Augmented virtuality based on stereoscopic reconstruction in multimodal image-guided neurosurgery: methods and performance evaluation

Displaying anatomical and physiological information derived from preoperative medical images in the operating room is critical in image-guided neurosurgery. This paper presents a new approach referred to as augmented virtuality (AV) for displaying intraoperative views of the operative field over three-dimensional (3-D) multimodal preoperative images onto an external screen during surgery. A calibrated stereovision system was set up between the surgical microscope and the binocular tubes. Three-dimensional surface meshes of the operative field were then generated using stereopsis. These reconstructed 3-D surface meshes were directly displayed without any additional geometrical transform over preoperative images of the patient in the physical space. Performance evaluation was achieved using a physical skull phantom. Accuracy of the reconstruction method itself was shown to be within 1 mm (median: 0.76 mm +/- 0.27), whereas accuracy of the overall approach was shown to be within 3 mm (median: 2.29 mm +/- 0.59), including the image-to-physical space registration error. We report the results of six surgical cases where AV was used in conjunction with augmented reality. AV not only enabled vision beyond the cortical surface but also gave an overview of the surgical area. This approach facilitated understanding of the spatial relationship between the operative field and the preoperative multimodal 3-D images of the patient.     

Two analog counters for neural network implementation

Simple analog circuits which are useful for the implementation of the synchronous Boltzmann machine learning algorithms are presented. A simple charge-transfer-based analog counter is described. The authors give a functional model of its behavior and analyze the differences between this model and the counter implementation. They also present simulation results and the test of a prototype. Along the same lines, they study a switched-current-based counter, which achieves better results (dynamic range, linearity) through higher complexity     

The anti-inflammatory profile of proquazone

Proquazone, 1-isopropyl-4-phenyl-7-methyl-2(1H)-quinazolinone is an orally effective anti-inflammatory analgesic and antipyretic compound in animal models. The compound is less ulcerogenic than indomethacin in the rat and appears to potentiate the anti-inflammatory and thymus involution effects of hydrocortisone in this species. That a nonacidic nonsteroidal compound would display a spectrum of anti-inflammatory activity similar to that previously found only with acidic compounds will be the subject of further investigations.     

An experimental model for visual studies of turbulent flow in porous materials

A two-dimensional experimental model has been developed to simulate turbulent flow in porous materials. It uses cross flow through a matrix of cylinders between parallel plexiglass plates. Matrix geometry was chosen to approximate a bed of packed spheres. Pressure loss and axial dispersion in several models have been measured over a wide range of flow rates in the non-Darcy region. Photographs have been taken of flow patterns developed in the transition from laminar to fully turbulent flow. All typical characteristics of flow through beds of packed spheres were exhibited; however, both pressure loss and dispersion differed somewhat when compared to similar three-dimensional flow.     

Architectures massivement paralleles pour la vision artificielle

This paper presents some massively parallel computers, especially those dedicated to image processing and artificial vision. After a discussion on the information processing principle in an architectural point of view, we analyse three representative machines: MPP (processor array), Connection Machine (hypercube machine) and Sphinx (pyramid machine). A comparative study of the implementation of image analysis is carried out. This paper also emphasizes the influence of integration technologies to the realization of the massively parallel computers.     

Logique multivalente

The authors are evolving the suitable tool to deal with the problem of the multivalued logic. It is shown that Post algebras traditionally used in this context are nothing but unitary commutative algebras over a finite field, making the design of combinatoric multivalued networks easier. Some examples are given.     

Relationship between microstructure, microhardness and corrosion sensitivity of an AA 2024-T3 friction stir welded joint

Corrosion sensitivity of a friction stir welded (FSW) AA2024-T3 aluminum alloy has been investigated using both normalized intergranular corrosion test (ASTM-G110) and local electrochemical open circuit potential measurements. In addition, Vickers microhardness and microstructural analysis have been performed.The HAZ close to the TMAZ is the most sensitive to intergranular corrosion because of the presence of continuous lines of S′(S) intergranular precipitates at grain boundaries. Pitting corrosion is due to the intermetallic particles. Their fragmentation produced by stirring effect modifies the pitting corrosion behavior. Microhardness variations depend on the relative volume fraction of GPB zones and S′(S) intragranular precipitates.     

CAO de circuits VLSI avec un compilateur de silicium

The objective of the student training presented here, is to initiate the 80 second year students of the ima (informatique — microondes — automatique) département of Eudil, to the cad of integrated circuits, using the silicon compiler Solo 1400 of theES2 (European silicon structures) company. A mini-design is achieved by groups of 2 students on Sun workstations, six of them coming fromcnfm funds as well as the Solo 1400 software. The design is carried out during 4 sessions of 4 hours each. Subjects are choosen to match the time that students have to achieve the design. Students have their design in charge just like an engineer in a research consultancy. A final technical report is worked out, comprehensively documented and used for the student work evaluation.     

Carbonyl mediated conductance through metal bound peptides: a computational study

Large increases in the conductance of peptides upon binding to metal ions have recently been reported experimentally. The mechanism of the conductance switching is examined computationally. It is suggested that oxidation of the metal ion occurs after binding to the peptide. This is caused by the bias potential placed across the metal-peptide complex. A combination of configurational changes, metal ion involvement and interactions between carbonyl group oxygen atoms and the gold leads are all shown to be necessary for the large improvement in the conductance seen experimentally. Differences in the molecular orbitals of the nickel and copper complexes are noted and serve to explain the variation of the improvement in conductance upon binding to either a nickel or copper ion.