A. Da Silva

Movement quantification in epileptic seizures: a new approach to video-EEG analysis

It is common that epileptic seizures induce uncoordinated movement in a patients body. This movement is a relevant clinical factor in seizure identification. Nevertheless, quantification of this information has not been an object of much attention from the scientific community. In this paper, we present our effort in developing a new approach to the quantification of movement patterns in patients during epileptic seizures. We attach markers at landmark points of a patients body and use a camera and a commercial video-electroencephalogram (EEG) system to synchronously register EEG and video during seizures. Then, we apply image-processing techniques to analyze the video frames and extract the trajectories of those points that represent the course of the quantified movement of different body parts. This information may help clinicians in seizure classification. We describe the framework of our system and a method of analyzing video in order to achieve the proposed goal. Our experimental results show that our method can reflect quantified motion patterns of epileptic seizures, which cannot be accessed by means of traditional visual inspection of video recordings. We were able, for the first time, to quantify the movement of different parts of a convulsive human body in the course of an epileptic seizure. This result represents an enhanced value to clinicians in studying seizures for reaching a diagnosis.

Friction stir spot welding of AA 1050 Al alloy and hot stamped boron steel (22MnB5)

Abstract The present study investigates the effect of joining parameters on the microstructural and mechanical characteristics of dissimilar friction stir spot welding (FSSW) between AA 1050 Al and 22MnB5 hot stamped boron steel. Mechanical performance has been evaluated by shear and microhardness testing. Optical microscopy has been used to investigate the microstructure generated in the different FSSW regions. A macrostructural examination has revealed the creation of mechanical interlocking in the Al steel connections. No volumetric defects or any other imperfection has been found in all FSSW connections. Shear failure load has increased with increasing both tool rotational speed and plunge depth for all FSSW connections. Higher plunge depth has improved the mechanical interlocking between lower and upper sheet due to the formation of a larger secondary flash. Encouraging results have been obtained using coated WC–Co tools in terms of durability and joint performance.

Energy weighting technique in Quantum Computed Tomography using a MPGD

In the present work a new system for Quantum Computed Tomography was developed and tested, envisaging its application to small animals and mammography imaging. It consists of a Micro-Patterned Gas Detector based on the Micro-Hole and Strip Plate, operating in single-photon counting mode. The Micro-Hole and Strip Plate allows the storage of the position of interaction and the energy information of each single X-ray photon. With this information it is possible to select the energy range to reconstruct the images of cross sections, enabling the enhancement of different structures according to their attenuation coeficients. It is also possible to use the energy information to weight each photon in the sinogram construction. In the present work we consider three types of weighting factors giving rise to three different types of images, namely Integrating, Counting and Energy Weighting Technique (EWT). For each CT acquisition the system allows us to construct any of these types of images without the need for extra measurements. Some features of the CT image improve with the application of the Energy Weighting Technique, namely the Signal-to-Noise Ratio (SNR), the image Contrast, and the Contrast-to-Noise Ratio (CNR). The maximum contrast enhancement was about 23%, the maximum SNR improvement was about 22% and the maximum CNR improvement was about 31% between integrating and EWT images.

Coupling X-Ray and optical tomography systems for in vivo examination of small animals

For the purpose of the co-registration of fluorescence optical signal and X-rays measurements, a multimodality tomographer has been developed in our laboratory. Such a system brings the possibility to get, on the same bench, in vivo both anatomical and functional information. Moreover, the information on the morphology of the animal can be used as a regularization factor in order to get the reconstructions of the biodistribution of fluorochromes more accurate and to reduce the computation time. A study on homogeneous phantoms was conducted to evaluate the feasibility, to test the linearity and the reproducibility, and to fix the parameters for the co-registration. More cumbersome phantoms (sacrificed mice) have then been considered and the test experiments were reproduced. Finally, results of a study conducted in vivo on mice bearing tumors in the lungs, tagged with different types of optical probes, are presented.

Fluorescence diffuse optical tomographic system for arbitrary shaped small animals

This paper presents a method based on fluorescence diffuse optical tomography for reconstructing the fluorescence yield of heterogeneous and arbitrary shaped medium such as small animals. The experimental set-up is presented and the associated reconstruction method making mouse inspection without immersion in optical index matching liquid (Intralipid and ink) possible is detailed. Some phantom experiments have been carried out to characterize this new system and to validate its use for non immersed heterogeneous media and a first experiment on a mouse is presented. These results validate further use of our system for biological studies of small animals.

From bench-top small animal diffuse optical tomography towards clinical imaging

Fluorescence enhanced diffuse optical tomography is an emergent diagnosis tool for the localization and the quantification of fluorescent probes; this technique comes as a supplement or sometimes replaces the classical ionizing radiation imaging techniques, and in particular if a simple , inexpensive, non invasive and accurate instrumentation is sought. For 4 years now, the CEA-LETI has built a base of knowledge in markers and instrumentation within the framework of small animal imaging. More recently, an instrumentation has been developed, the purpose of which is a specific approach to the examination of underlying structures, deeply embedded within the tissues, and in fine for human being screening.

In vivo fluorescence molecular optical imaging: from small animal towards clinical applications

Fluorescence enhanced diffuse optical tomography is an emergent diagnosis tool for the localization and the quantification of fluorescent probes. This technique can be considered as a complement but sometimes could also replace the classical ionizing radiation imaging techniques, and in particular if a simple, inexpensive, non invasive and accurate instrumentation is sought. The term molecular imaging can be broadly defined as the in vivo characterization and measurement of biological processes at the cellular and molecular level. For 5 years now, the CEA-LETI has built a base of knowledge in markers and instrumentation within the framework of small animal imaging. More recently, for the purpose of a specific approach for deep tissue screening, a dedicated instrumentation has been developed for human being examination.

Study of structure/property relationships of diffusion bonded Ti6Al4V + 10 wt-%TiC particulate composite

Abstract Ti–C particulate reinforced Ti6Al4V metal matrix composites (Ti6Al4V + 10 wt-%TiC) have demonstrated a high strength-to-weight ratio as well as good high temperature properties. A poor fusion welding performance is commonly observed in these materials making solid-state diffusion bonding a potential process to produce complex structural components. This work aims to characterise the microstructure and the mechanical properties of Ti6Al4V + 10 wt-%TiC diffusion bonded joints. Microstructural evaluation has been performed using both optical and scanning electron microscopy. Mechanical characterisation consisted of room temperature microflat tensile tests for the different bonding conditions and microhardness along the joint. The best results were associated with a bonding temperature of 1000°C and pressure 5 MPa together with bonding times ranging from 35 to 60 min.

Energy resolving CT systems using Medipix2 and MHSP detectors

Energy resolved imaging has been possible with a newest generation of radiation detectors with photon counting and spectroscopic capabilities. This innovation gives the possibility to enhance the image quality by applying techniques using the energy information. In this work two X-ray Computed Tomography (CT) Systems were assembled with two different energy resolving detectors: Medipix2 and MicroHole & Strip Plate (MHSP). These detectors have the aforesaid characteristics and showed a good performance for X-ray imaging. The Energy Weighting Technique (EWT) and Basis Material Decomposition (BMD) techniques were applied with good results. An improvement of 31% in the CNR was achieved by applying the EWT in the MHSP data and, using Medipix2, two basis materials (Carbon based and Aluminium) were decomposed successfully with densities close to the real values.

Model Reduction by Multiresolution Method Applied to Fluorescence Diffuse Optical Tomography

This paper is devoted to the Fluorescence Diffuse Optical Tomography. This inverse problem relies on an iterative algorithm based on solutions of partial differential equations. The goal of the paper is to present a multiresolution technique applied to these equations, with the objective of computation complexity reduction. The effectiveness of the approach is then illustrated on a practical example.