Three-Dimensional Description of Pulmonary Deposition of Inhaled Aerosol Using Data from Multimodality Imaging

Three-dimensional assessment of pulmonary deposition of inhaled aerosol may be performed using SPECT. Trie use of aligned anatomical images enables improved accuracy of quantification and anatomical localization of deposition. Methods: Techniques of analyzing these data and their application to deposition studies of two nebulizer-generated aerosols (mass median diameters 1.5 and 6.5 μm, respectively) in 12 normal subjects are described. The deposition data were transformed to a standard hemispherical shape and the mean distribution pattern for each aerosol evaluated. Deposition by airway generation was then calculated using a spatial model of airway morphology. The results were compared to those from planar image analysis. Results: The hemispherical transform yielded considerably more qualitative information on deposition pattern. The central-to-peripheral concentration ratio between conducting and alveolated airways was 5.27 for the coarser aerosol and 2.43 for the fine. The two-dimensional spatial estimates of the ratio were 2.61 and 2.03 respectively. Conclusion: Analysis of multimodality imaging data considerably enhanced information on deposition compared to planar imaging. It provides new data on aerosol deposition which will be of value to physicians involved in drug inhalation therapy.