Automated detection of vascular structures is of great importance in understanding the mechanism, diagnosis, and treatment of many vascular pathologies. However, automatic vascular detection continues to be an open issue because of difficulties posed by multiple factors, such as poor contrast, inhomogeneous backgrounds, anatomical variations, and the presence of noise during image acquisition. In this paper, we propose a novel 2-D/3-D symmetry filter to tackle these challenging issues for enhancing vessels from different imaging modalities. The proposed filter not only considers local phase features by using a quadrature filter to distinguish between lines and edges, but also uses the weighted geometric mean of the blurred and shifted responses of the quadrature filter, which allows more tolerance of vessels with irregular appearance. As a result, this filter shows a strong response to the vascular features under typical imaging conditions. Results based on eight publicly available datasets (six 2-D data sets, one 3-D data set, and one 3-D synthetic data set) demonstrate its superior performance to other state-of-the-art methods.
Recent studies have emphasized group creativity as a social-cultural conception, but they lack a focus on the relationship between group creativity and knowledge creation. This paper aims to build a framework for group creativity in a learning context which includes both theoretical understanding and empirical methodology. Thus, a literature review is led by the following questions: How has creativity theory been developed from individual to group level? From a social-cultural perspective, how can group creativity, knowledge creation, and their relationship be understood? And what methods have been employed to study group creativity? As the review demonstrates, creativity theory has been driven by new insights from recent sociology studies. Three focuses have been shaped from group creativity studies: 1) group creativity in context, 2) group-level creative synergy, and 3) strategies for developing group creativity. Individual knowledge is a potential resource for group creativity, and group creativity could be a driver of knowledge creation. Empirically, group creativity can be examined through both qualitative and quantitative approaches, which also calls for a creative combination of methodologies in future studies
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