No description available.

Thesis (M.S.)--University of Hong Kong, 1988.

Thesis (M.S.)--University of Hong Kong, 1988. / Also available in print.

published_or_final_version / Surgery / Master / Master of Surgery

The bulk of this thesis will be devoted to the development of the new anastomotic technique and descriptions of the various experimental systems designed to test the anastomosis, together with the results obtained.

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2005. / David N. Ku, Committee Chair ; Alexander Rachev, Committee Co-Chair ; Elliot L. Chaikof, Committee Member. Includes bibliographical references.

Είναι πλέον αποδεκτό ότι οι αγγειακές βιολογικές διαδικασίες επηρεάζονται από την τοπική αιμοδυναμική. Πειράματα in vivo, in vitro και αριθμητικές μελέτες επιβεβαίωσαν ότι τα μοντέλα της ροής στην αρτηριοφλεβική αναστόμωση (ΑΦΑ) είναι αυστηρά εξαρτημένα από τη γεωμετρία της περιοχής. Στην παρούσα εργασία μελετήθηκε το πεδίο ροής του αίματος σε "εικονικές γεωμετρίες" των ΑΦΑ μέσω μεθόδων υπολογιστικής ρευστομηχανικής. Με τον όρο "εικονική γεωμετρία" καλούμε μια γεωμετρία που δεν προσδιορίζεται από μετρήσεις σε πραγματικές αναστομώσεις αλλά προσομοιάζει προσεγγιστικά σ'αυτή. Ως οριακές συνθήκες του προβλήματος ετέθησαν κατανομές ταχύτητας που είχαν μετρηθεί σε συγκεκριμένες θέσεις εισόδου στο επίπεδο αρτηρίας και φλέβας της ΑΦΑ. Η μελέτη του πεδίου ροής περιλαμβάνει την κατανομή ταχυτήτων σε όλη την περιοχή της ΑΦΑ, τον προσδιορισμό και μελέτη των περιοχών ανακυκλοφορίας, κατανομή των πιέσεων και των διατμητικών τάσεων στο τοίχωμα της ΑΦΑ. Η μελέτη του πεδίου ροής περιλαμβάνει τη σύγκριση των υπολογιστικά λαμβανομένων μεγεθών με τα αντίστοιχα αποτελέσματα εκ της βιβλιογραφίας. Σε ένα ξεχωριστό μέρος της εργασίας αναλύονται οι ΑΦΑ και οι τεχνικές τους, οι επιπλοκές τους καθώς και τα εμβιομηχανικά χαρακτηριστικά τους. Επίσης αναλύεται η συσχέτιση των αιμοδυναμικών διαταραχών με την ανάπτυξη ινομυϊκής υπερπλασίας. / It is widely accepted that the vascular biological procedure is influenced by the local hemodynamics. Experiments in vivo, in vitro and numerical studies have confirmed that the flow models in Arteriovenous Anastomosis (AVA) depend strongly on the area geometry. This project goes through the flow distribution in “virtual geometries”of AVA using computational fluid dynamics (CFD). The term “virtual geometry” refers to a type of geometry which is not determined by calculations of real anastomosis but roughly simulates it. The boundary conditions of the problem were the velocity distributions that were calculated in specific entrance points in artery and vein of the AVA. The study of the flow distribution encompasses the velocity distribution in the whole area of the AVA, the specification and investigation of back flow areas, the distribution of pressure and shear stress in the AVA walls. It also encompasses the comparison of computated results to the equivalent measurements accumulated from the international bibliography. A separate chapter of this study refers to different kinds of AVA and their techniques, complications and biomechanical characteristics. Furthermore, it elaborates the correlations of the hemodynamical disorders and intimal hyperplasia.

Ένας από τους παράγοντες που ενοχοποιούνται για την ανάπτυξη ινομυϊκής υπερπλασίας στη φλεβική αναστόμωση των συνθετικών αρτηριοφλεβικών μοσχευμάτων, είναι η διαταραχή των αιμοδυναμικών συνθηκών στην περιοχή της αναστόμωσης. Για τον υπολογισμό της ροής, δηλαδή των πεδίων ταχύτητας, διατμητικής τάσης και στροβιλισμού, στην περιοχή αυτή, χρησιμοποιούνται μέθοδοι της υπολογιστικής δυναμικής των ρευστών, οι οποίες προϋποθέτουν γνώση της τριδιάστατης γεωμετρίας των αγγείων και του μοσχεύματος. Στην παρούσα διπλωματική εργασία αναπτύσσεται μια μεθοδολογία και ο αντίστοιχος αλγόριθμος για τον προσδιορισμό της τριδιάστατης γεωμετρίας της κεντρικής γραμμής των αγγείων από διεπίπεδη αγγειογραφία, όπου η σχέση των δύο συστημάτων αναφοράς θεωρείται άγνωστη, καθώς και για τη σχεδίαση κυκλικών διατομών σε επιλεγμένες θέσεις για την προσέγγιση του αγγειακού αυλού. Η μέθοδος βασίζεται στην θεωρία των Metz – Fencil (1989) και απαιτεί την εκ των προτέρων γνώση δύο ζευγών αντίστοιχων σημείων στις προβολές για τον προσδιορισμό της σχέσης που συνδέει τα δύο συστήματα αναφοράς. Για την αναγνώριση αντίστοιχων σημείων στις προβολές χρησιμοποιείται η τεχνική της επιπολικής γραμμής, ενώ η ανακατασκευή της κεντρικής γραμμής πραγματοποιείται με χρήση παραμετρικής φυσικής spline. Πραγματοποιήθηκε έλεγχος της μεθόδου με χρήση πρότυπης γεωμετρίας και διαπιστώθηκε ότι η ακρίβεια της ανακατασκευής εξαρτάται από το πλήθος και την ποιότητα των σημείων ελέγχου της spline. Τελικά, η μέθοδος εφαρμόστηκε σε πρότυπο αντικείμενο, γνωστής γεωμετρίας, ανάλογης αυτής που λαμβάνεται σε πραγματικές αγγειογραφικές προβολές αρτηριοφλεβικής αναστόμωσης στην περιοχή της καρωτίδας και διαπιστώθηκε ότι ανακατασκευάζει με καλή ακρίβεια την κεντρική γραμμή του αντικειμένου. / One of the factors that have been incriminated for the growth of fibromuscular hyperplasia at the anastomosis of the synthetic arteriovenous implant, is the disturbance of the hemodynamic conditions at the region of the anastomosis. For the computation of the flow at this region, that is the fields of velocity, shear stress and rotation, methods of computational flow dynamics are used, which require that the 3D geometry of the vessels and the implant are known in advance. In this thesis, we developed a methodology and the respective algorithm for the determination of the 3D geometry of the central line of the vessels from biplane angiography, for which the relation of the two systems of coordinates are unknown, as well as for the drawing of circular cross section at selected positions for approximation of arterial lumen. The method is based on the theory of C.E.Metz and L.E.Fencil (1989) and requires the knowledge of two pairs of respective points on the views in advanced in order to calculate the rotation matrix and the translation vector that relate the two systems of coordinates. For recognition of respective points on the two views the epipolar line technique is being used, while the central line is reconstructed using a parametric natural spline. The method was tested using a model and it showed that the accuracy of the reconstruction depends on the number and the quality of the control points of the spline. Finally, the method was implemented on a model object with geometry, analogous to that we get from real angiographic views of arteriovenous anastomosis at the region of the carotid artery, and its central line was reconstructed with very good accuracy.

O autor realizou um estudo anatômico da região lateral e proximal da perna por meio de dissecção anatômica em cadáver, de exame arteriográfico e de mapeamento com Doppler em pacientes, visando a descrição da artéria denominada fibular superior, que se origina no tronco tíbio-fibular em 70% dos casos, da artéria fibular, em 20% e da artéria tibial anterior, em 10% e participa na irrigação do músculo sóleo e gastrocnêmio. Este vaso possui características adequadas para a realização de micro-anastomose. Após a conclusão da parte anatômica-descritiva, o autor aplicou o retalho derivado da artéria fibular superior, denominado retalho súpero-lateral da perna, na reconstrução de defeitos cutâneos e defeitos complexos tridimensionais, localizados no pé e tornozelo, em 10 pacientes, obtendo bons resultados / The author performed an anatomical study of the proximal and lateral aspect of the leg, consisting of cadaver dissection, arteriogram and Doppler mapping, in order to disclose the features of a new vessel, denominated superior peroneal artery. It originates from the tibiofibular trunk in 70 % of times, from the peroneal artery, 20%, and from the anterior tibial artery, 10%. It contributes to nourish the soleous and the lateral gastrocnemius muscle. The superior peroneal vessels are also suitable for microanastomosis. Therefore, the flap derived from the superior peroneal artery, called superolateral leg flap (SLL), was used for lower leg reconstructions in 10 patients, in two of them as chimeric flap for complex tridimensional defects, with good results

Introdução: as alças vasculares podem prover o suprimento sanguíneo adequado para um retalho microcirúrgico em um leito desfavorável, como fratura exposta ou área irradiada após a ressecção de tumores. Apesar de realizadas na prática clínica, há falta de estudos demonstrando quais os fatores são responsáveis pelo seu sucesso. Objetivo: avaliar, em coelhos, qual é a influência do desenho da alça de veia femoral com anastomose na artéria femoral, na presença de fluxo (patência) após sete dias. Método: Trinta e nove coelhos foram submetidas à microanastomose arteriovenosa com técnica microcirúrgica. As alças foram acomodadas em dois desenhos, um, chamado \"circular\" e outro, o mais alongado possível sem dobras na alça. Os parâmetros avaliados foram: presença ou não de fluxo, sinais de hemólise, alterações hemodinâmicas sofridas pela veia submetida à pressão arterial. Resultados: Após sete dias, o fluxo estava presente em 68% das alças \"anguladas\" e em 75% das alças \"circulares\" (p > 0,05). Houve, intragrupo, diminuição estatisticamente significante da pCO2 e aumento estatisticamente significante do pH. Não houve diferença estatisticamente significante no restante dos parâmetros avaliados entre os dois modelos de alça. Conclusão: O desenho da alça vascular arteriovenosa na pata do coelho não interfere na sua patência em um período de sete dias / Introduction: the vascular loops can provide adequate blood supply to a microsurgical flap in an unfavorable bed as open fracture or irradiated area after resection of tumors. Although performed in clinical practice, there is a lack of studies showing which factors are responsible for their success. Objective: To evaluate, in rabbits, which is the influence in the presence of flow (patency) of femoral vein loop design in anastomosis of the femoral artery after seven days. Method: Thirty-nine rabbits were subjected to arteriovenous microanastomosis with microsurgical technique. The loops were accommodated in two designs, one named \"circular\" and the other, the more elongated possible without folds. The parameters evaluated were: presence or absence of flow, hemolysis, hemodynamic changes suffered by vein submitted to blood pressure. Results: After seven days, the flow was present in 68% of angled loops and 75% of the \"circular\" loops (p > 0.05). There was intra-group, statistically significant decrease in the pCO2 and statistically significant increase in pH. There was no statistically significant difference in the rest of the parameters evaluated between the two loop models. Conclusion: The design of arteriovenous vascular loops in the rabbit paw does not interfere with its patency over a period of seven days