JP2003114202A - Radiation image photographing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To change the degree of edge emphasis when acquiring a radiation image having the emphasized edge of a subject by irradiating the subject with a coherent radiation. SOLUTION: An X-ray source 14 is constituted from a radiation source 11 for emitting a synchrotron radiation, a plurality of crystals 13A, 13B, 13C having different sizes respectively, for monochromatizing the synchrotron radiation into a monochromatic X-ray (hereafter referred to simply as an X-ray), and a changing means 14 for positioning some of the crystals 13A, 13B, 13C on the optical path of the synchrotron radiation. The crystals 13A, 13B, 13C can enhance the coherency of the X-ray 12 and heighten the degree of edge emphasis in reverse proportion to the size thereof. Consequently, the degree of the edge emphasis of the subject 21 can be changed in the acquired radiation image, by changing the used crystal 13A, 13B, 13C corresponding to the subject 21 by the changing means 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation image capturing apparatus for irradiating a subject with radiation having coherence to obtain a radiation image in which an edge of the subject is emphasized.

[0002]

2. Description of the Related Art Conventionally, radiation (X-ray, α
Rays, β rays, γ rays, electron rays, ultraviolet rays, etc.) to radiate the radiation that has passed through the subject, and the detector is a stimulable phosphor sheet or a radiation detection panel in which a plurality of detection elements are two-dimensionally arranged. The image data representing the radiation image of the object is obtained by performing the image detection, the image data is subjected to various image processing, and then the image data is reproduced.

Here, in the method using the stimulable phosphor sheet, a part of the radiation energy transmitted through the subject is accumulated, and when excitation light is irradiated thereafter, stimulated emission light of a light amount corresponding to the accumulated energy is emitted. Using the stimulable phosphor (stimulable phosphor), the radiation image information of the subject is recorded on the sheet-shaped stimulable phosphor (that is, the stimulable phosphor sheet), and the stimulable phosphor sheet is used as a laser beam. Is a method of generating stimulated emission light by scanning with excitation light such as, and photoelectrically reading the generated stimulated emission light to obtain image data representing a radiation image of a subject. Further, the method using the radiation detection panel uses a radiation detection panel in which a plurality of detection elements are two-dimensionally arranged, and generates an electric signal in each detection element according to the radiation dose applied to the radiation detection panel. This is a method of obtaining image data representing a radiation image of a subject based on this electric signal.

By the way, the radiation image thus obtained represents the difference in the intensity of the transmitted radiation in the subject as an image. For example, when a subject including a bone part and a soft part is photographed, the radiation that has passed through the bone part is greatly attenuated, so that the amount of radiation that reaches the detector is small, but the radiation that has passed through the soft part is not significantly attenuated, so that the detection is performed. The radiation dose reaching the vessel is relatively high. Therefore, in the case of such a subject, a radiographic image in which the bone portion is white and the soft portion is black and the contrast difference is large, that is, a large amount of information is obtained. Note that such a radiation image is referred to as an intensity information radiation image.

However, for example in breast cancer diagnosis,
When the subject is mainly composed of only the soft part, the difference in radiation attenuation amount due to the tissue is not so large, so that only a radiation image with a small contrast difference, that is, a small amount of information can be obtained.

Therefore, there has been proposed a phase contrast imaging method for visualizing a phase difference of radiation caused by passing through a subject. In this phase contrast imaging method, since radiation is an electromagnetic wave similar to light and a wave propagates and propagates, when two different substances are irradiated with radiation, the difference in how the radiation propagates in the substance causes The subject is photographed based on the fact that the phases of the radiation waves are different before and after the transmission of the substance, resulting in a phase difference. Here, when the subject is a soft part, the phase difference of the radiation becomes larger than the difference of the attenuation amount of the radiation, so the phase contrast imaging method is used to capture the phase difference of the radiation as a phase contrast image. This makes it possible to visualize a subtle difference in tissues contained in the soft part. For the phase contrast imaging method, see `` Pe
ter Cloetens, et al., "Quantitative aspects of coh
erent hard X-ray imaging: Talbot image and hologra
phic reconstruction ", Proc, SPIE, Vol.3154 (1977),
72-82 (Reference 1) "and" Peter Cloetens, et al., "
Hard x-ray phase imaging using simple propagation
of a coherent synchrotron radiation beam ", J. Phys.
D: Appl. Phys. 32 (1999), A145-A151 (reference 2) "for details. According to these documents, image data representing a plurality of radiation images is obtained by performing imaging using a two-dimensional detector at a plurality of imaging positions having different distances from the subject, and the image data is determined in advance using the plurality of image data. By performing the operation based on the algorithm,
A phase contrast image can be generated.

On the other hand, in the phase contrast imaging method, an edge-enhanced imaging method is known in which only the edges of the object are emphasized for imaging (for example, Japanese Patent Laid-Open No. 2000-24).
5721). This edge-enhanced imaging method is an imaging method in which radiation having coherence is applied to an object and a radiation image of the object is obtained using a two-dimensional detector at an imaging position at a predetermined distance from the object. When imaging is performed in this manner, diffraction fringes appear on the edge of the subject in the radiation image due to the diffraction phenomenon, and as a result, a radiation image in which the edge of the subject is emphasized is obtained.

Here, as a radiation source having coherence, a radiation source using a microfocus tube is known. Also, in order to enhance the degree of edge enhancement, X-rays emitted from a high-intensity radiation source that emits synchrotron radiation are monochromaticized by crystals such as silicon, and the monochromatic X-rays obtained by this are used for imaging. It is also known how to do it.

[0009]

However, depending on the subject, the edge-enhanced shooting may make it difficult to detect the subject. For example, when performing edge enhancement imaging of the breast, since the mammary gland of the elderly person's breast degenerates and the fat content increases, the edge enhancement imaging is very effective to emphasize the calcification component contained in the breast. . On the other hand, since the mammary gland is developed in the breast of a young person, the edge of the mammary gland and the edge of the calcified portion overlap. For this reason, when edge-enhanced imaging is performed, overlapping edges are emphasized, and the radiation image becomes very difficult to see. Therefore, it is preferable to reduce the degree of edge enhancement when photographing a breast of a young person.

The present invention has been made in view of the above circumstances, and an object thereof is to be able to change the degree of edge enhancement.

[0011]

A radiographic image capturing apparatus according to the present invention is for implementing an edge-enhanced image capturing method, and is provided with a radiation source that emits coherent radiation, and irradiates the subject with the radiation. In a radiation image capturing apparatus that captures a radiation image in which an edge of the subject is emphasized by detecting radiation that has passed through the subject, a focus size of the radiation source is determined according to a desired degree of enhancement of the edge. Is provided with a size changing means for changing.

In the radiation image capturing apparatus according to the present invention, the radiation source is composed of a plurality of radiation sources having a plurality of focal spot sizes, and the size changing means is
A means for switching the plurality of radiation sources may be used.

Further, in the radiation image capturing apparatus according to the present invention, the radiation source is a primary radiation source that emits the radiation, and a secondary radiation that reflects the radiation emitted from the primary radiation source to obtain a monochromatic ray. It may consist of a source.

Further, in the radiographic image capturing apparatus according to the present invention, the secondary radiation source is composed of a plurality of crystals of silicon or the like having different sizes, and the size changing means is arranged to switch the plurality of crystals by a switching operation. It may be a means for positioning any crystal on the optical path of the radiation emitted from the primary radiation source.

Here, the "crystal" is, for example, a Pyrex (registered trademark) glass deposited with gold as long as it has the effect of reflecting the radiation emitted from the primary radiation source to obtain a monochromatic light. As described above, it also includes those artificially formed. Pyrex (registered trademark)
The reflector made by vapor-depositing gold on glass is described as follows: "Hard X-ray interference experiment using a total reflection slit, Proceedings of the 48th Joint Lecture on Applied Physics (2001.3.) No.2, pp.713, 29p-ZA-
It is described in 3).

[0016]

According to the radiation image capturing apparatus of the present invention, the focus size of the radiation source is changed according to the desired degree of enhancement of the edge of the subject. Here, in order to make the diffraction phenomenon remarkable and to emphasize the edge strongly, it is necessary to increase the coherence of the radiation applied to the subject. On the other hand, it is known that the smaller the focal size of the radiation source, the higher the coherence of radiation. Therefore, by changing the focus size of the radiation source according to the desired degree of enhancement of the edge, the degree of coherence of the radiation is changed, and the edge of the subject in the radiation image has the desired degree of enhancement. Can be Therefore, the degree of edge enhancement can be changed according to the subject to obtain a more easily visible radiation image.

Further, the radiation source is composed of a plurality of radiation sources having a plurality of focal spot sizes, and the size changing means is a means for switching between the plurality of radiation sources, whereby the focal spot size of the radiation source is simplified. Can be changed.

Further, if the radiation source is composed of a primary radiation source that emits radiation and a secondary radiation source that reflects the radiation emitted from the primary radiation source to make it monochromatic, the radiation source is simplified. Can be configured to.

Furthermore, when the radiation source is composed of a primary radiation source and a secondary radiation source and the secondary radiation source is a crystal, the size of the crystal corresponds to the focal point size of the radiation source. That is, the smaller the crystal size, the smaller the focal size, and the higher the coherence of the obtained radiation. Therefore, if the secondary radiation source is made up of a plurality of crystals and the size changing means is a means for locating any one of the crystals on the optical path of the radiation emitted from the primary radiation source, a simpler configuration is achieved. The focus size of the radiation source can be changed.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic block diagram showing the configuration of a radiographic image capturing apparatus according to an embodiment of the present invention. As illustrated in FIG. 1, the radiation image capturing apparatus according to the present embodiment transmits an X-ray source 10 that irradiates a subject with X-rays having coherence, a subject support unit 20 that supports a subject 21, and a subject 21. A recording unit 30 that detects X-rays and obtains image data S1 representing a plurality of X-ray images of a subject.
With.

The X-ray source 10 includes a radiation source 11 which emits synchrotron radiation and a plurality of monochromatic X-rays (hereinafter simply referred to as X-rays) 12 which are different in size (this embodiment). Crystal 3A, 1)
3B, 13C and any of the crystals 13A, 13B, 13
Position C on the optical path of the synchrotron radiation and set X
A monochromatic X-ray 12 is obtained by including a changing means 14 for changing the focal point size of the radiation source 10 and reflecting the synchrotron radiation emitted from the radiation source 11 by any of the crystals 13A, 13B, 13C. Is.

Silicon may be used as the crystals 13A, 13B and 13C. In addition, a reflector obtained by vapor-depositing gold on Pyrex (registered trademark) glass is used as a crystal 13A, 13A.
You may use as B and 13C.

The subject support unit 20 includes a support base 24 that supports the subject 21.

The recording unit 30 is composed of a plurality of detection elements arranged two-dimensionally, and includes a detection panel 31 arranged at a predetermined distance from the subject 21, and a plurality of detection elements constituting the detection panel 31. The reading means 33 reads the electric signal to obtain the image data S1.

In this embodiment, since the X-ray 12 has coherence, when the image data S1 representing the radiation image of the subject 21 is obtained by the detection panel 31 located at a position distant from the subject 21, the subject 21 is diffracted. Diffraction fringes appear on the edges of, and as a result, a radiation image in which the edges of the subject 21 are emphasized is obtained.

On the other hand, the smaller the focal size of the X-ray source 10, the higher the coherency of the X-rays 12. Also, crystal 1
Regarding 3A, 13B, and 13C, the smaller the size, the smaller the focal size, and the higher the coherence of the X-ray 12. Furthermore, the higher the coherence of the X-rays 12, the more prominent the diffraction phenomenon, and the stronger the degree of edge enhancement. In this embodiment, the crystals 13 of a plurality of sizes are used.
A, 13B, and 13C are prepared, and one of the crystals 1 is changed by using the changing unit 14 according to the desired degree of edge enhancement.
3A, 13B and 13C are arranged on the optical path of the synchrotron radiation. Therefore, the crystal 13 positioned on the optical path of the synchrotron radiation light
The degree of coherence of the X-ray 12 differs depending on the size of A, 13B, and 13C, and as a result, the degree of edge enhancement of the subject 21 in the obtained radiation image can be changed. Specifically, the smaller the size of the crystal used, the higher the coherence of the X-rays 12 and the greater the degree of edge enhancement.

The changing means 14 is shown in FIG.
As shown in FIG. 3, it may be composed of a disk 14A in which crystals 13A, 13B, 13C are arranged around the rotation axis thereof, and a motor 14B for rotating the disk 14A. Also,
As shown in FIG. 2B, crystals 13A, 13B, 13C
A rectangular support plate 14C in which the
It may be composed of a mechanism 14D for sliding C.

Next, the operation of this embodiment will be described. FIG. 3 is a flowchart showing the operation of this embodiment. First, the changing means 14 positions one of the crystals 13A, 13B, and 13C on the optical path of the synchrotron radiation to change the focus size of the X-ray source 10 so that a desired degree of edge enhancement can be obtained. Yes (Step S
1). Subsequently, the radiation source 11 is driven to reflect the synchrotron radiation light at any of the crystals 13A, 13B, 13C, whereby monochromatic X-rays 12 are emitted from the X-ray source 10, and X-rays are emitted to the subject 21. 12 is irradiated (step S2). Then, the reading means 33 reads the electric signals of the plurality of detection elements constituting the detection panel 31 to acquire the image data S1 representing the radiation image of the subject 21 (step S3), and the processing is ended. The image data S1 is used for reproduction by a monitor or print output by a printer.

Here, depending on the type of the subject 21, the radiographic image may be difficult to see by performing edge-enhanced photography. For example, considering the case of performing edge enhancement imaging of the breast, since the mammary gland of the elderly person is degenerated and the fat content increases, the edge enhancement imaging is extremely useful for emphasizing the calcification component contained in the breast. It is valid. On the other hand, since the mammary gland is developed in the breast of a young person, the edge of the mammary gland and the edge of the calcified portion overlap. For this reason, when edge-enhanced imaging is performed, overlapping edges are emphasized, and the radiation image becomes very difficult to see.

According to this embodiment, the size of the crystals 13A, 13B, 13C that reflect the synchrotron radiation is switched by the changing means 14 according to the desired degree of edge enhancement, and the focus size of the X-ray source 10 is changed. Is changed to change the degree of edge enhancement of the subject 21 in the radiation image. Therefore, when the breast of an elderly person is used as the subject 21, by using the crystal 13C of the smallest size in order to further emphasize the edge, the degree of edge emphasis can be increased and a more readable radiographic image can be obtained. . On the other hand, when the breast of a young person is used as the subject 21, by using the crystal 13A of the largest size in order to reduce the degree of edge enhancement, the degree of edge enhancement can be weakened and a more readable radiographic image can be obtained. it can.

Therefore, the degree of edge enhancement can be changed according to the subject 21 to obtain a more visible radiation image.

Not only the breast but also industrial products having a complicated structure, for example, are imaged by the radiation image capturing apparatus according to the present embodiment to change the degree of edge enhancement and obtain a radiation image that is easy to see. be able to.

In the above embodiment, the recording unit 3
Although the image is taken using the detection panel 31 at 0, as in the other embodiment shown in FIG.
Instead of this, the stimulable phosphor sheet 61 may be used for taking an image.

When an image is taken using the stimulable phosphor sheet 61 in this way, the sheet 61 is irradiated with excitation light to generate stimulated emission light, and this stimulated emission light is photoelectrically converted. The reading means 70 for reading obtains image data S1 representing an X-ray image.

Further, in the above embodiment, the radiation source 11
Although the one that emits synchrotron radiation is used as, it is not limited to this. In addition, the subject 21
Although a monochromatic X-ray is used as the X-ray 12 for irradiating the object, it is not limited to the monochromatic X-ray.

Further, in the above embodiment, the subject 21 is irradiated with X-rays, but if the subject 21 has coherence, radiation other than X-rays (α-rays, β-rays, γ-rays) is used.
Ray, electron beam, ultraviolet ray, etc.) may be used.

[Brief description of drawings]

FIG. 1 is a schematic block diagram showing a configuration of a radiation image capturing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a changing unit.

FIG. 3 is a flowchart showing the operation of this embodiment.

FIG. 4 is a schematic block diagram showing the configuration of a radiation image capturing apparatus according to another embodiment of the present invention.

[Explanation of symbols]

10 X-ray source 11 radiation sources 12 X-ray 13A, 13B, 13C crystals 14 Change means 20 Subject support 21 subject 30 recording section 31 Detection panel 61 Storage phosphor sheet 70 reading means

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) G21K 5/02 G21K 5/02 X F term (reference) 2G001 AA01 BA11 BA18 CA01 GA01 GA06 HA09 HA13 JA02 KA01 KA20 LA01 2G088 EE01 FF02 GG19 JJ05 KK32 2H013 AC04 AC05 4C093 CA04 DA06 EA01 EA03 FA15 FA60

Claims (4)

[Claims] 1. A radiation source that emits coherent radiation is provided, the subject is irradiated with the radiation, and the radiation transmitted through the subject is detected to capture a radiation image in which the edge of the subject is emphasized. The radiographic image capturing apparatus further comprises size changing means for changing a focus size of the radiation source according to a desired degree of enhancement of the edge. 2. The radiation source according to claim 1, wherein the radiation source includes a plurality of radiation sources having a plurality of focal spot sizes, and the size changing unit is a unit that switches the plurality of radiation sources. Image capture device. 3. The radiation source comprises a primary radiation source that emits the radiation and a secondary radiation source that reflects the radiation emitted from the primary radiation source to monochromate it. Item 1. The radiation image capturing apparatus according to Item 1 or 2. 4. The secondary radiation source is composed of a plurality of crystals having different sizes, and the size changing unit is configured to emit any one of the plurality of crystals from the primary radiation source by a switching operation. The radiation image capturing apparatus according to claim 3, wherein the radiation image capturing apparatus is a unit that is located on the optical path of the radiation.