Variability and inhomogeneity of radon progeny deposition patterns in human bronchial airways

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 the biological variability of the lung structure, and (ii) the local distribution of nuclides deposited within a given airway bifurcation resulting from the inhomogeneity of flow patterns and associated deposition mechanisms. Because of the stochastic nature of particle transport within the lungs in general, and within airway bifurcations in particular, this variability can be described mathematically by stochastic models. In addition to average values, stochastic models also provide information about the statistical distributions of nuclide deposition patterns, reflecting intra- and inter-subject variability in radon progeny deposition.