The objective of the present work is to apply the plasma clearance parameters to
strontium, previously determined in our laboratory, to improve the biokinetic and dosimetric models of
strontium-90 ((90)Sr) used in radiological protection; and also to apply this data for the estimation of the radiation doses from
strontium-89 ((89)Sr) after administration to patients for the treatment of the painful bone
metastases. Plasma clearance and urinary excretion of stable
strontium tracers of
strontium-84 ((84)Sr) and
strontium-86 ((86)Sr) were measured in GSF-National Research Center for Environment and Health (GSF) in 13 healthy German adult subjects after
intravenous injection and
oral administration. The
biological half-life of
strontium in plasma was evaluated from 49 plasma concentration data sets following
intravenous injections. This value was used to determine the transfer rates from plasma to other organs and tissues. At the same time, the long-term retention of
strontium in soft tissue and whole body was constrained to be consistent with measured values available. A physiological urinary path was integrated into the biokinetic model of
strontium. Parameters were estimated using our own measured urinary excretion values. Retention and excretion of
strontium were modeled using compartmental transfer rates published by the International Commission on Radiological Protection (ICRP), the SENES Oak Ridge Inc. (SENES), and the Urals Research Center for Radiation Medicine (TBM). The results were compared with values calculated by applying our GSF parameters (GSF). For the dose estimation of (89)Sr, a bone
metastases model (GSF-M) was developed by adding a compartment, representing the
metastases, into the
strontium biokinetic model. The related parameters were evaluated based on measured data available in the literature. A set of biokinetic parameters was optimized to represent not only the early plasma kinetics of
strontium but also the long-term retention measured in soft tissue and whole body. The ingestion dose coefficients of (90)Sr were computed and compared with different biokinetic model parameters. The ingestion dose coefficients were calculated as 2.8 x 10(-8), 2.1 x 10(-8), 2.5 x 10(-8) and 3.8 x 10(-8) Sv Bq(-1) for ICRP, SENES, TBM and GSF model parameters, respectively. Moreover, organ absorbed dose for the
radiopharmaceutical of (89)Sr in bone
metastases therapy was estimated based on the GSF and ICRP biokinetic model parameters. The effective doses were 3.3, 1.8 and 1.2 mSv MBq(-1) by GSF, GSF-M, and ICRP Publication 67 model parameters, respectively, compared to the value of 3.1 mSv MBq(-1) reported by ICRP Publication 80. The absorbed doses of red bone marrow and bone surface, 17 and 21 mGy MBq(-1) calculated by GSF parameters, and 7.1 and 8.8 mGy MBq(-1) by GSF-M parameters, are comparable to the clinical results of 3-19 mGy MBq(-1) for bone marrow and 16 mGy MBq(-1) for bone surface. Based on the GSF-M model, the absorbed dose of (89)Sr to
metastases was estimated to be 434 mGy MBq(-1). The
strontium clearance half-life of 0.25 h from the plasma obtained in the present study is obviously faster than the value of 1.1 h recommended by ICRP. There are no significant changes for ingestion dose coefficients of (90)Sr using different model parameters. A model including the
metastases was particularly developed for dose estimation of (89)Sr treatment for the
pain of bone
metastases.