JP2009039360A - Radiographic apparatus and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a low radiation exposure dose used for auxiliary imaging to be executed for obtaining an optimum imaging timing to be made automatically adjustable in a radiography. <P>SOLUTION: In the radiographic apparatus for determining the imaging timing of first radiography using a main image obtained by the first radiography by a first radiation exposure dose and an auxiliary image obtained by second radiography by a second radiation exposure dose lower than the first radiation exposure dose, an imaging control part 113 repeats the radiography while changing the radiation exposure dose in the range of the exposure dose smaller than the first radiation exposure dose, a motion detection part 111 detects the motion amount of a subject from a plurality of imaged images obtained by the radiography, and a motion amount comparison part 112 and the imaging control part 113 search the minimum radiation exposure dose required for detecting the motion amount of the subject on the basis of the detected motion amount and determine the searched radiation exposure dose as the second radiation exposure dose. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a radiation imaging apparatus and a control method thereof, and particularly relates to moving image capturing using radiation.

  In recent years, a medical X-ray fluoroscopic diagnosis apparatus has been widely used in a diagnosis that uses a digital image from conventional analog imaging. Along with this, digital images continuously taken by X-ray are displayed on a monitor as moving image data, or stored in a memory or a hard disk device, thereby being used for diagnosis or treatment.

  In such moving image shooting, both improvement in diagnostic accuracy and reduction in exposure to the subject are required. More specifically, a photographed image used for diagnosis (hereinafter referred to as a “real photographed image”) is analyzed to detect a change in the subject, and the frame rate of subsequent regular photography, that is, the photographing timing is controlled based on the result. Or control the amount of X-ray irradiation. A technique for obtaining a diagnostic image with a low X-ray dose by such control is proposed in Patent Document 1.

  However, in the case where the motion of the subject is detected using only the actual captured image as in the above-described proposal, if the frame rate is low, the followability to the motion is deteriorated. For this reason, when there is a large change in the movement of the subject, an appropriate imaging timing may be lost, and as a result, there may be a disadvantage in terms of diagnostic accuracy.

  As a conventional technique for solving the above problems, in order to obtain appropriate imaging timing, an image captured by low-dose X-ray irradiation (hereinafter referred to as an auxiliary imaging image) is analyzed separately from the main imaging, A technique for suppressing the exposure dose has been proposed (Patent Document 2). Here, in the photographing of the auxiliary photographing image, photographing is performed by low-dose X-ray irradiation in which the irradiation amount can be manually set or fixed low-dose X-ray irradiation set in advance.

In this technique, in imaging using a tissue with periodic motion such as the heart and lungs as a subject, the phase of the subject is detected by analyzing an image taken with low-dose X-ray irradiation. Then, only when the subject is in a desired state, the actual captured image is captured with the normal X-ray irradiation amount.
JP-A-5-192319 JP-A-2005-342088

  However, in Patent Document 2, the control of the X-ray irradiation amount in capturing an auxiliary image is performed by manual setting or a preset fixed setting. For this reason, it is difficult to optimize the low X-ray irradiation amount in capturing an auxiliary captured image when controlling the imaging timing by detecting the phase of the subject using the auxiliary captured image. As a result, there is a problem that the total exposure dose to the subject cannot be sufficiently reduced due to the accumulation of low X-ray irradiation.

  The present invention has been made to solve the above-described problems. In radiation imaging, the low radiation dose used for auxiliary imaging executed to obtain optimal imaging timing can be automatically adjusted, and The aim is to reduce the total exposure.

A radiation imaging apparatus according to the present invention for solving the above-described problems has the following configuration. That is,
A main captured image obtained by the first radiography with the first radiation dose, and an auxiliary captured image obtained by the second radiography with the second radiation dose lower than the first radiation dose; A radiographic apparatus that determines an imaging timing of the first radiographic imaging using
Imaging control means for repeating radiography while changing the radiation dose in a range of dose smaller than the first radiation dose;
Detecting means for detecting a movement amount of a subject from a plurality of captured images obtained by the imaging control means;
Based on the amount of motion detected by the detecting means, a determining means for searching for the minimum radiation dose necessary for detecting the amount of motion of the subject and determining the searched radiation dose as the second radiation dose. With.

Moreover, the control method of the radiation imaging apparatus by this invention for solving said subject is as follows.
A main captured image obtained by the first radiography with the first radiation dose, and an auxiliary captured image obtained by the second radiography with the second radiation dose lower than the first radiation dose; A method of controlling a radiation imaging apparatus that determines an imaging timing of the first radiation imaging using
An imaging control step of repeating radiography while changing the radiation dose within a range of dose smaller than the first radiation dose;
A detection step of detecting a movement amount of a subject from a plurality of captured images obtained by the shooting control step;
Based on the amount of motion detected in the detection step, a minimum radiation dose necessary for detecting the amount of motion of the subject is searched, and the determined radiation dose is determined as the second radiation dose. With.

  According to the present invention, in radiography, it is possible to automatically adjust the low X-ray irradiation amount in auxiliary imaging for obtaining an optimal imaging timing, and further reduce the total X-ray exposure dose to the subject. Is possible.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. Hereinafter, a case where the radiation imaging apparatus of the present invention is applied to an X-ray fluoroscopic diagnosis apparatus will be described.

<First Embodiment>
FIG. 1 is a block diagram showing the overall configuration of the X-ray fluoroscopic diagnosis apparatus in the first embodiment. As shown in FIG. 1, the X-ray fluoroscopic diagnosis apparatus as a radiation imaging apparatus according to this embodiment includes a sensor unit 101, an X-ray generation apparatus 104, a controller 107, and an operation unit 114.

  The sensor unit 101 includes an X-ray sensor 102 and a sensor control unit 103. The X-ray sensor 102 is configured by a solid-state imaging device that reacts to X-rays and can convert the detected X-rays into electrical signals corresponding to the intensity and output the electrical signals. Alternatively, the X-ray sensor 102 includes a unit that combines a phosphor that generates fluorescence (visible light) according to X-ray energy and a photoelectric conversion element that converts visible light into an electrical signal according to the intensity thereof. Is done. The raw image digital data output from the X-ray sensor 102 is sent to the controller 107. In addition, the sensor control unit 103 performs sensor drive control including processing for generating a data output timing signal of the X-ray sensor 102 in response to a timing instruction from the imaging control unit 113, output mode setting of the X-ray sensor 102, and the like. Do. A high-speed digital interface such as LVDS (Low Voltage Differential Signaling) is used between the sensor unit 101 and the controller 107 for data transfer. In addition, asynchronous serial communication such as UART is used between the sensor unit 101 and the controller 107 for parameter input / output.

  The X-ray generator 104 includes an X-ray tube 105 and an X-ray pulse control unit 106. The X-ray tube 105 emits pulsed X-rays in response to a timing signal from the X-ray pulse control unit 106. In addition, the X-ray pulse control unit 106 performs processing for outputting an X-ray exposure timing signal to the X-ray tube 105 under the set exposure conditions in accordance with a timing instruction and setting parameters from the imaging control unit 113. Do. The actual captured image is acquired by causing the X-ray pulse control unit 106 to execute the first radiation imaging (X-ray imaging) with the first radiation irradiation amount (X-ray irradiation amount). In addition, the auxiliary captured image causes the X-ray pulse control unit 106 to execute second radiation imaging (X-ray imaging) with a second radiation dose (X-ray dose) smaller than the first radiation dose. Obtained at.

  The controller 107 includes an image processing unit 108, an encoding unit 109, a display image transmission unit 110, a motion detection unit 111, a motion amount comparison unit 112, and a shooting control unit 113. For input / output of parameters between the X-ray generator 104 and the controller 107, asynchronous serial communication or a low-latency network protocol such as CAN (Controller Area Network) is used.

  By continuously sending timing instructions to the X-ray generator 104 and the sensor unit 101, X-ray fluoroscopic images can be continuously captured. In continuous shooting, for example, 30 fps moving image data can be generated by a timing instruction 30 times per second.

  The image processing unit 108 receives the raw image digital data output from the sensor unit 101 and performs predetermined image processing. Here, the image processing includes image quality enhancement processing such as correction, noise removal, and dynamic range improvement depending on the characteristics of the X-ray sensor. In addition, the image processing unit 108 sends the image-processed data to the motion detection unit 111, and at the same time, performs processing for sending only image data taken for diagnosis, that is, display image data, to the encoding unit 109. The encoding unit 109 performs lossless compression encoding processing on the display image data subjected to image processing, and sends the display image data to the display image transmission unit 110. The controller 107 and the operation unit 114 are connected by a network using Gigabit Ethernet (registered trademark). The display image transmission unit 110 performs packetization of image data and network protocol processing, and transmits data to the operation unit 114 via the network.

  The motion detection unit 111 performs a process of calculating respective motion amounts in the continuously captured main captured image data and auxiliary captured image data at the time of capturing for obtaining the captured image (hereinafter referred to as diagnostic imaging). Note that the motion amount may be calculated separately for the main captured image data and the auxiliary captured image data, or may be used together. However, when the main image data and the auxiliary image data are used together, the amount of motion is calculated after the level of the average value of the pixel values of the main image data and the auxiliary image data is adjusted. Further, when adjusting the low X-ray irradiation amount for the auxiliary captured image (hereinafter referred to as low X-ray irradiation adjustment), the respective motion amounts in the image data captured by the same X-ray irradiation are calculated ( This will be described later with reference to FIG. Alternatively, at the time of adjusting the low X-ray irradiation amount, a process of calculating the amount of movement of each of the continuously captured image data is performed (described later in FIG. 10 (second embodiment)). Note that the algorithm for motion detection is widely used as the prior art, and therefore the description thereof is omitted here. For example, it is conceivable that the difference between each pixel is simply calculated, and the motion amount of the entire subject is calculated from the difference amount or the ratio to all the pixels, or it is determined from the value of the motion vector. As the calculation of the motion vector, for example, a method of calculating the motion amount of the entire subject by combining the motion vectors in units of macro blocks can be considered.

  The motion amount comparison unit 112 compares the difference in motion amount between the image data captured by the same X-ray irradiation received from the motion detection unit 111 or the continuously captured image data when adjusting the low X-ray irradiation amount.

  The imaging control unit 113 determines the imaging interval and the X-ray irradiation amount at the time of acquiring the actual captured image according to the amount of motion calculated by the motion detection unit 111 at the time of diagnostic imaging, and determines the sensor unit 101 and the X-ray generation device 104. A process for sending an imaging timing instruction and a parameter instruction is performed. At the time of adjusting the low X-ray irradiation amount, the imaging control unit 113 adjusts the low X-ray irradiation amount according to the comparison result of the motion amount comparison unit 112, and instructs the sensor unit 101 and the X-ray generator 104 to perform an imaging timing instruction. Send parameter instructions. In addition, the imaging control unit 113 executes processing for sending parameter instructions to the sensor unit 101 and the X-ray generator 104 in accordance with imaging conditions based on instructions from the operation unit 114.

  The operation unit 114 includes a display system 115, a display device 116, a console 117, and a storage device 118, and includes a PC (personal computer) and peripheral devices connected thereto. In the present embodiment, the display system 115 is realized by a PC main body and application software that operates on the PC main body. The display system 115 receives encoded photographed image data transmitted from the controller 107 through the network, performs a data decoding process, and then outputs the data to the display device 116 or stores it in the storage device 118. In response to an operation from the console 117, various instructions to the controller 107 such as start / stop of shooting and setting of a shooting mode are performed through the network.

  Next, the operation of the imaging control unit 113 shown in FIG. 1 will be described with reference to the flowchart of FIG.

  In step S <b> 201, the imaging control unit 113 uses the operation unit 114 to set the frame rate when adjusting the low X-ray irradiation amount, the maximum and minimum values of the low X-ray irradiation amount, and the display image frame rate when acquiring the actual captured image. And initial conditions for various imaging such as X-ray irradiation dose. Here, the maximum value of the low X-ray dose does not need to obtain an image quality for diagnosis, but at least an X-ray dose that provides an image quality that can reliably detect the motion of the subject. That is.

  Next, in step S202, the imaging control unit 113 executes setting of an X-ray irradiation amount, setting of a sensor readout mode, and the like according to the imaging conditions acquired in step S201. The setting of the X-ray irradiation amount and the sensor readout mode is executed by issuing a setting parameter command to the sensor control unit 103 and the X-ray pulse control unit 106. In step S <b> 203, the shooting control unit 113 waits until a shooting start instruction is issued from the operation unit 114.

  When an imaging start instruction is given here, in step S204, the imaging control unit 113 instructs the motion amount comparison unit 112 to adjust the X-ray irradiation amount when imaging the auxiliary imaging image. Adjust the amount. In short, the process of step S204 is a process of searching for the minimum radiation dose necessary for detecting the amount of movement of the subject. The process of step S204 will be described more specifically with reference to the flowchart of FIG.

  In step S301, the imaging control unit 113 irradiates low X-rays at the adjustment stage (hereinafter referred to as adjusted low X-rays), or low X-rays (hereinafter referred to as reference low X-rays) capable of detecting motion, that is, Judgment is made as to whether or not irradiation is performed with the maximum value of low X-rays. This determination is made based on whether the previous imaging was an imaging with the adjusted low X-ray or the reference low X-ray. That is, when the reference low X-ray is irradiated in the immediately preceding imaging, the process proceeds to step S306 to perform the adjustment low X-ray irradiation. On the other hand, when the adjusted low X-ray is irradiated in the immediately preceding process, the process proceeds to step S302 to irradiate the reference low X-ray. In this way, imaging with adjusted low X-rays and imaging with reference low X-rays are performed alternately. In the low X-ray dose adjustment after step S301, the sensor readout mode set in step S202 is used.

  In step S <b> 302, the imaging control unit 113 issues an imaging timing instruction command for irradiating the reference low X-ray to the sensor control unit 103 and the X-ray pulse control unit 106. Subsequently, in step S303, the imaging control unit 113 instructs the motion detection unit 111 to temporarily store the captured image data. In response to this instruction, the motion detection unit 111 calculates the amount of motion from the previous image data acquired by the temporarily stored reference low X-ray irradiation and the currently captured image data. Next, in step S304, the imaging control unit 113 reads the amount of motion calculated by the motion detection unit 111. Then, the imaging control unit 113 passes the motion amount to the motion amount comparison unit 112, stores the motion amount in the motion amount comparison unit 112 in step S305, and returns to step S301.

  On the other hand, if it is determined in step S301 that the adjusted low X-ray is irradiated, the process proceeds to step S306. In step S306, the imaging control unit 113 issues an imaging timing instruction command for irradiating the adjusted low X-ray to the sensor control unit 103 and the X-ray pulse control unit 106. In this embodiment, in this step, the low X-ray dose that is initially set is the minimum value of the low X-ray dose acquired in step S201 in FIG.

  In step S307, the imaging control unit 113 checks whether image data has already been acquired with the adjusted low X-ray dose. If the image data has not been acquired with the adjusted low X-ray dose, that is, if it is the first imaging with the adjusted low X-ray dose, the process proceeds to step S308. In step S308, the imaging control unit 113 instructs the motion detection unit 111 to temporarily store captured image data. If image data has already been acquired with the same adjusted low X-ray dose, that is, if it is the second imaging with the adjusted low X-ray dose, the process proceeds to step S309. In step S309, the imaging control unit 113 calculates the amount of motion from the previous image data acquired by the adjusted low X-ray irradiation temporarily stored in the motion detection unit 111 and the image data just captured. Then, the imaging control unit 113 passes the motion amount from the motion detection unit 111 to the motion amount comparison unit 112. In this way, the motion amount for the two images taken with the same adjusted low X-ray dose is provided to the motion amount comparison unit 112. In step S310, the imaging control unit 113 compares the amount of movement at the time of adjusted low X-ray irradiation with the amount of movement at the time of reference low X-ray irradiation stored in step S305. Then, if the comparison result matches within a certain range, the process is terminated. If the comparison results do not match, in step S311, the adjusted low X-ray dose set in step S306 is increased, and the process returns to step S301.

  Steps S301 to S311 described above are processes for adjusting the low X-ray dose for detecting the movement of the subject in the present embodiment.

  When the adjustment of the X-ray dose during auxiliary imaging is completed, diagnostic imaging is performed in step S205. A detailed flow of the processing in step S205 is shown in FIG.

  In step S401, the shooting control unit 113 checks whether or not it is the shooting timing of the display image at the currently set frame rate, that is, the main shooting image. If it is the imaging timing, in step S402, the imaging control unit 113 sends an imaging timing instruction command based on the normal X-ray irradiation amount for acquiring the actual captured image to the sensor control unit 103 and the X-ray pulse control unit 106. Issue. Subsequently, in step S <b> 404, the imaging control unit 113 instructs the display image transmission unit 110 to transmit a display image for one frame. If it is determined in step S401 that it is not the display image capturing timing, that is, if it is the capturing timing of the auxiliary captured image, the process proceeds to step S403. In step S403, the imaging control unit 113 issues an imaging timing instruction command based on the low X-ray dose determined in step S404, and the process proceeds to S405.

  In step S405, the imaging control unit 113 reads the motion amount calculated from the image data captured in step S402 or step S403 from the motion detection unit 111. Next, in step S406, the imaging control unit 113 resets the display image frame rate in accordance with the read amount of motion. That is, the display image frame rate is reduced when the amount of motion is smaller than the current amount, and conversely is increased when the amount of motion is large.

  Steps S401 to S406 described above indicate the imaging process for one frame of an image. By repeating this series of processes, it is possible to perform diagnostic moving image imaging as a continuous image in this embodiment. The above is a flow showing the process of step S205.

  When a series of diagnostic imaging processes are performed in step S205, it is checked in step S206 whether or not there is an instruction to move the imaging area by a predetermined distance or more from the operation unit 114. If there is such an instruction, the process returns to step S204 to adjust the low X-ray dose. That is, every time the imaging region is changed by a predetermined distance or more, the low X-ray dose adjustment is repeated. On the other hand, if there is no such instruction, the process proceeds to step S207. In step S207, it is checked whether or not there has been a photographing end instruction from the operation unit 114, and if there is, the process is terminated, and if there is not, the process from step S205 is repeated.

  FIG. 5 shows the transition from low X-ray dose adjustment to diagnostic imaging in this embodiment, X-ray dose, subject movement during diagnostic imaging, and the correlation of the acquisition timing of the actual captured image over time. FIG.

  In FIG. 5, reference numeral 501 denotes the X-ray dose and the exposure timing. A medium-length arrow indicated by 502 is a reference low X-ray dose during the low X-ray dose adjustment period, and indicates that imaging is performed with a fixed dose. A short arrow indicated by 503 is an adjusted low X-ray dose during the low X-ray dose adjustment period, and has a variable radiation dose. In the present embodiment, during the low X-ray dose adjustment period, the amount of motion is detected while changing the variable radiation dose, and the low X-ray dose is determined based on the detected amount of motion. A long arrow indicated by reference numeral 504 is a normal intensity X-ray irradiation amount for the actual captured image in the diagnostic imaging period. A short arrow 505 indicates a low X-ray irradiation amount for an auxiliary captured image in the diagnostic imaging period. Reference numeral 506 denotes the amount of movement of the subject during the diagnostic imaging period, and the curve indicated by 507 represents the transition of the amount of movement of the subject over time. Reference numeral 508 represents the timing for acquiring the actual captured image used for diagnosis, and the portion masked with diagonal lines as indicated by 509 is the acquisition timing.

  As shown in FIG. 5, the low X-ray dose is first adjusted, and diagnostic imaging is performed when the adjustment is completed. When the imaging region moves, the low X-ray dose is adjusted again, and diagnostic imaging is performed when the adjustment is completed. X-ray irradiation for obtaining an auxiliary captured image at the time of diagnostic imaging is performed at a low X-ray dose 505 determined in the low X-ray dose adjustment period. As indicated by the change 507 in the amount of motion over time of the diagnostic imaging period and the X-ray irradiation amount 501, when the amount of motion is small, the number of X-ray irradiations for obtaining the main imaging image is thinned out, Controls the frame rate to be displayed. Also in this case, low X-ray irradiation for auxiliary imaging for motion amount detection is performed at a fixed high frame rate, so even if the amount of motion suddenly increases, the amount of motion can be detected immediately and quickly. In addition, it is possible to switch to display image shooting at a high frame rate.

  FIG. 6 is an enlarged view of the low X-ray dose adjustment period shown in FIG. As shown in FIG. 6, X-ray imaging using the reference low X-ray dose 502 and X-ray imaging performed while increasing or decreasing the variable adjusted low X-ray dose 503 are performed alternately. Further, imaging with the same variable adjusted low X-ray dose is performed twice. In FIG. 6, reference numeral 601 represents the amount of movement of the subject when adjusting the low X-ray dose. Reference numeral 602 denotes the amount of movement of a subject between images photographed at the reference low X-ray dose 502 (hereinafter referred to as a first amount of movement), and reference numeral 603 denotes the amount of movement of the subject between images shot at the adjusted low X-ray dose 503. (Hereinafter referred to as second movement amount). The first and second motion amounts 602 and 603 are sequentially compared, and the adjusted low X-ray irradiation amount is increased step by step. When the first and second motion amounts match within a certain range, the diagnostic imaging period A low X-ray dose 505 is determined in order to obtain an auxiliary captured image.

FIG. 7 and FIG. 8 are diagrams showing photographed images accompanying the movement of the subject. In FIG. 7, 701 represents a captured image of a certain frame (X _n ), and 703 represents a captured image of the next frame (X _{n + 1} ). Reference numeral 701 shows a contracted state of the heart (702) as an object, and a next frame 703 shows a state where the contracted state (704) is shifted to the expanded state (705). The amount of movement in this case is represented by an arrow in the figure, and the movement speed is large because the heart is a relatively fast movement.

FIG. 8 also shows a captured image 801 of a certain frame (X _n ) and a captured image 803 of the next frame (X _{n + 1} ). The captured image 801 shows the contracted state of the lung (802) as a subject, and the captured image 803 of the next frame shows a state of transition from the contracted state (804) to the expanded state (805). Since the lungs move relatively slowly, the arrows indicating the amount of movement are also short, indicating that the amount of movement is small. However, since the ratio of the photographic subject to the entire screen is large, the area where the image moves is widened.

  The value of the motion amount of the motion detection unit 111 is calculated as a large amount of motion regardless of whether the motion speed is high as in the heart shown in FIG. 7 or the motion region is wide as in the lung shown in FIG. It is supposed to be. Further, the comparison of the amount of movement at the time of adjusting the low X-ray irradiation amount performed by the movement amount comparison unit 112 can be realized by comparing the magnitude of the amount of movement shown in FIGS.

  In the present embodiment, the method of gradually adjusting the low X-ray dose during adjustment of the low X-ray dose from a low value to a high value has been described as an example. Needless to say, it is also possible to use a method or a method of adjusting by a bisection method.

  Further, in this embodiment, the readjustment of the low X-ray irradiation amount is performed only when the imaging region is moved. However, the readjustment may be performed after a certain period. That is, the adjustment of the low X-ray dose may be performed periodically.

Second Embodiment
Next, a second embodiment will be described. FIG. 9 is a flowchart showing a low X-ray dose adjustment process of the fluoroscopic diagnostic apparatus according to the second embodiment. Note that the overall configuration, the overall control flow, and the diagnostic imaging flow are the same as those in the first embodiment, and a description thereof will be omitted here.

  In step S <b> 901, the imaging control unit 113 issues an imaging timing instruction command for irradiating the adjusted low X-ray to the sensor control unit 103 and the X-ray pulse control unit 106. In this example, in this step, the low X-ray dose that is initially set is the maximum value of the low X-ray dose acquired in step S201 in FIG.

  In step S <b> 902, the imaging control unit 113 acquires a motion amount calculated from continuously captured image data from the motion detection unit 111, and passes this to the motion amount comparison unit 112. In step S903, the imaging control unit 113 temporarily stores the movement amount in the movement amount comparison unit 112.

  In step S904, it is checked whether the number of temporarily stored motion amounts to be compared with the currently calculated motion amount is sufficient. In the present embodiment, it is assumed that only the previous motion amount is compared, but the present invention is not limited to this. For example, it will be apparent to those skilled in the art that there are various variations such as comparing the previous and second previous movement amounts. If there is a motion amount to be compared (comparison data), the process proceeds to step S905. If there is no motion amount to be compared, the process returns to step S901.

  In step S905, the imaging control unit 113 compares the amount of movement and checks whether it is stable within a certain range. If the amount of movement is not stable, the process proceeds to step S906, and if the amount of movement is stable, the process proceeds to step S907.

  In step S <b> 906, the imaging control unit 113 sets a flag (unstable X-ray dose detection flag) indicating that an X-ray dose that results in an unstable motion amount has been detected, and clears all stored motion amounts. Then, the process proceeds to step S908.

  In step S907, the imaging control unit 113 checks whether the unstable X-ray dose detection flag is set. When the flag is set, it indicates that the motion detection is found to be stable after detecting the X-ray dose that makes motion detection unstable. Therefore, in step S908, the imaging control unit 113 clears the flag and clears the stored motion amount, and then ends the process. On the other hand, if the unstable X-ray dose detection flag flag is not set in step S907, the process proceeds to step S910.

  In step S910, if the unstable X-ray dose detection flag is not set in the step of adjusting the low X-ray dose, the imaging control unit 113 decreases the X-ray dose and sets the unstable X-ray dose detection flag. If so, the X-ray irradiation dose is increased. Thereafter, the process returns to step S901.

  Steps S901 to S910 described above are the process for adjusting the low X-ray dose for detecting the movement of the subject in the second embodiment.

  FIG. 10 is a diagram showing the time lapse of the movement amount and the X-ray irradiation amount when the low X-ray irradiation amount adjustment shown in the flowchart of FIG. 9 is performed, and is an alternative to FIG. 5 of the first embodiment. It is. In FIG. 10, reference numeral 1001 denotes the amount of movement of the subject between images taken with the adjusted low X-ray dose 503. The amount of motion between consecutive images is compared, and the adjusted low X-ray irradiation amount is gradually reduced until the amount of motion is stable within a certain range and the amount of motion becomes unstable. Then, after the movement becomes unstable, the adjusted low X-ray dose is gradually increased. Thereafter, when the amount of movement is stabilized within a certain range, the low X-ray irradiation amount 505 for the auxiliary captured image in the diagnostic imaging period is determined. As described above, in the low X-ray dose adjustment period of the second embodiment, X-ray imaging is performed while increasing the dose from the lowest X-ray dose, and from a captured image taken at a timing close in time. The movement of the subject is detected. When the detected change in the amount of motion exceeds the first threshold (after an unstable period) and falls within the second threshold smaller than the first threshold, stable imaging is performed. It is determined that an image has been obtained. That is, in the second embodiment, the radiation irradiation amount immediately before the detected fluctuation of the movement amount exceeds the threshold is determined as the minimum radiation irradiation amount necessary for detecting the movement amount of the subject.

  As described above, according to each of the above-described embodiments, in the X-ray diagnosis, the amount of X-ray irradiation at the time of capturing an auxiliary captured image for motion detection necessary for obtaining good moving image capturing while suppressing the X-ray exposure amount Is automatically controlled to a dose that is close to the minimum necessary to detect the movement of the subject. That is, based on the amount of motion detected by repeating radiography while changing the amount of radiation, the minimum amount of radiation required to detect the amount of motion of the subject is searched, and the searched amount of radiation is supported. It is determined by the radiation dose at the time of taking a photographed image. For this reason, it is possible to further reduce the total X-ray exposure dose to the subject.

  Although the embodiment has been described in detail above, the present invention can take an embodiment as a system, apparatus, method, program, storage medium, or the like. Specifically, the present invention may be applied to a system composed of a plurality of devices, or may be applied to an apparatus composed of a single device.

  In the present invention, the functions of the above-described embodiments are achieved by supplying a software program directly or remotely to a system or apparatus, and the computer of the system or apparatus reads and executes the supplied program code. Including the case. In this case, the supplied program is a computer program corresponding to the flowchart shown in the drawings in the embodiment.

  Accordingly, since the functions of the present invention are implemented by computer, the program code installed in the computer also implements the present invention. In other words, the present invention includes a computer program itself for realizing the functional processing of the present invention.

  In that case, as long as it has the function of a program, it may be in the form of object code, a program executed by an interpreter, script data supplied to the OS, or the like.

  Examples of the computer-readable storage medium for supplying the computer program include the following. For example, floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, MO, CD-ROM, CD-R, CD-RW, magnetic tape, nonvolatile memory card, ROM, DVD (DVD-ROM, DVD- R).

  As another program supply method, a client computer browser is used to connect to a homepage on the Internet, and the computer program of the present invention is downloaded from the homepage to a recording medium such as a hard disk. In this case, the downloaded program may be a compressed file including an automatic installation function. It can also be realized by dividing the program code constituting the program of the present invention into a plurality of files and downloading each file from a different homepage. That is, a WWW server that allows a plurality of users to download a program file for realizing the functional processing of the present invention on a computer is also included in the present invention.

  Further, the program of the present invention may be encrypted, stored in a storage medium such as a CD-ROM, and distributed to users. In this case, a user who has cleared a predetermined condition is allowed to download key information for decryption from a homepage via the Internet, execute an encrypted program using the key information, and install the program on the computer. You can also.

  In addition to the functions of the above-described embodiment being realized by the computer executing the read program, the embodiment of the embodiment is implemented in cooperation with an OS or the like running on the computer based on an instruction of the program. A function may be realized. In this case, the OS or the like performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.

  Furthermore, the program read from the recording medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, so that part or all of the functions of the above-described embodiments are realized. May be. In this case, after a program is written in the function expansion board or function expansion unit, the CPU or the like provided in the function expansion board or function expansion unit performs part or all of the actual processing based on the instructions of the program.

It is a block diagram showing the whole structure of the X-ray fluoroscopic diagnostic apparatus by 1st Embodiment. It is a flowchart showing the whole control which the imaging | photography control part 113 by 1st Embodiment performs. It is a flowchart showing the control at the time of low X-ray irradiation amount adjustment by 1st Embodiment. It is a flowchart showing the control at the time of diagnostic imaging | photography by 1st Embodiment. FIG. 4 is a diagram showing a transition from low X-ray dose adjustment to diagnostic imaging according to the first embodiment, X-ray dose, subject movement amount during diagnostic imaging, and correlation of acquisition timing of a main captured image over time. is there. It is a figure showing the time passage of the X-ray irradiation amount of the low X-ray irradiation amount adjustment period and the amount of movement of the subject according to the first embodiment. It is a figure showing the picked-up image with the motion of the to-be-photographed object by 1st Embodiment. It is a figure showing the picked-up image with the motion of the to-be-photographed object by 1st Embodiment. It is a flowchart showing the control at the time of low X-ray irradiation amount adjustment by 2nd Embodiment. It is a figure showing X-ray irradiation amount of the low X-ray irradiation amount adjustment period by 2nd Embodiment, and time passage of a subject's movement amount.

Claims (12)

A main captured image obtained by the first radiography with the first radiation dose, and an auxiliary captured image obtained by the second radiography with the second radiation dose lower than the first radiation dose; A radiographic apparatus that determines an imaging timing of the first radiographic imaging using
Imaging control means for repeating radiography while changing the radiation dose in a range of dose smaller than the first radiation dose;
Detecting means for detecting a movement amount of a subject from a plurality of captured images obtained by the imaging control means;
Based on the amount of motion detected by the detecting means, a determining means for searching for the minimum radiation dose necessary for detecting the amount of motion of the subject and determining the searched radiation dose as the second radiation dose. A radiation imaging apparatus comprising:   The apparatus further comprises a control unit that repeats the operations of the imaging control unit, the detection unit, and the determination unit for determining the second radiation dose every time the imaging region is changed. The radiation imaging apparatus according to 1.   The radiation according to claim 1, further comprising a control unit that periodically repeats the operations of the imaging control unit, the detection unit, and the determination unit for determining the second radiation dose. Shooting device. The imaging control means performs imaging with a fixed radiation dose sufficient to detect the amount of movement of the subject, and imaging with a variable radiation dose that increases or decreases within a range of the dose smaller than the fixed radiation dose. Run alternately,
The detection means detects a first motion amount from an image obtained by imaging with the fixed radiation dose, and detects a second motion amount from an image obtained by imaging with the variable radiation dose. Detect
4. The determination unit according to claim 1, wherein the determination unit searches for a minimum variable radiation dose in which a difference between the first movement amount and the second movement amount is within a predetermined range. The radiation imaging apparatus of Claim 1. The imaging control means repeats radiography while reducing the radiation dose,
The detection means detects a movement of a subject from a captured image captured at a timing close in time,
The determining means determines the radiation irradiation amount immediately before the fluctuation of the motion amount detected by the detection means exceeds a threshold value as the minimum radiation irradiation amount necessary for detecting the motion amount of the subject. Item 4. The radiation imaging apparatus according to any one of Items 1 to 3. A main captured image obtained by the first radiography with the first radiation dose, and an auxiliary captured image obtained by the second radiography with the second radiation dose lower than the first radiation dose; A method of controlling a radiation imaging apparatus that determines an imaging timing of the first radiation imaging using
An imaging control step of repeating radiography while changing the radiation dose within a range of dose smaller than the first radiation dose;
A detection step of detecting a movement amount of a subject from a plurality of captured images obtained by the shooting control step;
Based on the amount of motion detected in the detection step, a minimum radiation dose necessary for detecting the amount of motion of the subject is searched, and the determined radiation dose is determined as the second radiation dose. A control method for a radiation imaging apparatus.   7. The method according to claim 6, further comprising a control step of repeating the imaging control step, the detection step, and the determination step for determining the second radiation dose every time the imaging region is changed. A control method of the radiation imaging apparatus described.   The radiation imaging apparatus according to claim 6, further comprising a control step of periodically repeating the imaging control step, the detection step, and the determination step for determining the second radiation dose. Control method. In the imaging control step, imaging with a fixed radiation dose sufficient to detect the amount of movement of the subject and imaging with a variable radiation dose that increases or decreases within a range of the dose smaller than the fixed radiation dose. Run alternately,
In the detection step, a first movement amount is detected from an image obtained by photographing with the fixed radiation dose, and a second motion amount is obtained from the image obtained by photographing with the variable radiation dose. Detect
9. The determination unit according to claim 6, wherein the determination step searches for a minimum variable radiation dose in which a difference between the first movement amount and the second movement amount is within a predetermined range. A method for controlling the radiation imaging apparatus according to claim 1. In the imaging control step, radiography is repeated while reducing the radiation dose,
In the detection step, the movement of the subject is detected from a photographed image photographed at a timing close in time,
In the determining step, the radiation irradiation amount immediately before the fluctuation of the motion amount detected in the detection step exceeds a threshold value is determined as the minimum radiation irradiation amount necessary for detecting the motion amount of the subject. Item 9. The method for controlling a radiation imaging apparatus according to any one of Items 6 to 8.   A computer program for causing a computer to execute the method for controlling a radiation imaging apparatus according to any one of claims 6 to 10.   A computer-readable storage medium storing the computer program according to claim 11.

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