Effect Of Absorption Edge Research Articles

Energy dependence of effective atomic numbers for photon energy absorption of vitamins

Mass - Energy absorption coefficient, Effective atomic numbers for photon energy absorption (ZPEA,eff) and photon interactions (ZPI,eff), of 8 Vitamins viz., vitamin-A (Retinol), 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 ZPEA,eff and ZPI,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 ZPI,eff and ZPEA,eff with energy are shown graphically. The substantial deviation occurs among ZPEA,eff and ZPI,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 ZPEA,eff and ZPI,eff which represents the absorbed dose, it is preferable to use ZPEA,eff instead of ZPI,eff in medical radiation dosimetry for the calculation of absorbed dose in the literature, there are no reports on the study of ZPEA,eff of selected vitamins. This inspired us to carry out the present work. In the present work, the ZPEA,eff has been calculated for selected vitamins namely Vitamin-A (Retinol), B2 (Riboflavin), B3 (Niacin), B7 (Biotin), B9 (Folic acid), B12 (Cobalamin), K1 (Phylloquinone) and P (Flavonoids) by a direct method in the energy region of 1 keV to 20 MeV using the µen/ρ values from the compilation of Hubbell and Seltzer 1 . The ZPEA,eff and ZPI,eff values have been found to change with energy and composition of the vitamins. The variations of ZPEA,eff and ZPI,eff with energy are shown graphically. The reasons for using ZPEA,eff rather than the commonly used ZPI,eff in medical radiation dosimetry for the calculation of absorbed dose in radiation therapy are discussed. The effect of absorption edge on ZPEA, eff and its variation with photon energy and the possibility of defining two set values of these parameters below the K-absorption edge of high-Z element present in the Biotin and cobalamin are discussed.

Effective atomic numbers for photon energy absorption of essential amino acids in the energy range 1 keV to 20 MeV

Effective atomic numbers for photon energy-absorption (ZPEAeff) of essential amino acids histidine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine have been calculated by a direct method in the energy region of 1keV to 20MeV. The ZPEAeff values have been found to change with energy and composition of the amino acids. The variations of mass energy-absorption coefficient, effective atomic number for photon interaction (ZPIeff) and ZPEAeff with energy are shown graphically. Significant differences exist between ZPIeff and the ZPEAeff in the energy region of 8–100keV for histidine and threonine; 6–100keV for leucine, lysine, tryptophan, phenylalanine and valine; 15–400keV for methionine. The effect of absorption edge on effective atomic numbers and the possibility of defining two set values of these parameters at the K-absorption edge of high-Z element present in the amino acids are discussed. The reasons for using ZPEAeff rather than the commonly used ZPIeff in medical radiation dosimetry for the calculation of absorbed dose in radiation therapy are also discussed.

Effective atomic numbers for photon energy absorption and photon attenuation of tissues from human organs

Effective atomic numbers for photon energy- absorption (Z pea eff) and photon interaction (Z pi eff) of human organs and tissues such as cortical bone, ovary, eye lens, testis, breast tissue, adipose tissue, lung tissue, soft tissue, soft tissue, (4-component), blood (whole), brain (grey/white matter), and skeletal muscle have been calculated by a direct method in the energy region of 1 keV to 20 MeV. The Z pea eff and Z pi eff values steadily increase, up to 8–50 keV, and steadily decrease up to 1.25–2.0 MeV for all of the substances studied. From 2.0 MeV, the values rise with the increase in energy, up to 20 MeV. Significant differences exist between the Z pi eff and Z pea eff in the energy region of 20–400 keV and 3–20 MeV for cortical bone; 15–150 keV for soft tissue, ovary, testis, blood, brain, lung, and skeletal muscle; 15–100 keV for breast tissue, eye lens, and soft tissue (4-component); and 10–100 keV for adipose tissue. A maximum difference of 28.37% is observed at 100 keV for cortical bone, and 30.43% at 40 keV for adipose tissue. For ovary, eye lens, testis, breast tissue, lung tissue, soft tissue, soft tissue (4-component), blood (whole), brain (grey/white matter), and skeletal muscle, a maximum difference of 31.74%, 29.60%, 31.87%, 30.61%, 31.47%, 31.52%, 29.95%, 31.63%, 32.36%, and 31.42%, respectively, is seen at 50 keV. The energy positions at which the maximum of Z pea eff and Z pi eff occurs differ. The single effective atomic number directly obtained using the program XMuDat (Z xmudat eff) are found to be higher compared to those of Z pea eff and Z pi eff values. The effect of absorption edge on effective atomic numbers, and its variation with photon energy and the possibility of defining 2 set values of effective atomic numbers below the absorption edges of elements present in the organs and tissues, are discussed.

Effective atomic numbers for photon energy absorption and energy dependence of some thermoluminescent dosimetric compounds

Effective atomic numbers for photon energy absorption and energy dependence (ED) of some selected pure thermoluminescent dosimetric (TLD) compounds such as LiF, CaCO 3, CaSO 4, CaSO 4 · 2H 2O, CdSO 4, SrSO 4 and BaSO 4 have been calculated in the energy region of 1 keV to 20 MeV. The more commonly used empirical formula for calculating the measure of ED in the energy region of interest in TL dosimeters through effective atomic numbers predicts higher values for all the materials studied compared to those ones calculated by direct method and by as much as 20% for SrSO 4. A modified formula fitted to directly calculated effective atomic number data gives better agreement within a maximum deviation of ±3.94% for all the TLD materials studied. Overall the effective atomic number varies linearly with ED in the photon energy range of 1 keV to 20 MeV and thereby confirming the validity of a more commonly employed method of using the effective atomic number to calculate the measure of the ED in TL dosimetry. Significant differences exist between the effective atomic numbers for photon interaction and photon energy absorption in the energy region 20–150 keV for LiF, 2–300 keV region for CaCO 3, CaSO 4 and CaSO 4 · 2H 2O, 3–1000 keV region for CdSO 4, 20–600 keV for SrSO 4 and 1–1000 keV for BaSO 4. The effect of absorption edge on effective atomic numbers and ED, their variation with photon energy and the possibility of defining two set values of these parameters below the K-absorption edge of high- Z element present in the TLD material are discussed.

Effective Atomic Numbers and Mass Attenuation Coefficients of Some Thermoluminescent Dosimetric Compounds for Total Photon Interaction

Effective atomic numbers for total gamma-ray interaction with some selected thermoluminescent dosimetric compounds such as barium acetate, barium sulfate, calcium carbonate, calcium sulfate, calcium sulfate dihydrate, cadmium sulfate (anhydrous), cadmium sulfate, strontium sulfate, and lithium fluoride have been calculated in the 1-keV to 20-MeV energy region. Experimental mass attenuation coefficients and effective atomic numbers for these compounds at selected photon energies of 26.3, 33.2, 59.54, and 661.6 keV have been obtained from good geometry transmission measurements and compared with theoretical values. The effect of absorption edge on effective atomic numbers and its variation with energy, and nonvalidity of the Bragg’s mixture rule at incident photon energies closer to the absorption edges of constituent elements of compounds are discussed.