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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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Calculation of kQ factors for Farmer-type ionization chambers following the recent recommendations on new key dosimetry data
摘要： Purpose: To calculate by Monte Carlo simulations kQ factors for Farmer-type ionization chambers in megavoltage photon beams using the new key dosimetry data recommended by the International Commission on Radiation Units and Measurements (ICRU) Report 90. Methods: Monte Carlo calculations were performed with the EGSnrc code system using both the ICRU 90 and the ICRU 37 data. Farmer-type ionization chambers with graphite and plastic walls and with graphite wall and a plastic waterproofing sleeve were considered (Nuclear Enterprise NE 2571, IBA FC65-G and FC65-P). kQ factors were calculated for photon beams in the range 6–25 MV using phase-space files as input radiation sources. The photon beam qualities in terms of TPR20,10 and %dd(10)x were established by simulating the depth-dose curves in water. Absorbed doses to the air cavity and to water were calculated using the egs_chamber user code with a target statistical uncertainty below 0.1%. Results: The update of key dosimetry data according to the ICRU report 90 had an impact of ?0.2% in the absorbed dose to water and up to 0.5% in the absorbed dose to the air cavity. Nevertheless, changes partially offset each other when entering in kQ as ratio, and the final impact on the kQ values was below 0.3%. Conclusions: The calculated values of kQ tend to be lower than the current values in the IAEA TRS-398 protocol with differences up to about 0.5%. A slightly better agreement (within 0.3%) is observed with the Monte-Carlo calculated values provided by the addendum to the AAPM’s TG-51 protocol.
关键词： Monte-Carlo calculated kQ,Beam quality correction factor,kQ,Radiotherapy dosimetry,ICRU 90
更新于2025-09-19 17:15:36
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Lanthanide-doped MgO: A case study on how to design new phosphors for dosimetry with tailored luminescent properties
摘要： In this work we systematically investigated undoped and lanthanide(Ln)-doped MgO with diverse dopant combinations, MgO:Ce,Ln and MgO:Tb,Ln, where Ln=Eu, Yb, Tm, Sm, Dy, Nd, as well as the same combinations with an additional 3 mol% Li dopant. We characterized the thermoluminescence (TL), optically stimulated luminescence (OSL), radioluminescence (RL), TL emission spectra and OSL emission spectra. Our investigation indicates that Ce3+ and Tb3+ act as recombination centers and their characteristic spectra are observed under thermal or optical stimulation. Conversely, TL measurements suggests that Sm3+, Tm3+ and Yb3+ probably act as electrons traps. The role of Li was investigated, since it was found to increase the RL, TL and OSL intensities in MgO. As part of the present investigation, we identified promising OSL materials sensitive to ionizing irradiation with distinct luminescent properties.
关键词： Optically stimulated luminescence,Dosimetry,Thermoluminescence,Lanthanides
更新于2025-09-19 17:15:36
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Studies on pelletized lithium magnesium borate TL material for eye lens dosimetry
摘要： Recent epidemiological studies in various cohorts confirm that radiation induced cataract may occur at a threshold dose as low as 0.5 Gy. ICRP has recognized the higher radiosensitivity of eye lens and recommended to reduce annual eye lens dose limit from 150 mSv to 20 mSv. Present dosimetry for eye lens is largely based on LiF based dosimeters. The present work is an attempt towards using near tissue equivalent lithium borate material namely lithium magnesium borate doped with terbium (LMB:Tb) in eye lens dosimetry. The material in powder form was synthesized using solid state sintering method and pelletized using poly tetra fluoro ethylene (PTFE) as binding agent. It was observed that 130 mg of 1mm thick LMB:Tb pellet bound with PTFE showed stable glow curve structure and attractive dosimetric features in terms of sensitivity, fading, linearity, reusability etc. A proposal of 1.5 mm Teflon encapsulation corresponding to tissue equivalent thickness of 3 mm was put forward for an ideal dosimeter for the measurement in terms of Hp(3). Energy and angular dependence studies based on FLUKA simulations suggest a flat response for the prototype design. In addition to PTFE, various tissue equivalent encapsulations such as polyimide, polyamide 6 and PMMA were also evaluated using FLUKA code.
关键词： thermoluminescence,Eye lens dosimetry,lithium borate phosphor
更新于2025-09-19 17:15:36
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Investigation of 3D diamond detector dosimetric characteristics
摘要： Recently, a polycrystalline chemical vapor deposited (pCVD) 3D diamond detector with graphitic in bulk electrodes, fabricated using a pulsed laser technique has been evaluated for photon beam radiation dosimetry during in-air exposure. The same 3D diamond detector, has now been investigated to evaluate its performance under clinically relevant conditions putting the detector inside a Polymethylmethacrylate (PMMA) phantom, to obtain higher precision dosimetric measurements. The detector leakage current was of the order of ±25 pA or less for bias voltages up to ?100 V. The 3D detector was tested for time stability and repeatability showing excellent performance with less than 0.6% signal variation. It also showed a linear response for low dose rates with a deviation from linearity of 2%. It was also possible to verify the detector response as a function of the depth in PMMA up to 18 cm.
关键词： Diamond Detectors,Radiotherapy concepts,Dosimetry concepts and apparatus
更新于2025-09-19 17:15:36
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Feasibility of a dual detector system to perform transit dosimetry and MV imaging in-vivo
摘要： In this work, a dual detector system for simultaneous in-vivo dosimetry and MV imaging was investigated. The ability to measure real-time water equivalent dose post transit for a heterogeneous phantom was demonstrated, illustrating its advantage over non-water equivalent EPID dosimetry. Identification of incorrect MU delivery as well as patient misalignment can be identified in the dose profiles and confirmed through co-registration with EPID images. The dual detector comprising of a silicon array detector “Magic Plate” (MP) and an EPID was positioned beneath the patient couch at a source to detector distance of 150 cm. Two pseudo lung phantoms were utilised in this study; identical, except for the inclusion of a water equivalent hidden target mimicking a tumour. The dosimetric accuracy of the MP was evaluated with EBT3 film and TPS calculations. The presence and position of the hidden target was detected and accurately co-registered between the dose profiles measured with MP and the EPID image. The system measured a difference in post transit doses through the two phantoms of (5.0 ±1.6) cGy due to the presence of the target, in agreement with the TPS calculation of 5.16 cGy. The capability of the system for error detection was confirmed when a deliberate 7 mm lateral shift of the phantom was observed in both the dose profiles measured with MP and the EPID images. The MP as a dosimetric real time detector is lucent in MV photon fields and does not obstruct the EPID field of view.
关键词： Portal imaging,Dosimetry concepts and apparatus
更新于2025-09-19 17:15:36
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Empirical Law to Evaluate the Skin Dose with Photon Beam Energy and Irradiation Field Size
摘要： The objective of this study is to evaluate mathematically an empirical law governs the skin dose with photon beam energy and irradiation field size based on experiment data of dose distributions. The dose distributions were expressed on percentage depth dose (PDD). The measurements of PDDs were done as a function of irradiation field size with an uncertainty of 2% as recommended by IAEA protocols. The skin dose corresponds to PDD at depth of 0 mm for photon beam energy of 6 and 18 MV. For these both photon beam energies, the skin dose increased linearly with irradiation field size and the skin dose rate decreased in power law as a function of irradiation field size with mathematical error under to 10%. This law allows us to predict the skin dose with irradiation field size for high radiotherapy quality and high protection of organ at risks.
关键词： skin dose,linac,dosimetry,radiotherapy,PDD
更新于2025-09-19 17:15:36
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Novel Gd3+-doped silica-based optical fiber material for dosimetry in proton therapy
摘要： Optical fibers hold promise for accurate dosimetry in small field proton therapy due to their superior spatial resolution and the lack of significant Cerenkov contamination in proton beams. One known drawback for most scintillation detectors is signal quenching in areas of high linear energy transfer, as is the case in the Bragg peak region of a proton beam. In this study, we investigated the potential of innovative optical fiber bulk materials using the sol-gel technique for dosimetry in proton therapy. This type of glass is made of amorphous silica (SiO2) and is doped with Gd3+ ions and possesses very interesting light emission properties with a luminescence band around 314 nm when exposed to protons. The fibers were manufactured at the University of Lille and tested at the TRIUMF Proton Therapy facility with 8.2–62.9 MeV protons and 2–6 nA of extracted beam current. Dose-rate dependence and quenching were measured and compared to other silica-based fibers also made by sol-gel techniques and doped with Ce3+ and Cu+. The three fibers present strong luminescence in the UV (Gd) or visible (Cu,Ce) under irradiation, with the emission intensities related directly to the proton flux. In addition, the 0.5 mm diameter Gd3+-doped fiber shows superior resolution of the Bragg peak, indicating significantly reduced quenching in comparison to the Ce3+ and Cu+ fibers with a Birks’ constant, kB, of (0.0162 ± 0.0003) cm/MeV in comparison to (0.0333 ± 0.0006) cm/MeV and (0.0352 ± 0.0003) cm/MeV, respectively. To our knowledge, this is the first report of such an interesting kB for a silica-based optical fiber material, showing clearly that this fiber presents lower quenching than common plastic scintillators. This result demonstrates the high potential of this inorganic fiber material for proton therapy dosimetry.
关键词： Bragg peak,dosimetry,Gd3+-doped silica,optical fibers,quenching,sol-gel technique,proton therapy
更新于2025-09-16 10:30:52
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Degradation prediction of a γ-ray radiation dosimeter using InGaP solar cells in a primary containment vessel of the Fukushima Daiichi Nuclear Power Station
摘要： Indium gallium phosphide (InGaP) solar cell with a superior high-radiation resistance is expected to be a powerful candidate for a dosimeter under a high-radiation dose rate environment. In this study, in order to predict the lifetime as the dosimeter using the InGaP solar cell, we clarify the effect of minority-carrier diffusion length (L) on a radiation-induced current as a dose signal in the InGaP solar cell by irradiation tests and empirical calculations. In the irradiation tests, the short-circuit current density (Jsc) as a function of the γ-ray dose rate is measured to estimate the L for the InGaP solar cell by irradiation tests. The operational lifetime as a detector using the InGaP solar cell under various dose rates is estimated by using the empirical calculations based on the relation between the L and absorbed dose. The results suggest that the dosimeter using InGaP solar cell is able to be used during more than 10 h in the primary containment vessel of the Fukushima Daiichi Nuclear Power Plant and it has a high potential of being a radiation-resistant dosimeter that would contribute to the decommissioning.
关键词： solar cell,operation lifetime,decommissioning,radiation-induced current,minority-carrier diffusion length,Dosimetry,InGaP compound semiconductor,degradation prediction
更新于2025-09-16 10:30:52
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Scattering metal waveguide based speckle-enhanced prism spectrometry
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2025-09-16 10:30:52
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Towards Automatically Controlled Dosing for Selective Laser Trabeculoplasty
摘要： Purpose: Selective laser trabeculoplasty (SLT) is a treatment option for open-angle glaucoma; however, it lacks an instant evidence for successful irradiation. So far ophthalmologists use the visible appearance of permanent champagnelike bubbles (macro bubbles) as an indicator for appropriate pulse energy. We hypothesize that micro bubbles, which start energetically far below the appearance of macro bubbles, already trigger the therapeutic benefit. Here we present two methods to capture the onset of these micro bubbles. Methods: The trabecular meshwork of freshly enucleated porcine eye globes was irradiated with a series of 15 pulses with a pulse duration of 1.7 ls and with increasing energy at a repetition rate of 100 Hz per each spot of 200 lm in diameter. An optical and an optoacoustic method have been developed and appropriate algorithms investigated towards the real-time detection of the onset of micro bubbles. Results: Both observation methods are capable of detecting micro bubble nucleation. Threshold radiant exposures were found at 310 6 137 mJ/cm2. By combination of both methods a sensitivity and specificity of 0.96 was reached. Conclusions: In case that the therapeutically demanded pressure reduction is already achieved with these micro bubbles, which needs to be proven clinically, then the methods presented here can be used in an automatic feedback loop controlling the laser irradiation. This will unburden the clinicians from any dosing during SLT. Translational Relevance: Automatic real-time pulse energy dosing based on the formation of micro bubbles in SLT significantly improves and facilitates the treatment for the physician.
关键词： dosimetry,selective laser trabeculoplasty,ophthalmology,micro bubble detection,ophthalmic optics and device
更新于2025-09-12 10:27:22