JP5845000B2 - Radiographic imaging method and apparatus - Google Patents

Description

  The present invention captures radiation images of a plurality of frames by continuously irradiating a living body into which a contrast medium is injected or a living body including an artificial object, and based on a detection signal of radiation transmitted through the living body. The present invention relates to a radiographic imaging method and apparatus for controlling the radiation dose in imaging of each frame.

  Conventionally, a patient's fluoroscopic image is obtained by continuously irradiating a patient with a radiation irradiation range and taking a plurality of frames of radiation images, and sequentially displaying the taken plurality of frames of radiation images. A radiographic imaging apparatus that displays (moving image) has been proposed.

  In addition to the above-described method of capturing and displaying a fluoroscopic image while fixing the radiation range to the patient, the radiation is continuously performed while moving the radiation range relative to the patient. A radiographic imaging apparatus has also been proposed that displays a plurality of frames of radiographic images captured by irradiation of the radiation as fluoroscopic images.

  In the apparatus that captures a plurality of frames of radiographic images by continuous irradiation as described above, for example, an AEC (Automatic) using a phototimer or the like so that the density of the radiographic images of each frame is constant. Exposure control) is performed (for example, Patent Document 1).

  In Patent Document 2, it is proposed to determine the radiation dose in the radiographing of the next frame based on the image signal of the previous frame so that the density of the radiographic image of each frame is constant. .

Japanese Patent Laid-Open No. 3-81999 JP 2010-273434 A

  Here, when taking a fluoroscopic image as described above, for example, injecting a contrast agent into a blood vessel and taking a contrast agent image of the blood vessel, or fluoroscopy of a patient in which an artificial object such as an artificial bone is embedded It is conceivable to take an image. In such a case, too, the phototimer or radiation image detection is performed when the AEC using the phototimer as described above or the radiation dose control based on the image signal of the previous frame is performed. Since the radiation is absorbed by the above-mentioned contrast agent or artificial object before the radiation reaches the vessel, the radiation dose is based on the detection signal reflecting the absorption of the radiation by the contrast agent or artificial object. However, there is a problem that the density of the radiographic image varies depending on the presence / absence or amount of a contrast agent or an artifact.

  Also, for example, when a contrast medium is injected in fluoroscopic imaging, the contrast medium flows through the patient's blood vessels and the like without staying in one place, so that the contrast medium is applied to all frames by fluoroscopic imaging. Therefore, it is necessary to set an appropriate dose of radiation throughout the entire fluoroscopic image taking into consideration this point.

  Similarly, when a fluoroscopic image is taken while moving the radiation irradiation range for a patient in which the artificial object is embedded, the image of the artificial object is reflected in all the frames obtained by photographing the fluoroscopic image. However, since the artifact is reflected in only a part of the frame, it is necessary to set an appropriate radiation dose throughout the fluoroscopic image taking into consideration this point.

  In view of the above circumstances, the present invention can set an appropriate dose of radiation throughout the entire series of imaging even when continuously imaging a living body including a living body into which a contrast medium is injected or an artificial object. Another object of the present invention is to provide a radiographic image capturing method and apparatus capable of capturing a radiographic image that is easy to check while suppressing density changes.

  The radiographic imaging device of the present invention includes a radiation source for continuously irradiating a living body into which a contrast agent is injected, and each frame detected by a radiographic image detector by radiography by continuous radiation irradiation. A radiation image acquisition unit that acquires a radiation image signal of the radiograph, and a radiation image signal for each frame acquired by the radiation image acquisition unit or a detection signal output from a radiation detector that detects radiation transmitted through the living body In a radiographic imaging apparatus including a radiation source control unit that controls a dose of radiation irradiated by a source, a frame including an image signal representing an image of a contrast agent is included in a radiographic image signal for each frame. A contrast agent frame specifying unit that specifies the agent frame, and the radiation source control unit emits radiation while the contrast agent frame is being captured. Characterized in that it is intended to maintain a constant dose of radiation irradiated by the source.

  In the radiographic imaging device of the present invention, the radiation source control unit is configured to capture the radiation dose while the contrast medium frame is being imaged, and a predetermined frame before the contrast medium frame is imaged. It can be assumed that the dose of radiation at the time.

  Further, the radiation source control unit can set the radiation dose while the contrast medium frame is captured as the radiation dose when the frame immediately before the contrast medium frame is captured.

  Further, the contrast agent frame specifying unit can specify the contrast agent frame based on the injection start timing and injection end timing of the contrast agent from the contrast agent injection device that injects the contrast agent into the living body.

  Further, the contrast agent frame specifying unit specifies a contrast agent frame based on difference information based on a radiographic image signal between predetermined frames among a plurality of radiographic image signals detected by continuous radiography. I can do it.

  Further, the contrast agent frame specifying unit acquires radiation dose information output from a radiation dose detection unit provided between the radiation source and the subject, and is detected by continuous radiography with the acquired dose information. The contrast agent frame can be specified based on the radiographic image signals of a plurality of frames.

  The radiographic imaging device of the present invention includes a radiation source that continuously irradiates radiation while relatively moving a radiation irradiation range with respect to a living body including an artifact, and radiography by continuous radiation irradiation. From a radiation image acquisition unit that acquires a radiation image signal for each frame detected by the radiation image detector, and a radiation image signal for each frame acquired by the radiation image acquisition unit or a radiation detector that detects radiation transmitted through a living body In a radiographic imaging apparatus including a radiation source control unit that controls a dose of radiation emitted from a radiation source based on an output detection signal, an image of an artifact is represented in a radiographic image signal for each frame. An artificial object frame specifying unit that specifies a frame including an image signal as an artificial object frame is provided. While the object frame is photographed, characterized in that the radiation source is intended to maintain a constant dose of radiation irradiated.

  In the radiographic imaging device of the present invention, the radiation source control unit is configured to capture the radiation dose while the artifact frame is being imaged, and a predetermined frame before the artifact frame is imaged. It can be assumed that the dose of radiation at the time.

  Further, the radiation source control unit can set the radiation dose while the artifact frame is captured as the radiation dose when the frame immediately before the artifact frame is captured.

  Further, the artifact frame specifying unit can specify the artifact frame based on the radiation dose information detected by the radiation dose detecting unit provided between the living body and the radiation image detector.

  The radiographic imaging method of the present invention acquires a radiographic image signal for each frame detected by a radiographic image detector by radiography by continuous irradiation of radiation to a living body into which a contrast agent is injected, and the acquired frame In a radiographic image capturing method for controlling a radiation dose based on a radiographic image signal for each frame or a detection signal output from a radiation detector that detects radiation transmitted through a living body, a contrast agent among radiographic image signals for each frame A frame including an image signal representing the image is identified as a contrast medium frame, and the dose of radiation is maintained constant while the contrast medium frame is captured.

  The radiographic image capturing method of the present invention provides a radiographic image detector for each frame detected by continuously radiographing a human body by moving a radiation irradiation range relative to a living body including an artifact. In a radiographic image capturing method for controlling a radiation dose based on a radiographic image signal acquired and a radiographic image signal for each acquired frame or a detection signal output from a radiation detector that detects radiation transmitted through a living body, Among the radiation image signals for each frame, the frame containing the image signal representing the image of the artifact is specified as the artifact frame, and the radiation dose is kept constant while the artifact frame is being photographed. It is characterized by that.

  According to the radiographic imaging method and apparatus of the present invention, a radiological image signal for each frame detected by a radiographic image detector is obtained by radiography by continuous irradiation of radiation to a living body into which a contrast agent is injected. In the case of controlling the radiation dose based on the acquired radiographic image signal for each frame or the detection signal output from the radiation detector that detects the radiation that has passed through the living body, the contrast agent among the radiographic image signals for each frame The frame containing the image signal representing the image of the image is specified as the contrast agent frame, and the dose of radiation is kept constant while the contrast agent frame is being shot. It is possible to set an appropriate radiation dose, and it is possible to take a radiation image that is easy to confirm while suppressing a change in density.

  Further, in the radiographic image capturing method and apparatus of the present invention, the radiation dose while the contrast medium frame is captured is the radiation dose when the predetermined frame is captured before the contrast medium frame is captured. In this case, it is possible to prevent the radiation dose from being set to a value larger than the original value due to the absorption of the radiation by the contrast agent, thereby solving the concern that the exposure dose of the patient increases.

  Further, when the radiation dose during the imaging of the contrast medium frame is the radiation dose when the frame immediately before the contrast medium frame is imaged, there is a concern that the exposure dose of the patient as described above increases. In addition, the density fluctuation of the radiographic image can be further suppressed, and a radiographic image that is easier to confirm can be taken.

  In addition, when the contrast agent frame is specified based on the injection start timing and the injection end timing of the contrast agent from the contrast agent injection device that injects the contrast agent into the living body, the real time is realized by a simple hardware configuration. The contrast medium frame can be specified, and the radiation dose can also be controlled in real time.

  Further, a contrast agent frame may be identified based on difference information based on a radiographic image signal between predetermined frames among a plurality of radiographic image signals detected by continuous radiography, and The radiation dose information output from the radiation dose detection unit provided between the subject and the subject is acquired, and based on the acquired dose information and the radiation image signals of a plurality of frames detected by continuous radiography. When the contrast agent frame is specified, the contrast agent frame can be specified by a simple calculation and configuration.

  According to the radiographic image capturing method and apparatus of the present invention, a radiographic image detector detects a human body continuously by radiographically moving a radiation range relative to a living body including an artifact. In the case of acquiring the radiation image signal for each frame and controlling the radiation dose based on the acquired radiation image signal for each frame or the detection signal output from the radiation detector that detects the radiation transmitted through the living body, Among the radiation image signals for each frame, the frame containing the image signal representing the image of the artifact is specified as the artifact frame, and the radiation dose is kept constant while the artifact frame is being photographed. As a result, it was possible to set an appropriate radiation dose throughout the entire series of radiographs, and to capture radiological images that were easy to check while suppressing changes in density. It can be.

  In the radiographic image capturing method and apparatus of the present invention, the radiation dose while the artifact frame is captured is the radiation dose when the predetermined frame is captured before the artifact frame is captured. In such a case, it is possible to prevent the radiation dose from being set to a value larger than the original value due to the absorption of the radiation by the artifact, thereby solving the concern that the exposure dose of the patient increases.

  In addition, when the radiation dose while the artifact frame is being taken is the radiation dose when the frame immediately before the artifact frame is taken, there is a concern that the patient exposure as described above may increase. In addition, the density fluctuation of the radiographic image can be further suppressed, and a radiographic image that is easier to confirm can be taken.

  In addition, when the artificial object frame is specified based on the radiation dose information detected by the radiation dose detection unit provided between the living body and the radiation image detector, a simple hardware configuration Can identify the artifact frame in real time and can also control the radiation dose in real time.

The block diagram which shows schematic structure of the whole radiographic imaging system using 1st Embodiment of the radiation exposure amount acquisition apparatus of this invention. The figure which shows schematic structure of the radiographic imaging apparatus in the radiographic imaging system of 1st Embodiment. The figure which shows an example of the specific structure of a contrast agent injection apparatus The flowchart for demonstrating the flow of imaging | photography and a display of a fluoroscopic image in the radiographic imaging system using 1st Embodiment of the radiation exposure amount acquisition apparatus of this invention. The figure which shows the timing chart which shows the relationship between the irradiation timing of a radiation, the charge accumulation timing in a radiographic image detector, and the detection signal of a contrast agent The flowchart for demonstrating the control method of the radiation dose of each flame | frame in the radiographic imaging apparatus of 1st Embodiment. The block diagram which shows schematic structure of the modification of the radiographic imaging system using 1st Embodiment of the radiation exposure amount acquisition apparatus of this invention. The figure for demonstrating the method to identify a contrast agent flame | frame based on the difference information of the density histogram between predetermined frames The figure for demonstrating an example of a contrast agent injection | pouring start frame and a contrast agent injection | pouring end frame The figure for demonstrating the method of specifying a contrast agent flame | frame based on the difference information of the corresponding pixel value between predetermined frames The figure for demonstrating the radiation dose detection part provided between the radiation source and the patient The figure for demonstrating the method to identify a contrast agent flame | frame based on the time fluctuation of the radiation dose detected by the radiation dose detection part, and the time fluctuation of the radiographic image signal detected by the radiographic image detector. The block diagram which shows schematic structure of the whole radiographic imaging system using 2nd Embodiment of the radiation exposure amount acquisition apparatus of this invention. The figure which shows schematic structure of the radiographic imaging apparatus in the radiographic imaging system of 2nd Embodiment. The figure which shows an example of the radiographic image detector provided with the 1st and 2nd dosimetry sensor The flowchart for demonstrating the flow of imaging | photography and a display of a fluoroscopic image in the radiographic imaging system using 2nd Embodiment of the radiation exposure amount acquisition apparatus of this invention. The figure which shows an example of the time fluctuation | variation of the radiation dose detected by the 1st and 2nd dosimetry sensor The flowchart for demonstrating the control method of the radiation dose of each flame | frame in the radiographic imaging apparatus of 2nd Embodiment.

  Hereinafter, an embodiment of a radiographic imaging system using the first exemplary embodiment of the radiographic imaging apparatus of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of the entire radiographic image capturing system of the present embodiment.

  As shown in FIG. 1, the radiographic image capturing system of the present embodiment includes a radiographic image capturing device 10 that captures a fluoroscopic image (moving image) of a patient, and a radiographic image that displays a fluoroscopic image captured by the radiographic image capturing device 10. A display device 20, a contrast medium injection device 30 for injecting a contrast medium into a patient's blood vessels, lymph vessels, and the like, and a system control device 40 for controlling the entire radiographic imaging system are provided.

  As shown in FIG. 1, the radiographic image capturing apparatus 10 includes an X-ray tube, a diaphragm, and the like, a radiation source 11 that irradiates the patient with radiation emitted from the X-ray tube and transmitted through the diaphragm, and transmits through the patient. The radiation image detector 12 that detects the radiation and outputs a radiation image signal representing the radiation image of the patient, the radiation image storage unit 13 that stores the radiation image signal output from the radiation image detector 12, and the radiographic imaging Contrast agent frame that identifies a frame including an image signal of a contrast agent image as a contrast agent frame among radiographic image signals of each frame stored in the radiographic image storage unit 13 and a control unit 14 that controls the entire apparatus 10 And a specifying unit 15.

  More specifically, the radiographic imaging device 10 of the present embodiment is configured as shown in FIG. 2, and a patient H into which a contrast medium is injected is placed on the imaging table 16, and the patient H is Imaging a contrast agent flowing in a blood vessel or the like in the patient H as a fluoroscopic image in a state where the radiation source 11 and the radiation image detector 12 provided opposite to the radiation source 11 are fixed at predetermined positions. It is.

  The radiographic image detector 12 can repeatedly perform recording and reading of radiographic images, and so-called direct recording, in which radiographic images are recorded by generating and accumulating charges by directly receiving radiation. A radiation image detector of the type may be used, or so-called indirect radiation image detection, in which radiation images are recorded by once converting the radiation into visible light, and converting the visible light into electric charge and storing it. A vessel may be used. As a method for reading out a radiographic image recorded by accumulating charges as described above, a so-called TFT in which a radiographic image signal is read out by turning on and off a TFT (thin film transistor) switch. A read-out type or a so-called optical read-out type in which a radiation image signal is read out by irradiating read light can be used, but not limited to this, other types may be used.

  The radiographic image capturing apparatus 10 of the present embodiment captures a fluoroscopic image (moving image) of a patient into which a contrast medium is injected by the contrast medium injecting apparatus 30 as described above. The radiation source 11 and the radiation image detector 12 are controlled so that a fluoroscopic image is taken. Specifically, the control unit 14 irradiates radiation from the radiation source 11 at a predetermined frame rate, and controls the radiation image detector 12 so that the radiation image is recorded and read out by the radiation irradiation. It is. Then, the radiation image signal for each frame output from the radiation image detector 12 is sequentially stored in the radiation image storage unit 13. Furthermore, when the control unit 14 of this embodiment stores the radiographic image signal for each frame in the radiographic image storage unit 13, information on whether or not the radiographic image signal of each frame is the radiographic image signal of the contrast agent frame. Will be described later in detail.

  In addition, the control unit 14 includes a radiation source control unit 14 a that controls an irradiation dose of radiation irradiated toward the patient by the radiation source 11. The radiation source control unit 14a controls the radiation dose at the time of photographing each frame based on the radiation image signal of each frame read from the radiation image storage unit 13. Further, the radiation source control unit 14a further determines that the radiographic image signal read from the radiographic image storage unit 13 is the radiographic image signal of the contrast agent frame in the contrast agent frame specifying unit 15, that is, During the imaging of the contrast medium frame, the radiation dose of the radiation irradiated by the radiation source 11 is kept constant. The operation of the radiation source control unit 14a will be described in detail later.

  The contrast agent frame specifying unit 15 specifies the contrast agent frame by determining whether or not information indicating that it is a contrast agent frame is added to the radiographic image signal read from the radiographic image storage unit 13. The specific information is output to the radiation source control unit 14a.

  The configuration of the radiographic imaging device 10 is not limited to the configuration in which the patient is imaged in the lying position as shown in FIG. 2, and the configuration in which the patient is imaged in the standing position may be used. It may be configured to be able to shoot in both the state and the prone state.

  The radiographic image display device 20 generates a display control signal by performing predetermined processing on the radiographic image signal for each frame read from the radiographic image storage unit 13 of the radiographic image capturing device 10, and generates the display control signal. Based on this, a fluoroscopic image of the patient is displayed on the monitor.

  The contrast agent injection device 30 automatically injects a contrast agent into a patient's blood vessel or the like based on an instruction input by a user or based on a preset contrast agent injection start timing. Specifically, for example, a contrast medium injecting unit 31 configured to inject a contrast medium into a blood vessel of a patient, an injection driving unit 32 that drives a contrast medium injecting operation of the contrast medium injecting unit 31, and an injection A control unit 33 that controls the operation of the drive unit 32 and the like, and a contrast agent injection detection sensor unit 34 that detects whether or not the contrast agent is being injected into the blood vessel of the patient from the contrast agent injection device 30. Yes.

  As the contrast medium injecting section 31, for example, an apparatus provided with a syringe 31a as shown in FIG. 3 and a piston 31b provided in the syringe 10 can be used.

  The injection drive unit 32 includes a plunger 32a connected to the piston 31b, a ball screw 32b connected to the plunger 32a, a motor 32c for rotating the ball screw 32b, and a potentiometer 32d for detecting the position of the plunger 32a. And.

  When a contrast agent injection instruction is input at the input unit 60 described later, a control signal is output from the system control device 60 to the control unit 33 of the contrast agent injection device 30, and the control unit 33 responds to the input control signal. Driving voltage is output to the motor 32c. The rotation of the motor 32c is transmitted to the ball screw 32b, and the rotation of the ball screw 32b moves the plunger 32a in the longitudinal direction of the syringe 31a, thereby moving the piston 31b. Then, a potentiometer 32d outputs a plunger position signal to the control unit 33, and the control unit 33 controls the rotation of the motor 32c in accordance with the fed back signal.

  The contrast agent injection detection sensor unit 34 detects that the contrast agent is discharged from the contrast agent injection unit 31. Specifically, for example, when an input of a contrast medium injection start instruction is accepted as ON / OFF information of a switch at the input unit 60, it is detected that the contrast medium is discharged by detecting the ON information. At the same time, it is detected that the contrast medium is not discharged by detecting the OFF information.

  In addition, when controlling so that the contrast medium is discharged while the switch is ON and the contrast medium is not discharged while the switch is OFF, the timing at which the switch is switched from OFF to ON is contrasted. It may be detected as the ejection start timing of the agent, detected as the contrast medium is being ejected while the switch is ON, and detected as the contrast agent ejection end timing when the switch is switched from ON to OFF.

  The contrast medium injection detection sensor 34 detects the driving power input to the motor 32c, and detects that the driving power is above a certain value, thereby detecting that the contrast medium is being discharged. Also good.

  Further, the contrast agent injection detection sensor unit 34 calculates the time change of the plunger position signal output from the potentiometer 32d, and detects that the time change amount of the position of the plunger 32a is equal to or greater than a certain value. You may make it detect that it is discharging.

  The contrast agent injection detection sensor unit 34 outputs the contrast agent detection signal to the control unit 14 of the radiographic image capturing apparatus 10.

  The system control device 40 outputs control signals to the radiographic image capturing device 10, the radiographic image display device 20, and the contrast medium injecting device 30 described above to control these operations, and input / output signals between these devices. The control is performed.

  Further, the system control apparatus 40 is provided with an input unit 50. The input unit 50 receives a predetermined instruction input by a user, and input such as imaging conditions and patient ID information. In addition, the input unit 50 includes a photographing switch 51. The imaging switch 51 receives an input of a radiation imaging start instruction and an imaging continuation instruction by the user. When the imaging switch 51 is pressed (ON) by the user, an imaging start instruction is input and imaging is performed. By continuing to hold down the switch 51, an instruction to continue shooting is input. Then, when the photographing switch 51 is released (OFF), a photographing end instruction is input. The input information received by the input unit 50 is output to each device by the system control device 40 as necessary.

  Next, the operation of the radiographic image capturing system of the present embodiment will be described with reference to the flowchart shown in FIG. Here, first, the flow of radiographic image capturing and display in the radiographic image capturing system of the present embodiment will be described.

  First, a patient as a subject is placed on an imaging stand or the like provided in the radiographic imaging device 10, and the patient is positioned (S10).

  Next, ID information and imaging conditions of the patient to be imaged are input by the user using the input unit 50 and set in the control unit 14 (S12). In this embodiment, it is assumed that information on an imaging region or imaging technique, a frame rate for imaging a fluoroscopic image, and the like are input as imaging conditions. The radiation source control unit 14a of the control unit 14 is preliminarily set with a table in which the information on the imaging region or the imaging technique and the radiation irradiation conditions are associated with each other. The radiation source control unit 14a receives the input imaging. An initial value of the radiation irradiation condition is acquired and set based on the information on the part or the imaging technique. Here, the radiation irradiation condition means a tube voltage, a tube current, an irradiation frequency, a duty of a radiation irradiation period and a non-irradiation period in one frame photographing, and the like.

  Next, the imaging switch 51 is pressed (ON) by the user, and an instruction to start imaging of the fluoroscopic image of the patient is input. In response to this input, the radiographic imaging device 10 is instructed to transmit the fluoroscopic image to the radiographic imaging device 10. A control signal is output so as to perform imaging, and the radiographic image capturing apparatus 10 starts capturing a fluoroscopic image in accordance with the input control signal (S14).

  Specifically, the X-ray tube of the radiation source 11 is controlled based on the input imaging conditions, and a predetermined dose of radiation is intermittently emitted toward the patient at a predetermined frame rate.

  The radiation that has passed through the patient is applied to the radiation image detector 12, photoelectrically converted by the radiation image detector 12, and stored as a charge signal.

  Each time the irradiation of the radiation of each frame is completed, the charge signal accumulated in the radiation image detector 12 is read by the control unit 14 and converted into a digital signal by an A / D converter (not shown). Thereafter, it is stored in the radiation image storage unit 13.

  FIG. 5 is a timing chart showing radiation irradiation timing from the X-ray tube of the radiation source 11 and charge accumulation timing in the radiation image detector 12. It should be noted that the period during which the radiographic image detector 12 is not accumulating charges (accumulation OFF period) is a period during which a charge signal is read from the radiographic image detector 12.

  As described above, the radiation irradiation by the X-ray tube and the recording and reading of the radiation image in the radiation image detector 12 are repeatedly performed at a predetermined frame rate, whereby the radiation image storage unit 13 stores the radiation for each frame. Image signals are stored sequentially.

  In addition, the dose control of the radiation irradiated by the radiation source 11 in the radiographing of each frame described above will be described in detail later.

  The radiographic image signals for each frame stored in the radiographic image storage unit 13 are sequentially read out and output to the radiographic image display device 20. The radiographic image display device 20 sequentially generates a display control signal based on the input radiographic image signal for each frame, and sequentially outputs the display control signal to the monitor to display the patient's fluoroscopic image on the monitor as a moving image ( S16).

  Here, when the user wants to observe a contrast medium image such as a blood vessel while taking and displaying a fluoroscopic image as described above, a contrast medium injection instruction is issued using the input unit 50. Input (S18).

  When a contrast medium injection instruction is input at the input unit 50, a control signal is output from the system control device 40 to the contrast medium injection device 30. The contrast medium injection device 30 starts injection of a contrast medium based on the input control signal. Specifically, the contrast medium injection section 31 is driven by the injection drive section 32 and a predetermined amount of contrast medium is discharged from the contrast medium injection section 31.

  At this time, the contrast agent injection detection sensor 34 provided in the contrast agent injection device 30 detects that the contrast agent has been ejected, and the detection signal is output to the control unit 14 of the radiographic imaging device 10 ( S20). When the contrast medium detection signal is input, the control unit 14 of the radiographic image capturing apparatus 10 receives an image of the contrast medium with respect to the radiographic image signal of the frame captured while the contrast medium detection signal is input. Is added as header information (hereinafter referred to as contrast medium frame information), and the radiographic image signal is stored in the radiographic image storage unit 13 together with the contrast medium frame information (S22). More specifically, for example, when a contrast medium detection signal is input to the radiographic image capturing apparatus 10 at the timing shown in FIG. 5, the radiographic images of the frames F1 and F2 captured during contrast medium injection. Contrast medium frame information is added to the signal and stored in the radiation image storage unit 13.

  And the radiographic image signal image | photographed during contrast agent injection | pouring is also read from the radiographic image memory | storage part 13, and is sequentially output to the radiographic image display apparatus 20, and the radiographic image display apparatus 20 is based on the input radiographic image signal. Display control signals are sequentially generated, and a radiographic image including a contrast agent image is displayed on the monitor based on the display control signals.

  Next, after the discharge of a predetermined amount of contrast agent from the contrast agent injection device 30 is completed and no contrast agent detection signal is detected by the contrast agent injection detection sensor unit 34, the contrast agent is detected with respect to the radiographic image signal that has been imaged The frame information is stored in the radiographic image storage unit 13 without being added, and the radiographic image signal for each frame is read from the radiographic image storage unit 13 in the same manner as described above, and a fluoroscopic image is displayed on the radiographic image display device 20. The

  Then, when the photographing switch 51 is released (OFF) by the user and an instruction to end fluoroscopic image capturing is input, the system control device 40 controls the radiographic image capturing device 10 to end the radiographic image capturing. The radiographic image capturing apparatus 10 ends the fluoroscopic image capturing in accordance with the input control signal (S26).

  The above is a flow of photographing and displaying a fluoroscopic image in the radiation image photographing system of the present embodiment.

  Next, control of the radiation dose in the radiographic imaging of each frame as described above will be described with reference to the flowchart shown in FIG. In addition, the irradiation dose here means the irradiation dose per unit time. In addition, the radiation dose in the radiography of each frame is assumed to be performed by changing the above-described radiation irradiation conditions by the radiation source control unit 14a.

  First, the radiation dose at the time of radiographic imaging of the first frame is set to the initial value input in S12 described above (S30).

  Then, at the time of imaging the first frame, the radiation dose of the initial value is emitted from the radiation source 11 under the control of the radiation source control unit 14a and irradiated to the patient (S32). The radiation that has passed through the patient is applied to the radiation image detector 12, is photoelectrically converted by the radiation image detector 12, and is stored as a charge signal (S34).

  As described above, when irradiation of one frame of radiation is completed (S36), the charge signal accumulated in the radiation image detector 12 is read out by the control unit 14 and stored as a radiation image signal in the radiation image storage unit 13 ( S38).

  Next, when the recording and reading of the one-frame radiographic image described above is completed, it is confirmed by the control unit 14 whether or not the imaging switch 51 has been pressed (ON) (S40).

  When the imaging switch 51 is pressed, whether or not one frame of the radiographic image signal stored in the radiographic image storage unit 13 as described above is the radiographic image signal of the contrast agent frame. Is confirmed by the radiation source controller 14a (S42).

  Specifically, one frame of the radiographic image signal stored in the radiographic image storage unit 13 is output to the contrast agent frame specifying unit 15, and the contrast agent frame specifying unit 15 performs the above-described operation on the input radiographic image signal. It is confirmed whether or not the contrast medium frame information is added. Then, when the contrast agent frame information is added to the radiographic image signal, the contrast agent frame specifying unit 15 determines that the radiographic image signal is a radiographic image signal of the contrast agent frame, and notifies that to the radiation source. Output to the controller 14a. On the other hand, when no contrast agent frame information is added to the radiographic image signal, the contrast agent frame specifying unit 15 determines that the radiographic image signal is a radiographic image signal other than the contrast agent frame, It outputs to the source control part 14a.

  Then, when it is input that the currently captured one-frame radiographic image signal is a radiographic image signal other than the contrast agent frame, the radiation source control unit 14a receives the currently captured one-frame radiographic image signal. Based on the above, the radiation dose to be used at the time of capturing the radiation image of the next frame is determined (S44). As the method for determining the radiation dose of the next frame based on the radiation image signal of the previous frame, the simplest method is to decrease the radiation dose as the size of the radiation image signal increases. Since more specific methods are already known, detailed description thereof is omitted.

  Then, at the time of capturing the radiation image of the next frame, the radiation source control unit 14a controls the radiation source 11 so that the radiation dose determined based on the radiation image signal of the previous frame is irradiated. . Then, S32 to S42 are repeated again.

  On the other hand, the radiation source control unit 14a changes the currently set radiation dose when it is input that the currently captured radiographic image signal of one frame is the radiographic image signal of the contrast agent frame. Keep it as it is. Then, S32 to S42 are repeated again.

  By controlling the radiation dose as described above, the radiation dose determined based on the radiographic image signal of the previous frame is from the start of fluoroscopic image capture until the contrast agent frame is imaged. It is set as the radiation dose in the radiographic image of the next frame, and while the contrast medium frame is being imaged, the radiation dose determined based on the radiographic image signal of the frame immediately before the contrast medium frame starts to be imaged An irradiation dose is set, and a constant radiation dose is maintained.

  In S40, when it is confirmed by the control unit 14 that the imaging switch 51 has been released (OFF), the radiation source control unit 14a stops the radiation irradiation from the radiation source 11, and the radiographic image is captured. Ends (S46).

  According to the radiographic imaging system of the first embodiment, a contrast medium frame is specified from a plurality of frames, and the dose of radiation is maintained constant while the contrast medium frame is captured. Therefore, an appropriate radiation dose can be set throughout the series of imaging, and a radiographic image with good image quality can be acquired.

  In the radiographic imaging system of the above-described embodiment, contrast medium frame information is added to the radiographic image signal of a frame captured while the contrast medium detection signal is detected by the contrast medium injection detection sensor unit 34. Thus, the contrast medium frame is specified, but the method of specifying the contrast medium frame is not limited to this. For example, as shown in FIG. 7, a contrast agent injection time acquisition unit 35 is provided instead of the contrast agent injection detection sensor unit 34, and the time when the contrast agent injection time acquisition unit 35 starts the injection of the contrast agent and the contrast agent And the time when the injection is completed.

  As the contrast medium injection start time and the contrast medium injection end time, for example, the time when the drive of the contrast medium injection unit 31 is started by the injection drive unit 32 and the time when the drive is completed may be acquired. You may make it acquire the timing with which the contrast agent injection | pouring start instruction | indication and the contrast agent injection | pouring completion instruction | indication were input using the input part 50 by the user.

  Then, the contrast agent injection start time and the contrast agent injection end time acquired by the contrast agent injection time acquisition unit 35, and the imaging time at which each frame is imaged by the radiographic image capturing device 10 (the radiographic image is captured in the radiographic image detector 12). (Recorded time) may be acquired by the contrast agent frame specifying unit 41, and a frame captured between the contrast agent injection start time and the contrast agent injection end time may be specified as the contrast agent frame.

  In the above description, the contrast agent frame information is added to the radiographic image signal of the frame taken after the contrast agent injection start timing in the contrast agent injection device 30, and the contrast agent frame is added based on the contrast agent frame information. However, the present invention is not limited to this. For example, in consideration of the time for which the contrast medium moves in the human body, the contrast medium starts from a frame after a predetermined number of frames have elapsed from the first frame to which the contrast medium frame information is added. It may be specified as a frame. Or you may make it add contrast agent flame | frame information with respect to the radiographic image signal after the frame after a predetermined number of frames progress from a contrast agent injection start timing.

  In the above description, the contrast medium frame is specified based on the signal output from the contrast medium injection device 30. However, the present invention is not limited to this. For example, in the contrast medium frame specifying unit 15, the radiation of the nth frame. The difference information between the image signal and the radiation image signal of the (n−1) th frame may be acquired, and the contrast agent frame may be specified based on the difference information.

  Specifically, for example, from the start of fluoroscopic image capture, as shown in FIG. 8, the density histogram of the radiographic image signal of the nth frame (n is an integer of 2 or more) and the radiographic image of the (n−1) th frame. A signal density histogram is sequentially calculated, and a subtraction histogram is calculated by sequentially subtracting the density histogram of the (n−1) th frame from the density histogram of the nth frame. As shown in FIG. 8, when a density value with a frequency exceeding a preset threshold value appears among the frequencies of the density values in the subtraction histogram, the nth frame is a contrast agent injection start frame. Identify. The density histogram shown in FIG. 8 is based on the premise that the image signal of the contrast agent image is blacker than the surroundings (the signal value is smaller than the surroundings). May be assumed to be white rather than the surroundings (the signal value is larger than the surroundings), in which case the subtraction histogram shown in FIG. 8 is inverted vertically.

  A frame from this contrast agent injection start frame until a contrast agent injection end frame to be described later appears is identified as a contrast agent frame. As for the frame during the injection of the contrast agent, the n-th frame and the (n + 1) -th frame are almost the same density histograms. Therefore, in the subtraction histogram of the n-th frame and the (n-1) -th frame, A density value with a frequency exceeding the set threshold does not appear.

  Then, after the contrast medium injection start frame is determined, in the subtraction histogram of the nth frame and the (n−1) th frame, if a density value with a frequency exceeding a preset threshold value appears again, It is assumed that the nth frame is a contrast agent injection end frame, and the frames after the contrast agent injection end frame are not contrast agent frames.

  That is, the contrast agent frame specifying unit 15 finally specifies the frames from the frame after the contrast agent injection start frame to the frame immediately before the contrast agent injection end frame as the contrast agent frame.

  FIG. 9 shows the contrast agent injection start frame f3 and the contrast agent injection end frame f9 specified by the specifying method as described above when the frames f1 to f10 are captured. In the example shown in FIG. 9, the frames f3 to f8 are specified as the contrast agent frames.

  In the above description, the subtraction histogram is obtained by subtracting the density histogram of the previous (n−1) frame from the density histogram of the nth frame, but the density histogram to be subtracted is not necessarily the first. (N-1) The density histogram of the frame may not be used. For example, the density histogram of any one of the frames that have already been determined not to be the contrast agent frame may be used. Or you may make it use the density | concentration histogram of the average value of arbitrary some frames of the some frames already determined not to be a contrast agent frame.

  Further, when the contrast agent frame is specified using the density histogram of the radiographic image signal as described above, for example, when the radiation dose irradiated by the radiation source 11 in a series of radiographic imaging changes, the density histogram Has an offset in the direction of the density axis, or is enlarged or reduced. Therefore, it is desirable to normalize the density histogram in the direction of the density axis. Note that the normalization method is almost the same as the technique of density adjustment between a plurality of images in the subtraction of a radiological image, and is a known method, and thus detailed description thereof is omitted.

  In the above description, the contrast agent injection start frame and the contrast agent injection end frame are specified using the density histogram of the radiographic image signal of each frame. However, the method for specifying these is not limited to this. Other methods may be used. Hereinafter, another method for specifying the contrast medium injection start frame and the contrast medium injection end frame will be described.

  First, as shown in FIG. 10, the pixel value at the pixel position (x, y) on the radiation image detector 12 of the radiation image signal of the nth frame is defined as QL (x, y, n), and the (n− When the pixel value of the pixel position (x, y) on the radiation image detector 12 of the radiation image signal of 1) is QL (x, y, n−1), all the pixels are calculated by calculating the following expression. Obtain D (x, y, n) for.

D (x, y, n) = QL (x, y, (n-1))-QL (x, y, n)
Then, D (x, y, n) is sequentially calculated for each frame, and the total number of pixels for which D (x, y, n) is greater than the first threshold a (a> 0) is the second. When the threshold value c is larger than the threshold c, the nth frame at that time is determined as the contrast agent injection start frame.

  Then, after determining the contrast agent injection start frame, the total number of pixels in which D (x, y, n) becomes smaller than the third threshold value b (b <0) becomes larger than the fourth threshold value d. In this case, the nth frame at that time is determined as a contrast agent injection end frame.

  The contrast agent injection start frame and the contrast agent injection end frame can also be specified by the method as described above. In the above determination method, it is assumed that the image signal of the contrast agent image is blacker than the surroundings (the signal value is smaller than the surroundings). It may be premised that the surroundings are whiter than the surroundings (the signal value is larger than the surroundings). In this case, the contrast medium injection start frame determination method and the contrast medium injection end frame determination method are reversed. It will be.

  As shown in FIG. 11, a radiation dose detection unit 17 is provided between the radiation source 11 and the patient H, and the radiation dose information and radiation output from the radiation dose detection unit 17 in the contrast medium frame identification unit 15. The contrast agent frame may be specified based on the radiographic image signal for each frame read from the image storage unit 13.

  Specifically, in parallel with the radiographic image capture and display as described above, the radiation dose emitted from the radiation source 11 is sequentially detected by the radiation dose detector 17, and the detected radiation dose is detected as a contrast agent. The frame specifying unit 15 acquires sequentially.

  Then, the contrast medium frame specifying unit 15 acquires the time variation of the input radiation dose, acquires the time variation of the radiation image signal for each frame sequentially read from the radiation image storage unit 13, and A contrast agent frame is identified based on two time variations.

  More specifically, the contrast agent frame specifying unit 15 acquires the time variation G (t) of the radiation dose as shown in FIG. 12 based on the input radiation dose, and for each input frame. Based on the radiographic image signal of E.E. I. (Exposure Index) is calculated, and E.P. I. Time fluctuation I. (T) is acquired.

  Here, the above-described E.I. I. Is an index of the dose of radiation that has passed through the patient and received by the radiation image detector 12.

  E. I. As for the calculation method, first, a predetermined calculation area is set in the radiation image of each frame. As the calculation area, for example, the entire area of the radiographic image, the area arbitrarily set by the user, the area defined based on the information on the imaging region, or the range of 10% of the image size from the center of the radiographic image. An area etc. can be adopted. Alternatively, for example, an area excluding a so-called blank area obtained based on a histogram of a radiographic image, an area of 90% of the total density width from the central density of the radiographic image, or the like can be employed. Or you may make it set a specific calculation area | region combining the conditions mentioned above.

  Next, the representative value V of the calculation area set above is calculated. As the representative value V, the density value itself of the radiation image, or a statistical feature value in which the average value of all density values, the median value, the mode value, or the trimmed average value is added to the density value itself, etc. Can do. Then, based on the representative value V, E.E. I. Is calculated.

E. I. = C ₀ × g (V)
g (V): inverse calibration function C ₀ : 100 · Gy (constant)
Note that g (V) is a function defined based on a radiographic image obtained with the quality of RQA5. The magnitude of the representative value V differs depending on the difference in sensitivity due to the difference in scintillators in the radiation image detector, the difference in the calculation region setting method or the calculation method of the representative value V described above, and g (V) is a function that normalizes the difference. In other words, if any radiation image detector type receives the same dose with the quality of RQA5, E.E. I. Will be almost the same value.

  Then, as shown in FIG. 12, the contrast agent frame specifying unit 15 obtains G (t) and E.E. I. The division value G (t) / E. I. The time variation of (t) is calculated. The contrast agent frame specifying unit 15 also acquires the detection timing of the radiation dose in the radiation dose detection unit 17 and the detection timing of the radiation image signal for each frame in the radiation image detector 12, and G (t ) And E. I. It is assumed that the time axes of (t) match.

  Then, the contrast agent frame specifying unit 15 uses G (t) / E. I. (T) is compared with a preset threshold value, and G (t) / E. I. When the value of (t) is equal to or greater than the threshold, the frame acquired at time t corresponding to the value is specified as a contrast agent frame.

  Next, an embodiment of a radiographic imaging system using the second embodiment of the radiographic imaging apparatus of the present invention will be described. FIG. 13 is a block diagram showing a schematic configuration of the entire radiographic image capturing system of the present embodiment.

  As shown in FIG. 13, the radiographic image capturing system of the second embodiment captures a fluoroscopic image (moving image) of a patient while relatively moving the radiation irradiation range and the radiographic image detector with respect to the patient. A radiographic image capturing device 60, a radiographic image display device 20 that displays a fluoroscopic image captured by the radiographic image capturing device 10, and a system control device 40 that controls the entire radiographic image capturing system are provided.

  As shown in FIG. 13, the radiographic image capturing device 60 is provided between the radiation source 11, the radiographic image detector 12, the radiographic image storage unit 13, the control unit 14, and the patient and the radiographic image detector 12. Radiation of a frame including an image signal of an image of a man-made object among the radiation image signals for each frame read out from the radiation image storage unit 13 and the radiation dose detection unit 18 that detects the radiation dose transmitted through the patient And an artifact frame specifying unit 19 that specifies an image signal as an artifact frame.

  And the radiographic imaging device 60 of this embodiment is comprised as shown in FIG. 14, The patient H in which the artificial object I (for example, artificial bone) was embedded in the body is installed on the imaging stand 16, The The patient is taken a fluoroscopic image while moving the radiation source 11 and the radiation image detector 12 in the direction of the arrow in FIG.

  The radiation source 11, the radiation image detector 12, and the radiation image storage unit 13 are the same as those in the first embodiment.

  The radiographic image capturing apparatus 60 according to the present embodiment captures a fluoroscopic image (moving image) of a patient in which an artifact is embedded as described above, and the control unit 14 performs the radiographic image capturing. As shown, the radiation source 11 and the radiation image detector 12 are controlled. Specifically, the control unit 14 irradiates radiation from the radiation source 11 at a predetermined frame rate, and controls the radiation image detector 12 so that the radiation image is recorded and read out by the radiation irradiation. It is. Then, the radiation image signal for each frame output from the radiation image detector 12 is sequentially stored in the radiation image storage unit 13.

  The radiation dose detector 18 is provided between the patient and the radiation image detector 12 as described above. In this embodiment, as shown in FIGS. 14 and 15, the radiation image detector 18 is provided. The first dose measurement sensor 18a and the second dose measurement sensor 18b provided on the 12 radiation irradiation surfaces. FIG. 15 is a view of the radiological image detector 12 of FIG. 14 as viewed from above.

  As shown in FIG. 15, the first dose measurement sensor 18 a and the second dose measurement sensor 18 b are provided along sides facing each other in the moving direction of the radiation image detector 12. In the present embodiment, as described above, the dose measurement sensor is provided along only the side corresponding to the moving direction, but it is more preferable to provide the dose measurement sensor along the four sides of the radiation image detector 12.

  As the first and second dosimetry sensors 18a and 18b, it is desirable to use a thin sensor that hardly absorbs radiation, for example, a sensor made of an organic photoelectric conversion material (OPC).

  In the present embodiment, the first and second dose measuring sensors 18a and 18b are provided on the radiation image detector 12. However, the present invention is not limited to this, and between the patient and the radiation image detector 12. If it exists, you may make it install in another predetermined position.

  The radiation dose detection unit 18 sequentially outputs the detected radiation dose information to the artifact frame specifying unit 19 in parallel with the photographing of the fluoroscopic image.

  The artifact frame specifying unit 19 is acquired by photographing a fluoroscopic image based on the radiation dose information output from the first dose measurement sensor 18a and the second dose measurement sensor 18b constituting the radiation dose detection unit 18. The artifact frame is specified from the plurality of frames.

  Further, the artifact frame specifying unit 19 of the present embodiment adds information indicating the artifact frame (hereinafter referred to as artifact frame information) to the radiation image signal of the frame determined to be the artifact frame. To remember. The operation of the artifact frame specifying unit 19 will be described in detail later.

  The radiographic image display device 20, the system control device 40, and the input unit 50 are the same as those in the first embodiment.

  Next, the operation of the radiographic image capturing system of the present embodiment will be described with reference to the flowchart shown in FIG. Here, first, the flow of radiographic image capturing and display in the radiographic image capturing system of the present embodiment will be described.

  First, a patient is installed on the imaging stand 16 provided in the radiographic imaging apparatus 10, and a patient is positioned (S50).

  Next, the user inputs ID information of a patient to be imaged and predetermined imaging conditions using the input unit 50, and the imaging conditions are set in the control unit 14 of the radiographic imaging apparatus 10 (S52). The shooting conditions are the same as those in the first embodiment.

  Next, the imaging switch 51 is pressed (ON) by the user, and an instruction to start imaging of the fluoroscopic image of the patient is input. In response to this input, the radiographic imaging device 10 is instructed to transmit the fluoroscopic image to the radiographic imaging device 10. A control signal is output to perform imaging, and the radiographic image capturing apparatus 10 starts capturing a fluoroscopic image according to the input control signal (S54).

  Specifically, the radiation source 11 and the radiation image detector 12 move relative to the patient in accordance with the input control signal, and the X-ray tube of the radiation source 11 is controlled based on the input imaging conditions. Then, a predetermined dose of radiation is intermittently emitted toward the patient at a predetermined frame rate.

  The radiation that has passed through the patient is applied to the radiation image detector 12, photoelectrically converted by the radiation image detector 12, and stored as a charge signal.

  Each time the irradiation of the radiation of each frame is completed, the charge signal accumulated in the radiation image detector 12 is read by the control unit 14 and converted into a digital signal by an A / D converter (not shown). Thereafter, it is stored in the radiation image storage unit 13.

  Note that the irradiation timing of radiation from the X-ray tube of the radiation source 11 and the charge accumulation timing in the radiation image detector 12 are the same as those in the timing chart of the first embodiment shown in FIG.

  Then, as described above, irradiation of radiation from the radiation source 11 and recording and reading of the radiation image in the radiation image detector 12 are repeatedly performed at a predetermined frame rate, so that the radiation image storage unit 13 stores each frame. Radiation image signals are sequentially stored.

  The radiographic image signals for each frame stored in the radiographic image storage unit 13 are sequentially read out and output to the radiographic image display device 20. The radiographic image display device 20 sequentially generates a display control signal based on the input radiographic image signal for each frame, and sequentially outputs the display control signal to the monitor to display the patient's fluoroscopic image on the monitor as a moving image ( S56).

  On the other hand, in parallel with the imaging and display of the fluoroscopic images as described above, the radiation transmitted through the patient by the first and second dose measuring sensors 18a and 18b provided on the radiation image detector 12 is obtained. The dose is sequentially detected, and the detected radiation dose is sequentially input to the artifact frame specifying unit 19 (S58).

  Then, the artifact frame specifying unit 19 acquires the temporal variation of the input radiation dose, and identifies the artifact frame in which the image of the artifact is reflected based on the temporal variation. (S60).

  Specifically, the artifact frame specifying unit 19 uses the radiation dose detected by the first dose measurement sensor 18a and the radiation dose detected by the second dose measurement sensor 18b as shown in FIG. The time variation of the radiation dose detected by each sensor as shown is acquired.

  Here, when the artificial object embedded in the patient passes above the first and second dosimetry sensors 18a and 18b, the radiation is absorbed by the artificial object before the radiation reaches each sensor. Therefore, as shown in FIG. 17, the radiation dose detected by each sensor becomes small.

  Using such a change, the artifact-frame specifying unit 19 starts upstream from the first time point t1 when the radiation dose detected by the first dosimetry sensor 18a disposed on the downstream side starts to decrease. A frame photographed until time point t2 when the radiation dose detected by the second dosimetry sensor 18b arranged on the side decreases once and returns to a substantially constant value is specified as an artifact frame. Note that the moving speed of the radiation source 11 and the radiation image detector 12 and the radiographic frame rate of the fluoroscopic image are set in advance in the artifact frame specifying unit 19, and these information and the first time point are set. The artifact frame is specified based on the time from t1 to the second time point t2.

  Then, the radiographic image signal of each frame read from the radiographic image storage unit 13 is also input to the artifact frame specifying unit 19, and the radiographic image signal of the frame specified as the artifact frame as described above is input. The artifact frame information is added as header information, and the radiation image signal is stored together with the artifact frame information (S62).

  Then, when the photographing switch 51 is released (OFF) by the user and an instruction to end fluoroscopic image capturing is input, the system control device 40 controls the radiographic image capturing device 10 to end the radiographic image capturing. Is output, and the radiographic image capturing apparatus 10 ends the fluoroscopic image capturing in accordance with the input control signal (S64).

  The above is a flow of photographing and displaying a fluoroscopic image in the radiation image photographing system of the present embodiment.

  Next, control of the radiation dose in the radiographic imaging of each frame as described above will be described with reference to the flowchart shown in FIG. In addition, the irradiation dose here means the irradiation dose per unit time. In addition, the radiation dose in the radiography of each frame is assumed to be performed by changing the above-described radiation irradiation conditions by the radiation source control unit 14a.

  First, the radiation dose at the time of radiographic imaging in the first frame is set to the initial value input in S52 described above (S70).

  Then, at the time of imaging the first frame, the radiation dose of the initial value is emitted from the radiation source 11 under the control of the radiation source control unit 14a and irradiated to the patient (S72). The radiation that has passed through the patient is applied to the radiation image detector 12, is photoelectrically converted by the radiation image detector 12, and is stored as a charge signal (S74).

  As described above, when the irradiation of one frame of radiation is completed (S76), the charge signal accumulated in the radiation image detector 12 is read out by the control unit 14 and stored as a radiation image signal in the radiation image storage unit 13 ( S78). At this time, the artifact frame specifying unit 19 specifies whether or not the radiation image signal read from the radiation image detector 12 is the radiation image signal of the artifact frame as described above. If it is a radiographic image signal, the artifact frame information is added and stored, and if it is not the radiographic image signal of the artifact frame, the artifact frame information is stored without being added.

  Next, when the recording and reading of the one-frame radiographic image described above is completed, it is confirmed by the control unit 14 whether or not the imaging switch 51 has been pressed (ON) (S80).

  When the photographing switch 51 is pressed, whether or not the one-frame radiation image signal stored in the artifact frame specifying unit 19 is the radiation image signal of the artifact frame as described above. Is confirmed by the radiation source controller 14a (S82).

  Specifically, one frame of radiation image signal stored in the artifact frame specifying unit 19 is input to the radiation source control unit 14a, and the radiation source control unit 14a performs the above-described artificial operation on the input radiation image signal. It is confirmed whether the object frame information is added. Then, when the artifact frame information is added to the radiation image signal, the radiation source control unit 14a determines that the radiation image signal is a radiation image signal of the artifact frame. On the other hand, when the artifact frame information is not added to the radiation image signal, the radiation source control unit 14a determines that the radiation image signal is a radiation image signal other than the artifact frame.

  If the radiation source control unit 14a determines that the currently captured radiographic image signal of one frame is a radiographic image signal other than the artifact frame, the radiation source control unit 14a is based on the currently captured radiographic image signal of one frame. Then, the radiation dose to be used for capturing the radiation image of the next frame is determined (S84). As the method for determining the radiation dose of the next frame based on the radiation image signal of the previous frame, the simplest method is to decrease the radiation dose as the size of the radiation image signal increases. Since more specific methods are already known, detailed description thereof is omitted.

  Then, at the time of capturing the radiation image of the next frame, the radiation source control unit 14a controls the radiation source 11 so that the radiation dose determined based on the radiation image signal of the previous frame is irradiated. . Then, S72 to S82 are repeated again.

  On the other hand, if the radiation source control unit 14a determines that the currently captured radiographic image signal of one frame is the radiographic image signal of the artifact frame, the currently set radiation dose is not changed. Keep it as it is. Then, S72 to S82 are repeated again.

  By controlling the radiation dose as described above, the radiation dose determined based on the radiographic image signal of the previous frame is from the start of fluoroscopic image capture until the artifact frame is imaged. It is set as the radiation dose in the radiographic image capture of the next frame, and while the artifact frame is being captured, the radiation dose determined based on the radiographic image signal of the frame immediately before the artifact frame begins to be captured An irradiation dose is set, and a constant radiation dose is maintained.

  In S80, when it is confirmed by the control unit 14 that the imaging switch 51 has been released (OFF), the radiation source control unit 14a stops the radiation irradiation from the radiation source 11, and the radiographic image is captured. Is completed (S86).

  According to the radiographic imaging system of the second embodiment, an artificial object frame is identified from a plurality of frames, and the radiation dose is maintained constant while the artificial object frame is being imaged. Therefore, an appropriate radiation dose can be set throughout the series of imaging, and a radiographic image with good image quality can be acquired.

  In the radiographic imaging system of the second embodiment, the artifact frame is specified based on the temporal variation of the radiation dose detected by the first and second dose measurement sensors 18a and 18. However, the present invention is not limited to this, and for example, an index such as a mark indicating an artificial object is provided for an artificial object embedded in a patient's body. The artifact frame may be specified by recognizing whether or not an image signal representing the index is included in the image. Note that the image recognition of the mark is a well-known technique, and therefore the description thereof is omitted here.

  In the radiographic imaging systems of the first and second embodiments, the radiographic image signal detected by the radiographic image detector 12 is used while the contrast agent frame or the artifact frame is not captured. Although the radiation dose is determined, the present invention is not limited to this. For example, the radiation dose may be determined using a phototimer used for general AEC (Automatic Exposure Control). Even in this case, the radiation dose during the imaging of the contrast agent frame may be set to the radiation exposure controlled by the phototimer immediately before the contrast agent frame starts to be imaged, for example. Good.

  In the radiographic imaging systems of the first and second embodiments, immediately before the contrast agent frame or the artifact frame starts to be imaged as the radiation dose during the imaging of the contrast agent frame or the artifact frame. The radiation dose determined based on the radiographic image signal of the frame is set. However, the present invention is not limited to this. For example, the initial radiation dose may be set and maintained. Alternatively, an average value, a mode value, a median value, or the like of the radiation dose used when photographing a plurality of past frames before the immediately preceding frame may be used.

DESCRIPTION OF SYMBOLS 10 Radiation imaging device 11 Radiation source 12 Radiation image detector 14 Control part 14a Radiation source control part 15 Contrast agent frame specific | specification part 17 Radiation dose detection part 18 Radiation dose detection part 18a 1st dose measurement sensor 18b 2nd dose measurement Sensor 19 Artifact frame specifying unit 20 Radiographic image display device 30 Contrast agent injection device 31 Contrast agent injection unit 32 Injection drive unit 33 Control unit 34 Contrast agent injection detection sensor unit 35 Contrast agent injection time acquisition unit 40 System control device 41 Contrast agent Frame specifying part 50 Input part 51 Shooting switch

Claims (7)

A radiation source that continuously emits radiation to a living body into which a contrast medium is injected, and radiation that acquires a radiation image signal for each frame detected by a radiation image detector by radiography by the continuous radiation irradiation Based on an image acquisition unit and a radiation image signal for each frame acquired by the radiological image acquisition unit or a detection signal output from a radiation detector that detects the radiation transmitted through the living body, the radiation source irradiates In a radiographic imaging apparatus comprising a radiation source control unit for controlling the radiation dose
A contrast agent frame specifying unit that automatically specifies a frame containing an image signal representing the image of the contrast agent among the radiographic image signals for each frame as a contrast agent frame;
The radiation image capturing apparatus according to claim 1, wherein the radiation source control unit maintains a constant dose of the radiation irradiated by the radiation source while the contrast medium frame is captured.   The radiation source control unit sets the radiation dose while the contrast medium frame is imaged as the radiation dose when the predetermined frame before the contrast medium frame is imaged. The radiographic image capturing apparatus according to claim 1, wherein the radiographic image capturing apparatus is provided.   The radiation source control unit is characterized in that the radiation dose while the contrast medium frame is imaged is used as the radiation dose when the frame immediately before the contrast medium frame is imaged. The radiographic imaging device according to claim 2.   The contrast agent frame specifying unit specifies the contrast agent frame based on an injection start timing and an injection end timing of the contrast agent from a contrast agent injection device that injects the contrast agent into the living body. The radiographic imaging device according to any one of claims 1 to 3, wherein   The contrast agent frame specifying unit specifies the contrast agent frame based on difference information based on a radiographic image signal between predetermined frames among a plurality of radiographic image signals detected by the continuous radiography. The radiographic imaging device according to any one of claims 1 to 3, wherein   The contrast medium frame specifying unit acquires radiation dose information output from a radiation dose detection unit provided between the radiation source and the subject, and the acquired dose information and the continuous radiography 4. The radiographic image capturing apparatus according to claim 1, wherein the contrast medium frame is specified based on the detected radiographic image signals of a plurality of frames. 5.   The radiographic image capturing apparatus according to claim 5, wherein the contrast agent frame specifying unit specifies the contrast agent frame based on difference information of a density histogram of a radiographic image signal between the frames.

Images