Background Adequate nasal air-conditioning is of greatest importance. Because detailed processes of nasal air-conditioning still are not completely understood, numerical simulations of intranasal temperature distribution and airflow patterns during inspiration and expiration were performed. Methods A three-dimensional model of the human nose based on computed tomography scans was reconstructed. A computational fluid dynamics application was used displaying temperature and airflow during respiration based on time-dependent boundary conditions. Results Absolute air temperature and velocity values vary depending on detection site and time of detection. Areas of low velocities and turbulence show distinct changes in air temperature. The turbinate areas prove to be the main regions for heat exchange. The numerical results showed excellent comparability to our in vivo measurements. Conclusion Numerical simulation of temperature and airflow based on computational fluid dynamics is feasible providing entirely novel information and an insight into air-conditioning of the human nose.

BACKGROUND:Radical surgical resection of the turbinates leads to a reduced intranasal air conditioning. The aim of this study was to determine the effect of turbinate resection on intranasal heating and airflow patterns using a numerical simulation.METHODS:A bilateral model of the human nose with resection of the turbinates on one side based on a CT-scan was reconstructed. A numerical simulation applying the computational fluid dynamics (CFD) solver Fluent 6.1.22 was performed displaying inspiratory intranasal air temperature and airflow patterns.RESULTS:Due to resection of the turbinates the airflow pattern is disturbed resulting in a spacious vortex throughout the entire nasal cavity. Hence, contact between air and surrounding nasal wall is less intense. Consequently, intranasal heating of the inspired air is relevantly reduced.CONCLUSIONS:Surgical resection of the turbinates leads to a disturbed intranasal air conditioning. The presented numerical simulation demonstrates the close relation between airflow patterns and heating.

Correction to: Blutflusssimulation mittels Computational-Fluid-Dynamics an aus CT-Daten rekonstruierten Aortenaneurysmata vor und nach Stent-Graft ImplantationRofo 2004; 177(01): 56-61DOI: 10.1055/s-2004-814667

Purpose: Radical sinus surgery disturbs intranasal humidification and heating of inspired air, resulting in reduced air conditioning mainly caused by a disturbed airflow. Therefore, the aim of this study was to simulate the intranasal airflow after radical sinus surgery during inspiration by means of numerical simulation.Material and methods: A bilateral model of the human nose with maxillectomy, ethmoidectomy, and resection of the lateral nasal wall and the turbinates oil one side based on a multislice computed tomographic scan was reconstructed. An unsteady numerical simulation displaying the intranasal airflow patterns applying the computational fluid dynamics solver Fluent 6.1.22 was performed.Results: Spacious vortices throughout the entire nasal cavity and the paranasal sinuses caused by the radical resections Occurred, causing a less-intense contact between air and the surrounding nasal wall. An enlargement of the nasal cavity volume and a reduction of the nasal surface area in ratio to the nasal cavity volume could be observed.Conclusions: Aggressive sinus surgery leads to disturbed intranasal air conditioning caused by disturbed intranasal airflow patterns and a reduction of the surface area in relation to the nasal volume. The presented numerical simulation demonstrates the close relation between air conditioning and intranasal airflow. It can be helpful to understand and interpret in vivo measured data of intranasal temperature and humidity. (c) 2005 Elsevier Inc. All rights reserved.

Eine der wichtigsten Funktionen der Nase ist die Erwärmung der Einatemluft. Bisher war eine in vivo- Messung der Lufttemperatur der gesamten Nasenhaupthöhle technisch nicht möglich. Hier bietet eine numerische Simulation neue Möglichkeiten. Ziel dieser Studie war die Simulation der Verteilung der inspiratorischen Lufttemperatur in der gesamten Nase anhand eines Computermodells. Aus CT-Datensätzen wurde ein realistisches, 3-dimensionales Nasenmodel erzeugt. Die Verteilung der intranasalen Lufttemperatur sowie das Strömungsverhalten der Luft wurden mit Hilfe einer Simulationsmethode der Computational Fluid Dynamics (CFD) dargestellt. Zur Validierung wurden die Ergebnisse der CFD mit in vivo- Temperaturmessungen an definierten intranasalen Messorten verglichen. Die numerische Simulation zeigt, dass der auffälligste Temperaturanstieg im vorderen Nasenabschnitt stattfindet. Vor allem im Bereich der Nasenmuscheln erfolgt eine ausgeprägte Erwärmung der Einatemluft. Intranasale Regionen mit hoher Lufttemperatur sind charakterisiert durch Wirbelbildung der Luft mit niedriger Strömungsgeschwindigkeit. Die Ergebnisse der numerischen Simulation sind mit den in vivo- Messungen gut vergleichbar. Das dargestellte Verfahren bietet erstmals die Möglichkeit, intranasale Lufttemperaturen während der Einatmung in der gesamten Nasenhaupthöhle darzustellen und zu beurteilen. Dabei scheinen die Muschelregionen besonders an der Erwärmung der Einatemluft beteiligt zu sein. Unsere Ergebnisse zeigen, dass ein enges Verhältnis zwischen Strömungsverhalten der Luft und Erwärmung der Luft besteht.

Background The most typical symptoms of patients with nasal septal perforation (SP) are crusting and recurrent nosebleed. The objective of the study was to determine the influence of SP on intranasal temperature profile and airflow patterns during inspiration by means of numerical simulation. Methods Two realistic bilateral models of the human nose with and without SP were reconstructed based on computed tomography (CT). A numerical simulation was performed. The intranasal air temperature distribution and airflow patterns during inspiration were displayed, analyzed, and compared. Results SP causes a highly disturbed airflow in the area of perforation. A spacious vortex within the perforation including various localized vortices was detected. A disturbed intranasal temperature distribution between the right and left nasal cavities developed. Conclusions The numerical simulation demonstrates the interaction between airflow patterns and heating of respiratory air. The disturbed airflow causes reduced air conditioning. This fact may contribute to crusting and recurrent nosebleed.

PURPOSE:Simulation, description and analysis of dynamic pressure in infrarenal abdominal aortic aneurysms (AAA) before and after endovascular repair.MATERIALS AND METHODS:During March 1996 and May 2001, 13 patients with AAA underwent endovascular treatment. The MDR-CT scans of these patients were used for the non-invasive analysis of the hemodynamics in the aorta with CFD software before and after endovascular repair. One pre-interventional and three post-interventional CT scans were analyzed for each patient.RESULTS:Compared to the pre-interventional simulation, endovascular treatment led to an average dynamic pressure decrease of 1057 Pa in 10 of 13 patients. During the subsequent course, the median of the dynamic pressure decreased in 8 of 13 patients. Vulnerable regions initially identified as high-pressure regions, like the docking area or the second stent limb, adapted to the pressure in the surrounding tissue in the course of time.CONCLUSION:CFD-based blood flow simulation offers the opportunity to analyze dynamic pressure in AAA before and after endovascular repair and allows a prognostic statement as to the possible homogenization of the pressure in abdominal stent-grafts.

Recovery of heat and water during expiration is an important but not yet fully understood function of the nose. The presented study investigated cooling of the expiratory air for heat recovery within the human nose applying numerical simulation. A numerical simulation in a bilateral three-dimensional model of the human nose based on computed tomography was employed. Temperature distribution and airflow patterns during expiration were displayed. Cooling of the expiratory air primarily takes place in the areas of inferior and middle turbinate. Areas of the highest decrease in temperature are characterized by turbulent airflow with vortices of low velocity. Numerical results showed good concordance with experimental in vivo temperature measurements. Heating of inspired air not only depends on inspiration but also on expiration. Cooling the warm expiratory air may be regarded as an important factor for heat recovery. Furthermore, the results demonstrate the close relation between heat exchange and airflow patterns.

OBJECTIVES/HYPOTHESIS:In vivo measurements of the intranasal air temperature are feasible. The present study was designed to reproduce temperature distributions within the human nasal cavity by means of numerical simulation. STUDY DESIGN:Numerical simulation. METHODS:Based on computed tomography (CT), a steady-state computational fluid dynamics (CFD) simulation was performed displaying the temperature distribution throughout the human nasal cavity during inspiration. The results of the numerical simulation were compared with in vivo temperature measurements. RESULTS:The numerical simulation demonstrated that the major increase of the inspiratory air temperature can be found in the anterior nasal segment, especially within the nasal valve area, which is comparable to in vivo measurements. Intranasal areas of high temperature were characterized by turbulent airflow with vortices of low velocity. The results of numerical simulation showed an excellent comparability to the results of previous in vivo measurements in the entire nasal cavity. CONCLUSION:The anterior nasal segment is the most effective part of the nose in heating of the ambient air. The findings demonstrated the complexity of the relationship between airflow patterns and heating of inspired air. A numerical simulation of the temperature distribution using CFD is practicable.

Objective:a basic standard of endovascular stent grafts repairing is the proximal aneurysmal neck must be at least 15～20mm in length.In this study,we try to study the effect of transrenal fixation of aortic stent grafts on morphology of renal arteries by comparing the preoperative and postoperative DSA and CT findings.Methods:13 abdominal aortic aneurysm (AAAs) underwent transrenal fixation of aortic stent grafts.Preoperative and postoperative DSA and CT examinations were all available.CT maximum intensity projection (MIP) was used for reconstruction of AAAs and renal arteries.Results:Preoperative DSA showed the length of proximal aneurysmal necks ranged from 5mm to 30.3mm(mean 18.5mm). Renal artery stenosis was found in 2 patients.The stenosis was about 50%.Postoperative DSA showed no new stenosis.4 stenoses were found by preoperative CT MIPs.Postoperative CT MIPs showed 3 endoleaks and 4 stenosis in 1 month.No new stenosis was observed in 12 patients 3 months later.Couclusion:Transrenal fixation of aortic stent grafts has no effect on morphology of renal arteries.It may be an effective interventional treatment for patients suffered from abdominal aortic aneurysm with more than one high risk factor for surgery.

Treatment of Abdominal Aortic Aneurysms (AAA) has seen dramatic improvements over the last years. With improved surgical methods the rate of mortality has been going down to about 20% and less today. One way to treat such an AAA is to implant stent grafts in order to channel the blood at its way through the aneurysm using endovascular methods. In this procedure the surgeon delivers the stent graft via a catheter inside the dilatation in which it unfolds, taking away the pressure from the weakened aortic wall. This method has been proven to work well and patients typically can be released as early as 24 hours after receiving this procedure. However, complications may occur after the treatment, which can include leakages and migration of the stent or even its elemental breakdown. The causes for these problems are not exactly known. In order to get a better understanding of the behavior of the complex mechanical systems simulation is a feasible approach. This requires adequate data gathering, for the individual patient, a feasible mathematical and numerical models, and substantial compute performance.

Zusammenfassung Die Navigation basierend auf einem Bildwandler ist eine neue Anwendung in der computerassistierten Chirurgie. Im Rahmen der vorliegenden Studie wurde die Präzision von Iso-C-Arm-basierten Bohrungen am proximalen Femur untersucht. An 9 Kunststoffknochen wurden je 2 Bohrungen mit 135° und 100° Anstiegswinkel zur Schaftachse in Richtung Femurkopf gesetzt. Als Ziel der 3,2-mm-Bohrkanäle wurde das Zentrum einer zuvor von kranial in den Femurkopf implantierten 4-mm-Stahlkugel gewählt. Die Bohrungen wurden standardisiert mit einer navigierten Bohrmaschine durchgeführt, die in einen Bohrständer integriert wurde. Die jeweilige Stellung des navigierten Bohrers vor Beginn der Bohrung und am tiefsten Punkt des Bohrkanals im Navigationsmodus wurde dokumentiert. Nach Anlage der Bohrkanäle wurde ein CT der Präparate angefertigt und über eine entsprechende Software die Koordinaten des Mittelpunktes des Eintritts und des Endes eines Bohrkanals und der Stahlkugel vermessen. Über eine Vektorrechnung erfolgte die Kalkulation des kleinsten Abstands zwischen der aus dem Zentrum des Anfangs und Endes des Bohrkanals definierten Geraden und dem Zentrum der Kugel, auf welche die Bohrung gerichtet war. Weiterhin wurden die Koordinaten des Schnittpunktes des Lotes zum Kugelzentrum mit der Geraden kalkuliert (x v , y v und z v ), um die Richtung der Abweichung des Bohrkanals vom Zentrum der Kugel zu evaluieren. Für die 135°-Bohrung ergab sich ein Median der kleinsten Abweichung des Zentrums des Bohrkanals und des Zentrums der Kugel von 2,5 (1,6–3,7) mm, bei der 100° Zielbohrung betrug der Median 3,1 (1,8–4,2) mm. Die Richtung der Abweichung zeigte bei allen 9 135°-Bohrungen tendenziell primär nach dorsal, während 4 der 100°-Bohrungen primär nach dorsal, 3 nach kranial und je eine nach kaudal und ventral abwichen. Aus unserer Sicht liegt für die bildwandlergestützte Navigation bei Anwendungen im Bereich des proximalen Femurs eine ausreichende Präzision und Reproduzierbarkeit vor. Diese Technik kann in Zukunft am Patienten eingesetzt werden.

The interest of this study is on analysing blood flow phenomena like velocity, pressure and wall shear stress in the aorta before and after treatment of abdominal aortic aneurysm by placement of an endovascular stent graft to get a better estimation of risk of rupture of the aneurysm and to optimise the shape of the stent grafts.The blood flow simulation is based on Finite Element Method (FEM). After segmentation of geometry of the aorta from CT scans a three dimensional mesh is generated. Then blood flow is simulated by means of the Computational Fluid Dynamics Software (CFD).

By means of Computational Fluid Dynamics (CFD) bloodflow in an abdominal aneurysm and in the implanted endovascular stentgraft can be visualized and analyzed. This method should help to predict the outcome of the procedure and to optimize stent design for every individually patient.

Seven homogeneous, semi-synthetic polyprenyl phosphates ranging in chain length from 20 to 95 carbon atoms and differing in the presence of saturated isoprene residues, were tested in several glycosyl transfer reactions catalyzed by yeast membranes. They were compared not only as acceptors of sugar phosphate from nucleoside diphosphate sugars but also as donors of the carbohydrate units to endogenous protein. All polyprenyl phosphates tested were effective substrates for the synthesis of mannosyl-lipid and differed by no more than a factor of two in activity. In contrast, a 5–8-fold preference for derivatives containing a saturated rather than an unsaturated α-isoprene residue was observed for utilization of the mannosyl-lipids as substrates for mannosylation of protein. The enzyme catalyzing the synthesis of N-acetylglucosaminylpyrophosphoryl-polyprenol showed the highest specificity and only polyprenyl phosphates resembling natural yeast dolichyl phosphate in nearly all respects were effective substrates. Mono-N-acetylglucosaminyl-lipids were glycosyl donors to protein only after conversion to more polar lipids containing additional residues of N-acetylglucosamine and mannose. In all reactions tested, changes in the chain length of the polyprenyl moiety had little or no effect on activity.