a b s t r a c tThe G-P fitting method has been used to compute the exposure build-up factor of teeth [enamel outer surface (EOS), enamel middle (EM), enamel dentin junction towards enamel (EDJE), enamel dentin junction towards dentin (EDJD), dentin middle (DM) and dentin inner surface (DIS)] for a wide energy range (0.015-15 MeV) up to the penetration depth of 40 mean free paths. The dependence of exposure build-up factor on incident photon energy, penetration depth, electron density and effective atomic number has also been studied. The computed exposure build-up factor is useful to estimate the relative dose distribution in different regions of teeth.
Background: Ionizing radiation is known to be harmful to human health. The shielding of ionizing radiation depends on the attenuation which can be achieved by three main rules, i.e. time, distance and absorbing material.
Materials and Methods:The mass attenuation coefficient, linear attenuation coefficient, Half Value Layer (HVL) and Tenth Value Layer (TVL) of X-rays (32 keV, 74 keV) and gamma rays (662 keV) are measured in Barium compounds.
Results and Discussion:The measured values agree well with the theory. The effective atomic numbers (Zeff) and electron density (Ne) of Barium compounds have been computed in the wide energy region 1 keV to 100 GeV using an accurate database of photon-interaction cross sections and the WinXCom program.
Conclusion:The mass attenuation coefficient and linear attenuation coefficient for BaCO3 is higher than the BaCl2, Ba(No3)2 and BaSO4. HVL, TVL and mean free path are lower for BaCO3 than the BaCl2, Ba(No3)2 and BaSO4. Among the studied barium compounds, BaCO3 is best material for x-ray and gamma shielding.
Computerized tomography (CT) number (it is a normalized value of the x ray absorption coefficient of a pixel in a computed tomogram) and the effective atomic number (Z(eff)) of teeth [enamel outer surface (EOS), enamel middle (EM), enamel dentin junction towards enamel (EDJE), enamel dentin junction towards dentin (EDJD), dentin middle (DM), and dentin inner surface (DIS)] have been calculated for photon interactions by a direct method in the energy range of 1 keV-100 GeV using the computer program, WinXCOM. The sum of the computed values are tabulated. The estimated CT numbers are tabulated. All of the selected materials show an almost constant Z(eff) value in the energy range 500 keV to 1.5 MeV. Also, it is expected that the computed CT numbers are useful in medical diagnosis. Dosimetric implication of mass attenuation coefficient in teeth has also been discussed.
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