Waldmann, Moritz; Rüttgers, Mario; Lintermann, Andreas; Schröder, Wolfgang
In: Journal of Engineering and Science in Medical Diagnostics and Therapy, vol. 5, iss. 3, 2022, ISSN: 2572-7958.
Fluid mechanical properties of respiratory flow such as pressure loss, temperature distribution, or wall-shear stress characterize the physics of a nasal cavity. Simulations based on computational fluid dynamics (CFD) methods are able to deliver in-depth details on respiration. Integrating such tools into virtual surgery environments may support physicians in their decision-making process. In this study, a lattice-Boltzmann (LB) flow solver is coupled to a level-set (LS) method to modify the shape of a nasal cavity at simulation run time in a virtual surgery. The geometry of a presurgical nasal cavity obtained from computer tomography (CT) datasets is smoothly adapted toward a postsurgical geometry given by the surgeon using an interpolation approach based on a LS method. The influence of the modification on the respiratory flow is analyzed in silico. The methods are evaluated by simulating a virtual surgery of a stenotic pipe and juxtaposing the results to cases using static geometries and by comparing them to literature findings. The results for both the stenotic pipe and the nasal cavity are in perfect agreement with the expected outcomes. For the nasal cavity, a shape is found that reduces the nasal resistance by 25.3% for inspiration at a volumetric flow rate of V˙=250 ml/s. The heating capability is retained despite the geometry modification. The simulation results support the surgeon in evaluating a planned surgery and in finding an improved surgery for the patient.
Waldmann, Moritz; Grosch, Alice; Witzler, Christian; Lehner, Matthias; Benda, Odo; Koch, Walter; Vogt, Klaus; Kohn, Christopher; Schröder, Wolfgang; Göbbert, Jens Henrik; Lintermann, Andreas
In: Medical & Biological Engineering & Computing , 2021.
Physics-based analyses have the potential to consolidate and substantiate medical diagnoses in rhinology. Such methods are frequently subject to intense investigations in research. However, they are not used in clinical applications, yet. One issue preventing their direct integration is that these methods are commonly developed as isolated solutions which do not consider the whole chain of data processing from initial medical to higher valued data. This manuscript presents a workflow that incorporates the whole data processing pipeline based on a Jupyter environment. Therefore, medical image data are fully automatically pre-processed by machine learning algorithms. The resulting geometries employed for the simulations on high-performance computing systems reach an accuracy of up to 99.5% compared to manually segmented geometries. Additionally, the user is enabled to upload and visualize 4-phase rhinomanometry data. Subsequent analysis and visualization of the simulation outcome extend the results of standardized diagnostic methods by a physically sound interpretation. Along with a detailed presentation of the methodologies, the capabilities of the workflow are demonstrated by evaluating an exemplary medical case. The pipeline output is compared to 4-phase rhinomanometry data. The comparison underlines the functionality of the pipeline. However, it also illustrates the influence of mucosa swelling on the simulation.
Inthavong, Kiao; Wong, Eugene; Tu, Jiyuan; Singh, Narinder (Ed.)
Springer, 2021, ISBN: 978-981-15-6716-2.
This book explores computational fluid dynamics in the context of the human nose, allowing readers to gain a better understanding of its anatomy and physiology and integrates recent advances in clinical rhinology, otolaryngology and respiratory physiology research. It focuses on advanced research topics, such as virtual surgery, AI-assisted clinical applications and therapy, as well as the latest computational modeling techniques, controversies, challenges and future directions in simulation using CFD software. Presenting perspectives and insights from computational experts and clinical specialists (ENT) combined with technical details of the computational modeling techniques from engineers, this unique reference book will give direction to and inspire future research in this emerging field.
EMBEC Abstract Book Contribution, 2020, ISBN: 978-961-243-411-3.
The RHINODIAGNOST services shall be organized in a rapid network providing new, additional decision aids, such as 3D models and flow simulations, for ENT physicians and radiologists” (taken from: http://www.rhinodiagnost.eu ). The Austrian coordinator of the Rhinodiagnost Project, AIT – Applied Information Technique Research Inc., developed an experimental station which allows the simulation of airflow in the nasal cavities using a 3D printed model. The system was designed as low cost system which doesn’t need great financial efforts and fits on a DIN-A-4 sized area of a desk
Lehner, Matthias; Benda, Odo
EMBEC Abstract Book Contribution, 2020, ISBN: 978-961-243-411-3.
In this work, results are presented for a CNN architecture which was developed specifically to classify different segments in CT images of the nasal cavity and paranasal sinuses automatically and accurately. This approach makes it possible to generate high quality segmentations of the frontal, maxillary, and sphenoid sinuses on both sides of the body, the oral and nasal cavities, bone, tissues, as well as the air outside the head surrounding the patient’s body in order to remove the latter conveniently.
Dietmar, Rafolt; Walter, Koch; Odo, Benda; Ewald, Unger
EMBEC Abstract Book Contribution, 2020, ISBN: 978-961-243-411-3.
In this project, we investigate the possibility to evaluate Computational Fluid Dynamics (CFD) in ENT, especially in rhino diagnostic, using pressure measurements on 3D-printed physical models in a testbed with artificial breathing. We are using the same set of individual segmented DICOM data (STL-format) for CFD analysis as well as to generate additive manufactured models, latter extended with a set of local pressure points.
Koch, Gerda; Koch, Walter
Developing an Online Training Module for ENT Students Miscellaneous
EMBEC Abstract Book Contribution, 2020, ISBN: 978-961-243-411-3.
A particular problem area that ENT head and neck operations (ENT: Ear-Nose-Throat) have to deal with is the air flow in the nasal cavities and paranasal sinuses. The extension of morphological diagnostics by a detailed functional analysis, i.e. the visualization of the nasal airflow and the physical analysis of its energetic properties, is a burning problem. The simulation of air flow by means of CFD (Computational Fluid Dynamics) is nowadays gaining inimportance for diagnostics and the visualization and simulation of air flows from the nostrils to the nasopharynx primarily enables a precise and high-quality 3D reconstruction of the nasal cavities. However, the successive validation and interpretation of CFD simulation results is a challenge for non-CFD specialists. The introduction of these new technologies requires special education and training for both students and medical experts to learn how to use different tools and methods in thepreparation of an operation. The ”flipped classroom”, a kind of blended learning, is a preferred method to support knowledge transfer not only to students and staff but also among all kinds of different members within organizations.
Grosch, Alice; Waldmann, Moritz; Göbbert, Jens Henrik; Lintermann, Andreas
In: Samo Mahnič-Kalamiza Tomaž Jarm, Aleksandra Cvetkoska (Ed.): 8th European Medical and Biological Engineering Conference (= EMBEC 2020), IFMBE Proceedings, pp. 57-65, Ljubljana, 2020.
Benefiting and accessing high-performance computing resources can be quite difficult. Unlike domain scientists with a background in computational science, non-experts coming from, e.g., various medical fields, have almost no chance to run numerical simulations on large-scale systems. To provide easy access and a user-friendly interface to supercomputers, a web-based service portal, which under the hood takes care of authentication, authorization, job submission, and interaction with a simulation framework is presented. The service is exemplary developed around a simulation framework capable of efficiently running computational fluid dynamics simulations on high-performance computers. The framework uses a lattice-Boltzmann method to simulate and analyze respiratory flows. The implementation of such a web-portal allows to steer the simulation and represents a new diagnostic tool in the field of ear, nose, and throat treatment.
Feng, Yu; Hayati, Hamideh; Bates, Alister J.; Walter, Koch; Matthias, Lehner; Odo, Benda; Ramiro, Ortiz; Gerda, Koch
Clinical CFD Applications 2 Book Chapter
In: Ithavong, Kiao; Singh, Narinder; Wong, Eurgene; Tu, Jiyuang (Ed.): Clinical and Biomedical Engineering in the Human Nose - A Computational Fluid Dynamics Approach, vol. 1, Chapter 10, pp. 225-253, Springer Nature Singapore Pte Ltd. 2021, 1, 2020, ISBN: 978-981-15-6715-5.
This chapter is the second of the two chapters demonstrating the wide variety of CFD studies in clinical applications presented from leading researchers in their respective fields. This chapter covers the latest research techniques and outcomes in whole lung modelling; Modeling the Effect of Airway Motion Using Dynamic Imaging; and Automatic reconstruction of the nasal geometry from CT scans.
Computational Meshing for CFD Simulations Book Chapter
In: Ithavong, Kiao; Singh, Narinder; Wong, Eurgene; Tu, Jiyuang (Ed.): Clinical and Biomedical Engineering in the Human Nose - A Computational Fluid Dynamics Approach, Chapter 6, pp. 85-115, Springer Nature Singapore Pte Ltd. 2021, 2020, ISBN: 978-981-15-6715-5.
In CFD modelling, small cells or elements are created to fill this volume. They constitute a mesh where each cell represents a discrete space that represents the flow locally. Mathematical equations that represent the flow physics are then applied to each cell of the mesh. Generating a high quality mesh is extremely important to obtain reliable solutions and to guarantee numerical stability. This chapter begins with a basic introduction to a typical workflow and guidelines for generating high quality meshes, and concludes with some more advanced topics, i.e., how to generate meshes in parallel, a discussion on mesh quality, and examples on the application of lattice-Boltzmann methods to simulate flow without any turbulence modelling on highly-resolved meshes.
Lintermann, Andreas; Schröder, Wolfgang
In: CEAS Aeronautical Journal, 2020, ISBN: 1869-5582.
Complex geometries pose multiple challenges to the field of computational fluid dynamics. Grid generation for intricate objects is often difficult and requires accurate and scalable geometrical methods to generate meshes for large-scale computations. Such simulations, furthermore, presume optimized scalability on high-performance computers to solve high-dimensional physical problems in an adequate time. Accurate boundary treatment for complex shapes is another issue and influences parallel load-balance. In addition, large serial geometries prevent efficient computations due to their increased memory footprint, which leads to reduced memory availability for computations. In this paper, a framework is presented that is able to address the aforementioned problems. Hierarchical Cartesian boundary-refined meshes for complex geometries are obtained by a massively parallel grid generator. In this process, the geometry is parallelized for efficient computation. Simulations on large-scale meshes are performed by a high-scaling lattice–Boltzmann method using the second-order accurate interpolated bounce-back boundary conditions for no-slip walls. The method employs Hilbert decompositioning for parallel distribution and is hybrid MPI/OpenMP parallelized. The parallel geometry allows to speed up the pre-processing of the solver and massively reduces the local memory footprint. The efficiency of the computational framework, the application of which to, e.g., subsonic aerodynamic problems is straightforward, is shown by simulating clearly different flow problems such as the flow in the human airways, in gas diffusion layers of fuel cells, and around an airplane landing gear configuration
Lintermann, Andreas; Meinke, Matthias; Schröder, Wolfgang
In: International Journal of Computational Fluid Dynamics, pp. 1-28, 2020, ISSN: 1061-8562.
Multi-physics simulations are at the heart of today's engineering applications. The trend is towards more realistic and detailed simulations, which demand highly resolved spatial and temporal scales of various physical mechanisms to solve engineering problems in a reasonable amount of time. As a consequence, numerical codes need to run efficiently on high-performance computers. Therefore, the frame- work Zonal Flow Solver (ZFS) featuring lattice-Boltzmann, finite-volume, discontinuous Galerkin, level set, and Lagrange solvers, has been developed. The solvers can be combined to simulate, e.g., quasi-incompressible and compressible flow, aeroacoustics, moving boundaries, and particle dynamics. In this manuscript, the multi-physics implementation of the coupling mechanisms are presented. The parallelization approach, the involved solvers, and their scalability on state-of-the-art heterogeneous high-performance computers are discussed. Various multi-physics applications complement the discussion. The results show ZFS to be a highly efficient and flexible multi-purpose tool that can be used to solve varying classes of coupled problems.
Waldmann, Moritz; Lintermann, Andreas; Choi, Yoon Jeong; Schröder, Wolfgang
In: New Results in Numerical and Experimental Fluid Mechanics , pp. 853-863, Springer International Publishing, Darmstadt, Germany, 2020.
Transverse maxillary deficiency is a common pathological condition. Patients suffering from this pathology often have narrowed airways compared to healthy humans. To cure such an anatomic defective position, a new method, the Miniscrew-Assisted Rapid Maxillary Expansion (MARME), has been developed. In previous studies, the effects of this treatment on respiration have been analyzed by examining the volume of a nasal cavity and the corresponding nasopharynx before and after treatment. In this study the fluid mechanical effects of MARME treatment on the respiratory flow and on the breathing capability are analyzed numerically. The realistic three-dimensional geometries of the nasal cavity employed for the simulation are reconstructed from Computer Tomography images. The flow within these geometries is simulated using a thermal Lattice-Boltzmann method. The results confirm that the respiratory resistance and the average wall-shear stress decrease after the MARME treatment. The heating capability, however, deteriorates.
In: Cingi, Celmal; Muluk, Nuray Bayar (Ed.): All Around the Nose - Basic Science, Diseases and Surgical Management, vol. 1, Chapter 9, pp. 75-84, Springer International Publishing, Cham, 2020, ISBN: 978-3-030-21216-2.
Tags: Allergic rhinitis, Endonasal rhinoplasty, Endoscopic sinus surgery, External rhinoplasty, Image-guided sinus surgery, Nasal polyposis, Nasal Reconstruction, Nasal trauma, Rhinosinusitis, Tumors of the nasal cavity| | |
Computational fluid dynamics methods enable to numerically predict complex flows with the help of computers. In the fields of Engineering and Physics they are already in use for decades to support design decissions and to get insight into complex physical phenomena. The simulation techniques have massively evolved over the past years and can nowadays be applied in medical context to analyze bio-fluidmechanical processes. Thanks to the continuous increase of computational power and parallelism as well as algorithmic advancements, accurate predictions of the flow in the nasal cavity are possible today. This chapter introduces the reader to the concepts of the computational fluid dynamics of the nose. It delivers some fundamentals on pre-processing medical image data, various techniques to generate computational meshes and gives an overview of methods to solve the governing equations of fluid motion. Thereby, advantages and disadvantages of the various approaches are explained. Subsequently, a variety of methods to analyze the flow and particle dynamics in the nasal cavity, ranging from streamline visualizations, pressure loss and temperature increase considerations, wall-shear stress and heat-flux distributions, to the analysis of the particle deposition behavior and transitional flow, is presented. The chapter concludes with how such methods can be used in clinical applications and elaborates how future developments might support decision making in medical pathways.
Akmenkalne, Liga; Prill, Matthias; Vogt, Klaus
In: Rhinology online, vol. Vol 2, pp. 81 - 86, 2019.
Background: The nasal valve area is the narrowest region of the entire upper airway. Numerous procedures and spreader devices are published to widen the nasal valve or to stabilize it, but the indications are based only on the surgeon’s experience.
Methods: In 30 healthy volunteers the deflection of elastic steel elements touching the lower nasal side at its deepest point was precisely measured by means of strain gauges. The deflection was calibrated by standard calibration devices. A special 4-phase-rhinomanometer (4RHINO/ Rhinolab/Germany) with a protective face mask allowed simultaneous measurements of the airflow and differential pressure. All signals were recorded simultaneously on both sides. The measurements have been carried out as unilateral measurements according to anterior rhinomanometry.
Results: Surprisingly the lateral nasal wall is already moving during quiet breathing. The airflow and its acceleration as well as the pressure difference generating a complete closure of the nose can be determined and has expectedly a high variance between individuals.
Conclusions: The elastography confirms the loops in 4-phase-rhinomanometry as symptomatic for the nasal valve elongation and will after developing as medical product allow the systematic quantitative measurement of the influence of the nasal valve on the nasal air stream.
Peksis, Kaspars; Unger, Juliane; Paulauska, Santa; Emsina, Aja; Blumbergs, Martins; Vogt, Klaus; Wernecke, Klaus-Dieter
In: Rhinology Online, vol. Vol 1, pp. 112 - 121, 2018.
Background: Children generally have a higher nasal resistance than adults. Growth changes the size and different anthropometric parameters of the nose. Logarithmic effective resistance and logarithmic vertex resistance were introduced as physically correct parameters for nasal obstruction. The previously published classification of obstruction derived from 36,500 measurements is missing data for patients aged 7 to 19 years.
Methodology: Rhinomanometry was performed before and after decongestion with 9 different anthropometric measurements in 225 children and adolescents. Correlations among age, anthropometric measurements, and logarithmic effective and vertex resistance were determined for both sexes, and regressions were calculated.
Results: The highest correlations with the resistance values were found between age, lateral nasal length, and logarithmic effective resistance. A highly significant linear regression between age and logarithmic effective resistance was also found. This was used for adaption of the classification of obstruction in adults to growing patients. The resistance of the nasal airways at the age of 7 years was about twice that in adults.
Conclusions: The linear regression equations can be used to suborder obstructions measured by four-phase rhinomanometry into classes for estimation of their severity according to age.
Koch, Walter; Schachenreiter, Jochen; Vogt, Klaus; Koch, Gerda
In: Journal on Systemics, Cybernetics and Informatics: JSCI, vol. 16, no. 1, pp. 60-64, 2018, ISBN: 1690-4524 (Online).
A special problem area which ENT-Head/Neck (ENT: Ear-Nose-Throat) surgery specialists have to deal with is the air flow in the nasal cavities and paranasal sinuses. It is a burning problem to extend the morphological diagnostic by detailed functional analysis, i.e. the visualization of the nasal air stream and the physical analysis of its energetic. The simulation of the airflow via CFD (Computational Fluid Dynamics) is nowadays gaining importance for diagnostics, and the visualization and simulation of airflows from the nostrils to the nasal pharynx afford in first place a precise and high quality 3D reconstruction of the nasal cavities. But the successive validation and interpretation of CFD simulation results is a challenge for non CFD specialists. The introduction of these new technologies requires special education and training for students as well as for medical experts in order to learn how to use and handle different tools and methods when preparing a surgery. “Flipped classroom”, a type of blended learning, is a preferred method for supporting knowledge transfer not only to students and employees but also among all kind of different members within organizations.
Kim, Soo-Yeon; Park, Young-Chel; Lee, Kee-Joon; Lintermann, Andreas; Han, Sang-Sun; Yu, Hyung-Seog; Choi, Yoon Jeong
In: The Angle Orthodontist, pp. 092917–656.1, 2018, ISSN: 0003-3219.
Objectives: To evaluate changes in the volume and cross-sectional area of the nasal airway before and 1 year after nonsurgical miniscrew-assisted rapid maxillary expansion (MARME) in young adults.
Materials and Methods: Fourteen patients (mean age, 22.7 years; 10 women, four men) with a transverse discrepancy who underwent cone beam computed tomography before (T0), immediately after (T1), and 1 year after (T2) expansion were retrospectively included in this study. The volume of the nasal cavity and nasopharynx and the cross-sectional area of the anterior, middle, and posterior segments of the nasal airway were measured and compared among the three timepoints using paired t-tests.
Results: The volume of the nasal cavity showed a significant increase at T1 and T2 (P < .05), while that of the nasopharynx increased only at T2 (P < .05). The anterior and middle cross-sectional areas significantly increased at T1 and T2 (P < .05), while the posterior cross-sectional area showed no significant change throughout the observation period (P > .05).
Conclusions: The results demonstrate that the volume and cross-sectional area of the nasal cavity increased after MARME and were maintained at 1 year after expansion. Therefore, MARME may be helpful in expanding the nasal airway.
Vogt, Klaus; Bachmann-Harildstad, Gregor; Lintermann, Andreas; Nechyporenko, Alina; Peters, Franz; Wernecke, Klaus-Dieter
In: Rhinology, vol. 56, 2018.
The report reflects an agreement based on the consensus conference of the International Standardization Committee on the Objective Assessment of the Nasal Airway in Riga, 2nd Nov. 2016.
The aim of the conference was to address the existing nasal airway function tests and to take into account physical, mathematical and technical correctness as a base of international standardization as well as the requirements of the Council Directive 93/42/EEC of 14 June 1993 concerning medical devices.
Rhinomanometry, acoustic rhinometry, peak nasal inspiratory flow, Odiosoft-Rhino, optical rhinometry, 24-h measurements, computational fluid dynamics, nasometry and the mirrow test were evaluated for important diagnostic criteria, which are the precision of the equipment including calibration and the software applied; validity with sensitivity, specificity, positive and negative predictive values, reliability with intra-individual and inter-individual reproducibility and responsiveness in clinical studies.
For rhinomanometry, the logarithmic effective resistance was set as the parameter of high diagnostic relevance. In acoustic rhinometry, the area of interest for the minimal cross-sectional area will need further standardization. Peak nasal inspiratory flow is a reproducible and fast test, which showed a high range of mean values in different studies. The state of the art with computational fluid dynamics for the simulation of the airway still depends on high performance computing hardware and will, after standardization of the software and both the software and hardware for imaging protocols, certainly deliver a better understanding of the nasal airway flux.
Lintermann, Andreas; Schröder, Wolfgang
In: Flow, Turbulence and Combustion, 2017, ISSN: 1386-6184.
The immense increase of computational power in the past decades led to an evolution of numerical simulations in all kind of engineering applications. New developments in medical technologies in rhinology employ computational fluid dynamics methods to explore pathologies from a fluid-mechanics point of view. Such methods have grown mature and are about to enter daily clinical use to support doctors in decision making. In light of the importance of effective respiration on patient comfort and health care costs, individualized simulations ultimately have the potential to revolutionize medical diagnosis, drug delivery, and surgery planning. The present article reviews experiments, simulations, and algorithmic approaches developed at RWTH Aachen University that have evolved from fundamental physical analyses using nose-like models to patient-individual analyses based on realistic anatomies and high resolution computations in hierarchical manner.