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Validation of aortic in-vitro strain measurement by Magnetic Resonance Imaging with realistic abdominal aortic aneurism phantom

Abstract : Introduction: Preoperative diagnostic protocols of abdominal aortic aneurysm (AAA) are today mainly based on the measurement of the aortic maximum diameter. This measurement is insufficient because the diameter is not a discriminant variable for predicting the rupture of the aorta. Recent works show the importance of determining the wall stress both due to the aortic shape, the pressure and the blood flow. The problem is very complex and requires the implementation of sophisticated models taking into account the heterogeneity of tissues and the complexity of flow. Then it is essential to validate the capacity of existing medical imaging systems to provide reliable measurements that will be introduced in these models., Method: The aim of this study is to verify the MRI's ability to provide reliable measurements, firstly for the deformation of the aortic wall, and secondly for the blood flow. Cine MRI acquisitions (SSFP sequence) enabled to accurately determine the geometry and deformation of the aneurysm and 4D flow MRI measurements (thanks to a 3D PC-MRI sequence) were used to quantify the velocities of the fluid. Measurements were carried out in vitro with an experimental device that simulated hemodynamic circulation on a realistic AAA phantoms in silicone that have properties closest as possible as the actual physiological conditions. The sequences were prospectively gated with the pressure signal given by a pressure sensor. The deformations of the phantom wall were then determined through solid modeling with Abaqus software in which the geometry and internal stresses determined by CFD modeling (pressure, Wall Shear Stress) were introduced (see Fig. 1). The deformations were compared with measurement made by stereovision. Moreover, blood flow estimation with MRI was compared with the fluid modelling performed with ANSYS software., Results: The obtained deformations with MRI are close to those obtained by stereovision with relative deviations less than 15% (see Fig.2). The comparison pixel to pixel between 4D Flow IRM and CFD is difficult because the spatial discretizations are different for the both technics. However the results of the mean instantaneous velocities are very similar between the two approaches throughout the cycle. Conclusion Our approach makes it possible to validate the ability of MRI to perform deformation measurements on phantom carried out with homogeneous materials and having complex geometries in which complex flow circulate. The first results showed the performance of the MRI to provide reliable raw data that can be included in the theoretical models., Figure 1. The different steps of the strain calculation, Figure 2. Maximal main strain comparison between stereovision and modelling obtained from IRM measurement, (C) 2016European Society of Cardiology
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https://hal-univ-bourgogne.archives-ouvertes.fr/hal-01418205
Contributeur : Le2i - Université de Bourgogne <>
Soumis le : vendredi 16 décembre 2016 - 14:27:20
Dernière modification le : vendredi 17 juillet 2020 - 14:54:10

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Yufei Wang, David Joannic, Patrick Juillion, P. Delassus, Aurélien Monnet, et al.. Validation of aortic in-vitro strain measurement by Magnetic Resonance Imaging with realistic abdominal aortic aneurism phantom. EURO CMR 2016, At FIRENZE (ITALIA), 2016, Florence, Italy. ⟨10.1093/ehjci/jew093.1⟩. ⟨hal-01418205⟩

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