Full Multiresolution Active Shape Models

Authors: Juan J Cerrolaza Arantxa Villanueva Federico M Sukno Constantine Butakoff Alejandro F Frangi Rafael Cabeza

Publish Date: 2012/05/12

Volume: 44, Issue: 3, Pages: 463-479

PDF Link

Abstract

The incorporation of a multiresolution image approach is one of the most popular variants of Active Shape Models ASMs providing a more robust algorithm and minimizing its initialization dependency Using the wavelet transform the present paper extends the multiresolution analysis to the shape space developing a novel multiresolution shape framework capable of being incorporated into most of ASM variants The tests performed with two different types of images face images AR database and chest radiographs JSRT database demonstrate how this new generation of algorithms significantly reduce the computational cost more than halving it while maintaining the same levels of accuracyThe work described in this study was supported by the Spanish Ministry of Science and Innovation with an FPU grant AP200703931 This work was also partially supported by the Spanish Ministry of Science and Innovation Ref TIN200914536C0201 Plan E and FEDERInvariance uniqueness and stability are desirable properties of shape descriptors 44 Chuang and Kuox 9 successfully derived these properties when using wavelets as shape descriptors under the assumption of a well defined starting point for the curves While this condition is easily satisfied in the case of open contours there exists an inherent uncertainty when dealing with closed ones In the absence of a prior registration the problem of starting point of the contour must be handled ad hoc since different starting points of the same shape will result in different wavelet coefficients Lohakan et al 37 solve this problem by defining the point of maximum curvature as starting point while Zhang et al 55 propose a starting point location strategy based on halfaxesangles ie the least counterclockwise angles formed by the line segments connecting the centroid to the nearest and farthest point of the contour However the PDM requires that the landmarks are placed in the same order and in the same places along the object’s contour ensuring thus a point correspondence and eliminating the need for a consistent localization of the starting point in every shape Nevertheless there still exists an uncertainty about whether or not the chosen starting point and thus the corresponding coarser versions of the shape significantly affects the final segmentation accuracy

Keywords: