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Electrocardiographic Imaging (ECGI) aims to reconstruct electrograms from the body surface potential measurements. Bad leads are usually excluded from the inverse problem solution. Alternatively, interpolation can be applied. This study explores how sensitive ECGI is to different bad-lead configurations and interpolation methods. Experimental data from a Langendorff-perfused pig heart suspended in a human-shaped torso-tank was used. Epicardial electrograms were acquired during 30 s (31 beats) of RV pacing using a 108-electrode array, simultaneously with torso potentials from 128 electrodes embedded in the tank surface. Six different bad lead cases were designed based on clinical experience. Inverse problem was solved by applying Tikhonov regularization i) using the complete data, ii) bad-leads-removed data, and iii) interpolated data, with 5 different methods. Our results showed that ECGI accuracy of an interpolation method highly depends on the location of the bad leads. If they are in the high-potential-gradient regions of the torso, a highly accurate interpolation method is needed to achieve an ECGI accuracy close to using complete data. If the BSP reconstruction of the interpolation method is poor in these regions, the reconstructed electrograms also have lower accuracy, suggesting that bad leads should be removed instead of interpolated. The inverse-forward method was found to be the best among all interpolation methods applied in this study in terms of both missing BSP lead reconstruction and ECGI accuracy, even for the bad leads located over the chest.

PURPOSE: Cortical visual impairment (CVI) is the most common cause of bilateral vision impairment in children in Western countries. Better quantitative tools for measuring vision are needed to assess these children, to allow measurement of their visual deficit, and to monitor their response to treatment and rehabilitation. The author performed a series of experiments to assess the use of the sweep visual evoked potential (VEP) as a quantitative tool for measuring vision in CVI. METHODS: The first experiment was a reliability measure (test/retest) of VEP grating acuity thresholds of 23 children with CVI. To validate the VEP procedure, VEP grating acuity was compared to a clinical measure of vision, the Huo scale, and to a psychophysical measure of vision, the Teller Acuity Card procedure. Finally, the sweep VEP was tested as a tool for defining optimal luminance conditions for grating acuity in 13 children with CVI, by measuring grating thresholds under 2 different luminance conditions: 50 and 100 candela per square meter (cd/m2). RESULTS: Retest thresholds were similar to original thresholds (r2 = 0.662; P = .003, 1-tailed t test). Grating VEP measures correlate significantly with the clinical index (r2 = 0.63; P = .00004). Teller acuity measurements are also similar to VEP measures in children (r2 = 0.64; P = .0005) but show lower acuities compared to the VEP for children with particularly low vision. Finally, 3 of 13 children tested under 2 background luminance conditions showed paradoxical improvement in grating threshold with dimmer luminance. CONCLUSIONS: The sweep VEP tool is a reliable and valid means for measuring grating acuity in children with CVI. The tool also shows promise as a means of determining the optimal visual environment for children with CVI.

This paper deals with the beginning of a research project dedicated to the study of snow distribution caused by wind. This project is based on the analysis of snow depths and meteorological data. These data have been collected on a Swiss site : the Stillberg. The measurement collection started in 1958. The first twelve years have been analysed. The analysis have begun with the selection of the snow transport events with strong and regular winds. Then, for each event, a map of snow balance and snow depth profiles have been produced. These graphic documents show the location of zones with suitable conditions for drifted snow to be accumulated., Cette communication présente les premiers développements d'un projet de recherche consacré à l'étude de la répartition spatiale de la neige transportée par le vent. Ce projet est basé sur le traitement des hauteurs de neige et des données météorologiques recueillies sur un site suisse : le Stillberg. La série des données remontent à 1958. Dans un premier temps, une analyse des douze premières années a été conduite. Cette analyse consiste à sélectionner les épisodes de transport de neige par vents forts et réguliers en direction, à représenter graphiquement ensuite les effets de chacun des épisodes choisis sous la forme de "carte du bilan de neige" et à représenter finalement les profiles de hauteurs de neige dans le versant. Ces documents graphiques permettent de déterminer les lieux favorables à l'accumulation de neige transportée par le vent.

PURPOSE: Investigation of the clinical, imaging, and in vivo MR spectroscopy (MRS) characteristics of disorders of mitochondrial function. METHODS: Clinical, imaging (five CT and 20 MR examinations), and MRS (six studies in five patients) findings in 19 patients with mitochondrial disorders were retrospectively reviewed. Results were critically analyzed and, when applicable, compared with results in the literature. RESULTS: Patients included four with mitochondrial encephalopathy with lactic acidosis and stroke-like episodes (MELAS), two with myoclonus, epilepsy, and ragged red fibers (MERRF), two with Kearns-Sayre syndrome, seven with Leigh syndrome, one with progressive cerebral poliodystrophy (Alpers syndrome), and three with trichopoliodystrophy (Menkes disease). MELAS, MERRF, and Kearns-Sayre tended to occur in older children and adults, whereas Leigh syndrome, Alpers syndrome, and Menkes disease occurred in infants and young children. All diseases involved gray matter early in their course, manifest primarily as T2 prolongation, with the deep cerebral nuclei being involved more often than the cerebral cortex. When T2 prolongation was seen in the white matter (MELAS, MERRF, Kearns-Sayre, Leigh), the peripheral and retrotrigonal white matter showed early involvement. Patients with Menkes disease showed rapidly progressive atrophy accompanied by large subdural hematomas. Proton MRS showed an elevated lactate level in involved regions of the brain; the lactate peak disappeared in old areas of T2 prolongation. CONCLUSIONS: Mitochondrial disorders have a wide range of both clinical and imaging findings. Although no one set of findings is diagnostic of these disorders, the combination of deep gray matter involvement and peripheral white matter involvement in young adults or children should suggest the diagnosis, especially when associated with an elevated lactate level on proton MRS.