Publications (3)6.07 Total impact
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Article: Endovascular procedures under near-real-time magnetic resonance imaging guidance: an experimental feasibility study.
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ABSTRACT: The purpose of this study was to assess the feasibility of insertion of endovascular stents and the precision of an open-field interventional magnetic resonance imaging (iMRI) system in an in vivo model. A feasibility study was undertaken at a university-affiliated hospital. Three male piglets with an average age of 6 months and a weight between 70 and 77 kg and two 3-month-old male piglets that weighed 40 to 44 kg were anesthetized. The five piglets underwent placement of nitinol stents inserted through the right femoral artery, under the guidance of a SIGNA-SP 0. 5T open-configuration iMRI unit. With a dedicated high-resolution near-real-time MRI sequence, the stent was guided and deployed onto a predefined target. The main outcome measures were the duration of the procedure from the beginning of positioning to the end of deployment of the stent, the final position of the stent in relation to the target on the iMRI screen, and comparison with autopsy findings. Three stents were deployed within the aorta at the level of the renal arteries, and two were deployed within the right iliac artery just below the aortic trifurcation. The average duration of the endovascular deployment was 13 minutes. There was an agreement of 0.6 mm in the position of the stent as observed on iMR images and found at autopsy. When the piglets were sacrificed, the average distance between the stents and the predefined target was 7. 8 mm, mostly because of the migration of one stent. Axial views allowed for accurate determination of stent impaction on the vascular wall. This study confirms the feasibility of stent deployment under near-real-time MRI guidance. It also emphasizes some inherent characteristics that hold promise with regard to other conventional techniques: stents and vascular structures are visualized in near-real-time in any desired plane, and the technique is performed without the potential adverse effects of ionizing radiations and iodinated contrast agents.Journal of Vascular Surgery 12/2000; 32(5):1006-14. · 3.21 Impact Factor -
Article: First-generation aortic endografts: analysis of explanted Stentor devices from the EUROSTAR Registry.
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ABSTRACT: To examine the structure and healing characteristics of chronically implanted Stentor endografts that were explanted due to migration, endoleak, thrombosis, or aneurysm expansion. The devices were harvested following reoperation (n = 5) or autopsy (n = 1) with implantation times ranging from 13 to 53 months. Structural modifications to the metal components were examined using radiography, endoscopy, and magnetic resonance imaging (MRI). Specimens taken from components of the modular stent-grafts were examined histologically and with scanning electron microscopy (SEM) to assess healing behavior. Physical and chemical stability of the nitinol wires and woven polyester graft material was evaluated using SEM and electron spectroscopy for chemical analysis. Although the endografts were retrieved for a variety of reasons, they exhibited similar healing and structural modifications. The woven polyester sleeve showed evidence of yarn shifting and distortion, yarn damage, and filament breakage leading to the formation of openings in the fabric. The luminal surface endografts showed incomplete healing characterized by a poorly organized, nonadherent thrombotic matrix of variable thickness. Radiographic and endoscopic observations indicated that structural failure of the grafts, particularly in the main aortic component, was related to severe compaction and dislocation of the metallic frame due to suture breaks. Corrosion marks were observed on some nitinol wires in all devices. Chemical analysis and ion bombardment of the nitinol wires revealed that the surface concentrations of titanium and nickel were not homogenous. The first layer was composed of carbon or organic elements, followed by a stratum of highly oxidized titanium with a low nickel concentration; the titanium-nickel alloy lay beneath these layers. Although the materials selected for construction of endovascular grafts appears judicious, the assembly of these biomaterials into various interrelated structures within the device requires further improvement.Journal of Endovascular Therapy 05/2000; 7(2):105-22. · 2.86 Impact Factor -
Article: La chirurgie vasculaire avec effraction tissulaire minimale pour exclusion d'anévrisme : intérêts et limites des essais chez l'animal
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ABSTRACT: The Vanguad™ endoprotheses were implanted transluminally through the femoral route and deployed at the site of surgically created aneurysms in the thoracic or abdominal aortas of dogs for prescheduled periods of implantation of 1 week, 1, 2 and 3 months. The in vivo dimensional stability of the endoprothesis was confirmed by angiography after insertion and before the sacrifice and by macroscopic observations after retrieval. Histological and scanning electron microscopic (SEM) studies were performed to assess the healing sequence of the device. Microscopic studies of the textile components and surface chemical analysis of the Nitinol wires by electron spectroscopy for chemical analysis (ESCA) were undertaken, after specimen cleaning to remove adherent tissue, to detect structural modifications to the textile structure and to evaluate the bioresilience of the Nitinol. Analysis of the angiograms after implantation and before the sacrifice revealed that morphological changes such as sliding and compression of the metal structure occurred initially after deployment and during implantation. Thrombogenicity of the luminal surface of the endoprotheses was low but the healing was still incomplete after 90 days of implantation. The lack of stability of the metal structure may explain the migration distally and the poor healing of the device. ESCA analysis showed that a physiosorbed passivation layer covered the surface of the Nitinol wires masking the nickel (Ni) component of the alloy. Ion bombardments of the surface of the wires confirmed the presence of a contaminated layer composed of carbon and other elements followed by a highly oxidized titanium (Ti) layer, and then, by the Ti/Ni alloy. Although innovative, the minimally-invasive endovascular technique for the treatment of aortic aneurysms is still in its infancy. Significant improvements are required in terms of ease of handling, effectiveness, innocuousness, biostability and healing.ITBM-RBM.
