Diffuse laser illumination for Maxwellian view Doppler holography of the retina

We describe the advantages of diffuse illumination in laser holography for ophthalmology. The presence of a diffusing element introduces an angular diversity of the optical radiation and reduces its spatial coherence, which spreads out the energy distribution of the illumination beam in the focal plane of the eyepiece. The field of view of digitally computed retinal images can easily be increased as the eyepiece can be moved closer to the cornea to obtain a Maxwellian view of the retina without compromising ocular safety. Compliance with American and European safety standards for ophthalmic devices is more easily obtained by preventing the presence of a laser hot spot observed in front of the cornea in the absence of a scattering element. Diffuse laser illumination does not introduce any adverse effects on digitally computed laser Doppler images.Comment: 9 page

Une situation discursive orale : apprendre à parler devant le groupe-classe (2 à 7 ans)

La recherche en cours concerne l'enseignement de l'oral à des enfants de 2 à 7 ans. L'article est centré sur l'apprentissage de la prise de parole en situation de discussion collective (conseil de type coopératif). La prise de parole, l'intervention à propos, le respect des règles de parole dans le groupe, pour donner son avis, faire une proposition, ont été particulièrement travaillés. L'identification des obstacles, la résolution des problèmes concernés mettent en lumière la nécessité de transformer les rapports et les rôles habituels des adultes et des enfants dans les situations de conseil. Elles montrent aussi l'efficacité d'activités de décentration et d'analyse de l'interlocution par ses propres acteurs.Le Cunff Catherine, Bressy Patricia, Koskas Michelle, Rolland Martine, Sanchez Magguy, Tschum Monique. Une situation discursive orale : apprendre à parler devant le groupe-classe (2 à 7 ans). In: Repères, recherches en didactique du français langue maternelle, n°2, 1990. Pratiques de communication, pratiques discursives en maternelle, sous la direction de Gilbert Ducancel et Hélène Romian. pp. 39-54

Visual assessment of diffusion weighted imaging infarct volume lacks accuracy and reliability

International audiencePurpose The DAWN trial (Diffusion weighted imaging or CT perfusion Assessment with clinical mismatch in the triage of Wake-up and late presenting strokes undergoing Neurointervention with Trevo) has demonstrated the benefits of thrombectomy in patients with unknown or late onset strokes, using automated software (RAPID) for measurement of infarct volume. Because RAPID is not available in all centers, we aimed to assess the accuracy and repeatability of visual infarct volume estimation by clinicians and the consequences for thrombectomy decisions based on the DAWN criteria. Materials and methods 18 physicians, who routinely depend on MRI for acute stroke imaging, assessed 32 MR scans selected from a prospective databaseover two independent sessions. Raters were asked to visually estimate the diffusion weighted imaging (DWI) infarct volume for each case. Sensitivity, specificity, and accuracy of the estimated volumes were compared with the available RAPID measurements for various volume cut-off points. Thrombectomy decisions based on DAWN criteria with RAPID measurements and raters’ visual estimates were compared. Inter-rater and intra-rater agreement was measured using kappa statistics. Results The mean accuracy of raters was <90% for all volume cut-points. Inter-rater agreement was below substantial for each DWI infarct volume cut-off points. Intra-rater agreement was substantial for 55–83% of raters, depending on the selected cut-off points. Applying DAWN criteria with visual estimates instead of RAPID measurements led to 19% erroneous thrombectomy decisions, and showed a lack of reproducibility. Conclusion The visual assessment of DWI infarct volume lacks accuracy and repeatability, and could lead to a significant number of erroneous decisions when applying the DAWN criteria