<title>Modelization of fetal cranial contour from ultrasound axial slices</title>

Abstract

The problem of the choice of slices angles, at the time of diagnosis of brain fetal malformations, is linked to the position of the fetus inside the uterus.The 3D reconstruction of intern parts ofthe brain and especially the callosus corpus can help to detect some malformations. This kind ofreconstruction pass by several steps that depend all on the initial segmentation step. The main difficulties of the segmentation are linked on the one hand to the inherent noise ofultrasound imaging and on the other hand to the matching of views ofthe 2D sequence to process.The 3D reconstruction stage require the defmition of a marker in the sequence to process. In agreement with physicians, we have used the cranial contour as reference on the one hand because it is considered as invariable and fixed and on the other hand because of its more pronounced contrast (due to the fact of its cartilaginous nature) that the other structures.Nevertheless, the classic techniques of segmentations have remained without effect (open contour, too noisy). Therefore, we have sought an other approach for the segmentation. Superposition of an ellipsoidal shape on digital ultrasound has put in obviousness the possibility ofmodelisation by this geometrical shape the cranial contour. Therefore, we have developed an algorithm allowing to defme automatically the ellipse. This method is based on a parametrically deformable model using elliptic FOURIER decomposition.

An Adaptive Snake Model for Ultrasound Image Segmentation: Modified Trimmed Mean Filter, Ramp Integration and Adaptive Weighting Parameters

“…Finally, the blurred disc image is corrupted by the speckle, which gives the ramp phantom image. The contrast-to-noise ratio (CNR) of the ramp phantom images is defined as (8) where cr f and cr b are the standard deviations of the speckle within and outside the blurred disc. Note that the speckles on the ramp edge of the blurred disc are not taken into count in computing cr f and cr b • Given a blurred disc image, the speckle in the ramp phantom image may be simulated in two possible ways.…”