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Untersuchung zu Einflussfaktoren auf das Therapieergebnis und Rezidivverhalten von operativ resezierten intrakraniellen Meningeomen
No full textThis thesis investigates the influence of different factors such as e.g. histological grade, patients' demographic data, peritumoral edema, tumor volume, surgical grade of resection and radiation on therapy outcomes and recurrence of patients with surgically resected intracranial meningiomas.
Meningiomas are among the most common primary brain tumors, and despite their generally benign nature, recurrence remains a relevant clinical challenge. The study analyzes a retrospective patient cohort with a total of 141 patients treated over at least 60 months, assessing variables such as tumor location, size, histopathological grade, extent of resection, peritumoral edema, Karnofsky Performance Scale score and adjuvant treatment. Statistical models were applied to identify independent predictors of progression-free and overall survival as well as risk factors for recurrence. For evaluation of therapy outcome Karnofsky Performance Scale (KPS) was used.
The results demonstrate that tumor size differs significantly in cases with recurrence during follow up. Age is also a significant factor for recurrence, wheres as the extent of resection is not. KPS Scores tended to be lower in patients with recurrence during follow up.
Furthermore, the findings highlight that individualized treatment strategies, based on a combination of clinical and histopathological factors, may improve prognosis and reduce recurrence rates. The study contributes to a better understanding of the multifactorial nature of meningioma recurrence and supports the development of standarized postoperative follow-up and therapeutic strategies.2025-12-0
Polylactic acid as a binder for lignocellulosic-based insulation materials
No full textDiese Forschungsarbeit untersucht die potenzielle Anwendung eines erneuerbaren Bindemittels in flexiblen Dämmstoffen, die aus lignozellulosehaltigen Rohstoffen hergestellt werden. Solche Materialien basieren auf Lignozellulosefasern und können sowohl aus Holzquellen wie Laub- und Nadelholz als auch aus Nichtholzquellen wie Kapokfasern gewonnen werden. Vor dem Hintergrund, dass die Holzindustrie derzeit verstärkt darauf abzielt, nicht erneuerbare Bindemittel wie Polymethylendiphenyldiisocyanat (pMDI) und Melaminharnstoff-Formaldehyd (MUF) zu substituieren, soll diese Arbeit auch das Potenzial der Verwendung von Polymilchsäure (PLA) als Bindemittel in flexiblen Dämmstoffen aus natürlichen Fasern erforschen.
Um das Verständnis der Leistungsfähigkeit der mit Naturfasern und Bindemitteln hergestellten Materialien zu vertiefen, wurden vier Forschungsstudien durchgeführt, die in vier Publikationen führten:
1. Die Entdeckung von Naturfaser-Dämmplatten und Naturklebstoffen mit Schwerpunkt auf Polymilchsäure (PLA) – Ein Überblick
Diese Arbeit bietet einen umfassenden Überblick über die Forschung zu Dämmstoffen aus Naturfasern und Naturklebstoffen, mit besonderem Fokus auf Polymilchsäure (PLA). Sie basiert auf der zunehmenden Besorgnis über den übermäßigen Einsatz erdölbasierter Ressourcen, der Wissenschaftler dazu veranlasst, verstärkt natürliche und erneuerbare Rohstoffe zu erforschen. Die Diskussion umfasst das wachsende Interesse an Naturfaserdämmplatten und die Rolle natürlicher Klebstoffe bei der Herstellung vollständig umweltfreundlicher Produkte. Die Leistungsbewertung dieser Dämmstoffe erfolgt üblicherweise anhand mechanischer und physikalischer Eigenschaften wie Biege-, Druck- und Zugfestigkeit, Dichte, Wasseraufnahme und Wärmeleitfähigkeit sowie unter Berücksichtigung der relevanten technischen Normen. Die Literatur verweist auf eine Vielzahl pflanzenbasierter Fasern, insbesondere Holzfasern, sowie auf natürliche Klebstoffquellen wie Lignin, Gerbstoffe und Proteine.
2. Holzfaserdämmplatten aus Laub- und Nadelhölzern mit Polymilchsäurefasern (PLA) als Bindemittel
Da Naturfasern eine hohe Variabilität aufweisen, wurden in dieser Studie flexible Dämmplatten aus verschiedenen Holzarten – Kiefer und Fichte (Nadelholz) sowie Buche und Birke (Laubholz) – mit Dichten von 80 kg/m³, 100 kg/m³ und 120 kg/m³ im Heißpressverfahren hergestellt. Als Bindemittel kamen Bikomponentenfasern aus zwei konzentrischen Schichten von PLA in einer Konzentration von 10 % (w/w, Trockenbasis) zum Einsatz. Es wurden technologische Eigenschaften wie kurzfristige Wasseraufnahme, Druckfestigkeit und thermisches Verhalten untersucht. Die Dichte hatte einen signifikanten Einfluss auf Wasseraufnahme, Druckfestigkeit und Wärmeleitfähigkeit; alle Eigenschaften nahmen mit steigender Dichte zu. Dämmplatten aus Laubholzfasern zeigten höhere Werte bei Wasseraufnahme und Druckfestigkeit als solche aus Nadelholz. Dämmplatten aus Nadelholz mit 80 kg/m³ wiesen eine geringere Wärmeleitfähigkeit auf als die aus Laubholz. Diese Ergebnisse unterstreichen das vielversprechende Potenzial zur Herstellung flexibler Holzfaserdämmplatten aus natürlichen und erneuerbaren Rohstoffen.
3. Holzfaserdämmplatten mit Polymilchsäure als Bindemittel hergestellt durch Heißpressen und Heißluftverfahren
In dieser Studie wurden Holzfaserdämmplatten (WFIB) unter Verwendung von Polymilchsäure (PLA) als erneuerbarem Bindemittel mittels zweier Verfahren hergestellt: Heißpressen (HP) und Heißluft (HA). Dabei wurden Platten mit Dichten von 60 kg/m³, 80 kg/m³ und 100 kg/m³ sowie PLA-Konzentrationen von 5 %, 10 % und 15 % gefertigt, um den Einfluss dieser Variablen auf die Leistung der Dämmplatten zu untersuchen. Holz- und PLA-Fasern wurden mittels Rasterelektronenmikroskopie (SEM) und Lichtmikroskopie analysiert. Die WFIBs wurden hinsichtlich physikalischer Eigenschaften wie Dichte und kurzfristiger Wasseraufnahme sowie mechanischer Eigenschaften wie Druckfestigkeit bewertet. Zudem erfolgte eine Untersuchung der thermischen Eigenschaften, darunter Wärmeleitfähigkeit und thermogravimetrische Analyse (TGA). Die Ergebnisse zeigten, dass die Dichte mit Wasseraufnahme, Druckfestigkeit und Wärmeleitfähigkeit korreliert. Die Zugabe von PLA verbesserte die mechanischen Eigenschaften, insbesondere die Druckfestigkeit, und erhöhte die kurzfristige Wasserbeständigkeit. Zusammenfassend konnten Holzfaserdämmplatten mit PLA als Bindemittel erfolgreich mittels Heißpressen und Heißluftverfahren hergestellt werden, wobei sie niedrige Wärmeleitfähigkeiten erzielten, die mit kommerziellen Produkten vergleichbar sind.
4. Leichte Dämmplatten aus Kapokfasern (Ceiba pentandra) mit Polymilchsäure oder Bikomponentenfasern als Bindemittel
Die Studie widmet sich der Entwicklung leichter Dämmplatten aus Kapokfasern, die mittels Heißluftverfahren hergestellt wurden. Die Zusammensetzung umfasst 95 % Kapokfasern und 5 % Polymilchsäure oder Bikomponentenfasern als Bindemittel. So entstanden Platten mit bemerkenswert niedrigen Dichten von 10 kg/m³, 15 kg/m³ und 20 kg/m³. Die Untersuchung umfasste technologische Eigenschaften wie Dichte, Porosität, Wasseraufnahme, Benetzbarkeit, Druckfestigkeit und Wärmeleitfähigkeit, welche mit handelsüblicher Glaswolle verglichen wurden. Es wurde eine direkte Korrelation zwischen Wasseraufnahme und Dichte festgestellt, wobei dichtere Materialien mehr Wasser aufnehmen. Alle gemessenen Kurzzeit-Wasserabsorptionswerte lagen unter 1 kg/m² und erfüllen somit kommerzielle Standards. Diese Leistung wird auf die geringe Dichte, die hohe Porosität sowie die natürliche hydrophobe Wachsbeschichtung der Kapokfaserzellwand zurückgeführt. Die Benetzbarkeitstests zeigten eine erhöhte Wasserresistenz der Kapokplatten. Hinsichtlich der Druckfestigkeit hatten Bindemitteltyp und Dichte bei den niedrigen getesteten Dichten keinen signifikanten Einfluss. Die Wärmeleitfähigkeit der Kapokplatten entsprach ebenfalls den gängigen kommerziellen Standards.This research explores the possible application of a renewable binder in the development of flexible insulation materials derived from lignocellulosic sources. These materials, based on lignocellulosic fibers, can be produced from wood sources, such as hardwoods and softwoods, as well as from non-wood sources like kapok fibers. Given the current emphasis in the wood-products industry on substituting non-renewable binders such as polymethylene diphenyl-diisocyanate (pMDI) and melamine urea formaldehyde (MUF), this research also aims to contribute to the exploration of the potential of using polylactic acid (PLA) as a binder in flexible insulation materials produced with natural fibers and binders. In order to deepen the understanding of the performance of the materials produced with natural fibers and binders, four research studies were conducted, resulting in four publications;
1. Discovering Natural Fiber-Insulation Boards and Natural Adhesives, focused on a Polylactic Acid (PLA) Application – a Review
This work presents a comprehensive overview of research centered around insulation products produced from natural fibers and natural adhesives, with a particular focus on polylactic acid (PLA). The study is grounded on the growing concern about the excessive use of petroleum-based resources, prompting scientists to shift their attention towards enhancing the use of natural-origin and renewable resources. The discussion extends to the increasing interest in natural-fiber insulation boards and the role of natural adhesives in supporting these boards to create a wholly eco-friendly product. Additionally, the performance of these natural-fiber insulation materials is typically evaluated through various mechanical and physical properties, including bending, compression, tensile strength, density, water absorption, and thermal conductivity, as well as the technical standards involved. The literature referenced in the study identifies a range of plant-based fibers, particularly wood fibers, alongside natural adhesive sources such as lignin, tannins, and proteins.
2. Wood-fiber insulation boards (WFIB) produced with hardwood and softwoods species and polylactic acid (PLA) fibers as a binder:
This study addresses the variability in natural fiber properties by producing flexible insulation boards from different wood species—pine and spruce (softwoods), and beech and birch (hardwoods)—with densities of 80 kg/m³, 100 kg/m³, and 120 kg/m³ using the hot press method. Bicomponent fibers, made of two concentric layers of polylactic acid (PLA), were employed as a renewable-origin binder at a 10 % (w/w, dry basis) proportion. Various technological properties, including short-term water absorption, compression strength, and thermal performance, were assessed. The density of WFIB significantly affects water absorption, compression strength, and thermal conductivity, with all these properties increasing as density increases. Insulation boards produced from hardwood fibers showed higher values for water absorption and compression strength compared to those made with softwoods. The insulation boards produced with softwoods with a density of 80 kg/m3 displayed lower thermal conductivities than those composed of hardwoods. This research highlights the promising potential of producing flexible wood fiber insulation boards utilizing natural and renewable fibers and binders.
3. Wood‑fiber insulation boards produced with polylactic acid as a binder by hot press and hot air:
In this research, wood fiber insulation boards (WFIB) were created using polylactic acid (PLA), a renewable and natural-origin binding agent, employing two techniques: hot pressing (HP) and hot air (HA). Boards with densities of 60 kg/m3, 80 kg/m3, and 100 kg/m3, along with PLA concentrations of 5 %, 10 %, and 15 %, were fabricated using both the hot press (HP) and hot air (HA) processes in order to evaluate and understand the effects of all these variables on insulation boards performance. The WFIBs were assessed in their physical properties, including density and short-term water absorption, as well as their mechanical property of compression resistance. Moreover, thermal characteristics such as thermal conductivity and thermogravimetric analysis (TGA) were evaluated. The wood and PLA fibers underwent examination with a scanning electron microscope (SEM) and an optical microscope. For the WFIBs produced, the density values correlate with trends in water absorption, compression strength, and thermal conductivity. The addition of polylactic acid (PLA) enhances the mechanical property of compression strength and improves the physical property of short-term water resistance. In conclusion, wood fiber insulation boards (WFIB) were successfully produced using polylactic acid (PLA) as a binder through both hot press (HP) and hot air (HA) techniques, achieving remarkably low thermal conductivity values that are on par with those of commercial products.
4. Lightweight Natural Fiber Insulation Boards Produced with Kapok Fiber (Ceiba pentandra) and Polylactic Acid or Bicomponent Fiber as a Binder
This research focuses on the development of lightweight insulation panels composed of kapok fibers and bound with either PLA or bicomponent fiber. The panels were manufactured using a hot-air process, with kapok fibers making up 95% of the composition and the binder comprising 5%. This composition and process result in remarkably low densities of 10 kg/m3, 15 kg/m3, and 20 kg/m3. The study evaluates technological attributes including density, porosity, water absorption, wettability, compression strength, and thermal conductivity of these panels, comparing them to commercially available glass wool. Findings indicate a direct correlation between water absorption rates and density, suggesting that denser materials tend to absorb more water. All measured short-term water absorption values are below 1 kg/m2, meeting commercial standards. This performance is attributed to the samples' low density and high porosity, along with the natural hydrophobic wax coating on the kapok fiber's cell wall. Similar results are observed in wettability tests, as the kapok fiber boards demonstrate a higher water resistance upon contact. When considering compression as a mechanical property, the binder type and density levels do not significantly influence compression characteristics at the tested low densities. Additionally, the thermal conductivity of the kapok-based panels aligns with commercial standards.2025-12-0
Development of Low-Order Scaling Multicomponent Methods
No full textThis work targets the development and application of low-order scaling multicomponent methods for efficient simulation of nuclear quantum effects (NQE) within complex systems. The awareness of NQEs is increasingly growing across various fields, including chemistry, biology, and materials science, where light nuclei, like protons, play an essential role in molecular interactions and properties. This thesis presents a systematic development and application of multicomponent methods based on the Nuclear-Electronic Orbital (NEO) framework developed by Hammes-Schiffer and coworkers. In general, the focus is placed on the implementation and optimization of multicomponent Hartree-Fock, density functional and Møller-Plesset perturbation theory, as well as composite correlation approaches. Overall, by addressing computational bottlenecks and notably expanding the scope of multicomponent methods, this work contributes to the development of an extended standard quantum chemistry toolbox and paves the way for routine simulations of NQEs.2026-01-2
Investigating visual coding by retinal ganglion cells in optogenetic models for vision restoration
No full textRetinal degeneration is one of the leading causes of blindness affecting more than 20 million people globally aged 50 years and older. Among various methods of vision restoration currently being explored, optogenetics has garnered much attention in the past decade. In this approach, naturally occurring light-sensitive molecules like Channelrhodopsin-2 (ChR2), rhodopsin or other engineered opsins are inserted into the neurons in the inner retina to play the role of light-sensing elements after the loss of photoreceptors. Previous studies have shown responses of retinal ganglion cells (RGCs) in blind animal models with optogenetically modified retinas mostly based on simple and artificial light stimuli. In this thesis, I focus on how implementing optogenetic therapy affects the cellular responses in the retina under more naturalistic stimulation. Furthermore, I address if we can develop strategies to optimize optogenetic stimulation to achieve as normal vision as possible. By conducting experiments using multielectrode arrays and recording spiking activity of RGCs in mouse retinas with both intact photoreceptors and RGCs expressing ChR2, we show that RGCs have strong responses under optogenetic stimulation by natural images with characteristic differences to photoreceptor-driven responses towards the same. We then sought to drive more similar responses in the optogenetically modified retina as in the normal retina by optimizing the optogenetic stimulation by transforming the inputs used for stimulation. Based on the differences in photoreceptor-driven and optogenetically-driven responses, the natural images were modified by methods such as thresholding and blurring and presented to the RGCs under ChR2 activation. We found that certain types of image modifications elicited stronger and also more similar responses to the photoreceptor-evoked responses than unmodified images under ChR2 activation. These findings may help in generating better optogenetic therapies in the future by optimizing stimulation of optogenetically modified retinas to achieve more natural vision. In the penultimate chapter of the thesis, I also investigate visual coding by retinal ganglion cells in mice which express Opto-mGluR6 (in their bipolar cells), another molecule which can be used for vision restorative optogenetic therapies.2026-01-2
Flows and forces in the early development of an averaged zebrafish embryo. A novel analysis pipeline for the dynamics of embryogenesis.
No full textOur current knowledge on collective cell phenomena such as wound healing,
cancer invasion and embryogenesis heavily relies on biochemistry. However,
new advances in the field of cell dynamics have shown how mechanosensing
plays a crucial role in such processes. Tackling the still open questions from
the new, fresh perspective of biophysics has proven to be an excellent complement
to the up-to-date studies, shining light into complex phenomena which
can not be fully understood relying only on genetics and chemical signaling.
Embryogenesis is a particularly intricate phenomenon, where an orchestration
of many interconnected mechanisms can transform a zygote into a complex,
living structure in a matter of hours. The initial collective motion
leading to the differentiation of the primordial germ layers in an embryo,
named gastrulation, are usually studied in fast developing organisms, such
as Xenopus, Drosophila melanogaster and Zebrafish (Danio rerio). Despite
the vast literature covering the first hours of gastrulation in several species,
some of the details about those collective motions in Zebrafish in particular
are still to be fully understood, such as the exact mechanics of doming
and epiboly. One such open question is the mechanism leading to the early
embryonic symmetry breaking, where the left-right asymmetry of the body
plan is established for the first time.
In this work we present a new approach to investigate that particular phenomenon
from a mechanical point of view. Our aim is to understand the
mechanical state of the embryonic tissue leading to its first symmetry breaking
during epiboly: the shield formation. We present a working pipeline
built for the construction of average embryonic datasets based solely on the
registration of cellular velocity fields, without the necessity for additional
fluorescent labels or hand-curated alignments. Along with it, we developed a
user-friendly analysis tool for the calculation of surface stresses as felt by in
vivo force sensors, versatile enough to be used in several biophysical contexts,
such as for the analysis of nuclear geometry. Together, these two tools enable
a novel insight into the mechanical evolution of the embryo prior and during
symmetry breaking. Our findings reveal the existence of a ventral-dorsal
mechanical polarity, representing a novel report, as evidenced by an in-depth
analysis of velocity fields and stress maps.2025-07-0
A Cross-Cultural Investigation of Privacy Perceptions Regarding Concerns, Responsibility, and Understandability
No full textIn today's data driven world, individuals' data is collected almost constantly. Whether it is apps on mobile phones or social media sites, companies collect, store, and process their users' data in order to enhance their services, to tailor marketing campaigns to each user, or to gather insights about users' behavior. Critically, individuals' Personally Identifiable Information (PII) is also collected which makes it important to control these data flows–a difficult task given the ubiquity of the data collection. It is nearly impossible for laypeople and experts alike to guess the amount of data which each individual company holds about them. Hence, technical tools and laws are in place that aim to protect individuals' privacy. A landmark regulation in this regard is the European General Data Protection Regulation (GDPR). It has been created in order to prevent malicious data practices and to protect EU citizens' data, but has since its inception influenced many data protection laws around the globe. While most criticism about the GDPR revolves around the introduced nuisances, such as cookie banners, it is also unclear whether the regulation protects against threats that individuals are most concerned about. This gap becomes especially apparent when considering the pervasive role of modern technology in everyday life, where data collection often happens unnoticed.
One of the devices collecting more data than most users assume are smart speakers. These devices are widely used and, while being convenient, collect a lot of speech data. This includes everyone who interacts with the smart speaker, i.e., all users in the household and visitors, who might not even be aware that a smart speaker is active. Hence, methods that protect people's privacy must be in place. To evaluate the efficacy of these protections, it is important to understand who users and bystanders perceive as most responsible to protect their privacy. Laws and technical solutions should adequately address these different data protection needs. Moreover, since smart speakers are used worldwide, it is important to consider cultural differences in these perceptions and whether diverse privacy control mechanisms are needed, based on the user's culture. Next to laws and regulations, technical solutions to protect privacy are also in place. However, they are often hard to locate and it is unclear who smart speaker users and bystanders perceive as responsible to conceptualize, implement, and activate them.
One widely used solution for privacy-preserving data collection is Differential Privacy (DP). Data processed under DP are perturbed in a way that balances the privacy needs of individuals in the data set and the need of data analysts to still extract useful information from the data. Thus, any individual whose data is in a DP data set has an extra layer of privacy.
One key challenge regarding DP is the difficulty of explaining it to laypeople, which is however needed as consent to data processing under the GDPR must be given in an informed way.
In this thesis, we first address the question of what smart speaker users and bystanders are most concerned about and who they believe bears the greatest responsibility for protecting their privacy. We do this via two large scale quantitative vignette studies aimed at smart speaker users and bystanders from Germany and the UK, to compare two countries in which citizens from both are protected by the GDPR, but that are still culturally diverse in dimensions that are relevant for privacy perceptions.
Next, we evaluate approaches to making DP more understandable for laypeople and measure what other factors are correlated to their data sharing attitudes. Here, we first replicate a mixed design study examining how different descriptions of DP are correlated with data sharing attitudes before conducting another mixed design study to investigate how visualizations compare to textual descriptions and which factors are ultimately correlated to an increase in data sharing attitudes if data is protected with DP. Both of these two studies primarily involve German participants to allow comparability.
The results indicate that most smart speaker users and bystanders are concerned about the device manufacturer, third parties, and the state. We show that the varying user groups have different perceptions in this regard and that cultural differences between Germany and the UK are indeed significant. Moreover, we discovered a trend towards a rising privacy concern in younger generations; something that points in the opposite direction of most previous research in this area.
Lastly, we show that understanding DP is not correlated to data sharing attitudes. While visualizations of DP perform poorly regarding participants' understandability, they are correlated with an increase in data sharing attitudes. Ultimately, though, the underlying privacy persona is the most significant factor w.r.t. a positive change in data sharing attitude when data is protected with DP.
Software on smart speakers needs to have Privacy-by-Default, i.e., that standard settings are set to the maximum data protection. However, they must also be flexible enough to allow users to change their privacy settings, if they want to take control of data processing. Moreover, solutions for bystanders are needed, as they are a large group affected by IoT data collection with almost no agency regarding their privacy. One possible solution are indicators of data collection.
Regarding DP, simple visualizations work well when trying to increase data sharing attitudes, but they do not increase understanding of the method. That means that for most people who are not experts, showing the implication of DP is a simple and effective way to increase trust in the method
Retrospektive Matched-Pair-Analyse einer intraoperativen lasergestützten Fluoreszenz-Perfusionsmessung des Magenschlauches im Rahmen einer Ösophagusresektion
No full textThe aim of this study was to analyze the influence of intraoperative application of an ILF in esophageal surgery on the occurrence of anastomotic leakage, postoperative morbidity and mortality, and length of hospital stay.2025-09-1
Total Syntheses of natural products derived from the liverwort using pi-acidic catalysts
No full textOver the years, many natural products and chemical structures derived from plants, animals, microorganisms and marine organisms have been used as an inspiration for the synthesis of small molecules. The knowledge of using nature for medicinal purpose is already established for a long time as the traditional medicine in the Far East utilizes natural products derived from a wide variety of lichens, mosses, and ferns. One of the mosses, the liverworts (Marchantiophyta) is commonly used in Japanese folk medicine as they exhibit antitumor, antiallergenic, diuretic and antibacterial activities. Extracts from liverworts were studied by Asakawa et.al. who identified several macrocyclic bisbibenzyls which account for their biological acitivity.
Herein, the total synthesis of (±)-Angustatin A, which was isolated from the liverwort Asterella angusta in 2013, is shown. This macrocyclic bisbibenzyl displays several interesting architectural features due to its constrained macrocycle. Additionally, a total synthesis approach towards another member of the macrocyclic bisbibenzyls, the Bazzanin K, is demonstrated.2025-08-0
In vitro performance of six combinations of adjustable differential pressure valves and fixed anti siphon devices with and without vertical motion
No full textShunt therapy using adjustable differential pressure valves combined with anti-siphon devices (ASDs) is a well-established approach for treating normal pressure hydrocephalus but continues to pose risks of severe complications, such as overdrainage. This study is aimed to analyze the flow characteristics of 3 commercial differential pressure valves paired with 2 different ASDs under static and dynamic conditions.
The differential pressure valves proGAV 2.0 [PG], CertasPlus [CP], and HakimMedos [HM] were evaluated in combination with the gravity-regulated ASD (ShuntAssistant [SA]) and the flow-regulated ASD (SiphonGuard [SG]. Flow data was recorded at differential pressures ranging from 4 to 40 cmH₂O in both stationary setups and during vertical oscillations at frequencies of 2, 3, and 4 Hz. Additionally, the impact of inclination angles (90° vs. 60°) on flow rates was assessed.
Results demonstrated that combinations with the gravity-regulated ASD allowed no or minimal flow at low differential pressures in static conditions, while a linear increase in flow occurred at higher pressures. Dynamic testing revealed significant flow increases for these combinations, proportional to oscillation frequency. In contrast, combinations with flow-regulated ASDs exhibited lower flow rates overall, and movement did not increase flow. Instead, the characteristic biphasic flow curve observed under static conditions was eliminated during motion.
The distinct flow characteristics of the ASDs highlight the critical importance of selecting appropriate valve combinations for clinical applications. The findings provide valuable insights into tailoring shunt systems to individual patient needs and mitigating complications associated with movement. Further studies should build upon these results to optimize shunt systems and reduce the incidence of overdrainage in clinical practice.2025-02-1
Erhebung echokardiographischer Parameter zur Quantifizierung der Pulmonalklappeninsuffizienz und Vergleich zur Schweregradbeurteilung im MRT
No full textPulmonary regurgitation (PR) is a common valvular disease in patients with congenital heart defects (CHD) and contributes to morbidity and mortality in the long-term. This retrospective analysis invastigated wether echocardiographic parameters are appropriate for quantification of PR. The study also investigated the prediction of pulmonary valve replacement (PVR), both in comparison to phase contrast (PC) flow measurements from cardiovascular magnetic resonance (CMR), as CMR has emerged as the the gold-standard for PR assessment. In this study continuous wave (CW) Doppler and colour flow images in echocardiographies from 53 patients with CHD were analysed.
Slope and jet-to-RVOT ratio correlated significantly with CMR-assessed regurgitation fraction (RF), whereas pressure half time (PHT) showed an inverse correlation. Patients with mild PR in CMR had significantly higher PHT, lower slope and jet-to-RVOT ratio than patients with moderate or severe regurgitation. The optimal cut-off values calculated from ROC analysis to differentiate severe from not-severe PR were 95 ms for PHT and 4.9 m/s2 for slope.
The requirement of pulmonary valve replacement (PVR) due to PR was the clinical endpoint of this study. The calculated cut-off values (PHT 95 ms, slope 4.9 m/s2) were used to test the prognostic performance of PHT and slope regarding the indication for PVR. Univariate logistic regression revealed, that a reduced PHT below 95 ms or an elevated slope above 4.9 m/s2 were significantly associated with a 3.3- and 15.8-increased risk for PVR recommendation. Logistic regression analysis showed that slope emerged as the most valuable parameter for predicting the indication for PVR (OR 12.9, 95% CI, 1.8–90.9, P = 0.010).
In conclusion, echocardiographic assessment appears useful and appropriate in the management of patients with PR.2025-02-1