title: Creation of an idealized nasopharynx geometry for accurate computational fluid dynamics simulations of nasal airflow in patient-specific models lacking the nasopharynx anatomy.
abstract: Virtual surgery planning based on computational fluid dynamics (CFD) simulations has the potential to improve surgical outcomes for nasal airway obstruction patients, but the benefits of virtual surgery planning must outweigh the risks of radiation exposure. Cone beam computed tomography (CT) scans represent an attractive imaging modality for virtual surgery planning due to lower costs and lower radiation exposures compared with conventional CT scans. However, to minimize the radiation exposure, the cone beam CT sinusitis protocol sometimes images only the nasal cavity, excluding the nasopharynx. The goal of this study was to develop an idealized nasopharynx geometry for accurate representation of outlet boundary conditions when the nasopharynx geometry is unavailable. Anatomically accurate models of the nasopharynx created from 30 CT scans were intersected with planes rotated at different angles to obtain an average geometry. Cross sections of the idealized nasopharynx were approximated as ellipses with cross-sectional areas and aspect ratios equal to the average in the actual patient-specific models. CFD simulations were performed to investigate whether nasal airflow patterns were affected when the CT-based nasopharynx was replaced by the idealized nasopharynx in 10 nasal airway obstruction patients. Despite the simple form of the idealized geometry, all biophysical variables (nasal resistance, airflow rate, and heat fluxes) were very similar in the idealized vs patient-specific models. The results confirmed the expectation that the nasopharynx geometry has a minimal effect in the nasal airflow patterns during inspiration. The idealized nasopharynx geometry will be useful in future CFD studies of nasal airflow based on medical images that exclude the nasopharynx.
authors.affiliation: Department of Otolaryngology and Communication Sciences, Medical College of Wisconsin, Milwaukee, WI, USA.|Biotechnology and Bioengineering Center, Medical College of Wisconsin, Milwaukee, WI, USA.
authors.forename: Azadeh
authors.initials: A
authors.lastname: A T Borojeni
authors.affiliation: Division of Head and Neck Surgery and Communication Sciences, Duke University Medical Center, Durham, NC, USA.|Computational Biology and Bioinformatics Program, Duke University, Durham, NC, USA.
authors.forename: Dennis O
authors.initials: DO
authors.lastname: Frank-Ito
authors.affiliation: Department of Otolaryngology/Head and Neck Surgery, University of North Carolina School of Medicine, Chapel Hill, NC, USA.
authors.forename: Julia S
authors.initials: JS
authors.lastname: Kimbell
authors.affiliation: Department of Otolaryngology and Communication Sciences, Medical College of Wisconsin, Milwaukee, WI, USA.
authors.forename: John S
authors.initials: JS
authors.lastname: Rhee
authors.affiliation: Department of Otolaryngology and Communication Sciences, Medical College of Wisconsin, Milwaukee, WI, USA.|Biotechnology and Bioengineering Center, Medical College of Wisconsin, Milwaukee, WI, USA.
authors.forename: Guilherme J M
authors.initials: GJM
authors.lastname: Garcia
mesh_terms: D003198:Computer Simulation; D006801:Humans; D057446:Hydrodynamics; D009296:Nasal Cavity / Q000033:anatomy & histology / Q000502:physiology / Q000601:surgery; D015508:Nasal Obstruction / Q000503:physiopathology / Q000601:surgery; D009305:Nasopharynx / Q000033:anatomy & histology* / Q000502:physiology / Q000601:surgery; D009666:Nose / Q000033:anatomy & histology / Q000502:physiology* / Q000601:surgery; D012119:Respiration
keywords: computational fluid dynamics (CFD); idealized nasopharynx; nasal airway obstruction; nasal resistance; nasal surgery; patient-specific numerical simulation