The Reconstruction Of Three Dimensional Models Of Pharyngeal Cavity And Study On Biomechanical Properties

The pharyngeal cavity is one of the organs for the gas exchange between human body and environment. The pharyngeal cavity and the nose cavity, the throat constitute upper respiratory tract, it is portal of human respiratory system. The pharyngeal cavity biomechanics model establishment is in the human body biomechanics model one of the most important tasks. Obstructive Sleep Apnea-Hypopnea Syndrome (OSAHS) has been realized that the periodic intermittent cessations of breathing or reductions in airflow resulted from OSAHS is closely related to the developed pathological change in shape of pharyngeal cavity of the patients. The abnormal structure of pharyngeal cavity and the anatomical change of the pharyngeal cavity may lead to many diseases, among which the DNS is regular and is widely found in the world. But because of the lack of proper biomechanical model and its numerical description for the course of adaptation, it is difficult to deeply explor and explains this process.In this paper, airflow distribution in pharyngeal cavity was investigated based on 3-dimensional reconstruction model to try to find the correlation between the pharyngeal cavity structure and the airflow characters. Knowledge of airflow in human pharyngeal is important for understanding many aspects of the biology and pathology in the respiratory tract. Through this research, we can more profoundly explore the outbreak, treatment and prevention of nasal diseases.Based on CT medical images of ten volunteers, the 3D FE model of the upper airway was reconstructed by using the method of surface rendering. The reconstruction three-dimensional models precisely preserve original configuration of upper airways. From the results of the numerical simulation, the airflow distribution in the whole cavity in the course of respiration can be obtained. The accuracy of reconstructed model in geometry structure was proved by acoustic rhinometry test, since it can quantify upper airway condition by drawing a graph plotting the distance vs. the cross-sectional area witch is corresponds to the typical anatomic structures of human upper airway.Numerical simulation was performed for the airflow in those pharyngeal cavities using the FEM and FVM. It is comparatively true that the established model reflect s t he real anatomical configuration. The Computed result obtained with the FEM was similar to the computed result obtained with the FVM. From the results of the numerical simulation, the airflow distribution in the pharyngeal cavity in the course of inspiration was obtained. Based on the data which came from the spiral computerized tomography images of the healthy person and patient with Obstructive Sleep Apnea-Hypopnea Syndrome (OSAHS), the three-dimensional models of upper airway cavity were reconstructed by the method of surface rendering. From the results of the numerical simulation, the airflow distribution uniformity in the health pharyngeal cavity and higher pressure difference and velocity gradient in the OSAHS patient was obtained.The surface reconstruction is adopted to build a three-dimensional finite element model in the upper airway and the soft palate for a healthy person and an OSAHS patient, respectively. The FE model correctly preserves anatomical configurations of the upper airway and the soft palate thus can be applied to compute the interaction of fluid-structure. With the result comparison between the healthy person and the OSAHS patient, it is found out that the pressure difference between the front and back of the airway is lower in the healthy person; the airflow distribution is uniform with free breath. However, the soft palate of the OSAHS patient is hypertrophic and the airflow channel around the soft palate is narrow with rapid increase in pressure and velocity gradients during the breathing. This leads to the resistance incensement in the airflow channels of the upper airway. On the other hand, higher pressure difference and velocity gradient of the airflow field not only excite larger displacement of the soft palate but also induce decreasing inner pressure as well as increasing transmural pressure in the upper airway.The mechanical properties of the soft palate, tongue and adenoid s were tested by experiments. The experimental data was analyzed, and the choosing of material parameter was reasonable in the Fluid-structure interaction study between airflow and soft palate.The main contributions were summarized and further works were suggested at the end of this dissertation.The research work in this paper is a part of National Natural Science foundation of China (fund number: 10472025; 10672036) and Natural Science Foundation of Liaoning Province, China (fund number: 20032109).