Optically Stimulated Luminescence Dosimetry Research Articles

Luminescence properties of SrB6O10:Ce,Gd phosphor for applications in OSL dosimetry and lighting

Strontium hexaborate (SrB6O10) doped with different metals and/or lanthanides has been studied widely as the thermoluminescence (TL) dosimeter. However, there is almost no dosimetry study concerning the utility of Optically Stimulated Luminescence (OSL) on SrB6O10. This preliminary study aims to examine the luminescence properties of SrB6O10 phosphor for their application in the areas of dosimetry and lighting technologies. Undoped and doped material to get an OSL dosimeter were synthesized by incorporating the dopants Ce3+, in the range of 0.1–0.7 % wt, and Gd3+, in the range of 0.1–1 % wt into the SrB6O10 structure using the solution combustion (SCS) method. The structural and morphological characterizations were performed using X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) methods, respectively. Two TL peaks of SrB6O10:Ce0.1%,Gd0.5% occurred at 70 °C and 182 °C after 1 Gy exposure to beta rays with a heating rate of 2 °C/s. The step annealing measurements were carried out to determine the traps responsible for the OSL signal. Various properties of the luminophore including dose-response and reusability were investigated using blue light stimulation. The phosphor showed a little variation of response up to 20 cycles within 2 % deviation (STD) from the first OSL readout. The OSL output within the range of 2–20 Gy was determined as linear. Radioluminescence (RL) measurement was investigated by emission in the range λem = 200–1000 nm. The parent compound displayed UV emission subdivided into UVA (315–400 nm), and UVB (280–315 nm) emissions at room temperature. The Chromaticity Coordinates (CIE) of SrB6O10:Ce0.1%,Gd0.5% were calculated as x = 0.2165, y = 0.1767. These remarkable characteristics show that, if developed, SrB6O10 could be used as an OSL dosimeter.

Luminescence properties of Ce and Be-doped CaAl12O19 for dosimetric and light-emitting applications

In this study, we reported the sol-gel production of cerium (Ce) and beryllium (Be)-doped calcium aluminate (CaAl12O19) and its luminescence properties for optically stimulated luminescence (OSL) dosimetry and light-emitting applications. Structural, morphological and elemental characteristics of the samples were examined by x-ray diffraction (XRD), Scanning electron microscope (SEM)/energy dispersive spectrum (EDS), x-ray fluorescence (XRF) and Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS) techniques. The maximum OSL intensity was achieved with 0.5 and 2% mol concentrations of Ce and Be dopants, respectively. We investigated the OSL and thermoluminescence (TL) properties of Ce and Be-doped CaAl12O19 by measuring energy storage for 24 h, dose-response in the range of 0.1 and 20 Gy, and reusability of the samples for 15 cycles. Photometric properties of the phosphors were investigated by evaluation of CIE chromaticity coordinate (x, y), CCT, and colour purity using its corresponding photoluminescence (PL) emission spectra. We also applied computerized glow curve deconvolution (CGCD), various heating rate methods, and the Tm-Tstop procedure to determine the trap localizations associated with the TL glow curve. The results of this study point out that CaAl12O19 crystals have the potential to be used as OSL dosimetry when appropriate dopants are used. This study may offer new possibilities in radiation dose detection and monitoring.

Dose-response dependencies of OSL dosimeters in conventional linacs and 1.5T MR-linacs: an experimental and Monte Carlo study

Objective. This work focuses on the optically stimulated luminescence dosimetry (OSLD) dose–response characterization, with emphasis on 1.5T MR-Linacs. Approach. Throughout this study, the nanoDots OSLDs (Landauer, USA) were considered. In groups of three, the mean OSLD response was measured in a conventional linac and an MR-Linac under various irradiation conditions to investigate (i) dose–response linearity with and without the 1.5T magnetic field, (ii) signal fading rate and its dependencies, (iii) beam quality, detector orientation and dose rate dependencies in a conventional linac, (iii) potential MR imaging related effects on OSLD response and (iv) detector orientation dependence in an MR-Linac. Monte Carlo calculations were performed to further quantify angular dependence after rotating the detector around its central axis parallel to the magnetic field, and determine the magnetic field correction factors, for all cardinal detector orientations. Main results. OSLD dose–response supralinearity in an MR-Linac setting was found to agree within uncertainties with the corresponding one in a conventional linac, for the axial detector orientation investigated. Signal fading rate does not depend on irradiation conditions for the range of 3–30 d considered. OSLD angular (orientation) dependence is more pronounced under the presence of a magnetic field. OSLDs irradiated with and without real-time T2w MR imaging enabled during irradiation yielded the same response within uncertainties. values were determined for all three cardinal orientations. Corrections needed reached up to 6.4%. However, if OSLDs are calibrated in the axial orientation and then irradiated in an MR-Linac placed again in the axial orientation (perpendicular to the magnetic field), then simulations suggest that can be considered unity within uncertainties, irrespective of the incident beam angle. Significance. This work contributes towards OSLD dose–response characterization and relevant correction factors availability. OSLDs are suitable for QA checks in MR-based beam gating applications and in vivo dosimetry in MR-Linacs.

Further characterization of BeO detectors for applications in external and medical dosimetry

Measuring absorbed doses with high precision and accuracy for clinical applications using Optically Stimulated Luminescence (OSL) dosimeters can help to optimize treatment to patients. Beryllium Oxide (BeO) is a nearly tissue-equivalent material that has the potential to increase the applicability of OSL dosimetry in medical dosimetry, but there has been limited research into its characterization. We present here the characterization of BeO dosimeters in terms of annealing temperature and duration, the effect of preheat treatment on short-term fading, energy and angular dependence, and discuss possible errors in laboratory conditions by using the OSL technique. Shorter readoutof 30 s when using stimulation power of ∼30 mW cm2 is feasible but preheating then becomes necessary. The fading behavior of BeO was found to be dose-dependent in this case. Reproduciblity of an OSL measurement with repositioning of the dosimeter in the reader and for the short reaout times was found to be ∼1%. Energy response was close to the theoretical values, which agrees with some but differs from other published studies, indicating that the OSL efficiency might vary. The angular dependence presented the greatest uncertainty factor. In summary, BeO dosimeters have the potential to be used in clinical applications for dose evaluation. However, care should be taken while handling and applying an optimized measurement procedure is necessary due to the complex luminescence mechanism of the material.

Addressing Current Challenges in OSL Dosimetry Using MgB4O7:Ce,Li: State of the Art, Limitations and Avenues of Research.

The objective of this work is to review and assess the potential of MgB4O7:Ce,Li to fill in the gaps where the need for a new material for optically stimulated luminescence (OSL) dosimetry has been identified. We offer a critical assessment of the operational properties of MgB4O7:Ce,Li for OSL dosimetry, as reviewed in the literature and complemented by measurements of thermoluminescence spectroscopy, sensitivity, thermal stability, lifetime of the luminescence emission, dose response at high doses (>1000 Gy), fading and bleachability. Overall, compared with Al2O3:C, for example, MgB4O7:Ce,Li shows a comparable OSL signal intensity following exposure to ionizing radiation, a higher saturation limit (ca 7000 Gy) and a shorter luminescence lifetime (31.5 ns). MgB4O7:Ce,Li is, however, not yet an optimum material for OSL dosimetry, as it exhibits anomalous fading and shallow traps. Further optimization is therefore needed, and possible avenues of investigation encompass gaining a better understanding of the roles of the synthesis route and dopants and of the nature of defects.

An overview study on the TL and OSL dosimetry patent processes over time

Since its discovery, ionizing radiation has been used in many different applications. Materials and methods have been developed to measure and quantify radiation doses. Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) are two techniques used for radiation dosimetry. Both TL and OSL are primarily applied in several areas, such as dating of ancient materials, equipment quality control and individual monitoring. One of the parameters to measure the knowledge and development of a technology is the number of patents related to the field. In this work, we established a methodology for patent search on the World Intellectual Property Organization (WIPO) database aiming to review the development of TL and OSL dosimetry over time. We concluded that along with the OSL technique development, the TL technique should continue to be explored in radiation dosimetry.

Optically Stimulated Luminescence in LiF–MgF2 system and its response as medical radiation dosimeter

Optically Stimulated Luminescence (OSL) based dosimeters are garnering attention in the field of radiation dosimetry due to a number of benefits like portable equipment, easy and efficient excitation and read out process, re-readability of the dose etc.. Though varieties of fluoroperovskites have been studied as OSL materials, no research on LiMgF3 (Lithium Magnesium Fluoride) as an OSL material has yet been conducted. In the current work, LiF–MgF2 system with a low effective atomic number was synthesized using the high temperature solid state reaction approach and its OSL dosimetry properties were investigated. The prepared sample was thoroughly characterized by employing a variety of techniques, such as X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and UV–Vis (ultraviolet–visible) spectrophotometry. The structure of the sample was found to be polycrystalline with size in the micrometre range. OSL properties of LMF have been investigated for different doses of gamma and beta along with related OSL kinetic parameters. It exhibits good dose linearity under blue stimulation for gamma (100 mGy - 700 Gy) and beta (30 mGy - 5Gy) radiation. We have also investigated the reusability (3%), reproducibility (2–3%), and fading (45% in 40 days) of the phosphor. To check the viability of the sample in radiation dosimetry under medical treatment in radiotherapy, various dosimetric properties were studied in Linear Accelerator (LINAC) x-rays in MV energy range and Cobalt-60 gamma radiation. These studies include the response of the phosphor to various energies (called energy dependence), field size effect, the effect of the dose rate of the radiation beam, and relative depth dose response. The overall response of the phosphor (comparable with ion chamber in RT experiments) makes the material a potential candidate to be used as an OSL phosphor in medical radiation dosimetry.

ASSESSMENT OF OCCUPATIONAL EXPOSURE TO EXTERNAL RADIATION AMONG WORKERS OF THREE COMMUNITY HOSPITALS IN SENEGAL.

Occupational radiation doses of 602 medical workers from the departments of Radiology, Thoracic and cardiovascular surgery, Operating room, Nuclear medicine, Radiotherapy and cardiology were evaluated during 2017 to 2021 in three hospitals in Senegal. Each hospital was subdivided into various occupational groups. Whole-body doses Hp(10), local skin doses Hp(0.07) and annual collective dose Hp(10) were measured by OSL (optically stimulated luminescence) dosimetry. The occupational groups with the highest radiation exposures, ~0.185mSv in 1y, were in the field of nuclear medicine, radiology, cardiology, Thoracic and cardiovascular surgery and Operating room. All results of the measured annual effective dose were below the ICRP (International Commission on Radiological Protection) dose limits of 20 mSv/y, averaged over any 5-y period.

Retrospective OSL Dosimetry With Common Pharmaceuticals and Food Supplements.

Several common pharmaceuticals such as ibuprofen, paracetamol, aspirin, oral contraceptives, drugs for the prevention of motion sickness and food supplements such as table vitamins and minerals have been studied for the purposes of retrospective dosimetry using optically stimulated luminescence (OSL). The essence is that the tablets with these drug substances contain additive crystalline materials which, after irradiation and stimulation, may exhibit luminescence. For most of the pharmaceuticals and food supplements, a radiation-induced dose-dependent OSL signal was detected. Subsequently, basic dosimetric characteristics of the materials were studied, specifically sensitivity changes during repeated OSL readings, dose response, zero-dose, minimum detectable dose (MDD) and fading. The most radiation sensitive materials were food supplements with Mg providing zero-dose and MDD values at the level of several mGy. For Mg supplements, considerable sensitivity changes in OSL signal were observed. Despite this, they could be corrected using a Single-Aliquot Regenerative-dose (SAR) protocol. The OSL signals of the other materials were relatively weak but they were well reproducible and exhibited linear dose response. The MDD values were variable among the materials and ranged from 0.1 to several Gy. However, for some of the pharmaceuticals, a very high and variable zero-dose of more than 3 Gy was observed that would rule out the possibility of dose reconstruction for triage purposes. The OSL signal exhibited a significant fading rate for most of the materials. The measurements for dose reconstruction should be performed as soon as possible after irradiation, i.e. within a maximum of a few days.

The role of heat treatment in improving photoluminescence and optically stimulated luminescence of HfO2

HfO2 is a metal oxide from the IV-B family whose properties have been widely applied in electronics and which displays an important blue emission. Despite this fact, few studies have been dedicated to understanding the role of heat treatment on its luminescence properties. Therefore, this study aimed to investigate the Photoluminescence (PL) and Optically Stimulated Luminescence (OSL) of HfO2 powder synthesized by the precipitation method and the influence of calcination on its luminescence. PL spectra results showed a broad emission band at about 2.6 eV, which was related to absorption at 4.1 eV. Green and blue stimulated luminescence spectra depicted emission bands in a similar region, varying between 2.44 up to 2.71 eV. The increase in the heat treatment temperature promoted signal enhancement, which could be associated with higher oxygen vacancy concentrations. OSL dose-response curves for the sample calcined at 1600 °C are linear up to 0.6 Gy and a good signal reproducibility is observed, which makes the material suitable for OSL dosimetry.

Luminescence characteristics of newly-developed MgB4O7:Ce3+,Na+ phosphor as an OSL dosimeter

In this study, dosimetric properties of Ce3+ and Na+ doped magnesium tetraborate (MgB4O7) phosphors synthesized by the solution combustion synthesis (SCS) method were investigated using optically stimulated luminescence (OSL) technique to develop OSL radiation dosimetry. The concentrations of Ce3+0.3%wt and Na+1–14%wt dopants in MgB4O7 were incorporated into it to improve the efficiency of luminescence. The results showed that the effect of Na+ substitution on MgB4O7:Ce3+0.3%wt lattice induced a remarkable improvement of both its thermoluminescence (TL) and OSL signals. The highest OSL signal of the synthesized phosphor was recorded at the MgB4O7:Ce3+0.3%wt,Na+14%wt phosphor. Its TL glow curve consists of two peaks located at ~70 °C and ~230 °C with a heating rate of 2 °C/s. These TL peaks were found to be optically sensitive to blue light excitation (λ = ~470 nm). X-ray diffraction (XRD), scanning electron microscopy (SEM), radioluminescence (RL) techniques have been employed to characterize the synthesized phosphor. The XRD pattern of MgB4O7:Ce3+0.3%wt,Na+14%wt phosphor with orthorhombic phase was observed in the specimen sintered at 900 °C. The RL spectrum of the MgB4O7:Ce3+0.3%wt,Na+14%wt phosphor revealed a strong and a weak emission peak located UV and red regions, respectively. OSL dosimetric properties of the phosphor were studied under beta radiation of 90Sr/90Y. The phosphor exhibited good linearity between 1 and 100 Gy. Minimum detectable dose (MDD) of the phosphor was calculated as 0.73 mGy. A good reusability property was determined up to 20 experimental cycles with a deviation of 4.5%. Short-time fading up to 24 h and long-time fading up to 4 weeks were studied. The results shows the MgB4O7:Ce3+0.3%wt,Na+14%wt phosphor can be proposed as a potential OSL dosimetry for radiation dose measurements in medicine using OSL technique.

DEVELOPMENTS IN THE USE OF THERMOLUMINESCENCE AND OPTICALLY STIMULATED LUMINESCENCE FROM MOBILE PHONES IN EMERGENCY DOSIMETRY.

Proposed physical dosimetry methods for emergency dosimetry in radiological, mass-casualty incidents include both thermoluminescence (TL) and optically stimulated luminescence (OSL). Potential materials that could feasibly be used for TL and OSL dosimetry include clothing, shoes and personal accessories. However, the most popular target of study has been personal electronics, especially different components from smartphones. Smartphones have been a focus because they are widely available and, in principle, may be viewed as surrogates for commercial TL or OSL dosimeters. The components of smartphones that have been studied include surface mount devices (such as resistors, capacitors and inductors) and glass materials, including front protective glass, display glass and (with more modern devices) back protective glass. This paper reviews the most recent developments in the use of TL and OSL with these materials and guides the way to future, and urgently needed, research.

Development of Ce3+ and Li+ co-doped magnesium borate glass ceramics for optically stimulated luminescence dosimetry

Magnesium tetraborate, MgB4O7, is an attractive host material for dosimetry due to the two characteristics: its low effective atomic number (Zeff = 8.4) and high neutron capture cross-section of the 10B isotope. Particularly, Ce3+ and Li+ ions co-doped MgB4O7 has shown optically stimulated luminescence (OSL) signal comparable to that of Al2O3:C, which is a well-known OSL dosimetry material. In this work, for further improvement of the dosimetric properties, a new synthesis route for MgB4O7:Ce3+-Li+ is described: glass-ceramic (GC) MgB4O7:Ce3+-Li+ samples were prepared by heat treatment of the magnesium borate glass with the composition, 25MgO–72B2O3–3Li2O-0.3Ce3+. The prepared GC samples show UV-blue radioluminescence assigned to the Ce3+ 5d → 4f transition under X-ray irradiation and two thermoluminescence (TL) glow peaks related to the shallow and deep electron traps. Although fading of the TL and OSL signal was observed due to electron release from the shallow traps, the electrons captured by deep traps were stable at room temperature. Particularly, GC samples annealed at 750 °C and 800 °C, named GC750 and GC800, showed stable OSL up to 10 h following β-ray irradiation, after an initial fading mainly due to the presence of shallow traps in the material. From the viewpoint of this fading ratio, GC750 and GC800 showed potential as a practical OSL dosimeter.

Verification using in vivo optically stimulated luminescent dosimetry of the predicted skin surface dose in patients receiving postmastectomy radiotherapy

The purpose of this study was to evaluate whether dose to the skin surface underneath bolus, was accurately predicted by a 3D treatment planning system (TPS) in patients receiving 50 Gy/25# postmastectomy radiotherapy (PMRT) using optically stimulated luminescent dosimetry (OSLD) for verification. In vivo dosimetry using OSLDs was performed in 20 consecutive patients receiving PMRT. An array of 9 OSLDs were applied to the chest wall or neobreast in a grid arrangement. Dosimetry data were recorded on 3 separate treatment fractions, averaged, and extrapolated to 25 fractions. On the 3D TPS, the predicted dose was calculated using the departmental planning algorithm at points corresponding to the OSLDs. The mean within patient difference between the planned and measured dose at each of the 9 points was calculated and Bland-Altman limits of agreement used to quantify the extent of agreement. Paired t-tests were used to test for evidence of systematic bias at each point. The coefficient of variation of the 3 OSLD readings per patient at each of the 9 points was low for 8 points (≤4.4%) demonstrating comparable dose received per fraction at these points. The mean ratio between the in vivo measured extrapolated OSLD (IVME OSLD) dose and the planned TPS dose ranged between 0.97 and 0.99 across all points (standard deviation range 0.05 to 0.08). The mean within patient difference between the IVME OSLD and planned TPS was <1 Gy at 7 of the 9 points and the t-test for evidence of systematic bias was significant (p = 0.03) at only 1 of the 9 points. Our commercially available 3D TPS closely predicted PMRT skin surface dose underneath bolus as verified by OSLDs. At all sites, the average ratio of delivered to predicted dose was >0.97 but <1. This practical and feasible OSLD assessment of only 3 of 25 fractions facilitates quality assurance of a TPS in predicting skin surface dose under bolus.

Dose to Lungs and Kidneys during Total Body Irradiation: Are We Delivering the Expected Dose?

Total Body irradiation (TBI)-based conditioning is key component for hemopoietic stem cell transplantation. TBI dose calculation is traditionally based on point-dose calculations based on estimates of body separation at different levels with the umbilicus as a reference point, an approach followed as standard protocol at most institutions. This homogenous dose calculation technique does not take into account tissue heterogeneity. Limited data exists for TPS-based TBI planning systems especially in the setting of lung and kidney partial transmission blocks, which is a void in our understanding of TBI dose delivery and is explored in this study. Primary objective of the study was to assess differences between radiation treatment planning software (TPS) estimated doses with heterogeneity correction and point calculation estimated doses when delivering TBI. Secondary objective was to validate accurate treatment delivery through optically stimulated luminescent dosimetry (OSLD) measurements at umbilicus obtained at first TBI fraction. Our retrospective study involved virtual dosimetric simulation of total body CT scan datasets in patients treated with a prescribed dose of 12 Gy in six fractions delivered twice daily over three days. Patients received TBI using a translating couch AP/PA technique with lung and kidney shielding (transmission blocks to achieve < 7 Gy point dose). The Varian Eclipse TPS was used to calculate the 3D dose distribution to the lungs, kidneys, and heart. Paired t-test with a significance value of 0.05 was used to compare means. 24 patients (Male-11, female-13; Age range: 23-60 years; Diagnosis: AML-7, ALL-8, HL-1, NHL-6, MDS-2) with total body CT scan datasets available were included in the analysis. Contrary to expected dose with shielding (< 7 Gy), the TPS simulated mean dose to lungs was 11.08 Gy (SD: 0.61, p= 9.66E-22) and to kidneys was 8.98 Gy (SD: 0.62, p: 2.31E-14). TPS mean dose to the unshielded heart was 11.38 Gy. Compared to the point dose calculation of 2 Gy at the midpoint of the umbilicus, the mean OSLD dose measured during the first fraction of treatment was 2.08 Gy (SD: 0.058, p: 2.07E-9). Using TPS of total body CT scan data, we demonstrated much higher than expected dose to lungs and kidneys than expected from point-based calculations. This study has triggered a comprehensive outcomes analysis of institutional data for assessing toxicities in patients receiving TBI 12 Gy-based conditioning prior to SCT with the goal to revisit the 7-Gy dose limit to the lungs and kidneys. Institutions are encouraged to pursue similar analyses of their TBI systems to refine dose to critical organs. (Supported by the Radiation Oncology Summer Research Fellowship and the Office of Student Research at the University of Maryland School of Medicine).

OSL dosimetry with protective glasses of modern smartphones: A fiber-optic, non-destructive approach

A non-destructive, optically stimulated luminescence (OSL) technique was tested on samples of back protective glasses from modern smartphones for possible application in post-exposure radiation triage following a radiological accident. Excitation light from a green-wavelength laser was directed to the samples using an optical fiber; the same optical fiber was used to direct the emission light from the sample to a photomultiplier tube. Excitation and emission beams were separated using a combination of a dichroic mirror, optical filters, and time resolution. It was found that all tested samples fell into two different categories. Category 1 included Gorilla Glass 3 (GG3) and Gorilla Glass 4 (GG4) samples, while Category 2 included samples from Gorilla Glass 5 (GG5) glass. The radiation sensitivity of samples from Category 1 was about one order of magnitude higher than that of Category 2 glass. Minimum detectable doses determined for the pulse OSL mode were about 1 Gy and 10 Gy for Categories 1 and 2, respectively, for samples measured immediately after irradiation. Fading of the OSL signal measured in the CW-OSL mode was ~75% and ~84% one day after irradiation and ~82% and ~88% over one week for Categories 1 and 2, respectively. It was concluded that the back glasses demonstrate a feasible line of future research for potential use as emergency OSL dosimeters, provided they were covered by an opaque cover both during and after an emergency exposure and are then analyzed within a few days following the incident.

A calcination study on BeO ceramics for radiation dosimetry

The aim of this study was to investigate the effect of calcination conditions on luminescence properties of BeO ceramics synthesized using co-precipitation and sol–gel methods. Structural and morphological characterizations were performed with X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM) analyses. The role of calcination temperature and duration on micrograins' phase formation, morphology, grain-growth behavior, and luminescence characteristics were examined. Radioluminescence (RL), Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) techniques were used to characterize the luminescence signals. In the RL spectra of BeO ceramics synthesized with two methods, the characteristic emission peak between 200 and 500 nm, along with a wide emission peak between 700 and 800 nm due to anion defects were observed. To achieve a promising BeO dosimeter with highly sensitive TL and OSL signals for OSL dosimetry, the appropriate calcination conditions were determined for the co-precipitation and sol–gel methods as 900 and 1000 °C for 4 h, respectively.

Commissioning of a new commercial Optically Stimulated Luminescence (OSL) dosimetry system for VMAT treatments verifications

A new commercial OSL dosimetry system was studied to analyze the possibility of its use for VMAT planning checks with end-to-end approach. The system was characterized and tested in conventional dose range (0,25–3 Gy). NanoDots (Landauer®), with new readout system MicroSTARii™, were characterized in terms of: signal decrease for repeated readings; angular, energy and dose-rate dependence. A calibration curve was obtained using 6 MV photon beam. Two VMAT plans, regarding lung lesions, were designed and optimized with: 6 MV, 600 MU/min, Eclipse TPS and Acuros XB algorithm for TrueBeam 2.5. Verification plans were created and performed both in RW3 and in anthropomorphic phantom, using end-to-end approach. The measurements in RW3 were compared to ion chamber measurement values. In anthropomorphic phantom, the OSLDs were allocated in apposite inserts, with different densities. NanoDots with new readout system MicroSTARii™ exhibited to be suitable for VMAT verifications with end-to-end approach in conventional fractionated treatments.

Impact of transverse magnetic fields on dose response of a nanoDot OSLD in megavoltage photon beams

PurposeWe investigated the impact of transverse magnetic fields on the dose response of a nanoDot optically stimulated luminescence dosimetry (OSLD) in megavoltage photon beams. MethodsThe nanoDot OSLD response was calculated via Monte Carlo (MC) simulations. The responses RQ and RQ,B without and with the transverse magnetic fields of 0.35–3 T were analyzed as a function of depth at a 10 cm × 10 cm field for 4–18 MV photons in a solid water phantom. All responses were determined based on comparisons with the response under the reference conditions (depth of 10 cm and a 10 cm × 10 cm field) for 6 MV without the magnetic field. In addition, the influence of air-gaps on the nanoDot response in the magnetic field was estimated according to Burlin’s general cavity theory. ResultsThe RQ as a function of depth for 4–18 MV ranged from 1.013 to 0.993, excepting the buildup region. The RQ,B increased from 2.8% to 1.5% at 1.5 T and decreased from 3.0% to 1.1% at 3 T in comparison with RQ as the photon energy increased. The depth dependence of RQ,B was less than 1%, excepting the buildup region. The top air-gap and the bottom air- gap were responsible for the response reduction and the response increase, respectively. ConclusionsThe response RQ,B varied depending on the magnetic field intensity, and the variation of RQ,B reduced as the photon beam energy increased. The air-gaps affected the dose deposition in the magnetic fields.

The Role of the Cu on OSL Emission in Gamma-LiAlO2:Cu Crystal

A large optically stimulated luminescence (OSL) response has been found from copper doped lithium aluminate (LiAlO2, LAO) which can be applicable in OSL dosimetry. After an irradiation at room temperature with x-rays, an optical absorption band peaking at 277 nm and a luminescence band near 354 nm appear which are assigned to Cu+ ions which occupy the Li+ sites. Based on the experimental study, we construct two models to study the optical spectra of Cu+ occupying the Li+ ion. One is an isolated defect in which Cu+ ions occupy the Li+ ions and present isolated CuLi. The other one is a CuLi bond with a neighboring lithium vacancy (CuLi-VLi). In this work, all calculations are based on density functionals theory (DFT). Advanced hybrid functionals is adopted to relieve the problem of DFT underestimating the band gap. We obtain the optical spectra containing electron‒phonon coupling, and the results are in good agreement with the experimental results. Furthermore, the optical properties of CuLi-VLi are investigated. We find the absorption and luminescence peak are located at 273 nm and 353 nm, which are assigned to the isolated CuLi, and the absorption band near 379 nm is assigned to the CuLi-VLi. To compare the relative stability of the two defects, we present the defect formation energies as a function of Fermi energy under Li-rich and Li-poor conditions, to demonstrate the isolated CuLi is more stable than CuLi-VLi for the Fermi level in the entire range of band gap under Li-rich condition.