Effective atomic numbers and electron densities of some biologically important compounds containing H, C, N and O in the energy range 145–1330 keV

Abstract

A semi-empirical relation which can be used to determine the total attenuation cross sections of samples containing H, C, N and O in the energy range 145–1332 keV has been derived based on the total attenuation cross sections of several sugars, amino acids and fatty acids. The cross sections have been measured by performing transmission experiments in a narrow beam good geometry set-up by employing a high-resolution hyperpure germanium detector at seven energies of biological importance such as 145.4 keV, 279.2 keV, 514 keV, 661.6 keV, 1115.5 keV, 1173.2 keV and 1332.1 keV. The semi-empirical relation can reproduce the experimental values within 1–2%. The total attenuation cross sections of five elements carbon, aluminium, titanium, copper and zirconium measured in the same experimental set-up at the energies mentioned above have been used in a new matrix method to evaluate the effective atomic numbers and the effective electron densities of samples such as cholesterol, fatty acids, sugars and amino acids containing H, C, N and O atoms from their effective atomic cross sections. The effective atomic cross sections are the total attenuation cross sections divided by the total number of atoms of all types in a particular sample. Further, a quantity called the effective atomic weight was defined as the ratio of the molecular weight of a sample to the total number of atoms of all types in it. The variation of the effective atomic number was systematically studied with respect to the effective atomic weight and a new semi-empirical relation for Zeff has been evolved. It is felt that this relation can be very useful to determine the effective atomic number of any sample having H, C, N and O atoms in the energy range 145–1332 keV irrespective of its chemical structure.

A novel approach to normalize Compton profiles of pure incoherent scatterers

“…One can easily envisage in the light of earlier results [8,9,21] that, as the incident energy is further increased, this upper limit on Z is only pushed far beyond 9. Although the region 1 < Z ef f < 9 appears very narrow, this is the region which corresponds to the Z ef f of a vast majority of composite materials of biological interest as well as H-, C-, N-and O-based polymers which find wide ranging applications in several fields of science and technology.…”

“…In a recent experimental work [9][10][11][12] on the determination of the effective atomic number, Z ef f , we have shown that H-, C-, N-and O-based composite materials such as sugars, aminoacids, fatty acids and several polymer samples behave like pure incoherent scatterers. This aspect is corroborated by the more recent works of Taylor [13] and Manohara et al [14].…”

Assessment of methods for estimation of effective atomic numbers of common human organ and tissue substitutes: waxes, plastics and polymers

“…Several authors have reported the effective atomic numbers for gaseous mixtures (Singh and Badiger, 2012), alcohols (Singh and Badiger, 2013), composite materials (Prasanna et al, 2010), solutions (Kulwant et al, 2001), dosimetric materials (Kiran and Venkata, 1997) and biological materials (Koç and Özyol, 2000;Shivalinge et al, 2005;Manjunathguru and Umesh, 2006;Demir et al, 2012). This study will be helpful for additional information and deciding the appropriate method for computation of the effective atomic numbers analogous to the experimental values.…”

Studies on mass attenuation coefficient, mass energy absorption coefficient, and kerma for Fe alloys at photon energies of 17.44 to 51.70 keV

“…Onder et al obtained mass attenuation coefficients, effective atomic numbers, and electron densities for TLD compounds [5]. Parthasaradhi et al determined mass attenuation coefficients of tissue equivalent samples in the energy range of 13-44 keV [6].…”