JP2014168504A - X-ray image diagnostic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray image diagnostic apparatus which can obtain an appropriate X-ray irradiation field region even in an X-ray image in which the periphery of a part of the X-ray irradiation field region is only a subject region with a pixel value approximate to that of an X-ray diaphragm shield region.SOLUTION: The X-ray image diagnostic apparatus includes: a boundary detection unit for detecting a boundary between an X-ray diaphragm shield region shielded by an X-ray diaphragm device and an X-ray irradiation field region which is not shielded in an X-ray image by using the difference of adjacent pixel values; a degree-of-variation calculation region setting unit for setting a region for calculating the degree of variation of the pixel values by using the boundary detected by the boundary detection unit; a degree-of-variation calculation unit for calculating the degree of variation of the pixel values in the region set by the degree-of-variation calculation region setting unit; and an X-ray irradiation field region determination unit for determining whether the position of the boundary set by the boundary detection unit is appropriate by using the degree of variation calculated by the degree-of-variation calculation unit, moving the position of the boundary to the appropriate position when it is determined that the position is not appropriate, and determining a region surrounded by using the boundary after movement as the position of the X-ray irradiation field region.

Description

  The present invention relates to an X-ray image diagnostic apparatus, and more particularly to detection of an X-ray irradiation field region in an X-ray image acquired by X-ray imaging.

In X-ray diagnostic imaging equipment, when irradiating a subject with X-rays and acquiring and diagnosing a desired X-ray image, a combination of multiple lead plates is used to prevent X-ray irradiation on subjects other than the diagnostic area. The X-ray field area is set using the configured X-ray aperture. For this reason, the acquired X-ray image includes an X-ray aperture shielding area that does not contribute to the diagnosis that the X-ray is blocked by the X-ray aperture. In addition, when displaying the acquired X-ray image on the display unit, only the X-ray irradiation field region excluding the X-ray aperture shielding region that does not contribute to diagnosis so as not to provide extra information to the interpretation doctor Is displayed.
Patent Document 1 describes a boundary between an X-ray aperture shielding area and an X-ray irradiation field area using a difference value of pixel values between adjacent pixels in an X-ray image acquired to detect the X-ray irradiation field area. It describes that an X-ray irradiation field area in an X-ray image is detected by detecting a line.

JP 2008-200075 A

  The X-ray image is generated by detecting the X-rays emitted from the X-ray generation unit by the X-ray detection unit. At this time, the X-ray irradiation field region in the X-ray image is transmitted through the subject. There is a subject area generated by detecting a line, and a direct line area generated by detecting the X-ray emitted from the X-ray generation unit directly by the X-ray detection unit without passing through the subject. . In the direct line area, the difference in pixel value between the X-ray aperture shielded area and the X-ray aperture shielded area is larger than the difference in pixel value between the subject area and the X-ray aperture shielded area because X-rays do not pass through the subject. Since the direct line region is generated at the end of the X-ray irradiation field region, it is effective to detect the X-ray irradiation field region using a difference value between adjacent pixels in the X-ray image as in Patent Document 1.

  However, in the case of an X-ray image in which only a subject area whose pixel value approximates that of the X-ray aperture shielding area is a part of the edge of the X-ray irradiation field area, only a difference in pixel values between adjacent pixels In the X-ray field area detected in, there was a risk of false detection of the X-ray field area.

  Therefore, an object of the present invention is to provide an appropriate X-ray image even if the X-ray image of only the subject region in which a part of the edge of the X-ray irradiation field region is similar in pixel value to the X-ray aperture shielding region. It is to provide an X-ray image diagnostic apparatus capable of obtaining an irradiation field region.

  In order to solve the above problems, the X-ray diagnostic imaging apparatus of the present invention is configured as follows.

  A boundary line detection unit that detects a boundary line between an X-ray aperture shielded area shielded by an X-ray diaphragm device and an unshielded X-ray irradiation field area in an X-ray image using a difference between adjacent pixel values; and A variation degree calculation region setting unit for setting a region for calculating a variation degree of the pixel value using the boundary line detected by the boundary line detection unit, and pixels in the region set by the variation degree calculation region setting unit A variation degree calculation unit that calculates a variation degree of the value, and using the degree of variation calculated by the variation degree calculation unit, determines whether the position of the boundary line set by the boundary line detection unit is appropriate. If it is determined that the position of the boundary line is appropriate, the X-ray irradiation field area determination unit determines that the area surrounded by the boundary line after the movement is moved as the position of the X-ray irradiation field area. And have That.

  According to the present invention, even if an edge of a part of the X-ray irradiation field region is an X-ray image of only the subject region whose pixel value is close to that of the X-ray aperture shielding region, the X-ray image is appropriately displayed. An X-ray diagnostic imaging apparatus that can determine an irradiation field region can be provided.

The block diagram which shows the whole structure of the X-ray image diagnostic apparatus of this invention The block diagram which shows the function of the image processing part of this invention The block diagram which shows the function structure of the X-ray irradiation field area | region detection part of this invention The figure for demonstrating operation | movement of the X-ray irradiation field area | region detection part of this invention The flowchart for demonstrating the operation | movement order of the X-ray irradiation field area | region detection part of this invention

  The X-ray diagnostic imaging apparatus of the present invention will be described in detail below with reference to the accompanying drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments of the invention, and the repetitive description thereof is omitted. FIG. 1 is a diagram showing an overall configuration of an X-ray image diagnostic apparatus according to the present invention. FIG. 2 is a diagram showing a functional configuration of the image processing unit of the present invention.

  The X-ray diagnostic imaging apparatus shown in FIG. 1 includes a top plate 102 on which a subject 101 is placed, an X-ray source 103 that irradiates the subject 101 with X-rays, and an X-ray irradiation field region for the subject 101. A diaphragm 104, a high voltage generator 105 that supplies power to the X-ray source 103, an X-ray detector 106 that is disposed at a position facing the X-ray source 103 and detects X-rays transmitted through the subject 101, An X-ray image processing unit 107 that performs image processing on the X-ray signal output from the X-ray detection unit 106, an external storage unit 108 that stores the X-ray image output from the X-ray image processing unit 107, A display unit 109 that displays an X-ray image, a control unit 110 that controls each of the above-described components, and an operation unit 111 that instructs the control unit 110 are provided.

  The X-ray source 103 has an X-ray tube that receives power supply from the high voltage generator 105 and generates X-rays. The X-ray source 103 may include an X-ray filter that selectively transmits X-rays having specific energy. The X-ray aperture device 104 has a plurality of X-ray shielding lead plates that shield X-rays generated from the X-ray source 103. Determine the radiation field area.

  The X-ray detection unit 106 is configured by, for example, a plurality of detection elements that detect X-rays arranged in a two-dimensional array, and is incident from the X-ray source 103 and transmitted through the subject 101. This device detects X-ray signals according to the dose.

  The X-ray image processing unit 107 includes an image conversion unit 201 that converts the X-ray signal output from the X-ray detection unit 106 into an X-ray image, and an X-ray irradiation field in the X-ray image converted by the image conversion unit 201. An X-ray irradiation field region detection unit 202 for detecting a region.

  The display unit 109 displays the X-ray irradiation field area detected by the X-ray image processing unit 107.

  Next, the X-ray irradiation field region detection unit 202 that is a feature of the present invention will be described in detail with reference to FIGS. 3 and 4 (a) to 4 (e). FIG. 3 is a diagram showing a functional configuration of the X-ray irradiation field region detection unit 202 of the present invention. FIG. 4 is a diagram for explaining the operation of the X-ray irradiation field region detection unit 202 of the present invention.

  FIG. 4A shows an X-ray image 401 of the chest of the subject 101 generated by the image conversion unit 201. The X-ray image 401 includes an X-ray diaphragm shielding region 402 where the X-rays irradiated from the X-ray generator 103 are blocked by the X-ray diaphragm device 104 and an X-ray irradiation field region 403 that is not blocked. is there. The X-ray irradiation field region 403 includes a direct ray region 404 that is generated when the X-ray emitted from the X-ray generation unit 103 is detected by the X-ray detection unit 106 without passing through the subject 101. There is a subject region 405 generated when the X-rays emitted from the X-ray generation unit 103 pass through the subject 101 and the X-ray detection unit 106 detects the transmitted X-rays. The subject region 405 includes a lung field portion 406 whose pixel value is close to the direct line region 404 and a diaphragm portion 407 whose pixel value is close to the X-ray aperture shielding region 402. The X-ray irradiation field region detection unit 202 includes a boundary line detection unit 301, a variation degree calculation region setting unit 302, a variation degree calculation unit 303, and an X-ray irradiation field region determination unit 304, and an image The X-ray image 401 generated by the conversion unit 201 is transmitted to the boundary line detection unit 301.

  The boundary line detection unit 301 detects a boundary line between the X-ray aperture shielding region 402 and the X-ray irradiation field region 403 in the X-ray image 401 transmitted from the image conversion unit 201. In the detection method, a plurality of positions where the difference Gs of pixel values between adjacent pixels is equal to or greater than a predetermined threshold Gsth are detected, and a straight line serving as a boundary line is obtained by Hough transform using the detected plurality of positions.

  Since the Hough change is a conventional technique, a description thereof is omitted here.

  The boundary line detection unit 301 detects a position that is equal to or greater than the threshold value Gsth from the outer periphery to the center of the X-ray image 401, and detects four boundary lines surrounding the X-ray irradiation field region 403.

  FIG. 4B shows four boundary lines U1, D1, L1, and R1 detected by the boundary line detection unit 301. There is a direct line region 404 at the upper left and upper right edges of the X-ray irradiation field region 403, and the boundary positions of the X-ray aperture shielding region 402 and the direct line region 404, for example, boundary positions Pul, Pur, Pl, Pr The pixel value difference is larger than the pixel value difference at the boundary position with the other X-ray aperture shielding region 402. On the other hand, the difference between the pixel values at the boundary position between the X-ray diaphragm shielding region 402 and the diaphragm portion 407, for example, the boundary position Pdc is smaller than the difference between the pixel values at the boundary position with the other X-ray diaphragm shielding region 402. . Further, the difference between the pixel values at the boundary position between the lung field portion 406 and the diaphragm portion 407, for example, the boundary position Pdr, is the pixel at the boundary position Pul, Pur, Pl, Pr based on the difference in pixel value at the boundary position Pdc. Takes a value close to the value difference.

  The threshold Gsth is set to an appropriate value in order to detect four boundary lines surrounding the X-ray irradiation field region 403. In the above case, the boundary originally includes the boundary position Pdc or is close to the boundary position Pdc. Although a line should be detected, a boundary line including the boundary position Pdr or close to the boundary position Pdc may be detected. The boundary line D1 shows an example in the case of erroneous detection. If the threshold value Gsth is set too low to detect the boundary position Pdc, the number of positions in the X-ray image 401 used for the Hough transform increases more than necessary, so that an appropriate boundary line cannot be detected.

  The variation degree calculation region setting unit 302 sets a variation degree calculation region for calculating a variation degree of pixel values in the X-ray image 401 using the boundary line detected by the boundary line detection unit 301. The variation degree calculation area is set in an area excluding the area surrounded by all the boundary lines detected by the boundary line detection unit 301 in the X-ray image 401. Specifically, the three boundary lines and the X-rays are set. An area surrounded by one side of the outer periphery of the image 401 is set as a variation degree calculation area.

  FIG. 4C shows four variation degree calculation regions SU1, SD1, SL1, and SR1 set by the variation degree calculation region setting unit 302. The variation calculation area SU1 is an area surrounded by three boundary lines U1, L1, and R1 and one side on the upper side of the X-ray image 401, and the variation calculation area SD1 is a boundary line D1, L1, This is a region surrounded by the three boundary lines of R1 and the lower side of the X-ray image 401. The variation calculation area SL1 is composed of the three boundary lines of the boundary lines U1, D1, and L1 and the X-ray image 401. The variation degree calculation area SR1 is an area surrounded by three boundary lines U1, D1, and R1 and one side on the right side of the X-ray image 401.

  The variation degree calculation unit 303 calculates the variation degree of the pixel value in each variation degree calculation region set by the variation degree calculation region setting unit 302 using the standard deviation.

  The X-ray irradiation field region determination unit 304 determines whether or not the region surrounded by the boundary lines U1, D1, L1, and R1 detected by the boundary line detection unit 301 is appropriate as the X-ray irradiation field region. Specifically, whether the standard deviations Ssu1, Ssd1, Ssl1, and Ssr1 of the variation degree calculation areas SU1, SD1, SL1, and SR1 calculated by the variation degree calculation unit 303 are within a preset threshold value Sth. If the determined standard deviation is larger than the threshold value Sth, the position of the boundary line that opposes one side of the X-ray image 401 among the boundary lines forming the variation degree calculation region is the center of the X-ray image 401. Is moved by a preset number of pixels in the direction from the outside to the outside.

  The standard deviation in the variation calculation region formed after the movement is calculated again by the variation calculation unit 303, and the X-ray irradiation field region determination unit 304 determines whether the calculated standard deviation is within the threshold Sth. judge.

  When the standard deviation calculated again is larger than the threshold value Sth, the position of the boundary line is further moved outward to obtain the position of the boundary line where the standard deviation is within the threshold value Sth. The X-ray irradiation field region determination unit 304 has confirmed that the standard deviation is within the threshold value Sth in all the variation degree calculation regions, so that the region surrounded by the boundary line detected by the boundary line detection unit 301 Is determined to be appropriate as the X-ray irradiation field region.

  Thereby, even when the boundary line is detected by mistake, the X-ray irradiation field region can be appropriately detected.

  In FIG. 4 (d), the position of the boundary line D1 is moved to D2 on the assumption that the standard deviation Ssd1 of the variation calculation area SD1 including the diaphragm portion 407 in addition to the X-ray aperture shielding area 402 is larger than the threshold value Sth. The figure when it does is shown.

  In the variation calculation area SD2 newly set using the boundary line D2, the portion of the diaphragm portion 407 is removed and only the X-ray aperture shielding area 402 is obtained. Therefore, the standard deviation Ssd2 of the variation degree calculation area SD2 is smaller than the standard deviation Ssd1 and can be determined to be within the threshold value Sth.

  The X-ray irradiation field region determination unit 304 displays the X-ray irradiation field region 403 determined to be appropriate by the above method in the X-ray image display region 408 of the display unit 109 as shown in FIG. Since only the X-ray irradiation field area 403 necessary for interpretation is displayed on the display unit 109, the interpretation doctor can concentrate on interpretation. Further, when displaying the X-ray irradiation field region 403 in the X-ray image display region 408, the enlargement ratio of the X-ray irradiation field region 403 may be adjusted so as to fill the X-ray image display region 408.

  Further, an X-ray image 401 in which an area other than a part determined as an X-ray irradiation field area by the X-ray irradiation field area determination unit 304 in the X-ray image 401 may be displayed in a single color, for example, black.

  Next, the operation sequence of the X-ray irradiation field region detection unit 202 of the present invention will be described with reference to the flowchart shown in FIG.

  In step S501, a boundary line between the X-ray aperture shielding region 402 and the X-ray irradiation field region 403 in the X-ray image 401 acquired by the boundary line detection unit 301 is detected.

  In step S502, the variation degree calculation region setting unit 302 sets a variation degree calculation region using the boundary line detected by the boundary line detection unit 301.

  In step S503, the variation degree calculation unit 303 calculates the variation degree in the variation degree calculation region.

  In step S504, it is determined whether or not the variation degree calculated by the variation degree calculation unit 303 by the X-ray irradiation field region determination unit 304 is appropriate. If it is determined to be appropriate, the process proceeds to step S505. If it is determined not to be appropriate, the position of the boundary line is moved and the process returns to step S503.

  In step S505, the X-ray irradiation field region determined to be appropriate by the X-ray irradiation field region determination unit 304 is displayed on the display unit 109.

  As described above, according to the X-ray image diagnostic apparatus of the present invention, an X-ray image of only a subject region in which a part of the edge of the X-ray irradiation field region approximates a pixel value with the X-ray aperture shielding region is obtained. Even if it exists, an X-ray irradiation field area | region can be determined appropriately and it can display on a display part.

  The X-ray image diagnostic apparatus of the present invention is not limited to this.

  In the above description, the X-ray irradiation field region determination unit 304 compares the standard deviation calculated by the variation degree calculation unit 303 with a preset threshold value Sth, thereby detecting the boundary line detected by the boundary line detection unit 301. The X-ray irradiation field area determination unit 304 is one standard deviation among the four standard deviations calculated by the variation degree calculation unit 303. Is far apart from the other three standard deviations, the standard deviation calculated from the standard deviation is not appropriate as the boundary that constitutes the X-ray field area. The boundary line may be moved so that the standard deviation is equivalent to the other three standard deviations, and the boundary line that is equivalent may be determined as an appropriate X-ray irradiation field region. Thereby, it is not necessary to set the threshold value Sth in advance.

  Further, the boundary line detection unit 301 detects a plurality of positions where the difference Gs of pixel values between adjacent pixels is equal to or greater than a predetermined threshold Gsth, and obtains a boundary line by Hough transform using the detected plurality of positions. The X-ray irradiation field region determination unit 304 uses the boundary line having the largest average difference between the pixel values at a plurality of positions used when obtaining the boundary line, the approximate boundary line, and one side of the outer periphery of the X-ray image. The standard deviation calculated in the variation degree calculation region that is set as a reference standard deviation may be used, and the position of another boundary line may be adjusted so as to approximate this reference standard deviation. A boundary detected using a position where the difference in pixel values is large is less likely to be erroneously detected. Thus, even when the remaining boundary line detected by the boundary line detection unit 301 is not appropriate as the boundary line constituting the X-ray irradiation field region, an appropriate X-ray irradiation field region can be obtained.

  101 Subject, 102 Top plate, 103 X-ray source, 104 X-ray diaphragm, 105 High voltage generator, 106 X-ray detector, 107 Image processor, 108 External storage, 109 Display, 110 Control, 111 Operation unit, 201 Image conversion unit, 202 X-ray irradiation field region detection unit, 301 Boundary line detection unit, 302 Variation degree calculation region setting unit, 303 Variation degree calculation unit, 304 X-ray irradiation field region determination unit, 401 X-ray image , 402 X-ray aperture shielding area, 403 X-ray irradiation field area, 404 direct ray area, 405 subject area, 406 lung field part, 407 diaphragm part, 408 X-ray image display area,

Claims (6)

  A boundary line detection unit that detects a boundary line between an X-ray aperture shielding area shielded by an X-ray diaphragm device in an X-ray image and an unshielded X-ray irradiation field area by using a difference between adjacent pixel values; A variation degree calculation region setting unit for setting a region for calculating a variation degree of a pixel value using the boundary line detected by the boundary line detection unit, and pixels in the region set by the variation degree calculation region setting unit A variation degree calculation unit for calculating a variation degree of the value, and using the variation degree calculated by the variation degree calculation unit, determine whether the position of the boundary line set by the boundary line detection unit is appropriate, and If it is determined that the boundary line is not suitable, an X-ray irradiation field area determination unit that moves the boundary line to an appropriate position and determines the area surrounded by the moved boundary line as the position of the X-ray irradiation field area. , X-rays image diagnosis apparatus characterized by having a. The X-ray image has a quadrangular shape, the boundary detection unit detects one boundary line in each of the upper, lower, left, and right directions, and the variation degree calculation region setting unit detects four lines detected by the boundary detection unit. The area surrounded by three boundary lines and one side of the outer periphery of the X-ray image is set as an area for calculating the degree of variation. X-ray diagnostic imaging equipment. The X-ray image diagnosis apparatus according to claim 2, wherein the variation degree calculation unit calculates a variation degree in the region set by the variation degree calculation region setting unit using a standard deviation. The X-ray irradiation field region determination unit determines whether the boundary position set by the boundary line detection unit is appropriate by comparing the standard deviation calculated by the variation degree calculation unit with a preset threshold value. The X-ray image diagnostic apparatus according to claim 3. The X-ray irradiation field region determination unit compares the standard deviation calculated by the variation degree calculation unit with the standard deviation calculated in another region, thereby determining the boundary line set by the boundary line detection unit. The X-ray image diagnostic apparatus according to claim 3, wherein the suitability of the position is determined. An X-ray source that irradiates the subject with X-rays, an X-ray diaphragm device that sets an X-ray irradiation field region for the subject, and transmitted X-rays of the subject that are arranged to face the X-ray source are detected An X-ray detection unit, an X-ray image processing unit that converts an X-ray output from the X-ray detection unit into an X-ray image, and a display unit that displays the X-ray image output from the image processing unit. Have
The X-ray image processing unit is configured to include the boundary line detection unit, the variation degree calculation region setting unit, the variation degree calculation unit, and the X-ray irradiation field region determination unit. The X-ray diagnostic imaging apparatus according to any one of claims 1 to 5, characterized in that

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