Predicting Eye Fixations on Complex Visual Stimuli Using Local Symmetry

Most bottom-up models that predict human eye fixations are based on contrast features. The saliency model of Itti, Koch and Niebur is an example of such contrast-saliency models. Although the model has been successfully compared to human eye fixations, we show that it lacks preciseness in the prediction of fixations on mirror-symmetrical forms. The contrast model gives high response at the borders, whereas human observers consistently look at the symmetrical center of these forms. We propose a saliency model that predicts eye fixations using local mirror symmetry. To test the model, we performed an eye-tracking experiment with participants viewing complex photographic images and compared the data with our symmetry model and the contrast model. The results show that our symmetry model predicts human eye fixations significantly better on a wide variety of images including many that are not selected for their symmetrical content. Moreover, our results show that especially early fixations are on highly symmetrical areas of the images. We conclude that symmetry is a strong predictor of human eye fixations and that it can be used as a predictor of the order of fixation

Discovering Argumentative Patterns in Energy Polylogues: A Macroscope for Argument Mining

A macroscope is proposed and tested here for the discovery of the unique argumentative footprint that characterizes how a collective (e.g., group, online community) manages differences and pursues disagreement through argument in a polylogue. The macroscope addresses broader analytic problems posed by various conceptualizations of large-scale argument, such as fields, spheres, communities, and institutions. The design incorporates a two-tier methodology for detecting argument patterns of the arguments performed in arguing by an interactive collective that produces views, or topographies, of the ways that issues are generated in the making and defending of standpoints. The design premises for the macroscope build on insights about argument patterns from pragma-dialectical theory by incorporating research and theory on disagreement management and the Argumentum Model of Topics. The design reconceptualizes prototypical and stereotypical argument patterns for characterizing large-scale argumentation. A prototype of the macroscope is tested on data drawn from six threads about oil-drilling and fracking from the subreddit Changemyview. The implementation suggests the efficacy of the macroscope’s design and potential for identifying what communities make controversial and how the disagreement space in a polylogue is managed through stereotypical argument patterns in terms of claims/premises, inferential relations, and presentational devices

4D-CTA improves diagnostic certainty and accuracy in the detection of proximal intracranial anterior circulation occlusion in acute ischemic stroke

INTRODUCTION:In acute ischemic stroke, imaging of the cranio-cervical vessels is essential for intra-arterial treatment selection. Fast, reliable and easy accessible imaging is necessary 24 hours a day, 7 days a week. Radiologists in training and non-expert readers often perform initial reviewing. In this pilot study, the potential benefit of adding 4Dimensional-CT Angiography (4D-CTA) to the patient selection protocol for intra-arterial therapy is investigated. MATERIALS AND METHODS:Twenty-five datasets of prospectively recruited patients, eligible for intra-arterial treatment, were enrolled. Four radiologists-in-training consecutively reviewed CTA, CT-Perfusion and 4D-CTA (post-processed from CTP datasets) and scored: occlusion-presence and diagnostic certainty (scale 1-10). Time-to-diagnosis was registered. RESULTS:Arterial occlusion was present in 8 patients. Accuracy improved from 88-92% after CTA and CTP assessment to 96-100% after 4D-CTA assessment (P-values >0,05). Mean diagnostic certainty improved from 7,2-8,6 to 8,8-9,3 (P-values all < 0,05). Mean time to diagnosis increased from 3, 5, 5 and 4 minutes after CTA to 9, 14, 12, and 10 minutes after 4D-CTA. CONCLUSION:4D-CTA as an additive to regular CTA and CT-Perfusion in patients with acute ischemic stroke eligible for intra-arterial treatment shows a tendency to increase diagnostic accuracy and improves diagnostic certainty, when reviewed by radiologist in training, while only mildly prolonging time to diagnosis

Patient selection protocol.

<p>Patient selection protocol.</p

Reviewing example of a patient that presented to the ER with right-sided hemiplegia and dysarthria.

<p>A difficult to read CTA due venous enhancement just siding the right MCA was performed, and intra-cranial vessels where initially declared patent. Only when reviewing the 4D-CTA data, the patient was transferred to the angio-suite for IA therapy. Below figs shows consecutively CTA, coronal MIP view, perfusion map and a freeze of the 4D-CTA.</p

Location of the 8 occlusions.

<p>Location of the 8 occlusions.</p

ROC curves and area under the curve (AUC) for diagnostic performance.

<p>Four different readers, comparing CTA alone, CTA + CTP, and CTA, CTP and 4DCTA.</p

Performance of the individual readers 1 to 4.

<p>Sensitivity, Specificity and accuracy in %. Diagnostic Certainty Scale 1–10 (10 being absolutely certain). Mean interpretation time in sec.</p