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- 2015
- Calibration process of OSL detectors
- Iodine-131
- OSL-BeO
- Dosimetry of staff and patients
- Optically Stimulated Luminescence (OSL)
- Akdeniz University
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A Radio-Fluorogenic Polymer-Gel Makes Fixed Fluorescent Images of Complex Radiation Fields
摘要： We review the development and application of an organic polymer-gel capable of producing fixed, three-dimensional fluorescent images of complex radiation fields. The gel consists for more than 99% of γ-ray-polymerized (~15% conversion) tertiary-butyl acrylate (TBA) containing ~100 ppm of a fluorogenic compound, e.g., maleimido-pyrene (MPy). The radio-fluorogenic effect depends on copolymerization of the MPy into growing chains of TBA on radiation-induced polymerization. This converts the maleimido residue, which quenches the pyrene fluorescence, into a succinimido moiety (SPy), which does not. The intensity of the fluorescence is proportional to the yield of free-radicals formed and hence to the local dose deposited. Because the SPy moieties are built into the polymer network, the image is fixed. The method of preparing the gel and imaging the radiation-induced fluorescence are presented and discussed. The effect is illustrated with fluorescent images of the energy deposited in the gel by beams of X-rays, electrons, and protons as well as a radioactive isotope.
关键词： polymer gel dosimetry,radio-fluorogenic co-polymerization,radio-fluorogenic gel,3D dose imaging,proton beam imaging,tertiary-butyl acrylate gel
更新于2025-09-23 15:23:52
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Initial evaluation of <scp>PET</scp> / <scp>CT</scp> with <sup>18</sup> F‐ <scp>FSU</scp> ‐880 targeting prostate‐specific membrane antigen in prostate cancer patients
摘要： This first-in-man study was carried out to evaluate the safety, whole-body distribution, dose estimation, and lesion accumulation of 18F-FSU-880, a newly developed probe targeting prostate-specific membrane antigen. Six prostate cancer patients with known metastatic lesions underwent serial whole-body PET/computed tomography (CT) with 18F-FSU-880. Blood and urine were analyzed before and after PET/CT. Accumulation of 18F-FSU-880 in organs and metastatic lesions in serial PET images were evaluated by measuring the standardized uptake values. From the biodistribution data, the organ doses and whole-body effective dose were calculated using OLINDA/EXM software. 18F-FSU-880 PET/CT could be carried out without significant adverse effects. High physiological uptake was observed in the salivary/lachrymal glands and kidneys. The effective dose was calculated to be 0.921 × 10?2 mSv/MBq. Known metastatic lesions were clearly visualized with high image contrast that increased with time, except in 1 patient, whose bone metastases were well-controlled and inactive. The PET/CT with 18F-FSU-880 could be carried out safely and could clearly visualize active metastatic lesions. The present results warrant further clinical studies with a larger number of cases to verify the clinical utility of 18F-FSU-880 PET/CT in the management of prostate cancer patients.
关键词： dosimetry,prostate cancer,prostate-specific membrane antigen,positron emission tomography/computed tomography,fluorine-18
更新于2025-09-23 15:23:52
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Seasonal Minimum and Maximum Solar Ultraviolet Exposure Measurements of Classroom Teachers residing in Tropical North Queensland, Australia
摘要： The risk of keratinocyte skin cancer, malignant melanoma and ultraviolet radiation (UVR)-induced eye disease is disproportionately higher in Australia and New Zealand compared to equivalent northern hemisphere latitudes. While many teachers are aware of the importance of reinforcing sun-safety messages to students, many may not be aware of the considerable personal exposure risk while performing outdoor duties in locations experiencing high to extreme ambient-UVR year-round. Personal erythemally-effective exposure of classroom teachers in tropical Townsville (19.3o S) was measured to establish seasonal extremes in exposure behavior. Mean daily personal exposure was higher in winter (91.2 J m-2, 0.91 Standard Erythema Dose (SED)) than summer (63.3 J m-2, 0.63 SED). The range of exposures represent personal exposures that approximate current national guidelines for Australian workers at the study latitude of approximately 1.2 SED (30 J m-2 effective to the International Commission on Non-Ionizing Radiation Protection). Similar proportions of teachers spent more than 1 hour outdoors per day in winter (28.6%) and summer (23.6%) as part of their teaching duties with seasonal differences having little effect on the time of exposure. Personal exposures for teachers peaked during both seasons near school meal-break times at 11:00 am and 1:00 pm respectively.
关键词： Teachers,Occupation,Ultraviolet,Dosimetry,Skin cancer
更新于2025-09-23 15:22:29
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Air-kerma strength determination of a new directional <sup>103</sup> Pd source
摘要： Purpose: A new directional 103Pd planar source array called a CivaSheet? has been developed by CivaTech Oncology, Inc., for potential use in low-dose-rate (LDR) brachytherapy treatments. The array consists of multiple individual polymer capsules called CivaDots, containing 103Pd and a gold shield that attenuates the radiation on one side, thus defining a hot and cold side. This novel source requires new methods to establish a source strength metric. The presence of gold material in such close proximity to the active 103Pd region causes the source spectrum to be significantly different than the energy spectra of seeds normally used in LDR brachytherapy treatments. In this investigation, the authors perform air-kerma strength (SK) measurements, develop new correction factors for these measurements based on an experimentally verified energy spectrum, and test the robustness of transferring SK to a well-type ionization chamber. Methods: SK measurements were performed with the variable-aperture free-air chamber (VAFAC) at the University of Wisconsin Medical Radiation Research Center. Subsequent measurements were then performed in a well-type ionization chamber. To realize the quantity SK from a directional source with gold material present, new methods and correction factors were considered. Updated correction factors were calculated using the MCNP6 Monte Carlo code in order to determine SK with the presence of gold fluorescent energy lines. In addition to SK measurements, a low-energy high-purity germanium (HPGe) detector was used to experimentally verify the calculated spectrum, a sodium iodide (NaI) scintillating counter was used to verify the azimuthal and polar anisotropy, and a well-type ionization chamber was used to test the feasibility of disseminating SK values for a directional source within a cylindrically symmetric measurement volume. Results: The UW VAFAC was successfully used to measure the SK of four CivaDots with reproducibilities within 0.3%. Monte Carlo methods were used to calculate the UW VAFAC correction factors and the calculated spectrum emitted from a CivaDot was experimentally verified with HPGe detector measurements. The well-type ionization chamber showed minimal variation in response (<1.5%) as a function of source positioning angle, indicating that an American Association of Physicists in Medicine (AAPM) Accredited Dosimetry Calibration Laboratory calibrated well chamber would be a suitable device to transfer an SK-based calibration to a clinical user. SK per well-chamber ionization current ratios were consistent among the four dots measured. Additionally, the measurements and predictions of anisotropy show uniform emission within the solid angle of the VAFAC, which demonstrates the robustness of the SK measurement approach. Conclusions: This characterization of a new 103Pd directional brachytherapy source helps to establish calibration methods that could ultimately be used in the well-established AAPM Task Group 43 formalism. Monte Carlo methods accurately predict the changes in the energy spectrum caused by the fluorescent x-rays produced in the gold shield.
关键词： TG43,directional sources,dosimetry,air-kerma strength,brachytherapy
更新于2025-09-23 15:22:29
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Development and evaluation of polycrystalline cadmium telluride dosimeters for accurate quality assurance in radiation therapy
摘要： For quality assurance in radiation therapy, several types of dosimeters are used such as ionization chambers, radiographic films, thermo-luminescent dosimeter (TLD), and semiconductor dosimeters. Among them, semiconductor dosimeters are particularly useful for in vivo dosimeters or high dose gradient area such as the penumbra region because they are more sensitive and smaller in size compared to typical dosimeters. In this study, we developed and evaluated Cadmium Telluride (CdTe) dosimeters, one of the most promising semiconductor dosimeters due to their high quantum efficiency and charge collection efficiency. Such CdTe dosimeters include single crystal form and polycrystalline form depending upon the fabrication process. Both types of CdTe dosimeters are commercially available, but only the polycrystalline form is suitable for radiation dosimeters, since it is less affected by volumetric effect and energy dependence. To develop and evaluate polycrystalline CdTe dosimeters, polycrystalline CdTe films were prepared by thermal evaporation. After that, CdTeO3 layer, thin oxide layer, was deposited on top of the CdTe film by RF sputtering to improve charge carrier transport properties and to reduce leakage current. Also, the CdTeO3 layer which acts as a passivation layer help the dosimeter to reduce their sensitivity changes with repeated use due to radiation damage. Finally, the top and bottom electrodes, In/Ti and Pt, were used to have Schottky contact. Subsequently, the electrical properties under high energy photon beams from linear accelerator (LINAC), such as response coincidence, dose linearity, dose rate dependence, reproducibility, and percentage depth dose, were measured to evaluate polycrystalline CdTe dosimeters. In addition, we compared the experimental data of the dosimeter fabricated in this study with those of the silicon diode dosimeter and Thimble ionization chamber which widely used in routine dosimetry system and dose measurements for radiation therapy.
关键词： X-ray detectors,Dosimetry concepts and apparatus,Solid state detectors,Materials for solid-state detectors
更新于2025-09-23 15:22:29
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An evaluation of computed tomography dose index measurements using a pencil ionization chamber and small detectors
摘要： The aim of this study was to compare the values of the computed tomography dose index 100 (CTDI100) obtained using two small detectors (i.e. a small ionization chamber and a small solid state detector) with those obtained from a 100-mm pencil ionization chamber for various input CT parameters: beam width, kVp, mAs, pitch, and head-body phantom variation. The measurement of CTDI100 using the 100-mm pencil chamber was carried out in a single rotation of axial mode, while the measurement using small detectors was carried out in helical mode. The differences of CTDI100 values obtained with two small detectors were about 7% for all variations. The differences of CTDI100 values obtained with small detectors and a 100-mm pencil ionization chamber for beam widths of more than 4 mm were within 40%. However, for the narrowest beam widths (4 mm), the difference between them was very large (about 150%).
关键词： computed tomography dose index (CTDI),CT dose profiler,small solid state detector,CT dosimetry,small detector,small ionization chamber
更新于2025-09-23 15:21:21
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A Monte Carlo based dosimetric characterization of Esteya <sup>?</sup> , an electronic surface brachytherapy unit
摘要： The purpose of this work is threefold: First, to obtain the phase-space of an electronic brachytherapy (eBT) system designed for surface skin treatments. Second, to explore the use of some efficiency enhancing (EFEN) strategies in the determination of the phase-space. Third, to use the phase-space previously obtained to perform a dosimetric characterization of the Esteya eBT system. Methods: The Monte Carlo study of the 69.5 kVp x-ray beam of the Esteya? unit (Elekta Brachytherapy, Veenendaal, The Netherlands) was performed with PENELOPE2014. The EFEN strategies included the use of variance reduction techniques and mixed Class II simulations, where transport parameters were fine-tuned. Four source models were studied varying the most relevant parameters characterizing the electron beam impinging the target: the energy spectrum (mono-energetic or Gaussian shaped), and the electron distribution over the focal spot (uniform or Gaussian shaped). Phase-spaces obtained were analyzed to detect differences in the calculated data due to the EFEN strategy or the source configuration. Depth dose curves and absorbed dose profiles were obtained for each source model and compared to experimental data previously published. Results: In our EFEN strategy, the interaction forcing variance reduction (VRIF) technique increases efficiency by a factor ~ 20. Tailoring the transport parameters values (C1 and C2) does not increase the efficiency in a significant way. Applying a universal cutoff energy EABS of 10 keV saves 84% of CPU time whilst showing negligible impact on the calculated results. Disabling the electron transport by imposing an electron energy cutoff of 70 keV (except for the target) saves an extra 8% (losing in the process 1.2% of the photons). The Gaussian energy source (FWHM = 10%, centered at the nominal kVp, homogeneous electron distribution) shows characteristic K-lines in its energy spectrum, not observed experimentally. The average photon energy using an ideal source (mono-energetic, homogeneous electron distribution) was 36.19 ± 0.09 keV, in agreement with the published measured data of 36.2 ± 0.2 keV. The use of a Gaussian-distributed electron source (mono-energetic) increases the penumbra by 50%, which is closer to the measurement results. The maximum discrepancy of the calculated percent depth dose with the corresponding measured values is 4.5% (at the phantom surface, less than 2 % beyond 1 mm depth) and 5% (for the 80% of the field) in the dose profile. Our results agree with the findings published by other authors and are consistent within the expected Type A and B uncertainties. Conclusions: Our results agree with the published measurement results within the reported uncertainties. The observed differences in PDD, dose profiles and photon spectrum come from three main sources of uncertainty: inter-machine variations, measurements and Monte Carlo calculations. It has been observed that a mono-energetic source with a Gaussian electron distribution over the focal spot is a suitable choice to reproduce the experimental data.
关键词： simulation efficiency,Monte Carlo simulation,electronic brachytherapy,surface treatment,dosimetry,x-ray source
更新于2025-09-23 15:21:21
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A Multiport Converter Interfacing Solar Photovoltaic Modules and Energy Storage with DC Microgrid
摘要： A novel real-time optical fibre X-Ray dosimeter for monitoring the radiation pulses delivered from a clinical linear accelerator (Linac) is presented. The primary focus of the sensor is to measure low doses of ionising X-ray radiation in real time (limited to 0.1-ms gate time of the detector). The sensor tip material scintillates upon exposure to X-ray energy and the resultant low-level visible light signal is coupled to a polymethyl methacrylate plastic optical fibre, which is used to guide it towards a distal avalanche photodiode-based detector. The detector measures the low-level scintillating light from the sensor, thereby converting the ionizing radiation energy to a measurable signal with a time resolution of 0.1 ms. Results show that the scintillating optical fibre X-ray dosimeter is capable of capturing the individual X-Ray pulses delivered by the Linac during normal operation. Further examination of the results demonstrates that the sensor is capable of measuring dose rate and, hence, dose with a linearity (R2 = 0.9995 ? 0.9999) and in a highly repeatable manner for dose rates in the range 100 to 600 monitor units/min.
关键词： optical fibre sensors,X-ray dosimetry,Clinical external beam radiotherapy,fluorescent and luminescent sensors,real time radiation dose measurement
更新于2025-09-23 15:21:01
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Combined temperature and radiation effects on radiation sensitive single-mode optical fibers
摘要： A novel real-time optical fibre X-Ray dosimeter for monitoring the radiation pulses delivered from a clinical linear accelerator (Linac) is presented. The primary focus of the sensor is to measure low doses of ionising X-ray radiation in real time (limited to 0.1-ms gate time of the detector). The sensor tip material scintillates upon exposure to X-ray energy and the resultant low-level visible light signal is coupled to a polymethyl methacrylate plastic optical fibre, which is used to guide it towards a distal avalanche photodiode-based detector. The detector measures the low-level scintillating light from the sensor, thereby converting the ionizing radiation energy to a measurable signal with a time resolution of 0.1 ms. Results show that the scintillating optical fibre X-ray dosimeter is capable of capturing the individual X-Ray pulses delivered by the Linac during normal operation. Further examination of the results demonstrates that the sensor is capable of measuring dose rate and, hence, dose with a linearity (R2 = 0.9995 ? 0.9999) and in a highly repeatable manner for dose rates in the range 100 to 600 monitor units/min.
关键词： optical fibre sensors,X-ray dosimetry,Clinical external beam radiotherapy,fluorescent and luminescent sensors,real time radiation dose measurement
更新于2025-09-23 15:21:01
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[IEEE 2019 Compound Semiconductor Week (CSW) - Nara, Japan (2019.5.19-2019.5.23)] 2019 Compound Semiconductor Week (CSW) - Enhancement of Infrared Photo-responses of the Schottky Gate Region of an n-AlGaAs/GaAs Heterojunction FET by a Second Light Illumination
摘要： As children develop, they differ from adults in a number of important ways, including anatomy, metabolism, immune system, and the extent of myelination of the nervous system. As a consequence, equivalent exposures to radiation from mobile phones result in different doses to specific tissues in children compared with adults. Higher doses are likely to have more severe implications in the young. A young child’s skull is not only smaller and thinner than an adult’s, but also has dielectric characteristics closer to those of soft tissues, probably due to a higher water content. The young skull better matches the electromagnetic characteristics of the skin and brain. As a result, finite-difference time-domain (FDTD) simulations confirm field penetration and higher specific absorption rate (SAR) in deeper structures in the young brain. If the peak spatial SAR (psSAR) is modeled in the entire head, as current testing standards recommend, the results for adults and children are equivalent. Our anatomically based evaluations rely on FDTD simulations of different tissues within the brain and confirm that the psSAR in a child’s brain is higher than in an adult’s brain.
关键词： dosimetry,mobile phone certification,finite-difference time-domain simulation,Specific absorption rate
更新于2025-09-23 15:21:01