DESCRIPTION OF PULMONARY DEPOSITION OF RADIOLABELED AEROSOL BY AIRWAYGENERATION USING A CONCEPTUAL 3-DIMENSIONAL MODEL OF LUNG MORPHOLOGY

Multi-modality medical imaging enables measurement of the three dimens ional spatial distribution of a radiolabeled aerosol within the lung ( Perring et al, 1994). A method is described for converting this inform ation to distribution by airway generation number. The deposition data were first transformed to a hemispherical shape based on the fraction al radial distance of each point in the lung from the centre of the lu ng to the corresponding extrapolated point on the periphery. A concept ual three dimensional hemispherical model of the spatial distribution of the airway network was then constructed based on the airway dimensi ons of the Weibel model and measurements of lung size and density dist ribution from computed tomography and magnetic resonance imaging. This then allowed description of the radiolabeled deposition data in the d ifferent airway generations. The principles of this process and an exa mple of its application to the measured 3D distribution of radiolabele d aerosol in a human subject are described. The potential applications of the technique in the validation of the results of deposition model ing and in clinical aerosol inhalation therapy are discussed.