修车大队一品楼qm论坛51一品茶楼论坛,栖凤楼品茶全国楼凤app软件 ,栖凤阁全国论坛入口,广州百花丛bhc论坛杭州百花坊妃子阁

oe1(光电查) - 科学论文

过滤筛选

出版时间
  • 2015
研究主题
  • Calibration process of OSL detectors
  • Iodine-131
  • OSL-BeO
  • Dosimetry of staff and patients
  • Optically Stimulated Luminescence (OSL)
应用领域
机构单位
  • Akdeniz University
72 条数据
?? 中文（中国） ▾

  • THE DEVELOPMENT OF A NOVEL ARRAY DETECTOR FOR OVERCOMING THE DOSIMETRY CHALLENGES OF MEASURING IN VERY SHORT PULSED CHARGED PARTICLE BEAMS: THE ELIDOSE PROJECT

    摘要： In-beam dose measurements are paramount for any application seeking to harness the effects of the radiation beam, so all the future applications of the laser accelerated beams (as generated in the ELI and CETAL projects) will need such measurements. With a very long history in measuring doses in charged particle beams, the medical and industrial applications setup a number of methods that could be also used for the dosimetry of the beams generated by laser pulses. Dose measurements rely heavily on what is seen as the gold standard in dose measurement: the ion chambers. Ion chambers have both limitations and advantages, and in our case the disadvantage could be the large number of corrections to be applied in order to calculate a correct dose from the measured charge. The ELIDOSE project tries to address these problems by proposing an array detector that would allow the simultaneous measurement of the recombination and polarity corrections, and of the dose. The detector consists of four identical ion chambers mounted together in a PMMA frame and the project will analyze its response to various charged particle beams and the reciprocal influences of the chambers on each other. These reciprocal influences of the four chambers are studied through the FLUKA modeling of the detector and, in order to hone the simulations of the detectors, we initially compared the results of the measurements performed with an Advanced MarkusTM chamber in the proton beam delivered at the 3-MV TandetronTM from IFIN-HH. The paper presents the results of these initial measurements and how these results will be used to modify the simulation parameters.

    关键词： dosimetry,ELIDOSE project,charged particle beams,FLUKA simulation,ion chambers

    更新于2025-09-09 09:28:46

  • Radio-Fluorogenic Gel Dosimetry with Coumarin

    摘要： Gel dosimeters are attractive detectors for radiation therapy, with properties similar to biological tissue and the potential to visualize volumetric dose distributions. Radio-fluorogenesis is the yield of fluorescent chemical products in response to energy deposition from ionizing radiation. This report shares the development of a novel radio-fluorogenic gel (RFG) dosimeter, gelatin infused with coumarin-3-carboxlyic acid (C3CA), for the quantification of imparted energy. Aqueous solutions exposed to ionizing radiation result in the production of hydroxyl free radicals through water radiolysis. Interactions between hydroxyl free radicals and coumarin-3-carboxylic acid produce a fluorescent product. 7-hydroxy-coumarin-3-carboxylic acid has a blue (445 nm) emission following ultra-violet (UV) to near UV (365–405 nm) excitation. Effects of C3CA concentration and pH buffers were investigated. The response of the RFG was explored with respect to strength, type, and exposure rate of high-energy radiation. Results show a linear dose response relationship independent of energy and type, with a dose-rate dependency. This report demonstrates increased photo-yield with high pH and the utility of gelatin-RFG for phantom studies of radiation dosimetry.

    关键词： radio-fluorogenic gel,luminescent dosimetry,radiation dosimetry,gel dosimetry

    更新于2025-09-04 15:30:14

  • The Calibration Process of OSL Detectors used for Staff and Patient Dosimetry in Hospital Environment

    摘要： The optically stimulated luminescence (OSL-BeO) dosemeter is increasingly being used as a dosimetric technique in various fields such as medical dosimetry. According to our fixed dose protocol, the activities of 3.7-7.4 GBq I-131 source is used for thyroid carcinoma therapy. The in house calibration process for usage of OSL’s at hospital was arranged according to the encapsulated I-131. The measurement point was planned in three different radial distances from source free in air. The dose-rate measurement was done by Geiger-Muller (GM), and then three pieces of OSL was placed in the same positions for one hour. The inverse square law consistency was found (R2=0.99). The calibration coefficient was calculated. For determining the performance of OSL at different dose rates, it used for personnel and patient dosimetry. The average annual dose/2mon to the whole body for all staff by OSL were 0.80 mSv. After administration of 3.7 GBq (100 mCi) therapeutic dose to selected patients, the average pectoral dose was 97.5+32.6 mSv. This calibration process is helpful for confidence of OSL detectors used for dosimetry of staff and patients treated with high activity I-131.

    关键词： Calibration process of OSL detectors,Iodine-131,OSL-BeO,Dosimetry of staff and patients,Optically Stimulated Luminescence (OSL)

    更新于2025-09-04 15:30:14

  • Spectral analysis of the <scp>EBT</scp> 3 radiochromic films for clinical photon and electron beams

    摘要： Purpose: To investigate the spectral response of the EBT3 radiochromic films to different beam qualities for radiation therapy dosimetry. Dose, dose rate, and inter-batch dependencies on the spectral response of the films are investigated as well. Methods: Pieces of EBT3 films placed between layers of solid water phantoms were irradiated with 6 and 15 MV photon beams, 6 and 10 MV-FFF photon beams, and 6 and 20 MeV electron beams at dose levels between 0.4-50 Gy. Net absorbance was measured as a function of wavelength from the spectra acquired in the wavelength range of 400-800 nm using a fiber-coupled spectrometer and broadband light source. Results: No significant change was observed in the absorption spectra of the EBT3 films irradiated with the same amount of dose using different beam qualities. Also, no spectral change with dose rate was observed. The measured net absorbance per Gy was independent of beam quality in the 1-50 Gy dose range. Slight differences in the spectral shape and absorption band positions were observed in film samples from different batches. The net absorbance spectra showed two absorption bands centered around 634-636 nm (primary) and 583-585 nm (secondary). However, depending on the film batch, for doses above a certain level the primary absorption band appears to “split” into two bands centered around ~624-628 and ~641-645 nm. Conclusions: The spectral shape of the EBT3 radiochromic films irradiated with photons (including FFF) and electron beams is beam quality and dose rate independent; however it varies with dose level, batch, and spectroscopy system used.

    关键词： EBT3,film dosimetry,Radiochromic film,absorption spectroscopy

    更新于2025-09-04 15:30:14

  • Calibration strategies for use of the nanoDot OSLD in CT applications

    摘要： Aluminum oxide based optically stimulated luminescent dosimeters (OSLD) have been recognized as a useful dosimeter for measuring CT dose, particularly for patient dose measurements. Despite the increasing use of this dosimeter, appropriate dosimeter calibration techniques have not been established in the literature; while the manufacturer offers a calibration procedure, it is known to have relatively large uncertainties. The purpose of this work was to evaluate two clinical approaches for calibrating these dosimeters for CT applications, and to determine the uncertainty associated with measurements using these techniques. Three unique calibration procedures were used to calculate dose for a range of CT conditions using a commercially available OSLD and reader. The three calibration procedures included calibration (a) using the vendor‐provided method, (b) relative to a 120 kVp CT spectrum in air, and (c) relative to a megavoltage beam (implemented with 60Co). The dose measured using each of these approaches was compared to dose measured using a calibrated farmer‐type ion chamber. Finally, the uncertainty in the dose measured using each approach was determined. For the CT and megavoltage calibration methods, the dose measured using the OSLD nanoDot was within 5% of the dose measured using an ion chamber for a wide range of different CT scan parameters (80–140 kVp, and with measurements at a range of positions). When calibrated using the vendor‐recommended protocol, the OSLD measured doses were on average 15.5% lower than ion chamber doses. Two clinical calibration techniques have been evaluated and are presented in this work as alternatives to the vendor‐provided calibration approach. These techniques provide high precision for OSLD‐based measurements in a CT environment.

    关键词： calibration,OSLD,dosimetry,CT

    更新于2025-09-04 15:30:14

  • Effect of Co-activation on the Thermoluminescence and Photoluminescence Properties of Nano-crystalline K2Ca2(SO4)3:Eu,Cu

    摘要： The effect of co-doping and change in dopant concentration on thermoluminescence (TL) properties of K2Ca2(SO4)3:Eu,Cu has been studied by varying the concentration of the two dopants europium and copper (0.05, 0.10, 0.20, 0.30 and 0.40 mol % equally divided between Eu and Cu). Chemical co-precipitation technique was used to prepare the co-doped phosphor K2Ca2(SO4)3:Eu,Cu. Using Williamson-Hall plot in the X-ray diffraction pattern of the phosphor, the size of the crystallites was estimated to be around 51.3-73.6 nm. Maximum TL sensitivity was obtained for 0.2 mol% concentration (0.1 mol% Eu and 0.1 mol% Cu). The co-doped phosphor was compared for its TL sensitivity with that of the singly doped phosphors K2Ca2(SO4)3:Eu, and K2Ca2(SO4)3:Cu and the standard TL dosimeter LIF:Mg, Ti (TLD-100). Higher TL peak intensity of co-doped phosphor compared to the singly doped phosphors K2Ca2(SO4)3:Eu and K2Ca2(SO4)3:Cu has been explained on the basis of energy transfer between the dopants. Photoluminescence studies of the co-doped and the singly doped samples confirm a positive energy transfer from Cu2+ to Eu2+. A linear TL response curve over a wide range of doses (10 Gy to 1 kGy) is a key factor that makes the present phosphor quite capable for dosimetric purposes.

    关键词： radiation dosimetry,up-conversion,nanophosphor,photoluminescence,thermoluminescence

    更新于2025-09-04 15:30:14

  • Estimate of Nonuniformity of Dose Distribution in Regime of Total Therapeutic Irradiation with In Vivo Dosimetry Using Semiconductor Detectors

    摘要： We have estimated the nonuniformity of the dose distribution along the body of a patient using in vivo dosimetry by semiconductor detectors with total therapeutic irradiation of cancer patients before bone marrow transplantation. The method of in vivo dosimetry was developed and used at the Blokhin Oncology Center since 2007. Based on the results of the investigation of 35 patients, we determined a mean nonuniformity of 10–15% of the dose distribution along the body of the patient, which conforms to international recommendations. We show a linear dependence of the accumulated dose on the mass of the patient.

    关键词： total irradiation,in vivo dosimetry,semiconductor detectors,radiation therapy

    更新于2025-09-04 15:30:14

  • On the instantaneous dose rate and angular dependence of monolithic silicon array detectors

    摘要： The use of small radiation fields characterized by very steep dose gradients is common in modulated arc x-ray radiotherapy. Dosimeters for quality assurance applications would ideally have sensitive volumes relatively small with respect to the field, along with negligible instantaneous dose rate and angular dependence. Silicon-based dosimeters can be fabricated with sensitive volumes < 100 μm across, provide a stable and near energy-independent response in megavoltage photon beams, along with a good linearity with accumulated dose and real-time read-out. However, their sensitivity is instantaneous dose rate and angular dependent. Monolithic silicon array detectors with sufficiently small sensitive volumes and pitch are suitable for high-resolution 2D dose mapping in radiation fields with steep dose gradients. The Octa is a 2D monolithic silicon array detector. It has 512 diode-sensitive volumes arranged with a sub-millimeter pitch. The physical characteristics of the substrate on which it is based, in terms of resistivity and defects concentration, strongly affect its performance. We report on the experimental characterization of two versions of the Octa, manufactured on a bulk and on an epitaxial substrate respectively. Their performance is compared and discussed in terms of their instantaneous dose rate and angular dependence in the context of quality assurance applications in small radiation fields delivered with modulated arc radiotherapy.

    关键词： small-field dosimetry,angular dependence,instantaneous dose rate dependence,2D monolithic silicon array detector

    更新于2025-09-04 15:30:14

  • Effect of Er3+ on NaSrB glass: thermoluminescence and structural analysis

    摘要： The present work reports the investigations on Er3+-doped sodium–strontium–borate glasses for their structural, optical and thermoluminescence (TL) properties. While the amorphous nature of the prepared glasses is confirmed by the powdered X-ray diffraction (XRD), some interesting features were found in the structure and Fourier-transform infrared (FTIR) studies such as the nanocrystallization and the presence of BO3 and BO4 structural units. Some physical parameters such as ion concentration, polaron radius, inter-nuclear distance, and field strength are calculated and analyzed. Optical band gap was found to be sensitive to the concentration of the dopants. TL glow curve exhibits a single peak but it shifts with variation in concentration of Er2O3. Calculation of kinetic parameters show that the prepared glasses exhibit second-order kinetics. The effective atomic number (Zeff) of prepared glasses is also calculated which indicates their suitability for application in radiation dosimetry.

    关键词： thermoluminescence,sodium–strontium–borate glasses,optical properties,radiation dosimetry,Er3+-doped,structural analysis

    更新于2025-09-04 15:30:14

  • Absorbed doses in salivary and thyroid glands from panoramic radiography and cone beam computed tomography

    摘要： Introduction: Panoramic radiography and cone beam computed tomography (CBCT) are very important in the diagnosis of oral diseases, however patients are exposed to the risk of ionizing radiation. This paper describes our study aimed at comparing absorbed doses in the salivary glands and thyroid due to panoramic radiography and CBCT and estimating radiation induced cancer risk associated with those methods. Methods: Absorbed doses of two CBCT equipment (i?CAT? Next Generation and SCANORA? 3D) and a digital panoramic device (ORTHOPANTOMOGRAPH? OP200D) were measured using thermoluminescent dosimeters loaded in an anthropomorphic phantom on sublingual, submandibular, parotid and thyroid glands. Results: Absorbed doses in the i?CAT? device ranged between 0.02 (+/?0.01) and 2.23 mGy (+/?0.03), in the SCANORA? device ranged from 0.01 (+/?0.01) to 2.96 mGy (+/?0.29) and in the ORTHOPANTOMOGRAPH? OP200D ranged between 0.04 mGy and 0.78 mGy. The radiation induced cancer risk was highlighted in the salivary glands, which received higher doses. The protocols that offer the highest risk of cancer are the high resolution protocols of CBCT equipment. Conclusion: CBCT exposes patients to higher levels of radiation than panoramic radiography, so the risks and benefits of each method should be considered. The doses in CBCT were dependent on equipment and exposure parameters, therefore adequate selection minimizes the radiation dose.

    关键词： Radiation dose,Cone beam computed tomography,Thermoluminescent dosimetry,Panoramic radiograph

    更新于2025-09-04 15:30:14