Regularized Image Reconstruction Algorithms for Positron Emission Tomography

Chang, Jiho; Anderson, J.M.M.; Votaw, John R.

doi:10.1109/tmi.2004.831224

Cited by 42 publications

(27 citation statements)

References 28 publications

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“…The projected density measurements at the recorded 90 lines of sight are reconstructed using TomoPy's penalized maximum likelihood algorithm with weighted linear and quadratic penalties [33]. The result of the reconstruction is a time-resolved ensemble-average density field, ρ(x, y, t), at z = 2 mm downstream of the nozzle tip.…”

Section: Methodsmentioning

confidence: 99%

A study on the relationship between internal nozzle geometry and injected mass distribution of eight ECN Spray G nozzles.

Matusik¹,

Duke²,

Sovis³

et al. 2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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Gasoline direct injection (GDI) nozzles are manufactured to meet geometric specifications with length scales on the order of a few hundred microns. The machining tolerances of these nominal dimensions are not always known due to the difficulty in accurately measuring such small length scales in a nonintrusive fashion. To gain insight into the variability of the machined dimensions as well as any effects that this variability may have on the fuel spray behavior, a series of measurements of the internal geometry and fuel mass distribution were performed on a set of eight nominally duplicate GDI "Spray G" nozzles provided by the Engine Combustion Network. The key dimensions of each of the eight nozzle holes were measured with micron resolution using full spectrum x-ray tomographic imaging at the 7-BM beamline of the Advanced Photon Source at Argonne National Laboratory. Fuel density distributions at 2 mm downstream of the nozzle tips were obtained by performing x-ray radiography measurements for many lines of sight. The density measurements reveal nozzle-to-nozzle as well as hole-to-hole density variations. The combination of high-resolution geometry and fuel distribution datasets allows spray phenomena to be linked to specific geometric characteristics of the nozzle, such as variability in the hole lengths and counterbore diameters, and the hole inlet corner radii. This analysis provides important insight into which geometrical characteristics of the nozzles may have the greatest importance in the development of the injected sprays, and to what degree these geometric variations might account for the total spray variability. The goal of this work is then to further the understanding of the relationship between internal nozzle geometry and fuel injection, provide input to improve computational models, and ultimately aid in optimizing injector design for higher fuel efficiency and lower emissions engines. KeywordsGDI, nozzle geometry, fuel spray density, fuel injector, DISI, Spray G, ECN, gasoline IntroductionTo fully realize the benefits of a gasoline direct injection (GDI) engine, precise control over the amount of injected fuel and the fuel-to-air mixing ratio is necessary. Any variations to the fuel spray distribution can affect the combustion process, and by extension the fuel efficiency and emissions levels. Modern multi-hole GDI nozzles generally feature a relatively complex step-hole geometry in which each hole might require knowledge of at least nine dimensions to accurately model. Due to the importance of the injection process on the output metrics of a GDI engine, a subset of internal combustion engine research has been dedicated to investigating the effects of nozzle geometry on the corresponding fuel spray distribution. X-ray spray tomography measurements of three six-hole GDI nozzles with varying hole patterns explored the effects of geometric asymmetries on the spray structure [1]. The authors found that the emitted fuel spray distribution varied between jet-like, hollow-coned, or crescent-shap...

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Section: Methodsmentioning

confidence: 99%

A study on the relationship between internal nozzle geometry and injected mass distribution of eight ECN Spray G nozzles.

Matusik¹,

Duke²,

Sovis³

et al. 2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

View full text Add to dashboard Cite

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“…(2). By these means, matrix inversions involved in (6), (12) and (17) which are now handled by the conjugate gradient method would be avoided.…”

Section: Discussionmentioning

confidence: 99%

“…An alternating optimization is performed where a likelihood estimate is followed by inference of the mixture model [11]. A monotonically decreasing surrogate objective function resulting in a closed form expression is proposed in [12] while the median root prior was also used to impose spatial smoothness and stabilize the solution [13]. Finally, a nonlocal prior was designed [14] where the definition of a pixel's neighborhood is broadened.…”

Section: Introductionmentioning

confidence: 99%

MAP tomographic reconstruction with a spatially adaptive hierarchical image model

Nikou

2017

2017 25th European Signal Processing Conference (EUSIPCO)

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“…The iterative reconstruction algorithms for tomography have demonstrated promising results in the ability to compute high-quality 3D images from less data. In which case, the application of iterative algorithms like the Simultaneous Iterative Reconstruction Technique (SIRT) [20], the Simultaneous Algebraic Reconstruction Technique (SART) [21], or other more complex techniques [22] for tomography reconstruction calculations allows qualitative data to be obtained. The ASTRA Toolbox [23] is a MATLAB and Python platform providing high-performance GPU primitives for 2D and 3D A set of neutron radiography images was collected by a CCD-based detector system with a maximum field of view of 20 cm × 20 cm.…”

Section: Methodsmentioning

confidence: 99%

Studies of Ancient Russian Cultural Objects Using the Neutron Tomography Method

et al. 2018

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Neutron radiography and tomography is a non-destructive method that provides detailed information about the internal structure of cultural heritage objects. The differences in the neutron attenuation coefficients of constituent elements of the studied objects, as well as the application of modern mathematical algorithms to carry out three-dimensional imaging data analysis, allow one to obtain unique information about the spatial distribution of different phases, the presence of internal defects, or the degree of structural degradation inside valuable cultural objects. The results of the neutron studies of several archaeological objects related to different epochs of the Russian history are reported in order to demonstrate the opportunities provided by the neutron tomography method. The obtained 3D structural volume data, as well as the results of the corresponding data analysis, are presented.

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Regularized Image Reconstruction Algorithms for Positron Emission Tomography

Cited by 42 publications

References 28 publications

A study on the relationship between internal nozzle geometry and injected mass distribution of eight ECN Spray G nozzles.

A study on the relationship between internal nozzle geometry and injected mass distribution of eight ECN Spray G nozzles.

MAP tomographic reconstruction with a spatially adaptive hierarchical image model

Studies of Ancient Russian Cultural Objects Using the Neutron Tomography Method

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