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Algorithm for Rapid Tomography of Gas Concentrations

Description: We present a new computed tomography method, the low third derivative (LTD) method, that is particularly suited for reconstructing the spatial distribution of gas concentrations from path-integral data for a small number of optical paths. The method finds a spatial distribution of gas concentrations that (1) has path integrals that agree with measured path integrals, and (2) has a low third spatial derivative in each direction, at every point. The trade-off between (1) and (2) is controlled by an adjustable parameter, which can be set based on analysis of the path-integral data. The method produces a set of linear equations, which can be solved with a single matrix multiplication if the constraint that all concentrations must be positive is ignored; the method is therefore extremely rapid. Analysis of experimental data from thousands of concentration distributions shows that the method works nearly as well as Smooth Basis Function Minimization (the best method previously available), yet is 100 times faster.
Date: June 27, 2000
Creator: Price, P.N.; Fischer, M.L.; Gadgil, A.J. & Sextro, R.G.
Partner: UNT Libraries Government Documents Department

Computed tomography:the details.

Description: Computed Tomography (CT) is a well established technique, particularly in medical imaging, but also applied in Synthetic Aperture Radar (SAR) imaging. Basic CT imaging via back-projection is treated in many texts, but often with insufficient detail to appreciate subtleties such as the role of non-uniform sampling densities. Herein are given some details often neglected in many texts.
Date: July 1, 2007
Creator: Doerry, Armin Walter
Partner: UNT Libraries Government Documents Department

Multi-Modality Phantom Development

Description: Multi-modality imaging has an increasing role in the diagnosis and treatment of a large number of diseases, particularly if both functional and anatomical information are acquired and accurately co-registered. Hence, there is a resulting need for multi modality phantoms in order to validate image co-registration and calibrate the imaging systems. We present our PET-ultrasound phantom development, including PET and ultrasound images of a simple prostate phantom. We use agar and gelatin mixed with a radioactive solution. We also present our development of custom multi-modality phantoms that are compatible with PET, transrectal ultrasound (TRUS), MRI and CT imaging. We describe both our selection of tissue mimicking materials and phantom construction procedures. These custom PET-TRUS-CT-MRI prostate phantoms use agargelatin radioactive mixtures with additional contrast agents and preservatives. We show multi-modality images of these custom prostate phantoms, as well as discuss phantom construction alternatives. Although we are currently focused on prostate imaging, this phantom development is applicable to many multi-modality imaging applications.
Date: March 20, 2009
Creator: Huber, Jennifer S.; Peng, Qiyu & Moses, William W.
Partner: UNT Libraries Government Documents Department

Three-dimensional architecture of hair-cell linkages as revealedby electron-microscopic tomography

Description: The senses of hearing and balance rest upon mechanoelectrical transduction by the hair bundles of hair cells in the inner ear. Located at the apical cellular surface, each hair bundle comprises several tens of stereocilia and a single kinocilium that are interconnected by extracellular proteinaceous links. Using electron-microscopic tomography of bullfrog saccular sensory epithelia, we examined the three-dimensional structures of ankle or basal links, kinociliary links, and tip links. We observed clear differences in the dimensions and appearances of the three links. We found two distinct populations of tip links suggestive of the involvement of two proteins or splice variants. We noted auxiliary links connecting the upper portions of tip links to the taller stereocilia. Tip links and auxiliary links show a tendency to adopt a globular conformation when disconnected from the membrane surface.
Date: July 28, 2006
Creator: Auer, Manfred; Koster, Bram; Ziese, Ulrike; Bajaj, Chandrajit; Volkmann, Niels; Wang, Da Neng et al.
Partner: UNT Libraries Government Documents Department

Marmousi-2: An Updated Model for the Investigation of AVO in Structurally Complex Areas

Description: We have created an elastic version of the IFF Marmousi model for use in AVO analysis in the presence of complex structure. The model is larger, includes larger offsets, lies in deeper water, includes surface streamer, multicomponent OBC and VSP acquisition, and contains more hydrocarbons than its predecessor. In addition to AVO analysis, we believe these data will be suitable for calibrating emerging technologies including converted wave tomography and vector seismic processing.
Date: April 30, 2002
Creator: Martin, G.S.; Marfurt, K.J. & Larsen, S.
Partner: UNT Libraries Government Documents Department

Grain boundary characterization in an X750 alloy

Description: Grain boundary chemistry in an X750 Ni alloy was analyzed by atom probe tomography in an effort to clarify the possible roles of elemental segregation and carbide presence on the stress corrosion cracking behavior of Ni alloys. Two types of cracks are observed: straight cracks along twin boundaries and wavy cracks at general boundaries. It was found that carbides (M23C6 and TiC) are present at both twin and general boundaries, with comparable B and P segregation for all types of grain boundaries. Twin boundaries intercept ?’ precipitates while the general boundaries wave around the ?’ and carbide precipitates. Near a crack tip, oxidation takes place on the periphery of carbide precipitate.
Date: November 1, 2012
Creator: Fisher, Kevin; Teysseyre, Sebastien & Marquis, Emmanuelle
Partner: UNT Libraries Government Documents Department

Demonstration of Emitted-Neutron Computed Tomography to Count Fuel Pins

Description: In this paper, we report demonstration of emitted-neutron computed tomography using fast fission neutrons to infer the geometry of sources of special nuclear material (SNM) such as fuel pins. In a proof-of-concept measurement at the Idaho National Laboratory’s (INL’s) Zero Power Physics Reactor (ZPPR) facility, an array of unirradiated Pu MOX fuel rodlets in a soup can were imaged, and a bias defect consisting of a single rodlet containing Pu replaced by one containing depleted uranium (DU) was detected. The imaging system employed in the demonstration is based on a newly constructed array of pixelated neutron detectors that are suitable for arrangement in a close-packed imaging array and whose active volume consists of liquid scintillator EJ-309 which allows neutron-gamma discrimination via pulse shape to enable pure fast-neutron imaging. The imaging array was used along with a radial collimator aperture in order to perform high quality fast-neutron imaging where tomographic reconstruction of slices through an object resolve neutron sources similar in dimension to a fuel pellet, or about 1 cm. Measurements were performed at Oak Ridge National Laboratory (ORNL) with neutron sources in addition to those performed at the INL’s ZPPR facility with Pu MOX fuel rodlets. An analogous capability to detect single-pin defects in spent fuel assemblies would be desirable, such as for safeguards verification measurements of spent fuel assemblies just prior to transferring them from the spent fuel cooling pool to long term dry cask storage. This paper describes the design and construction of the present imager, characterization measurements with neutron sources at ORNL, measurements with SNM at INL’s ZPPR facility, and feasibility of building an analogous imager for spent fuel measurements.
Date: July 1, 2012
Creator: Hausladen, P. A.; Blackston, M. A.; Brubaker, E.; Chichester, D. L.; Marleau, P. & Newby, R. J.
Partner: UNT Libraries Government Documents Department

Position Ring System using Anger Type Detectors

Description: The overall objective of our project was to develop PET scanners and imaging techniques that achieve high performance and excellent image quality. Our approach was based upon 3-D imaging (no septa) with position-sensitive Anger-logic detectors, whereby the encoding ratio of resolution elements to number of photo-multiplier tube channels is very high. This design led to a series of PET systems that emphasized cost-effectiveness and practicality in a clinical environment.
Date: December 14, 2004
Creator: Joel S. Karp, principal investigator
Partner: UNT Libraries Government Documents Department

An Ultra-Precise System for Electrical Resistivity Tomography Measurements

Description: The objective of this research was to determine the feasibility of building and operating an ERT system that will allow measurement precision that is an order of magnitude better than existing systems on the market today and in particular if this can be done without significantly greater manufacturing or operating costs than existing commercial systems. Under this proposal, we performed an estimation of measurement errors in galvanic resistivity data that arise as a consequence of the type of electrode material used to make the measurements. In our laboratory, measurement errors for both magnitude and induced polarization (IP) were estimated using the reciprocity of data from an array of electrodes as might be used for electrical resistance tomography using 14 different metals as well as one non-metal - carbon. In a second phase of this study, using archival data from two long-term ERT surveys, we examined long-term survivability of electrodes over periods of several years. The survey sites were: the Drift Scale Test at Yucca Mountain, Nevada (which was sponsored by the U. S. Department of Energy as part of the civilian radioactive waste management program), and a water infiltration test at a site adjacent to the New Mexico Institute of Mines and Technology in Socorro, New Mexico (sponsored by the Sandia/Tech vadose program). This enabled us to compare recent values with historical values and determine electrode performance over the long-term as well as the percentage of electrodes that have failed entirely. We have constructed a prototype receiver system, made modifications and revised the receiver design. The revised prototype uses a new 24 bit analog to digital converter from Linear Technologies with amplifier chips from Texas Instruments. The input impedance of the system will be increased from 107 Ohms to approximately 1010 Ohms. The input noise level of the system has ...
Date: December 9, 2008
Creator: LaBrecque, Douglas J & Adkins, Paula L
Partner: UNT Libraries Government Documents Department

Scattered Neutron Tomography Based on A Neutron Transport Inverse Problem

Description: Neutron radiography and computed tomography are commonly used techniques to non-destructively examine materials. Tomography refers to the cross-sectional imaging of an object from either transmission or reflection data collected by illuminating the object from many different directions.
Date: July 1, 2007
Creator: Charlton, William
Partner: UNT Libraries Government Documents Department

Policy Implications of the Computed Tomography (CT) Scanner

Description: A report by the Office of Technology Assessment (OTA) that looks specifically at the Computed Tomography (CT) scanner and examines "current Federal policies and current medical practices to determine whether a reasonable amount of justification should be provided before costly new medical technologies and procedures are put into general use," (quoted from p. iii).
Date: November 1978
Creator: United States. Congress. Office of Technology Assessment.
Partner: UNT Libraries Government Documents Department

Computed tomography status

Description: Computed tomography (CT) is a relatively new radiographic technique which has become widely used in the medical field, where it is better known as computerized axial tomographic (CAT) scanning. This technique is also being adopted by the industrial radiographic community, although the greater range of densities, variation in samples sizes, plus possible requirement for finer resolution make it difficult to duplicate the excellent results that the medical scanners have achieved.
Date: January 1, 1983
Creator: Hansche, B.D.
Partner: UNT Libraries Government Documents Department

Microaspiration for high-pressure freezing: a new method for ultrastructural preservation of fragile and sparse tissues for TEM and electron tomography

Description: High-pressure freezing is the preferred method to prepare thick biological specimens for ultrastructural studies. However, the advantages obtained by this method often prove unattainable for samples that are difficult to handle during the freezing and substitution protocols. Delicate and sparse samples are difficult to manipulate and maintain intact throughout the sequence of freezing, infiltration, embedding, and final orientation for sectioning and subsequent TEM imaging. An established approach to surmount these difficulties is the use of cellulose microdialysis tubing to transport the sample. With an inner diameter of 200 micrometers, the tubing protects small and fragile samples within the thickness constraints of high-pressure freezing, and the tube ends can be sealed to avoid loss of sample. Importantly, the transparency of the tubing allows optical study of the specimen at different steps in the process. Here, we describe the use of a micromanipulator and microinjection apparatus to handle and position delicate specimens within the tubing. We report two biologically significant examples that benefit from this approach, 3D cultures of mammary epithelial cells and cochlear outer hair cells. We illustrate the potential for correlative light and electron microscopy as well as electron tomography.
Date: February 13, 2008
Creator: Auer, Manfred; Triffo, W.J.; Palsdottir, H.; McDonald, K.L.; Inman, J.L.; Bissell, M.J. et al.
Partner: UNT Libraries Government Documents Department

Quantitative Clinical Evaluation of a Simultaneous PETI MRI Breast Imaging System

Description: A prototype simultaneous PET-MRI breast scanner has been developed for conducting clinical studies with the goal of obtaining high resolution anatomical and functional information in the same scan which can lead to faster and better diagnosis, reduction of unwanted biopsies, and better patient care.
Date: April 3, 2013
Creator: J., Schlyer D. & Schlyer, D.J.
Partner: UNT Libraries Government Documents Department

Digital Radiography and Computed Tomography (DRCT) Product Improvement Plan (PIP)

Description: The Idaho National Laboratory (INL) has been developing and deploying x-ray inspection systems for chemical weapons containers for the past 12 years under the direction of the Project Manager for Non-Stockpile Chemical Materiel (PMNSCM). In FY-10 funding was provided to advance the capabilities of these systems through the DRCT (Digital Radiography and Computed Tomography) Product Improvement Plan (PIP), funded by the PMNSCM. The DRCT PIP identified three research tasks; end user study, detector evaluation and DRCT/PINS integration. Work commenced in February, 2010. Due to the late start and the schedule for field inspection of munitions at various sites, it was not possible to spend sufficient field time with operators to develop a complete end user study. We were able to interact with several operators, principally Mr. Mike Rowan who provided substantial useful input through several discussions and development of a set of field notes from the Pueblo, CO field mission. We will be pursuing ongoing interactions with field personnel as opportunities arise in FY-11.
Date: December 1, 2010
Creator: Roney, Tim; Pink, Bob; Wendt, Karen; Seifert, Robert & Smith, Mike
Partner: UNT Libraries Government Documents Department

Final Report 2007: DOE-FG02-87ER60561

Description: This project involved a multi-faceted approach to the improvement of techniques used in Positron Emission Tomography (PET), from radiochemistry to image processing and data analysis. New methods for radiochemical syntheses were examined, new radiochemicals prepared for evaluation and eventual use in human PET studies, and new pre-clinical methods examined for validation of biochemical parameters in animal studies. The value of small animal PET imaging in measuring small changes of in vivo biochemistry was examined and directly compared to traditional tissue sampling techniques. In human imaging studies, the ability to perform single experimental sessions utilizing two overlapping injections of radiopharmaceuticals was tested, and it was shown that valid biochemical measures for both radiotracers can be obtained through careful pharmacokinetic modeling of the PET emission data. Finally, improvements in reconstruction algorithms for PET data from small animal PET scanners was realized and these have been implemented in commercial releases. Together, the project represented an integrated effort to improve and extend all basic science aspects of PET imaging at both the animal and human level.
Date: April 26, 2007
Creator: Kilbourn, Michael R
Partner: UNT Libraries Government Documents Department

P- and S-body wave tomography of the state of Nevada.

Description: P- and S-body wave travel times collected from stations in and near the state of Nevada were inverted for P-wave velocity and the Vp/Vs ratio. These waves consist of Pn, Pg, Sn and Sg, but only the first arriving P and S waves were used in the inversion. Travel times were picked by University of Nevada Reno colleagues and were culled for inclusion in the tomographic inversion. The resulting tomographic model covers the entire state of Nevada to a depth of {approx}90 km; however, only the upper 40 km indicate relatively good resolution. Several features of interest are imaged including the Sierra Nevada, basin structures, and low velocities at depth below Yucca Mountain. These velocity structure images provide valuable information to aide in the interpretation of geothermal resource areas throughout the state on Nevada.
Date: April 1, 2010
Creator: Preston, Leiph
Partner: UNT Libraries Government Documents Department

Image reconstruction for a Positron Emission Tomograph optimized for breast cancer imaging

Description: The author performs image reconstruction for a novel Positron Emission Tomography camera that is optimized for breast cancer imaging. This work addresses for the first time, the problem of fully-3D, tomographic reconstruction using a septa-less, stationary, (i.e. no rotation or linear motion), and rectangular camera whose Field of View (FOV) encompasses the entire volume enclosed by detector modules capable of measuring Depth of Interaction (DOI) information. The camera is rectangular in shape in order to accommodate breasts of varying sizes while allowing for soft compression of the breast during the scan. This non-standard geometry of the camera exacerbates two problems: (a) radial elongation due to crystal penetration and (b) reconstructing images from irregularly sampled data. Packing considerations also give rise to regions in projection space that are not sampled which lead to missing information. The author presents new Fourier Methods based image reconstruction algorithms that incorporate DOI information and accommodate the irregular sampling of the camera in a consistent manner by defining lines of responses (LORs) between the measured interaction points instead of rebinning the events into predefined crystal face LORs which is the only other method to handle DOI information proposed thus far. The new procedures maximize the use of the increased sampling provided by the DOI while minimizing interpolation in the data. The new algorithms use fixed-width evenly spaced radial bins in order to take advantage of the speed of the Fast Fourier Transform (FFT), which necessitates the use of irregular angular sampling in order to minimize the number of unnormalizable Zero-Efficiency Bins (ZEBs). In order to address the persisting ZEBs and the issue of missing information originating from packing considerations, the algorithms (a) perform nearest neighbor smoothing in 2D in the radial bins (b) employ a semi-iterative procedure in order to estimate the unsampled data and (c) ...
Date: April 1, 2000
Creator: Virador, Patrick R.G.
Partner: UNT Libraries Government Documents Department

Detection and Assessment Using Positron Emission Tomography of Genetically Determined Defects in Myocardial Fatty Acid Utilization. Final report, 8/1/93-6/30/97

Description: An approach using positron emission tomography (PET) was developed, validated and used to measure myocardial fatty acid metabolism in patients with inherited forms of heart failure. Abnormalities were correlated with the severity of the clinical illness. The approach developed was also shown to identify abnormalities in myocardial fatty acid metabolism in some patients with acquired forms of heart failure. The PET technique thus permits identification of abnormal fatty acid metabolism and provides an approach to evaluate the efficacy of interventional strategies.
Date: April 9, 2000
Creator: Bergmann, Steven R.
Partner: UNT Libraries Government Documents Department