Thermoluminescence Dosimetry System Research Articles

Comparison of the performance of two thermoluminescent dosimetry systems for the personal dose-equivalent Hp(10) measurement.

The performance of two thermoluminescent dosimetry systems (RGD-3D and RE2000) manufactured in China and Finland was compared. Both of these dosimetry systems demonstrated satisfactory results as their performance met the requirements of the standard. The two dosimetry systems showed similar performance in the energy response. The RGD-3D dosimetry system performed better in nonlinear response, minimum detectable level and blind sample tests, whereas the RE2000 dosimetry system showed better stability.

Results and analysis of an intercomparisons study for individual monitoring services of Latin American and Caribbean regions.

The aim of this paper is to present the results obtained by the Latin-American and Caribbean personal dosimetry services that participated, with the support of IAEA, in the 2020-Eurados whole-body dosemeter intercomparison for photon radiation. All participant services in this study use thermoluminescent dosimetry (TLD) systems except one that uses optically stimulated luminescence (OSL) dosemeters. Data analysis shows that 93.4% of the results are within the acceptance range, according to International ISO Standard ISO 14146: 2018. The evaluation of the trumpet curves shows that only three laboratories presented a few dosemeters results outside the limits of acceptability. Participation in this Eurados intercomparison exercise gave the Latin American and Caribbean laboratories the opportunity to show compliance with their own quality management system, to compare results with other participants and to develop plans for improving their dosimetry systems. It also gave the assurance that occupational doses are being measured properly and following the international standards in the regions.

Type-testing of the TLD system used for the assessing the eye lens doses due to ionising radiation

Individual monitoring service at the Department for Radiation and Environmental Protection of Vinca Institute of Nuclear Sciences performs individual whole-body and extremities monitoring of exposed workers, using thermoluminescent dosimetry (TLD) method. The dosemeters for eye-lens personal dose equivalent measurements, Hp(3), are not regularly used at the workplaces in Serbia, even though the individual monitoring method is accredited and available at the dosimetry service. Type testing of Hp(3) dosemeters based on LiF: Mg,Ti, placed in modified ring holders was done following the changes in ISO 4037:2019 and IEC 62387:2020. The type testing was done by varying radiation-based influence quantities: photon energies ranging from 33.3 keV up to 1.25 MeV, angle of incidence values of 0°, 45°, 60°, 75°, dose range from 0.05 mSv to 10 Sv. The results show that the passive dosimetry monitoring system satisfies IEC 62387:2020 requirements in the mandatory range of influence quantities, except for the lowest tested energy of 33 keV, when incident radiation angle is ±60° and higher.

Characterization of Thermoluminescent Dosimetry Systems According to the IEC 62387:2020 Standard.

A need for detailed testing of individual monitoring systems used in accredited service at the Vinca Institute of Nuclear Sciences was recognized following changes in individual, workplace, and environmental monitoring passive dosimetry systems acceptability criteria stated in IEC 62387:2020 and changes related to reference fields used in radiation protection defined in ISO 4037:2019. Reliability and accuracy of dosimetry data acquired by passive dosimetry systems used for individual monitoring is assured by carrying out type tests. In this manner, the effects of different radiation influence quantities are examined. Passive dosimetry systems comprised of an LiF:Mg,Ti (TLD-100) detector card placed in two different holder models (8814 and 8850) and the Harshaw TLD Model 6600 Plus Automated Reader were tested. Type tests were done in an extended range of photon energies from 40 keV up to 1.25 MeV, angle of incidence values of ±45° and ± 60° for both vertical and horizontal dosimeter orientation, and in the dose range from 0.05 mSv to 1 Sv. Both dosimetry system configurations perform in line with IEC 62387:2020 within mandatory range for tested influence quantities. Dosimeters that use the 8850 holder type showed less pronounced energy and angular dependence of the response in the low-energy range.

Quality control measures of thermoluminescent dosimetry system used in environmental radiation monitoring

Objective To discuss the quality control measures of the thermoluminescent dosimetry system and to verify its propriety of when used in environmental radiation monitoring. Methods The quality control measures included the stability test, the dispersibility screening and the uncertainty evaluation of measurement results of the TLD reader and TLD detector, in addition, the environmental radiation accumulated dose monitoring results obtained by the high pressure ionization chamber were compared with those by the thermoluminescent dosimetry system. Results The variation range of TLD reader’s light source coefficient is within 0.070~0.073 during the preheating and measuring process, which meets the requirements of stability; The χ 2 value of the TLD detector is 2.088, which obeys the normal distribution; The thermoluminescent dosimetry system’s nonlinear response, coefficient of variation and energy response meet the measurement requirements; There is a deviation of −6.58% the largest between the cumulative dose obtained by TLD and the high pressure ionization chamber. Conclusion The quality control measures discussed in this paper can be used as a reference for similar thermoluminescent dosimetry system. Our system has passed all the tests and can meet the environmental radiation cumulative dose monitoring requirements. 摘要： 目的 探讨热释光测量系统的质量控制方法, 验证热释光测量系统能否准确有效的用于环境辐射水平监测。 方法 采取的环境辐射监测用热释光测量系统质量控制方法包括热释光测量系统的稳定性检验、热释光探测器的分 散性筛选、测量结果不确定度评定, 并与高气压电离室测量方法进行对比。 结果 读出器预热及测读过程中光源系数 变化范围在 0.070~0.073, 稳定性符合使用要求; 热释光探测器的 χ 2 值为 2.088, 服从正态分布;热释光测量系统满足 非线性响应、变异系数和能量响应的计量要求; 热释光累积剂量测量结果与高气压电离室相比偏差最大 −6.58%。 结论 本实验室采取的质控措施可作为同类热释光测量系统的质控措施的参考;本实验室的热释光测量系统通过了 各项检验, 满足环境辐射累积剂量监测的使用要求。

Natural dead sea salt and retrospective dosimetry.

Accidents resulting in widespread dispersal of radioactive materials have given rise to a need for materials that are convenient in allowing individual dose assessment. The present study examines natural Dead Sea salt adopted as a model thermoluminescence dosimetry system. Samples were prepared in two different forms, loose-raw and loose-ground, subsequently exposed to 60Co gamma-rays, delivering doses in the range 2-10Gy. Key thermoluminescence (TL) properties were examined, including glow curves, dose response, sensitivity, reproducibility and fading. Glow curves shapes were found to be independent of given dose, prominent TL peaks for the raw and ground samples appearing in the temperature ranges 361-385 ºC and 366-401 ºC, respectively. The deconvolution of glow curves has been undertaken using GlowFit, resulting in ten overlapping first-order kinetic glow peaks. For both sample forms, the integrated TL yield displays linearity of response with dose, the loose-raw salt showing some 2.5 × the sensitivity of the ground salt. The samples showed similar degrees of fading, with respective residual signals 28days post-irradiation of 66% and 62% for the ground and raw forms respectively; conversely, confronted by light-induced fading the respective signal losses were 62% and 80%. The effective atomic number of the Dead Sea salt of 16.3 is comparable to that of TLD-200 (Zeff 16.3), suitable as an environmental radiation monitor in accident situations but requiring careful calibration in the reconstruction of soft tissue dose (soft tissue Zeff 7.2). Sample luminescence studies were carried out via Raman and Photoluminescence spectroscopy as well as X-ray diffraction, ionizing radiation dependent variation in lattice structure being found to influence TL response.

Performance evolution of TLD-700H/600H dosimetry system at extended issue periods

Results of a comprehensive study of the TLD-700H/600H (Harshaw 8840/8841) dosimetry system performance for an extended issue period are presented and discussed. The results provide a technical justification to use the current dosimetry system issues periods up to almost 600 days, far beyond the current 95-day issue period used at the Naval Dosimetry Center (NDC). Extending (or reducing) the issue period has a statistically significant effect on the uncertainty of the dose equivalent values measured within the dosimetry system. In order to accommodate the use of various issue periods for the dosimetry system, the lower limit of detection (LLD) linear model is proposed. A possible limitation of this model (dose fading) is discussed. The factors responsible for both time independent and dependent LLD components are identified. The thermoluminescent residual signal and dosimetry system calibration are responsible for the time-independent LLD component; whereas the factors for time-dependent LLD component are dose fading, radiation background and its standard deviation. Simple formulae for photon and neutron LLDs at variable dosimeter issue periods are proposed. As a result of the experimental study conducted, multiple LLD components were numerically evaluated for the four-element TLD-700H/600H dosimetry system at different issue periods. Implementation of these formulae in the Dose Program may provide a more accurate LLD estimation for each reported dose equivalent at any technically justified dosimeter issue period.

Characterization of three solid state dosimetry systems for use in high energy photon dosimetry audits in radiotherapy

The IAEA Dosimetry Laboratory (DOL) aims to improve the accuracy of clinical dosimetry in hospitals world-wide by providing independent remote audits for high energy photon beams. A thermoluminescent dosimetry (TLD) system has been used by the DOL to provide audit services for over 47 years. Two additional systems: an optically stimulated luminescent dosimetry (OSLD) system and a radiophoto luminescent dosimetry (RPLD) system underwent a commissioning process. The systems’ parameters, reading methodology and the dosimetric characteristics were investigated and compared.The read-out procedure for each system was established and optimized. Dosimetric characteristics such as reproducibility, signal fading with time after irradiation, signal per dose dependence and energy response were investigated. Additional tests to check signal depletion per readout and individual sensitivities of dosimeters were performed for RPLDs and OSLDs and also reading position dependence for the RPLD system was checked.The reproducibility of 4 readings of one dosimeter is 0.48% for TLDs, 0.16% for OSLDs and 0.15% for RPLDs. The fading effect after 100 days was 4% for TLD, 2% for OSLD and 0.4% for RPLD. Energy response of TLDs and RPLDs is comparable, higher corrections were found for OSLDs. The RPLD dose-response is sub-linear whereas TLD and OSLD response is supra-linear at the dose range under study (1–4 Gy). The TLD reading procedure is destructive but OSLDs and RPLDs can be read repeatedly and the signal depletion per reading is 0.036% for OSLDs and 0.017% for RPLDs. The sensitivity correction factors for RPLDs and OSLDs were determined with the standard deviation in response of 1000 dosimeters of 2.2% for OSLD and 0.9% for RPLD. The combined standard uncertainties (k = 1) are 1.60% for TLDs, 1.46% for OSLDs and 1.51% for RPLDs.All three systems can be successfully used for auditing purposes if corrections for all described effects are applied.

Two-dimensional thermoluminescence dosimetry system for proton beam quality assurance

The response of a large-area two-dimensional (2D) thermoluminescence (TL) dosimetry system with 20 × 20 cm2 TL LiF:Mg,Cu,P foils, developed at the Institute of Nuclear Physics PAN was studied for doses of therapeutic proton beams with energies of 80 MeV, 150 MeV and 225 MeV. The one-hit detector model fitted to measured dose response yielded characteristic doses of 227 Gy, 209 Gy and 203 Gy respectively. The system was applied to investigate geometrical parameters of spots produced by proton pencil beams at the Bronowice Cyclotron Centre IFJ PAN. Mean spot sizes measured with TL foils were compared with mean spot sizes calculated for Gafchromic® films. It was shown that the 2D TL system was capable to measure the spot size up to peak doses of 20 Gy without additional correction for dose response. For measurements of the spot size using Gafchromic® EBT3 films an additional calibration must be applied to correct for the non-linear response for doses exceeding 1 Gy.

Characterising an aluminium oxide dosimetry system.

In vivo dosimetry is recommended as a defence-in-depth strategy in radiotherapy treatments and is currently employed by clinics around the world. The characteristics of a new optically stimulated luminescence dosimetry system were investigated for the purpose of replacing an aging thermoluminescence dosimetry system for in vivo dosimetry. The stability of the system was not sufficient to satisfy commissioning requirements and therefore it has not been released into clinical service at this time.

A Comparative study of radiation doses and treatment area dependence in thermoluminescence dosimetry systems and metal oxide semiconductor field effect transistors

Aim: This study aims at examining the differences between thermoluminescense dosimeters and metal oxide semiconductor field effect transistors in terms of radiation doses at different photon energies treatment area dependence in patients who recieved radiotherapy at the Department of Radiation Oncology, Inonu University. Material and Methods: Thermoluminescense dosimeter systems and metal oxide semiconductor field effect transistors were used at 6MV and 25MV in the range of 25-1000 cGy radiation doses to examine radiation dose dependence. Results were evaluated by taking measurements of treatment areas 5x5, 10x10, 15x15, 20x20, 25x25, 30x30, and 40x40 cm2, respectively, to specify treatment area dependence of these systems. Results: In both thermoluminescense dosimeters (TLD) and metal oxide semiconductor field effect transistors (MOSFET), reading values at 6 MV and 25 MV photon energies remained up to 800 cGy. We observed that both systems deviate from linearity at doses above 800 cGy. In TLDs, we recorded a %±1 (6 MV photon energy) and %+4 (25 MV photon energy) change in reading values. This change was %±1 (6 MV photon energy) and %+4 (25 MV photon energy) in MOSFETs. Conclusion: Both dosimeter systems have advantages and disadvantages in terms of accuracy and applicability. Being familiar with dosimeter systems is very important in identifying the accuracy of dose to be admisnistered.

Applications of TLDs in Radiation Dosimetry

An increasing amount of public interest in environmental monitoring programmes is being focused on the environmental impact of radiation arising from nuclear power operations and the corresponding detection of slight variations in the natural radiation background. The primary objective of individual monitoring for external radiation is to assess, and thus limit, radiation doses to individual workers. Supplementary objectives are to provide information about the trends of these doses and about the conditions in places of work and to give information in the event of accidental exposure. Depending on the kind of radiation hazard, the ICRP recommended maximum permissible dose (MPD) values. These are the maximum dose equivalent values, which are not expected to cause appreciable body injury to a person during his lifetime. Thermoluminescent Dosimetry (TLD) has been developed during 1960-70 for various applications in medicine and industry. TLD, the most advanced and most intensively studied integrating dosimeter system, has now reached the stage at which it may replace or supplement film dosimetry. TLD systems are widely applied to environmental monitoring programmes near nuclear installations. TLD systems with high reproducibility in the milli roentgen dose range are required in order to measure exposures equal to that resulting from an exposure rate of 10μR h-1 during field periods of from several days up to a year. A brief list of applications specific to radiation oncology is given here. In radiation oncology dosimetric accuracy demanded is of the order of 2-5%. TLDs offer a clear solution since their precision meets this criteria. Contents

Clinical tests of large area thermoluminescent detectors under radiotherapy beams

Abstract Two-dimensional (2D) thermoluminescence (TL) dosimetry systems based on LiF:Mg,Cu,P, together with the newly developed, based on CaSO4:Dy, were tested under radiotherapy beams. The detectors were irradiated in a water phantom with 6 MV X-ray beams from linac and read with a dedicated TLD reader. Dose distributions of differently shaped fields and of a full stereotactic plan were measured and compared with planned distributions. Maximum distance-to-agreement (DTA) in the penumbra region was 1 mm for both LiF:Mg,Cu,P and CaSO4:Dy TL sheets, for all the measured fields. Maximum percentage dose difference (DA%) between planned and measured dose value in low dose gradient regions was up to 11% for LiF:Mg,Cu,P TL sheets and 18% for CaSO4:Dy TL sheets. Concerning the full stereotactic plan, the percentage of points with γ-index below 1 is 54.9% for the LiF:Mg,Cu,P-based foil and 96.9% for the CaSO4:Dy TL sheets. Both 2D TL detector types can be considered to be a promising tool for bi-dimensional dose measurements in radiotherapy. Non-homogeneity, presumably due to the TL sheets manufacture, still affects dosimetric distribution and the agreement between planned and measured distributions may depend on the chosen sample.

The Response of 2D TL Foils After Doses of Co-60 Gamma-ray, 6 MV X-ray and 60 MeV Proton Beams Applied in Radiotherapy

A Two-dimensional Thermoluminescence Dosimetry (2D TLD) system has been developed at the Institute of Nuclear Physics (IFJ PAN) in Krakow, Poland. The system consists of TLD foils and of a TL reader equipped with a 200 200 mm 2 heater and a CCD camera. The foils contain LiF:Mg,Cu,P powder mixed with ETFE polymer pressed at high temperature. The CCD camera is able to read out 2D images of TL light in real time, and the re-usable foils are flexible, mechanically stable and waterresistant. We have determined the response of our 2D TL foils after doses of Co-60 gamma-ray, 6MV X-ray and 60MeV proton radiotherapy beams, over the range between 1 and 30Gy, as required in clinical dosimetry. In measurements, performed at the German Cancer Research Center (DKFZ), at the Heidelberg Ion-Beam Therapy Center (HIT) and at the IFJ PAN, we compared the dose response of our foils with those of Kodak R EDR2 and Gafchromic R EBT films. We find both the sensitivity (signal per dose) and the characteristic (saturation) dose of our 2D TL foils to be higher than those of the EDR2 and EBT films, for all beam modalities tested.

EURADOS self-sustained programme of intercomparisons for individual monitoring services

Within EURADOS working group 2, a system for self-sustained intercomparisons for individual monitoring services for external radiation was developed. With the intercomparison results, the participants can show compliance within their quality management system, compare their results with those from other participants and develop plans for improvement of their system. The costs of the exercises are covered by the participants fees. In this programme, the first intercomparison exercise for whole-body dosemeters has been executed in 2008 with 62 participating dosimetry systems from participants across Europe. In general, film systems show the largest deviations, although the results of some participants indicate that it is possible to achieve results with a film system with similar quality as for thermoluminescence dosimetry (TLD) systems. A second intercomparison has been organised for extremity dosemeters in 2009. For 2010 it is planned to organise a second intercomparison for whole-body dosemeters.

Energy response of different types of RADOS personal dosemeters with MTS-N (LiF:Mg,Ti) and MCP-N (LiF:Mg,Cu,P) TL detectors

The photon energy response of different RADOS (Mirion Technologies) personal dosemeters with MTS-N (LiF:Mg,Ti) and MCP-N (LiF:Mg,Cu,P) thermoluminescence (TL) detectors was investigated. Three types of badges were applied. The irradiation with reference photon radiation qualities N (the narrow spectrum series), and S-Cs and S-Co nuclide radiation qualities, specified in ISO 4037 [International Organization for Standardization (ISO). X and gamma reference radiations for calibrating dosemeters and doserate meters and for determining their response as a function of photon energy. ISO 4037. Part 1-4 (1999)], in the energy range of 16-1250 keV, were performed at the Dosimetry Laboratory Seibersdorf. The results demonstrated that a readout of a single MTS-N or MCP-N detector under the Al filter can be used to determine Hp(10) according to requirements of IEC 61066 [International Electrotechnical Commission (IEC). Thermoluminescence dosimetry systems for personal and environmental monitoring. International Standard IEC 61066 (2006)] for TL systems for personal dosimetry. The new RADOS badge with the experimental type of a holder (i.e. Cu/Al filters) is a very good tool for identifying the radiation quality (photon energy).

Application of dosimetry systems and cytogenetic status of the child population exposed to diagnostic X‐rays by use of the cytokinesis‐block micronucleus cytome assay

Low-dose ionizing radiation used for medical purposes is one of the definite risk factors for cancer development, and children exposed to ionizing radiation are at a relatively greater cancer risk as they have more rapidly dividing cells than adults and have longer life expectancy. Since cytokinesis-block micronucleus cytome (CBMN Cyt) assay has become one of the standard endpoints for radiation biological dosimetry, we used that assay in the present work for the assessment of different types of chromosomal damage in children exposed to diagnostic X-ray procedures. Twenty children all with pulmonary diseases between the ages of 4 and 14 years (11.30 ± 2.74) were evaluated. Absorbed dose measurements were conducted for posterior-anterior projection on the forehead, thyroid gland, gonads, chest and back. Doses were measured using thermoluminescence and radiophotoluminescent dosimetry systems. It was shown that, after diagnostic X-rays, the mean total number of CBMN Cyt assay parameters (micronucleus, nucleoplasmic bridges and nuclear buds) was significantly higher than prior to diagnostic procedure and that interindividual differences existed for each monitored child. For the nuclear division index counted prior and after examination, no significant differences were noted among mean group values. These data suggest that even low-dose diagnostic X-ray exposure may induce damaging effect in the somatic DNA of exposed children, indicating that immense care should be given in both minimizing and optimizing radiation exposure to diminish the radiation burden, especially in the youngest population.

Primary DNA Damage Assessed With the Comet Assay and Comparison to the Absorbed Dose of Diagnostic X-rays in Children

The aim of this work is to assess DNA damage in peripheral blood lymphocytes of children prior to and following airway X-ray examinations of the chest using the alkaline comet assay and to compare data with the measured absorbed dose. Twenty children with pulmonary diseases, between the ages of 5 and 14 years, are assessed. Absorbed dose measurements are conducted for posterior-anterior projection on the forehead, thyroid gland, gonads, chest, and back. Doses are measured using thermoluminescent and radiophotoluminescent dosimetry systems. Differences between tail lengths, tail intensity, and tail moments as well as for the long-tailed nuclei before and after exposures are statistically significant and are dependent on the individual. The results demonstrate the usefulness of the comet assay as a measure of X-ray damage to lymphocytes in a clinical setting. Doses measured with both dosimeters show satisfactory agreement (0.01 mSv) and are suitable for dosimetric measurements in X-ray diagnostics.

TLD dosimetry for microbeam radiation therapy at the European Synchrotron Radiation Facility

A two-dimensional (2-D) thermoluminescence (TL) dosimetry system consisting of LiF:Mg,Cu,P (MCP-N)-based TL foils and a TLD reader equipped with a CCD camera and the large size (72 mm in diameter) planchete heater, developed at the Institute of Nuclear Physics (IFJ PAN, was applied for 2-D dosimetry of X-ray microbeam radiation therapy (MRT) at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. Highly collimated X-ray microplanar beams, with average energy of 107 keV, beam width of 25, 50 and 75 μ m and the centre-to-centre (c-t-c) distances between the beams of 100, 200 and 400 μ m , were used to irradiate 10 × 10 × 0.3 mm 3 TLD foils. The entrance dose of 20 Gy was applied for all the microbeam exposures. The average doses determined with TLD foils differ from a few percent to about 30% from the nominal values. The peak-to-valley dose ratios (PVDRs) were calculated for different beam width settings and spacing between them. The PVDRs are, from 11% to 17%, smaller than predicted by Monte Carlo calculations. Despite this shortcoming is believed to result from the TL light scattering within the transparent TLD foil, the 2-D TLD system seems to be a promising tool for microbeam dosimetry.

Experience of type testing Harshaw advanced TLD system to new IEC-61066 standard

The recently released IEC 61066:2006 standard [IEC 61066:2006. International Standard, Thermoluminescence Dosimetry Systems for Personal and Environmental Monitoring] is a new guideline for type testing a TLD dosimetry system. A few main changes made in this standard include harmonizing the reference radiation and calibration with ISO standards, integrating the basic uncertainty analysis, and aligning IEC uncertainty requirements on dosimetry systems with those stated in ICRP Publication 75. We tested to this standard with an advanced Harshaw TLD system: Model 8800 Plus Reader and LiF:Mg,Cu,P dosemeter. This work describes the more than 10 tests in four major categories and provides the learning experience in uncertainty analysis.