode Ray Tube) display.

[0020] The memory 18 is realized by, for example, a semiconductor memory element such as a RAM (Random Access Memory), a flash memory, a hard disk, an optical disk, etc. The memory 18 receives and stores, for example, X-ray image data generated by the processing circuitry 20. The memory 18 also stores programs corresponding to various functions that are read and executed by the processing circuitry 20.

[0021] The communication interface 19 is configured by, for example, a network card, a network adapter, etc. Under the control of the processing circuit 20, the communication interface 19 transmits and receives various information to and from external devices connected via a network.

[0022] The processing circuitry 20 controls the overall operation of the X-ray diagnostic apparatus 1. For example, the processing circuitry 20 has a control function 20a, a generation function 20b, and a display control function 20c. The processing circuitry 20 is realized by, for example, a processor.

[0023] For example, the processing circuitry 20 reads out and executes a program corresponding to the control function 20a from the memory 18, thereby controlling a control device (not shown) and adjusting the aperture of the aperture blades of the X-ray aperture 12 to control the irradiation range of the X-rays irradiated onto the subject P. Also, for example, the control function 20a controls the control device and adjusts the position of the filter of the X-ray aperture 12 to control the distribution of the X-ray dose. Also, for example, the control function 20a controls the control device and adjusts the movement of the top board 13.

[0024] Furthermore, the processing circuitry 20 reads out a program corresponding to the generation function 20b from the memory 18 and executes it to generate X-ray image data using the detection signal converted from the X-rays by the X-ray detector 15, and stores the generated X-ray image data in the memory 18. Furthermore, the generation function 20b performs various image processing on the X-ray image data stored in the memory 18. For example, the generation function 20b performs noise reduction processing using an image processing filter and scattered ray correction on the X-ray image data.

[0025] Furthermore, the processing circuitry 20 reads out a program corresponding to the display control function 20c from the memory 18 and executes it to display the X-ray image data that has been subjected to various image processing by the generation function 20b on the display 17. Furthermore, the display control function 20c displays a GUI on the display 17 for receiving instructions from the operator.

[0026] In the X-ray diagnostic apparatus 1 shown in FIG. 1, each processing function is stored in the memory 18 in the form of a program executable by a computer. The processing circuitry 20 is a processor that reads and executes the programs from the memory 18 to realize the function corresponding to each program. In other words, the processing circuitry 20, after reading each program, has the function corresponding to the read program. While FIG. 1 illustrates a case in which the control function 20a, the generation function 20b, and the display control function 20c are each realized by a single processing circuitry 20, the embodiment is not limited to this. For example, the processing circuitry 20 may be configured by combining multiple independent processors, and each processor may execute a program to realize each processing function. Furthermore, each processing function of the processing circuitry 20 may be realized by being distributed or integrated as appropriate across a single or multiple processing circuits.

[0027] Next, the X-ray tube controller 100 provided in the X-ray high voltage device 10 will be described with reference to Fig. 2. Fig. 2 is a configuration diagram showing an example of the X-ray tube controller 100 according to the first embodiment. As shown in Fig. 2, the X-ray tube controller 100 includes a transformer 101 and a substrate 102, and is connected to the X-ray tube 11.

[0028] The transformer 101 steps down the AC current supplied from the inverter and then passes it through a path including the secondary coil of the transformer 101 and the filament 111. For example, the transformer 101 is composed of a primary coil to which the AC current from the inverter is input, and a secondary coil with fewer turns than the primary coil. As a result, the transformer 101 supplies the filament 111 with an AC current (filament current) that is converted so as to increase in accordance with the ratio of the turns of the primary coil and secondary coil.

[0029] The inverter is an example of a high-voltage generating device, and is provided, for example, on the substrate 102, and generates a high voltage under the control of a processing circuit 30 described later. For example, the inverter boosts AC current supplied from an AC power supply (not shown), and then passes the boosted current through a path including the inverter and the primary coil of the transformer 101.

[0030] As shown in FIG. 2, the substrate 102 is provided with a processing circuit 30. The processing circuit 30 has a control function 30a, an acquisition function 30b, and a setting function 30c. The processing circuit 30 is realized by, for example, a processor. For example, the processing circuit 30 performs various controls of the X-ray tube control device 100 by reading and executing a program corresponding to the control function 30a from the memory 18. For example, the control function 30a controls an inverter to control the filament current supplied to the filament 111. Furthermore, for example, the control function 30a controls the inverter to adjust the application of voltage to the X-ray tube 11 via a high-voltage transformer (not shown), thereby controlling the on / off of X-rays irradiated to the subject P.

[0031] That is, the control function 30a controls the filament current that heats the filament 111 to control the emission of thermoelectrons, and controls the acceleration of the thermoelectrons emitted from the filament toward the target by controlling the application of voltage to both poles of the X-ray tube 11. Here, the tube current flowing through the X-ray tube 11 is proportional to the filament current. Therefore, the control function 30a changes the tube current by changing the magnitude of the filament current supplied to the filament 111. Furthermore, the control function 30a changes the voltage (tube voltage) applied to both poles of the X-ray tube 11 to change the energy of the X-rays. The control function 30a controls the tube current and tube voltage described above based on the X-ray conditions received from the processing circuit 20.

[0032] Furthermore, the control function 30a controls the supply of a filament current to the filament 111 of the X-ray tube 11 to generate X-rays of a first X-ray energy and X-rays of a second X-ray energy different from the first X-ray energy. For example, the control function 30a stops the supply of the filament current by turning off the drive of the inverter. Here, the control function 30a controls the supply of the filament current based on a supply stop time for stopping the supply of the filament current, which will be described in detail later.

[0033] Furthermore, for example, the processing circuit 30 acquires the magnitude (effective value, amplitude, etc.) of the filament current and the magnitude (effective value, amplitude, etc.) of the actual tube current by reading and executing a program corresponding to the acquisition function 30b from the memory 18. For example, when acquiring the filament current, the AC current on the primary coil side of the transformer 101 indicated by the arrow 201 in FIG. 2 is acquired on the substrate 102, and the acquired AC current is converted to a DC current and input to an A / D (Analog-to-Digital) converter. The acquisition function 30b acquires the output from the A / D converter as the filament current.

[0034] 2 is acquired and supplied to a resistor on the circuit board 102, and the voltage across the resistor is input to the A / D converter. The acquisition function 30b acquires the tube current based on the output from the A / D converter and the resistance value. The acquisition function 30b also acquires the supply stop time, which will be described in detail later.

[0035] For example, the processing circuit 30 sets the supply stop time by reading and executing a program corresponding to the setting function 30c from the memory 18. This will be described in detail later.

[0036] In the configuration diagram shown in FIG. 2, each processing function is stored in memory 18 in the form of a computer-executable program. The processing circuit 30 is a processor that reads and executes the programs from memory 18 to realize the functions corresponding to the programs. In other words, the processing circuit 30, after reading each program, has the functions corresponding to the read programs. While FIG. 2 illustrates a case in which the control function 30a, the acquisition function 30b, and the setting function 30c are each realized by a single processing circuit 30, the embodiment is not limited to this. For example, the processing circuit 30 may be configured by combining multiple independent processors, and each processor may execute a program to realize each processing function. Furthermore, each processing function of the processing circuit 30 may be realized by being distributed or integrated as appropriate across a single or multiple processing circuits.

[0037] The term "processor" used in the above description refers to circuits such as a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an Application Specific Integrated Circuit (ASIC), a programmable logic device (e.g., a Simple Programmable Logic Device (SPLD), a Complex Programmable Logic Device (CPLD), and a Field Programmable Gate Array (FPGA)). The processor realizes its functions by reading and executing programs stored in memory 18.

[0038] Note that each processor in this embodiment is not limited to being configured as a single circuit per processor, but may be configured as a single processor by combining multiple independent circuits to realize its functions. Also, while FIG. 1 illustrates a single memory 18 storing programs corresponding to each processing function, multiple memories 18 may be distributed and the processing circuits 20 and 30 may read corresponding programs from the individual memories 18. Instead of storing programs in the memory 18, the programs may be directly embedded in the processor circuitry. In this case, the processor realizes its functions by reading and executing the programs embedded in the circuitry.

[0039] The above describes an example of the configuration of the X-ray diagnostic apparatus 1. With this configuration, the X-ray diagnostic apparatus 1 according to this embodiment improves the second output accuracy in dual-energy imaging through processing by the processing circuitry 30, which will be described in detail below.

[0040] First, the second output (pulse irradiation) in dual-energy imaging will be described. FIG. 3 is a diagram showing an example of a waveform of a tube current in dual-energy imaging according to a comparative example. Here, the horizontal axis of FIG. 3 corresponds to time. The vertical axis of FIG. 3 corresponds to the filament current, the actual measured value of the tube current (Actual mA), and the actual measured value of the tube voltage (Act kV). FIG. 3 also shows waveforms when normal control is performed with the setting conditions of the first output in dual-energy imaging set to "a1 kV, b1 mA" and the setting conditions of the second output set to "a2 kV, b2 mA." Note that "a1<a2」、「b1> b2".

[0041] As shown in Figure 3, when the first output is low energy and the second output is high energy, and imaging is performed with a short time between outputs, the first output shows a pulse-like waveform in line with the set conditions, but the tube current (mA) for the second output may exceed the set conditions. This is because the filament temperature corresponding to low-energy imaging is higher than the filament temperature corresponding to high-energy imaging, and so if the time between the end of low-energy imaging and the start of high-energy imaging is short, the filament temperature does not drop completely and does not transition to the targeted filament temperature.

[0042] Therefore, the X-ray tube control device 100 according to this embodiment executes control to temporarily stop the supply of filament current during dual-energy imaging, thereby achieving a rapid change in filament temperature in a short period of time and improving the accuracy of the second output during dual-energy imaging. The processing performed by the X-ray tube control device 100 will be described in detail below.

[0043] FIG. 4 is a diagram showing an example of processing in the X-ray tube control device 100 according to the first embodiment. Here, the horizontal axis in FIG. 4 corresponds to time and corresponds to filament current. FIG. 4 also schematically shows control of the filament current in the first output (low-energy imaging) and the second output (high-energy imaging) of dual-energy imaging. That is, FIG. 4 shows a case in which the tube voltage associated with the first output (first X-ray irradiation) is lower than the tube voltage associated with the second output (second X-ray irradiation), and the tube current associated with the first output (first X-ray irradiation) is higher than the tube current associated with the second output (second X-ray irradiation).

[0044] 4, in the X-ray tube control device 100, first, the control function 30a controls the supply of a weak filament current for preheating to the filament 111 of the X-ray tube 11 prior to the first output. Then, in response to pressing of the imaging switch for dual-energy imaging, the control function 30a controls the supply of a pre-flash filament current to the filament 111 to rapidly raise the filament temperature and cause the tube current to reach a set value. After that, when the tube current stabilizes, the control function 30a reduces the filament current to that for main heating in order to maintain it, and continues to supply the filament current for main heating until the first output is completed.

[0045] When the first output ends, the control function 30a stops the supply of the filament current as shown in the stop section in Fig. 4. That is, the control function 30a stops the supply of the filament current during the period from the end of the first output (first X-ray irradiation corresponding to the first X-ray energy) until the start of the second output (second X-ray irradiation corresponding to the second X-ray energy). Specifically, the control function 30a stops the supply of the filament current during the period until the start of the second X-ray irradiation so that the tube current in the second X-ray irradiation corresponding to the second X-ray energy becomes the target tube current for the second X-ray irradiation.

[0046] As explained in Fig. 3, in the case of normal control in which the supply of filament current is not stopped after the first output, the filament temperature may not reach the targeted filament temperature, resulting in a decrease in output accuracy in the second output. In other words, the temperature may not drop to the set filament temperature, but may end up higher than the set filament temperature, resulting in the tube current at the start of the second output being higher than the set value. However, in the X-ray tube control device 100 according to this embodiment, by providing a section in which the supply of filament current is stopped as shown in Fig. 4, the filament temperature can be rapidly lowered, and the filament temperature can be brought to the targeted filament temperature.

[0047] Here, the control function 30a stops the supply of the filament current based on the supply stop time set for each X-ray condition. The supply stop time is the time for stopping the supply of the filament current, and is acquired by the acquisition function 30b. For example, the memory 18 stores the supply stop time set for each combination of the tube current in the first output and the tube current in the second output. The acquisition function 30b acquires the corresponding supply stop time from the memory 18 based on the X-ray conditions set for imaging the subject.

[0048] The control function 30a controls the supply of the filament current based on the supply stop time acquired by the acquisition function 30b. That is, the control function 30a stops the supply of the filament current in response to the end of the first output (first X-ray irradiation), and starts the supply of the filament current for the second output (second X-ray irradiation) to the filament 111 on the condition that the supply stop time has elapsed.

[0049] Here, after the supply stop time has elapsed, the control function 30a stops controlling the preheating of the filament and starts controlling the main heating of the filament 111 based on the X-ray conditions for the second output (second X-ray irradiation). That is, after the stop section, the control function 30a stops supplying the filament current for preheating and starts supplying the filament current for main heating, as shown in Fig. 4. Then, the control function 30a continues supplying the filament current for main heating until the second output is completed, and after the second output is completed, reduces the filament current to the preheating filament current.

[0050] An example of control by the X-ray tube control device 100 will be described below. FIG. 5 is a diagram showing an example of control of filament current by the X-ray tube control device 100 according to the first embodiment. The horizontal axis of FIG. 5 corresponds to time. The vertical axis of FIG. 5 corresponds to the filament current, the actual measured value of the tube current (Actual mA), and the actual measured value of the tube voltage (Act kV). FIG. 5 also shows waveforms obtained by the above control, with the X-ray conditions for the first output in dual-energy imaging being "a1 kV, b1 mA" and the X-ray conditions for the second output being "a2 kV, b2 mA." Note that "a1<a2」、「b1> b2".

[0051] As shown in FIG. 5, first, a filament current is supplied for imaging under the X-ray conditions of "a1 kV, b1 mA" (X-ray conditions for the first X-ray irradiation) for the first output, and the supply of the filament current is stopped upon completion of the first output. After the supply stop time has elapsed, a filament current is supplied for imaging under the X-ray conditions of "a2 kV, b2 mA" (X-ray conditions for the second X-ray irradiation) for the second output. As a result, it was confirmed that the set tube current of "b2 mA" flows stably during the second output. In this way, the X-ray tube control device 100 according to this embodiment can improve the output accuracy of the second output by stopping the supply of the filament current after the end of the first output and before the start of the second output.

[0052] Furthermore, as shown in FIG. 5, the X-ray tube control device 100 according to this embodiment enables imaging for BMD1 examination in a short time. Thus, the X-ray tube control device 100 according to this embodiment can rapidly lower the filament temperature by stopping the supply of filament current, thereby shortening the time between the first and second outputs. For example, BMD examination requires specialized positioning, which places a heavy burden on subjects (especially elderly subjects) associated with positioning during imaging. By shortening the time between the first and second outputs, such subject burden can be alleviated. Furthermore, because dual-energy imaging quantitatively analyzes the results of two imaging sessions, shortening the time between the first and second outputs can also reduce the effects of body movement and improve the accuracy of the analysis results.

[0053] Next, the supply stop time for stopping the supply of filament current will be described. As described above, the supply stop time is set for each combination of the tube current at the first output and the tube current at the second output, and is stored in memory 18. That is, the supply stop time is determined based on the X-ray conditions for the first output (first X-ray irradiation), the X-ray conditions for the second output (second X-ray irradiation), and the period between the first output (first X-ray irradiation) and the second output (second X-ray irradiation), and is stored in memory 18. For example, an initial supply stop time is determined by performing a test scan in advance to determine the shortest supply stop time during which the tube current at the second output of dual-energy scanning flows stably at a set value. Such an initial supply stop time is determined for each combination of X-ray conditions and stored in memory 18.

[0054] Here, the X-ray tube control device 100 according to this embodiment can adjust the supply stop time based on the result of dual-energy imaging. Specifically, the setting function 30c calculates the difference between the result of the current dual-energy imaging and a set value (target value), and adjusts the supply stop time when the difference exceeds a threshold. More specifically, the setting function 30c calculates a new supply stop time based on the result of the previous dual-energy imaging and the supply stop time in the previous dual-energy imaging, and the result of the current dual-energy imaging and the supply stop time in the current dual-energy imaging.

[0055] FIG. 6 is a diagram for explaining processing by the setting function 30c according to the first embodiment. The horizontal axis of FIG. 6 corresponds to the supply stop time (Parameter). The vertical axis of FIG. 6 corresponds to the actual measurement value of the tube current (Act mA). For example, when the difference between the actual measurement value (Current) of the second output in the current dual-energy imaging and the target value (Set mA) exceeds the threshold "accuracy range 3% (±3%)," the setting function 30c calculates a new supply stop time (New Para) based on the actual measurement value (Current) of the second output in the current dual-energy imaging and the supply stop time (Parameter) of the second output in the previous dual-energy imaging, and the actual measurement value (Prev) of the second output in the previous dual-energy imaging. Note that the above thresholds are merely examples and can be set arbitrarily.

[0056] For example, the setting function 30c calculates the new supply stop time based on the following formulas (1) and (2).

[0057] k=abs(Current Act-Prev Act) / abs(Current Para-Prev Para) ···(1) New Para=Pre Para+abs(Set mA-Act mA) / k ···(2)

[0058] That is, as shown in equation (1), the setting function 30c calculates a coefficient "k" that indicates the effect that the amount of change in the parameter (amount of change in the supply stop time) has on the actual measurement value from the absolute value of the difference between the current actual measurement value (Current Act) and the previous actual measurement value (Prev Act) and the absolute value of the difference between the current supply stop time (Current Para) and the previous supply stop time (Prev Para).

[0059] Then, the setting function 30c calculates a new supply stop time (New Para) by adding the absolute value of the difference between the target value (Set mA) and the actual measured value (Act mA) divided by the coefficient "k" to the previous supply stop time (Current Para), as shown in equation (2).

[0060] Here, the setting function 30c can adjust the supply stop time based on various actual measurement values. For example, the setting function 30c sets the supply stop time so that the difference between at least one of the tube current in the second output (second X-ray irradiation) and the product of the tube current in the second output (second X-ray irradiation) and the irradiation time of the second output (second X-ray irradiation) and the target value corresponding to the at least one of the tube current and the irradiation time is equal to or less than a threshold value. The irradiation time is, for example, a pulse width.

[0061] FIG. 7 is a diagram showing an example of actual measurement values ​​according to the first embodiment. The horizontal axis of FIG. 7 corresponds to time (s). The vertical axis of FIG. 7 corresponds to tube current (mA). FIG. 7 also shows the transition of tube current during the second output of dual-energy imaging. For example, the setting function 30c uses the actual measurement value of the tube current during the second output (Act mA) to set a new supply stop time according to the above-described formulas (1) and (2). That is, the setting function 30c substitutes the actual measurement value of the tube current during the second output of the previous dual-energy imaging and the actual measurement value of the tube current during the second output of the current dual-energy imaging into the previous actual measurement value (Prev Act) and the current actual measurement value (Current Act) in the above-described formula (1), respectively. The setting function 30c also substitutes the set value and actual measurement value of the tube current during the second output of the current dual-energy imaging into the target value (Set mA) and actual measurement value (Act mA) in the above-described formula (2), respectively.

[0062] Here, when comparing the difference between the tube current in the second output (second X-ray irradiation) and the corresponding target value with a threshold, the setting function 30c calculates the difference between the target value and the arithmetic average of multiple tube current values ​​acquired over a partial time span of the irradiation time. That is, when using the actual measured value of the tube current, the setting function 30c can select multiple values ​​from the multiple tube current values ​​acquired during the second output and use the average of these values ​​as the actual measured value. For example, the setting function 30c may use the arithmetic average of the tube current values ​​over several milliseconds of the second output as the actual measured value. Alternatively, a single peak value may be extracted from the multiple tube current values ​​acquired during the second output and used as the actual measured value.

[0063] 7, the setting function 30c can also set a new supply stop time using the product (Act mAs) of the tube current at the second output and the irradiation time at the second output according to the above-mentioned formulas (1) and (2). That is, the setting function 30c calculates the area of ​​"mA×s" at the second output of the previous dual-energy imaging and the area of ​​"mA×s" at the second output of the current dual-energy imaging, and substitutes these values ​​for the previous actual measurement value (Prev Act) and the current actual measurement value (Current Act) in the above-mentioned formula (1). The setting function 30c also substitutes the set value of "mAs" and the actual measurement value of "mAs" at the second output of the current dual-energy imaging into the target value (Set mA) and the actual measurement value (Act mA), respectively, in the above-mentioned formula (2).

[0064] Furthermore, the setting function 30c can adjust the supply stop time using pixel values ​​of the X-ray image in addition to using the actual measured value of the tube current. For example, the setting function 30c sets the supply stop time so that the difference between the pixel values ​​of the X-ray image collected by the second output (second X-ray irradiation) and the pixel values ​​of the X-ray image estimated from the X-ray conditions for the second output (second X-ray irradiation) is equal to or less than a threshold.

[0065] In such a case, first, a test scan is performed in advance for each X-ray condition, and the pixel value obtained by the X-rays that do not pass through the subject is obtained as the target value. In the second output of the actual dual-energy scan of the subject, the setting function 30c acquires the pixel value (actual measurement value) in the area where the X-rays do not pass through the subject, and when the difference between the acquired pixel value (actual measurement value) and the target value exceeds the threshold, sets the supply stop time using the above formulas (1) and (2).

[0066] Specifically, the setting function 30c acquires pixel values ​​(actual measured values) of the region where X-rays do not pass through the subject in the second output of the previous dual-energy imaging and pixel values ​​(actual measured values) of the region where X-rays do not pass through the subject in the second output of the current dual-energy imaging, and substitutes them into the previous actual measured value (Prev Act) and the current actual measured value (Current Act) in the above formula (1). In addition, the setting function 30c substitutes the target pixel values ​​in the second output of the current dual-energy imaging and pixel values ​​(actual measured values) of the region where X-rays do not pass through the subject into the target value (Set mA) and the actual measured value (Act mA) in the above formula (2).

[0067] In addition, the pixel value may be a representative value selected from pixel values ​​in an area where X-rays do not pass through the subject, or the average value of pixel values ​​in an area where X-rays do not pass through the subject may be used.

[0068] When adjusting the initially set supply stop time, there is no difference in the supply stop time between the previous dual-energy imaging and the current dual-energy imaging, and the parameter change amount is "0." Therefore, the supply stop time cannot be adjusted using the above equations (1) and (2). Therefore, when adjusting the initially set supply stop time, the setting function 30c adjusts the supply stop time using the actual measured value and target value of the second output of the current dual-energy imaging. For example, if the actual measured value is higher than the target value, the setting function 30c adjusts the supply stop time so that it is longer.

[0069] As described above, the supply stop time is adjusted by the initial setting and setting function 30c in the section between the first and second outputs of dual-energy imaging, but the section between the first and second outputs of dual-energy imaging varies depending on various conditions, so the supply stop time is set within the section that varies depending on various conditions.

[0070] For example, the period between the first output (first X-ray irradiation) and the second output (second X-ray irradiation) is determined depending on whether or not an X-ray signal is read between the readout of the X-ray signal based on the first output (first X-ray irradiation) and the readout of the X-ray signal based on the second output (second X-ray irradiation). When X-rays transmitted through a subject are converted into electrical signals by an FPD and the electrical signals corresponding to image data are read out to generate an X-ray image, electric charges corresponding to the image data may remain inside the FPD even after the electrical signals are read out. In this case, the residual electric charges may appear as an afterimage in the next X-ray image. Therefore, the afterimage can be addressed by performing a blank readout between the first output and the second output to prevent the afterimage.

[0071] Therefore, the controllable period during which the supply of the filament current is stopped varies depending on whether or not the empty readout is performed, and the supply stop time is set accordingly. Figures 8A and 8B are diagrams showing an example of the controllable period during which the supply of the filament current is stopped according to the first embodiment. Here, Figure 8A shows the controllable period when the above-mentioned empty readout is performed, and Figure 8B shows the controllable period when the empty readout is not performed.

[0072] As shown in the lower diagram of FIG. 8A, when performing a blank readout to prevent image retention, a blank readout (Dark1) is set between the readout corresponding to the first output (Xray1) and the readout corresponding to the second output (Xray2) in the FPD readout. Therefore, as shown in the upper diagram of FIG. 8A, the second output begins after the blank readout (Dark1) ends, and the controllable period during which the supply of filament current is stopped is from the end of the first output to the start of the second output, including the time for the blank readout. In this case, the filament drive control includes the supply stop time in the controllable period including the time for the blank readout, as shown by line L1. While there is a limit to how much the time between the first and second outputs can be shortened, a longer supply stop time can be set.

[0073] On the other hand, if no blank readout is performed to prevent image retention, the controllable period extends from the end of the first output to the start of the second output, as shown in FIG. 8B. In other words, the controllable period without blank readout is shorter than when blank readout is performed. Therefore, in this case, the filament drive control includes the supply stop time in the controllable period, which does not include the time for blank readout, as shown by line L1 in FIG. 8B, thereby further shortening the time between the first and second outputs. If the supply stop time does not fall within the controllable period, the time between the first and second outputs may be set to be longer.

[0074] Furthermore, for example, the period between the first output (first X-ray irradiation) and the second output (second X-ray irradiation) is determined according to the irradiation time of the first output (first X-ray irradiation). The settable range of the irradiation time of the first output changes based on the time from the end of the first output to the start of the second output and the control time required to control the filament. Here, if the irradiation time of the first output is extended, the controllable period during which the supply of filament current is stopped becomes shorter. In other words, the time during which the supply of filament current is stopped is set within the controllable period determined according to the irradiation time of the first output.

[0075] 9A and 9B are diagrams showing an example of a controllable period for stopping the supply of filament current according to the first embodiment, where Fig. 9A shows the controllable period when the irradiation time of the first output is not changed, and Fig. 9B shows the controllable period when the irradiation time of the first output is changed.

[0076] For example, if the irradiation time in the first output is not changed, a fixed time width becomes the controllable section as shown in Figure 9A, and in this case, the filament drive control is a control that includes a supply stop time in the controllable section of the fixed time width, as shown by line L1 in Figure 9A.

[0077] On the other hand, when the irradiation time of the first output is changed, the time width of the controllable section changes according to the length of the irradiation time set within the settable range of ms, as shown in Figure 9B. Therefore, in this case, in the filament drive control, the supply stop time shown by line L1 in Figure 9B becomes shorter as the irradiation time of the first output becomes longer. Note that if the supply stop time does not fall within the controllable section, the time between the first output and the second output may be set to be longer.

[0078] Next, an example of a processing procedure by the X-ray tube control device 100 will be described with reference to Figs. 10 and 11. Fig. 10 is a flowchart showing an example of a processing procedure for filament current control by the X-ray tube control device 100 according to the first embodiment. Fig. 11 is a flowchart showing an example of a processing procedure for adjusting a supply stop time by the X-ray tube control device 100 according to the first embodiment. Note that the supply stop time adjustment processing shown in Fig. 11 is performed after the processing for filament current control in dual-energy imaging shown in Fig. 10 is completed. However, the processing shown in Fig. 11 may be performed automatically in response to the completion of the processing shown in Fig. 10, or the processing shown in Fig. 11 may be performed in response to an input operation by the operator to start the processing after the processing shown in Fig. 10 is completed.

[0079] In the filament current control process of the X-ray tube control device 100 according to the first embodiment, as shown in FIG. 10, the acquisition function 30b acquires the X-ray conditions (step S101) and acquires the supply stop time corresponding to the X-ray conditions (step S102).

[0080] Next, the control function 30a controls the first output of the dual energy imaging based on the X-ray conditions (step S103), and stops the supply of the filament current in accordance with the end of the first output (step S104).Then, the control function 30a determines whether or not the supply stop time has elapsed since the supply of the filament current was stopped (step S105).

[0081] Here, if the supply stop time has elapsed (step S105, Yes), the control function 30a starts supplying the filament current based on the X-ray conditions and controls the second output of the dual-energy imaging (step S106). Note that the control function 30a is in a standby state from the time the supply of the filament current is stopped until the supply stop time has elapsed (step S105, No).

[0082] 11, in the supply stop time adjustment process of the X-ray tube control device 100 according to the first embodiment, the setting function 30c acquires the result of dual-energy imaging (step S201) and determines whether the difference between the actual measurement value and the target value in the second output of dual-energy imaging is less than the threshold value (step S202). If the difference between the actual measurement value and the target value in the second output of dual-energy imaging is less than the threshold value (Yes in step S202), the setting function 30c ends the process.

[0083] On the other hand, if the difference between the actual measurement value and the target value in the second output of dual-energy imaging exceeds the threshold (step S202, No), the setting function 30c determines whether the parameter (supply stop time) is the initial parameter (step S203). That is, the setting function 30c determines whether the current parameter has been changed from the initial setting parameter. Here, if the current parameter is the initial setting parameter (step S203, Yes), the setting function 30c changes the initial setting parameter to a new parameter (supply stop time) based on the difference between the actual measurement value and the target value in the second output of dual-energy imaging (step S205).

[0084] On the other hand, if it is determined in step S203 that the current parameters are not the initial setting parameters (step S203, No), the setting function 30c calculates new parameters by determining the effect of the parameter change on the actual measurement value from the results of the previous dual-energy imaging and the current dual-energy imaging (step S204).The setting function 30c then changes the current parameters to the calculated parameters (step S205).

[0085] As described above, according to the first embodiment, the control function 30a controls the supply of filament current to the X-ray tube filament to generate X-rays of a first X-ray energy and X-rays of a second X-ray energy different from the first X-ray energy, and stops the supply of filament current during the period from the end of the first X-ray irradiation corresponding to the first X-ray energy to the start of the second X-ray irradiation corresponding to the second X-ray energy. Therefore, the X-ray tube controller 100 according to the first embodiment can rapidly reduce the filament temperature, thereby improving the output accuracy of the second output in dual-energy imaging. As a result, the X-ray tube controller 100 facilitates analysis using, for example, the DEXA method.

[0086] Furthermore, the X-ray tube control device 100 can rapidly reduce the filament temperature, thereby shortening the time between the first and second outputs in dual-energy imaging. As a result, the X-ray tube control device 100 shortens the time required for two imaging operations in dual-energy imaging, for example, thereby reducing the burden on the subject related to positioning during imaging and improving analysis accuracy by suppressing the effects of body movement.

[0087] Another method for improving the accuracy of the second output in dual-energy imaging is to apply control that adjusts the amount of filament current between pulses, but this method is complicated because it requires using a formula to calculate the filament current amount and control time, and then controlling the inverter drive frequency based on that.In contrast, the X-ray tube control device 100 according to this embodiment simply controls the stopping of the supply of filament current, making it easy to improve the accuracy of the second output in dual-energy imaging.

[0088] Furthermore, according to the first embodiment, the tube voltage for the first X-ray irradiation is lower than the tube voltage for the second X-ray irradiation, and the tube current for the first X-ray irradiation is higher than the tube current for the second X-ray irradiation. Therefore, the X-ray tube control device 100 according to the first embodiment can improve the output accuracy of the second output under X-ray conditions where the filament current for the second output is lower than that for the first output.

[0089] Furthermore, according to the first embodiment, the acquisition function 30b acquires a supply stop time, which is the time for stopping the supply of filament current. The control function 30a stops the supply of filament current upon completion of the first X-ray irradiation, and starts supplying filament current for the second X-ray irradiation to the filament upon the elapse of the supply stop time. Therefore, the X-ray tube control device 100 according to the first embodiment can improve the output accuracy of the second output in dual-energy imaging simply by applying a preset supply stop time.

[0090] Furthermore, according to the first embodiment, the control function 30a stops the supply of the filament current during the period until the start of the second X-ray irradiation so that the tube current in the second X-ray irradiation corresponding to the second X-ray energy becomes the target tube current for the second X-ray irradiation. Therefore, the X-ray tube control device 100 according to the first embodiment can control the tube current in the second output to become the target value.

[0091] Furthermore, according to the first embodiment, the supply stop time is determined based on the X-ray conditions for the first X-ray irradiation, the X-ray conditions for the second X-ray irradiation, and the period between the first and second X-ray irradiations. Therefore, the X-ray tube control device 100 according to the first embodiment can use an appropriate supply stop time.

[0092] Furthermore, according to the first embodiment, the setting function 30c sets the supply stop time so that the difference between at least one of the tube current for the second X-ray irradiation and the product of the tube current for the second X-ray irradiation and the irradiation time for the second X-ray irradiation and the target value corresponding to the at least one of the two is equal to or less than a threshold value. Furthermore, the setting function 30c sets the supply stop time so that the difference between the pixel values ​​of the X-ray image acquired by the second X-ray irradiation and the pixel values ​​of the X-ray image estimated from the X-ray conditions for the second X-ray irradiation is equal to or less than a threshold value. Therefore, even after operation has started, the X-ray tube control device 100 according to the first embodiment can adjust the supply stop time to an appropriate time using any of the tube current, mAs, and pixel values. As a result, the X-ray tube control device 100 can correct the influence of deviations due to changes over time and constantly maintain high output accuracy.

[0093] Furthermore, according to the first embodiment, when comparing the difference between the tube current in the second X-ray irradiation and the corresponding target value with a threshold, the setting function 30c calculates the difference between the target value and the average value of multiple tube current values ​​acquired over a partial time width of the irradiation time. Therefore, the X-ray tube control device 100 according to the first embodiment can use an appropriate value even when using the value of the tube current.

[0094] Furthermore, according to the first embodiment, the period between the first X-ray irradiation and the second X-ray irradiation is determined depending on whether or not an X-ray signal is read between the readout of the X-ray signal based on the first X-ray irradiation and the readout of the X-ray signal based on the second X-ray irradiation. Furthermore, the period between the first X-ray irradiation and the second X-ray irradiation is determined depending on the irradiation time of the first X-ray irradiation. Therefore, the X-ray tube control device 100 according to the first embodiment can perform control depending on the difference in the period between the first output and the second output.

[0095] Furthermore, according to the first embodiment, after the supply stop time has elapsed, the control function 30a does not control the preheating of the filament, but starts controlling the main heating of the filament based on the X-ray conditions for the second X-ray irradiation. Therefore, the X-ray tube control device 100 according to the first embodiment can control the second output in dual-energy imaging with simple control.

[0096] (Other embodiments) The above-described embodiment can be applied to analyses other than DEXA analysis as long as dual-energy imaging is performed. For example, the above-described filament current control may be applied to subtraction using the 2-Shot method that utilizes dual-energy imaging.

[0097] The components of each device according to the above-described embodiments are conceptual and functionally independent, and are not necessarily physically configured as shown in the drawings. In other words, the specific form of distribution and integration of each device is not limited to that shown in the drawings, and all or part of the devices can be functionally or physically distributed and integrated in any unit depending on various loads, usage conditions, etc. Furthermore, all or any part of the processing functions performed by each device can be realized by a CPU and a program analyzed and executed by the CPU, or can be realized as hardware using wired logic.

[0098] The X-ray tube control method described in the above-described embodiments can be realized by executing a prepared X-ray tube control program on a computer such as a personal computer or a workstation. This X-ray tube control program can be distributed via a network such as the Internet. This X-ray tube control program can also be recorded on a computer-readable recording medium such as a hard disk, flexible disk (FD), CD-ROM, MO, or DVD, and executed by being read from the recording medium by a computer.

[0099] According to at least one of the embodiments described above, it is possible to improve the output accuracy of the second scan in dual-energy imaging.

[0100] Although several embodiments of the present invention 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, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention described in the claims and their equivalents. [Explanation of symbols]

[0101] 1 X-ray diagnostic equipment 10. X-ray high voltage device 11 X-ray tube 30 Processing circuit 30a Control Function 30b Acquisition function 30c setting function 111 Filament

Claims

1. a control unit that controls supply of a filament current to a filament of the X-ray tube to generate X-rays of a first X-ray energy and X-rays of a second X-ray energy different from the first X-ray energy, the control unit stops the supply of the filament current during a period from when a first X-ray irradiation corresponding to the first X-ray energy ends until when a second X-ray irradiation corresponding to the second X-ray energy starts.

2. a tube voltage for the first X-ray irradiation is lower than a tube voltage for the second X-ray irradiation; The X-ray tube control device according to claim 1 , wherein a tube current associated with the first X-ray exposure is higher than a tube current associated with the second X-ray exposure.

3. an acquisition unit that acquires a supply stop time that is a time for stopping the supply of the filament current; 2. The X-ray tube control device according to claim 1, wherein the control unit stops supplying the filament current in response to completion of the first X-ray irradiation, and starts supplying the filament current related to the second X-ray irradiation to the filament on condition that the supply stop time has elapsed.

4. 2. The X-ray tube control device according to claim 1, wherein the control unit stops the supply of the filament current during a period until the second X-ray irradiation is started so that a tube current in the second X-ray irradiation corresponding to the second X-ray energy becomes a target tube current for the second X-ray irradiation.

5. 4. The X-ray tube control device according to claim 3, wherein the supply stop time is determined based on an X-ray condition for the first X-ray irradiation, an X-ray condition for the second X-ray irradiation, and a period between the first X-ray irradiation and the second X-ray irradiation.

6. 4. The X-ray tube control device according to claim 3, further comprising a setting unit that sets the supply stop time so that a difference between a target value corresponding to at least one of a tube current in the second X-ray irradiation and a product of the tube current in the second X-ray irradiation and an irradiation time of the second X-ray irradiation is equal to or less than a threshold value.

7. 7. The X-ray tube control device according to claim 6, wherein when comparing a difference between a tube current in the second X-ray irradiation and a corresponding target value with the threshold, the setting unit calculates a difference between an arithmetic average of a plurality of tube current values ​​acquired over a partial time width of the irradiation time and the target value.

8. 4. The X-ray tube control device according to claim 3, further comprising a setting unit that sets the supply stop time so that a difference between a pixel value of an X-ray image acquired by the second X-ray irradiation and a pixel value of an X-ray image estimated from an X-ray condition related to the second X-ray irradiation is equal to or less than a threshold value.

9. 2. The X-ray tube control device according to claim 1, wherein a period between the first X-ray irradiation and the second X-ray irradiation is determined depending on whether or not an X-ray signal is read out between a readout of an X-ray signal based on the first X-ray irradiation and a readout of an X-ray signal based on the second X-ray irradiation.

10. The X-ray tube control device according to claim 1 , wherein the period between the first X-ray irradiation and the second X-ray irradiation is determined according to an irradiation time of the first X-ray irradiation.

11. 4. The X-ray tube control device according to claim 3, wherein the control unit does not control preheating of the filament after the supply stop time has elapsed, but starts controlling main heating of the filament based on X-ray conditions for the second X-ray irradiation.

12. an X-ray tube that generates X-rays; a control unit that controls supply of a filament current to a filament of the X-ray tube to generate X-rays of a first X-ray energy and X-rays of a second X-ray energy different from the first X-ray energy, the control unit stops the supply of the filament current during a period from when a first X-ray irradiation corresponding to the first X-ray energy ends until when a second X-ray irradiation corresponding to the second X-ray energy starts.

13. 13. The X-ray diagnostic apparatus according to claim 12, wherein the X-ray tube is capable of generating X-rays suitable for general radiography.

14. a control step of controlling supply of a filament current to a filament of an X-ray tube to generate X-rays of a first X-ray energy and X-rays of a second X-ray energy different from the first X-ray energy, the control step stops the supply of the filament current during a period from completion of a first X-ray irradiation corresponding to the first X-ray energy to start of a second X-ray irradiation corresponding to the second X-ray energy.

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