JP3131827U - Radiation detector - Google Patents

Abstract

Provided is a radiation detection apparatus capable of bringing a subject into close contact with a photo timer.
[Means] A concave portion is provided in the lid portion 21 of the housing 2. An exposure radiation detector 3 such as a phototimer is disposed in the recess. With this configuration, the distance between the surface of the apparatus and the detection surface is shortened by the depth of the recess. In addition, the attenuation of incident radiation is reduced by the thickness of the recess. Therefore, the object and the detection surface can be brought close to each other while maintaining the mechanical strength, and the image quality is improved. In addition, since the attenuation amount of radiation is reduced, it is possible to take an image with a lower dose.
[Selection] Figure 1

Description

The present invention relates to a two-dimensional radiation detector capable of detecting a transmission image of radiation such as X-rays, and more particularly to an arrangement in which a radiation detector for exposure control such as a phototimer is arranged.

As shown in FIG. 4A, the conventional radiation detection apparatus includes a two-dimensional radiation detector 101 held on the bottom surface of the housing 102 and exposure radiation detection disposed on the radiation incident surface of the housing 102. And a radiation shielding member 104 disposed on the back side of the radiation incident surface of the housing 102 (see, for example, Patent Document 1).

In addition, FIG.4 (b) is the figure which looked at the radiation detection apparatus from the radiation entrance plane side. In order to make the shape of the radiation shielding member 104 easy to understand, the upper right part of the radiation incident surface of the exposure radiation detector 103 and the housing 102 is cut out and displayed. That is, the radiation shielding member 104 is disposed in the peripheral portion on the back side of the radiation incident surface of the housing 102 and is not disposed in the central portion. The radiation shielding member 104 is for preventing incident radiation from being irradiated to a portion other than the two-dimensional radiation detector 101 as much as possible. When the radiation shielding member 104 is arranged at the center portion, the shadow is applied to the two-dimensional radiation detector 101. It is inconvenient.

The two-dimensional radiation detector 101 integrates, for a certain period, the radiation R incident on the two-dimensional radiation detector 101 out of the radiation Ri emitted from the radiation source P such as an X-ray tube and transmitted through the subject M. Then, an electrical signal corresponding to the spatial intensity distribution of the radiation R is generated. Here, since the dynamic range of the two-dimensional radiation detector 101 is finite, it is necessary to control (exposure control) the time of radiation emitted from the radiation source P so as to be appropriately within the dynamic range. Therefore, an exposure control radiation detector 103 such as a photo timer is provided between the two-dimensional radiation detector 101 and the subject M, and the radiation dose from the start of radiation irradiation is integrated in real time. Control is performed to stop radiation irradiation from the radiation source P when a predetermined value is exceeded. This control is called AEC (Automatic Emission Control) control and is generally used (see, for example, Patent Document 2).

Japanese Patent Application No. 2005-144250 JP 2005-509482 A

In radiography, it is necessary to improve the image quality by bringing the subject and the detection surface of the two-dimensional radiation detector into close contact with each other as much as possible to achieve low scattered radiation and a low magnification. In addition, it is desirable that the amount attenuated by the housing is as small as possible for improving S / N or low-dose imaging. Therefore, it is desirable that the radiation incident surface of the casing be as thin as possible. However, simply thinning the casing has caused problems such as a decrease in mechanical strength of the casing and bending of the incident surface.

In view of such problems, an object of the present invention is to provide a radiation detection apparatus capable of bringing a subject into close contact while maintaining the mechanical strength of a housing.

In order to achieve the above object, the present invention has the following configuration. That is, the two-dimensional radiation detector according to claim 1 holds the radiation detector and the radiation detector inside, and at least the radiation detection of the two-dimensional radiation detector on the front or back surface on the radiation incident side. It has the housing | casing in which the recessed part which has an area larger than an area was formed, and the radiation detector for exposure arrange | positioned at the said recessed part.

The radiation detection apparatus according to claim 2 is the radiation detection apparatus according to claim 1, wherein the casing is formed with a main body portion for holding the two-dimensional radiation detector and the concave portion. A lid portion, and the main body portion and the lid portion are engaged with each other.

The radiation detection apparatus according to claim 3 is the radiation detection apparatus according to claim 1 or 2, further comprising a radiation shielding member arranged in a predetermined region on the back surface of the housing on the radiation incident side. It is characterized by having.

The radiation detection apparatus according to claim 4 is the radiation detection apparatus according to claim 3, wherein the recess is a through hole, and the area of the recess is not provided with the shielding member. It is characterized by being larger than the area of the region.

The radiation detection apparatus according to claim 5 is the radiation detection apparatus according to claim 3 or 4, wherein the two-dimensional radiation detector includes a radiation conversion layer that converts radiation into an electrical signal; A readout substrate for reading out electrical signals from the radiation conversion layer; a readout control circuit for controlling readout processing of the readout substrate; and an amplification circuit for amplifying the readout electrical signals, and the readout control. The circuit and the amplifier circuit are arranged in a region where incident radiation is shielded by the shielding member.

Furthermore, the radiation detection apparatus according to claim 6 is the radiation detection apparatus according to any one of claims 3 to 5, wherein the shielding member is sintered tungsten.

The radiation detection apparatus according to claim 1 of the present invention operates as follows. That is, the distance between the surface of the apparatus and the detection surface is shortened by the depth of the recess. In addition, the attenuation of incident radiation is reduced by the thickness of the recess.

By such an action, the subject and the detection surface can be brought close to each other while the mechanical strength is substantially maintained, and the image quality is improved. By reducing the thickness partially, the strength can be maintained as compared with the case where the overall thickness is reduced. In addition, the overall strength can be increased by combining with the radiation detector for exposure placed in the thinned portion. It can be maintained. In addition, since the attenuation amount of radiation is reduced, it is possible to take an image with a lower dose.

Further, the radiation detection apparatus according to claim 2 can be manufactured by attaching a two-dimensional radiation detector to the main body portion and covering the lid portion with the two-dimensional radiation detector. Therefore, assembly and disassembly are facilitated. Furthermore, the distance between the inner surface of the housing and the detection surface can be adjusted to some extent by the engaging portion.

According to the radiation detection apparatus of the third aspect, the incident radiation is transmitted through the lid, its peripheral part is shielded by the shielding member, and its central part is transmitted and detected by the two-dimensional radiation detector. .
With this action, it is possible to significantly reduce the influence of backscattered rays and the like caused by radiation irradiation on unnecessary areas. In addition, it is possible to suppress the influence of backscattered rays and the like due to radiation irradiation to unnecessary areas. The backscattered rays are radiation in which incident radiation is scattered inside, and a part thereof is incident on the two-dimensional radiation detector from behind the two-dimensional radiation detector, and appears as noise in the detection result.

According to the radiation detection apparatus of the fourth aspect, the incident radiation in the detection area is not attenuated at all by the housing but is attenuated only by the exposure radiation detector and detected by the two-dimensional radiation detector.
Therefore, the distance between the subject and the incident surface can be further shortened, which contributes to the improvement of the image quality. Furthermore, since there is no attenuation by the housing, there is an effect that it is possible to take an image with a lower dose.

According to the radiation detection apparatus of the fifth aspect, the incident radiation is transmitted through the lid, its peripheral portion is shielded by the shielding member, and its central portion is transmitted and detected by the two-dimensional radiation detector. . At this time, the transmitted incident radiation is not directly applied to the readout circuit or the amplification circuit.
Therefore, since the direct readout circuit and the amplification circuit are not affected by incident radiation, there is an effect that the element is not deteriorated without being affected by radiation-derived noise.

Furthermore, according to the radiation detection apparatus which concerns on Claim 6, a tap process can be given to the shielding member which consists of sintered tungsten.
Therefore, there is an effect that a fixing method by screwing can be employed.

[First embodiment]
With reference to FIG. 1, the structure of the radiation detection apparatus which concerns on this invention is demonstrated. As shown in FIG. 1, the radiation detection apparatus according to the present embodiment includes a two-dimensional radiation detector 1 held on the bottom surface of a housing 2 and exposure radiation detection arranged on the radiation incident surface of the housing 2. And a radiation shielding member 4 disposed on the back side of the radiation incident surface of the housing 2.

Moreover, the housing | casing 2 is comprised from the main-body part 22 and the cover part 21, and is engaged by screwing, adhesion | attachment, and other methods by the side surface. A concave portion 211 is formed in the lid portion 21, and the exposure radiation detector 3 is disposed in the concave portion. The exposure radiation detector 3 may be adhered to the recess 211 or may simply have a fitting structure. A fitting structure is preferable because it can be replaced with various phototimers at the time of use.

As a material constituting the housing 2, aluminum, iron, stainless steel, sintered tungsten, other single metals or alloys, carbon, FRP, CFRP, or the like can be used. The material can be variously changed as long as the material and shape exhibit rigidity sufficient to hold the two-dimensional radiation detector. However, the lid portion 21 is desirably formed of a material having a high radiation transmittance, and carbon or CFRP is preferable. In particular, CFRP is more preferable because it has a function of shielding external noise. On the other hand, the main body 22 is preferably formed of a material having a low radiation transmittance. Further, a material having a low radiation reflectance and a high radiation absorption rate is most preferable. This is to prevent incident radiation from coming out of the housing 2 again. In particular, sintered tungsten is preferable because both the radiation transmittance and the reflectance are low while maintaining rigidity. Therefore, it can be said that the main body 22 is preferably formed of a material having a higher radiation transmittance than the lid 21.

Further, the two-dimensional radiation detector 1 is arranged in the order of the radiation conversion layer 11, the readout substrate 12, and the holding substrate 15 from the incident surface side.

The radiation conversion layer 11 refers to a thick film of a substance that directly converts radiation such as amorphous selenium or polycrystalline CdZnTe into electric charges, or one that converts radiation such as CsI into electromagnetic waves of other wavelengths such as visible light. In addition, various modes can be changed as long as it has a function of receiving radiation and converting it into an electrical signal.

The readout substrate 12 is an active matrix substrate or a substrate in which switching elements and charge storage means are arranged in a matrix like a CCD. In addition, as long as the radiation conversion layer 11 has a function of reading the spatial distribution of radiation as an electrical signal, the mode can be variously changed.

The holding substrate 15 holds the radiation conversion layer 11 and the readout substrate 12 and is fixed to the main body portion 22 via the stud 221.

In order to read out the electrical signal using the readout substrate 12, the readout control circuit 13 for controlling the opening and closing of the switching element included in the readout substrate 12, the amplification circuit 14 for amplifying the readout electrical signal, and the amplified electrical signal Is required to be converted into a digital signal and transferred to an external device. In the present embodiment, the readout substrate 12 and the control transfer circuit 17 are connected by a plurality of flexible cables 16, and the readout control circuit 13 and the amplification circuit 14 are mounted on the flexible cable 16.

Here, the radiation shielding member 4 is disposed in a predetermined region of the lid portion 21. Arranging in the predetermined area means arranging in a radiation detection area so that the shadow of the radiation shielding member 4 does not overlap. Here, the radiation detection area refers to an area where the spatial distribution of the radiation R can be extracted as a digital signal from the control transfer circuit 17 when the radiation R enters the radiation conversion layer 11. Therefore, when the incident radiation R is parallel light, it is necessary that the radiation shielding member 4 does not exist immediately above the radiation detection area. However, since radiation is usually emitted from a point source, it is often cone-shaped. Therefore, when the maximum distance (maximum SID) between the radiation source P in actual use and the detection surface of the radiation conversion layer 11 is known, the shadow of the radiation shielding member 4 is the radiation at the maximum SID in actual use. It is most desirable to arrange at a position that is substantially adjacent to the outside of the detection area.

In the radiation detection apparatus of this embodiment, the distance D between the incident surface of the radiation detection apparatus and the incident surface of the two-dimensional radiation detector is shorter by the thickness D3 of the recess than in the case of the conventional technique (FIG. 4). Become. Furthermore, the absorption of radiation by the lid 21 can be reduced.

The readout control circuit 13 and the amplification circuit 14 are arranged by the radiation shielding member 4 in a region where the radiation R does not reach. Therefore, it is possible to prevent the radiation R from acting on these circuits and generating noise. Further, deterioration of the semiconductor element due to radiation can be prevented.

[Second Embodiment]
Next, another embodiment of the present invention will be described with reference to FIG. First, it differs from the above-described embodiment in that the recess 221 is a through hole.
In this case, it is necessary that the radiation shielding member 4 is disposed at least inside the through hole. This is because the periphery of the bottom surface of the exposure radiation detector 3 from the through hole is joined to the radiation shielding member 4 and the side surface is joined to the lid portion 21 of the housing 2. In addition, it is the same as that of Embodiment 1 about not only joining but also a fitting structure.

Since it is configured in this way, the distance D can be further reduced. Moreover, since the absorption of incident radiation by the lid 21 can be eliminated, it is possible to take a lower dose.

In FIG. 2, the radiation shielding member 4 is engaged with the lid portion 21 by screws 5. In the present embodiment, the radiation shielding member 4 is made of sintered tungsten, and the screw hole 41 can be formed by tapping. Therefore, the radiation shielding member 4 can be engaged with the lid 21 by the screw 5.
With this configuration, the coupling strength between the lid portion 21 and the radiation shielding member 4 can be increased. Therefore, even when the exposure radiation detector 3 is directly joined to the radiation shielding member 4, even when a load is applied to the exposure radiation detector 3, the radiation shielding member 4 is prevented from peeling off from the lid portion 21. be able to.

In addition, this embodiment also includes the aspect which uses only the center vicinity of a recessed part as a through-hole.

[Third embodiment]
In the first and second embodiments, the concave portion is provided on the surface of the lid portion 21, but may be provided on the back surface as shown in FIG. 3. In this case, there is an advantage that the surface of the radiation detection apparatus can be made completely flat. The exposure radiation detector 3 always requires an exposure value transfer cable 31. By providing a recess on the back surface and disposing the exposure radiation detector 3 in the recess, the exposure value transfer cable 31 is provided. The cable 31 can be bundled together with a cable for transferring image data from the control transfer circuit 17 to an external device, and can be led out of the radiation detection apparatus through a cable outlet 222 provided in the main body 22. Furthermore, since the radiation R can be measured at a position closer to the two-dimensional radiation detector 1, exposure control with high accuracy is possible. The purpose of exposure control is to estimate the integrated value of the radiation incident on the two-dimensional radiation detector 1, so that measuring the radiation dose at a position close to the two-dimensional radiation detector 1 improves the accuracy. It is because it connects.

In the first embodiment, the radiation shielding member 4 is not essential. However, in the second embodiment, the radiation shielding member 4 is essential. This is because the radiation shielding member 4 also functions as a holding member for the exposure radiation detector 3.

In all the embodiments, when there is no processing circuit such as the readout circuit 13, the amplification circuit 14, the holding substrate 15, the flexible cable 16, and the control transfer circuit 17, the arrangement location may be different. In that case, the effect that the adverse effect on the processing circuit due to the incident radiation can be reduced is not achieved, but the distance D between the subject M and the detection surface of the two-dimensional radiation detector is shortened, and There is an effect that attenuation of the incident radiation Ri can be reduced.

In all the embodiments, the case 2 has been described as being divided into the lid portion 21 and the main body portion 22. However, the case 2 may be a single piece or may be further divided into a plurality of parts. . However, assembling is facilitated by separating the lid portion 21 and the main body portion 22. The built-in components are preferably fixed to the bottom surface or top surface of the housing 2, and in that case, it is desirable from the viewpoint of work efficiency that the housing 2 is divided into upper and lower parts and assembled. is there. Also, in the case where maintenance is performed after disassembling again after completion of assembly, it is preferable that the components are separated into upper and lower parts because access to the built-in components is facilitated.

When the housing 2 is integrated, it can be assembled by a process of creating a built-in component and forming the housing 2 around it.

Although the radiation detector according to the present invention has been described in detail above, the present invention is not limited to such an embodiment. For example, the present invention can be applied to non-destructive inspection apparatuses other than medical uses.

It is a figure which shows 1st embodiment of this invention. It is a figure which shows 2nd embodiment of this invention. It is a figure which shows 3rd embodiment of this invention. It is a figure which shows the radiation detection apparatus which concerns on a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Two-dimensional radiation detector 11 Radiation conversion layer 12 Reading board 13 Reading control circuit 14 Amplifying circuit 15 Holding board 16 Flexible cable 17 Control transfer circuit 18 Image data transfer cable 2 Case 21 Lid part 22 Body part 3 Exposure radiation detection Device 31 Exposure value transfer cable 4 Radiation shielding member 41 Screw hole 5 Screw 211 Radiation incident surface 212 Recess 221 Stud 222 Cable outlet 101 Two-dimensional radiation detector 102 Case 103 Exposure radiation detector 104 Radiation shielding member M Subject Ri Incident radiation R Transmission radiation P Radiation source

Claims (6)

A two-dimensional radiation detector and a housing that holds the radiation detector inside and has a recess having a larger area than at least the radiation detection area of the two-dimensional radiation detector on the front or back surface of the radiation incident side And a radiation detector for exposure disposed in the recess. The housing includes a main body holding the two-dimensional radiation detector and a lid formed with the recess, and the main body and the lid are engaged with each other. The radiation detection apparatus according to claim 1. The radiation detection apparatus according to claim 1, further comprising a radiation shielding member disposed in a predetermined region on the back surface of the housing on the radiation incident side. The radiation detecting apparatus according to claim 3, wherein the recess is a through hole, and an area of the recess is larger than an area of a region where the shielding member is not disposed. The two-dimensional radiation detector includes a radiation conversion layer that converts radiation into an electrical signal, a readout substrate for reading out an electrical signal from the radiation conversion layer, a readout control circuit that controls a readout process of the readout substrate, An amplification circuit that amplifies the read electrical signal, and the readout control circuit and the amplification circuit are arranged in a region where incident radiation is shielded by the shielding member. The radiation detection apparatus according to claim 3 or 4. The radiation detection apparatus according to claim 3, wherein the shielding member is sintered tungsten.

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