Mass -Energy absorption coefficient, Effective atomic numbers for photon energy absorption (Z PEA,eff ) and photon interactions (Z PI,eff ), of 8 Vitamins viz.,, B2 (Riboflavin), B3 (Niacin), B7 (Biotin), B9 (Folic acid), B12 (Cobalamin), K1 (Phylloquinone) and P (Flavonoids) were computed for the energy range 1 keV to 20 MeV. Variation of these parameters has been studied as a function of incident photon energy. The Z PEA,eff and Z PI,eff values have been found to change with energy and composition of the biological molecules. The variations of mass energy-absorption coefficient, effective atomic number for photon interaction Z PI,eff and Z PEA,eff with energy are shown graphically. The substantial deviation occurs among Z PEA,eff and Z PI,eff in the energy range 5-100 keV for Retinol and Phylloquinone. The deviation is also observed for Riboflavin, Niacin, Folic acid, Flavonoids in the energy range 8 -100 keV, and for Biotin (15-150 keV) and for Cobalamin (6-200 keV). The substantial change occurs between Z PEA,eff and Z PI,eff which represents the absorbed dose, it is preferable to use Z PEA,eff instead of Z PI,eff in medical radiation dosimetry for the calculation of absorbed dose in radiation therapy
I. IntroductionThe amount of energy that is actually deposited in the medium is important in evaluating biological effects, explaining the response of a radiation detector and other applications. For this purpose, one can define a linear energy-absorption coefficient, µ en . This coefficient includes only the energy absorbed in the medium from photoelectrons, Compton electrons and the electron-positron pair. But, energy carried away by scattered Compton photons, annihilation radiation and bremsstrahlung radiation is not included.A more detailed version of the energy-deposition quantity is the mass energy-absorption coefficient, µ en /ρ, and can be described more clearly through the use of intermediate quantity called mass energy-transfer coefficient. Mass energy-transfer coefficient, µ tr /ρ, is the mass attenuation coefficient multiplied by the fraction of energy of the interacting photons which is transferred to charged particles as kinetic energy. Hence, µ tr /ρ is a measure of the average fractional amount of incident photon energy transferred to charged particles as kinetic energy due to all types of interaction of photons with matter.The mass energy-absorption coefficient, µ en /ρ, takes into account the fraction of the kinetic energy that is subsequently lost in radiative energy loss processes as the charged particles slow down to rest in the absorbing medium. The net kinetic energy of charged particles is in turn, a more or less valid approximation to the amount of photon energy made available for the production of chemical, biological and other effects associated with exposure to ionizing radiation. Therefore µ en /ρ has an essential role in estimating the absorbed dose in medical and health physics. The µ/ρ and µ en /ρ are basic quantity used in calculation of the penetration and the energy depositio...
