04 Fakultät Energie-, Verfahrens- und Biotechnik
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/5
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Item Open Access Ein maschinenbezogenes Qualitätssicherungssystem für die intensitätsmodulierte Strahlentherapie : Entwicklung, Einführung, Untersuchung und Vergleich mit einem patientenplanbezogenen Qualitätssicherungssystem(2013) Hummel, Daniel; Gromoll, Christian (PD Dr.-Ing. habil.)Die dosimetrische Verifikation jedes Patienten-Bestrahlungsplans ist aktuell das Standardverfahren zur Qualitätssicherung der IMRT. Aufgrund der Eigenschaften und Beschränkungen der dabei eingesetzten Strahlungsdetektoren, Verifikationsmethoden und Vergleichsverfahren ist jedoch nur eine begrenzte Dosisgenauigkeit und Ortsauflösung erreichbar. Die dafür festgelegten Toleranzen können häufig nicht an allen Messpunkten eingehalten werden. Zudem ist es bei steigender Anzahl an mit IMRT behandelten Patienten nicht mehr möglich, jeden einzelnen Plan messtechnisch zu verifizieren. In einem maschinenbezogenen Qualitätssicherungssystem kann auf die Messung jedes einzelnen Patientenplans verzichtet werden, wenn alle IMRT-relevanten Kennmerkmale separat konstanzgeprüft werden. Ein solches QS-System wurde für eine Klinik entwickelt, eingeführt und getestet. Mittels einer täglich durchgeführten Testsequenz und wenigen zusätzlichen Messungen können alle wichtigen Kennmerkmale in kleinen Prüfintervallen geprüft und engere Toleranzen eingehalten werden. Damit sind eine höhere Dosisgenauigkeit, Patientensicherheit und Behandlungsqualität erreichbar. Für große Patientenzahlen ist ein maschinenbezogenes QS-System zudem effizienter als ein patientenplanbezogenes.Item Open Access Modeled 3D-structures of proteobacterial transglycosylases from glycoside hydrolase family 17 give insight in ligand interactions explaining differences in transglycosylation products(2021) Linares-Pastén, Javier A.; Jonsdottir, Lilja Björk; Hreggvidsson, Gudmundur O.; Fridjonsson, Olafur H.; Watzlawick, Hildegard; Karlsson, Eva NordbergThe structures of glycoside hydrolase family 17 (GH17) catalytic modules from modular proteins in the ndvB loci in Pseudomonas aeruginosa (Glt1), P. putida (Glt3) and Bradyrhizobium diazoefficiens (previously B. japonicum) (Glt20) were modeled to shed light on reported differences between these homologous transglycosylases concerning substrate size, preferred cleavage site (from reducing end (Glt20: DP2 product) or non-reducing end (Glt1, Glt3: DP4 products)), branching (Glt20) and linkage formed (1,3-linkage in Glt1, Glt3 and 1,6-linkage in Glt20). Hybrid models were built and stability of the resulting TIM-barrel structures was supported by molecular dynamics simulations. Catalytic amino acids were identified by superimposition of GH17 structures, and function was verified by mutagenesis using Glt20 as template (i.e., E120 and E209). Ligand docking revealed six putative subsites (-4, -3, -2, -1, +1 and +2), and the conserved interacting residues suggest substrate binding in the same orientation in all three transglycosylases, despite release of the donor oligosaccharide product from either the reducing (Glt20) or non-reducing end (Glt1, Gl3). Subsites +1 and +2 are most conserved and the difference in release is likely due to changes in loop structures, leading to loss of hydrogen bonds in Glt20. Substrate docking in Glt20 indicate that presence of covalently bound donor in glycone subsites -4 to -1 creates space to accommodate acceptor oligosaccharide in alternative subsites in the catalytic cleft, promoting a branching point and formation of a 1,6-linkage. The minimum donor size of DP5, can be explained assuming preferred binding of DP4 substrates in subsite -4 to -1, preventing catalysis.Item Open Access Multifrequente Impedanztomographie zur Darstellung der elektrischen Impedanzverteilung im menschlichen Thorax(2000) Li, Jianhua; Faust, Uwe (Prof. Dr-Ing.)Im Rahmen der vorliegenden Arbeit wird die elektrische Impedanztomographie (EIT) zur Abbildung der elektrischen Impedanz des menschlichen Thorax eingesetzt. Systematisch untersucht werden der Aufbau des Meßsystems, Algorithmen zur Rekonstruktion, und die Anwendungs-möglichkeiten der EIT. In dem realisierten System werden 32 Elektroden verwendet. Jede zweite Elektrode dient ausschließlich zur Einspeisung eines konstanten sinusförmigen Wechselstromes von 12,5 kHz - 800 kHz, die verbleibenden zur Messung der entstehenden Spannungen. Zur Verringerung des Einflusses der Verbindungs-kabel werden aktive Elektroden sowohl für die Stromeinspeisung als auch für die Spannungsmessung entwickelt. Ein auf der Finite-Elemente- und Newton-Methode basierender iterativer Algorithmus zur Bildrekonstruktion wird entwickelt und durch Computer-Simulationen optimiert. Basierend auf der Newton-Methode wird ein lineares Verfahren zur Rekonstruktion der Veränderung der Impedanz bezüglich einer homogenen Referenzverteilung eingeführt. Anhand eines Thorax-Modells werden erstmals die Einflüsse der inhomogenen Referenz auf die Rekonstruktion untersucht. Zur Überprüfung des Abbildungssystems wird als Phantom ein Widerstandsnetz eingesetzt. Untersucht werden die Einflüsse der Abweichung der Kontur des FE-Modells von der Realität auf die Abbildungsqualität. Weiter wird der Zusammenhang zwischen dem rekonstruierten und dem wahren Wert sowie der Ausdehnung der Widerstands-änderung im Phantom hergestellt. Die Frequenzabhängigkeit der Impedanz-verteilung wird quantitativ abgebildet. Das realisierte System wird am menschlichen Thorax in mehreren Ebenen in vivo angewandt. Die durch Lungenventilation und Herzaktivität hervorgerufenen Impedanz-änderungen werden mit einer Bildrate von 80 Bilder/s abgebildet. Untersucht wird auch der Zusammenhang zwischen dem Impedanz-kardiogramm (IKG) und den rekonstruierten Bildern. Damit gelingt eine auf Messung begründete Interpretation des Verlaufs des IKG.Item Open Access Vascular response on a novel fibrin-based coated flow diverter(2021) Mühl-Benninghaus, Ruben; Fries, Frederik; Kießling, Mara; Tomori, Toshiki; Krajewski, Stefanie; Simgen, Andreas; Bauer, Sabina; Hey, Natascha; Brynda, Eduard; Taborska, Johanka; Riedel, Tomáš; Reith, Wolfgang; Cattaneo, Giorgio; Brochhausen, ChristophDue to thromboembolic complications and in-stent-stenosis after flow diverter (FD) treatment, the long-term use of dual antiplatelet treatment (DAPT) is mandatory. The tested nano-coating has been shown to reduce material thrombogenicity and promote endothelial cell proliferation in vitro. We compared the biocompatibility of coated (Derivo Heal) and non-coated (Derivo bare) FDs with DAPT in an animal model. Derivo® bare (n = 10) and Derivo® Heal (n = 10) FD were implanted in the common carotid arteries (CCAs) of New Zealand white rabbits. One additional FD, alternately a Derivo bare (n = 5) or Derivo Heal (n = 5), was implanted in the abdominal aorta (AA) for assessment of the patency of branch arteries. Histopathological examinations were performed after 28 days. Angiography was performed before and after FD implantation and at follow-up. Statistical analysis of the included specimens showed complete endothelialization of all FDs with no significant differences in neointima thickness between Derivo® bare and Derivo® Heal (CCA: p = 0.91; AA: p = 0.59). A significantly reduced number of macrophages in the vessel wall of the Derivo Heal was observed for the CCA (p = 0.02), and significantly reduced fibrin and platelet deposition on the surface of the Derivo Heal was observed for the AA. All branch arteries of the stented aorta remained patent. In this animal model, the novel fibrin-based coated FD showed a similar blood and tissue compatibility as the non-coated FD.Item Open Access Investigation of tracer gas transport in a new numerical model of lung acini(2022) Schmidt, Christoph; Joppek, Christoph; Trinkmann, Frederik; Takors, Ralf; Cattaneo, Giorgio; Port, JohannesObstructive pulmonary diseases are associated with considerable morbidity. For an early diagnosis of these diseases, inert gas washouts can potentially be used. However, the complex interaction between lung anatomy and gas transport mechanisms complicates data analysis. In order to investigate this interaction, a numerical model, based on the finite difference method, consisting of two lung units connected in parallel, was developed to simulate the tracer gas transport within the human acinus. Firstly, the geometries of the units were varied and the diffusion coefficients ( D ) were kept constant. Secondly, D was changed and the geometry was kept constant. Furthermore, simple monoexponential growth functions were applied to evaluate the simulated data. In 109 of the 112 analyzed curves, monoexponential function matched simulated data with an accuracy of over 90%, potentially representing a suitable numerical tool to predict transport processes in further model extensions. For total flows greater than 5 × 10 -4 ml/s, the exponential growth constants increased linearly with linear increasing flow to an accuracy of over 95%. The slopes of these linear trend lines of 1.23 µl -1 ( D = 0.6 cm 2 /s), 1.69 µl -1 ( D = 0.3 cm 2 /s), and 2.25 µl -1 ( D = 0.1 cm 2 /s) indicated that gases with low D are more sensitive to changes in flows than gases with high D .Item Open Access Zirconia-toughened alumina ceramic wear particles do not elicit inflammatory responses in human macrophages(2023) Porporati, Alessandro Alan; Mödinger, Yvonne; Fischer, Sarah; Polajžer, Sara; Mettang, Melanie; Deisinger, Ulrike; Podlogar, Matejka; Trebše, Rihard; Lovšin, NikaTen percent of patients undergoing total hip arthroplasty (THA) require revision surgery. One of the reasons for THA are wear particles released from the implants that can activate the immune defense and cause osteolysis and failure of the joint implant. The discrepancies between reports on toxicity and immunogenicity of the implant materials led us to this study in which we compared toxicity and immunogenicity of well-defined nanoparticles from Al2O3, zirconia-toughened alumina (ZTA), and cobalt chrome (CoCr), a human THP-1 macrophage cell line, human PBMCs, and therefrom-derived primary macrophages. None of the tested materials decreased the viability of THP-1 macrophages nor human primary macrophages at the 24 h time point, indicating that at concentrations from 0.05 to 50 µm3/cell the tested materials are non-toxic. Forty-eight hours of treatment of THP-1 macrophages with 5 µm3/cell of CoCr and Al2O3 caused 8.3-fold and 4.6-fold increases in TNF-α excretion, respectively, which was not observed for ZTA. The comparison between THP-1 macrophages and human primary macrophages revealed that THP-1 macrophages show higher activation of cytokine expression in the presence of CoCr and Al2O3 particles than primary macrophages. Our results indicate that ZTA is a non-toxic implant material with no immunogenic effects in vitro.Item Open Access In vivo comparison of braided (Accero) and laser-cut intracranial stents (Acclino, Credo) : evaluation of vessel responses at subacute and mid-term follow-up in a rabbit model(2020) Mühl-Benninghaus, Ruben; Tomori, Toshiki; Krajewski, Stefanie; Dietrich, Philipp; Simgen, Andreas; Yilmaz, Umut; Brochhausen, Christoph; Kießling, Mara; Reith, Wolfgang; Cattaneo, GiorgioThis study aimed to investigate in vivo two stent technologies, with particular emphasis on thrombogenicity and inflammatory vessel remodeling processes. The micro-stents tested in this study were developed for intracranial aneurysm treatment. In our study twelve, New Zealand white rabbits were divided into two groups: 18 laser-cut stents (LCS) and 18 braided stents (BS) were impanated without admiration of antiplatelet medication. Three stents were implanted into each animal in the common carotid artery, subclavian artery, and abdominal aorta. Digital subtraction angiography was performed before and after stent implantation and at follow-up for the visualization of occurring In-stent thromboembolism or stenosis. The Stents were explanted for histopathological examination at two different timepoints, after 3 and 28 days. Angiographically neither in-stent thrombosis nor stenosis for both groups was seen. There was a progressive increase in the vessel diameter, which was more pronounced for BS than for LCS. We detected a higher number of thrombi adherent to the foreign material on day 3 for BS. On day 3, the neointima was absent, whereas the complete formation observed was on day 28. There was no significant difference between both groups regarding the thickness of the neointima. The in vivo model of our study enabled the evaluation of blood and vessel reactions for two different stent technologies. Differences in vessel dimension and tissue around the stents were observed on day 28. Histological analysis on day 3 enabled the assessment of thrombotic reactions, representing an important complementary result in long-term studies.