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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
341

Positron emission tomography (PET) image reconstruction by density estimation

Pawlak, Barbara 17 September 2007 (has links)
PET (positron emission tomography) scans are still in the experimental phase, as one of the newest breast cancer diagnostic techniques. It is becoming the new standard in neurology, oncology and cardiology. PET, like other nuclear medicine diagnostic and treatment techniques, involves the use of radiation. Because of the negative impact of radioactivity to our bodies the radiation doses in PET should be small. The existing computing algorithms for calculating PET images can be divided into two broad categories: analytical and iterative methods. In the analytical approach the relation between the picture and its projections is expressed by a set of integral equations which are then solved analytically. The Fourier backprojection (FBP) algorithm is a numerical approximation of this analytical solution. Iterative approaches use deterministic (ART = Algebraic Reconstructed Technique) or stochastic (EM = Expectation Maximization) algorithms. My proposed kernel density estimation (KDE) algorithm also falls also into the category of iterative methods. However, in this approach each coincidence event is considered individually. The estimate location of the annihilation event that caused each coincidence event is based on the previously assigned location of events processed earlier. To accomplish this, we construct a probability distribution along each coincidence line. This is generated from previous annihilation points by density estimation. It is shown that this density estimation approach to PET can reconstruct an image of an existing tumor using significantly less data than the standard CT algorithms, such as FBP. Therefore, it might be very promising technique allowing reduced radiation dose for patients, while retaining or improving image quality.
342

Towards an improved microwave tomography system

Gilmore, Colin 12 January 2010 (has links)
This dissertation outlines work taken towards the understanding, implementation, and improvements to the process of creating of quantitative images of the bulk-electrical parameters of the interior of unknown objects via the use of electromagnetic scattering data. Improvements are considered to both theory and experiments using low-power radiation in the microwave frequency range, known as Microwave Tomography (MWT). A detailed derivation of the Multiplicative-Regularized Contrast-Source Inversion (MR-CSI) method is given, and we compare the performance of MR-CSI with the other leading inversion technique used in MWT: the Gauss Newton/Distorted Born Iterative Method. The inversion results of the two algorithms are very similar, and thus most of the differences between them are in the relative ease of implementation and computational resource use. We further introduce a new version of the CSI algorithm, based on the Finite-Difference method. Using this algorithm, we show that when accurate information about a scatterer is known before the inversion process, this information is best utilized as an artificial computational background, as opposed to an initial guess of the scatterer. The MWT problem is also formulated inside of a conductive enclosure, which significantly changes the physics, and resultant Green's function, of the MWT problem. The implications and possible advantages of this type of MWT are discussed, and synthetic inversion results for a circular enclosed system are presented. These results show that the enclosure is capable of improving the inversion in some regions, although more research is required to realize the full potential of conductive-enclosure MWT. In the final section, experimental results from both open-region and conductor-enclosed type MWT systems developed at the University of Manitoba are shown. For the open-region system, we show that antenna coupling is a major factor affecting the data collection, and provide a simple method for avoiding the frequencies where this coupling is too strong to prevent effective imaging. For the conductor-enclosed type system, we have found the system to be extremely sensitive to presence of antennas in the chamber, and show that effective MWT imaging is possible in this type of system by taking the antenna elements into account in the inverse solver.
343

NIR imaging of vascular endothelial cells using Cy5.5-lectin conjugates

Nguyen, Cecilia 27 February 2012 (has links)
The objective of this study was to develop a fluorescent near-infrared endothelial cell binding conjugate using Lycopersicon esculentum lectin and Cy5.5 N-hydroxysuccinimide ester for the purpose of imaging the microvascular network in mouse hearts under in vivo and ex vivo conditions. Cy5.5-lectin conjugate was synthesized with a dye/protein ratio of 2.90 ± 1.54 (n=6). Mouse hearts were successfully labelled in both in vivo and ex vivo and showed similar labelling patterns. Cy5.5-lectin labelling patterns and that of ICAM2 and FITC-lectin co-localized, indicating binding to endothelial cells. Finally, it was shown that Cy5.5-lectin is capable of visualizing, in real-time, areas of normal and abnormal heart perfusion at resolutions of 76.8 pixels/mm. Areas of the heart that were not perfused post-ligation displayed no Cy5.5 staining on histological sections and during real-time cardiac imaging of intact hearts showed minimal fluorescent signal (~35 a.u.) compared to areas where normal perfusion occurred (~150 a.u.).
344

Probing the Oligomeric Status of G Protein-Coupled Receptors by Forster Resonance Energy Transfer and Single-Particle Fluorescence

Strokach, Alexey 28 November 2013 (has links)
Much evidence indicates that G protein-coupled receptors can form oligomers, but the size and stability of those oligomers has not been well characterised. We used single-particle tracking (SPT) and Förster resonance energy transfer (FRET) to measure the oligomeric size of the M2 muscarinic receptor, a prototypical class A GPCR, in live cells. Single-particle intensity distributions that we obtained for the monomeric control CD86 and the dimeric control CD28 are nearly identical, and no conclusion about the oligomeric size of M2 receptors could be drawn from SPT measurements. FRET measurements allowed us to distinguish the monomeric control CD86 from the dimeric controls CD28 and caveolin-1, and the pattern of efficiencies produced by M2 receptors is similar to the pattern produced by the monomers but not the dimers. The view of M2 muscarinic receptors as transient oligomers appears to be the most consistent with other studies using different biochemical and biophysical techniques.
345

Probing the Oligomeric Status of G Protein-Coupled Receptors by Forster Resonance Energy Transfer and Single-Particle Fluorescence

Strokach, Alexey 28 November 2013 (has links)
Much evidence indicates that G protein-coupled receptors can form oligomers, but the size and stability of those oligomers has not been well characterised. We used single-particle tracking (SPT) and Förster resonance energy transfer (FRET) to measure the oligomeric size of the M2 muscarinic receptor, a prototypical class A GPCR, in live cells. Single-particle intensity distributions that we obtained for the monomeric control CD86 and the dimeric control CD28 are nearly identical, and no conclusion about the oligomeric size of M2 receptors could be drawn from SPT measurements. FRET measurements allowed us to distinguish the monomeric control CD86 from the dimeric controls CD28 and caveolin-1, and the pattern of efficiencies produced by M2 receptors is similar to the pattern produced by the monomers but not the dimers. The view of M2 muscarinic receptors as transient oligomers appears to be the most consistent with other studies using different biochemical and biophysical techniques.
346

Fusion of radar and imaging sensor data for target tracking

Romine, Jay Brent 12 1900 (has links)
No description available.
347

Ultrasonic tapered phased arrays for three-dimensional imaging

Pao, Tsang-Long 05 1900 (has links)
No description available.
348

Subband coding of images with recursive allpass filters using vector quantization

Jeanrenaud, Philippe 12 1900 (has links)
No description available.
349

Subband analysis-synthesis and edge modeling methods for image coding

Eddins, Steven L. 12 1900 (has links)
No description available.
350

Magnetic resonance imaging measurements of pulsatile hemodynamics in a model of the human abdominal aorta

Moore, James E., Jr. 05 1900 (has links)
No description available.

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