JP4699167B2 - X-ray diagnostic imaging equipment - Google Patents

Description

  The present invention relates to an X-ray image diagnosis in which a transmitted X-ray of a subject is detected by an X-ray flat panel detector (hereinafter sometimes referred to as FPD) in which a semiconductor X-ray detection element is two-dimensionally arranged. In particular, the present invention relates to an X-ray diagnostic imaging apparatus that uses a wide-field FPD to mechanically move a narrow-field X-ray image without mechanically moving the FPD after positioning the FPD at an examination site. .

In recent years, X-ray diagnostic apparatuses have been digitized. The reason is that the medium for detecting X-ray images is changing from image intensifiers, which are X-ray films and analog optical images, to FPD that can convert X-rays directly into digital electrical signals. .
Since such FPD is positioned as an alternative to X-ray film, a wide field of view is adopted so that a wide range of parts such as the abdomen, chest, and thigh of the subject can be obtained at one time. Yes.
This wide-field FPD is used not only for the wide-field region but also for fluoroscopic imaging of a narrow-field region, and these regions are shared to obtain an X-ray image.

As an example, an X-ray tube that irradiates a subject with X-rays and an imaging system that uses an FPD that detects X-rays transmitted through the subject are attached to a C-arm support, and the C-arm supports the X-ray tube. X-ray fluoroscopic imaging comprising a holding mechanism that is rotatable around an arc center and that holds the imaging system movably in a direction perpendicular to the X-ray radiation axis when the X-ray tube and the imaging system are facing each other. An apparatus is disclosed in Patent Document 1.
Japanese Patent Laid-Open No. 2001-95790

However, since the disclosed technique is a mechanical operation in which the X-ray tube and the imaging system (FPD) move in a direction perpendicular to the X-ray radiation axis at the time of facing, real-time measurement such as cardiac examination Is necessary, it is difficult to obtain an X-ray image by following the X-ray tube and the imaging system in real time with respect to the beat of the heart.
In other words, since the heart is moving, it is necessary to set the region of interest by looking at the X-ray image at the time of expansion of the heartbeat. Positioning the X-ray tube and the imaging system is difficult with the mechanical moving means.

  In addition, the disclosed technique moves the X-ray tube and the imaging system in order to prevent the X-ray tube and the imaging system from coming into contact with the subject, the ceiling, the floor, or the wall. Since it must be moved and positioned at the examination site, this positioning operation requires a lot of labor.

  Therefore, by using an FPD with a large field of view, the X-ray image area can be arbitrarily set by controlling the X-ray irradiation range irradiated to the subject, and the movement and rotation of the C-arm support device is minimized. In some cases, the effective field of view of the FPD can be moved without moving the C-arm supporter or moving the subject.

However, in the method in which the effective field of view of the FPD is moved as described above, when the effective field of view is reduced, the area on the display screen is the same as when the effective field of view is large. In addition, since the X-ray absorption rate varies greatly depending on the presence or absence of a lung field, a stable X-ray fluoroscopic image cannot be obtained.
This occurs because X-rays are controlled under the same X-ray conditions even when the size of the effective field of view changes, and there is no suggestion in Patent Document 1 regarding this problem.

  The present invention has been made in view of the above circumstances, and the object of the present invention is to position the X-ray flat panel detector as an imaging system on the examination site without moving the detector. An object of the present invention is to provide an X-ray diagnostic imaging apparatus capable of high-quality X-ray images in a narrow visual field even if the line flat detector is a wide-field detector.

The above-mentioned subject is achieved by the following means.
(1) An X-ray source that irradiates a subject with X-rays, and an X-ray detector that is disposed opposite to the X-ray source and detects a plurality of two-dimensionally arranged X-ray detection elements that detect the transmitted X-rays of the subject. X-ray irradiation area setting means for setting an X-ray irradiation area to the subject, an X-ray irradiation area setting means for setting the X-ray irradiation area setting means arranged on the X-ray irradiation side of the X-ray source An X-ray image diagnostic apparatus comprising: an X-ray diaphragm means for focusing X-rays in a radiation irradiation area; and a display means for displaying an X-ray image detected by the X-ray flat panel detector. Means for determining the corresponding effective visual field area of the X-ray flat panel detector; association means for associating the determined effective visual field area with the detection area of the X-ray flat panel detector; and the correlated X-rays Means for reading and controlling X-ray detection data in the detection region of the flat detector, and the X-ray based on the read X-ray image data And an X-ray control signal generating means for generating X-ray control signal for controlling the X-ray dose radiated from configure.

  (2) Furthermore, a feedback signal calculation area setting means for setting an area for calculating a signal to be fed back to the X-ray control signal generation means within the effective visual field area detected by the X-ray flat panel detector is further provided, The X-ray control signal generation means generates an X-ray control signal by feeding back the pixel value of the area set by the feedback signal calculation area setting means.

  As described above, the X-ray image diagnostic apparatus of the present invention obtains the effective visual field area of the X-ray flat panel detector corresponding to the X-ray irradiation area set by the operator, and the effective visual field area and the detection area of the X-ray flat panel detector. An area for calculating a signal to be fed back to the X-ray control signal generating means in the image area of the X-ray image in the effective visual field area by reading out the X-ray detection data of only the associated detection area Since the X-ray control signal is generated by feeding back the pixel value of this area to the X-ray control signal generation means, and the X-ray is controlled using the generated X-ray control signal, the effective visual field Even if the field of view is reduced by moving the X-ray, the X-ray is controlled under an appropriate X-ray condition corresponding to this field of view, and the detector is moved after positioning the X-ray flat panel detector as an imaging system at the examination site. Without the X-ray The X-ray image also narrow viewing region area detector is a detector with a wide viewing can be high quality ones.

  (3) The feedback signal calculation area setting means sets an area that is smaller than the set area and increases at a predetermined rate as the effective visual field becomes smaller.

  The X-ray diagnostic imaging apparatus configured in this way obtains a larger feedback signal corresponding to the image area as the effective visual field area becomes smaller in the image area set by the feedback signal calculation area setting means. The feedback signal is calculated using the pixel value of the set area, the X-ray control signal is generated using the feedback signal, and the X-ray is controlled by the X-ray control signal. As a result, the X-ray dose is appropriate for the size of the effective field of view, and the average value of the pixels varies greatly even when bones and lung fields are present in the field of view, especially when the effective field of view is small. As a result, a stable X-ray fluoroscopic image can be obtained.

(4) Further, an effective visual field size threshold setting means for setting an effective visual field area size threshold of the effective visual field area, and a comparison means for comparing the effective visual field size threshold and the effective visual field size obtained by the means for obtaining the effective visual field area. when the effective and field size means for storing the X-ray condition in the nearest field of view size threshold, the provided, when the effective visual field size is equal to or more than the said effective field size threshold the X-ray control signal generating means X-rays are controlled by the X-ray control signal generated in step S1 , and when the effective visual field size is less than the effective visual field size threshold, the X-ray condition at the effective visual field size closest to the effective visual field size threshold stored in the storage means To control X-rays.

As described above, the threshold value of the effective visual field size is provided, the threshold value is compared with the set effective visual field size, and the feedback signal is calculated when the effective visual field size is equal to or greater than the threshold value. The fluoroscopic X-ray is controlled by the generated X-ray control signal, and when the effective visual field size is less than the threshold value, that is, when the effective visual field size is extremely small, the effective signal closest to the threshold value is not calculated without calculating a feedback signal. Since the fluoroscopic X-ray is controlled under the X-ray condition in the visual field size, even when bones, catheters, guide wires, etc. having a high X-ray absorption rate exist in the feedback signal calculation area, these are not affected, Stable X-ray control can be performed, and thereby a high-quality X-ray fluoroscopic image can be obtained.

(5) Area enlarging means for enlarging the X-ray image of the effective visual field area detected by the X-ray flat panel detector, and an enlargement ratio of the image enlarged by the area enlarging means, and the examination site of the subject and It can be arbitrarily changed in response to an instruction from the operator including the fluoroscopic direction.
As a result, the fluoroscopic X-ray dose can be made appropriate for the examination site and the X-ray fluoroscopic direction, and the operator can easily be determined.

(6) The signal fed back to the X-ray control signal generation means is an average value of pixels in the area set by the feedback signal calculation area setting means.
Thus, since the average pixel value in the feedback signal calculation area is obtained and this average pixel value is used as the feedback signal, the calculation of the feedback signal becomes easy.

  According to the present invention, after positioning the X-ray flat panel detector at the examination site, the X-ray irradiation area is set by the X-ray diaphragm means without mechanically moving the detector, and the optimum X corresponding to this area is set. Since X-rays are controlled by obtaining line conditions, it is possible to acquire stable high-quality X-ray fluoroscopic images from wide-field areas to narrow-field areas using a wide-field X-ray flat panel detector. it can.

Hereinafter, preferred embodiments of an X-ray diagnostic imaging apparatus according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a diagram showing a configuration of an X-ray image diagnostic apparatus of the present invention.
The X-ray diagnostic imaging apparatus of FIG. 1 includes an X-ray tube 3 that generates X-rays to be irradiated to a subject 2 placed on a bed 1, and an irradiation range of X-rays to be irradiated to the subject 2. Restricted X-ray movable diaphragm device 4 and X-ray plane detection for detecting the transmitted X-rays of the subject 2 disposed opposite to the X-ray tube 3 and the X-ray movable diaphragm device 4 and converting them into digital image data (FPD) 5, the X-ray tube 3 and the X-ray movable diaphragm device 4 at one end and the X-ray flat panel detector 5 at the other end and the ceiling-suspended C-arm support 6 for supporting these, A C-arm control unit 7 that controls the position of the C-arm support 6 to control the positioning of the X-ray tube 3 and the X-ray movable diaphragm device 4 and the X-ray flat panel detector 5 in the diagnosis target region of the subject 2 And the X-ray diaphragm operating device 8 for setting the X-ray irradiation range, and the X-ray irradiation range set by the X-ray diaphragm operating device 8 are input and the X-ray movable diaphragm device 4 controls the X-ray irradiation range. X An aperture control unit 9 and an X-ray aperture range signal from the X-ray aperture control unit 9 are input to obtain an effective field of view of the X-ray flat panel detector 5 and the effective field of view of the X-ray flat panel detector 5 An effective visual field control unit 10 corresponding to a detection region, and an X-ray detection signal from the X-ray flat panel detector 5 and an effective visual field signal from the effective visual field control unit 10 are input and subjected to necessary image processing for diagnosis X The image processing unit 11 that generates line image data and generates a signal to be fed back to the X-ray control unit 12 (to be described later) so that the brightness of the X-ray image displayed on the display unit 14 (to be described later) becomes a predetermined value, and the effective Generates a signal for controlling X-rays emitted from the X-ray tube 3 based on an effective visual field signal from the visual field control unit 10, a feedback signal from the image processing unit 11, and an X-ray condition set by an operation unit 15 described later. X-ray control unit 12 to perform and control from this X-ray control unit 12 A DC high voltage (hereinafter referred to as tube voltage) applied between the anode and cathode of the X-ray tube 3 corresponding to No. is generated, and a current (hereinafter referred to as tube current) flowing between the anode and cathode of the X-ray tube 3 is generated. X-ray high-voltage apparatus 13 having a function of flowing a predetermined time (X-ray irradiation time) and display control of the X-ray image data generated by the image processing unit 11 to an X-ray image. And a controller 15 for controlling the entire system by setting various control signals such as setting of the examination site, setting of the X-ray condition, setting of the position signal of the C-arm support 5 and the like. Configured.

As is well known, the X-ray movable aperture device 4 is provided with a pair of upper and lower restricting blades mainly made of lead for adjusting the X-ray irradiation field, and the upper and lower restricting blades are arranged in a grid pattern, A pair of restricting blades facing each other are configured to move in parallel, and an X-ray irradiation field is arbitrarily set using these independently movable X-ray stops.
The X-ray movable diaphragm device 4 having such a configuration adjusts the X-ray irradiation field of the pyramid using the X-rays emitted from the focal point of the X-ray tube 3 as a line cone.
Therefore, the X-ray irradiation range (X-ray irradiation field) is adjusted by controlling the position of the limiting blade of the X-ray movable diaphragm device 4 by the control signal generated by the X-ray diaphragm control unit 9.

  The X-ray irradiation field is input to the X-ray diaphragm control unit 9 by the irradiation field setting signal set by the operator in the X-ray diaphragm operation unit 8, and the X-ray diaphragm control unit 9 uses the X-ray movable diaphragm device. The X-ray diaphragm blade position control signal is generated by the X-ray diaphragm control unit 9 so that the position of the four restriction blades becomes the set irradiation field setting position, and the X-ray movable diaphragm device is generated by the generated control signal. Set the X-ray field by controlling the position of the 4 limiting blades.

The X-ray flat panel detector (FPD) 5 is a semiconductor digital X-ray detector that obtains a digital image in real time in order to see and take an X-ray image directly as a digital image.
This X-ray flat panel detector 5 has an indirect conversion method and a direct conversion method depending on the X-ray conversion method, and the present invention can be applied to any conversion method, but here the indirect conversion method is used. And
This indirect conversion type X-ray flat detector 5 includes a scintillator that converts X-rays transmitted through the subject 2 into light, and a photodiode (for example, an amorphous silicon type) that converts light output from the scintillator into electric charge. X-ray image data is obtained by reading out the charge of the photodiode via a switching element (e.g., TFT (Thin Film Transistor)), depending on the X-ray dose transmitted through the subject 2. A large number of detectors for converting into electrical signals are arranged in a planar matrix, and the X-ray dose becomes an electrical image signal converted into an electrical signal by each of the detectors.
This electrical image signal is read out to the image processing unit 11, and further converted into a digital image signal by an analog / digital converter to perform various image processing, thereby generating X-ray image data.

The effective field control unit 10 sets the X-ray irradiation field set by the X-ray movable diaphragm device 4 as an effective field, and this effective field is the position control signal of the X-ray diaphragm blades generated by the X-ray diaphragm control unit 9. Therefore, this signal is input to the effective visual field control unit 10 and converted into the effective visual field of the X-ray flat panel detector.
The converted effective field of view is associated with the positions of the X-ray detection elements (pixels) arranged side by side in the plane matrix of the X-ray flat detector 5, and this is output to the image processing apparatus 11.

The image processing device 11 is an X-ray detection signal of the effective visual field based on positional relation information between the effective visual field associated with the effective visual field control unit 10 and the X-ray detection element (pixel) of the X-ray flat panel detector 5. The read signal is converted into a digital value, and the converted digital data is subjected to offset (dark current) correction and gain correction of the X-ray detector 5, and various image processing is performed on the correction data. X-ray image data to be displayed on the display unit 14 is generated.
The X-ray image data is enlarged as necessary, and the display is controlled to display the X-ray image on the display unit 14.

  Further, the image processing device 11 calculates a feedback signal to be fed back to the X-ray control unit 12 so that the luminance of the X-ray fluoroscopic image displayed on the display unit 14 becomes a predetermined luminance value, The X-ray control unit 12 generates an X-ray control signal based on the feedback signal, and controls the X-ray high-voltage device 13 so that X-rays corresponding to the control signal are emitted from the X-ray tube 3 .

(First embodiment)
Fig. 2 is an enlarged view of the effective field image and this image.Fig. 2 (a) is the output image of the entire field of view of the X-ray flat detector 5 (image a), and (b) is the X-ray movable aperture device 4. An image showing the effective visual field area with the X-ray irradiation field limited by dotted lines (in fact, the area outside the dotted lines is limited by the X-ray diaphragm blades and the subject 2 is not irradiated with X-rays, In order to make the effective field of view easy to understand, the effective field of view is surrounded by a dotted line), (c) is the effective field of (b), and the effective images b, c, d, e, (d) are the above In this example, the effective field of view is reduced in the order of b⇒c⇒d⇒e in images b ', c', d ', and e' obtained by enlarging the image of (c).
The effective visual field information is obtained from the effective visual field control unit 10, and based on this information, the effective visual field image is enlarged by the image processing unit 11 at an enlargement ratio corresponding to the effective visual field.
The effective field of view of b, c, d, and e is set by the operator using the X-ray aperture operation device 8.
As described above, the X-ray irradiation field can be reduced as much as possible to reduce the exposure X-ray dose to the subject 2.

Next, a method for calculating a feedback signal to be fed back to the X-ray control unit 12 will be described with reference to FIG.
FIG. 3 is the same as (a), (b), (c) in FIG. 2 up to (a), (b), (c) in FIG. Regions for calculating the feedback signal are shown in the enlarged images b ₁ , c ₁ , d 1 , and e ₁ enlarged at a rate by a solid line as shown in the figure.

  The calculation area of the feedback signal shown in (d) of FIG. 3 is a predetermined area smaller than the enlarged image area even if the effective visual field is different. For example, about 50% of the effective visual field is the calculation area. is there.

The image processing unit 11 calculates the feedback signal calculation region using the effective visual field size information from the effective visual field control unit 10, and obtains an average value of pixels in the calculation region (the average value of the pixels is the display value) The average value is fed to the X-ray control unit 12 (corresponding to the luminance value of the X-ray image displayed on the unit 14).
Then, the X-ray controller 12 increases the X-ray dose when the average value of the pixels is smaller than a predetermined value, and conversely when the average value is larger than the predetermined value, An X-ray control signal for reducing the dose is generated, and X-rays corresponding to the generated control signal are emitted from the X-ray tube 3.
The generated X-ray control signal is a control signal corresponding to at least one of tube voltage, tube current, and X-ray exposure time which are X-ray conditions.

The X-ray image diagnostic apparatus according to the first embodiment of the present invention configured as described above operates as follows, and this operation will be described with reference to the flowchart of FIG.
(1) The operator sets inspection conditions such as an inspection site and X-ray fluoroscopic conditions using the operation device 15 (step S1).
(2) When the operator sets the X-ray irradiation field using the X-ray aperture operation device 8, this information is input to the X-ray aperture control unit 9 (step S2).
The X-ray diaphragm control unit 9 generates a position control signal for the X-ray diaphragm blades of the X-ray movable diaphragm device 4 for the set irradiation field, and the X-ray movable diaphragm device 4 is generated based on the generated control signal. To control.
(3) The X-ray aperture control unit 9 outputs effective field region information corresponding to the X-ray irradiation field set by the X-ray movable aperture device 4 to the effective field control unit 10, and the effective field control unit 10 Then, the effective visual field area is associated with the X-ray detection area of the X-ray flat panel detector 5, and this is output to the image processing unit 11 (step S3).
(4) X-rays corresponding to the X-ray conditions set by the operating device 15 are emitted from the X-ray tube 3, and the X-ray image data transmitted through the subject 2 is detected by the X-ray flat detector 5, X-ray image data of the X-ray detection region corresponding to the effective visual field region is read into the image processing unit 11 (step S4).
(5) The X-ray image in the read effective field area is enlarged (step S5).

(6) A feedback signal calculation area for controlling X-rays is set in the enlarged X-ray image area (step S6).
(7) The average value of the pixels in the set calculation area is calculated (step S7).
(8) The calculated average pixel value is fed back to the X-ray control unit 12, and the X-ray control unit 12 increases the X-ray dose when the average value of the pixels is smaller than a predetermined value set in advance. Conversely, when the average value is larger than a predetermined value set in advance, an X-ray control signal for reducing the X-ray dose is generated. (Step S8).
(9) X-ray fluoroscopy is performed with X-rays corresponding to the generated X-ray control signal, and this fluoroscopic image is displayed on the display unit 14 (step S9).

As described above, the first embodiment of the present invention enlarges the effective field image of the X-ray flat panel detector, sets a predetermined area in the enlarged image area, and calculates the average value of the pixels in this area as the X-ray. Feedback to the control unit to control X-rays.
As a result, even if the effective field of view is moved and the field of view is reduced, X-rays are controlled under the X-ray conditions corresponding to this field of view. Therefore, after positioning the X-ray flat panel detector as the imaging system at the examination site Without moving the detector, even if the X-ray flat detector is a wide-field detector, an X-ray image in a narrow-field region can be made to have high image quality.

  Note that the feedback signal calculation area for correcting the X-ray control signal may be configured to be arbitrarily changeable according to the examination site, the purpose of diagnosis, or an instruction from the operator. Here, the calculation is performed based on the enlargement area, but feedback may be performed using a value based on the area before enlargement.

(Second Embodiment)
In the first embodiment, as shown in FIG. 3 (c), when b⇒c⇒d⇒e and the effective field of view becomes small, the same area is displayed on the display screen, but in the subject 2, the above feedback is performed. It is conceivable that the signal calculation area becomes too small and a stable X-ray fluoroscopic image cannot be obtained because the X-ray absorption rate varies greatly depending on the presence or absence of bones or lung fields present in the calculation area.
This is because when the calculation area becomes small, the average value of the pixel values greatly fluctuates due to the entry of bones and lung fields.

Therefore, in the second embodiment of the present invention, the calculation area of the feedback signal is varied according to the effective visual field size, which will be described with reference to FIG.
In FIG. 5, (a) is the output image of the entire field of view of the X-ray flat detector 5 (image of a), (b) is the effective field area where the X-ray irradiation field is limited by the X-ray movable diaphragm device 4 by dotted lines. Enclosed image, (c) is an effective image b, c, d, e, (d) is the effective field area of (b), and (d) is an enlargement of the image of (c), 50% of this enlarged image The images b ₁ , c ₁ , d ₁ , e ₁ , and (e) enlarging the above-mentioned (d) enlarged image by enlarging the feedback signal calculation area according to the enlargement ratio, and calculating in enclosed _{b 2, c 2, d 2} , e 2 of the image area with a solid line, is an example of reducing the effective field of view in the order of B⇒c⇒d⇒e.

That is, the calculation area of the feedback signal is
(1) In the case of b of the image, to enlarge the field of view (b ₁ image), and calculates the region of 50% a feedback signal of the enlarged image (area surrounded by the solid line in b _2).
(2) In the case of the image c, the effective field of view is enlarged (c ₁ image), and 60% of the enlarged image is set as a feedback signal calculation area (area surrounded by the solid line c ₂ ).
(3) In the case of the image d, the effective field of view is enlarged (d ₁ image), and 70% of the enlarged image is set as a feedback signal calculation area (area surrounded by a solid line d ₂ ).
(4) In the case of the image e, the effective field of view is enlarged (e ₁ image), and 80% of the enlarged image is set as a feedback signal calculation area (area surrounded by the solid line e ₂ ).
(5) If the effective visual field is extremely small, 100% of the image obtained by enlarging the effective visual field may be used as the feedback signal calculation region.

  As described above, the second embodiment according to the present invention increases the ratio of the feedback signal calculation area to the effective field as the effective field becomes smaller. The relationship between the magnification ratio of the effective field of view and the ratio of the area for calculating the feedback signal from the magnified image is tabulated, and the image corresponding to the effective field obtained by the effective field control unit 10 is tabulated. The feedback signal calculation area may be obtained by multiplying the enlarged image area by the ratio of the feedback signal calculation area tabulated in the table, or the effective visual field and the effective visual field expansion ratio. And the ratio of the area for calculating the feedback signal from this enlarged image is programmed as a variable and calculated by this And it may be.

  The ratio of the feedback signal calculation area to the effective visual field is a reasonable value from clinical experience, and this varies depending on the examination site. Therefore, even if it is obtained with reference to the tabulated data or obtained by a program. What is necessary is just to set also considering the said test | inspection site | part.

The image processing unit 11 calculates the feedback signal calculation region using the effective visual field size information from the effective visual field control unit 10, and obtains an average value of pixels in the calculation region (the average value of the pixels is the display value) The average value is fed to the X-ray control unit 12 (corresponding to the luminance value of the X-ray image displayed on the unit 14).
Then, the X-ray controller 12 increases the X-ray dose when the average value of the pixels is smaller than a predetermined value, and conversely when the average value is larger than the predetermined value, An X-ray control signal for reducing the dose is generated, and X-rays corresponding to the generated control signal are emitted from the X-ray tube 3.
The generated X-ray control signal is a control signal corresponding to at least one of tube voltage, tube current, and X-ray exposure time which are X-ray conditions.

The X-ray image diagnostic apparatus according to the second embodiment of the present invention configured as described above operates as follows, and this operation will be described with reference to the flowchart of FIG.
(1) The operator sets inspection conditions such as the inspection site and X-ray fluoroscopic conditions using the operation device 15 (step S11), and then enlarges the X-ray image in the effective visual field region
Since the processing up to (Step S15) is the same as in the first embodiment, the description thereof is omitted.
(2) A feedback signal calculation area is set in the X-ray image area enlarged in step S15 (step S16).
The feedback signal calculation area is set to increase at a predetermined ratio corresponding to the size of the effective visual field so that the effective visual field becomes smaller as the effective visual field becomes smaller.
(3) The average value of the pixels in the set calculation area is calculated (step S17).
(4) The calculated average pixel value is fed back to the X-ray control unit 12, and the X-ray control unit 12 increases the X-ray dose when the average value of the pixels is smaller than a predetermined value set in advance. Conversely, when the average value is larger than a predetermined value set in advance, an X-ray control signal for reducing the X-ray dose is generated. (Step S18).
(5) X-ray fluoroscopy is performed with the X-ray corresponding to the generated X-ray control signal, and this fluoroscopic image is displayed on the display unit 14 (step S19).

  According to the second embodiment of the present invention, the ratio of the feedback signal calculation area to the effective field of view is increased as the effective field of view of the feedback signal calculation area decreases. Even if the lung field exists, the average value of the pixels does not fluctuate greatly, and a stable X-ray fluoroscopic image can be obtained.

Note that the ratio of the feedback signal calculation area for correcting the X-ray control signal to the effective visual field is not limited to that in FIG. 5 and may be set arbitrarily.
Further, it can be arbitrarily changed in accordance with the examination site, the diagnostic purpose, or the operator's instruction.

(Third embodiment)
In the second embodiment, the effective field of view is set to be extremely small and 100% of the image in which the effective field of view is enlarged is used as a feedback signal calculation region, and when bones are present in a part of the calculation region, It can be considered that the average value of the pixel values in the calculation region greatly fluctuates because the bone X-ray absorption rate is large, and the feedback signal becomes too large to perform stable X-ray control.
This is because, for example, after inserting a catheter and repeating fluoroscopy and imaging, when trying to reduce the exposure of the subject by displaying only the tip of the catheter by drug injection etc., 2 to 2 on the subject This is because the average value of pixels is greatly influenced by the presence of a catheter and a guide wire in order to image an area of about 3 cm.

FIG. 7 is an explanatory diagram of feedback signal calculation according to the second embodiment of the present invention when the effective visual field is set to be extremely small.
Fig. 7 shows the image in the process of changing the effective visual field size and the X-ray conditions at that time. The effective visual field size changes from e⇒f⇒g⇒h⇒j⇒k, h If the field size is extremely small, the feedback signal is not calculated for this field size h, and the X-ray condition Xg at the field size of g before the field size h is maintained. Perform fluoroscopy at.
Then, when the field of view is enlarged to the size of j, the calculation of the feedback signal is resumed, and the calculation of the feedback signal is continued to the field of view size of k. Under the X-ray conditions generated by the calculated feedback signal, Perform fluoroscopy.

Thus, the effective field size, field size whether threshold for calculating the feedback signal, i.e., an expiration field size threshold, if the effective field size of less than that size, the feedback signal is not calculated, the X-ray fluoroscopy is performed under the X-ray condition of the visual field size closest to the effective visual field size threshold larger than the visual field size, and the calculation of the feedback signal is resumed when the visual field size exceeds the threshold.

FIG. 7 shows a case where the threshold value of the effective visual field size is g visual field size, and the X-ray conditions are as follows.
(1) In the case of e, when the effective field of view in FIG. 5b is enlarged and 50% of the enlarged image is used as the feedback signal calculation area, correction is performed using the feedback signal calculated in this calculation area. X-ray condition is Xe.
(2) In the case of f, when the effective field of view in FIG. 5c is enlarged, and 60% of the enlarged image is used as the feedback signal calculation area, correction is performed using the feedback signal calculated in this calculation area. The X-ray condition is Xf.
(3) In the case of g, the effective field of view in FIG. 5d above is enlarged, and 70% of the enlarged image is used as the feedback signal calculation area, and correction is performed with the feedback signal calculated in this calculation area. The X-ray condition is Xg.
(4) In the case of h, the effective visual field of e in FIG. 5 is enlarged, and the area of 80% of the enlarged image is used as a feedback signal calculation area. Since it is less than the threshold value of the effective visual field size, the feedback signal is not calculated, and is maintained at the same Xg as the X-ray condition of g in (3).
( 5 ) In the case of j, the effective visual field size is larger than the threshold when the effective visual field is expanded from h in (4) above, and 70% of the enlarged image is used as the feedback signal calculation region. Therefore, the calculation of the feedback signal is resumed, and the X-ray condition corrected with the feedback signal calculated in this calculation region is Xj.
( 6 ) In the case of k, the effective field of view is enlarged from j in (5) above, and the feedback signal calculated in this calculation area is obtained when 60% of the enlarged image is set as the calculation area of the feedback signal. The X-ray condition corrected with is Xk.

The X-ray image diagnostic apparatus according to the second embodiment of the present invention configured as described above operates as follows, and this operation will be described with reference to the flowchart of FIG.
(1) The processing from the operator setting inspection conditions such as the inspection site and X-ray fluoroscopic conditions using the operation device 15 (step S21) to enlarging the X-ray image in the effective visual field region (step S25) Since it is the same as that of the said 1st Embodiment and 2nd Embodiment, the description is abbreviate | omitted.

(2) It is determined whether the effective visual field size (effective visual field region) is equal to or greater than an effective visual field size threshold value stored in advance in the storage unit of the image processing unit 11 (step S26), and the effective visual field size is the effective visual field size. If it is equal to or larger than the visual field size threshold value, the process proceeds to step S27. If the effective visual field size is less than the effective visual field size threshold value, the process proceeds to step S30, and processing corresponding to each is executed.
(3) If the effective field size is equal to or greater than the effective field size threshold, a feedback signal calculation region is set in the enlarged X-ray image region (step S27).
(4) The average value of the pixels in the set calculation area is calculated (step S28).

(5) The calculated average pixel value is fed back to the X-ray control unit 12, and the X-ray control unit 12 increases the X-ray dose when the average value of the pixels is smaller than a predetermined value set in advance. Conversely, when the average value is larger than a predetermined value set in advance, an X-ray control signal for reducing the X-ray dose is generated. (Step S29).
(6) When the set effective visual field size is less than the effective visual field size threshold, the X-ray condition of the effective visual field size stored in the storage unit of the X-ray control unit 12 closest to the effective visual field size threshold is set. Read from the storage unit, and generate an X-ray control signal from the read X-ray condition. (Step S30).
(7) X-ray fluoroscopy is performed with X-rays corresponding to the generated X-ray control signal, and this fluoroscopic image is displayed on the display unit 14 (step S31).

As described above, the third embodiment of the present invention provides an effective visual field size threshold value, compares this threshold value with the set effective visual field size, and provides feedback when the effective visual field size is equal to or greater than the threshold value. A signal is calculated and an X-ray control signal is generated based on the calculated signal to control fluoroscopic X-rays. When the effective visual field size is less than the threshold value, that is, when the effective visual field size is extremely small, a feedback signal is calculated. Without controlling the fluoroscopic X-rays in the X-ray condition in the effective visual field size closest to the threshold, even if there is a bone, catheter, guidewire, etc. with a high X-ray absorption rate in the feedback signal calculation area Thus, stable X-ray control can be performed without being affected by these effects, and a high-quality X-ray fluoroscopic image can be obtained.

Note that the ratio of the feedback signal calculation region for correcting the X-ray control signal to the effective visual field is not limited to that in FIG. 7 and may be set arbitrarily.
Further, it can be arbitrarily changed in accordance with the examination site, the diagnostic purpose, or the operator's instruction.

Further, even if the effective field size is less than the threshold value, if the effective field position is moved by the X-ray movable diaphragm device 4 without changing the effective field size, the movement of the effective field position is not performed. it is necessary to calculate the feedback signal a feedback calculation region from the time an off-effective field of view when decided just before the X-ray condition to 100%.
Also in this case, the effective visual field control unit 10 obtains information necessary for calculating the feedback signal from the X-ray aperture control unit 9, and the image processing unit 11 calculates the feedback signal.

The figure which shows the structure of the X-ray-image diagnostic apparatus by this invention. The figure which shows the output image of an X-ray plane detector, the effective visual field image, and the example which expanded this image. Explanatory drawing of the feedback signal calculation method in the 1st Embodiment of this invention. 3 is a flowchart for explaining the operation of the first exemplary embodiment of the present invention. Explanatory drawing of the feedback signal calculation method in the 2nd Embodiment of this invention. 6 is a flowchart for explaining the operation of the second exemplary embodiment of the present invention. Explanatory drawing of the feedback signal calculation method in the 3rd Embodiment of this invention. 10 is a flowchart for explaining the operation of the third exemplary embodiment of the present invention.

Explanation of symbols

2 Subject, 3 X-ray tube, 4 X-ray movable diaphragm, 5 X-ray flat panel detector (FPD), 8 X-ray diaphragm operator, 9 X-ray diaphragm controller, 10 Effective field controller, 11 Image processing , 12 X-ray control unit, 13 X-ray high-voltage device, 14 display unit, 15 controller, a X-ray flat panel detector output image, b to e effective field image, b 'to e' effective field image expansion Image, image of 50% region of b _{1 to} e ₁ b 'to e', image showing b _{2 to} e ₂ feedback signal calculation region, Xe, Xf, Xg, Xj, Xk X-ray control signal

Claims (4)

X-ray plane detection comprising an X-ray source for irradiating the subject with X-rays and a plurality of two-dimensionally arranged X-ray detection elements arranged opposite to the X-ray source and detecting the transmitted X-rays of the subject An X-ray irradiation area setting means for setting an X-ray irradiation area for the subject, and an X-ray irradiation area set on the X-ray irradiation side of the X-ray source and set by the X-ray irradiation area setting means An X-ray diagnostic imaging apparatus comprising: X-ray diaphragm means for focusing X-rays; and display means for displaying an X-ray image detected by the X-ray flat panel detector,
Means for determining an effective visual field region of the X-ray flat panel detector corresponding to the X-ray irradiation region; association means for correlating the determined effective visual field region with the detection region of the X-ray flat panel detector; Means for reading out and controlling X-ray detection data in the detection area of the X-ray flat panel detector, and an area smaller than the effective visual field area in the read effective visual field area, the effective visual field area Is set by a feedback signal calculation region setting means for setting a feedback signal calculation region for controlling the X-ray dose emitted from the X-ray source, which increases at a predetermined rate as the value becomes smaller, and the feedback signal calculation region setting means. and X-ray control signal generating means is fed back to the pixel value of the region that generates an X-ray control signal for controlling the X-ray dosage, further comprising a X-ray image diagnostic apparatus according to claim. Effective field size threshold setting means for setting an effective field size threshold for the effective field area, comparison means for comparing the effective field size threshold with the effective field size obtained by the means for obtaining the effective field area, and the effective field size Means for storing X-ray conditions at an effective field size closest to the size threshold;
When the effective visual field size is equal to or greater than the effective visual field size threshold value, X-rays are controlled by the X-ray control signal generated by the X-ray control signal generating means, and when the effective visual field size is less than the effective visual field size threshold value 2. The X-ray diagnostic imaging apparatus according to claim 1, wherein X-rays are controlled under an X-ray condition with an effective visual field size closest to the effective visual field size threshold stored in the storage unit.   An area enlarging means for enlarging an X-ray image of the effective visual field area detected by the X-ray flat panel detector, and an enlargement ratio of the image magnified by the area enlarging means as the examination site of the subject and X-ray fluoroscopy The X-ray diagnostic imaging apparatus according to claim 1, further comprising means that can be arbitrarily changed in response to an instruction from an operator including a direction.   4. The X according to claim 1, wherein the signal fed back to the X-ray control signal generation unit is an average value of pixels in an area set by the feedback signal calculation area setting unit. 5. Line image diagnostic device.

Images