The Alestle - Vol. 54 No. 42 - 02/21/2002

Vol. 54 No. 4

Civil Procedure--In Personam Actions and the Nonresident Motorist Statutes

International audienc

Characterisation of metallic mordants in Subarctic Athapaskan quillwork: a PIXE-RBS study on replicate samples

Native American quillwork collections remain little studied due to the limited availability of quillwork material for sampling. In this paper we explore the use of non-invasive Particle Induced X-Ray Emission (PIXE) and Rutherford Backscattering Spectrometry (RBS) to characterise metallic residues in a set of modern porcupine quills prepared with a range of metallic mordants. PIXE analysis was used to determine the concentrations of various mordants present, while RBS analysis allowed additional information on the depth-profiling of the mordants at the surface of the quills to be obtained.Les collections nord-amérindiennes décorées avec la technique de la teinture des piquants de porc-épic restent très peu étudiées, en raison de la difficulté de prélever ce type de collections. Dans cet article, nous explorons l’utilisation de l’analyse par faisceau d’ions (PIXE-RBS) pour la caractérisation de résidus métalliques sur des piquants de porc-épic de référence préparés en laboratoire avec différents mordants. L’analyse PIXE nous a permis de caractériser les concentrations de mordants métalliques présents à la surface des piquants de porc-épic, tandis que l’analyse par rétrodiffusion de Rutherford (RBS) nous a permis d’obtenir des informations complémentaires sur la répartition de ces mordants dans les couches superficielles de la kératine

Quantitative myocardial perfusion MRI using arterial spin labeling

La perfusion est un facteur important dans la viabilité et la fonction du myocarde. Des atteintes microvasculaires diffuses, précédant l'infarctus ou l'insuffisance cardiaque sont impliqués dans bon nombre de pathologies cardiaques. Ce travail vise à améliorer les techniques existantes de mesure quantitatives et non-invasive de la perfusion myocardique par marquage de spins artériels (ASL). La première partie de mon travail de thèse a consisté en la mise place chez la souris d'une technique alternative pour mesurer la perfusion myocardique. Celle-ci est basée sur un marquage pulsé et régulièrement répété afin de construire un état d'équilibre de l'aimantation sous l'influence de la perfusion (approche steady-pulsed ASL). Le modèle théorique associé à cette technique spASL a été développé en parallèle afin de quantifier le flux sanguin tissulaire. Il a été montré que spASL permettait d'obtenir un résultat similaire aux techniques existantes avec en plus, les avantages d'améliorer la sensibilité au signal de perfusion ainsi que de réduire le temps d'acquisition. Dans un second temps, un transfert vers l'imagerie clinique pour une application chez l'homme a été entrepris. Le marquage de type spASL a été conservé et le module de lecture a été adapté aux spécificités de l'imagerie cardiaque chez l'homme pour une acquisition en respiration libre. Un post-traitement dédié qui comprend une correction de mouvement rétrospective a ensuite vu le jour afin d'améliorer la robustesse de nos mesures. Parallèlement aux développements conduits chez l'homme, nous avons exploité l'approche spASL chez l'animal en proposant diverses améliorations en fonction des études menées.Myocardial blood flow is an important factor of tissue viability and function. Diffuse changes in microcirculation preceding heart failure are involved in various cardiac pathologies. This work aim at improving existing techniques allowing quantitative and non-invasive myocardial perfusion assessment using arterial spin labeling. The first step of my work was to design an alternative approach to quantify myocardial blood flow in mice. The so called steady-pulsed ASL (spASL) is based on a regularly repeated pulsed labeling in order to build up a stationary regime of the magnetization under the influence of perfusion. The associated theoretical model has been developed in parallel to quantify tissue blood flow. We have shown that spASL allows to obtain similar results than the previously employed techniques, with the additional advantages of an increased sensitivity to the perfusion signal and a reduced acquisition time. A transfer towards clinical imaging for human applications was then undertaken. The spASL labeling scheme has been preserved while adapting the readout module to the specificities of cardiac MRI when applied to free-breathing human acquisitions. A dedicated post-processing, which includes a retrospective motion correction, has emerged subsequently to improve the robustness of our measurements. In parallel to the developments made for human studies, some optimization of the spASL technique when applied to rodent have been carried out depending on the conducted studies

Recent Developments in Small Animal Cardiovascular MRI

This review is intended to give a comprehensive overview over new cardiovascular magnetic resonance (CMR) method developments and refinements dedicated to the fully non-invasive in vivo exploration of the rodent heart. Unlike other cardiovascular imaging techniques, CMR techniques exist in many modalities giving access to parameters characterizing morphology, global and regional function, blood flow, myocardial structure, cell damage, metabolism and other molecular processes in mouse and rat models of human disease. But even in healthy animals, small animal CMR techniques can help exploring general physiological and biochemical mechanisms in vivo. New magnetic resonance imaging methods and imaging protocols are actively being developed by the entire CMR community with the goal of widening the spectrum of observable and measurable myocardial properties. This report also includes a selection of application studies using recent CMR methodology in this field. Beyond giving new insights into pathophysiologic processes, these studies underline the growing usefulness of CMR in a small animal research context

Cardiovascular Magnetic Resonance of Myocardial Structure, Function, and Perfusion in Mouse and Rat Models

This review summarizes small-animal cardiovascular magnetic resonance (CMR) techniques that are being actively developed at present. Taking into account with few exceptions only literature of the past 2 years it shows that small-animal CMR has become an important and versatile analysis tool in many biomedical studies. The relatively complex signal formation and detection in magnetic resonance offers numerous ways of creating and modulating image contrast as a function of the specific needs. Although most new small-animal CMR developments are done within the scientific MR community, the MR manufacturers have readily contributed in making these techniques robust and available for routine application studies. Unlike other cardiovascular imaging techniques, CMR is used in many facets to assess morphology, global and regional function, blood flow, myocardial structure, cell damage, metabolism, and other molecular processes for studying mouse and rat models of human disease as well as general biochemical mechanisms in vivo

Myocardial arterial spin labeling

International audienceArterial spin labeling (ASL) is a cardiovascular magnetic resonance (CMR) technique for mapping regional myocardial blood flow. It does not require any contrast agents, is compatible with stress testing, and can be performed repeatedly or even continuously. ASL-CMR has been performed with great success in small-animals, but sensitivity to date has been poor in large animals and humans and remains an active area of research. This review paper summarizes the development of ASL-CMR techniques, current state-of-the-art imaging methods, the latest findings from pre-clinical and clinical studies, and future directions. We also explain how successful developments in brain ASL and small-animal ASL-CMR have helped to inform developments in large animal and human ASL-CMR