JP2015167793A - X-ray imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray imaging apparatus which reduces the exposure dose of a subject and accurately and emphatically displays a device to improve the visibility of the device.SOLUTION: A marker detection part 19 detects the position of a marker provided in a stent in an X-ray image acquired by an image formation part 25. A movement distance calculation part 21 calculates the movement ratio of a leaf on the basis of the detected position of the marker. A collimator control part 13 controls drive for each leaf on the basis of the calculated movement rate. The leaf is controlled by the collimator control part 13 to be driven to the position where the X-ray irradiated from an X-ray tube 5 is irradiated to a range including the stent and the vicinity of the stent. Therefore, an X-ray imaging apparatus can prevent an operator to lose sight of the stent while reducing the exposure dose of a subject in PCI.

Description

  The present invention relates to an X-ray imaging apparatus that is effective for interventional treatment and the like that captures an image of a region including a device inserted into a body of a subject, and particularly emphasizes and emphasizes the device in the image. The present invention relates to a technique for displaying an image.

  In the medical field, coronary intervention treatment (PCI: Percutaneous Coronary Intervention) is performed on patients with myocardial infarction or angina. In the coronary intervention treatment, a catheter having a guide wire inside is inserted into a blood vessel of a subject, and the catheter is allowed to reach the coronary artery of the heart via the blood vessel. The position of the catheter inserted into the body of the subject is confirmed at any time by continuously taking X-ray images.

  A stent is used as a device used for coronary intervention treatment. A stent is a cylindrical medical device made of metal or the like, and is placed in a stenotic portion of a coronary artery that is expanded using a balloon to hold a blood vessel from a lumen. By placing the stent in the coronary artery, the therapeutic effect of the catheter is improved. In recent years, a plurality of stents are often placed in order to improve the therapeutic effect. In this case, if a gap is generated between a previously placed stent and a newly placed stent, the blood vessel may be narrowed in the gap. Therefore, confirming the position of the stent is extremely important in treatment.

  Conventionally, in order to improve the visibility of a stent inserted into the body of a subject, X-ray images are continuously captured using a stent having a feature point such as a marker. Then, the captured X-ray images for a plurality of frames are superimposed. When superimposing, the stent can be highlighted by superimposing the feature points provided on the stent as a reference (see, for example, Patent Documents 1 and 2).

JP 2005-510288 A JP 2012-505006 A

However, the conventional example having such a configuration has the following problems.
That is, in the conventional apparatus, the examination time in the intervention treatment becomes longer and the time for taking an X-ray image becomes longer. Therefore, there is a concern that the exposure dose of the subject increases. In addition, an object that is confused with the stent, such as a metal object other than the stent, may appear on the X-ray image in accordance with the heartbeat and respiration of the subject. In this case, when superimposing X-ray images based on the feature points of the stent, an object that is confused with the stent is erroneously detected as the feature point, so that the stent may not be suitably highlighted.

  The present invention has been made in view of such circumstances, and an X-ray imaging apparatus capable of reducing the exposure dose of a subject and accurately highlighting the device to improve its visibility. The purpose is to provide.

In order to achieve such an object, the present invention has the following configuration.
That is, in the X-ray imaging apparatus according to the present invention, an X-ray source that irradiates a subject with X-rays, an X-ray detection unit that detects X-rays transmitted through the subject, and the X-ray detection unit output An image forming unit that forms an X-ray image of a region including a device inserted into the body of a subject using a detection signal, and a shielding unit that shields X-rays. A collimator for controlling the irradiation field; a collimator control means for controlling the opening and closing movement of the shielding part; and a marker detection means for detecting the position of the marker provided in the device in the X-ray image formed by the image forming part. And a movement distance calculation means for calculating a movement distance of the shielding portion based on the position of the marker detected by the marker detection means, and the collimator control means has a movement distance calculated by the movement distance calculation means. Base Te, X-rays irradiated from the X-ray source, and is characterized in that for controlling the opening and closing movement of the shield portion to be irradiated to the area including the vicinity of the device and the device.

  [Operation and Effect] According to the X-ray imaging apparatus of the present invention, the marker detection means detects the position of the marker provided in the device in the X-ray image formed by the image forming unit. Then, the moving distance calculating means calculates the moving distance of the shielding part based on the detected marker position. The collimator control means controls the opening / closing movement of the shielding part based on the calculated movement distance.

  The collimator control means controls the opening / closing movement of the shielding unit so that the X-ray irradiated from the X-ray source is irradiated to the device and a range including the vicinity of the device. That is, the range irradiated with X-rays is limited to the range including the device and the vicinity of the device. Therefore, the exposure dose of the subject can be suitably reduced. Further, since the X-ray irradiation range is limited to a range including the device and the vicinity of the device, it is possible to suitably avoid erroneously recognizing an object confused with the device, such as a metal object other than the device. Accordingly, it is possible to avoid the operator from losing sight of the device while appropriately reducing the exposure dose of the subject in a surgical technique such as PCI.

  In the above-described invention, it is preferable that the marker detection unit includes a detection instruction unit that instructs the marker detection unit to detect the position of the marker in the X-ray image formed by the image forming unit.

  [Operation / Effect] According to the X-ray imaging apparatus of the present invention, the detection instruction unit instructs the marker detection unit to detect the position of the marker in the X-ray image formed by the image forming unit. In this case, when the detection instruction unit instructs the marker detection unit, the collimator controls the opening / closing movement of the shielding unit based on the movement distance calculated by the movement distance calculation unit. Therefore, when performing PCI, the operator can operate the detection instruction unit as necessary to control the opening / closing movement of the shielding unit so that the X-ray is irradiated to a range including the vicinity of the device. it can.

  In the above-described invention, it is preferable that the detection instruction means is a switch or a button provided in the X-ray imaging apparatus.

  [Operation / Effect] According to the X-ray imaging apparatus of the present invention, the instruction to the marker detection means by the detection instruction means is performed by operating a switch or a button. Therefore, by a simpler operation, the operator can control the opening / closing movement of the shielding unit so that the X-ray is irradiated to the range including the vicinity of the device and the device.

  Further, in the above-described invention, the detection instruction unit may be an X-ray image formed by the image forming unit with respect to the marker detection unit after a lapse of a certain time from the start of X-ray irradiation by the X-ray source. It is preferable to instruct to detect the position of the marker.

  [Operation / Effect] According to the X-ray imaging apparatus of the present invention, the detection instructing means is formed by the image forming section on the marker detecting means after a lapse of a certain time from the start of X-ray irradiation by the X-ray source. An instruction is given to detect the position of the marker in the X-ray image. Therefore, in the PCI, an operation for causing the detection instruction unit to instruct the marker detection unit by the operator becomes unnecessary. Therefore, even if the operator fails to operate the detection instruction unit, the detection instruction unit can reliably execute the instruction to the marker detection unit. Further, since the step of operating the detection instruction means can be omitted, X-ray imaging can be performed more efficiently.

  Further, in the above-described invention, it further includes a shielding unit stopping unit that stops the opening / closing movement of the shielding unit, and the detection instruction unit releases the stop of the opening / closing movement of the shielding unit by the shielding unit stopping unit. It is preferable to instruct the marker detection unit to detect the position of the marker in the X-ray image formed by the image forming unit.

  [Operation / Effect] According to the X-ray imaging apparatus of the present invention, the detection instruction means instructs the marker detection means when releasing the stop of the opening / closing movement of the shielding portion by the shielding portion stopping means. Is done. In this case, since the cancellation of the shielding unit stopping means and the instruction to the marker detecting means by the detection instructing means are linked, the operator does not need to operate the detection instructing means. Therefore, even if the operator fails to operate the detection instruction unit, the detection instruction unit can reliably execute the instruction to the marker detection unit. Further, since the step of operating the detection instruction means can be omitted, X-ray imaging can be performed more efficiently.

  In addition, the X-ray irradiation range includes the device and the vicinity of the device immediately after starting the X-ray irradiation by canceling the shielding unit stopping means in advance before the X-ray irradiation by the X-ray source. Can be limited to a range. Therefore, it becomes possible to reduce the exposure dose of the subject more effectively.

  In the above-described invention, an image of the device is formed from an integration unit that forms an integrated image by superimposing a plurality of X-ray images having the same phase formed by the image forming unit, and an integrated image formed by the integration unit. It is preferable to include a cutout display unit that cuts out and displays.

  [Operation / Effect] According to the X-ray imaging apparatus of the present invention, the integrating unit forms an integrated image by superimposing a plurality of X-ray images having the same phase formed by the image forming unit. The cutout display unit cuts out and displays the image of the device from the integrated image formed by the integrating unit. Since the X-ray images having the same phase are superimposed, the image of the device in the integrated image becomes clearer than the individual X-ray images. Then, since the image of the device is cut out from the integrated image by the cut-out display unit, the operator mistakenly recognizes an object confused with the device, such as a metal object other than the device, by checking the image of the cut-out device. Can be suitably avoided. Therefore, in an operation method such as PCI, the operator can perform treatment while confirming a device image with higher visibility.

  According to the X-ray imaging apparatus according to the present invention, according to the X-ray imaging apparatus according to the present invention, the marker detection means detects the position of the marker provided in the device in the X-ray image formed by the image forming unit. To do. Then, the moving distance calculating means calculates the moving distance of the shielding part based on the detected marker position. The collimator control means controls the opening / closing movement of the shielding part based on the calculated movement distance. The collimator control means controls the opening / closing movement of the shielding unit so that the X-ray irradiated from the X-ray source is irradiated to the device and a range including the vicinity of the device. That is, the range irradiated with X-rays is limited to the range including the device and the vicinity of the device. Therefore, the exposure dose of the subject can be suitably reduced. Further, since the X-ray irradiation range is limited to a range including the device and the vicinity of the device, it is possible to suitably avoid erroneously recognizing an object confused with the device, such as a metal object other than the device. Accordingly, it is possible to avoid the operator from losing sight of the device while appropriately reducing the exposure dose of the subject in a surgical technique such as PCI.

1 is a schematic diagram illustrating a configuration of an X-ray imaging apparatus according to Embodiment 1. FIG. 1 is a schematic diagram illustrating a configuration of a collimator according to a first embodiment. (A) is the schematic explaining the structure which a shielding board restrict | limits the breadth of X-ray, (b) is sectional drawing explaining the structure of a collimator. 1 is a schematic diagram illustrating a configuration of a catheter according to Example 1. FIG. 1 is a schematic diagram illustrating a positional relationship in a blood vessel of a catheter according to Example 1. FIG. (A) is a figure explaining the basic operation | movement of the X-ray imaging apparatus which concerns on Example 1, (b) is a figure explaining the image which the clipping display part concerning Example 1 displays. 5 is a flowchart for explaining an operation process for controlling a collimator in the X-ray imaging apparatus according to Embodiment 1; FIG. 3 is a schematic diagram illustrating a process of calculating a movement rate in the X-ray imaging apparatus according to Embodiment 1. (A) has shown the X-ray image before moving a leaf, (b) has shown the range obstruct | occluded by the leaf by the movement of a leaf. FIG. 3 is a schematic diagram illustrating the operation of the collimator according to the first embodiment. (A) shows a state where the movement rate of the leaf 35a is 0%, and (b) shows a state where the movement rate of the leaf 35a is 100%. 6 is a schematic diagram illustrating a configuration of a collimator according to Embodiment 2. FIG. (A) is the schematic explaining the structure which a shielding board restrict | limits the breadth of X-ray, (b) is sectional drawing explaining the structure of a collimator. In the X-ray imaging apparatus which concerns on Example 2, the range blocked | interrupted by the leaf by the movement of the leaf is shown. It is the schematic explaining the process of calculating a movement rate in the X-ray imaging apparatus which concerns on a modification. (A) has shown the X-ray image before moving a leaf, (b) has shown the range obstruct | occluded by the leaf by the movement of a leaf. It is the schematic explaining the structure of the X-ray imaging apparatus which concerns on a modification.

  Embodiment 1 of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram illustrating the configuration of the X-ray imaging apparatus according to the first embodiment.

<Description of overall configuration>
As shown in FIG. 1, the X-ray imaging apparatus 1 according to the first embodiment includes a top plate 3, an X-ray tube 5, a collimator 7, an X-ray detector 9, an X-ray irradiation control unit 11, and a collimator. An open / close unit 13, a detector control unit 15, an image processing unit 17, a marker detection unit 19, a movement distance calculation unit 21, and a main control unit 23 are provided. The top 3 places a subject M in a horizontal posture. The X-ray tube 5 irradiates the subject M with X-rays. The X-ray tube 5 corresponds to the X-ray source in the present invention.

  A collimator 7 is provided below the X-ray tube 5 to limit the X-rays emitted from the X-ray tube 5 to a cone shape that is a pyramid. The X-ray tube 5 and the X-ray detector 9 are disposed to face each other with the top plate 3 interposed therebetween. The X-ray detector 9 detects X-rays that are transmitted through the subject M from the X-ray tube 5, converts them into electrical signals, and outputs them as X-ray detection signals. In the first embodiment, a flat panel detector (FPD) is used as the X-ray detector 9. The X-ray detector 9 corresponds to the X-ray detection means in the present invention.

  The X-ray irradiation control unit 11 is connected to the X-ray tube 5 and controls the X-ray dose irradiated from the X-ray tube 5, the timing for irradiating X-rays, and the like. The collimator opening / closing unit 13 is connected to the collimator 7 and controls the opening / closing movement of a leaf, which will be described later. The detector control unit 15 is connected to the X-ray detector 9 and controls the operation of reading the charge signal converted by the X-ray detector 9, that is, the X-ray detection signal. The collimator opening / closing unit 13 corresponds to collimator control means in the present invention.

  The image processing unit 17 includes an image forming unit 25, an integrating unit 27, and a cutout display unit 29. The image forming unit 25 is provided after the X-ray detector 9, and the integrating unit 27 is provided after the image forming unit 25. A cut-out display unit 29 is provided after the integrating unit 27. The marker detection unit 19 is provided downstream of the image forming unit 25, and the movement distance calculation unit 21 is provided downstream of the marker detection unit 19. The movement distance calculation unit 21 is connected to the collimator opening / closing unit 13.

  The marker detection unit 19 corresponds to the marker detection unit in the present invention, and the movement distance calculation unit 21 corresponds to the movement distance calculation unit in the present invention. The X-ray irradiation control unit 11, the collimator opening / closing unit 13, the detector control unit 15, and the image processing unit 17 are comprehensively controlled by the main control unit 23.

  The X-ray imaging apparatus 1 further includes a detection instruction unit 31. The detection instruction unit 31 is connected to the marker detection unit 19 and controls on / off of the marker detection unit 19. Examples of the configuration of the detection instruction unit 31 include buttons and switches provided in the X-ray imaging apparatus 1. The detection instruction unit 31 corresponds to detection instruction means in the present invention.

  The collimator 7 is provided with a leaf 35 below it. As shown in FIG. 2A, the leaf 35 has a configuration in which four plate-like leaves 35a to 35d are combined. The width of the X-ray field B irradiated from the X-ray focal point A is determined by the position of each of the leaves 35a to 35d. Each of the leaves 35a to 35d is provided with a driving motor. The collimator opening / closing unit 13 appropriately adjusts the position of each of the leaves 35a to 35d by independently controlling the driving of each motor. The leaf 35 corresponds to the shielding part in the present invention.

  The leaf 35a and the leaf 35b move in the x direction (longitudinal direction of the top plate 3) as shown in FIG. That is, the leaf 35a adjusts the irradiation width in the x direction for the X-ray beam 37 irradiated from the focal point A. For example, the irradiation width of the X-ray beam 37 in the x direction is changed from P to Q by moving the leaf 35a and the leaf 35b from the position indicated by the solid line to the position indicated by the dotted line.

  Similarly, the leaf 35c and the leaf 35d move in the y direction (short direction of the top 3). That is, the leaf 35c and the leaf 35d adjust the irradiation width of the X-ray beam 37 in the y direction.

  FIG. 3 is a schematic view showing the configuration of the catheter 39 used for coronary intervention treatment (PCI). The catheter 39 includes a guide wire 41 inside. A stent 43 is provided at the distal end of the guide wire 41. The stent 43 includes a plurality of markers 45. In the first embodiment, the number of markers 45 is two, but the number of markers 45 may be changed as appropriate. Of the two markers 45, one marker 45 a is provided on the distal end side of the stent 43, and the other marker 45 b is provided on the proximal end side of the stent 43.

  The stent 43 is a lattice-shaped cylindrical body made of a metal wire such as stainless steel. In PCI, the stent 43 is placed in a narrowed portion of the coronary artery. Then, the deployed stent 43 is inflated with a balloon, and the inflated stent 43 is placed in a blood vessel, so that the coronary artery can be expanded and blood flow can be kept normal. The marker 45 is made of a radiopaque material, and clearly shows the position of the stent 43 in the X-ray image in PCI. Examples of the material constituting the marker 45 include metals such as gold, platinum, and tantalum.

<Description of operation>
Next, the operation of the X-ray imaging apparatus according to Embodiment 1 will be described. In performing PCI, a small hole is made in the base of the subject's thigh and the catheter 39 is inserted into the blood vessel. 4 shows a state in which the catheter 39 is inserted into the blood vessel 47 having the branch tube 49 and the branch tube 51, and the stent 43 is inserted into the branch tube 49 together with the guide wire 41.

  The catheter 39 inserted into the blood vessel of the subject M is continuously imaged by the X-ray imaging apparatus 1. That is, X-rays are intermittently emitted from the X-ray tube 5 to the subject M. X-rays transmitted through the subject M are detected by the X-ray detector 9. The detected X-ray is converted into an electrical signal and output to the image forming unit 25 as an X-ray detection signal. Note that the collimator 7 is appropriately controlled by the collimator controller 13 so that the X-ray irradiation range irradiated from the X-ray tube 5 to the subject M is the stent 43 and the vicinity thereof according to the control process described later. .

  The image forming unit 25 intermittently forms an X-ray image 53 on which the catheter 39 and the stent 43 are projected based on the output X-ray detection signal. In the embodiment, the X-ray image 53 is taken at a frame rate of about 15 to 30 FPS, for example. Each of the X-ray images 53 formed in the image forming unit 25 is transmitted to the integrating unit 27.

  The accumulating unit 27 superimposes a plurality of newly formed X-ray images 53 in order to highlight the real-time image of the stent 43. In the first embodiment, the number of sheets to be superimposed is five, but the number of sheets may be changed as appropriate. In FIG. 5A, the newest X-ray image 53 transmitted from the image forming unit 25 is taken as an X-ray image 53a, and the X-ray image 53a is followed by the newest X-ray image 53, which are indicated by reference numerals 53b to 53e. To do. In FIG. 5 and subsequent figures, the blood vessel 47 including the branch pipes 49 and 51 shown in FIG. 4 is schematically shown by a thin line.

  The positions of the catheter 39 and the stent 43 shown in each of the X-ray images 53a to 53e differ depending on the pulse and respiration of the subject M. Therefore, the accumulating unit 27 superimposes the X-ray images 53a to 53e with each of the markers 45 as a reference, and acquires a superimposed image 55. The acquired superimposed image 55 is transmitted to the cutout display unit 29.

  The cutout display unit 29 cuts out and enlarges the stent 43 displayed in the superimposed image 55 and acquires an enlarged image 57. Then, as shown in FIG. 5B, the cutout display unit 29 displays the acquired enlarged image 57 as a combined image 58 together with the X-ray image 53a. In the enlarged image 57, the image of the stent 43 projected on each of the X-ray images 53a to 53e is overlaid on the basis of the marker 45, and further enlarged and cut out. Therefore, the image of the stent 43 displayed in the enlarged image 57 is excellent in visibility. The X-ray image 53 a is the newest image that shows a real-time image of the stent 43. Therefore, the operator can confirm the real-time image of the stent 43 in a more preferable state by performing PCI while confirming the combined image 58.

<Control process of collimator>
Next, in the X-ray imaging apparatus according to the first embodiment, a process of controlling the collimator 7 when an X-ray image is intermittently acquired will be described. FIG. 6 is a flowchart for explaining a process for controlling the collimator 7.

Step S1 (marker detection)
Each of the X-ray images 53 that are intermittently formed in the image forming unit 25 is transmitted to the integrating unit 27 and simultaneously to the marker detecting unit 19. Then, in order to appropriately control the collimator 7, the detection instruction unit 31 is turned on in advance. The detection instruction unit 31 that has been turned on transmits a signal to the marker detection unit 19 to turn the marker detection unit 19 on. The marker detection unit 19 that has been turned on detects all the coordinates of the marker 45 displayed on the X-ray image 53.

  In the first embodiment, the lower left corner of the X-ray image 53 is a reference point Ro, and the coordinates of the reference point Ro are (0, 0). The coordinates of the vertex Ra at the upper right end in the X-ray image 53 are set to (m, n). In the first embodiment, since the size of the X-ray image 53 is 1024 pixels × 1024 pixels, m = n = 1024 is set for convenience. Further, the coordinates of the marker 45a are (x1, y1), and the coordinates of the marker 45b are (x2, y2). The coordinates of each marker 45 detected by the marker detection unit 19 are transmitted to the movement distance calculation unit 21.

Step S2 (calculation of rectangle D)
As illustrated in FIG. 7A, the movement distance calculation unit 21 first calculates a rectangle D that includes the marker 45a and the marker 45b. The length of the rectangle D in the x-axis direction is obtained by the equation (x2-x1), and the length in the y-axis direction is obtained by the equation (y2-y1). The coordinates of each vertex of the rectangle D are (x1, y1), (x1, y2), (x2, y1), (x2, y2).

  The rectangle D includes all the markers 45 and has the smallest area. However, in reality, the position of the marker 45 may be shifted out of the rectangle D due to respiration of the subject M, heartbeat, or the like. Therefore, it is necessary to make the range of X-ray irradiation wider than the rectangle D.

Step S3 (calculation of rectangle E)
Therefore, the movement distance calculation unit 21 next calculates a rectangle E having a wider range in the vertical and horizontal directions than the rectangle D. In the first embodiment, the rectangle E has a wider range of 100 pixels vertically and horizontally than the rectangle D. However, the distance by which the rectangle E is wider than the rectangle D may be changed as appropriate. The coordinates of each vertex of the rectangle E are (x1-100, y1-100), (x1-100, y2 + 100), (x2 + 100, y1-100), (x2 + 100, y2 + 100). The length of the rectangle E in the x-axis direction is obtained by the equation (x2-x1 + 200), and the length in the y-axis direction is obtained by the equation (y2-y1 + 200).

Step S4 (calculation of moving distance)
Then, the movement distance calculation unit 21 calculates the movement rate for each of the leaves 35a to 35d based on the calculated coordinates of the rectangle E so that the range irradiated with X-rays is within the range of the rectangle E. . For example, the state in which the leaf 35a has a movement rate of 0% is a state in which the leaf 35a circumscribes the X-ray irradiation field B and the leaf 35a is not reflected in the X-ray image 53 (FIG. 8A). The state in which the movement rate of the leaf 35a is 100% is a state in which the entire X-ray irradiation field B is blocked by the leaf 35a moved in the x direction and nothing appears in the X-ray image 53 (FIG. 8B). )). At this time, the distance that the leaf 35a moves in the x direction is W.

As shown in FIG. 7B, the leaf 35a circumscribing RoRb moves so as to cover the region surrounded by RoRbSaSc. Since the length of RoSc is x1-100 and the length of RoRc is m, the movement rate of the leaf 35a is calculated using the following equation (1).
{(X1-100) / m} × 100 (%) (1)
Similarly, the leaf 35b circumscribed by RaRc moves so as to cover the region surrounded by RaRcSdSb. Since the length of RcSd is m− (x2 + 100) and the length of RoRc is m, the movement rate of the leaf 35b is calculated using the following equation (2).
{(M−x2−100) / m} × 100 (%) (2)

Further, the leaf 35c circumscribed by RaRb moves so as to cover the region surrounded by RaRbTaTb. Since the length of RbTa is n- (y2 + 100) and the length of RoRb is n, the mobility of the leaf 35c is calculated using the following equation (3).
{(N−y2−100) / n} × 100 (%) (3)
Further, the leaf 35d circumscribing RoRc moves so as to cover the region surrounded by RoRcTcTd. Since the length of RoTc is y1-100 and the length of RoRb is n, the movement rate of the leaf 35d is calculated using the following equation (4).
{(Y1-100) / n} × 100 (%) (4)

  The movement rate distance calculation unit 21 calculates the movement rate for each of the leaves 35a to 35d using the expressions shown in (1) to (4). Then, based on the calculated movement rate, the movement rate distance calculation unit 21 calculates a distance by which the collimator control unit 13 moves each of the leaves 35a to 35d.

The distance by which the collimator control unit 13 moves the leaf 35a in the x direction is defined as Wa. When the movement rate of the leaf 35a is 100%, the distance that the leaf 35a moves in the x direction is W. Therefore, the movement distance Wa is calculated by the following calculation formula (5).
Wa = W {(x1-100) / m} (5)
When the movement rate of the leaf 35b is 100%, the distance that the leaf 35b moves in the x direction is W as in the case of the leaf 35a. Therefore, if the distance by which the leaf 35b is moved in the x direction is Wb, the movement distance Wb is calculated by the following calculation formula (6).
Wb = W {(m−2−100) / m} (6)

Next, let Ya be the distance by which the collimator controller 13 moves the leaf 35c in the y direction. If the distance that the leaf 35c moves in the y direction when the movement rate of the leaf 35c is 100% is Y, the movement distance Ya is calculated by the following equation (7).
Ya = Y {(n−2−100) / n} (7)
When the movement rate of the leaf 35d is 100%, the distance that the leaf 35d moves in the y direction is Y as in the case of the leaf 35c. Therefore, if the distance by which the leaf 35d is moved in the y direction is Yb, the movement distance Yb is calculated by the following calculation formula (8).
Yb = Y {(y1-100) / n} (8)

Step S5 (leaf movement)
The movement rate distance calculation unit 21 calculates the movement distance for each of the leaves 35 a to 35 d using the equations shown in (5) to (8), and transmits the calculated movement distance to the collimator control unit 13. The collimator control unit 13 horizontally moves each of the leaves 35a to 35d based on the transmitted movement distance. As a result, as shown in FIG. 7B, in the X-ray image 53, the range with halftone dots is blocked by each of the leaves 35 a to 35 d, so that only the inside of the rectangle E is irradiated with X-rays. It will be.

  By having such a configuration, in the X-ray imaging apparatus 1 according to the present invention, it is possible to irradiate only the inside of the rectangle E, that is, the stent 43 and the vicinity thereof. Therefore, the exposure dose of the subject M can be suitably suppressed without losing sight of the stent 43 in the X-ray image 53.

  Next, Embodiment 2 of the present invention will be described with reference to the drawings. Note that the same components as those in the X-ray imaging apparatus according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the X-ray imaging apparatus according to the second embodiment, a leaf 59 is provided below the collimator 7. As shown in FIG. 9A, the leaf 59 has a configuration in which four plate-like leaves 59a to 59d are combined. The width of the X-ray field B irradiated from the X-ray focal point A is controlled by the leaves 59a to 59d.

  Each of the leaves 59a to 59d is provided with a driving motor. The collimator opening / closing unit 13 adjusts the opening / closing movement of the leaves 59a to 59d by controlling the drive of the motor. However, in the first embodiment, the four leaves 35a to 35d constituting the leaf 35 are configured to be driven independently. On the other hand, in the second embodiment, the leaves 59a and 59b facing each other in the x direction are interlocked, and the leaves 59c and 59d facing each other in the y direction are interlocked.

  As shown in FIG. 9B, the leaf 59a and the leaf 59b are opposite to each other in the x direction (longitudinal direction of the top plate 3) with respect to the central axis 37a of the X-ray beam 37 emitted from the X-ray focal point A. Move synchronously in the direction. That is, the leaves 59a and 59b adjust the irradiation width of the X-ray beam 37 in the x direction. For example, when narrowing the irradiation width of the X-ray beam 37, the leaf 59a and the leaf 59b are synchronously moved from the position indicated by the solid line to the position indicated by the dotted line. As the leaves 59a and 59b move, the irradiation width of the X-ray beam 37 in the x direction is changed from P to Q.

  Similarly, the leaf 59c and the leaf 59d are synchronously moved in directions opposite to each other in the y direction (short direction of the top 3) with reference to the central axis 37a of the X-ray beam 37 emitted from the X-ray focal point A. That is, the leaf 59c and the leaf 59d adjust the irradiation width of the X-ray beam 37 in the y direction.

  Next, a mechanism for controlling the collimator 7 when an X-ray image is intermittently captured in the X-ray imaging apparatus according to the second embodiment will be described. In addition, since the process which concerns on step S1-S3 is common in Example 1 among the processes which control the collimator 7, detailed description is abbreviate | omitted.

Step S4 (calculation of moving distance)
Based on the coordinates of the rectangle E calculated in the same manner as in the first embodiment, the movement distance calculation unit 21 performs the following for each of the leaves 59a to 59d so that the range irradiated with X-rays is within the range of the rectangle E. A temporary movement rate is calculated.

First, the movement distance calculation unit 21 calculates the movement rate of the leaves 59a and 59b. Therefore, it is assumed that the leaf 59a circumscribed by RoRb moves so as to cover the region surrounded by RoRbSaSc, and the movement distance calculation unit 21 uses the calculation formula shown in the following (1) similarly to the first embodiment. The provisional movement rate of the leaf 59a is calculated.
{(X1-100) / m} × 100 (%) (1)
Moreover, the movement distance calculation part 21 calculates the temporary movement rate of the leaf 59b using the calculation formula shown by the following (2).
{(M−x2−100) / m} × 100 (%) (2)

  Then, the movement distance calculation unit 21 compares the movement rate calculated by the calculation formula (1) with the movement rate calculated by the calculation formula (2) and selects a smaller value. Then, the selected value is calculated as the actual movement rate G of the leaves 59a and 59b. In the second embodiment, G = {(x1-100) / m} × 100.

Next, the movement distance calculation unit 21 calculates the movement rate of the leaves 59c and 59d. Therefore, it is assumed that the leaf 59c circumscribed by RaRb moves so as to cover the region surrounded by RaRbSaSb, and the movement distance calculation unit 21 uses the calculation formula shown in (3) below to temporarily move the leaf 59c. Calculate the rate.
{(N−y2−100) / n} × 100 (%) (3)
Further, the movement distance calculation unit 21 calculates a temporary movement rate of the leaf 59d using a calculation formula shown in the following (4).
{(Y1-100) / n} × 100 (%) (4)

  The movement distance calculation unit 21 compares the movement rate calculated by the calculation formula (3) with the movement rate calculated by the calculation formula (4), and selects a smaller value. Then, the selected value is calculated as the actual movement rate H of the leaf 59c and the leaf 59d. In the second embodiment, H = {(y1-100) / n} × 100.

  The movement rate distance calculation unit 21 calculates the distance by which the collimator control unit 13 moves each of the leaves 59a to 59d based on the calculated values of the movement rate G and the movement rate H.

The distances by which the collimator control unit 13 moves the leaves 59a and 59b in the x direction are denoted by Wa and Wb, respectively. The distance that the leaf 59a and the leaf 59b move in the x direction when the movement rate is 100% is W. Since the actual moving rates of the leaves 59a and 59b are both G, the moving distance Wa and the moving distance Wb are calculated by the following calculation formula (5).
Wa = Wb = WG / 100 = W {(x1-100) / m} (5)

Next, the distances by which the collimator controller 13 moves the leaves 59c and 59d in the y direction are assumed to be Ya and Yb, respectively. The distance that the leaf 59c and the leaf 59d move in the y direction when the movement rate is 100% is Y. Since the actual moving rates of the leaves 59c and 59d are both H, the moving distance Ya and the moving distance Yb are calculated by the following calculation formula (6).
Ya = Yb = YH / 100 = Y {(y1-100) / n} (6)

Step S5 (leaf movement)
The movement rate distance calculation unit 21 calculates the movement distance for each of the leaves 35 a to 35 d using the calculation formulas shown in (5) to (6), and transmits the calculated movement distance to the collimator control unit 13. The collimator controller 13 causes the leaves 59a and b to move synchronously in the x direction and the leaves 59c and 59d synchronously move in the y direction based on the transmitted movement distance. As a result, as shown in FIG. 10, in the X-ray image 53, the range with halftone dots is blocked by each of the leaves 59 a to 59 d.

  By having such a configuration, in the X-ray imaging apparatus according to the second embodiment, the opening and closing of the leaf 59 provided in the collimator 7 can be appropriately controlled so that only the stent 43 and its vicinity can be irradiated with X-rays. . Therefore, the exposure dose of the subject M can be suppressed without losing sight of the stent 43 in the X-ray image 53.

  In the X-ray imaging apparatus according to the second embodiment, the leaves 59a and 59b are interlocked, and the leaves 59c and 59d are interlocked. Therefore, the collimator 7 can be controlled with a simpler configuration, and X-rays can be irradiated only to the stent 43 and its vicinity.

  The present invention is not limited to the above embodiment, and can be modified as follows.

  (1) In each of the embodiments described above, the configuration of the detection instruction unit 31 is a button or switch provided in the X-ray imaging apparatus 1, but is not limited thereto. That is, the detection instruction unit 31 is connected to the X-ray irradiation control unit 11. Then, after the X-ray irradiation control unit 11 controls to irradiate X-rays from the X-ray tube 5, the detection instruction unit 31 may be turned on after a certain time has elapsed. In this case, the operator does not need to perform an operation to turn the detection instruction unit 31 on. Therefore, even if the operator fails to operate the detection instruction unit 31 in the PCI, the detection instruction unit 31 can be turned on more reliably. In addition, since the step of operating the detection instruction unit 31 can be omitted, X-ray imaging can be performed more efficiently.

  As another modification for controlling on / off of the detection instruction unit 31, there is a configuration in which the detection instruction unit 31 is turned on when the leaf 35 is movable. That is, in the X-ray imaging apparatus 1B according to the modification, as shown in FIG. The leaf stop unit 61 locks the leaf 35 to stop the opening / closing movement of each leaf 35. The detection instruction unit 31 is turned off when the leaf stop unit is turned on, and the detection instruction unit 31 is turned on when the leaf stop unit is turned off. The leaf stop portion 61 corresponds to the shielding portion stop means in the present invention.

  When the operator does not use the X-ray imaging apparatus 1, the operator turns on the leaf stop 61 to prevent the leaf 35 from malfunctioning. When the X-ray imaging is performed, the leaf stop unit 61 is turned off. When the leaf stop 61 is turned off, the lock applied to the leaf 35 when performing X-ray imaging is released, and each leaf 35 can be opened and closed. At this time, the detection instruction unit 31 is turned on in conjunction with the leaf stop unit 61 that has been turned off.

  In the X-ray imaging apparatus 1B according to the modification, the detection instruction unit 31 is turned on / off in conjunction with the leaf stop unit on / off. Therefore, it is not necessary for the operator to bother to turn on the detection instruction unit 31 when performing X-ray imaging. Further, the X-ray irradiation range is limited to the range of the rectangle E immediately after the start of X-ray irradiation by turning off the leaf stop 61 in advance before the X-ray tube 5 performs X-ray irradiation. be able to. Therefore, the exposure dose of the subject M can be reduced more effectively.

  (2) In each of the embodiments described above, the lower left corner of the X-ray image 53 is used as the reference point Ro when calculating the movement rate. However, the position of the reference point Ro may be changed as appropriate. For example, as shown in FIG. 11A, the center of the X-ray image 53 may be the reference point Ro and the coordinates may be (0, 0). By having such a configuration, when the collimator 7 is configured by two pairs of interlocking leaves as in the second embodiment, the movement rate can be calculated using a simpler configuration. That is, among the markers 45e to 45h provided on the stent 43, the marker detection unit 19 detects the marker 45e whose x coordinate is farthest from the reference point Ro and the marker 45f whose y coordinate is farthest from the reference point Ro. .

The coordinates of the marker 45e are (xe, ye), and the absolute value of xe is x'e. Also, the coordinates of the marker 45f are (xf, yf), and the absolute value of yf is y'f. In the case where the rectangle E is widened by 100 pixels vertically and horizontally as compared with the rectangle D as in each embodiment, the movement rates of the leaves 59a and 59b can be calculated using the following equation (9). .
{(Mx-e-100) / m} × 100 (%) (9)
Then, the movement rate of the leaf 59c and the leaf 59d can be calculated using the following equation (10).
{(N−y′f−100) / n} × 100 (%) (10)

  The collimator control unit 13 moves each of the leaves 59a to 59d based on the movement rate calculated by the expressions (9) and (10). As a result, as shown in FIG. 11 (b), the range with halftone dots in the X-ray image 53 is blocked by each of the leaves 59a to 59d. By having such a configuration, even when the number of markers 45 provided on the stent 43 is large, the movement rate of each of the leaves 59a to 59d can be increased by detecting two of the markers 45e and 45f. It can be calculated.

  (3) In each Example mentioned above, it is good also as a structure which repeats the process of step S1-S5 suitably while performing PCI. In this case, since the position of the rectangle E is recalculated in accordance with the position of the stent 43 in the X-ray image 53, the X-ray irradiated to the subject M is always controlled to be in an appropriate range. Therefore, the exposure dose of the subject M can be kept lower.

DESCRIPTION OF SYMBOLS 1 ... X-ray imaging apparatus 5 ... X-ray tube (X-ray source)
7 ... Collimator 9 ... X-ray detector (X-ray detection means)
13: Collimator control unit (collimator control means)
17: Image processing unit 19: Marker detection unit (marker detection means)
21 ... Movement distance calculation unit (movement distance calculation means)
31 ... Detection instruction section (detection instruction means)
35 ... Leaf (shielding part)
39 ... catheter 43 ... stent (device)
45: Marker

Claims (6)

An X-ray source for irradiating the subject with X-rays;
X-ray detection means for detecting X-rays transmitted through the subject;
An image forming unit that forms an X-ray image of an area including a device inserted into the body of a subject using a detection signal output by the X-ray detection unit;
A collimator that includes a shielding unit that shields X-rays, and controls an X-ray irradiation field irradiated from an X-ray source;
Collimator control means for controlling the opening and closing movement of the shielding part;
Marker detecting means for detecting the position of a marker provided in the device in the X-ray image formed by the image forming unit;
A moving distance calculating means for calculating a moving distance of the shielding part based on the position of the marker detected by the marker detecting means;
The collimator control unit is configured to block the X-ray emitted from the X-ray source based on the movement distance calculated by the movement distance calculation unit so as to irradiate the device and a range including the vicinity of the device. An X-ray imaging apparatus that controls opening and closing movements of the unit. The X-ray imaging apparatus according to claim 1,
An X-ray imaging apparatus comprising: a detection instruction unit that instructs the marker detection unit to detect the position of the marker in an X-ray image formed by the image forming unit. The X-ray imaging apparatus according to claim 2,
The X-ray imaging apparatus, wherein the detection instruction means is a switch or button provided in the X-ray imaging apparatus. The X-ray imaging apparatus according to claim 2 or 3,
The detection instruction unit detects the position of the marker in the X-ray image formed by the image forming unit with respect to the marker detection unit after a lapse of a certain time from the start of X-ray irradiation by the X-ray source. X-ray imaging apparatus that gives instructions. The X-ray imaging apparatus according to any one of claims 2 to 4,
Further comprising shielding part stopping means for stopping the opening and closing movement of the shielding part,
The detection instructing unit detects the position of the marker in the X-ray image formed by the image forming unit with respect to the marker detecting unit when releasing the opening / closing movement of the shielding unit by the shielding unit stopping unit. An X-ray imaging apparatus that gives instructions to do so. The X-ray imaging apparatus according to any one of claims 1 to 5,
An integrating unit that forms an integrated image by superimposing a plurality of X-ray images of the same phase formed by the image forming unit;
An X-ray imaging apparatus comprising: a cutout display unit that cuts out and displays an image of the device from an integrated image formed by the integration unit.

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