196 research outputs found
Brain Tumor Synthetic Segmentation in 3D Multimodal MRI Scans
The magnetic resonance (MR) analysis of brain tumors is widely used for
diagnosis and examination of tumor subregions. The overlapping area among the
intensity distribution of healthy, enhancing, non-enhancing, and edema regions
makes the automatic segmentation a challenging task. Here, we show that a
convolutional neural network trained on high-contrast images can transform the
intensity distribution of brain lesions in its internal subregions.
Specifically, a generative adversarial network (GAN) is extended to synthesize
high-contrast images. A comparison of these synthetic images and real images of
brain tumor tissue in MR scans showed significant segmentation improvement and
decreased the number of real channels for segmentation. The synthetic images
are used as a substitute for real channels and can bypass real modalities in
the multimodal brain tumor segmentation framework. Segmentation results on
BraTS 2019 dataset demonstrate that our proposed approach can efficiently
segment the tumor areas. In the end, we predict patient survival time based on
volumetric features of the tumor subregions as well as the age of each case
through several regression models
Magnetic pattern at supergranulation scale: the Void Size Distribution
The large-scale magnetic pattern of the quiet sun is dominated by the
magnetic network. This network, created by photospheric magnetic fields swept
into convective downflows, delineates the boundaries of large scale cells of
overturning plasma and exhibits voids in magnetic organization. Such voids
include internetwork fields, a mixed-polarity sparse field that populate the
inner part of network cells. To single out voids and to quantify their
intrinsic pattern a fast circle packing based algorithm is applied to 511
SOHO/MDI high resolution magnetograms acquired during the outstanding solar
activity minimum between 23 and 24 cycles. The computed Void Distribution
Function shows a quasi-exponential decay behavior in the range 10-60 Mm. The
lack of distinct flow scales in such a range corroborates the hypothesis of
multi-scale motion flows at the solar surface. In addition to the
quasi-exponential decay we have found that the voids reveal departure from a
simple exponential decay around 35 Mm.Comment: 6 pages, 8 figures, to appear in Astronomy and Astrophysic
Seismic Fault Preserving Diffusion
This paper focuses on the denoising and enhancing of 3-D reflection seismic
data. We propose a pre-processing step based on a non linear diffusion
filtering leading to a better detection of seismic faults. The non linear
diffusion approaches are based on the definition of a partial differential
equation that allows us to simplify the images without blurring relevant
details or discontinuities. Computing the structure tensor which provides
information on the local orientation of the geological layers, we propose to
drive the diffusion along these layers using a new approach called SFPD
(Seismic Fault Preserving Diffusion). In SFPD, the eigenvalues of the tensor
are fixed according to a confidence measure that takes into account the
regularity of the local seismic structure. Results on both synthesized and real
3-D blocks show the efficiency of the proposed approach.Comment: 10 page
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