JP2013240416A - X-ray diagnostic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve image quality of diagnostic images to be obtained while suppressing the total dose of a subject when irradiating the subject with X-rays and making a diagnosis.SOLUTION: Sections formed by partitioning a plane of a certain height on a top plate 2 where a subject P is mounted into a plurality of planes, is set and the subject P is irradiated with X-rays while monitoring integral dose of the X-rays with which the section is irradiated, so that the dose of the X-rays to be applied is increased to improve the image quality of diagnostic images to be obtained before the integral dose of the X-rays with which each section is irradiated reaches a threshold, whereas when the integral dose of the X-rays with which a certain section is irradiated reaches the threshold, the dose of the X-rays with which the certain section is irradiated is reduced to suppress the exposure to the subject P, and thus, the diagnostic images of high image quality are obtained while suppressing the total exposure of the subject P.

Description

  Embodiments described herein relate generally to an X-ray diagnostic apparatus.

  In recent years, X-ray diagnostic apparatuses that irradiate a subject with X-rays generated from an X-ray tube and diagnose the subject have become widespread. In such X-ray diagnostic apparatuses, the dose of X-rays generated from X-rays There is known a switch that can be switched between a high-dose mode in which the dose is increased and a low-dose mode in which the dose of generated X-rays is reduced (see Patent Document 1 below).

JP 2008-36278 A

  Switching of the X-ray dose mode is performed by switching a changeover switch. For this reason, when diagnosis is started in the high-dose mode, diagnosis in the high-dose mode is continued unless the changeover switch is operated, and when diagnosis is started in the low-dose mode, it is low unless the changeover switch is operated. Diagnosis in dose mode continues.

  Here, high-dose mode diagnosis provides a high-quality diagnostic image, but the amount of exposure of the subject increases, and low-dose mode diagnosis reduces the amount of exposure of the subject, but the resulting diagnostic image has low image quality. Become. Thus, the exposure dose and the image quality of the diagnostic image have a trade-off relationship.

  The present invention has been made to solve such a problem, and its purpose is to provide an image quality of a diagnostic image obtained while suppressing the total exposure amount of the subject when diagnosing the subject by irradiating the subject with X-rays. It is an object to provide an X-ray diagnostic apparatus that can increase the image quality.

  The X-ray diagnostic apparatus according to the embodiment detects a top plate on which a subject is placed, an X-ray tube that generates X-rays that irradiate the subject on the top plate, and X-rays transmitted through the subject An X-ray detector that is connected to the X-ray detector, an image generation unit that generates a diagnostic image of the subject based on the detected X-ray, and a plurality of planes divided into a certain height on the top plate A section setting unit for setting a section, a section specifying section for specifying a section located in the irradiation field irradiated with X-rays generated from the X-ray tube, and a section located in the irradiation field. A dose calculation unit that calculates the dose of irradiated X-rays, a dose integration unit that calculates an integrated dose by integrating the dose of X-rays irradiated to individual sections, and the integrated dose in each section reaches the threshold X-ray that is irradiated to the integrated dose monitoring unit that monitors whether or not the integrated dose has reached the threshold Comprising of a dose reduction setting unit for reducing the dose, the.

It is a block diagram which shows the structure of the X-ray diagnostic apparatus of 1st Embodiment. It is a schematic diagram which shows the some division set to the plane of a certain height on a top plate. It is a block diagram which shows the relationship between a division specific | specification part, a dose calculation part, a dose integrating | accumulating part, an integrated dose monitoring part, and an exposure reduction setting part. It is a schematic diagram which shows the relationship between each division and the X-ray irradiation field, (a) shows the case where the integrated dose has not reached the threshold in all the divisions located in the X-ray irradiation field, (b) The case where the integrated dose of one section located in the X-ray irradiation field reaches the threshold value is shown. It is a graph which shows the integrated dose of a certain division during a diagnosis, the X-ray dose mode generated from an X-ray tube, and the image quality of the diagnostic image produced | generated from the division, (a) is the integrated dose of the division. Shows a case where the threshold does not reach the threshold, and (b) shows a case where the integrated dose of the section reaches the threshold. It is a flowchart explaining the control which switches the X-ray dose mode according to the integrated dose of each division located in the X-ray irradiation field. In 2nd Embodiment, it is a graph which shows the integrated dose of a certain division under diagnosis, the dose mode of the X-rays generated from an X-ray tube, and the image quality of the diagnostic image produced | generated from the division. It is a flowchart explaining the control which switches the X-ray dose mode into two steps according to the integrated dose of each division located in the X-ray irradiation field.

  Hereinafter, embodiments will be described with reference to the drawings.

(First embodiment)
A first embodiment will be described with reference to FIGS. As shown in FIG. 1, the X-ray diagnostic apparatus 1 according to the present embodiment is provided on a bed (not shown) and the top 2 on which the subject P is placed, and the X-ray with respect to the subject P. X-ray irradiation unit 3 that irradiates the X-ray, a high voltage supply unit 4 that supplies a high voltage necessary for X-ray irradiation to the X-ray irradiation unit 3, and an X-ray that detects X-rays transmitted through the subject P Image generation for generating a diagnostic image of the subject P based on the detection unit 5, the movable mechanism unit 6 for moving the top plate 2 and other movable members, and the X-ray detection data detected by the X-ray detection unit 5. Unit 7 and an image display unit 8 connected to the image generation unit 7 to display a diagnostic image generated.

  Furthermore, the X-ray diagnostic apparatus 1 inputs X information based on the information input from the input operation unit 9 for inputting information on the subject P and various information for driving the X-ray diagnostic apparatus 1 and the input operation unit 9. A system control unit 10 that controls each part of the X-ray diagnostic apparatus 1 and controls an X-ray dose irradiated to each section A and A1 (see FIGS. 2 and 4), which will be described later, and is connected to the system control unit 10 And an integrated dose display unit 11 for displaying the integrated dose of X-rays irradiated to each of the sections A and A1.

  The X-ray irradiation unit 3 includes an X-ray tube 12 that generates X-rays to be irradiated to the subject P on the top 2, and an irradiation field B (described later) that is a range in which the X-rays are irradiated. An X-ray restrictor 13 having an aperture for adjusting the X-ray, a quality filter 14 for removing soft X-rays out of X-rays generated from the X-ray tube 12, and a compensation filter 15 for absorbing X-rays. Yes. The X-ray tube 12 is a vacuum tube that generates X-rays. Electrons are emitted from a cathode (filament), and the emitted electrons are accelerated by a high voltage and collide with a tungsten anode to generate X-rays. The X-ray diaphragm 13 is disposed between the X-ray tube 12 and the subject P placed on the top 2, and the range of the irradiation field B irradiated with X-rays by adjusting the diaphragm of the diaphragm unit. Is configured to be variable. The quality filter 14 and the compensation filter 15 are provided so as to be movable in a direction crossing the X-ray irradiation direction by a filter movable mechanism (to be described later) in the movable mechanism 6. The movement of the quality filter 14 and the compensation filter 15 may be performed integrally or separately.

  The high voltage supply unit 4 includes a high voltage generator 16 that generates a high voltage, and an X current such as a tube current, a tube voltage, and an X-ray pulse rate applied to the X-ray tube 12 in accordance with a control signal from the system control unit 10. And a high voltage control circuit 17 for controlling the irradiation condition.

The X-ray detector 5 includes an X-ray detector 18 that receives X-rays generated from the X-ray tube 12 and transmitted through the subject P and detects the incident X-rays as analog signals, and an X-ray detector. An X-ray scattered light component passing through the subject P disposed between the AD converter 19 that converts the analog signal detected at 18 into a digital signal and the top 2 and the X-ray detector 18 is an X-ray. And a grid 20 for preventing the light from entering the detector 18. The grid 20 is composed of a set of two sheets arranged in an orthogonal direction, and one grid 20 is provided so as to be movable by a grid movable mechanism described later in the movable mechanism section 6.

  The movable mechanism unit 6 includes a top plate movable mechanism 21 that moves the top plate 2 in the vertical direction and the longitudinal direction (the body axis direction of the placed subject P), the X-ray irradiation unit 3, and the X-ray detection unit 5. Is movable in the horizontal direction, up and down direction, and in the direction that changes the tilt angle with respect to the top plate 2, and the movable filter that moves the quality filter 14 and the compensation filter 15 in a direction crossing the X-ray irradiation direction. A mechanism 23, a diaphragm movable mechanism 24 that moves the diaphragm portion of the X-ray diaphragm 13, a grid movable mechanism 25 that moves a single grid 20, and a movable mechanism control circuit that controls the movable mechanisms 21 to 25. 26. The grid 20 moved by the grid moving mechanism 25 is disposed between the top 2 and the X-ray detector 18, and the X-ray scattered light component transmitted through the subject P is incident on the X-ray detector 18. It is possible to move between a blocking position for preventing this and a retracted position that allows the scattered light component of X-rays that have been retracted from the disposed position and transmitted through the subject P to enter the X-ray detector 18. Yes.

  The image generation unit 7 is a part that generates a diagnostic image of the subject P based on the X-ray detection data detected by the X-ray detector 18 and then converted into a digital signal by the AD converter 19. Is provided with a pixel value calculation unit 27 for calculating the pixel value of each pixel of the X-ray detector 18 and an image quality correction unit 28 for correcting the image quality of the diagnostic image to be generated. In the pixel value calculation unit 27, the pixel value of each pixel of the X-ray detector 18 that detects X-rays is calculated, and a diagnostic image is generated using the calculation result. The image quality correction unit 28 is configured to clarify the contrast of the diagnostic image when the dose of X-rays generated from the X-ray tube 12 decreases.

  The system control unit 10 includes the image generation unit 7, the X-ray tube 12, the high voltage control circuit 17, the X-ray detector 18, and the system control circuit 29 that controls the movable mechanism control circuit 26. The storage unit 30 stores information transmitted from the units 7, 12, 17, 18, 26, information input from the input operation unit 9, and various programs.

  Furthermore, the system control unit 10 sets a section A (see FIG. 2) divided into a plurality of sections on a plane with a certain height on the top 2 based on information input from the input operation unit 9. Among the set sections A, the section specifying unit 32 that specifies the sections A and A1 (see FIG. 4) located in the irradiation field B of the X-rays generated from the X-ray tube 12, and the irradiation field B A dose calculation unit 33 for calculating the dose of X-rays irradiated to the respective sections A and A1, and the sections A and A1 by integrating the X-ray doses irradiated to the sections A and A1. A dose integrating unit 34 for obtaining an integrated dose for each, an integrated dose monitoring unit 35 for monitoring whether or not the integrated dose in each of the sections A and A1 has reached the threshold, and an integrated dose in a certain section A1 has reached the threshold In some cases, the exposure reduction setting unit 36 reduces the X-ray dose irradiated to the section A1. It is provided.

  Here, in the case of reducing the dose of X-rays irradiated to the section A1 (see FIG. 4B described later) in which the integrated dose has reached the threshold, the following is set by the exposure reduction setting unit 36. One or more of the processes to be described are performed in combination.

One of the processes for reducing the dose of X-rays irradiated to the section A1 whose accumulated dose has reached the threshold is to increase the tube voltage applied to the X-ray tube 12. This process is performed by controlling the high voltage control circuit 17 by the system control circuit 29. When the tube voltage applied to the X-ray tube 12 is increased, the energy of X-rays generated from the X-ray tube 12 is increased, and the X-rays generated are increased so that the subject P is irradiated with the X-rays. In this case, the dose of X-rays that pass through the subject P without being absorbed by the subject P and reach the X-ray detector 18 increases. That is, when the tube voltage applied to the X-ray tube 12 is increased, the X-ray dose detected by the X-ray detector 18 is maintained even if the X-ray dose generated from the X-ray tube 12 is reduced. Is done. Here, in the control of the X-ray dose generated from the X-ray tube 12, the X-ray dose detected by the X-ray detector 18 (or the pixel value detected by the X-ray detector 18) is constant. Has been done so. Therefore, by increasing the tube voltage of the X-ray tube 12, the dose of X-rays generated from the X-ray tube 12 can be reduced, and the X-rays irradiated to the section A1 whose accumulated dose has reached the threshold value can be reduced. The dose can be reduced.

  Another process for reducing the dose of X-rays applied to the section A1 where the integrated dose has reached the threshold is to lower the pulse rate of the tube voltage applied to the X-ray tube 12. This process is performed by controlling the high voltage control circuit 17 by the system control circuit 29. As the pulse rate of the tube voltage applied to the X-ray tube 12 decreases, the number of X-rays generated from the X-ray tube 12 per unit time decreases. Therefore, by lowering the pulse rate of the tube voltage applied to the X-ray tube 12, the dose of X-rays generated from the X-ray tube 12 can be reduced, and irradiation to the section A1 where the integrated dose has reached the threshold value X-ray dose can be reduced.

  Another process for reducing the dose of X-rays applied to the section A1 where the integrated dose has reached the threshold is to increase the gain of the X-ray detector 18. This process is performed by controlling the X-ray detector 18 by the system control circuit 29. By increasing the gain of the X-ray detector 18, the pixel value detected by the X-ray detector 18 is maintained even when the X-ray dose input to the X-ray detector 18 decreases. Therefore, by increasing the gain of the X-ray detector 18, the dose of X-rays generated from the X-ray tube 12 can be reduced, and the X-rays irradiated to the section A1 where the integrated dose has reached the threshold value. The dose can be reduced.

  Another process for reducing the dose of X-rays irradiated to the section A1 where the integrated dose has reached the threshold is to increase the number of added pixels for binning (pixel addition) of the X-ray detector 18. is there. This process is performed by controlling the X-ray detector 18 by the system control circuit 29. By increasing the number of binning added pixels of the X-ray detector 18, the pixel value detected by the X-ray detector 18 is maintained even when the X-ray dose input to the X-ray detector 18 decreases. The Therefore, by increasing the binning of the X-ray detector 18, the dose of X-rays generated from the X-ray tube 12 can be reduced, and the X-rays irradiated to the section A1 where the integrated dose has reached the threshold value. The dose can be reduced.

  Another process for reducing the dose of X-rays irradiated to the section A1 where the integrated dose has reached the threshold is to change the inclination angle of the X-ray tube 12 and the X-ray detector 18 with respect to the top plate 2. That is. This process is performed by controlling the imaging system movable mechanism 22 by the system control circuit 29. Then, by changing the inclination angle of the X-ray tube 12 and the X-ray detector 18 with respect to the top 2, the X-ray generated from the X-ray tube 12 is irradiated to the section A1 where the integrated dose has reached the threshold value. Can be avoided. Therefore, by changing the inclination angle of the X-ray tube 12 and the X-ray detector 18 with respect to the top plate 2, the dose of X-rays irradiated to the section A1 where the integrated dose has reached the threshold can be reduced. .

Another process for reducing the dose of X-rays irradiated to the section A1 where the integrated dose has reached the threshold is to change the irradiation direction of the X-rays from the X-ray tube 12 from the lower side of the top 2 Is to change. This process is applicable when the X-ray tube 12 and the X-ray detector 18 are attached to the C-type arm, and is performed by controlling the imaging system movable mechanism 22 by the system control circuit 29. By irradiating X-rays from below the top plate 2, the distance from the X-ray tube 12 to the section A1 increases, and the dose of X-rays irradiated to the section A1 whose accumulated dose has reached the threshold is reduced. Can be made.

  Another process for reducing the dose of X-rays irradiated to the section A1 where the integrated dose has reached the threshold is to reduce the aperture of the X-ray diaphragm 13 so that the section A1 has reached the threshold. Is to deviate from the X-ray irradiation field B. This process is performed by controlling the diaphragm movable mechanism 24 by the system control circuit 29. By reducing the aperture of the X-ray diaphragm 13 so that the section A1 in which the integrated dose has reached the threshold value deviates from the X-ray irradiation field B, the section A1 in which the integrated dose has reached the threshold value is irradiated. X-ray dose can be reduced.

  Another process for reducing the dose of X-rays irradiated to the section A1 where the integrated dose has reached the threshold is a radiation quality filter between the X-ray tube 12 and the subject P on the top 2. 14 and covering the section A1 where the integrated dose has reached the threshold value by the quality filter 14. This process is performed by controlling the filter movable mechanism 23 by the system control circuit 29. By covering the section A1 in which the integrated dose has reached the threshold with the radiation filter 14, the soft X-rays are removed by the quality filter 14, and the X-ray irradiated to the section A1 in which the integrated dose has reached the threshold. The dose can be reduced.

  Another process for reducing the dose of X-rays irradiated to the section A1 where the integrated dose has reached the threshold is a compensation filter 15 between the X-ray tube 12 and the subject P on the top 2. And the compensation filter 15 covers the section A1 in which the integrated dose has reached the threshold value. This process is performed by controlling the filter movable mechanism 23 by the system control circuit 29. By covering the section A1 in which the integrated dose has reached the threshold value with the compensation filter 15, it is possible to reduce the X-ray dose irradiated to the section A1 in which the integrated dose has reached the threshold value.

  Another process for reducing the dose of X-rays irradiated to the section A1 in which the integrated dose has reached the threshold is arranged between the top plate 2 and the X-ray detector 18 in an orthogonal direction. The X-ray scattered light component that has passed through the subject P passes through the subject P through one of the two grids 20 positioned at a blocking position that prevents the scattered light component from entering the X-ray detector 18. The scattered light component of the X-rays is moved to a retreat position that allows the X-ray scattered light component to enter the X-ray detector 18. This process is performed by controlling the grid moving mechanism 25 by the system control circuit 29. By moving one grid 20 to the retracted position, the amount of X-ray scattered light incident on the X-ray detector 18 can be increased, and the dose of X-rays generated from the X-ray tube 12 can be reduced. The dose of X-rays irradiated to the section A1 whose dose has reached the threshold can be reduced. In this process, not only one grid 20 but also two grids 20 may be moved to the retreat position.

  FIG. 2 is a schematic diagram showing a plurality of rectangular sections A set on a plane having a certain height on the top board 2. The setting of these sections A is performed by inputting information on the height dimension “H” from the top plate 2 to the plane and the vertical and horizontal dimensions of each section A from the input operation unit 9, and performing system control based on the input information. This is performed by the section setting unit 31 of the unit 10.

  FIG. 3 is a block diagram showing the relationship among the section specifying unit 32, the dose calculating unit 33, the dose integrating unit 34, the integrated dose monitoring unit 35, and the exposure reduction setting unit 36 provided in the system control unit 10. It is.

  The section specifying unit 32 is a part that specifies the section A to be irradiated with X-rays, and includes top plate position information from the top plate movable mechanism 21, imaging system position information from the imaging system movable mechanism 22, and a diaphragm movable mechanism. The throttle opening degree information from 24 is input. The section specifying unit 32 specifies the section A located in the X-ray irradiation field B based on these pieces of information.

  The dose calculation unit 33 includes the X-ray irradiation information from the high voltage control circuit 17, the top plate position information from the top plate movable mechanism 21, the imaging system position information from the imaging system movable mechanism 22, and the filter movable mechanism 23. The quality filter position information and the compensation filter position information are input. The dose calculation unit 33 calculates the X-ray dose irradiated to each section A based on the input information. The calculation of the dose in the dose calculation unit 33 is performed using a well-known surface dose simple conversion method (Non Dosimetry Dosimetry: NDD method) or the like. The identification of the section A by the section specifying unit 32 and the calculation of the dose by the dose calculation unit 33 are performed every unit time (for example, 1 second).

  A section specifying unit 32 and a dose calculating unit 33 are connected to the dose integrating unit 34. The dose integrating unit 34 integrates the dose calculated by the dose calculating unit 33 for each section A specified by the section specifying unit 32.

  A dose integrating unit 34 is connected to the integrated dose monitoring unit 35. The integrated dose monitoring unit 35 monitors whether or not the integrated dose of each section A has reached a threshold value.

  An integrated dose monitoring unit 35 is connected to the exposure reduction setting unit 36. The exposure reduction setting unit 36 is switched to the “ON state” when the integrated dose of a certain section A1 located in the X-ray irradiation field B reaches a threshold, and all of the exposure reduction setting units 36 located in the X-ray irradiation field B In the case where the integrated dose in the section A has not reached the threshold value, it is configured to be switched to the “off state”. When the exposure reduction setting unit 36 is switched to the “on state”, the X-ray dose mode generated from the X-ray tube 12 becomes the low-dose mode and the X-ray dose generated from the X-ray tube 12 is small. Thus, the dose of X-rays irradiated to the section A1 where the integrated dose reaches the threshold value in the irradiation field B and the other section A located in the irradiation field B is reduced. Further, when the section A1 in which the integrated dose has reached the threshold value deviates from the X-ray irradiation field B as the table 2 or the X-ray irradiation unit 3 moves, the exposure reduction setting unit 36 is “off state”. The X-ray dose mode generated from the X-ray tube 12 becomes the standard dose mode, and the X-ray dose generated from the X-ray tube 12 returns to the original state and increases.

  FIG. 4 is a schematic diagram showing the relationship between the sections A and A1 and the X-ray irradiation field B. FIG. 4A shows a case where the integrated dose has not reached the threshold in all of the plurality of sections A located in the X-ray irradiation field B. FIG. FIG. 4B shows a case where the integrated dose in one section A1 among the plurality of sections A and A1 located in the X-ray irradiation field B reaches the threshold value.

  As shown in FIG. 4A, when the integrated dose has not reached the threshold in all of the plurality of sections A located in the irradiation field B, the exposure reduction setting unit 36 is switched to the “off state”. The X-ray dose mode generated from the X-ray tube 12 is maintained in the standard dose mode.

  On the other hand, as shown in FIG. 4B, when there is a section A1 in which the integrated dose has reached the threshold in the plurality of sections A and A1 located in the irradiation field B, the exposure reduction setting unit 36 The X-ray dose mode of the X-ray generated from the X-ray tube 12 is changed to the low-dose mode, and the dose of X-rays irradiated to the sections A and A1 located in the irradiation field B is reduced. Is done.

  FIG. 5 is a graph showing the accumulated dose in a certain section A, A1 during diagnosis, the X-ray dose mode generated from the X-ray tube 12, and the image quality of the diagnostic image generated from the section A, A1. Yes, (a) shows the case where the integrated dose of the section A does not reach the threshold during diagnosis, and (b) shows the case where the integrated dose of the section A1 reaches the threshold during diagnosis.

As shown in FIG. 5A, when the accumulated dose in the section A does not reach the threshold value during diagnosis, the exposure reduction setting unit 36 is maintained in the “off state” and the X-ray tube is maintained. The dose mode of X-rays generated from 12 is maintained in the standard dose mode, and the image quality of the generated diagnostic image is maintained at the standard image quality.

  As shown in FIG. 5B, when the accumulated dose for the section A1 reaches the threshold after the “T” time has elapsed from the start of diagnosis, the exposure reduction setting unit 36 is switched to the “ON state” at that time. The dose mode of X-rays generated from the X-ray tube 12 is switched to the low-dose mode. After this switching, the dose of X-rays irradiated to the sections A and A1 located in the irradiation field B is reduced. . Note that, as the dose of irradiated X-rays is reduced, the quality of the generated diagnostic image becomes low.

  The upper limit value of the accumulated dose shown in the graph of FIG. 5 means an allowable value of the accumulated dose of X-rays irradiated in the diagnosis. When the cumulative dose for the section A1 reaches this upper limit value, for example, a warning that the cumulative dose has reached the upper limit value is issued, and further, diagnosis is made by stopping the X-ray irradiation according to prior settings. You can also choose to stop.

  FIG. 6 is a flowchart for explaining the switching of the dose mode during the diagnosis of the subject P (switching of the exposure reduction setting unit 36). When the diagnosis is started, a section located in the irradiation field and irradiated with X-rays is specified by the section specifying unit 32 (step S1), and the dose of X-rays irradiated to each section located in the irradiation field is a dose. Calculated by the calculation unit 33 (step S2), the calculated dose is integrated for each section by the dose integration unit 34 (step S3), and it is determined whether the integrated dose has reached the threshold value in any of the sections. Monitored by the monitoring unit 35 (step S4).

  If the integrated dose does not reach the threshold value in any section (NO in step S4), the process returns to step S1. Here, at the start of diagnosis, the exposure reduction setting unit 36 is switched to the “off state”, and the dose mode of X-rays generated from the X-ray tube 12 is the standard dose mode.

  On the other hand, when the integrated dose reaches the threshold value in any section (YES in step S4), the dose reduction setting unit 36 is switched to the “on state” and the X-ray dose mode generated from the X-ray tube 12 is set. Is switched to the low-dose mode (step S5).

  After the dose mode is switched to the low-dose mode, the section specifying unit 32 is specified by the section specifying unit 32 and positioned in the irradiation field and irradiated with X-rays (step S6), as in steps S1 to S3 described above. The dose of X-rays irradiated to each section located in the field is calculated by the dose calculation section 33 (step S7), and the calculated dose is integrated by the dose integration section 34 for each section (step S8).

  After the processes of steps S5 to S8 are performed, the integrated dose monitoring unit 35 monitors whether or not the integrated dose has reached the upper limit value in any of the sections (step S9), and the integrated dose reaches the threshold value. The section specifying unit 32 determines whether or not the section that has been removed is out of the X-ray irradiation field (step S10).

  If the accumulated dose reaches the upper limit value in any of the sections (YES in step S9), a warning that the accumulated dose has reached the upper limit value is given (step S11), and if preset, X-rays are set. The diagnosis by irradiating is stopped (step S12). If it is not preset, after the warning (step S11), the process continues to step S10.

On the other hand, when the section where the integrated dose has reached the threshold value is out of the irradiation field (YES in step S10), the exposure reduction setting unit 36 is switched to the “off state” and is generated from the X-ray tube 12.
The dose mode of the line is switched to the standard dose mode (step S13), and the diagnosis in the standard dose mode is continued.

  According to the present embodiment, when the diagnosis is started by irradiating the subject P with X-rays, the image quality is improved by increasing the dose of X-rays irradiated to the subject P by setting the dose mode to the standard dose mode. A high standard image quality diagnostic image can be obtained. In addition, if a section where the accumulated dose of X-rays is higher than the threshold occurs during diagnosis, the dose of X-rays irradiated to that section can be automatically reduced, and an increase in the accumulated dose for that section can be suppressed. The amount of X-ray exposure to the subject P can be suppressed. On the other hand, when the section where the accumulated dose of X-rays reaches the threshold is out of the X-ray irradiation field, the exposure reduction setting unit 36 is switched to the “off state” to return the dose mode to the standard dose mode. In addition, a high-quality standard-quality diagnostic image can be obtained again.

(Second Embodiment)
A second embodiment will be described with reference to FIGS. In addition, the same code | symbol is attached | subjected to the same component as the component demonstrated in 1st Embodiment, and the overlapping description is abbreviate | omitted.

  The basic configuration of the second embodiment is the same as that of the first embodiment. The difference between the second embodiment and the first embodiment is that, in the second embodiment, the threshold of the integrated dose is set to the first threshold value and the second threshold value (first threshold value <second threshold value), The X-ray dose mode generated from the X-ray tube 12 is set to be switchable between a standard dose mode, a first low-dose mode, and a second low-dose mode. When the integrated dose in a certain section located in the irradiation field reaches the first threshold, the dose mode is switched to the first low-dose mode, and the integrated dose in a certain section located in the irradiation field becomes the second threshold. If reached, the dose mode is switched to the second low dose mode.

  The exposure reduction setting unit 36 is provided to be switchable between an “off state”, a “first on state”, and a “second on state” according to the accumulated dose monitored by the accumulated dose monitoring unit 35. ing. When the exposure reduction setting unit 36 is switched to the “off state”, the dose mode of X-rays generated from the X-ray tube 12 is switched to the standard dose mode, and the exposure reduction setting unit 36 is set to the “first on state”. When switched, the X-ray dose mode generated from the X-ray tube 12 is switched to the first low-dose mode, and when the exposure reduction setting unit 36 is switched to the “second ON state”, the X-ray tube 12 is switched to the second low-dose mode.

  FIG. 7 is a graph showing the accumulated dose for a certain section during diagnosis, the X-ray dose mode generated from the X-ray tube 12, and the image quality of the diagnostic image generated from the section.

  This graph shows that when the time “T1” has elapsed from the start of diagnosis, the cumulative dose of a certain section reaches the first threshold, and when the time “T2” has elapsed from the start of diagnosis, the cumulative dose of a certain section The case where the threshold is reached is shown.

  When the accumulated dose in a certain section reaches the first threshold when the time “T1” has elapsed from the start of diagnosis, the exposure reduction setting unit 36 is switched from the “off state” to the “first on state”, and the dose mode is changed. The standard dose mode is switched to the first low dose mode. Thereby, the dose of X-rays irradiated to the section where the integrated dose has reached the first threshold is reduced, and the image quality of the generated diagnostic image becomes the first low image quality lower than the standard image quality.

  When the accumulated dose in a certain section reaches the second threshold when the time “T2” has elapsed from the start of diagnosis, the exposure reduction setting unit 36 is switched from the “first on state” to the “second on state”. The mode is switched from the first low dose mode to the second low dose mode. Thereby, the dose of X-rays irradiated to the section where the integrated dose has reached the second threshold is further reduced, and the image quality of the generated diagnostic image is reduced to the second low image quality lower than the first low image quality. Become.

  FIG. 8 is a flowchart for explaining the switching of the dose mode during the diagnosis of the subject P (switching of the exposure reduction setting unit 36). When the diagnosis is started, a section located in the irradiation field irradiated with X-rays is specified by the section specifying unit 32 (step S21), and the dose of X-rays irradiated to each section located in the irradiation field is determined. Calculated by the dose calculator 33 (step S22), the calculated dose is integrated by the dose integrator 34 for each section (step S23), and whether or not the integrated dose has reached the first threshold in any section Is monitored by the integrated dose monitor 35 (step S24).

  If the integrated dose does not reach the first threshold value in any section (NO in step S24), the process returns to step S21. Here, at the start of diagnosis, the exposure reduction setting unit 36 is switched to the “off state”, and the dose mode of X-rays generated from the X-ray tube 12 is the standard dose mode.

  On the other hand, if the accumulated dose reaches the first threshold value in any section (YES in step S24), the exposure reduction setting unit 36 is switched to the “first on state” and is generated from the X-ray tube 12. The dose mode of the line is switched to the first low dose mode (step S25).

  After the dose mode is switched to the first low-dose mode, as in steps S21 to S23 described above, the section specifying unit 32 specifies the section irradiated with X-rays (step S26), and the dose calculating section 33 Calculation of the dose of X-rays irradiated to each section (step S27) and dose integration for each section by the dose integration unit 34 (step S28) are performed.

  After the processes in steps S25 to S28 are performed, the section specifying unit 32 determines whether or not the section in which the integrated dose has reached the first threshold is out of the X-ray irradiation field (step S29). Whether or not the accumulated dose has reached the second threshold value in the section is monitored by the accumulated dose monitoring unit 35 (step S30).

  When the section where the integrated dose has reached the first threshold value is out of the irradiation field (YES in step S29), the exposure reduction setting unit 36 is switched to the “off state” and X-rays generated from the X-ray tube 12 are emitted. The dose mode is switched to the standard dose mode (step S31).

  Further, when the accumulated dose reaches the second threshold value in any section (YES in step S30), the exposure reduction setting unit 36 is switched to the “second on state” and is generated from the X-ray tube 12. The dose mode of the line is switched to the second low dose mode (step S32).

  After the dose mode is switched to the second low-dose mode, as in steps S21 to S23 (or steps S26 to S28) described above, identification of the section irradiated with X-rays by the section specifying unit 32 (step S33). ), Dose calculation of the X-rays irradiated to each section by the dose calculation unit 33 (step S34), and dose integration for each section by the dose integration unit 34 (step S35).

  After the processes of steps S32 to S35 are performed, whether or not the accumulated dose has reached the upper limit value in any of the sections is monitored by the accumulated dose monitoring unit 35 (step S36). The section specifying unit 32 determines whether or not the section that has reached is out of the X-ray irradiation field (step S37).

When the accumulated dose reaches the upper limit value in any of the sections (YES in step S36), a warning that the accumulated dose has reached the upper limit value is given (step S38). The diagnosis by irradiating is stopped (step S39). If it is not preset, after the warning (step S38), the process continues to step S37.

  In addition, when the section where the integrated dose has reached the second threshold value is out of the irradiation field (YES in step S37), the exposure reduction setting unit 36 is switched to the “off state” and is generated from the X-ray tube 12. The dose mode of the line is switched to the standard dose mode (step S40), and the diagnosis in the standard dose mode is continued.

  According to the present embodiment, when the diagnosis is started by irradiating the subject P with X-rays, the image quality is improved by increasing the dose of X-rays irradiated to the subject P by setting the dose mode to the standard dose mode. A high standard image quality diagnostic image can be obtained. In addition, when a section where the accumulated dose of X-rays is higher than the first threshold occurs during diagnosis, the accumulated dose for the section is increased by lowering the X-ray generated from the X-ray tube to the first low-dose mode. The amount of X-ray exposure to the subject P can be suppressed. Furthermore, when a section where the accumulated X-ray dose is higher than the second threshold occurs during diagnosis, the X-ray generated from the X-ray tube is lowered to the second low-dose mode to increase the accumulated dose for that section. Further, the amount of X-ray exposure to the subject P can be suppressed. On the other hand, when the section where the accumulated dose of X-rays has reached the second threshold is out of the X-ray irradiation field, the exposure reduction setting unit 36 is switched to the “off state” and the dose mode is returned to the standard dose mode. Therefore, a high-quality standard diagnostic image can be obtained again.

  In the present embodiment, two threshold values (first threshold value and second threshold value) of accumulated dose in a certain section are set, and the dose mode of X-rays generated from the X-ray tube 12 is set to 2 according to the threshold values. Although the case of changing in stages has been described as an example, three or more threshold values are set, and the dose mode of X-rays generated from the X-ray tube 12 is changed in three or more stages according to the threshold values. In that case, an increase in the amount of X-ray exposure to the subject P during diagnosis can be further suppressed.

  As described above, according to the X-ray diagnostic apparatus 1 of the present embodiment, a section is set by dividing a plane having a certain height on the top 2 on which the subject P is placed, and the section. By performing X-ray irradiation on the subject P while monitoring the accumulated dose of X-rays emitted to the object, the X-ray dose is increased before the accumulated dose of X-rays for each section reaches the threshold value. The image quality of the obtained diagnostic image can be improved, and when the accumulated dose of X-rays for a certain section reaches a threshold value, the X-rays irradiated to the section are reduced to reduce the X-ray irradiation on the subject P. Exposure dose can be reduced. Thereby, it is possible to obtain a diagnostic image with high image quality while suppressing the total exposure amount of the subject P.

  As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. This embodiment and its modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

2 Top plate 7 Image generation unit 12 X-ray tube 13 X-ray restrictor 14 Quality filter 15 Compensation filter 18 X-ray detector 20 Grid 28 Image quality correction unit 31 Division setting unit 32 Division specifying unit 33 Dose calculation unit 34 Dose integration unit 35 Integrated dose monitoring unit 36 Exposure reduction setting unit P Subject

Claims (4)

A top plate on which the subject is placed;
An X-ray tube for generating X-rays for irradiating the subject on the top plate;
An X-ray detector for detecting X-rays transmitted through the subject;
An image generation unit that generates a diagnostic image of the subject based on the X-rays connected to the X-ray detector and detected;
A section setting unit for setting a plurality of sections partitioned on a plane of a certain height on the top plate;
A section specifying unit for specifying the section located in an irradiation field irradiated with X-rays generated from the X-ray tube among the set sections;
A dose calculation unit for calculating a dose of X-rays irradiated to the section located in the irradiation field;
A dose integrating unit for obtaining an integrated dose obtained by integrating the doses of X-rays irradiated to the individual sections;
An integrated dose monitoring unit that monitors whether or not the integrated dose of each of the sections has reached a threshold;
An exposure reduction setting unit for reducing the dose of X-rays applied to the section where the integrated dose has reached a threshold;
An X-ray diagnostic apparatus comprising:   The exposure reduction setting unit increases the tube voltage applied to the X-ray tube, decreases the pulse rate of the tube voltage applied to the X-ray tube, increases the gain of the X-ray detector, Increasing the number of added pixels for binning of the X-ray detector, changing an inclination angle of the X-ray tube and the X-ray detector with respect to the top plate, and irradiation of X-rays from the X-ray tube Changing the direction from below the top plate, reducing the aperture of the X-ray diaphragm provided between the X-ray tube and the subject, and the X-ray tube and the subject A quality filter between the X-ray tube, a compensation filter between the X-ray tube and the subject, and two sheets disposed between the top plate and the X-ray detector. At least one of retracting at least one of the grids from the placement position Or X-ray diagnostic apparatus according to claim 1, characterized in that a combination of two or more.   Two or more threshold values are set, and the X-ray dose irradiated from the X-ray tube decreases as the threshold value at which the integrated dose reaches increases. Item 3. The X-ray diagnostic apparatus according to Item 1 or 2. An image quality correction unit for clarifying a contrast of a diagnostic image generated by the image generation unit when the dose of X-rays generated from the X-ray tube is reduced by the exposure reduction setting unit. The X-ray diagnostic apparatus according to any one of 1 to 3.

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