JPWO2014013881A1 - X-ray fluoroscopic apparatus and control method of X-ray fluoroscopic apparatus - Google Patents

Abstract

In order to suppress blurring and blurring of the captured image when shooting at a reverse tilt position, the X-ray fluoroscopic device has a tiltable posture of the bed top plate 17 that can be tilted and the long axis of the bed top plate 17 with respect to the horizontal plane. A parameter calculation unit 19 that calculates a posture parameter indicating the movement, a motion detection unit 151 that detects the magnitude of the movement of the subject based on X-ray images of consecutive frames, and the subject based on the posture parameter. Based on the allowable motion value set by the allowable motion value setting unit 152 and the allowable motion value setting unit 152 for setting the allowable motion value indicating how much the sample motion is allowed, the motion control for imaging is performed. An imaging control unit 155 for performing

Description

  The present invention relates to an X-ray fluoroscopic apparatus, and more particularly to improvement in image quality of an inspection performed by tilting a bed top.

  The X-ray fluoroscopic imaging apparatus obtains an X-ray signal of a subject by irradiating the subject with X-rays and detecting the transmitted X-rays with an X-ray detector. The X-ray fluoroscopic apparatus displays a captured image (still image) or a fluoroscopic image (moving image) on the display unit by processing the X-ray signal in the image processing unit. If the subject moves during X-ray image capturing, the captured image may be blurred. Therefore, in the patent document, the image is obtained by reducing the exposure time (exposure pulse width) per frame of the X-ray tube according to the magnitude of the movement of the subject between frames of consecutive fluoroscopic images. A technique for effectively suppressing the blur is disclosed.

JP 2002-58665 A

  However, Patent Document 1 does not consider a case where the inspection is performed with the bed top plate tilted. In particular, the head direction of the subject on the bed is downward from the straight line extending in the horizontal direction, and the position of the subject's foot on the bed is upward from the straight line extending in the horizontal direction (hereinafter referred to as `` reverse tilt position '') ), It is necessary to maintain a state in which the subject holds the handrail provided on the bed in order to maintain a stationary state, which may cause the subject to move. If the subject moves during the examination, the examination may be prolonged or an imaging mistake may be caused. If the examination at the reverse tilt position is prolonged, there is a possibility that the load for maintaining the stationary state of the subject is further increased, and that the subject is likely to move, and a vicious circle may occur.

  The present invention has been made in view of the above problems, and provides a technique capable of suppressing blurring of a captured image obtained by imaging performed at a reverse tilt position and improving image quality.

  In order to solve the above-mentioned problem, the X-ray fluoroscopic apparatus according to the present invention sets a movement allowable value of the magnitude of movement of the subject based on a posture parameter indicating the tilt posture of the bed top plate, and this movement Based on the allowable value, operation control for photographing is performed.

  According to the present invention, it is possible to provide an X-ray fluoroscopic imaging apparatus capable of suppressing blurring of a captured image obtained by imaging performed at a reverse tilt position and improving image quality.

Functional block diagram showing a schematic configuration of an X-ray fluoroscopic apparatus according to the present embodiment Flow chart showing the flow of inspection in the first embodiment Explanatory drawing which shows the process which detects the value m which shows the magnitude | size of a subject's motion Explanatory drawing which shows an example of the time transition of the magnitude | size of movement The flowchart which shows the flow of the setting value calculation process which concerns on 1st embodiment. It is explanatory drawing which shows an example of the table which matched and prescribed | regulated the movement allowable value and the inclination angle, (a) shows an example using a continuous function, (b) shows step by step using a discontinuous function. A changed example is shown. It is explanatory drawing which shows an example of the table which matched and defined waiting time and inclination angle, (a) shows an example using a continuous function, and (b) changes in steps using a discontinuous function. An example is shown. The flowchart which shows the flow of the setting value calculation process which concerns on 2nd embodiment. It is explanatory drawing which shows the table used for calculation of movement allowable value and waiting time, (a) shows an example of a table which specified and defined movement allowable value and inclination time, (b) is waiting time and inclination An example of the table which prescribes | regulated by matching time is shown. The flowchart which shows the flow of processing of a third embodiment. It is an explanatory diagram showing a table used to determine the X-ray irradiation conditions at the time of imaging, (a) shows an example of a table that defines a motion allowable value and a pulse width, (b) is a motion allowable value, An example of a table in which pulse width and tube current are defined in association with each other is shown. (C) is an example of a table in which movement allowable value, pulse width, tube current, and focus size are defined in association with each other. Show. It is explanatory drawing which shows the table used for determination of the X-ray irradiation conditions at the time of imaging | photography, Comprising: (a) shows an example of the table which prescribed | regulated standby time and pulse width, (b) shows standby time and pulse width. And (c) shows an example of a table in which the motion allowable value, the pulse width, the tube current, and the focus size are defined in association with each other. FIG.

  The present invention relates to an X-ray source that generates X-rays, a bedtop that mounts a subject, an X-ray that is disposed to face the X-ray source across the bedtop and transmits the subject An X-ray detector that outputs an electric signal corresponding to the intensity of transmitted X-rays and an image processing unit that generates an X-ray image based on the electric signal, and for each successive frame, an X-ray image An X-ray fluoroscopic apparatus that performs fluoroscopy to generate a radiograph and radiographing to generate an X-ray image composed of a still image, and supports the bed by tilting the long axis of the couch top with respect to a horizontal plane An apparatus, a parameter calculation unit that calculates a posture parameter indicating an inclination posture of the bed top plate, a motion detection unit that detects the magnitude of the movement of the subject based on an X-ray image of the continuous frame, The movement allowable value of the magnitude of movement of the subject at the time of imaging is set as the posture parameter. A motion allowable value setting unit that is set based on a meter, and a shooting control unit that performs operation control for the shooting based on the motion allowable value set by the motion allowable value setting unit. To do.

  The X-ray fluoroscopic apparatus measures an elapsed time after the magnitude of movement of the subject falls below the allowable movement value, and compares the elapsed time with a preset standby time. A part may be further provided. In this case, the photographing control unit may perform operation control for the photographing when the elapsed time exceeds the standby time.

  The X-ray fluoroscopic apparatus may further include a standby time setting unit that sets the standby time according to the posture parameter. In this case, the elapsed time measuring unit may compare the set standby time with the elapsed time.

  The parameter calculation unit may include an angle calculation unit that calculates an inclination angle of a major axis of the bed top plate with respect to the horizontal plane. In this case, the movement allowable value setting unit sets the movement allowable value to be larger as the head side of the bed top plate is relatively lower than the foot side of the bed top plate based on the tilt angle. May be.

  The parameter calculation unit may include an angle calculation unit that calculates an inclination angle of a major axis of the bed top plate with respect to the horizontal plane. In this case, the waiting time setting unit sets the waiting time to be shorter as the head side of the bed top plate is relatively lower than the foot side of the new board top plate based on the tilt angle. Also good.

  The parameter calculation unit may include an inclination time measurement unit that measures an inclination time indicating a time from when the head side of the bed top plate is positioned relatively lower than the foot side of the bed top plate. In this case, the motion allowable value setting unit may set the motion allowable value to be larger as the inclination time becomes longer.

  The parameter calculation unit may include an inclination time measurement unit that measures an inclination time indicating a time from when the head side of the bed top plate is positioned relatively lower than the foot side of the bed top plate. In this case, the standby time setting unit may set the standby time shorter as the inclination time becomes longer.

  The X-ray fluoroscopic apparatus may further include an X-ray irradiation condition setting unit that controls to reduce the exposure time in the imaging as the allowable motion value increases.

  The X-ray irradiation condition setting unit increases the exposure energy of X-rays used for the imaging when the exposure time in the imaging is decreased so that the X-ray dose in a predetermined imaging is constant. However, when the exposure time in the imaging is increased, the X-ray exposure energy used for the imaging may be controlled to decrease.

  The X-ray source may include a large focal point forming unit having a relatively large focal point size and a small focal point forming unit having a relatively small focal point size. The X-ray irradiation condition setting unit generates the X-ray using the large focus forming unit when the allowable motion value is equal to or greater than a first threshold value, and the allowable motion value is smaller than the first threshold value. In this case, the X-ray may be controlled to be generated using the small focus forming unit.

  The X-ray fluoroscopic imaging apparatus may further include an X-ray irradiation condition setting unit that controls to reduce the exposure time in the imaging as the standby time becomes shorter.

  The X-ray irradiation condition setting unit increases the exposure energy of X-rays used for the imaging when the exposure time in the imaging is decreased so that the X-ray dose in a predetermined imaging is constant. However, when the exposure time in the imaging is increased, the X-ray exposure energy used for the imaging may be controlled to decrease.

  The X-ray source may include a large focal point forming unit having a relatively large focal point size and a small focal point forming unit having a relatively small focal point size. And, when the standby time is shorter than the second threshold, the X-ray irradiation condition setting unit generates the X-ray using the large focus forming unit, and when the standby time is equal to or greater than the second threshold, The X-ray may be controlled to be generated using the small focus forming unit.

  The present invention will be described below with reference to the drawings. Throughout the drawings, the same components are denoted by the same reference numerals, and redundant description is omitted.

  First, a schematic configuration of the X-ray fluoroscopic apparatus according to the present embodiment will be described based on FIG. FIG. 1 is a functional block diagram showing a schematic configuration of the X-ray fluoroscopic apparatus according to the present embodiment.

  The X-ray fluoroscopic imaging apparatus 10 shown in FIG. 1 acquires an X-ray image for each continuous frame, acquires X-ray images consisting of moving images, and acquires X-ray images consisting of still images, X-ray fluoroscopic apparatus capable of performing X-ray generation, and is disposed opposite to the X-ray source 11 for generating X-rays, detects X-rays transmitted through the subject 2, and detects transmitted X-rays An X-ray detector 12 that outputs an electrical signal corresponding to the intensity of the image, an image processor 13 that generates an X-ray image based on the electrical signal output from the X-ray detector 12, and an X-ray image are stored Between the image storage unit 14, the control unit 15 that controls the operation of each part of the X-ray fluoroscopic apparatus 10, the image display unit 16 that displays an X-ray image, and the X-ray source 11 and the X-ray detector 12. The table top 17 that is placed and mounts the subject 2, the bed support device 18 that supports the long axis of the bed table 17 by tilting it with respect to the horizontal plane, and the tilt posture of the bed table 17 It includes a parameter calculation unit 19 that calculates the to attitude parameters, the.

  In the first embodiment described below, the parameter calculation unit 19 includes an angle calculation unit 191 that calculates the inclination angle θ of the major axis l1 of the bed top plate 17 with respect to the horizontal plane Ls. In addition, in the second embodiment, the parameter calculation unit 19 has the head side of the couch top 17 relatively lower than the foot side of the couch top 17 based on the inclination angle θ in addition to the angle calculation unit 191. A tilt time measuring unit 192 is further included for measuring the time from the reverse tilt position. The tilt angle θ is calculated as the tilt angle θ> 0 when the foot side of the subject on the bed top 17 is higher than the horizontal plane Ls. Therefore, when the tilt angle θ> 0, the subject 2 placed on the bed top 17 is in the reverse tilt position. Since the inclination time calculation unit 192 is used in the second embodiment, it is not an essential component in the first embodiment.

  The X-ray source 11 has an X-ray tube that generates X-rays. The X-ray source 11 may include an X-ray filter that selectively transmits X-rays having specific energy, a diaphragm device that sets an X-ray irradiation region, and the like.

  The X-ray detector 12 is configured by, for example, a plurality of detection elements that detect X-rays arranged in a two-dimensional array, and the incident X-rays irradiated from the X-ray source 11 and transmitted through the subject 2 It is a device that detects and outputs X-ray signals (electrical signals) according to the quantity.

  The image processing unit 13 generates an X-ray image based on the X-ray signal output from the X-ray detector 12. An X-ray image is generated for each frame during fluoroscopy.

  The image storage unit 14 stores the X-ray image generated by the image processing unit 13.

  The control unit 15 compares the continuous frames (n-1th sheet, nth sheet, etc.) stored in the image storage unit 14 to detect the magnitude of the movement of the subject 2, and the posture Based on the parameters, a motion allowable value setting unit 152 that sets a motion allowable value indicating how much the motion of the subject 2 is allowed to be allowed, and after the subject motion falls below the motion allowable value until imaging A standby time setting unit 153 that sets a standby time that determines how long to wait, and an elapsed time after the movement of the subject falls below the allowable movement value, and a predetermined standby time An elapsed time measurement unit 154 that performs comparison, an imaging control unit 155 that performs operation control for imaging when the elapsed time exceeds the standby time, and an X-ray irradiation condition during fluoroscopy, for example, an exposure time (exposure time) X-ray condition setting unit 156 for changing and setting X-ray irradiation conditions such as (pulse width) and exposure energy Comprises according to the set X-ray irradiation conditions for each time fluoroscopy and during photographing, the X-ray source control unit 157 for controlling the operation of the X-ray source 11 so that the X-rays are irradiated, the. Since the fluoroscopy condition control unit 156 is used in the third embodiment, it is not an essential component in the first and second embodiments.

  The elapsed time measurement unit 154 measures the elapsed time after the movement of the subject becomes less than the motion allowable value, but may measure an actual value of the elapsed time, or may replace the actual value with a frame. The number may be measured. The standby time setting unit 153 sets the standby time in units of time when the elapsed time measurement unit 154 measures actual values, and sets the standby time in units of frames when the elapsed time measurement unit 154 measures the number of frames. To do.

  When the elapsed time exceeds the standby time, the imaging control unit 155 may output a predetermined X-ray irradiation condition at the time of imaging to the X-ray source control unit 157 to generate X-rays, or wait for the operator When the operator operates only an exposure button (not shown), the X-ray irradiation conditions at the time of imaging are output to the X-ray source control unit 157 to generate X-rays. Also good.

  The image processing unit 13, the image storage unit 14, and the control unit 15 may be configured by a combination of a program that realizes the function of each component and hardware that executes the program. The image display unit 16 may be configured using an image display device such as a CRT or a liquid crystal monitor.

<First embodiment>
The first embodiment is an embodiment in which a tilt angle is used as a posture parameter indicating the posture of a subject, and a motion allowable value and a standby time are set using the tilt angle. Hereinafter, the first embodiment will be described with reference to FIGS. FIG. 2 is a flowchart showing a flow of inspection in the first embodiment. FIG. 3 is an explanatory diagram showing processing for detecting a value m indicating the magnitude of movement of the subject. FIG. 4 is an explanatory diagram showing an example of the temporal transition of the magnitude of movement. FIG. 5 is a flowchart showing a flow of setting value calculation processing according to the first embodiment.

  FIG. 6 is an explanatory diagram illustrating an example of a table that defines the allowable motion value and the inclination angle in association with each other, where (a) illustrates an example using a continuous function, and (b) uses a discontinuous function. Here is an example that changes step by step.

  FIG. 7 is an explanatory diagram showing an example of a table that defines the standby time and the inclination angle in association with each other, where (a) shows an example using a continuous function, and (b) shows a discontinuous function. An example of changing in stages will be shown. In the following description, the simplest examination will be described by taking an example of a technique of performing one imaging after one fluoroscopy, but a plurality of continuous imaging may be performed after the fluoroscopy. Further, in the series of examinations, the set of fluoroscopy and imaging may be repeated a plurality of times, and in this case, the processing shown in FIG. 2 may be repeated. Further, the number of fluoroscopy and imaging and the combination pattern may differ depending on the correspondence of the inspection technique, but different patterns can be accommodated by appropriately combining the processes in FIG. Hereinafter, description will be made along the order of the steps in FIG.

  Prior to the start of the examination, the subject 2 is placed on the couch top 17 and X-ray irradiation conditions used for fluoroscopy and imaging are set. As an example of the X-ray irradiation conditions, for example, a tube voltage (kV), a tube current (mA), and a pulse width (s) used in each of imaging and fluoroscopy are set. Thereafter, the inspection is started.

(Step S1)
A set value calculation process for the motion allowable value and the standby time is started (S1). Details of this set value calculation processing will be described later.

(Step S2)
The fluoroscopy is started, and an initial value (n = 1) of the frame number n is set (S2).

(Step S3)
The elapsed time measuring unit 154 sets the elapsed time t to an initial value (t = 0). In the present embodiment, the number of frames is counted as the elapsed time (S3).

(Step S4)
An X-ray image of the nth frame is generated (S4). The X-ray source control unit 157 emits X-rays from the X-ray source 11 according to the set irradiation conditions, the X-ray detector 12 detects the X-rays that have passed through the subject 2, and according to the transmitted X-ray intensity Outputs X-ray signals. The image processing unit 13 generates an X-ray image for each frame based on the output X-ray signal, and outputs it to the image storage unit 14. The image storage unit 14 stores an X-ray image.

(Step S5)
The motion detection unit 151 reads and compares the x-ray image of the (n-1) th frame and the x-ray image of the nth frame from the image storage unit 14, and compares the value m (hereinafter referred to as “motion magnitude”). m ”) (S5). In this step, as shown in FIG. 3, the X-ray image 30 of the (n-1) th frame and the X-ray image 31 of the n-th frame are read, and a difference image 32 between these two images is generated. Then, the number of pixels constituting the non-overlapping area (difference area) 32a in the difference image 32 is counted, and this value is calculated as the motion magnitude m. By counting the number of pixels, the area of the subject region captured in the other X-ray image can be obtained with reference to the subject region captured in one X-ray image, and the movement of the subject A value indicating the magnitude of is obtained.

(Steps S6, S7)
The motion detection unit 151 compares the motion magnitude m calculated in step S5 with the motion allowable value set in step S1-2 in the setting value calculation process described later, and the motion magnitude m <motion It is determined whether the value is acceptable (S6). If not, the process proceeds to step S7, and the frame number n is incremented by one (S7). After that, the process returns to step S3, and the processes after step S3 are repeated. If affirmative, the process proceeds to step S8.

(Step S8)
The elapsed time measuring unit 154 increments the elapsed time (the number of frames) t after the magnitude m of the motion becomes less than the motion allowable value by one (S8).

(Step S9)
The elapsed time measurement unit 154 determines whether or not the elapsed time t is equal to or longer than the standby time (number of frames) set in step S1-3 in the setting value calculation process described later (S9). The process of this step will be described with reference to FIG. FIG. 4 is an explanatory diagram showing an example of the relationship between the magnitude of movement and the elapsed time.

Elapsed time measuring unit 154, the magnitude of the motion to measure the elapsed time t from the frame number n _alpha when it becomes less than the motion allowable value m. For example, when the standby time = the number of frames x, if the elapsed time t = n _{(α + x)} or more, it is determined affirmative and the process proceeds to step S11. If it is less than the elapsed time t = n _{(α + x)} , it is determined negative and the process proceeds to step S10.

When the elapsed time is expressed as an actual measurement value of time, the elapsed time from time t ₀ when the magnitude of the movement is less than the allowable movement value m is measured. In the standby time setting unit 153, for example, when standby time = t _x is set, it is determined as affirmative if it is t _x hours after time t _0, and is determined as negative if it is less than t _x .

(Step S10)
Increment frame number n. Thereafter, the process returns to step S4, and the processes after step S4 are repeated (S10).

(Step S11)
The X-ray source control unit 157 interrupts the fluoroscopy, and the imaging control unit 155 performs operation control for imaging (S11). The imaging control unit 155 may perform automatic imaging by exposing the X-ray source control unit 157 to X-rays according to predetermined X-ray irradiation conditions for imaging. Further, when the imaging control unit 155 notifies the operator that the standby time has elapsed and the operator operates an imaging button (X-ray exposure button) (not shown), the X-ray source control unit 157 is set in advance. Imaging may be performed by irradiating the X-ray source 11 with X-rays according to the X-ray irradiation conditions at the time of imaging. For example, a message may be displayed on the image display unit 16 or may be notified by voice.

(Steps S12, S13)
If the inspection is ended, the process proceeds to step S13, the set value calculation process is ended (S13), and the inspection is ended. When the inspection is continued, the process returns to step S2 to resume fluoroscopy.

  Next, the setting value calculation process will be described in the order of steps in FIG.

(Step S1-1)
The angle calculation unit 191 starts detecting the inclination angle θ of the bed top plate 17. The detected data of the inclination angle θ is output to the motion allowable value setting unit 152 and the standby time setting unit 153 (S1-1). After step S1-1 ends, the process proceeds to both step S1-2 and step S1-3.

(Step S1-2)
The motion allowable value setting unit 152 acquires the tilt angle θ calculated in S1-1, and sets a motion allowable value according to this (S1-2). The allowable motion value setting unit 152 sets the allowable motion value to increase as the inclination angle θ increases. The allowable motion value setting unit 152 includes data that associates the allowable motion value with the tilt angle in advance, and sets the allowable motion value corresponding to the tilt angle θ acquired with reference to this data.

  An example of this data will be described with reference to FIG. In FIG. 6 (a), it is defined that the allowable motion value continuously increases as the tilt angle increases.

  Further, as shown in FIG. 6 (b), the allowable motion value may be increased stepwise according to the inclination angle. The number of steps may be larger or smaller than shown in (b) of FIG. Further, the step widths may not be uniform. For example, the step width may be defined to be smaller as the inclination angle is larger. Further, in (b) of FIG. 6, the case where it is included and the case where it is not included may be defined in reverse.

(Step S1-3)
The standby time setting unit 153 acquires the slope time θ calculated in step S1-1, and sets the standby time according to this (S1-3). The standby time setting unit 153 sets the standby time to become shorter as the inclination angle θ increases. The standby time setting unit 153 previously includes data in which the standby time is associated with the inclination angle, and sets the standby time corresponding to the inclination angle θ acquired with reference to this data.

  An example of this data will be described with reference to FIG. In FIG. 7 (a), it is defined that the standby time is continuously shortened as the inclination angle increases.

  Further, as shown in (b) of FIG. 7, the standby time may be shortened stepwise as the inclination angle increases. The number of steps may be larger or smaller than shown in (b) of FIG. Further, the step widths may not be uniform. For example, the step width may be defined to be smaller as the inclination angle is larger. Furthermore, in (b) of FIG. 7, the case where it is included and the case where it is not included may be defined in reverse.

(Step S12)
It is determined whether or not to end the set value calculation process. If the result is negative, the process returns to step S1-1, the process from S1-1 onward is repeated, and if the result is positive, the process proceeds to step S13. Usually, it is determined to be negative in this step while the inspection continues. As a result, while the examination is continued, the set value calculation process is continuously executed independently of the fluoroscopy and the imaging process. Then, in the determination processing at step S5 and step S9, the latest motion allowable value and standby time are read and used for the determination processing.

  According to the present embodiment, at the reverse tilt position, the subject is loaded to maintain a stationary state, and the subject is likely to move. As a result, the image is likely to be blurred or blurred due to the subject's motion. However, according to the present embodiment, the standby time is shortened as the load increases, and the time until photographing is shortened by increasing the motion tolerance. As a result, it is possible to suppress blurring and blurring of image quality due to the movement of the subject.

<Second embodiment>
The second embodiment is an embodiment in which an allowable time and a standby time are set based on an elapsed time (hereinafter referred to as “inclination time”) since the reverse inclination position is used as a posture parameter, based on the inclination time. Since the flow of inspection in the second embodiment is the same as that in the first embodiment, the description thereof will be omitted, and the setting value calculation process according to the second embodiment will be described below based on FIGS. FIG. 8 is a flowchart showing a flow of set value calculation processing according to the second embodiment. FIG. 9 is an explanatory diagram showing a table used for calculating the allowable motion value and the standby time, in which (a) shows an example of a table in which the allowable motion value and the inclination time are defined in association with each other, and (b) An example of the table which prescribed | regulated and matched waiting time and inclination time is shown. Hereinafter, description will be made along the order of steps in FIG.

(Steps S1-11, S1-12)
Similar to step S1-1, the angle calculation unit 191 starts measuring the tilt angle (S1-11), and determines whether the tilt angle θ exceeds 0 (S1-12). If the determination is affirmative, the process proceeds to step S1-13, and if the determination is negative, the process returns to step S1-11.

(Step S1-13)
The tilt time calculation unit 192 starts measuring the tilt time (S1-13). The measured inclination time is output to the motion allowable value setting unit 152 and the standby time setting unit 153. After this step is completed, the process proceeds to both step S1-14 and step S1-15.

(Step S1-14)
The motion allowable value setting unit 152 acquires the tilt time calculated in step S1-13, and sets a motion allowable value according to this (S1-14). The motion allowable value setting unit 152 sets the motion allowable value to increase as the tilt time increases. The allowable motion value setting unit 152 includes data that associates the allowable motion value with the tilt time in advance, and sets the allowable motion value corresponding to the tilt time acquired with reference to this data.

  An example of the above data will be described based on (a) of FIG. In FIG. 9 (a), it is defined that the allowable motion value increases continuously as the tilt time becomes longer. The allowable motion value set in this step is output to the motion detection unit 151 and used for the determination process in step S6.

(Step S1-15)
The standby time setting unit 153 acquires the slope time calculated in step S1-13, and sets the standby time according to this (S1-15). The standby time setting unit 153 sets the standby time to become shorter as the tilt time becomes longer. The standby time setting unit 153 previously includes data in which the standby time is associated with the inclination time, and sets the standby time corresponding to the inclination time acquired with reference to this data.

  An example of the above data will be described with reference to (b) of FIG. In FIG. 9 (b), it is defined that the standby time is continuously shortened as the inclination time becomes longer. The standby time set in this step is output to the elapsed time measuring unit 154 and used for the determination process in step S9.

(Step S12)
It is determined whether or not to terminate the set value calculation process. If the result is negative, the process returns to step S1-11, the process from S1-11 is repeated, and if the result is affirmative, the process proceeds to step S13.

  According to the present embodiment, the movement of the subject is expected to increase as the state of the reverse tilt position becomes longer. Even in such an examination, image blurring or blurring due to the movement of the subject is expected. Can be effectively suppressed.

<Third embodiment>
The third embodiment is an embodiment in which the X-ray irradiation conditions at the time of imaging are controlled according to the motion allowable value or the standby time. In the present embodiment, the X-ray irradiation conditions at the time of imaging change according to the allowable motion value or the standby time, but it does not matter from which posture parameter the allowable motion value and the standby time are calculated. Therefore, since the third embodiment may be combined with any of the first embodiment and the second embodiment, first, an embodiment combined with the first embodiment will be described as an example. Hereinafter, the third embodiment will be described with reference to FIGS.

  FIG. 10 is a flowchart showing a process flow of the third embodiment. FIG. 11 is an explanatory diagram showing a table used for determining the X-ray irradiation conditions at the time of imaging, in which (a) shows an example of a table that continuously defines the allowable motion value and the pulse width, and (b) Shows an example of a table that continuously defines the movement allowable value, the pulse width and the tube current in association with each other, and (c) shows the movement allowable value, the pulse width, the tube current, and the focus size, An example of a table that is defined in association with is shown. FIG. 12 is an explanatory diagram showing a table used for determining the X-ray irradiation conditions at the time of imaging, in which (a) shows an example of a table defining the standby time and the pulse width, and (b) shows the standby time. And (c) shows an example of a table in which the allowable motion value, the pulse width, the tube current, and the focus size are defined in association with each other. It is explanatory drawing which shows an example. In the following, description will be made in the order of the steps in FIG.

(Step S20)
After step S11, the X-ray condition setting unit 156 acquires the motion allowable value set in step S1-2, and sets the X-ray irradiation condition according to this (S20). Thereafter, the process proceeds to step S12. In this step, the X-ray condition setting unit 156 controls to reduce the exposure time (exposure pulse width) at the time of imaging as the allowable motion value increases. In the example of FIG. 11 (a), control is performed so that the pulse width continuously decreases as the allowable motion value increases. As another example, the pulse width may be controlled to be reduced stepwise.

  In addition, as another example of controlling the X-ray irradiation conditions, the X-ray dose (mAs) in one imaging is set before the start of examination, and the allowable value of movement is large with the value kept constant. Accordingly, the exposure time during imaging (exposure pulse width) may be reduced and the exposure energy may be increased. When the exposure energy increases at least one of the tube current and the tube voltage, the exposure energy increases, and when at least one of the tube current and the tube voltage decreases, the exposure energy also decreases.

  (B) of FIG. 11 shows an example in which the exposure time (exposure pulse width) and the tube current are changed according to the motion allowable value while keeping the X-ray dose in one imaging constant. In FIG. 11 (b), the product of the pulse width (s) and the tube current (mA) corresponding to each motion allowance coincides with the preset X-ray dose (mAs). FIG. 11B shows an example in which the pulse width (s) and the tube current (mA) are continuously changed. However, these may be changed stepwise.

In addition, as shown in FIG. 11 (c), while keeping the X-ray dose in one imaging constant, the exposure time (exposure pulse width) is decreased as the motion allowance increases, The focal spot size of the X-ray source 11 may be switched from a small one to a large one. In this example, the X-ray source 11 includes a large focal point forming unit that forms a focal point having a relatively large focal point size (for example, a focal point size of 0.6 mm or more) and a relatively small focal point size (for example, a focal point size of 0.3 mm). And a small focal point forming part for forming a focal point. When the allowable motion value is equal to or less than the first threshold value m _TH , the X-ray condition setting unit 156 controls to generate X-rays using the small focus forming unit, and the allowable motion value is less than the first threshold value m _TH . Is larger, the X-ray condition setting unit 156 controls to generate X-rays using the large focus forming unit. In the example of (c) of FIG. 11, when the motion allowable value is m ₀ , the pulse width is set to W ₀ and the tube current is set to mA ₀ . Thereafter, the control is performed so that the pulse width continuously decreases and the tube current increases as the allowable motion value increases.

When the motion allowable value exceeds the first threshold value m _TH (m ₀ <m _TH ), the X-ray condition setting unit 156 switches the focal point size of the X-ray source 11 from the small focal point to the large focal point, and the pulse width thereof. Is changed to W ₁ and the tube current is set to mA ₁ (mA ₀ <mA ₁ ). Thereafter, the exposure time (exposure pulse width) at the time of imaging is further decreased and the exposure energy is increased in accordance with the increase in the allowable motion value.

  The specific example of the focal spot size is only an example. Also, the focus size is not limited to two stages, and switching of three or more stages may be performed. Further, the pulse width and the tube current may be changed and controlled not only continuously but stepwise.

  By changing the focal point size of the X-ray source 11 to a large one, a large exposure energy can be obtained in the X-ray source 11. In general, when imaging a stationary subject, the image tends to be blurred by increasing the focal size of the X-ray source 11. However, when imaging a moving subject, the exposure time of the subject can be shortened because the exposure energy of the X-ray source 11 is increased. Can be suppressed.

  In the above embodiment, the X-ray irradiation condition at the time of imaging is changed and set according to the motion allowable value, but the X-ray irradiation condition may be changed and set according to the standby time. In this case, in step S20, the standby time set in step S1-5 is read, and the X-ray irradiation conditions are set based on this.

  For example, as shown in FIG. 12 (a), the exposure time (exposure pulse width) during imaging may be controlled to increase as the standby time (number of frames) becomes longer.

  In addition, as shown in FIG. 12 (b), while keeping the X-ray dose in a predetermined one-time shooting constant, the exposure time at the time of shooting (the number of frames) increases as the standby time (number of frames) increases. The exposure pulse width may be increased and the exposure energy may be decreased.

Furthermore, as shown in FIG. 12 (c), the exposure time during exposure (exposure) increases as the standby time (the number of frames) increases while keeping the X-ray dose in one predetermined imaging constant. The focal spot size may be switched from a relatively large one to a smaller one, and the tube current and / or tube voltage may also be changed in order to increase the radiation pulse width and reduce the exposure energy. In the example of FIG. 12 (c), the X-ray source 11 includes a large focal point forming unit that forms a relatively large focal point size and a small focal point forming unit that forms a relatively small focal point size. . When the standby time (number of frames) is t ₀ , the pulse width is set to W ₀ and the tube current is set to mA ₀ . At this time, the focal size of the X-ray source 11, in accordance with the relatively large tube current mA _0, keep selecting the larger focus. Thereafter, control is performed so that the pulse width continuously increases and the tube current decreases as the standby time increases.

When the standby time exceeds the second threshold value t _TH (t ₀ <t _TH ), the X-ray condition setting unit 156 switches the focal point size of the X-ray source 11 from the large focal point to the small focal point, and sets its pulse width. Change the setting of W ₁ (W ₀ <W ₁ ) and tube current to mA ₁ (mA ₀ > mA ₁ ). Thereafter, as the standby time becomes longer, the exposure time at the time of imaging (exposure pulse width) is controlled to be longer, and the tube current and / or the tube voltage are set so that the exposure energy becomes constant. Decrease.

According to this embodiment, the tendency of the magnitude of movement of the subject is determined based on the allowable movement value or the standby time, and when the movement is relatively large, the exposure time at the time of imaging is shortened. It is possible to suppress blurring of the image due to the movement of the specimen.
<Other embodiments>
In the first embodiment, the allowable motion value and the standby time are set based on the tilt angle in the first embodiment, and in the second embodiment, the motion allowable value corresponding to each is set using both the tilt angle and the tilt time. A candidate for a candidate and a waiting time may be calculated, and one motion allowable value and a waiting time may be determined based on them. For example, if the motion allowable value candidate calculated based on the inclination angle and the inclination time is ma and mb, and ma <mb, the value mb calculated from the inclination time may be used as the motion allowable value mb. . The same applies to the standby time. As described above, by determining the allowable motion value and the standby time using a plurality of posture parameters, it is possible to detect the imaging timing according to the state of the subject. For example, even if the tilt angle is the same, if the tilt time is longer, the subject is expected to move more easily, so the motion allowance obtained from the tilt time is greater than the motion allowance obtained from the tilt angle. In the case of a large value, it is possible to more effectively suppress image blurring due to motion by using the motion allowance obtained from the tilt time.

  In addition, the tilt time may be an elapsed time every time since the tilt angle becomes zero, or the cumulative tilt time in one inspection may be used before and after the tilt angle becomes zero. If the slope time is the same each time, the same allowable movement value and waiting time are the same in the first half of the inspection and the second half of the inspection, but by using the cumulative inclination time, the larger movement allowable value and shorter are closer to the end of the inspection. It is easy to set the waiting time, and it can be expected that the examination is performed in consideration of the movement of the subject who is fatigued by the examination load due to the reverse tilt position.

  Further, in the above embodiment, both the allowable motion value and the standby time are obtained based on the posture parameter, but only one of them is detected based on the posture parameter, and the other is using a fixed value that does not depend on the posture parameter. Also good. For example, only the allowable motion value may be calculated based on the posture parameter, and the standby time may be a fixed value, for example, 2 seconds. On the contrary, only the waiting time may be calculated based on the posture parameter, and the allowable motion value may be a fixed value, for example, the number of pixels Pa of the difference image. Furthermore, the posture parameter is not limited to the tilt angle and the tilt time, and any type may be used as long as it represents a tilt posture.

  Further, the characteristics (functions) of the tables shown in FIGS. 6, 7, 9, 11, and 12 are not limited to the above. For example, each characteristic may change in a curved line, or may change not only continuously but also in stages. For example, in (a) of FIG. 6, it is specified to be linearly increased, but as another aspect, it is specified to be a curved shape in which the change rate of the allowable motion value increases as the inclination angle increases. May be. In addition, in FIG. 7 (a), it is defined as a straight line, but as another aspect, it may be defined as a curved line in which the change rate of the standby time increases as the inclination angle increases.

  Further, in FIG. 9 (a), it is defined to increase linearly, but as another aspect, it is specified to be curved so that the rate of change of the allowable motion value increases as the tilt time increases. May be. Further, the change control may be performed not only continuously but step by step (stepwise). In (b) of FIG. 9, it is defined in a straight line shape, but as another aspect, it may be defined in a curved shape such that the change rate of the standby time increases as the slope time becomes longer, or continuous. It may be specified to change step by step rather than intentionally.

  2 Subject, 10 X-ray fluoroscope, 11 X-ray source, 12 X-ray detector, 13 Image processing unit, 14 Image storage unit, 15 Control unit, 16 Image display unit, 17 Couch top, 18 Couch support device , 19 Parameter calculator

The X-ray fluoroscopic imaging apparatus 10 shown in FIG. 1 acquires an X-ray image for each continuous frame, acquires X-ray images consisting of moving images, and acquires X-ray images consisting of still images, X-ray fluoroscopic apparatus capable of performing X-ray generation, and is disposed opposite to the X-ray source 11 for generating X-rays, detects X-rays transmitted through the subject 2, and detects transmitted X-rays storing the X-ray detector 12 you output an electric signal corresponding to the intensity, the image processing unit 13 for generating an X-ray image based on the electric signal output from the X-ray detector 12, an X-ray image Between the X-ray source 11 and the X-ray detector 12, the image storage unit 14, the control unit 15 that controls the operation of each part of the X-ray fluoroscopic apparatus 10, the image display unit 16 that displays the X-ray image The table top 17 on which the subject 2 is mounted, the bed support device 18 that supports the long axis of the bed table 17 by tilting it with respect to the horizontal plane, and the tilt posture of the bed table 17 are shown. It includes a parameter calculation unit 19 that calculates the energizing parameters, the.

In the first embodiment described below, the parameter calculation unit 19 includes an angle calculation unit 191 that calculates the inclination angle θ of the major axis L1 of the bed top plate 17 with respect to the horizontal plane Ls. In addition, in the second embodiment, the parameter calculation unit 19 has the head side of the couch top 17 relatively lower than the foot side of the couch top 17 based on the inclination angle θ in addition to the angle calculation unit 191. An inclination time calculation unit 192 is further included for measuring the time after the reverse inclination position is reached. The tilt angle θ is calculated as the tilt angle θ> 0 when the foot side of the subject on the bed top 17 is higher than the horizontal plane Ls. Therefore, when the tilt angle θ> 0, the subject 2 placed on the bed top 17 is in the reverse tilt position. Since the inclination time calculation unit 192 is used in the second embodiment, it is not an essential component in the first embodiment.

(Step S1-3)
The standby time setting unit 153 acquires the inclination angle θ calculated in step S1-1, and sets the standby time according to this (S1-3). The standby time setting unit 153 sets the standby time to become shorter as the inclination angle θ increases. The standby time setting unit 153 previously includes data in which the standby time is associated with the inclination angle, and sets the standby time corresponding to the inclination angle θ acquired with reference to this data.

In the reverse tilt position, a load is applied to the subject to maintain a stationary state, and the subject tends to move. As a result, image blurring and blurring due to the subject's movement are likely to occur. For example, the standby time is shortened as the load increases, and the time until photographing is shortened by increasing the motion tolerance. As a result, it is possible to suppress blurring and blurring of image quality due to the movement of the subject.

Although the movement of the subject is expected to increase as the state of the reverse tilt position becomes longer , according to the present embodiment, image blurring or blurring due to the movement of the subject is also observed in such a situation. Can be effectively suppressed.

Claims (14)

An X-ray source that generates X-rays, a bed top plate on which the subject is mounted, and the X-ray source disposed opposite to the X-ray source across the bed top plate, detects the X-rays transmitted through the subject, An X-ray detector that outputs an electrical signal corresponding to the intensity of transmitted X-rays, and an image processing unit that generates an X-ray image based on the electrical signal,
An X-ray fluoroscopic apparatus that performs fluoroscopy for generating an X-ray image for each successive frame and imaging for generating an X-ray image composed of a still image,
A bed support device that supports the long axis of the bed table inclined with respect to a horizontal plane;
A parameter calculation unit for calculating a posture parameter indicating the tilt posture of the bed top;
A motion detector for detecting the magnitude of the movement of the subject based on the X-ray images of the continuous frames;
A movement allowable value setting unit that sets a movement allowable value of the magnitude of movement of the subject at the time of imaging based on the posture parameter;
An imaging control unit that performs operation control for the imaging based on the motion allowable value set by the motion allowable value setting unit;
X-ray fluoroscopic apparatus characterized by comprising: An elapsed time measurement unit that measures an elapsed time after the magnitude of the movement of the subject falls below the allowable movement value, and compares the elapsed time with a preset standby time;
When the elapsed time exceeds the standby time, the shooting control unit performs operation control for the shooting.
2. The X-ray fluoroscopic apparatus according to claim 1, wherein A standby time setting unit for setting the standby time according to the posture parameter;
The elapsed time measuring unit compares the set standby time with the elapsed time.
3. The X-ray fluoroscopic apparatus according to claim 2, wherein The parameter calculation unit includes an angle calculation unit that calculates an inclination angle of a long axis of the bed top plate with respect to the horizontal plane,
The movement allowable value setting unit sets the movement allowable value to be larger as the head side of the bed top plate is relatively lower than the foot side of the bed top plate based on the tilt angle.
2. The X-ray fluoroscopic apparatus according to claim 1, wherein The parameter calculation unit includes an angle calculation unit that calculates an inclination angle of a long axis of the bed top plate with respect to the horizontal plane,
The waiting time setting unit sets the waiting time to be shorter as the head side of the bed top plate is relatively lower than the foot side of the bed top plate based on the tilt angle. The X-ray fluoroscopic apparatus according to claim 3. The parameter calculation unit includes an inclination time measurement unit that measures an inclination time indicating a time from when the head side of the bed top plate is relatively lower than the foot side of the bed top plate,
The movement allowable value setting unit sets the movement allowable value to be larger as the inclination time becomes longer.
2. The X-ray fluoroscopic apparatus according to claim 1, wherein The parameter calculation unit includes an inclination time measurement unit that measures an inclination time indicating a time from when the head side of the bed top plate is relatively lower than the foot side of the bed top plate,
The standby time setting unit sets the standby time shorter as the inclination time becomes longer,
4. The X-ray fluoroscopic apparatus according to claim 3, wherein An X-ray irradiation condition setting unit that controls to reduce the exposure time in the imaging as the movement allowable value increases,
2. The X-ray fluoroscopic apparatus according to claim 1, wherein The X-ray irradiation condition setting unit increases the exposure energy of X-rays used for the imaging when the exposure time in the imaging is decreased so that the X-ray dose in a predetermined imaging is constant. And, when increasing the exposure time in the imaging, control to reduce the X-ray exposure energy used for the imaging,
9. The X-ray fluoroscopic apparatus according to claim 8, wherein The X-ray source includes a large focal point forming unit having a relatively large focal point size and a small focal point forming unit having a relatively small focal point size,
The X-ray irradiation condition setting unit generates the X-ray using the large focus forming unit when the motion allowable value is equal to or greater than a first threshold, and when the motion allowable value is smaller than the first threshold, Control to generate the X-ray using the small focus forming unit,
9. The X-ray fluoroscopic apparatus according to claim 8, wherein As the waiting time becomes shorter, further comprising an X-ray irradiation condition setting unit for controlling to reduce the exposure time in the imaging,
4. The X-ray fluoroscopic apparatus according to claim 3, wherein The X-ray irradiation condition setting unit increases the exposure energy of X-rays used for the imaging when the exposure time in the imaging is decreased so that the X-ray dose in a predetermined imaging is constant. 12. The X-ray fluoroscopic imaging apparatus according to claim 11, wherein when the exposure time in the imaging is increased, the X-ray exposure energy used for the imaging is controlled to be reduced. The X-ray source includes a large focal point forming unit having a relatively large focal point size and a small focal point forming unit having a relatively small focal point size,
The X-ray irradiation condition setting unit generates the X-ray using the large focal point forming unit when the standby time is shorter than a second threshold, and when the standby time is equal to or greater than the second threshold, Control to generate the X-ray using a focus forming unit,
12. The X-ray fluoroscopic apparatus according to claim 11, wherein: A step of performing fluoroscopy for generating an X-ray image for each successive frame, a step of performing imaging for generating an X-ray image composed of a still image, and a bed top plate on which a subject is mounted with a long axis of the bed top plate A step of tilting with respect to a horizontal plane; a step of calculating a posture parameter indicating a tilt posture of the bed top; and a step of detecting a magnitude of movement of the subject based on an X-ray image of the continuous frame; , Setting a motion allowable value of the magnitude of the movement of the subject when performing the imaging based on the posture parameter, and controlling the operation for the imaging based on the set motion allowable value. A control method for the X-ray fluoroscopic apparatus characterized by comprising:

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