Rhinomanometry Versus Computational Fluid Dynamics: Correlated, but Different Techniques

2020 ◽  
pp. 194589242095015
Author(s):  
Giancarlo B. Cherobin ◽  
Richard L. Voegels ◽  
Fábio R. Pinna ◽  
Eloisa M. M. S. Gebrim ◽  
Ryan S. Bailey ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Nasal Resistance ◽  
Nasal Patency ◽  
Low Correlation ◽  
Before And After ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Experiments

Background Past studies reported a low correlation between rhinomanometry and computational fluid dynamics (CFD), but the source of the discrepancy was unclear. Low correlation or lack of correlation has also been reported between subjective and objective measures of nasal patency. Objective: This study investigates (1) the correlation and agreement between nasal resistance derived from CFD (RCFD) and rhinomanometry (RRMN), and (2) the correlation between objective and subjective measures of nasal patency. Methods Twenty-five patients with nasal obstruction underwent anterior rhinomanometry before and after mucosal decongestion with oxymetazoline. Subjective nasal patency was assessed with a 0-10 visual analog scale (VAS). CFD simulations were performed based on computed tomography scans obtained after mucosal decongestion. To validate the CFD methods, nasal resistance was measured in vitro (REXPERIMENT) by performing pressure-flow experiments in anatomically accurate plastic nasal replicas from 6 individuals. Results Mucosal decongestion was associated with a reduction in bilateral nasal resistance (0.34 ± 0.23 Pa.s/ml to 0.19 ± 0.24 Pa.s/ml, p = 0.003) and improved sensation of nasal airflow (bilateral VAS decreased from 5.2 ± 1.9 to 2.6 ± 1.9, p < 0.001). A statistically significant correlation was found between VAS in the most obstructed cavity and unilateral airflow before and after mucosal decongestion (r = −0.42, p = 0.003). Excellent correlation was found between RCFD and REXPERIMENT (r = 0.96, p < 0.001) with good agreement between the numerical and in vitro values (RCFD/REXPERIMENT = 0.93 ± 0.08). A weak correlation was found between RCFD and RRMN (r = 0.41, p = 0.003) with CFD underpredicting nasal resistance derived from rhinomanometry (RCFD/RRMN = 0.65 ± 0.63). A stronger correlation was found when unilateral airflow at a pressure drop of 75 Pa was used to compare CFD with rhinomanometry (r = 0.76, p < 0.001). Conclusion CFD and rhinomanometry are moderately correlated, but CFD underpredicts nasal resistance measured in vivo due in part to the assumption of rigid nasal walls. Our results confirm previous reports that subjective nasal patency correlates better with unilateral than with bilateral measurements and in the context of an intervention.

Microfabricated Cavities for Adhesive Capture of Stem Cells Under Flow

2007 ◽  
Author(s):  
Dooyoung Lee ◽  
Kuldeepsinh Rana ◽  
Karin Lee ◽  
Lisa A. DeLouise ◽  
Michael R. King
Keyword(s):  
Fluid Dynamics ◽  
Stem Cells ◽  
Computational Fluid Dynamics ◽  
Blood Flow ◽  
Shear Stresses ◽  
Computational Fluid Dynamics Cfd ◽  
Future Work ◽  
Flow Experiments

In previous work, we have described the adhesive capture of circulating stem cells to surfaces coated with adhesive selectin protein, both in vitro and in vivo. Here we describe PDMS surfaces microfabricated to contain an array of square 80 × 80 × 80 micron cavities. These cavities are intended to provide a local bioreactor environment to culture stem cells over extended periods of time, while sheltered from the higher shear stresses of the surrounding blood flow external of the cavities. In this paper we present in vitro flow experiments with polymeric, blood cell-sized microspheres, showing the creation of stable vortices within the microscale cavities. Computational fluid dynamics (CFD) was performed to predict the velocity field within the cavity, and for comparison with experimentally determined microsphere velocities. Future work will establish the ability to place local chemoattract molecules within the cavity interior, and the ability to accumulate viable stem cells within these cavities.

Computational fluid dynamics applied to the ventilation of small-animal laboratory cages

2020 ◽  
pp. 002367722093771
Author(s):  
Ira Katz ◽  
Kateryna Voronetska ◽  
Mickaël Libardi ◽  
Matthieu Chalopin ◽  
Patricia Privat ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Noble Gas ◽  
Small Animal ◽  
Toxicity Testing ◽  
Exposure Period ◽  
In Vitro Models ◽  
Gas Distribution

Several studies based on in vivo or in vitro models have found promising results for the noble gas argon in neuroprotection against ischaemic pathologies. The development of argon as a medicinal product includes the requirement for toxicity testing through non-clinical studies. The long exposure period of animals (rats) during several days results in technical and logistic challenges related to the gas administration. In particular, a minimum of 10 air changes per hour (ACH) to maintain animal welfare results in extremely large volumes of experimental gas required if the gas is not recirculated. The difficulty with handling the many cylinders prompted the development of such a recirculation-based design. To distribute the recirculating gas to individually ventilated cages and monitor them properly was deemed more difficult than constructing a single large enclosure that will hold several open cages. To address these concerns, a computational fluid dynamics (CFD) analysis of the preliminary design was performed. A purpose-made exposure chamber was designed based on the CFD simulations. Comparisons of the simulation results to measurements of gas concentration at two cage positions while filling show that the CFD results compare well to these limited experiments. Thus, we believe that the CFD results are representative of the gas distribution throughout the enclosure. The CFD shows that the design provides better gas distribution (i.e. a higher effective air change rate) than predicted by 10 ACH.

scholarly journals Herbst appliance effects on pharyngeal airway ventilation evaluated using computational fluid dynamics

2017 ◽  
Vol 87 (3) ◽  
pp. 397-403 ◽  
Author(s):  
Tomonori Iwasaki ◽  
Hideo Sato ◽  
Hokuto Suga ◽  
Ayaka Minami ◽  
Yuushi Yamamoto ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Three Dimensional ◽  
Control Group ◽  
Herbst Appliance ◽  
Oropharyngeal Airway ◽  
Pharyngeal Airway ◽  
Obstructive Sleep ◽  
Before And After ◽  
Computational Fluid Dynamics Cfd

ABSTRACT Objective: To evaluate the effect of a Herbst appliance on ventilation of the pharyngeal airway (PA) using computational fluid dynamics (CFD). Materials and Methods: Twenty-one Class II patients (10 boys; mean age, 11.7 years) who required Herbst therapy with edgewise treatment underwent cone-beam computed tomography (CBCT) before and after treatment. Nineteen Class I control patients (8 boys; mean age, 11.9 years) received edgewise treatment alone. The pressure and velocity of the PA were compared between the groups using CFD based on three-dimensional CBCT images of the PA. Results: The change in oropharyngeal airway velocity in the Herbst group (1.95 m/s) was significantly larger than that in the control group (0.67 m/s). Similarly, the decrease in laryngopharyngeal airway velocity in the Herbst group (1.37 m/s) was significantly larger than that in the control group (0.57 m/s). Conclusion: The Herbst appliance improves ventilation of the oropharyngeal and laryngopharyngeal airways. These results may provide a useful assessment of obstructive sleep apnea treatment during growth.

scholarly journals A proof-of-concept study of the in-vivo validation of a computational fluid dynamics model of personalized radioembolization

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Raúl Antón ◽  
Javier Antoñana ◽  
Jorge Aramburu ◽  
Ana Ezponda ◽  
Elena Prieto ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Three Dimensional ◽  
Patient Specific ◽  
Percentage Points ◽  
Pet Ct ◽  
Voxel Dosimetry ◽  
Computational Fluid Dynamics Cfd ◽  
Intraarterial Therapy

AbstractRadioembolization (RE) with yttrium-90 (90Y) microspheres, a transcatheter intraarterial therapy for patients with liver cancer, can be modeled computationally. The purpose of this work was to correlate the results obtained with this methodology using in vivo data, so that this computational tool could be used for the optimization of the RE procedure. The hepatic artery three-dimensional (3D) hemodynamics and microsphere distribution during RE were modeled for six 90Y-loaded microsphere infusions in three patients with hepatocellular carcinoma using a commercially available computational fluid dynamics (CFD) software package. The model was built based on in vivo data acquired during the pretreatment stage. The results of the simulations were compared with the in vivo distribution assessed by 90Y PET/CT. Specifically, the microsphere distribution predicted was compared with the actual 90Y activity per liver segment with a commercially available 3D-voxel dosimetry software (PLANET Dose, DOSIsoft). The average difference between the CFD-based and the PET/CT-based activity distribution was 2.36 percentage points for Patient 1, 3.51 percentage points for Patient 2 and 2.02 percentage points for Patient 3. These results suggest that CFD simulations may help to predict 90Y-microsphere distribution after RE and could be used to optimize the RE procedure on a patient-specific basis.

scholarly journals Multi-modality cerebral aneurysm haemodynamic analysis: in vivo 4D flow MRI, in vitro volumetric particle velocimetry and in silico computational fluid dynamics

2019 ◽  
Vol 16 (158) ◽  
pp. 20190465 ◽  
Author(s):  
Melissa C. Brindise ◽  
Sean Rothenberger ◽  
Benjamin Dickerhoff ◽  
Susanne Schnell ◽  
Michael Markl ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Cerebral Aneurysm ◽  
Patient Specific ◽  
4D Flow Mri ◽  
4D Flow ◽  
Relative Residence Time ◽  
Flow Mri

Typical approaches to patient-specific haemodynamic studies of cerebral aneurysms use image-based computational fluid dynamics (CFD) and seek to statistically correlate parameters such as wall shear stress (WSS) and oscillatory shear index (OSI) to risk of growth and rupture. However, such studies have reported contradictory results, emphasizing the need for in-depth multi-modality haemodynamic metric evaluation. In this work, we used in vivo 4D flow MRI data to inform in vitro particle velocimetry and CFD modalities in two patient-specific cerebral aneurysm models (basilar tip and internal carotid artery). Pulsatile volumetric particle velocimetry experiments were conducted, and the particle images were processed using Shake-the-Box, a particle tracking method. Distributions of normalized WSS and relative residence time were shown to be highly yet inconsistently affected by minor flow field and spatial resolution variations across modalities, and specific relationships among these should be explored in future work. Conversely, OSI, a non-dimensional parameter, was shown to be more robust to the varying assumptions, limitations and spatial resolutions of each subject and modality. These results suggest a need for further multi-modality analysis as well as development of non-dimensional haemodynamic parameters and correlation of such metrics to aneurysm risk of growth and rupture.

Evaluating the Effect of Sinex® (0.05% Oxymetazoline) Nasal Spray on Reduction of Nasal Congestion Using Computational Fluid Dynamics

2015 ◽  
Vol 137 (8) ◽  
Author(s):  
Aravind Kishore ◽  
Lauren Blake ◽  
Chengming Wang ◽  
Shan Ba ◽  
Gary Gross
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Nasal Congestion ◽  
Nasal Resistance ◽  
Parallel Circuit ◽  
Computational Fluid Dynamics Cfd ◽  
Magnetic Resonance Imaging Mri ◽  
Circuit Analogy ◽  
Pressure Boundary Conditions ◽  
Previous Clinical Study

Computational fluid dynamics (CFD) was used to simulate air flow changes in reconstructed nasal passages based on magnetic resonance imaging (MRI) data from a previous clinical study of 0.05% Oxymetazoline (Vicks Sinex Micromist®). Total-pressure boundary conditions were uniquely applied to accommodate low patency subjects. Net nasal resistance, the primary simulation outcome, was determined using a parallel-circuit analogy and compared across treatments. Relative risk (RR) calculations show that for a 50% reduction in nasal resistance, subjects treated with Sinex® are 9.1 times more likely to achieve this after 8 hr, and 3.2 times more likely after 12 hr compared to Sham.

scholarly journals Hemodynamic Study of a Patient-Specific Intracranial Aneurysm: Comparative Assessment of Tomographic PIV, Stereoscopic PIV, In Vivo MRI and Computational Fluid Dynamics

2021 ◽  
Author(s):  
Xiaolin Wu ◽  
Stefanie Gürzing ◽  
Christiaan Schinkel ◽  
Merel Toussaint ◽  
Romana Perinajová ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Intracranial Aneurysm ◽  
Comparative Assessment ◽  
Patient Specific ◽  
4D Flow Mri ◽  
4D Flow ◽  
Flow Mri

Abstract Introduction Wall shear stress (WSS) is associated with the growth and rupture of an intracranial aneurysm. To reveal their underlying connections, many image-based computational fluid dynamics (CFD) studies have been conducted. However, the methodological validations using both in vivo medical imaging and in vitro optical flow measurements were rarely accompanied in such studies. Methods In the present study, we performed a comparative assessment on the hemodynamics of a patient-specific intracranial saccular aneurysm using in vivo 4D Flow MRI, in silico CFD, in vitro stereoscopic and tomographic particle imaging velocimetry (Stereo-PIV and Tomo-PIV) techniques. PIV experiments and CFD were conducted under steady state corresponding to the peak systole of 4D Flow MRI. Results The results showed that all modalities provided similar flow features and overall surface distribution of WSS. However, a large variation in the absolute WSS values was found. 4D Flow MRI estimated a 2- to 4-fold lower peak WSS (3.99 Pa) and a 1.6- to 2-fold lower mean WSS (0.94 Pa) than Tomo-PIV, Stereo-PIV, and CFD. Bland-Altman plots of WSS showed that the differences between PIV-/CFD-based WSS and 4D Flow MRI-based WSS increase with higher WSS magnitude. Such proportional trend was absent in the Bland-Altman comparison of velocity where the resolutions of PIV and CFD datasets were matched to 4D Flow MRI. We also found that because of superior resolution in the out-of-plane direction, WSS estimation by Tomo-PIV was higher than Stereo-PIV. Conclusions Our results indicated that the differences in spatial resolution could be the main contributor to the discrepancies between each modality. The findings of this study suggest that with current techniques, care should be taken when using absolute WSS values to perform a quantitative risk analysis of aneurysm rupture.

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