Snakes: Active Contour Models - Banff International Research ...
Incorporating Global Information into Active Contour Models Anthony Yezzi Georgia Institute of Technology Snakes: Active Contour Models Snakes or Active Contours pose the segmentation as an energy minimization problem. Kass, Witkins & Terzopoulos. ESnake Eext dp Eint dp
C Initialization C Final Segmentation Local Minima One major drawback of Active Contour model is the tendency to get stuck in Local minima caused by subtle irrelevant edges and image features. Initialization
Final Segmentation Avoiding Local Minima Balloon Force: (Cohen) EBal Eds ds C Makes assumption about the initialization. Biased final segmentation result.
Region-based Energy: EReg inside C C Fin dA
( I in ) 2 outside C Fout dA 2 ( I ) out
Makes Strong assumptions about the image. Image Domain Global minimum of Edge-based Energy: EEdge ( s)ds C Global minimal path for open curves/geodesics. (Cohen & Kimmel) Not suitable for closed curves (Geodesic Active Contours used instead) Active Geodesics Region-based active contour
segmentation with a Global Edgebased Constraint Edge-based Segmentation Globally Optimal Geodesic Active Contours (GOGAC) Appleton B. and Talbot H. Introduce an artificial cut in the image domain and search for an optimal open geodesic with end points on either side of the cut. Test Image
GOGAC Propagating Fronts Purely Region-Based Segmentation Region-based energy minimization. Chan-Vese Model (Mumford-Shah special case) EReg
inside C ( I in ) 2 dA Initialization outside C ( I out ) 2 dA Final Segmentation Incorporating Region-based
Energy in Edge-based Segmentation Test Image Propagating Fronts Closed Curve with least Region-based Energy Saddle Points Associated Closed Curves Active Geodesics
Reverse roles of Source/saddle point Initialization away from object boundary Minimize the region-based energy and restrict evolution to a single local degree of freedom: translation of saddle point in the normal direction to the curve at that point. p EReg FRe g ds C Continuum of Closed geodesics 1/(|| I || 1)
Test Image Propagating Fronts Segmentation Region-based Evolution Move Saddlepoint New Source Propagating Fronts Segmentation after 3rd iteration
Segmentation after 2nd iteration Evolution (Left Ventricle Segmentation) Iterations 4 to 18 Right Ventricle Segmentation User can interact with the segmentation algorithm by adding poles and zeros, to attract and repel the contour towards desired edges.
Red X Additional Pole (Repeller) Green X Additional Zero (Attractor) Initial Right Ventricle Segmentation with Active Geodesics Segmentation after adding a repeller Final segmentation with 2 repellers and 1 attractor Cell Segmentation Active geodesic-based segmentation with three different initializations
Edge-based GOGAC segmentation for three different initializations Nuclei Segmentation Nuclei segmentation with same initialization as the previous slide Region-based Chan-Vese segmentation for nucleus segmentation
29 consanguineous families from Eastern Turkey having type 1 and type 3 VWD were supplied by Dr. J. Ingerslev, Denmark and Dr. T. Gürsel, Turkey. One patient was homozygous. Gene deletion exons 26-34 New mutation, decreased large multimers. Ware et...
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