JPS61102579A - Detecting device for radiation source position - Google Patents

Abstract

PURPOSE:To obtain a detecting device which has high sensitivity, high spatial resolution, and fast responsibility by an inexpensive means by improving the detection sensitivity and spatial resolution by using a coded aperture plate, and providing an optical reproduction plate behind a sincillator and performing optical direct reproduction. CONSTITUTION:gamma rays or X rays emitted from one point of a radiation source 1 pass through the aperture plate 2 to form a shadow similar to the aperture opening pattern on the surface of a radiation-light converting element (plate) 3. Light emitted by the element 3 is transmitted through or absorbed by the optical reproduction plate 4 according to the similar pattern determined by the aperture of the aperture plate 2 and an optical position detecting element 5 detects the transmitted light. Then, the signal from preamplifier part 6 including preamplifiers 61-64 which receive the electric signal from the element 5 is used by a position calculating device 7 to calculate the position of a radiation source 1. Thus, a real-time reproduced image is obtained and its constitution means is simple and inexpensive.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention detects γ (gamma) rays or X-rays emitted from a radioactive substance η etc. in one or two dimensions, and This invention relates to a radiation source position detection device that images the position and distribution and determines the radiation source hard skin distribution. The present invention is applied as a human body or floor contamination inspection device, and a positioning device for beam welding.

[Conventional technology]

Conventionally, there has been a device for this purpose as shown in Figure S.

In the figure, (1) is the radiation yfMm, (00) is the radiation source position detection device that detects the radiation from this radiation source, such as X Ni, and the collimator (rto) and radiation detection element (λ). O).

Yet another conventional device is shown in FIG. In the figure, (/l is a radiation source, (3CO) is a stationary radiation source position detection device, a parallel multi-hole collimator (310), a scintillator (320) which is a radiation detection element, and a plurality of photomultiplier tubes (, y3o).

Next, the operation will be explained. In FIG.

Radiation such as gamma rays or
2(1)IIC&'! , a scintillation detector, a gas-filled ionization chamber, a semiconductor detector, etc. are used. The spatial efficiency of detection is determined by the input aperture diameter d and depth t of the collimator (2tO). The highest sensitivity is exhibited when the radiation source f/l is on the axis of the collimator hole, and the output of the detection device (, 2co) changes in response to the deviation of the radiation source f/l from the center position.

Reduce the input aperture diameter d of the collimator (rio).

If the depth t is made longer, the detection response e+ to the deviation can be increased by a bit, but the radiation source (/l) and the detection device (2
The detection efficiency 71'-determined by the distance from the radiation source (θO) and the collimator aperture diameter d decreases.
In practice, it is necessary to increase the aperture diameter d to greatly increase the radiation transmission efficiency, so that only poor detection position accuracy can be obtained.

Example of the 6th pottery + 1, stationary radiometer that fits in with the wheel diagram example, 4
The source position is similar to the starting position (,7oo)', and since the range of this position τ detection device diameter is the detection field of view, the detection device (,yoo
) is not necessary, and there is no need to move 1 within the detection field of view.
The swimming speed is uniform. Now, radiation〃・4 sources (r@ from /l
The emission is isodirectional in all azimuthal directions.

Only γ-rays in a certain direction toward the scintillator (Jco θ), which is a radiation detection element, are transmitted and detected by the parallel porous collimator (Jto). The transmittance of radiation such as γ-rays is usually l
approximately /θ ~10 per hole. This transmitted radiation is absorbed and detected by the next scintillator (3λ0).

In this way, of the radiation emitted from the radiation source (/l), only the component parallel to the holes of the collimator (3XO) (and therefore perpendicular to the plane of the scintillator (J and Q)) is selectively transmitted, and the radiation source (1) When the radiation is absorbed by a scintillator (330), it is converted into scintillation light, which is sent to multiple photomultiplier tubes (330).
o) and an external position calculation circuit (not shown).
A position signal (X, Y coordinates) corresponding to each collimator hole is obtained for each radiation event.

Therefore, as in the example shown in FIG. 3, if the radiation source intensity is weak, the diameter of each aperture of the parallel multi-hole collimator (3tO) must be increased to deteriorate the position detection accuracy.

[Problem that the invention seeks to solve]

Since the conventional radiation position detection device is configured as described above, when the intensity of the radiation to be measured + iIl source is weak, it is difficult to increase the spatial position resolution because the detection efficiency determined by the collimator is low. The results were also only one-dimensional.

In addition, the stationary type uses a large number of photomultiplier tubes, which has the disadvantage of being expensive.

This invention was made in order to eliminate the drawbacks of the conventional ones as mentioned above, and is an inexpensive means with high sensitivity.

The purpose of this invention is to provide a high-speed response radiation position detection device with crystal spatial resolution.

[Means for solving problems]

In a broad sense, the configuration of the technical means of the present invention for achieving the above object is to optically convert gamma rays or In a radiation source position detection device for imaging distribution, an opening is provided between a radioactive substance and a radiation detector to transmit or block γ-rays or X-rays directed from the radioactive substance toward the radiation detector according to a predetermined spatial pattern. r
an aperture plate, a flat N-ray-light conversion element that absorbs and emits RA or X-rays that pass through the opening of the aperture plate;
This radiation-light conversion element and optical position detection means for detecting light, and between the radiation-light conversion element and the optical position detection means, the radiation-light conversion sender also moves toward the optical position detection stage. A light transmitting opening that transmits or blocks light according to a similar pattern determined by the pattern of the aperture plate is provided at a position such that the light intensity distribution on the optical position detection stage due to the transmitted light has a large peak. It is characterized by the use of recycled boards.

[For production]

According to the invention, the basic configuration is a radiation-to-light conversion element and an optical position detection stage, and a coded aperture plate is provided between the radiation source and the radiation-to-photo conversion element.

A reproducing plate is provided between the radiation-light emitting element and the optical position detecting means, and the radiation source position is determined by optically modulating and demodulating the radiation from the radiation source in real time.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

In Figure 1, (l) is a radiation source, (c) is an aperture plate that passes or blocks radiation according to a predetermined pattern, and (J) detects radiation that passes through the aperture plate (-). A radiation-to-light conversion element (3) is a light reproducing plate that transmits or absorbs the light emitted by the radiation-to-light conversion element (3) through the aperture of an aperture plate (3) according to a certain pattern. j) is an optical position detection element that detects the transmitted light from the optical 11 raw plate (g), and (6) is a preamplifier (t/) to (2) that receives the electrical signal from the optical position detection element (3). t, 41).

And (7) is a position f↓ output device that calculates the position of the radiation source (1) using the signal from the preamplifier section (6).

In the radiation position detection device described above, the radiation source (/l
When the radiation emitted from one point passes through the aperture plate (2), a silhouette similar to the aperture opening pattern is formed on the surface of the radiation-light conversion element (plate) (J). This conversion element (3) includes a scintillator that reacts with radiation to produce scintillation light.

NaI (Tt)) is widely used.

Since the opening pattern of the aperture plate (C) is predetermined, the L: picture (strictly speaking, the emission intensity distribution) on the radiation-light conversion element (3) is used to back-calculate which point in the measurement field is affected. You can. This also applies when there are many radiation sources distributed within the measurement area;
) distribution of o (x + y) - aperture plate (2)
Let the silhouette formed on the wing turn be A(X, Y)-f (3) and p(x, y).

Σ Σ PrX1 , Yj ) = (0(XIII', Yp
') ・A(Xi+Xm, Yj +Yn') )
-(/In

The aperture plate (2) has a radiation source (1) and a conversion element (3).
The dimensional scale on the aperture plate (c) is the radiation source (1) and the conversion element (3).
It is set as //2 of the above dimension scale. The problem in this case is to solve O(X, Y) from the above equation (1),
P(Xi.

A(X, Y) from which O(X, Y) can be easily obtained from yJ)
)' is a binary matrix with elements /, θ), and the aperture pattern A(X, Y) can be determined according to this (for example, the aperture pattern A(X, Y) corresponding to A well-known example is the vaginal introitus, which corresponds to the binary □ and is il cover.

, a binary sequence with pseudorandomness (“/” and “0
There is a permutation of °°), and a matrix is created along with the M~ series 1.1-order remainder series, etc. This match.

Light fi-(X,y)-G(Xi-t-X,Yj+
Y)=NrXi=Yj=.

There is a binary inverse matrix G whose elements are l" and "0", where N is the total number of aperture openings.

Using this inverse matrix G from the shadow picture formed on the variable element (,71), we can easily obtain the distribution o(X, Y) as follows:
is found. 7i'll.

Ichigo JL(,,”;,; O(Xm,Yn)#A(X
i+Xm, Yj-1-Yn)) *G(xi+x, y
, 1+y) 1Σ-Σo(xm, yp) A(Xi+Xm, Y,
1+Yn)・YnAm YjXi G(Xi+X, Yj+Y) -H-0(X, Y) Published by Ya Xr. Q(Yn,Xm)
(Except when Xm-X, Yn-Yi) N N
ΣΣ 1-o(x, y)+-YnXm O(Xm, Yn)
-AA here (all Yn*Xm) In other words, Y on the background of NΣΣO(Xm, Yn)
41 to nXm! It is played with the strength of Jo (X, Y),
The above equation (c) redirects the light from the shadow puppet P(Xi, Yj) through a light reproducing plate (ri) having an aperture with an open pattern of light transmission and shielding determined by the inverse matrix G. The intensity of the background is constant regardless of the position, so it can be easily subtracted if necessary.The transmitted light from the optical reproducing plate (4) is detected by the optical position detection element <3). be done.

With the above, spatial modulation (
It has been shown that the original image can be precisely reproduced (demodulated) for the detected image after Equation (1) by using Equation (C) above.

As a result, by employing the aperture method, the configuration example of the present invention has the first feature that the detection sensitivity is N times higher than that of the conventional method. This means that the radiation that comes out from one point on the radiation source and passes through the N openings on the aperture plate (C) passes through the optical reproducing plate (R), and then appears as one point on the optical position detection element If). This is because it is detected.

Furthermore, a second feature of the configuration of the present invention is that an optical mask pattern of the reproduction matrix G is created and the reproduction calculation is directly performed optically.

Conventionally, a coded signal obtained by a coded aperture is once stored as image data in an image memory, and then reproduced by computer processing as a reproduction method.

However, the method of directly reproducing the light emitted from the radiation-to-light conversion element proposed by the present invention can be fully realized from the explanation given below. Since this method is a direct method, it has a simple configuration, and has the advantage that a reconstructed image can be obtained in real time.

Now, the radiation emitted from one point 0 (X, Y) of the radiation source (/> in the same direction passes through the six holes of the aperture plate (C) based on a certain spatial efficiency, and they have a certain detection efficiency. εl
is detected by the optical position detection element (51).

The number of detected radiations detected for each hole within a certain period of time statistically fluctuates around the average value "l".

Furthermore, when one radiation is irradiated to the radiation-light conversion element (3), Nph-E/ΔE scintillation photons are generated depending on its energy E (however, ΔE is equal to the generation of one scintillation photon). average energy consumed). Of these scintillation photons, after passing through the aperture of the light reproduction plate (ri), they are detected by the photodetection element (
The average number of photons detected in 3) -/b is il・Nphri. However, a is the distance from the output surface of the radiation-light conversion element (3) to the optical reproducing plate (4').

b is the size of the aperture diameter of the optical reproduction plate (Hiro); here, the aperture shape is square, and b is the length of its side).

ε is the detection efficiency of the optical position detection element (5). Normally, the average number of photons nu is small and has large statistical fluctuations. Therefore, the image quality of the directly reproduced image is often thought to be poor.

However, when two statistical events are connected in a cascade, the overall statistical standard deviation σ is.

In the case of the first stage (aperture plate (3)) and the second stage (optical regeneration sheet metal, σ/ = '/Frσ, = t/J crystal, therefore, even if the average number of photons 5 is small, the average number of detected radiations -7 If a sufficiently large hole (σ) is obtained, the standard deviation σ can be made small to the extent that it does not pose a practical problem.In the case of a pinhole or parallel hole type, in order to obtain the same spatial resolution, the statistical standard deviation is //F/, whereas in direct image reproduction using a coded aperture (3), there are N numerical apertures and the signal size is N/2 times larger, so N can be kept sufficiently large. Therefore, it can be seen that images with better statistical accuracy can be obtained by direct reproduction compared to the conventional parallel-hole type.

Additionally, compared to computer image reproduction using conventional coded annocratics, this method has the advantage that no calculation processing is required and images can be obtained in real time.Here, optical position detection will be explained. The optical image on the surface of the optical position detection element (Sl) obtained through the image reproduction process by the optical reproduction plate (4') is
j) A charge distribution corresponding to the optical image is formed inside the light image.

In this case, the optical reproducing plate is arranged so that the light intensity distribution on the surface of the optical position detection element (5) has a large peak. Now, point (X) on the surface of the optical position detection element (j).

Consider the detection of light incident on Y). The charge formed around the point (X, Y) inside the element (j) is divided into preamplifiers (61) and (63) provided at both ends of the resistive electrode, and is extracted as an X coordinate signal. . Since the opposite electrode is also perpendicular to the X signal electrode, it can be extracted as a Y coordinate signal from each preamplifier (6λ) and (6da). These four output signals S X tr S X J
I S y / l and SY co are the following position calculator (7
), the position output S of the point signal is transmitted to the optical position detection element fj) when the radiation source (/) is a point source.
X + S Y and its signal strength S are determined as follows.

S = Sxt + SX! 8x = SX/ / 5 Sy = SY/ / S This means that the optical position detection element (j) in Fig. 1 has a charge distribution o(
This method calculates the center of gravity position (Centroid) of x, y), and although the target is limited to point radiation sources, position errors can be reduced even if the spatial resolution of the measurement system deteriorates.

Also, the same type of violet usually has a small light-receiving surface.

As shown in Fig. 2, an imaging lens (ff) is often used (at 1° or more, the positioning of the light corresponding to each radiation detection event is performed; Images accumulated over a certain period of time using a picture tube may be read out sequentially from the edge of one screen, or charges converted from light to charge due to the internal photoelectric effect may be sequentially read out using voltage clock pulses. A charge-coupled two-dimensional detection element may also be used.

In addition, when the radiation source to be measured (1) is weak and has low energy, the optical position detection element (left) is equipped with an image amplifier in front of the optical position sensitive detection element (51) as shown in Figure 3. (s, y) and fiber play) (!2) may be installed.

Similarly, as a conversion element (3), as shown in the figure.

An image amplifier (33) having an output fluorescent surface (3)) can be attached to the output surface of a scintillator (a radiation-light conversion material made of a single or composite crystal or a vapor deposited material) (31)6. Examples and ia diagram examples.

This is a modified example of the basic configuration shown in FIG. 7, in which a means such as an image amplifier is added to enhance the brightness, and it is also applicable to the above-mentioned usage conditions.

In the above embodiment, a two-dimensional direct light reproducing means using a two-dimensional aperture has been described, but a -dimensional one may also be used. That is, the spatial pattern of the aperture plate and the optical reproducing plate may be one-dimensional, and the optical position detection element may be a primary element.

〔Effect of the invention〕

As described above, according to the present invention, a coded aperture plate is used to improve detection sensitivity and spatial resolution, and an optical regeneration plate is provided at the rear of the scintillator to perform optical direct regeneration, so real-time reproduction imitation is possible. This has the effect that the construction means thereof can be simple and inexpensive.

[Brief explanation of drawings]

Drawing 1 shows radiation Bp, source position l&
2 is a diagram showing a radiation position detection device according to another embodiment of the present invention, and FIG. 3 is a diagram showing an embodiment of an optical position detection element used in the present invention. Fig. 4' is a schematic diagram showing the radiation-to-light conversion element used in the present invention, Fig. S is a diagram showing a conventional radiation-fM source position detection device, and Fig. is a diagram showing another conventional radiation source position detection.
・Life radiation - light conversion element, ftl1...light regeneration plate, (
5)... Light position, detection element, (g)... Optical lens, (
31)...scintillator, (32)...fluorescent surface, (,?
j)... Image amplifier, (St)... Optical position sensitive detection +. (Yo3)...Image amplifier. Note that the numeral 41 in section 1 indicates the same or different parts. 1 - 1 inch flood 2 Figure crow 3 figure - U - Horse 4 figure Helmet 5 figure Ne installation

Claims (7)

[Claims] (1) In a radiation source position detection device that optically converts gamma rays or an aperture plate provided with an aperture between which the gamma rays or X-rays traveling from the radioactive substance toward the radiation detector are transmitted or blocked according to a predetermined spatial pattern, the gamma rays or A radiation-light conversion element in the form of a plate that absorbs X-rays and emits light;
A light position detection means for detecting light from the radiation-light conversion element, and a light position detection means for detecting light from the radiation-light conversion element toward the light position detection means between the radiation-light conversion element and the light position detection means. A light reproducing device in which a light transmission aperture that transmits or blocks light according to a similar pattern determined by the pattern of the aperture plate is provided at a position where the light intensity distribution of the transmitted light on the light position detection means has a large peak. A radiation source position detection device characterized in that a plate is arranged. (2) The optical position detection means detects the optical position due to the internal photoelectric effect.
The radiation source position detection device according to claim 1, which is an image pickup tube that sequentially performs charge conversion and charge readout by electron beam sweeping. (3) The optical position detecting means detects the optical position due to the internal photoelectric effect.
The radiation source position detection device according to claim 1, which is a charge-coupled two-dimensional detection element that sequentially reads out the converted charges using voltage clock pulses. (4) The optical position detecting means is arranged between the optical reproducing plate and the optical position detector so that the light receiving surface of the transmitted light from the optical reproducing plate is made smaller by using a light refraction effect. 3. The radiation source position detecting device according to claim 1, wherein the radiation source position detecting device includes an imaging lens having a radiation detection element, and a distance between the radiation detection element and the imaging lens is a lens focal length. (5) The radiation according to any one of claims 1 to 4, wherein the optical position detection means includes an optical image amplifier that two-dimensionally amplifies incident light and an optical position-sensitive detection element. Source position detection device. (6) The radiation-light conversion means is provided with a scintillator on the input side that absorbs and emits light when X-rays or γ-rays are incident, and a fluorescent surface is arranged on the output side of the scintillator to provide an image with enhanced brightness. A radiation source position detection device according to any one of claims 1 to 4, comprising an image amplifier. (7) The spatial pattern of the aperture plate and the optical reproducing plate is one-dimensional, and the optical position detection element is a one-dimensional detection element.
The radiation source position detection device described in 2.