Fast fluid extensions for image registration algorithms

ABSTRACT The present paper shows a sytematic way to derive fluid-like registration equations. The novel technique is demonstrated for the case of optical flow-based and diffusion-based registration

Determination of pore size distribution at the cell-hydrogel interface

<p>Abstract</p> <p>Background</p> <p>Analyses of the pore size distribution in 3D matrices such as the cell-hydrogel interface are very useful when studying changes and modifications produced as a result of cellular growth and proliferation within the matrix, as pore size distribution plays an important role in the signaling and microenvironment stimuli imparted to the cells. However, the majority of the methods for the assessment of the porosity in biomaterials are not suitable to give quantitative information about the textural properties of these nano-interfaces.</p> <p>Findings</p> <p>Here, we report a methodology for determining pore size distribution at the cell-hydrogel interface, and the depth of the matrix modified by cell growth by entrapped HepG₂cells in microcapsules made of 0.8% and 1.4% w/v alginate. The method is based on the estimation of the shortest distance between two points of the fibril-like network hydrogel structures using image analysis of TEM pictures. Values of pore size distribution determined using the presented method and those obtained by nitrogen physisorption measurements were compared, showing good agreement. A combination of these methodologies and a study of the cell-hydrogel interface at various cell culture times showed that after three days of culture, HepG₂cells growing in hydrogels composed of 0.8% w/v alginate had more coarse of pores at depths up to 40 nm inwards (a phenomenon most notable in the first 20 nm from the interface). This coarsening phenomenon was weakly observed in the case of cells cultured in hydrogels composed of 1.4% w/v alginate.</p> <p>Conclusions</p> <p>The method purposed in this paper allows us to obtain information about the radial deformation of the hydrogel matrix due to cell growth, and the consequent modification of the pore size distribution pattern surrounding the cells, which are extremely important for a wide spectrum of biotechnological, pharmaceutical and biomedical applications.</p

A NEW EQUATION FOR NONLINEAR IMAGE REGISTRATION WITH CONTROL OVER THE VORTEX STRUCTURE IN THE DISPLACEMENT FIELD

The goal of nonparametric image registration lies in the solution of highly nonlinear partial differential equations. We present a new partial differential equation for the nonlinear image registration that can be used for the registration of images with textured and complex shaped motifs. The new equation allows to control the vortex structure in the registration field. For many image registration problems, the required transformation should not contain vortices. The application field of the new equation is not restricted to biomedical imaging. Index Terms — Biomedical image processing, Image registration, Nonlinear differential equations, Partial differential equations 1

An Approach to the Computation of the Euler Number by means of the Vertex Chain Code

We present an approach to compute the number of holes in binary images using the Vertex Chain Code (VCC); the VCC was developed for representing and analyzing 2D shapes composed of cells. Using this code, it is possible to relate the outer to inner vertices of any 2D shape and to find interesting properties. Now, in this paper, we describe more properties of the VCC, such as the computation of the connected regions in a hole, the analysis of complementary chains, the computation of the number of holes in a binary shape or image, the computation of the Euler number, and the detection of convex and concave shapes. Finally, in order to illustrate the capabilities of proposed methods, we present the computation of topological properties of examples of objects of the real world