The inherent variability of morphological and physiological lung parameters
can cause significant statistical variations in the deposition patterns of
inhaled radon progeny in the human lungs. From a dosimetric point of view,
the two major sources of variability are (i) the statistical distribution
of nuclides deposited among all airways in a given generation, caused by th
e biological variability of the lung structure, and (ii) the local distribu
tion of nuclides deposited within a given airway bifurcation resulting from
the inhomogeneity of flow patterns and associated deposition mechanisms. B
ecause of the stochastic nature of particle transport within the lungs in g
eneral, and within airway bifurcations in particular, this variability can
be described mathematically by stochastic models. In addition to average va
lues, stochastic models also provide information about the statistical dist
ributions of nuclide deposition patterns, reflecting intra- and inter-subje
ct variability in radon progeny deposition. (C) 2000 Elsevier Science Ltd.
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