JP2014194375A - Radiation measuring device - Google Patents

Abstract

【Task】
In a radiation measurement device characterized by using a pinhole collimator and arranging radiation detection elements in a column, simply synthesizing the signals of the radiation detection elements arranged in a column causes blurring due to the difference in imaging range, In particular, there is a drawback that the resolution of the peripheral portion is lower than that of the central portion.
[Solution]
Each image is acquired for a plurality of radiation detection element groups arranged at an appropriate distance from the pinhole collimator, the size of the image is normalized with the imaging range of each radiation detection element group, and then each radiation is detected. An image obtained from the detection element group is synthesized.
[Selection] Figure 1

Description

  The present invention relates to a radiation measuring apparatus that can visualize radiation.

  To measure the radiation dose on roads, parks, and houses, it is common to measure the radiation dose with a radiation meter, but the radiation dose is locally high due to the accumulation of radioactive materials. In order to specify a “hot spot” as a place, it is necessary to measure many places in order to specify the distribution of radiation, and the measurement takes a long time and a lot of labor.

Special table 2008-523405 gazette JP 2010-185752 A JP 2010-185753 A

  The principle of operation of a radiation camera is that radiation from a radiation source interacts with radiation detection elements arranged in a matrix through a collimator such as a pinhole or a coded mask made of a radiation shielding material such as lead or tungsten. Thus, the position of the radiation source and the energy of the radiation are determined from the electrical signals obtained directly or indirectly, and these are displayed as the brightness and hue of the image.

  Here, it is conceivable to increase the volume of the radiation detection element 1 in order to improve the radiation detection sensitivity. However, the radiation detection element 1 has a problem that it is difficult to form a crystal having a large shape.

  The present invention provides a radiation measurement apparatus that solves the above-described problems, improves the detection sensitivity of radiation, and can acquire a higher resolution image.

The outline of a representative one of the inventions disclosed in the present application will be briefly described as follows.
(1) A pinhole collimator, a plurality of radiation detection elements for detecting radiation that has passed through the holes of the pinhole collimator, and a plurality of stages of the plurality of radiation detection elements for each group according to the distance from the pinhole collimator A radiation detector card to be arranged; and a radiation image generating means for synthesizing and outputting a radiation image obtained for each group of the plurality of radiation detecting elements arranged in a plurality of stages, the radiation image generating means, The radiographic image obtained for each group is subjected to an image size correction process according to the distance between each group and the pinhole collimator, and the radiographic image after the correction process is synthesized and output. It is a radiation measuring device.

  ADVANTAGE OF THE INVENTION According to this invention, the detection sensitivity of a radiation can be improved and the radiation measuring device which can acquire a higher resolution image can be provided.

It is a figure which shows the arrangement | sequence method and imaging | photography range of the radiation detection element of a radiation measuring device. It is a figure which shows the external appearance of a radiation measuring device. It is a figure which shows the structure of the radiation detector card | curd of a radiation measuring device. It is a figure which shows the holding method of the radiation detector card | curd of a radiation measuring device. It is a figure which shows the structure of the radiation detector module of a radiation measuring device. It is a figure which shows the holding method of the radiation detector module of a radiation measuring device. It is a figure which shows the structure of the radiation camera of a radiation measuring device. It is a figure which shows the synthetic | combination method of the image in a radiation measuring device. It is a figure which shows the principle of operation of the radiation camera of a radiation measuring device. It is a figure which shows the function block diagram of the image synthesis | combination in a radiation measuring device.

  As a radiation measuring apparatus that can visualize the distribution state of radiation, there is a configuration as shown in FIG. 2, and this radiation measuring apparatus 21 superimposes an image of radiation measured by the radiation camera 22 and an image captured by the optical camera 23, Furthermore, the distance to the object is measured with the distance meter 24, and the radiation dose at the position of the object is calculated, so that the intensity of the radiation is displayed by a color difference or the like, and the radiation dose in a wide range is measured in a short time. be able to. As shown in FIG. 10, the display device receives the radiographic image generated by the radiographic image generation means 102 in the signal processing means 100 using the signal obtained by the radiographic camera 22 and the signal obtained by the optical camera 23. The superimposed image with the optical image generated by the optical image generation unit 101 is displayed. Here, the display device is provided outside the radiation measurement device, but a display unit may be provided as a configuration of the radiation measurement device.

The configuration of the radiation camera 22 of the radiation measuring apparatus 21 shown in FIG. 2 will be described below.
FIG. 3 shows a primary array structure of the radiation detection elements 1. As the radiation detection element 1, a compound semiconductor crystal of cadmium telluride is used, and a platinum electrode is deposited on one side and indium is deposited on the other side to form a semiconductor structure. It arrange | positions on the straight line on the positive electrode substrate 31, and is further connected to the negative electrode flexible substrate 32 from the top. A conductive adhesive is used for connection. The radiation detection element 1 is divided into four electrodes, and one radiation detection element 1 constitutes four pixels of the image. In this case, four radiation detection elements 1 are arranged in one row for 16 pixels. Further, the arrangement of the radiation detection elements 1 divides the radiation detection element A group 11 and the radiation detection element B group 12 into an upper stage and a lower stage as shown in FIG. 3 in order to increase the detection sensitivity of the radiation detector. Are arranged. In this way, by arranging the radiation detection elements, which are difficult to form a large crystal, in a plurality of stages, it is possible to increase the detection sensitivity even with a small crystal. Although an example in which two stages are arranged is shown here, the present invention is not limited to this, and three or more stages may be arranged.

  In addition, since the positive electrode substrate 31 has electrodes on both sides, the radiation detection element 1 can be similarly disposed on the back side of the positive electrode substrate 31. In this way, the radiation detector card 2 in which the radiation detection elements 1 are arranged in two rows and two rows is configured.

  As shown in FIG. 4, the radiation detector card 2 is incorporated in a radiation detector card holding member 33 configured to accommodate a total of eight radiation detector cards 2.

  Finally, as shown in FIG. 5, 16 rows of radiation detection elements 1 can be arranged by eight radiation detector cards 2. This constitutes a radiation detector module 34 having 16 × 16 pixels. The number of radiation detection elements arranged on the radiation detector card and the number of radiation detector cards incorporated in the radiation detector card holding member are not limited to this and can be variously changed.

  As shown in FIG. 6, the radiation detector module 34 is housed in a radiation detector module holding member 35 made of a material that shields radiation, and also shields radiation on the front surface of the imaging surface as shown in FIG. A pinhole collimator 3 made of a material to be attached is attached to constitute a radiation camera 22.

  On the other hand, FIG. 9 shows the principle of radiation detection by the semiconductor detection element in this embodiment regarding the electrical operation and signal processing of radiation detection. In this embodiment, as described above, a cadmium telluride crystal is used as the radiation detecting element 1, and platinum is deposited on one side surface and indium is deposited on the other side surface to form a semiconductor structure. Basically, a P layer, a depletion layer, and an N layer are formed in the same manner as a Schottky diode normally used in an electronic circuit.

  When radiation is incident on a depletion layer in which no carrier exists in the radiation detection element 1, the radiation causes ionization to generate electrons and holes. Since a negative bias voltage is applied to the negative electrode 37, which is the platinum electrode side, by a high voltage power supply 95 via a load resistor 91, electrons and holes generated by ionization of radiation are converted into indium electrodes (positive electrode 36). ) And platinum electrode (negative electrode 37) and converted to a pulse current flowing through the load resistor 91. The pulse current is amplified by the low noise amplifier 92 and then measured as a wave height distribution by the multichannel wave height analyzer 93. Based on this wave height distribution, the spectrum analyzer 94 analyzes and processes the signal peak portion, and the radionuclide and its amount can be obtained.

  By the way, in order to increase the radiation detection sensitivity of the radiation detection apparatus, it is necessary to increase the length or thickness of the radiation detection element 1 so that the range of the radiation inside the radiation detection element 1 is increased. . In this embodiment, for this purpose, as shown in FIG. 3, the radiation detection element 1 is divided into the radiation detection element A group 11 and the radiation detection element B group 12 so as to be arranged in a column in the direction in which the radiation is detected. It is arranged.

  However, as shown in FIG. 1 schematically showing the arrangement of the radiation detection elements 1 of the pinhole collimator 3 and the radiation detector card 2 and the positional relationship between the radiation detection elements A group 11 and the radiation detection elements B group 12, the radiation detection elements Since the distance from the pinhole collimator 3 inevitably differs between the A group 11 and the radiation detection element B group 12, the radiation detection element A group 11 and the radiation detection element B group 12 have the same shape. The shooting range will be different. Therefore, as shown in FIG. 1, the imaging range of the radiation detection element A group 11 is wider than the imaging range of the radiation detection element B group 12 for the subject 4. Therefore, when the image obtained by the radiation detection element A group 11 and the image obtained by the radiation detection element B group 12 simply added in a column are added, blur due to the difference in the photographing range and the focal length occurs. In particular, the resolution of the peripheral part may be lower than that of the central part. This is a particular problem in applications where the position of the radiation source is identified from the image obtained by the radiation camera 22 of the radiation measuring device 21, and may cause a case where the exact position of the radiation source cannot be recognized, or an incorrect position. It is necessary to deal with situations such as recognizing

  Therefore, in this embodiment, in order to improve the detection sensitivity, the radiation image generating unit 102 in FIG. 10 uses the radiation detection element A group 11 and the radiation detection element B group 12 to form a multi-stage arrangement. The radiation image obtained by the element group is subjected to signal processing corresponding to the distance from the pinhole collimator 3 to each radiation detection element group, and these are combined to generate and output a synthesized radiation image. r. A specific synthesis method will be described below with reference to FIG.

  As shown in FIG. 8, the image obtained by the radiation detection element A group 11 and the radiation detection element B group 12 has an image size of the subject 4 with respect to the imaging range from the pinhole collimator 3 to the radiation detection element group. In the case of FIG. 8, the size of the image of the subject 4 obtained by the radiation detection element B group 12 is L2 / L1 times as large as the image obtained by the radiation detection element A group 11 in the case of FIG. .

  Therefore, in this embodiment, when combining the images obtained by the radiation detection element A group 11 and the radiation detection element B group 12, the image obtained by the radiation detection element A group 11 is used as a reference. The images obtained by the radiation detection element B group 12 are reduced to L1 / L2 times so that the size of the subject 4 becomes equal when the images are combined, and the respective images are combined.

  In this way, the radiation detection element 1 is composed of the radiation detection element A group 11 and the radiation detection element B group 12, and images obtained from the respective radiation detection element groups are normalized within the imaging range and combined to detect radiation. The detection sensitivity of the apparatus 21 with respect to the radiation as the radiation camera 22 can be increased, and problems such as blur due to a difference in imaging range can be solved.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the invention. Not too long.

DESCRIPTION OF SYMBOLS 1 Radiation detection element 2 Radiation detector card 3 Pinhole collimator 4 Subject 11 Radiation detection element A group 12 Radiation detection element B group 21 Radiation measuring device 22 Radiation camera 23 Optical camera 24 Distance meter 31 Positive electrode side electrode substrate 32 Negative electrode side electrode flexible Substrate 33 Radiation detector card holding member 34 Radiation detector module 35 Radiation detector module holding member 36 Positive electrode side electrode 37 Negative electrode side electrode 91 Load resistance 92 Low noise amplifier 93 Multichannel wave height analyzer 94 Spectrum analyzer 95 High voltage power supply 100 Signal processing unit 101 Optical image generation means 102 Radiation image generation means 103 Image composition means

Claims (1)

A pinhole collimator,
A plurality of radiation detection elements for detecting radiation that has passed through the holes of the pinhole collimator;
A radiation detector card in which the plurality of radiation detection elements are arranged in a plurality of stages for each group according to the distance from the pinhole collimator;
A radiation image generating means for combining and outputting the radiation images obtained for each group of the plurality of radiation detection elements arranged in a plurality of stages;
With
The radiological image generation unit performs an image size correction process on the radiographic image obtained for each group according to the distance between each group and the pinhole collimator, and synthesizes the radiographic image after the correction process. A radiation measuring apparatus characterized by outputting the output.

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