Robust point correspondence applied to two and three-dimensional image registration

Accurate and robust correspondence calculations are very important in many medical and biological applications. Often, the correspondence calculation forms part of a rigid registration algorithm, but accurate correspondences are especially important for elastic registration algorithms and for quantifying changes over time. In this paper, a new correspondence calculation algorithm, CSM (correspondence by sensitivity to movement), is described. A robust corresponding point is calculated by determining the sensitivity of a correspondence to movement of the point being matched. If the correspondence is reliable, a perturbation in the position of this point should not result in a large movement of the correspondence. A measure of reliability is also calculated. This correspondence calculation method is independent of the registration transformation and has been incorporated into both a 2D elastic registration algorithm for warping serial sections and a 3D rigid registration algorithm for registering pre and postoperative facial range scans. These applications use different methods for calculating the registration transformation and accurate rigid and elastic alignment of images has been achieved with the CSM method. It is expected that this method will be applicable to many different applications and that good results would be achieved if it were to be inserted into other methods for calculating a registration transformation from correspondence

Stability of corner points in scale space - The effects of small non-rigid deformations

To provide a good basis for the registration of medical images we search for reliable feature points using a scale-space approach. Our main concern is with 2D images: we analyze corner points, defined by differential invariants, at increasing scales. The number and position of corner points change in the scale-extended space, which define moving paths or orbits. To extract them we use a fast and reliable algorithm, based on iso-surface techniques, which automatically finds the corresponding singularities in scale space. We then get a representation of orbits that is very convenient both for detection at a coarse scale and localization at a fine scale. We find that the significance of corner points depends not only on their scale-space life-time but also on how they are related to curvature inflexion points. We investigate some topological changes of orbits which can be observed following image transformations. Afterwards we examine whether features, stable at multiple scales, are stabl..

Exploratory Analysis of Facial Growth

this paper we will compare two methods for analysing growth of faces. We will concentrate on on the shape and size of the profile of the face. The two methods differ in the way that the individual profiles are registered. In the first method Generalised Procrustes Analysis is used to register the profiles. This technique can cause some errors due to mis-registration. In the second method the profiles of each individual are registered together using the Iterative Closest Point Algorithm (ICP) (Besl and McKay, 1992). See Morris et al. (1999) for fuller details of the algorithms discussed here

Multiscale Representation and Analysis of Features from Medical Images

We address here the problem of multiscale extraction and representation of characteristic points based on iso-surface techniques. Our main concern is with 2D images: we analyze corner points at increasing scales using the Marching Lines algorithm. Since we can exploit the intrinsic nature of intensity of medical images, segmentation of components or parameterization of curves is not needed, in contrast with other methods. Due to the direct use of the coordinates of points, we get a representation of orbits, which is very convenient both for detection at coarse scale and for localization at ne scale. We nd that the significance of corner points depends not only on their scale-space lifetime but also on their relationship with curvature inflexion points