| Objective:To establish a visual three-dimensional reconstruction model of fine pharyngeal recess anatomical structure in normal adult Chinese,to obtain the detailed physical morphological parameters of the pharyngeal recess by measuring,to study the distribution characteristics of the pharyngeal recess in normal adults by using computer fluid mechanics?CFD?,to reveal the anatomical factors of the prone site of nasopharyngeal carcinoma from the point of view of airflow dynamics,and to study the pathogenesis of nasopharyngeal carcinoma from the aspect of structural function.Based on the above research platform,by comparing airflow field parameters of normal pharyngeal recess with simulated different sizes of space occupation in unilateral pharyngeal recess,to quantitative analysis the changes of nasal respiratory airflow before and after cancer and the influence of tumor volume on ventilation function.And to establish a three-dimensional model of nasal cavity,nasopharyngeal cavity and pharyngeal recess in nasopharyngeal carcinoma patients with different primary unilateral pharyngeal recess involvement,the numerical results obtained under the same experimental conditions are used for verification,to provide a new research approach for the early clinical diagnosis of nasopharyngeal carcinoma,with a view to provide a reference for the follow-up early intervention and guidance of clinical individualized precise treatment.Methods:Four normal adult Chinese and three patients with nasopharyngeal carcinoma originating from unilateral pharyngeal recess diagnosed by pathology but untreated were selected to obtain corresponding imaging data through CBCT scan of maxillofacial region,and import them into the medical image processing software Mimics20.0 for three-dimensional reconstruction of nasal cavity,nasopharynx cavity and pharyngeal recess.Reverse engineering software Geomagic Studio 12.0 was used to optimize the preliminary reconstructed 3D model,including smoothing,creating curved patches,constructing grids,and fitting curved surfaces,and separately dividing the pharyngeal recess for physical measurement.Then,import the complete 3D numerical model into the mechanical software ANSYS 15.0 for mesh generation,finite element calculation and data analysis.The distribution characteristics of normal pharyngeal recess were analyzed by pressure,velocity,flow trajectory,wall shear stress and other parameters.In order to exclude the differences of individual nasal cavity,the three-dimensional model of unilateral pharyngeal recess occupying 1 cm3,5cm3and 10cm3was simulated on the basis of pharyngeal recess structure of one normal person,and all numerical simulations were carried out under the same experimental conditions,and the distribution parameters of the air flow field were compared with those of normal subjects;then the simulated space occupying numerical results are compared with the real nasopharyngeal carcinoma patient air flow field distribution rule.Results:?1?In this study,the 3d structural parameters of eleven normal pharyngeal recess were measured as follows:caliber:4.34±1.48mm,inner diameter:11.39±1.82mm,thickness:4.84±1.03mm,height:21.30±2.35mm,its volume of air cavity:825.71±319.78 mm3,that is 0.83±0.32ml,and the accuracy is 0.01.?2?Under steady-state breathing conditions with a constant ventilation volume of 500ml/s,the total nasal resistance range of 4 normal adults measured was 0.102?0.17Pa·s·ml-1.Whether inhaled or exhaled,the maximum values of pressure gradient,air flow velocity and wall shear force are all located in the nasal threshold;compared with other parts of the nasopharyngeal cavity,the local pressure of the pharyngeal recess is lager,and the low velocity vortex state in the fossa is opposite to the flow direction of the main airflow,with average velocity is 1.24m/s,and the shear stress at the bottom wall of pharyngeal recess is relatively high,followed by the posterior wall of the nasopharynx,with values of 0.58±0.2Pa and 0.31±0.2Pa,respectively.?3?The parameters of simulated unilateral pharyngeal recess occupying 1cm3,5cm3,10cm3compared with normal human pharyngeal recess airflow field show:When the space occupation was confined to the pharyngeal recess only,whether inhaling or exhaling,the total nasal resistance value is slightly smaller than that of the normal person,the airflow velocity and wall shear stress at the affected area were larger than those in the normal person,and the affected area showed a faster laminar flow,and there was no significant change in the unaffected pharyngeal recess;With the increase of space occupying volume,the total nasal resistance,airflow velocity and wall shear stress in the affected part all increased gradually,while the airflow velocity and wall shear stress on the affected side increased compared with that on the healthy side.?4?The results of airflow field in primary unilateral pharyngeal recess nasopharyngeal carcinoma patients show:When unilateral pharyngeal recess becomes shallow,the total nasal resistance is 0.042pa·s·ml-1,airflow velocity and wall shear stress around tumor on the affected side were higher than that on the healthy side of pharyngeal recess,and the airflow on the affected side was laminar flow with higher velocity,while the flow in the healthy side of pharyngeal recess was still low velocity vortex.With the increase of tumor volume and affected range,there was no significant change in the pharyngeal recess on the healthy side,while airflow velocity and wall shear stress on the affected side increased,and the total nasal resistance increased significantly in the expiratory phase.Conclusion:?1?The visualized three-dimensional reconstruction model of fine pharyngeal recess anatomical structure in normal Chinese was established,and the detailed physical morphological parameters of pharyngeal recess structure were obtained,providing data reference for quantitative anatomical study of pharyngeal recess.?2?Using CFD to study the characteristics of the airflow field in the pharyngeal recess, from the analysis of total nasal resistance,intra-fossa pressure,low-velocity eddy current form,wall shear force distribution,etc.When harmful particles,bacteria,or EB virus are deposited and repeatedly rubbed the epithelium of the fossa,and effective self-cleaning and irrigating intervention cannot be obtained in the pharyngeal recess,long-term local harmful substance stimulation can cause tissue damage and malignant transformation.From the biomechanical point of view,there is a certain correlation between the characteristics of airflow field in pharyngeal recess structure and the occurrence of nasopharyngeal carcinoma,which opens a new path for the study of the pathogenesis of nasopharyngeal carcinoma.?3?Through numerical simulation of unilateral pharyngeal recess occupied by different size tissues,compared with normal human pharyngeal recess airflow field parameters,quantitative analysis of the early pathological changes of nasopharyngeal carcinoma limited in pharyngeal recess,its concealment and absence of obstruction of nasal ventilation are the important reasons for the low clinical consultation rate.With the increase of tumor volume,the nasopharyngeal airflow field gradually changes.?4?For the first time,a three-dimensional reconstruction model of nasal cavity,nasopharyngeal cavity and pharyngeal recess was established in nasopharyngeal carcinoma patients with different range primary unilateral pharyngeal recess involvement,and the airflow distribution law obtained under the same experimental conditions was similar to the above simulation results,providing a new research approach for early diagnosis and prevention of clinical nasopharyngeal carcinoma. |
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