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Abstract: DEXA (dual-energy X-ray absorption) is widely used in airport scanners, industrial scanners and bone densitometers. DEXA determines the properties of materials by measuring the absorption differences of X-rays from a bremsstrahlung tube source with and without filtering. Filtering creates a beam with a higher mean energy, which causes lower material absorption. The absorption difference between measurements (those with a filter subtracted from those without a filter) is a positive number that increases with the effective atomic number of the material. In this paper, the concept of using a filter to create a dual beam and an absorption difference in materials is applied to radiation from a 252Cf source, called NEUDEG (neutron and dual-energy gamma absorption). NEUDEG includes absorptions for fast neutrons as well as the dual photon beams and thus an incentive for developing the method is that, unlike DEXA, it is inherently sensitive to the hydrogen content of materials. In this paper, a model for the absorption difference and absorption sum in NEUDEG is presented using the combined gamma ray and fast neutron mass attenuation coefficients. Absorption differences can be either positive or negative in NEUDEG, increasing with increases in the effective atomic number and decreasing with increases in the hydrogen content. Sample sets of absorption difference curves are calculated for materials with typical gamma-ray and fast neutron mass attenuation coefficients. The model, which uses tabulated mass attenuated coefficients, agrees with experimental data for porcelain tiles and polyethylene sheets. The effects of “beam hardening” are also investigated. [Copyright &y& Elsevier]

It has been reported that LiF as commonly used thermoluminescent dosimeter (TLD) has a flat energy response, yet the energy dependence as radioluminescent (RL) detector has not been reported up to now. LiF is a near-tissue-equivalent material with a low effective atomic number, leading to its intrinsic virtue of flat energy response, theoretically. In this paper, Super-MC software was employed to simulate the energy deposition of LiF, the energy response of which was compared with NaI, and then the influence of the size of the detector on energy response was also investigated. Finally, the experimental verification of RL energy response was performed based on an in-house developed detector coupled LiF:Mg,Ti crystal with SiPM. The experimental energy responses (with respect to 137Cs) of three volume detector show good agreement (within ±30% in the range of 33 keV–1.25 MeV) with MC simulation results, which proved that LiF:Mg,Ti has a flat energy response, and it is feasible to obtain real-time dose-rate from count-rate collection without traditional method of hardware compensation or energy spectrum acquisition. In conclusion, this scheme can be a promising candidate for the rapid and accurate real-time dosimetry in the future, simplifying detector structure and measurement algorithm. • The energy dependence of LiF as RL detector has not been reported up to now. • MC software was employed to simulate the energy deposition of LiF. • The experimental verification of RL energy response was performed. • LiF:Mg,Ti as a RL detector showed a flat energy. • The real-time dose-rate can be obtained without energy response correction. [ABSTRACT FROM AUTHOR]

Currently, common radioluminescent (RL) materials have their own advantages and disadvantages in real-time dosimetry. The most attractive RL materials are tissue equivalent materials with stable sensitivity, weak afterglow, and a wide dose-rate linear range. LiF has a low effective atomic number, and previous studies have reported the RL sensitivity of LiF:Mg,Ti is dose-dependent. LiF:Mg,Cu,P can also emit RL during irradiation, which may be used for real-time dose monitoring. The purpose of this paper is to investigate dose characteristics of RL in LiF:Mg,Cu,P based on a developed optical fiber system and a commercial TL/OSL reader (Risφ TL/OSL-DA-20C/D). The results indicated that the RL sensitivity of LiF:Mg,Cu,P is not as good as Al 2 O 3 :C, but comparable to LiF:Mg,Ti. It can be inferred that LiF:Mg,Cu,P is suitable for high dose rate measurements. LiF:Mg,Cu,P showed almost a constant sensitivity to absorbed dose and a weak afterglow signal, which implies the accurate dose rates can be obtained quickly without sensitivity corrections. In addition, LiF:Mg,Cu,P has a good linear dose-rate response ranging from 0.76 mGy/h to 8.02 Gy/h, similar to LiF:Mg,Ti, and a superior repeatability (∼1.36%) to LiF:Mg,Ti. In conclusion, LiF:Mg,Cu,P is a competitive RL material for real-time dosimetry with its own advantages. • The RL sensitivity of LiF:Mg,Cu,P is comparable to LiF:Mg,Ti. • LiF:Mg,Cu,P showed almost a constant sensitivity to absorbed dose. • The accurate dose rates can be obtained without sensitivity corrections. • LiF:Mg,Cu,P has a good linear dose-rate response ranging from 0.76 mGy/h to 8.02 Gy/h. • LiF:Mg,Cu,P is a competitive RL material for real-time dosimetry with its own advantages. [ABSTRACT FROM AUTHOR]

Abstract: The effective atomic number (Zeff ) and electron density (Nel ) of hydroxyapatite (HA) and cortical bone have been computed for total photon interaction in the wide energy range of 1 keV–100 GeV using WinXCom. The variations of effective atomic number and electron density with energy of HA are compared with that of cortical bone. GP. fitting method has been used to compute energy absorption and exposure build-up factor of HA for wide energy range (0.015 MeV–15 MeV) up to the penetration depth of 40mean free path. The computed absorption build-up factor is used to estimate specific absorbed fraction of energy (Ф) and relative dose of photon in HA. Build-up factor increases with increase of penetration depth. The results of the present paper will also help in estimating safe dose levels for radiotherapy patients and also will be useful in dosimetry and diagnostics. [Copyright &y& Elsevier]

In most jurisdictions, the presently imposed annual eye-lens dose limits are 150 mSv for occupational and 15 mSv for the general public. These limits were based on a 1991 recommendations of the International Commission on Radiological Protection (ICRP), in its publication 60, and they were reiterated in 2007 in the ICRP publication 103. However, recent re-analyses of available epidemiological data appear to indicate that the onset of cataracts may occur at doses as low as 0.5 Gy. This led the ICRP to recommend, in the 2012 publication 118, the lowering of the annual dose limits to the lens of the eye of 20 mSv, averaged over 5 years, with no dose exceeding 50 mSv for any one year. The annual eye-lens dose limit for the general public remained at 15 mSv. The reduction of the eye-lens annual dose limit by nearly one order of magnitude led to large research efforts, including in the area of personal dose monitoring. This paper presents the results of a performance study of H p (0.07) dosemeters which were modified to allow the measurement of H p (3,α). The dosemeters were provided by four Canadian nuclear facilities, and one United States medical institution. Hence, five different technologies were tested for a variety of photon qualities and one standard beta field. The motivation to use H p (0.07) dosemeters was to show that it is possible to leverage dosimetry technologies already in place at various institutions. It was found that, using a low atomic number filter of nominally 300 mg cm−2 in mass thickness, most of the dosemeters considered would provide acceptable performances for the measurement of H p (3,α). [ABSTRACT FROM AUTHOR]