3,135 research outputs found
Fitting tree model with CNN and geodesics to track vesselsand application to Ultrasound Localization Microscopy data
Segmentation of tubular structures in vascular imaging is a well studied
task, although it is rare that we try to infuse knowledge of the tree-like
structure of the regions to be detected. Our work focuses on detecting the
important landmarks in the vascular network (via CNN performing both
localization and classification of the points of interest) and representing
vessels as the edges in some minimal distance tree graph. We leverage geodesic
methods relevant to the detection of vessels and their geometry, making use of
the space of positions and orientations so that 2D vessels can be accurately
represented as trees. We build our model to carry tracking on Ultrasound
Localization Microscopy (ULM) data, proposing to build a good cost function for
tracking on this type of data. We also test our framework on synthetic and eye
fundus data. Results show that scarcity of well annotated ULM data is an
obstacle to localization of vascular landmarks but the Orientation Score built
from ULM data yields good geodesics for tracking blood vessels.Comment: This work has been submitted to the IEEE for possible publication.
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Chan-Vese Attention U-Net: An attention mechanism for robust segmentation
When studying the results of a segmentation algorithm using convolutional
neural networks, one wonders about the reliability and consistency of the
results. This leads to questioning the possibility of using such an algorithm
in applications where there is little room for doubt. We propose in this paper
a new attention gate based on the use of Chan-Vese energy minimization to
control more precisely the segmentation masks given by a standard CNN
architecture such as the U-Net model. This mechanism allows to obtain a
constraint on the segmentation based on the resolution of a PDE. The study of
the results allows us to observe the spatial information retained by the neural
network on the region of interest and obtains competitive results on the binary
segmentation. We illustrate the efficiency of this approach for medical image
segmentation on a database of MRI brain images
Deformable Voxel Grids for Shape Comparisons
We present Deformable Voxel Grids (DVGs) for 3D shapes comparison and
processing. It consists of a voxel grid which is deformed to approximate the
silhouette of a shape, via energy-minimization. By interpreting the DVG as a
local coordinates system, it provides a better embedding space than a regular
voxel grid, since it is adapted to the geometry of the shape. It also allows to
deform the shape by moving the control points of the DVG, in a similar manner
to the Free Form Deformation, but with easier interpretability of the control
points positions. After proposing a computation scheme of the energies
compatible with meshes and pointclouds, we demonstrate the use of DVGs in a
variety of applications: correspondences via cubification, style transfer,
shape retrieval and PCA deformations. The first two require no learning and can
be readily run on any shapes in a matter of minutes on modest hardware. As for
the last two, they require to first optimize DVGs on a collection of shapes,
which amounts to a pre-processing step. Then, determining PCA coordinates is
straightforward and brings a few parameters to deform a shape
An Application of CLP: Checking the Correctness of Theorems in Geometry
International audienceConstraint Logic Programming can be advantageously used to deal with quadratic constraints stemming from the verification of planar geometry theorems. A hybrid symbolic--numeric representation involving radicals and multiple precision rationals is used to denote the results of quadratic equations. A unification--like algorithm tests for the equality of two expressions using that representation. The proposed approach also utilizes geometric transformations to reduce the number of quadratic equations defining geometric constructions involving circles and straight lines. A large number (512) of geometry theorems has been verified using the proposed approach. Those theorems had been proven correct using a significantly more complex (exponential) approach in a treatise authored by Chou in 1988. Even though the proposed approach is based on verification -rather than strict correctness utilized by Chou- the efficiency attained is polynomial thus making the approach useful in classroom situations where a construction attempted by student has to be quickly validated or refuted
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