WO2019123758A1 - Système de capture d'image à différence de phase à rayons x - Google Patents

Système de capture d'image à différence de phase à rayons x Download PDF

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Publication number
WO2019123758A1
WO2019123758A1 PCT/JP2018/036091 JP2018036091W WO2019123758A1 WO 2019123758 A1 WO2019123758 A1 WO 2019123758A1 JP 2018036091 W JP2018036091 W JP 2018036091W WO 2019123758 A1 WO2019123758 A1 WO 2019123758A1
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Prior art keywords
ray
grating
image
detection area
positional deviation
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PCT/JP2018/036091
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English (en)
Japanese (ja)
Inventor
直樹 森本
木村　健士
太郎 白井
貴弘 土岐
哲 佐野
日明 堀場
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株式会社島津製作所
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Priority to JP2019560806A priority Critical patent/JP7021676B2/ja
Publication of WO2019123758A1 publication Critical patent/WO2019123758A1/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/02—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material
    • G01N23/04—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and forming images of the material
    • G01N23/041—Phase-contrast imaging, e.g. using grating interferometers

Definitions

  • the present invention relates to an X-ray phase-contrast imaging system, and more particularly to acquisition of misalignment of a grating of an X-ray phase-contrast imaging apparatus for imaging using a plurality of gratings and adjustment of the grating position.
  • X-ray phase contrast imaging systems are known. Such an X-ray phase contrast imaging system is disclosed, for example, in WO 2014/030115.
  • WO 2014/030115 discloses an X-ray phase contrast imaging system for imaging a phase contrast image by detecting moire fringes generated by translating a source grating.
  • the X-ray phase contrast imaging system disclosed in the above-mentioned WO 2014/030115 comprises an X-ray source, a source grating, a phase grating, an absorption grating, and a detector. including.
  • This X-ray phase difference imaging apparatus is a so-called Talbot-Lau interferometer.
  • the X-ray phase difference imaging system disclosed in Patent Document 1 acquires a translation signal for translating the source grating so that the moire fringes have a predetermined period, and the source grating is obtained based on the acquired translation signal.
  • the source grating is obtained based on the acquired translation signal.
  • the Talbot-Lau interferometer X-rays that have passed through the source grating are irradiated to the phase grating.
  • the irradiated X-rays are diffracted when passing through the phase grating, and form a self-image of the phase grating at a position separated by a predetermined distance (talbot distance).
  • the period of the self-image of the formed phase grating is so small that it can not be detected by a general purpose detector. Therefore, in the Talbot-Lau interferometer, an absorption grating is disposed at a position where a self-image of the phase grating is formed, to form a moire fringe which can be detected even by a general-purpose detector.
  • slight changes in the self-image are detected by performing multiple imaging (fringe scanning imaging) while translating any one of the gratings in the periodic direction of the grating, and a phase contrast image is obtained. You can get
  • unintended moiré fringes occur when the relative position between the phase grating and the absorption grating deviates from the designed position.
  • an artifact (virtual image) is generated in the captured image due to the unintended moire fringe.
  • “unintended moiré fringes” refers to moiré fringes that occur in a state in which a subject is not arranged and that are caused by a shift in relative position between the phase grating and the absorption grating.
  • artifact (virtual image) refers to the disturbance of the phase contrast image or the deterioration of the image quality of the phase contrast image, which is caused due to unintended moiré fringes.
  • the present invention has been made to solve the above-described problems, and provides an X-ray phase difference imaging system capable of easily maintaining the same imaging conditions without updating air data. It is.
  • an x-ray phase contrast imaging system comprises an x-ray source, an x-ray detector for detecting irradiated x-rays, an x-ray source and an x-ray detector And a plurality of gratings including a first grating for passing X-rays between them and a second grating for causing interference with the self-image of the first grating, and grating movement for moving the gratings at regular intervals
  • An image processing unit that generates a phase differential image based on the mechanism, the first X-ray image acquired without arranging the subject, and the second X-ray image acquired by arranging the subject; And a controller for acquiring a positional deviation, the controller being a grating in the optical axis direction connecting the X-ray source and the X-ray detector based on the pixel value of the phase differential image generated by the image processor.
  • the control unit controls the X-ray source and the X-ray detector based on the pixel values of the phase differential image generated by the image processing unit.
  • the positional deviation of the lattice in the direction of the optical axis connecting the two the positional deviation of the lattice in the direction orthogonal to the direction of the slit of the lattice, or the positional deviation of the lattice due to rotation about the optical axis Is configured.
  • the control unit can acquire (update) the positional deviation based on the pixel value of the acquired phase differential image.
  • the positional deviation of the grating (change in imaging conditions) can be easily acquired simply by generating a phase differential image by normal imaging.
  • the same imaging condition can be easily maintained without updating the air data.
  • the control unit generates the phase differential image to obtain the positional deviation of the grating a plurality of times, and the first X generated in advance. It is configured to use a line image.
  • the phase differential image is generated based on the first X-ray image generated in advance and the second X-ray image generated anew.
  • the phase differential image can be generated only by newly capturing the second X-ray image, and the user does not have to acquire the first X-ray image again.
  • the X-ray phase difference imaging system preferably further includes a position adjustment mechanism for adjusting the position of the grating, and the control unit adjusts the position of the grating based on the obtained displacement of the grating.
  • the mechanism is configured to perform adjustment control. According to this structure, since the position adjustment mechanism adjusts the position of the grid, the user does not have to perform an operation of adjusting the position of the obtained grid. As a result, since the same imaging conditions can be more easily maintained, the burden on the user can be reduced.
  • the control unit controls the position adjusting mechanism to adjust the position of the grating based on the obtained position shift of the grating every time one phase differential image is generated or a plurality of phase differential images are generated.
  • the same imaging condition can be maintained as accurately as possible by adjusting the position of the grid by the position adjustment mechanism each time the position shift of the grid is acquired.
  • the frequency at which the position adjustment mechanism adjusts the position is compared to the case where the position is adjusted each time one sheet is generated. It can be reduced. As a result, it is possible to reduce the time required to adjust the position of the grid while maintaining the imaging conditions in a range that causes no practical problems.
  • the control unit acquires an average value or a median value of pixel values at a plurality of places in each detection area of the plurality of detection areas set in the phase differential image
  • the grid is configured to obtain positional deviation. According to this configuration, the distribution of pixel values in the detection area can be obtained. Further, by taking an average value or a median value from a plurality of acquired pixel values, it is possible to eliminate an extreme numerical value (outlier) caused by noise or the like, so that accurate positional deviation can be obtained.
  • At least one of misalignment of the grating in a direction orthogonal to the direction of slits of the grating or misalignment of the grating due to rotation about the optical axis are set on a line parallel to the direction of the slit of the lattice, with the center point of the detection area being interposed.
  • positional deviation due to rotation around the optical axis, and positional deviation of the grating in a direction perpendicular to the direction of the slits of the lattice are positional deviations with a straight line orthogonal to the direction of the slit passing through the central point of the detection area as a boundary. Differences tend to appear. Therefore, with the above configuration, positional deviation of the grating in a direction orthogonal to the direction of the slits of the grating or positional deviation of the grating due to rotation around the optical axis can be easily obtained from the phase differential image.
  • the detection area for acquiring positional deviation of the grid in the direction of the optical axis connecting the X-ray detector and the X-ray detector is set at two places on the line orthogonal to the slit direction of the grid across the center point of the detection area .
  • misalignment of the grating in the optical axis direction is likely to occur in a direction perpendicular to the direction of the slits of the grating, and is less likely to occur in a direction parallel to the direction of the slits of the grating. Therefore, with the above configuration, positional deviation of the grating in the direction of the optical axis connecting the X-ray source and the X-ray detector can be easily obtained from the phase differential image.
  • the detection area is , And is set near the outer periphery of the imaging region of the second phase differential image. According to this structure, since the detection area can be set to the outer peripheral portion where the positional deviation due to rotation is large, it becomes easy to obtain the positional deviation. Therefore, the detection accuracy of positional deviation can be improved.
  • the control unit When the pixel value in the detection area is less than the threshold value, the detection area is set to a portion in the phase differential image that does not include the subject. With this configuration, it is possible to set, as the detection area, a place where there is no change in the pixel value due to the reflection of the subject. As a result, it is possible to accurately obtain the amount of change in pixel value due to misalignment of the grid.
  • the control unit If the pixel value in the detection area is less than the threshold value, the detection area is reset.
  • the detection area can be set while avoiding the part where the pixel value changes because the subject is reflected. Thereby, it is possible to prevent the change of the pixel value due to the reflection of the subject, so it is possible to accurately obtain the change amount of the pixel value due to the positional deviation of the grid.
  • the image processing unit is based on the first X-ray image and the second X-ray image. , Generating at least one of a dark field image and an absorption image, and the control unit is configured to reset the detection area when the pixel value of the dark field image or the pixel value of the absorption image is less than a threshold value. It is done.
  • the control unit controls the subject in the detection area when the detection area includes the subject. It is comprised so that position shift may be acquired using the part which is not included. According to this structure, it is possible to obtain the pixel value using only the pixel value of the portion which has no influence on the pixel value due to the reflection of the subject in the detection area set in advance. As a result, resetting of the detection area is facilitated.
  • FIG. 1 shows the overall structure of an X-ray phase contrast imaging system according to an embodiment of the present invention.
  • FIG. 7 shows an example of a position adjustment mechanism according to an embodiment of the present invention. It is a figure which shows an example of the detection area provided in the grating
  • FIG. 5 is a schematic view showing a differential phase image generated by the shift of a grating according to an embodiment of the present invention.
  • (A) shows a phase differential image in a state in which no positional deviation has occurred or in a state in which positional deviation in the X-axis direction has occurred.
  • (B) shows the phase differential image of the state which position shift has produced in the Z-axis direction.
  • (C) shows the phase differential image of the state which the shift has produced in Rz axial direction. It is a flowchart which shows acquisition and adjustment operation of positional offset of the X-ray phase difference imaging system by one Embodiment of this invention. It is a flowchart which shows setting operation
  • the X-ray phase difference imaging system 100 is an apparatus for imaging the inside of the subject T using the phase difference of the X-rays passing through the subject T. Further, the X-ray phase difference imaging system 100 is an apparatus for imaging the inside of the subject T by using a Talbot effect.
  • the X-ray phase-contrast imaging system 100 can be used, for example, for imaging the inside of a subject T as an object in a nondestructive inspection application. In addition, for example, in medical applications, the X-ray phase difference imaging system 100 can be used for imaging the inside of a subject T as a living body.
  • the X-ray phase difference imaging system 100 includes an X-ray source 1, a first grating 2, a second grating 3, an X-ray detector 4, an image processing unit 5, and a control unit 6. , A position adjusting mechanism 7 and a lattice moving mechanism 8.
  • the direction from the X-ray source 1 toward the first grating 2 is the Z2 direction
  • the opposite direction is the Z1 direction
  • the Z1 direction and the Z2 direction are collectively the Z axis direction.
  • the direction orthogonal to the Z axis and going from the back side to the front side in the drawing is the Y1 direction, the opposite direction is the Y2 direction, and the Y1 direction and the Y2 direction are collectively the Y axis direction.
  • the upper direction in the drawing is the X1 direction
  • the lower direction in the drawing is the X2 direction
  • the X1 direction and the X2 direction are collectively referred to as the X axis direction.
  • slits are formed in the Y-axis direction.
  • the X-axis direction is an example of the “direction orthogonal to the direction of the slits of the grating” in the claims.
  • the Z-axis direction is an example of the “optical axis direction connecting the X-ray source and the X-ray detector” in the claims.
  • the X-ray source 1 is configured to generate X-rays by applying a high voltage and to irradiate the generated X-rays in the Z1 direction.
  • the first grating 2 has a plurality of slits 2a arranged in a predetermined cycle (pitch) d1 in the X-axis direction, and an X-ray phase change portion 2b.
  • Each of the slits 2a and the X-ray phase change portion 2b is formed to extend linearly. Further, each slit 2a and the X-ray phase change portion 2b are formed to extend in parallel with each other.
  • the first grating 2 is a so-called phase grating.
  • the first grating 2 is disposed between the X-ray source 1 and the second grating 3 and is irradiated with X-rays from the X-ray source 1.
  • the first grating 2 forms a self-image (not shown) of the first grating 2 by the Talbot effect.
  • an image (self-image) of the grid is formed at a predetermined distance (talbot distance) from the grid. This is called Talbot effect.
  • the second grating 3 has a plurality of X-ray transmitting portions 3a and X-ray absorbing portions 3b arranged in the X axis direction at a predetermined period (pitch) d2.
  • Each of the X-ray transmitting parts 3a and the X-ray absorbing parts 3b is formed to extend in a straight line. Further, each of the X-ray transmitting parts 3a and the X-ray absorbing parts 3b is formed to extend in parallel.
  • the second grating 3 is a so-called absorption grating.
  • the first grating 2 and the second grating 3 are gratings having different roles, but the slit 2a and the X-ray transmitting portion 3a transmit X-rays. Further, the X-ray absorbing portion 3b plays a role of shielding the X-ray, and the X-ray phase change portion 2b changes the phase of the X-ray due to the difference in refractive index with the slit 2a.
  • the second grating 3 is disposed between the first grating 2 and the X-ray detector 4, and the X-rays having passed through the first grating 2 are irradiated.
  • the second grating 3 is disposed at a position separated from the first grating 2 by a Talbot distance.
  • the second grating 3 interferes with the self-image of the first grating 2 to form moire fringes (not shown) on the detection surface of the X-ray detector 4.
  • the X-ray phase-contrast imaging system 100 includes the first grating 2 and the second grating 3 as a plurality of gratings, and the first grating 2 in the Z1 direction from the X-ray source 1 to the X-ray detector 4 , And the second grid 3 are arranged in this order.
  • the X-ray detector 4 is configured to detect the irradiated X-rays, convert the detected X-rays into an electrical signal, and read the converted electrical signal as an image signal.
  • the X-ray detector 4 is, for example, an FPD (Flat Panel Detector).
  • the X-ray detector 4 is composed of a plurality of conversion elements (not shown) and pixel electrodes (not shown) disposed on the plurality of conversion elements. The plurality of conversion elements and the pixel electrodes are arrayed in the X direction and the Y direction in a predetermined cycle (pixel pitch).
  • the X-ray detector 4 is configured to output the acquired image signal to the image processing unit 5.
  • the image processing unit 5 Based on the image signal output from the X-ray detector 4, the image processing unit 5 arranges the first X-ray image photographed without arranging the subject T and the second X photographed by arranging the subject T. Acquire a line image. The image processing unit 5 also generates a contrast image based on the first X-ray image and the second X-ray image.
  • the generated contrast image is, for example, a phase differential image, an absorption image, or a dark field image.
  • the phase differential image is obtained by calculating and imaging changes in X-ray phase of air data and sample data.
  • the absorption image is a diagram in which the phase difference is represented by the gray level of the image by utilizing the fact that the X-ray is absorbed when there is a subject T and the phase difference between the part without the subject T and the X-ray occurs.
  • the dark-field image is a diagram representing the structure of the subject T by imaging the distribution of the X-rays scattered on the surface of the subject T using the fact that X-rays are strongly scattered at dense locations.
  • control unit 6 Based on the pixel values in the phase differential image generated by the image processing unit 5, the control unit 6 causes positional deviation in the optical axis direction (Z-axis direction), positional deviation in the X axis direction, or rotation about the optical axis (Rz At least one of the positional displacements due to the rotation of.
  • the control unit 6 is configured to obtain pixel values from within the detection area 9 (see FIG. 3) and obtain positional deviation of the grid.
  • FIG. 3 is a view of the first grating 2 as viewed in the Z2 direction from the X-ray source 1 to the second grating 3. In addition, the slit is omitted.
  • the detection area 9 is an area which is provided in the imaging area 10 and collects pixel values used to acquire positional deviation.
  • the control unit 6 is configured to obtain an average value or a median value of pixel values at a plurality of places in each detection area 9 of the plurality of detection areas 9 set in the phase differential image, and to obtain positional deviation of the grid. It is done.
  • the control unit 6 is configured to calculate an average value of pixel values based on pixel values acquired from a plurality of locations in the detection area 9. Alternatively, the control unit 6 is configured to select a median based on pixel values acquired from a plurality of locations.
  • the control unit 6 is configured to use a first X-ray image generated in advance, when generating the phase differential image and acquiring the positional deviation of the grating a plurality of times.
  • the control unit 6 is configured to perform control of adjusting the position of the grating by the position adjusting mechanism 7 based on the obtained positional deviation of the grating every time one phase differential image is generated or a plurality of phase differential images are generated. There is.
  • the user sets the frequency of position adjustment in the control unit 6 based on the frequency of occurrence of grid misalignment or the like.
  • the control unit 6 is configured as one of the following.
  • the detection area 9 is set to a part not including the subject T in the phase differential image, the detection area 9 is reset, or the positional deviation is acquired using the part in the detection area 9 not including the subject T.
  • the control unit 6 is configured to reset the detection area 9 when the pixel value of the dark field image or the pixel value of the absorption image generated by the image processing unit 5 is less than the threshold value.
  • the position adjustment mechanism 7 includes a base 70, a stage support 71, a stage 72 on which a grid is placed, a first drive 73, a second drive 74, and a third drive. 75, a fourth drive unit 76, and a fifth drive unit 77.
  • the first drive unit 73 to the fifth drive unit 77 each include, for example, a motor and the like.
  • the stage 72 is configured by a connecting portion 72a, a rotating portion 72b around the Z-axis direction, and a rotating portion 72c around the X-axis direction.
  • the first drive unit 73, the second drive unit 74, and the third drive unit 75 are respectively provided on the upper surface of the base unit 70.
  • the first drive unit 73 is configured to reciprocate the stage support unit 71 in the Z-axis direction.
  • the second drive unit 74 is configured to rotate the stage support unit 71 around the Y-axis direction.
  • the third drive unit 75 is configured to reciprocate the stage support unit 71 in the X-axis direction.
  • the stage support portion 71 is connected to the connecting portion 72 a of the stage 72, and the stage 72 also moves with the movement of the stage support portion 71.
  • the fourth drive unit 76 is configured to reciprocate the rotation unit 72b around the Z-axis direction in the X direction.
  • the bottom surface of the pivoting portion 72b in the Z-axis direction is formed in a convex curved shape toward the connecting portion 72a, and is reciprocated in the X-axis direction to pivot the stage 72 around the central axis in the Z direction.
  • the fifth drive unit 77 is configured to reciprocate the rotation unit 72c around the X-axis direction in the Z-axis direction.
  • the bottom surface of the rotation portion 72c around the X axis direction is formed in a convex curved shape toward the rotation portion 72b around the Z axis direction axis, and the stage 72 is moved in the X axis direction by reciprocating in the Z axis direction. It is configured to pivot around.
  • the position adjustment mechanism 7 is configured to be able to adjust the first grating 2 or the second grating 3 in the Z direction by the first drive unit 73. Further, the position adjustment mechanism 7 is configured to be able to adjust the grating in the rotational direction (Ry direction) around the Y-axis direction by the second drive unit 74. Further, the position adjustment mechanism 7 is configured to be able to adjust the grid in the X direction by the third drive unit 75. Further, the position adjustment mechanism 7 is configured to be able to adjust the grating in the rotation direction (Rz direction) around the Z-axis direction by the fourth drive unit 76.
  • the position adjustment mechanism 7 is configured to be able to adjust the grating in the rotation direction (Rx direction) around the X-axis direction by the fifth drive unit 77. Reciprocation in each axial direction is, for example, several mm, respectively. Further, the pivotable angles of the rotation direction Rx around the X axis direction, the rotation direction Ry around the Y axis direction, and the rotation direction Rz around the Z axis direction are, for example, several degrees, respectively.
  • the alignment mechanism 7 is connected to at least one of the first grating 2 and the second grating 3.
  • the grating moving mechanism 8 is configured to move the first grating 2 in the lattice plane (in the XY plane) at a constant interval in a direction (X-axis direction) orthogonal to the lattice direction based on a signal from the control unit 6 It is done. Specifically, the grating moving mechanism 8 divides the period d2 of the second grating 3 into n and moves the second grating 3 stepwise by d2 / n.
  • n is a positive integer.
  • the lattice moving mechanism 8 includes, for example, a stepping motor, a piezo actuator, and the like.
  • the detection area 9 will be described based on FIG. FIG. 3 is a view of the first grating 2 viewed in the Z2 direction from the X-ray source 1 to the second grating 3. In addition, the slit is omitted.
  • the detection area 9 is provided in the imaging area 10.
  • the imaging area 10 refers to an area where a contrast image can be acquired.
  • the detection area 9 is an area which is provided in the imaging area 10 and collects pixel values used to acquire positional deviation.
  • the lattice period and the arrangement pattern of the imaging area 10 are not changed. That is, since the detection area 9 does not have to be provided by changing the period of the grid and the arrangement pattern, it is easy for the user to create the grid.
  • the detection area 9 may be set near the outer peripheral edge of the imaging area 10 of the phase differential image.
  • the detection area 9 is provided at two locations in the upper and lower (Y-axis direction) or two locations on the left and right (X-axis direction) with respect to the center point C of the detection area 9. Alternatively, it is provided at a total of four places vertically (Y-axis direction) and left-right (X-axis direction) across the center point C of the detection area 9.
  • the detection area 9 for acquiring positional deviation of the grid in the optical axis direction (Z-axis direction) connecting the X-ray source 1 and the X-ray detector 4 is a slit of the grid across the center point C of the detection area 9 Are set at two places on a line (line in the X-axis direction) orthogonal to the direction of. If there is no misalignment between the first grating 2 and the second grating 3 or if there is misalignment in the X-axis direction between acquisition of air data and acquisition of sample data, as shown in FIG. As shown in (A), a phase differential image of a uniform image without contrast of light and shade (bright and dark) is obtained.
  • phase differential image has a contrast of gradation in the direction (X-axis direction) orthogonal to the direction of the slits of the grating.
  • phase differential image to be obtained is from the acquisition of air data to the acquisition of sample data.
  • a detection area 9 for acquiring at least one positional deviation of the lattice in a direction (X-axis direction) orthogonal to the orientation of the slits of the lattice, or the positional deviation of the lattice due to rotation about the optical axis (Rz) are set at two points on a line (line in the Y-axis direction) parallel to the direction of the slits of the grating with the center point C of the detection area 9 interposed therebetween.
  • two detection areas 9 are set on a line (line in the Y-axis direction) parallel to the direction of the slits of the grating, with the center point C of the detection area 9 interposed therebetween.
  • X-rays are obliquely incident on the slit when moving away from the center point C of the imaging region 10 in the X-axis direction, so the aspect ratio of the depth to the width of the slit of the grid portion causess attenuation of x-rays.
  • FIG. 4C is a schematic view for explaining the obtained phase differential image, and the obtained phase differential image has different shades of gray (brightness and darkness) depending on the change from the acquisition of air data to the acquisition of sample data. The occurrence of) is different.
  • the detection area 9 is set to a portion where the subject T in the phase differential image is not reflected because the pixel value decreases when the subject T is captured.
  • the detection area 9 is set in the vicinity of the outer peripheral edge of the imaging area 10 of the phase differential image.
  • the positional deviation due to rotation increases with distance from the center of the imaging region 10. Therefore, in the case of performing precise position adjustment, it is preferable that the detection area 9 be away from the center of the imaging area 10.
  • the phase differential image is generated based on the step curve of the X-ray when the grating moving mechanism 8 translates the first grating 2 in the X-axis direction.
  • the phase differential image is obtained by arranging the subject T with respect to the step curve of the X-ray in the case where the subject T is not arranged by using refraction of the X-ray passing through the subject T. It is generated by imaging the magnitude of the phase shift of the step curve.
  • the pixel values of the differential phase image represent the phase shift. Since the X-rays are refracted when passing through the subject T, the X-rays are not refracted in the area where the subject T is not present in the same image. Therefore, no phase shift occurs in the portion where the subject T is not present.
  • phase shift occurs in a portion where the subject T is not present, it is considered that a positional shift occurs in either the first grating 2 or the second grating 3. Therefore, by acquiring the pixel values of the portion of the phase differential image without the subject T, the phase shift is obtained, and the positional shift of the grid is obtained from the phase shift.
  • step S1 X-rays are emitted from the X-ray source 1 without arranging the subject T.
  • the X-rays pass through the first grating 2 and the second grating 3 and reach the X-ray detector 4.
  • the X-ray detector 4 detects the irradiated X-ray.
  • step S2 the X-ray detector 4 acquires a first X-ray image from the detected X-rays.
  • the first X-ray image may be acquired once when the use of the X-ray phase contrast imaging system 100 is started.
  • step S3 the subject T is placed, and the X-ray source 1 emits X-rays.
  • the X-rays are irradiated to the subject T, and when the X-rays impinge on the subject T, refraction of the X-rays occurs, and as a result, a phase shift occurs and interference fringes occur in the second grating 3.
  • step S4 the X-ray detector 4 acquires a second X-ray image from the detected X-rays.
  • the image processing unit 5 generates a phase differential image based on the first X-ray image acquired in step S2 and the second X-ray image acquired in step S4.
  • step S6 the control unit 6 acquires pixel values in the detection area 9 from the phase differential image including the detection area 9 and the imaging area 10 generated in step S5.
  • step S7 positional deviation is acquired from the acquired pixel value.
  • Positional displacement [Delta] X 1 in the X-axis direction, positional displacement [Delta] Z 1 and positional deviation DerutaRz 1 by the optical axis (Rz) around the rotation of the optical axis direction (Z-axis) is determined by the formula shown below.
  • p 1 p 2 represents the period of the lattice, and the unit is m.
  • ⁇ u , ⁇ d , ⁇ w , ⁇ r represent the average of the pixel values in each detection area 9, and the unit is radian.
  • R 1 represents the distance between the gratings
  • D represents the distance from the center of the imaging area 10 to the detection area 9, and the unit is m.
  • step S8 based on the acquired positional deviation, the control unit 6 controls the position adjustment mechanism 7 to adjust the position of the grid.
  • the above is the operation of acquiring the positional deviation and adjusting the position of the grid.
  • step S1 the X-ray phase difference imaging system 100 emits X-rays from the X-ray source 1 in a state where there is no subject T.
  • the X-rays pass through the first grating 2 and the second grating 3 and reach the X-ray detector 4.
  • the X-ray detector 4 detects the irradiated X-ray.
  • step S2 the X-ray detector 4 acquires a first X-ray image from the detected X-rays.
  • step S3 the control unit 6 acquires a pixel value from the first X-ray image and sets a threshold value.
  • step S4 the X-ray source 1 emits X-rays in a state where the subject T is disposed.
  • the X-rays are emitted to the subject T, and a self-image is formed on the second grating 3.
  • the X-ray detector 4 detects the generated self-image.
  • step S5 the X-ray detector 4 acquires a second X-ray image from the detected X-rays.
  • the image processing unit 5 generates a contrast image based on the first X-ray image acquired in step S2 and the second X-ray image acquired in step S5.
  • step S7 a detection area 9 is set in an absorption image or a dark field image which is one of the generated contrast images.
  • the control unit 6 acquires a pixel value from the detection area 9 of the absorption image or the dark field image.
  • step S9 the control unit 6 compares the acquired pixel value with the threshold value.
  • step S10 the control unit 6 acquires the pixel value from the phase differential image, and starts acquiring the positional deviation. If the pixel value is less than the threshold value, the process proceeds to step S11, where the control unit 6 sets the place for acquiring the pixel value to another place in the same detection area 9. Alternatively, the control unit 6 sets the detection area 9 at another place. Then, the process returns to step S8, and the control unit 6 acquires a pixel value from the reset detection area 9. Moving to step S9, the control unit 6 compares the acquired pixel value with the threshold value. Finally, after the detection area 9 is set in the area not including the subject T, the control unit 6 starts acquisition of positional deviation.
  • the control unit 6 controls the light connecting the X-ray source 1 and the X-ray detector 4 based on the pixel value of the phase differential image generated by the image processing unit 5. Configured to obtain at least one misalignment of the grating in the axial direction, the misalignment of the grating in the direction orthogonal to the orientation of the slits of the grating, or the misalignment of the grating due to rotation about the optical axis ing. By doing this, even when positional deviation of the grid occurs, the control unit 6 can acquire (update) the positional deviation based on the pixel value of the acquired phase differential image.
  • the positional deviation of the grating (change in imaging conditions) can be easily acquired simply by generating a phase differential image by normal imaging.
  • the same imaging condition can be easily maintained without updating the air data.
  • the control unit 6 In the X-ray phase difference imaging system 100 of the present embodiment, preferably, the control unit 6 generates a first phase differential image and acquires a positional deviation of the grating a plurality of times, the first generated in advance. It is configured to use an x-ray image. By doing so, a phase differential image is generated based on the first X-ray image generated in advance and the second X-ray image generated anew. Thus, the phase differential image can be generated only by newly capturing the second X-ray image, and the user does not have to acquire the first X-ray image again.
  • the X-ray phase difference imaging system 100 of the present embodiment further includes a position adjustment mechanism 7 for adjusting the position of the grating, and the control unit 6 determines the position of the grating based on the acquired positional deviation of the grating.
  • the position adjustment mechanism 7 is configured to perform adjustment control. By doing this, since the position adjustment mechanism 7 adjusts the position of the grid, the user does not have to perform the work of adjusting the position of the obtained grid. As a result, since the same imaging conditions can be more easily maintained, the burden on the user can be reduced.
  • control unit 6 controls the position adjusting mechanism 7 to adjust the position of the grating based on the obtained position shift of the grating every time one phase differential image is generated or a plurality of phase differential images are generated. It is configured. By doing this, the same imaging condition can be maintained as accurately as possible by adjusting the position of the grid by the position adjusting mechanism 7 each time the position shift of the grid is acquired. Further, by adjusting the position of the grating by the position adjustment mechanism 7 each time a plurality of phase differential images are generated, the frequency at which the position adjustment mechanism 7 adjusts the position can be reduced compared to each time one sheet is generated. it can. As a result, it is possible to reduce the time required to adjust the position of the grid while maintaining the imaging conditions in a range that causes no practical problems.
  • the control unit 6 determines the average value or median value of pixel values at a plurality of locations in each detection region 9 of the plurality of detection regions 9 set in the phase differential image. It is configured to obtain and obtain grid misalignment. With this configuration, the distribution of pixel values in the detection area 9 can be obtained. Further, by taking an average value or a median value from a plurality of acquired pixel values, it is possible to eliminate an extreme numerical value (outlier) caused by noise or the like, so that accurate positional deviation can be obtained.
  • the detection area 9 for acquiring at least one positional deviation of the lattice in the direction orthogonal to the direction of the slits of the lattice or the positional deviation of the lattice due to rotation about the optical axis Two points are set on a line parallel to the direction of the slits of the lattice with the center point C in between.
  • positional deviation due to rotation around the optical axis and positional deviation of the grating in a direction perpendicular to the direction of the slits of the grating are defined by a straight line orthogonal to the direction of the slit passing through the center point C of the detection area 9 as a boundary.
  • a positional difference tends to appear. Therefore, with the above configuration, it is possible to easily acquire positional deviation of the grating in a direction orthogonal to the direction of the slits of the lattice or positional deviation of the grating due to rotation around the optical axis.
  • the X-ray source The detection area 9 for acquiring positional deviation of the grid in the optical axis direction connecting the 1 and the X-ray detector 4 is 2 on the line orthogonal to the direction of the slit of the lattice across the center point C of the detection area 9. Location is set.
  • misalignment of the grating in the optical axis direction is likely to occur in a direction perpendicular to the direction of the slits of the grating, and is less likely to occur in a direction parallel to the direction of the slits of the grating. Therefore, with the above configuration, positional deviation of the grating in the direction of the optical axis connecting the X-ray source 1 and the X-ray detector 4 can be easily obtained from the phase differential image.
  • the detection area 9 can be set to the outer peripheral portion where the positional deviation due to rotation is large, so it becomes easy to acquire the positional deviation. Therefore, the detection accuracy of positional deviation can be improved.
  • the control unit 6 is configured to set the detection area 9 to a portion not including the subject T in the second phase differential image. By doing this, it is possible to set in the detection area 9 a place that is not affected by the change in pixel value due to the reflection of the subject T. As a result, the amount of change in pixel value due to positional deviation can be accurately acquired.
  • the positional deviation of the grid is acquired.
  • the image processing section 5 in the configuration in which the control area 6 resets the detection area 9 when the pixel value in the detection area 9 is less than the threshold, preferably, the image processing section 5 generates at least one of a dark field image or an absorption image based on the first X-ray image and the second X-ray image, and the control unit 6 generates a pixel value or an absorption image of the dark field image Is configured to reset the detection area 9 if the pixel value of the pixel is less than the threshold value.
  • the control unit 6 causes the subject T to be included in the detection area 9.
  • the positional deviation is acquired using a portion in the detection area 9 which does not include the subject T.
  • the third grating may be provided between the X-ray source 1 and the first grating 2.
  • the third grating is disposed between the X-ray source 1 and the first grating 2 and is irradiated with X-rays from the X-ray source 1.
  • the third grating is configured to set the X-rays that have passed through the slits as line light sources corresponding to the positions of the slits.
  • the coherence of the X-ray irradiated from the X-ray source can be enhanced by the third grating.
  • control unit 6 In the case where the detection area 9 includes the subject T, the control unit 6 describes the case of changing the detection area 9. However, the control unit 6 may reduce the detection area 9. Alternatively, the control unit 6 may issue a warning and the user may reset the detection area 9.
  • the threshold value is set based on the pixel value of the first X-ray image, but the second X-ray image or a portion where the subject T of the contrast image generated from the second X-ray image is not shown It may be obtained from When acquiring from a contrast image, the threshold may be set in consideration of variations in pixel values of the background of the contrast image.
  • the pixel value to be compared with the threshold value may be a second X-ray image or a phase contrast image generated from the second X-ray image.
  • Reference Signs List 1 X-ray source 2 first grating 3 second grating 4 X-ray detector 5 image processing unit 6 control unit 7 position adjustment mechanism 8 grating moving mechanism 9 detection region 100 X-ray phase difference imaging system

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Abstract

L'invention concerne un système de capture d'image à différence de phase à rayons X (100) comprenant une source de rayons X (1), un détecteur de rayons X (4), une pluralité de réseaux et une unité de commande (6). L'unité de commande (6) acquiert au moins l'un des déplacements de position, c'est-à-dire, un déplacement de position de réseau dans la direction d'un axe optique reliant la source de rayons X (1) et le détecteur de rayons X (4), un déplacement de position de réseau dans la direction orthogonale à la direction de fente de réseau, et un déplacement de position de réseau dû à une rotation autour de l'axe optique.
PCT/JP2018/036091 2017-12-22 2018-09-27 Système de capture d'image à différence de phase à rayons x WO2019123758A1 (fr)

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JP2012148068A (ja) * 2010-12-27 2012-08-09 Fujifilm Corp 放射線画像取得方法および放射線画像撮影装置
JP2015529510A (ja) * 2012-08-20 2015-10-08 コーニンクレッカ フィリップス エヌ ヴェ 微分位相コントラスト撮像における複数オーダの位相調整のためのソース格子対位相格子距離の位置合わせ
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JP2011218139A (ja) * 2010-03-26 2011-11-04 Fujifilm Corp 放射線撮影システム及び位置ずれ判定方法
JP2012148068A (ja) * 2010-12-27 2012-08-09 Fujifilm Corp 放射線画像取得方法および放射線画像撮影装置
JP2012143497A (ja) * 2011-01-14 2012-08-02 Fujifilm Corp 放射線撮影システム及びその制御方法
JP2015529510A (ja) * 2012-08-20 2015-10-08 コーニンクレッカ フィリップス エヌ ヴェ 微分位相コントラスト撮像における複数オーダの位相調整のためのソース格子対位相格子距離の位置合わせ
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