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1
Content available remote Approximating Algebraic Tomography Methods by Filtered Backprojection : A Local Filter Approach
100%
Plantagie L. , Batenburg K. J.
Fundamenta Informaticae
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2014
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tom Vol. 135, nr 1/2
1--19
EN
Filtered Backprojection is the most widely used reconstruction method in transmission tomography. The algorithm is computationally efficient, but requires a large number of low-noise projections acquired over the full angular range to produce accurate reconstructions. Algebraic reconstruction methods on the other hand are in general more robust with respect to noise and can incorporate the available angular range in the underlying projection model. A drawback of these methods is their higher computational cost. In a recent article, we demonstrated that for linear algebraic reconstruction methods, a filter can be computed such that applying Filtered Backprojection using this filter yields reconstructions that approximate the algebraic method. In the present work, we explore a modification of this approach, where we use more than one algebraic filter in the reconstructions, each covering a different region of the reconstruction grid. We report the results of a series of experiments to determine the how well the reconstruction and approximation accuracy of this approach.
2
Content available remote An Open Source GPU Accelerated Framework for Flexible Algebraic Reconstruction at Synchrotron Light Sources
100%
Shkarin A. , Ametova E. , Chilingaryan S. , Dritschler T. , Kopmann A. , Vogelgesang M. , Shkarin R. , Tsapko S.
Fundamenta Informaticae
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2015
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tom Vol. 141, nr 2/3
259--274
EN
The recent developments in detector technology made possible 4D (3D + time) X-ray microtomographywith high spatial and time resolutions. The resolution and duration of such experiments is currently limited by destructive X-ray radiation. Algebraic reconstruction technique (ART) can incorporate a priori knowledge into a reconstruction model that will allow us to apply some approaches to reduce an imaging dose and keep a good enough reconstruction quality. However, these techniques are very computationally demanding. In this paper we present a framework for ART reconstruction based on OpenCL technology. Our approach treats an algebraic method as a composition of interacting blocks which performdifferent tasks, such as projection selection, minimization, projecting and regularization. These tasks are realised using multiple algorithms differing in performance, the quality of reconstruction, and the area of applicability. Our framework allows to freely combine algorithms to build the reconstruction chain. All algorithms are implemented with OpenCL and are able to run on a wide range of parallel hardware. As well the framework is easily scalable to clustered environment with MPI. We will describe the architecture of ART framework and evaluate the quality and performance on latest generation of GPU hardware from NVIDIA and AMD.
3
Content available Acoustic Wave Correlation Tomography of Time-Varying Disordered Structures
100%
Samelsohn G. , Tapuchi S.
Archives of Acoustics
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2018
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tom Vol. 43, No. 4
647--655
EN
An original model based on first principles is constructed for the temporal correlation of acoustic waves propagating in random scattering media. The model describes the dynamics of wave fields in a previously unexplored, moderately strong (mesoscopic) scattering regime, intermediate between those of weak scattering, on the one hand, and diffusing waves, on the other. It is shown that by considering the wave vector as a free parameter that can vary at will, one can provide an additional dimension to the data, resulting in a tomographic-type reconstruction of the full space-time dynamics of a complex structure, instead of a plain spectroscopic technique. In Fourier space, the problem is reduced to a spherical mean transform defined for a family of spheres containing the origin, and therefore is easily invertible. The results may be useful in probing the statistical structure of various random media with both spatial and temporal resolution.
4
Content available Tomographic system based on Plasma Focus X-rays
88%
Venere M. , Moreno C. H. , Clausse A. , Barbuzza R. , Del Fresno M.
Nukleonika
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2001
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tom Vol. 46, suppl. 1
93--94
EN
A system oriented to develop an image processing system, which takes advantage of radiation flashes from a plasma focus, by optimizing the emission-detection-reconstruction procedure, is presented. A computer technique for 3D reconstructions was combined with radiographic images of objects X-rayed with a compact plasma focus. The technique is able to automatically determine the position of the rotation axis, reconstruct the 3D-attenuation map, and display inner cuts. The system was demonstrated in introspective tomographic imaging of a stainless steel BNC elbow.
5
Content available remote Interpolation-based reconstruction methods for tomographic imaging in 3D Positron Emission Tomography
75%
Li Y. , Kummert A. , Boschen F. , Herzog H.
International Journal of Applied Mathematics and Computer Science
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2008
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tom 18
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nr 1
63-73
EN
Positron Emission Tomography (PET) is considered a key diagnostic tool in neuroscience, by means of which valuable insight into the metabolism function in vivo may be gained. Due to the underlying physical nature of PET, 3D imaging techniques in terms of a 3D measuring mode are intrinsically demanded to assure satisfying resolutions of the reconstructed images. However, incorporating additional cross-plane measurements, which are specific for the 3D measuring mode, usually imposes an excessive amount of projection data and significantly complicates the reconstruction procedure. For this reason, interpolation-based reconstruction methods deserve a thorough investigation, whose crucial parts are the interpolating processes in the 3D frequency domain. The benefit of such approaches is apparently short reconstruction duration, which can, however, only be achieved at the expense of accepting the inaccuracies associated with the interpolating process. In the present paper, two distinct approaches to the realization of the interpolating procedure are proposed and analyzed. The first one refers to a direct approach based on linear averaging (inverse distance weighting), and the second one refers to an indirect approach based on two-dimensional convolution (gridding method). In particular, attention is paid to two aspects of the gridding method. The first aspect is the choice of the two-dimensional convolution function applied, and the second one is the correct discretization of the underlying continuous convolution. In this respect, the geometrical structure named the Voronoi diagram and its computational construction are considered. At the end, results of performed simulation studies are presented and discussed.
6
Content available Acoustic Wave Correlation of Time-Varying Disordered Structures
63%
Samelsohn G. , Tapuchi S.
|
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tom 43
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nr 4
7
Content available remote Interpolation-based reconstruction methods for tomographic imaging in 3D positron emission tomography
51%
Li Y. , Kummert A. , Boschen F. , Herzog H.
International Journal of Applied Mathematics and Computer Science
|
2008
|
tom Vol. 18, no 1
63-73
EN
Positron Emission Tomography (PET) is considered a key diagnostic tool in neuroscience, by means of which valuable insight into the metabolism function in vivo may be gained. Due to the underlying physical nature of PET, 3D imaging techniques in terms of a 3D measuring mode are intrinsically demanded to assure satisfying resolutions of the reconstructed images. However, incorporating additional cross-plane measurements, which are specific for the 3D measuring mode, usually imposes an excessive amount of projection data and significantly complicates the reconstruction procedure. For this reason, interpolation-based reconstruction methods deserve a thorough investigation, whose crucial parts are the interpolating processes in the 3D frequency domain. The benefit of such approaches is apparently short reconstruction duration, which can, however, only be achieved at the expense of accepting the inaccuracies associated with the interpolating process. In the present paper, two distinct approaches to the realization of the interpolating procedure are proposed and analyzed. The first one refers to a direct approach based on linear averaging (inverse distance weighting), and the second one refers to an indirect approach based on two-dimensional convolution (gridding method). In particular, attention is paid to two aspects of the gridding method. The first aspect is the choice of the two-dimensional convolution function applied, and the second one is the correct discretization of the underlying continuous convolution. In this respect, the geometrical structure named the Voronoi diagram and its computational construction are considered. At the end, results of performed simulation studies are presented and discussed.
8
Content available Analysis of upper respiratory tract segmentation features to determine nasal conductance
51%
Avrunin O. , Nosova Y. , Shushliapina N. , Abdelhamid I. Y. , Avrunin O. , Kyrylashchuk S. , Moskovchuk O. , Mamyrbayev O.
Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska
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2022
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tom T. 12, nr 4
35--40
EN
The paper examines the features of segmentation of the upper respiratory tract to determine nasal air conduction. 2D and 3D illustrations of the segmentation process and the obtained results are given. When forming an analytical model of the aerodynamics of the nasal cavity, the main indicator that characterizes the configuration of the nasal canal is the equivalent diameter, which is determined at each intersection of the nasal cavity. It is calculated based on the area and perimeter of the corresponding section of the nasal canal. When segmenting the nasal cavity, it is first necessary to eliminate air structures that do not affect the aerodynamics of the upper respiratory tract - these are, first of all, intact spaces of the paranasal sinuses, in which diffuse air exchange prevails. In the automatic mode, this is possible by performing the elimination of unconnected isolated areas and finding the difference coefficients of the areas connected by confluences with the nasal canal in the next step. High coefficients of difference of sections between intersections will indicate the presence of separated areas and contribute to their elimination. The complex configuration and high individual variability of the structures of the nasal cavity does not allow segmentation to be fully automated, but this approach contributes to the absence of interactive correction in 80% of tomographic datasets. The proposed method, which takes into account the intensity of the image elements close to the contour ones, allows to reduce the averaging error from tomographic reconstruction up to 2 times due to artificial sub-resolution. The perspective of the work is the development of methods for fully automatic segmentation of the structures of the nasal cavity, taking into account the individual anatomical variability of the upper respiratory tract.
PL
W pracy przeanalizowano cechy segmentacji górnych dróg oddechowych w celu określenia powietrznego przewodnictwa nosowego. Przedstawiono zdjęcia 2D i 3D procesu segmentacji oraz uzyskanych wyników. Podczas formowania analitycznego modelu aerodynamiki jamy nosowej głównym wskaźnikiem charakteryzującym konfigurację kanału nosowego jest ekwiwalentna średnica, którą wyznacza się na każdym skrzyżowaniu jam nosowych. Jest ona obliczana na podstawie pola powierzchni i obwodu odpowiedniego odcinka kanału nosowego. Podczas segmentacji jamy nosowej w pierwszej kolejności należy wyeliminować struktury powietrzne, które nie wpływają na aerodynamikę górnych dróg oddechowych – są to przede wszystkim nienaruszone przestrzenie zatok przynosowych, w których dominuje rozproszona wymiana powietrza. W trybie automatycznym jest to możliwe dzięki eliminacji niepołączonych izolowanych obszarów i znalezieniu, w kolejnym kroku, współczynników różnicy obszarów połączonych konfluencjami z przewodem nosowym. Wysokie współczynniki różnic przekrojów pomiędzy skrzyżowaniami będą wskazywały na obecność wydzielonych obszarów i przyczynią się do ich eliminacji. Złożona konfiguracja i duża zmienność osobnicza struktur jamy nosowej nie pozwala na pełną automatyzację segmentacji, jednak takie podejście przyczynia się do braku konieczności interaktywnej korekcji w 80% zestawów danych tomograficznych. Zaproponowana metoda, uwzględniająca intensywność elementów obrazu znajdujących się blisko konturu, pozwala na nawet 2-krotne zmniejszenie błędu uśredniania z rekonstrukcji tomograficznej, wynikającego ze sztucznej subrozdzielczości. Perspektywą pracy jest opracowanie metod w pełni automatycznej segmentacji struktur jamy nosowej z uwzględnieniem indywidualnej zmienności anatomicznej górnych dróg oddechowych.
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