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

✍ Scribed by S.R. Manohara; S.M. Hanagodimath

• Publisher: Elsevier Science
• Year: 2007
• Tongue: English
• Weight: 210 KB
• Volume: 264
• Category: Article
• ISSN: 0168-583X
• DOI: 10.1016/j.nimb.2007.08.018

✦ Synopsis

Effective atomic numbers for photon energy-absorption (Z PEAeff ) 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 1 keV to 20 MeV. The Z PEAeff 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 (Z PIeff ) and Z PEAeff with energy are shown graphically. Significant differences exist between Z PIeff and the Z PEAeff in the energy region of 8-100 keV for histidine and threonine; 6-100 keV for leucine, lysine, tryptophan, phenylalanine and valine; 15-400 keV 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 Z PEAeff rather than the commonly used Z PIeff in medical radiation dosimetry for the calculation of absorbed dose in radiation therapy are also discussed.