X-ray imaging diagnostic apparatus and method for processing X-ray images

Abstract

To correct a distortion in an image in oblique incidence, and improve the accuracy of measurement using an X-ray image captured by oblique incident imaging in an X-ray image diagnostic apparatus equipped with an oblique incident function.SOLUTION: In calculating a physical amount using an X-ray image captured at a predetermined incident angle using an X-ray image diagnostic apparatus, the incident angle is received from an oblique incident mechanism part of the X-ray image diagnostic apparatus, and a distortion in the X-ray image caused by the oblique incidence of an X-ray onto a subject is calculated using the incident angle. Also, a predetermined measurement operation in the X-ray image is received through a screen of an output device, and the physical amount is calculated on the image. In this case, the physical amount on the image is corrected using the calculated distortion of the X-ray image, and the physical amount in an actual subject is calculated.SELECTED DRAWING: Figure 4

Description

【Technical Field】 【0001】 The present invention relates to an X-ray imaging diagnostic apparatus, and more particularly, to a method for processing an X-ray image obtained by irradiating a subject with X-rays obliquely and taking a picture. 【Background Art】 【0002】 An X-ray imaging diagnostic apparatus is a device that irradiates a subject with X-rays while the subject is placed on a fluoroscopic table housing an X-ray detector, and detects transmitted X-rays with the X-ray detector to take a picture. In an X-ray imaging diagnostic apparatus, in order to be able to take a picture of a desired part of a subject placed on the top plate of the fluoroscopic table from a desired angle, a mechanism for supporting an X-ray tube that generates X-rays, a mechanism for supporting the top plate, and a mechanism for connecting the support mechanism of the X-ray tube and the support mechanism of the top plate are each provided with various slide mechanisms, rotation mechanisms, and the like. 【0003】 For example, in the X-ray fluoroscopic imaging apparatus disclosed in Patent Document 1, in addition to basic mechanisms such as a slide mechanism for moving the top plate in the body axis direction of the subject and a direction orthogonal thereto and a rotation mechanism for rotating the top plate with respect to a stand portion supporting each support mechanism, a support mechanism that enables the X-ray tube to move in the vertical direction, a mechanism that enables the X-ray tube to slide or rotate with respect to the support mechanism, etc., a mechanism for rotating the X-ray tube around the axis in the body axis direction of the subject, that is, the axis in the longitudinal direction of the top plate is provided. 【0004】 This X-ray fluoroscopic imaging apparatus enables an injection (short-side injection) of irradiating the subject with X-rays obliquely by rotating the X-ray tube around the axis in the body axis direction. By injecting X-rays and taking a picture, it becomes possible to obtain various X-ray images useful for diagnosis. 【0005】 On the other hand, in X-ray imaging diagnosis, there is a demand for measuring, for example, the width and length of blood vessels or the degree of bending (angle) of bones and blood vessels using an X-ray image, and an apparatus having such a measurement function is also known (Patent Document 2). 【Prior Art Documents】 【Patent Documents】 【0006】 [Patent Document 1] Japanese Patent Publication No. 2021-97809 [Patent Document 2] International Publication No. 2014 / 034294 [Disclosure of the Invention] [Problems that the invention aims to solve] 【0007】 In X-ray images obtained through injection radiography, the distance from the X-ray source differs on both sides of the image's center (i.e., the center of the X-ray irradiation area). This causes reversal in image magnification and reduction, resulting in image distortion. When measuring distances and angles using such X-ray images obtained through injection radiography, the measured values ​​on the image will differ from the actual distances and angles of the subject, making accurate measurements impossible. 【0008】 Patent Document 1 describes methods for addressing image density unevenness caused by different distances from the X-ray source in short-axis rheological imaging, such as controlling X-ray intensity and correcting through image processing. However, it does not address the issue of image distortion. 【0009】 The present invention aims to correct image distortion during X-ray injection and improve the accuracy of measurements using X-ray images taken during injection, in an X-ray imaging diagnostic apparatus equipped with an injection function. [Means for solving the problem] 【0010】 To solve the above problems, the X-ray imaging diagnostic apparatus of the present invention includes an image processing unit that calculates image distortion (positional displacement) according to the angle of entry. Based on the calculated distortion of each position on the image, the image processing unit corrects the distances and angles measured on the image and calculates and presents the actual distances and angles. 【0011】 In other words, the X-ray imaging diagnostic apparatus of the present invention comprises a top plate that houses an X-ray detector and on which a subject is placed, an X-ray tube that generates X-rays, a support unit that supports the X-ray tube at a position opposite the X-ray detector with the subject in between, and an image processing unit that generates an X-ray image using the X-rays detected by the X-ray detector. The support unit has a mechanism for rotating the X-ray tube about an axis parallel to the long axis of the top plate, and the image processing unit includes a distortion calculation unit that calculates the distortion of the X-ray image caused by the X-rays entering the subject using the rotation angle about the axis of the X-ray tube. 【0012】 Furthermore, the present invention relates to a method for processing X-ray images, which is a method for processing X-ray images taken at a predetermined entry angle using an X-ray diagnostic imaging apparatus, and includes the steps of: receiving the entry angle from the X-ray diagnostic imaging apparatus; calculating the distortion of the X-ray image caused by the entry of X-rays into the subject using the said entry angle; receiving a predetermined measurement operation in the X-ray image; and calculating a physical quantity corresponding to the predetermined measurement operation using the calculated distortion of the X-ray image. [Effects of the Invention] 【0013】 According to the present invention, by calculating the amount of deviation which varies depending on the injection angle, physical quantities measured using X-ray images, such as distance and angle, can be corrected and calculated based on this amount of deviation. This improves the accuracy of measurements even when using X-ray images taken during injection that are distorted. [Brief explanation of the drawing] 【0014】 [Figure 1] A diagram showing the overall configuration of an X-ray imaging diagnostic apparatus to which the present invention is applied. [Figure 2] This diagram illustrates the mechanism of an X-ray imaging diagnostic apparatus to which the present invention is applied, showing (A) the case when no injection imaging is performed and (B) the case when injection imaging is performed. [Figure 3] Functional block diagram of an X-ray imaging diagnostic system. [Figure 4] In the diagram illustrating injection, (A) shows an image taken without injection, and (B) shows an image taken with injection. [Figure 5]Figure for explaining image distortion occurring at the time of shooting [Figure 6] Flowchart showing the processing of the image processing unit of Embodiment 1 [Figure 7] Figure for explaining the measurement function of Embodiment 1. (A) is a figure showing a measurement operation, and (B) is a figure showing an example table of measurement results [Figure 8] Figure showing an example of a table used for distortion calculation [Figure 9] Figure for explaining a subject model [Figure 10] Figure for explaining the calculation of coefficients using the table of FIG. 8 [Figure 11] Flowchart showing the processing of the image processing unit of Embodiment 2 [Figure 12] Figure for explaining the measurement function of Embodiment 2. (A) is a figure showing a measurement operation, and (B) is a figure showing an example display of measurement results 【Mode for Carrying Out the Invention】 【0015】 Hereinafter, embodiments of the X-ray image diagnostic apparatus of the present invention will be described with reference to the drawings. 【0016】 The X-ray image diagnostic apparatus 1 includes an imaging system including an X-ray tube and its support mechanism arranged in an imaging room that blocks normal X-rays, and an operation system arranged in an operation room or the like separate from the imaging room. As shown in FIG. 1, the imaging system includes an X-ray tube 60 that generates X-rays, an aperture device 80, and a top plate 40 on which a subject S is placed. An X-ray detector (FPD: Flat Panel Detector in the figure) 70 that detects X-rays that have passed through the subject S is housed in the top plate 40. The operation system includes an operation console 200, a high-voltage generation unit 300 that supplies a high voltage to the X-ray tube 60, a processing device 500 that generates an X-ray image from the X-ray signal detected by the FPD 70 and performs its processing, an output device 600 that displays an image, and the like. 【0017】 Although not shown in Figure 1, the X-ray imaging apparatus 1 is equipped with a mechanism to support and move the X-ray tube 60 and a mechanism to support and move the tabletop. The specific configuration of these mechanisms is not particularly limited and is similar to that of known X-ray imaging apparatuses. However, the X-ray imaging apparatus 1 of this embodiment has a function to rotate the X-ray tube 60 around an axis parallel to the longitudinal direction of the tabletop 40 on which the subject S is placed, and perform irradiation imaging. The irradiation angle is determined by the rotation angle due to this function. There are two types of irradiation: irradiation around an axis parallel to the longitudinal direction (body axis irradiation) and irradiation around an axis parallel to the short direction. In this embodiment, the case of body axis irradiation will be explained as an example. Therefore, in the following explanation, "irradiation" will mean "body axis irradiation". 【0018】 As an example, an example of an X-ray imaging diagnostic apparatus equipped with an injection imaging function is shown in Figures 2(A) and (B). The X-ray imaging diagnostic apparatus 1 shown in Figure 2 is a device with a mechanism similar to the X-ray fluoroscopy apparatus disclosed in Patent Document 1, and comprises a top plate 40 supported by a stand 10 via support arms 20, a support column 30 supported by the stand 10 via support arms 20, and a tube support 50 connected to the upper end of the support column 30, with the X-ray tube 60 that generates X-rays being supported by the tube support 50. The X-ray detector 70 is housed inside the top plate 40, and the subject is placed above it. The X-rays irradiated from the X-ray tube 60 and transmitted through the subject are detected by the X-ray detector 70 and sent to the processing unit 500 to obtain an X-ray image. 【0019】 The top plate 40, support arm 20, support column 30, and tube support section 50 are equipped with sliding and rotating mechanisms. In addition, the tube support section 50 that supports the X-ray tube 60 is equipped with a mechanism that slides the X-ray tube 60 in the short-side direction of the top plate 40 (Figure 2(A): arrow A3), as well as a rotation mechanism that causes it to oscillate around axis R. 【0020】 By operating these sliding and rotating mechanisms, for example, as shown by arrows A1 to A4 in Figure 2(B), the positional relationship between the X-ray tube 60, the X-ray detector 70 housed in the top plate 40, and the subject can be changed in various ways without moving the subject on the top plate 40. Furthermore, X-rays generated by the X-ray tube 60 and whose irradiation range is defined by the diaphragm device 80 can be irradiated from an oblique direction from the front of the subject, i.e., poroscopy can be performed. 【0021】 The operation of the X-ray tube 60, the diaphragm 80, and the mechanisms that move them (their drive systems 100) is performed by technicians or doctors (hereinafter referred to as users) via the control console 200. 【0022】 The processing unit 500 can be composed of a computer (PC) equipped with memory and a CPU or GPU, and its functions are executed by the CPU / GPU reading a predetermined program. However, some functions may be performed by programmable ICs such as ASICs or FPGAs. As shown in Figure 3, the processing unit 500 is equipped with an output device 600 including a display device and an input device 800 for inputting data necessary for processing and user commands as auxiliary devices. The input device 800 may include a mouse or a pointing device, and input is performed by operating a GUI such as a cursor or pointer displayed on the display device with these devices. It is also possible for some or all of the functions of the input device 800 to be performed by the control console 200 (Figure 1). 【0023】 The processing unit 500, specifically as shown in Figure 3, includes an imaging control unit 510 that controls the imaging system in response to user commands made via the control console 200, an image generation unit 520 that generates an X-ray image using the X-ray signal from the X-ray detector 70, an image processing unit 530 that performs various image processing on the image data generated by the image generation unit 520, and a display control unit 540 that displays the image data as display data on the output device 600. 【0024】 The image processing unit 530 performs general image processing such as image scaling, density correction, and black and white inversion, as well as measurement functions for measuring on the image. The measurement function allows the user to specify positions and line segments on the displayed image and measure physical quantities such as distance and angle. Therefore, as shown in Figure 3, the image processing unit 530 includes a measurement unit 531 that performs distance measurement and angle measurement, for example. Furthermore, the image processing unit 530 in this embodiment includes processing to correct distortions that occur in the image when the above-mentioned lithography is performed, and includes a function (distortion calculation unit 533) that calculates distortion-corrected distances and angles when performing measurement functions. 【0025】 The specific processing of the image processing unit 530 (particularly the distortion calculation unit 533) will be described later, but first, the distortion that occurs in the X-ray image due to irradiation imaging will be explained with reference to Figures 4 and 5. Figure 4(A) shows the case when no irradiation is performed, i.e., when imaging is performed with the X-ray tube 60 in the position (angle 0) as shown in Figure 2(A), and (B) shows the case when irradiation imaging is performed, i.e., when imaging is performed with the X-ray tube 60 rotated to a predetermined rotation angle as shown in Figure 2(B). As shown in Figure 4(A), when no X-rays are irradiated, the resulting X-ray image 700a shows that the X-rays are evenly distributed around the center of the image where they are irradiated perpendicularly, so there is no bias in the X-rays due to the direction of irradiation. However, as shown in (B), in the X-ray image 700b obtained when irradiation is performed, the center of the subject S is shifted from the center of the image (shown by the dotted line), and the distortion differs on the left and right sides of the image: the right side is narrower horizontally and wider vertically, while the left side is wider horizontally and narrower vertically. 【0026】 Therefore, as shown in Figure 5, the distance A on the screen will differ from the actual distance B at the subject. Figures 4(B) and 5 exaggerate the distortion, and in reality, it may not be visible, but if distance measurements are taken, accurate values ​​cannot be obtained. 【0027】 In this embodiment, when the measurement function is selected, the image processing unit 530 receives information on the rotation angle of the X-ray tube 60 during injection imaging, i.e., the injection angle (for example, the injection angle is recorded as information attached to the image data), from the imaging system (tube support unit 50), and calculates a measured value corrected for the distortion during injection using the injection angle and the value measured on the image by the measurement unit 531. The position of each part of the subject on the image can be calculated using the geometric relationship between each part and the X-ray source (distance between each part and the X-ray source, the X-ray irradiation direction and angle from the center of the X-ray for each part, and the injection angle), but in this embodiment, the positional displacement (distortion) of each part is easily calculated using measured values ​​obtained in advance using a subject model, and the actual measured value (on the subject) is calculated using this. The specific calculation method will be explained in the embodiment described later. 【0028】 According to this embodiment, distortion of X-ray images obtained by injection imaging can be corrected, and in particular, when calculating physical quantities related to the shape of the subject tissue, the accuracy of calculating physical quantities can be improved by correcting the physical quantities using the distortion. 【0029】 The following describes embodiments for distance measurement and angle measurement, focusing on the functions of the image processing unit 530. 【0030】 <Embodiment 1> In this embodiment, the measurement unit 531 accepts user selection and performs distance measurement. Figure 6 shows the procedure for distance measurement. 【0031】 First, the image generation unit 520 creates an X-ray image using the transmitted X-rays detected by the X-ray detector (FPD) 70, and the image display unit 540 displays this image on the output device 600 (S1). Next, when the user selects the distance measurement function via the input device 800 (S2), the measurement unit 531 accepts the specification of a line segment on the screen (S3). 【0032】 To specify a line segment, for example, as shown in Figure 7(A), the starting point p1 of the line segment L is specified on the display device (output device 600) screen showing the X-ray image 700 using cursor or pointer operations with the input device 800, and the ending point p2 of the line segment is specified by dragging the mouse a predetermined distance. As a result of this operation, the specified line segment is displayed on the screen of the output device 600. 【0033】 The measurement unit 531 uses the coordinates of the starting and ending points (coordinates in the image) and the information on the emission angle associated with the image data to calculate the actual length of the line segment, i.e., the distance between the starting and ending points (S4). The distance calculation includes a process of converting the coordinates of the starting and ending points in the image to the coordinates on the subject (actual coordinates), and a process of calculating the distance based on the actual coordinates. 【0034】 In the case of X-ray irradiation, the amount of deviation between the coordinates in the image and the actual coordinates can be calculated using the irradiation angle, the distance between the X-ray source and the subject, the irradiation angle relative to the X-ray center, etc. However, in this embodiment, instead of calculating it for each coordinate, the amount of deviation is simply calculated according to the distance from the center of the image using values ​​that have been discretely measured in advance. 【0035】 Specifically, a subject model of a predetermined size is used, images are taken at multiple exposure angles, and the amount of coordinate shift relative to zero exposure angle is measured and stored as a table. As the subject model, a square (cuboid) with the average thickness of a typical adult body is used, and a portion of the table of measured values ​​is shown in Figure 8. In the table in Figure 8, a model with a square size of 25 mm x 25 mm is placed in four quadrants with the center of the image (center of the irradiated X-ray) as the origin, as shown in Figure 9, and images are taken at different exposure angles. For each exposure angle, the measured coordinates on the image at the four corners (P1, P2, P3, P4) of each quadrant are shown. The table in Figure 8 also includes similarly measured values ​​for a model with a size of 50 mm x 50 mm. 【0036】 The table in Fig. 8 is, for example, a part of a large table or an example. The measured values are not only at the four corners (4 points) of the four quadrants but may also be subdivided. Also, the table can be extended by measuring the sizes of the subject models smaller than 25×25 or larger than 50×50. In Fig. 8, the measured values for the incident angles of 0° (no incidence), 7.5°, and 15° are shown. However, for the incident angle, within the movable range of the device, it can be measured in small increments and tabulated. 【0037】 Furthermore, in this embodiment, a rectangular parallelepiped model is used as the subject model, but an ellipsoidal model closer to the human body may also be used. In any case, the accuracy of strain calculation can be improved by using the values measured using the model. 【0038】 Next, the coordinates of the actually captured image are corrected using such a table. As shown in Fig. 7(A), the coordinates of the image are the coordinates (B1x, B1y) of the starting point and the coordinates (B2x, B2y) of the ending point of the line segment L specified on the screen via the input device 800. 【0039】 The strain calculation unit 533 refers to the table, determines which values in the table the coordinates of the starting point and the ending point measured by the measurement unit 531 correspond to, calculates a correction coefficient for correcting the coordinate deviation, and calculates the coordinates (A1x, A1y), (A2x, A2y) of the actual image using the following formula (1). A1x = α·B1x, A1y = β·B1y (1) (where α and β represent correction coefficients respectively) 【0040】 For example, if the incident angle is 7.5° or less (e.g., 5°), as shown by the square in Fig. 10, refer to the column of body axis incidence 0° < θ ≦ 7.5°. Also, if the coordinates of the starting point are in the first quadrant when the image center is (0, 0) and the x - coordinate (B1x) is in the range of 0 to +25, use the value (25.3) in the row of 0 < x < 25 to calculate the correction coefficient α using the following formula. α = 25 / 25.3 【0041】 If the y coordinate (B1y) is in the range of +25 to +50, the correction coefficient β is calculated by the following formula using the value (50.2) of the row where 25 < x < 50. β = 50 / 50.2 【0042】 When the value of this coefficient is applied to the above-mentioned formula (1) in the case of coordinates (B1x, B1y) = (30, 70), A1x = (25 / 25.3) × 30 = 29.644 A1y = (50 / 50.2) × 70 = 69.721 The actual coordinates become (29.6, 69.7). 【0043】 For the coordinates of the end point (B2x, B2y) as well, the actual coordinates (A2x, A2y) can be calculated in the same manner. 【0044】 In this way, by using the table, the calculation of distortion can be performed at high speed. Also, by using the measured value based on the subject model as the deviation amount, the accuracy of distortion calculation can be improved. 【0045】 The measurement unit 531 calculates the distance from the start point to the end point using the coordinates corrected in this way (S4). 【0046】 Finally, the image display unit 540 displays the calculated distance (actual distance) on the screen where the measurement operation is being performed. A display example is shown in FIG. 7(B). In this example, numerical values indicating the distance are displayed below the line segment. However, the display method is not limited to this example, and any method such as providing a block for displaying the measurement value separately from the X-ray image and displaying it can be adopted. 【0047】 As described above, according to the present embodiment, since the distortion calculation unit 533 corrects the coordinates on the screen obtained by the measurement operation using the injection angle and then calculates the distance, highly accurate measurement can be performed without being affected by the distortion of the image obtained by the injection imaging. 【0048】 Furthermore, according to this embodiment, since measured values ​​are compiled into a table in advance, and correction coefficients are calculated and corrected using the values ​​in the table, precise calculations for each coordinate are unnecessary, and measurement results can be displayed in real time. In particular, when representative values ​​are used for the four quadrants of a two-dimensional plane, the calculation of distortion can be further simplified and accelerated. In addition, the accuracy of the correction coefficient can be arbitrarily adjusted by how the table is designed. 【0049】 <Embodiment 2> In this embodiment, the measurement unit 531 performs angle measurement. Angle measurement is performed, for example, when measuring the curvature of bones or the course of blood vessels. In this embodiment, the configuration of the image processing unit 530 is the same as in Embodiment 1, and includes the measurement unit 531 and the strain calculation unit 533. The procedure for angle measurement according to this embodiment will be described below with reference to Figure 11. 【0050】 In this embodiment as well, the image display unit 540 displays on the output device 600 (S10) and the user selects a measurement function via the input device 800 (S20), similar to Embodiment 1. However, here, an angle measurement function is accepted as the measurement function. In the angle measurement function, the measurement unit 531 accepts the specification of two or more line segments that define an angle on the screen (S30). The specification of line segments is the same as the specification of line segments in Embodiment 1, for example, by clicking or dragging with the mouse to determine the coordinates of the start and end points of the line segments. When this operation is performed, the line segments shown in Figure 12(A) are displayed on the screen, and characters identifying the line, such as "L1", are displayed near the line segments. Similarly, the start and end points of the second line segment are defined, and the line segment and its name "L2" are displayed. 【0051】 When the two line segments are defined, the distortion calculation unit 533, similar to Embodiment 1, determines a correction coefficient to correct the coordinates of the start and end points of the line segments L1 and L2 to the actual coordinates (of the subject in real space) by referring to a table (for example, Figure 8), and calculates the actual coordinates (S40). 【0052】 That is, if the correction coefficients in the x-direction calculated for the start and end points of line segments L1 and L2 are α1, α2, α3, α4, and the correction coefficients in the y-direction are β1, β2, β3, β4, then the actual coordinates of these line segments L1 and L2 (A1x, A1y) ​​~ (A4x, A4y) are as follows: A1x = α1 × B1x, A1y = β1 × B1y A2x = α² × B²x, A2y = β² × B²y A3x = α3 × B3x, A3y = β3 × B3y A4x = α⁴ × B⁴x, A4y = β⁴ × B⁴y 【0053】 The measurement unit 531 uses the actual coordinates calculated by the strain calculation unit 533 to calculate the angle between line segments L1 and L2 as follows (S50). 【0054】 First, substitute the corrected coordinates of the starting and ending points into the linear equations (y=ax+b, y=cx+d) representing line segments L1 and L2 to calculate the coefficients that determine the line segments and the intercepts (a,b,c,d). Then, using these coefficients and intercepts, calculate the angle φ using the following formula. tanφ = |ac| / |1 + (a*c)| 【0055】 The image display unit 540 outputs the angle calculated by the measurement unit 531 to the output device 600 (S50). Figure 12(B) shows an example of angle information displayed on the display screen of the output device 600. In this example, the angle information "∠L1-L2:(φ)" is displayed near the second line segment. 【0056】 Furthermore, if the measurement function continues and the user draws a third line segment L3 (S60), the angles between line segments L1 and L3, and between line segments L2 and L3 may be calculated, and angle information such as "∠L1-L3:(φ2)" and "∠L2-L3:(φ3)" may be calculated near line segment L3. Alternatively, the system may accept the selection of line segment L1 or L2 via mouse operation, or after accepting the specification of a fourth line segment L4, calculate either the angle between line segments L1 and L3 or the angle between line segments L2 and L3, or calculate the angle between line segments L3 and L4. Angle information is added in this way. 【0057】 According to this embodiment, the measurement unit 531 corrects the coordinates of the line segment using the strain calculated by the strain calculation unit 533, and then calculates the angle between the line segments, thereby providing highly accurate angle information. Furthermore, by using a table in the strain calculation, the angle between the line segments can be displayed immediately after selecting a line segment while the angle measurement function is operating, improving the real-time performance of the measurement function. 【0058】 The embodiments described above utilize the calculated strain when performing distance measurement and angle measurement in the X-ray imaging diagnostic apparatus of the present invention. However, the measurement function may perform distance measurement and angle measurement simultaneously, and it is also possible to further extend it to perform area measurement and the like. 【0059】 Furthermore, the figures and tables described in the embodiments are merely examples, and the present invention is not limited to these; they can be modified as appropriate. [Explanation of symbols] 【0060】 1: X-ray imaging diagnostic device, 10: Stand, 30: Support column, 40: Top plate, 50: Tube support, 60: X-ray tube, 70: X-ray detector (FPD), 80: Aperture device, 100: Fluoroscopy table, 200: Control console, 300: High voltage generator, 500: Processing unit, 510: Imaging control unit, 520: Image generation unit, 530: Image processing unit, 531: Measurement unit, 533: Distortion calculation unit, 600: Output device, 800: Input device

Claims

[Claim 1] The device comprises a top plate that houses an X-ray detector and on which the subject is placed, an X-ray tube that generates X-rays, a support that supports the X-ray tube in a position opposite the X-ray detector with the subject in between, and an image processing unit that generates an X-ray image using the X-rays detected by the X-ray detector. The support portion has a mechanism for rotating the X-ray tube about an axis parallel to the long axis of the top plate. The image processing unit includes a distortion calculation unit that calculates distortion of the X-ray image caused by the irradiation of X-rays into the subject using the rotation angle of the X-ray tube about the axis, and a measurement unit that receives measurement operations performed by the user on the X-ray image displayed on the display device and calculates a physical quantity that includes the angle between predetermined line segments of the subject tissue as a physical quantity relating to the shape of the subject tissue. An X-ray image diagnostic apparatus characterized in that, upon receiving a measurement operation performed by the user, the strain calculation unit corrects the physical quantity measured by the measurement unit using the strain calculated by the strain calculation unit, and presents both on the X-ray image to the user. [Claim 2] An X-ray imaging diagnostic apparatus according to claim 1, The X-ray imaging diagnostic apparatus is characterized in that the strain calculation unit maintains a table showing the relationship between the X-ray entry angle determined by the rotation angle and the amount of displacement of each position on the image relative to the image when the entry angle is zero, and calculates strain using the table. [Claim 3] The apparatus comprises a top plate for housing an X-ray detector and on which a subject is placed, an X-ray tube for generating X-rays, a support for supporting the X-ray tube at a position opposite the X-ray detector with the subject in between, and an image processing unit for generating an X-ray image using the X-rays detected by the X-ray detector, The support portion has a mechanism for rotating the X-ray tube about an axis parallel to the long axis of the top plate. The image processing unit includes a distortion calculation unit that calculates distortion of the X-ray image caused by the irradiation of X-rays into the subject using the rotation angle of the X-ray tube around the axis, and a measurement unit that receives measurement operations performed by the user on the X-ray image displayed on the display device and calculates physical quantities related to the shape of the subject tissue. The distortion calculation unit maintains a table showing the relationship between the X-ray entry angle determined by the rotation angle and the amount of displacement of each position on the image relative to the image when the entry angle is zero, and uses this table to calculate the distortion. The X-ray image diagnostic apparatus is characterized in that, upon receiving a measurement operation performed by the user, the image processing unit corrects the physical quantity measured by the measurement unit using the strain calculated by the strain calculation unit and presents both together to the user on the X-ray image. [Claim 4] An X-ray imaging diagnostic apparatus according to claim 2 or 3, The X-ray imaging diagnostic apparatus is characterized in that, in the table, the displacement amount is a value measured for each of multiple injection angles for the subject model. [Claim 5] An X-ray imaging diagnostic apparatus according to claim 2 or 3, The X-ray imaging diagnostic apparatus is characterized in that, in the table, the displacement amount is the measured value of a representative position in each of the four quadrants of a two-dimensional plane with the image center at (0,0). [Claim 6] An X-ray imaging diagnostic apparatus according to claim 1 or 3, The X-ray imaging diagnostic apparatus is characterized in that the aforementioned physical quantity further includes the distance between predetermined positions in the subject tissue. [Claim 7] An X-ray imaging diagnostic apparatus according to claim 5, The X-ray image diagnostic apparatus is characterized in that the measurement unit receives a designation of a line segment on an X-ray image displayed on a display device, corrects the start and end positions of the received line segment using the distortion calculated by the distortion calculation unit, and calculates the distance of the line segment on the subject corresponding to the line segment on the X-ray image. [Claim 8] An X-ray imaging diagnostic apparatus according to claim 1 or 3, The X-ray image diagnostic apparatus is characterized in that the measurement unit receives the designation of two or more line segments on an X-ray image displayed on a display device, corrects the start and end positions of each received line segment using the amount of distortion calculated by the distortion calculation unit, and calculates an angle on the subject that corresponds to the angle formed by the two or more line segments on the X-ray image. [Claim 9] A method for processing X-ray images taken at a predetermined insertion angle using an X-ray diagnostic imaging device, The X-ray imaging diagnostic device receives the injection angle, A step of calculating the distortion of the X-ray image caused by the X-ray exposure to the subject using the said exposure angle. A step of receiving a predetermined measurement operation in the X-ray image, and The process includes a step of calculating a physical quantity corresponding to the predetermined measurement operation using the distortion of the calculated X-ray image, The aforementioned physical quantity includes the angle between predetermined line segments of the subject tissue. X-ray image processing methods.

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