title: A study of effective atomic number and electron density of gel dosimeters and human tissues for scattering of gamma rays: momentum transfer, energy and scattering angle dependence.
abstract: The objective of this work was to study water- and tissue-equivalent properties of some gel dosimeters, human tissues and water, for scattering of photons using the effective atomic number (Zeff). The Rayleigh to Compton scattering ratio (R/C) was used to obtain Zeffand electron density (Ne) of gel dosimeters, human tissues and water considering a 10-2-109momentum transfer, q (Å-1). In the present work, a logarithmic interpolation procedure was used to estimate R/C as well as Zeffof the chosen materials in a wide scattering angle (1°-180°) and energy range (0.001-100 MeV). The Zeffof the chosen materials was found to increase as momentum transfer increases, for q > ~1 Å-1. At fixed scattering angle and energy, Zeffof the material first increases and then becomes constant for high momentum transfers (q ≥ 3 Å-1), which indicates that Zeffis almost independent of energy and scattering angle for the chosen materials. Based on the Zeffdata and the continuous momentum transfer range (10-2-109Å-1), MAGIC, PAGAT and soft tissue were found to be water-equivalent materials, since their differences (%) relative to water are significantly low (≤3.2 % for MAGIC up to 103Å-1, ≤2.9 % for PAGAT up to 109Å-1, and ≤3.8 % for soft tissue up to 109Å-1), while the Fricke gel was not found to be water equivalent. PAGAT was found to be a soft tissue-equivalent material in the entire momentum transfer range (<4.3 %), while MAGAT has shown to be tissue equivalent for brain (≤8.1 % up to 10 Å-1) and lung (<8.2 % up to 10 Å-1) tissues. The Fricke gel dosimeter has shown to be adipose tissue equivalent for most of the momentum range considered (<10 %).
authors: Department of Physics, Faculty of Science, Ataturk University, 25240, Erzurum, Turkey. mkurudirek@gmail.com.
authors: Murat
authors: M
authors: Kurudirek
mesh_terms: D004583:Electrons; D005720:Gamma Rays; D005782:Gels; D006801:Humans; D011874:Radiometry / Q000379:methods*; D012542:Scattering, Radiation
chemical_list: D005782:Gels
keywords: Compton scattering; Effective atomic number; Gel dosimeters; Rayleigh scattering; Water