WO2014125944A1 - Dosimètre de rayonnement - Google Patents

Dosimètre de rayonnement Download PDF

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Publication number
WO2014125944A1
WO2014125944A1 PCT/JP2014/052339 JP2014052339W WO2014125944A1 WO 2014125944 A1 WO2014125944 A1 WO 2014125944A1 JP 2014052339 W JP2014052339 W JP 2014052339W WO 2014125944 A1 WO2014125944 A1 WO 2014125944A1
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WO
WIPO (PCT)
Prior art keywords
radiation
scintillator
reflector
radiation dosimeter
ionizing radiation
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PCT/JP2014/052339
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English (en)
Japanese (ja)
Inventor
石川　正純
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国立大学法人北海道大学
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Application filed by 国立大学法人北海道大学 filed Critical 国立大学法人北海道大学
Publication of WO2014125944A1 publication Critical patent/WO2014125944A1/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/02—Dosimeters
    • G01T1/023—Scintillation dose-rate meters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/16—Measuring radiation intensity
    • G01T1/161—Applications in the field of nuclear medicine, e.g. in vivo counting

Definitions

  • the present invention relates to a radiation dosimeter that counts light from a scintillator to detect an ionizing radiation dose.
  • Patent Document 1 discloses a radiation dosimeter that detects ionizing radiation using a very small scintillator.
  • light obtained by a scintillator is supplied to a photoelectric converter via an optical fiber, and is converted into an electrical signal here.
  • the incident amount of ionizing radiation is detected by counting the peak of the obtained electric signal. According to the apparatus of this patent document 1, it is possible to detect a patient's exposure to ionizing radiation by wearing a detection unit including a small scintillator on a patient.
  • ionizing radiation dose detection includes a relatively high energy for the treatment and a relatively low energy such as X-ray fluoroscopy. Therefore, it is desired that the radiation dosimeter can detect an appropriate radiation dose in a wide energy range.
  • the present invention relates to a scintillator that emits light by incident ionizing radiation, a photoelectric converter that converts light output from the scintillator into an electric current, and outputs from the photoelectric converter that have two or more intensities.
  • a comparison unit for comparing with a threshold value, a counter for counting the number of events whose intensity is two or more threshold values or more, and obtaining two or more count values, and weighting two or more obtained count values And calculating a dose of ionizing radiation according to the count value after weighted addition obtained by the calculation unit.
  • the two or more count values obtained using the two or more threshold values are opposite to fluctuations in the energy level of ionizing radiation when the count values are normalized and compared. This shows the tendency.
  • the scintillator includes a reflector that covers a surface of the scintillator on the ionizing radiation incident side and reflects light from the scintillator, and the reflector absorbs even low energy of the ionizing radiation. Consists of few light elements.
  • the reflector is made of plastic.
  • the reflector is made of polyethylene.
  • accurate radiation dose detection can be performed even when the energy of incident ionizing radiation changes in a wide range.
  • the detection part 10 is comprised from the scintillator 12 and the reflector 14 which covers the front-end
  • the scintillator 12 is, for example, a hemisphere having a radius of about 250 ⁇ m, and a plastic scintillator is suitable.
  • the material of the scintillator 12 is described in Patent Document 1.
  • the reflector 14 covers the hemispherical tip surface of the scintillator 12 as a whole, and for example, a polyethylene film is used.
  • An optical fiber 16 having a diameter of 0.5 mm is connected to the base side of the hemispherical scintillator 12.
  • a shield material 18 is disposed so as to cover the surface of the optical fiber 16 and the surface of the reflector 14. For example, black polyethylene is used for the shield material 18.
  • the scintillator 12 converts incident X-rays into light (optical signal), and the optical signal enters the optical fiber 16.
  • the reflector 14 reflects an optical signal emitted from the scintillator 12 to the tip side and sends it to the optical fiber 16.
  • the other end of the optical fiber 16 is connected to the photomultiplier tube 20.
  • the photomultiplier tube 20 is a photoelectric converter, and an optical signal supplied from the optical fiber 16 is converted into an electric signal corresponding to its intensity.
  • a signal amplifier 22 is connected to the photomultiplier tube 20, and an electric signal from the photomultiplier tube 20 is amplified here.
  • the output of the signal amplifier 22 is input to two discriminators 24-1 and 24-2, which are comparison units.
  • the discriminators 24-1 and 24-2 are respectively supplied with the threshold value 1 and the threshold value 2 from the threshold value setting unit 26, and the signal level of the input electric signal is Those with threshold value 1 and threshold value 2 or more are discriminated as events.
  • the discriminators 24-1 and 24-2 respectively obtain event signals that are the comparison results with the threshold values 1 and 2 and output them.
  • the two event signals from the discriminators 24-1 and 24-2 are input to the counters 28-1 and 28-2, respectively counted, and two count values are input to the arithmetic unit 30.
  • the computing unit 30 weights and adds the two count values and outputs the result as an incident X-ray dose.
  • it is also possible to obtain an incident X-ray dose by obtaining three or more count values by using three or more threshold values and weighting and adding them.
  • the dosimeter of this embodiment is called SOF (Scintillator with Optical Fiber Dosimeter).
  • SOF Silicon Fluorescence Fluorescence
  • an ion chamber ionization chamber: 15 cc SFD ion chamber manufactured by PTW
  • PSD Principal Skin Dosimeter; manufactured by Unfors
  • SDM Skin Dose Monitor; manufactured by McMAHON Medical Incorporated
  • an acceleration voltage (X-ray tube voltage) of an X-ray tube is often obtained as X-ray energy information. Therefore, the X-ray tube voltage is used as X-ray (radiation) energy information.
  • FIG. 2 shows the relationship between the measured value by the ion chamber and the measured value of the SOF when the X-ray dose is changed at three types of X-ray tube voltages of 110 kV, 75 kV, and 40 kV. .
  • the X-ray tube voltage is constant, good linearity can be obtained in the range of 2 to 2000 ⁇ Gy, and the dose can be appropriately measured by SOF.
  • the horizontal axis represents the dose from the ion chamber
  • the vertical axis represents the dose of SOF
  • the results for three types of X-ray tube voltages are shown separately.
  • X-ray tube voltages are represented by 110 kV (square), 75 kV (circle), and 40 kV (triangle). From this, it can be seen that the sensitivity of the SOF varies depending on the X-ray tube voltage.
  • FIG. 4 shows changes in sensitivity relative to changes in the X-ray tube voltage.
  • the relative sensitivity to the X-ray tube voltage is shown for three dosimeters of SOF (black circle), PSD (white circle), and SDM (square). That is, the relative sensitivity at the X-ray tube voltage of 40 to 110 kV is shown by standardizing the measured value of the X-ray tube voltage of 80 kV often used in IVR fluoroscopy as 1.
  • FIG. 5 shows the relative sensitivity (normalized at an X-ray tube voltage of 80 kV) when the X-ray tube voltage is changed with the reflector 14 having a thickness of 100 ⁇ m and a threshold value of 6 keV.
  • the values indicated by white circles are actually measured values.
  • the influence was examined by changing the threshold value in the range of 1 keV to 10 keV by Monte Carlo simulation (simulation code: EGS4). In this case, it turns out that a tendency changes according to the object of a threshold value.
  • the discrimination threshold for the detected X-ray energy is 6 keV, it matches the SOF detection value, indicating that a correct simulation is being performed.
  • FIG. 6 shows a case where the thickness of the TiO 2 reflector 14 is 50 ⁇ m. From this, it can be seen that the tendency of sensitivity changes depending on the thickness of the reflector 14.
  • FIG. 7 shows the relative sensitivity when the material of the reflector 14 is changed to polyethylene and the threshold value is changed in the range of 1 keV to 10 keV.
  • the polarity (increasing tendency, decreasing tendency) of the tendency of relative sensitivity to the X-ray tube voltage differs depending on the threshold value.
  • FIG. 8 shows two cases of threshold values of 1 keV (square) and 12 keV (circle).
  • the relative sensitivity in the case of two threshold values is opposite to that of the relative sensitivity 1. That is, at a threshold value of 1 keV, the relative sensitivity is less than 1 even if the X-ray tube voltage is less than 80 kV, and at a threshold value of 12 keV, the relative sensitivity is not limited even if the X-ray tube voltage is less than 80 kV. Greater than 1.
  • sensitivity to changes in the X-ray tube voltage can be compensated by combining the characteristics of relative sensitivity at the two threshold values.
  • the count value (detection dose) of 1 keV and the count value (detection dose) of 12 keV are weighted and added 1: 1.8
  • the two detection doses of the X-ray tube voltage 80 kV are weighted and added together.
  • FIG. 9 shows SOF (Measured) (black circle) which is the measurement result of SOF, PSD (Measured) (diamond) which is the measurement result of PSD, SDM measurement result (Measured) (triangle), and SOF threshold value 6 keV.
  • EGS4 SOF Th: 6keV
  • EGS4 Double Threshold
  • white circle which is the result of weighted addition of 1: 1.8 of the SOF threshold values 1 keV and 12 keV. It is. That is, the white circles are normalized by multiplying the count values (detected doses) in the two cases of 1 keV and 12 keV as the above-described threshold values by multiplying each by a weight of 1: 1.8.
  • the relative sensitivity fluctuation is within 1% in a wide range of the X-ray tube voltage of 40 kV to 110 kV.
  • the characteristics indicated by the white squares in the figure are the simulation results when the threshold value is 6 kV, which is in good agreement with the characteristics of the black circle that is the actual detection result of SOF. I can confirm.
  • detection results of PSD and SDM are also shown. It can be seen that the sensitivity fluctuation is smaller when the two threshold values of SOF are used.
  • the relative sensitivity changes greatly by changing the threshold value. It is preferred to select an appropriate set of relative sensitivities. What is necessary is just to select a suitable thing by simulating in the stage where the specification about SOF was determined. In addition, it is preferable to select two relative sensitivities that are basically in reverse, but the number is not necessarily limited to two, and relative sensitivities at three or more threshold values may be weighted and added. .
  • polyethylene is used for the reflector 14, but it is also preferable to use other plastics such as polypropylene instead of polyethylene.
  • the element has a large atomic weight, the amount of absorption for low energy radiation increases, and the above-mentioned sensitivity characteristics for the radiation energy of the count value cannot be obtained. It is considered that the sensitivity characteristics as described above can be obtained for radiation having a low energy and a low absorption amount.
  • a metal can be used, and a plastic in which aluminum or the like is mixed is also suitable.
  • the threshold value is indicated by the magnitude of the energy change, it is actually a threshold value for the magnitude (current value or voltage value) of the electric signal that is the output of the signal amplifier 22, and is a discrete value. What is necessary is just to set the threshold value in the terminator 24 to appropriate two (plurality). Furthermore, other signal processing as described in Patent Document 1 may be performed.
  • X-rays have been described as the ionizing radiation to be detected, other ionizing radiations such as ⁇ -rays can be similarly applied.
  • a plurality of threshold values in the discriminator 24 are used, and the two addition results obtained by the counter 28 are weighted and added by the arithmetic unit 30.
  • appropriate dose detection can be performed by compensating the sensitivity change with respect to the energy level of the ionizing radiation to be detected.
  • the material of the reflector that covers the scintillator 12 is preferably plastic, particularly polyethylene, so that the sensitivity change tendency (polarity) with respect to the magnitude of the energy of the ionizing radiation to be detected according to the magnitude of the threshold value. Is the opposite. Therefore, sensitivity compensation can be performed on the detection results at the two threshold values by weighted addition using appropriate weights.
  • the sensitivity characteristic at one threshold value is mathematically compensated, it cannot compensate for the influence of changes in the surrounding conditions such as scattered radiation, but by using the sensitivity characteristic at two threshold values, It will be possible to compensate for changes in sensitivity characteristics according to changes in the situation.

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  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Molecular Biology (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Engineering & Computer Science (AREA)
  • Biomedical Technology (AREA)
  • General Health & Medical Sciences (AREA)
  • Medical Informatics (AREA)
  • Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
  • Optics & Photonics (AREA)
  • Measurement Of Radiation (AREA)

Abstract

La présente invention compense des changements de sensibilité à l'énergie de rayonnement et détecte la dose du rayonnement. Un scintillateur (12) émet une lumière par un rayonnement ionisant incident. Un convertisseur (20) photoélectrique convertit une lumière qui est délivrée en sortie par le scintillateur (12) en un courant électrique. Une unité (24) de comparaison compare l'intensité d'une sortie provenant du convertisseur (20) photoélectrique à au moins deux valeurs seuils, et un compteur (28) compte les nombres d'évènements dans lesquels l'intensité est supérieure ou égale aux au moins deux valeurs seuils, respectivement, pour obtenir au moins deux valeurs de comptage. Une unité (30) de calcul détecte la dose du rayonnement ionisant selon une valeur de comptage après addition pondérée, la valeur de comptage étant obtenue par addition pondérée des au moins deux valeurs de comptage obtenues.
PCT/JP2014/052339 2013-02-15 2014-01-31 Dosimètre de rayonnement WO2014125944A1 (fr)

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JP2013027375A JP2016095134A (ja) 2013-02-15 2013-02-15 放射線線量計
JP2013-027375 2013-02-15

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2016130038A1 (fr) * 2015-02-13 2016-08-18 Otkrytoe Aktsionernoe Obschestvo "Intersoft Evraziya" Dosimètre-radiomètre-spectromètre miniature

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR101975787B1 (ko) * 2016-12-02 2019-05-09 한국원자력연구원 방사성 핵종을 검출하는 방법, 이를 이용한 방사성 핵종 검출공정, 및 이를 위한 방사선 검출장치
WO2018101598A1 (fr) * 2016-12-02 2018-06-07 Korea Atomic Energy Research Institute Procédé de détection de radionucléides, processus de détection de radionucléides utilisant ce dernier et détecteur de rayonnement destiné à ce dernier
KR101962370B1 (ko) * 2017-03-29 2019-03-26 한국원자력연구원 방사성 핵종을 검출하는 방법, 이를 이용한 방사성 핵종 검출공정, 및 이를 위한 방사선 검출장치
KR102644122B1 (ko) * 2021-09-17 2024-03-06 (주)네오시스코리아 핵종판별을 위한 방사선 스펙트럼의 온도보상방법

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0519062A (ja) * 1991-07-11 1993-01-26 Aloka Co Ltd 放射線線量計
JP2002062359A (ja) * 2000-08-21 2002-02-28 Aloka Co Ltd 放射線測定装置
WO2008117821A1 (fr) * 2007-03-27 2008-10-02 Kabushiki Kaisha Toshiba Panneau scintillant et détecteur de rayonnement
JP2008256630A (ja) * 2007-04-09 2008-10-23 Fuji Electric Systems Co Ltd エネルギー補償型シンチレーション式光子線量計
JP2008292245A (ja) * 2007-05-23 2008-12-04 Toshiba Corp 放射線検出器
JP2010107198A (ja) * 2008-10-28 2010-05-13 Fujifilm Corp 放射線画像検出器

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0519062A (ja) * 1991-07-11 1993-01-26 Aloka Co Ltd 放射線線量計
JP2002062359A (ja) * 2000-08-21 2002-02-28 Aloka Co Ltd 放射線測定装置
WO2008117821A1 (fr) * 2007-03-27 2008-10-02 Kabushiki Kaisha Toshiba Panneau scintillant et détecteur de rayonnement
JP2008256630A (ja) * 2007-04-09 2008-10-23 Fuji Electric Systems Co Ltd エネルギー補償型シンチレーション式光子線量計
JP2008292245A (ja) * 2007-05-23 2008-12-04 Toshiba Corp 放射線検出器
JP2010107198A (ja) * 2008-10-28 2010-05-13 Fujifilm Corp 放射線画像検出器

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2016130038A1 (fr) * 2015-02-13 2016-08-18 Otkrytoe Aktsionernoe Obschestvo "Intersoft Evraziya" Dosimètre-radiomètre-spectromètre miniature

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