Description of Pulmonary Deposition of Radiolabeled Aerosol by Airway Generation Using a Conceptual Three Dimensional Model of Lung Morphology

Multi-modality medical imaging enables measurement of the three dimensional spatial distribution of a radiolabeled aerosol within the lung (Perring et al, 1994) A method is described for converting this information to distribution by airway generation number. The deposition data were first transformed to a hemispherical shape based on the fractional radial distance of each point in the lung from the centre of the lung to the corresponding extrapolated point on the periphery. A conceptual three dimensional hemispherical model of the spatial distribution of the airway network was then constructed based on the airway dimensions of the Weibel model (Weibel, 1991) and measurements of lung size and density distribution from computed tomography and magnetic resonance imaging. This then allowed description of the radiolabeled deposition data in the different airway generations. The principles of this process and an example of its application to the measured 3D distribution of radiolabeled aerosol in a human subject are described. The potential applications of the technique in the validation of the results of deposition modelling and in clinical aerosol inhalation therapy are discussed.