JP2002000594A - X-ray detector, its manufacturing method and ct system using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray detector capable of constituting an X-ray detecting element array having a little crosstalk and uniform characteristics and a CT system capable of obtaining a tomographic image of a high quality having no artifact using the same by improving a positional accuracy of a partition wall plate for separating channels and/or segments in a slice direction. SOLUTION: The X-ray detecting element array is manufactured by mounting photoelectric converters 6 on a substrate 1, disposing a scintillator 2 thereon, forming a groove for isolating channels and/or slices on the scintillator 2, filling a light reflecting resin 8 in the groove to form a light reflecting layer, forming a groove 11 for inserting the partition wall plate 9 except the reflecting layer of a sufficient thickness for reflecting the light on the filled light reflecting resin layer 8, and fixing the plate 9 to the groove 11. A plurality of the arrays are arranged in a polygonal state at a substantially equal angular pitch on a substantially circular arc at a focus of an X-ray tube 14 as a center in the channel direction and the slice direction to constitute the X-ray detector 13 for the X-ray CT system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray detector for detecting X-ray transmission data, and more particularly to an X-ray detector comprising a scintillator and a photoelectric conversion element, which is aligned with a light receiving portion of the photoelectric conversion element. X-ray detector capable of achieving high accuracy and uniform detection characteristics of a plurality of X-ray detection elements and reducing crosstalk, and a tomographic image effective for diagnosis free of ring artifacts can be obtained using this detector. X
The present invention relates to a line CT apparatus.

[0002]

2. Description of the Related Art In an X-ray CT apparatus, it is desired to reduce the time required to obtain one CT image in order to improve the throughput of the apparatus. There are the following two methods for reducing this time. (1) Reduction of the time required for one rotation of the scanner (2) Increase in the number of tomographic images that can be captured per rotation of the scanner (1) Regarding (1), the weight of the X-ray tube, The rotation speed has been improved.
On the other hand, regarding (2), in the X-ray detector, two or more rows of the X-ray detection elements which have been arranged one-dimensionally in the channel direction until now are arranged in the slice direction (direction orthogonal to the channel direction). Is achieved by arranging a plurality of rows.

[0003] Such an X-ray detector is called a multi-slice X-ray detector, and an X-ray CT apparatus using the same is called a multi-slice X-ray CT apparatus. On the other hand, a conventional one-dimensional array X-ray detector is called a single-slice X-ray detector, and an X-ray CT apparatus using the same is called a single-slice X-ray CT apparatus. X-ray C above
As an X-ray detector used in a T device, a solid-state detector using a scintillator has come to be widely used in contrast to a conventional ionization chamber system using xenon gas.

This solid-state detector has the advantage that the number of X-ray detections can be increased, so that the spatial resolution is remarkably improved.
For example, as disclosed in Japanese Patent Application Laid-Open No. 62-112092, a scintillator that generates light by irradiation of radiation and a photoelectric conversion element that converts light generated by the scintillator into a current are mounted on a substrate. An X-ray detecting element is arranged in a substantially arc-shaped polygon. Each X-ray detection element includes a multi-channel photoelectric conversion element arranged on a substrate, a scintillator stacked thereon, and a connector unit for connecting the photoelectric conversion element to a detection circuit or the like, and the scintillator is Corresponding to a plurality of segments of the photoelectric conversion element, a groove for separating channels is formed for a single slice type X-ray detector, and a groove for separating channels and slices is formed for a multi-slice type X-ray detector. A partition plate is inserted into these grooves to reduce X-ray and light crosstalk between segments.

As described above, since a multi-element array is required for an X-ray CT detector, a single-channel chip is not used for arranging a single-channel chip as a light detecting element for converting output light of a scintillator into an electric signal. A photodetector array having a plurality of channels formed on a chip is often used.

In this photodetector element array, elements must be arranged at high density in a limited mounting space. Therefore, a semiconductor device such as a silicon photodiode is generally used, and a conventional single slice type is used. X
The photodetector array of the X-ray detector is a one-dimensional array in which the light receiving section and the output signal are separated only in a single channel direction. Are divided into a channel direction and a slice direction orthogonal to the channel direction.

[0007] Such one-dimensional and two-dimensionally arranged photodetector arrays and their outputs are taken out because it is necessary to use the X-ray incident side (the scintillator mounting surface) as a common electrode and the back surface as a separation electrode. It is necessary to electrically separate the back surface of the silicon wafer chip on which the photodiode pattern is formed.

For this reason, it is necessary to provide a structure in which a groove is formed for each element to separate the elements, so that machining is required. In this mechanical processing, a groove is formed from the back side of the silicon wafer chip on which the photodiode pattern is formed to the very edge of the surface to separate each element.

In particular, in a multi-slice type X-ray CT apparatus, changing the measurement slice width requires not only changing the incident X-ray beam width but also changing the element width of the X-ray detection element in the slice direction. The X-ray detection element is divided into multiple parts in the slice direction, and the measurement slice width is changed by changing the combination of outputs from the divided elements.

For this reason, the photodetector array used for the X-ray detector of the multi-slice type X-ray detector is divided into many in the slice direction, and each output can be guided to an external circuit in a desired combination. Must be combined with a switch array. Normally, this switch array is arranged in the vicinity of the photodetector array and directly connected between them by a wire bonding method. Further, the output of the switch array is connected to a wiring board by a wire bonding method, and a connector provided on the board is used to connect an external circuit. I was trying to pick up the signal.

In order to manufacture the above one-dimensional and two-dimensional X-ray detecting elements in an array, a scintillator having a predetermined area and a photodiode array having a plurality of channels are combined. The scintillator is also manufactured by finishing the individual channel width and slice width dimensions in line with the light receiving surface position of the photodiode array, bonding and fixing, and inserting a partition plate between each scintillator to prevent crosstalk Although it is possible, since the positioning in the slice direction and the channel direction requires accuracy of about ± 0.05 mm or less, it is difficult to position each scintillator with high accuracy. Therefore,
As a method of aligning the arrangement of each element with high precision, a scintillator plate large enough to cover all channels and slices of the array is adhered to the light receiving surface of the photodiode array with a transparent adhesive, and then exposed from the end of the scintillator There is a method in which groove processing is performed on the scintillator based on the pattern of the photodiode being used as a reference to separate channel slices. Further, a partition plate provided with a light reflection layer on the surface in the groove separated by the groove processing is inserted and fixed.

If the separation groove does not reach the photodiode, the crosstalk between channels in the array and the crosstalk between the arrays will be different, and a ring-shaped artifact will occur at a position corresponding to the end channel of the measured image. Since this occurs, the groove processing needs to completely separate the scintillator and reach the separation groove to the photodiode.

[0013]

In the X-ray detector manufactured in this manner, the segment separation layer in the channel direction and the slice direction contains a substance having a function of light reflection and X-ray absorption such as TiO ₂ . Compared to the case of forming only with resin, since it is formed with a thinner layer, the X-ray utilization efficiency is improved.

However, since the light reflection layer provided on the partition plate inserted into the separation groove must be formed uniformly and firmly on a thin partition plate of about 100 μm, the partition plate on which the reflection layer is formed is formed. In addition, the cost increases, and it is difficult to make the gap between the separation groove and the plate serving as the reflection layer uniform, so that the light reflectance differs depending on the position in the segment as shown in FIG. That is, FIG.
In the case where the distance between the slice direction partition plate 3 and the scintillator 2 ₁ having scintillator 2 ₁ a light reflecting layer inserted in the separation groove 11 'between 2 ₂ differs locations and B locations of the stomach scintillator 2 _{At 1} the X-rays are converted to photons 20,
The photons 20 are reflected by the light reflecting layer of the partition plate 3 in the slice direction and return to the scintillator, resulting in a difference in the detection sensitivity distribution of the scintillator. Will cause artifacts.

In order to obtain a good image free of artifacts, it is necessary that the characteristics are uniform with little variation between segments. As described above, in the conventional method of forming the segment separation layer, even if the pitch and the detection element characteristics of each segment are uniform, if the positional accuracy of the partition plate separating each of the segments is poor, the detection characteristics between the segments are reduced. A difference occurs, which results in deterioration of image quality.

For this reason, the positioning accuracy of the partition plate in the channel and slice thickness direction is an important factor that affects the detector performance. In addition, there is a method of improving the positioning accuracy by reducing the gap between the plate and the groove by narrowing the width of the separation groove, but the thickness of the partition plate and the thickness of the light reflection layer must be strictly controlled. Therefore, there is a problem that the cost is further increased and the reflectance is reduced due to the light reflecting layer rubbing against the separation groove.

Accordingly, an object of the present invention is to improve the positional accuracy of the partition plate for separating each segment in the channel or slice direction, and to form an X-ray detecting element array with extremely little crosstalk and uniform characteristics. An object of the present invention is to provide a line detector and an X-ray CT apparatus capable of obtaining a high-quality tomographic image without artifacts using the detector.

[0018]

The above object is achieved by the following means.

(1) A plurality of photoelectric conversion elements arranged on a substrate, a scintillator arranged on the photoelectric conversion elements and divided into a plurality corresponding to individual photoelectric conversion elements, and separating the scintillators. In an X-ray detector including a plurality of X-ray detection element arrays each including a separator, a light reflection layer is provided at least at an end of the scintillator between scintillators into which the separators are inserted, and between these light reflection layers. An X-ray detector having a structure in which the partition plate is provided.

(2) The above X-ray detector can be realized by the following manufacturing method.

1) A photoelectric conversion element is mounted on a substrate, a scintillator is arranged thereon, and this is adhered to the photoelectric conversion element. A channel or a groove for slice separation is formed in the scintillator. The groove is filled with a light-reflective resin to form a light-reflective layer, and the filled light-reflective resin layer is formed with a groove for inserting a partition plate, leaving a reflective layer thick enough to reflect light. A manufacturing method comprising fixing the above-mentioned partition plate to the substrate.

2) A photoelectric conversion element is mounted on a substrate, a scintillator is arranged thereon, and this is adhered to the photoelectric conversion element. A channel or a groove for slice separation is formed in the scintillator. A groove in which a light reflecting resin is formed by filling the groove and the upper surface of the scintillator with a light reflecting resin, and a partition plate is inserted by leaving a light reflecting layer formed in the groove with a reflection layer having a thickness sufficient for light reflection. And forming the partition plate in the groove.

3) A scintillator is adhered to a glass plate, a channel or a groove for slice separation is formed in the scintillator, and the groove is filled with a light reflecting resin to form a light reflecting layer. A groove for inserting a partition plate is formed in the reflective resin layer, leaving a reflective layer having a thickness sufficient for light reflection, and the partition plate is fixed to this groove to form a scintillator array. Manufacturing method that is fixed to

(3) An X-ray source, an X-ray detector arranged opposite to the X-ray source, holding the X-ray source and the X-ray detector, and driven to rotate around the subject. An X-ray CT apparatus comprising: a rotating disk; and image reconstruction means for reconstructing a tomographic image of the subject based on the intensity of X-rays detected by the X-ray detector. An X-ray CT apparatus using the X-ray detector of (1) to (4) above.

By using the above-described structure and manufacturing method for the X-ray detector, a scintillator that separates at a high-precision pitch obtained by groove processing in the formation of each segment of a channel or a slice thickness, from a scintillator to a photoelectric conversion element array. The groove that reaches is filled with a resin containing a substance having a light reflection function such as TiO ₂ , and the center of the filled layer is grooved leaving a sufficient light reflection layer, and light is applied to the groove as an X-ray absorption layer. If each segment is separated by inserting a partition plate on which no reflective layer is formed, costly formation of the reflective layer on the partition plate can be eliminated, and the light reflective layer is attached to the scintillator side. The structure does not need to manage the gap between the partition plate and the groove. Therefore, the position accuracy of the partition plate for separating each segment in the channel or slice direction is improved, and an X-ray detector with extremely small crosstalk and uniform characteristics can be obtained. The apparatus can obtain high-quality tomographic images without artifacts.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to FIGS.

(Structure of X-ray detecting element array) FIG. 1 is a view showing the appearance of an X-ray detecting element array according to the present invention.
A silicon photodiode array (in the drawing, below the scintillator 2 and not shown in the drawing, is mounted on the printed board 1), and the scintillator 2 is fixed to the light receiving portion thereof with a transparent adhesive. ing. In the scintillator 2, the boundaries between the slice and channel segments are separated by grooves reaching the silicon photodiode, and the slice direction partition plate 3 and the channel direction partition plate 4 are inserted and fixed in the grooves. A connector 5 is attached to the printed circuit board 1. The connector 5 is connected to the output of the silicon photodiode (not shown), and takes out the output of the silicon photodiode to an external circuit. When X-rays enter the scintillator 1, the scintillator emits light in accordance with the intensity of the X-rays, and the emitted light output is converted into an electric signal by a silicon photodiode, and the converted electric signal is transmitted through the connector 5. To an external circuit. The partition plates 3 and 4 prevent crosstalk of light between adjacent slices and channels and crosstalk of X-rays due to scattering from a scintillator, and the surfaces of the partition plates 3 and 4 increase the light reflectance. Molybdenum, tungsten, or the like on which aluminum is deposited is suitable in order for the light emitted from the scintillator to efficiently reach the light receiving surface of the silicon photodiode. Molybdenum and tungsten are effective not only for light but also for X-ray crosstalk.

FIG. 2 is a cross-sectional view of the boundary between channels in the portion A in FIG. The partition plate 4 in the channel direction is adhered to the scintillator 2 by a transparent adhesive 7.
The separation groove of the scintillator 2 is a silicon photodiode 6
Cut to a depth that reaches
Can prevent crosstalk. The separation groove is formed at the center of the dead zone 6b of the silicon photodiode 6. Next, a manufacturing process of the X-ray detection element array will be described. In addition, a light reflecting resin is provided on the side surface of the scintillator 2 or the side surface and the upper surface of the scintillator 2 bonded with the transparent adhesive 7, which will be described in detail in the following manufacturing method.

(Method of Manufacturing X-ray Detecting Element Array) FIG. 3 is a view showing a manufacturing process of the X-ray detecting element array according to the first embodiment of the present invention. In FIG. 3A, the printed circuit board 1
The silicon photodiode 6 is mounted thereon, and the scintillator 2 is disposed thereon, and is adhered to the silicon photodiode 6. The silicon photodiode 6 has a sensitive zone 6a and a dead zone 6b. As shown in FIG.
When it is necessary to perform slice separation (multi-slice X-ray detector), a groove is formed after the scintillator 2 and the silicon photodiode 6 are bonded, and a groove is formed on the scintillator 2 for channel separation. go,
The groove is filled with the light reflecting resin 8. The slice separating groove is also filled with the light reflecting resin 8, and the slice separating layer is grooved while leaving the light reflecting resin 8 thick enough to reflect the light, and the partition plate 9 is formed in the groove.
Insert

Next, as shown in FIG. 3 (c), a groove 11 is formed in the channel separation layer while leaving a light reflecting resin 8 having a thickness sufficient for reflection. Then, as shown in FIG. 3D, the partition plate 9 is inserted into the processed groove 11 and fixed. Also in the groove processing in the channel direction, the partition plate can be positioned with high precision by performing the groove processing based on the pattern of the silicon photodiode slightly exposed from the end of the scintillator. Thus, an X-ray detection element array separated in the slice direction and the channel direction is completed.

FIG. 4 is a view showing a manufacturing process of the X-ray detecting element array according to the second embodiment of the present invention. FIG. 4A is a diagram showing an arrangement relationship between the scintillator 2 and the silicon photodiode 6, which is the same as FIG. 3A of the first embodiment. It is necessary to separate slices (multi-slice X
In the case of a line detector), after bonding the scintillator 2 to the silicon photodiode 6, a groove for slice separation is formed. As shown in FIG. 4B, a groove is formed in the scintillator 2 for channel separation, and the groove is filled with a light reflecting resin 8. Filling the slice separation groove with the light reflecting resin 8,
At the same time, a light reflecting layer is formed on the upper surface of the scintillator with the light reflecting resin 8.

Then, the slice separation layer is grooved while leaving the light reflection resin 8 having a thickness sufficient for reflection, and the partition plate 9 is formed in the groove 11.
Insert Next, as shown in FIG. 4C, a groove is formed in the channel separation layer while leaving a light reflecting resin 8 having a thickness sufficient for reflection. Then, as shown in FIG. 4D, the partition plate 9 is inserted into the groove processed as described above and fixed.
By manufacturing in such a process, the upper reflective layer can be formed at the same time, and a structure that prevents optical crosstalk in the upper reflective layer can be obtained.

FIG. 5 is a view showing a manufacturing process of the X-ray detecting element array according to the third embodiment of the present invention. First, FIG.
As shown in (a), the scintillator 2 is bonded to the glass plate 10. When it is necessary to perform slice separation (multi-slice X-ray detector), the scintillator 2 is bonded to the glass plate 10 and then grooved. This scintillator 2
A groove is formed for channel separation, and the groove is filled with the light reflection resin 8 and the slice separation groove is also filled with the light reflection resin 8, so that the slice separation layer has a sufficient light reflection thickness for light reflection. A groove is formed while the resin 8 is left, and the partition plate 9 is inserted into the groove. This is shown in FIG. As shown in FIG. 5C, the channel separation layer is grooved while leaving a light reflecting resin 8 having a sufficient thickness for reflection, and a partition plate 9 is inserted into the groove 11. It is fixed to the reflective resin 8. Then, as shown in FIG. 5D, the scintillator array formed above is bonded to the silicon photodiode 6. In this method, since it is not necessary to perform groove processing on the silicon photodiode, it is possible to provide the pattern of the printed circuit board in the dead zone of the silicon photodiode.
The degree of freedom of the pattern is increased.

According to the structure and manufacturing method of the X-ray detecting element array described above, the gap between the separation groove and the plate serving as the reflection layer becomes substantially uniform as shown in FIG. That is, the light reflecting resin 8 is provided on both ends of the separation groove between the scintillators or on both ends and on the upper surface, and the partition plate 9 is inserted into the separation groove surrounded by the light reflection resin 8. 8 is fixed with a transparent adhesive, so that the X-rays are converted into photons 20 by the scintillator, and the difference in the amount of the photons 20 reflected by the light reflecting resin 8 and returning to the scintillator is extremely small. It becomes smaller (C and D in FIG. 6). This makes the detection sensitivity distribution of the scintillator uniform,
The problem of sensitivity variation between the segments due to the deterioration of the positional accuracy of the partition plate separating each segment is solved.

(X-ray CT apparatus using X-ray detector according to the present invention) X-ray using the X-ray detecting element array according to the present invention described above.
FIG. 7 shows an example in which a line detector is mounted on an X-ray CT apparatus. In FIG. 7, a detector container 13 is mounted on a rotating plate 19 so as to face the X-ray tube 14. Inside the detector container 13, an X-ray detection element array 12 processed and assembled according to the description of FIGS. 1 to 5 is arranged in a polygonal shape having a substantially circular arc centered on the focal point of the X-ray tube 14. Further, a collimator plate group 15 for removing scattered radiation entering from a direction other than the focal point of the X-ray tube 14 is placed at the X-ray incidence portion of the X-ray detection element array 12. An amplification circuit unit 18 for amplifying a signal from the detection element is placed outside the detector container 13. An opening 21 is provided at the center of the rotating plate 19, and the rotation of the rotating plate 19 around the subject 17 placed in the opening 21 causes the subject 17 to rotate.
The measurement of the amount of X-ray transmission from all circumferential directions can be performed. In the case of a multi-slice type X-ray CT apparatus, the X-ray detection element array 12 and the collimator plate group 15 are arranged also in the slice direction.

X-ray C using the above-described X-ray detector of the present invention
Since the T apparatus can make the detection characteristics of the X-ray detecting element between channels and slices uniform, a high-quality tomographic image free of ring artifacts can be obtained. Since slice data can be measured, a plurality of high-quality tomographic images can be obtained in one scan.

[0037]

As described above, according to the present invention, it is not necessary to form a light reflection layer on the partition plate for preventing light and X-ray crosstalk between the channel and the slice segment. Since the alignment accuracy of the partition plate in the thickness direction is improved and the gap between the partition plate and the groove separating the segment is no longer required to be managed, X-rays having extremely small crosstalk of light and X-rays and having uniform characteristics are eliminated. An X-ray detector capable of forming a row of X-ray detection elements and an X-ray CT apparatus capable of obtaining a high-quality tomographic image without artifacts using the detector can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing the appearance of an X-ray detection element array according to the present invention.

FIG. 2 is a diagram showing details of a cross section of a boundary in a channel direction of the X-ray detection element array according to the present invention shown in FIG.

FIG. 3 is a diagram showing a first embodiment of a manufacturing process of the X-ray detecting element array according to the present invention.

FIG. 4 is a diagram showing a second embodiment of the manufacturing process of the X-ray detection element array according to the present invention.

FIG. 5 is a diagram showing a third embodiment of the manufacturing process of the X-ray detection element array according to the present invention.

FIG. 6 is a diagram used for explaining the effect of light reflection according to the present invention.

FIG. 7 is a diagram showing an example in which an X-ray detector using an X-ray detection element array according to the present invention is mounted on an X-ray CT apparatus.

FIG. 8 is a diagram used for explaining light reflection according to a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Printed circuit board, 2 ... Scintillator, 3 ... Slice direction partition board (with light reflection layer), 4 ... Channel direction partition board (with light reflection layer), 5 ... Connector, 6 ... Silicon photodiode, 6a ... Silicon photodiode sensitive zone, 6b ... Silicon photodiode dead zone, 7 ... Transparent adhesive, 8 ... Light reflecting resin, 9 ... Partition plate ( No light reflection layer), 10: glass plate, 11: groove, 12: X-ray detector array, 13: detector container, 14: X-ray tube, 15: scattering X-ray prevention collimator, 17 subject, 18 amplifying device, 19 rotating plate, 20 photons converted from X-rays

Claims (5)

[Claims] 1. A plurality of photoelectric conversion elements arranged on a substrate, a scintillator arranged on the photoelectric conversion elements and divided into a plurality corresponding to the individual photoelectric conversion elements, and an isolation for separating the scintillators. An X-ray detector comprising a plurality of X-ray detection element arrays each comprising a plate, wherein a light reflection layer is provided at least at the end of the scintillator between the scintillators into which the separators are inserted, and between these light reflection layers. An X-ray detector comprising the partition plate. 2. A photoelectric conversion element is mounted on a substrate, a scintillator is arranged thereon, and the scintillator is bonded to the photoelectric conversion element. A channel or a groove for slice separation is formed in the scintillator. The groove is filled with a light-reflective resin to form a light-reflective layer, and the filled light-reflective resin layer is formed with a groove for inserting a partition plate, leaving a reflective layer thick enough to reflect light. A method for manufacturing an X-ray detector comprising the above-mentioned partition plate fixed thereto. 3. A photoelectric conversion element is mounted on a substrate, a scintillator is arranged thereon, and the scintillator is bonded to the photoelectric conversion element. A channel or a groove for slice separation is formed in the scintillator. A groove in which a light reflecting resin is formed by filling the groove and the upper surface of the scintillator with a light reflecting resin, and a partition plate is inserted by leaving a light reflecting layer formed in the groove with a reflection layer having a thickness sufficient for light reflection. And manufacturing the X-ray detector by fixing the partition plate in the groove. 4. A scintillator is bonded to a glass plate, a channel or a groove for slice separation is formed in the scintillator, and the groove is filled with a light-reflecting resin to form a light-reflecting layer. Form a groove to insert a partition plate, leaving a reflective layer of sufficient thickness for light reflection in the reflective resin layer,
A method for manufacturing an X-ray detector, comprising forming a scintillator array by fixing a partition plate to the groove and fixing the scintillator array to a photoelectric conversion element. 5. An X-ray source, an X-ray detector arranged to face the X-ray source, and a rotation that holds the X-ray source and the X-ray detector and is driven to rotate around an object. A disk and the X
5. An X-ray CT apparatus comprising: an image reconstruction unit configured to reconstruct an image of the tomographic image of the subject based on the intensity of the X-ray detected by the X-ray detector.
X-ray CT using the X-ray detector described in 1 above
apparatus.