JPH11113890A - Inspection method and device for x-ray detector, and x-ray ct system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inspect a condition of an adhesive part while still mounting an X-ray detector on a using device by inspecting an adhesive condition of scintillators on the basis of capacitance of photodiodes in the X-ray detector using the photodiodes where the scintillators are adhered to light receiving surfaces. SOLUTION: In a detector module of an X-ray CT system, under surfaces (light emitting surfaces) of plural scintillators 242 to 248 arranged in parallel to each other, are superposed on upper surfaces (light receiving surfaces) of plural photodiodes 272 to 278 formed in parallel to each other on a semiconductor substrate 270, and both are adhered together by an adhesive 350. The emitting light from the respective scintillators 242 to 248 to emit the light according to intensity of X-rays incident from above, is detected by the respective photodiodes 272 to 278. In such a detector module 240, capacitance of the photodiodes 272 to 278 is measured, and when the capacitance is reduced to a prescribed value or less, it is judged as the degradation of an adhesive part of the scintillators 242 to 248.

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 inspection method and apparatus and an X-ray CT apparatus, and more particularly to an X-ray detector inspection method and apparatus using a photodiode having a scintillator bonded to a light receiving surface. The present invention relates to an X-ray CT apparatus provided with such an inspection device.

[0002]

2. Description of the Related Art In an X-ray CT (computed tomography) apparatus, an X-ray irradiation / detection system is rotated (scanned) around an object.
(scan)) to measure projection data (data) of the subject by X-rays in a plurality of view directions around the subject, and generate a tomographic image based on the projection data (reconstruction). It is supposed to.

An X-ray irradiator has an X-ray beam (b) having a width encompassing an imaging range and having a predetermined thickness in a direction perpendicular thereto.
eam). The X-ray detection device detects X-rays by a multi-channel X-ray detector in which a large number of X-ray detection elements are arranged in an array in the direction of the width of the X-ray beam.

[0004] Each channel of the X-ray detector is composed of a scintillator that emits light when irradiated with X-rays and a photodiode that detects the amount of light emitted. The scintillator is adhered to the light receiving surface of the photodiode with an adhesive.

[0005]

The bonding portion between the scintillator and the photodiode is formed during the process of using the X-ray CT apparatus.
It degrades over time due to thermal or mechanical stress, and in severe cases it may lead to delamination.

[0006] Deterioration or peeling of the bonded portion lowers the performance of X-ray detection and lowers the image quality of the reconstructed image. However, conventionally, when peeling of the bonded portion is suspected, the operation of the X-ray CT apparatus has to be stopped and the X-ray detector has to be removed for examination, which has not been easy.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an X-ray inspection method for inspecting the state of a bonding portion between a scintillator and a photodiode while an X-ray detector is mounted on a utilization device. An object of the present invention is to provide a detector inspection method and apparatus and an X-ray CT apparatus.

[0008]

As a result of various studies on a scintillator type X-ray detector, the present inventors have found that the capacitance of a photodiode having a scintillator adhered to a light receiving surface is more constant than that of a photodiode alone. It was found that the percentage increased. Further, the inventors have found that this capacitance becomes a value close to the capacitance value of the photodiode alone when the bonded portion is peeled off. The present invention takes advantage of this fact.

(1) According to a first aspect of the present invention, there is provided an X-ray detector using a photodiode in which a scintillator is bonded to a light-receiving surface, and a bonding state of the scintillator based on the capacitance of the photodiode. Is inspected.

(2) A second invention for solving the above problems is an inspection apparatus for an X-ray detector using a photodiode in which a scintillator is adhered to a light receiving surface, wherein the capacitance of the photodiode is measured. It is characterized by comprising a measuring means and a judging means for judging the adhesion state of the scintillator based on the measured value of the capacitance.

(3) According to a third aspect of the present invention, an X-ray irradiating means, an X-ray detecting means using a plurality of photodiodes having a scintillator adhered to a light receiving surface, and an X-ray detecting means Tomographic image generating means for generating a tomographic image of the X-ray passing area based on a line detection signal; measuring means for measuring the capacitance of the photodiode;
Determining means for determining an adhesion state of the scintillator based on the measured value of the capacitance.

[0012] In the third invention, it is preferable to provide a notice means for giving a notice of deterioration of the adhesion state of the scintillator based on the history of the measured values, in terms of taking preventive measures or precautionary measures.

In this case, it is preferable to transmit the history of the measured values to the maintenance organization through a communication line in order to make the precautionary measures or precautionary measures more effective. (Operation) In the present invention, the capacitance of the photodiode is measured, and the deterioration or peeling of the bonded portion of the scintillator is determined based on the measured value.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiment.

FIG. 1 shows a block diagram of an X-ray CT apparatus.
The figure is shown. This device is an example of an embodiment of the present invention.
The configuration of the present apparatus shows an example of an embodiment relating to the apparatus of the present invention. An example of an embodiment of the method of the present invention is shown by the operation of the present apparatus.

(Configuration) As shown in FIG. 1, the present apparatus comprises a scanning gantry 2, a photographing table 4,
An operation console 6 is provided.

The scanning gantry 2 has an X-ray tube 20.
An X-ray (not shown) emitted from the X-ray tube 20 is shaped into a fan-shaped X-ray beam by a collimator 22 and is irradiated on a detector array 24. The X-ray tube 20 and the collimator 22 are one example of an embodiment of the X-ray irradiating means in the present invention.

The detector array 24 is an example of an embodiment of the X-ray detecting means according to the present invention. Detector array 24
Has a plurality of X-ray detection elements arranged in an array in the direction of the width of the fan-shaped X-ray beam. The configuration of the detector array 24 will be described later.

The X-ray tube 20, collimator 22 and detector array 24 constitute an X-ray irradiation / detection system. The configuration of the X-ray irradiation / detection system will be described later. A data collection unit 26 is connected to the detector array 24. The data collection unit 26 collects detection data of individual X-ray detection elements of the detector array 24.

The data collecting section 26 is provided with a means for measuring the capacitance, and measures the capacitance of the photodiode in each X-ray detecting element. The data collection unit 26 is an example of an embodiment of the measuring unit in the present invention. The data collection unit 26 will be described later.

The irradiation of X-rays from the X-ray tube 20 is controlled by an X-ray controller (controller) 28. The illustration of the connection relationship between the X-ray tube 20 and the X-ray controller 28 is omitted.

The collimator 22 is controlled by a collimator controller 30. The illustration of the connection relationship between the collimator 22 and the collimator controller 30 is omitted.

The above-described X-ray tube 20 to collimator controller 30 are mounted on the rotating unit 32 of the scanning gantry 2. The rotation of the rotation unit 32 is controlled by a rotation controller 34. The illustration of the connection relationship between the rotation unit 32 and the rotation controller 34 is omitted.

The imaging table 4 carries a subject (not shown) into and out of the X-ray irradiation space of the scanning gantry 2. The relationship between the subject and the X-ray irradiation space will be described later.

The operation console 6 has a central processing unit 60. The central processing unit 60 is, for example, a computer
(computer) etc. To the central processing unit 60, a control interface (interface) 62 is connected. The scanning gantry 2 and the imaging table 4 are connected to the control interface 62.

The central processing unit 60 has a control interface 6
2, the scanning gantry 2 and the imaging table 4 are controlled. The data acquisition unit 26, the X-ray controller 28, the collimator controller 30, and the rotation controller 34 in the scanning gantry 2 are controlled by the control interface 62. It should be noted that illustration of individual connections between these units and the control interface 62 is omitted.

A data acquisition buffer 64 is also connected to the central processing unit 60. Data collection buffer 6
4 is connected to the data collection unit 26 of the scanning gantry 2. The data collected by the data collection unit 26 is input to the data collection buffer 64. Data collection buffer 6
4 temporarily stores the input data.

The central processing unit 60 also has a storage device 6.
6 are connected. The storage device 66 stores various data, reconstructed images, programs, and the like.
The display device 68 and the operation device 70 are also connected to the central processing unit 60. The display device 68 displays a reconstructed image and other information output from the central processing unit 60. The operation device 70 is operated by an operator, and inputs various instructions and information to the central processing unit 60.

FIG. 2 shows a schematic configuration of the detector array 24. The detector array 24 forms a multi-channel X-ray detector in which a large number (for example, about 1000) of X-ray detection elements 24 (i) are arranged in an arc shape. i is a channel number, for example, i = 1 to 1000. The X-ray detection element 24 (i) will be described later.

FIG. 3 shows the relationship among the X-ray tube 20, the collimator 22, and the detector array 24 in the X-ray irradiation / detection system. 3A is a front view, and FIG. 3B is a side view.
As shown in the figure, X-rays emitted from the X-ray tube 20 are:
The beam is shaped into a fan-shaped X-ray beam 40 by the collimator 22 and is applied to the detector array 24. In FIG. 3A, a fan-shaped X-ray beam 4
0 indicates the spread, that is, the width of the X-ray beam 40.
FIG. 3B shows the thickness of the X-ray beam 40.

By crossing the body axis with the fan surface of such an X-ray beam 40, for example, as shown in FIG.
Is placed in the X-ray irradiation space. X
The subject 8 sliced by the line beam 40
Is projected onto the detector array 24. The thickness of the X-ray beam 40 at the isocenter of the subject 8 gives the slice thickness th of the subject 8. The slice thickness th is determined by the X-ray passing aperture of the collimator 22.

The X-ray irradiation / detection system including the X-ray tube 20, the collimator 22, and the detector array 24 rotates (scans) around the body axis of the subject 8 while maintaining their mutual relationship. A plurality (for example, 100
Projection data of the subject is collected at the view angle of 0).
The collection of projection data is performed by a system including the detector array 24, the data collection unit 26, and the data collection buffer 62.

Based on the projection data collected in the data collection buffer 62, the central processing unit 60 generates a tomographic image, that is, performs image reconstruction. Central processing unit 60
Is an example of an embodiment of a tomographic image generation unit according to the present invention. Image reconstruction is performed, for example, by using projection back data of, for example, 1000 views obtained by one rotation scan, for example, using filtered back-projection (filtered back-projection).
It is performed by processing according to the n) method.

FIGS. 5, 6 and 7 show detector array 2
4 shows a schematic configuration of a detector module (module) constituting No. 4. 5 is a plan view, FIG. 6 is a cross-sectional view along AA, and FIG. 7 is an exploded view.

As shown in these figures, the detector module 240 has a plurality of scintillators 242 to 248 arranged in parallel with each other. Multiple scintillators 242
248 each constitute an individual channel in the detection array 24. The scintillators 242 to 248 are integrated by a bonding material 250.

The detector module 240 also has a plurality of photodiodes 272 to 278 formed on the semiconductor substrate 270 in parallel with each other. Semiconductor base 270
Is mounted on a base 290 by, for example, bonding.

The arrangement of the photodiodes 272 to 278 corresponds to the arrangement of the scintillators 242 to 248. The photodiodes 272 to 27 shown in FIG.
8, the lower surfaces (light emitting surfaces) of the scintillators 242 to 248 shown in FIG. The adhesive 310 is an optical adhesive.

Such a detector module 240 is represented by X
A plurality of detectors are arranged adjacent to each other in the direction of the width of the line beam 40 to form the detector array 24 shown in FIG. The base 290 is fixed to a predetermined support frame (not shown) or the like by appropriate means.

X-rays enter the scintillators 242 to 248 from above in FIG. Scintillators 242 to 24
8 emits light in accordance with the intensity of the incident X-ray. Light emitted from the scintillators 242 to 248 is detected by the photodiodes 272 to 278, respectively.

Scintillator 242 and photodiode 2
72 pairs, scintillator 244 and photodiode 27
Four pairs, scintillator 246 and photodiode 276
Pair and scintillator 248 and photodiode 27
8 correspond to the X-ray detecting elements 24 shown in FIG.
Form (i).

FIG. 8 shows the configuration of an electric circuit for X-ray detection.
One channel of the detector array 24 is shown. As shown in the figure, the equivalent circuit of the photodiode 24k is
Diode 90, capacitor 92, resistor 9
4 and a DC constant current source 96 in parallel.

A connector (connect) is connected to such a parallel circuit.
or) The integration circuit 100 is connected via 98. The integration circuit 100 exists in the data collection unit 26. The integration circuit 100 includes an operational amplifier (OP amplifier) 10
2, the positive input terminal is connected to common, the negative input terminal is connected to a resistor 104, the negative input terminal is connected to the output terminal via a capacitor 106, and a switch 108 is connected to the capacitor 106 in parallel. Connected and configured.

In such a circuit, when X-rays enter the scintillator, the current of the DC constant current source 96 changes according to the intensity of the incident light.
The input current of 0 changes. Such an input current is integrated and output as an X-ray detection signal.

Similar X-ray detection circuits are formed for all the channels of the detector array 24 so as to obtain X-ray detection signals. Photodiode 24
As shown in FIG. 9, the capacitance measuring circuit 110 is connected to k by switching. The capacitance measuring circuit 110 is an example of an embodiment of a measuring unit according to the present invention. The capacitance measurement circuit 110 exists in the data collection unit 26. Switching is performed by the control interface 62.

The capacitance measuring circuit 110 includes a capacitor 9
2 is measured. The measurement values are collected by the data collection buffer 64.
Under the control of the control interface 62, the capacitances of all the photodiodes of the detector array 24 are measured, and the measurements are collected in a data collection buffer 64.

The central processing unit 60 determines the bonding state between the scintillator and the photodiode based on the measured capacitance value collected in the data collection buffer 64. The central processing unit 60 is an example of an embodiment of a determination unit according to the present invention.

As the reference value for the judgment, for example, a stored value of the capacitance of the photodiode of each channel measured at the time of completion inspection of the detector array 24 or the like is used. Alternatively, when the X-ray CT apparatus is completed, the capacitance measuring circuit 110
Alternatively, data obtained by measuring the capacitance of the photodiode of each channel may be used.

(Operation) The operation of the present apparatus will be described. The X-ray irradiation / detection system scans the subject 8 and, for example, 1000 views of projection data are collected in the data collection buffer 62. Based on the projection data, the central processing unit 60 performs image reconstruction using, for example, a filtered back projection method. The reconstructed image is displayed on the display device 68 and stored in the storage device 66.

The measurement of the capacitance of the photodiode in the detector array 24 is performed, for example, before the start of daily operation of the apparatus or after the end of operation, and it is determined whether or not there is an abnormality in the bonded portion based on the measured value. Is done.

When the bonded portion deteriorates with time due to thermal or mechanical stress, the capacitance of the photodiode decreases. When the rate of decrease in the measured value deviates from the predetermined limit, the central processing unit 60 determines that, and notifies the abnormality of the corresponding channel through the display device 68. Accordingly, the operator can accurately and easily confirm the channel in which the adhesive portion has deteriorated, and can perform a replacement or a repair or the like at an appropriate timing.

The history of capacitance measurements for each photodiode indicates a trend in the degradation of the bond. Therefore, the central processing unit 60 can predict when replacement or repair is required based on the history of the measured values. Based on such a prediction, a maintenance person or the like can take preventive measures or advance preparations and the like at an early stage.

Further, if the history of the measured values is sent to a maintenance organization such as a maintenance / service center via a communication line, more effective prevention or preparation can be performed.

The inspection method and apparatus of the X-ray detector for the X-ray CT apparatus have been described above. However, the inspection method and apparatus of the present invention are not limited to the X-ray CT apparatus, but may be other X-ray apparatuses. It is needless to say that the present invention can be applied to inspection of a scintillator type X-ray detector.

[0054]

As described above in detail, according to the present invention, for an X-ray detector using a photodiode having a scintillator bonded to a light receiving surface, the bonding state of the scintillator is inspected based on the capacitance of the photodiode. Thus, it is possible to realize an inspection method and apparatus for an X-ray detector and an X-ray CT apparatus for inspecting a state of a bonding portion between a scintillator and a photodiode while the X-ray detector is mounted on a utilization device.

[Brief description of the drawings]

FIG. 1 is a block diagram of a device according to an example of an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a detector array in an apparatus according to an embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of an X-ray irradiation / detection system in an apparatus according to an embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of an X-ray irradiation / detection system in an apparatus according to an embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of a detector module in an apparatus according to an embodiment of the present invention.

FIG. 6 is a schematic configuration diagram of a detector module in an apparatus according to an example of an embodiment of the present invention.

FIG. 7 is a schematic configuration diagram of a detector module in an apparatus according to an embodiment of the present invention.

FIG. 8 is an electrical connection diagram of an X-ray detection system in an apparatus according to an embodiment of the present invention.

FIG. 9 is an electrical connection diagram of a capacitance measurement system in the device according to an example of the embodiment of the present invention.

[Explanation of symbols]

 2 Scanning Gantry 20 X-ray Tube 22 Collimator 24 Detector Array 26 Data Collection Unit 28 X-ray Controller 30 Collimator Controller 32 Rotation Unit 34 Rotation Controller 4 Imaging Table 6 Operation Console 60 Central Processing Unit 62 Control Interface 64 Data Collection Buffer 66 Storage Device 68 display device 70 operating device 8 subject 40 X-ray beam 24 (i) X-ray detecting element 240 detector module 242 to 248 scintillator 250 bonding material 270 semiconductor substrate 272 to 278 photodiode 290 base 310 adhesive 96 DC constant current source 98 connector 100 integration circuit 110 capacitance measurement circuit

Claims (3)

[Claims] 1. An X-ray detector using a photodiode in which a scintillator is bonded to a light receiving surface, wherein an adhesion state of the scintillator is inspected based on a capacitance of the photodiode. Inspection method. 2. An inspection apparatus for an X-ray detector using a photodiode in which a scintillator is bonded to a light receiving surface, comprising: a measuring unit for measuring a capacitance of the photodiode; A determination means for determining an adhesion state of the scintillator by using the inspection apparatus. 3. An X-ray irradiator, an X-ray detector using a plurality of photodiodes having a scintillator adhered to a light receiving surface, and an X-ray passing area based on an X-ray detection signal of the X-ray detector. A tomographic image generating means for generating a tomographic image of, a measuring means for measuring a capacitance of the photodiode, and a judging means for judging an adhesion state of the scintillator based on a measured value of the capacitance. An X-ray CT apparatus characterized in that: