A biokinetic model for systemic technetium in adult humans.

This paper reviews biokinetic data for technetium and proposes a biokinetic model for systemic technetium in adult humans. The development of parameter values focuses on data for pertechnetate TcO(-)(4) the most commonly encountered form of technetium and the form expected to be present in body fluids. The model is intended as a default model for occupational or environmental intake of technetium, i.e. applicable in the absence of form- or site-specific information. Tissues depicted explicitly in the model include thyroid, salivary glands, stomach wall, right colon wall, liver, kidneys, and bone. Compared with the ICRP's current biokinetic model for occupational or environmental intake of technetium (ICRP 1993, 1994), the proposed model provides a more detailed and biologically realistic description of the systemic behaviour of technetium and is based on a broader set of experimental and medical data. For acute input of (99m)Tc (T(1/2) = 6.02 h) to blood, the ratios of cumulative (time-integrated) activity predicted by the current ICRP model to that predicted by the proposed model range from 0.4-7 for systemic regions addressed explicitly in both models. For acute input of (99)Tc (T(1/2) = 2.1 × 10(5) year) to blood, the corresponding ratios range from 0.2-30.