WO2013084659A1

WO2013084659A1 - Radiography device

Info

Publication number: WO2013084659A1
Application number: PCT/JP2012/079020
Authority: WO
Inventors: 温之橋本; 村越　大
Original assignee: 富士フイルム株式会社
Priority date: 2011-12-05
Filing date: 2012-11-08
Publication date: 2013-06-13
Also published as: JP2013138835A

Abstract

A radiography device (1) is provided with a radiation delivery unit (11), a first grid (31) having a periodic structure in at least one direction, and a detection unit (14) which includes a radiation image detector (30). The first grid forms a radiation image including a periodic intensity distribution by radiation that passes through the first grid. The detection unit detects the radiation image and acquires radiation image data, and is configured so that a relative incidence direction of central radiation with respect to the subject can be changed in a plane that passes through the subject and is parallel to the periodic direction of the periodic structure of the first grid.

Description

Radiography equipment

The present invention relates to a radiation imaging apparatus.

X-rays are used as a probe for seeing through the inside of a subject because they have characteristics such as attenuation depending on the atomic numbers of elements constituting the substance and the density and thickness of the substance. X-ray imaging is widely used in fields such as medical diagnosis and non-destructive inspection.

In general X-ray imaging, a subject is placed between an X-ray source that emits X-rays and an X-ray image detector that detects an X-ray image, and a transmission image of the subject is captured. In this case, each X-ray radiated from the X-ray source toward the X-ray image detector has characteristics (atomic number, density, thickness) of the substance constituting the subject existing on the path to the X-ray image detector. ), The light is incident on the X-ray image detector. As a result, an X-ray transmission image of the subject is detected and imaged by the X-ray image detector. X-ray image detectors include a combination of an X-ray intensifying screen and film, a stimulable phosphor (accumulating phosphor), and a flat panel detector (FPD: Flat Panel Detector) using a semiconductor circuit. Widely used.

However, the X-ray absorptivity becomes lower as a substance composed of an element having a smaller atomic number, and the difference in the X-ray absorptivity is small in a soft tissue or soft material of a living body. There is a problem that (contrast) cannot be obtained. 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 the amount of X-ray absorption between the two is small, so that it is difficult to obtain image contrast.

Against the background of such problems, in recent years, an X-ray phase for obtaining an image (hereinafter referred to as a phase contrast image) based on an X-ray phase change (angle change) by an object instead of an X-ray intensity change by an object. Imaging research is actively conducted. In general, it is known that when X-rays are incident on an object, the interaction is higher in phase than in X-ray intensity. For this reason, in X-ray phase imaging using a phase difference, it is possible to obtain a high-contrast image even for a weakly absorbing object having a low X-ray absorption ability, for example, an interphalangeal joint of a hand or a foot, an elbow joint, This is useful for visualizing the cartilage of joints such as knee joints.

As a kind of such X-ray phase imaging, in recent years, an X-ray imaging apparatus using an X-ray Talbot interferometer comprising two transmission diffraction gratings (phase type grating and absorption type grating) and an X-ray image detector has been proposed. It has been devised (for example, see Patent Documents 1 and 2).

In the X-ray Talbot interferometer, a first diffraction grating (phase type grating or absorption type grating) is arranged behind a subject, and a specific distance (Talbot interference distance) determined by the grating pitch of the first diffraction grating and the X-ray wavelength. The second diffraction grating (absorption type grating) is disposed only downstream, and the X-ray image detector is disposed behind the second diffraction grating. The Talbot interference distance is a distance at which X-rays that have passed through the first diffraction grating form a self-image (hereinafter referred to as a G1 image) that exhibits a periodic intensity distribution due to the Talbot interference effect. And modulated by the interaction (phase change) between the subject and the X-rays disposed between the X-ray source and the first diffraction grating.

In the X-ray Talbot interferometer, the moiré fringes generated by the superposition of the G1 image and the second diffraction grating are detected, and the phase of the subject is analyzed by analyzing the modulation of the periodic pattern appearing in the image corresponding to the moire fringes. Get information. For example, a fringe scanning method is known as a method for analyzing a periodic pattern appearing in an image. According to this fringe scanning method, the second diffraction grating is arranged with respect to the first diffraction grating in a direction substantially parallel to the plane of the first diffraction grating and substantially parallel to the grating pitch direction of the first diffraction grating. , Taking multiple shots while translating the grating pitch of the second diffraction grating at equal scan pitches, and refracting the subject from the change in the corresponding signal value for each pixel between the obtained multiple image data An X-ray angular distribution (phase shift differential image) is obtained, and a phase contrast image of the subject can be obtained based on the angular distribution.

International Publication No. 08/102598 International Publication No. 08/102685

The X-ray imaging apparatuses described in

Patent Documents

1 and 2 support an X-ray source, a first diffraction grating, a second diffraction grating, a detector, and a subject table arranged in a vertical direction by an arm member. The subject table is arranged between the X-ray source and the first diffraction grating, or between the first diffraction grating and the second diffraction grating.

The phase derivative acquired by the fringe scanning method is related to the grating period direction of the first diffraction grating, and the phase contrast image obtained based on this phase derivative includes each object of the subject that intersects the grating period direction. The edge of the part is depicted, and in particular, the edge substantially perpendicular to the lattice period direction is clearly depicted. In other words, the arrangement of the subject is restricted by the lattice period direction. For example, in order to clearly depict the cartilage of a joint in a phase contrast image of a joint such as an interphalangeal joint, an elbow joint, or a knee joint, it is preferable to arrange fingers, arms, and legs substantially along the lattice period direction.

When the subject is photographed under the above conditions, the region of interest of the subject often overlaps the non-interest region. For example, when cartilage of a joint such as an interphalangeal joint, an elbow joint, or a knee joint is a region of interest, these regions often overlap with a bone that is a non-region of interest. This is because the joint gap where the cartilage exists does not necessarily exist in a direction perpendicular to the long axis direction of the bone. If the region of interest overlaps with the non-region of interest, the non-region of interest not only becomes a shadow shadow, but bones that are generally hard tissue greatly attenuate X-rays, making it difficult to obtain a clear phase contrast image. .

The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a radiation imaging apparatus capable of obtaining a clear phase contrast image by causing radiation to enter a subject from an appropriate direction.

A radiation irradiation unit, a first grating having a periodic structure in at least one direction, and a detection unit including a radiation image detector, wherein the first grating is caused by radiation passing through the first grating. A radiographic image including a periodic intensity distribution is formed, and the detection unit detects the radiographic image to acquire radiographic image data, and a relative incident direction of central radiation with respect to the subject passes through the subject and the first A radiation imaging apparatus configured to be changeable in a plane parallel to the periodic direction of the periodic structure of the grating.

According to the present invention, radiation can be incident on the subject from an appropriate direction, and a clear phase contrast image can be obtained.

It is a schematic diagram which shows the structure of an example of a radiography apparatus for describing embodiment of this invention. It is a control block diagram of the radiography apparatus of FIG. It is a perspective view which shows the structure of the imaging | photography part of the radiography apparatus of FIG. It is a side view which shows the structure of the imaging | photography part of the radiography apparatus of FIG. It is a schematic diagram which shows the structure of the radiographic image detector contained in the radiography apparatus of FIG. It is a schematic diagram which shows the mechanism for changing the periodic pattern of the image acquired by the radiographic image detector of FIG. It is a schematic diagram for demonstrating the refraction | bending of the radiation by a to-be-photographed object. It is a schematic diagram for demonstrating an example of the production | generation method of the phase contrast image by the fringe scanning method in the radiography apparatus of FIG. It is a graph which shows the signal waveform of the pixel of the image data obtained by the production | generation method of the phase contrast image of FIG. It is a schematic diagram for demonstrating the other example of the production | generation method of the phase contrast image in the radiography apparatus of FIG. It is a graph which shows the signal waveform of the pixel of the image data obtained by the production | generation method of the phase contrast image of FIG. It is a schematic diagram for demonstrating the modification of the production | generation method of the phase contrast image of FIG. It is a schematic diagram for demonstrating the other modification of the production | generation method of the phase contrast image of FIG. It is a schematic diagram for demonstrating the other modification of the production | generation method of the phase contrast image of FIG. It is a schematic diagram for demonstrating the other example of the production | generation method of the phase contrast image in the radiography apparatus of FIG. It is a schematic diagram which shows the mechanism which changes the relative incident direction of the central radiation with respect to a to-be-photographed object in the radiography apparatus of FIG. It is a schematic diagram showing the X-ray passing through the region of interest of the subject in relation to the incident direction of the central X-ray. FIG. 2 is a schematic diagram illustrating a mechanism for correcting a change in relative positional relationship between a region of interest of a subject, a radiation irradiation unit, a first lattice, and a detection unit in the radiographic apparatus of FIG. 1. FIG. 6 is a schematic diagram illustrating another example of a mechanism for correcting a change in relative positional relationship between a region of interest of a subject, a radiation irradiation unit, a first lattice, and a detection unit in the radiographic apparatus of FIG. 1. It is a schematic diagram which shows the structure of the other example of a radiography apparatus for describing embodiment of this invention. It is a control block diagram of the radiography apparatus of FIG. It is a schematic diagram which shows the occupation space of the radiography apparatus of FIG. 1 and the radiography apparatus of FIG. FIG. 21 is a schematic diagram illustrating a mechanism for correcting a change in relative positional relationship between a region of interest of a subject, a radiation irradiation unit, a first lattice, and a detection unit in the radiographic apparatus of FIG. 20. It is a schematic diagram which shows the structure of the other example of a radiography apparatus for describing embodiment of this invention. It is a schematic diagram which shows the structure of the other example of a radiography apparatus for describing embodiment of this invention. It is a schematic diagram which shows the structure of the other example of a radiography apparatus for describing embodiment of this invention. It is a schematic diagram which shows the structure of the other example of the radiography apparatus for describing embodiment of this invention. It is a schematic diagram for demonstrating an example of the production | generation method of the phase contrast image in the radiography apparatus of FIG. It is a schematic diagram which shows the structure of the other example of the radiography apparatus for describing embodiment of this invention. It is a schematic diagram for demonstrating an example of the production | generation method of the phase contrast image in the radiography apparatus of FIG. It is a schematic diagram which shows the structure of the other example of a radiography apparatus for describing embodiment of this invention. It is a schematic diagram which shows the structure of the other example of a radiography apparatus for describing embodiment of this invention.

FIG. 1 shows a configuration of an example of a radiographic apparatus for explaining an embodiment of the present invention, and FIG. 2 shows a control block of the radiographic apparatus of FIG.

The X-ray imaging apparatus 1 is roughly divided into an X-ray imaging apparatus main body 2 and a console 3. The X-ray imaging apparatus body 2 includes an X-ray irradiation unit 11 that irradiates the subject H with X-rays, and an imaging unit that detects X-rays emitted from the X-ray irradiation unit 11 and transmitted through the subject H, and generates image data. 12 and a structure 13 that supports the X-ray irradiation unit 11 and the imaging unit 12. The console 3 controls the operation of each part of the X-ray imaging apparatus body 2 such as the exposure operation of the X-ray irradiation unit 11 and the imaging operation of the imaging unit 12 based on the operation of the operator, and is acquired by the imaging unit 12. The processed image data is processed to generate a phase contrast image.

The structure 13 is connected to the stand 61 so as to be rotatable around a base 60 fixed to the floor, a stand 61 installed on the base 60, and a turning shaft 62 held in the stand 61 (in the direction of arrow a in the figure). And an arm member 63. The X-ray irradiation unit 11 is attached to one end portion of the arm member 63, and the imaging unit 12 is attached to the other end portion of the arm member 63 and is disposed to face the X-ray irradiation unit 11. Yes.

The stand 61 is installed on the base 60 so as to be capable of translational movement in a horizontal direction (in the direction of arrow b in the figure) in a plane orthogonal to the turning shaft 62, and the stand 61 has a translational drive unit for performing the translational movement. 64 is provided. The stand 61 includes a plurality of support columns 61a, and is configured to be extendable / contractable in the vertical direction (the direction of arrow c in the figure). The stand 61 is provided with an expansion / contraction driving unit 65 for performing expansion / contraction. ing. In addition, the stand 61 is provided with a rotation drive unit 66 for turning the arm member 63.

The X-ray irradiation unit 11 includes an X-ray tube 18 as an X-ray source and a collimator unit 19. The X-ray tube 18 is of an anode rotating type, and is a filament (not shown) as an electron emission source (cathode) according to a high voltage applied from the high voltage generator 16 based on the control of the X-ray source control unit 17. X-rays are generated by emitting an electron beam from the motor and causing it to collide with the rotating anode 18a rotating at a predetermined speed. The colliding portion of the rotating anode 18a with the electron beam becomes the X-ray focal point 18b. The collimator unit 19 has a movable collimator 19 a that limits the irradiation field so as to shield a portion of the X-rays emitted from the X-ray tube 18 that does not contribute to the inspection area of the subject H.

The imaging unit 12 includes an X-ray image formed by a first absorption type grating 31 for detecting an X-ray phase change (angle change) caused by the subject H and an X-ray that has passed through the first absorption type grating 31. And a detection unit 14 that detects (hereinafter, this X-ray image is referred to as a G1 image). The first absorption type grating 31 and the detection unit 14 are housed in a housing and configured as one unit.

Although the details will be described later, the X-ray imaging apparatus 1 generates a phase contrast image using a fringe scanning method. The detection unit 14 includes a second absorption grating 32 superimposed on the G1 image, An X-ray image detector 30 that detects the G1 image on which the second absorption type grating 32 is superimposed, and a scanning mechanism 33 that translates the second absorption type grating 32 at a predetermined pitch are provided. The scanning mechanism 33 is configured by an actuator such as a piezoelectric element, for example.

The X-ray imaging apparatus main body 2 is provided with a subject table 15 on which the subject H is placed. The subject table 15 is supported by a pedestal 67 installed on the base 60, and more specifically between the X-ray irradiation unit 11 and the imaging unit 12, more specifically, the X-ray irradiation unit 11 and the first absorption grating 31. It is arranged between.

The console 3 is provided with a control device 20 comprising a CPU, ROM, RAM and the like. The control device 20 includes an input device 21 through which an operator inputs an imaging instruction and the content of the instruction, an arithmetic processing unit 22 that performs arithmetic processing on the image data acquired by the imaging unit 12 and generates an X-ray image, and X A storage unit 23 for storing line images, a monitor 24 for displaying X-ray images and the like, and an interface (I / F) 25 connected to each unit of the X-ray imaging apparatus 1 are connected via a bus 26. .

As the input device 21, for example, a switch, a touch panel, a mouse, a keyboard, or the like can be used. By operating the input device 21, X-ray imaging conditions such as X-ray tube voltage and X-ray irradiation time, imaging timing, and the like. Is entered. The monitor 24 includes a liquid crystal display or the like, and displays characters such as X-ray imaging conditions and X-ray images under the control of the control device 20.

3 and 4 schematically show the configuration of the photographing unit 12.

The first absorption type grating 31 includes a substrate 31a and a plurality of X-ray shielding portions 31b (high radiation absorption portions) disposed on the substrate 31a. Similarly, the second absorption grating 32 includes a substrate 32a and a plurality of X-ray shielding portions 32b (high radiation absorption portions) arranged on the substrate 32a. The

substrates

31a and 32a are each formed of an X-ray transmissive member such as silicon, glass, resin, or the like that transmits X-rays.

The X-ray shielding part 31b is configured by a linear member extending in one direction in a plane orthogonal to the optical axis (the locus of the central X-ray) C of the X-ray bundle emitted from the X-ray irradiation part 11. As a material of each X-ray shielding part 31b, a material excellent in X-ray absorption is preferable, and for example, a heavy metal such as gold or platinum is preferable. These X-ray shielding portions 31b can be formed by a metal plating method or a vapor deposition method. Then, the X-ray shielding portion 31b is in a plane perpendicular to the optical axis C of the X-ray, the direction (hereinafter, x and direction) orthogonal to the one direction at a constant grating pitch p ₁ to each other a predetermined distance d ₁ is arranged with a gap.

The X-ray shielding part 32b is also composed of a linear member extending in one direction in a plane orthogonal to the optical axis C of the X-ray bundle emitted from the X-ray irradiation part 11. As a material of each X-ray shielding part 32b, a material having excellent X-ray absorption such as heavy metals such as gold and platinum is preferable, and these X-ray shielding parts 32b can be formed by a metal plating method or a vapor deposition method. is there. Then, X-ray shielding portion 32b, in the plane orthogonal to the optical axis C of the X-ray, at a constant grating pitch p ₂ in the direction (x-direction) orthogonal to the one direction, at a predetermined interval d ₂ from each other Are arranged.

Since the first and

second absorption gratings

31 and 32 configured as described above do not give a phase difference to incident X-rays but give an intensity difference, they are also called amplitude gratings. The slit portions (low radiation absorbing portions) that are the regions of the distances d ₁ and d ₂ may not be voids. For example, the gaps may be filled with an X-ray low absorbing material such as a polymer or a light metal. Good.

The first and

second absorption gratings

31 and 32 are configured to geometrically project the X-rays that have passed through the slit portion regardless of the presence or absence of the Talbot interference effect. Specifically, by setting the distances d ₁ and d ₂ to a value sufficiently larger than the effective wavelength of the X-rays emitted from the X-ray irradiation unit 11, most of the X-rays included in the irradiation X-rays are slit portions. It is configured to pass through while maintaining straightness without diffracting. For example, when tungsten is used as the rotary anode 18a and the tube voltage is 50 kV, the effective wavelength of X-ray is about 0.4 mm. In this case, if the distances d ₁ and d ₂ are about 1 to 10 μm, most of the X-rays are geometrically projected without being diffracted at the slit portion.

Since the X-ray radiated from the X-ray irradiation unit 11 is not a parallel beam but a cone beam with the X-ray focal point 18b as a light emitting point, the G1 image is enlarged in proportion to the distance from the X-ray focal point 18b. The The slits of the second absorption type grating 32 are determined so as to substantially match the pattern of the periodic intensity distribution of the G1 image at the position of the second absorption type grating 32. That is, when the distance from the X-ray focal point 18b to the first absorption grating 31 is L ₁ and the distance from the first absorption grating 31 to the second absorption grating 32 is L ₂ , the grating pitch p ₂ is determined so as to satisfy the relationship of the following formula (1).

In the Talbot interferometer, the distance L ₂ from the first absorption type grating 31 to the second absorption type grating 32 is limited to the Talbot interference distance determined by the grating pitch of the first diffraction grating and the X-ray wavelength. In the present X-ray imaging apparatus 2, the first absorption grating 31 projects the incident X-rays without diffracting, and the G1 image is present at all positions behind the first absorption grating 31. because similarly obtained, the distance L _2, can be set independently of the Talbot distance.

Although the imaging unit 12 does not constitute a Talbot interferometer, the Talbot interference distance Z when it is assumed that X-rays are diffracted by the first absorption type grating 31 is the grating pitch p of the first absorption type grating 31. ₁ , using the grating pitch p _{2 of} the second absorption grating 32, the X-ray wavelength (effective wavelength) λ, and a positive integer m, the following expression (2).

Expression (2) is an expression representing the Talbot interference distance when the X-ray emitted from the X-ray irradiation unit 11 is a cone beam, “Timm 、 Weitkamp, et al., Proc. Of SPIE, Vol. 6318, It is known from “2006 63180S-1”.

In the present X-ray imaging apparatus 2, the distance L ₂ is set to a value shorter than the minimum Talbot interference distance Z when m = 1 for the purpose of reducing the thickness of the imaging unit 12. That is, the distance L ₂ is set to a value in the range satisfying the following equation (3).

Incidentally, Talbot distance Z by the following equation (4) and in the case of X-rays emitted from the X-ray irradiation unit 11 can be regarded as substantially parallel beams, a distance L _2, the value of the range that satisfies the following equation (5) Set to.

However, the distance L ₂ does not necessarily satisfy the expressions (3) to (5), and deviates from the expressions (3) to (5), for example, when there is no request for thinning of the photographing unit 12. Range values can also be taken.

FIG. 5 schematically shows the configuration of the X-ray image detector 30.

The X-ray image detector 30 uses a flat panel detector (FPD: Flat Panel Detector) based on a thin film transistor (TFT: Thin Film Transistor) panel, and converts a plurality of pixels 40 by converting X-rays into electric charges. Are two-dimensionally arranged on the TFT active matrix substrate, a scanning circuit 42 for controlling the charge readout timing from the image receiver 41, the charges accumulated in each pixel 40 are read out, and the charges are converted into image data. And a data transmission circuit 44 that transmits the image data to the arithmetic processing unit 22 via the I / F 25 of the console 3. The scanning circuit 42 and each pixel 40 are connected by a scanning line 45 for each row, and the readout circuit 43 and each pixel 40 are connected by a signal line 46 for each column.

Each pixel 40 is a direct conversion type in which X-rays are directly converted into electric charges by a conversion layer (not shown) such as amorphous selenium and the converted electric charges are stored in a capacitor (not shown) connected to the lower electrode. The X-ray detection element can be configured. A TFT switch (not shown) is connected to each pixel 40, and the gate electrode of the TFT switch is connected to the scanning line 45, the source electrode is connected to the capacitor, and the drain electrode is connected to the signal line 46. When the TFT switch is turned on by the drive pulse from the scanning circuit 42, the charge accumulated in the capacitor is read out to the signal line 46.

Each pixel 40 can also be configured as an indirect conversion type X-ray detection element that uses a scintillator that converts X-rays into visible light, and converts visible light converted by the scintillator into electric charge and accumulates it. It is. Examples of the phosphor forming the scintillator include terbium activated gadolinium oxide (Gd ₂ O ₂ S: Tb) and thallium activated cesium iodide (CsI: Tl). The X-ray image detector is not limited to an FPD based on a TFT panel, and various X-ray image detectors based on a solid-state imaging device such as a CCD sensor or a CMOS sensor can also be used.

The readout circuit 43 includes an integration amplifier circuit, an A / D converter, a correction circuit, and an image memory. The integrating amplifier circuit integrates the charges output from each pixel 40 via the signal line 46, converts them into a voltage signal (image signal), and inputs it to the A / D converter. The A / D converter converts the input image signal into digital image data and inputs the digital image data to the correction circuit. The correction circuit performs offset correction, gain correction, and linearity correction on the image data, and stores the corrected image data in the image memory. As correction processing by the correction circuit, correction of X-ray exposure amount and exposure distribution (so-called shading) and pattern noise (for example, TFT) depending on the control conditions (drive frequency and readout period) of the X-ray image detector 30 are performed. Correction of the leak signal of the switch) may be included.

The X-ray image detector 30 is arranged so that the image receiving surface thereof is orthogonal to the optical axis C of the X-ray bundle. Typically, the row direction or the column direction in the array of the pixels 40 of the image receiving unit 41 is the first. The one absorption type grating 31 is arranged so as to be parallel to the grating pitch direction (x direction).

In the imaging unit 12 configured as described above, a G1 image exhibiting a periodic intensity distribution reflecting the lattice structure of the first absorption type grating 31 is formed by the X-rays that have passed through the first absorption type grating 31. The The G1 image is intensity-modulated by being superimposed on the second absorption grating 32, and the intensity-modulated G1 image is captured by the X-ray image detector 30. The pattern period p ₁ ′ of the periodic intensity distribution of the G1 image at the position of the second absorption type grating 32 and the substantial grating pitch p ₂ ′ of the second absorption type grating 32 (substantial pitch after manufacture) Is slightly different due to manufacturing errors and placement errors. Among these, the arrangement error means that the substantial pitch in the x direction changes due to the relative inclination and rotation of the first and

second absorption gratings

31 and 32 and the distance between the two changes. I mean.

Due to the minute difference between the pattern period p ₁ ′ of the G1 image and the grating pitch p ₂ ′ of the second absorption type grating 32, the image contrast on the X-ray image detector 30 includes moire fringes. The period T in the x direction of the moire fringes is expressed by the following equation (6), where L is the distance from the X-ray focal point 18b to the X-ray image detector 30.

In order to detect the moire fringes by the X-ray image detector 30, the arrangement pitch P of the pixels 40 in the x direction needs to satisfy at least the following equation (7), and further satisfies the following equation (8). Are preferred (where n is a positive integer).

Expression (7) means that the arrangement pitch P of the pixels 40 is not an integral multiple of the period T of the moire fringes, and the moire fringes can be detected in principle even when n ≧ 2. is there. Expression (8) means that the arrangement pitch P of the pixels 40 is made smaller than ½ of the period T of moire fringes.

Since the arrangement pitch P of the pixels 40 is a value determined in terms of design (generally about 100 μm) and is difficult to change, the magnitude relationship between the arrangement pitch P of the pixels 40 and the period T of moire fringes is shown. For the adjustment, the positions of the first and

second absorption gratings

31 and 32 are adjusted, and at least one of the pattern period p ₁ ′ of the G1 image and the grating pitch p ₂ ′ of the second absorption grating 32 is set. It is preferable to change the period T of moire fringes by changing one.

FIG. 6 schematically shows a method of changing the period T of moire fringes.

The change of the moire fringe period T can be performed by relatively rotating one of the first and

second absorption gratings

31 and 32 about the optical axis C. For example, a relative rotation mechanism 50 that rotates the second absorption grating 32 relative to the first absorption grating 31 relative to the optical axis C is provided. When the second absorption type grating 32 is rotated by the angle θ by the relative rotation mechanism 50, the substantial grating pitch in the x direction of the second absorption type grating 32 is changed from “p ₂ ′” → “p ₂ ′”. / Cos θ ”, and as a result, the period T of moire fringes changes (FIG. 6A).

As another example, the change in the period T of the moire fringes is performed by centering one of the first and

second absorption gratings

31 and 32 on an axis perpendicular to the optical axis C and along the y direction. This can be done by relatively inclining. For example, a relative inclination mechanism 51 that inclines the second absorption type grating 32 relative to the first absorption type grating 31 about the axis in the direction orthogonal to the optical axis C and along the y direction. Provide. When the second absorption type grating 32 is inclined by the angle α by the relative inclination mechanism 51, the substantial lattice pitch in the x direction of the second absorption type grating 32 is changed from “p ₂ ′” → “p ₂ ′”. X cos α ”, and as a result, the period T of moire fringes changes (FIG. 6B).

As another example, the period T of the moire fringes can be changed by relatively moving one of the first and

second absorption gratings

31 and 32 along the direction of the optical axis C. it can. For example, with respect to the first absorption type grating 31, the second absorption type grating 32 is changed so as to change the distance L ₂ between the first absorption type grating 31 and the second absorption type grating 32. A relative movement mechanism 52 that relatively moves along the direction of the optical axis C is provided. When the second absorption type grating 32 is moved by the movement amount δ to the optical axis C by the relative movement mechanism 52, the G1 image of the first absorption type grating 31 projected on the position of the second absorption type grating 32. The pattern period of “p ₁ ′” → “p ₁ ′ × (L ₁ + L ₂ + δ) / (L ₁ + L ₂ )” changes, and as a result, the period T of moire fringes changes (FIG. 6C). ).

In the present X-ray imaging apparatus 2, the imaging unit 12 does not constitute a Talbot interferometer as described above, and therefore the distance L ₂ can be freely set. A mechanism for changing the period T of moire fringes by changing ₂ can be suitably employed. The change mechanism (relative rotation mechanism 50, relative tilt mechanism 51, and relative movement mechanism 52) of the first and

second absorption gratings

31 and 32 for changing the period T of the moiré fringes is a piezoelectric element or the like. It can be configured by an actuator.

When the subject H is arranged on the subject table 15 arranged between the X-ray irradiation unit 11 and the first absorption type grating 31, the periodic intensity distribution of the G1 image is modulated by the subject H, and the G1 image And the moire fringes due to the superposition of the second absorption type grating 32 are also modulated. This modulation amount is proportional to the angle of the X-ray deflected by the refraction effect by the subject H. The image acquired by the X-ray image detector 30 includes a periodic pattern corresponding to moire fringes, and a phase contrast image of the subject H can be generated by analyzing the periodic pattern.

Hereinafter, a method for analyzing a periodic pattern of an image will be described.

[Analysis method 1]
FIG. 7 shows one X-ray refracted according to the phase shift distribution Φ (x) of the subject H in the x direction.

Reference numeral 55 indicates an X-ray path that goes straight when the subject H does not exist. The X-ray that travels along the path 55 passes through the first and

second absorption gratings

31 and 32 and is an X-ray image. The light enters the detector 30. Reference numeral 56 indicates an X-ray path refracted and deflected by the subject H when the subject H exists. X-rays traveling along this path 56 are shielded by the second absorption type grating 32 after passing through the first absorption type grating 31.

The phase shift distribution Φ (x) of the subject H is expressed by the following formula (9), where n (x, z) is the refractive index distribution of the subject H and z is the direction in which the X-ray travels.

The G1 image projected from the first absorptive grating 31 to the position of the second absorptive grating 32 is displaced in the x direction by an amount corresponding to the refraction angle φ due to refraction of X-rays at the subject H. become. This displacement amount Δx is approximately expressed by the following equation (10) based on the fact that the refraction angle φ of X-rays is very small.

Here, the refraction angle φ is expressed by Expression (11) using the X-ray wavelength λ and the phase shift distribution Φ (x) of the subject H.

Thus, the displacement amount Δx of the G1 image due to the refraction of X-rays at the subject H is related to the phase shift distribution Φ (x) of the subject H. This displacement amount Δx is related to the phase shift amount ψ of the signal of each pixel of the image data (the signal phase difference between when the subject H is present and when it is not present) as shown in the following equation (12). Yes.

Accordingly, by obtaining the phase shift amount ψ of the signal of each pixel, the refraction angle φ is obtained from the equation (12), and the differential amount of the phase shift distribution Φ (x) is obtained using the equation (11). By integrating with respect to x, the phase shift distribution Φ (x) of the subject H, that is, the phase contrast image of the subject H can be generated. In the X-ray imaging apparatus 1, the phase shift amount ψ is calculated using a fringe scanning method described below.

In the fringe scanning method, one of the first and second

absorption type gratings

31 and 32 is translated in a stepwise manner with respect to the other grating in the grating pitch direction of the grating, and the G1 image is periodically generated. Imaging is performed while changing the phase of the periodic arrangement of the X-ray shielding portions 32b of the second absorption type grating 32 with respect to the intensity distribution. In the present X-ray imaging apparatus 2, the second absorption type grating 32 is moved by the scanning mechanism 33 (see FIG. 1), but the first absorption type grating 31 may be moved.

As the second absorption type grating 32 moves, the moire fringes move, and the translation distance (the amount of movement in the x direction) is one period of the grating period of the second absorption type grating 32 (grating pitch p ₂ ). (Ie, when the phase change reaches 2π), the moire fringes return to their original positions. Pixel changes such moire fringes, while the grating pitch p ₂ moves the second absorption-type grating 32 by an integral fraction, captured by the X-ray image detector 30, a plurality of obtained image data A plurality of signal values are acquired every time, and the arithmetic processing unit 22 performs arithmetic processing to obtain a phase shift amount ψ of the signal of each pixel.

FIG. 8 schematically shows how the second absorption grating 32 is moved by the scanning pitch (p ₂ / M) obtained by dividing the grating pitch p ₂ into M (an integer of 2 or more).

The scanning mechanism 33 translates the second absorption type grating 32 in order to M scanning positions of k = 0, 1, 2,..., M−1. In the same figure, the initial position of the second absorption grating 32 is the same as the dark part of the G1 image at the position of the second absorption grating 32 when the subject H is not present. The initial position is k = 0, 1, 2,..., M−1.

First, at the position of k = 0, X-rays that are not refracted by the subject H mainly pass through the second absorption type grating 32. Next, when the second absorption grating 32 is moved in order of k = 1, 2,..., The X-rays passing through the second absorption grating 32 are not refracted by the subject H. While the line component decreases, the X-ray component refracted by the subject H increases. In particular, at k = M / 2, mainly only the X-rays refracted by the subject H pass through the second absorption type grating 32. When k = M / 2 is exceeded, on the contrary, the X-ray component that is refracted by the subject H decreases in the X-rays that pass through the second absorption grating 32, while the X-ray that is not refracted by the subject H. The line component increases. When images are taken by the X-ray image detector 30 at each position of k = 0, 1, 2,..., M−1, M signal values are obtained for each pixel. Hereinafter, a method of calculating the phase shift amount ψ of the signal of each pixel from the M signal values will be described.

When the signal value of each pixel when the second absorption type grating 32 is at the position k is I _k (x), I _k (x) is expressed by the following equation (13).

Here, x is a coordinate in the x direction of each pixel, A ₀ is the intensity of the incident X-ray, and _An is a value corresponding to the contrast of the signal (where n is a positive integer). ). Φ (x) represents the refraction angle φ as a function of the pixel coordinate x.

Next, using the relational expression of the following expression (14), the refraction angle φ (x) is expressed as the following expression (15).

Here, arg [] means extraction of the declination, and corresponds to the phase shift amount ψ of the signal of each pixel. Therefore, the refraction angle φ (x) is obtained by calculating the phase shift amount ψ of the signal of each pixel from the M signal values obtained for each pixel based on the equation (15).

FIG. 9 shows the signal waveform of one pixel that changes with the fringe scanning.

The M signal values obtained for each pixel periodically change with the period of the grating pitch p _{2 with} respect to the position k of the second absorption type grating 32. A broken line in FIG. 9 indicates a signal waveform when the subject H does not exist, and a solid line in FIG. 9 indicates a signal waveform when the subject H exists. The phase difference between the two waveforms corresponds to the phase shift amount ψ of the signal of each pixel.

Since the refraction angle φ (x) corresponds to the differentiation of the phase shift distribution Φ (x) as shown in the above equation (11), the refraction angle φ (x) is integrated along the x axis. A phase shift distribution Φ (x) is obtained. In the above description, the y-coordinate regarding the y-direction of the pixel is not taken into consideration. However, by performing the same calculation for each y-coordinate, a two-dimensional phase shift distribution Φ (x, y) is obtained. The above calculation is performed by the calculation processing unit 22, and the calculation processing unit 22 stores the phase shift distribution Φ (x, y) in the storage unit 23 as a phase contrast image.

[Analysis method 2]
FIG. 10 shows another example of a method for generating a phase contrast image in the X-ray imaging apparatus 1.

In the method described below, a plurality of pixels arranged in a direction intersecting with the moire fringe are analyzed as a unit, and the phase shift amount ψ of the signal of each pixel is calculated from one image data.

In the example shown in FIG. 10, the first and second

absorption type gratings

31 and 32 are arranged so as to be relatively rotated by an angle θ about the optical axis C, and the G1 image and the second absorption type grating are arranged. 32 is relatively rotated by an angle θ, and moire fringes having periodicity in the y direction are generated. Therefore, the analysis is performed with a plurality of pixels arranged in the y direction intersecting the moire fringes as one unit U. In the example shown in FIG. 10, five pixels arranged in the y direction are set as one unit U.

As described above, the G1 image is displaced in the x direction by an amount corresponding to the refraction angle φ due to the refraction of X-rays at the subject H, and the moire fringes are displaced in the y direction as the G1 image is displaced in the x direction. Will do. As shown in FIG. 11, the phase of the signal waveform formed by interpolating the signal value of the pixel group constituting the unit changes for each unit with the displacement of the moire fringes. The phase difference between the waveform of the signal waveform (FIG. 11A) when the subject H is not present and the signal waveform (FIG. 11B) when the subject H is present is the phase of the pixel signal included in the unit. This corresponds to the displacement amount ψ.

Then, the phase shift amount ψ of the signal of each pixel can be obtained by performing the above analysis for each unit while shifting the unit of the pixel group to be analyzed, for example, by one pixel in the y direction. That is, the phase shift amount ψ of the k-th pixel 40 of the signal at the row of the y direction of pixels 40, the signal value of the k-th pixel 40 as _{_{_{_{I k, [I k, I}}}} k + 1, I k + 2, I k + 3, 5 signal values of I _{k + 4} ] and 5 signal values of [I _{k + 1} , I _{k + 2} , I _{k + 3} , I _{k + 4} , I _{k + 5} ] are used as the phase shift amount ψ of the signal of the (k + 1) th pixel 40. Can be obtained respectively. Note that the above analysis can be performed for each unit while shifting the unit of the pixel group by a plurality of pixels in the y direction within a range of 5 pixels or less as one unit. For example, assuming that each pixel is shifted by two pixels, the phase shift amount ψ of the signal of each of the kth and k + 1th pixels 40 uses five signal values of [I _k , I _{k + 1} , I _{k + 2} , I _{k + 3} , I _{k + 4} ]. , K + 2 and k + 3 pixels 40 can be obtained by using five signal values of [I _{k + 2} , I _{k + 3} , I _{k + 4} , I _{k + 5} , I _{k + 6} ]. .

The refraction angle φ is obtained from the phase shift amount ψ of the signal of each pixel using the equation (12), and the differential amount of the phase shift distribution Φ (x) is obtained using the equation (11), and this is integrated with respect to x. Thus, the phase shift distribution Φ (x) of the subject H, that is, the phase contrast image of the subject H is generated.

It should be noted that the above analysis is possible if the moire fringes are resolved with 3 pixels or more arranged in the y direction as a unit. Therefore, the relationship to be satisfied between the moire period T in the y direction and the pitch P of the pixels 40 in the y direction is expressed by the following expression (16) when the G1 image is rotated, and the second absorption type grating 32 is rotated. Is given by the following equation (17).

Note that the number of pixels as a unit is preferably the number of pixels over which at least one period of the moire period T in the y direction is arranged. Here, when the moire period T in the y direction is set to be approximately M times the arrangement pitch P of the pixels 40 in the y direction (M is an integer), and the M pixels 40 are taken as one unit, the pixel 40 The signal values of the k-th pixel 40 in the y-direction array are I _k , and the M signal values of I _k to I _{k + M−1} are the first and second absorption gratings 31 in the fringe scanning method described above. , 32 is equivalent to M signal values acquired for the kth pixel 40 when the grid pitch is moved in the grid pitch direction at a scan pitch obtained by dividing the grid pitch into M pieces. .

FIG. 12 shows a modification of the analysis method of FIG.

In the example shown in FIG. 12, the grating pitch p _{2 of} the second absorption grating 32 is different from the pitch p ₁ ′ of the G1 image, and moire fringes having periodicity in the x direction are generated. In order to make the grating pitch p _{2 of} the second absorption grating 32 different from the pitch p ₁ ′ of the G1 image, for example, one of the first and

second absorption gratings

31 and 32 is set in the direction of the optical axis C. May be moved relative to each other, or the grating pitch of each of the first and

second absorption gratings

31 and 32 may be adjusted.

Then, the above analysis is performed with a plurality of pixels arranged in the x direction intersecting the moire fringes as one unit U. In the example shown in FIG. 12, four pixels arranged in the x direction are set as one unit U. However, in this example, the above analysis can be performed by resolving moire fringes using three or more pixels arranged in the x direction as one unit. The relationship to be satisfied between the period T of moire fringes in the x direction and the pitch P of the pixels 40 is expressed by the following equation (18).

FIG. 13 shows another modification of the analysis method of FIG.

In the example shown in FIG. 13, the grating pitch p ₂ of the second absorption grating 32 is different from the pitch p ₁ ′ of the G1 image, and the second absorption grating 32 rotates relative to the G1 image. Moire fringes having periodicity are generated in the direction intersecting the x direction and the y direction.

As described above, if the moire fringe is resolved with three or more pixels arranged in the direction intersecting the moire fringe as a unit, the phase shift amount ψ of the signal of the pixel included in the unit is calculated for each unit. Therefore, in this example, the analysis can be performed with a plurality of pixels of 3 pixels or more arranged in the x direction as one unit U (FIG. 13A), or a plurality of pixels of 3 pixels or more arranged in the y direction can be analyzed. Analysis can also be performed as one unit U (FIG. 13B).

FIG. 14 shows another modification of the analysis method of FIG.

In the example shown in FIG. 10, the pattern period direction (x direction) of the periodic intensity distribution of the G1 image matches the row direction or the column direction in the array of the pixels 40 in the X-ray image detector 30. In the example shown in FIG. 4, the first absorption type grating 31 and the X-ray image detector 30 are disposed so as to be relatively rotated with the optical axis C as the center, whereby the periodic intensity distribution pattern of the G1 image is obtained. Both the row direction and the column direction in the arrangement of the pixels 40 intersect with the periodic direction (x direction). Also in this case, as described above, if the moire fringe is resolved with a plurality of pixels of three or more pixels arranged in the direction intersecting the moire fringe as a unit, the signal of the pixel included in the unit for each unit. The phase shift amount ψ can be calculated.

According to the analysis method 2 described above, a phase contrast image can be generated from one periodic pattern image, and thus only one imaging is required. Therefore, the first absorption type grating 31 or the second between multiple imagings. Therefore, the movement of the absorption type grating 32 and the scanning mechanism 33 that requires high accuracy are not required. Therefore, it is possible to improve the shooting workflow and simplify the apparatus. In addition, it is possible to eliminate the deterioration in image quality caused by the movement of the subject between each photographing.

[Analysis method 3]
FIG. 15 shows another example of a method for generating a phase contrast image in the X-ray imaging apparatus 1.

In the method described below, the periodic pattern of the image corresponding to the moire fringe is analyzed using Fourier transform and inverse Fourier transform instead of the above-described fringe scanning method, and a phase contrast image is generated. It should be noted that when generating moire fringes, the apparatus configuration in the examples shown in FIGS. 10 to 14 described above can be suitably used.

The periodic pattern of the image corresponding to the moire fringes formed by superimposing the G1 image and the second absorption type grating 32 can be expressed by the following equation (19), and the equation (19) is expressed by the following equation (20). Can be rewritten.

In Expression (19), a (x, y) represents the background, b (x, y) represents the amplitude of the spatial frequency component corresponding to the basic period of the periodic pattern, and (f _0x, f _0y ) represents the period. Represents the basic period of the pattern. In the formula (20), c (x, y) is represented by the following formula (21).

Therefore, information on the refraction angle φ (x, y) can be obtained by extracting the component of c (x, y) or c ^* (x, y). Here, equation (20) becomes the following equation (22) by Fourier transform.

In the formula _{_{_{(22), F (f x}}} , f y), A (f x, f y), C (f x, f y) , respectively f (x, y), a (x, y), c It is a two-dimensional Fourier transform for (x, y).

When one-dimensional gratings such as the first and

second absorption gratings

31 and 32 are used, the spatial frequency spectrum of the image has at least A (f _x , f _y ) as shown in FIG. a peak derived _{from, C (f x, f y} ) and ^{_{C * (f x, f y}} ) 3 peaks and the peak of the spatial frequency component corresponding to the fundamental period of the periodic pattern from the results across this . A _{_(f} x, f _y) peak derived from the origin, _{_{also, C (f x, f y}} ) and ^{_{_{C * (f x, f y}}} ) peak derived from the _{_{(± f 0x, ± f 0y}} ) It occurs at the position of (combined same order).

In order to obtain the refraction angle φ (x, y) from the spatial frequency spectrum of the image, a region including the peak frequency of the spatial frequency component corresponding to the basic period of the periodic pattern is cut out so that the peak frequency overlaps the origin of the frequency space. Move the clipped area and perform inverse Fourier transform. Then, the refraction angle φ (x, y) can be obtained from the complex number information obtained by the inverse Fourier transform. The method for generating the phase contrast image from the refraction angle φ (x, y) is the same as the above-described fringe scanning method.

According to the analysis method 3 described above, a phase contrast image can be generated from one periodic pattern image, and thus only one imaging is required. Therefore, the first absorption type grating 31 or the second between multiple imagings. Therefore, the movement of the absorption type grating 32 and the scanning mechanism 33 that requires high accuracy are not required. Therefore, it is possible to improve the shooting workflow and simplify the apparatus. In addition, it is possible to eliminate the deterioration in image quality caused by the movement of the subject between each photographing.

In the above-described methods 1 to 3 for analyzing the periodic pattern of the image, the differential of the refraction angle φ with respect to the x direction which is the grating pitch direction of the first absorption type grating 31, that is, the differential of the phase shift distribution Φ is obtained. In the phase contrast image obtained based on the differentiation of Φ, the edge of the subject H that intersects the grating pitch direction of the first absorption grating 31 is depicted, and particularly in the grating pitch direction of the first absorption grating 31. The edge of the subject H that is substantially orthogonal is clearly depicted. That is, the arrangement of the subject H is restricted by the lattice pitch direction of the first absorption-type lattice 31. Therefore, when taking joints such as interphalangeal joints, elbow joints, and knee joints as subjects and using the cartilage parts (joint space) of these joints as the region of interest, in order to clearly depict the cartilage part, The legs are preferably arranged substantially along the lattice pitch direction (x direction) of the first absorption type lattice 31.

The joint generally has a convex joint head and a concave glenoid fossa that receives the joint head. Accordingly, in many cases, the cartilage portion that is the region of interest and the bone portion that is the non-region of interest overlap each other when viewed in the traveling direction of the X-rays that pass through the region of interest.

Therefore, in the present X-ray imaging apparatus 1, the relative incident direction of the center X-ray with respect to the subject is reduced so that the non-interesting region overlaps the region of interest of the subject H under the above-described restrictions on the placement of the subject H. To change.

FIG. 16 shows a mechanism for changing the relative incident direction of the central X-ray with respect to the subject.

In the present X-ray imaging apparatus 1, an arm member 63 that supports the X-ray irradiation unit 11 and the imaging unit 12 is connected to a stand 61 so as to be able to turn around a turning shaft 62, and the arm member 63 is turned. As a result, the incident direction of the center X-ray C with respect to the subject H placed on the subject table 15 is changed.

The turning shaft 62 of the arm member 63 is parallel to the extending direction (y direction) of the X-ray shielding part 31b of the first absorption type grating 31. In other words, the imaging unit 12 including the first absorption type grating 31 is attached to the arm member 63 so that the extending direction of the X-ray shielding part 31 b of the first absorption type grating 31 is parallel to the turning shaft 62. It has been. In such a configuration, the incident direction of the center X-ray with respect to the subject H placed on the subject table 15 is rotated in a plane orthogonal to the turning shaft 62 as the arm member 63 turns around the turning shaft 62. Note that a C-arm can be used as the arm member 63, and the plane on which the incident direction of the central X-ray is rotated can be appropriately inclined in the y direction.

FIG. 17 shows X-rays passing through the region of interest of the subject H in relation to the incident direction of the central X-ray C.

FIG. 17 shows a case where the knee joint is the subject H and the cartilage portion is the region of interest. In the knee joint, the femur and tibia constituting the knee joint are arranged in the lattice pitch direction (x direction) of the first absorptive lattice 31 on the placement surface of the substantially horizontal subject table 15 in accordance with the above-described restrictions on the placement of the subject. ).

In the illustrated example, when the cartilage part as the region of interest and the bone part (femur or tibia) as the non-interest region are overlapped, the oblique direction inclined by the angle θ around the turning axis 62 from the vertical direction is seen. The overlap is less than the overlap when viewed in the vertical direction. Therefore, when the incident direction of the central X-ray is the oblique direction of the incident angle θ, it is possible to obtain an image in which the obstruction shadow and the attenuation of the X-ray caused by the non-interest area are suppressed.

The oblique angle θ is set by, for example, setting an optimum oblique angle for each subject type in advance and inputting the subject type or the oblique angle corresponding to the subject type in the input device 21 of the console 3. Can do. Based on the oblique angle set here, the control device 20 of the console 3 controls the drive unit 66, and the arm member 63 is turned by the drive unit 66.

Further, the oblique insertion angle θ can be set based on a fluoroscopic image obtained by performing fluoroscopy while turning the arm member 63. For example, in a fluoroscopic image, it is possible to select and set an oblique insertion angle at which the cartilage portion (joint space) as a region of interest is the widest. Alternatively, in the fluoroscopic image, it is possible to select and set an oblique angle at which the intensity of the X-ray transmitted through the cartilage portion as the region of interest is highest. The selection / setting of the oblique insertion angle may be performed by, for example, an operator, or the calculation processing unit 22 of the console 3 detects a region of interest using an appropriate image processing technique such as image recognition, and automatically It can also be configured to be performed.

FIG. 18 shows a mechanism for correcting a change in the relative positional relationship between the region of interest of the subject H and the X-ray irradiation unit 11 and the imaging unit 12.

The subject H is typically arranged so that the region of interest is positioned on the optical axis C where the extension of the pivot shaft 62 of the arm member 63 intersects, but the region of interest is related to the subject thickness. May be off the extension of the. In addition, for a patient whose limb position change is difficult, it may be difficult to place the region of interest on the optical axis C. When the region of interest is located off the extension of the turning shaft 62, the relative positional relationship between the X-ray irradiating unit 11 and the imaging unit 12 and the region of interest of the subject H varies with the turning of the arm member 63. Change. Then, with the change in the relative positional relationship, for example, in the image acquired by the X-ray image detector 30, the position of the region of interest of the subject H changes, and the magnification of the region of interest changes. In the present X-ray imaging apparatus 1, the arm member 63 is translated in a plane orthogonal to the turning shaft 62 of the arm member 63 in conjunction with the turning of the arm member 63, and X-ray irradiation accompanying the turning of the arm member 63 is performed. Changes in the relative positional relationship between the unit 11 and the imaging unit 12 and the region of interest of the subject H are corrected.

In the example shown in the figure, the subject table 15 is disposed below the pivot shaft 62 in the vertical direction, and the region of interest of the subject H placed on the subject table 15 is disposed below the pivot shaft 62 in the vertical direction. And located on the optical axis C (FIG. 18A). Hereinafter, this state is referred to as an initial state.

When the arm member 63 is turned by the angle θ from the above initial state, the region of interest ROI deviates from the optical axis C. Thereby, the region of interest ROI of the subject H in the image acquired by the X-ray image detector 30 moves to the edge of the image (FIG. 18B).

For example, the translation drive unit 64 (see FIG. 2) moves the arm member 63 against the change in the relative positional relationship between the X-ray irradiation unit 11 and the imaging unit 12 and the region of interest that cause the movement of the region of interest ROI in the image. It can be corrected by moving it horizontally and repositioning the region of interest ROI on the optical axis C (FIG. 18C).

When the arm member 63 is turned by the angle θ from the initial state, the distance L _ROI from the X-ray irradiation unit 11 to the region of interest ROI of the subject H along the optical axis C is shortened. Thereby, the enlargement ratio of the region of interest of the subject H is increased (FIG. 18B).

In response to a change in the relative positional relationship between the region of interest and the X-ray irradiation unit 11 and the imaging unit 12 that cause a change in the enlargement ratio of the region of interest in the image, for example, an arm member is formed by the expansion / contraction drive unit 65 (see FIG. 2). It can be corrected by moving 63 in the vertical direction and making the distance L _ROI equal to the initial state (FIG. 18D).

By appropriately combining the horizontal and vertical translational movements of the arm member 63, a relative positional relationship between the X-ray irradiation unit 11 and the imaging unit 12 in the initial state and the region of interest is formed, and the region of interest in the image is displayed. It is also possible to correct both movement and change in magnification.

The translational movement of the arm member 63 described above is performed by the translational movement of the stand 61 in the horizontal direction and the vertical extension of the stand 61. The control device 20 of the console 3 controls the drive units 64 and 65 (see FIG. 2) according to the set oblique insertion angle θ, translates the stand 61 in the horizontal direction, and expands and contracts in the vertical direction. .

Instead of the configuration in which the arm member 63 is translated in the horizontal and vertical directions as described above, the subject table 15 is supported by the pedestal 67 so as to be able to translate in the horizontal and vertical directions, and the pedestal 67 that supports the subject table 15. Are provided with a translation drive unit for performing horizontal translation of the subject table 15 and a lift drive unit for performing translational movement in the vertical direction. As shown in FIG. 19, the subject table 15 is moved in the horizontal and vertical directions. It is good also as a structure made to translate. The refraction of the X-ray generated by passing through the subject H is only a few μrad, and the modulation of the moire fringe caused by this refraction and the phase change of the signal obtained by analyzing the moire fringe by the above-described fringe scanning method are also slight. is there. When such a slight change is measured, the relative position shift of the X-ray focal point 18b and the first and

second absorption gratings

31 and 32 affects the detection accuracy of the phase information of the subject H. By adopting a configuration in which the subject table 15 is translated in place of the arm member 63, the tilt and vibration of the X-ray irradiation unit 11 and the imaging unit 12 supported by the arm member 63 can be prevented or suppressed. Thereby, the relative position shift of the X-ray focal point 18b and the first and

second absorption gratings

31 and 32 can be prevented or suppressed, and the detection accuracy of the phase information of the subject H can be improved.

As described above, according to the X-ray imaging apparatus 1, X-rays can be incident on the subject H from an appropriate direction, and a clear phase contrast image can be obtained.

Further, since most of the X-rays are not diffracted by the first absorption type grating 31 and geometrically projected onto the second absorption type grating 32, high spatial coherence is required for the irradiated X-rays. Instead, a general X-ray source used in the medical field can be used. The distance L ₂ from the first absorption type grating 31 to the second absorption type grating 32 can be set to an arbitrary value, and the distance L ₂ is set smaller than the minimum Talbot interference distance in the Talbot interferometer. Therefore, the photographing unit 12 can be downsized (thinned). Further, almost all wavelength components of the irradiated X-ray contribute to the projection image (G1 image) from the first absorption type grating 31 and the contrast of the moire fringe is improved. Therefore, the detection sensitivity of the phase information of the subject H is detected. Can be improved.

It is assumed that the second grating is superimposed on the projected image of the first grating to generate moire fringes, and therefore the first and second gratings are both absorption type gratings. However, the present invention is not limited to this. As described above, the present invention is also useful when the Moire fringes are generated by superimposing the second grating on the Talbot interference image. Therefore, the first grating is not limited to the absorption type grating but may be a phase type grating.

In addition, although the image obtained by imaging the phase shift distribution Φ is described as being stored or displayed as a phase contrast image, the phase shift distribution Φ is obtained by integrating the differential amount of the phase shift distribution Φ obtained from the refraction angle φ. Thus, the differential amount of the refraction angle φ and the phase shift distribution Φ is also related to the X-ray phase change by the subject. Therefore, an image of the refraction angle φ and an image of the differential amount of the phase shift are also included in the phase contrast image.

Further, the above-described phase contrast image generation processing may be performed on the moire fringes obtained by photographing (pre-photographing) in the absence of a subject, and the phase contrast image may be obtained. This phase contrast image reflects, for example, phase unevenness (initial phase shift) caused by non-uniformity of the first and

second absorption gratings

31 and 32. By subtracting the phase contrast image in the pre-photographing from the phase contrast image obtained by photographing (main photographing) in the presence of the subject, a phase contrast image in which the phase unevenness of the photographing unit 12 is corrected can be obtained. .

FIG. 20 shows a configuration of another example of the radiation imaging apparatus for explaining the embodiment of the present invention, and FIG. 21 shows a control block of the radiation imaging apparatus of FIG. Elements common to the X-ray imaging apparatus 1 shown in FIG. 1 are denoted by common reference numerals, and description thereof is omitted or simplified.

The X-ray imaging apparatus 1 shown in FIG. 1 is configured to change the incident direction of the central X-ray with respect to the subject H by turning the arm member 63 that supports the X-ray irradiation unit 11 and the imaging unit 12. In the X-ray imaging apparatus 71 shown in FIG. 20, the incident direction of the central X-ray with respect to the subject H is relatively changed by tilting the subject table 15. Accordingly, in the X-ray imaging apparatus main body 72, the arm member 63 that supports the X-ray irradiation unit 11 and the imaging unit 12 is fixed in a state of being arranged along the vertical direction (z direction).

The subject table 15 is supported by a pedestal 73 installed on the base 60, and more specifically between the X-ray irradiation unit 11 and the imaging unit 12, more specifically, the X-ray irradiation unit 11 and the first absorption grating 31. It is arranged between.

The pedestal 73 supports the subject table 15 so that the subject table 15 can be tilted around the tilting shaft 74 parallel to the extending direction (y direction) of the X-ray shielding part 31 b of the first absorption grating 31. Is provided with a raising / lowering drive unit 75 for raising and lowering the subject table 15. The pedestal 73 supports the subject table 15 so as to be able to translate in the horizontal direction (x direction) in a plane orthogonal to the raising and lowering shaft 74 and to be able to move up and down in the vertical direction. A translation drive unit 76 for performing translational movement of the table 15 and an elevation drive unit 77 for performing elevation movement are provided.

Also in the present X-ray imaging apparatus 71, the relative incident direction of the center X-ray with respect to the subject is changed so that the overlap of the non-interest region with the region of interest of the subject H is reduced. In the present X-ray imaging apparatus 71, the incident direction of the central X-ray with respect to the subject H placed on the subject table 15 is changed by raising and lowering the subject table 15.

The raising / lowering axis 74 of the subject table 15 is parallel to the extending direction (y direction) of the X-ray shielding part 31b of the first absorption type grating 31. In such a configuration, the incident direction of the central X-ray with respect to the subject H placed on the subject table 15 is rotated in a plane orthogonal to the tilting shaft 74 as the subject table 15 is tilted.

FIG. 22 shows the space occupied by the apparatus main body 72 of the X-ray imaging apparatus 71 and the apparatus main body 2 of the X-ray imaging apparatus 1 described above.

When assuming use in a general hospital radiographing room, the distance L from the X-ray irradiation unit 11 to the X-ray image detector 30, that is, the length of the arm member 63 is typically 1 to 2 m. Set to On the other hand, although depending on the type of the subject H, the width W of the subject table 15 when the subject is a joint such as an interphalangeal joint, an elbow joint, or a knee joint is typically larger than the length of the arm member 63 described above. Is much smaller. Therefore, when the incident angle θ is obtained, according to the configuration (FIG. 22A) in which the subject table 15 of the X-ray imaging apparatus 71 is tilted to change the incident direction of the central X-ray, FIG. The space A occupied by the apparatus main body can be reduced as compared with the configuration (FIG. 22B) in which the arm member 63 is turned to change the incident direction of the central X-ray.

Further, according to the configuration in which the subject table 15 of the X-ray imaging apparatus 71 is tilted and the incident direction of the central X-ray is changed, the inclination of the X-ray irradiation unit 11 and the imaging unit 12 supported by the arm member 63 can be increased. Vibration can be prevented or suppressed. Thereby, the relative position shift of the X-ray focal point 18b and the first and

second absorption gratings

FIG. 23 shows a mechanism for correcting a change in the relative positional relationship between the region of interest of the subject H and the X-ray irradiation unit 11 and the imaging unit 12.

When the region of interest of the subject H is located away from the tilting axis 74 of the subject table 15, the region of interest of the subject H with the X-ray irradiating unit 11 and the imaging unit 12 as the subject table 15 is tilted. The relative positional relationship between and changes. Then, with the change in the relative positional relationship, for example, in the image acquired by the X-ray image detector 30, the position of the region of interest of the subject H changes, and the magnification of the region of interest changes. In the present X-ray imaging apparatus 71, the subject table 15 is translated in a plane orthogonal to the tilting axis 74 of the subject table 15 in conjunction with the tilting of the subject table 15, and accompanying the tilting of the subject table 15. The change in the relative positional relationship between the X-ray irradiation unit 11 and the imaging unit 12 and the region of interest of the subject H is corrected.

In the illustrated example, the region of interest ROI of the subject H placed on the placement surface on the substantially horizontal subject table 15 and the raising / lowering axis 74 of the subject table 15 are both located on the optical axis C. The raising / lowering shaft 74 is located below the region of interest ROI in the vertical direction (FIG. 23A). Hereinafter, this state is referred to as an initial state.

The region of interest ROI deviates from the optical axis C when the subject table 15 is tilted from the horizontal by an angle θ from the above initial state. Thereby, the region of interest of the subject H in the image acquired by the X-ray image detector 30 moves to the edge of the image (FIG. 23B).

In order to change the relative positional relationship between the X-ray irradiation unit 11 and the imaging unit 12 and the region of interest ROI that cause the movement of the region of interest ROI in the image, for example, the subject table 15 is moved in the horizontal direction to thereby display the region of interest ROI. Can be corrected by positioning it again on the optical axis C (FIG. 23C).

Also, when the subject table 15 is tilted from the horizontal by the angle θ from the above initial state, the distance from the X-ray irradiation unit 11 along the optical axis C to the region of interest of the subject H becomes longer. Thereby, the enlargement ratio of the region of interest ROI of the subject H is reduced (FIG. 23B).

For the change in the relative positional relationship between the X-ray irradiation unit 11 and the imaging unit 12 and the region of interest that cause a change in the enlargement ratio of the region of interest ROI in the image, for example, the subject table 15 is moved in the vertical direction, and the distance Correction can be made by making L _ROI equal to the distance in the initial state (FIG. 23D).

By appropriately combining the horizontal and vertical translational movements of the subject table 15, the relative position relationship between the region of interest and the X-ray irradiation unit 11 and the imaging unit 12 in the initial state is formed. It is also possible to correct both movement and change in magnification.

The translational movement of the subject table 15 is performed by the horizontal translational movement and the vertical movement of the pedestal 73. The control device 20 of the console 3 controls the drive units 76 and 77 (see FIG. 21) according to the set oblique insertion angle θ, and translates the subject table 15 in the horizontal and vertical directions.

In addition, although it can also be set as the structure which translates and moves the arm member 63 to a horizontal direction and a perpendicular direction like the X-ray imaging apparatus 1 mentioned above, the X-ray irradiation part 11 supported by the arm member 63, and imaging | photography. From the viewpoint of preventing or suppressing the inclination and vibration of the unit 12, it is preferable that the subject table 15 is corrected by translational movement in the horizontal direction and the vertical direction.

FIG. 24 shows the configuration of another example of the radiation imaging apparatus for explaining the embodiment of the present invention.

In the X-ray imaging apparatus 1 shown in FIG. 1 and the X-ray imaging apparatus 71 shown in FIG. 20, the first absorption type grating 31 is a one-dimensional grating in which X-ray shielding portions 31b are arranged in the x direction, and the second Similarly, the absorption type grating 32 is also assumed to be a one-dimensional grating, but the first and second

absorption type gratings

31 and 32 are not limited to the one-dimensional grating. In the example shown in FIG. 24, the first and second

absorption type gratings

31 and 32 are configured as two-dimensional gratings. One of the first and second absorption-

type gratings

31 and 32 is a two-dimensional mesh having a linear X-ray shielding portion arranged in the x direction and the y direction, respectively. The lattice is a checkered two-dimensional lattice. In the illustrated example, the first absorption type grating 31 is configured as a mesh-like two-dimensional grating, and the second absorption type grating 32 is configured as a checkered two-dimensional grating.

The pivot shaft 62 (see FIG. 1) of the arm member 63 that supports the X-ray irradiation unit 11 and the imaging unit 12 extends a plurality of X-ray shielding units 31b arranged in the x direction of the first absorption grating 31. The incident direction of the center X-ray with respect to the subject H placed on the subject table 15 is orthogonal to the pivot axis 62 as the arm member 63 pivots around the pivot axis 62. It is rotated in the plane to be

By making the first and

second absorption gratings

31 and 32 into a two-dimensional grating, the differential of the phase shift distribution Φ with respect to the two directions of the x direction and the y direction which are the grating pitch directions of the first absorption grating 31 Is obtained. As described above, in the phase contrast image obtained based on the differentiation of the phase shift distribution Φ with respect to the x direction, the edge of the subject H intersecting with the x direction is depicted, and the phase shift distribution Φ with respect to the y direction is differentiated. The edge of the subject H that intersects in the y direction is depicted in the phase contrast image obtained based on this, and a clearer phase contrast image of the subject H can be obtained by combining these two phase contrast images. .

When the first and second

absorption type gratings

31 and 32 are two-dimensional gratings, the example shown in FIG. 24 changes the incident direction of the center X-ray with respect to the subject H by turning the arm member 63. However, like the X-ray imaging apparatus 71 shown in FIG. 20, the incident direction of the central X-ray with respect to the subject H can be relatively changed by tilting the subject table 15. .

FIG. 25 shows the configuration of another example of the radiation imaging apparatus for explaining the embodiment of the present invention.

The X-ray imaging apparatus 81 shown in FIG. 25 differs from the X-ray imaging apparatus 1 shown in FIG. 1 in that the first absorption grating 31 is disposed between the X-ray irradiation unit 11 and the subject table 15. ing.

The first absorption type lattice 31 is held by the holding member 34 and is attached to the arm member 63 via the holding member 34. Since the holding member 34 is supported by the arm member 63 in a cantilever shape, it is preferable that the holding member 34 has high rigidity. For example, a member having higher rigidity than the substrate 31a of the first absorption type lattice 31 is used. preferable. Thereby, the relative position shift of the X-ray focal point 18b and the first and

second absorption gratings

In the configuration described above, the subject H is disposed between the first absorption type grating 31 and the second absorption type grating 32, but the first object formed at the position of the second absorption type grating 32. The G1 image of the absorption type grating 31 is modulated by the subject H. Similar to the X-ray imaging apparatus 1 described above, the G1 image is intensity-modulated by superimposition with the second absorption grating 32, and the intensity-modulated G1 image is captured by the X-ray image detector 30. . Therefore, also in this X-ray imaging apparatus, a phase contrast image of the subject H can be obtained based on the principle described above.

In this X-ray imaging apparatus, the subject H is irradiated with X-rays whose dose is almost halved by the shielding by the first absorption type grating 31. Therefore, the exposure amount of the subject H is set to the X-ray described above. It can be reduced to about half that of the photographing apparatus 1.

Arranging the subject between the first absorption type grating 31 and the second absorption type grating 32 can be applied to any of the X-ray imaging apparatuses described above.

FIG. 26 shows a configuration of another example of the radiation imaging apparatus for explaining the embodiment of the present invention.

26 differs from the X-ray imaging apparatus 1 shown in FIG. 1 in that the multi-slit 35 is provided in the X-ray irradiation unit 11.

In the X-ray imaging apparatus 1 described above, when the distance from the X-ray irradiation unit 11 to the X-ray image detector 30 is set to a distance (1 m to 2 m) as set in a general hospital imaging room, The blur of the G1 image due to the focal size of the X-ray focal point 18b (generally about 0.1 mm to 1 mm) is affected, and there is a possibility that the image quality of the phase contrast image is degraded. Therefore, it is conceivable to install a pinhole immediately after the X-ray focal point 18b to effectively reduce the focal spot size. However, if the aperture area of the pinhole is reduced to reduce the effective focal spot size, the X-ray focal point is reduced. Strength will fall. In the present X-ray imaging apparatus 91, in order to solve this problem, the multi-slit 35 is disposed immediately after the X-ray focal point 18b.

The multi slit 35 is an absorption type grating (third absorption type grating) having the same configuration as that of the first and second

absorption type gratings

31 and 32, and a plurality of X-ray shielding portions extending in one direction are provided in the first slit. The first and second

absorption type gratings

31 and 32 are periodically arranged in the same direction (x direction) as the

X-ray shielding portions

31b and 32b. The purpose of the multi-slit 35 is to form small focal light sources (dispersed light sources) arranged at a predetermined pitch in the x direction by partially shielding the radiation emitted from the X-ray focal point 18b.

The lattice pitch p ₃ of the multi-slit 35 needs to be set to satisfy the following formula (23), where L ₃ is the distance from the multi-slit 35 to the first absorption-type lattice 31.

Expression (23) indicates that the projection image (G1 image) of the X-rays emitted from the small-focus light sources dispersedly formed by the multi-slit 35 by the first absorption-type grating 31 is the position of the second absorption-type grating 32. This is a geometric condition for matching (overlapping).

In addition, since the position of the multi-slit 35 is substantially the X-ray focal position, the grating pitch p2 of the _second absorption grating 32 is determined so as to satisfy the relationship of the following equation (24).

As described above, in the present X-ray imaging apparatus 91, the G1 images based on the plurality of small focus light sources formed by the multi-slit 35 are superimposed, so that the image quality of the phase contrast image is reduced without reducing the X-ray intensity. Can be improved.

Note that as the analysis method of the periodic pattern of the image acquired by the X-ray image detector 30, any of the analysis methods 1 to 4 described above can be applied, but the first absorption type centering on the optical axis C is used. When the grating 31 is rotated, the multi-slit 35 can also be rotated together with the first absorption type grating 31 so that the grating pitch direction thereof coincides with the grating pitch direction of the first absorption type grating 31. preferable.

The multi slit 35 can be applied to any of the X-ray imaging apparatuses described above.

FIG. 27 shows the configuration of another example of a radiation imaging apparatus for explaining an embodiment of the present invention. Elements common to the example of the X-ray imaging apparatus shown in FIG. 1 are denoted by common reference numerals, and description thereof is omitted or simplified.

An X-ray imaging apparatus 101 shown in FIG. 27 is roughly divided into an X-ray imaging apparatus main body 102 and a console 3. The X-ray imaging apparatus main body 102 includes an X-ray irradiation unit 11, an imaging unit 112, and a subject table 15. And. The X-ray irradiation unit 11 and the imaging unit 112 are supported by the arm member 63 of the structure 13. The subject table 15 is supported by a pedestal 67.

The imaging unit 112 includes a first absorption grating 31 and an X-ray image detector 130 that detects a G1 image formed by X-rays that have passed through the first absorption grating 31. The X-ray image detector 130 includes an image receiving unit 41 in which a plurality of pixels 40 that convert and store X-rays into electric charges are two-dimensionally arranged. To be sent to the console 3.

The plurality of pixels 40 are arranged at an arrangement pitch capable of resolving the periodic intensity distribution of the G1 image formed on the image receiving surface of the X-ray image detector 130. Specifically, the arrangement pitch P of the pixels 40 is set to a pitch of 1/2 or less, preferably 1/5 or less of the pattern period p ₁ ′ of the periodic intensity distribution of the G1 image, which is generally several μm. The image receiving unit 41 in which a plurality of pixels are arranged at such a minute arrangement pitch is a CCD sensor or CMOS in which a readout circuit for reading out the electric charge accumulated in each pixel 40 is formed on a semiconductor substrate made of single crystal silicon or the like. A solid-state image sensor such as a sensor can be used as a base. In addition, as long as the image receiving portion 41 satisfies the arrangement pitch P of the pixels 40 described above, an image receiving portion 41 configured based on a TFT panel can also be used.

In the above configuration, the G1 image is formed on the X-ray image detector 130. Then, when the subject H is arranged on the subject table 15 arranged between the X-ray irradiation unit 11 and the imaging unit 112, more specifically between the X-ray irradiation unit 11 and the first absorption type grating 31. The periodic intensity distribution of the G1 image is modulated by the subject H. The image acquired by capturing the G1 image by the X-ray image detector 130 includes a periodic pattern corresponding to the periodic intensity distribution of the G1 image. By analyzing this periodic pattern, the phase contrast of the subject H is analyzed. An image can be generated.

Hereinafter, a method for analyzing a periodic pattern of an image in the X-ray imaging apparatus 101 will be described.

[Analysis method 1]
The analysis of the periodic pattern of the image can be performed, for example, by the above-described fringe scanning method. First, the G1 image projected from the first absorption-type grating 31 to the position of the X-ray image detector 130 is displaced in the x direction by an amount corresponding to the refraction angle φ due to refraction of X-rays at the subject H. It will be. This displacement amount Δx is approximately expressed by the following equation (25) based on the small X-ray refraction angle φ. L ₄ indicates the distance from the first absorption type grating 31 to the X-ray image detector 130.

Here, the refraction angle φ is expressed by Equation (26) using the X-ray wavelength λ and the phase shift distribution Φ (x) of the subject H.

Thus, the displacement amount Δx of the G1 image due to the refraction of X-rays at the subject H is related to the phase shift distribution Φ (x) of the subject H. This displacement amount Δx is related to the phase shift amount ψ of the signal of each pixel of the image data as shown in the following equation (27).

Therefore, by obtaining the phase shift amount ψ of the signal of each pixel, the refraction angle φ is obtained from the equation (27), and the differential amount of the phase shift distribution Φ (x) is obtained using the equation (26). By integrating with respect to x, the phase shift distribution Φ (x) of the subject H, that is, the phase contrast image of the subject H can be generated. The phase shift amount ψ is calculated using a fringe scanning method.

That is, the first absorption type grating 31 is translated in a stepwise manner relative to the X-ray image detector 130 in the grating pitch direction (x direction) of the grating, and the period of the pixel 40 with respect to the periodic intensity distribution of the G1 image. Shooting while relatively changing the phase of the target array. The movement of the first absorption type grating 31 can be performed by the scanning mechanism 33.

As the first absorption type grating 31 moves, the G1 image moves, and the translation distance (the amount of movement in the x direction) is one period of the grating period of the first absorption type grating 31 (grating pitch p ₁ ). (Ie, when the phase change reaches 2π), the G1 image returns to its original position. Such a change in the G1 image is picked up by the X-ray image detector 130 while moving the first absorption grating 31 by a distance of an integer of the grating pitch p ₁ , and a plurality of image data obtained. A plurality of signal values are obtained from each pixel, and the arithmetic processing unit 22 performs arithmetic processing to obtain a phase shift amount ψ of the signal of each pixel. Then, the refraction angle φ is obtained from the phase shift amount ψ of the signal of each pixel using the equation (27), and the differential amount of the phase shift distribution Φ (x) is obtained using the equation (26). By integrating, the phase shift distribution Φ (x) of the subject H, ie, the phase contrast image of the subject H is generated.

[Analysis method 2]
FIG. 28 shows another example of a method for generating a phase contrast image in the X-ray imaging apparatus 101.

A plurality of pixels arranged in a direction corresponding to the lattice pitch direction (x direction) of the first absorption type lattice 31 is used as a unit, and for each unit, signal values I of a plurality of pixels constituting the unit are interpolated. In the example shown in the figure, signal values of a plurality of pixels are interpolated by a sine curve, and at least three points are sufficient for interpolation by the sine curve, and therefore three adjacent pixels are used as a unit.

As described above, the G1 image is displaced in the x direction by an amount corresponding to the refraction angle φ due to refraction of X-rays at the subject H. Along with the displacement of the G1 image, the phase of the signal waveform formed by interpolating the signal values I of a plurality of pixels constituting the unit changes for each unit. The phase difference between the waveform of the signal waveform (FIG. 28A) when the subject H is not present and the signal waveform (FIG. 28B) when the subject H is present is the phase of the signal of the pixel included in the unit. This corresponds to the displacement amount ψ. The refraction angle φ is obtained from the phase shift amount ψ of the signal of each pixel using the equation (27) and the differential amount of the phase shift distribution Φ (x) is obtained using the equation (26), and this is integrated with respect to x. Thus, the phase shift distribution Φ (x) of the subject H, that is, the phase contrast image of the subject H is generated.

Note that the first absorption-type grating is assumed that the grating pitch direction (x-direction) of the first absorption-type grating 31 coincides with the row direction or the column direction in the arrangement of the pixels 40 in the X-ray image detector 130. Although the description has been made assuming that three pixels arranged in the lattice pitch direction of 31, that is, the pattern periodic direction of the periodic intensity distribution of the G1 image, are taken as one unit, the direction intersecting the periodic intensity distribution pattern of the G1 image If the periodic intensity distribution of the G1 image is resolved with a plurality of pixels of three or more arranged in a unit as a unit, the phase shift amount ψ of the signal of the pixel included in the unit can be calculated for each unit. Therefore, the first absorption grating 31 and the X-ray image detector 130 are arranged such that the row direction and the column direction in the arrangement of the pixels 40 intersect with the pattern period direction of the periodic intensity distribution of the G1 image. However, the optical axis C may be relatively rotated around the optical axis C.

[Analysis method 3]
Similarly to the X-ray imaging apparatus 1 described above, the X-ray imaging apparatus 101 can also generate a phase contrast image by analyzing a periodic pattern of an image using Fourier transform and inverse Fourier transform. In this case, the periodic pattern of the image corresponds to moire fringes formed by superimposing the G1 image and the second absorption grating 32 in the X-ray imaging apparatus 1. 101 corresponds to the periodic intensity distribution of the G1 image.

As described above, according to the X-ray imaging apparatus 101, the periodic intensity distribution of the G1 image is detected using a detector having a pixel pitch smaller than the period of the periodic intensity distribution of the G1 image, and this is analyzed to obtain phase information. Since the pixel pitch is small, the spatial resolution is excellent. Since the second absorption grating 32 is not interposed, the accuracy of the phase information can be improved.

The X-ray imaging apparatus 101 is configured to change the incident direction of the central X-ray with respect to the subject H by turning the arm member 63. However, like the X-ray imaging apparatus 71 shown in FIG. It is also possible to configure such that the incident direction of the center X-ray with respect to the subject H is relatively changed by raising and lowering the subject table 15.

In the X-ray imaging apparatus 101, the first absorption type grating 31 can be configured as a two-dimensional grating.

Further, in the X-ray imaging apparatus 101, the first absorption type grating 31 can be disposed between the X-ray irradiation unit 11 and the subject table 15.

Also in the X-ray imaging apparatus 101, the multi-slit 35 (see FIG. 26) described above can be provided in the X-ray irradiation unit 11. In this case, the multi-slit lattice pitch p ₃ is set to satisfy the following expression (28), where L ₃ is the distance from the multi-slit to the first absorption-type lattice 31.

Expression (28) indicates that the projection image (G1 image) of the X-rays emitted from the small focus light sources dispersedly formed by the multi-slits by the first absorption grating 31 coincides with the position of the X-ray image detector 130. It is a geometrical condition for doing (overlapping).

FIG. 29 shows the configuration of another example of the radiation imaging apparatus for explaining the embodiment of the present invention. Note that elements common to the above-described

X-ray imaging apparatuses

1 and 101 are denoted by common reference numerals, and description thereof is omitted or simplified.

An X-ray imaging apparatus 201 shown in FIG. 29 is roughly divided into an X-ray imaging apparatus main body 202 and a console 3. The X-ray imaging apparatus main body 202 includes an X-ray irradiation unit 11, an imaging unit 212, and a subject table 15. And. The X-ray irradiation unit 11 and the imaging unit 112 are supported by the arm member 63 of the structure 13. The subject table 15 is supported by a pedestal 67.

The imaging unit 212 includes a first absorption grating 31 and an X-ray image detector 230 that detects a G1 image formed by X-rays that have passed through the first absorption grating 31. The X-ray image detector 230 includes an image receiving unit 41 in which a plurality of pixels 40 that convert X-rays into electric charges and store them are two-dimensionally arranged, read out the electric charges accumulated in each pixel 40, and read them out as image data. To be sent to the console 3.

The plurality of pixels 40 are arranged at an arrangement pitch that causes moiré in relation to the period of the periodic intensity distribution of the G1 image formed on the image receiving surface of the X-ray image detector 230. Specifically, the arrangement pitch P of the pixels 40 is an arrangement pitch that is substantially the same as the period of the periodic intensity distribution of the G1 image, which is generally several μm.

In the above configuration, there is a slight difference between the pattern period p ₁ ′ in the x direction of the periodic intensity distribution of the G1 image and the arrangement pitch P in the x direction of the pixels 40 (not limited to design differences, but manufacturing errors and arrangement errors). If there is a difference due to this, moire occurs in the image acquired by the X-ray image detector 230. The X-ray imaging apparatus 201 generates a phase contrast image of the subject H by analyzing the moire.

Since the arrangement pitch P of the pixels 40 is a value determined by design and is difficult to change, the relationship between the arrangement pitch P of the pixels 40 and the pattern period p ₁ ′ of the G1 image in generating moire. Is adjusted by adjusting the position of the first absorption grating 31 and changing the pattern period p ₁ ′ of the G1 image. As a mechanism for changing the pattern period of the G1 image, a mechanism similar to the above-described relative rotation mechanism 50, relative tilt mechanism 51, and relative movement mechanism 52 (all refer to FIG. 6) can be used.

In the relationship between the arrangement pitch P of the pixels 40 and the pattern period p ₁ ′ of the G1 image, the period T in the x direction of moire generated in the image is expressed by the following equation (29).

When the subject H is arranged between the X-ray irradiation unit 11 and the absorption grating 31, moire generated in an image acquired by the X-ray image detector 230 is modulated by the subject H. This modulation amount is proportional to the angle of the X-ray deflected by the refraction effect by the subject H. Therefore, a phase contrast image of the subject H can be generated by analyzing this moire.

Hereinafter, an analysis method of image moire in the X-ray imaging apparatus 201 will be described.

[Analysis method 1]
The analysis of the periodic pattern of the image can be performed, for example, by the above-described fringe scanning method. First, the G1 image projected from the first absorption type grating 31 to the position of the X-ray image detector 230 is displaced in the x direction by an amount corresponding to the refraction angle φ due to refraction of X-rays at the subject H. It will be. This displacement amount Δx is related to the phase shift distribution Φ (x) of the subject H, as is apparent from the above equations (25) and (26).

As the G1 image is displaced in the x direction, the moire is also displaced in the x direction. When the displacement amount Δx of the G1 image reaches the period p ₁ ′, the moire returns to the original state. Is expressed by the following equation (30) using the displacement amount Δx of the G1 image.

The displacement amount ΔX is related to the phase shift amount ψ of the signal of each pixel of the image data as shown in the following equation (31).

That is, the first absorption type grating 31 is translated in a stepwise manner relative to the X-ray image detector 230 in the grating pitch direction (x direction) of the grating, and the period of the pixel 40 with respect to the periodic intensity distribution of the G1 image. Shooting while relatively changing the phase of the target array. The movement of the first absorption type grating 31 can be performed by the scanning mechanism 33.

As the first absorption type grating 31 moves, the moire also moves, and the translation distance (amount of movement in the x direction) reaches one period (grating pitch p ₁ ) of the grating period of the first absorption type grating 31. Then (ie, when the phase change reaches 2π), the moire returns to the original state. Such movement of the absorption-type grating 31 with a change in the moiré taken while one scan pitch of an integral fraction of the grating pitch p _1, a plurality of signal values from a plurality of image data for each pixel obtained The phase shift amount ψ of the signal of each pixel is obtained by obtaining and performing arithmetic processing in the arithmetic processing unit 22. Then, the refraction angle φ is obtained from the phase shift amount ψ of the signal of each pixel using the equation (27), and the differential amount of the phase shift distribution Φ (x) is obtained using the equation (26). By integrating, the phase shift distribution Φ (x) of the subject H, ie, the phase contrast image of the subject H is generated.

In the above-described moire analysis by the fringe scanning method, the moire moves as a whole with the relative movement between the first absorption grating 31 and the X-ray image detector 230, so the moire cycle is set to the image size. It is applicable even if it is longer than that.

[Analysis method 2]
FIG. 30 shows another example of a method for generating a phase contrast image in the X-ray imaging apparatus 201.

A plurality of pixels adjacent to each other in the direction corresponding to the lattice pitch direction (x direction) of the first absorption type lattice 31 is used as a unit, and the signal value I of the plurality of pixels constituting the unit is interpolated for each unit. In the illustrated example, signal values of a plurality of pixels are interpolated by a sine curve, and at least three points are sufficient for interpolation by the sine curve, and therefore, three adjacent pixels are used as a unit. When the pattern period p ₁ ′ of the G1 image and the arrangement pitch P of the pixels 40 are in a relationship that causes moiré in the image, the signal values I of a plurality of pixels constituting the unit are interpolated for each unit. The period of the signal waveform is a moire period T.

As described above, the G1 image is displaced in the x direction by an amount corresponding to the refraction angle φ due to refraction of X-rays at the subject H. When the G1 image is displaced by Δx in the x direction, the moire is also displaced by ΔX in the x direction, and the phase of the signal waveform changes. The phase difference between the waveform of the signal waveform (FIG. 30A) when the subject H is not present and the signal waveform (FIG. 30B) when the subject H is present is the phase of the signal of the pixel included in the unit. This corresponds to the displacement amount ψ. The refraction angle φ is obtained from the phase shift amount ψ of the signal of each pixel using the equation (27) and the differential amount of the phase shift distribution Φ (x) is obtained using the equation (26), and this is integrated with respect to x. Thus, the phase shift distribution Φ (x) of the subject H, that is, the phase contrast image of the subject H is generated.

Note that the first absorption-type grating is assumed that the grating pitch direction (x-direction) of the first absorption-type grating 31 coincides with the row direction or the column direction in the arrangement of the pixels 40 in the X-ray image detector 230. Although the description has been made assuming that the three pixels arranged in the lattice pitch direction of 31, that is, the pattern period direction of the periodic intensity distribution of the G1 image, are taken as one unit, with respect to the pattern period direction of the periodic intensity distribution of the G1 image, The first absorption type grating 31 and the X-ray image detector 230 are relatively rotated around the optical axis C so that both the row direction and the column direction in the arrangement of the pixels 40 intersect. May be.

[Analysis method 3]
Similarly to the X-ray imaging apparatus 101 described above, the present X-ray imaging apparatus 201 can also analyze the periodic pattern of an image using Fourier transform and inverse Fourier transform to generate a phase contrast image. In this case, the periodic pattern of the image corresponds to the periodic intensity distribution of the G1 image in the X-ray imaging apparatus 101 described above, but the periodic intensity distribution of the G1 image and the X in the X-ray imaging apparatus 201 described above. This corresponds to moire caused by interference with the periodic arrangement of the pixels 40 of the line image detector 230.

As described above, according to the X-ray imaging apparatus 201, it is acquired by the X-ray image detector 230 due to interference between the pattern period p ₁ ′ of the G1 image and the pixel pitch P of the X-ray image detector 230. A moire is generated in the image, and a phase contrast image is generated based on the moire modulation caused by the subject H. In general, the S / N tends to decrease as the pixel 40 in the X-ray image detector 230 becomes smaller. However, the pixel arrangement pitch in the X-ray image detector is such that the periodic intensity distribution of a fine G1 image can be detected. There is no need to reduce the S / N, and the S / N can be secured to improve the accuracy of the phase information.

The X-ray imaging apparatus 201 has a configuration in which the incident direction of the central X-ray with respect to the subject H is changed by turning the arm member 63, but like the X-ray imaging apparatus 71 shown in FIG. It is also possible to configure such that the incident direction of the center X-ray with respect to the subject H is relatively changed by raising and lowering the subject table 15.

Also in the X-ray imaging apparatus 201, the first absorption type grating 31 can be configured as a two-dimensional grating.

Also in the X-ray imaging apparatus 201, the first absorption type grating 31 can be disposed between the X-ray irradiation unit 11 and the subject table 15.

Also in the X-ray imaging apparatus 201, similarly to the X-ray imaging apparatus 101 described above, the multi-slit 35 (see FIG. 26) can be provided in the X-ray irradiation unit 11.

FIG. 31 shows a configuration of another example of the radiation imaging apparatus for explaining the embodiment of the present invention. Elements common to the X-ray imaging apparatus 1 shown in FIG. 1 are denoted by common reference numerals, and description thereof is omitted or simplified.

31 differs from the X-ray imaging apparatus 1 shown in FIG. 1 in that the subject table 15 is separated from the X-ray imaging apparatus main body 2. The X-ray imaging apparatus 301 shown in FIG.

The subject table 15 is attached to an appropriate pedestal. The pedestal is configured separately from the structure 13 that supports the X-ray irradiation unit 11 and the imaging unit 12 (the first and second

absorption type gratings

31 and 32 and the X-ray image detector 30). The table 15 is separated from the X-ray imaging apparatus main body 2.

According to the above configuration, the X-ray irradiating unit 11 and the imaging unit are affected by the impact when the subject H is placed on the subject table 15 and the vibration caused by the movement (body movement) of the subject H during or during imaging. As described above, the displacement of the relative positions of the X-ray focal point 18b and the first and

second absorption gratings

31 and 32 can be prevented or suppressed. Thus, the detection accuracy of the phase information of the subject H can be improved.

The configuration in which the subject table 15 is separated from the X-ray imaging apparatus main body 2 can be applied to any of the X-ray imaging apparatuses described above.

FIG. 32 shows a configuration of another example of the radiation imaging apparatus for explaining the embodiment of the present invention. In addition, description is abbreviate | omitted or simplified by attaching | subjecting a common code | symbol to the element which is common in the X-ray imaging apparatus 1 mentioned above.

The above-described X-ray imaging apparatus 1 irradiates X-rays substantially vertically downward, and basically performs imaging in a supine position or a sitting position when imaging a human, as shown in FIG. The X-ray imaging apparatus 401 is different from the X-ray imaging apparatus 1 described above in that X-rays are irradiated in a substantially horizontal direction, and performs imaging in a standing position when imaging a human.

In the X-ray imaging apparatus 401, the X-ray irradiation unit 11, the first absorption type grating 31, the second absorption type grating 32, and the X-ray image detector 30 are arranged in this order in the substantially horizontal direction, and the arm member 63. The subject table 15 is provided such that the subject H placed thereon is disposed between the X-ray irradiation unit 11 and the first absorption type grating 31.

The subject table 15 is vertically below the extension of the pivot shaft 62 of the arm member 63, and the region of interest of the subject H placed thereon (the cartilaginous portion of the knee joint in the illustrated example) extends the pivot shaft 62. It is preferable to arrange at a height located above. According to this, the region of interest does not deviate from the irradiation field even when the arm member 63 rotates, and the enlargement ratio does not change.

In addition, when the region of interest of the subject H deviates from the irradiation field with the turning of the arm member 63 and the enlargement ratio changes, the arm member 63 and the subject table 15 are moved horizontally and in conjunction with the turning of the arm member 63. You may make it translate in a perpendicular direction.

In imaging of knee joints, there is a high need for imaging in a state where a load is applied in an upright position, and thus a standing type apparatus (horizontal apparatus) such as the X-ray imaging apparatus 401 is preferable.

The X-ray imaging apparatus 401 is configured to change the incident direction of the central X-ray with respect to the subject H by turning the arm member 63. However, like the X-ray imaging apparatus 71 shown in FIG. It is also possible to configure such that the incident direction of the center X-ray with respect to the subject H is relatively changed by raising and lowering the subject table 15.

Also in this X-ray imaging apparatus 401, the first absorption type grating 31 can be configured as a two-dimensional grating.

Also in the present X-ray imaging apparatus 401, the first absorption grating 31 can be disposed between the X-ray irradiation unit 11 and the subject H placed on the subject table 15.

Also in the X-ray imaging apparatus 401, similarly to the X-ray imaging apparatus 101 described above, the multi-slit 35 (see FIG. 26) can be provided in the X-ray irradiation unit 11.

Also in the present X-ray imaging apparatus 401, as in the X-ray imaging apparatus 201 described above, the second absorption grating 32 is omitted, and the interference between the pattern period of the G1 image and the pixel pitch of the X-ray image detector. The phase contrast image can be generated based on the modulation caused by the moiré subject H generated by the above.

Also in the X-ray imaging apparatus 401, the subject table 15 can be separated from the X-ray imaging apparatus main body.

In the above description, the case where general X-rays are used as radiation has been described, but the present invention is not limited to X-rays, and radiation other than X-rays such as α-rays and γ-rays can also be used. It is.

In the present invention, the rotation plane of the relative incident direction of the center X-ray with respect to the subject is not limited to a plane completely parallel to the grating pitch direction of the first absorption type grating 31, and includes a substantially parallel plane. For example, in the example shown in FIGS. 10 and 13, when the first absorption type grating 31 is rotated around the optical axis C, the center X-ray associated with the turning of the arm member 63 or the tilting of the subject table 15 The rotation plane in the relative incident direction is inclined by the rotation angle θ of the first absorption grating 31 with respect to the grating pitch direction of the first absorption grating 31, but the rotation angle θ of the first absorption grating 31. Is actually a minute angle of about 1 to 2 degrees or less, and the rotation plane of the relative incident direction of the center X-ray is substantially parallel to the grating pitch direction of the first absorption type grating 31.

As for the X-ray imaging apparatus other than the X-ray imaging apparatus 1 described above, the first grating is not limited to the absorption type grating but can be a phase-type grating as in the X-ray imaging apparatus 1.

As described above, the present specification discloses the following radiographic apparatuses (1) to (21), and includes an oblique insertion mechanism that allows X-rays to enter the subject from an appropriate direction. Accordingly, it is possible to suppress obstacle shadows and X-ray attenuation caused by the non-interest region, and a clear phase contrast image can be obtained.

(1) A radiation irradiation unit, a first grating having a periodic structure in at least one direction, and a detection unit including a radiation image detector, wherein the first grating passes through the first grating. A radiation image including a periodic intensity distribution is formed by the radiation to be generated, and the detection unit detects the radiation image to acquire radiation image data, and a relative incident direction of the central radiation with respect to the subject passes through the subject. A radiation imaging apparatus configured to be changeable in a plane parallel to a periodic direction of the periodic structure of the first grating.
(2) The radiographic apparatus according to (1), wherein the radiation irradiating unit, the first grating, a structural unit supporting the detecting unit, and the structural unit around a rotation axis orthogonal to the plane. A radiation imaging apparatus comprising: a rotation driving unit that rotates the rotation unit.
(3) The radiographic apparatus according to (2), further including a translational drive unit that translates the structural unit in the plane.
(4) The radiographic apparatus according to (3), wherein the translation drive unit is controlled so that the central radiation passes through the same region of the subject before and after the change of the incident direction of the central radiation. Radiation imaging apparatus comprising a unit.
(5) The radiographic apparatus according to (3) or (4), wherein the distance from the radiation irradiation unit to the subject along the central radiation is the same before and after the change of the incident direction of the central radiation. A radiation imaging apparatus comprising a control unit that controls the translation drive unit.
(6) The radiation imaging apparatus according to (2), wherein the rotation axis passes through the arrangement position of the subject.
(7) The radiographic apparatus according to (1), wherein the radiographic apparatus is disposed between the radiation irradiating unit and the first grating or between the first grating and the detecting unit, and the subject is placed thereon A radiation imaging apparatus comprising: a subject table to be moved; and a tilt drive unit that tilts the subject table about a tilt axis orthogonal to the plane.
(8) The radiation imaging apparatus according to (7), further including a translation drive unit that translates the subject table in the plane.
(9) The radiographic apparatus according to (8), wherein the translation drive unit is controlled so that the central radiation passes through the same region of the subject before and after the change of the incident direction of the central radiation. Radiation imaging apparatus comprising a unit.
(10) In the radiographic apparatus according to (8) or (9), the distance from the radiation irradiation unit to the subject along the central radiation is the same before and after the change of the incident direction of the central radiation. A radiation imaging apparatus comprising a control unit that controls the translation drive unit.
(11) The radiation imaging apparatus according to (7), wherein the tilting shaft passes through the position where the subject is disposed.
(12) The radiographic apparatus according to any one of (1) to (11), further including a setting unit that sets an incident direction of the central radiation, wherein the setting unit changes an incident direction of the central radiation. A radiation imaging apparatus that performs fluoroscopy while setting the incident direction of the central radiation based on fluoroscopic image data acquired by the radiographic image detector.
(13) The radiographic apparatus according to (12), wherein the setting unit monitors the size of an image region corresponding to the region of interest of the subject in the fluoroscopic image data, and the size of the image region is the largest. A radiation imaging apparatus that sets the incident direction of the central radiation in a large incident direction.
(14) In the radiographic apparatus according to (12), the setting unit monitors a contrast value of an image region corresponding to the region of interest of the subject in the fluoroscopic image data, and the contrast value of the image region is the highest. A radiation imaging apparatus that sets the incident direction of the central radiation in a high incident direction.
(15) In the radiographic apparatus according to any one of (1) to (14), the first grating is an absorption grating, and the period is obtained by geometrically projecting incident radiation. Radiography apparatus for forming a radiographic image including a spatial intensity distribution.
(16) In the radiographic apparatus according to any one of (1) to (14), the first grating is an absorption type grating or a phase type grating, and causes a Talbot effect on incident radiation. A radiation imaging apparatus that forms a radiation image including a periodic intensity distribution.
(17) The radiation imaging apparatus according to any one of (1) to (16), wherein the radiation irradiating unit partially shields a radiation source and radiation emitted from the radiation source to focus the radiation source. A radiation imaging apparatus having a multi-slit for dispersion.
(18) In the radiographic apparatus according to any one of (1) to (17), the detection unit further includes a second grating superimposed on the radiographic image, and the radiographic image detector includes: A radiation imaging apparatus for detecting the radiation image on which the second grating is superimposed.
(19) The radiographic apparatus according to any one of (1) to (17), wherein the radiographic image detector has a resolution capable of resolving the periodic intensity distribution of the radiographic image, and A radiation imaging device that detects a radiation image.
(20) The radiographic apparatus according to any one of (1) to (17), wherein the radiological image detector has a resolution that causes moiré in relation to a period of the periodic intensity distribution of the radiographic image. A radiation imaging apparatus for detecting the radiation image;
(21) The radiographic apparatus according to any one of (1) to (20), wherein a phase contrast image of a subject is obtained based on at least one radiographic image data acquired by a detection unit of the radiographic apparatus. A radiation imaging apparatus including an arithmetic processing unit for generation.

According to the present invention, it is possible to provide a radiation imaging apparatus capable of obtaining a clear phase contrast image by making radiation incident on an object from an appropriate direction.

Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
This application is based on a Japanese patent application filed on December 5, 2011 (Japanese Patent Application No. 2011-266165) and a Japanese patent application filed on October 26, 2012 (Japanese Patent Application No. 2012-236817). Incorporated herein by reference.

DESCRIPTION OF SYMBOLS 1 X-ray imaging apparatus 2 X-ray imaging apparatus main body 3 Console 11 X-ray irradiation part 12 Imaging part 13 Structure 14 Detection part 15 Subject stand 18 X-ray tube 20 Control apparatus 21 Input device 22 Arithmetic processing part 23 Storage part 24 Monitor 26 Bus 30 X-ray image detector 31 First absorption type grating 31a Substrate 31b X-ray shielding part 32 Second absorption type grating 32a Substrate 32b X-ray shielding part 60 Base 61 Stand 62 Rotating shaft 63 Arm member 64 Translation drive part 65 Telescopic drive unit 66 Rotation drive unit 71 X-ray imaging device 72 X-ray imaging device main body 72 Device main body 73 Base 74 Erecting shaft 75 Elevating drive unit 76 Translation drive unit 77 Elevating drive unit

Claims

A radiation irradiation unit;
A first grating having a periodic structure in at least one direction;
A detector including a radiation image detector;
With
The first grating forms a radiation image including a periodic intensity distribution by radiation passing through the first grating;
The detection unit detects the radiographic image to acquire radiographic image data;
A radiation imaging apparatus configured such that a relative incident direction of central radiation with respect to a subject can be changed in a plane passing through the subject and parallel to a periodic direction of the periodic structure of the first grating.
The radiation imaging apparatus according to claim 1,
A structure that supports the radiation irradiator, the first grating, and the detector;
A rotation drive unit that rotates the structure unit around a rotation axis orthogonal to the plane;
A radiographic apparatus comprising:
The radiographic apparatus according to claim 2,
A radiation imaging apparatus comprising a translation drive unit that translates the structure unit in the plane.
The radiographic apparatus according to claim 3,
A radiation imaging apparatus comprising: a control unit that controls the translation drive unit so that the central radiation passes through the same region of the subject before and after the change of the incident direction of the central radiation.
The radiographic apparatus according to claim 3,
A radiation imaging apparatus comprising: a control unit that controls the translation drive unit so that a distance from the radiation irradiation unit to the subject along the central radiation is the same before and after the change of the incident direction of the central radiation.
The radiographic apparatus according to claim 2,
The rotation shaft is a radiation imaging apparatus that passes through the arrangement position of the subject.
The radiation imaging apparatus according to claim 1,
A subject table placed between the radiation irradiating unit and the first grating or between the first grating and the detecting unit and on which the subject is placed;
A tilting drive unit for tilting the subject table about a tilting axis perpendicular to the plane;
A radiographic apparatus comprising:
The radiographic apparatus according to claim 7,
A radiation imaging apparatus comprising a translation drive unit that translates the subject table in the plane.
The radiographic apparatus according to claim 8,
A radiation imaging apparatus comprising: a control unit that controls the translation drive unit so that the central radiation passes through the same region of the subject before and after the change of the incident direction of the central radiation.
The radiographic apparatus according to claim 8,
A radiation imaging apparatus comprising: a control unit that controls the translation drive unit so that a distance from the radiation irradiation unit to the subject along the central radiation is the same before and after the change of the incident direction of the central radiation.
The radiographic apparatus according to claim 7,
The raising / lowering axis is a radiation imaging apparatus passing through the arrangement position of the subject.
The radiation imaging apparatus according to claim 1,
A setting unit for setting the incident direction of the central radiation;
The radiographic apparatus that sets the incident direction of the central radiation based on fluoroscopic image data acquired by the radiological image detector by performing fluoroscopy while changing the incident direction of the central radiation.
The radiographic apparatus according to claim 12,
The setting unit monitors the size of an image region corresponding to the region of interest of the subject in the fluoroscopic image data, and sets the incident direction of the central radiation in an incident direction in which the size of the image region is the largest. apparatus.
The radiographic apparatus according to claim 12,
The setting unit monitors a contrast value of an image region corresponding to the region of interest of the subject in the fluoroscopic image data, and sets the incident direction of the central radiation to an incident direction having the highest contrast value of the image region. apparatus.
The radiation imaging apparatus according to claim 1,
The first grating is an absorption grating, and forms a radiation image including the periodic intensity distribution by geometrically projecting incident radiation.
The radiation imaging apparatus according to claim 1,
The first grating is an absorption grating or a phase grating, and generates a Talbot effect on incident radiation to form a radiation image including the periodic intensity distribution.
The radiation imaging apparatus according to claim 1,
The radiation irradiating unit includes a radiation source and a multi-slit that partially shields the radiation emitted from the radiation source and disperses the focal point.
The radiation imaging apparatus according to claim 1,
The detection unit further includes a second grating superimposed on the radiation image,
The radiation image detector is a radiation imaging apparatus that detects the radiation image on which the second grating is superimposed.
The radiation imaging apparatus according to claim 1,
The radiation image detector has a resolution capable of resolving the periodic intensity distribution of the radiation image and detects the radiation image.
The radiation imaging apparatus according to claim 1,
The radiographic image detector has a resolution for generating moire in relation to a period of the periodic intensity distribution of the radiographic image, and detects the radiographic image.
The radiation imaging apparatus according to claim 1,
A radiation imaging apparatus comprising: an arithmetic processing unit that generates a phase contrast image of a subject based on at least one radiation image data acquired by the detection unit of the radiation imaging apparatus.