The objective of this paper is to evaluate performance of the level set approach applied to segmentation and tracking of noisy 3D images of computer-simulated blood-vessel phantoms and artificial ...vascular trees. Of particular interest was the segmentation of thin vessels, with diameter smaller that voxel size. Flood fill technique was also explored, for comparison. Quantitative measures of segmentation accuracy were used for the methods evaluation. It was demonstrated, that the level set method provides good segmentation results even for noisy images. This promising result encourages its future application for vascularity modeling based on MR images.
This paper provides — through the use of cluster analysis — objective confirmation of the relevance of texture description applied to vascular tree images. Moreover, it is shown that unsupervised ...selection of significant texture parameters in the datasets corresponding to noisy images becomes feasible if the search for relevant attributes is guided by the clustering stability–based optimization criterion.
The issue of vessel tracking in a novel, simultaneous ToF-SWI (time-of flight, susceptibility weighted imaging) 3D images is considered. Properties of the ToF-SWI images are discussed briefly. ...Results of arterial tree tracking by means of multiscale filtering, flod-fill and level set methods are presented and compared. Human brain and phantom MR images are used in the study. Topics of future research aimed at modeling and quantitative analysis of the vasculature, on the basis of segmentation of ToF-SWI, are addressed.
The anthropogenic pressure on the environment depends on the spatial scale. It is crucial to prioritise conservation actions at different spatial scales to be cost-efficient. Using horizon scanning ...with the Delphi technique, we asked what the most important conservation problems are in Poland at local and national scales. Twenty-six participants, PhD students, individually identified conservation issues important at the local and national scales. Each problem was then scored and classified into broader categories during the round discussions. Text mining, cross-sectional analyses, and frequency tests were used to compare the context, importance scores, and frequency of identified problems between the two scales, respectively. A total of 115 problems were identified at the local scale and 122 at the national scale. Among them, 30 problems were identical for both scales. Importance scores were higher for national than local problems; however, this resulted from different sets of problems identified at the two scales. Problems linked to urbanisation, education, and management were associated with the local scale. Problems related to policy, forestry, and consumerism were more frequent at the national scale. An efficient conservation policy should be built hierarchically (e.g. introducing adaptive governance), implementing solutions at a national scale with the flexibility to adjust for local differences and to address the most pressing issues.
PDF
