| The structure of human tissue is closely related to the normal physiological function of it,the anatomy of the nose and nasopharynx is fine and complex,the conventional examination methods are often limited to different degrees in terms of applicability and observation ability.The most important physiological function of the nose is the passage of respiratory airflow.Therefore,whether the distribution characteristics of airflow field through the nose and nasopharyngeal cavity is one of the inducing factors leading to the occurrence and development of diseases in this part is a new issue that modern scholars have paid attention to.In this paper,a biomechanical numerical model of the structure of the nasal and nasopharyngeal cavity was established,and the mechanical-related calculation and analysis were carried out on this model,aiming to explore the etiology and pathogenesis of the disease in this region from the perspective of biomechanics,and to provide some reference for the selection of clinical treatment schemes for the nasopharyngeal space-occupying lesions.This paper mainly includes the following two parts:1.The biomechanics study on nasal and nasopharynx numerical model then analyze the correlation between the architectural feature and the occurrence of nasopharyngeal carcinomaObjective:To build the biomechanics numerical model of normal people's nasal and pharyngonasal cavity,use the methord of hydromechanical,analysis the characteristic of the flow field,then to analysis the correlation between the unique airflow dynamics characteristics in pharyngeal recess and the occurrence and development of nasopharyngeal carcinoma,may make a new breakthrough in the study of the etiology and pathogenesis of nasopharyngeal carcinoma from the perspective of biomechanics,and then acquire the clinical application value of “early precaution ? early intervention ? early treatment”for the nasopharyngeal carcinoma "vulnerable" groups such as EBV masculine?clear and definite family history and so on.Methods:1.CT scan data of nasal and nasopharyngeal cavity in healthy adult male with pharyngeal recess open were collected.The scanning range was from the bottom of middle cranial fossa to the most tip plane of uvula.2.Then imported the data into Mimics 20.0 software,according to the different gray values corresponding to the different tissue densities of human body,we used the software to remove the irrelevant areas,builded the model of nasal and pharyngonasal cavity,obtained the Binary STL formatted file.3.Imported the STL format file into Geomagic studio 12.0 software to smooth the reconstructed model and repair the irregular area,after denoising and surface partitioning,a complete 3-d model of the smooth surface saved in iges format will be obtained.4.Divided the obtained model into volume grid and surface grid,and imported them into ANSYS workbench for numerical simulation and analysis of airflow field.Results:1.The pressure in the nasal and nasopharyngeal airway was gradually decreased from the anterior nostril to the nasopharynx in the inspiratory phase,while in the exhalation phase it was on the contrary,the pressure drop between the anterior nostril and the nasopharynx was about 140 Pa,the pressure gradient was greater in nasal threshold region and the front part of inferior nasal concha than the other parts of the nasal cavity,accounting for 46% and 25% of the total pressure gradient of the airway;the pressure gradient distribution in nasopharyngeal cavity was greatest in the pharyngeal recess mouth,then in the posterior wall of nasopharyngeal roof,and then in the lower part of nasopharynx,accounting for 55%?30% and 15% of the total pressure gradient in nasopharynx.2.During the whole respiratory process,obvious low flow rate areas were continuously observed at the open part of pharyngeal recess and the top part of the nasopharynx,with the flow rates about 1.1m/s and 1.5m/s,The relatively low flow rate and eddy current resulted in that the particles carried in the airflow were not easy to be discharged with respiration and deposit locally.3.Whether inspiratory or expiratory phase,the “triadius entrance” formed by pharyngonasal cavity and both sides of the open part of pharyngeal recess persist exist existed whirlpool,result in the rate of deposition of unhealthy particle increased obviously,the unhealthy stimulation may cause the normal local tissue cells abnormal hyperplasia and metaplasia then eventually lead to the occurrence of tumor.Conclusion:1.The finite element biomechanical numerical model of nasal and nasopharyngeal cavity based on multi-slice spiral CT images has high authenticity and accuracy,established by the method of finite element numerical simulation of nasal and nasopharyngeal numerical model,analyzed the airflow field characteristics,found that the open part of pharyngeal recess and the top part of the nasopharynx a persistent low velocity and eddy current.2.Continuous abnormal stimulation will lead to normal epithelial structure turn into epithelial abnormal hyperplasia or even metaplasia then complete canceration.In the process of human respiration,there is a continuous low flow rate and eddy current around the open part of pharyngeal recess and the top part of the nasopharynx,which makes it easy for the particles of undesirable stimulant to deposit there,which is an important factor leading to the occurrence of tumors in the population "susceptible" to nasopharyngeal cancer.2.Numerical modeling the influence of nasopharyngeal occupying lesions on the opening function of eustachian tubeObjective:To establish the finite element numerical model of healthy people nasal and nasopharyngeal cavity containing the eustachian tube structure,simulate eustachian tube dysfunction caused by different level of space-occupying lesions in nasopharynx,analyze the pathogenesis of eustachian tube dysfunction caused by occupying lesions in nasopharynx from the perspective of biomechanics,in order to provide some reference for prevention or intervention of the disease and the selection of treatment.Methods:This part also used the first part of study materials,established the biomechanics numerical model of nasal and nasopharyngeal containing the eustachian tube structure(modeling method is the same as part 1),imported the result into ANSYS workbench for numerical simulation,then analyzed the influence of the movement of eustachian cushion and the eustachian tube opening function caused by space-occupying lesions in pharyngeal recess.Results:1.Under the 0.1N traction value of the eustachian cushion muscle,with the change of time,the displacement of the edge of eustachian cushion presented the development law of weibull distribution: the maximum displacement increased gradually at first,and the maximum value of it appeared at t=5ms,about 1.1mm;then it gradually decayed,the displacement data was close to 0mm from t=10ms to t=20ms.2.Relative to the normal muscle traction effect,under 30% tumor resistance,the maximum displacement at the edge of eustachian cushion was about 0.88 mm,and the peak value was about 20% lower;the maximum displacement at the stress place of the eustachian cushion was about0.38 mm,and the peak value was about 24% lower;under 50% tumor resistance,the maximum displacement at the edge of eustachian cushion was about 0.65 mm,and the peak value was about 41% lower,the maximum displacement at the stress place of the eustachian cushion was about 0.30 mm,and the peak value was about 40% lower;under 100% tumor resistance,the maximum displacement at the edge of eustachian cushion was about 0.50 mm,and the peak value was about 55% lower,the maximum displacement at the stress place of the eustachian cushion was about 0.18 mm,and the peak value was about 64% lower;with the increase of tumor resistance,the fluctuation of the displacement curve of eustachian cushion became obvious;tumor in pharyngeal recess had a certain mechanical obstruction to eustachian cushion movement.Conclusion:1.The established biomechanical numerical models of the nasal and nasopharyngeal cavity containing the eustachian tube structure was with certain reliable data,which can reflect the pathogenesis of eustachian tube dysfunction caused by nasopharyngeal occupying lesions in nasopharynx from the perspective of biomechanics.2.The occupying lesions in pharyngeal recess may lead to limit the movement of the eustachian cushion,affect the opening of the eustachian tube,influence the eustachian tube's function of regulating middle ear pressure,then resulting in a series of related clinical symptoms of middle ear pressure imbalance.3.The clinical intervention of the occupying lesions in nasopharynx should give sufficient activity space for the eustachian cushion,in order to facilitate the recovery of the physiological function of the eustachian tube. |
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