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1

Effect of collagen fibres and elastic lamellae content on the mechanical behaviour of abdominal aortic aneurysms

Kobielarz Magdalena

Acta of Bioengineering and Biomechanics

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2020

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Vol. 22, no. 3

9--21

EN

Purpose: The main purpose of this study was a detailed analysis of the mechanical and structural characteristics of human abdominal aneurysms in comparison with normal abdominal aortae and determination of the correlations between their mechanical behaviour and the microstructural content. Methods: Various mechanical properties, i.e., mechanical failure properties, elastic moduli, inflection point coordinates, index of anisotropy and incompressibility were determined under uniaxial loading conditions in the circumferential and axial directions. Constitutive parameters were derived from the commonly used constitutive model proposed by Holzapfel et al. [9]. The microstructural arrangement was examined by histological staining supported by scanning electron microscopy analysis. The content of collagen fibres and elastic lamellae was tested in relation to mechanical properties and constitutive parameters. Results: Significant differences were found in the microstructural arrangement and layer composition of the aneurysmal specimens, compared to the normal aorta group. The mechanical properties and constitutive parameters of the aneurysmal specimens were significantly altered, indicating a weakening of the load-bearing properties of the walls of the aneurysms. A comparative analysis discovered significant correlations between structural composition and mechanical parameters, in particular with respect to the number of collagen fibres and failure stress, which can be important for clinical evaluation of abdominal aortic aneurysm (AAA) rupture. Conclusions: Changes in the content of collagen fibres and elastic lamellae correlate with mechanical and constitutive parameters, indicating AAA severity

2

Analiza dawek promieniowania podczas zabiegów implantacji stentgraftów do aorty brzusznej

Świętoń Faustyna, Król Małgorzata, Stachyra Sylwester, Uryniak Adam

Inżynier i Fizyk Medyczny

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2019

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Vol. 8, nr 6

473--477

PL

Wprowadzenie: Wewnątrznaczyniowa technika zaopatrywania tętniaków aorty brzusznej jest mało inwazyjną metodą, która wykazuje dużą skuteczność leczenia. Wiąże się jednak z narażeniem zarówno pacjenta, jak i personelu medycznego na promieniowanie jonizujące. Cel: A naliza dawek promieniowania p odczas z abiegów implantacji stentgraftów do aorty brzusznej. Materiał i metoda: Analiza retrospektywna danych 50 pacjentów z rozpoznanym tętniakiem aorty brzusznej leczonych z zastosowaniem implantacji stentgraftów. W analizie zostały uwzględnione następujące parametry: wiek, płeć, BMI, wymiar poprzeczny tętniaka, rodzaj tętniaka, a także liczba zużytych elementów stentgraftu. Wyniki: Odnotowano istotność statystyczną wpływu BMI oraz wymiaru poprzecznego tętniaka na wartość Air Kerma (AK) i Dose Area Product (DAP), a także liczby elementów stentgraftu na wartości AK, DAP i czasu fluoroskopii. Nie odnotowano istotnie statystycznego wpływu rodzaju tętniaka na wartości dawek promieniowania. Wnioski: BMI oraz wymiar poprzeczny tętniaka wpływają na wzrost wielkości wartości AK i DAP, a liczba zastosowanych elementów stentgraftu na wzrost wartości AK, DAP i czas fluoroskopii.

EN

Introduction: The intravascular technique of abdominal aortic aneurysms treatment is a minimally invasive method that demonstrates high efficacy. However, it exposes the patient and staff to ionizing radiation. Aim: A nalysis o f r adiation d oses d uring s tent g raft i mplantations to the abdominal aorta. Material and method: A retrospective analysis of 50 patients with were diagnosed abdominal aortic aneurysm treated with stent graft implantation. The following parameters were included in the analysis: age, sex, BMI, transverse dimension of the aneurysm, type of aneurysm, as well as the number of used elements of the stent graft. Results: Statistical significance of the impact of BMI and transverse aneurysm dimension on the Air Kerma (AK) and Dose Area Product (DAP) values as well as the number of stent grafts on AK, DAP and fluoroscopy time were recorded. There was no significant statistical effect of the type of aneurysm on radiation doses. Conclusions: The BMI and the transverse dimension of the aneurysm influence the increase in the value of AK and DAP, and the number of applied elements of stentgraft increases the AK, DAP and fluoroscopy time.

3

Geometric verification of the validity of Finite Element Method analysis of Abdominal Aortic Aneurysms based on Magnetic Resonance Imaging

Domagała Z., Stępak H., Drapikowski P., Kociemba A., Pyda M., Karmelita-Katulska K., Dzieciuchowicz Ł., Oszkinis G.

Biocybernetics and Biomedical Engineering

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2018

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Vol. 38, no. 3

544--555

EN

The currently used criterion of maximum transverse diameter for the Abdominal Aortic Aneurysm treatment has some limitations. Attempts to create individualized, therapeutic strategies are being conducted, including biomechanical assessment of rupture risk of an aneurysm based on the Finite Element Analysis of the geometric models. The usual approach is to use the results of the computed tomography imaging to build a three-dimensional model of the aneurysm. The FEA is then performed and the resulting stress is analysed to estimate the risk of rupture. Although such an approach brings significant improvements over the traditional maximum diameter method, it is difficult to ensure the validity of the assumptions made. This paper presents a method to evaluate the correctness of such an approach. The emergence of gated Magnetic Resonance Imaging allows registering aneurysm in both the systolic and diastolic phase of cardiac cycle. The corresponding geometric models are built and the results of the FEA applied to the diastolic model are compared with the actual deformation of the aneurysm observed in the patient's body. Thus, it is possible to verify whether the individualized diagnostic approach applied to a specific patient was correct. The geometry of the reference and the analysed models were compared using the Differential Surface Area Method. The average geometry error equals 1.65%. In the best case the error amounts to 1.04%, in the worst to 3.00%. The obtained results provide evidence that the Finite Element Analysis is a reliable method and can be potentially used for individualized diagnostics and treatment.

4

A methodological review of data mining techniques in predictive medicine: An application in hemodynamic prediction for abdominal aortic aneurysm disease

Paramasivam V., Yee T. S., Dhillon S. K., Sidhu A. S.

Biocybernetics and Biomedical Engineering

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2014

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Vol. 34, no. 3

139--145

EN

Modern clinics and hospitals need accurate real-time prediction tools. This paper reviews the importance and present trends of data mining methodologies in predictive medicine by focusing on hemodynamic predictions in abdominal aortic aneurysm (AAA). It also provides potential data mining working frameworks for hemodynamic predictions in AAA. These frameworks either allow the coupling between a typical computational modeling simulation and various data mining techniques, using the existing medical datasets of real-patient and mining it directly using various data mining techniques or implementing visual data mining approach to already available computed results of various hemodynamic features within the AAA models. These approaches allow the possibility of statistically predicting rupture potentials of aneurismal patients and ideally provide an alternate solution for substituting tedious and time-consuming computational modeling. Prediction trends of patient-specific aneurismal conditions via mining huge volume of medical data can also speed up the decision making process in real life medicine.

5

Experimental characterization of the mechanical properties of the abdominal aortic aneurysm wall under uniaxial tension

Kobielarz M., Jankowski L. J.

Journal of Theoretical and Applied Mechanics

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2013

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Vol. 51 nr 4

949--958

EN

Although many researchers have made the assumption that the abdominal aortic aneurysym (AAA) wall behaves as an incompressible and isotropic material, the experimental evidence for it is insufficient. Hence, the assumptions about the incompressibility and isotropy of the AAA wall were verified through analysis of stretch ratios of samples excised from the aneurysms walls. The stretch ratios were calculated on the basis of a real-time analysis of geometric dimensions of samples subjected to uniaxial tension. It was proved that the walls of abdominal aortic aneurysms can be modelled as an incompressible and isotropic material. Using histological techniques, the assumption concerning the negligence of shear stress in the analysis of AAA wall stresses was indirectly validated. The results were incorporated into a hyperelastic constitutive equation.

6

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.

7

Analiza porównawcza składu pierwiastkowego ścian aorty brzusznej i tętniaka aorty brzusznej

Kobielarz M., Marycz K., Szotek S., Będziński R.

Engineering of Biomaterials

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2009

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Vol. 12, no. 89-91

185--187

PL

Głównym celem pracy było określenie procentowego składu pierwiastkowego ścian zdrowej aorty brzusznej (NAA) i tętniaka aorty brzusznej (AAA) na podstawie mikroanalizy rentgenowskiej (Rtg) dla dużej populacji materiału badawczego, ażeby sprawdzić użyteczność metody do różnicowania (na poziomie molekularnym) materiału biologicznego pod kątem zmian chorobowych. Dla żadnego z analizowanych pierwiastków nie odnotowano, na poziomie istotności p=0,05, istotnych statystycznie zmian w procentowym rozkładzie pierwiastków między preparatami ścian zdrowych aort brzusznych oraz tętniaków. Na podstawie uzyskanych wyników wykazano, biorąc pod uwagę wielkość grup badawczych, że zastosowana metoda nie umożliwia różnicowania materiału biologicznego na założonym poziomie istotności.

EN

The main aim of paper was evaluation of chemical elements composition of normal abdominal aortic walls (NAA) and abdominal aortic aneurysms walls (AAA) based on X-ray microanalysis for a numerous and diversified population in order to differentiate (on molecular level) biological materials according pathological changes. For neither of analyzed elements were noticed statistically significant on the confidence level p=0,05 differences between NAA walls and AAA walls. On the basis of the obtained results it can be concluded that used methods isn’t sufficient to differentiation of biological materials according pathological changes.

8

Właściwości mechaniczne i strukturalne tętniaków aorty brzusznej

Kobielarz M., Szotek S., Kuropka P., Kaleta K.

Engineering of Biomaterials

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2008

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Vol. 11, no. 81-84

98--100

PL

W celu oszacowania prawdopodobieństwa przerwania ciągłości ściany tętniaka aorty brzusznej (AAA) konieczne jest zbadanie warunków obciążeniowych odpowiedzialnych za to zdarzenie, a także identyfikacja zmian zachodzących w strukturze ściany tego naczynia w procesie rozwoju schorzenia. Stąd, głównym celem prezentowanej pracy jest określenie mechanicznych oraz strukturalnych właściwości ścian tętniaków aorty brzusznej oraz preparatów zdrowych aort. W tym celu zastosowano test jednoosiowego rozciągania próbek wyciętych z pobranych preparatów w dwóch prostopadłych do siebie kierunkach: wzdłużnym oraz obwodowym, a także przeprowadzono histologiczne badania mikrostruktury ściany naczyń. Na podstawie przeprowadzonego testu wytrzymałościowego wykreślono krzywą naprężenie-odkształcenie dla każdego przebadanego przypadku i wyznaczono charakterystyczne wielkości opisujące wytrzymałość oraz sztywność przebadanych próbek. Uzyskane wyniki wskazują na istotny wzrost sztywności w przypadku preparatów ścian tętniaków, co szczególnie zaznaczyło się w kierunku obwodowym.

EN

To estimate when an abdominal aortic aneurysm (AAA) may rupture, it is necessary to understand the forces responsible for this event and structural alterations lead to changes in the mechanical properties of the tissue. Hence, the main goal of presented study is determination and assessment of mechanical and structural properties of the walls of normal abdominal aortas and abdominal aortic aneurysms. With this end in view uniaxial tensile tests of the specimens cut out from the walls of abdominal aortic aneurysms and normal abdominal aortas in two directions - longitudinal and circumferential - have been carried out and histological study has been performed. On the basis of these tests the stress-strain relationships have been determined for each investigated specimen and the maximum tangential modulus as well as the ultimate tensile strength has been assigned. The results indicate the increase of tissue stiffness in the case of abdominal aortic aneurysms, especially in the circumferential direction.