• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1677
  • 1354
  • 299
  • 188
  • 89
  • 75
  • 52
  • 44
  • 29
  • 23
  • 16
  • 15
  • 15
  • 15
  • 15
  • Tagged with
  • 4562
  • 1743
  • 1295
  • 895
  • 761
  • 627
  • 623
  • 562
  • 544
  • 465
  • 463
  • 446
  • 432
  • 406
  • 405
  • 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.

Enhanced polarization-sensitive optical coherence tomography (EPS-OCT) for characterization of tissue anisotropy

Kemp, Nathaniel Joseph 28 August 2008 (has links)
Not available / text

Scattering correction and image restoration in neutron radiography and computed tomography

Abdelrahman, Magdy Shehata 04 April 2011 (has links)
Not available / text

A HRCT and immunohistochemistry study on bronchiectasis

Lam, Sing-chi., 藍承志. January 2004 (has links)
published_or_final_version / abstract / toc / Diagnostic Radiology / Master / Master of Research in Medicine

Respiratory motion correction for positron emission tomography

Dikaios, Nikolaos January 2012 (has links)
No description available.

Tomographic Reconstruction of Wavefront Aberrations using Multiple Laser Guide Stars

Milton, Norman Mark January 2009 (has links)
Tomographic reconstruction using multiple laser guide stars (MLGS) will be required by the next generation of extremely large (30 m class) telescopes (ELT). Modal decomposition of wavefront phase using Zernike polynomials is a widely used technique in adaptive optics (AO) research. However, this approach breaks down with the large number of degrees of freedom required by ELTs.This research proposes the use of an alternative basis, the disk harmonic functions, to overcome the disadvantages of the Zernike basis at high spatial resolution. A method of fast, analytic, modal tomographic modeling is developed and used for fast calculation of reconstruction matrices used on-sky at the MMT telescope.The specific reconstruction techniques of ground layer adaptive optics and laser tomography adaptive optics using MLGS are presented along with the results of on-sky experiments at the MMT. In addition to developing a laser AO instrument for the MMT, these experiments provide a test bed for validating the reconstruction techniques that will be critical to the success of ELTs.An approach to using real-time wavefront sensor and deformable mirror telemetry from the MLGS system to estimate the vertical distribution of turbulence in the atmosphere is also presented.

Stochastic Estimation of Hydraulic Spatial Properties

Xiang, Jianwei January 2007 (has links)
A tomographic survey provides different coverages and perspectives on subsurface heterogeneity--incompletely overlapping information about the subsurface. Fusion of these pieces of information expands and enhances the capability of a conventional survey, provides cross-validation, and constrains inherently ill-posed field-scale inverse problems. In this study, we explore the possibility of using river stage variation for basin-scale subsurface tomographic surveys. Basin-scale tomography requires energy sources of great strengths; spatially and temporally varying natural stimuli are ideal energy sources for this purpose. Specifically, we use numerical models to simulate groundwater level changes in response to temporal and spatial variations of river stage in a hypothetical groundwater basin. We then exploit the relation between temporal and spatial variations of well hydrographs and river stage to image the heterogeneous characteristics of the basin.Next, we apply the hydraulic tomography testing technique and analysis algorithm to synthetic fractured media. The application aims to explore the potential utility of the technique and the algorithm for characterizing fracture zone distribution and their connectivity. Results of this investigation show that using hydraulic tomography with a limited number of wells can map satisfactorily the fracture zone distribution and the general pattern of its connectivity although estimated hydraulic property fields are smooth. As the number of wells and monitoring ports increases, the fracture zone distribution and connectivity becomes more vivid and the estimated hydraulic properties approach the true values.Further we develop a new parameter identification method that allows for simultaneous inclusion of all observed hydrographs from hydraulic tomography to map aquifer heterogeneity. A procedure is then recommended to diagnose and denoise observed hydrographs. Subsequently, we introduce methods that exploit these processed hydrographs for estimating effective parameters, boundary conditions, and statistical spatial structures of heterogeneity, which are the required inputs for the new hydraulic tomography analysis method. This new method and the data processing procedure are tested in a synthetic aquifer and subsequently applied to a sand box experiment. The estimated parameter fields for the sand box experiment are validated by predicting the head distribution induced by an independent pumping test, which was not used in the hydraulic tomography analysis.

Characterization of silicon photomultiplier readout designs for use in positron emission tomography systems

Liu, Chen-Yi 29 October 2011 (has links)
Geiger-mode avalanche photodiodes, or silicon photomultipliers, are promising light sensors for the next generation Positron Emission Tomography (PET) scanners. The sensor is being used in the scanner’s gamma ray detector to measure scintillation light. This thesis describes the test results of three gamma ray detectors that utilize silicon photomultipliers. The first one is a commercial detector, and the other two are custom made. The detectors are tested for their 511 keV photon energy and timing resolution, as well as their ability to measure light from small scintillator crystals. The two custom made detectors had smaller active area, but outperformed the commercial detector in energy resolution. The introduction of buffer amplifiers improved the timing resolution of one detector. All three detectors had their crystal decoding ability limited by signal multiplexing and the sensor’s dark noise. Finally, a detector design was proposed for the PET system being developed in our group.

A technique for improving data acquisition and resolution in positron emission tomography /

Dagher, Alain. January 1985 (has links)
No description available.

Quantitation in positron emission tomography

Strother, S. C. (Steven Charles), 1955- January 1986 (has links)
No description available.

Combining positron emission tomography (PET) data with neuroanatomical constraints : comparing models of single-word processing

Nikelski, Erwin James. January 1996 (has links)
The focus of this paper is to apply some of the new analytic techniques to positron emission tomography (PET) data in order to test the neuroanatomical plausibility of two very specific models of language processing: the model of Geschwind (1965), and that of Petersen et al. (1988; 1989). Model plausibility was assessed by fitting both models to a word repetition and a synonym generation rCBF PET dataset using methods based on the examination of interregional correlations, and structural equation modeling. / Physiologically-based regions of interest were defined a priori through a review of PET activation literature. The current study demonstrated (1) the feasibility of using a priori defined physiological regions of interest in model evaluation, (2) the advantages of using structural equation modeling over interregional correlations, and (3) that neither model proved to be a particularly good fit to the data.

Page generated in 0.0736 seconds