Sharif Digital Repository

An acinus is defined as the complex of airways supplied by one first order respiratory or transitional bronchiole. In this part, the replenishment of oxygen at the alveolar surface occurs by a combination of convective air flow with diffusion of oxygen in the air. So for studying gas exchange in the lung, modeling gas species transport and exchange in an acinus is important. Due to lacking direct measurements of the distribution of oxygen (or carbon dioxide) concentration in the acinus, several mathematical models have been developed and studied by numerical simulations. But in none of them the influence of breathing pattern and the role of blood flow in restricting the gas exchange rate have... 

In respiratory system of live bodies, different mechanical phenomena such as air suction, diffusion and deposition of particles and transport of species between air and blood take place. Furthermore, the geometry of lung is a complex and multi scale geometry. In order to reduce these complexities, the acinus behavior is transformed to numerical functions which can be used as boundary conditions for simulating upper generations of the lung. Hence, in current study, the air flow suction of the lung is described as a function of the mechanical properties of the lung tissue. This task is fulfilled by modeling the flow for different Elastic moduli and taking fluid structure interaction into... 

In this work, a new methodology for modeling the whole lung using porous media is presented. Dealing with the details of the proposed method establishes the need for some tools. Proposed method combines data extraction from lung images to identify large airways, porosity and porous region boundaries. Combining some sequential images, change in properties with time could be obtained. To obtain behavior of this porous media with respect to flow, a method based on the classification of bifurcations and gas exchange areas and pore scale modeling of these classes is proposed. All these require a specifically designed numerical tool. Development of this tool is the subject of the next parts of... 

An anatomically accurate model of conducting airways is essential for adequately simulating gas mixing and fluid distribution. In the current study, Lindenmayer systems (L-systems) as a type of graph grammars method has been formulated to generate bronchial tree structure in human lung. It has been considered that the structure of bronchial tree is divided into two main parts: 1) The central airways (from the trachea to segmental bronchi); and 2) the dichotomous branching structure (from segmental bronchi to alveolar duct). Nine parametric rewriting rules incorporating within physiological laws of the airway branching are used to generate each parts of the bronchial tree. Comparison of the... 

Particle retention and clearance is a major concern in the treatment of pulmonary diseases. Inhaled materials into the nasal and lung airways include gases/vapors, liquid droplets and soluble/insoluble particulate matter which can be toxic or therapeutic (or both). For example, nanoparticles (NPs), as part of nanomedicine, are now being used as drug carriers for passive and active targeting of solid tumors and inflamed tissue. However, natural and especially manmade NPs can also be harmful, such as carbon nanotubes (CNTs), asbestos fibers and ambient toxic pollutants, based on epidemiological and pathological studies of occupational and environmental exposures. In fact, ultrafine particles... 

The bronchial tree consists of two main parts: conducting airways and respiratory airways. Parametric Lindenmayer System (L-System) has been used for modeling of the structure. The conducting airways are divided into two parts: central region consisting of trachea up to segmental bronchi and bronchioles located in the bronchopulmonary segments. The boundary of these segments has been found by image processing techniques. Stochastic Parametric L-system has been used for modeling of acinar region. To find the characteristic properties of conducting airways and respiratory bronchioles, an intelligent method has been developed. The parameters of the model are either age dependent or...