WO2008038491A1

WO2008038491A1 - Radiographic device

Info

Publication number: WO2008038491A1
Application number: PCT/JP2007/066880
Authority: WO
Inventors: Shintarou Muraoka
Original assignee: Konica Minolta Medical & Graphic, Inc.
Priority date: 2006-09-28
Filing date: 2007-08-30
Publication date: 2008-04-03

Abstract

It is possible to provide a radiographic device capable of preventing image quality change caused by imaging magnification by controlling the radiation dose applied from a radiation source in accordance with the imaging magnification set by magnification setting means.

Description

Specification

Radiation imaging equipment

Technical field

TECHNICAL FIELD [0001] The present invention relates to a radiographic image capturing apparatus, and more particularly, to a radiographic image capturing apparatus capable of capturing a phase contrast image.

Background art

[0002] Generally, a radiographic imaging apparatus that uses an action of radiation passing through a substance is widely used for medical diagnostic imaging, non-destructive inspection, and the like. In particular, for radiographic imaging devices used for mammography, a method has been used in which a subject is fixed on a subject table integrated with a radiographic image detector. However, this method does not increase the contrast of the image enough to capture the actual size of the subject, and medical imaging is used to interpret the fine structure of a specific part such as a diseased part of the breast. There was a problem that the image was not clear enough for the device.

[0003] Therefore, in recent years, a radiographic image capturing apparatus that captures a phase contrast image has been proposed. A phase contrast image is also called a refraction contrast image. Previously, it was obtained by imaging with monochromatic parallel radiation obtained from a radiation source such as SPring-8, or with a microfocus radiation source having a focal spot size of about 10 m). Although it has been said that it can be obtained, it has been found that it can also be obtained with a radiation source (small focal radiation source with a focal size of 30 to 300 (11 m)) used in general medical facilities.

[0004] For example, Patent Document 1 discloses a technique for obtaining an edge enhancement effect without using synchrotron radiation that requires a large device or an X-ray light source having a small X-ray focal point size until it can be regarded as a point light source. Are listed. According to this patent document 1, when the X-ray focal spot size D is 30 m) or more, the distance R1 from the X-ray tube as a radiation source to the subject is Rl≥ (D-7) / 200 (m). It is shown that an edge-enhanced image can be obtained when the distance R2 between the subject and the X-ray detector is 0.15 (m) or more. At this time, the magnification ratio = (R1 + R2) / R1. Here, the enlargement ratio is the ratio of the size of the subject in the radiographic image to the actual size of the subject, and is synonymous with the imaging magnification. [0005] By the way, when changing the enlargement ratio (that is, imaging magnification) in a conventional radiographic imaging apparatus that performs phase contrast imaging, for example, as described in Patent Document 2, the above-described R1 is fixed. This is done by changing R2.

Patent Document 1: JP 2001-91479 A

Patent Document 2: Japanese Patent Laid-Open No. 2004-173879

Disclosure of the invention

Problems to be solved by the invention

FIG. 9 shows a detector holding unit 12 that holds a radiation source 6, a subject H, and a radiation image detector (X-ray detector) when a breast is imaged by phase contrast imaging in a conventional radiographic imaging device. (The numbers in the figure indicate the magnification), and schematically shows the positional relationship between the floor and ceiling in the imaging room where phase contrast imaging is performed. In the conventional radiographic imaging apparatus, the distance R1 between the radiation source 6 and the subject H is fixed, so that the radiation source 6 is positioned vertically upward by the distance R1 of the subject H (Fig. 9 ( a)). That is, the top position of the radiation source 6 is increased according to the subject position (when the subject H is a breast, the height from the floor surface to the subject H). On the other hand, there is a limit to the space in the shooting room. Therefore, imaging cannot be performed when the height of the breast that is subject H is high, such as a patient with a high height, and the distance between subject H and the ceiling is less than R1 (FIG. 9 (b)). Further, the position of the detector holding unit 12 is determined based on the position of the subject H and the enlargement ratio, and R2 increases as the enlargement ratio increases. For this reason, there are cases where the enlargement ratio that can be photographed is limited, such as a patient whose height is low and the position of the breast that is subject H is low (Fig. 9 (c)).

[0007] Therefore, in order to reduce the restriction on performing the phase contrast imaging as described above, R1 + R2, that is, the distance between the radiation source 6 and the detector holding unit 12 is constant, and according to the enlargement ratio. The applicant of the present application has applied for a radiographic imaging device that adjusts the relative distance between the radiation source 6 and the detector holder 12 with respect to the subject H.

However, if the relative distance between the radiation source 6 and the detector holding unit 12 with respect to the subject H is adjusted according to the magnification rate, the distance R1 between the radiation source 6 and the subject H changes depending on the magnification rate, so that the subject H is reached. However, depending on the magnification rate, the image quality changes, and it is impossible to maintain a constant image quality. [0009] An object of the present invention is to prevent the image quality from changing depending on the imaging magnification in the radiographic image capturing apparatus.

Means for solving the problem

The object of the present invention can be achieved by the following configurations.

[0011] 1. a radiation source for irradiating a subject;

Detector holding means for holding a radiation image detector for detecting radiation from the radiation source transmitted through the subject;

An object table disposed between the radiation source and the detector holding means and holding the subject;

Magnification setting means for setting the shooting magnification;

Adjusting means for adjusting a relative distance between the subject table and the detector holding means according to the set photographing magnification;

A radiographic imaging apparatus comprising: a control means for detecting an irradiation amount from the radiation source and controlling the radiation source!

The control means variably controls the radiation dose emitted from the radiation source in accordance with the imaging magnification set by the magnification setting means.

Yes

[0012] 2. The focal size D of the radiation source is 30 (m) or more,

The distance R1 from the radiation source to the subject is Rl≥ (D-7) / 200 (m),

2. The radiographic imaging apparatus according to 1, wherein a distance L (m) from the radiation source to the detector holding means is 0.95 (m) to 1.14 (m).

[0013] 3. The radiographic imaging apparatus according to 1 or 2, wherein a distance R2 from the subject to the detector holding means is R2≥0.15 (m).

[0014] 4. Radiation source power distance Rl to the subject, distance R2 from the subject to the detector holding means,

When the distance L (= R1 + R2) (m) from the radiation source to the detector holding means is set, the distance L is constant, the position of the subject is relatively variable, and the imaging magnification (= L / Rl) is changed. Place.

[0015] 5. The radiation according to 4, wherein the control means controls the radiation dose from the radiation source so that the radiation dose reaching the subject is constant even when the imaging magnification is changed. Image shooting device.

[0016] 6. The radiographic imaging device according to 4 or 5, wherein the control means increases the amount of irradiation from the radiation source as the imaging magnification decreases!

The invention's effect

[0017] According to the present invention, the radiation that can prevent the image quality from changing according to the imaging magnification by variably controlling the radiation dose emitted from the radiation source according to the imaging magnification set by the magnification setting means. An image capturing device can be provided.

Brief Description of Drawings

FIG. 1 is a diagram showing a configuration example of a breast image photographing apparatus 1 according to the present invention.

FIG. 2 is a diagram schematically showing the internal configuration of the imaging device main body 2 of the breast image capturing device 1

Yes

FIG. 3 is a block diagram showing a functional configuration of breast image capturing apparatus 1.

FIG. 4 is a diagram for explaining the principle of phase contrast imaging.

[Fig. 5] Radiation source 6 and subject when breast image is taken with breast imaging device 1

It is a figure which shows typically the positional relationship of H, the detector holding | maintenance part 12, a floor surface, and a ceiling.

[FIG. 6] The results of visibility evaluation of each captured image when the distance L (R1 + R2) between the radiation source 6 and the detector holding unit 12 and the magnification rate are changed in the mammography apparatus 1 are shown. FIG.

[Figure 7] (a) is a diagram schematically showing the relationship between R1 and R2 at each enlargement ratio (1.75 times, 1.46 times, 2.63 times) when Rl + R2 = 1140. (B) shows that Rl + R2 = 1140, and R when radiographing was performed at each magnification with the same radiation dose as the radiation irradiation stop condition.

It is a figure which shows the visibility evaluation result of I, R2, average mammary gland dose, and image quality.

FIG. 8 is a flowchart showing an irradiation dose control process executed by the control device 16.

[Fig. 9] When a mammogram is taken with a conventional radiographic apparatus for mammography. FIG. 6 is a diagram schematically showing the positional relationship between the radiation source 6, the subject H, the detector holding unit 12, the floor surface, and the ceiling.

Explanation of symbols

[0019] 1 Breast imaging apparatus

2 Camera unit

3 Support base

4 Support shaft

6 Radiation source

7 Aperture device

8 Holding member

9 Main unit

10 Subject table

11 Compression plate

12 Detector holder

13 Radiation dose detector

14 Operating device

14a input device

14b display

15 Power supply

16 Control unit

17 Drive unit

18 Position detector

19 Drive unit

20 Nox

BEST MODE FOR CARRYING OUT THE INVENTION

[0020] (Breast imaging device 1)

The breast image capturing apparatus 1 according to the present embodiment is a radiographic image capturing apparatus that performs phase contrast imaging. Hereinafter, the configuration of the breast imaging apparatus 1 will be described with reference to the drawings. FIGS. 1 and 2 show a configuration example of the mammography apparatus 1. FIG. 1 is a diagram illustrating an example of an external configuration of the breast imaging apparatus 1, and FIG. 2 is a diagram schematically illustrating an internal configuration of the imaging apparatus main unit 2 of the breast imaging apparatus 1 illustrated in FIG. . In FIG. 2, the radiation dose detection unit 13, the operation device 14, the power supply unit 15, the drive device 17 and the drive device 19 are connected to the control device 16 (shown in FIG. 3) of the main body 9! Power Not shown here! / As shown in FIG. 1, in the breast imaging apparatus 1, a support base 3 is provided on a main body 9 so as to be movable up and down, and a support shaft 4 provided on the support base 3 is provided on the support base 3. The imaging device main body 2 is supported via the. The support base 3 is moved up and down by being driven by a drive device 17 constituted by a motor or the like. The imaging device main body 2 can be raised and lowered by raising and lowering the support base 3 by the drive device 17, and can be rotated by the drive device 17 about the support shaft 4.

[0022] A radiation source 6 for radiating radiation is provided on the upper part of the imaging apparatus main body 2. The radiation source 6 is connected to the main body 9 via the support shaft 4 and the support base 3. Is connected to the power supply 15 The radiation source 6 is applied with a tube voltage and a tube current by the power supply unit 15. At the radiation outlet of the radiation source 6, an aperture locus of an aperture device 7 as an irradiation field adjustment device for adjusting the radiation field is provided so as to be freely opened and closed.

[0023] The radiation source 6 is preferably a rotating anode X-ray tube. In this rotating anode X-ray tube, X-rays are generated when an electron beam emitted from the cathode collides with the anode. This is incoherent (incoherent) like natural light and is not divergent X-ray but divergent light. If the electron beam continues to hit the place where the anode is fixed, the anode will be damaged by the generation of heat. Therefore, in a normal X-ray tube, the anode is rotated to prevent a decrease in the life of the anode. The electron beam is made to collide with a certain size plane of the anode, and the generated X-rays are emitted toward the subject H from the plane of the certain size anode. This plane is called a focus. The focus size D m) is the length of one side when the focus is square, the length of the short side when the focus is rectangular or polygonal, and the diameter when the focus is circular.

[0024] The larger the focal spot size D, the more radiation is irradiated. Since a radiation dose of a certain level or more is practically required to penetrate the human body, the mammography apparatus 1 can irradiate the radiation dose necessary for photographing the human body, and the focal spot size D is D≥ 30 m) Release of It is preferable to have a ray source 6!

[0025] At the lower part of the imaging apparatus main body 2, a detector holding a force set containing a stimulable phosphor sheet, for example, as a radiation image detector (radiation detector) for detecting radiation transmitted through the subject H The part 12 is attached to a position below the subject table 10 and extending substantially perpendicularly from the radiation source 6 so as to face the radiation source 6. The uppermost surface of the radiation image detector held by the detector holding unit 12 coincides with the uppermost surface of the detector holding unit 12. As shown in FIG. 2, the radiation source 6 and the detector holding unit 12 are attached to the holding member 8, and the holding member 8 allows the distance L between the radiation source 6 and the detector holding unit 12 (R1 to be described later) + R2) is maintained at a certain distance. The holding member 8 can be moved up and down by driving a driving device 19 composed of a motor or the like. The raising and lowering of the holding member 8 by the driving device 19 keeps the radiation source 6 and the detector holding unit 12 at a certain distance. While going up and down. The distance L between the radiation source 6 and the detector holding unit 12 is preferably set to L≥ 0.95 (m) from the viewpoint of visibility when outputting a photographed image as a result of intensive research! (See Figure 6).

[0026] As a radiation image detector, for example, a screen (intensifying screen) / film, an FPD (flat panel detector), or the like may be used in addition to the above-described force set containing the photostimulable phosphor sheet. Good.

[0027] At the position below the radiation source 6 and above the detector holding unit 12 in the imaging apparatus main body 2 and extending substantially perpendicularly from the radiation source 6, the subject table 10 holding the subject H also with a lower force and A compression plate 11 is provided for pressing and fixing the subject H from above. As shown in FIG. 2, the subject table 10 is attached to the holder 5 of the photographing apparatus main body 2 and moves up and down in accordance with the raising and lowering of the photographing apparatus main body 2 by the driving device 17. Thus, the height of the subject table 10 can be adjusted according to the position of the subject H (breast position). The compression plate 11 is configured to be movable up and down along a support shaft (not shown) provided in the photographing apparatus main body 2.

The position of the compression plate 11 is detected by a position detection unit 18 (shown in FIG. 3) and output to the control device 16 of the main body unit 9. As the position detector 18, a method using photometry using infrared rays, a method in which a line resistance is provided on the rail of the support shaft that slides the compression plate 11, and a position is determined from the measured resistance value can be adopted. [0029] A radiation dose detection unit 13 for detecting the radiation dose irradiated is provided on the surface of the detector holding unit 12 opposite to the surface facing the subject table 10. The radiation dose detection unit 13 is, for example, a sensor composed of a semiconductor or the like. The radiation dose detected by the radiation dose detection unit 13 is output to the control device 16 of the main body unit 9.

[0030] The main body 9 includes a control device 16 including a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). FIG. 3 shows an example of the functional configuration of the breast image capturing apparatus 1. As shown in FIG. 3, the control device 16 includes a radiation dose detection unit 13 for detecting the irradiated radiation dose, a keyboard touch panel for setting imaging conditions such as an enlargement ratio (imaging magnification) and an imaging direction, An input device 14a having a position adjustment switch (upward adjustment switch for adjusting upward, downward adjustment switch for adjusting downward) for adjusting the position of the subject table 10, and a display device 14b such as a CRT display or a liquid crystal display are provided. The operation device 14, the power source 15 that is the power source of the device, the drive device 17 that raises and lowers the imaging device main body 2 by rotating the support base 3 and rotates the imaging device main body 2, and the position of the compression plate 11 A position detection unit 18 for detection and a drive device 19 for raising and lowering the holding member 8 are connected via a bus 20. The ROM of the control device 16 stores a control program for controlling each part of the mammography apparatus 1, and the CPU controls the operation of each part of the mammography apparatus 1 in cooperation with this control program. To control phase contrast.

[0031] Here, the principle of phase contrast imaging will be described with reference to FIG. In the phase contrast imaging, a certain distance R2 is provided between the subject H and the radiation image detector 12a, and as shown in FIG. Emphasis) to obtain an image. As schematically shown in Fig. 4, the radiation from the radiation source 6 is refracted when passing through the subject H, and the radiation density Dr inside the boundary of the subject H becomes sparse, and the outside of the subject H passes through the object. Radiation density Dr increases due to overlapping with radiation that does not. In this way, the edge that is the boundary of the subject H is enhanced as an image. This is a phenomenon that arises from the difference in refractive index between subject H and air. This is an edge-enhanced image.

[0032] Further, in addition to edge enhancement at the boundary between air and the subject shown in principle in FIG. Even in the body H, the same effect can be obtained at the boundary part of the part having different refractive index. In the present invention, the boundary portion of the subject H is expressed as a boundary portion with a substance having a different refractive index with respect to radiation.

[0033] In order to obtain this edge-enhanced image with a sensitivity range and device size within the practical range in a medical facility, when the focus size D (μm) is 30 (am) or more, from the radiation source 6 to the subject H It is found that it is preferable that the distance R1 satisfies the equation Rl≥ (D—7) / 200 (m), and the distance R2 between the subject H and the radiation image detector is 0.15 m or more. Te! /, Ru (see Japanese Patent Publication No. 2001-91479). Here, D substituted in the equation Rl≥ (D—7) / 200 (m) is the numerical value when the focal spot size is expressed in terms of [I m, for example, focal spot size D = 30 m). If so, Rl≥ (30—7) / 200 = 0.115 (m).

[0034] When R1 is smaller than the distance represented by the equation Rl≥ (D-7) / 200 (m), the ability to obtain an edge-enhanced image is difficult or difficult to recognize. Also, as R1 becomes larger, the intensity of the radiation becomes weaker and more space is required.

[0035] By removing the distance R2 from the subject H to the radiation image detector by 0.15 (m) or more, the scattered radiation from the subject H that deteriorates the sharpness of the radiation image can be removed. In addition, edge enhancement is easily recognized.

[0036] When R2 is 0.15 m or more, enlargement ratio = (Rl + R2) / R1. Here, with respect to R 1, the starting point is the position of the focal point of the radiation source 6, and the location of the radiation source 6 is clearly shown in the normal commercial radiation source 6. The end point is the center line of the subject H fixed by the subject table 10 that fixes the subject position. Here, the center line of the subject H is a position equidistant from the subject table 10 and the compression plate 11. For R2, the starting point is the center line of the subject H, and the end point is the uppermost surface of the plane that receives the radiation of the radiation image detector, that is, the uppermost surface of the detector holding unit 12.

[0037] The breast image capturing device 1 has a focal size D≥30 (m) so that the effect (edge enhancement effect) as the phase contrast can be exhibited. Therefore, the distance L (in the range satisfying the distance Rl≥ (D-7) / 200 (m) from the radiation source 6 to the subject H and the distance R2≥0.15 (m) between the subject H and the radiation image detector = R1 + R2) The positions of the radiation source 6 and the detector holding unit 12 with respect to the subject table 10 are adjusted so that is constant.

That is, when shooting conditions including a shooting direction are set by the input device 14a at the time of shooting, the control device 16 sets the set shooting direction to a shooting direction that requires the rotation of the shooting device main body 2. If it is an imaging direction that requires rotation, for example, MLO (Medio- Lateral Oblique) for imaging the breast from an oblique direction force, the drive unit 17 uses the imaging device main body. 2 Rotate the entire body by a predetermined amount. When the position adjustment switch of the input device 14a is pressed, the control device 16 controls the drive device 17 accordingly to adjust the position of the object table 10. The operator adjusts the position of the compression plate 11 by an operator such as a photography engineer, and the subject H is pressed and fixed by the compression plate 11, and an enlargement factor in phase contrast photographing by the input device 14a as a magnification setting means (this embodiment In this case, the controller 16 selects the movement amount of the subject table 10 and the position information from the position detection unit 18. The position of the subject H is specified according to the position of the subject table 10 and the holding device 8 is moved up and down by controlling the driving device 19 according to the positions of the subject table 10 and the compression plate 11 and the set enlargement ratio. Adjust the relative distance between the radiation source 6 and the detector holder 12 relative to. At this time, the positions of the radiation source 6 and the detector holding unit 12 having an enlargement ratio set to (R1 + R2) / R1 are calculated so that the radiation source 6 and the detector holding unit 12 are obtained. The holding member 8 is moved up and down. When imaging is instructed by the input device 14a, the control device 16 applies a tube voltage and a tube current to the radiation source 6 from the power supply unit 15 to irradiate the subject H with radiation, and detects the radiation dose. Unit 13 Force When the output radiation dose reaches the preset radiation dose, the power source unit 15 stops the radiation irradiation from the radiation source 6.

[0039] The adjustment of the relative distance between the radiation source 6 and the detector holder 12 with respect to the subject table 10 satisfies R1≥ (D-7) / 200 (m) and R2≥0.15 (m). Do in range. When the input enlargement ratio does not satisfy this range, the control device 16 displays an error message on the display device 14b.

As described above, the control device 16 controls the driving device 19 to raise and lower the holding member 8, thereby adjusting the relative distance between the radiation source 6 and the detector holding unit 12 with respect to the subject table 10. A stage is realized.

FIG. 5 shows a radiation source 6, a subject H, a detector holding unit 12 (numbers in the figure indicate an enlargement ratio), and a phase when a breast image is captured by the breast image capturing apparatus 1 according to the present embodiment. The positional relationship of the floor surface and the ceiling in the imaging room which performs contrast imaging is schematically shown. As shown in FIG. 5, in the present embodiment, the distance L of R1 + R2 is constant even if the enlargement ratio changes, so that as the enlargement ratio increases, the floor surface and the detector holding unit 12 Therefore, if the subject position is low, it is not possible to secure the distance and the enlargement ratio that can be taken is not limited. As a result, the range of subject positions where phase contrast imaging is possible can be expanded and applied to more patients. (Evaluation of visibility of breast imaging device 1)

Hereinafter, the distance L between the radiation source 6 and the detector holder 12 and the visibility evaluation result of the captured image will be described.

[0042] Fig. 6 shows that R1 + R2, which is the distance L between the radiation source 6 and the detector holder 12, is 1555, 1140, 950, 750 (mm), and an enlarged skewer is provided for each Rl + R2. 1. Shows the visibility evaluation results of each captured image when mammography was performed at a magnification of 75 and 1.46. The evaluation was performed by visual evaluation based on a four-level evaluation. ◎: Very good, ○: Good, △: Normal, so-so (determined to be acceptable for diagnosis), X: Bad. The evaluation was performed for each item shown in Figure 6.

[0043] In the evaluation, the mammography apparatus 1 used was a prototype manufactured by Konica Minolta MG Co., Ltd., and the radiological image detector used was the company's Regius Plate RP-5PM and Regius Cascette RC-110M. The focal spot size D was D = 100 m). The radiographic image detector after mammography is read with a regius model 190 manufactured by Konica Minolta Co., Ltd. at a reading pixel pitch of 43.75 (111), and the read image is output at a writing pitch of 25 m) with a drypro model 793. did. At this time, each pixel of the scanned image and each pixel of the output image are output without any interpolation processing corresponding to 1: 1, and an image with a magnification of 1.75 times has a life size (actual size) and a magnification of 1. A 46x image was output at 0.83x actual size. In addition, when shooting at an enlargement ratio of 1.46 times, 1.25x enlargement interpolation processing was performed and output was performed at a writing pitch of 25 (am) using the enlarged interpolation image. And visibility There was no difference.

[0044] Here, the factor contributing to the "output" item is the distance of R1. In general, if the amount of radiation per unit time that reaches the subject H where R1 is large is small, a sufficient signal value (SN ratio) cannot be obtained, and therefore a sufficient density at the time of film output cannot be obtained. Here, the numerical value in parentheses in the “Output” item is the value indicating each mammary gland dose when the average mammary gland dose (AGD) is 1 when Rl + R2 = 1140, magnification 1.75 times It is.

[0045] A factor contributing to the "uniformity" item is the distance of R1. Generally, if R1 is too small, radiation cannot be irradiated on the entire surface of the radiation image detector, resulting in unevenness and low uniformity.

The factor that contributes to “sharpness” and “graininess” is the enlargement ratio. In general, the larger the enlargement ratio, the better the image.

[0047] The factor that contributes to the "scattered radiation content" is R2, and in general, the larger R2, the more the scattered radiation is removed and a better image is obtained.

[0048] Factors contributing to the “phase contrast effect (edge enhancement effect)” are the enlargement ratio and R2, and the larger the enlargement ratio and R2, the more the phase contrast effect is obtained, and the better the image is.

“Comprehensive evaluation” is a result of evaluating the visibility of the entire image.

[0050] As a result of the visibility evaluation, in the case of R1 + R2 ≥ 950 (mm), both the phase contrast effect and the overall evaluation were evaluated to be acceptable for diagnosis. That is, when Rl + R2≥950 (mm), it was confirmed that an image acceptable for diagnosis could be obtained by comparing with a radiographic imaging device that performs phase contrast imaging with Rl + R2 fixed. Furthermore, it was confirmed that if 1140≥R1 + R2≥950 (mm), good images can be obtained in diagnosis.

[0051] The above evaluation results show an example in which the focal spot size D = 100 (11 m). However, if D is 30 (µm) or more, it is effective even if it is not 100 (m).

[0052] As described above, according to the present embodiment, the focal point size D≥ 30 (m) of the radiation source, the distance Rl≥ (D-7) / 200 (m) from the radiation source to the subject, the radiation Radiation image that can guarantee the phase contrast effect of the captured image by setting the source force to the distance L (m) = 0.95 (m) to ί · 14 (m). Can provide shooting equipment [0053] Also, according to the present embodiment, by setting the distance R2≥0.15 (m) to the subject force detector holding means, the scattered radiation from the subject H that deteriorates the sharpness of the radiographic image is obtained. Since removal and edge enhancement can be easily recognized, it is possible to provide a radiographic image capturing apparatus that can guarantee the phase contrast effect of a captured image.

Furthermore, according to the present embodiment, the distance L from the radiation source to the detector holding means is constant (= R 1 + R2), the position of the subject is relatively variable, and the imaging magnification (= L / By changing R1), it is possible to provide a radiographic imaging device that can facilitate imaging and prevent the image quality from changing depending on the imaging magnification.

(Control of radiation dose)

In the evaluation of visibility shown in Fig. 6, the force that was taken with all the radiation doses used as the radiation irradiation stop condition being the same, like the mammography unit 1, from the radiation source to the detector holding means In a radiographic imaging device that keeps the distance L (= R1 + R2) constant, R1 changes when the enlargement ratio changes.Therefore, when the same radiation dose is irradiated, it reaches the subject H due to the change in the enlargement ratio. As a result, the average mammary dose (AGD) and the exposure dose to subject H change. Since most breast cancers also produce mammary tissue power, it is necessary to irradiate the mammary tissue with an optimal dose of radiation, and if the average mammary dose decreases, the density of the mammary tissue cannot be obtained on the film image, and diagnostic performance Affects. Also, if the radiation dose is too high, the exposure amount of the subject H increases, which is not preferable.

[0055] Fig. 7 (a) schematically shows the relationship between R1 and R2 at each enlargement ratio (1.75 times, 1.46 times, 2.63 times) when Rl + R2 = 1140. . Figure 7 (b) shows the visibility of Rl, R2, average mammary gland dose, and image quality when Rl + R2 = 1140 and all the radiation doses used as radiation stop conditions are taken at the same magnification. The evaluation result of is shown. Note that the various conditions at the time of shooting and outputting the image that was the object of visibility evaluation in FIG. 7 (b) are the same as those in FIG.

[0056] The average mammary gland dose is substantially inversely proportional to the square of the distance R1 between the radiation source 6 and the subject H as shown in FIGS. 6 and 7 (b). Therefore, if the magnification was 1.46 times and 2.63 times under the same radiation irradiation stop conditions as when the magnification rate was 1.75 times, the average mammary gland dose was 0.7 times and 2 times, respectively. Tripled. In other words, when taking an image at an enlargement ratio of 1.46 times under the same radiation irradiation stop conditions as when the enlargement ratio is 1.75 times, a sufficient average mammary dose cannot be obtained, and the image quality deteriorates.

[0057] Therefore, the control device 16 variably controls the radiation to be irradiated according to the enlargement ratio. In the following, radiation control will be described by taking as an example the case where Rl + R2 = 1140.

[0058] As described above, since the average mammary gland dose is approximately inversely proportional to the square of R1, if VO is the radiation dose (or irradiation time) that is the radiation stop condition when the magnification is 1.75 times The radiation dose VI when the magnification factor is 1.46 is

Vl = VO X (780/650) ^ 2 = 1. 44 If XVO is controlled, an average mammary gland dose equivalent to that obtained at 1.75 times is obtained. Radiation dose V2 when magnification is 2.63 times

If the control is done so that V2 = V0 X (430/650) ^ 2 = 0.44 XV0, the average mammary gland dose equivalent to that obtained at 1.75 times is obtained.

Therefore, the control device 16 performs the irradiation radiation dose control process shown in FIG. 8, and controls the irradiation dose to be irradiated. The irradiation radiation dose control process is a process realized by a software process in cooperation with the CPU of the control device 16 and a program stored in the ROM, and a control unit is realized by executing the process. Note that the start of this processing is when various settings and adjustments have been completed and the camera is in a shooting standby state. Various settings from the input device 14a, including the enlargement ratio, subject table 10, compression plate, etc. 11. Adjustment of the position of the radiation source 6 and detector holder 12 has been completed.

[0060] In FIG. 8, when an instruction for photographing is given from the input device 14a (step S I; YES), the power supply unit

The tube voltage and tube current are applied to the radiation source 6 by 15 and radiation irradiation is started (step S2). Next, the set enlargement factor is determined, and if it is determined that it is 1.75 times the set value (step S3; YES), the radiation is output until the output value from the radiation dose detector 13 reaches V0. If irradiation is continued and it is determined that the output value SV0 from the radiation dose detector 13 has reached or exceeded (step S4; YES), radiation irradiation from the radiation source 6 is stopped (step S8), and this process Ends.

[0061] If it is determined in step S3 that the set enlargement ratio is not 1.75 times (step S3). (Step S3; NO), it is determined whether or not the set magnification is 2.63 times. 2. If it is determined that it is 63 times (Step S5; YES), the radiation dose detection unit 13 Irradiation is continued until the output value of 0.44 XV0 reaches 0.44 XV0, and if it is determined that the output value from the radiation dose detector 13 has reached 0.44 XV0 or more (step S4; YES), the radiation source Radiation from 6 is stopped (step S8), and this process ends.

[0062] On the other hand, if it is determined in step S5 that the set enlargement ratio is not 2.63 times (step S5; NO), the output value from the radiation dose detector 13 reaches 1.44 XV0. Until it is determined that the output value from the radiation dose detector 13 has reached 1.44 XV0 or higher (step S7; YES), the radiation from the radiation source 6 is stopped ( Step S8), this process ends.

[0063] In FIG. 8, even when the force R1 + R2 described with reference to the case of Rl + R2 = 1140 is used as another example, the radiation irradiation stop condition can be controlled according to the distance of R1. it can. In other words, when the radiation irradiation stop condition (radiation dose) that gives the optimum image quality at the reference magnification rate X0 is V0, the radiation dose Vn that is the radiation irradiation stop condition for other magnification factors Xn is

Vn = V0 X {(R1 when the magnification is Xn) / (R1 when the magnification is X0) By controlling the irradiation of the radiation source 6 so that Γ2, the image quality varies depending on the magnification! It is possible to prevent / or deterioration.

[0064] In addition, when the image data obtained at an enlargement ratio of 2.63 is reduced to 1 / 1.75 and used as a 1.5x (= 2.6 3 / 1.75) enlarged spot shooting Because only a very small area of the subject is irradiated with radiation, the radiation irradiation stop condition may be the same as the magnification factor of 1.75.

[0065] Further, in the irradiation radiation dose control process! /, The distance of the force Rl + R2 determined to variably control the radiation dose irradiated from the radiation source 6 according to the magnification rate is determined. In this case (constant), the relationship between the magnification and the distance of R1 is 1: 1 (proportional relationship), so the radiation dose may be variably controlled by the distance of R1.

[0066] As described above, according to the present embodiment, the amount of radiation from the radiation source is controlled so that the amount of radiation reaching the subject H is constant even when the imaging magnification is changed. It is possible to provide a radiographic imaging device that can prevent the image quality from changing due to the power S.

[0067] Also, according to the present embodiment, since the imaging magnification is smaller! /, The amount of irradiation from the radiation source is increased, so that radiographic imaging that can prevent the image quality from changing depending on the imaging magnification can be prevented. An apparatus can be provided.

[0068] As described above, according to the present invention, the image quality can be adjusted according to the imaging magnification by variably controlling the radiation dose emitted from the radiation source in accordance with the imaging magnification set by the magnification setting means. It is possible to provide a radiographic image capturing apparatus that can prevent the change of the temperature.

[0069] The power described above for the mammography apparatus 1 in the present embodiment has been described above. The description in the embodiment is a preferred example of the mammography apparatus 1 according to the present invention, and is not limited thereto. It is not a thing. Further, the detailed configuration and detailed operation of the mammography apparatus 1 can be appropriately changed without departing from the spirit of the present invention.

Claims

The scope of the claims

[1] A radiation source that irradiates the subject with radiation,

Magnification setting means for setting the shooting magnification;

To a radiographic imaging apparatus comprising a control means for detecting an irradiation amount from the radiation source and controlling the radiation source!

Yes

[2] The focal spot size D of the radiation source is 30 (m) or more,

The radiographic imaging according to claim 1, wherein a distance L (m) from the radiation source to the detector holding means is 0.95 (m) to; 1.14 (m). apparatus.

[3] The radiographic imaging device according to claim 1 or 2, wherein a distance R2 from the subject to the detector holding means is R2≥0.15 (m).

[4] A distance R1 from the radiation source to the subject, a distance R2 from the subject to the detector holding means,

When the distance L (= R1 + R2) (m) from the radiation source to the detector holding means is set, the distance L is constant, the position of the subject is relatively variable, and the imaging magnification (= L / The radiographic image capturing apparatus according to any one of claims 1 to 3, wherein Rl) is changed.

[5] The range of claim 4 wherein the control means controls the radiation dose from the radiation source so that the radiation dose reaching the subject is constant even when the imaging magnification is changed. The radiographic imaging device according to item.

[6] The radiographic imaging device according to [4] or [5], wherein the control means increases the irradiation amount from the radiation source as the imaging magnification decreases.