estimation of photon specific absorbed fractions in digimouse voxel phantom using monte carlo simulation code fluka

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.