Wyniki wyszukiwania - BazTech

1

Numerical simulations of the pulsatile blood flow in the different types of arterial fenestrations: Comparable analysis of multiple vascular geometries

Tyfa Z., Obidowski D., Reorowicz P., Stefańczyk L., Fortuniak J., Jóźwik K.

Biocybernetics and Biomedical Engineering

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2018

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Vol. 38, no. 2

228--242

EN

In medical terms, fenestration stands for an anomaly within the circulatory system in which the blood vessel lumen is divided into two separate channels that rejoin in the distal part of this vessel. The primary objective of this research was to analyze the impact of the left vertebral artery (LVA) and basilar artery (BA) fenestrations on the blood flow characteristics in their regions and downstream, in the cerebral circulation. The geometrical data, obtained from the angio-Computed Tomography, were the basis for the generation of a 3D model in SolidWorks 2015. In order to observe the flow characteristics within the whole spatial domain, computational fluid dynamics was involved in performing simulations of the blood flow in the patient-specific arterial system (beginning with the aortic arch and finishing with the Circle of Willis). To examine the flow distribution changes resulting from altered fenestration geometries, additional models were built. The blood flow velocity, volume flow rate and shear stress distribution were analyzed within this study. It was proven that the length/size/ position of the fenestration altered the flow characteristics in different manners. The investigations showed that the patient-specific LVA, at the V3 section (extracranial part of the artery located between the spine and the skull), is not a reason of aneurysm formation. However, BA fenestration at the proximal segment might be a possible reason of future aneurysm formation. It was proven that the computational fluid dynamics tool could support medical diagnostic procedures and multivessel brain vascular disease treatment planning.

2

3D blood vessels reconstruction based on segmented CT data for further simulations of hemodynamic in human artery branches

Polańczyk A., Strzelecki M., Woźniak T., Szubert W., Stefańczyk L.

Foundations of Computing and Decision Sciences

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2017

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Vol. 42, No. 4

359--371

EN

We aimed at the reconstruction of the branches of human aortic arch for blood perfusion analysis used later in the Computational Fluid Dynamic (CFD). The reconstruction was performed based on segmentation results obtained from CT data. Two segmentation algorithms, region growing and level set were implemented. Obtained binary segmentation results were next evaluated by the expert and corrected if needed. The final reconstruction was used for preparation of a numerical grid and for further calculation of blood hemodynamic. The collected data composed of blood velocity and blood flow rate in function of time were compared with USG-Doppler data. Results demonstrate that proposed algorithm may be useful for initial reconstruction of human cardiac system, however its accuracy needs to be improved as further manual corrections are still needed.

3

3D vascular tree segmentation using a multiscale vesselness function and a level set approach

Woźniak T., Strzelecki M., Majos A., Stefańczyk L.

Biocybernetics and Biomedical Engineering

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2017

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Vol. 37, no. 1

66--77

EN

The paper presents a method aimed at segmentation of a vascular network in 3D medical data. The method implements an extended version of a vesselness function that considers multiscale image filtering to emphasize vessels of different diameters. This function is combined with a level set approach based on a Chan–Vese model. The proposed method was evaluated on medical images of the brain and hand vasculature. These images were obtained by different modalities, including angio-CT and two MR acquisition protocols. The proposed technique was quantitatively validated for the tree phantom image by assessing segmentation accuracy and for the angio-CT images by estimating diameters of vessel fragments. Two radiologists provided also qualitative evaluation of this approach. It was demonstrated that this method ensures correct segmentation of a vessel tree in the analyzed images. Moreover, it enables detection of thinner vessel branches when compared to single scale vesselness function approaches.

4

Effects of stent-graft geometry and blood hematocrit on hemodynamic in Abdominal Aortic Aneurysm

Polańczyk A., Podyma M., Stefańczyk L., Zbiciński I.

Chemical and Process Engineering

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2012

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Vol. 33, nr 1

53-61

EN

CFD technique was used to determine the effect of a stent-graft spatial configuration and hematocrit value on blood flow hemodynamic and the risk of a stent-graft occlusion. Spatial configurations of an endovascular prosthesis placed in Abdominal Aortic Aneurysm (AAA) for numerical simulations were developed on the basis of AngioCT data for 10 patients. The results of calculations showed that narrows or angular bends in the prosthesis as well as increased hematocrit affects blood flow reducing velocity and WSS which might result in thrombus development.

5

Symulacje komputerowe jako metoda oceny ryzyka wystąpienia zakrzepu po zabiegu wszczepienia protezy wewnątrznaczyniowej u pacjentów z tętniakiem brzusznego odcinka aorty

Polańczyk A., Stefańczyk L., Zbiciński I.

Inżynieria i Aparatura Chemiczna

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2010

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Nr 2

103-104

PL

Czynnikami zwiększającymi ryzyko powstania zakrzepu u pacjentów po zabiegu wszczepienia stent-graftu są przestrzenna konfiguracja, zagięcie kątowe lub przewężenia odnogi protezy. W pracy zastosowano model 3D przepływu krwi w protezach wewnątrznaczyniowych u 10 pacjentów po operacji wstawienia stent-graftu do oceny hemodynamiki przepływającej krwi. Wyniki obliczeń wskazują, że występowanie zagięć kątowych lub przewężeń odnogi protezy powodują zmiany hemodynamiki przepływu, które mogą prowadzić do zwiększonego ryzyka powstawania zakrzepu.

EN

The methane fermentation process has long been used as a method of organic matter utilization and biogas production. In this work a polyimide membrane was used with success to enhance the methane content in biogas from the Polish agricultural plant. At 68% CH4 in feed gas, 82% methane content was achieved. Biogas with methane content over 70% is very promising as an alternative energy source and it can be the feed in a cogeneration generator.

6

Segmentacja drzewa oskrzelowego z wykorzystaniem algorytmu zamykania otworów

Postolski M., Janaszewski M., Fabijańska A., Babout L., Jędrzejczyk M., Stefańczyk L.

Automatyka / Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie

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2009

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T. 13, z. 3/1

949-957

PL

Niezawodna segmentacja ludzkich drzew oskrzelowych ze zbiorów wolumetrycznych pochodzących z tomografii komputerowej (CT) jest ważnym elementem analizy danych w zastosowaniach klinicznych. W tym artykule został zaprezentowany nowatorski algorytm segmentacji drzewa oskrzelowego bazujący na geometrii i topologii dyskretnej. Proponowana metoda jest w pełni automatyczna, i posiada zalety dobrze zdefiniowanych pojęć matematycznych. Otwory występują w ścianach oskrzeli z wielu powodów np. są wynikiem szumów. Otwory są częstym problemem w poprzednio zaprezentowanych metodach, wykorzystujących rozrost obszaru i mogą powodować wyciek algorytmów segmentacji do otaczających oskrzela części płuc. Nowoczesność prezentowanego algorytmu polega na zastosowaniu dedykowanego algorytmu zamykania otworów, który zamknie wszystkie występujące otwory w drzewie oskrzelowym. Wyniki eksperymentów wykazały, że algorytm jest niezawodny i generuje wyniki dokładne oraz dobrej jakości.

EN

Reliable segmentation of a human airway tree from volumetric computer tomography (CT) data sets is the most important step for further analysis in many clinical applications. In this paper the original airway segmentation algorithm based on discrete topology and geometry is presented. The proposed method is fully automated and takes advantage of well defined mathematical notions. Holes occur in bronchial walls due to many reasons, for example they are results of noise. Holes are common problem in previously proposed methods because in some areas they can cause the segmentation algorithms to leak into surrounding parenchyma parts of a lung. The novelty of the approach consist in the application of a dedicated hole closing algorithm which closes all disturbing holes in a bronchial tree. The experimental results showed that the method is reliable and generate good quality and accurate results.