JP5071676B2 - X-ray apparatus with pulse fluoroscopy mode - Google Patents

Description

  The present invention relates to an X-ray apparatus that obtains a fluoroscopic image by exposing X-rays to a subject.

  In recent years, various types of X-ray apparatuses have been developed for each fluoroscopic object and fluoroscopic purpose. As one of them, an X-ray apparatus having a pulse fluoroscopy mode capable of reducing the exposure dose of the subject by making the X-rays exposed to the subject into a pulse shape is known.

FIG. 7 is a block diagram of a conventional X-ray apparatus having a pulse fluoroscopy mode. X-ray apparatus 1 'is mainly, the X-ray tube 10 of the rotary anode for generating X-rays, the X-ray tube controller for controlling the filament current I _F and the pulse-shaped tube voltage V _T of the X-ray tube 10 20 ′, a table 3 on which the subject 2 is placed, an image intensifier (II) 4 and the like, an input unit 8 for receiving various commands from the operator, and each unit based on the commands And a control unit 9 for controlling. A target 11 and a filament 12 made of tungsten or the like are provided inside the X-ray tube 10. The X-ray tube control unit 20 ′ has a tube voltage control unit 21 and a filament heating unit 22.

In the standby state is not performed fluoroscopy, the voltage value of the pulsed tube voltage V _T output from the tube voltage control unit 21 is 0 [V]. Further, the filament heater 22 may flow a minute filament current I _F toward the filament 12 to preheat the filament 12.

The fluoroscopy of the subject 2 is started when the operator inputs a command to that effect via the input unit 8. When finger age is entered perspective state, filament heating unit 22 increases the filament current I _F to heat the filament 12. Simultaneously, tube voltage control unit 21 begins to output a pulsed tube voltage V _T having a predetermined pulse width. Thus, vigorously collide with thermal electrons target 11 emitted from the filament 12, along with the flow tube current I _T to a target 11 from the tube voltage control unit 21, X-rays toward the target 11 in the subject 2曝Be shot. The X-rays transmitted through the subject 2 are I. After being converted into a visible image at 4, image processing is appropriately performed, and a fluoroscopic image of the subject 2 is observed on the monitor 7.

FIG. 8 shows operation waveforms of the X-ray apparatus 1 ′. In this figure, (A) is the filament current I _F , (B) is the filament temperature T _F , (C) is the pulsed tube voltage V _T , (D) is the tube current I _T , and (E) is the subject 2. The waveform of the X-ray dose XR of the X-rays exposed toward is shown. In either of the waveform, is performed switching from the standby state to the transparent state at time t _1, it is assumed that the switching from the perspective state at time t ₂ to the standby state is performed.

In the standby state of the time 0 to t _1, the filament 12 minute filament current _{I F0} for preheating flows, the filament 12 has a temperature _{T F0} accordingly. At this time, tube voltage control unit 21 does not output the pulse-shaped tube voltage V _T. Therefore, the X-ray dose XR of X-rays exposed toward the subject 2 during standby is 0 or very small.

When a command perspective starting at time _{t 1} is input, the filament current _{I F} immediately increases from _{I F0} to _{I F1} (see FIG. 8 (A)). At the same time, the tube voltage control unit 21 starts outputting the pulsed tube voltage V _T having the voltage value V _T1 (see FIG. 8C). In this case, the filament temperature T _F shown in FIG. 8 (B) is not reached immediately to a temperature T _F1 corresponding to the current I _F1, increases gradually in accordance with thermal inertia. Therefore, even the tube current _{I T} and X dose XR, (see FIG. 8 (D) (E)), respectively, increases gradually toward the tube current _{I T1} and X dose XR ₁ a target.

That is, the conventional X-ray apparatus 1 ′ shown in FIG. 7 has a problem that a suitable fluoroscopic image cannot be observed because the X-ray amount XR is insufficient for a certain period after the start of fluoroscopy. . In view of such a problem, various X-ray apparatuses intended to secure a target X-ray dose XR immediately after the start of fluoroscopy and obtain a suitable fluoroscopic image have been studied (for example, Patent Document 1). reference).
JP-A-8-195294

In X-ray apparatus according to Patent Document 1, as shown in FIG. 9, the filament current I _F immediately after the beginning perspective to accelerate the temperature rise of the filament 12 by overshooting to I _F1, X dose XR is a target The time to reach the X-ray dose XR ₁ is shortened. However, in general it is difficult to accurately control the overshoot amount of the filament current I _F, by an excessive current flows through the filament 12, the filament 12 there is a risk of deteriorated or damaged.

In addition to this, during a certain period after the start fluoroscopy, X-rays apparatus and which is adapted compensate for the lack of the pulsed tube voltage V _T X dose by increasing the XR, filament current I _F and the pulsed tube voltage V An X-ray apparatus is also known in which the shortage of the X-ray dose XR is compensated by changing the processing in the image processing unit 6 without changing the setting of _T. However, the increase in the pulse tube voltage V _T has a problem that the contrast of the finally obtained fluoroscopic image is lowered. Further, the change in the image processing has a problem that the fluoroscopic image becomes too bright after the filament temperature reaches a predetermined temperature.

  Accordingly, an object of the present invention is to provide an X-ray apparatus capable of stably obtaining a suitable fluoroscopic image immediately after the start of fluoroscopy.

The present inventor has conducted extensive studies to solve the above problem, during the period from immediately after the start fluoroscopy until the filament temperature reaches a predetermined temperature, the pulse width of the pulsed tube voltage V _T of the perspective state of the normal The present inventors have found that a suitable fluoroscopic image can be obtained by extending the time for exposing the subject to X-rays by extending the pulse width beyond the pulse width, thereby completing the present invention.

That is, an X-ray apparatus according to the present invention includes a tube voltage control unit that outputs a pulsed tube voltage and whose pulse width can be switched, and a filament heating unit that causes a predetermined filament current to flow through the filament to generate heat. When a fluoroscopic start command is input, the tube voltage control unit starts outputting the pulsed tube voltage, and the filament heating unit increases the filament current to heat the filament. An X-ray apparatus that performs fluoroscopic observation of a subject by X-rays generated by colliding a thermoelectron emitted from the filament with a target, wherein the tube voltage control unit receives the command after the command is input. For a predetermined period until the temperature of the filament reaches the temperature of the steady fluoroscopic state, the pulse width of the pulse tube voltage is set to the steady fluoroscopic state. And switches to be wider than the pulse width.
Note that the term “steady fluoroscopic state” in the present specification means a state after the filament temperature reaches a target temperature (for example, T _{F1 in} FIG. 2B) in the fluoroscopic state. . Even when the filament temperature fluctuates and falls below the target temperature once after the steady fluoroscopic state is reached, it is assumed that the steady fluoroscopic state continues if the fluctuation is small.

  In the X-ray apparatus, the predetermined period is a period from when the command is input until a tube current reaches 70% to 100% of a normal fluoroscopic state, or after the command is input. A period between the time when the temperature of the filament reaches 70% to 100% of the normal fluoroscopic state can be set.

  Further, the time at which the predetermined period ends may be measured and stored in advance, and when the time comes, the pulse width of the pulse tube voltage may be switched to a pulse width in a steady fluoroscopic state.

  The predetermined period may be determined and stored in advance by observing a fluoroscopic image obtained by preliminary fluoroscopic imaging performed before the main fluoroscopy.

  Further, the pulse width may be switched in a stepwise manner during the predetermined period.

  According to the present invention, it is possible to provide an X-ray apparatus capable of stably obtaining a suitable fluoroscopic image immediately after the start of fluoroscopy.

  Hereinafter, preferred embodiments of an X-ray apparatus according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a block diagram of the X-ray apparatus according to the first embodiment. The X-ray apparatus 1 controls a rotating anode type X-ray tube 10 that generates X-rays for exposure to a subject 2, and a filament current _IF and a pulsed tube voltage V _T of the X-ray tube 10. An X-ray tube control unit 20 for performing the test, and a table 3 for placing the subject 2 thereon. A target 11 and a filament 12 made of tungsten or the like are provided inside the X-ray tube 10.

The X-ray tube control unit 20 includes a tube voltage control unit 21, a filament heating unit 22, and a timer 23. Among them, a tube voltage control unit 21 is able to arbitrarily control the voltage value and pulse width of the pulsed tube voltage V _T to be output toward the X-ray tube 10. In addition, the timer 23 notifies the tube voltage control unit 21 that a predetermined time has elapsed after receiving a fluoroscopic start command (described later).

  In addition, the X-ray apparatus 1 is an I.I. I. 4, a system comprising a camera 5 and an image processing unit 6, a monitor 7 for displaying a fluoroscopic image obtained by the system, an input unit 8 for receiving various commands from an operator, and controlling each unit based on the commands And a control unit 9. I. I. 4 detects an X-ray amount XR of X-rays transmitted through the subject 2 and converts the X-ray amount XR into a visible image. The camera 5 and the image processing unit 6 are connected to the I.D. I. The visible image obtained in 4 and image processing are performed, and a fluoroscopic image to be displayed on the monitor 7 is generated.

Further, from the input unit 8, the instruction to start and end perspective, the set value of the filament current I _F and the pulse-shaped tube voltage V _T is input. The input unit 8 accepts input of various conditions such as the type (state) of the subject 2 and the contrast of the fluoroscopic image as necessary. In this embodiment, the input unit 8 has a foot pedal. When the operator depresses the foot pedal, a fluoroscopic start command is transmitted to each unit through the control unit 9, and when the step is stopped, a fluoroscopy end command is transmitted to each unit. The

Standby state, namely in a state where the foot pedal is not depressed in the input unit 8, the voltage value of the pulsed tube voltage V _T output from the tube voltage control unit 21 is 0 [V]. Further, the filament heater 22 may flow a minute filament current I _F toward the filament 12 to preheat the filament 12.

When the foot pedal is being in perspective state depressed, with filament heating unit 22 to heat the filament 12 increases the filament current I _F, the tube voltage control unit 21 a pulsed tube voltage V _T having a predetermined pulse width Start outputting. Thus, vigorously collide with thermal electrons target 11 emitted from the filament 12, along with the flow tube current I _T to a target 11 from the tube voltage control unit 21, X-rays toward the target 11 in the subject 2曝Be shot. The X-ray transmitted through the subject 2 is I.D. I. 4 and a fluoroscopic image of the subject 2 is generated.

FIG. 2 shows operation waveforms of the X-ray apparatus 1 according to the first embodiment. In this figure, (A) is the filament current I _F , (B) is the filament temperature T _F , (C) is the pulsed tube voltage V _T , (D) is the tube current I _T , and (E) is the subject 2. The waveform of the X-ray dose XR of the X-rays exposed toward is shown. In either of the waveform, is performed switching from the standby state to the transparent state at time t _1, it is assumed that the switching from the perspective state at time t ₄ to the standby state is performed.

In the standby state of the time 0 to t _1, the filament 12 minute filament current _{I F0} for preheating flows, the filament 12 has a temperature _{T F0} accordingly. At this time, tube voltage control unit 21 does not output the pulse-shaped tube voltage V _T. Therefore, the X-ray dose XR of X-rays exposed toward the subject 2 during standby is 0 or very small.

When a command perspective starting at time _{t 1} is input, the filament current _{I F} immediately increases from _{I F0} to _{I F1} (see FIG. 2 (A)). In this case, gently increases as the filament temperature _{T F} is the thermal inertia of FIG 2 (B), (in the present embodiment, after 2s from fluoroscopy start) time _{T 3} reaches a temperature _{T F1} corresponding to the current _{I F1} in To do. Therefore, even the tube current _{I T} and X dose XR, (see FIG. 2 (D) (E)), respectively, increases gradually toward the tube current _{I T1} and X dose XR ₁ a target.

As described above, the timer 23 notifies the tube voltage control unit 21 that a predetermined period has elapsed since the instruction to start fluoroscopy. In the present embodiment, the first notification is made when 1 s has elapsed after the input of the command (time t ₂ ), and the second notification is made when 1 s (total 2 s) has passed (time t ₃ ). The That is, in this embodiment, the filament temperature _{T F} is split the time to reach a predetermined temperature _{T F1,} and the time period _t 1 ~t _2, in a period of time _t 2 ~t _3.

The number of periods to be divided is not limited to two, but can be three or more. For example, the first notification may be given after 0.5 s, the second notification after 0.5 s, and the third notification after 1 s (total 2 s). Incidentally, in view of the division of the period is mandatory is Ku, but may be at the time t ₃ when the transparent state of the normal one-time notification is performed to obtain a suitable fluoroscopic image without much complicating the control Therefore, it is preferable to divide into two or three periods.

  Various methods are conceivable as a method for determining the predetermined time. In this embodiment, the predetermined time is determined with reference to a fluoroscopic image obtained by preliminary fluoroscopy. Preliminary fluoroscopy is performed to determine fluoroscopic conditions before the main fluoroscopy, and is performed by actually performing fluoroscopy with a phantom that simulates a human body during installation adjustment. The operator looks at the fluoroscopic image obtained by the preliminary fluoroscopy, and determines how many seconds have passed after inputting the fluoroscopic start command to obtain the desired fluoroscopic image. For example, if it is determined that a desired fluoroscopic image can be obtained after 2 s, “2 s” is stored in the timer 23 through the input unit 8. When it is desired to divide the period until the steady fluoroscopic state is reached into a plurality of periods, the time for notification is input.

Referring again to FIG. 2, at the fluoroscopic state at time t _1, a tube voltage control unit 21 starts the output of the pulse-shaped tube voltage V _T having a predetermined pulse width (see FIG. 2 (C)). The pulse width of the pulse tube voltage V _T is gradually reduced every time notification from the timer 23 is received.

As shown in FIG. 2C, in this embodiment, the pulse width is 6 ms (duty ratio 50%) during the period (time t _{1 to} t ₂ ) until the first notification is received, that is, the first 1 s. Be controlled. The pulse width is controlled to 5 ms (duty ratio 50%) during a period (time t _{2 to} t ₃ ) from when the first notification is received until the second notification is received. Thereafter, when a steady state is reached at time t ₃ , the pulse width is switched to 4 ms (Duty ratio 50%). Thereafter, a tube voltage control unit 21 keeps outputting a pulse tube voltage V _T with the pulse width of 4ms until a command perspective ends.

When the pulse width of the pulse tube voltage V _T changes, the pulse width of the X-rays exposed to the subject 2 also changes accordingly. That is, in this embodiment, the pulse width of the X-rays, the period of time _t 1 ~t ₂ is controlled to about 6 ms, a period of time _t 2 ~t ₃ is controlled to about 5 ms, a transparent state of the normal and time _{t 3} or later is controlled to about 4 ms (see FIG. 2 (E)).

  In summary, in the X-ray apparatus according to the present embodiment, the X-ray pulse width is controlled to be wider than the normal fluoroscopic state for a predetermined period after the start of fluoroscopy. That is, in the X-ray apparatus according to the present embodiment, the X-ray exposure time is controlled to be longer than the normal fluoroscopic state until the filament temperature reaches the target temperature. Thereby, the shortage of the X-ray dose immediately after the start of fluoroscopy is compensated, and a suitable fluoroscopic image can be obtained stably immediately after the start of fluoroscopy.

  FIG. 3 is a block diagram of the X-ray apparatus according to the second embodiment. The X-ray tube control unit 20 of the X-ray apparatus 1 has a current sensor 24 instead of the timer 23. Since other configurations are the same as those of the X-ray apparatus according to the first embodiment, the description thereof is omitted here.

Current sensor 24 is disposed between the tube voltage control unit 21 and the target 11, for detecting the tube current I _T flows from the tube voltage control unit 21 toward the target 11. When the tube current I _T reaches a predetermined current value, indicating that the current sensor 24 to the tube voltage control unit 21 is notified.

As shown in FIG. 4 (D), in this embodiment, the tube current I _T is the first notification when a rose to 80% of the predetermined current I _T1 (time t _2). Then, at time _{t 2,} the tube current _{I T} is the ascending the second indication up to 95% of the predetermined current _{I T1.} Whenever notified, the pulse width of the pulsed tube voltage V _T output from the tube voltage control unit 21 is gradually stepwise narrowing are the same as in Example 1.

Here, generally, when the tube current I _T reaches 70% of the perspective state of the normal, almost no way inferior fluoroscopic image is known to be obtained with transparent state steady. Thus, the pulse width of the pulsed tube voltage V _T, when the tube current I _T reaches 70% to 100% of the perspective state of the normal, it is desirable to switch to the pulse width of the perspective state of the normal.

  FIG. 5 is a block diagram of the X-ray apparatus according to the third embodiment. The X-ray tube control unit 20 of the X-ray apparatus 1 has a temperature sensor 25 instead of the timer 23. Since other configurations are the same as those of the X-ray apparatus according to the first embodiment, the description thereof is omitted here.

The temperature sensor 25 is disposed in the vicinity of the filament 12 and directly or indirectly detects the filament temperature _TF . When the filament temperature _TF reaches a predetermined temperature, the temperature sensor 25 notifies the tube voltage control unit 21 accordingly.

As shown in FIG. 6 (B), in this embodiment, the filament temperature T _F is the first notification when a rose to 80% of the predetermined temperature T _F1 (time t _2). Then, at time _{t 2,} the filament temperature _{T F} is rises to the second indication to 95% of the predetermined temperature _{T F1.} Whenever notified, the pulse width of the pulsed tube voltage V _T output from the tube voltage control unit 21 is gradually stepwise narrowing are the same as in Example 1.

Here, it is generally known that when the filament temperature _TF reaches 70% of the steady fluoroscopic state, a fluoroscopic image substantially inferior to the steady fluoroscopic state is obtained. Therefore, it is desirable to switch the pulse width of the pulse tube voltage V _{T to} the pulse width of the steady fluoroscopic state when the filament temperature _TF reaches 70% to 100% of the normal fluoroscopic state.

  Eventually, in the X-ray apparatus according to Examples 2 and 3 as well, the X-ray pulse width in a predetermined period from the start of fluoroscopy is controlled to be wider than the normal fluoroscopy state, and thus the X-ray dose is insufficient immediately after the start of fluoroscopy. Therefore, a suitable fluoroscopic image can be obtained stably immediately after the start of fluoroscopy.

  Further, in Examples 2 and 3, the actual tube current or the actual filament temperature is detected, and the pulse width is switched according to the result. Therefore, even when the degree of thermal inertia of the filament changes due to variations in the filament, etc., the pulse width of the pulse tube voltage can be switched according to the situation, so the X-ray pulse width can be controlled more optimally. can do.

Note that the timer 23 of the first embodiment can be added to the X-ray apparatus according to the second and third embodiments. In this configuration, for example, in the first fluoroscopy, the tube current _IF or the filament temperature _TF is detected in real time by the current sensor 24 or the temperature sensor 25, and the pulse width is switched based thereon. At this time, the timer 23 measures and stores the time from when the fluoroscopic start command is input until the pulse width is switched. In the second and subsequent fluoroscopy, the pulse width is switched based on the time stored in the timer 23 without referring to the actual filament temperature _TF or the like.

  Thus, by performing simple control using only the timer 23, it is possible to perform optimal control with the same pulse width as that using the current sensor 24 or the temperature sensor 25 in the second and subsequent fluoroscopy. .

1 is a block diagram of an X-ray apparatus according to Embodiment 1. FIG. It is an operation | movement waveform of the X-ray apparatus which concerns on Example 1, Comprising: (A)-(E) is an operation | movement waveform of a filament current, a filament voltage, a pulsed tube voltage, a tube current, and an X-ray dose, respectively. 3 is a block diagram of an X-ray apparatus according to Embodiment 2. FIG. It is an operation | movement waveform of the X-ray apparatus which concerns on Example 2, Comprising: (A)-(E) is an operation | movement waveform of a filament current, a filament voltage, a pulsed tube voltage, a tube current, and an X-ray dose, respectively. 6 is a block diagram of an X-ray apparatus according to Embodiment 3. FIG. It is an operation | movement waveform of the X-ray apparatus which concerns on Example 3, Comprising: (A)-(E) is an operation | movement waveform of a filament current, a filament voltage, a pulsed tube voltage, a tube current, and X dose, respectively. It is a block diagram of the conventional X-ray apparatus. It is an operation | movement waveform of the conventional X-ray apparatus, Comprising: (A)-(E) are the operation waveforms of a filament current, a filament voltage, a pulsed tube voltage, a tube current, and an X-ray dose, respectively. It is an operation | movement waveform of another conventional X-ray apparatus, Comprising: (A)-(E) is an operation | movement waveform of a filament current, a filament voltage, a pulsed tube voltage, a tube current, and an X-ray dose, respectively.

Explanation of symbols

1 X-ray apparatus 2 Subject 3 Table 4 I.
5 Camera 6 Image processing unit 7 Monitor 8 Input unit 9 Control unit 10 X-ray tube 11 Target 12 Filament 20 X-ray tube control unit 21 Tube voltage control unit 22 Filament heating unit 23 Timer 24 Current sensor 25 Temperature sensor

Claims (6)

An X-ray tube control unit having a tube voltage control unit that outputs a pulsed tube voltage and whose pulse width can be switched, and a filament heating unit that heats the filament by supplying a predetermined filament current, starts fluoroscopy When the command is input, the tube voltage control unit starts to output the pulsed tube voltage, and the filament heating unit increases the filament current to heat the filament, and the thermoelectrons emitted from the filament are An X-ray apparatus that performs fluoroscopy of a subject with X-rays generated by colliding with a target,
The tube voltage control unit sets the pulse width of the pulsed tube voltage to a pulse width in a steady fluoroscopic state for a predetermined period from when the command is input until the temperature of the filament reaches a temperature in a steady fluoroscopic state. An X-ray apparatus characterized by switching so as to become wider.   2. The X-ray apparatus according to claim 1, wherein the predetermined period is a period from when the command is input until the tube current reaches 70% to 100% of a normal fluoroscopic state. .   2. The X according to claim 1, wherein the predetermined period is a period from when the command is input until the temperature of the filament reaches 70% to 100% of a normal fluoroscopic state. Wire device.   The time at which the predetermined period ends is measured and stored in advance, and the pulse width of the pulsed tube voltage is switched to a pulse width in a steady fluoroscopic state when the time is reached. The X-ray apparatus as described in.   The X-ray apparatus according to claim 1, wherein the predetermined period is determined and stored in advance by observing a fluoroscopic image obtained by preliminary fluoroscopic imaging performed before the main fluoroscopy.   2. The X-ray apparatus according to claim 1, wherein the pulse width is switched so as to be gradually reduced during the predetermined period.

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