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1

Numerical insights into the determinants of stent performance for the management of aneurysm with a visceral vessel attached

Li Zhongyou, Chen Chong, Chen Yu, Wang Zhenze, Jiang Wentao, Tian Xiaobao

Acta of Bioengineering and Biomechanics

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2021

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Vol. 23, no. 2

41--53

EN

Purpose: As the factors affecting the efficacy of the bare-metal stent in the treatment of aneurysm with a visceral vessel attached were not fully understood, we aimed to discuss the effects of different characteristics of the stent on the hemodynamics and flexibility in the treatment of the aneurysm. Methods: Single-layer (with different strut widths) and multi-layer (with a different number of struts) stent models divided into three porosity groups, with porosities of 72.3, 60.5, and 52.4%, were modeled for a comparison of their hemodynamic isolation and flexibility performance via computational fluid dynamics and finite element methods. Results: The velocity and timeaveraged wall shear stress decreased more noticeably with multi-layer stent interventions. A higher oscillatory shear index and relative residence time occurred at the aneurysmal sac wall after multi-layer stents were employed. Time-averaged wall shear stress on the aneurysmal wall decreased with an increase in the number of struts or a decrease in pore size, but oscillatory shear index and relative residence time increased as the number of struts increased or the pore size decreased. Besides, all stents affect the branch patency slightly. In the bending test, when the porosity exceeded 60.5%, multi-layer stents were more flexible. Conclusion: The number of struts or pore size of stent dominated the isolation in the management of the aneurysm and affected the flexibility significantly when the porosity was below 60.5%. These findings may contribute to the special design of the stent in the treatment of such types of aneurysms.

2

Effect of dissection on the mechanical properties of human ascending aorta and human ascending aorta aneurysm

Kozuń Marta, Płonek Tomasz, Jasiński Marek, Filipiak Jarosław

Acta of Bioengineering and Biomechanics

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2019

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Vol. 21, no. 2

127--134

EN

The aim of the presented work is to determine (i) mechanical properties of the ascending aorta wall (DAA) and the wall of the ascending aortic aneurysm (DAAA), in which spontaneous dissection resulting from the evolving disease occurred, and (ii) the strength of the interface between the layers in the above-mentioned vessels. Methods: The mechanical tests were divided into two steps. In the first step the mechanical properties of the of DAA and DAAA walls were examined on the basis of uniaxial stretching until rapture. In the next step the mechanical parameters of the interface between layers of DAA and DAAA walls were determined by the peeling test. Results: Higher values of tensile strength (max) and Young’s modulus (E) were obtained for the DAAA group, to which the dissecting wall of the ascending aortic aneurysm was classified. For circumferential samples, the difference between the DAAA and DAA groups was 39% in the case of tensile strength and 70% in the case of the Young’s modulus. Conclusions: Summarizing, the studies performed showed that the dissection process is different in the case of the ascending aortic aneurysm wall and the ascending aorta wall. The wall of the ascending aortic aneurysm is more susceptible to dissection, as evidenced by lower values of the mechanical parameters of the interface between the intima and the media-adventitia complex. The obtained results of mechanical properties tests confirm that dissection and aneurysm should be treated as separate disease entities that may coexist with each other.

3

Ocena morfometryczna podziału środkowych tętnic mózgowych prawidłowych i z tętniakiem

Kawlewska E., Hehnel N., Wolański W., Ćmiel-Smorzyk K., Kaspera W.

Aktualne Problemy Biomechaniki

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2016

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z. 11

53--58

PL

W artykule przeprowadzono analizę morfologiczną tętnic środkowych mózgu w miejscu podziału na tętnicę skroniową i czołową. Trójwymiarowe modele tętnic pacjentów zostały wygenerowane w środowisku Mimics na podstawie zdjęć angioTK. Analizowano tętnice 24 pacjentów z tętniakiem oraz 24 pacjentów zdrowych, u których badanie angioTK wykonano w ramach rutynowej diagnozy innych schorzeń. Uzyskaną bazę danych podsumowano metodami statystki opisowej, porównywano m.in. średnie wartości pól przekrojów, obwodów i średnic poszczególnych naczyń, a także kąty pomiędzy tętnicami. Praca stanowi podstawę do dalszej wielowymiarowej analizy statystycznej.

EN

In this paper it was performed the morphological analysis of bifurcation geometry in middle cerebral arteries. The three-dimensional models of arteries were obtained from angiography images from 24 healthy people and 24 patients with aneurysm. There were analyzed the mean values and quartiles of diameters, areas, circumferences and angles. It was also calculated kurtosis, to check whether the distribution is normal. The studies are the basis for further, multivariate statistical analysis.

4

Analiza przepływu krwi w tętnicach mózgowych

Adamczuk K., Wolański W., Kaspera W.

Aktualne Problemy Biomechaniki

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2016

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z. 11

9--14

PL

W pracy przedstawiono analizę numeryczną przepływu krwi (CFD) w tętnicach mózgowych środkowych. Symulacja komputerowa została przeprowadzona z wykorzystaniem modeli tętnic, które wysegmentowano na podstawie obrazów tomografii komputerowej dla dwóch odmiennych fizjologicznie przypadków: tętnicy: prawidłowej oraz tętnicy patologicznej z tętniakiem. Przeprowadzone komputerowe symulacje przepływu umożliwiły uzyskać rozkład ciśnienia, naprężenia ścinającego WSS oraz prędkości przepływu krwi w naczyniach. Wyniki obliczeń umożliwiły porównanie wyznaczonych czynników hemodynamicznych pod kątem patofizjologii naczynia z tętniakiem. Dodatkowo symulacje przepływu mogą uzupełnić wiedzę z zakresu mechanizmów powstawania tętniaków oraz stratyfikacji ryzyka ich uszkodzenia.

EN

he article presents the analysis of blood flow in cerebral central arteries. On the basis of the images from the CT scan a few models of cerebral arteries were created. Models include: physiologically correct arteries and pathological arteries with aneurysm. Computer simulations were carried out for all models, which enabled to obtain a distribution of pressure, shear stress WSS and the velocity of blood flow in vessels. The results of calculations allowed the comparison of the hemodynamic factors for the correct and pathologic artery with aneurysm. In addition, flow simulations can complement the knowledge of the mechanisms and the risk of aneurysm damage.

5

Patient-specific hemodynamics and stress-strain state of cerebral aneurysms

Ivanov D., Dol A., Polienko A.

Acta of Bioengineering and Biomechanics

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2016

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Vol. 18, no. 2

9--17

EN

Purpose: Approximately 5% of the adult population has one or more cerebral aneurysm. Aneurysms are one of the most dangerous cerebral vascular pathologies. Aneurysm rupture leads to a subarachnoid hemorrhage with a very high mortality rate of 45–50%. Despite the high importance of this disease there are no criteria for assessing the probability of aneurysm rupture. Moreover, mechanisms of aneurysm development and rupture are not fully understood until now. Methods: Biomechanical and numerical computer simulations allow us to estimate the behavior of vessels in normal state and under pathological conditions as well as to make a prediction of their postoperative state. Biomechanical studies may help clinicians to find and investigate mechanical factors which are responsible for the initiation, growth and rupture of the cerebral aneurysms. Results: In this work, biomechanical and numerical modeling of healthy and pathological cerebral arteries was conducted. Patient-specific models of the basilar and posterior cerebral arteries and patient-specific boundary conditions at the inlet were used in numerical simulations. A comparative analysis of the three vascular wall models (rigid, perfectly elastic, hyperelastic) was performed. Blood flow and stress-strain state of the two posterior cerebral artery aneurysm models was compared. Conclusions: Numerical simulations revealed that hyperelastic material most adequately and realistically describes the behavior of the cerebral vascular walls. The size and shape of the aneurysm have a significant impact on the blood flow through the affected vessel and on the effective stress distribution in the aneurysm dome. It was shown that large aneurysm is more likely to rupture than small aneurysm.

6

Numerical investigations of the unsteady blood flow in the end-to-side arteriovenous fistula for hemodialysis

Jodko D., Obidowski D., Reorowicz P., Jóźwik K.

Acta of Bioengineering and Biomechanics

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2016

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Vol. 18, no. 4

3--13

EN

Purpose: The aim of this study was to investigate the blood flow in the end-to-side arteriovenous (a-v) fistula, taking into account its pulsating nature and the patient-specific geometry of blood vessels. Computational Fluid Dynamics (CFD) methods were used for this analysis. Methods: DICOM images of the fistula, obtained from the angio-computed tomography, were a source of the data applied to develop a 3D geometrical model of the fistula. The model was meshed, then the ANSYS CFX v. 15.0 code was used to perform simulations of the flow in the vessels under analysis. Mesh independence tests were conducted. The non-Newtonian rheological model of blood and the Shear Stress Transport model of turbulence were employed. Blood vessel walls were assumed to be rigid. Results: Flow patterns, velocity fields, the volume flow rate, the wall shear stress (WSS) propagation on particular blood vessel walls were shown versus time. The maximal value of the blood velocity was identified in the anastomosis – the place where the artery is connected to the vein. The flow rate was calculated for all veins receiving blood. Conclusions: The blood flow in the geometrically complicated a-v fistula was simulated. The values and oscillations of the WSS are the largest in the anastomosis, much lower in the artery and the lowest in the cephalic vein. A strong influence of the mesh on the results concerning the maximal and area-averaged WSS was shown. The relation between simulations of the pulsating and stationary flow under time-averaged flow conditions was presented.

7

Ocena histologiczna i ultrastrukturalna ścian tętniaków aorty brzusznej

Kobielarz M., Maksymowicz K., Kaleta K., Kuropka P., Marycz K., Będziński R.

Engineering of Biomaterials

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2010

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Vol. 13, no. 99-101

83--87

PL

Rozwój tętniaków, w tym aorty brzusznej (AAA) jest dynamicznym procesem, który zachodzi w wyniku wieloczynnikowego, patologicznego remodelingu tkanki łącznej ściany aorty. Badania strukturalne ścian naczyń tętniczych (zdrowych i z tętniakiem) przeprowadzono w oparciu o analizę histologiczną i ultrastrukturalną. Analiza porównawcza wyników wykazała, że w przypadku preparatów ścian tętniaków aorty brzusznej odnotowano cały szereg zmian, które są charakterystyczne dla rozważanego schorzenia, w tym: wzmożony proces neowaskularyzacji oraz obecność nacieku zapalnego. Ponadto, odnotowano zatarcie granic między warstwami oraz redukcję ich grubości, co szczególnie zaznaczyło się w przypadku błony wewnętrznej. Zaobserwowano istotny ubytek włókien elastynowych oraz zmienny co do intensywności w poszczególnych przypadkach ubytek włókien kolagenowych. Wykazano także, że zmiany w liczbie włókien tkanki łącznej odgrywają kluczową rolę w procesie rozwoju AAA.

EN

The development of abdominal aortic aneurysm (AAA) is a dynamic process proceeding as a result of the multi-factor pathological remodelling of the connective tissue. Structural investigations of normal and aneurismal vessels were carried out on the basis of histological and ultrastructural examinations. A comparative analysis of the experimental results revealed a whole series of changes characteristic of the AAA walls (intensified neovascularisation and inflammatory infiltrations). In addition, the boundaries between the layers were found to be blurred and the thickness of the layers was reduced. A substantial loss of elastin fibres and a case-specific loss of collagen fibres were observed. The number of connective tissue fibres play a key role in the AAA development.

8

Complex analysis of rupture risk of intracranial saccular aneurysms upon hemodynamic and geometric parameters

Szafrański K.

Biocybernetics and Biomedical Engineering

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2009

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Vol. 29, no. 1

43-59

EN

The paper includes a new concept of assessment of rupture risk of intracranial saccular aneurysms using geometric and hemodynamic parameters of aneurysm, artery and blood. Previous decision systems are mainly based on the size of aneurysm and frequency of subarrachnoid hemorrhages, therefore after performing simulation tests it has been proved that the complex assessment of clinical cases is possible thanks to evaluation of shape and size coefficient of a secondary aneurysm occurring on the surface of a primary aneurysm, width of a primary aneurysm neck, curvature of an artery on which a primary aneurysm is located and the size of blood impingement area at artery wall. The paper contains results of the simulation tests of blood flow in the primary and secondary aneurysm, as well as verification of proposed criteria of rupture risk assessment for 5 clinical cases.

9

Radiologia interwencyjna. Wewnątrznaczyniowe leczenie tętniaków naczyń mózgowych

Zawadzki M., Kordecki K., Nowicki M., Walecki J.

Acta Bio-Optica et Informatica Medica. Inżynieria Biomedyczna

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2008

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Vol. 14, nr 1

77-81

PL

Radiologia interwencyjna (IR - Interventional Radiology) jest dynamicznie rozwijającą się dziedziną współczesnej medycyny. Obejmuje ona szeroką gamę minimalnie inwazyjnych zabiegów, przeprowadzanych pod kontrolą badań obrazowych. Metodami radiologii interwencyjnej leczone są m.in. schorzenia ośrodkowego układu nerwowego, układu krwionośnego - choroby aorty i naczyń obwodowych, pokarmowego, rozrodczego, moczowego, a także kostno-stawowego. Radiologia interwencyjna staje się realizacją trendu minimalnie inwazyjnej, a maksymalnie skutecznej terapii. W wielu schorzeniach zastępuje bądź uzupełnia metody operacyjne, pozwala na skrócenie hospitalizacji, zmniejszenie liczby powikłań oraz szybszy powrót pacjentów do zdrowia. Poniższy artykuł stanowi początek cyklu poglądowych publikacji na temat radiologii interwencyjnej. Ze względu na aspekt historyczny, a także niewątpliwe coraz większą rolę tych zabiegów w terapii pacjentów z chorobami naczyniowymi ośrodkowego układu nerwowego, jako pierwsze zostaną omówione zabiegi wewnątrznaczyniowe z zakresu neuroradiology interwencyjnej. W artykule szczegółowo omówiono leczenie tętniaków wewnątrzczaszkowych. Kolejne publikacje poświęcone będą wewnątrznaczyniowej terapii tętniaków aorty i naczyń obwodowych, radiologii interwencyjnej w onkologii, gastrologii, ginekologii, urologii urazach wielonarządowych oraz ortopedii.

10

Image segmentation on example of intracranial aneurysm. Its application to medical decision support system

Tomczak K.

Zeszyty Naukowe Politechniki Rzeszowskiej. Elektrotechnika

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2005

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z. 28 [223]

207-212

EN

This work presents the chosen existing segmentation methods and its role in experts system. The paper is focused on both basis and assumptions of a medical decision support system, which is expected to play an important role in indicating a solution in case of intracranial aneurysm. The primary problems of developing such a system are also mentioned.

PL

Celem tej pracy jest opisanie podstaw systemu wspomagania decyzji, który powinien grać główną role w wykrywaniu i diagnozowaniu tętniaków wewnątrzczaszkowych. Praca ta opisuje wybrane metody segmentacji obrazów oraz ich przewidywaną rolę w stworzeniu systemu ekspertowego. Podstawowe problemy, w stworzeniu takiego systemu, zostały również przedstawione.

11

Analysis of the mechanical parameters of human brain aneurysm

Brigitta K. T., Raffai G., Bojtar I.

Acta of Bioengineering and Biomechanics

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2005

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Vol. 7, nr 1

3-22

EN

Cardiovascular disease is one of the most frequent reasons of mortality in the western word. Nowadays the mechanical properties of biological soft tissues were treated from a continuum mechanical perspective. The aim of this article is to investigate the mechanical response of arterial tissue. We present some three-dimensional finite element model to study the mechanical effects. The arterial wall is composed mainly of an isotropic matrix materiał (elastin) and collagen fibers from two families which are arranged in symmetncal spirals. These fibers induce the anisotropy in the materiał response. So the constitutive law of an artery is orthotropic. We want to develop a new constitutive law for arterial wall mechanics. In addition we make a comparative study of some material model used in the literature to describe the mechanical response of arteries. These are the following models: 1. Linearly elastic model. 2. Neo-Hookean model for incompressible materials. 3. Mooney-Rivlin model for incompressible materials. For this reason we make uniaxial and biaxial measurements to have appropriate parameters for the underlying material models. We investigate the biomechanical properties of strips from human cerebral aneurysms from surgery and cadavers. (An aneurysm is a bulge along a blood vessel.) Meridional and circumferential. thick and thin parts were distinguished respectively. This paper focuses on the analysis of the haemodynamic pattern and biophysical properties of cerebral aneurysms. diagnosed aiid delineated in living human individuals. The aim of this research is to estimate stresses at critical points of the aneurysm wall and its parent artery, and to estimate the likelihood of a later aneurysm rupture.