WO2013027519A1

WO2013027519A1 - Radiography device and unwrapping method

Info

Publication number: WO2013027519A1
Application number: PCT/JP2012/068572
Authority: WO
Inventors: 拓司多田
Original assignee: 富士フイルム株式会社
Priority date: 2011-08-22
Filing date: 2012-07-23
Publication date: 2013-02-28
Also published as: JP2014217397A

Abstract

The objective of the present invention is to decrease unwrapping errors. An X-ray imaging detector (13) detects X-rays which are emitted from an X-ray source (11) and which pass through a first grating (21) and a second grating (22), and generates image data. A phase differential image generating section (40) generates a phase differential image on the basis of the image data. A suitable/unsuitable region detector (42) detects unsuitable regions in which unwrapping errors tend to occur in the phase differential image, and sets the other regions as suitable regions. An unwrapping section (43) sets starting points (P0-P6) along a penetration line which only passes through the suitable regions and penetrates the phase differential image in one direction, and performs unwrapping along linear paths (R0-R6) orthogonal to the alignment direction of the starting points (P0-P6). The unwrapping section (43) also performs unwrapping between the starting points (P0-P6) and along wraparound paths (WR0, WR1) which pass through pixels in the suitable regions that remain behind the unsuitable regions when seen from the starting points (P0-P6).

Description

Radiation imaging apparatus and unwrap processing method

The present invention relates to a radiation imaging apparatus that detects a phase differential image based on a phase change of radiation by a subject, and a phase differential image unwrap processing method.

Radiation, such as X-rays, has a characteristic of decaying depending on the weight (atomic number) of the elements constituting the substance and the density and thickness of the substance. Focusing on this characteristic, X-rays are used as a probe for seeing through the inside of a subject in fields such as medical diagnosis and nondestructive inspection.

A general X-ray imaging apparatus includes an X-ray source that emits X-rays and an X-ray image detector that detects X-rays. Take a picture of the line. In this case, X-rays emitted from the X-ray source are absorbed and attenuated when passing through the subject, and then enter the X-ray image detector. As a result, an image based on an X-ray intensity change by the subject is detected by the X-ray image detector.

Since the X-ray absorption ability is lower with an element having a smaller atomic number, there is a problem that a change in X-ray intensity is small and a sufficient contrast cannot be obtained in an image in a soft body tissue or soft material. For example, most of the components of the cartilage part constituting the joint of the human body and the joint fluid in the vicinity thereof are water, and the difference in X-ray absorption capacity between the two is small, so that it is difficult to obtain contrast.

Against the background of such problems, research on X-ray phase imaging for obtaining an image based on the phase change of the X-ray by the subject instead of the change in the intensity of the X-ray by the subject has been actively conducted in recent years. X-ray phase imaging is a method of imaging the phase change of X-rays, focusing on the fact that the phase change of X-rays incident on the subject is larger than the intensity change. Can also obtain a high-contrast image.

In order to enable such X-ray phase imaging, an X-ray imaging apparatus is proposed in which first and second gratings are arranged in parallel at a predetermined interval between an X-ray source and an X-ray image detector. (For example, refer to Patent Document 1).

In this X-ray imaging apparatus, the first periodic pattern image is generated when the X-ray source passes through the first grating, and the second grating partially shields the first periodic pattern image. Two periodic pattern images are generated. The X-ray image detector detects the second periodic pattern image and generates image data. The subject is disposed, for example, between the X-ray source and the first grating, and the subject undergoes a phase change in the X-ray, thereby modulating the first periodic pattern image. By detecting this modulation amount through the second periodic pattern image, the X-ray phase change can be imaged.

This method is called the fringe scanning method. In this fringe scanning method, the second grating is intermittently moved in the direction parallel to the plane of the first grating and perpendicular to the grating line direction of the first grating with respect to the first grating. Image data is generated by shooting during the stop. Based on the obtained plurality of image data, an intensity modulation signal representing an intensity change of the pixel value accompanying the movement of the second lattice is generated for each pixel. For each pixel, the phase shift amount of the intensity modulation signal (the phase shift amount from the case where the subject does not exist) is calculated, and the phase shift amount is imaged to obtain an image representing the modulation amount. Since this image represents the differential amount of the phase change (phase shift) of the X-rays by the subject, it is called a phase differential image.

As described in Patent Document 1, the phase shift amount of the intensity modulation signal is calculated by using a function (arg [...]) for extracting a complex argument or an arctangent function (tan ^-1 [...]). Since the phase differential image is calculated, the phase differential image is expressed by a value convolved (wrapped) in the range of the function used for the calculation (from −π to + π or from −π / 2 to + π / 2). . In the phase differential image wrapped in this way, jumps (discontinuous points) corresponding to the above-described range occur at locations where the upper limit of the range changes from the lower limit or locations where the lower limit changes to the upper limit. For this reason, the wrapped phase differential image is subjected to an unwrap process for eliminating the discontinuity and making it continuous (for example, see Patent Document 2).

Generally, unwrap processing is performed in order along a predetermined route from a predetermined position in the image as a starting point (for example, refer to Patent Document 3). Specifically, when a discontinuous point is detected in the path, the discontinuous point is determined by uniformly adding or subtracting a value corresponding to the range of the function to data on the path after the discontinuous point. It becomes continuous without.

WO2004 / 058070 JP 2011-045655 A JP 2008-082869 A

However, when the subject includes a high-absorber having a high X-ray absorption ability such as a bone part, the attenuation of X-rays is large in the high-absorber, and the intensity and amplitude of the intensity modulation signal are reduced. There is a problem that the calculation accuracy of the phase shift amount is lowered, and an unwrapping error is likely to occur in the region of the phase differential image corresponding to the high absorber. In this unwrapping error, there are discontinuities at places that are not originally discontinuous points. Due to the decrease, there is a case where the unwrapping process is not performed without being determined as a discontinuous point.

For example, as shown in FIG. 17, in the wrapped phase differential image, when setting the starting point in the region of the bone part that is a high-absorber, and performing the unwrapping process along the path that goes downward from the starting point, Unwrap errors are likely to occur in the bone region. When an unwrap error occurs, an error value (a value corresponding to the range of the above function) is sequentially added to or subtracted from the path after that point. As a result, the phase differential image after the unwrap process has a difference in the path direction of the unwrap process. A streak of noise along the line occurs. This streak noise overlaps with a soft tissue (cartilage portion) that is a target portion of X-ray phase imaging, and obstructs imaging of the soft tissue.

An object of the present invention is to provide a radiation imaging apparatus and an unwrap processing method that can reduce unwrap errors.

To achieve the above object, the radiation imaging apparatus of the present invention includes a radiation detector, a grating unit, a phase differential image generation unit, an OK / NG region detection unit, and an unwrap processing unit. The radiation detector detects the radiation emitted from the radiation source and transmitted through the subject to generate image data. The grating portion is disposed between the radiation source and the radiation detector. The phase differential image generation unit generates a phase differential image represented by a value wrapped in a predetermined range based on the image data. The OK / NG area detection unit detects an NG area in which an unwrap error is likely to occur from the phase differential image, and sets an area other than the NG area as an OK area. The unwrap processing unit sets a starting point in the OK area, and unwraps only the OK area.

In addition, it further includes an offset image storage unit that stores the phase differential image generated by the phase differential image generation unit without placing the subject as an offset image, the unwrap processing unit, for the phase differential image and the offset image, It is preferable to perform an unwrap process. In this case, it is preferable to further include an offset processing unit that subtracts the offset image after the unwrap processing from the phase differential image after the unwrap processing.

The unwrap processing unit sets starting points in order along the through lines that pass only through the OK region and pass through the phase differential image in one direction, and performs unwrap processing between the starting points and a straight path perpendicular to the through lines from each starting point. It is preferable to perform an unwrapping process along the line.

Further, it is preferable that the unwrap processing unit further performs unwrap processing on the pixels in the OK region remaining behind the NG region when viewed from each starting point. In this case, it is preferable to further include a starting point direction determination unit that determines the setting direction of each starting point so that the number of unwrapping processes for the pixels remaining behind the NG region is reduced.

Further, it is preferable that the unwrap processing unit sets each starting point along one side of the phase differential image.

In addition, when the phase differential image is divided into a plurality of OK regions by the NG region, the unwrap processing unit preferably sets a starting point in each OK region and performs unwrap processing for each OK region.

The grating unit generates a second periodic pattern image by partially shielding the first periodic pattern image and a first grating that generates a first periodic pattern image by passing radiation from a radiation source. It is preferable to have the second lattice. The radiation image detector detects the second periodic pattern image and generates image data.

In this case, it is preferable that the grating unit further includes a scanning mechanism that moves the first grating or the second grating at a predetermined scanning pitch and sequentially sets the plurality of scanning positions. The radiation image detector detects the second periodic pattern image at each scanning position and generates image data. The phase differential image generation unit generates a phase differential image based on a plurality of image data generated by the radiation image detector at a plurality of scanning positions.

It is preferable that the scanning mechanism moves the first grating or the second grating in a direction perpendicular to the grating line. The scanning mechanism may move the first grating or the second grating in a direction inclined with respect to the grating line.

Further, the phase differential image generation unit may generate a phase differential image based on single image data obtained by the radiation detector.

Further, it is preferable that the OK / NG region detection unit detects the NG region based on one or a combination of the average intensity, amplitude, and visibility of the intensity modulation signal representing the intensity change of the pixel value.

Further, the image processing apparatus may further include an NG region image replacement unit that replaces the NG region of the phase differential image using any one of an absorption image, a differential image of the absorption image, and a small-angle scattering image created based on the intensity modulation signal. preferable.

Further, the first grating is an absorption grating, and it is preferable that the first periodic pattern image is generated by geometrically optically projecting incident radiation. The first grating may be an absorption grating or a phase grating, and may generate a first periodic pattern image by causing a Talbot effect to incident radiation.

It is also preferable to provide a multi-slit that partially blocks the radiation emitted from the radiation source and disperses the focal point.

Further, the unwrap processing method of the present invention detects an NG region in which an unwrap error is likely to occur from a phase differential image represented by a value wrapped in a predetermined range, and sets a region other than this NG region as an OK region. And a step of setting a starting point in the OK area and unwrapping only the OK area.

According to the present invention, an NG region in which an unwrapping error is likely to occur is detected from a phase differential image represented by a value wrapped in a predetermined range, the other region is set as an OK region, and the origin is set in the OK region. Since it is set and only the OK area is unwrapped, unwrapping errors are reduced.

It is a block diagram which shows the structure of an X-ray imaging apparatus. It is a schematic diagram which shows the structure of a X-ray image detector. It is explanatory drawing explaining the structure of the 1st and 2nd grating | lattice. It is a graph which shows an intensity | strength modulation signal. It is a block diagram which shows the structure of an image process part. It is a flowchart explaining the procedure of the unwrap processing method. It is a figure explaining the starting method of an unwrap process, and the setting method of a path | route. It is a figure which shows the phase differential image in which several OK area | region exists. It is a figure explaining an unwrap process. It is a flowchart explaining the effect | action of the X-ray imaging apparatus at the time of pre imaging | photography. It is a flowchart explaining the effect | action of the X-ray imaging apparatus at the time of this imaging | photography. It is a figure explaining another setting method of the starting point of an unwrap process, and a course. It is a block diagram which shows the structure of the image process part provided with the origin direction determination part. It is a figure explaining another setting method of the starting point of an unwrap process, and a course. It is a figure explaining the example which performs an unwrap process in order for every pixel from one starting point. It is a block diagram which shows the structure of the image process part provided with the NG area | region image replacement part. It is explanatory drawing explaining the conventional unwrap process.

In FIG. 1, an X-ray imaging apparatus 10 includes an X-ray source 11, a grating unit 12, an X-ray image detector 13, a memory 14, an image processing unit 15, an image recording unit 16, an imaging control unit 17, a console 18, and a system. A control unit 19 is provided. As is well known, the X-ray source 11 includes a rotary anode type X-ray tube (not shown) and a collimator (not shown) for limiting the X-ray irradiation field, and is controlled by the imaging control unit 17. Based on the above, X-rays are emitted toward the subject H.

The grating unit 12 includes a first grating 21, a second grating 22, and a scanning mechanism 23. The first and

second gratings

21 and 22 are disposed to face the X-ray source 11 in the Z direction, which is the X-ray irradiation direction. A space is provided between the X-ray source 11 and the first grating 21 so that the subject H can be arranged. The X-ray image detector 13 is a flat panel detector using a semiconductor circuit, and is disposed close to the back of the second grating 22. The detection surface 13a of the X-ray image detector 13 exists on the XY plane orthogonal to the Z direction.

The first lattice 21 has a lattice plane on the XY plane, and a plurality of X-ray absorption portions 21a and X-ray transmission portions 21b extending in the Y direction (lattice direction) are formed on the lattice plane. . The X-ray absorption parts 21a and the X-ray transmission parts 21b are alternately arranged along the X direction to form a striped pattern. Similar to the first grating 21, the second grating 22 includes a plurality of X-ray absorption parts 22 a and X-ray transmission parts 22 b that extend in the Y direction and are alternately arranged along the X direction. The

X-ray absorbing portions

21a and 22a are formed of a metal having X-ray absorption properties such as gold (Au) and platinum (Pt). The X-ray transmissive

portions

21b and 22b are formed of an X-ray transmissive material such as silicon (Si) or resin, or a gap.

The first grating 21 partially passes the X-rays emitted from the X-ray source 11 to generate a first periodic pattern image (hereinafter referred to as a G1 image). This G1 image substantially coincides with the lattice pattern of the second lattice 22 at the position of the second lattice 22. The second grating 22 partially shields the G1 image generated by the first grating 21 to generate a second periodic pattern image (hereinafter referred to as G2 image).

The X-ray image detector 13 detects the G2 image and generates image data. The memory 14 temporarily stores the image data read from the X-ray image detector 13. The image processing unit 15 generates a phase differential image based on the image data stored in the memory 14, and generates a phase contrast image based on the phase differential image. The image recording unit 16 records a phase differential image and a phase contrast image.

The scanning mechanism 23 intermittently moves the second grating 22 in the X direction, and changes the position (scanning position) of the second grating 22 with respect to the first grating 21 in a stepwise manner. The drive unit of the scanning mechanism 23 is configured by a piezoelectric actuator or an electrostatic actuator, and is driven based on the control of the imaging control unit 17 at the time of stripe scanning described later. The memory 14 stores image data obtained by the X-ray image detector 13 at each scanning position of the second grating 22 with respect to the first grating 21.

The console 18 includes an operation unit 18a and a monitor 18b. The operation unit 18a is configured by a keyboard, a mouse, and the like, and sets imaging conditions such as tube voltage, tube current, and irradiation time of the X-ray source 11, selection of an imaging mode (main imaging or pre-imaging), imaging execution instruction, and the like. The operation input can be performed. The main imaging is an imaging mode performed with the subject H placed between the X-ray source 11 and the first grating 21. Pre-imaging is an imaging mode performed without placing the subject H between the X-ray source 11 and the first grating 21. The pre-photographing is used to acquire a background component (offset image) caused by a manufacturing error or arrangement error of the first and

second gratings

21 and 22.

The monitor 18b displays photographing information such as photographing conditions, and a phase differential image and a phase contrast image recorded in the image recording unit 16. The system control unit 19 comprehensively controls each unit according to a signal input from the operation unit 18a.

2, the X-ray image detector 13 includes a plurality of pixels 30 arranged two-dimensionally, a gate scanning line 33, a scanning circuit 34, a signal line 35, and a readout circuit 36. As is well known, the pixel 30 includes a pixel electrode 31 for collecting charges generated in a semiconductor film such as amorphous selenium (a-Se) by incident X-rays, and a TFT (for reading the charges collected by the pixel electrode 31). Thin Film Transistor) 32.

The gate scanning line 33 is provided for each row of the pixels 30. The scanning circuit 34 applies a scanning signal for turning on / off the TFT 32 to each gate scanning line 33. The signal line 35 is provided for each column of the pixels 30. The readout circuit 36 reads out electric charges from the pixels 30 through the signal lines 35, converts them into image data, and outputs them. The detailed layer configuration of each pixel 30 is the same as the layer configuration described in Japanese Patent Laid-Open No. 2002-26300.

As is well known, the readout circuit 36 includes an integration amplifier, an A / D converter, a correction circuit (none of which is shown), and the like. The integrating amplifier integrates the charges output from each pixel 30 through the signal line 35 to generate an image signal. The A / D converter converts the image signal generated by the integrating amplifier into digital image data. The correction circuit performs dark current correction, gain correction, linearity correction, and the like on the image data, and inputs the corrected image data to the memory 14.

The X-ray image detector 13 is not limited to a direct conversion type that directly converts incident X-rays into electric charges, but converts incident X-rays into visible light with a scintillator such as cesium iodide (CsI) or gadolinium oxysulfide (GOS). Alternatively, an indirect conversion type in which visible light is converted into electric charge by a photodiode may be used. The X-ray image detector 13 is not limited to a radiographic image detector based on a TFT panel, and a radiographic image detector based on a solid-state imaging device such as a CCD sensor or a CMOS sensor can also be used. .

In FIG. 3, X-rays irradiated from the X-ray source 11 are cone beams having the X-ray focal point 11a as a light emitting point. The first grating 21 is configured to project the X-rays that have passed through the X-ray transmission part 21b substantially geometrically. Specifically, the width of the X-ray transmission part 21b in the X direction is set to a value sufficiently larger than the effective wavelength of X-rays radiated from the X-ray source 11, and straightness is achieved without diffracting most of the X-rays. It is realized by letting it pass while keeping. For example, when tungsten is used as the rotating anode of the X-ray source 11 and the tube voltage is 50 kV, the effective wavelength of X-rays is about 0.4 mm. In this case, the width of the X-ray transmission part 21b may be about 1 to 10 μm. The same applies to the second grating 22.

The G1 image generated by the first grating 21 expands in proportion to the distance from the X-ray focal point 11a. The grating pitch p ₂ of the second grating 22 is determined so as to coincide with the periodic pattern of the G1 image at the position of the second grating 22. Specifically, the grating pitch p ₂ of the second grating 22 is the grating pitch of the first grating 21 p ₁ , the distance L ₁ between the X-ray focal point 11 a and the first grating 21, the first grating 21. When the distance L ₂ between the lattice 21 and the second lattice 22 is set, the following equation (1) is set to be substantially satisfied. Hereinafter, the coordinates in the X, Y, and Z directions are x, y, and z.

The G1 image is modulated by the phase change in the X-ray caused by the subject H. The modulation amount reflects the X-ray refraction angle φ (x) of the subject H. FIG. 3 illustrates an X-ray path emitted from the X-ray focal point 11a. Reference numeral X1 indicates a path along which the X-ray goes straight when the subject H does not exist. X-rays traveling along the path X 1 pass through the first and

second gratings

21 and 22 and enter the X-ray image detector 13. Reference numeral X2 indicates an X-ray path refracted by the subject H when the subject H exists. X-rays traveling along the path X <b> 2 pass through the first grating 21 and are then absorbed by the X-ray absorption unit 22 a of the second grating 22.

X-rays are refracted according to the phase shift distribution Φ (x) representing the amount of X-ray phase change by the subject H. This phase shift distribution Φ (x) is expressed by the following equation (2), where X-ray wavelength is λ and refractive index distribution of the subject H is n (x, z). Here, the y-coordinate is omitted for simplification of description.

This phase shift distribution Φ (x) is in the relationship of the refraction angle φ (x) of X-ray and the following equation (3).

The amount of displacement Δx in the X direction at the position of the second grating 22 between the X-ray traveling along the path X1 and the X-ray traveling along the path X2 is based on the fact that the refraction angle φ (x) of the X-ray is very small. It is approximately represented by the following formula (4).

Thus, it can be seen that the displacement Δx is proportional to the differential value of the phase shift distribution Φ (x). This displacement amount Δx can be detected by a fringe scanning method, and as a result, a phase differential image is obtained.

In the present embodiment, a value obtained by dividing the grating pitch p ₂ into M pieces (p ₂ / M) is set as a scanning pitch, and the scanning mechanism 23 intermittently moves the second grating 22 in the X direction at this scanning pitch. By doing so, fringe scanning is performed. M is an integer greater than or equal to 3, for example, it is preferable that M = 5. During each stop of the second grating 22, X-rays are emitted from the X-ray source 11 and a G2 image is detected by the X-ray image detector 13. By this fringe scanning, M pieces of image data are obtained, and M pixel values are obtained for each pixel 30 of the X-ray image detector 13.

As shown in FIG. 4, the M pixel values I _k periodically change with respect to the scanning position k (k = 0, 1, 2,..., M−1) of the second grating 22. . The scanning position k is a position that is discrete in the X direction by a scanning pitch (p ₂ / M). Hereinafter, a signal representing a change in the pixel value I _k with respect to the scanning position k is referred to as an intensity modulation signal.

The broken line in the figure indicates an intensity modulation signal obtained without the subject H being placed. On the other hand, a solid line indicates an intensity modulation signal in which the phase difference amount ψ (x) is generated by the subject H in a state where the subject H is arranged. This phase shift amount ψ (x) is in the relationship of the displacement amount Δx and the following equation (5).

Therefore, for each pixel 30, a phase differential image is obtained by obtaining the phase shift amount ψ (x) of the intensity modulation signal based on the M pixel values I _k obtained by the fringe scanning.

When the above formula (1) is not satisfied slightly, or when the rotation around the Z direction or the inclination with respect to the XY plane is slightly generated between the first grating 21 and the second grating 22. , Moire fringes occur in the G2 image. The moire fringes are moved by the movement of the second grating 22, the movement distance in the X-direction coincides with the original moiré fringe reaches the grating pitch p _2, detects the amount of movement of the moire fringes Thus, the actual movement amount of the second grating 22 can be detected with high accuracy.

Next, a method for calculating the phase shift amount ψ (x) will be described. The intensity modulation signal is generally expressed by the following formula (6).

Here, A ₀ represents the average intensity of the incident X-ray, A _n represents the amplitude of the intensity-modulated signal. “N” is a positive integer and “i” is an imaginary unit. As shown in FIG. 4, when the intensity modulation signal draws a sine wave, n = 1.

In this embodiment, since the scanning pitch (p ₂ / M) is constant, the following expression (7) is satisfied.

When the above equation (7) is applied to the above equation (6), the phase shift amount ψ (x) is represented by the following equation (8).

Here, arg [...] is a function that extracts the argument of a complex number. Further, the phase shift amount ψ (x) can also be expressed by the following equation (9) using an arctangent function.

Since the deviation angle of the complex number ranges from −π to + π, when the phase shift amount ψ (x) is calculated based on the above equation (8), the phase shift amount ψ (x) is − Take a value that is convolved (wrapped) in the range of π to + π. On the other hand, since the range of the arc tangent function is usually in the range of −π / 2 to + π / 2, when the phase shift amount ψ (x) is calculated based on the above equation (9), The phase shift amount ψ (x) takes a value convolved in a range of −π / 2 to + π / 2. In the above equation (9), the range of the arc tangent function can be expanded from −π to + π by determining the denominator and the sign of the numerator in the arc tangent function. Therefore, the phase shift amount ψ (x) can be calculated in the range of −π to + π based on the above equation (9).

In the present embodiment, an image represented by data obtained by calculating the phase shift amount ψ (x) for each pixel 30 is referred to as a phase differential image. Note that an image represented by data obtained by multiplying or adding a phase shift amount ψ (x) by a constant may be a phase differential image.

In FIG. 5, the image processing unit 15 includes a phase differential image generation unit 40, an offset image storage unit 41, an OK / NG region detection unit 42, an unwrap processing unit 43, an offset processing unit 44, and a phase contrast image generation unit 45. ing. The phase differential image generation unit 40 uses M image data acquired by fringe scanning and stored in the memory 14 in main photographing or pre-photographing, and performs calculation based on the above equation (8) or the above equation (9). By doing so, a phase differential image is generated.

The phase differential image generated by the phase differential image generation unit 40 at the time of pre-photographing is stored in the offset image storage unit 41 as an offset image. The phase differential image generated by the phase differential image generation unit 40 during the main photographing is input to the unwrap processing unit 43. In addition, when the offset image is input again from the phase differential image generation unit 40, the offset image storage unit 41 deletes the stored offset image and then stores the input offset image.

The OK / NG area detection unit 42 detects an area where an unwrap error is likely to occur in the phase differential image (hereinafter referred to as an NG area) based on the M image data stored in the memory 14, and other than this NG area This area is the OK area. OK / NG area detection unit 42 for each pixel 30, the average intensity _{A 0} is lower than the threshold region of the intensity modulated signal, the amplitude _{A 1} is lower than the threshold area or visibility _A 1 / _{A 0} is lower than the threshold region, Detect as NG area.

This NG region corresponds to a high-absorber region included in the subject H (such as a bone portion having a high X-ray absorption ability when the subject H is a human body). This is based on the fact that the average intensity A ₀ , the amplitude A ₁ , or the visibility A ₁ / A ₀ decreases due to the X-rays being absorbed by the high absorber. The NG region may be detected by combining two or more of the average intensity A ₀ , the amplitude A ₁ , and the visibility A ₁ / A ₀ . In addition, when the NG regions are scattered and cannot be obtained as an aggregate region having a certain size, the size of the detected NG region may be adjusted by changing the threshold value.

The unwrap processing unit 43 unwraps only the OK region with respect to the phase differential image input from the phase differential image generation unit 40. The unwrap processing unit 43 also unwraps only the OK region for the offset image stored in the offset image storage unit 41.

The offset processing unit 44 performs offset correction by subtracting the offset image after unwrapping from the phase differential image after unwrapping. Specifically, the pixel value is subtracted within the corresponding pixel 30. The phase contrast image generating unit 45 generates a phase contrast image representing the phase shift distribution by integrating the phase differential image after the offset correction along the X direction. The phase differential image after the offset correction and the phase contrast image are recorded in the image recording unit 16.

Next, an unwrap processing method by the unwrap processing unit 43 will be described with reference to FIGS. FIG. 7 shows the phase differential image as an image of 10 × 7 pixels for the sake of simplicity of explanation. In this phase differential image, the NG area detected by the OK / NG area detection unit 42 is shown. The OK area is an area other than the NG area.

First, the starting point for starting the unwrapping process is set for each row or column of the phase differential image (step S10). In this step, a through line that passes only through the OK region and penetrates the phase differential image in the X direction or the Y direction is searched, and a starting point is set along one of the through lines. In FIG. 7, since there are penetrating lines in each of the X direction and the Y direction, the penetrating lines along the shorter Y direction are given priority, and starting points P0 to P6 are set in one of them. Here, the starting points P0 to P6 are set along the X direction end (short side) of the phase differential image.

After the starting points P0 to P6 are set in this way, linear straight paths R0 to R6 having the starting points P0 to P6 as starting points in a direction (X direction) orthogonal to the through line where the starting points P0 to P6 are set. Is set, and the unwrapping process is executed along each of the straight paths R0 to R6 (step S11). These straight paths R0 to R6 are not set in the NG area. Therefore, behind the NG area viewed from the starting points P0 to P6, pixels that belong to the same OK area as the starting points P0 to P6 but do not have the straight paths R0 to R6 set remain.

Specifically, in step S11, first, unwrap processing is performed in order along the straight line route R0 from the starting point P0, and when the unwrap processing of the straight line route R0 ends, the unwrapping processing of the starting point P1 is performed with reference to the starting point P0. Thereafter, the unwrapping process is sequentially performed from the starting point P1 along the straight path R1. Then, the unwrapping process is not performed on the pixels remaining behind the NG area in the same row as the straight line R1, and the unwrapping process of the starting point P2 is performed with the starting point P1 as a reference. Thereafter, the unwrapping process is performed in the same procedure, and when the unwrapping process for the straight line route R6 is finished, the step S11 is finished.

Thereafter, a wraparound path is set for the pixels remaining behind the NG area, and a wraparound process is performed for performing an unwrap process along the wraparound path (step S12). Specifically, in this step, the wraparound path WR0 is set for pixels remaining in the same row as the straight line route R1, and the wraparound path WR1 is set for pixels remaining in the same row as the straight line route R5. The wraparound route WR0 is unwrapped from the pixel P0a on the adjacent straight route R0. The wraparound path WR1 is unwrapped from the pixel P6a on the adjacent straight path R6.

In addition, as shown in FIG. 8, as a result of the NG area dividing the phase differential image, a plurality of OK areas may exist. In this case, steps S10 to S12 are executed individually for each OK area. The above unwrapping process is performed in the same manner for the phase differential image obtained by the main photographing and the offset image performed by the pre photographing.

As shown in FIG. 9, the unwrapping process on each path sequentially detects discontinuous points DP that change from the upper limit to the lower limit of the range of the function of the above equation (8) or the above equation (9), or from the lower limit to the upper limit. In this process, the data after the detected discontinuous point DP is uniformly added or subtracted with a value corresponding to this range to eliminate the discontinuous point DP and to make the data continuous.

Next, the operation of the X-ray imaging apparatus 10 will be described with reference to the flowcharts shown in FIGS. When the shooting mode is selected using the operation unit 18a (step S20), it is determined whether or not the selected shooting mode is pre-shooting (step S21). If it is pre-photographing, a standby state for photographing instructions is entered (step S22).

When an imaging instruction is given using the operation unit 18a (YES in step S22), the X-ray source 11 X is scanned at each scanning position k while the second grating 22 is moved by a predetermined scanning pitch by the scanning mechanism 23. Radiation and detection of the G2 image by the X-ray image detector 13 are performed (step S23). As a result of the fringe scanning, M pieces of image data are generated and stored in the memory 14.

Thereafter, the image data for M sheets stored in the memory 14 is read by the image processing unit 15. In the image processing unit 15, a phase differential image is generated by the phase differential image generation unit 40 (step S24). This phase differential image is stored in the offset image storage unit 41 as an offset image (step S25). The pre-photographing operation ends here. Note that this pre-imaging may be performed at least once in a state in which the subject H is not disposed when the X-ray imaging apparatus 10 is started up, and need not be performed every time before the main imaging.

Next, when the subject H is arranged and the main imaging is selected by selecting the imaging mode in step S20 (NO in step S21), the imaging instruction standby state is set (step S30). When a photographing instruction is given using the operation unit 18a (YES in step S30), the same stripe scanning as in step S23 is performed (step S31), and M pieces of image data are stored in the memory 14. Thereafter, similarly, the phase differential image is generated by the phase differential image generation unit 40 (step S32).

Then, based on the image data stored in the memory 14, the NG area and the OK area are detected by the OK / NG area detecting unit 42 (step S33). When the NG region and the OK region are detected, the unwrap processing unit 43 applies the above-described OK regions for the phase differential image generated in step S32 and the offset image stored in the offset image storage unit 41, respectively. Is unwrapped (step S34). Thereafter, the offset processing unit 44 performs offset correction for subtracting the unwrapped offset image from the unwrapped phase differential image (step S35). Thereby, subtraction of the pixel value is performed in the corresponding pixel 30.

The phase contrast image is generated by the phase contrast image generation unit 45 integrating the phase differential image after the offset correction (step S36). The phase differential image and the phase contrast image after the offset correction are recorded in the image recording unit 16 and then displayed on the monitor 18b (step S37).

As described above, in the unwrapping process in step S34, an NG region where an unwrapping error is likely to occur is detected, and the unwrapping process is performed only for an OK region other than the NG region. An image is obtained. Since soft tissue (cartilage portion or the like), which is a region of interest in X-ray phase imaging, exists outside the NG region, it is prevented that imaging of the soft tissue is inhibited by noise due to unwrapping errors.

In the above-described embodiment, each time the unwrap process is performed on one of the plurality of straight paths R0 to R6, the unwrap process is performed between the start point of the straight path and the start point of the next straight path. However, before the unwrap processing of the straight paths R0 to R6, the unwrap processing is first performed between the starting points of the respective starting points P0 to P6, and each of the straight paths R0 to R6 is started from each of the starting points P0 to P6 after the unwrapping process. You may unwrap.

Conversely, after unwrapping each of the straight paths R0 to R6, the unwrap processing is performed between the starting points of the respective starting points P0 to P6, and the data of each of the straight paths R0 to R6 after the unwrapping is obtained as the starting point P0 after the unwrapping process. It may be shifted according to the data of P6.

Further, in the above embodiment, in the unwrap processing, when a through line that passes only through the OK region and penetrates the phase differential image is searched for and there are through lines in both the X direction and the Y direction, the Y direction is given priority. The starting points P0 to P6 are set along the Y direction. However, as shown in FIG. 12, the starting points P0 to P9 may be set along the X direction with priority on the X direction. In this case, each straight path R0 to R6 is set along the Y direction. The wraparound path WR0 is appropriately set so as to cover the pixels remaining behind the NG region when viewed from the starting points P0 to P9. Since the specific unwrap processing method is the same as that of the said embodiment, detailed description is abbreviate | omitted.

Further, as shown in FIG. 13, an origin / direction determination unit 50 that determines whether to set the origin along the Y direction or along the X direction based on the shape of the NG area is provided with an OK / NG area detection unit. 42 and the unwrap processing unit 43 may be provided. The starting point direction determination unit 50 determines the starting point setting direction so that the number of wraparound processes performed on the pixels remaining behind the NG region is reduced.

For example, when the starting point is set along the Y direction as shown in FIG. 7, the wrapping process is required for two lines along the X direction (lines including the starting points P1 and P5). The number of times is two. On the other hand, when the starting point is set along the X direction as shown in FIG. 12, a wraparound process is required for six lines along the Y direction (lines including the starting points P4 to P9). The number of wraparound processes is 6. Therefore, when the NG area has the shape shown in FIGS. 7 and 12, the starting point direction determination unit 50 determines the Y direction in which the necessary number of wraparound processes is reduced as the starting point setting direction. The unwrap processing unit 43 performs unwrapping by setting each starting point in the direction determined by the starting point direction determining unit 50.

In the above embodiment, in the unwrap processing, the starting point is set along the X-direction end or the Y-direction end of the phase differential image, but it is not always necessary to set the starting point along the end portion of the phase differential image. . For example, as shown in FIG. 14, starting points P0 to P6 are set, and a straight path is set in a direction (positive direction and negative direction of the X direction) orthogonal to the arrangement direction (Y direction) of each starting point P0 to P6. Also good.

Further, in the above embodiment, in the unwrap processing, the starting point is set in each column or each row so that the unwrap processing is performed for each column or each row of the phase differential image. One starting point (starting point) may be set in the OK region, and the pixels adjacent to the starting point may be unwrapped in order.

For example, as shown in FIG. 15A, a start point P0 is set in the OK region, and pixels adjacent in the X direction and the Y direction from this start point P0 are unwrapped. Next, as shown in FIG. 15B, the pixels adjacent in the X direction and the Y direction are unwrapped from each unwrapped pixel. At this time, if the adjacent pixel is a pixel belonging to the NG area, it is not considered and the unwrapping process is not performed. Further, when the adjacent pixel is an adjacent pixel of another pixel that has been unwrapped, priority is given to one of them. Here, the adjacent pixel in the X direction has priority over the adjacent pixel in the Y direction. Thereafter, the unwrapping process may be advanced in the same manner.

Further, in the above embodiment, the unwrap processing unit 43 unwraps only the OK region for the offset image stored in the offset image storage unit 41. However, the unwrap processing is performed on the entire offset image. May be. As shown in FIG. 8, when there are a plurality of OK regions and the phase differential image obtained by the main imaging is unwrapped for each OK region, the unwrapping is performed independently for each OK region. Since the data may be greatly shifted between the OK regions after the processing, the shift amount is estimated from the offset image subjected to the unwrap processing as a whole, and each phase differential image after the unwrap processing is estimated based on the shift amount. You may correct | amend the difference of an OK area | region.

In the above-described embodiment, the OK / NG region detection unit 42 detects an NG region in which an unwrapping error is likely to occur based on the average intensity, amplitude, or visibility of the intensity modulation signal. Is not limited to this, and an area where variation between pixels of the average intensity of the intensity modulation signal (that is, dispersion between pixels of the absorption image) or dispersion between pixels of the phase differential image is larger than a predetermined value is detected as an NG area. May be. In addition, it is preferable that the dispersion | variation between the pixels of this phase differential image is a dispersion | variation to the direction (X direction) orthogonal to the lattice line of the 1st and 2nd grating |

lattices

21 and 22. FIG.

In addition, an absolute value is taken for each pixel of the phase differential image, and an edge portion of the superabsorbent region can be detected by detecting a portion where the absolute value exceeds a predetermined value. The region may be detected as an NG region.

Also, an area where the average intensity or the maximum intensity of the intensity modulation signal is larger than a predetermined value and the intensity modulation signal is saturated may be detected as an NG area. This saturation of the intensity modulation signal is likely to occur in a pixel region (elementary region) that is directly transmitted to the X-ray image detector 13 through the first and

second gratings

21 and 22 without passing through the subject H. When the intensity modulation signal is saturated, the phase shift amount ψ (x) cannot be obtained accurately, and this unaccompanied region is also a region where unwrapping errors are likely to occur. You may combine the above detection criteria suitably.

Furthermore, when a defect occurs in the X-ray image detector 13, the first grating 21, or the second grating 22, or dust or the like adheres, the pixel value of the predetermined pixel 30 is always high or low. May be. The region where such a pixel defect occurs is a region where an unwrapping error is likely to occur because the average intensity, amplitude, or visibility of the intensity modulation signal indicates an abnormal value. Such a pixel defect region can also be detected as an NG region by appropriately combining the above detection criteria.

In the above embodiment, since the unwrapping process is not performed in the NG area, the NG area of the phase differential image that is finally recorded in the image recording unit 16 and displayed on the monitor 18b is a noise in which discontinuous points remain. May result in a large image. Therefore, as shown in FIG. 16, an NG region image replacement unit 51 may be provided in the image processing unit 15.

The NG region image replacement unit 51 generates an absorption image, a differential image of the absorption image, or a small-angle scattered image based on the M image data stored in the memory 14 at the time of the actual photographing, and corresponds to the NG region of the image. The portion to be replaced is inserted into the NG area of the phase differential image after offset correction. Similarly, the NG area of the phase contrast image may be replaced. The absorption image is generated by imaging the average intensity of the intensity modulation signal. The differential image of the absorption image is generated by differentiating the absorption image in a predetermined direction (for example, the X direction). The small angle scattered image is generated by imaging the amplitude of the intensity modulation signal.

In the above-described embodiment, the subject H is disposed between the X-ray source 11 and the first grating 21, but the subject H is disposed between the first grating 21 and the second grating 22. You may arrange.

In the above-described embodiment, the second grating 22 is moved in the direction (X direction) perpendicular to the grid lines during fringe scanning. However, the second grid 22 is inclined with respect to the grid lines (XY plane). May be moved in a direction not orthogonal to the X direction and the Y direction. This moving direction may be any direction as long as it is within the XY plane and other than the Y direction. In this case, the scanning position k may be set based on the X-direction component of the movement of the second grating 22. By moving the second grating 22 in a direction inclined with respect to the grid line, the stroke (movement distance) required for scanning for one period of the fringe scanning becomes longer, and the movement accuracy is improved.

Moreover, in the said embodiment, although the 2nd grating | lattice 22 is moved at the time of fringe scanning, it replaces with the 2nd grating | lattice 22, and the 1st grating | lattice 21 is moved to the direction orthogonal to the grid line, or the direction which inclines. May be.

In the first embodiment, the X-ray source 11 that emits cone-beam X-rays emitted from the X-ray source 11 is used. However, an X-ray source that emits parallel-beam X-rays is used. Is also possible. In this case, instead of the above equation (1), the first and

second gratings

21 and 22 may be configured so as to substantially satisfy p ₂ = p ₁ .

Moreover, in the said embodiment, the X-rays inject | emitted from the X-ray source 11 are made to inject into the 1st grating | lattice 21, and although the X-ray source 11 is a single focus, immediately after the emission side of the X-ray source 11 ( The X focus may be dispersed by providing a multi-slit (source grating) described in WO 2006/131235 between the X-ray source 11 and the first grating 21). As a result, it becomes possible to use a high-power X-ray source and the X-ray dose is improved, so that the image quality of the phase differential image is improved. In this case, the pitch p _{0 of the} multi-slit needs to satisfy the following formula (10). Here, the distance L ₀ represents the distance from the multi slit to the first grating 21.

When the multi-slit is provided in this way, the position of the multi-slit becomes the position of the X-ray focal point, so the distance L _{1 in the} above embodiment is replaced with the distance L ₀ .

In addition, when the multi-slit is provided, the first and second gratings 21 are used in addition to performing the fringe scanning by moving the first grating 21 or the second grating 22 while the multi-slit is fixed. , 22 is fixed, and the multi-slit is moved to perform the fringe scanning. In this case, the multi-slit may be intermittently moved in the X direction using a value (p ₀ / M) obtained by dividing the multi-slit pitch p ₀ by M as described above. As a result, the scanning position k of the multi-slit 60 with respect to the first and

second gratings

21 and 22 is sequentially changed to k = 0, 1, 2,..., M−1.

Moreover, in the said embodiment, although the 1st grating | lattice 21 is comprised so that incident X-ray may be projected geometrically optically, as known in WO2004 / 058070 etc., the 1st grating | lattice 21 is comprised. May be configured to generate the Talbot effect. In order to generate the Talbot effect in the first grating 21, a small-focus X-ray light source or the multi-slit may be used so as to enhance the spatial coherence of X-rays.

If the Talbot effect in the first grating 21 occurs, the self-image of the first grating 21 (G1 image) occurs at a distance in the Z direction by the Talbot distance Z _m from the first grating 21. Therefore, it is necessary to distance L ₂ from the first grid 21 to the second grid 22 and Talbot distance Z _m. In this case, the first grating 21 can be a phase-type grating.

Talbot distance Z _m is dependent on the beam shape of the structure and the X-ray of the first grating 21. For example, the first grating 21 are absorption type grating, X-rays emitted from the X-ray source 11 in the case of a cone beam shape, Talbot distance Z _m is represented by the following formula (11). Here, “m” is a positive integer. In this case, the grating pitches p ₁ and p ₂ are set so as to substantially satisfy the above formula (1) (however, when a multi-slit is used, the distance L ₁ is replaced with the distance L ₀ ).

Further, when the first grating 21 is a phase-type grating that applies phase modulation of π / 2 to the X-ray, and the X-ray emitted from the X-ray source 11 has a cone beam shape, the Talbot distance Z _m is And expressed by the following formula (12). Here, “m” is “0” or a positive integer. In this case, the grating pitches p ₁ and p ₂ are set so as to substantially satisfy the above formula (1) (however, when a multi-slit is used, the distance L ₁ is replaced with the distance L ₀ ).

In addition, when the first grating 21 is a phase-type grating that imparts π phase modulation to X-rays and the X-rays emitted from the X-ray source 11 have a cone beam shape, the Talbot distance Z _m is as follows. It is represented by Formula (13). Here, “m” is “0” or a positive integer. In this case, since the pattern period of the G1 image is ½ times the grating period of the first grating 21, the grating pitches p ₁ and p ₂ are set so as to substantially satisfy the following expression (14). (However, when using a multi-slit, the distance _{L 1} is replaced by a distance _{L 0).}

The first grating 21 is absorption grating, if X-rays emitted from the X-ray source 11 is a parallel beam shape, Talbot distance Z _m is represented by the following formula (15). Here, “m” is a positive integer. In this case, the lattice pitches p ₁ and p ₂ are set so as to substantially satisfy the relationship of p ₂ = p ₁ .

Further, when the first grating 21 is a phase-type grating that applies phase modulation of π / 2 to X-rays, and the X-rays emitted from the X-ray source 11 are parallel beams, the Talbot distance Z _m is It is represented by the following formula (16). Here, “m” is “0” or a positive integer. In this case, the lattice pitches p ₁ and p ₂ are set so as to substantially satisfy the relationship of p ₂ = p ₁ .

When the first grating 21 is a phase type grating that imparts π phase modulation to X-rays, and the X-rays emitted from the X-ray source 11 are parallel beams, the Talbot distance Z _m is It is represented by Formula (17). Here, “m” is “0” or a positive integer. In this case, since the pattern period of the G1 image is ½ times the grating period of the first grating 21, the grating pitches p ₁ and p ₂ almost satisfy the relationship of p ₂ = p _1/2. Set to

In the above embodiment, the grating portion 12 is provided with the two gratings of the first and

second gratings

21 and 22. However, the second grating 22 may be omitted and only the first grating 21 may be used. Is possible.

For example, by using an X-ray image detector described in Japanese Patent Laid-Open No. 2009-133823, the second grating 22 can be omitted and only the first grating 21 can be provided. This X-ray image detector is a direct conversion type X-ray image detector including a conversion layer that converts X-rays into electric charges and a charge collection electrode that collects electric charges converted in the conversion layer. The charge collection electrode includes a plurality of linear electrode groups. One linear electrode group is obtained by electrically connecting linear electrodes arranged at a constant period, and is arranged so that the phases thereof are different from those of other linear electrode groups. This linear electrode group functions as the second grating 22, and the presence of a plurality of linear electrode groups allows detection of a plurality of G2 images having different phases in one imaging. Therefore, in this configuration, the scanning mechanism 23 can be omitted.

Further, there is a method in which the scanning mechanism 23 is omitted and a phase differential image is generated based on single image data obtained by the X-ray image detector 13 via the first and

second gratings

21 and 22. As this method, there is a pixel division method filed by the present applicant as Japanese Patent Application No. 2010-256241. In this pixel division method, the first grating 21 and the second grating 22 are slightly rotated around the Z direction, and moire fringes having a period in the Y direction are generated in the G2 image. The single image data obtained by the X-ray image detector 13 is divided into groups of pixel rows (pixels arranged in the X direction) having different phases from each other with respect to the moire fringes, and a plurality of divided image data is obtained. A phase differential image is generated in the same procedure as the above-described fringe scanning method, assuming that the images are based on a plurality of different G2 images by fringe scanning. In this pixel division method, the intensity modulation signal described above is expressed as a change in intensity of pixel values for one cycle of moire fringes generated in single image data.

Further, similarly to the pixel division method, the scanning mechanism 23 is omitted, and the phase differential image is obtained based on the single image data obtained by the X-ray image detector 13 via the first and

second gratings

21 and 22. As a generation method, a Fourier transform method described in WO2010 / 050484 is known. This Fourier transform method obtains a Fourier spectrum by performing a Fourier transform on the single image data, separates a spectrum corresponding to a carrier frequency (a spectrum carrying phase information) from the Fourier spectrum, and then reverses the spectrum. This is a method of generating a phase differential image by performing Fourier transform. In this Fourier transform method, the intensity modulation signal described above is expressed as a change in intensity of pixel values for one cycle of moire fringes generated in a single image data, as in the case of the pixel division method.

The present invention can be applied to an industrial radiography apparatus and the like in addition to a radiography apparatus for medical diagnosis. In addition to X-rays, gamma rays or the like can be used as radiation.

DESCRIPTION OF SYMBOLS 10 X-ray imaging apparatus 12 Grating part 20 X-ray image detector 21 1st grating | lattice 21a X-ray absorption part 21b X-ray transmission part 22 2nd grating | lattice 22a X-ray absorption part 22b X-ray transmission part 30 Pixel 31 Pixel electrode 33 Gate scanning line 35 Signal line

Claims

A radiation detector that detects radiation emitted from the radiation source and transmitted through the subject to generate image data; and
A grating portion disposed between the radiation source and the radiation detector;
Based on the image data, a phase differential image generation unit that generates a phase differential image represented by a value wrapped in a predetermined range;
An OK / NG area detection unit that detects an NG area that is likely to cause an unwrap error from the phase differential image, and sets an area other than the NG area as an OK area;
An unwrap processing unit that sets a starting point in the OK region and unwraps only the OK region;
A radiation imaging apparatus comprising:
An offset image storage unit that stores the phase differential image generated by the phase differential image generation unit in a state where the subject is not disposed as an offset image;
The radiation imaging apparatus according to claim 1, wherein the unwrap processing unit performs the unwrap processing on the phase differential image and the offset image.
The radiation imaging apparatus according to claim 2, further comprising an offset processing unit that subtracts the offset image after the unwrap processing from the phase differential image after the unwrap processing.
The unwrap processing unit sets a starting point in order along a penetrating line that passes only through the OK region and penetrates the phase differential image in one direction, and unwraps between the starting points, and passes from the starting point to the penetrating line. The radiation imaging apparatus according to claim 1, wherein unwrap processing is performed along an orthogonal straight path.
The radiation imaging apparatus according to claim 4, wherein the unwrap processing unit further performs unwrap processing on pixels in the OK region remaining behind the NG region as viewed from each starting point.
The radiation according to claim 5, further comprising a starting point direction determination unit that determines a setting direction of each starting point so that the number of unwrapping processes for pixels remaining behind the NG region is reduced. Shooting device.
The radiation imaging apparatus according to claim 4, wherein the unwrap processing unit sets the starting points along one side of the phase differential image.
When the phase differential image is divided into a plurality of OK regions by the NG region, the unwrap processing unit sets the starting point in each OK region, and performs the unwrap processing for each OK region. The radiation imaging apparatus according to claim 1, wherein:
The grating unit includes a first grating that generates a first periodic pattern image by passing radiation from the radiation source, and a second periodic pattern image that partially shields the first periodic pattern image. A second lattice that generates
The radiation imaging apparatus according to claim 1, wherein the radiation image detector generates the image data by detecting the second periodic pattern image.
The grating unit further includes a scanning mechanism that moves the first grating or the second grating at a predetermined scanning pitch and sequentially sets a plurality of scanning positions.
The radiation image detector detects the second periodic pattern image at each scanning position to generate image data;
The phase differential image generation unit generates the phase differential image based on a plurality of image data generated by the radiation image detector at the plurality of scanning positions. Radiography equipment.
The radiation imaging apparatus according to claim 10, wherein the scanning mechanism moves the first grating or the second grating in a direction orthogonal to the grating line.
The radiation imaging apparatus according to claim 10, wherein the scanning mechanism moves the first grating or the second grating in a direction inclined with respect to the grating line.
10. The radiation imaging apparatus according to claim 9, wherein the phase differential image generation unit generates the phase differential image based on single image data obtained by the radiation detector.
The OK / NG area detecting unit detects the NG area based on one or a combination of an average intensity, an amplitude, and a visibility of an intensity modulation signal representing an intensity change of a pixel value. The radiation imaging apparatus according to any one of ranges 10 to 13.
An NG region image replacement unit that replaces the NG region of the phase differential image using any one of an absorption image, a differential image of the absorption image, and a small-angle scattering image created based on the intensity modulation signal; The radiation imaging apparatus according to claim 14, wherein:
15. The radiation according to claim 14, wherein the first grating is an absorption grating, and the first periodic pattern image is generated by geometrically projecting incident radiation. Shooting device.
15. The first periodic pattern image according to claim 14, wherein the first grating is an absorption grating or a phase grating, and generates the first periodic pattern image by causing a Talbot effect to incident radiation. Radiography equipment.
The radiation imaging apparatus according to claim 14, further comprising a multi-slit that partially blocks radiation emitted from the radiation source and disperses the focal point.
Detecting an NG region in which an unwrapping error is likely to occur from a phase differential image represented by a value wrapped in a predetermined range, and setting a region other than the NG region as an OK region;
Setting a starting point in the OK region and unwrapping only the OK region;
An unwrap processing method comprising: