Despite significant progress in computer vision, pattern recognition, and image analysis, artifacts in imaging still hampers the progress in many scientific fields relying on the results of image analysis. We here present an advanced image-based artifacts suppression algorithm for high-resolution tomography. The algorithm is based on guided filtering of a reconstructed image mapped from the Cartesian to the polar coordinates space. This postprocessing method efficiently reduces both ring- and radial streak artifacts in a reconstructed image. Radial streak artifacts can appear in tomography with an off-center rotation of a large object over 360 degrees used to increase the reconstruction field of view. We successfully applied the developed algorithm for improving x-ray phase-contrast images of human post-mortem pineal gland and olfactory bulbs.
The method of Computed Tomography (CT) has progressed throughout the past decade with advances in CT apparatus and program parts that have resulted in an increasing number of CT applications. Today innovative CT Xray detectors have high spatial resolution till a tenth or hundredth of a micron. However, itsfield of view is significantly limited. The object being scanned with a high resolution does not always completely enter in (covered by) the field of view of the detector. The collected projections data may be incomplete. The use of incomplete data in classical reconstruction methods leads to image quality loss. This paper provides a new advanced reconstruction method that demonstrates image quality improvements compared with classical methods when incomplete data collected. The method uses the hypothesis about the consistency of object description in sinogram space and reconstruction space. Input data for the algorithm proposed are incomplete data, and the output data are the reconstructed image and the confidence values for all pixels of the image (reconstruction reliability). A detailed description of the algorithm is presented. Its quality characteristics are based on Shepp-Logan phantom studies.
Computer vision for biomedical imaging applications is fast developing and at once demanding field of computer science. In particular, computer vision technique provides excellent results for detection and segmentation problems in tomographic imaging. X-ray phase contrast Tomography (XPCT) is a noninvasive 3D imaging technique with high sensitivity for soft tissues. Despite a considerable progress in XPCT data acquisition and data processing methods, the problem in degradation of image quality due to artifacts remains a widespread and often critical issue for computer vision applications. One of the main problems originates from a sample alteration during a long tomographic scan. We proposed and tested Simultaneous Iterative Reconstruction algorithm with Total Variation regularization to reduce the number of projections in high resolution XPCT scans of ex-vivo mouse spinal cord. We have shown that the proposed algorithm allows tenfold reducing the number of projections and, therefore, the exposure time, with conservation of the important morphological information in 3D image with quality acceptable for computer graphics and computer vision applications. Our research paves a way for more effective implementation of advanced computer technologies in phase contrast tomographic research.
The paper presents a novel method for suppression of the orthotropic stripe artifacts typical for sensitive optical detector arrays. The algorithm is based on the guided filtering technique where the guidance image is constructed from the input frame in a way that removes artifacts from local contrast structures while disregarding the low-frequency distortions. The artifact suppression procedure was applied to the images of human faces taken with the IR -- THz camera in the diagnosis of psycho-emotional states. In this case, the presence of orthotropic artifacts prevents digital image stabilization. We also demonstrated that adaptation of the alg
Theranostics is an innovative research field that aims to develop high target specificity cancer treatments by administering small metal-based nanoparticles (NPs). This new generation of compounds exhibits diagnostic and therapeutic properties due to the high atomic number of their metal component. In the framework of a combined research program on low dose X-ray imaging and theranostic NPs, X-ray Phase Contrast Tomography (XPCT) was performed at ESRF using a 3 μm pixel optical system on two samples: a mouse brain bearing melanoma metastases injected with gadolinium NPs and, a mouse liver injected with gold NPs. XPCT is a non-destructive technique suitable to achieve the 3D reconstruction of a specimen and, widely used at micro-scale to detect abnormalities of the vessels, which are associated to the tumor growth or to the development of neurodegenerative diseases. Moreover, XPCT represents a promising and complementary tool to study the biodistribution of theranostic NPs in biological materials, thanks to the strong contrast with respect to soft tissues that metal-based NPs provide in radiological images. This work is relied on an original imaging approach based on the evaluation of the contrast differences between the images acquired below and above K-edge energies, as a proof of the certain localization of NPs. We will present different methods aiming to enhance the localization of NPs and a 3D map of their distribution in large volume of tissues.
We present in this paper the basic principle of novel X-ray optics composed of confocal nested reflecting mirrors that allows
more photons from a source of X-ray radiation to be accepted compared with a single mirror and that can be fabricated using
relatively cheap microfabrication tools. In order to optimize relevant parameters of the proposed system, we developed a ray-
tracing code for nested surfaces. The choice of parameters of the mirror system (length, position, eccentricity, etc.) is carried
out starting from theoretical considerations, which have been recently developed and, through simple equations, give optimal
parameters of X-ray mirrors providing a maximal acceptance angle of the system.
The idea of an X-ray waveguide has its origin in 1974 from a paper of Spiller and Segmuller1, but only then years ago2-5
it has been demonstrated that a submicrometer X-ray beam could be produced by the waveguides. From the first
experiments up to now the efficiency has been improved by three orders of magnitude6, and a nanometer beam confined
in two directions has been also produced7. Recently, as it will be shown in this paper, the possibility to use waveguides
with laboratory sources has been also demonstrated. The unique characteristics of the beam produced by the waveguides
(nanometer beam size, high degree of coherence, well defined beam profile, etc.) make it appealing for several
applications in microimaging, microdiffraction, etc. In this work the principles of X-ray waveguides together with the
view of the present activity and applications of this optics will be presented.