Impact of aneurysmal geometry on intraaneurysmal flow: a computerized flow simulation study.

INTRODUCTION: This study was performed to assess the effect of aneurysm geometry on parameters that may have an impact on the natural history of intracranial aneurysms, such as intraaneurysmal flow pressure and shear stress. METHODS: Flow was simulated in 21 randomly selected aneurysms using finite volume modeling. Ten aneurysms were classified as side-wall aneurysms, with either single-sided or circumferential involvement of the parent artery wall, and 11 as bifurcation aneurysms (symmetric or asymmetric), with an axis either perpendicular or parallel to the parent artery. The flow patterns were classified as either jet or vortex types (with regular or irregular vortex flow). Pressures and shear stresses were characterized as evenly or unevenly distributed over the aneurysm wall and neck. RESULTS: All side-wall and four of the bifurcation aneurysms with a perpendicular axis had a vortex type flow pattern and seven bifurcation aneurysms with a parallel axis (four symmetric and two asymmetric) had a jet flow pattern. Jet type flow was associated with an uneven pressure distribution in seven out of seven aneurysms. Vortex type flow resulted in an even pressure distribution in five out of six aneurysms with an irregular flow pattern and six out of eight with a regular flow pattern. No firm relationship could be established between any geometrical type and shear stress distribution. Only 1 of 14 aneurysms with a perpendicular axis, but 4 of 7 aneurysms with a parallel axis, had ruptured. CONCLUSION: Aneurysm geometry does have an impact on flow conditions. Aneurysms with a main axis parallel to the parent artery have a tendency to have a jet flow pattern and uneven distribution of unsteady pressure. These aneurysms may have a higher rate of rupture as than those with a main axis perpendicular to the parent artery.

Laboratory tests for strength paramaters of brain aneurysms.

The presentation is focused on the analysis of biophysical properties of cerebral aneurysms, diagnosed and delineated in living human individuals. An aneurysm is a bulging out of a part of the wall of a blood vessel. The aim of our research was to delineate flow patterns inside the aneurysm and its parent artery, to estimate stresses at critical points of the aneurysm wall, to model the haemodynamic effect of different surgical and endovascular tools in order to define the optimal one in a particular case, and to estimate the likelihood of a later aneurysm rupture. For this reason we carried out a lot of different laboratory tests to analyse the mechanical parameters of the aneurysm wall. We made a comparative study of some material models reported in the literature to describe the mechanical response of arteries. These are models for incompressible materials. For this reason we perform uniaxial and biaxial measurements to have appropriate parameters for the models of underlying material.

[A biomechanical study of the mechanical stress transmission of dental implants using finite element analysis. Part II. Experiments]. / Fogászati implantátumok mechanikai feszültség-atadásának biomechanikai vizsgálata végeselemes analízissel. II. Rész vizsgálatok.

In the first part of this two-part study the possible uses of finite element analysis in studying the stress transmission of dental implants were reviewed. In the present second part our own experiments are presented. In the first series the effect of the geometric parameters and load types on mechanical stresses arising around cylindrical implants in bone were studied with 2D and 3D finite element analysis. In the second series the stress transmissions of various implant geometries were compared and an attempt was made to determine the optimal implant shape from the point of view of stress transmission.