Radiophotoluminescence Dosimetry Research Articles

Tissue-equivalent radiophotoluminescence dosimetry materials based on production of luminescent molecules via radiation chemical reactions

Radiophotoluminescence (RPL) has been a key phenomenon in dosimetry. Most materials exhibiting RPL are inorganic single crystals, glasses, and ceramics. Recently, similar phenomena (i.e., fluorescence after irradiation) have been realized in soft matters, such as liquids, gels, and organic solids, on the basis of the radiation-induced production of fluorescent molecules. Dosimeters showing such phenomena are attractive from the viewpoints of their tissue equivalence, flexibility, scalability, and workability. The objective of this paper is to present an overview of such dosimeters with emphasis on the radiation chemical reactions used in the materials. Moreover, the sensitivity and the measurable range is introduced.

Monte Carlo verification of the holder correction factors for the radiophotoluminescent glass dosimeter used by the IAEA in international dosimetry audits.

The International Atomic Energy Agency (IAEA), jointly with the World Health Organization (WHO), has operated a postal dosimetry audit program for radiotherapy centers worldwide since 1969. In 2017 the IAEA introduced a new methodology based on radiophotoluminescent dosimetry (RPLD) for these audits. The detection system consists of a phosphate glass dosimeter inserted in a plastic capsule that is kept in measuring position with a PMMA holder during irradiation. Correction factors for this holder were obtained using experimental methods. In this work these methods are described and the resulting factors are verified by means of Monte Carlo simulation with the general-purpose code PENELOPE for a range of photon beam qualities relevant in radiotherapy. The study relies on a detailed geometrical representation of the experimental setup. Various photon beams were obtained from faithful modeling of the corresponding linacs. Monte Carlo simulation transport parameters are selected to ensure subpercent accuracy. The simulated correction factors fall in the interval 1.005-1.008 (±0.2%), with deviations with respect to experimental values not larger than 0.2(2)%. This study corroborates the validity of the holder correction factors currently used for the IAEA audits.

CHARACTERISATION OF RADIOPHOTOLUMINESCENCE DOSIMETRY SYSTEM FOR INDIVIDUAL MONITORING.

Performance evaluation is typically assessed as part of the approval procedure to verify that a dosimetry system fulfils specified national or international type-test requirements under representative exposure conditions that are expected to mimic workplace fields from the radiological activities being monitored. The International Atomic Energy Agency Radiation Safety Technical Services Laboratory has recently implemented an integrated radiophotoluminescence (RPL) personal dosimetry system developed by Chiyoda Technol Corporation. This paper reports on the successful verification of dosimetric performance properties of the RPL dosimetry system to IEC 62387:2020, in which the badges were exposed to a range of radiation energies and angles of incidence as well as other influence parameters. Characteristics under test included the coefficient of variation, non-linearity of response due to dose dependence as well as the energy and angular response to photon and beta radiation.

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.

A comparison of dosimetric properties of three solid state dosimetry systems for dosimetry audit in radiotherapy

Published Article,The purpose of this study is to investigate and compare characteristics of three solid state dosimetry systems in order to determine working parameters and corrections needed for remote dosimetry audits of high energy photon and electron beams. The following systems were investigated: a thermo luminescent dosimetry (TLD) system (TLD-100, PCL3 reader), an optically stimulated luminescent dosimetry (OSLD) system (nanoDots, microStar reader) and a radiophoto luminescent dosimetry (RPLD) system (GD 302M, FGD-1000 reader).

The applicability of radiophotoluminescence dosemeter (RPLD) for measuring medical radiation (MR) doses

The applicability of radiophotoluminescence dosimetry was determined by assessing various radiophotoluminescence dosemeter (RPLD) properties for measuring medical radiation doses from radiation sources of a continuous spectrum. The RPLD was found to be accurate for measuring doses in diagnostics (50-125 keV) and radiation therapy (6, 10 and 18 MV photons, 6 and 15 MeV electrons). The RPLD shows excellent dose linearity (R(2) > 0.99), reproducibility and batch uniformity, and minimal fading and accurate accumulated dose measurement. The dosemeter material is independent of photon energy in the diagnostic range; however, the dosemeter requires additional calibration in the mammography energy range and also for accurate dose measurement with photon or electron energies in radiation therapy. RPLD measurements with a tin filter show considerable angular dependence at angles exceeding 50° between the photon beam and the normal to the long axis of the dosemeter. The RPLD measurement accuracy at high doses can be improved with optimised pre-heating schemes.

Solid state metathesis of CaSO 4:Eu 2 + phosphor

CaSO 4:Dy, is a well known phosphor for radiation dosimetry using thermoluminescence. CaSO 4:Eu 3+ and CaSO 4:Eu 2+ phosphors also find applications in radio-photoluminescence dosimetry and photoluminescent liquid crystal displays (PLLCD), respectively. Various syntheses of these phosphors are known. In this paper solid state metathesis of CaSO 4:Eu using domestic microwave oven is described for the first time. The synthesis is fast, the entire process being completed within few minutes. The phosphor is characterized using XRD and PL techniques.

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.

Deposition and characterization of titania–silica optical multilayers by asymmetric bipolar pulsed dc sputtering of oxide targets

Titania–silica (TiO2/SiO2) optical multilayer structures have been conventionally deposited by reactive sputtering of metallic targets. In order to overcome the problems of arcing, target poisoning and low deposition rates encountered there, the application of oxide targets was investigated in this work with asymmetric bipolar pulsed dc magnetron sputtering. In order to evaluate the usefulness of this deposition methodology, an electric field optimized Fabry Perot mirror for He–Cd laser (λ = 441.6 nm) spectroscopy was deposited and characterized. For comparison, this mirror was also deposited by the reactive electron beam (EB) evaporation technique. The mirrors developed by the two complementary techniques were investigated for their microstructural and optical reflection properties invoking atomic force microscopy, ellipsometry, grazing incidence reflectometry and spectrophotometry. From these measurements the layer geometry, optical constants, mass density, topography, surface and interface roughness and disorder parameters were evaluated. The microstructural properties and spectral functional characteristics of the pulsed dc sputtered multilayer mirror were found to be distinctively superior to the EB deposited mirror. The knowledge gathered during this study has been utilized to develop a 21-layer high-pass edge filter for radio photoluminescence dosimetry.

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.

Synthesis of [formula omitted], [formula omitted] and [formula omitted] phosphors

CaSO 4 : Dy is a well-known phosphor for radiation dosimetry using thermoluminescence. CaSO 4 : Eu , phosphors also find applications in radio-photoluminescence dosimetry and PLLCD. Various syntheses of these phosphors are described and optimum procedures are suggested. Effects of various preparation methods on luminescence characteristics are discussed in terms of elimination of unwanted impurities, grain size, etc.

Radiophotoluminescence dosimetry using a small spherical glass: a preliminary phantom study

A radiophotoluminescence dosimetry has been proposed using a spherical silver-activated phosphate glass with a diameter of 1.5 mm. A 6 MV photon dose of 2 Sv (2 Gy) was delivered to 14 spherical glass samples placed between two solid water phantoms at a depth of 10 cm. The samples were positioned within a 20 x 20 mm(2) centred at beam axis to ensure uniform dose absorption. A normalised output from a read-out system was obtained by simultaneously measuring luminescence from a non-irradiated reference and that from an irradiated reference to eliminate background contamination and time-varying fluctuation of the readout system, leading to a normalised standard deviation of 1.8%. A dose up to 3.5 Sv (3.5 Gy) was delivered to three spherical glass samples positioned between two solid water phantoms at a depth of 10 cm. The normalised output increased linearly with the applied dose.

Redox reactions, radio-photoluminescence and thermoluminescence in

phosphors find applications in dosimetry of ionizing radiations. Phosphors having Dy or Tm activators are high-sensitivity thermoluminescence dosimetry materials, while the phosphors with Eu or Sm activators are the proposed materials for radio-photoluminescence dosimetry. Mechanisms of several processes related to various luminescence phenomena, however, are not yet properly understood. Usually, all phosphors are prepared under identical conditions and comparative studies are carried out. It is shown here that the form in which the impurity is incorporated and the nature of defects produced is quite different in than in . The results presented throw light on the mechanism for thermoluminescence, radio-photoluminescence, incorporation of the impurity and conversion.

The Thermoluminescence of Toshiba FD-1 and FD-7 RPL Glass

The thermoluminescent response of Toshiba FD-1 and Toshiba FD-7 radiophotoluminescent dosimetry glass to 60Co ? radiation has been studied at doses of up to 66 kGy air kerma and 590 kGy air kerma respectively. The FD-1 glass was in the form of rods 1 mm in diameter by 6 mm long whereas the FD-7 glass was in the form of blocks of 4.6 mm square and 1.47 mm thick. The FD-1 rods had a pre-dose signal equivalent to 180 Gy and were useable up to the maximum dose studied although the response-dose curve was slightly supralinear at low doses. The FD-7 samples had a predose of 6.2 Gy and began to show severe saturation beyond about 1 kGy. The specific TL efficiencies (counts.mg.-1.Gy-1) of the two glass types have been compared with LiF and BeO and found to be some six orders of magnitude lower.

Photoluminescence Dosimetry: Progress and Present State of Art

Abstract The considerable progress in the readout technique for photoluminescent glass dosemeters is examined with emphasis on the application potential for individual monitoring. Radiophotoluminescence dosimetry (PLD) systems using a narrow pulsed UV laser excitation of flat glass detectors and an automatic readout are now commercially available and show improved dosimetric properties, in particular an internal pre-dose suppression, a dose range of 0.03 mSv to 10 Sv, a photon energy range extended down to 15 keV, a simultaneous indication of different dose quantities such as exposure Hx and directional dose equivalent H'(10) and the possibility of an estimation of radiation quality and incidence. Recent progress in PLD is reviewed with respect to the pulsed UV laser excitation, the improvement of the dosimetric properties by using an optimised flat glass dosemeter and the automatic readout which allows large scale evaluation and the application of different modes of evaluation, in particular vertical and horizontal scanning of the glass. The modern Toshiba readout systems FGD-10 and FGD-20 for glass dosemeters, prototype tested at KfK, are expected to be reliable dosimetry systems for large scale application in personnel and environmental monitoring, showing dosimetric properties which are comparable if not superior to those of TLD systems.

Photoluminescence Dosimetry: Progress and Present State of Art

The considerable progress in the readout technique for photoluminescent glass dosemeters is examined with emphasis on the application potential for individual monitoring. Radiophotoluminescence dosimetry (PLD) systems using a narrow pulsed UV laser excitation of flat glass detectors and an automatic readout are now commercially available and show improved dosimetric properties, in particular an internal pre-dose suppression, a dose range of 0.03 mSv to 10 Sv, a photon energy range extended down to 15 keV, a simultaneous indication of different dose quantities such as exposure Hx and directional dose equivalent H'(10) and the possibility of an estimation of radiation quality and incidence. Recent progress in PLD is reviewed with respect to the pulsed UV laser excitation, the improvement of the dosimetric properties by using an optimised flat glass dosemeter and the automatic readout which allows large scale evaluation and the application of different modes of evaluation, in particular vertical and horizontal scanning of the glass. The modern Toshiba readout systems FGD-10 and FGD-20 for glass dosemeters, prototype tested at KfK, are expected to be reliable dosimetry systems for large scale application in personnel and environmental monitoring, showing dosimetric properties which are comparable if not superior to those of TLD systems.

A New Method for the UV Excitation in Radiophotoluminescence Dosimetry

Abstract A new type 2 W miniature halogen tungsten incandescent lamp working in an 'over-power' single pulse mode with higher incandescent colour temperature for UV excitation is used in the reading of fluoroglass for radiophotoluminescence dosimetry. A reliable, portable and low cost field reader for the fluoroglass dosemeter with a low energy consumption has been designed employing this new method of UV excitation.