This work investigates flow measurement capabilities within meso- and micro-scaled medically relevant devices using particle image velocimetry (PIV). Medical devices can be particularly challenging to validate due to small length scales and complex geometries, which can reduce measurement accuracy by introducing noise and reducing available signal. Although the sources of such problems are often device specific, the effective outcome is a reduction in the signal-to-noise ratios (SNRs) of PIV images and correlations. This effort utilizes advanced PIV processing and post-processing techniques to establish protocols for achieving high accuracy PIV measurements in challenging flow environments. This investigation takes place within three wide-ranging medically related devices. First, channel flow in a microfluidic device is investigated to evaluate improvements in measurement accuracy gained using phase correlations in comparison to confocal microscopy. This work found substantial improvements in error with respect to the ensemble field for phase correlations while only moderate improvements were observed for confocal imaging with standard processing techniques. Secondly, an evaluation of stenting procedures was executed resulting in the first published PIV and computational fluid dynamics (CFD) joint study on bifurcating stents. This work analyzes steady flow in three bifurcation angles and four different single- and double-stenting procedures, which are clinically used in coronary bifurcations. Finally, a medical device analog was evaluated to develop a comprehensive CFD validation dataset, including a full uncertainty analysis for velocity and wall shear stress as well as estimates for pressure fields and relevant flow statistics including Reynolds stresses and dissipation. / Ph. D.

Pancreatic pseudocyst is a common complication of pancreatitis. Pseudocysts may require decompression when they become painful, infected, or start compressing surrounding organs. Decompression is achieved by endoscopic cystogastrostomy. Recently, the use of lumen-apposing metal stent (LAMS) for cystogastrostomy has gained popularity due to ease of use and high technical success. LAMS has a wider lumen, which allows for direct endoscopic necrosectomy in the cases of walled-off necrosis. Our patient is a 30-year-old male who presented with massive hematemesis and dizziness. He had a history of chronic alcohol-induced pancreatitis. Three weeks before the presentation, he underwent a cystogastrostomy with LAMS placement to treat a 10-cm walled-off necrosis. Urgent computed tomography (CT) scan did not reveal any acute finding suggestive of bleeding. Esophagogastroduodenoscopy showed blood protruding from the LAMS with a large clot formation. Attempts to stop bleeding were unsuccessful. He underwent CT angiography of the abdomen. CT angiography showed a bleeding pseudoaneurysm (PA) believed to be a complication of the LAMS. Subsequently, multiple coils were placed in the splenic artery near the PA. The patient continued to improve without a further drop in hemoglobin and was eventually discharged. PA formation and subsequent rupture is a rare delayed complication of LAMS. It may lead to massive gastrointestinal bleeding with a high mortality rate. Diagnostic delays have resulted in increased mortality by 60%. In this article, we present a case of massive gastrointestinal bleeding due to a ruptured splenic artery PA presenting as a delayed complication of LAMS.

Healthcare providers often are faced with the challenge of determining an appropriate length of dual antiplatelet therapy (DAPT) for patients who have had percutaneous coronary intervention and stent placement. This is an especially challenging clinical decision for patients with drug-eluting stents, as several studies show different results when assessing risk and benefit.

No description available.

No description available.

京都大学 / 新制・課程博士 / 博士(医学) / 甲第24966号 / 医博第5020号 / 新制||医||1069(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 江木 盛時, 教授 浅野 雅秀, 教授 湊谷 謙司 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Die interventionelle Radiologie hat sich in den letzten Jahrzehnten zunehmend auf palliativmedizinische sowie onkologische Bereiche ausgeweitet und kann durch minimal-invasive Therapieoptionen gerade in vulnerablen Patientenkollektiven attraktive Behandlungsmöglichkeiten zur Verfügung stellen. Die tumorbedingte untere Einflussstauung ist ein seltenes Krankheitsbild und stellt eine schwere symptomatische Komplikation einer malignen Grunderkrankung dar. Dabei kommt es im Rahmen dieser Grunderkrankung durch die Primärtumormasse oder Metastasen zu extrinsischer Kompression der Vena cava inferior (VCI), Gefäßinvasion oder Thrombusbildung. Ziel der Dissertationsarbeit ist es, den technischen und klinischen Erfolg der Sinus-XL ® Stentimplantation in die Vena cava inferior bei einer tumorbedingten unteren Einflussstauung zu untersuchen. Als technischer Erfolg wurde dabei die problemlose Stentimplantation mit anschließender Aufhebung der VCI-Stenose/Okklusion und Revaskularisation der VCI definiert. Bezüglich des klinischen Erfolges wurde der Frage nachgegangen, inwieweit die Stentimplantation die typischen Symptome einer unteren Einflussstauung (Ödeme der unteren Extremität, Aszites und Anasarka) lindern und bestenfalls eliminieren kann. In der vorliegenden Arbeit sind dazu retrospektiv die Daten von insgesamt 21 Patienten (11 Frauen, 10 Männer) mit einem medianen Alter von 61 Jahren (19-92 Jahre), die zwischen Oktober 2010 und Januar 2021 aufgrund einer tumorbedingten unteren Einflussstauung mit einem Sinus-XL ® Stent endovaskulär versorgt wurden, ausgewertet worden. Zur Quantifizierung der klinischen Symptomatik wurde für das jeweilige Symptom ein Scoring-System entwickelt bzw. modifiziert. Der technische Erfolg belief sich auf 100% (21/21). Postinterventionell konnte zudem eine signifikante Reduktion des transstenotischen Druckgradienten (p = 0,008) und eine signifikante Aufweitung des Stenosendiameters (p < 0,001) erreicht werden. Die primäre und primär-assistierte Stentoffenheit betrug 92,9 % (13/14) und 100% (14/14), die anatomische Stentoffenheit (< 50% Restenose) belief sich auf 53,3 % (8/15). Die Reinterventionsrate lag bei 4,8 % (1/21). Schwerwiegende Komplikationen traten nicht auf. Der klinische Erfolg bezüglich der Ödeme der unteren Extremität belief sich auf 82,4 % (14/17), 93,8 % (15/16) sowie auf 85,7 % (18/21) und zeigte in allen betrachteten Zeitintervallen eine signifikante Scorewertreduktion (p < 0,001). Das klinische Outcome bezüglich der Ödeme war bei kürzeren Stenosen/Obstruktionen signifikant besser (p = 0,025). Bezüglich einer intrahepatischen Segmentbeteiligung, der transstenotischen Druckgradienten, der absoluten Gradientenreduktion sowie der Überlebenszeit nach der Intervention zeigten sich hingegen keine als klinisch relevant einzustufende Ergebnisse. Ein eindeutiger Effekt der Intervention auf die Symptome Anasarka und Aszites konnte nicht nachgewiesen werden. Diesbezüglich zeigten sich klinische Erfolgsraten von 42,9 % (6/14) und 5,3 % (1/19). Im postinterventionellen Verlauf konnten außerdem signifikante Reduktionen der präinterventionellen Harnstoffwerte sowie des Körpergewichtes der Patienten verzeichnet werden. Zusammenfassend zeigt die vorliegende Arbeit, dass die Sinus-XL ® Stentimplantation geeignet ist, eine tumorbedingte Vena cava inferior-Stenose/Obstruktion aufzuheben und eine Revaskularisation der VCI zu erreichen. Die klinischen Symptome einer unteren Einflussstauung – insbesondere bezogen auf die Ödeme der unteren Extremität und mit Einschränkungen bezogen auf die Symptome Aszites und Anasarka – können ebenfalls durch die Stentimplantation gelindert und teilweise sogar langanhaltend eliminiert werden. Die Sinus-XL ® Stentimplantation sollte daher stets als Therapieoption bei tumorbedingten unteren Einflussstauungen in Erwägung gezogen werden. Nicht zuletzt stellt die Stentimplantation auch eine sichere und komplikationsarme Intervention dar. Weitere Studien, bestenfalls multizentrische Studien, sind jedoch notwendig, um die dargestellten Ergebnisse weiter zu untermauern. / In recent decades interventional radiology has increasingly expanded into palliative as well as oncologic settings and can provide attractive treatment options through minimal-invasive therapies, especially in vulnerable patient populations. Malignant obstruction of the inferior vena cava (IVC) is a rare clinical condition and represents a severe symptomatic complication of an underlying malignant disease. Extrinsic compression of the inferior vena cava, vascular invasion or thrombus formation occur as part of the underlying disease. The aim of this work is to investigate the technical and clinical success of Sinus-XL ® stent implantation into the inferior vena cava in case of malignant obstruction of the inferior vena cava. Technical success was defined as the successful stent implantation with subsequent resolution of the stenosis/occlusion and revascularization of the IVC. Regarding clinical success, the question was addressed to what extent stent implantation can alleviate and, at best, eliminate the typical symptoms of malignant IVC obstruction (lower extremity edema, ascites and anasarca). Therefore data from a total of 21 patients (11 women, 10 men) with a median age of 61 years (19-92 years) who underwent endovascular treatment with a Sinus-XL ® stent for malignant IVC obstruction between October 2010 and January 2021 was retrospectively analyzed. In order to quantify the extent of the clinical symptoms a scoring system was developed or modified for each symptom. The technical success was 100% (21/21). After the intervention a significant reduction of the transstenotic pressure gradient (p = 0.008) and a significant widening of the stenotic diameter (p < 0.001) were achieved. Primary and primary-assisted stent patency were 92.9% (13/14) and 100% (14/14), anatomic stent patency (< 50% restenosis) was 53.3% (8/15). The reintervention rate was 4.8% (1/21). No major complications occurred. The clinical outcome regarding lower extremity edema was 82.4% (14/17), 93.8% (15/16), and 85.7% (18/21), showing a significant score reduction in all time intervals considered (p < 0.001). Clinical outcome regarding edema was significantly better with shorter stenosis/obstruction (p = 0.025). In contrast, with regard to intrahepatic segment involvement, transstenotic pressure gradients, absolute gradient reduction, and survival time after the intervention, there were no results that could be classified as clinically relevant. A clear effect of the intervention on the symptoms of anasarca and ascites could not be demonstrated. In this regard, clinical success rates of 42.9% (6/14) and 5.3% (1/19) were shown. In the post-interventional course, significant reductions of the pre-interventional urea levels as well as of the patients´ body weight could also be recorded. In conclusion, the present work shows that Sinus-XL ® stent implantation is suitable to resolve malignant IVC obstruction and to achieve revascularization of the IVC. The clinical symptoms - especially related to lower extremity edema and with limitations related to the symptoms of ascites and anasarca - can be alleviated by stent implantation and in some cases even eliminated. Sinus-XL ® stent implantation should therefore always be considered as a therapeutic option for malignant IVC obstruction. Last but not least, stent implantation also represents a safe and low-complication intervention. However, further studies, at best multicenter studies, are necessary to further substantiate the presented results.

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No description available.

Stent is one of the coronary angioplasty techniques that expands the narrowed coronary arteries due to the accumulation of fat, cholesterol and other substances in the lumen of the arteries. The major complication of stent is restenosis. Current development of drug-eluting stents shows successfully reduce the occurrence of restenosis. Other than using drugs, electrostatic self assembled (ESAd) thin films may be the potential candidates to prevent restenosis. ESA is a process to fabricate thin films bases on the electrostatic attraction between two oppositely charges. We used this technique to fabricate four PVP films and four PEI films. All films were examined by XPS and AFM. XPS data showed our coatings were successfully fabricated on substrates. AFM images revealed PVP coating was uniform, but PEI coatings had different morphologies due to diffusion and pH during the process. Three preliminary hemocompatibility testes were performed to evaluate the hemocompatibility of the coatings. Platelet adhesion study showed the thin films inhibited platelet adhesion. All thin films were able to inhibit coagulation and were less cytotoxic. The studies suggested the ESA films were potentially hemocompatible. / Master of Science