Imaging performance of a dedicated radiation transparent RF coil on a 1.0 Tesla inline MRI-linac

This work describes the first imaging studies on a 1.0 Tesla inline MRI-Linac using a dedicated transmit/receive RF body coil that has been designed to be completely radio transparent and provide optimum imaging performance over a large patient opening.
 Methods: A series of experiments was performed on the MRI-Linac to investigate the performance and imaging characteristics of a new dedicated volumetric RF coil: (1) numerical electromagnetic simulations were used to measure transmit efficiency in two patient positions; (2) image quality metrics of signal-to-noise ratio (SNR), ghosting and uniformity were assessed in a large diameter phantom with no radiation beam; (3) radiation induced effects were investigated in both the raw data (k-space) and image sequences acquired with simultaneous irradiation; (4) radiation dose was measured with and without image acquisition; (5) RF heating was studied using an MR-compatible fluoroptic thermometer and; (6) the in vivo image quality and versatility of the coil was demonstrated in normal healthy subjects for both supine and standing positions.
 Results: Daily phantom measurements demonstrated excellent imaging performance with stable SNR over a period of 3 months (42.6 ± 0.9). Simultaneous irradiation produced no statistical change in image quality (p>0.74) and no interference in raw data for a 20 20 cm radiation field. The coil was found to be efficient over large volumes and negligible RF heating was observed. Volunteer scans acquired in both supine and standing positions provided artefact free images with good anatomical visualisation.
 Conclusions: The first completely radio transparent RF coil for use on a 1.0 Tesla MRI-Linac has been described. There is no impact on either the imaging or dosimetry performance with a simultaneous radiation beam. The open design enables imaging and radiotherapy guidance in a variety of positons.&#13

Approche expérimentale d'une ligne de transmission par fibre optique

Cet article présente une série de trois TP permettant d'appréhender concrètement les problématiques liées au domaine des communications optiques. Chaque séance de TP est dédiée à un élément essentiel d'une ligne de transmission optique (émetteur, fibre optique, amplificateur à fibre dopée) et l'accent est mis sur l'étude d'aspects fondamentaux accessibles avec un appareillage courant et bon marché

Etude et réalisation d'un détecteur d'électrons rétrodiffusés à faible bruit pour l'imagerie in situ

A backscattered electron detector (BSE) with flexible light pipe utilizing optical fibres between the scintillator and the photomultiplier tube was constructed and set up in our transportable scanning microscope (MEBIS). It has a good detection quantum efficiency (DQE), a large bandwidth and is well adapted for chemical characterisation of bulk specimens.Un détecteur d'électrons rétrodiffusés (BSE) avec une liaison flexible par faisceau de fibres optiques entre le scintillateur et le photomultiplicateur a été élaboré et installé dans notre Microscope Electronique à Balayage In Situ (MEBIS). Il possède une bonne efficacité quantique de détection (DQE), une large bande passante et une résolution en numéro atomique $Z$ bien adaptée à la caractériation chimique de la surface des échantillons massifs étudiés

Diodes électroluminescentes à base de tris(8-hydroxyquinoline) aluminium : rôle des couches de transport

Nous avons étudié, par des mesures électriques, des diodes mono et multicouche à base d'Alq3. L'ajout de couches de transport améliore de façon significative les caractéristiques électriques ainsi que l'intensité lumineuse de ces diodes. D'autre part, nous avons montré que les diodes à trois couches paraissent avoir une meilleur stabilité que celles à une ou deux couches

ÉTUDE DU PHÉNOMÈNE DE CONDUCTION ÉLECTRIQUE DANS LES ISOLANTS SOLIDES SOUS HAUTE PRESSION HYDROSTATIQUE

Par l'effet de la pression, on essaiera de mettre en évidence la prédominance d'un mode de conduction (électronique ou ionique) dans les isolants solides en utilisant les modèles théoriques classiques basés sur les variations de la conductivité du matériau. Les mesures de conductivité sont effectuées sur du Polyéthylène basse densité et du Polystyrène. Chaque matériau présente un mécanisme de conduction bien particulier à la pression atmosphérique.The predominance of a conduction mechanism (electronic or ionic) in solid insulators could be proved by using the classical theories based on the conductivity variations of the material with the pressure. Conductivity measurements are made on low density Polyethylene and Polystyrene. At atmospheric pressure, one of these mechanisms is observed in these materials

Influence of poly (3,4-ethylenedioxythiophene)-poly (styrenesulfonate) in polyfluorene-based light-emitting diodes: Evidence of charge trapping at the organic interface

International audienceAlthough the improvement of the indium tin oxide (ITO) anode by PEDOT:PSS has often been reported in literature, the origin of it is not well known. In this paper, we investigate polyfluorene-based devices with a relatively high work function (Al) cathode by electroabsorption (EA) spectroscopy and thermally stimulated current (TSC) techniques. A 0.9 V increase of built-in voltage evidenced by EA in PFV-based devices was similar to that obtained previously in PFO-based devices. It was inconsistent with the work function difference between ITO (4.9 eV) and PEDOT:PSS (5.2 eV). The formation of new types of traps related to the presence of the PEDOT:PSS layer was detected by TSC in PF-N-Ph based devices, confirming that the PEDOT:PSS/PF contact layer acts as an electron trapping surface. We conclude that the TSC technique should allow a deeper characterization of charge traps created at the electrodes and a better modelling of charge injection in future studies

Stabilization of discotic liquid organic thin films by ITO surface treatment

Discotic liquid crystals (LCs) are promising materials in the field of electronic components and, in particular, to make efficient photovoltaic cells due to their good charge transport properties. These materials generally exhibit a mesophase in which the disk-shaped molecules can selfassemble into columns, which favorize charge displacement, and may align themselves uniformly on surfaces to form well-oriented thin films. In order to orientate such a columnar thin film on an indium tin oxide (ITO) substrate, the film is heated up to the temperature range of the isotropic liquid phase and subsequently cooled down again. This treatment may lead not only to the desired alignment, but also to dewetting, which leads to an appreciable inhomogeneity in film thickness and to short circuits during the realization of photovoltaic cells. In this article, we describe how this dewetting and the film morphology can be influenced by ITO surface treatments. The chemical modifications of the surface by these treatments were studied by X-ray photoelectron spectroscopy (XPS). Such ITO treatments are shown to be efficient to prevent thin film dewetting when combined with rapid cooling through the isotropic-to-LC phase transition

Electrical characterization of ITO/CuPc/Al diodes using temperature dependent capacitance spectroscopy and I-V measurements

International audienc