Research On 3D Modeling Of Lower Respiratory Tract And Its Hydrodynamic Characteristics

Respiratory structural disease is one of the basic structural changes of chronic respiratory diseases.Lung function and CT were used to evaluate the changes of respiratory structure and function in clinic.However,the deficiency lies in the separation of function and image,which can not directly indicate the relationship between image structural changes and lung function.Modeling the airway based on 3D high-definition CT images can directly see the threedimensional structure of the airway,while computational fluid dynamics(CFD)can further simulate the breathing process based on the three-dimensional airway model,and study the relationship between the airway structure and airflow changes.Thus,the changes of airway structure and lung function were associated.In this study,three-dimensional reconstruction of airway based on threedimensional CT was used to obtain the three-dimensional model of airway in specific patients,and the changes of airway hydrodynamic characteristics were studied based on the three-dimensional model of airway.The main research contents are as follows(1)The difference of image data between COPD patients and normal volunteers was analyzed based on CT three-dimensional modeling method.In this paper,the original DICOM data of inspiratory phase high-resolution CT in 5 normal subjects and 7 COPD patients were used for three-dimensional reconstruction of airway,lung and low-density area of lung.The parameters of airway cross-sectional area,lung volume and low-density area of lung were collected for statistical analysis.The study found that there was significant difference in the mean value of Sin/Sout、V/Sout and(V-Vl)/Sout between the COPD group and the normal group(P<0.05).And there was a significant negative correlation between the ratio and pulmonary function parameters such as FEV1%.(2)Based on the three-dimensional airway models of 5 normal subjects and 7 COPD patients,the difference of flow field between COPD patients and normal subjects was analyzed.The study found that under the same conditions,the static pressure difference of COPD group was significantly higher than that of normal group,while the dynamic pressure difference was lower than that of normal group.It was found that the reduction of peripheral airway in COPD patients resulted in the increase of static pressure difference,while the conservation of total airway pressure resulted in the decrease of dynamic pressure difference.This is consistent with the characteristics of increased airway resistance and airway obstruction in COPD patients.(3)Inhalation of drugs is one of the main means of continuous treatment for various chronic respiratory diseases in stable stage.In this study,the deposition and distribution of 2-8 μm inhaled particles in the real airway under three groups of different respiratory states were studied by using the DPM model.The results show that the deposition of particles is related to the inertia of particles,turbulent expansion and secondary flow.Therefore,the deposition mainly occurred on the lateral side of the airway curvature,the inner surface of the bifurcated ridge and the inner surface near the bifurcated ridge,and the annular groove formed by the compression of the airway cartilage ring.Turbulence makes the distribution of particles more uniform in the airway,but the effect of turbulence decreases with the increase of particle size.Large diameter particles are mainly deposited on the lower surface of the airway due to inertial force.