Three-dimensional modeling and automatic analysis of the human nasal cavity and paranasal sinuses using the computational fluid dynamics method

Targeted drug delivery to the deviated regions of the human nasal cavities: An in silico investigation and in vitro validation

BACKGROUND AND OBJECTIVE

Delivering drugs to the deviated regions in patients with nasal septal deviation is vital for the treatment but challenging due to the complex shape of the nasal cavity and the intersubject variability in the nasal anatomies. While previous studies have focused on drug delivery to standard areas like the olfactory region, none have specifically looked at how drugs are deposited in the deviated regions. The current study numerically investigates six drug administration parameters aiming to control and maximize drug deposition in the deviated regions of the nasal cavity in three types of septal deviations.

METHODS

Three-dimensional models are created using CT scans from three patients, with S-shaped, C-shaped, and reverse C-shaped septal deviations, and the deviated regions are identified by the detailed slice-by-slice inspection method. Eulerian and Lagrangian simulations are performed for the fluid flow and drug delivery, incorporating all six drug administration parameter variations. Further, in-house experiments are performed on a three-dimensional printed transparent nasal cavity to validate the pressure drop and drug deposition patterns.

RESULTS

It is observed that increasing the spray half-cone angle decreases the targeted deposition in the C, reverse C, and left side of the S-shaped models. On the contrary, a wider half-cone angle (20°) and cone radius (2 mm) enhances targeted deposition on the right side of the S-shaped model. The ideal particle size range for all models is 10 to 16 µm. Lower initial particle velocities (1 m/s and 3 m/s) lead to maximum targeted deposition in the C and left side of the S-shaped models, while higher ones (14 m/s and 8m/s) enhance targeted deposition in the reverse C and right side of the S-shaped model, respectively. Optimized administration angles accurately direct particles to deviated regions, with patient-specific adjustments achieving better outcomes. Increased flow rates enhance both total and targeted depositions. Head orientation adjustments are effective for deviations in the middle and lower regions but have a limited impact when deviation presents in the anterior regions.

CONCLUSIONS

The study's findings help unveil the effective targeted drug delivery strategies, provide insights for the better design of the nasal spray device, and improve personalized treatment efficacy for patients with septal deviations.

Computational Modeling of Nasal Cavity Aerodynamics: Implications for Surgical Outcomes and Targeted Drug Administration

The primary goal of sinonasal surgery is to improve a patient's quality of life, which is generally achieved by enhancing drug delivery (eg, saline rinses, nasal steroids) and nasal airflow. Both drug delivery and nasal airflow are dependent on the anatomic structure of the sinonasal cavity and the relationship between this anatomy and airflow and drug delivery can be studied using computational fluid dynamics (CFD). CFD generally uses computed tomography scans and computational algorithms to predict airflow or drug delivery and can help us understand surgical outcomes and optimize drug delivery for patients. This study employs CFD to simulate nasal airflow dynamics and optimize drug delivery in the nasal cavity to highlight the utility of CFD for studying sinonasal disease. Utilizing COMSOL Multiphysics software, we developed detailed models to analyze changes in airflow characteristics before and after functional endoscopic sinus surgery, focusing on pressure distribution, velocity profiles, streamline patterns, and heat transfer. This research examines the impact of varying levels of nasal airway obstruction on airflow and heat transfer. In addition, we explore the characteristics of nasal drug delivery by simulating diverse spray parameters, including particle size, spray angle, and velocity. Our comprehensive approach allows for the visualization of drug particle trajectories and deposition patterns, providing crucial insights for enhancing surgical outcomes and improving targeted drug administration. By integrating patient-specific nasal cavity models and considering factors such as airway outlet pressure, this study offers valuable data on pressure cross-sections, flow rate variations, and particle behavior within the nasal passages. The findings of this research can be useful for both surgical planning and the development of more effective nasal drug delivery methods, potentially leading to enhanced clinical outcomes in respiratory treatment.

Characterization of anatomical variations of the nasal cavity in a subset of European patients and their impact on intranasal drug delivery

Anatomical 3D-printed nasal casts are valuable models to investigate intranasal drug deposition, providing preclinical data that cannot be obtained in animal models. However, these models are limited since they are often derived from a single patient or represent a mean of several groups. The present study aimed to better characterize the anatomical differences of the nasal cavity in a European sub-population and to assess the potential impact of anatomical variations on intranasal deposition by medical devices. Ninety-eight cranial computed tomography scans of patients were selected and analyzed in 2D and 3D conformations. They showed symmetry of cavities and a high level of heterogeneity of measurements, especially volume and area, in the population. Three anatomical groups with distinct nasal geometry were identified and 3D nasal casts of the most representative patient of each group were printed. Fluorescein was administered using three medical devices: a nasal spray, a sonic jet nebulizer and a prototype mesh-nebulizer. The deposition profiles were compared with the Aeronose® as a reference. Our results show that anatomical variations influenced the deposition profiles depending on the device, with a higher variation with spray and the mesh-nebulizer. This work emphasises the importance of anatomical parameters on drug intranasal deposition and the need to evaluate inhaled drugs on different 3D nasal casts reflecting the target population.

Imaging Nasal Obstruction: An Objective Evaluation for a Subjective Complaint

Nasal obstruction (NO) is a common clinical symptom characterized by a subjective sensation of insufficient airflow through the nasal cavity and may result from various factors, including changes in nasal anatomy, inflammatory conditions, tumoral lesions, and other etiologies. While a thorough medical history and physical examination can often identify its cause, imaging is usually necessary to fully understand the problem. Computed tomography (CT) is the primary imaging modality used to evaluate the nasal cavity and paranasal sinuses, allowing for the identification of potential causes and structural abnormalities. However, when soft tissue characterization is required, magnetic resonance imaging (MRI) is also useful. Understanding the anatomical and pathological basis of NO is crucial for accurate diagnosis and appropriate management. Imaging techniques provide valuable information for identifying the underlying causes of NO and guiding treatment decisions. This article reviews the normal anatomy of the nasal cavity and adjacent paranasal sinuses as well as the several conditions that may affect breathing comfort (tumors, inflammatory diseases, bony and cartilaginous anatomical variants, and "nonobstructive" mucosal thickenings), showing their normal presentation on CT and MRI.

Computational Rhinology: Unraveling Discrepancies between In Silico and In Vivo Nasal Airflow Assessments for Enhanced Clinical Decision Support

Computational rhinology is a specialized branch of biomechanics leveraging engineering techniques for mathematical modelling and simulation to complement the medical field of rhinology. Computational rhinology has already contributed significantly to advancing our understanding of the nasal function, including airflow patterns, mucosal cooling, particle deposition, and drug delivery, and is foreseen as a crucial element in, e.g., the development of virtual surgery as a clinical, patient-specific decision support tool. The current paper delves into the field of computational rhinology from a nasal airflow perspective, highlighting the use of computational fluid dynamics to enhance diagnostics and treatment of breathing disorders. This paper consists of three distinct parts-an introduction to and review of the field of computational rhinology, a review of the published literature on in vitro and in silico studies of nasal airflow, and the presentation and analysis of previously unpublished high-fidelity CFD simulation data of in silico rhinomanometry. While the two first parts of this paper summarize the current status and challenges in the application of computational tools in rhinology, the last part addresses the gross disagreement commonly observed when comparing in silico and in vivo rhinomanometry results. It is concluded that this discrepancy cannot readily be explained by CFD model deficiencies caused by poor choice of turbulence model, insufficient spatial or temporal resolution, or neglecting transient effects. Hence, alternative explanations such as nasal cavity compliance or drag effects due to nasal hair should be investigated.

Numerical analysis of the ostiomeatal complex aeration using the CFD method

We aimed to analyse ostiomeatal complex (OMC) aeration using the computational fluid dynamics (CFD) method of simulation based on human craniofacial computed tomography (CT) scans. The analysis was based on CT images of 2 patients: one with normal nose anatomy and one with nasal septal deviation (NSD). The Reynolds-Average Simulation approach and turbulence model based on linear eddy viscosity supplemented with the two-equation k-[Formula: see text] SST model were used for the CFD simulation. As a result, we found differences in airflow velocity through the ostiomeatal complex in patients with a normal nose and those with NSD. In a patient with NSD, the flow is turbulent in contrast to the normal nose (laminar flow). A faster (more intensive) airflow through the OMC was observed in the wider nasal cavity of the patient with NSD than on the narrower side. In addition, we want to emphasise the higher speed of airflow through the apex uncinate process area towards the ostiomeatal complex during exhalation, which, in the presence of secretions in the nose, predisposes to its easier penetration into the sinuses of the anterior group.

Accuracy of virtual rhinomanometry

Introduction: This paper describes the results of research aimed at developing a method of otolaryngological diagnosis based on computational fluid dynamics, which has been called Virtual Rhinomanometry.

Material and methods: Laboratory studies of airflows through a 3D printed model of nasal cavities based on computed tomography image analysis have been performed. The CFD results have been compared with those of an examination of airflow through nasal cavities (rhinomanometry) of a group of 25 patients.

Results: The possibilities of simplifying model geometry for CFD calculations have been described, the impact of CT image segmentation on geometric model accuracy and CFD simulation errors have been analysed, and recommendations for future research have been described.

Conclusions: The measurement uncertainty of the nasal cavities’ walls has a significant impact on CFD simulations. The CFD simulations better approximate RMM results of patients after anemization, as the influence of the nasal mucosa on airflow is then reduced. A minor change in the geometry of the nasal cavities (within the range of reconstruction errors by CT image segmentation) has a major impact on the results of CFD simulations.

Maxillary sinus aeration analysis using computational fluid dynamics

The maxillary sinus aeration using the computational fluid dynamics (CFD) method based on individual adult patients’ computed tomography (CT) scans were analyzed. The analysis was based on CT images of 4 patients: one with normal nose anatomy and three with nasal septal deviation (NSD) and concha bullosa (CB). The CFD simulation was performed using the Reynolds-Average Simulation approach and turbulence closure based on linear eddy viscosity supplemented with the two-equation k-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\omega$$\end{document}ω SST model. As a result, it was found that the lower part of NSD has the most significant impact on the airflow change within the maxillary sinuses compared to CB and the upper part of NSD. In a healthy nose, the airflow in the sinuses is continuous, while NSD and CB change this flow into pulsatile. Multiple changes in the direction of flow during one respiratory phase were observed. The flow intensity within the maxillary sinus opening is lower on the NSD side. The concept of vorticity measure is introduced to evaluate and compare various patients qualitatively. Typically, the lowest values of such measures are obtained for healthy airways and the highest for pathological changes in the nasal cavity.

The Role of 3D Printing in Planning Complex Medical Procedures and Training of Medical Professionals-Cross-Sectional Multispecialty Review

Medicine is a rapidly-evolving discipline, with progress picking up pace with each passing decade. This constant evolution results in the introduction of new tools and methods, which in turn occasionally leads to paradigm shifts across the affected medical fields. The following review attempts to showcase how 3D printing has begun to reshape and improve processes across various medical specialties and where it has the potential to make a significant impact. The current state-of-the-art, as well as real-life clinical applications of 3D printing, are reflected in the perspectives of specialists practicing in the selected disciplines, with a focus on pre-procedural planning, simulation (rehearsal) of non-routine procedures, and on medical education and training. A review of the latest multidisciplinary literature on the subject offers a general summary of the advances enabled by 3D printing. Numerous advantages and applications were found, such as gaining better insight into patient-specific anatomy, better pre-operative planning, mock simulated surgeries, simulation-based training and education, development of surgical guides and other tools, patient-specific implants, bioprinted organs or structures, and counseling of patients. It was evident that pre-procedural planning and rehearsing of unusual or difficult procedures and training of medical professionals in these procedures are extremely useful and transformative.

Research Active Posterior Rhinomanometry Tomography Method for Nasal Breathing Determining Violations

This study analyzes the existing methods for studying nasal breathing. The aspects of verifying the results of rhinomanometric diagnostics according to the data of spiral computed tomography are considered, and the methodological features of dynamic posterior active rhinomanometry and the main indicators of respiration are also analyzed. The possibilities of testing respiratory olfactory disorders are considered, the analysis of errors in rhinomanometric measurements is carried out. In the conclusions, practical recommendations are given that have been developed for the design and operation of tools for functional diagnostics of nasal breathing disorders. It is advisable, according to the data of dynamic rhinomanometry, to assess the functioning of the nasal valve by the shape of the air flow rate signals during forced breathing and the structures of the soft palate by the residual nasopharyngeal pressure drop. It is imperative to take into account not only the maximum coefficient of aerodynamic nose drag, but also the values of the pressure drop and air flow rate in the area of transition to the turbulent quadratic flow regime. From the point of view of the physiology of the nasal response, it is necessary to look at the dynamic change to the current mode, given the hour of the forced response, so that it will ensure the maximum possible acidity in the legend. When planning functional rhinosurgical operations, it is necessary to apply the calculation method using computed tomography, which makes it possible to predict the functional result of surgery.

Three-dimensional structure of the basal lamella of the middle turbinate

The middle turbinate’s basal lamella (3BL) is a variable landmark which needs to be understood in endoscopic transnasal skull base surgery. It comprises an anterior frontal and a posterior horizontal part and appears in its simplest depiction to be “L”-shaped, when viewed laterally. In this study we analyzed its 3D morphology and variations focusing on a precise and systematic description of the anatomy. CBCTs of 25 adults, 19 cadavers and 6 skulls (total: 100 sides) were investigated with the 3DSlicer software, creating 3D models of the 3BL. We introduced a novel geometrical classification of the 3BL’s shape, based on segments. We analyzed their parameters and relationship to neighboring structures. When viewed laterally, there was no consistent “L”-shaped appearance of the 3BL, as it is frequently quoted. A classification of 9 segment types was used to describe the 3BL. The 3BLs had in average of 2.95 ± 0.70 segments (median: 3), the most frequent was the horizontal plate (23.05% of all segments), next a concave/convex plate (22.71%), then a sigma plate (22.37%). Further types were rare. We identified a horizontal plate in 68% of all lateral views whilst 32% of the 3BLs were vertical. A sigma–concave/convex–horizontal trisegmental 3BL was the most common phenotype (27%). Globally, the sigma–concave/convex pattern was present in 42%. The 3BL adhered the ethmoidal bulla in 87%. The segmenting method is eligible to describe the 3BL’s sophisticated morphology.

Mitigation effect of face shield to reduce SARS-CoV-2 airborne transmission risk: Preliminary simulations based on computed tomography

We aimed to develop a model to quantitatively assess the potential effectiveness of face shield (visor) in reducing airborne transmission risk of the novel coronavirus SARS-CoV-2 during the current COVID-19 pandemic using the computational fluid dynamics (CFD) method. The studies with and without face shield in both an infected and healthy person have been considered in indoor environment simulation. In addition to the influence of the face shield and the synchronization of the breathing process while using the device, we also simulated the effect of small air movements on the SARS-CoV-2 infection rate (outdoor environment simulation). The contact with infectious particles in the case without a face shield was 12-20 s (s), in the presence of at least one person who was positive for SARS-CoV-2. If the infected person wore a face shield, no contact with contaminated air was observed during the entire simulation time (80 s). The time of contact with contaminated air (infection time) decreases to about 11 s when the surrounding air is still and begins to move at a low speed. Qualitative differences between simulations performed on the patients with and without the face shield are clearly visible. The maximum prevention of contagion is probably a consequence of wearing a face shield by an infected person. Our results suggest that it is possible to determine contact with air contaminated by SARS-CoV-2 using the CFD method under realistic conditions for virtually any situation and configuration. The proposed method is probably the fastest and most reliable among those based on CFD-based techniques.