JP2001188096A - Method for manufacturing radiation detector of two- dimensional array type and x-ray shield wall - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation detector which is equipped with a collimator that can be easily worked, functions with high accuracy and can be manufac tured at much lower costs. SOLUTION: Vertical groove shields 11a and lateral groove shields 11b are formed by irradiating a photosensitive glass 1 with ultraviolet rays with a mask by an ultraviolet-ray mask exposure method, processing the glass, etching it with an acid, making grooves shaped like a lattice in the direction of the incidence of X rays and filling and encapsulating the powder of heavy metal like tungsten into the grooves. The shields 11a and the shields 11b are used as a collimator for an X-ray shield wall arrayed two-dimensionally, and a radiation detector is constituted by combining with the collimator an X-ray detector component (a scintillator array 4, a photoelectric conversion element 5, a scanning circuit 7 and a glass substrate 6) that is compatible with the collimator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray CT apparatus, and more particularly to detecting cone-shaped X-rays transmitted through a subject with a large number of radiation detecting elements arranged in an array via a collimator. The present invention relates to a two-dimensional array radiation detector.

[0002]

2. Description of the Related Art An X-ray CT apparatus emits X-rays from an X-ray tube, is focused on a fan-shaped X-ray beam by a collimator at an emission port, and is opposed to the X-ray tube with respect to a subject. An arc-shaped collimator and a detector arranged in a rotating manner are rotated, the detector captures X-ray information transmitted through the subject, and the signal is processed by a computer to obtain an X-ray tomographic image of the subject. . X-rays radiated from the X-ray tube are transmitted straight through the subject and scattered by the subject, and scattered by the subject. To prevent this, a collimator is provided in front of the detector. In this collimator, an X-ray shielding wall is formed of a material that is difficult to transmit X-rays for each channel in front of detectors arranged one-dimensionally. The detector is an X-ray detector element consisting of a scintillator element that converts X-rays into light, and a photodiode that detects the light converted by this scintillator element and outputs it as an electric signal, with the X-ray tube at the center. Approximately 500 to 1000 channels are arranged in an arc.

[0003] From the mechanical arrangement in manufacturing, 8 to 30 scintillators and photodiodes combined by optical bonding are arranged on a substrate to constitute one module. It is arranged in a substantially arc shape continuously on the circumference, combined with a collimator, and
For solid state detectors. FIG. 4 shows the structure of the collimator. The collimator includes an arc-shaped support plate 32, an arc-shaped support plate 33 on which support rods 34 are supported from both ends of the surface of the support plate 32, and the support plate 33 and the support plate 32.
And an X-ray shielding plate 35 inserted and fixed in the direction of incidence of the X-ray beam from the X-ray tube.

[0004] The X-ray shielding plate 35 has a support plate 32 and a support plate 33 on both sides thereof, and is fixed with a fixing adhesive. This fixing and bonding work has a hollow space having a shape along the entire outer shape of the collimator, and is cut in advance into a jig frame having a number of vertical grooves into which the X-ray shielding plate 35 can be fitted along the inner space of this space. X-ray shielding plate 35
The X-ray shielding plate 35 is inserted vertically along the groove.
After the upper and lower surfaces are integrally bonded to the support plate 32 and the support plate 33, the upper and lower surfaces are pulled out from the frame to either one of the upper and lower sides. Alternatively, the support plate 32 and the support plate 33 are provided with grooves into which both ends of the X-ray shielding plate 35 can be inserted, and the X-ray shielding plate 35 is fitted into the grooves and fixed with a fixing adhesive. The directions in which the X-ray shielding plates 35 are fixed are bonded and fixed such that they converge in the focal direction of the X-ray tube. When the grooves are provided and fixed, the grooves are processed so that the directions of the grooves converge in the focal direction of the X-ray tube.

[0005] The collimator to which the X-ray shielding plate 35 is fixed is fixed by a fixing screw above a detector section on which a photodiode array and a scintillator array are mounted on a substrate. The positional accuracy of the collimator and the detector is high. It is set accurately and the detection sensitivity of each detector is made uniform and maximum. Then, an integrated body of the collimator and the detector is attached to the main housing.

[0006]

The conventional radiation detector is configured as described above. However, in a detector arranged one-dimensionally in a channel direction (a direction perpendicular to the body axis of the subject), Since only one slice is obtained for a tomographic image, scanning must be performed many times to obtain a multilayer tomographic image. In order to obtain a large amount of slice data at one time, a two-dimensional array type radiation detector in which X-ray detection elements are arranged not only in the channel direction but also in a slice direction orthogonal to the channel direction (body axis direction of the subject) can be considered. Therefore, a detector that is used together with a cone beam X-ray tube to collect multi-slice data of a minute slice pitch in a short time is expected.

FIG. 5 shows the proposed two-dimensional array type detector. The slice-direction collimator 27 and the channel-direction collimator 2 are formed in an arc shape around the X-ray source 26.
8 and the detection element array 29 are provided in three stages, and the X-ray source 2
6 are formed in a converged structure. Slice direction collimator 27 and channel direction collimator 28
Is provided with a support (not shown) made of a thin plate at the front and rear, and a groove into which the collimator plate 30b and the collimator plate 30a can be inserted is formed, and the collimator plates 30b and 30a are fixed to the grooves. Is supported. In the structure of the collimator of this detector, both the support and the collimator plates 30b and 30a are expensive, and in particular, the support must be subjected to complicated groove processing, so that it cannot be manufactured with high accuracy. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and the support for supporting the collimator can be easily processed, and can be manufactured with higher accuracy, and the material cost of the support and the collimator can be reduced. It is an object of the present invention to provide a two-dimensional array type radiation detector capable of obtaining many tomographic images at one time.

[0009]

In order to achieve the above object, a two-dimensional array type radiation detector according to the first aspect of the present invention comprises:
A line detector unit and a collimator plate are provided with a collimator device fixed to a support, and transmitted X-rays obtained by irradiating a subject with a cone-shaped X-ray beam from an X-ray source are transmitted through the collimator device. In the two-dimensional array type radiation detector configured to be guided to the X-ray detector via the X-ray detector, the X-ray detector parallel to the X-ray detector in the X-Y direction at predetermined intervals in the X-ray incident direction. An X-ray shielding wall in which a lattice groove is formed, and the lattice groove is filled with an X-ray absorbing material, and an X-ray detector unit arranged corresponding to the X-ray shielding wall.

According to a second aspect of the present invention, a photosensitive glass body is exposed to light using an optical pattern mask with an ultraviolet light source, the exposed portion is crystallized by a heat development process, and after re-exposure, is etched with an acid. 2. A two-dimensional array type radiation detector according to claim 1, wherein lattice-shaped grooves are formed at predetermined intervals in the X-ray incident direction, and the grooves are filled with an X-ray absorbing material. It is.

The two-dimensional array type radiation detector of the present invention is constructed as described above, and the tungsten powder or the like that absorbs X-rays is formed on a glass body at predetermined intervals in the X-ray incidence direction in the vertical and horizontal directions. Filled and sealed in two-way latticed grooves,
Since it is used as a collimator for a two-dimensionally arranged X-ray shielding wall and a two-dimensional array type X-ray detector unit is combined with the collimator, many tomographic images can be obtained at one time. it can. The processing of the lattice-shaped grooves in the glass body is performed by performing light exposure using an optical pattern mask with an ultraviolet light source, crystallizing the exposed portions by heat development, re-exposure, and etching with acid. ,
It can be easily manufactured with high accuracy. Further, since heavy metal powder such as tungsten or molybdenum is used as a material for the X-ray shielding wall, the cost is reduced as compared with a conventional tungsten plate, so that the cost is reduced.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a two-dimensional array type radiation detector according to the present invention will be described with reference to FIG. FIG. 1 is a diagram showing a cross section of a two-dimensional array type radiation detector of the present invention. This two-dimensional array type radiation detector is constructed by filling the vertical and horizontal grooves of the photosensitive glass 1 with an X-ray absorbing material and blocking the vertical grooves 11a.
A collimator having a two-dimensional X-ray shielding wall formed by a lateral groove shielding 11b, a detector having a photoelectric conversion element 5, a scintillator array 4, and a scanning circuit 7 provided on a glass substrate 6, the collimator and the detector And spacers 15a for vertically arranging them at predetermined intervals.
The position of the collimator and the detector is accurately adjusted and fixed by 15.

When the photosensitive glass 1 is irradiated with ultraviolet rays, the irradiated portion is easily crystallized, and when heated to promote the reaction, it is crystallized. And then irradiate again with ultraviolet light,
When etching is performed with an acid, the irradiated portion is etched, and a sharp edge is formed at the boundary between the non-irradiated portion and a groove is formed. The depth of the groove is determined by the material of the photosensitive glass 1, the intensity of the ultraviolet light, and the exposure time, and can be controlled. The external dimensions are 300 x 3 in length x width depending on the application.
00mm-600 × 600mm, thickness 1mm-10
mm. The vertical groove shield 11a and the horizontal groove shield 11b are formed by filling a lattice-like groove formed in the photosensitive glass 1 by an optical pattern mask exposure method with a heavy metal powder such as tungsten or molybdenum. .15mm ~
1.0 mm, the width of the portion to be a groove is 0.05 mm to 0.1 mm.
3 mm. The direction of the groove is formed so as to converge in the X-ray incident direction, and the heavy metal powder filled in the groove is uniformly hardened by flowing an adhesive such as epoxy over the surface, and is sealed. The vertical groove shield 11a and the horizontal groove shield 11b remove unnecessary scattered radiation, function as a collimator, and can capture necessary transmitted X-ray information transmitted through the subject to the detector.

Next, a method of manufacturing the collimator will be described.
As shown in FIG. 2, the manufacturing process includes (a) preparing a photosensitive glass, (b) preparing an exposure mask, (c) exposing, (d) developing, and (e) filling an X-ray shielding material. First,
(A) The photosensitive glass 1 is externally dimensioned to 300 × 300 mm.
Prepare from 600 to 600 mm and thickness from 1 to 10 mm according to the application. Next, (b) an optical pattern mask 2 for exposing the photosensitive glass 1 is formed. The white line portion shown in FIG. 2 indicates a portion through which light is transmitted. A pattern is formed on the transparent film so that the pitch 2a is 0.15 to 1.0 mm and the width of the groove portion (white line portion) is 0.05 to 0.3 mm depending on the application.

Next, (c) the ultraviolet point light source 3 is prepared, and when the distance L between the photosensitive glass 1 and the ultraviolet point light source 3 is set as a two-dimensional array type radiation detector, all the openings of the collimator are set. Is usually L, so that
= 0.5 to 1.0 m. A mask 2 is set on the upper surface of the photosensitive glass 1, the intensity of the ultraviolet point light source 3 is set to a predetermined value, and exposure is performed for a predetermined time. At this time, the photosensitive glass 1
When the internal reflection occurs at the bottom surface of the photosensitive glass 1, a material having a higher refractive index than the photosensitive glass 1 may be coated on the back surface. Next, (d) the exposed portion is crystallized by a heat development treatment, and re-exposed. Then, the portion exposed by the acid is etched. It can be observed that the lattice-shaped grooves 8 are formed on the photosensitive glass 1 so as to converge in the X-ray incident direction. Further, the thickness of the remaining portion of the groove is 0.5 or less.

Next, (e) a heavy metal powder such as tungsten or molybdenum is filled in the lattice-shaped grooves 8. The heavy metal powder having a particle diameter sufficiently smaller than the groove is used. At the time of filling, the filler may be naturally dropped into the lattice-shaped groove 8 or may be pressed and compacted. In order to enclose the X-ray shielding wall made of the heavy metal powder thus formed, an adhesive such as epoxy is uniformly flowed over the surface and cured. Further, it may be sealed by bonding with a material having a good X-ray transparency, such as a thin plate of aluminum or carbon. Instead of filling with heavy metal powder, the lattice-shaped groove 8 may be filled with heavy metal such as molybdenum or tungsten by vapor deposition by MOCVD. In this case, a heavy metal is deposited in the step (e ′) shown in FIG. 2, and the heavy metal deposited on the surface of the opening of the collimator in the next step (f) is removed by polishing. Further, as shown in step (g), the entire surface is exposed and re-exposed to improve the X-ray transmittance.
A method may be adopted in which development and acid treatment are performed to remove all glass portions other than the pin hole (positioning hole 15) fitted with the sensor.

On the other hand, as shown in FIG. 1, the detector includes a scintillator array 4 on a glass substrate 6 and a photo-diode such as a photodiode bonded to the lower surface of the scintillator array 4 via an adhesive having good light transmittance. It comprises a conversion element 5 and a scanning circuit 7 for electronic scanning. When the X-rays enter the upper surface of the scintillator array 4, the X-rays are converted into light in the scintillator array 4, and the emitted light is detected by the photoelectric conversion element 5, converted into an electric signal, and incident from the scanning circuit 7. A signal proportional to the dose is extracted.

As a method of converting an incident X-ray into an electric signal, a method in which a panel surface is processed with a Gd ₂ O ₂ S ceramic scintillator on an array, a method in which a CdWO ₄ single crystal is processed in an array, a CsI columnar crystal, etc. A scintillator array is provided, in which X-rays are converted to light, and light is converted to electricity by the next-stage photoelectric conversion element 5, and an X-ray conversion semiconductor element such as a-Se is directly provided on a substrate. , C
There is a direct conversion flat panel type on which dZnTe, CdTe, or the like is formed. In each case, the incident X-ray is scanned by the scanning circuit 7 and read as an electric signal.

FIG. 3 shows a signal readout scanning circuit 7 of the detector. When X-rays enter, the scintillator array 4 shown in FIG. 1 emits light according to the incident dose, and the light enters the photoelectric conversion element 24 such as a photodiode. The photoelectric conversion element 24 generates an electric charge according to the incident light. On the detector board,
A horizontal gate line 22 and a vertical read signal line 23 are wired corresponding to each photoelectric conversion element 24, and each photoelectric conversion element 24 is connected to an FET 25 serving as a gate valve. The sequential signal of the gate driver circuit 20 is
By sending the signal to the ET 25, the FET 25 is switched, and the charge signal of the photoelectric conversion element 24 is transferred to the read signal line 23.
, And sequentially input to the read amplifier circuit 21. Then, an X-ray image signal is sent from the readout amplifier circuit 21 to an external circuit.

Finally, the collimator and the detector are separated from each other by a predetermined distance using the spacer 15a shown in FIG. Are uniformly and maximally detected. And what integrated the collimator and the detector is attached to the main housing.

In the above embodiment, the collimator for the X-ray CT apparatus has been described. However, the collimator can be used as a grid for a flat panel sensor used in general radiography and fluoroscopy. In this case, as a specification example, the thickness of the photosensitive glass 1 is 1.5 mm, and the outer dimensions are 430 × 4.
The pitch is 30 mm, the pitch is 0.15 mm, and the width of the groove is 0.05 mm.

[0022]

The two-dimensional array type radiation detector of the present invention is configured as described above, and heavy metal powder such as tungsten or molybdenum is formed on a photosensitive glass body in the X-ray incident direction by a photomask exposure method. Is filled and sealed in a lattice-shaped groove, which is used as a collimator of a two-dimensionally arranged X-ray shielding wall, and is configured by combining a two-dimensional array type X-ray detector corresponding to the collimator. Many tomographic images can be obtained at one time. Since the lattice-shaped grooves are accurately manufactured by the photomask exposure method and the collimator is correctly oriented to the focus direction of the X-ray tube, X-rays are detected with scattered radiation generated from the subject completely removed. As a result, an image with a good S / N ratio can be obtained. Furthermore, the use of the photomask exposure method simplifies the manufacturing process. In addition, since heavy metal powder is used for the material of the X-ray shielding wall, the cost is lower than that of a conventional tungsten plate, and the cost is low. Will be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of a two-dimensional array type radiation detector of the present invention.

FIG. 2 is a diagram for explaining a method of manufacturing a collimator of a two-dimensional array type radiation detector according to the present invention.

FIG. 3 is a diagram showing an X-ray signal detection circuit of the two-dimensional array type radiation detector of the present invention.

FIG. 4 is a diagram showing a collimator of a conventional radiation detector.

FIG. 5 is a diagram illustrating a proposed two-dimensional array radiation detector.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photosensitive glass 2 ... Mask 2a ... Pitch 2b ... Groove width 3 ... Ultraviolet point light source 4 ... Scintillator array 5 ... Photoelectric conversion element 6 ... Glass substrate 7 ... Scanning circuit 8 ... Grid-shaped groove 9 ... W powder 10 ... Adhesive material 11a ... vertical groove shielding 11b ... horizontal groove shielding 15 ... positioning hole 15a ... spacer 20 ... gate driver circuit 21 ... readout amplifier circuit 22 ... gate line 23 ... readout signal line 24 ... photoelectric conversion element 25 ... FET 26 ... X-ray source 27 ... Slice direction collimator 28 ... Channel direction collimator 29 ... Detector element array 30a ... Collimator plate 30b ... Collimator plate 31 ... Detector element 32 ... Support plate 33 ... Support plate 34 ... Support rod 35 ... X-ray shielding plate

Claims (2)

[Claims] An X-ray detector section and a collimator device having a collimator plate fixed to a support, wherein a transmitted X-ray obtained by irradiating a subject with a cone-shaped X-ray beam from an X-ray source is provided. In the two-dimensional array type radiation detector configured to be guided to the X-ray detector unit via the collimator device, the glass body is disposed at a predetermined interval in the XY direction parallel to the X-ray detector unit. An X-ray shielding wall in which a lattice groove is formed in the X-ray incident direction and the lattice groove is filled with an X-ray absorbing material, and an X-ray detector unit arranged corresponding to the X-ray shielding wall are provided. Characteristic two-dimensional array radiation detector. 2. A photosensitive glass body is exposed to light using an optical pattern mask by an ultraviolet light source, and the exposed portion is crystallized by a heat development process. 2. A X-ray used in a two-dimensional array type radiation detector according to claim 1, wherein a lattice-shaped groove is formed in the X-ray incident direction by using the X-ray absorbing material.
A method of manufacturing a line shielding wall.