• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 5
  • 2
  • 1
  • Tagged with
  • 8
  • 8
  • 4
  • 4
  • 4
  • 3
  • 3
  • 3
  • 3
  • 3
  • 2
  • 2
  • 2
  • 2
  • 2
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Untersuchungen zur Erzeugung und Dosierung dünner Flüssigkeitsschichten auf Walzen

Berg, Martin 04 August 1999 (has links)
Das Ziel der Arbeit besteht in der Ermittlung einer optimalen Lösung für den Verarbeitungsvorgang ¨Beschichtung mit dünnen Flüssigkeitsschichten¨. Die Untersuchungen sind dabei auf hochviskose Flüssigkeiten, insbesondere Offsetdruckfarbe, fokussiert. Sinkende Auflagenhöhen in der Druckindustrie erfordern Beschichtungseinrichtungen, die reaktionsschnell sind, schnell einen stationären Betriebszustand erreichen und eine hohe Reproduziergenauigkeit aufweisen. Zunächst findet eine Analyse des Standes der Technik und eine systematische Untersuchung des Verarbeitungsvorgangs statt. Dabei erfolgt eine Unterteilung in fünf Teilaufgaben: Separieren und Beschleunigen, Dosieren, Vergleichmäßigen, Auftragen und Rückführen. Für unbekannte Teillösungen werden Prinzipversuche durchgeführt. Die Synthese möglicher Teillösungen ergibt mehrere Gesamtlösungen. Die beste Gesamtlösung wird in einem Versuchsstand umgesetzt. Dort erfolgen mit einer ausgewählten Offsetfarbe Experimente zum Dosierverhalten und zu auftretenden Belastungen. Die Experimente beinhalten Einflüsse von Parametern, die während des Betriebs variiert werden können. Zur Verifikation der Ergebnisse dienen theoretische Modelle, welche die vorhandene Strömung abbilden und das Dosierverhalten simulieren. Vergleiche zwischen Experimenten und Simulationen ermöglichen Aussagen über eine Vorherbestimmbarkeit des Dosierverhalten für geänderte geometrische und ki-nematische Randbedingungen und stoffliche Eigenschaften.
2

How to improve prescription of inhaled salbutamol by providing standardised feedback on administration

Neininger, Martina P., Kaune, Almuth, Bertsche, Astrid, Rink, Jessica, Musiol, Juliane, Frontini, Roberto, Prenzel, Freerk, Kiess, Wieland, Bertsche, Thilo 16 February 2015 (has links) (PDF)
Background: The effectiveness of inhaled salbutamol in routine care depends particularly on prescribed dosage and applied inhalation technique. To achieve maximum effectiveness and to prevent drug-related problems, prescription and administration need to work in concert. Methods: We performed a controlled intervention pilot study with 4 consecutive groups in a general paediatric unit and assessed problems in salbutamol prescribing and administration. Control group [i]: Routine care without additional support. First intervention group [ii]: We carried out a teaching session for nurses aimed at preventing problems in inhalation technique. Independently from this, a pharmacist counselled physicians on problems in salbutamol prescribing. Second intervention group [iii]: Additionally to the first intervention, physicians received standardised feedback on the inhalation technique. Follow-up group [iv]: Subsequently, without any delay after the second intervention group had been completed, sustainability of the measures was assessed. We performed the chi-square test to calculate the level of significance with p ≤ 0.05 to indicate a statistically significant difference for the primary outcome. As we performed multiple testing, an adjusted p ≤ 0.01 according to Bonferroni correction was considered as significant. Results: We included a total of 225 patients. By counselling the physicians, we reduced the number of patients with problems from 55% to 43% (control [i] vs. first intervention [ii], n.s.). With additional feedback to physicians, this number was further reduced to 25% ([i] vs. [iii], p < 0.001). In the follow-up [iv], the number rose again to 48% (p < 0.01 compared to feedback group). Conclusions: Teaching nurses, counselling physicians, and providing feedback on the quality of inhalation technique effectively reduced problems in salbutamol treatment. However, for success to be sustained, continuous support needs to be provided. Trial registration: German Clinical Trials register: DRKS00006792.
3

Positron Emission Tomography for the dose monitoring of intra-fractionally moving Targets in ion beam therapy

Stützer, Kristin 26 June 2014 (has links) (PDF)
Ion beam therapy (IBT) is a promising treatment option in radiotherapy. The characteristic physical and biological properties of light ion beams allow for the delivery of highly tumour conformal dose distributions. Related to the sparing of surrounding healthy tissue and nearby organs at risk, it is feasible to escalate the dose in the tumour volume to reach higher tumour control and survival rates. Remarkable clinical outcome was achieved with IBT for radio-resistant, deep-seated, static and well fixated tumour entities. Presumably, more patients could benefit from the advantages of IBT if it would be available for more frequent tumour sites. Those located in the thorax and upper abdominal region are commonly subjected to intra-fractional, respiration related motion. Different motion compensated dose delivery techniques have been developed for active field shaping with scanned pencil beams and are at least available under experimental conditions at the GSI Helmholtzzentrum für Schwerionenforschung (GSI) in Darmstadt, Germany. High standards for quality assurance are required in IBT to ensure a safe and precise dose application. Both underdosage in the tumour and overdosage in the normal tissue might endanger the treatment success. Since minor unexpected anatomical changes e.g. related to patient mispositioning, tumour shrinkage or tissue swelling could already lead to remarkable deviations between planned and delivered dose distribution, a valuable dose monitoring system is desired for IBT. So far, positron emission tomography (PET) is the only in vivo, in situ and non-invasive qualitative dose monitoring method applied under clinical conditions. It makes use of the tissue autoactivation by nuclear fragmentation reactions occurring along the beam path. Among others, +-emitting nuclides are generated and decay according to their half-life under the emission of a positron. The subsequent positron-electron annihilation creates two 511 keV photons which are emitted in opposite direction and can be detected as coincidence event by a dedicated PET scanner. The induced three-dimensional (3D) +- activity distribution in the patient can be reconstructed from the measured coincidences. Conclusions about the delivered dose distribution can be drawn indirectly from a comparison between two +-activity distributions: the measured one and an expected one generated by a Monte-Carlo simulation. This workflow has been proven to be valuable for the dose monitoring in IBT when it was applied for about 440 patients, mainly suffering from deep-seated head and neck tumours that have been treated with 12C ions at GSI. In the presence of intra-fractional target motion, the conventional 3D PET data processing will result in an inaccurate representation of the +-activity distribution in the patient. Fourdimensional, time-resolved (4D) reconstruction algorithms adapted to the special geometry of in-beam PET scanners allow to compensate for the motion related blurring artefacts. Within this thesis, a 4D maximum likelihood expectation maximization (MLEM) reconstruction algorithm has been implemented for the double-head scanner Bastei installed at GSI. The proper functionality of the algorithm and its superior performance in terms of suppressing motion related blurring artefacts compared to an already applied co-registration approach has been demonstrated by a comparative simulation study and by dedicated measurements with moving radioactive sources and irradiated targets. Dedicated phantoms mainly made up of polymethyl methacrylate (PMMA) and a motion table for regular one-dimensional (1D) motion patterns have been designed and manufactured for the experiments. Furthermore, the general applicability of the 4D MLEM algorithm for more complex motion patterns has been demonstrated by the successful reduction of motion artefacts from a measurement with rotating (two-dimensional moving) radioactive sources. For 1D cos2 and cos4 motion, it has been clearly illustrated by systematic point source measurements that the motion influence can be better compensated with the same number of motion phases if amplitudesorted instead of time-sorted phases are utilized. In any case, with an appropriate parameter selection to obtain a mean residual motion per phase of about half of the size of a PET crystal size, acceptable results have been achieved. Additionally, it has been validated that the 4D MLEM algorithm allows to reliably access the relevant parameters (particle range and lateral field position and gradients) for a dose verification in intra-fractionally moving targets even from the intrinsically low counting statistics of IBT-PET data. To evaluate the measured +-activity distribution, it should be compared to a simulated one that is expected from the moving target irradiation. Thus, a 4D version of the simulation software is required. It has to emulate the generation of +-emitters under consideration of the intra-fractional motion, their decay at motion state dependent coordinates and to create listmode data streams from the simulated coincidences. Such a revised and extended version that has been compiled for the special geometry of the Bastei PET scanner is presented within this thesis. The therapy control system provides information about the exact progress of the motion compensated dose delivery. This information and the intra-fractional target motion needs to be taken into account for simulating realistic +-activity distributions. A dedicated preclinical phantom simulation study has been performed to demonstrate the correct functionality of the 4D simulation program and the necessity of the additional, motionrelated input parameters. Different to the data evaluation for static targets, additional effort is required to avoid a potential misleading interpretation of the 4D measured and simulated +-activity distributions in the presence of deficient motion mitigation or data processing. It is presented that in the presence of treatment errors the results from the simulation might be in accordance to the measurement although the planned and delivered dose distribution are different. In contrast to that, deviations may occur between both distributions which are not related to anatomical changes but to deficient 4D data processing. Recommendations are given in this thesis to optimize the 4D IBT-PET workflow and to prevent the observer from a mis-interpretation of the dose monitoring data. In summary, the thesis contributes on a large scale to a potential future application of the IBT-PET monitoring for intra-fractionally moving target volumes by providing the required reconstruction and simulation algorithms. Systematic examinations with more realistic, multi-directional and irregular motion patterns are required for further improvements. For a final rating of the expectable benefit from a 4D IBT-PET dose monitoring, future investigations should include real treatment plans, breathing curves and 4D patient CT images.
4

Untersuchungen zur Erzeugung und Dosierung dünner Flüssigkeitsschichten auf Walzen

Berg, Martin 14 June 1999 (has links)
Das Ziel der Arbeit besteht in der Ermittlung einer optimalen Lösung für den Verarbeitungsvorgang ¨Beschichtung mit dünnen Flüssigkeitsschichten¨. Die Untersuchungen sind dabei auf hochviskose Flüssigkeiten, insbesondere Offsetdruckfarbe, fokussiert. Sinkende Auflagenhöhen in der Druckindustrie erfordern Beschichtungseinrichtungen, die reaktionsschnell sind, schnell einen stationären Betriebszustand erreichen und eine hohe Reproduziergenauigkeit aufweisen. Zunächst findet eine Analyse des Standes der Technik und eine systematische Untersuchung des Verarbeitungsvorgangs statt. Dabei erfolgt eine Unterteilung in fünf Teilaufgaben: Separieren und Beschleunigen, Dosieren, Vergleichmäßigen, Auftragen und Rückführen. Für unbekannte Teillösungen werden Prinzipversuche durchgeführt. Die Synthese möglicher Teillösungen ergibt mehrere Gesamtlösungen. Die beste Gesamtlösung wird in einem Versuchsstand umgesetzt. Dort erfolgen mit einer ausgewählten Offsetfarbe Experimente zum Dosierverhalten und zu auftretenden Belastungen. Die Experimente beinhalten Einflüsse von Parametern, die während des Betriebs variiert werden können. Zur Verifikation der Ergebnisse dienen theoretische Modelle, welche die vorhandene Strömung abbilden und das Dosierverhalten simulieren. Vergleiche zwischen Experimenten und Simulationen ermöglichen Aussagen über eine Vorherbestimmbarkeit des Dosierverhalten für geänderte geometrische und ki-nematische Randbedingungen und stoffliche Eigenschaften.
5

How to improve prescription of inhaled salbutamol by providing standardised feedback on administration: a controlled intervention pilot study with follow-up

Neininger, Martina P., Kaune, Almuth, Bertsche, Astrid, Rink, Jessica, Musiol, Juliane, Frontini, Roberto, Prenzel, Freerk, Kiess, Wieland, Bertsche, Thilo January 2015 (has links)
Background: The effectiveness of inhaled salbutamol in routine care depends particularly on prescribed dosage and applied inhalation technique. To achieve maximum effectiveness and to prevent drug-related problems, prescription and administration need to work in concert. Methods: We performed a controlled intervention pilot study with 4 consecutive groups in a general paediatric unit and assessed problems in salbutamol prescribing and administration. Control group [i]: Routine care without additional support. First intervention group [ii]: We carried out a teaching session for nurses aimed at preventing problems in inhalation technique. Independently from this, a pharmacist counselled physicians on problems in salbutamol prescribing. Second intervention group [iii]: Additionally to the first intervention, physicians received standardised feedback on the inhalation technique. Follow-up group [iv]: Subsequently, without any delay after the second intervention group had been completed, sustainability of the measures was assessed. We performed the chi-square test to calculate the level of significance with p ≤ 0.05 to indicate a statistically significant difference for the primary outcome. As we performed multiple testing, an adjusted p ≤ 0.01 according to Bonferroni correction was considered as significant. Results: We included a total of 225 patients. By counselling the physicians, we reduced the number of patients with problems from 55% to 43% (control [i] vs. first intervention [ii], n.s.). With additional feedback to physicians, this number was further reduced to 25% ([i] vs. [iii], p < 0.001). In the follow-up [iv], the number rose again to 48% (p < 0.01 compared to feedback group). Conclusions: Teaching nurses, counselling physicians, and providing feedback on the quality of inhalation technique effectively reduced problems in salbutamol treatment. However, for success to be sustained, continuous support needs to be provided. Trial registration: German Clinical Trials register: DRKS00006792.
6

Positron Emission Tomography for the dose monitoring of intra-fractionally moving Targets in ion beam therapy

Stützer, Kristin January 2014 (has links)
Ion beam therapy (IBT) is a promising treatment option in radiotherapy. The characteristic physical and biological properties of light ion beams allow for the delivery of highly tumour conformal dose distributions. Related to the sparing of surrounding healthy tissue and nearby organs at risk, it is feasible to escalate the dose in the tumour volume to reach higher tumour control and survival rates. Remarkable clinical outcome was achieved with IBT for radio-resistant, deep-seated, static and well fixated tumour entities. Presumably, more patients could benefit from the advantages of IBT if it would be available for more frequent tumour sites. Those located in the thorax and upper abdominal region are commonly subjected to intra-fractional, respiration related motion. Different motion compensated dose delivery techniques have been developed for active field shaping with scanned pencil beams and are at least available under experimental conditions at the GSI Helmholtzzentrum für Schwerionenforschung (GSI) in Darmstadt, Germany. High standards for quality assurance are required in IBT to ensure a safe and precise dose application. Both underdosage in the tumour and overdosage in the normal tissue might endanger the treatment success. Since minor unexpected anatomical changes e.g. related to patient mispositioning, tumour shrinkage or tissue swelling could already lead to remarkable deviations between planned and delivered dose distribution, a valuable dose monitoring system is desired for IBT. So far, positron emission tomography (PET) is the only in vivo, in situ and non-invasive qualitative dose monitoring method applied under clinical conditions. It makes use of the tissue autoactivation by nuclear fragmentation reactions occurring along the beam path. Among others, +-emitting nuclides are generated and decay according to their half-life under the emission of a positron. The subsequent positron-electron annihilation creates two 511 keV photons which are emitted in opposite direction and can be detected as coincidence event by a dedicated PET scanner. The induced three-dimensional (3D) +- activity distribution in the patient can be reconstructed from the measured coincidences. Conclusions about the delivered dose distribution can be drawn indirectly from a comparison between two +-activity distributions: the measured one and an expected one generated by a Monte-Carlo simulation. This workflow has been proven to be valuable for the dose monitoring in IBT when it was applied for about 440 patients, mainly suffering from deep-seated head and neck tumours that have been treated with 12C ions at GSI. In the presence of intra-fractional target motion, the conventional 3D PET data processing will result in an inaccurate representation of the +-activity distribution in the patient. Fourdimensional, time-resolved (4D) reconstruction algorithms adapted to the special geometry of in-beam PET scanners allow to compensate for the motion related blurring artefacts. Within this thesis, a 4D maximum likelihood expectation maximization (MLEM) reconstruction algorithm has been implemented for the double-head scanner Bastei installed at GSI. The proper functionality of the algorithm and its superior performance in terms of suppressing motion related blurring artefacts compared to an already applied co-registration approach has been demonstrated by a comparative simulation study and by dedicated measurements with moving radioactive sources and irradiated targets. Dedicated phantoms mainly made up of polymethyl methacrylate (PMMA) and a motion table for regular one-dimensional (1D) motion patterns have been designed and manufactured for the experiments. Furthermore, the general applicability of the 4D MLEM algorithm for more complex motion patterns has been demonstrated by the successful reduction of motion artefacts from a measurement with rotating (two-dimensional moving) radioactive sources. For 1D cos2 and cos4 motion, it has been clearly illustrated by systematic point source measurements that the motion influence can be better compensated with the same number of motion phases if amplitudesorted instead of time-sorted phases are utilized. In any case, with an appropriate parameter selection to obtain a mean residual motion per phase of about half of the size of a PET crystal size, acceptable results have been achieved. Additionally, it has been validated that the 4D MLEM algorithm allows to reliably access the relevant parameters (particle range and lateral field position and gradients) for a dose verification in intra-fractionally moving targets even from the intrinsically low counting statistics of IBT-PET data. To evaluate the measured +-activity distribution, it should be compared to a simulated one that is expected from the moving target irradiation. Thus, a 4D version of the simulation software is required. It has to emulate the generation of +-emitters under consideration of the intra-fractional motion, their decay at motion state dependent coordinates and to create listmode data streams from the simulated coincidences. Such a revised and extended version that has been compiled for the special geometry of the Bastei PET scanner is presented within this thesis. The therapy control system provides information about the exact progress of the motion compensated dose delivery. This information and the intra-fractional target motion needs to be taken into account for simulating realistic +-activity distributions. A dedicated preclinical phantom simulation study has been performed to demonstrate the correct functionality of the 4D simulation program and the necessity of the additional, motionrelated input parameters. Different to the data evaluation for static targets, additional effort is required to avoid a potential misleading interpretation of the 4D measured and simulated +-activity distributions in the presence of deficient motion mitigation or data processing. It is presented that in the presence of treatment errors the results from the simulation might be in accordance to the measurement although the planned and delivered dose distribution are different. In contrast to that, deviations may occur between both distributions which are not related to anatomical changes but to deficient 4D data processing. Recommendations are given in this thesis to optimize the 4D IBT-PET workflow and to prevent the observer from a mis-interpretation of the dose monitoring data. In summary, the thesis contributes on a large scale to a potential future application of the IBT-PET monitoring for intra-fractionally moving target volumes by providing the required reconstruction and simulation algorithms. Systematic examinations with more realistic, multi-directional and irregular motion patterns are required for further improvements. For a final rating of the expectable benefit from a 4D IBT-PET dose monitoring, future investigations should include real treatment plans, breathing curves and 4D patient CT images.
7

Increasing the dosing accuracy of a screw dosing device by inline measurement of the product density

Kruppa, Felix, Weiß, Uta, Oberdorfer, Berend, Wilke, Bernd 19 March 2024 (has links)
Fine-powdered bulk materials exhibit high compressibility even under low pressure. The dosing error in volumetric dosing devices increases fundamentally with increasing product compressibility. In order to increase the dosing accuracy of a volumetric dosing of powdered bulk solids, the dosing process must be adapted to the product parameters. The most important parameter is the time-variable product density. With a pure volumetric dosage, it has a direct influence on the actually filled product quantity. Attempts are often made to obtain feedback by means of a scale in order to continuously adjust the volume. However, this is often associated with a delay. In this article, the approach is to measure the product mass flow directly by means of a microwave sensor and to regulate it to a predetermined mass flow. The experimental investigations were carried out with a screw dosing device FVS 3111. Two scenarios were tested: on the one hand, the integration of the sensor directly at the product delivery point, whereby the difference of the average value of the dosed quantity to the target weight could be improved with the sample product coffee; on the other, the sensor was integrated directly at the beginning of the screw and the remaining product flow was simulated. A reduction of the standard deviation compared with the conventional control could also be achieved, but here, the difference between the average of the dosed quantity and the nominal quantity is greater. The cause is presumed to be the too generalized assumption of product behaviour in the case of vertical conveying by means of a screw. In summary, the dosing accuracy of a screw dosing device could be increased by measuring and regulating the mass flow and thus the costs of a manufactured packaging could be reduced.
8

Dosis - Wirkungs - Studie zum Einsatz von inhalativem Stickstoffmonoxid bei Patienten mit schwerem akutem Lungenversagen

Bösel, Matthias 06 July 2004 (has links)
Studienziel: Untersuchung der Dosis-Wirkung von inhalativem Stickstoffmonoxid (NO) bei Patienten mit schwerem akuten Lungenversagen (ARDS) und der diese Wirkung beeinflussenden Faktoren. Design: Prospektive, offene Beobachtungsstudie. Setting: Universitäts-Klinikum. Intensivstation. Patienten: 26 Intensivpatienten mit hohem pulmonal-vaskulärem Druck (PAP) bei zugrunde liegendem ARDS. Behandlung: Patienten mit ARDS wurden einer Therapie mit konventioneller Beatmung und Beimischung von inhalativem NO zugeführt. Das Protokoll sah die Applikation von NO in steigender Dosierung von 0,01 parts per million (ppm), 0,01 ppm, 1, 10 und 100 ppm vor. Zischen den Messungen wurden für 15 bis 20 Minuten Nullmessungen durchgeführt. Ein Anstieg des pulmonal-areriellen Sauerstoffdrucks (Pao2) um 20% wurde als "Responding" definiert. Messungen: Es wurden die Parameter des pulmonalen Gasaustausches wie PaO2, PaCo2 und CaO2 gemessen. Des Weiteren wurden die Werte für den mittleren systemischen Blutdruck (AP), den mittleren pulmonal-arteriellen Druck (PAP), den systemischen Widerstand (SVR), den pulmonalvaskulären Widerstand (PVR), die Herzfrequenz (HR), den Herzindex (CI), das Herz-Zeit-Volumen (HZV), den Wedgedruck (PCWP) und die venöse Beimischung registriert. Ergebnisse: NO verursachte einen dosisabhängigen Anstieg des Pao2 von 0,01 bis 10 ppm (p / STUDY OBJECTIVE: To determine the dose responsiveness to nitric oxide in adult patients with acute respiratory distress syndrom (ARDS), especially in those patients with pulmonary hypertension. To find factors influencing the response to NO. DESIGN: Prospective, open, nonblinded observation study. SETTING: University teaching hospital. PATIENTS: 26 ICU patients suffering from ARDS demonstrating pulmonary hypertension. INTERVENTIONS: Patients with severe acute respiratory distress syndrome received inhalation therapy with NO. Inhaled NO was sequentially titrated from 0,01 parts per million to 0,1 ppm, 1, 10, and 100 ppm at 15-minute intervals followed by a 15 to 20 min OFF interval. Changes in hemodynamics and gas exchange were monitored. An increase of at least 20 % in the oxygenation index was considered as a therapeutic response. MEASUREMENTS: Heart rate, mean arterial pressure, mean pulmonary arterial pressure, pulmonary vascular resistance (PVR), peripheral vascular resistance, cardiac index,rigt to left shunting , venous admixture and right ventricular ejection fraction were monitored throughout the study, as well as the Pao2, Cao2 and PaCo2. RESULTS: 26 patients received inhaled NO. Nitric oxide induced a dose-dependent increase in Pao2 for inspiratory nitric oxide concentrations ranging between 0.01 and 10 ppm (p

Page generated in 0.0379 seconds