JPS6263880A - Radiation detector - Google Patents

Abstract

PURPOSE:To reduce an artifact caused by the quantity of a crosstalk, and to reduce a sensitivity difference between elements by structuring the titled detector so that light is not incident on a dead zone from the outside by providing a light shielding film on the upper face of the dead zone. CONSTITUTION:A radiation detector is constituted so that a photoelectric transducer 15 to which a scintillator block 13 has been connected is stuck onto a substrate 16, and an output signal from each element is fetched from a connector socket 17. In a PIN type silicon photodiode which is used as a photoelectric transducer of this radiation detector, its width is determined by a (p) diffusion layer 5, and it is separated from the adjacent element by a dead zone 8. This detector is structured so that light is not incident on the dead zone 8 from the outside, by providing a light shielding film 1 on the upper face of this dead zone 8. In this way, the quantity of a crosstalk between the elements of the photoelectric transducer array in a connecting part of a multielement scintillator 13 and the photoelectric transducer array 15 can be reduced to <=1%, and an artifact can be reduced.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a multi-element solid-state radiation device comprising a plurality of scintillators and a plurality of optical conversion elements used in a computer-based X-ray tomography bag E (X-ray CT device). Regarding detectors, in particular,
The present invention relates to a detector structure suitable for reducing crosstalk between detection elements.

[Background technology]

First, the second method of the X-ray CT apparatus according to the present invention will be explained. An X-ray source that emits fan-shaped beam X-rays and a multi-element radiation detector are installed facing each other at a predetermined distance. In this method, a tomographic image of the subject is obtained by rotating the detector, emitting X-rays from multiple directions, measuring the intensity distribution of the X-rays, and processing the data with a computer.

This type of apparatus has the disadvantage that if there is a sensitivity difference in a particular element of the nine-element radiation detector, a concentric false image corresponding to that element is likely to occur.

Therefore, we decided to develop a multi-element solid-state emitter consisting of a scintillator and a photoelectric conversion element! ! An example in which variations in sensitivity occur between elements in a line detector will be described.

FIG. 4 shows an example using a block of four elements, in which the scintillator block 13 includes scintillators A,
~A4-B +~B4, light receiving section 5AI~5
A, photoelectric conversion element array 15 consisting of 5B1 to 5B.
A and 15B are fixed via a transparent sheet 14 for preventing a decrease in shunt resistance of the photoelectric conversion element. These four element blocks are arranged in a circular arc shape, and the photoelectric conversion element array 15A is adjacent to the adjacent photoelectric conversion element array 15B with a gap C in between.

Furthermore, FIG. 5 shows the detailed structure of the connection portion between the scintillator block 13 and the photoelectric conversion element arrays 15A and 15B, and shows the X-rays incident on the scintillator block 13.
8 or the radiation is converted into light and the photoelectric conversion element array 1
5A, 15B light receiving section 5 A t ~ 5 Aa , 5
It enters B1-5B4 and is converted into a current signal. The scintillator A4 is separated from the adjacent scintillator by a partition plate 11 or ]2, and the light emitted by the scintillator A4, for example, is received by the corresponding light receiving section 5A4, so that the intensity distribution can be accurately measured.

However, in FIG. 5, the light emitted from the scintillator A3 of the scintillator block 13 is the light 9A that is incident on the light receiving section 5A3 of the photoelectric conversion element array 15A corresponding thereto.
, the light 9 incident in the direction of the dead zone 8 and the adjacent light receiving section 5
A light 10A incident on a is generated. Furthermore, the light emitted from the scintillator A4 generates light lO which does not enter the light receiving section 5A of the corresponding photoelectric conversion element array 45A but enters the dead zone 8 of the adjacent photoelectric conversion element array 15B. In a diode, when light enters the intrinsic semiconductor (i-layer) layer, which is a dead zone, electron pairs are generated. Although the amount thereof is small at 20 to 30% of the light receiving portion, it mixes with the signals of adjacent elements, resulting in so-called crosstalk, and the separation of signal differences between elements becomes poor. Also,
Since there is a gap C in the element at the connection between the photoelectric conversion element arrays 15A and 15B, the light 10 incident in the direction of the dead zone has almost no effect on the photoelectric conversion element 5B+ corresponding to the adjacent scintillator B1. I will not do it. In such a state, if radiation of the same intensity is incident on all elements, the difference in optical output between scintillator A4 and scintillator B1 will not be cursed, but the intensity of the incident radiation changes in the arrangement direction of the elements. In this case, the measured values are discontinuous between the detection elements corresponding to the connection portions of the photoelectric conversion element array. When creating an image using such measurement values,
There was a problem in that a ring-shaped or streak-shaped false image (artifact) was generated by the detection element located at the connection part of the photoelectric conversion element array, and the nine images were significantly changed.

As a means to solve this problem, for example,
The technique described in Japanese Patent Publication No. 58574, namely, interposing a transparent sheet having opaque stripes formed thereon and having a width narrower than the width of the dead area of the scintillator and the photodiode (photoelectric conversion element), Radiation detectors have been proposed.

However, as a result of studying such conventional radiation detectors, it was found that the light 9 incident on the dead zone of the photoelectric conversion element shown in FIG. It turns out that there is a problem that affects the output. In other words, it was found that there is light energy sensitivity in the dead zone.

[Purpose of the invention]

An object of the present invention is to develop a technology that can prevent measured values from changing discontinuously between detection elements at the connection part of the array in a radiation detector configured by arranging a plurality of photoelectric conversion element arrays. The purpose is to provide.

Another object of the present invention is to provide a dead zone of a photoelectric conversion element.

The purpose of the present invention is to provide a technology that can prevent light from entering from outside.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief overview of one typical invention disclosed in this application is as follows.

In other words, the cause of discontinuity in the measurement between the detection elements at the connection part of the photoelectric conversion element array is the existence of optical crosstalk between the elements, and in order to solve this, it is necessary to The goal is to reduce indigo. The cause of this crosstalk is that the dead zone provided to separate the elements in the array is sensitive to light energy, and by creating a structure in which no light enters this dead zone, the cross This reduces the amount generated in the evening.

[Structure of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described below with reference to embodiments and drawings.

Note that throughout the description of the embodiments, parts having the same functions are given the same reference numerals, and repeated explanations thereof will be omitted.

FIG. 1 is a cross-sectional view of a PIN type silicon first diode array of a radiation detector according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing the structure of another embodiment of the light shielding film of FIG. figure,
FIG. 3 is a perspective view showing the overall schematic configuration of the radiation detector of this embodiment.6 The radiation detector of this embodiment consists of a multi-element photoelectric conversion element array, and each photoelectric conversion element is For example, a PIN type silicon photodiode as shown in FIG. 1 is used.

Note that the PIN type silicon first diode is.

It is widely used because it matches well with the scintillator's emission wavelength.

In the radiation detector of this embodiment using the PIN type silicon photodiode, the width of one photoelectric conversion element is determined by the p diffusion layer 5, as shown in FIG. separated by 8,
This portion is an intrinsic semiconductor layer (i-layer) 6. - When the dimension (pitch) of the element is in+m, the width of the diffusion layer 50 which is the light receiving part is 0.80 mm, and the width is 0.2 mm (200 mm).
A common dimension is to divide the element by a dead zone of tt m).

The radiation detector of this embodiment has a structure in which a light shielding film 1 is provided on the upper surface of the dead zone 8 so that no light enters the dead zone 8 from the outside.

As shown in FIG. 1, the shape of the light shielding film 1 is that it is provided in a strip shape on the antireflection film 4 by vacuum evaporation, and a part of it is connected to the intrinsic semiconductor layer 6 so that no charge is accumulated in the operating state. I'm trying to prevent it from happening.

In addition, the light shielding film 1, as shown in FIG.
It may be formed by screen printing using a light-impermeable resin paste on the antireflection film 4, which is the surface of the N-type silicon fiber diode array. In this case, setting the film thickness to 30 to 50 μm will have a great effect6.Also, by gluing a light-impermeable resin film ring band with a thickness of 100 μm or less on top of the FIF8, , the same effect can be obtained. The thickness of this resin film is
When it is 100 μm or more, the scintillator block and P
It is preferable to use a thinner film because the gap in the IN-type silicon photodiode array becomes larger.

Furthermore, in the example shown in FIGS. 1 and 2, the p' expansion 18! On the upper surface of the layer 5, a power supply electrode 2 made of aluminum foil is provided in the same layer as the antireflection film 4.

A power supply electrode 3 is provided on the back surface of the D-type silicon substrate 7.

In the radiation detector of this embodiment, as shown in FIG. 3, a photoelectric conversion element array 15 to which a scintillator block 13 is connected is bonded to one side of a substrate 16.

Output signals from each element are taken out from connector sockets 1-17.

In this embodiment, four elements are used as a -block, but the input HX
The line is converted into light by the scintillator block 13, and is incident on the photoelectric conversion element array 15L.

In the conventional radiation detector configuration, the amount of light leaking between each element to the adjacent element was 3 to 4% as a result of actual measurements, but in the radiation detector configuration of this example, the amount of light leaking to the adjacent element was approximately 1%. and decreased significantly.

When a multi-element solid-state radiation detector is constructed by arranging a plurality of radiation detector blocks shown in FIG. 3, the difference in the amount of light leakage between the elements at the connection part of the photoelectric conversion element array is 1% at most. The change in measurement data due to this phenomenon was smaller than the limit value at which artifacts would occur in the reproduced image.

As can be seen from the above description, according to this embodiment, the light shielding film l is provided on the upper surface of the dead zone 8 to prevent light from entering the dead zone 8 from the outside, so that the multi-element scintillator block 13 Since the amount of crosstalk between the elements of the photoelectric conversion element array 15 at the connection portion between the photoelectric conversion element array 15 and the photoelectric conversion element array IS can be reduced to 1% or less, artifacts caused by the amount of crosstalk can be reduced.

As a result, a multi-element solid-state radiation detector with small sensitivity differences between elements can be created, and artifacts in reproduced images of the XmCT apparatus can be removed.

〔effect〕

As explained above, according to the present invention, the amount of crosstalk between the elements of the photoelectric conversion element array at the connection part between the multi-element scintillator and the photoelectric conversion element array can be reduced to 1% or less. Artifacts can be reduced.

It goes without saying that the present invention is not limited to the embodiments described above, and can be modified in various ways without departing from the spirit thereof.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a PIN-type silicon photodiode array of a radiation detector according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the structure of another embodiment of the light-speed Ti film of FIG. 1. , FIG. 3 is a perspective view showing the overall schematic configuration of the radiation detector of this embodiment. FIGS. 4 and 5 are diagrams for explaining problems at the coupling portion between the scintillator block and the photoelectric conversion element array in a conventional four-element radiation detector block. In the figure, 1... light shielding film, 8... dead zone, 13...
Scintillator block 15... photoelectric conversion element array.

Claims (5)

[Claims] (1) In a multi-element radiation detector consisting of multiple scintillators that emit light due to radiation and multiple photoelectric conversion elements, the multiple photoelectric conversion elements are provided on the same substrate, and the scintillator is fixed in close contact with each photoelectric conversion element. A radiation detector characterized in that the photoelectric conversion elements are separated by a dead zone, and an object for blocking light from the outside is provided in the dead zone. (2) Claim 1, wherein the photoelectric conversion element is a PIN type silicon photodiode.
Radiation detector described in section. (3) The radiation detector according to claim 1 or 2, wherein the object that blocks light from the outside is formed by depositing metal and electrically connecting it to the substrate. . (4) The object that blocks light from the outside is formed by screen-printing a light-impermeable resin paste in the form of a strip. Detector. (5) The object that blocks light from the outside is formed by adhering a band-shaped thin resin film that does not transmit light. Radiation detector.