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排序方式： 共有321条查询结果，搜索用时 0 毫秒
151.
A laser-scanning 2D dosimetry system based on the Optically Stimulated Luminescence (OSL) signal from Al2O3 films was built and demonstrated. The main challenge of using the OSL from Al2O3 for 2D dosimetry by laser scanning is the long lifetime (∼35 ms) of the main luminescence centers in this material (F-centers). In this work, we demonstrated the possibility of performing 2D dosimetry by laser scanning using a combination of the fast UV emission of F+-centers (lifetime <7 ns) and the slow F-center emission of Al2O3:C, and an algorithm to correct for the slow F-center luminescence lifetime. We also investigated the possibility of using Al2O3:C,Mg, to take advantage of its greater F+-center emission compared to Al2O3:C. Results from 6 MV photon beam irradiations from a clinical linear accelerator were compared to radiographic and radiochromic film profiles showing a good qualitative agreement. 相似文献
152.
Kenji Kinashi Yusuke Miyashita Kenji Ishida Yasukiyo Ueda 《Journal of Physical Organic Chemistry》2012,25(5):427-430
A composite film containing photochromic spiropyran dye 1 and BaFCl:Eu was developed for X‐ray dose measurement at a level of a few dozen gray (Gy). The reflectance intensity at selected wavelength, obtained from X‐radiation, can be satisfactorily related to the absorbed dose in the range of 0−30 Gy. The composite film shows significant color change in the visible region, and the sensitivity of the composite to the absorbed dose was achieved based on the high molar extinction coefficient of the photomerocyanine form of dye 1. For practical application, the photoinduced blue area indicates an X‐radiated area, and the initial pale pink area indicates an unexposed area. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
153.
Hany A. Shousha 《辐射效应与固体损伤》2013,168(3):192-196
Patient doses from computed tomography (CT) examinations are usually expressed in terms of dose index, organ doses, and effective dose. The CT dose index (CTDI) can be measured free-in-air or in a CT dosimetry phantom. Organ doses can be measured directly in anthropomorphic Rando phantoms using thermoluminescent detectors. Organ doses can also be calculated by the Monte Carlo method utilizing measured CTDI values. In this work, organ doses were assessed for three main CT examinations: head, chest, and abdomen, using the different mentioned methods. Results of directly measured doses were compared with calculated doses for different organs in the study, and also compared with published international studies. 相似文献
154.
155.
For the first time the feasibility of using beryllium oxide (BeO) ceramics as a fibre-coupled radioluminescent dosimeter is investigated. BeO ceramic exhibits both radioluminescence (RL) and optically stimulated luminescence (OSL), and has the potential to be a near tissue equivalent alternative to Al2O3:C. A BeO fibre-coupled radioluminescence dosimeter is demonstrated and characterised for 6 MV X-rays and superficial X-ray energies, 150 kVp and 120 kVp. Based on the results, we demonstrate the capability of the RL BeO FOD for accurate and reproducible dose measurements with a linear dose rate and dose response. It has also been found that the percentage depth dose curves for 6 MV agreed with ion chamber measurements to within 2%, except in the build up region. For the 150 kVp and 120 kVp photon beams, the depth dose measurements agreed with ion chamber measurements to within 2.5% and 4%, respectively. 相似文献
156.
This study reports on the application of the MOSkin™ dosimeter in MSCT imaging for the real-time measurement of absorbed organ point doses in a tissue-equivalent female anthropomorphic phantom. MOSkin™ dosimeters were placed within the phantom to measure absorbed point organ doses for 2 commonly applied clinical scan protocols, namely the renal calculus scan and the pulmonary embolus scan. Measured organ doses in the imaged field of view were found to be in the dose range 4.7–9.5 mGy and 16.2–27.4 mGy for the renal calculus scan and pulmonary scan protocols respectively. For the derivation of effective dose, using the more recent ICRP 103 tissue weighting factors (wT) compared to that of the ICRP 60 wT resulted in a difference in the derived effective dose by up to 0.8 mSv (−20%) in the renal calculus protocol and up to 1.8 mSv (18%) in the pulmonary embolus protocol. This difference is attributed to the reduced radiosensitivity of the gonads and the increased radiosensitivity of breast tissue in the latest ICRP 103 assigned wT. The results of this study show that the MOSkin™ dosimeter is a useful real-time tool for the direct assessment of organ doses in clinical MSCT examinations. 相似文献
157.
Electron paramagnetic resonance (EPR) is an easy, fast, and reliable tool for identification of irradiated food. Untreated nuts may encounter hazards of carrying several pathogens or microbial contamination; walnuts are of specific importance due to their nutritional and medicinal values, and hence walnut processing via gamma irradiation is a necessary step. EPR was employed for the identification and dosimetry of Cs-137 gamma-irradiated walnuts (shells and kernels). Several important parameters were studied, such as spectral features, microwave power dependence of signal intensities, and short- and long-term time dependences. Responses of walnut shells and kernels to different radiation doses in the range 0–10 kGy were investigated. Results confirmed that EPR is a suitable tool for the identification and dosimetry of irradiated walnuts using either their shells or only kernels. 相似文献
158.
Photoneutrons induced by two high energies range from the Elekta medical linear accelerator (10 and 18 MV) were measured by nuclear track detectors (NTDs). CR-39 NTD in contact with converter screen slide films, natural boron of thickness 40 μm coated on the polyester film (BN1). Detectors were exposed at 100 cm SSD with field size 20×20 on the patient table, with chest phantom and with build-up Perspex used for high-energy exposure. CR-39 registers the thermal neutron by the (n–α) reaction with the thin layer of boron and the fast neutron was measured through the (n–p) elastic scattering with the H2 molecules in the CR-39 constituents.It was found that the total neutron dose (thermal and fast) from the 18 MV X-ray is higher than that of 10 MV. The measured thermal neutron dose is relatively smaller than the fast neutron dose in the case of direct exposure at the two X-ray energies. On the other hand, in the case of measurements on phantom and upon the use of build-up Perspex sheets, the ratio of fast to that of thermal is less than that of direct exposure. 相似文献
159.
A newly released processless Gafchromic EBT3 film was investigated for its response to ultraviolet radiation (UVR) at three different wavelengths: 365 (UVA), 302 (UVB) and 254 nm (UVC). The change in the film's optical density was dependent on the radiance exposure and UV wavelength and was found to correlate with the UV intensity. The dynamic range of the EBT3 films is ～5 to ～60 J/cm2 for UVA and UVB and ～5 to ～300 J/cm2 for UVC. The dose sensitivity of EBT3 films for UVA and UVB radiation was approximately 10 times higher than that for UVC radiation. The results indicate the suitability of EBT3 films for quantitative and qualitative measurements of UVR exposure. 相似文献
160.
Ryota Asayama Jianqing Wang Osamu Fujiwara 《Electronics and Communications in Japan》2014,97(9):28-34
Safety standards and guidelines for radio‐frequency exposure are being set based on whole‐body averaged SARs (WBA‐SARs) and localized average SARs. In Japan, the WBA‐SAR and 1 g localized average SAR are set at 0.4 W/kg and at 8 W/kg, respectively, except for the arms and legs and surface of body. The safety limits of WBA‐SARs were determined from observing the behavior destruction of animals for radio‐frequency exposure, but those of localized average SARs were determined under the assumption that a spatial peak SAR value does not exceed 20‐fold WBA‐SARs without their biological evidences. In this paper, to confirm whether or not the above assumption is valid, we calculated WBA‐SARs and voxel SARs in the frequency range from 50 MHz to 2 GHz in anatomical‐based human numerical models for pregnant woman and 3‐year‐child for vertically and horizontally polarized far‐field exposures, and derived the histogram and cumulative relative frequency of voxel SARs to obtain the quantitative relationship between WBA‐SARs and voxel SARs. As a result, we found that 99.90‐percentile voxel SARs are not exceeding 20‐fold WBA‐SARs, while 99.00‐percentile voxel SARs are smaller than 10‐fold WBA‐SARs in both human models. 相似文献