Human lung morphology models for particle deposition studies

Knowledge of human lung morphology is of paramount importance in calculatin g deposition patterns of inhaled particulate matter (PM) to be used in the definition of ambient air quality standards. Due to the inherently complex nature of the branching structure of the airway network, practical assumpti ons must be made for modeling purposes. The most commonly used mathematical models reported in the literature that describe PM deposition use Weibel's model A morphology. This assumes the airways of the lung to be a symmetric , dichotomously branching system. However, computer simulations of this mod el, when compared to scintigraphy images, have shown it to lack physiologic al realism (Martonen et al., 1994a). Therefore, a more physiologically real istic model of the lung is needed to improve the current PM dosimetry model s Herein a morphological model is presented that is based on laboratory dat a from planar gamma camera and single-photon emission computed tomography ( SPECT) images. Key elements of this model include: The parenchymal wall of the lung is defined in mathematical terms, the whole lung is divided into d istinct left and right components, a set of branching angles is derived fro m experimental measurements, and the branching network is confined within t he discrete left and right components (i.e., there is no overlapping of air ways). In future work, this new more physiologically realistic morphologica l model can be used to calculate PM deposition patterns for risk assessment protocols.