Dissertations / Theses: 'Stentai'

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Brikas, Marijus. "Silicio ir metalų mikroapdirbimas didelio impulsų pasikartojimo dažnio pikosekundiniais lazeriais." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2011. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2011~D_20110324_161301-79480.

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Disertacijos tikslas yra ištirti didelio impulsų pasikartojimo dažnio pikosekundinių lazerių pritaikomumą medžiagų mikroapdirbimui, bei išaiškinti tokių lazerių spinduliuotės sąveikos su metalais ir siliciu ypatybes. Eksperimentiškai buvo ištirta abliacijos slenksčio ir akumuliacijos koeficiento priklausomybė nuo lazerio impulso trukmės siliciui ir metalams. Sukurtas ir eksperimentiškai patvirtintas modelis optimalioms fokusavimo sąlygoms surasti, siekiant maksimalios abliacijos spartos. Didelei impulso energijai, medžiagos nugarinimo efektyvumas mažėja dėl ekranuojančio plazmos poveikio. Įvairių impulso trukmių lazeriai buvo panaudoti silicio gręžimui bei pjovimui. Paviršiaus spektroskopijos metodais, nustatyta, kad pjovimo metu silicis yra legiruojamas anglimi iki 5 µm gylio iš atmosferoje esančio anglies dvideginio, o susidariusi silicio karbido fazė įtakoja lazerinio pjovimo kokybę silicio bandinio gylyje. Taikant didelio impulsų pasikartojimo dažnio pikosekundinius lazerius sudėtingos formos detalių gamybai, rasti sąryšiai tarp paviršiaus šiurkštumo bei proceso parametrų. Pjaunant lazeriu stentus iš Nitinolio, šilumos nukreipimas nuo ruošinio riboja galimą panaudoti lazerio vidutinę galią ir tuo pačiu pasiekiamą efektyvųjį pjovimo greitį; Vykdant sidabro ir aukso abliaciją pikosekundiniu lazeriu skystyje, generuojamos siauro dydžių skirstinio nanodalelės, kurios sudaro stabilius koloidinius tirpalus.
The objective of the thesis is to investigate applicability of high pulse repetition rate picosecond lasers for microfabrication and to clarify high repetition rate pulse interaction with metals and silicon. The ablation threshold and accumulation rate dependence on the laser pulse duration for silicon and metals has been experimentally studied. The model of optimal focus conditions for the maximum ablation rate was developed and experimentally confirmed. The material evaporation rate decreases duo to plasma screening for high pulse energies. Various pulse length lasers have been used for cutting and drilling of silicon. In this work key properties of laser radiation, radiation absorption, ablation and plasma formation are discussed. Surface spectroscopy methods have shown that laser cutting of silicon in the air leads to the cut surface doping with carbon atoms up to 5 µm depth from carbon dioxide in the atmosphere, and the resulting silicon carbide influences the laser cut quality. Testing of applicability of high pulse repetition rate picosecond lasers for the production of complex shapes, relationships between surface roughness and process parameters were determined. Heat abstraction from the workpiece, during laser cutting of stents from nitinol, limits the potential use of the average laser power and the effective cutting speed The silver and gold picosecond laser ablation in the liquid medium generates a narrow size distribution of nanoparticles, which form a stable... [to full text]

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Brikas, Marijus. "Microprocessing of silicon and metals with high pulse repetition rate picosecond lasers." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2011. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2011~D_20110324_161348-78636.

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The objective of the thesis is to investigate applicability of high pulse repetition rate picosecond lasers for microfabrication and to clarify high repetition rate pulse interaction with metals and silicon. The ablation threshold and accumulation rate dependence on the laser pulse duration for silicon and metals has been experimentally studied. The model of optimal focus conditions for the maximum ablation rate was developed and experimentally confirmed. The material evaporation rate decreases duo to plasma screening for high pulse energies. Various pulse length lasers have been used for cutting and drilling of silicon. In this work key properties of laser radiation, radiation absorption, ablation and plasma formation are discussed. Surface spectroscopy methods have shown that laser cutting of silicon in the air leads to the cut surface doping with carbon atoms up to 5 µm depth from carbon dioxide in the atmosphere, and the resulting silicon carbide influences the laser cut quality. Testing of applicability of high pulse repetition rate picosecond lasers for the production of complex shapes, relationships between surface roughness and process parameters were determined. Heat abstraction from the workpiece, during laser cutting of stents from nitinol, limits the potential use of the average laser power and the effective cutting speed The silver and gold picosecond laser ablation in the liquid medium generates a narrow size distribution of nanoparticles, which form a stable... [to full text]
Disertacijos tikslas yra ištirti didelio impulsų pasikartojimo dažnio pikosekundinių lazerių pritaikomumą medžiagų mikroapdirbimui, bei išaiškinti tokių lazerių spinduliuotės sąveikos su metalais ir siliciu ypatybes. Eksperimentiškai buvo ištirta abliacijos slenksčio ir akumuliacijos koeficiento priklausomybė nuo lazerio impulso trukmės siliciui ir metalams. Sukurtas ir eksperimentiškai patvirtintas modelis optimalioms fokusavimo sąlygoms surasti, siekiant maksimalios abliacijos spartos. Didelei impulso energijai, medžiagos nugarinimo efektyvumas mažėja dėl ekranuojančio plazmos poveikio. Įvairių impulso trukmių lazeriai buvo panaudoti silicio gręžimui bei pjovimui. Paviršiaus spektroskopijos metodais, nustatyta, kad pjovimo metu silicis yra legiruojamas anglimi iki 5 µm gylio iš atmosferoje esančio anglies dvideginio, o susidariusi silicio karbido fazė įtakoja lazerinio pjovimo kokybę silicio bandinio gylyje. Taikant didelio impulsų pasikartojimo dažnio pikosekundinius lazerius sudėtingos formos detalių gamybai, rasti sąryšiai tarp paviršiaus šiurkštumo bei proceso parametrų. Pjaunant lazeriu stentus iš Nitinolio, šilumos nukreipimas nuo ruošinio riboja galimą panaudoti lazerio vidutinę galią ir tuo pačiu pasiekiamą efektyvųjį pjovimo greitį; Vykdant sidabro ir aukso abliaciją pikosekundiniu lazeriu skystyje, generuojamos siauro dydžių skirstinio nanodalelės, kurios sudaro stabilius koloidinius tirpalus.

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Čibiras, Sigitas Vladas. "Methods of interventional pediatric cardiology in treatment of congenital heart diseases: immediate and long-term results." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2010. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2010~D_20100204_100248-32962.

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Objective - to assess possibilities and specific characteristics of pediatric cardiology in treatment of congenital heart diseases (CHD), to evaluate efficacy of curative per-catheter procedures by means of analysis of immediate and long-term results. Retrospective study. The data of 422 patients who underwent 467 CHD palliative-curative procedures during the period since 1971 till 2007 were analyzed. It was postulated that balloon atrial septostomy resulted in statistically significant increase of atrial septal defect, increase of arterial blood oxygen saturation and decrease of interatrial preasure gradient (PG). Balloon pulmonary valvulotomy (BPV) is one of the most common curative procedures; this procedure has an effect of marked decrease of pressure gradient between the right ventricle and right atrium; development of pulmonary artery valve insufficiency is the most common complication of this procedure. The long - term results of BPV are less positive when higher PG prior the procedure is present and residual PG after the procedure is 36mmHg and higher. It was postulated, that closure of small (less than 3 mm) persistent ductus arteriosus using Cook coils may compete with surgical treatment successfully. It was stated, that the efficacy of balloon angioplasties of aorta, caval veins and pulmonary artery branches is transient; treatment using stents is more effective. It was postulated, that closure of congenital and postsurgical anomalies connections using coils is... [to full text]
Disertacijos objektas yra nustatyti intervencinės pediatrinės kardiologijos galimybes ir ypatumus, gydant įgimtas širdies ydas (ĮŠY), įvertinti gydomųjų perkateterinių procedūrų efektingumą, remiantis ankstyvųjų ir vėlyvųjų rezultatų analize. Tai retrospektyvus tyrimas. Analizuoti 422 ligonių duomenys, kuriems 1971 - 2007 m. buvo atliekamos 467 įgimtų širdies ydų paliatyvinės - gydomosios procedūros. Nustatyta, kad po balioninės tarpprieširdinės pertvaros septostomijos, statistiškai reikšmingai padidėja prieširdžių pertvaros defektas, didėja arterinio kraujo įsotinimas deguonimi ir mažėja spaudimų skirtumas (SS) tarp prieširdžių. Balioninė plaučių arterijos valvuloplastika (BPV) yra viena iš dažniausiai taikomų gydomųjų procedūrų, jos efektas – ryškus SS tarp dešiniojo skilvelio ir plaučių arterijos (PA) sumažėjimas, o pagrindinė komplikacija – PA vožtuvo nesandarumo vystymasis. BPV vėlyvieji rezultatai blogesni, kai yra didelis SS prieš procedūrą, o po procedūros liekamasis SS ≥ 36mmHg. Nustatyta, kad mažų iki 3mm AAL kimšimas Cook spiralėmis gali sėkmingai konkuruoti su operaciniu gydymu. Rasta, kad aortos, tuščiųjų venų ir plaučių arterijos šakų balioninės plastikos efektas trumpalaikis, o gydymas stentais daug sėkmingesnis. Nustatyta, kad anomalinių įgimtų ir pooperacinių kraujagyslinių jungčių užkimšimas spiralėmis yra saugus ir efektyvus gydymo metodas.

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Hettl, Johanna [Verfasser]. "Vergleich eines Paclitaxel-freisetzenden Stents mit einem Everolimus-freisetzenden Stent / Johanna Hettl." Ulm : Universität Ulm. Medizinische Fakultät, 2012. http://d-nb.info/1029295808/34.

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Dailida, Robertas. "Stabdžių bandymo stendo modernizavimas." Bachelor's thesis, Lithuanian Academic Libraries Network (LABT), 2014. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2014~D_20140716_105956-24937.

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Dviračių stabdžių bandymo stendas yra skirtas, nustatyti įtvirtinto dviračio stabdžių efektyvumui. Jų veikimą esant skirtingomis oro sąlygomis (lietus, purvas ir t.t.). Dviračio slydimo atstumui ir stabdant stabdančiūjų dalių susidevėjimui. Šis stendą modernizuojame pritaikant greičio matuoklį, kuris nustato besisukančio (bandomojo dviračio) rato greitį. Įrenginys gaminamas iš paprastų medžiagų, kurias būtų galima nusipirkti metalu prekiaujančiose įmonėse. Standartinius gaminius (tokius kaip guoiai, holo davikliai ir t.t.) taipogi galima įsigyti specializuotuose parduotuvėse. Būtent gaminamoms detalėms naudojamos medžiagos – plienas C45, konstrukcinis plienas S235, kaprolonas. Įrenginio gamybai nereikia didelio kiekio medžiagų, taigi medžiagos bus naudojamos iš likučių esančių gamyklos sandelyje. Reikės suprojektuoti ir pagaminti, stabdžių bandymo stendui, besisukančio rato greičio matuokį, kuris bandymu metu leis nustatyti bandomojo dviračio besisukančio rato greitį. Ratukas yra pristumiamas, prie bandomojo rato, 400N jėga. Pagal gautus skaičiavimus skersinė jėga ašelę veikia – 128 N jėga, o lenkimo momentas tik 4 N/m, tai nesukels konstrukcijoje jokių žymių deformacijų. Dviračių stabdžių stendo modernizacija reikalinga – dėl to, kad bandymų stendas naudojamas, bandymų centre, kuriame tikrinama naujų gaminių kokybė. Šie bandymai turi atitikti standartus, o standartai reikalauja... [toliau žr. visą tekstą]
The theme of this bachelor project of Mechanical Engineering is contemporary, i.e. about the latest technology in modern industry, where everything is fully computerized and systematized. In this bachelor project we analyze the modernization of bicycle brake stand. The main purpose of this technical modernization is to create and adapt a device which measures the speed of spinning wheel of trial bike. As the brake stand is used for investigational purposes, during the tests, we have to follow standards (LST 14766) which we use to create design of the device. The device is designed to be an open, easily accessible place. Freely access was necessary in order to connect the device to a computer, which treated the information and performed calculations. In this project, we will examine several different options for analysis. After selecting the optimal one, we will try to perform technical calculations. Economical analysis showed that manufacturing, i.e. from designing to final product, will take long approximately about seven days. Total manufacturing costs to produce two speed meter devices would be 3386, 92 Lt. Cost of single device – 1693, 46 Lt. The product price can change depending on product standards and designing time.

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Frahnow, Andreas [Verfasser]. "Lebensqualitätsentwicklung nach Implantation von drug eluting stents im Vergleich zu bare metal stents : eine Analyse des Deutschen Drug Eluting Stent-Registers (DES.DE) / Andreas Frahnow." Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2019. http://d-nb.info/1202042147/34.

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Johnsen, Ludger [Verfasser], and Wolfgang [Akademischer Betreuer] Reith. "Das Stent-gestützte Coiling unter Verwendung des Acandis Acclino 1.9F Stents / Ludger Johnsen ; Betreuer: Wolfgang Reith." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2019. http://d-nb.info/1213294630/34.

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Costa, Ricardo Alves da. "Achados ultrassonográficos em lesões de bifurcação coronária tratadas com stent único versus estratégia com dois stents." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/98/98131/tde-19092011-075117/.

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Estudos comparativos prévios com inclusão de lesões de bifurcação selecionadas sugerem ausência de benefício de implante eletivo de dois versus stent único. No entanto, a aplicabilidade do técnica provisional parece ser dependente da complexidade da lesão de bifurcação. A área luminar da lesão após tratamento percutâneo, conforme medida pelo ultrassom intracoronário, tem demonstrado valor preditivo significante na evolução tardia dos pacientes submetidos a ICP. Os objetivos desta análise foram avaliar as dimensões luminares de lesões de bifurcação coronária complexas tratadas por ICP, conforme a análise pelo ultrassom, e correlacionar os achados com os resultados imediatos e tardios. Também objetivou-se identificar preditores angiográficos e ultrassonográficos de falência do ramo lateral nos diferentes passos do tratamento e seguimento. Entre maio de 2008 e agosto de 2009, 59 pacientes portadores de lesão de bifurcação complexa, com comprometimento significativo (estenose > 50%) dos dois ramos e lesão no ramo lateral extendendo-se além do óstio, foram abordados inicialmente com pré-dilatação do ramo lateral, a qual foi realizada com sucesso (estenose < 50%, fluxo TIMI 3, sem dissecção) em 54 pacientes (91,5%). Esse pacientes foram então randomizados para tratamento com stent único (estratégia provisional) (n = 27) versus stent duplo (n = 27). Durante o procedimento, 6 pacientes alocados no grupo stent único apresentaram falência do tratamento no ramo lateral (estenose residual >50%, fluxo TIMI < 3 ou dissecção), sendo que, 5 pacientes receberam stent adicional no ramo lateral para otimizar o resultado angiográfico. Ao final do procedimento, os valores médios e desvios padrão (DP) da área mínima do lúmen no óstio do ramo lateral (desfecho primário) foram 3,37 (1,62) mm2 no grupo stent único versus 5,50 (1,41) mm2 no grupo stent duplo (p < 0,001), conforme a alocação randômica. No seguimento angiográfico de 9 meses, as taxas de reestenose no ramo lateral foram 21,7% no grupo stent único versus 4% no grupo stent duplo (p = 0,06), sendo que, todas as recorrências envolveram a localização ostial. Considerando-se o tratamento recebido, a taxa de reestenose no ramo lateral foi significantemente maior nos pacientes tratados com stent único versus stent duplo (27,8% versus 3,3%, p = 0,01). Os preditores de falência da estratégia provisional foram: excêntricidade da lesão (p = 0,02), área mínima do lúmen (p = 0,08) e diâmetro mínimo do lúmen no óstio do ramo lateral (p = 0,06), extensão da lesão (p = 0,09) e percentual de estenose (p = 0,07) do ramo lateral. Com relação a reestenose angiográfica no ramo lateral, os preditores foram: área mínima do lúmen no óstio do ramo lateral ao final do procedimento (p = 0,03), tratamento com stent duplo (p = 0,02), diâmetro mínimo do lúmen (p = 0,03) e percentual de estenose (p = 0,02) no óstio do ramo lateral ao final do procedimento, ganho imediato no óstio do ramo lateral (p = 0,09) e diâmetro de referência do ramo lateral (p = 0,03). Estes resultados sugerem que lesões de bifurcação coronária complexas beneficiam-se de tratamento percutâneo com abordagem inicial com estratégia de dois stents, sendo que, tal benefício esteve relacionado a obtenção de maior área luminar no óstio do ramo lateral.
Previous comparative studies including selected bifurcation lesions have shown no advantage of elective double stenting implantation versus single stenting. However, the applicability of the provisional technique appears to be dependent on the bifurcation lesion complexity. The lesion luminal area after percutaneous treatment, as assessed by intravascular ultrasound, has demonstrated significant predictive value in the late follow-up of patients undergoing PCI. The objectives of this analysis were to evaluate the lesion luminal dimensions of complex coronary bifurcation lesions, as assessed by intravascular ultrasound, and to correlate such findings with acute and late outcomes. Also, it was aimed to identify angiographic and intravascular ultrasound predictors of side branch failure throughout the procedural steps and follow-up. Between may 2008 and august 2009, 59 patients with complex bifurcation lesions, including significant involvement (> 50% stenosis) of both branches and side branch lesion length extending from its ostium, were approached initially with side branch predilatation, which was successful (< 50% stenosis, TIMI 3 flow, no dissection) in 54 patients (91.5%). These patients were then randomized for treatment with single stenting (provisional strategy) (n = 27) versus double stenting (n = 27). During procedure, 6 patients allocated in the single stenting arm presented side branch failure (> 50% residual stenosis, TIMI flow < 3 or dissection), given that 5 patients received an additional stent in the side branch in order to optimize the angiographic result. At final procedure, the mean value and standard deviation (SD) for minimum lumen area at the side branch ostium (primary endpoint) were 3.37 (1.62) mm2 in single stenting versus 5.50 (1.41) mm2 in double stenting (p < 0.001), according to the randomized allocation. In the angiographic follow-up at 9 months, the restenosis rates in the side branch were 21.7% in single stenting versus 4% in double stenting (p = 0.06), given that all recurrences involved the ostial location. Considering the treatment received, the side branch restenosis rate was significantly increase among patients treated with single stenting versus double stenting (27.8% versus 3.3%, p = 0.01). The predictors of provisional strategy failure were: lesion eccentricity (p = 0.02), minimum lumen area (p = 0.08) and minimum lumen diameter in the side branch ostium (p = 0.06), lesion length (p = 0.09) and percent diameter stenosis (p = 0.07) of the side branch. Regarding angiographic restenosis in the side branch, predictors were: minimum lumen area in the side branch ostium at final procedure (p = 0.03), treatment with double stenting (p = 0.02), minimum lumen diameter (p = 0.03) and percent diameter stenosis (p = 0.02) in the side branch ostium at final procedure, acute gain at the side branch ostium (p = 0.09) and side branch reference diameter (p = 0.03). These results suggest that complex coronary bifurcation lesions may benefit from a primary percutaneous approach with double stenting strategy, given that most such benefit was associated with a larger lumen area obtained at the side branch ostium.

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Botadra, Dharam. "Stent Tester: Design and Application." OpenSIUC, 2012. https://opensiuc.lib.siu.edu/theses/863.

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Cardiovascular diseases which include high blood pressure, coronary heart diseases, heart failure, stroke and peripheral arterial diseases (PAD) affect one out of three American adults or 105 million people. By 2030, the prevalence of cardiovascular disease is estimated to rise 10 percent to more than 40 percent of American adults, or 116 million people. Approximately 8 million people in the United States have PAD, including 12-20% of individuals older than age 60. The main reason of PAD is obstruction of blood flow through lower extremities causing Atherosclerosis. The major artery affected in the lower extremities due to PAD is superficial femoral artery (SFA). Huge numbers of clinical procedures like superficial femoral artery stenting, balloon angioplasty, and percutaneous transluminal intervention are done to treat the disease. Thorough in vitro (biological phenomena made to occur outside the human body) testing of this kind should reduce the risk of in vivo (biological phenomena occurring inside the human body) stent failure and thus lead to increased survivability for patients suffering with cardiovascular diseases and PAD. It has been recognized that a metal subjected to a repetitive or fluctuating stress will fail at a stress much lower than that required to cause failure on a single application of load. As per literature review, typically SFA stents survive no more than 12-18 months until the first fracture is detected in MRI. There was a need of a customized designed device such that it would simulate realistic blood pressure conditions and test the capacity the SFA stents. Commercially, the stents are tested under accelerated cyclic loading conditions at different frequencies for longer cycle periods. In order to demonstrate how stents perform once deployed into an artery, a testing device was required which will simulate arterial blood pressure variations and compressive loads over artery as close as possible to human body. The stent tester documented in this report is capable of subjecting a stent to appropriate physiological loading by deploying it in a simulated vessel and subjecting it to external compression. Loading of this kind was performed at frequencies at 60 Hz and, as such, simulating one million heartbeats of artery pulsation. The primary purpose of this thesis was to successfully design stent tester which cycles artificial fluid simulating blood pressure in arteries and superimposing cyclic compression of stent deployed in an artificial artery. The goal was to obtain a test machine that allows for a cost effective testing of cardiovascular and peripheral stents. Another goal was to externally compress the arterial wall subjected to compressive load with the help of an air controlled mechanical piston attached with load cell assembly. The load cell measures the amount of load applied over the silicone tubing. The design of the device contains two peristaltic pumps which alternate pressure every second by pumping distilled water via plastic tubing. The stent was crimped with the guide wire catheter and deployed in the silicone artery (diameter 11mm O.D) from Dynatek labs. Wall and bridge stents (Medtronic, Schneider Inc.) 10 x 39 mm were used for testing with and without external load. Industrial pressure transducer S-10 (Wika Instruments Corporation) ranging from 0-5 PSI (0-259mmHg) is used to monitor the pressure in the artificial artery. The pressure transducer is connected to the data logger (Omega om320) which serially communicates with computer. The silicon mock test artery was 20cm long so that stents used in various arterial interventions can be tested. The silicon artery has primary advantages over rubber latex artery which are clarity and close resemblance to human artery and durable (ideal for long term durability tests). Preliminary results from literature review show that stent materials, based on its mechanical properties survive for more than one million heartbeats. To demonstrate the capacity of current design a nitinol stent was tested under physiological conditions at 60Hz frequency. A load of 980 grams for 2001 - 5000 heartbeats, 1.98 kg for 5001 - 10000 heartbeats, 4.25 kg for 10001 - 25000 heartbeats and 6.54 kg for 25001 - 50000 heartbeats was applied over the artificial artery. The mechanical piston with load cell assembly was allowed to externally compress the artificial artery. Partial functionality of device was demonstrated by running it for one million heartbeats and 48000 compressive cycles. The device was successfully designed and has the capacity to cycle artificial fluid simulating blood pressure changes in arteries and have demonstrated the ability to test any type of stents. The device was designed efficient which was simulated in an acceptable pressure range as compared to human blood pressure and allow for compression of stent in a cyclic testing pattern. The system was maintained to as close as between diastolic value of 76mmHg to diastolic 122mmHg pressure range. The device was run for about one million heartbeats and it was observed that the NiTi stent successfully survived. The stent was observed visually with a magnifying glass for any cracks or failure at intervals of 500, 1000, 2000, 5000, 10000, 25000, 50000 and one million heartbeats respectively. After running the device for one week at a frequency of 60Hz, no fractures on the stent were visually observed. However, the stent was deformed from the center. Data analysis showed that the mean diastolic and systolic pressure measurements for intervals with no load were found to be statistically significant i.e. in acceptable range. However, the device design lacks stability due to various reasons like device operates in an open looped system, has bubbles in the artificial artery which might be producing varying pressure values and variation in applying load. The device was partly unable to simulate arterial blood pressure changes under no loading conditions. Efforts are being made to improve the design of the device to make it realistic simulation of variation in arterial blood pressure for long term durable testing of the stents.

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Martinez, Adam W. "Design and development of an elastin mimetic stent with therapeutic delivery potential." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/45926.

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Stenting remains a common treatment option for atherosclerotic arteries. The main drawback of early stent platforms was restenosis, which has been combated by drug eluting stents; however, these stents have suffered from a higher incidence of late stage thrombosis. To address current stenting limitations, the major research focuses have been the development of the next generation of drug eluting stents and first generation bioabsorbable stents. The main objective of this dissertation was the design and development of a new class of bioabsorbable stent composed of elastin mimetic protein polymers. The first phase explored different stent design schemes and fabrication strategies. Successfully fabricated stents were then mechanically tested to ensure they possessed sufficient mechanical strength. Additionally, described herein is the potential to modulate the properties of the elastin mimetics through different crosslinking strategies. We have demonstrated that chemical crosslinking allows for the tailoring of the physical, mechanical, drug delivery, and endothelialization properties of these materials. The potential for drug delivery from this elastin mimetic stent was benchmarked as was the potential to endothelialize these stents. Furthermore, we developed the necessary delivery systems to allow for deployment in the rat aorta model.

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Ong, Andrew Teck Leong. "The unrestricted use of paclitaxel-eluting stents and eirolimus-eluting stents in the Rotterdam T-SEARCH and RESEARCH Registries: Studies on efficacy, safety, stent thrombosis, cost eff ectiveness and the future." [S.l.] : Rotterdam : [The Author] ; Erasmus University [Host], 2007. http://hdl.handle.net/1765/10526.

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Grudtner, Marco Aurelio. "Análise histológica e histomorfométrica de carótidas após o implante de stent de cromocobalto sem e com revestimento de polímero : modelo experimental porcino." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2009. http://hdl.handle.net/10183/24269.

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Introdução: Apesar dos avanços significativos no tratamento endovascular das doenças arteriais coronarianas e periféricas, a reestenose intra-stent continua sendo o principal limitante a médio prazo desses procedimentos. O mecanismo da reestenose intra-stent é principalmente a hiperplasia intimal, já que o stent impede a retração elástica aguda e resiste ao remodelamento geométrico negativo tardio. A hiperplasia intimal ocorre basicamente em resposta à formação de trombo local, à inflamação e às dissecções intimais e mediais secundárias à injúria causada pelo stent, sendo o grau de resposta intimal a base dos efeitos a longo prazo. O uso de stents com hastes menores e revestidos com drogas ou polímeros tem sido considerado uma nova alternativa para a prevenção da reestenose intra-stent. Objetivo: Analisar a resposta arterial ao implante de stent de cromo-cobalto sem e com revestimento de polímero Camouflage® em artérias carótidas de suínos, utilizando os seguintes parâmetros histológicos: grau de endotelização, conteúdo de células musculares lisas, grau de angiogênese, conteúdo de fibrina, grau de inflamação e injúria; além da análise histomorfométrica. Método: Stents balões-expansíveis de cromo-cobalto ( 8 stents CC Flex e 5 stents CC Flex Proactive) de 4 x 16 mm foram implantados em artérias carótidas comuns de oito suínos jovens, sendo um stent liberado em cada artéria. Após 30 dias, as artérias contendo os stents foram removidas, fixadas e coradas pelos métodos de hematoxilina/eosina e Verhoeff/Van Giesson. O segmento arterial contendo o stent foi dividido em 3 blocos distintos: proximal, médio e distal. Os cortes histológicos foram obtidos utilizando-se micrótomo de impacto (Polycut S, Leica, Alemanha) equipado com navalha de tungstênio de 16 cm, tipo D (Leica, Alemanha), com 5 ^m de espessura. A navalha de tungstênio mantém as hastes dos stents intactas nas secções transversas, minimizando os artefatos potenciais causados pela retirada dos stents. A avaliação foi realizada através de critérios histológicos e histomorfométricos. Resultados: Todos os stents foram implantados com sucesso e sem dificuldades técnicas. A análise histológica em 30 dias evidenciou alto grau de endotelização em todos os segmentos avaliados e leve à moderada infiltração de células musculares na íntima. Observou-se baixo grau de angiogênese em cerca de 50% dos segmentos avaliados e ausência completa de deposição de fibrina em pelo menos 80%, com distribuição semelhante entre os grupos. A resposta inflamatória e o grau de injúria causadas pelas hastes dos stents também foram discretas e similares entre os grupos e não houve correlação entre resposta inflamatória e injúria e desses parâmetros com a área de neoíntima. O grau de obstrução neo-intimal identificada neste período foi pequeno (15,1% +/- 8,38 CC Flex x 15,5%+/- 5,39 CC Flex ProActive) e estatisticamente não significativo entre os grupos (p=0,785). Conclusão: Os achados deste estudo experimental sugerem que o uso de stents de cromo-cobalto revestidos com polímero Camouflage® em artérias carótidas de suínos parece estar associado, pelo menos no curto prazo, a uma resposta histológica semelhante àquela encontrada após o implante de stents de cromo-cobalto não revestidos. Neste período não se observou uma menor hiperplasia intimal em virtude do revestimento de polímero.
Introduction: Despite all the advances in the endovascular treatment of coronary and peripheral artery diseases, in-stent restenosis is still the main limiting factor of these procedures in the medium and long-term. The mechanism of in-stent restenosis is mainly the intimal hyperplasia, as the stent prevents acute elastic recoil and later negative geometric arterial remodeling. Intimal hyperplasia occurs basically in response to the formation of local thrombus, inflammation and intimal and medial dissections secondary to the injury caused by the stent, with the degree of intimal response being the cause of long-term effects. Coating drug-eluting stents with polymers and drugs with thinner struts have been considered a new alternative for in-stent restenosis prevention. Objective: Analyse the arterial response to the cobalt-chromium stent implant with and without polymer coating Camouflage® in carotid arteries of pigs, using the following histological parameters: degree of endothelialization, smooth muscle cells (SMC) content, degree of angiogenesis, intimal fibrin content, degree of inflammation and injury; plus histomorphometric analysis. Method: Cobaltchromium balloon-expandable stents (8 CC Flex stents and 5 CC Flex Proactive), 4 x 16 mm, were deployed in common carotid arteries of 8 young pigs, with one stent being deployed in each artery. After 30 days, the arteries containing the stents were removed and underwent fixation and staining using the hematoxilin/eosin and Verhoeff /Van Giesson methods. The arterial segment containing the stent was divided into 3 distinct portions: proximal, middle and distal. The histological sections were obtained using impact microtome (Polycut S, Leica, Germany), equipped with a 16 cm, type D, 5 ^m thick tungsten knife (Leica, Germany). The tungsten knife maintains the stent shaft intact in cross sections, minimizing the potential artifacts caused by stent removal. The evaluation was carried out using histological and histomorfometric criteria. Results: All the stents were deployed with success and with no technical difficulties. The histological analysis performed after 30 days showed a high level of endothelialization in all the evaluated portions and mild to moderate infiltration of the SMC in the intima layer. A low level of angiogenesis of about 50% of the evaluated portions was observed and a complete absence of fibrin deposition in at least 80% of the portions, with similar distribution among the groups. The inflammatory response and the level of injury caused by the struts of the stents were also minimum and this was similar among the groups. There was no correlation between inflammatory response and injury and between the two latter parameters and the neo-intima area. The level of neo-intimal obstruction identified in this period was small (15,1% +/- 8,38 CC Flex x 15,5%+/- 5,39 CC Flex ProActive ) and no statistical significance between the groups (p=0,785). Conclusion: The findings of this experimental study suggest the use of balloonexpandable cobalt-chromium stents coated with polymer Camouflage® in carotid arteries of pigs seems to be associated, at least in the short-term, with a similar histological response to that found in the implantation of non-coated cobalt-chromium stents. In this period, a lower intimal hyperplasia was not observed with polymer coating stents.

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Vechietti, Fernanda Albrecht. "Estudo das temperaturas de transformação de fases e da caracterização da superfície da liga NiTi submetida a diferentes tratamentos térmicos para aplicação em órtese metálica." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2012. http://hdl.handle.net/10183/79840.

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As temperaturas de transformações de fases são essenciais para trabalhar e caracterizar as ligas de NiTi, podendo-se assim, aproveitar de maneira eficiente suas propriedade de memória de forma e superelasticidade. O objetivo deste trabalho foi caracterizar as temperaturas de transformações de fases (As, Af, Ms, Mf, Rs, Rf) e a superfície de chapas e fios quanto a sua morfologia e a molhabilidade da liga NiTi submetidos a diferentes tratamentos térmicos para aplicação como órtese coronária. Tratamentos térmicos influenciam diretamente nas temperaturas de transformações de fases e na superfície do material, portanto os fios e chapas foram submetidos a diferentes tratamentos térmicos com diferentes tempos e temperaturas adquirindo diferentes colorações. Os fios foram submetidos a tratamentos térmicos de têmpera e temperaturas de 530 e 570°C, sendo analisados por DSC (Differencial Scanning Calorimeter), microscopia óptica e microdureza. Quando comparados com o fio sem tratamentos térmico mostraram mudanças nas temperaturas de transformações de fases. O fio com tratamento térmico de 570ºC apresentou as melhores temperaturas para aplicação como material biomédico. As superfícies dos fios foram analisadas por microscopia eletrônica de varredura (MEV), e devido ao seu diâmetro de 0,15 mm não foi possível analisar o material por microscopia de força atômica (AFM) e molhabilidade. As análises foram feitas em chapas com os mesmos tratamentos térmicos realizados nos fios para que se pudesse chegar a um resultado semelhante. Nas amostras de chapas os tratamentos térmicos variaram entre 500 (envelhecimento), 570 e 850°C e as temperaturas de transformação de fases foram analisadas por DSC e as superfícies por AFM, MEV e molhabilidade. As chapas com tratamento térmico de 500 e 570° C apresentaram temperaturas de transformação Af acima da temperatura corporal o que torna o material não indicado para aplicação como órtese (stent). A amostra 3 com tratamento térmico de 850° C não apresentou temperatura de transição martensítica. A análise de AFM teve como principal função escolher a rugosidade topográfica adequada ao ancoramento celular e revelou que a chapa azul foi a mais indicada em uso como órtese coronária.
The phases transformation temperatures are essential to work and to characterize the NiTi alloys and may thus take advantage efficiently its properties shape memory and superelastic. The objective of this study was to characterize the phase transformation temperatures (As, Af, Ms, Mf, Rs, Rf) and the surface of sheet and wires sufferes morphology and wettability of the NiTi alloy subjected to different heat treatments to application as a coronary stent. Heat treatments directly influence in the temperatures of phase transformations and on the material surface, so the wires and sheet were subjected to different heat treatments with different times and temperatures, getting different colors. The wires were subjected to heat treatments of 530 and 570 °C and analyzed by DSC (Differential Scanning Calorimeter), optical microscopy and microhardness. When compared with the wire without heat treatment showed changes in the temperatures of phase transformations. The blue color wire showed the best temperatures for application as biomedical materials. The wires surfaces were analyzed by scanning eletron microscopy (SEM) and due to its diameter of 0.15 mm was not possible to analyze the material by atomic force microscopy (AFM) and wettability. Therefore, the analyzes were performed in plates with the same heat treatments carried out on the wires so that it could reach to a similar result. In the plates the heat treatments ranged between 500 (aging), 570 and 850 °C and the phase transformation temperatures were analyzed by DSC and the surfaces by AFM , SEM and wettability. The plate with heat treatment to 500 °C showed the best phases transformation temperatures. The heat treatment sheet 500 and 570 °C to the temperature above the transformation temperature Af body which makes the material is not suitable for use as the prosthesis (stent). Sample 3 with heat treatment at 850 °C showed no martensite transition temperature. The AFM analysis had as main function choose the appropriate topographic roughness to the cellular anchor and revealed that a blue plate was the most suitable for use as a coronary stent.

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Wachleski, Jacqueline. "Avaliação dos níveis séricos de MRP-8/14 conforme a apresentação clínica e a evolução pós-tratamento da doença arterial coronariana." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2013. http://hdl.handle.net/10183/118330.

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Introdução: A doença arterial coronariana constitui uma das maiores causas de morbidade e mortalidade no mundo atual. O mecanismo inflamatório exerce papel fundamental sobre a aterogênese e as formas de apresentação da doença arterial coronariana (DAC). O MRP-8/14 é uma proteína inflamatória que possui importante função na interação dos leucócitos com o endotélio, demonstrando ser um potencial biomarcador na DAC. Objetivo: Avaliar a relação dos níveis séricos de MRP-8/14 com a apresentação clínica e com a evolução da DAC após o tratamento da lesão-alvo com implante de stent. Metodologia: Este estudo avaliou os níveis séricos de 95 pacientes divididos em 5 grupos: (1) grupo I - controle (indivíduos hígidos); (2) grupo II - lesões leve a moderada, ou seja, lesões obstrutivas entre 20% e 50% em 1 ou mais artérias coronárias; (3) grupo III - angina estável e lesão 50% em 1 ou mais artérias coronárias; (4) grupo IV - síndrome coronariana aguda sem supradesnível do segmento ST angina instável e IAM sem supradesnível do segmento ST (IAM-SSST); e (5) grupo V- síndrome coronariana aguda e supradesnível do segmento ST IAM com supradesnível do segmento ST (IAM-SSST), nas primeiras 12 horas de início dos sintomas. Os indivíduos dos grupos I e II foram submetidos à uma única coleta sanguínea, enquanto os pacientes dos grupos III, IV e V foram submetidos a uma coleta sanguínea imediatamente antes da intervenção coronária percutânea com implante de stent seguida de coletas sanguíneas seriadas em 6, 18 e 48 horas e em 7 dias após o implante de stent. Resultados: A análise comparativa dos níveis séricos de MRP- 8/14 na primeira coleta entre os 5 grupos em estudo evidenciou diferença estatisticamente significativa do grupo I (controle) em relação aos demais grupos grupo I= 0,110,10μg/mL vs grupo II= 0,500,13μg/mL; grupo III= 1,830,70μg/mL; grupo IV= 3,661,81μg/mL; e grupo V= 3,541,52μg/mL; p<0,001. Também houve diferença estatisticamente significativa do grupo II em comparação aos grupos III, IV e V (p<0,001); e do grupo III em relação aos grupos IV (p=0,045) e V (p=0,002). Não houve diferença estatisticamente significativa quando comparados os grupos IV e V (p=1,00). Quanto à evolução da DAC pós-implante de stent, não houve diferença estatisticamente significativa dos níveis séricos de MRP-8/14 entre as coletas seriadas nos grupos analisados (III, IV e V). A análise dos níveis séricos de MRP-8/14 em relação ao tempo de evolução do IAM-CSST (grupo V) não evidenciou diferença estatisticamente significativa (p=0,685), mesmo quando comparados os pacientes com tempo de evolução do IAM-CSST inferior a 3 horas com os pacientes com tempo de evolução do IAM-CSST compreendido entre 3 e 12 horas (p=0,492). Conclusões: Os níveis séricos de MRP-8/14 apresentam-se progressivamente elevados conforme a gravidade da DAC e permanecem continuamente elevados mesmo após o tratamento da lesão-alvo com implante de stent por pelo menos 7 dias. O MRP-8/14 também apresenta-se como um potencial biomarcador precoce do infarto agudo do miocárdio.
Introduction: The coronary artery disease is a major cause of morbidity and mortality nowadays in the world. The inflammatory mechanism plays a fundamental role in atherogenesis as well as in the coronary artery disease (CAD) presentation. MRP-8/14 is an inflammatory protein that has an important function in the leukocyte-endothelial cell interaction, showing to be a potential biomarker for CAD. Objective: Assess the relation between the serum levels of MRP-8/14 and the CAD clinical presentation and evolution after treating the target lesion with stent deployment. Methodology: This study assessed the serum levels of 95 patients divided into 5 groups: (1) group I – control (healthy individuals); (2) group II – mild-to-moderate lesions, that is, obstructive lesions between 20% and 50% in 1 or more coronary arteries; (3) group III – stable angina and lesion 50% in 1 or more coronary arteries; (4) group IV – acute coronary syndrome without ST segment elevation unstable angina and non-ST segment elevation myocardial infarction (NSTEMI); and group V – acute coronary syndrome with ST segment elevation ST segment elevation myocardial infarction (STEMI) within the first 12 hours of symptom onset. A single blood sample was collected from the individuals from groups I and II, while in patients from groups III, IV and V blood samples were collected immediately before percutaneous coronary intervention with stent deployment followed by serial blood samples collected 6, 18, and 48 hours and 7 days after stent deployment. Results: The comparative analysis of the serum levels of MRP-8/14 in the first blood sample collection between the 5 groups under study showed a statistically significant difference in group I (control) with relation to the other groups [group I = 0.11±0.10μg/mL vs. group II=0.50±0.13μg/mL; group III =1.83±0.70μg/mL; group IV =3.66±1.81μg/mL; and group V = 3.54±1.52μg/mL; p<0.001]. There was also a statistically significant difference in group II compared to groups III, IV, and V (p<0.001); and in group III with relation to groups IV (p<0.045) and V (p<0.002). There was no statistically significant difference between groups IV and V when compared (p=1.00). Regarding CAD evolution after stent deployment, there was no statistically significant difference in the serum levels of MRP-8/14 between the serial samples in the analyzed groups (III, IV, and V). The analysis of MRP-8/14 levels in relation to STEMI evolution over time did not evidence statistically significant difference (p=0.685), even when patients with STEMI within 3 hours after onset of symptoms were compared with patients with STEMI between 3 and 12 hours after onset of symptoms (p= 0,492). Conclusions: The serum levels of MRP-8/14 show to be progressively increased according to CAD severity and remain continuously increased even after target lesion treatment with stent deployment for at least 7 days. MRP-8/14 also shows to be a potential early biomarker for acute myocardial infarction.

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Zakaras, Andrius. "Valdikliu programavimo mokomasis stendas." Bachelor's thesis, Lithuanian Academic Libraries Network (LABT), 2010. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2010~D_20100907_094312-58855.

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Šiais laikais sparčiai kylant pramonei ir automatikai, labai svarbų vaidmenį atlieta valdymo sistemos. Todėl valdymo sistemos yra kuriamos naudojantis įvairiais programuojamais loginiais valdikliais (PLV). [1] Pagal tarptautinį IEC 1131 standartą PLV apibrėžiamas taip: pramoninėje aplinkoje naudoti pritaikyta skaitmeninė elektroninė sistema, turinti programuojamą atmintį, į kurią įrašomos vartotojo valdymo programos, skirtos specifinėms loginėms, valdymo nuoseklumo, laiko intervalų nustatymo, įvykių skaičiavimo, aritmetinėms funkcijoms realizuoti ir pasitelkus skaitmeninius bei analoginius įėjimo/išėjimo modulius, įvairiems įrenginiams bei procesams valdyti. Toks standartu reglamentuotas PLV apibrėžimas parodo, kad programuojamieji loginiai valdikliai yra šiuolaikiška, universali ir labai plačiai taikoma įvairių automatikos sistemų valdymo priemonė. Todėl valdiklių programavimo mokymo priemonės yra labai svarbios ir aktualios ugdant reikiamos kvalifikacijos būsimuosius specialistus. Programuojamųjų loginių valdiklių (PLV) mokymas turi teikti malonumą.[5] Tokį mokymą leidžia atlikti realybei artimos užduotys ir procesai, t.y. realūs objektai ir juose vykstantys procesai. Bet iš kur gauti realius įrengimus ir nemažas lėšas jiems įsigyti? Ar tai galima padaryti nenaudojant realių objektų? Galima, todėl ir Sukonstruotas valdiklių programavimo mokomasis stendas, kuriuo norima parodyti, kaip galima virtualiai valdyti įvairius įrenginius naudojant tik personalinį kompiuterį (PC)... [toliau žr. visą tekstą]
The task of my bachelor's final thesis is training equipment of programmable controllers. This case dedicated for practical education PLC training using simulated proceses. We can try simulate virtual object in real time with program EasyVeep (Vizualated Equipment Emulation Program). This case compose from PLC, EasyPort D-16 interface and EasyVeep program. In this bachelor i programed hot water tank in two programming language: Ladder Diagram and Statement List.

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Bonello, Laurent. "Nouveaux bio-marqueurs predictifs de la thrombose et de la restenose chez les patients coronariens traites parangioplastie coronaire avec implantation d'une endoprothèse." Thesis, Aix-Marseille 2, 2011. http://www.theses.fr/2011AIX22954.

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L’angioplastie coronaire est la première forme de revascularisation coronaire. Elle présente cependant 2 limites qui restreignent encore son utilisation : la thrombose et la resténose de stent. La thrombose de stent est un événement précoce associé à une mortalité élevée. Les plaquettes y jouent un rôle déterminant. Le développement de tests fonctionnels plaquettaires permettant d’analyser le niveau de réactivité plaquettaire sous traitement a permis de mettre en évidence les limites de celui-ci sur le plan biologique. Nous avons démontré l’impact clinique de l’utilisation de ces tests dans la prédiction et la réduction du risque de thrombose de stent chez des patients traités par angioplastie coronaire. La resténose est quant à elle une complication tardive de l’angioplastie coronaire avec implantation d’un stent non-actif. Sa physiopathologie repose sur des mécanismes de lésion et de régénération endothéliale. Des marqueurs endothéliaux circulants ont récemment été développés. Nous avons montré qu’ils pouvaient permettre d’évaluer la lésion et la régénération endothéliale induite par une angioplastie coronaire. Les cellules endothéliales circulantes s’élèvent transitoirement après l’angioplastie et ce de façon variable en fonction de la réactivité plaquettaire sous traitement démontrant les interactions étroites entre ces différents acteurs. Dans le même temps, on observe une mobilisation de progéniteurs d’origine médullaire suite à l’angioplastie. Nos travaux suggèrent un rôle clé de la régénération endothéliale dans la cicatrisation vasculaire après angioplastie. En effet, il apparait que la proportion de progéniteurs de profil de différenciation endothélial en réponse à l’angioplastie coronaire détermine la survenue d’une resténose intra-stent. Ces données ouvrent la voie à une meilleure compréhension des mécanismes physiopathologie menant à la resténose mais aussi à des perspectives thérapeutiques intéressantes
Percutaneous coronary intervention is the most commonly used revascularization technique. However it has 2 main complications limiting its widespread: stent thrombosis and in stent restenosis. Stent thrombosis is an early event associated with a high mortality rate. Platelets are key in its physiopathology. The availability of platelet function tests allowing to determine platelet reactivity levels under therapy showed a variable ant platelet effect following aspirin and clopidogrel intake. We further demonstrated that tailoring anti platelet therapy according to platelet function tests results decrease the rate of stent thrombosis following PCI without increasing bleedings. In stent-restenosis is a late complication of PCI with bare metal stents. The pathophysiology of in-stent restenosis is dependent on the lesion and regeneration of the endothelium. Circulating endothelial biomarkers have recently been developed. We have demonstrated that this marker allow to evaluate the lesion and regeneration of the endothelium following PCI. We evidenced a transient increase in circulating endothelial cells following PCI which is dependent on the level of platelet reactivity inhibition demonstrating the interaction between platelets and the endothelium. At the same time, PCI induces mobilization of progenitor cells which is detectable early after the intervention. Our work suggests that these progenitor cells have a key role in endothelial regeneration after PCI. We evidenced for the first time that the proportion of endothelial progenitor cells among progenitor cells mobilized after PCI determine the occurrence of in stent restenosis. Altogether these data give critical inside into vascular regeneration after PCI in human and on the mechanisms associated with in stent restenosis thus providing new potential therapeutic target

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Yugueros, Castellnou Xavier. "Estudio experimental in vitro de la técnica del stent paralelo en la reparación endovascular de los aneurismas de la aorta abdominal." Doctoral thesis, Universitat de Barcelona, 2019. http://hdl.handle.net/10803/669918.

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El stent paralelo es una técnica utilizada en la reparación endovascular de los aneurismas complejos de la aorta abdominal con muy buenos resultados aunque todavía no totalmente estandarizada. El objetivo de este estudio ha sido evaluar mediante modelos in vitro, parámetros técnicos fundamentales (grado de sobredimensión, la mejor manera de medirlo y la mejor combinación de materiales) en dos configuraciones distintas de stent paralelo: en 2 y 3 chimeneas (chEVAR) para la reparación de los aneurismas sin cuello infrarrenal; y en configuración tipo sándwich para preservar la arteria hipogástrica. Para ello se recrearon modelos sintéticos de una aorta visceral y de una extensión iliaca siguiendo los diámetros y las características anatómicas habituales en la práctica clínica. En ellos se introdujeron distintos dispositivos con distinto grado de sobredimensión, reproduciendo el mismo procedimiento y simulando las mismas condiciones fisiológicas in vivo. El análisis de cada reconstrucción se realizó mediante tomografía computarizada (TC) y un programa de procesamiento de imagen evaluando el área de gutters (zonas no cubiertas ni por el stent paralelo ni por la endoprótesis principal), el grado de compresión de los stents y la presencia o ausencia de malposicionamiento o infolding (replegado de la endoprótesis principal generando nuevos gutters). Respecto a la configuración en 2-3 chimeneas viscerales, los resultados obtenidos fueron a favor de una mejor adaptación de los componentes a sobredimensiones crecientes (15%, 30% o 40%), con una tendencia no significativa a una menor área de gutters. A mayor sobredimensión se evidenció también una tendencia a una mayor compresión del stent paralelo y sobre todo a un mayor riesgo infolding, especialmente en aquellos modelos con 3 stents paralelos, sobredimensiones extremas (> 30%) y combinaciones de materiales de baja fuerza radial. Por todo ello, se consideró que la sobredimensión entorno al 30% es la idónea al reducir al mínimo el área de gutters sin generar compresión significativa de la rama visceral ni tampoco infolding. Analizando las distintas combinaciones de materiales, nuestros resultados mostraron que tanto para 2 como para 3 chimeneas, los stents balón expandibles y las endoprótesis de alta fuerza radial, se comprimen menos que las combinaciones de baja fuerza radial aunque a expensas de una significativa mayor área de gutters. A raíz de dichos resultados no se pudo extrapolar una recomendación clínica especifica al respecto. Respecto al configuración en sándwich para preservar el flujo hipogástrico, los resultados mostraron un comportamiento parecido con una reducción progresiva del área de gutters a mayor sobredimensión de diámetro (<30%, 30-55%, 55-75% y > 75%), aunque a expensas de una mayor compresión del stent paralelo y de un mayor infolding. Se consideró por tanto una sobredimensión de diámetros entre el 30 y el 55% como la idónea, al reducir al mínimo el área de gutters sin generar compresión significativa de la rama visceral ni tampoco infolding Respecto las distintas formas de medición de la sobredimensión, se obtuvo una correlación prácticamente perfecta entre la sobredimensión de áreas clásicamente descrita con la sobredimensión de perímetros y la de diámetros, recomendando el uso de esta última al simplificar de manera importante la planificación del procedimiento. Respecto a los distintos dispositivos analizados, no se obtuvieron diferencias en las variables evaluadas salvo una tendencia no significativa a un menor infolding con la utilización de stents autoexpandibles como dispositivo para la arteria iliaca interna.
Parallel stenting is a surgical procedure used in endovascular repair of complex abdominal aortic aneurysms. The objective of this study has been to evaluate, using in vitro models, some critical technical aspects (oversizing degree, the best way to measure as well as best device combination) in two parallel stent different configurations: 2 and 3 visceral chimneys (chEVAR) and in a sandwich configuration to preserve the hypogastric artery. Synthetic models of a visceral aorta and an iliac extension were constructed following the usual anatomical diameters and characteristics. In them, different devices with different oversizing degree were introduced, reproducing the same procedure and simulating the same physiological conditions as in vivo. The analysis of each reconstruction was performed using computed tomography (CT) and image processing software. Main variables were gutter area (area not covered by either the parallel stent or the main endograft), stent compression and malpositioning or infolding (internal folding of the main endograft generating new gutters). Regarding 2-3 visceral chimney configuration, 30% was the best oversizing degree, reducing gutter area to the minimum without significant branch compression or infolding. Analyzing best device combination, balloon expandable stents and high radial force endografts, were associated with less compression than low radial force materials but at the expense of a significantly larger gutter area. Regarding sandwich configuration to preserve hypogastric flow, our results showed that 30 - 55% diameter oversizing was the best, being associated with less gutter area without significant visceral branch compression or infolding. Analyzing oversizing measuring methods, a practically perfect correlation was obtained between all of them, (areas, perimeters and diameters) recommending the use of the latter as significantly simplifying procedure planning. Regarding device combinations, no clear differences were obtained excepting a non-significant tendency to lower infolding with self-expanding stents for the internal iliac artery.

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Borinski, Mauricio Armando [Verfasser]. "Stent Implantation in homozygoten ApolipoproteinE-defizienten Ratten und die in vitro und in vivo Evaluation eines geflochtenen Polyurethan-basierten Stents / Mauricio Armando Borinski." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2013. http://d-nb.info/1037106814/34.

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Stenman, Jakob. "mRNA-expression-based classification of solid tumors : development of accurate amplification-based quantification techniques." Helsinki : University of Helsinki, 2002. http://ethesis.helsinki.fi/julkaisut/laa/kliin/vk/stenman/.

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20

Slhessarenko, Juliano Rasquin. "Efeito da dose elevada de ataque de Rosuvastatina na concentração sérica de marcadores inflamatórios na fase aguda da intervenção coronária percutânea com implante de stents metálicos." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/98/98131/tde-02012018-141935/.

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Introdução: Nas últimas décadas, a reestenose tem sido o \"calcanhar de Aquiles\" da intervenção coronária percutânea (ICP), limitando seus resultados no médio e longo prazo. Estudos preliminares demonstraram que após a injúria inicial com catéter balão e/ou com stents coronarianos, há desnudação endotelial, dissecção, deposição plaquetária e atração de leucócitos como resposta imediata, podendo levar à reestenose no seguimento mais tardio. A injúria local na parede arterial após implante de stent pode promover a expressão genética e liberação de mediadores inflamatórios, interleucinas, proteínas de fase aguda e fatores de coagulação, deposição de plaquetas e formação de trombos. Estes processos podem estar diretamente relacionados ao prognóstico da doença cardiovascular, porém são escassos os estudos que caracterizem a resposta inflamatória aguda pós-implante de stent coronariano e à ocorrência de eventos adversos. Objetivos: Neste estudo, pretendeu-se avaliar os efeitos de dose de ataque de Rosuvastatina (40mg) sobre a resposta inflamatória aguda após implante de stent coronariano, bem como correlacionar as variações das concentrações de citocinas e a respectiva expressão gênica. Métodos: Pacientes portadores de doença coronária estável sem uso de estatina (há mais de 7 dias), submetidos à intervenção coronária percutânea eletiva em artéria coronária nativa foram randomizados para receberem dose única de ataque de rosuvastatina (40 mg via oral, 3 horas prévias ao procedimento; Grupo Tratado (GT); n=63) versus Grupo Controle (GC) (Ausência da administração de rosuvastatina); n=61. Foram obtidas amostras do sangue periférico antes da administração via oral da medicação (A), 3 horas após medicação (B) e 3 horas após implante do stent coronariano (C). Avaliou-se hemograma completo, dosagem de proteína C reativa (PCR), óxido nítrico (NO) e análise da expressão dos genes e das proteínas, por meio de RT-qPCR e multiplex luminex, dos mediadores IL-1 ?, IL-6, IL-8, PAI-1, MCP- 1, TNF-? e TGF-?. Os pacientes foram acompanhados clinicamente por doze meses após o procedimento. Resultados: Os grupos não apresentaram diferenças significantes em relação às características clínicas, angiográficas e técnicas, com exceção da ICP para lesões em bifurcação, mais comum no GC (19,7% versus 6,2%; p=0,032). Para a expressão gênica, observou-se redução para IL-6 (p<0,001), da IL-1 ? (p=0,016) e PAI-1 (p=0,002) no Grupo Tratado. Para as interleucinas analisadas, observou-se uma diminuição progressiva nas concentrações de IL-6 0,209 pg/ml (IC 0,156;0,28 p<0,001), IL-1? 0,491 pg/ml (IC 0,349;0,692; p<0,001) e PAI-1 0,986 pg/ml com pinteração<0,001) no Grupo Tratado. Houve redução da concentração de PCR no tempo C no GT (p=0,04). Para o NO, ocorreu elevação dos valores do tempo A para C no Grupo Tratado (p=0,004). Na fase intra-hospitalar, ocorreu mais infarto periprocedimento entre os pacientes do Grupo Controle (23% vs 4,7%; p=0,004). No acompanhamento clínico de 12 meses ocorreram mais eventos combinados no Grupo Controle GC (9,8% vs 1,6%; p=0,058). Conclusão: Os resultados deste estudo demonstraram que a rosuvastatina em sua dose de ataque máxima preconizada (40mg), reduz os níveis séricos de marcadores inflamatórios agudos (IL-1 ?, IL-6, PAI-1 e PCR), com incremento dos valores de NO após ICP.
Restenosis remains as the \"Achilles\' heal\" of interventional cardiology, limiting the mid to long term efficacy of percutaneouos coronary interventions (PCI). Preliminary studies have shown that after initial injury with balloon catheter and/or metallic stents, there is endothelial denudation, dissection, platelet deposition and leukocyte attraction as an immediate response, which might limit the late benefits of PCI. Local injury to the arterial wall after stent implantation may promote the gene expression and release of inflammatory mediators, interleukins, acute phase proteins and coagulation factors, platelet deposition and thrombus formation, which are directly related to the prognosis of cardiovascular disease. Despite their importance, there are few studies that characterize the acute inflammatory response after coronary stent implantation and correlate it to the occurrence of adverse events.Objectives: We sougth to evaluate the effects of the loading dose of Rosuvastatin (40mg) on the acute inflammatory response after PCI with mettalic stents, as well as to correlate the variations in cytokine levels and their respective gene expression. Methods: Patients with stable coronary disease without statin (>=7 days) undergoing elective PCI to de novo lesions in the native coronary arterywere randomized to receive a loading dose of 40 mg of rosuvastatin [N = 63] versus a control group (CG) (absence of loading dose); [N = 61]. Blood samples were obtained prior to oral administration of the statin (A), 3 hours after medication (B) and 3 hours after PCI (C). The following laboratory tests were conducted: complete blood count, C-reactive protein (CRP), nitric oxide (NO) and analysis of gene and protein expression by means of RT-qPCR and multiplex luminex, IL-1 mediators, IL-6, IL-8, PAI-1, MCP-1, TNF-? and TGF-?. Clinical follow up was achieved up to 12 months after the procedure. Results: The groups did not significantly differ regarding clinical, angiographic and procedure characteristics, except for the higher amount of bifurcation lesions in the CG (19.7% versus 6.2%, p = 0.032). Among patients pre treated wit the statin, there was a reduction in gene expression for IL-6 (p <0.001), IL-1? (p = 0.016) and PAI-1 (p = 0.002). For the IL analyses, a progressive decrease in the concentrations of IL-6 0.209 pg / ml (IC 0.156; 0.28 p <0.001), IL-1? 0.491 pg / ml (IC 0.349; 0.692, p <0.001) and PAI-1 0.986 pg / ml with paving <0.001) were observed among patients treated with the statin. Furthermore, a progressive reduction in the concentration of CRP was observed in the three timepoints among patients of the rosuvastatin cohort (p = 0.04). An increase in NO concentration was observed from timepoint A to C in the statin group (p = 0.004). During the in hospital period, more periprocedural MI occurred among patients in the control group (23% vs 4.7%, p = 0.004). Also, 12-month MACE rate was higher in the control group (9.8% vs 1.6%, p = 0.058). Conclusion: Pre loading with high dose of rosuvastatin resulted in a marked reduction in the expression of the main inflammatory markers (IL-1 ?, IL-6, PAI-1 and CRP) associated with restenosis after PCI with stents. Additionally, an increase in the NO blood concentration and expression was noticed among these patients.

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Arauz, Garofalo Gianluca. "Prospects of microwave spectrometry for vascular stent monitoring. Towards a non-invasive and non-ionizing follow-up alternative." Doctoral thesis, Universitat de Barcelona, 2017. http://hdl.handle.net/10803/404376.

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Throughout this thesis we have assessed the prospects of microwave spectrometry (MWS) as a non-ionizing non-invasive monitoring alternative for stented patients in a very early proof-of-concept stage. In Chapter 1 we have provided a generalist retrospective medical background along with a state-of-the-art summary of existing microwave-based stent monitoring approaches. First, we have introduced cardiovascular diseases in general, and ischemic heart disease in particular. Next we have reviewed how percutaneous coronary interventions addressed the medical problem represented by atherosclerosis, giving a special emphasis to balloon angioplasty, bare-metal stenting and drug-eluting stenting. We have further exposed how the outcomes of such revolutionary strategies were compromised by the high rates of post-procedural complications, making unavoidable the invasive and ionizing follow-up of stented patients. Finally, we have summarized existing non-invasive and non-ionizing stent monitoring alternatives based in microwave techniques. In Chapter 2 we have introduced the working principle of our MWS setup. We have first presented how this arrangement can obtain the absorbance of a stent as a function of the frequency and the incidence angle of the microwave fields. We have also shown how these data are combined in a single two-dimensional chart, and how we recognize therein the characteristic resonance frequencies of stents at a glance. As an example, we have presented a typical absorbance diagram to illustrate the general features of such resonances. In particular we have highlighted that these resonances are discrete and have multi-lobed angular patterns. In Chapter 3 we have characterized many stents having a wide variety of nominal sizes to better understand their characteristic resonances in terms of microwave scattering. First, we have found that the resonance frequency obeys a reciprocal dependence on the stent length. This has allowed us to obtain an empirical expression for such relationship just by adjusting two fitting parameters. However, we have not been able to find an analogous expression for the dependence on the stent diameter. In any case, while investigating the latter, we have unexpectedly uncovered how the particular stent architecture influences the corresponding resonance frequencies. By gathering all these individual results we have finally suggested a straightforward half-theoretical half-empirical model linking the resonance frequencies of stents with their structural integrity (through their length), with their particular architecture (through the scaling factor), as well as with their surrounding medium (through the dielectric permittivity and the magnetic permeability). We have also theoretically estimated the resonance frequencies of implanted stents from their corresponding values in free space conditions, showing that in vivo resonance frequencies should be around one order of magnitude smaller than their free space counterparts. Finally, in Chapters 4 and 5 we have explored the potential diagnostic capabilities of MWS in two possible scenarios: stent fracture (SF) and in-stent neoatherosclerosis (ISNA). We have started both chapters reviewing the incidence, the medical implications, and the mechanism of these two stent-related complications. SF has been evaluated in Chapter 4 by means of two “fracture tests” consisting in a successive series of strut cuts. We have shown that MWS provides qualitative indicators for single and multiple strut fractures (downshift of the fundamental resonance frequency), and also quantitative indicators for single or multiple complete transverse linear SFs (split and upshift of that frequency). ISNA has been evaluated in Chapter 6 by means of four ``cholesterol tests'' consisting in a gradual process of increasing cholesterol deposition. We have shown that MWS provides an indicator for a growing presence of cholesterol around a stent (downshift of the fundamental resonance frequency). We have concluded this chapter calculating the theoretical evolution of the resonance frequencies along a cholesterol deposition process, estimating the upper limit for the resonance frequency displacement. Taking together the results we have reported in Chapters 5 and 6, we have shown that MWS could potentially warn about SF and ISNA.

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Adam, Zulfiquar. "The SSTARS (STeroids and stents Against Re-Stenosis) Trial : different stent alloys and the use of peri-procedural oral corticosteroids to prevent in-segment restenosis." Thesis, Durham University, 2016. http://etheses.dur.ac.uk/12023/.

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Stent design and technological modifications to allow for anti-proliferative drug elution influence restenosis rates following percutaneous coronary intervention (PCI). The main aim of this study was to investigate whether peri-procedural administration of corticosteroids or the use of thinner strut cobalt alloy stents would reduce rates of binary angiographic restenosis (BAR) after PCI. In addition, the role of the acute phase highly sensitive C-Reactive protein (hs-CRP) in restenosis in bare metal stents (BMS) was also investigated. This was a two centre, mixed single and double blinded, randomised controlled trial using a factorial design. The use of prednisolone was compared against placebo, starting at least six hours pre-PCI and continued for 28 days post-PCI. Additionally, cobalt chromium (CoCr) stents were compared to stainless steel (SS) alloy stents, in patients admitted for PCI. The primary end-point was BAR at six months. Three hundred and fifteen (359 lesions) were randomly assigned to either placebo (n=145) or prednisolone (n=170) and SS (n=160) or CoCr (n=160). The majority (58%) presented with an acute coronary syndrome (ACS), 11% had diabetes and 287 (91%) completed angiographic follow up. The primary endpoint, binary angiographic restenosis, occurred in 26 cases in the placebo group (19.7%) versus 31 cases in the prednisolone group (20.0%) respectively, p=1.00. For the comparison between SS and CoCr stents, BAR occurred in 32 patients (21.6%) versus 25 patients (18.0%) respectively, p=0.46. Hs-CRP was monitored at 5 points during the trial. The pre-PCI hs-CRP measurement was ≤5mg/l in 213 patients (71%) of whom only 28 (13%) had a raised CRP at day 7. There was some evidence of prednisolone suppressing hs-CRP response at day 7 (-5.98 mg/L, 95%CI: -8.35 to -3.61, p < 0.001). There was no correlation between lowering hs-CRP and stenosis diameter at follow-up. This study showed that treating patients with a moderately high dose of prednisolone to cover most of the period of inflammation associated with restenosis in BMS did not reduce the incidence of BAR. There was also no significant reduction in six month BMS restenosis rates with stents composed of CoCr alloy compared to SS alloy and no observed relationship to hs-CRP.

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23

Bozsak, Franz. "Optimisation de stents actifs." Phd thesis, Ecole Polytechnique X, 2013. http://pastel.archives-ouvertes.fr/pastel-00858100.

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L'utilisation de stents actifs (DES) a révolutionné le traitement de l'athérosclérose. Le relargage contrôlé de médicaments anti-prolifératifs dans la paroi artérielle (PA) a permis de réduire fortement le taux de resténose intra-stent. Mais le risque de thromboses intra-stents tardives demeure un enjeu majeur des DES en partie lié au retard de cicatrisation de la PA endommagée lors de l'implantation. Cette thèse présente une méthode d'optimisation du design des DES afin d'inhiber la resténose sans affecter la cicatrisation. Pour quantifier la performance des différents designs, un modèle numérique décrivant l'écoulement sanguin et le transport de médicaments dans les artères stentées a été développé. Il prend en compte la structure multi-couches de la PA et les interactions du médicament avec les cellules. Un algorithme d'optimisation est couplé au modèle afin d'identifier les DES optimaux. L'optimisation du temps de relargage ainsi que de la concentration initiale du médicament dans le revêtement du DES ont un effet significatif sur la performance. Lorsque le médicament utilisé est le paclitaxel, les solutions optimales consistent à relarguer le produit à des concentrations nettement inférieures à celles des DES actuels soit pendant quelques heures, soit pendant une durée d'un an. Pour le sirolimus, un relargage lent est nécessaire. Les formes optimales des spires du DES sont toujours allongées mais profilées seulement lorsque le relargage est rapide. Ces résultats permettent d'expliquer en partie les performances des différents DES récents et révèlent un fort potentiel d'amélioration dans la conception des DES par rapport aux dispositifs commerciaux actuels.

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McGinty, Sean. "Stents and arterial flows." Thesis, University of Strathclyde, 2010. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=12396.

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Yamaji, Kyohei. "Bare-metal Stent Thrombosis and In-stent Neoatherosclerosis." Kyoto University, 2012. http://hdl.handle.net/2433/158059.

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Martins, Kleber Bomfim Araújo. "Estudo randomizado da intervenção coronária percutânea após administração da rosuvastatina para prevenção de infarto do miocárdio periprocedimento." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/98/98131/tde-15072014-100936/.

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Introdução: Embora a intervenção coronária percutânea esteja associada a baixos índices de complicações, o infarto do miocárdio periprocedimento tem sido apontado como um fator negativo nos resultados clínicos. Os ensaios clínicos randomizados e as revisões sistemáticas recentes confirmaram que uma alta dose de estatina antes da intervenção coronária percutânea eletiva reduz o risco para a ocorrência do infarto do miocárdio periprocedimento. Objetivos: O objetivo desta pesquisa foi aferir a eficácia da pré-administração de uma dose de ataque de rosuvastatina na redução do infarto do miocárdio periprocedimento em pacientes submetidos à intervenção coronária percutânea eletiva com stent coronário. Métodos: De março de 2011 a dezembro de 2013, um total de 528 pacientes portadores de doença coronária estável em uso de estatina (há mais de 7 dias), submetidos à intervenção coronária percutânea eletiva em artéria coronária nativa (e lesão não reestenótica) foram randomizados prospectivamente em único centro, para receberem dose única de ataque de rosuvastatina (40 mg via oral, 2 a 6 horas prévio ao procedimento; grupo rosuvastatina; n=264) versus tratamento padrão (ausência da administração de rosuvastatina; grupo controle; n=264). O objetivo primário foi analisar a incidência intra-hospitalar de infarto do miocárdio periprocedimento (elevação da fração miocárdica da creatina-quinase massa maior que 3 vezes o limite superior do normal). Os objetivos secundários foram analisar a incidência da elevação da fração miocárdica da creatina-quinase massa acima de 1 vez o limite superior do normal e a incidência de eventos adversos graves como infarto agudo do miocárdio com supra desnível do segmento ST, revascularização emergencial do vaso-alvo (percutânea ou cirúrgica) e óbito intra-hospitalar. Resultados: O desfecho primário ocorreu em 7,6% dos pacientes tratados com rosuvastatina e em 4,8% no grupo controle (p = 0,200); ao consideramos o desfecho secundário (elevação da fração miocárdica da creatina-quinase maior que uma vez o limite superior do normal), verificamos que o grupo rosuvastatina apresentou mais desfechos quando comparado ao grupo controle (26,2% vs 18,4%, p = 0,039). Não houve diferença nos eventos adversos graves intra-hospitalar sendo 0% no grupo da rosuvastatina e 0,8% no controle devido a infarto agudo do miocárdio com supradesnível do segmento ST. Conclusões: Esta pesquisa sugere que a administração de dose de ataque de rosuvastatina prévio à intervenção coronária percutânea eletiva, em pacientes com doença coronária estável e em uso de estatina, aumenta a chance de elevação da fração miocárdica da creatina-quinase massa. Este efeito não foi significante para o desfecho primário (infarto do miocárdio periprocedimento) que foi pouco frequente neste estudo, mas foi significante para o desfecho secundário (elevação da creatina-quinase massa acima de 1 vez o limite superior do normal). As taxas de eventos clínicos adversos graves intra-hospitalar não foram afetadas pelo tratamento.
of complications, periprocedural myocardial infarction has been appointed as a negative factor in clinical outcomes. Randomized clinical trials and recent systematic reviews have confirmed that a high dose of statin before elective percutaneous coronary intervention reduces the risk of periprocedural myocardial infarction. Objectives: The objective of this study was to assess the efficacy of a loading dose of rosuvastatin pre-administration in reducing periprocedural myocardial infarction, in patients undergoing elective percutaneous coronary intervention with stable coronary artery disease on statin use for more than 7 days. Methods: From March 2011 to December 2013, a total of 528 patients with stable coronary artery disease on statin use (more than 7 days) who underwent elective percutaneous coronary intervention in native artery (and non restenosis lesion) were prospectively randomized in a single center to receive either a pre-procedural loading dose of Rosuvastatin (40 mg oral, 2 to 6 hours prior to the procedure; rosuvastatin group, n=264) or standard treatment (without administration of rosuvastatin; control group, n = 264). The primary endpoint was in-hospital stay incidence of periprocedural myocardial infarction (creatine kinase-myocardial band elevation greater than the three times the upper limit of normal). The secondary end points were in hospital stay incidence of creatine kinase-myocardial band elevation greater than once the upper limit of normal and the incidence of major adverse events as acute myocardial infarction with ST segment elevation, emergency target vessel revascularization (percutaneous or surgical) and death. Results: The primary end point occurred in 7.6% of patients treated with rosuvastatin loading dose and in 4.8% in the control group (p = 0.200); there was a higher incidence in elevation of post-procedural creatine kinase-myocardial band greater than once the upper limit of normal in the rosuvastatin group (26.2% vs 18.4%, p = 0.039). There were no differences in the rate of major adverse events with 0% in the rosuvastatin group and 0.8% in control driven by acute myocardial infarction with ST-segment elevation in hospital stay. Conclusions: This study suggest that loading dose of rosuvastatin prior to elective percutaneous coronary intervention, in patients with stable coronary disease on prior statin use increases the chance of creatine kinase-myocardial band elevation. This effect was not significant for the primary outcome (periprocedural myocardial infarction) that was uncommon in this study, but was significant for the secondary outcome (creatine-kinase elevation once the upper limit of normal). The rates of major adverse major events were not affected by treatment during hospital stay.

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Elksnys, Vaidas. "Spausdinimo įrenginio “CITIZEN-MD910” patikros stendas." Bachelor's thesis, Lithuanian Academic Libraries Network (LABT), 2011. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2011~D_20110804_091858-44674.

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Spausdinimo įrenginys „CITIZEN MD-910“ naudojamas kasos aparatuose, kaip kliento ir kontrolinės juostų spausdintuvas. Šis spausdintuvas plačiai naudojamas šiuose kasos aparatuose: ELCOM EURO-2000M, CASIO FE-800, DATECS MP-500, KONIC SR508F. Šiuos spausdintuvus remontuojant kasos aparatuose, iškyla pavojus, panaikinti kasos aparato atmintį, kurioje saugomi programiniai ir apyvartų duomenys. Spausdinimo įrenginio „CITIZEN MD-910“ patikros stendas kuriamas, tam, kad palengvinti kasos aparatų remonto darbus, taip sumažinant tikimybę panaikinti remontuojamo kasos aparato atmintį. Darbo tikslas – išnagrinėti spausdinimo įrenginio „CITIZEN MD-910“ veikimo principą, elektrines bei mechanines charakteristikas. Taip pat, išsiaiškinti spausdintuvo dvigubos galvos adatų išsidėstymą, sukurti spausdinimo algoritmą, simbolių biblioteką ir valdymo programą. Spausdintuvas „CITIZEN MD-910“ bus dedamas į stendą ir pasiuntus į jį iš valdymo programos tekstą, tikrinamas jo veikimas. Stendas atitiks spausdintuvo realų darbinį režimą. Iš to, kaip vyks spausdinimas, ir iš atspausdinto teksto ant popieriaus juostos, bus sprendžiama apie spausdintuvo mechaninius ir elektronikos gedimus, adatų veikimą ir jų mušimo jėgą į popierių, bei tinkamumą tolesnei eksploatacijai. Spausdinimo įrenginio „CITIZEN MD-910“ patikros stendo pagrindinė kūrimo priežastis yra ta, jog nėra sukurtų panašių analogų, kurie palengvintų šių kasos aparatų spausdinimo įrenginių remonto darbus.
Dot impact printer mechanism “CITIZEN MD-910” is used in cash registers as a printer for customer receipts and journal paper ribbons. This printer is widely used in the cash registers such as ELCOM EURO-2000M, CASIO FE-800, DATECS MP-500, KONIC SR508F. Repairing these printers inside the cash registers there is a risk to delete the cash register’s memory in which programs and data of a turnover is stored. The dot impact printer mechanism “CITIZEN MD-910” test stand is being worked out to make the cash registers repairing easier and in this way to reduce the risk of deleting cash registers memory. The printer “CITIZEN MD-910” will be placed in the test stand and its work will be tested by sending text from the operating program into it. The stand will simulate real working conditions of the printer. Analyzing the printing process and the printed text on the paper ribbon it will be possible to decide on printer’s mechanical and electrical damage, work of wires and force they dot the paper, also, further usability. There are no similar analogues which could make the repairing of the cash registers dot impact printer mechanism “CITIZEN MD-910” easier and this is the main reason to work out the dot impact printer mechanism “CITIZEN MD-910” test stand.

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Jasaitis, Mintaras. "Saugos elektros tinkle įvertinimo laboratorinis stendas." Bachelor's thesis, Lithuanian Academic Libraries Network (LABT), 2013. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2013~D_20130823_095804-73762.

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Šiame baigiamajame darbe buvo suprojektuotas ir sumontuotas saugos elektros tinkle įvertinimo laboratorinis stendas. Parinkta elektros įranga, atitinkanti EĮĮT saugos sąlygas. Tinklo ir žmogaus apsaugos nuo elektros sistema suprojektuota panaudojus šiuolaikines technologijas. Sudaryta stendo principinė elektrinė ir išdėstymo schema. Atliktas IT, TT, TN-C, TN-S tinklo pavojingumo tyrimas. Tyrimo metu buvo nagrinėjamas tinklas avariniame režime ir žmogaus rizikos laipsnis, eksploatuojant gedimą turintį imtuvą.Saugos įvertinimo stendui parinkta ir aprašyta elektros įranga: įtampos įjungimas; viršsrovių apsauga; srovės nuotėkio apsauga; keičiamos C ir N laidų varžos; keičiamos šaltinio neutralės ir vartotojo įžeminimo varžos; keičiamos laidų izoliacijos varžos; tinklo atjungimo nuo šaltinio trukmės matavimo prietaisas; įtampos matavimo prietaisas; trumpojo jungimo mygtukas; instaliacinių laidų parinkimas.
The laboratory kit for safety evaluation in electrical network was created and installed in this final bachelor thesis. According to the safety conditions and requirements, the electrical equipment was selected. Network’s and human’s protection against electrical system was designed using modern technologies. Principal electrical and layout schemes of laboratory kit were drawn. The reasearch was conducted of a danger in IT, TT, TN-C, TN-S electrical network. At the time of research the electrical network was analysed in emergency modes and the human's level of risk was investigated while operating electrical equipment with defects. The electrical equipment for safety evaluation kit was selected and described in this project: voltage switch, overcurrent protection, residual-current device protection, variable C and N wire resistance, variable neutral and local earth ground resistance, variable wire insulation resistance, currents cut-off stopwatch, voltage measuring device, short circuit button, installation wiring selection.

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29

Nilsson, Jonas. "Hitta in : Rundvandring i Sundsvalls Stenstad." Thesis, Mittuniversitetet, Avdelningen för informations- och kommunikationssystem, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-27140.

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Målet med detta projekt är att designa och bygga en prototyp på en mobil applikation för Android och iOS som guidar och lockar användare till intressanta platser i Sundsvalls Stenstad. Detta med hjälp av information i form av text, bild och video samt gamification, alltså att göra guiden till en typ av spel. Arbetet har genomförts metodiskt med regelbundna möten med projektets idébärare för feed-back och design av appen. Byggnation av appen följde och resulterade i en app med funktioner som karta med användarens position och intressanta platser markerade, inbyggd QR-läsare för incheckning på platser och ett poängsystem för att samla poäng när man besöker platser. Arbetet har visat att man trots begränsad tid kan göra en prototyp på beskriven app.

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Oliveira, Flavio Roberto Azevedo de. "Avaliação da eficácia tardia após o implante de um stent miniaturizado, farmacológico versus não-farmacológico, em artérias coronárias de pequeno calibre." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/98/98131/tde-03082012-070905/.

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Os vasos de fino calibre apresentam maior risco para reestenose e revascularização da lesão alvo. Limitações relacionadas com a navegabilidade dos sistemas de dilatação por balão e menor capacidade de acomodação da neoíntima podem contribuir para isto. O stent autoexpansível de nitinol Sparrow® dedicado a vaso de calibre < 2,75 mm, resultou num conjunto com perfil de um fio-guia 0,014\". Testado na forma de stent de metal puro no estudo CARE I, revelou-se seguro e eficaz em vasos de fino calibre. Este estudo avaliou, de forma pioneira, o despenho de um stent autoexpansível farmacológico neste cenário. O objetivo primário foi comparar a perda luminal tardia no vaso-alvo pela angiografia coronária quantitativa ao final de oito meses, entre os stents Sparrow® farmacológico e não farmacológico, em coronárias com diâmetro de referência < 2,75 mm. Casuística e métodos: Os pacientes foram randomizados de forma prospectiva em dois grupos para procedimento de angioplastia: um grupo com o emprego o stent Sparrow® farmacológico (sirolimus), e ou outro grupo com o stent Sparrow® na versão não farmacológica. Análise pela angiografia coronária quantitativa foi realizada imediatamente antes e após o procedimento e aos oito meses, com seguimento clínico de 24 meses. Foi utilizado o programa IBM SPSS Statistics® para análise estatística e foi considerado nível de significância de 5% e poder de 80% para o cálculo do tamanho da amostra. Resultados: 24 pacientes foram randomizados, 12 no grupo com stent farmacológico Sparrow® e 12 no grupo com a versão não farmacológica. Na avaliação angiográfica aos oito meses verificou-se significativa redução de perda luminal tardia no grupo com o stent farmacológico Sparrow® em comparação com grupo com a versão não farmacológica (0,25 + 0,16 mm versus 0,97 + 0,76 mm, p = 0,008, IC 95% de -1,19 ; -0,22). No seguimento clínico de 12 meses, não foram observados eventos cardíacos adversos maiores (morte, infarto ou necessidade de revascularização do vaso alvo) no grupo com stent farmacológico. Não ocorreu trombose intrastent. Conclusão: Em pacientes submetidos à angioplastia transluminal percutânea em artérias coronárias com diâmetro de referência < 2,75 mm, o emprego do stent farmacológico autoexpansível Sparrow®, em comparação com a versão não farmacológica do mesmo stent, resultou em significativa redução de perda luminal tardia, sem ocorrência de eventos clínicos que deponham contra a segurança do dispositivo pesquisado.
Small vessels represent a group with high risk for restenosis and target lesion revascularization. Limitations associated with navigability of balloon dilation systems and less accommodating of the neointima may contribute to this. The self-expanding Sparrow® stent system dedicated to the vessel size <2.75 mm resulted in a profile similar to a 0.014\" guide wire angioplasty. Tested as bare metal stent in the CARE trial I, the Sparrow® stent system has proved to be safe and effective in small vessels. This study evaluated, for the first time, the performance of a self-expanding drug eluting stent in this scenario. The primary objective was to compare the in-stent late lumen loss by quantitative coronary angiography at the end of eight months between the Sparrow® drug-elutig stent and Sparrow® bare metal stent in coronary arteries with reference diameter <=2.75 mm. Materials and methods: Patients were prospectively randomized (1:1) Analysis by quantitative coronary angiography was performed immediately before and after the procedure and at eight months with clinical follow-up to 12 months. We used the IBM® SPSS for statistical analysis and was considered a significance level of 5% and 80% power for the calculation of sample size. Results: 24 patients were randomized, 12 in each group. At Eight months follow-up there was significant reduction in late lumen loss in the Sparrow® drug-eluting stent group compared to the Sparrow® bare metal stent group (0.25 ± 0.16 mm vs. 0.97 + 0.76 mm, p = 0.008, 95% CI -1.19 to -0.22). Up to 12 months of clinical follow-up there no cases of death, myocardial infarction and target vessel revascularization Of note, there was no stent thrombosis. Conclusion: In patients undergoing percutaneous transluminal angioplasty in coronary arteries with reference diameter <= 2.75 mm, the use of Sparrow® drug-eluting stent, compared to the Sparrow® bare metal stent, resulted in significant less late loss without occurrence of clinical events that weigh against the security of device.

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Grudtner, Marco Aurelio. "Análise morfométrica da parede arterial após o implante de stent em aorta abdominal de suínos : estudo comparativo entre stents metálicos não recobertos e recobertos com politetrafluoroetileno." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2001. http://hdl.handle.net/10183/2935.

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O espessamento intimal e a reestenose que ocorrem após os procedimentos de angioplastia transluminal percutânea e/ou o implante de stents representam uma causa freqüente de falência destes procedimentos. O principal achado patológico responsável pela reestenose parece ser a hiperplasia intimal, já que o dispositivo intravascular é resistente ao remodelamento arterial geométrico. O propósito deste estudo é avaliar, através da morfometria digital, o espessamento intimal presente nas regiões da parede arterial imediatamente proximal e distal ao implante de um stent metálico em configuração em “Z “ não recoberto ou recoberto com PTFE. Vinte e cinco suínos de raça mista, com seis a dez semanas de idade, pesando em média 20 kg foram divididos em três grupos. No grupo I, cinco animais foram submetidos à exposição cirúrgica retroperitoneal da aorta abdominal, aortotomia e manipulação com uma bainha introdutora de 12 F. O grupo II incluiu dez animais que foram submetidos ao implante de um stent metálico auto-expansível não recoberto. No grupo III, incluindo também dez animais, foram implantados stents recobertos com PTFE. Após quatro semanas, todos os animais foram sacrificados e o segmento aorto-ilíaco foi removido. Quatro animais foram excluídos do estudo por trombose da aorta (um animal do grupo II e três animais do grupo III). Para a análise morfométrica foram utilizados os testes não paramétricos de Wilcoxon e de Kruskal-Wallis, para as comparações, respectivamente, no mesmo grupo e entre os grupos. Foi adotado o nível de significância de 5% ( p< 0,05). Quando os espécimes da parede arterial, imediatamente proximal e distal aos stents foram comparados, nenhuma diferença estatisticamente significativa foi encontrada entre as áreas luminal, intimal, média ou índice intimal em cada grupo. Na comparação entre os grupos, as áreas intimal, média e o índice intimal não demonstraram variação estatisticamente significativa. Foram identificadas diferenças entre os grupos quanto às áreas luminais proximais (p = 0,036) e distais (p=0,044). Pelo teste de comparações múltiplas para Kruskal-Wallis (Teste de Dunn) identificou-se diferença significativa entre os grupos I e II. Entretanto, quando estas variáveis foram controladas pelo fator peso (relação área luminal/peso) a diferença não foi mais observada. Concluímos que, após quatro semanas, stents recobertos com PTFE induzem um espessamento intimal justa-stent similar ao observado com stents não recobertos ou com a simples manipulação arterial com uma bainha introdutora. Neste modelo experimental suíno, de curto seguimento, o revestimento com PTFE não foi responsável por adicional espessamento intimal.
Intimal thickening and restenosis occurring after angioplasty and/or stent deployment constitutes a frequent determinant of failure of these procedures. The main pathologic finding responsible for restenosis seems to be intimal hyperplasia, since the intravascular device is resistant to geometric arterial wall remodeling. The purpose of this study is to evaluate, by means of digital morphometry, the intimal thickening present in the regions of the arterial wall proximal and distal to the implant of a naked or PTFE covered stainless steel Z stent. Twenty five crossbred pigs, 6 to 10 weeks old, weighing between 14 and 32 kg (average= 20 kg) kg were divided in three groups. Group I included five animals that were submitted to retroperitoneal exposure of the aorta, aortotomy and simple insertion of a 12 F sheath. Group II included those animals in which a naked stent was deployed. Finally, in group III included the use of a PTFE covered stent. After four weeks, all animals were submitted to euthanasia and the aorto-iliac segment was removed. Four animals were excluded from the study due to aortic thrombosis (one from group II and three from group III). Morphometric analysis was performed using the non-parametric Wilcoxon and Kruskal-Wallis tests to compare data within the group, and across groups, respectively. When specimens of the arterial wall immediately proximal and distal to the stents were compared, no statistically significant difference could be established regarding luminal, intimal and media areas or intimal index. It was not possible to find significant differences between the intimal and medial areas or the intimal index. According to the Kruskal-Wallis test, a significant difference between proximal (p=0,036) and distal (p=0,044) luminal areas was observed between groups. The Dunn test identified differences between groups I and II. However, when these variables were corrected regarding the weight factor (luminal area/ weight index) this difference was no longer seen. We conclude that, after four weeks, covered PTFE stents generate an intimal thickening similar to uncovered stents or simple catheter manipulation. In this experimental model, the PTFE material was not responsible for additional intimal thickening during this limited period of time.

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Zouvi, João Paulo. "Implante direto de stent : efeitos no fluxo coronariano epicárdico, na microcirculação e na resposta inflamatória sistêmica." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2006. http://hdl.handle.net/10183/11346.

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Wombacher, Ralf. "Polymere als Beschichtungsmaterialien für Stents." [S.l.] : [s.n.], 2003. http://archiv.ub.uni-marburg.de/diss/z2003/0095/.

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Bozsak, Franz. "Optimization of Drug-Eluting Stents." Palaiseau, Ecole polytechnique, 2013. https://pastel.hal.science/pastel-00858100.

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L'utilisation de stents actifs (DES) a révolutionné le traitement de l'athérosclérose. Le relargage contrôlé de médicaments anti-prolifératifs dans la paroi artérielle (PA) a permis de réduire fortement le taux de resténose intra-stent. Mais le risque de thromboses intra-stents tardives demeure un enjeu majeur des DES en partie lié au retard de cicatrisation de la PA endommagée lors de l'implantation. Cette thèse présente une méthode d'optimisation du design des DES afin d'inhiber la resténose sans affecter la cicatrisation. Pour quantifier la performance des différents designs, un modèle numérique décrivant l'écoulement sanguin et le transport de médicaments dans les artères stentées a été développé. Il prend en compte la structure multi-couches de la PA et les interactions du médicament avec les cellules. Un algorithme d'optimisation est couplé au modèle afin d'identifier les DES optimaux. L'optimisation du temps de relargage ainsi que de la concentration initiale du médicament dans le revêtement du DES ont un effet significatif sur la performance. Lorsque le médicament utilisé est le paclitaxel, les solutions optimales consistent à relarguer le produit à des concentrations nettement inférieures à celles des DES actuels soit pendant quelques heures, soit pendant une durée d'un an. Pour le sirolimus, un relargage lent est nécessaire. Les formes optimales des spires du DES sont toujours allongées mais profilées seulement lorsque le relargage est rapide. Ces résultats permettent d'expliquer en partie les performances des différents DES récents et révèlent un fort potentiel d'amélioration dans la conception des DES par rapport aux dispositifs commerciaux actuels
Drug-eluting stents (DES), which release anti-proliferative drugs into the arterial wall in a controlled manner, have drastically reduced the rate of in-stent restenosis and revolutionized the treatment of atherosclerosis. However, late stent thrombosis remains a safety concern of DES, mainly due to delayed healing of the wound inflicted during DES implantation. We present a framework to optimize DES design such that restenosis is inhibited without affecting the healing process. To this end, we have developed a computational model of blood flow and drug transport in stented arteries which provides a metric for quantifying DES performance. The model takes into account the multi-layered structure of the arterial wall and incorporates a reversible binding model to describe drug interaction with the cells of the arterial wall. The model is coupled to a novel optimization algorithm that minimizes the DES performance metric to identify optimal DES designs. We show that optimizing the period of drug release from DES and the initial drug concentration within the coating has a drastic effect on DES performance. Optimal paclitaxel-eluting stents release the drug either within a few hours or slowly within a year at concentrations considerably lower than current DES. Optimal sirolimus-eluting stents require a slow drug release. Optimal strut shapes for DES are elongated and can be streamlined only if the drug release occurs quickly. The results offer explanations for the performance of recent DES designs, demonstrate the potential for large improvements in DES design relative to the current state of commercial devices, and define guidelines for implementing these improvements

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Da, Silveira Eduardo. "Cost-effectiveness decision analyses comparing covered to uncovered self-expandable metal stents to elective or on-demand polyethylene stent changes in patients with distal malignant biliary obstruction." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84091.

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Introduction. Endoscopic placement of stents is the preferred treatment for palliation of obstructive symptoms in non-operative candidates but significant differences in procedure and stent-related costs, patency of stents survival of patients exist. Aim. To determine the cost-effectiveness of two strategies using Polyethylene (PE) stents (PE with replacement on demand; PE with routine exchange every 3 months), as well as uncovered (U-SEMS) and covered self-expandable metal stent (C-SEMS) in the management of distal malignant biliary obstruction. Methods. A Markov model comparing four different initial approaches was designed: (1) PE stent with replacement on demand (PE-D); (2) PE stent changed every 3 months (PE-Q3); (3) U-SEMS or (4) C-SEMS. Probabilities and parameters for distribution were abstracted from randomized controlled trials and imputed to a 12-month time horizon. Effectiveness was calculated as number of occlusion-free months. Procedural and complication-related costs were obtained from the Canadian Institute for Health Information and a Provincial perspective was adopted. A probabilistic cost-effectiveness analysis using Monte Carlo simulations was utilized to obtain a posterior joint distribution for costs and effectiveness. Average and incremental net health benefits, probabilities of cost-effectiveness and value of information were determined across a range of willingness to pay (Rc) values. Results. PE-D has the lowest CE ratio, followed by C-SEMS at an incremental cost-effectiveness ratio (ICER) of $146.64$/month of stent patency. C-SEMS has the lowest CE ratio under the following scenarios: probability of survival at 12 months greater than 83%, ERCP costs higher than $1,282.90, cost C-SEMS less than $1,485.60 and cost ratio between ERCP and C-SEMS greater than 0.4. In the probabilistic analysis, PE-D is the strategy with the highest probability of cost-effectiveness for willingness to pay values lower than $150.60. How
Conclusion. Conditional to the willingness to pay and current Canadian costs, PE-D and C-SEMS are the strategies with the highest probabilities of cost-effectiveness. However, a significant level of uncertainly remains and wrong decisions will occur given the existent information. Acquisition of further knowledge to decrease the uncertainty level may be indicated if it costs less than the opportunity losses.

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Franke, Joachim, Peter Spillmann, Helmut Eschkötter, and Gert Morschek. "Ergebnis der Biopuster-Demonstrationsanlage der BMA Stendal." Universität Potsdam, 2000. http://opus.kobv.de/ubp/volltexte/2005/336/.

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Van, Aswegen Karl. "Dynamic modelling of a stented aortic valve." Thesis, Link to the online version, 2008. http://hdl.handle.net/10019/1747.

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Shedden, Laurie. "The intelligent stent." Thesis, University of Strathclyde, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.549389.

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Radic, Katarina. "Der Einfluss von Drug-Eluting-Stents und Bare-Metal-Stents auf die Ergebnisse nach notfallmäßiger Bypassoperation." Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-166326.

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Keevy, Pieter-André. "Finite element tool for modelling stent deployment to aid stent design." Master's thesis, University of Cape Town, 2004. http://hdl.handle.net/11427/3256.

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Irsale, Swagat Appasaheb Adanur Sabit. "Polymeric textile stents prototyping and modeling /." Auburn, Ala., 2005. http://repo.lib.auburn.edu/2005%20Summer/doctoral/IRSALE_SWAGAT_42.pdf.

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Traiven, Charlie. "Stonehenge-mer än bara stora stenar." Thesis, Uppsala universitet, Institutionen för arkeologi och antik historia, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-307412.

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Stonehenge is a place of mystery and wonder, where it stands as a last witness to long forgotten religious practices and rituals, and its sophisticated stone structure still makes a huge impression after over 4000 years. And it raises questions as to how it was built, and why? Stonehenge is today one of the world`s most famous megalithic monument in the world, and in its right. But Stonehenge is more than just big stones;it has a much longer and richer history than that. Stonehenge also has many surrounding monuments, from the same time period, and thought of as today, to coexist and fill different, specific functions, as a ritual landscape. The more archaeologists learn about Stonehenge, the more complex the picture gets. Today, the understanding of Stonehenge lies just as much in the surrounding landscape, as in the monument itself.

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Park, Kenneth Stuart. "Stents for transcatheter aortic valve replacement." Master's thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/27372.

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Rheumatic heart disease (RHD) is the leading cause of aortic valve disease in the world. Surgery to repair or replace the diseased valves is the only means to save a patient's life once the disease becomes symptomatic. Transcatheter aortic valve replacement (TAVR) has revolutionised the treatment of age-related degenerative aortic valve disease, but is currently not suitable for the majority of RHD sufferers due to the rapid degeneration of flexible leaflet valves in younger patients, contraindications of commercial devices to regurgitant or non-calcific aortic valve disease, and also due to resource or funding limitations. The current research project aimed to develop and test novel compressible balloon-expandable stents suitable for patients with symptomatic rheumatic aortic valve disease, and which would allow for a percutaneous polymeric valve to be manufactured, be crimped onto balloon-based devices, and be expanded into a compliant or non-calcific native aortic valve. Several stent concepts were developed and evaluated using Finite Element Analysis (FEA) and two favoured concepts were selected for more complex FEA, in which the balloon was simulated using an Ogden material model, and rigorous testing. The stent material, a nickel-cobalt-chromium alloy, was modelled as an isotropic elasto-plastic material with isotropic hardening. The novel stent designs incorporated a native leaflet-mimicking crown shape for continuous leaflet attachment and mechanisms to anchor the stented valve within compliant aortic roots. The first of the favoured designs provided tactile location during delivery and anchored using self-expanding arms on a balloon-expandable frame of the same material ("self-locating stents"). The second design anchored using arms that protruded during deployment as a consequence of plastic deformation incurred during crimping ("expanding arm stents"). Prototypes were successfully manufactured through laser cutting and electropolishing and showed good surface quality. In vitro testing included determination of crimping and expansion behaviour and measurement of mechanical properties such as resistance to migration in the anatomy. Valve performance was evaluated through in vitro haemodynamics in a pulse duplicator and durability was tested in a high-cycle fatigue tester. Simulated use testing was performed using cadaveric animal hearts. Finally, valves were also implanted into the aortic valve position of pigs (in acute termination experiments) through a transapical approach in order to verify valve deployment behaviour and function in vivo, and determine the stent's ability to anchor in the native anatomy. Stents could be crimped to diameters below 6mm and deployed using commercial balloons and proprietary non-occlusive deployment devices. FEA simulations of stent crimping and deployment matched experimental behaviour well and provide a tool to optimise stent performance. Peak Von Mises stresses during deployment (1437 MPa and 1633 MPa for self-locating and expanding arm stents, respectively) were comparable to a "zig-zag" stent simulated for control purposes (1650 MPa). Radial strength, evaluated for expanding arm stents, was lower than the Control stent (116 N vs. 347 N). This design, although predicted to be safe under fatigue loading, had a lower fatigue safety factor than the Control stent. Stents resisted migration to forces of at least 22 N, which is four times greater than physiological loading on the valves. Polymeric valves incorporating the stents were constructed and demonstrated good in vitro haemodynamic performance (Effective Orifice Areas ≥2.0cm², ΔP<9 mmHg, regurgitation <6%) and durability of over 400 million cycles. Designs functioned as intended in simulated use tests. Valves constructed using self-locating stents could be successfully deployed without rapid pacing in eight of nine pigs, and valve position was correct in seven of these. Valves of expanding arm stents remained anchored in six of eight attempted implants in pigs. This study has demonstrated proof of concept for a novel balloon-expandable stent for a polymeric transcatheter heart valve that is capable of anchoring in a compliant native aortic valve.

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Souza, Juliana Facchini de. "Estudo da difusão de fluido em uma artéria coronária." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/82/82131/tde-09042014-103404/.

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Atualmente, as doenças cardiovasculares são apontadas como as principais causas de mortes no Brasil e no mundo. Essas doenças são causadas pelo comprometimento das artérias, principalmente as artérias coronárias. Essas artérias possuem a importante função de transportar nutrientes ao próprio coração, possibilitando que o mesmo exerça sua tarefa de suprir todo o resto do corpo com elementos essenciais à sobrevivência do indivíduo. Este trabalho é sobre um estudo do comportamento dessas artérias quando ocorre a difusão de um fluido através de suas paredes. Primeiramente, estudou-se a composição das artérias coronárias, suas funções e patologias, para extrair elementos para compor um modelo fisicamente realístico e analiticamente tratável. Devido à sua composição histológica em três túnicas, a artéria coronária foi modelada como um cilindro elástico composto de cilindros ocos e concêntricos. Investigou-se então a solução do problema da difusão de um fluido em duas e três camadas, sendo esta última configuração geométrica mais próxima da realidade. Por fim, estudou-se a difusão de um fármaco contido em um stent farmacológico, cuja função é desobstruir uma artéria aterosclerosada e evitar sua reestenose.
Currently, cardiovascular diseases are known to be the primary cause of death in Brasil and worldwide. These diseases are caused by the malfunction of the arteries, especially the coronary arteries. These arteries have the important role of transporting nutrients to the heart itself, allowing it to exert its main task of providing the rest of the body with essential elements to the survival of an individual. This work is about a study of the diffusion of a fluid through the walls of a coronary artery. First, the composition of the coronary arteries, their functions, and pathologies were studied to extract elements that could be used to construct a model that is both physically realistic and analytically amenable to analysis. Due to its histologic composition in three layers, a coronary artery was modeled as an elastic cylinder composed of hollow and concentric cylinders. The solution of the diffusion problem of a fluid in two and three layers was studied, being this last geometrical configuration the closest to reality. Finally, the diffusion of a drug contained in a pharmacological stent was investigated. The main task of this type of stent is to clear an atherosclerotic artery and to avoid its restenosis.

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VIEIRA, Nancy Helena Lopes da Silva. "Avaliação dos níveis séricos de troponina I em pacientes submetidos à angioplastia coronariana com implante de stent." Universidade Federal de Goiás, 2009. http://repositorio.bc.ufg.br/tede/handle/tde/1770.

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Made available in DSpace on 2014-07-29T15:29:19Z (GMT). No. of bitstreams: 1 dissertacao nancy vieira.pdf: 795865 bytes, checksum: dfeac68319198e6608dcf82885225d60 (MD5) Previous issue date: 2009-11-23
Bakground: The presence of an increase in troponin I (cTnI) is common in patients who have undergone a percutaneous coronary intervention (PCI), but it is questionable if the myocardial lesion occurring in the intervention allows one to identify patients with a greater risk of presenting adverse cardiac events (ACE) .Objective : The overall objective of the study was to evaluate the immediate evolution of cardiac troponin I (cTnI) in patients undergoing elective coronary angioplasty with stenting, and also compare patients with serum changes after the procedure of coronary angioplasty stenting, with the clinical variables and the occurrence of adverse cardiac events (ACE) following 12 months.. Methods: This is a study of a prospective cut, which evaluates 49 consecutive patients who underwent coronary angioplasty with stent implantation. A cTnI serum dosage was done both before and after the procedure. Patients with a cut off >1.0 ng/mL before implantation were excluded. All the others received follow up for one year, to record the presence of ACE (death, acute myocardial infarction, another angioplasty). Results: cTnI serum elevations occurred in 21(45.7%) of the patients after the PCI. At the end of the follow up period, 11(23.9%) of the patients presented adverse cardiac events. There was no association between the cTnI serum elevation and the presence of ACE in the follow up. Conclusions: The elevation of cTnI found after a coronary angioplasty with stent implantation was frequent in our sample, but these elevations in serum did not show any association with clinical variables and the occurrence of adverse cardiac events following 12 months
A presença da elevação da troponina I(cTnI) é comum em pacientes submetidos a uma intervenção coronariana percutânea (ICP), porém é questionado se a lesão miocárdica ocorrida na intervenção permite identificar pacientes com maior risco de apresentar eventos cardíacos adversos. Objetivo: O objetivo geral do estudo foi avaliar o comportamento evolutivo imediato dos níveis séricos de troponina I (cTnI), em pacientes submetidos eletivamente à angioplastia coronária com implante de stent , e também, comparar pacientes com alterações séricas pós-procedimento de angioplastia coronária com implante de stent, com as variáveis clínicas e a ocorrência de eventos cardíacos adversos (ECA) no seguimento de 12 meses. Metodologia: Este é um estudo de coorte prospectivo, que avaliou 49 pacientes consecutivos, submetidos à angioplastia coronariana com implante de stent. Fez-se dosagens séricas de cTnI antes e após o procedimento. Pacientes com cut off > 1,0 ng/mL antes do implante foram excluídos, e os demais foram acompanhados em um ano de seguimento, para registro da presença de ECA (óbito, infarto do miocárdio e nova angioplastia). Resultados: Ocorreram elevações séricas de cTnI em 21(45,7%) dos pacientes após a ICP. Ao término do seguimento 11(23,9%) dos pacientes apresentaram eventos cardíacos adversos. A correlação entre a elevação sérica da cTnI e a presença de ECA no seguimento não mostrou associação. Conclusão: A elevação da cTnI encontrada após uma angioplastia coronariana com o implante de stent foi freqüente em nossa amostra, porém estas elevações séricas não apresentaram nenhuma associação com as variáveis clínicas e a ocorrência de eventos cardíacos adversos no seguimento de 12 meses

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Claudino, Persio Achôa. "Angioplastia do bulbo carotídeo com colocação de stent: acompanhamento clínico e radiológico." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/5/5151/tde-22022010-144231/.

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Objetivo: Avaliar os resultados clínicos e radiológicos tardios de pacientes submetidos à angioplastia carotídea com colocação de stent (ACS) por doença aterosclerótica estenosante bulbar e determinar se o método é efetivo na prevenção de novos eventos isquêmicos cerebrais e se o método é durável na manutenção perviedade arterial. Métodos: Acompanhamos clinicamente e radiologicamente, por ultra-som Doppler (USD) e angiografia cerebral com subtração óssea digital (DSA), pacientes com estenose do bulbo carotídeo por doença aterosclerótica submetidos a ACS no período de janeiro de 2002 a maio de 2005 realizadas nos INRAD-HCFMUSP e Hospital Santa Marcelina de Itaquera. Resultados: 80 pacientes submetidos 84 ACS foram acompanhados clinicamente e radiologicamente num período entre 25 a 66 meses, média 43,8 meses, com um único caso de reestenose grave intra-stent (1,2%) e um único caso de novo evento isquêmico cerebral (1,3%). Conclusão: A ACS é um método durável na manutenção da perviedade do bulbo carotídeo e eficiente a longo prazo na redução de eventos isquêmicos cerebrais em pacientes com doença aterosclerótica do bulbo carotídeo.
Objective: to evaluate the long-term clinic and radiologic results for the patients submitted to angioplasty with stent implantation because estenotic atherosclerosis disease of the carotid bulb and to determine if ACS is effective to prevent the cerebral ischemic attack and durable to keep the carotid bulb opened. Methods: We follow-up clinically and radiologically, by ultrasound with color and spectral Doppler (USD) and with digital subtraction angiography (DSA), patients with atherosclerotic disease of the carotid bulb submitted to ACS realized between January of 2002 and may of 2005 in the INRAD-HCFMUS and Hospital Santa Marcelina de Itaquera. Results: 80 patients who underwent 84 ACS were evaluated clinically and radiologically in the long-term follow-up, 25 to 66 months, with media of the 43,8 months, with only one case of restenosis (1,2%) and only one case of new ischemic event (1,3%). Conclusion: The ACS é a effective method to keep the carotid bulb opened and it is efficient to prevent new ischemic event in patients with atherosclerotic disease of the carotid bulb.

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Vilkas, Voldemaras. "Dviračių rėmų bandymų statinėmis ir dinaminėmis apkrovomis stendas." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2004. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2004~D_20040616_140434-45430.

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The theme of Master project of Energetics engineering is actual because in nowadays it is important not only design and functionality of bicycle, but also safety and technological tests of bycicle frame, fork and other part corresponding to international standarts. In Master project was created system for dynamic changing force applying on dynamic pedal and wheel strenght tests. Results of practical pedal pushing research and computations of modelated pedaling system were similar. Analysis of pneumatic cylinder and proportional pressure regulator (using Centaurus Plus modeling program) showed that it is necessary to reduce cylinder working cell volume to enable system to repeat 3 Hz set signals. Using algorithms models was created program for data input, processing and visualizing of testing stand. This program was kindly evaluated by specialists of Technological Test center of Faculty of Technology.

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Perugini, Enrico. "Lˊimaging 3D per la quantificazione della stenosi mitralica." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2018.

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Nell’elaborato presentato si espone l’ecocardiografia tridimensionale tempo reale, le sue caratteristiche e i suoi vantaggi rispetto la tomografia (gold standard) e l’ecografia convenzionale. Nel dettaglio viene presentato uno studio riferito alle valvole cardiache e alle loro principali patologie, quali calcificazione e stenosi. Vengono introdotte la calcificazione dell’anulus mitralico, un processo cronico degenerativo nella base fibrosa della valvola mitrale; la stenosi mitralica, la quale si verifica a causa di un restringimento della valvola e una non totale o incompleta apertura della stessa; la malattia della valvola calcifica aortica, caratterizzata da uno spessore maggiore dei lembi, irrigidimento, calcificazione (senza una fusione delle commessure) e con una considerevole ostruzione; in fine la stenosi aortica, un progressivo restringimento della valvola aortica che rimane tutt’oggi un processo ancora da definire completamente e non esistono trattamenti in grado di cambiare il corso della malattia. Tramite l’elevata risoluzione, la tomografia computerizzata multistrato fornisce uno strumento di imaging di riferimento per la quantificazione di calcio e per il calcolo dell’area dell’orifizio in una valvola stenotica. I contro di questa tecnica consistono nell’esposizione da parte del paziente a dosi nocive di raggi x e nella inesistenza di un approccio quantitativo convalidato. Con l’avvento dell’ecocardiografia 3D real-time è diventato possibile superare i metodi di studio delle strutture cardiache, ovviare ai limiti delle già esistenti tecniche, aumentare la precisione delle misure di parametri per la quantificazione di calcificazione e stenosi.

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Vearick, Samanta Bianchi. "Confecção e avaliação de órtese de nitinol auto-expansível com aplicação em vias aéreas." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2006. http://hdl.handle.net/10183/6856.

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Este trabalho tem como objetivo a confecção de órtese auto-expansível, utilizando fios da liga de nitinol para aplicação em vias aéreas. O processo iniciou na obtenção de um trançado manual e posterior determinação de gabaritos para a confecção das órteses. Após a trançagem, as órteses são submetidas a tratamento térmico a 530ºC, o que gera uma coloração superficial que varia com o tempo de permanência no forno. Essas colorações apresentam variações da cor parda, roxa, azul escura e azul clara, que foram avaliadas mediante testes de variação dimensional, ensaios de compressão e fadiga. Sendo apresentada também a metalografia do fio utilizado na trançagem. As órteses de cor azul escura apresentaram melhor comportamento mecânico e com estas foram realizados ensaios de fadiga. A avaliação da órtese in vivo, foi feita na traquéia de gatos, utilizados na experimentação animal, pelo Hospital de Clínicas de Porto Alegre. Devido ao resultado positivo dessa avaliação, obteve-se autorização para novo estudo do Ministério da Saúde, pela sua Comissão Nacional de Ética em Pesquisa – CONEP, para o implante em vias aéreas humanas, em fase de implementação.

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50

Carluccio, Anna Maria. "Protesi vascolari e stent." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2018.

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Le malattie cardiovascolari sono una delle maggiori cause di morte nel mondo, per questo nel corso della storia si è cercato di sviluppare dispositivi da impianto sempre migliori per la cura delle malattie che riguardano l’apparato cardiocircolatorio. Le malattie più frequenti che colpiscono i vasi sanguigni sono stenosi e aneurisma. Uno dei metodi attualmente usati per curare questo tipo di malattie riguarda l’applicazione di “protesi vascolari”, dispositivi medici che vengono impiantati permanentemente allo scopo di ripristinare l’efficacia di un tratto vascolare che, per qualsiasi motivo, non riesce a svolgere adeguatamente le sue funzioni. Ne esistono di diverso tipo, sia naturali che sintetiche, e la ricerca in questo settore si occupa di realizzare protesi innovative per sopperire ai limiti di quelle naturali e svolgere al meglio il loro compito. In particolare lo sviluppo di protesi di piccolo diametro presenta ancora delle limitazioni. Questo argomento è ampiamente trattato nel capitolo 2. L'angioplastica coronarica transluminale (PTA), che consiste nell’inserire un “catetere a palloncino” nel tratto stenotico, espanderlo e ripristinare il lume originale, è stata la prima rivoluzione nella cura di un vaso stenotico. La seconda rivoluzione nella cardiologia interventistica è lo stent in metallo nudo (BMS), ovvero una struttura metallica cilindrica a maglie in grado di sostenere meccanicamente le pareti del vaso stenotico e di sopperire ai limiti della PTA. La terza rivoluzione è rappresentata dai DES (Drug-Eluting-Stent), ovvero stent metallici rivestiti da materiali polimerici contenenti sostanze attive che vengono rilasciate nell’ organismo dopo l’impianto. La quarta rivoluzione, ancora in fase di studio, sarà la realizzazione di stent biodegradabili, sul modello dei DES, che, dopo aver svolto la loro funzione, si dissolvono. Il terzo capitolo della presente tesi fa riferimento proprio allo studio di questi nuovi dispositivi.

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Dissertations / Theses on the topic 'Stentai'

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