JP3138324B2 - Radiation measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation measuring apparatus having a well or through-hole scintillator.

[0002]

2. Description of the Related Art In the fields of medicine, biology, engineering, and the like, dosimetry of radiation contained in various samples (for example, animals, vegetables, fruits, seafood, soil, and the like) is performed.

[0003] Among such radiation measurement apparatuses for performing radiation measurement, an apparatus using a so-called well-type scintillator is known. The apparatus includes a well for storing a test tube formed in an upper portion thereof, and a test tube containing a sample to be measured includes a well-type scintillator inserted into the well from above, and radiation generated from the sample emits light with the scintillator. The generated photons are detected by, for example, a photomultiplier tube or the like, and the radiation dose of the sample is calculated. There is also a radiation measuring apparatus in which a through hole is formed in a scintillator instead of a well.

A radiation measuring apparatus having such a scintillator is widely used in various fields because it can measure radiation of various objects as long as the sample enters a test tube.

[0005]

However, in a conventional radiation measuring apparatus having a well-type or through-hole-type scintillator, since the height of a sample in a test tube varies depending on the sample, the radiation height depends on the height of the sample. When the detection efficiency changes, and particularly when the height of the sample is high, there is a problem that the accuracy of the radiation detection result is inferior because the detection leakage increases.

Here, various types of wells formed in the well type scintillator can be formed in accordance with the test tube. Therefore, it is not preferable to make the depth of the well too large. That is, when the size of the scintillator becomes large, there arises a problem that the photomultiplier tube must be enlarged or a plurality of photomultipliers must be arranged in order to capture the light emitted from the scintillator. This is the same with a through-hole type radiation measurement device,
There is a restriction that the length of the through hole itself cannot be too long.

Therefore, in a conventional radiation measuring apparatus having a well-type or through-hole type scintillator, FIG.
The height of the sample in the well or through hole of the scintillator is low as shown in
%, But the detection efficiency decreases as the height of the sample approaches the depth of the well or through hole.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a small-sized radiation measuring apparatus capable of accurately detecting radiation regardless of the height of a sample. is there.

[0009]

In order to achieve the above object, the present invention provides a well-type or through-hole type storage section, and a test tube containing a sample to be measured is inserted into the storage section from above. Scintillator, the photomultiplier tube joined to the scintillator, a height detector to detect the height of the sample in the test tube, an efficiency table storing the relationship between the height of the sample and the detection efficiency, A circuit for calculating the amount of radiation by inputting the output of the photomultiplier, and referring to the efficiency table, based on a detection efficiency corresponding to the height of the sample detected by the height detector. And an operation circuit for correcting and outputting the operation result.

[0010]

According to the above construction, when a test tube containing a sample is inserted into the well or through hole of the scintillator, the height of the sample is detected by the height detector, and the arithmetic circuit is operated according to the height. As a result, the detection efficiency is corrected, and it becomes possible to finally obtain an accurate radiation dose.

[0011]

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

FIG. 1 shows the overall configuration of a radiation measuring apparatus according to the present invention. FIG. 2 is an enlarged view of the main part. First, a description will be given with reference to FIG.

The well type scintillator 10 is, for example, Nal
(Tl) Scintillator, well 1 above
0a is formed. The diameter of the well 10a is the test tube 1
The diameter of the test tube 12 is slightly larger than the diameter of the test tube 2. Below the well type scintillator 10, a photomultiplier tube (PMT) 14 is joined and arranged. The radiation emitted from the sample 16 is the well-type scintillator 10
The photons generated by this are converted to photomultiplier tubes 14
It is detected by.

The height l of the sample 16 is, in this embodiment,
It is detected by a height detector 18 fixed above the well type scintillator 10. In the present embodiment, as the height detector 18, a capacitance type detector capable of detecting the presence of a sample in a non-contact manner is used. Therefore, the test tube 12 held by the manipulator 20 moves the well 1 from above.
When descending with respect to 0a, the height detector 18 can detect the height of the sample 16 without contact, that is, the length from the bottom end of the test tube 12 to the upper surface of the sample 16.

The sample 16 is not limited to a liquid sample.
Since soil, animals, fruits and the like can be put in, it is desirable to use a capacitance type height detector as in this embodiment. That is, some of the samples 16 are difficult to detect electromagnetically, and when light is used, if the samples 16 are different, an extreme difference in transparency occurs, and it is difficult to detect the height.

Therefore, when the test tube 12 is lowered, the height l of the sample 16 is detected by the height detector 18. In this case, when the height of the sample 16 is considerably higher than the depth of the well 10a. Therefore, it is desirable that the height detector 18 be disposed at a certain distance above the well-type scintillator 10 so as to cope with such a case.

Returning to FIG. 1, after the detection signal output from the photomultiplier 14 is amplified by the amplifier 22, only a pulse of a certain level is extracted by the wave height discriminator 24 and counted by the counting circuit 26. You. The count result is sent to the microcomputer 28. On the other hand, the capacitance signal detected by the height detector 18 is
After being amplified by, it is sent to the sample height detection unit 32.

That is, the height detector 18 itself outputs a signal corresponding to the capacitance of the sample 16 in front of it. In the sample height detector 32, the height of the test tube 12 held by the manipulator 20 is measured. Taking into account the descent speed,
The height of the sample is calculated from the duration of the signal indicating the presence of the sample 16 from the height detector 18. The height of the sample is sent to the microcomputer 28.

The microcomputer 28 performs the overall control of the radiation measuring apparatus, the calculation of the radiation dose, and the correction calculation thereof, and is connected to an efficiency table 34 as shown in the figure.

FIG. 3 shows the relationship between the sample height stored in the efficiency table 34 and the detection efficiency. In addition,
The vertical axis is indicated by a relative ratio, and Z indicates the height of the well.

As shown, it is understood that the detection efficiency decreases as the height of the sample increases. That is, since the three-dimensional entire circumference of the sample 16 is not surrounded by the scintillator, the amount of radiation that does not reach the scintillator increases. Therefore, the detection efficiency is
It is considered that it basically depends on the height of the sample 16 and does not basically depend on the diameter of the test tube, that is, the lateral width of the sample.

Returning to FIG. 1, the microcomputer 28
Calculates the amount of radiation based on the count result detected by the counting circuit 26. After the calculation, the detection efficiency is obtained by referring to the efficiency table 34 according to the height of the sample, and the calculated radiation dose is calculated. The corrected radiation dose is obtained by performing an operation of multiplying the reciprocal of the detection efficiency. Then, the obtained radiation dose is displayed on the display 36.

FIG. 4 shows a through hole type scintillator 4.
0 to a through hole 4 which is a through hole for accommodating the test tube 12
A through-hole type radiation measuring device in which Oa is formed is shown. Even in such a device, the height detector 18
Is provided, the detection efficiency can be corrected, and as a result, radiation can be measured with high accuracy.

As described above, according to the radiation measuring apparatus of the present invention, correction is performed according to the height of the sample based on the characteristics of the well type or through hole type scintillator,
The amount of radiation can be accurately determined.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of a radiation measuring apparatus according to the present invention.

FIG. 2 is a partially enlarged view showing a main part of the radiation measuring apparatus according to the present invention.

FIG. 3 is a characteristic diagram showing a relationship between a sample height and detection efficiency.

FIG. 4 is a partially enlarged view showing a through-hole type embodiment.

[Explanation of symbols]

 Reference Signs List 10 well scintillator 12 test tube 14 photomultiplier tube 16 sample 18 height detector 28 microcomputer 34 efficiency table 40 through-hole scintillator

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-302981 (JP, A) Japanese Utility Model Showa 62-44289 (JP, U) Japanese Utility Model Showa 58-99676 (JP, U) (58) Field (Int.Cl. ⁷ , DB name) G01T 1/20

Claims (2)

(57) [Claims] 1. A scintillator in which a well or through-hole type storage part is formed and a test tube containing a sample to be measured is inserted into the storage part from above, and a photomultiplier tube joined to the scintillator. A height detector for detecting the height of the sample in the test tube; an efficiency table storing the relationship between the height of the sample and the detection efficiency; and calculating the amount of radiation by inputting the output of the photomultiplier tube A calculation circuit that corrects and outputs a calculation result based on the detection efficiency corresponding to the height of the sample detected by the height detector with reference to the efficiency table. Characteristic radiation measurement device. 2. The radiation measuring apparatus according to claim 1, wherein the height detector is a capacitance type detector that can detect the height of the sample without contact.