JP5833816B2 - Radiation imaging device - Google Patents

Description

  The present invention relates to a radiation imaging apparatus that performs imaging by irradiating a subject such as a person with radiation.

  In an X-ray imaging apparatus, X-rays that have passed through a subject are converted into visible light by a scintillator, and the visible light reaches an imaging device. And the image according to the intensity distribution of the X-ray which reached | attained the X-ray imaging device can be obtained with the output of an image sensor.

  When performing X-ray imaging, the X-ray imaging apparatus may receive a load from the subject, and thus needs to have strength to withstand this load. In view of this, there is a case where strength is given to a case constituting the exterior of the X-ray imaging apparatus. Specifically, the thickness of the case is increased, or the case has a double structure.

  In the configuration in which the case is strong, it is difficult to bring the scintillator close to the subject. That is, when the thickness of the case is increased, the scintillator is moved away from the subject by the thickness of the case. Even when the case has a double structure, the scintillator leaves the subject.

  Since the focal point of the X-ray source is not a point but a certain area, a penumbra (blurred image) occurs. Here, as the distance between the subject and the scintillator increases, the X-ray image enlarges and the penumbra also enlarges, causing the X-ray image to blur. That is, it becomes difficult to improve the resolution of the X-ray image.

The present invention is a radiation imaging apparatus that performs an imaging operation using radiation applied to a subject, and includes a scintillator, a light shielding layer, a plurality of imaging units , a lens bracket, and a flat reinforcing plate. The scintillator converts radiation into visible light. The light shielding layer is disposed on the subject side with respect to the scintillator, and is exposed to the outer surface of the radiation imaging apparatus and can contact the subject. In addition, the light shielding layer allows radiation to pass and shields visible light. Each imaging unit includes an imaging device that photoelectrically converts visible light generated by the scintillator, and a lens that condenses the visible light generated by the scintillator toward the imaging device. The plurality of imaging units are arranged side by side in a predetermined plane. The lens bracket is used for holding lenses in a plurality of imaging units. The reinforcing plate is disposed between the scintillator and the imaging unit , and is disposed at a position away from the imaging unit and the lens bracket. Lead particles are dispersed therein and have light transmittance. The thickness of the reinforcing plate is rather thick than the thickness of the total in the scintillator and the light-shielding layer, the optical path of the visible light incident to each part of the imaging surface of the imaging device, the mutually equal position the optical path length from each part, the reinforcing plate It is the thickness to be located inside.

  Here, the light shielding layer that shields visible light without disturbing the passage of radiation can be brought into contact with the scintillator. Thereby, the scintillator can be brought closer to the subject, and the radiation can reach the scintillator while suppressing the diffusion of the radiation that has passed through the subject. The thickness of the light shielding layer can be set to 1 mm or less, for example.

  Further, the reinforcing plate can be brought into contact with the scintillator. Thereby, the visible light generated by the scintillator can be easily guided to the imaging device via the reinforcing plate. When radiation reaches the scintillator, visible light is generated as diffused light. By bringing the reinforcing plate into contact with the scintillator, the diffusion of visible light can be suppressed by the photorefractive action of the reinforcing plate.

The reinforcing plate can be formed of an acrylic resin . As the thickness of the reinforcement plate can withstand the load acting on the radiation imaging apparatus. Here, examples of the load acting on the radiation imaging apparatus include a load when the subject leans on the radiation imaging apparatus and a load when the subject rides on the radiation imaging apparatus.

  Lead particles can be dispersed in the reinforcing plate. Dispersing the lead particles can attenuate the radiation passing through the reinforcing plate. Depending on the characteristics of the scintillator, there is a possibility that the radiation passes through the reinforcing plate and is directed to the image sensor without being converted into visible light. In this case, the radiation passing through the reinforcing plate can be attenuated by dispersing lead particles in the reinforcing plate. Thereby, it can suppress that a radiation reaches | attains an image pick-up element, noise can be contained in the output of an image pick-up element by radiation, or deterioration of an image pick-up element by radiation can be suppressed.

  According to the present invention, by arranging the reinforcing plate between the scintillator and the imaging element, the scintillator can be brought close to the subject while ensuring the strength of the radiation imaging apparatus. It is possible to improve the resolution of the image obtained by the radiation imaging apparatus by suppressing the penumbra (image blur) by the amount the scintillator is brought closer to the subject. In addition, by using a light-transmitting reinforcing plate, visible light generated by the scintillator can be easily guided to the image sensor.

1 is a schematic diagram showing an X-ray imaging system. It is a front view of an X-ray imaging device. It is XX sectional drawing of FIG. It is the schematic which shows the cross section of an X-ray imaging device. It is the schematic which shows the cross section of the X-ray imaging device which is a comparative example.

  Examples of the present invention will be described below.

  An X-ray imaging apparatus (corresponding to a radiation imaging apparatus) that is Embodiment 1 of the present invention will be described. FIG. 1 is a schematic diagram of an X-ray imaging system including the X-ray imaging apparatus of the present embodiment.

  The X-ray imaging system 1 includes an X-ray irradiation apparatus 10 that irradiates a subject 30 with X-rays, and an X-ray that performs an imaging operation by receiving X-rays that are irradiated from the X-ray irradiation apparatus 10 and transmitted through the subject 30. And an imaging device 20. The X-ray irradiation apparatus 10 and the X-ray imaging apparatus 20 are arranged so as to sandwich the subject 30.

  The X-ray imaging system 1 can be used in medical diagnosis, industrial nondestructive inspection, and the like. That is, examples of the subject 30 include subjects such as animals such as humans and nondestructive inspection targets such as the internal structure of buildings. In FIG. 1, the imaging surface of the X-ray imaging apparatus 20 is arranged along the vertical direction, but the present invention is not limited to this. For example, the imaging surface of the X-ray imaging device 20 can be arranged along a horizontal plane. The X-ray irradiation apparatus 10 and the X-ray imaging apparatus 20 only need to face each other, and the position (in other words, the direction) where the X-ray irradiation apparatus 10 and the X-ray imaging apparatus 20 are arranged can be set as appropriate.

  Next, the X-ray imaging apparatus 20 will be described with reference to FIGS. FIG. 2 is a front view of the X-ray imaging apparatus 20 and shows the internal structure of the X-ray imaging apparatus 20 in a partial region. 3 is a cross-sectional view taken along the line XX of FIG. 2 and shows a part of the X-ray imaging apparatus 20. The cross section shown in FIG. 3 is a surface orthogonal to the imaging surface of the X-ray imaging device 20.

  As shown in FIG. 2, the X-ray imaging apparatus 20 has 16 imaging areas A1 to A16. The imaging areas A1 to A16 are arranged in 4 rows and 4 columns in the same plane. The configurations of the imaging areas A1 to A16 are the same. In the present embodiment, sixteen imaging areas A1 to A16 are provided. However, the present invention is not limited to this, and the number of imaging areas and the arrangement of the imaging areas can be set as appropriate.

  A plurality of imaging units 40 are arranged in each of the imaging areas A1 to A16. The imaging units 40 are arranged in 3 rows and 4 columns in each of the imaging areas A1 to A16. Each imaging unit 40 receives the X-rays emitted from the X-ray irradiation apparatus 10 and outputs an electrical signal. In addition, the number of the imaging units 40 arrange | positioned in each imaging area A1-A16, and how to arrange the imaging units 40 can be set suitably.

  As shown in FIG. 3, the X-ray imaging apparatus 20 includes an upper case 21 and a lower case 22 that accommodate the imaging unit 40 and the like. The upper case 21 and the lower case 22 constitute an exterior of the X-ray imaging apparatus 20 and have a function of preventing visible light from entering the X-ray imaging apparatus 20.

  A seal member 23 is provided at a connection portion between the upper case 21 and the lower case 22. The seal member 23 is made of an elastic member such as rubber, and has a function of securing a sealing property at a connection portion between the upper case 21 and the lower case 22. Further, as shown in FIG. 2, the seal member 23 is disposed along outer edges (corresponding to connection portions) of the upper case 21 and the lower case 22.

  The upper case 21 is formed with an opening 21a for allowing X-rays irradiated from the X-ray irradiation apparatus 10 to pass therethrough. The opening 21a is closed by a top plate (corresponding to a light shielding layer) 24. The top plate 24 constitutes the outer surface of the X-ray imaging apparatus 20, and the subject 30 comes into contact therewith. The top plate 24 has a function of preventing visible light from entering the X-ray imaging apparatus 20. The top plate 24 is preferably formed of a material that hardly attenuates X-rays guided to the imaging unit 40. For example, the top plate 24 can be formed of carbon.

  An inner plate 25 is disposed inside the X-ray imaging apparatus 20, and the inner plate 25 overlaps the top plate 24. A scintillator 26 is disposed between the top plate 24 and the inner plate 25, and the top plate 24 and the inner plate 25 are in contact with the scintillator 26. The scintillator 26 converts X-rays irradiated from the X-ray irradiation apparatus 10 into visible light, and is used as a radiation detector. Since the configuration of the scintillator 26 is known, a detailed description thereof will be omitted.

  Since the inner plate 25 is in contact with the scintillator 26, the visible light generated by the scintillator 26 is directly incident on the inner plate 25. Then, the visible light passes through the inner plate 25 and is guided to the imaging unit 40. The inner plate 25 can be formed of a material that transmits visible light and hardly attenuates visible light.

  As a material of the inner plate 25, for example, glass, acrylic, polyethylene terephthalate, or polycarbonate can be used. The inner plate 25 is thicker than the top plate 24 and the scintillator 26.

  In this embodiment, the inner plate 25 is brought into contact with the scintillator 26, but there may be a gap between the inner plate 25 and the scintillator 26. Further, in this embodiment, the top plate 24 is brought into contact with the scintillator 26, but there may be a gap between the top plate 24 and the scintillator 26.

  Next, the configuration of the imaging unit 40 will be described. The imaging unit 40 includes a lens 41 and an imaging element 43. The visible light that has passed through the inner plate 25 is collected by the lens 41 and reaches the image sensor 43. The image sensor 43 receives visible light, performs photoelectric conversion, and accumulates electric charges. The accumulated charge is output at a predetermined timing.

  In this embodiment, a CCD (Charge Coupled Device) sensor is used as the image sensor 43. A CMOS (Complementary Metal Oxide Semiconductor) sensor can also be used as the image sensor 43. The image sensor 43 is connected to the camera substrate via a bonding wire. Here, the camera substrate 28 is provided for each of the imaging areas A1 to A16 described above, and the imaging element 43 of the imaging unit 40 included in each of the imaging areas A1 to A16 is connected.

  The signals output from the plurality of imaging units 40 (imaging elements 43) arranged in the imaging areas A1 to A16 are subjected to predetermined signal processing, so that an X-ray image corresponding to the subject 30 is generated. . Specifically, an X-ray image is generated in each of the imaging areas A1 to A16, and one X-ray image corresponding to the subject 30 is obtained by connecting the X-ray images corresponding to each of the imaging areas A1 to A16. Can be obtained.

  The lens 41 is held by a lens holder 42, and the lens holder 42 is held by a lens bracket 27. Here, the lens bracket 27 is provided for each of the above-described imaging areas A1 to A16, and holds the lens holder 42 of the imaging unit 40 included in each of the imaging areas A1 to A16.

  In this embodiment, in each of the imaging areas A1 to A16, one unit including a plurality of imaging units 40 and the lens bracket 27 is configured, and this unit is arranged in a matrix (4 rows and 4 columns) as shown in FIG. ). Since each of the imaging areas A1 to A16 can manufacture a unit including the plurality of imaging units 40 and the lens bracket 27, the flatness of the mounting surface for mounting the imaging unit 40 in each of the imaging areas A1 to A16 is set. Can be secured. And it can make it easy to ensure the flatness in the area including all of the imaging areas A1 to A16. Note that a plurality of imaging units 40 can be arranged in one imaging area including all of the imaging areas A1 to A16 without being divided into the imaging areas A1 to A16.

  The lens bracket 27 and the camera substrate 28 are supported by a first frame 29 a and a second frame 29 b that are the skeleton of the X-ray imaging apparatus 20.

  According to the present embodiment, the scintillator 26 is only covered with the top plate 24, and the scintillator 26 can be brought close to the subject 30. As a result, the X-rays immediately after passing through the subject 30 can be made to easily reach the scintillator 26, penumbra (blurring of the X-ray image) can be suppressed, and the resolution of the X-ray image can be improved.

  That is, since the X-rays that have passed through the subject 30 can reach the scintillator 26 without being dispersed, penumbra (X-ray image blur) can be suppressed. In addition, the X-ray intensity distribution immediately after passing through the subject 30 and the X-ray intensity distribution reaching the scintillator 26 can be substantially matched. As a result, an X-ray image corresponding to the subject 30 can be easily obtained, and the resolution of the X-ray image can be improved. Here, as the scintillator 26 is further away from the top plate 24 (in other words, the subject 30), the X-rays that reach the scintillator 26 are more easily dispersed, and the X-ray image is more likely to be blurred.

  When X-ray imaging is performed using the X-ray imaging apparatus 20, the subject 30 leans against the top plate 24 or the subject 30 gets on the top surface of the top plate 24, so that a load is applied to the top plate 24 and the scintillator 26. . In the present embodiment, since the inner plate 25 is stacked on the top plate 24 and the scintillator 26, the inner plate 25 can receive a load. Thereby, it is possible to prevent the top plate 24 and the scintillator 26 from being excessively bent or damaged. Here, the thickness of the inner plate 25 can be appropriately set based on the load (assumed upper limit value) acting on the X-ray imaging apparatus 20.

  Visible light generated by the scintillator 26 becomes scattered light. However, by disposing the inner plate 25 having light transmittance at a position adjacent to the scintillator 26, the visible light is suppressed from being scattered. It can be easily guided to the imaging unit 40.

  Further, by arranging the inner plate 25 between the scintillator 26 and the imaging unit 40, the imaging unit 40 can easily focus on the visible light image formed by the scintillator 26. This point will be specifically described with reference to FIGS. 4 and 5.

  FIG. 4 shows a cross section of an X-ray imaging apparatus as a comparative example. In the configuration illustrated in FIG. 4, the scintillator 26 is not disposed between the scintillator 26 and the imaging unit 40, and visible light generated by the scintillator 26 is directly incident on the imaging unit 40. In the configuration shown in FIG. 4, two plates 50 are arranged on the subject side of the scintillator 26 in order to ensure the strength of the X-ray imaging apparatus. The imaging unit 40 has an angle of view F.

  In the configuration shown in FIG. 4, an image of visible light is formed in the plane of the scintillator 26, and this visible light is incident on the imaging surface of the imaging unit 40 (imaging device 43). Here, the optical path of visible light incident on the outer edge PO of the imaging surface is different from the optical path of visible light incident on the central portion PC of the imaging surface. Specifically, the optical path of visible light incident on the central portion PC is longer than the optical path of visible light incident on the outer edge PO. For this reason, distortion may occur in the X-ray image.

  The configuration shown in FIG. 5 is the configuration of the X-ray imaging apparatus of the present embodiment. In this embodiment, since the inner plate 26 is disposed between the scintillator 26 and the imaging unit 40, the optical path of visible light that enters the outer edge PO of the imaging surface and the visible light that enters the center PC of the imaging surface. The optical path of light can be made substantially coincident. Here, the curve C indicates a position where the optical path lengths from the imaging surface (including the center portion PC and the outer edge portion PO) are equal. Thus, according to the present embodiment, it is possible to suppress the occurrence of variations in the optical path length of visible light that reaches the imaging surface. Thereby, distortion of an X-ray image can be suppressed.

  In this embodiment, the top plate 24 and the scintillator 26 are stacked, but the present invention is not limited to this. For example, a light shielding film that shields visible light can be attached to the surface of the scintillator 26 that faces the subject 30, or a light shielding material that shields visible light can be applied.

  On the other hand, the inner plate 25 can contain lead particles. By including lead particles, X-rays passing through the inner plate 25 can be attenuated. Even if the X-rays reach the scintillator 26, the rate of conversion from X-rays to visible light changes according to the characteristics of the scintillator 26, and the X-rays may pass through the scintillator 26 toward the imaging unit 40. There is.

  Therefore, by dispersing lead particles in the inner plate 25, X-rays from the scintillator 26 can be attenuated by the inner plate 25, and X-rays can be prevented from reaching the imaging unit 40. If X-rays are prevented from reaching the imaging unit 40, noise is included in the output of the imaging unit 40 (imaging element 43), or deterioration of the imaging unit 40 due to X-rays is suppressed. Can do. By suppressing noise from being included in the output of the imaging unit 40 (imaging device 43), it is possible to suppress a decrease in contrast and resolution of an image obtained by the X-ray imaging operation.

  Here, it is preferable that the lead particles are dispersed substantially uniformly with respect to the entire inner plate 25. If the density of the lead particles varies greatly depending on the position in the inner plate 25, the intensity of the X-rays reaching the imaging unit 40 will be different. In this case, the output from the plurality of imaging units 40 varies, and the degree of deterioration of the plurality of imaging units 40 varies. Therefore, dispersion of the X-ray intensity distribution reaching the plurality of imaging units 40 can be suppressed by dispersing the lead particles substantially uniformly.

  On the other hand, if the content of the lead particles is excessively increased, the visible light generated by the scintillator 26 is difficult to reach the imaging unit 40. For this reason, the content of the lead particles can be appropriately set while taking into consideration the X-ray attenuation effect and the visible light attenuation effect. As a method for adjusting the content of lead particles, for example, preparing a plurality of plates having substantially the same content of lead particles, and changing the number of stacked plates, the content of lead particles is changed. Can be made.

1: X-ray imaging system 10: X-ray irradiation device 20: X-ray imaging device (radiation imaging device) 21: Upper case 22: Lower case 23: Seal member 24: Top plate (light shielding layer) 25: Inner plate (reinforcing plate) )
26: scintillator 27: lens bracket 28: camera board 29a: first frame 29b: second frame 30: subject 40: imaging unit 41: lens 42: lens holder 43: imaging elements A1 to A16: imaging area

Claims (4)

A radiation imaging apparatus that performs an imaging operation using radiation irradiated to a subject,
A scintillator that converts radiation into visible light;
A light-shielding layer disposed on the subject side with respect to the scintillator, exposed to the outer surface of the radiation imaging apparatus and contactable with the subject, allowing radiation to pass through and shielding visible light;
Has a IMAGING element that converts photoelectrically visible light generated by the scintillator, and a lens for condensing the visible light generated by the scintillator toward the imaging device, are arranged side by side in a predetermined plane A plurality of imaging units,
A lens bracket for holding the lens in the plurality of imaging units;
Be between the scintillator and the imaging unit, wherein is arranged at a position away from the imaging unit and the lens bracket, a flat reinforcement plate lead particles therein to have a dispersed light transmissive, Have
The thickness of the reinforcing plate is thicker than the total thickness of the scintillator and the light shielding layer, and the optical path lengths from the respective parts are equal to each other in the optical path of the visible light incident on each part in the imaging surface of the imaging element. A radiation imaging apparatus characterized in that the position is a thickness at which the position is located inside the reinforcing plate .   The radiation imaging apparatus according to claim 1, wherein the light shielding layer is in contact with the scintillator.   The radiation imaging apparatus according to claim 1, wherein the reinforcing plate is in contact with the scintillator.   The radiation imaging apparatus according to claim 1, wherein the reinforcing plate is made of an acrylic resin.