ABSTRACT
BACKGROUND: For preclinical evaluations of radiopharmaceuticals, most studies are carried out on mice. Electron specific absorbed fractions (SAF) values have had vital role in the assessment of absorbed dose. In past studies, electron SAFs were given for limited source target pairs using older reports of human organ compositions. OBJECTIVE: Electron specific absorbed fraction values for monoenergetic electrons of energies 15, 50, 100, 500, 1000 & 4000 keV were evaluated for the Digimouse voxel phantom incorporated in Monte Carlo code FLUKA. From the latest report (International Commission on Radiological Protection ICRP) 110, organ compositions and densities were adopted. MATERIAL AND METHODS: We have used the Digimouse voxel phantom which was incorporated in Monte Carlo code FLUKA. Simulation studies were performed using FLUKA. The organ sources considered in this study were lungs, skeleton, heart, bladder, testis, stomach, spleen, pancreas, liver, kidney, adrenal, eye and brain. The considered target organs were lungs, skeleton, heart, bladder, testis, stomach, spleen, pancreas, liver, kidney, adrenal and brain. Eye and brain were considered as target organs only for eye and brain as source organs. RESULTS: The electron SAF values for self-irradiation decreases with increasing electron energy. The electron SAF values for cross-irradiation are also found to be dependent on the electron energy and the geometries of source and target. Organ masses and electron SAF values are presented in tabular form. CONCLUSION: The results of this study will be useful in evaluating the absorbed dose to various organs of mice similar in size to the present study.
ABSTRACT
BACKGROUND: Most preclinical studies are carried out on mice. For internal dose assessment of a mouse, specific absorbed fraction (SAF) values play an important role. In most studies, SAF values are estimated using older standard human organ compositions and values for limited source target pairs. OBJECTIVE: SAF values for monoenergetic photons of energies 15, 50, 100, 500, 1000 and 4000 keV were evaluated for the Digimouse voxel phantom incorporated in Monte Carlo code FLUKA. The organ sources considered in this study were lungs, skeleton, heart, bladder, testis, stomach, spleen, pancreas, liver, kidney, adrenal, eye and brain. The considered target organs were lungs, skeleton, heart, bladder, testis, stomach, spleen, pancreas, liver, kidney, adrenal and brain. Eye was considered as a target organ only for eye as a source organ. Organ compositions and densities were adopted from International Commission on Radiological Protection (ICRP) publication number 110. RESULTS: Evaluated organ masses and SAF values are presented in tabular form. It is observed that SAF values decrease with increasing the source-to-target distance. The SAF value for self-irradiation decreases with increasing photon energy. The SAF values are also found to be dependent on the mass of target in such a way that higher values are obtained for lower masses. The effect of composition is highest in case of target organ lungs where mass and estimated SAF values are found to have larger differences. CONCLUSION: These SAF values are very important for absorbed dose calculation for various organs of a mouse.
