Radiophotoluminescent Dosimeter Research Articles

Radiation dose reduction by using low dose CT protocol of thorax

Abstract CT makes up to 67% of radiation from medical sources. Therefore emphasizes is especially on the importance of reducing doses and the introduction of procedures with the lowest possible dose received by the patient. The so called low dose CT protocol was studied for some chest diagnosis however it was not investigated for the patients with lymphoproliferative diseases. Lymphoproliferative diseases, including most lymphomas involve a large number of younger and middle age patients i.e. patients in the reproductive period of life. A CT exam of these patients is indispensable method for the diagnosis, and later for long life monitoring of the effectiveness of therapy. The aim of this work was to compare the patient doses between two different CT protocols of thorax in patients with this diagnosis. The entrance surface doses were measured and compared using standard CT protocol of thorax which implies 120 kV and 160 mA conditions and low dose CT protocol using 120 kV and 30 mA conditions while maintaining image quality. The study involved 60 patients. Each patient underwent two different CT thorax protocols during regular follow up of the disease. The doses were measured using LiF:Mg,Ti (TLD-100) thermoluminescent (TL) and GD-352M radiophotoluminescent (RPL) dosimeters on the thyroid, eye lens, sternum and gonads. The results showed that low dose protocol yielded with the reduction of doses by the factor of 1.8–15 on the eye lens, 1.0–9.1 on the thyroid, 2.5–7.0 on sternum and 0.3–12.8 on gonads, respectively. The doses were significantly lower using low dose CT protocol while the image quality for lymph node presentation was satisfactory according to European criteria. Therefore the use of low dose CT protocol as a standard for patients with lymphoproliferative disorders is highly recommended.

Development of bead-type radiophotoluminescence glass dosimeter applicable to various purposes

Bead-type radiophotoluminescence (RPL) glass dosimeters were well fabricated with a gas-particle jet flame system for glass melting-cooling process. A rod of silver-activated phosphate glass was pulverized into micrometer-size particles. Spherical glass particles were formed from the pulverized glass particles in the high-temperature jet flame owing to the surface tension of the glass material. Some groups of spherical glass particles were irradiated with X-rays and their RPL was demonstrably observed for their exposure to UV light. A flexible RPL glass sheet was also made of bead-type RPL glass dosimeters and was useful for radiation imaging. Bead-type RPL glass dosimeters are expected to be used for dose monitoring in highly radioactively-contaminated area. ► We developed bead-type radiophotoluminescence glass dosimeters. ► Bead-type glass RPL dosimeters are satisfactorily used as radiation dosimeters. ► A flexible RPL glass sheet is made of bead-type RPL glass dosimeters.

Calculated angular responses of an RPL dosemeter to photon and beta radiation

The calculated dose equivalent response as a function of the angle has been examined for the radiophotoluminescent (RPL) glass dosemeter that was exposed to narrow series X-ray, N-60, N-80, N-100, N-150, N-200, N-250, N-300, photon sources ((60)Co and (137)Cs) and beta-ray emitter ((90)Sr/(90)Y) while mounted on an ISO water slab phantom. The angular dose equivalent responses H(p)(10) and H(p)(0.07) were calculated using the Monte Carlo MCNPX code. The RPL dosemeter and the phantom were rotated in the horizontal and vertical planes from a variety of angles of interest. The results were compared with the experimental data. Good agreement was found between the measured and calculated values of the relative dose equivalent angular responses of the RPL dosemeter.

Personal monitor glass badge: theoretical dosemeter response calculated with the Monte Carlo transport code MCNPX

This paper describes the results of the simulation of a radiophotoluminescent (RPL) dosemeter with the Monte Carlo transport code MCNPX. The aim of this study is to calculate the response with MCNPX of the RPL dosemeter in terms of equivalent doses H(p) (0.07) and H(p)(10) using X-ray photon radiation qualities N series, together with S-Cs and S-Co nuclide radiation qualities, specified in ISO 4037-1. After comparison with reference values versus experimental results, the deviation of the theoretical responses of the RPL dosemeter proved to be lower than 5 % for reference values and lower than 10 % for experimental results. This good correlation validates the model over the energy range studied.

New Radiophotoluminescence Glass Dosimeter with Specialized Radiation-Sensitive Surface Layer

A new radiophotoluminescence (RPL) dosimeter with a specialized radiation-sensitive surface layer was successfully fabricated from phosphate glass by the melting method. The radiation-sensitive surface layer, which was measured using an excitation laser and a fluorescence microscope, was formed through the thermal diffusion of silver atoms. It was found from RPL observations that the diffusion coefficient of silver atoms in phosphate glass was about 1.4 µm2/s at 400 °C and activation energy for silver atoms was about 0.7 eV. It was also confirmed that the newly synthesized dosimeter showed a satisfactory response to alpha rays and the effect of the annealing process on the dosimeter could be estimated on the basis of a thermal diffusion model of silver atoms in the glass.

Gamma rays induced defect centers in phosphate glass for radio-photoluminescence dosimeter

Abstract Gamma induced defect centers of undoped phosphate glasses and the influence of these centers on the sensitivity and build-up time of silver-doped phosphate glasses were investigated. According to the ratio of oxygen and phosphorus ions (O/P) in phosphate glass, the basic glasses were polyphosphate glass (O/P = 3.07), metaphosphate glass (O/P = 3) and ultraphosphate glass (O/P = 2.93). Concentration of Ag + was 2 mol%. Defect centers induced by gamma rays of three base glasses were detected by Electron paramagnetic resonance (EPR) and optical absorption spectra. Three kinds of defect centers were observed and the characteristics of the hyperfine splitting doublets were quite similar in these glass samples. All the defect centers are phosphorus and oxygen related radiation-induced hole trapped defect centers (POHC) and electron centers PO 3 2 − and PO 4 4− . Based on EPR and optical absorption spectra, polyphosphate glasses have the highest relative POHC concentration. The fluorescence spectra and EPR spectra of silver-doped glasses were measured. The results indicate that polyphosphate glasses have the highest sensitivity and shortest build-up time of three silver-doped phosphate glasses which are related to the concentration of POHC.

Response of radiophotoluminescent dosimeters to neutrons

Radiophotoluminescent (RPL) glass dosimeter type SC-1 has been studied with respect to use it as a photon dosimeter in mixed neutron + gamma fields. SC-1 is composed of the flat glass element placed in a plastic capsule. Energy compensation tin filters to all directions shield the glass card in the capsule. This type of dosimeter was primarily designed for the measurements of photon dose and for use in environmental monitoring around nuclear plants and for accident dosimetry. For a gamma dosimeter to be useful in a mixed neutron + gamma field it is desirable that the neutron sensitivity is small and accurately known. The response has been characterized for 14.5 MeV neutrons, 238Pu–Be spectra and thermal neutrons. The results show that the plastic holder has an influence to the response. The comparison with TLD-700 shows lower responses for neutrons for all spectra investigated. The relative low neutron sensitivity of RPL dosimeter type SC-1 enables its use for photon dosimetry in the mixed neutron + gamma fields.

A HISTORY OF RADIATION DETECTION INSTRUMENTATION

A review is presented of the history of radiation detection instrumentation. Specific radiation detection systems that are discussed include the human senses, photography, calorimetry, color dosimetry, ion chambers, electrometers, electroscopes, proportional counters, Geiger Mueller counters, scalers and rate meters, barium platinocyanide, scintillation counters, semiconductor detectors, radiophotoluminescent dosimeters, thermoluminescent dosimeters, optically stimulated luminescent dosimeters, direct ion storage, electrets, cloud chambers, bubble chambers, and bubble dosimeters. Given the broad scope of this review, the coverage is limited to a few key events in the development of a given detection system and some relevant operating principles. The occasional anecdote is included for interest.

A history of radiation detection instrumentation.

A review is presented of the history of radiation detection instrumentation. Specific radiation detection systems that are discussed include the human senses, photography, calorimetry, color dosimetry, ion chambers, electrometers, electroscopes, proportional counters, Geiger Mueller counters, scalers and rate meters, barium platinocyanide, scintillation counters, semiconductor detectors, radiophotoluminescent dosimeters, thermoluminescent dosimeters, optically stimulated luminescent dosimeters, direct ion storage, electrets, cloud chambers, bubble chambers, and bubble dosimeters. Given the broad scope of this review, the coverage is limited to a few key events in the development of a given detection system and some relevant operating principles. The occasional anecdote is included for interest.

Burst X-ray detection using RMSAFE

Abstract The function of the radiation monitoring system Radiation Monitoring System Applicable to Fusion Experiments (RMSAFE) is well verified to detect burst radiation, that is, radiation generated suddenly and explosively. When an increase in 50 ms integrated count from a radiation monitor, which is recorded and updated every 10 ms in the system CPU, is encountered to exceed a pre-set level, RMSAFE recognizes it as an outbreak of burst radiation and alters its recording mode so that the burst event data is saved in a specified file. In this study, we detected X-rays arising from Compact Helical System (CHS), a high-temperature plasma experimental device, in order to verify that RMSAFE is able to detect radiation bursts successfully and accurately. Increases in the dose of radiation due to X-rays from CHS were observed concurrently at various observation points in several plasma shots. The weekly accumulated values of radiation dose observed by RMSAFE in the CHS torus hall were consistent with the results of integrated dose measurements by thermoluminescent dosimeter (TLD) and by radiophotoluminescent dosimeter (RPLD), and furthermore, the general decreasing tendency of the observed dose with the distance from the CHS torus was clearly seen, though detailed radiation patterns might be dependent on source plasma and other conditions. These results support our conclusion that RMSAFE is able to successfully detect burst X-rays.

温度による個人被曝線量計の測定値への影響（ＩＩ）―ＯＳＬ線量計・ガラス線量計―

The current study was performed to investigate the influence of high temperature on the value of radiation dose measured by optically stimulated liminescence (OSL) dosimeter or radio photo luminescence (RPL) dosimeter (glass dosimeter) . Serial measurements of temperature in the car confirmed that it can rise to 80°C or higher in the area irradiated with sun beam. The relationship between the temperature and the radio dose measured by X-ray irradiated OSL dosimeter or glass dosimeter under the condition from 50°C to 90°C after the set of 3h. to 72h.The value measured by OSL dosimeter tended to be lower with higher temperature or longer setting time. On the other hand, those factors did not influence the value measured by glass dosimeter.

Investigation on Environmental Radiation Dose in Akita Prefecture and Radiophotoluminescence Dosimeters Used in Environmental Monitoring.

CaSO4: Tm thermoluminescence dosimeters and radiophotoluminescence dosimeters were used to carry out an investigation of indoor and outdoor environmental radiation in Akita Prefecture, Japan, during the period from April to October 1994. The results showed that the average absorbed-dose rate in air from outdoor terrestrial gamma-radiation was 38.8nGy h-1 with a range of 26.6-50.2nGy h-1. The indoor average absorbed-dose rate of wooden houses was 40.2nGy h-1 with a range of 29.5-50.4nGy h-1, and for concrete buildings it was 55.3nGy h-1 with a range of 41.7-66.9nGy h-1. The indoor weighted average absorbed-dose rate of concrete buildings was 42.9nGy h-1. Among different geological areas, the gamma-radiation absorbed-dose rate of andesite was the highest (50.2nGy h-1), and alluvium was the lowest (30.3nGy h-1). As for the results of measurement the two kinds of dosimeters were quite similar. Eighty-two percent of the results of measurement from twenty-eight monitoring sites where the two kinds of dosimeters were used coincided within ±5%, and there were only two sites where the difference was larger than 10%; deviations were +10% and +11%, respectively. These results indicated that the radiophotoluminescence dosimeter is also suitable for the measurement of environmental radiation.

Methods and means of checking thermoluminescent and radiophotoluminescent dosimeters

The authors discuss methods of checking thermoluminescent and radiophotoluminescent dosimeters which are used often in monitoring radiation safety in various areas including nuclear power stations. When the dosimeters are checked in the fields of standard beta-ray sources, it is recommended that the standard absorbed-dose or equivalent-dose measures for beta radiation should be sources of /sup 90/Sr + /sup 90/Y, /sup 204/Tl, and /sup 147/Pm. Various safety guidelines are discussed.

Radiation damage to electronic components

Characteristic properties are presented of some 40 different electronic components (resistors, capacitors, diodes, transistors, and integrated circuits) which were irradiated in a nuclear reactor up to 10 15 n/cm 2 ( E>1 MeV). Complete circuits (e.g. rf amplifiers and detectors, mixers, differential amplifiers, voltage-to-frequency converters, oscillators, power supplies) were irradiated near the CERN Intersecting Storage Rings up to 10 6 Rad (RPL) (dose measured with radiophotoluminescent dosimeters) under simulated operational conditions. Representative measured parameters, such as resistance, capacitance, forward voltage, reverse current, toggle frequencies, are given in graphs as a function of radiation dose. The results are discussed in detail and lead to the over-all conclusion that the operation of electronic components and circuits is seriously affected by radiation environments with doses in the order of 10 13 n/cm 2 or 10 4 Rad (RPL); some components and circuits fail completely at doses of 10 14 n/cm 2 or 10 5 Rad (RPL).

Photon Dosimetry by Luminescence Methods

A brief, elementary introduction to the dosimetry of photon radiation fields using thermoluminescent and radio-photoluminescent dosimeters is presented. This presentation should be useful for both teachers and students desiring to learn more about the important subject of health physics.

A preliminary study of thermoluminescent dosimetry.

A miniature solid state dosimeter based on the phenomenon of thermoluminescence (1) is presently being investigated in our laboratory for introduction into an in vivo dosimetry system, previously described by the authors (1, 3, 4). The radiation-sensitive element is a manganese-activated calcium fluoride phosphor. Development of this phosphor was carried on at the U. S. Naval Research Laboratory by Schulman et al. (2). The dosimeter we are using is in the form of a needle, 10 mm. long and less than 1 mm. in outside diameter. It is sealed within a glass tube and read by heating at a constant rate. Heating liberates electrons which were trapped during irradiation, and these electrons attempt to return to their ground state by emitting energy in the form of blue-green light. A graph of fluorescent intensity vs. time, generated at a constant heating rate, is called a “glow curve.” Either the area under the glow curve, or its peak, may be used to read the dosimeters; we prefer to use the former. This area may be measured by electronically integrating the current output while the glow curve is traced. The most difficult problem in developing the reader system has proved to be the mounting of the photomultiplier assembly in the area of the heating circuit. The dosimeter is a relative device. It is calibrated by exposing a large number of dosimeters to different radiation modalities. Since the response is linear, the area under the glow curve increases as the exposure increases. A calibration factor having the dimensions of roentgens per unit area may thus be determined. The act of reading destroys the electron traps. Hence, this dosimeter cannot provide a permanent exposure record nor can it be used as a cumulative device. This fact plus its sensitivity and range distinguish it from the radiophotoluminescent dosimeter (3, 4). The range of the thermoluminescent dosimeter is estimated to be from 10−5 to 105 r, a span of ten decades. Like the radiophotoluminescent dosimeter (3), it is energy dependent and corrective shielding is required. The shielded and unshielded dosimeters will be subjected to x-rays from 260 kv to 1 Mv, cobalt 60, radium, and iridium 192 in air, and at various positions in depth of phantoms with varying portal sizes to determine the effect of energy on response. When satisfactory shields have been evolved, exposures will be made in animals. Thermoluminescent dosimeters developed to date have been of the large bulb type. Our work deals solely with miniature dosimeters similar to those being used in Discoverer satellites. Our objective is the development of a second generation of implant dosimeters for radiation dosage verification (4) and inhomogeneity studies with radiation therapy equipment as well as with diagnostic x-rays in specific anatomic areas, while patients undergo various examinations. The thermoluminescent dosimeter is intended to complement, not to supplant, the radiophotoluminescent dosimeter.

Multiple implant dosimetry.

Low-atomic-number, silver-activated radiophotoluminescent glass-needle dosimeters were placed within a four-portal, 10-mil wall gold shield and implanted in a 38-pound dog. Over 150 needles were implanted, by a trocar technic (Fig. 1). Implants were made in three planes, so that most of the vital organs were pierced (Fig. 2). The shielded needles were placed in a PE-320 polyethylene tube. Spacing of 0.25 inch between needles was maintained by inserting plastic cylindrical spacers. An average of 50 needles located in at least three traverses, in the same plane, were exposed at a T.S.D. of 110 cm. to 260-kvp x-rays delivered at 30 ma, with 1 mm. Al and 0.5 mm. Cu filtration. A circular portal 7 cm. in diameter was used. At mid-exposure, the dog was turned over and the total exposure completed. The gold shield designed to achieve energy-independence (1, 2) is shown in the insert in Figure 1. The theory of this dosimeter and its response have been reported by the authors (3–7). Prior to exposure for dosimetri...