Bone marrow dosimetry for mice: exposure from bone-seeking 89,90Sr

Abstract

Studies of radiobiological effects in murine rodents exposed to internal radiation in the wild or in laboratory experiments require a dosimetric support. The main problem of bone marrow (BM) dosimetry for boneseeking β-emitters is dosimetric modeling due to the fact that the bone is a heterogeneous structure with complex microarchitecture. To date, there are several approaches to calculating the absorbed dose in BM, which mostly use rough geometric approximations. Recently, in the framework of studies of people exposed to 90 Sr in the Urals, a new approach (SPSD) has been developed. The aim of current study was to pilot test the possibility of extension of the SPSD-approach elaborated for humans to mice. The computational phantoms of femur bones of laboratory animals (C57BL/6, C57BL/6J, BALB/c, BALB/cJ) aged 5-8 weeks (growing) and >8 weeks (adults) were created. The dose factors to convert the 89,90 Sr activity concentrations in a bone tissue into units of the dose rate absorbed in the bone marrow were estimated as follows: DFSr-90(BMTBV+CBV) is equal to 1.75±0.42 and 2.57±0.93 (μGy day -1 ) per (Bq g -1 ) for growing and adults, respectively; DFSr-89(BMTBV+CBV) is equal to 1.08±0.27 and 1.66±0.67 (μGy day -1 ) per (Bq g -1 ) for growing and adults, respectively. These results are about 2.5 times lower than skeleton-average DF, calculated assuming the homogenous bone, where source and target coincide. The study demonstrates the possibility of application of the SPSD-approach elaborated for humans to non-human mammals.