Image-Based Morphometry and Airflow Simulation in Rat Lungs

Detailed knowledge of the fate of aerosols in the lung is essential in understanding the effect of exposure to airborne particulate matter and infectious agents and in assessing the efficiency of inhaled drug therapy. Detailed, yet non-invasive, studies of peripheral aerosol deposition are almost impossible in humans. Thus, understanding the fate of aerosols in the lung requires the use of computational and/or animal models in which more invasive techniques can be used. In this study, using magnetic resonance (MR) images of rat lungs, we (1) built three dimensional (3D) models of the airway tree and (2) quantified lobar volumes. Flow simulations were then performed in one of the airway models. Flow conditions were set to be similar to that used in an experimental study where rats were exposed to aerosols [1]. Airflow boundary conditions at the outlets of the airways are unknown and therefore typically a zero pressure boundary condition is prescribed [2]. To test the validity of the zero pressure condition, two types of boundary conditions were described: (a) zero pressure at each of the outlets and (b) flow resistance at each outlet. Flow resistance allows for the flow rate distribution to be defined based on lung volume and airway cross sectional area. The flow results from the computational model may be used to solve the particle dynamics equation and therefore allow for future comparison with the ventilation experiments.