Dosimetry of inhaled 219Rn progeny

Abstract

During prostate cancer treatment with 223Ra. 219Rn (actinon) occurs and may be exhaled by the patient. Nurses and other hospital employees may inhale this radionuclide and its decay products. The alpha-emitting decay products of actinon deposited within a body will irradiate tissues and organs. Therefore. it is necessary to evaluate organ doses of actinon progeny. The purpose of this study is to set up a dosimetric method to assess dose coefficients for actinon progeny. The effective dose coefficients were calculated separately for three modes. The unattached mode which concerned the activity median thermodynamic diameter (AMTD) of 1 nm. and the nucleation and accumulation modes which are represented by activity median aerodynamic diameters (AMAD) of 60 and 500 nm respectively. The recent biokinetic models of actinon progeny developed in the Occupational Intakes of Radionuclides (OIR) publications series of the International Commission of Radiological Protection (ICRP) were implemented on BIOKMOD (Biokinetic Modeling) to calculate the number of nuclear transformations per activity intake of actinon progeny. The organ equivalent and effective dose coefficients were determined using the dosimetric approach of the ICRP. The inhalation dose coefficients of actinon progeny are dominated by the contribution of lung dose. The calculated dose coefficients of 211Pb and 211Bi are 5.78 × 10-8 and 4.84 × 10-9 Sv.Bq-1 for unattached particles (AMTD = 1 nm). and 1.4 × 10-8 and 3.55 × 10-9 Sv.Bq-1 for attached particles (AMAD = 60 nm). and 7.37 × 10-9 and 1.91 × 10-9 Sv.Bq-1 for attached particles (AMAD = 500 nm). These values are much closer to those of the recently published ICRP 137.

Keywords: 211Bi; 211Pb; actinon; biokinetic models; dose coefficient; dosimetric models; inhalation.