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Magnitude-based PDFF (Proton Density Fat Fraction) and R 2 ∗ mapping with resolved water-fat ambiguity is extended to calculate field inhomogeneity (field map) using the phase images. The estimation is formulated in matrix form, resolving the field map in a least-squares sense. PDFF and R 2 ∗ from magnitude fitting may be updated using the estimated field maps. The limits of quantification of our voxel-independent implementation were assessed. Bland-Altman was used to compare PDFF and field maps from our method against a reference complex-based method on 152 UK Biobank subjects (1.5 T Siemens). A separate acquisition (3 T Siemens) presenting field inhomogeneities was also used. The proposed field mapping was accurate beyond double the complex-based limit range. High agreement was obtained between the proposed method and the reference in UK. Robust field mapping was observed at 3 T, for inhomogeneities over 400 Hz including rapid variation across edges. Field mapping following unambiguous magnitude-based water-fat separation was demonstrated in-vivo and showed potential at 3 T. [ABSTRACT FROM AUTHOR]

Abstract Background In many regions of the world, vaccine hesitancy has become an important concern to public health. A key part of any effective solution to it is to gain an in-depth understanding of the problem: its scope, who holds hesitant views and for which reasons. Methods We adapt the original 10-item Vaccine Hesitancy Scale (VHS), which targets parental attitudes, to a more generic version that captures general attitudes to vaccination. We use this adapted VHS in a sample of 1402 British citizens, selected from a large online panel (N > 1,000,000) based on quota for age, gender, educational attainment and region (response rate 43%). The existence of VHS subscales is evaluated via exploratory and confirmatory factor analysis. We describe the extent of vaccine hesitancy in the sample, and use simple and multiple regression analysis to examine associations between respondent characteristics and vaccine hesitancy. Results Despite ambiguities in defining hesitancy, we found that a substantial part of our sample held hesitant views about vaccination, particularly for those items reflecting aversion to risks of side effects. Four percent responded in a hesitant way to all ten items and ninety to at least one of the ten items. In line with recent studies in other populations, we identified two subscales within the VHS: lack of confidence in the need for vaccines and aversion to the risk of side effects. We found significant associations between hesitancy and various respondent characteristics but the predictive power of these associations remained limited. Conclusion Our study suggests that whereas a substantial percentage of the British population is vaccine hesitant, these views are not clustered in typical demographic features. The small but important adaptation of the VHS to target general attitudes seems to result in highly similar psychometric characteristics as the original scale that exclusively targets parents. We provide suggestions for further validation of the VHS. [ABSTRACT FROM AUTHOR]

Abstract Eye movement modeling examples (EMME) are video modeling examples with the model's eye movements superimposed. Thus far, EMME on problem-solving tasks seem to be effective for guiding students' attention, but this does not translate into higher learning outcomes. We therefore investigated the role of ambiguity of the verbal explanation and prior knowledge in the effectiveness of EMME on geometry problems. In Experiment 1, 57 university students observed EMME or regular video modeling examples (ME) with ambiguous verbal explanations. Eye-tracking data revealed that –as in prior research with unambiguous explanations- EMME successfully guided students' attention but did not improve test performance, possibly due to students' high prior knowledge. Therefore, Experiment 2, was conducted with 108 secondary education students who had less prior knowledge, using a 2 (EMME/ME) x 2 (ambiguous/unambiguous explanations) between-subjects design. Verbal ambiguity did not affect learning, but students in the EMME conditions outperformed those in the ME conditions. Highlights • Eye movement modeling examples (EMME) guide attention via the model's eye movements. • Two experiments examined EMME's effectiveness for learning to solve problems. • University and secondary students learned geometry problem solving with/without EMME. • EMME improved secondary but not university students learning. • EMME effectiveness seems to depend on the level of prior knowledge of the learner. [ABSTRACT FROM AUTHOR]