6,041 research outputs found
An active curve approach for tomographic reconstruction of binary radially symmetric objects
This paper deals with a method of tomographic reconstruction of radially
symmetric objects from a single radiograph, in order to study the behavior of
shocked material. The usual tomographic reconstruction algorithms such as
generalized inverse or filtered back-projection cannot be applied here because
data are very noisy and the inverse problem associated to single view
tomographic reconstruction is highly unstable. In order to improve the
reconstruction, we propose here to add some a priori assumptions on the looked
after object. One of these assumptions is that the object is binary and
consequently, the object may be described by the curves that separate the two
materials. We present a model that lives in BV space and leads to a non local
Hamilton-Jacobi equation, via a level set strategy. Numerical experiments are
performed (using level sets methods) on synthetic objects
Visual Quality Enhancement in Optoacoustic Tomography using Active Contour Segmentation Priors
Segmentation of biomedical images is essential for studying and
characterizing anatomical structures, detection and evaluation of pathological
tissues. Segmentation has been further shown to enhance the reconstruction
performance in many tomographic imaging modalities by accounting for
heterogeneities of the excitation field and tissue properties in the imaged
region. This is particularly relevant in optoacoustic tomography, where
discontinuities in the optical and acoustic tissue properties, if not properly
accounted for, may result in deterioration of the imaging performance.
Efficient segmentation of optoacoustic images is often hampered by the
relatively low intrinsic contrast of large anatomical structures, which is
further impaired by the limited angular coverage of some commonly employed
tomographic imaging configurations. Herein, we analyze the performance of
active contour models for boundary segmentation in cross-sectional optoacoustic
tomography. The segmented mask is employed to construct a two compartment model
for the acoustic and optical parameters of the imaged tissues, which is
subsequently used to improve accuracy of the image reconstruction routines. The
performance of the suggested segmentation and modeling approach are showcased
in tissue-mimicking phantoms and small animal imaging experiments.Comment: Accepted for publication in IEEE Transactions on Medical Imagin
A Time-Evolving 3D Method Dedicated to the Reconstruction of Solar plumes and Results Using Extreme Ultra-Violet Data
An important issue in the tomographic reconstruction of the solar poles is
the relatively rapid evolution of the polar plumes. We demonstrate that it is
possible to take into account this temporal evolution in the reconstruction.
The difficulty of this problem comes from the fact that we want a 4D
reconstruction (three spatial dimensions plus time) while we only have 3D data
(2D images plus time). To overcome this difficulty, we introduce a model that
describes polar plumes as stationary objects whose intensity varies
homogeneously with time. This assumption can be physically justified if one
accepts the stability of the magnetic structure. This model leads to a bilinear
inverse problem. We describe how to extend linear inversion methods to these
kinds of problems. Studies of simulations show the reliability of our method.
Results for SOHO/EIT data show that we are able to estimate the temporal
evolution of polar plumes in order to improve the reconstruction of the solar
poles from only one point of view. We expect further improvements from
STEREO/EUVI data when the two probes will be separated by about 60 degrees
3D correlative single-cell imaging utilizing fluorescence and refractive index tomography
Cells alter the path of light, a fact that leads to well-known aberrations in
single cell or tissue imaging. Optical diffraction tomography (ODT) measures
the biophysical property that causes these aberrations, the refractive index
(RI). ODT is complementary to fluorescence imaging and does not require any
markers. The present study introduces RI and fluorescence tomography with
optofluidic rotation (RAFTOR) of suspended cells, quantifying the intracellular
RI distribution and colocalizing it with fluorescence in 3D. The technique is
validated with cell phantoms and used to confirm a lower nuclear RI for HL60
cells. Furthermore, the nuclear inversion of adult mouse photoreceptor cells is
observed in the RI distribution. The applications shown confirm predictions of
previous studies and illustrate the potential of RAFTOR to improve our
understanding of cells and tissues.Comment: 15 pages, 5 figure
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