273 Matching Results

Search Results

Advanced search parameters have been applied.

Polarized light propagation through tissue and tissue phantoms

Description: We show that standard tissue phantoms can be used to mimic the intensity and polarization properties of tissue. Polarized light propagation through biologic tissue is typically studied using tissue phantoms consisting of dilute aqueous suspensions of microspheres. The dilute phantoms can empirically match tissue polarization and intensity properties. One discrepancy between the dilute phantoms and tissue exist: common tissue phantoms, such as dilute Intralipid and dilute 1-{micro}m-diameter polystyrene microsphere suspensions, depolarize linearly polarized light more quickly than circularly polarized light. In dense tissue, however, where scatterers are often located in close proximity to one another, circularly polarized light is depolarized similar to or more quickly than linearly polarized light. We also demonstrate that polarized light propagates differently in dilute versus densely packed microsphere suspensions, which may account for the differences seen between polarized light propagation in common dilute tissue phantoms versus dense biologic tissue.
Date: February 8, 2000
Creator: Sankaran, V; Walsh, J T JR & Maitland, D J
Partner: UNT Libraries Government Documents Department

Ultrasonic Calibration Wire Test Phantom

Description: We designed and built a phantom consisting of vertical wires maintained under tension to be used as an ultrasonic test, calibration, and reconstruction object for the Lawrence Livermore National Laboratory annular array scanner. We provide a description of the phantom, present example data sets, preliminary reconstructions, example metadata, and MATLAB codes to read the data.
Date: September 24, 2004
Creator: Lehman, S K; Fisher, K A; Werve, M & Chambers, D H
Partner: UNT Libraries Government Documents Department

Microwave Hematoma Detector for the Rapid Assessment of Head Injuries

Description: A non-invasive microwave device for the detection of epi/subdural hemorrhaging (hematoma) is under current development. The final device will be highly portable and allow real time assessment of head injuries, thereby satisfying early detection needs of the field technician as well as providing a tool for repetitious monitoring of high-risk individuals. The device will adopt the advanced technology of micropower impulse radar (MIR) which is a state of the art low cost ultra wide band (UWB) microwave radar developed here at LLNL. It will consist of a MIR transmitting and receiving module, a computer based signal processing module, and a device-to-patient signal coupling module--the UWB antenna. The prototype design is being guided by the needs of the patient and the practitioner along with the prerequisites of the technology including issues such as the specificity of the device, efficacy of diagnosis, accuracy, robustness, and patient comfort. The prototype development follows a concurrent approach which .includes experiments designed to evaluate requirements of the radar and antenna design, phantom development to facilitate laboratory investigations, and investigation into the limits of adapting pre-existing non-medical MIR devices to medical applications. This report will present the accomplishments and project highlights to date in the fiscal year 1999. Future project projections will also be discussed.
Date: February 11, 2000
Creator: Hadded, W.; Chang, J.; Rosenbury, T.; Dallum, G.; Welsch, P.; Scott, D. et al.
Partner: UNT Libraries Government Documents Department

An in-phantom comparison of neutron fields for BNCT

Description: Previously, the authors have developed the in-phantom neutron field assessment parameters T and D (Tumor) for the evaluation of epithermal neutron fields for use in BNCT. These parameters are based on an energy-spectrum-dependent neutron normal-tissue RBE and the treatment planning methodology of Gahbauer and his co-workers, which includes the effects of dose fractionation. In this paper, these neutron field assessment parameters were applied to The Ohio State University (OSU) design of an Accelerator Based Neutron Source (ABNS) (hereafter called the OSU-ABNS) and the Brookhaven Medical Research Reactor (BMRR) epithermal neutron beam (hereafter called the BMRR-ENB), in order to judge the suitability of the OSU-ABNS for BNCT. The BMRR-ENB was chosen as the basis for comparison because it is presently being used in human clinical trials of BNCT and because it is the standard to which other neutron beams are most often compared.
Date: January 1, 1998
Creator: Woollard, J.E.; Blue, T.E. & Capala, J.
Partner: UNT Libraries Government Documents Department

First Results for a Novel Superconducting Imaging-Surface Sensor Array

Description: A superconducting imaging-surface system was constructed using 12 coplanar thin-film SQUID magnetometers located parallel to and spaced 2 cm from a 25 cm diameter lead imaging-plane. Some measurements included two additional sensors on the ''back'' side of the superconducting imaging-plane to study the field symmetry for our system. Performance was measured in a shielded can and in the open laboratory environment. Data from this system has been used to: (a) understand the noise characteristics of the dewar-SQUID imaging plate arrangement, (b) to verify the imaging principle, (c) measure the background rejection factor of the imaging plane, and (d) compare superconducting materials for the imaging plane. A phantom source field was measured at the sensors as a function of phantom distance from the sensor array to verify the imaging theory. Both the shape and absolute value of the measured and predicted curves agree very well indicating the system is behaving as a gradiometer in accordance with theory. The output from SQUIDs located behind the imaging surface that sense background fields can be used for software or analog background cancellation. Fields arising from sources close to the imaging plane were shielded form the background sensors by more than a factor of 1000. Measurement of the symmetry of sensor sensitivity to uniform fields exactly followed theoretical predictions.
Date: September 13, 1998
Creator: Kraus, R.R.; Flynn, E.R.; Espy, M.A.; Matlashov, A.; Overton, W.; Peters, M.V. et al.
Partner: UNT Libraries Government Documents Department

Optimization of Dedicated Scintimammography Procedure Using Detector Prototypes and Compressible Phantoms

Description: Results are presented on the optimization of the design and use of dedicated compact scintimammography gamma cameras. Prototype imagers with a field-of-view (FOV) of 5 cm x 5 cm, 10 cm x 10 cm and 15 cm x 20 cm were used in either a dual modality mode as an adjunct technique to digital x-ray mammography imagers or as stand-alone instruments such as dedicated breast SPECT and planar imagers. Experimental data was acquired to select the best imaging modality (SPECT or planar) to detect small lesions using Tc{sup 99m} radio-labeled pharmaceuticals. In addition, studies were preformed to optimize the imaging geometry. Results suggest that the preferred imaging geometry is planar imaging with two opposing detector heads while the breast is under compression, however further study of the dedicated breast SPECT is warranted.
Date: October 1, 2000
Creator: Majewski, S.; Kieper, D.; Curran, E.; Keppel, C.; Kross, B.; Palumbo, A. et al.
Partner: UNT Libraries Government Documents Department

Dual energy iodine contrast CT with monochromatic x-rays

Description: Computed tomography (CT) with monochromatic x-ray beams was used to image phantoms and a live rabbit using the preclinical Multiple Energy Computed Tomography (MECT) system at the National Synchrotron Light Source. MECT has a horizontal fan beam with a subject apparatus rotating about a vertical axis. Images were obtained at 43 keV for single-energy studies, and at energies immediately below and above the 33.17 keV iodine K-edge for dual-energy subtraction CT. Two CdWO{sub 4}-photodiode array detectors were used. The high-resolution detector (0.5 mm pitch, uncollimated) provided 14 line pair/cm in-plane spatial resolution, with lower image noise than conventional CT. Images with the low-resolution detector (1.844-mm pitch, collimated to 0.922 mm detector elements) had a sensitivity for iodine of {approx} 60 {micro}g/cc in 11-mm channels inside a 135 mm-diameter acrylic cylindrical phantom for a slice height of 2.5 mm and a surface does of {approx} 4 cGy. The image noise was {approx} 1 Hounsfield Unit (HU); it was {approx} 3 HU for the same phantom imaged with conventional CT at approximately the same dose, slice height, and spatial resolution ({approx} 7 lp/cm). These results show the potential advantage of MECT, despite present technical limitations.
Date: December 31, 1995
Creator: Dilmanian, F.A.; Wu, X.Y. & Kress, J.
Partner: UNT Libraries Government Documents Department

Polarized Light Propagation in Biological Tissue and Tissue Phantoms

Description: Imaging through biologic tissue relies on the discrimination of weakly scattered from multiply scattered photons. The degree of polarization can be used as the discrimination criterion by which to reject multiply scattered photons. Polarized light propagation through biologic tissue is typically studied using tissue phantoms consisting of dilute aqueous suspensions of microsphere. We show that, although such phantoms are designed to match the macroscopic scattering properties of tissue (i.e.. the scattering coefficient, {mu}{sub 3}, and scattering anisotropy, g), they do not accurately represent biologic tissue for polarization-sensitive studies. In common tissue phantoms, such as dilute Intralipid and dilute 1-{micro}m-diameter polystyrene microsphere suspensions, we find that linearly polarized light is depolarized more quickly than circularly polarized light. In dense tissue, however, where scatterers are often located in close proximity to one another, circularly polarized light is depolarized similar to or more quickly than linearly polarized light. We also demonstrate that polarized light propagates differently in dilute versus densely packed microsphere suspensions, which may account for the differences seen between polarized light propagation in common dilute tissue phantoms versus dense biologic tissue.
Date: December 10, 1999
Creator: Sankaran, V.; Walsh, J.T. & Maitland, D.
Partner: UNT Libraries Government Documents Department

Air Kerma Calibration Factors and kch Values for PTW Soft X-ray, NACP and Roos Ionization Chambers at Very Low X-ray Energies (0.035 mm - 1.0 mm Al HVL)

Description: Several national and international protocols have been established for the dosimetry of x-ray beams used in radiotherapy. For the very low energy x-rays (0.035mm-1.0 mm Al HVL) only two codes are available: the UK IPEMB Code of Practice and the German standard, DIN 6809 Part 4. The measurement of very low energy x-ray beams is normally performed with parallel plate ionization chambers calibrated at a standards laboratory and characterized by an air kerma calibration factor N{sub k}. According to the IPEMB Code of Practice the absorbed dose in the user's beam should be determined by taking measurements with the parallel plate chamber positioned such that its entrance window is at the surface of a full-scatter water equivalent phantom. The absorbed dose to water can then be determined using an equation which includes a factor, k{sub ch}, which accounts for the change in response of the ionization chamber between the calibration in air and measurement at the surface of the phantom. N{sub k} and k{sub ch} values for the PTW soft X-ray, NACP and Roos ionization chambers are reported. It was found that k{sub ch} values varied from about 1.01 to 1.08 depending on the chamber, beam quality and phantom material. It is recommended that the IPEMB Code of Practice should be revised to incorporate these values.
Date: July 8, 1999
Creator: Ipe, Nisy E.
Partner: UNT Libraries Government Documents Department

Creation of a Reference Image with Monte Carlo Simulations for Online EPID Verification of Daily Patient Setup

Description: Patient positioning accuracy remains an issue for external beam radiotherapy. Currently, kilovoltage verification images are used as reference by clinicians to compare the actual patient treatment position with the planned position. These images are qualitatively different from treatment-time megavoltage portal images. This study will investigate the feasibility of using PEREGRINE, a 3D Monte Carlo calculation engine, to create reference images for portal image comparisons. Portal images were acquired using an amorphous-silicon flat-panel EPID for (1) the head and pelvic sections of an anthropomorphic phantom with 7-8 mm displacements applied, and (2) a prostate patient on five treatment days. Planning CT scans were used to generate simulated reference images with PEREGRINE. A correlation algorithm quantified the setup deviations between simulated and portal images. Monte Carlo simulated images exhibit similar qualities to portal images, the phantom slabs appear clearly. Initial positioning differences and applied displacements were detected and quantified. We find that images simulated with Monte Carlo methods can be used as reference images to detect and quantify set-up errors during treatment.
Date: January 30, 2002
Creator: Descalle, M-A; Chuang, C & Pouliot, J
Partner: UNT Libraries Government Documents Department

Edge Zonal Flows and Blob Propagation in Alcator C-Mod

Description: Here we describe recent measurements of the 2-D motion of turbulence in the edge and scrape-off layer (SOL) of the Alcator C-Mod tokamak. This data was taken using the outer midplane gas puff imaging (GPI) camera, which views a 6 cm radial by 6 cm poloidal region near the separatrix just below the outer midplane [1]. The data were taken in Ohmic or RF heated L-mode plasmas at 400,000 frames/sec for {approx}50 msec/shot using a Phantom 710 camera in a 64 x 64 pixel format. The resulting 2-D vs. time movies [2] can resolve the structure and motion of the turbulence on a spatial scale covering 0.3-6 cm. The images were analyzed using either a 2-D cross-correlation code (Sec. 2) or a 2-D blob tracking code (Sec. 3).
Date: July 25, 2011
Creator: Zweben, S; Agostini, M; Davis, B; Grulke, O; Hager, R; Hughes, J et al.
Partner: UNT Libraries Government Documents Department

SQUID-Detected Microtesla MRI in the presence of Metal

Description: In magnetic resonance imaging (MRI) performed at fields of 1 T and above, the presence of a metal insert can distort the image because of susceptibility differences within the sample and modification of the radiofrequency fields by screening currents. Furthermore, it is not feasible to perform nuclear magnetic resonance (NMR) spectroscopy or acquire a magnetic resonance image if the sample is enclosed in a metal container. Both problems can be overcome by substantially lowering the NMR frequency. Using a microtesla imaging system operating at 2.8 kHz, with a superconducting quantum interference device (SQUID) as the signal detector, we have obtained distortion-free images of a phantom containing a titanium bar and three-dimensional images of an object enclosed in an aluminum can; in both cases high-field images are inaccessible.
Date: September 6, 2006
Creator: Moessle, Michael; Han, Song-I.; Myers, Whittier; Lee, Seung-Kyun; Kelso, Nathan; Hatridge, Michael et al.
Partner: UNT Libraries Government Documents Department

Influence of Manufacturing Processes on the Performance of Phantom Lungs

Description: Chest counting is an important tool for estimating the radiation dose to individuals who have inhaled radioactive materials. Chest counting systems are calibrated by counting the activity in the lungs of phantoms where the activity in the phantom lungs is known. In the United States a commonly used calibration phantom was developed at the Lawrence Livermore National Laboratory and is referred to as the Livermore Torso Phantom. An important feature of this phantom is that the phantom lungs can be interchanged so that the counting system can be challenged by different combinations of radionuclides and activity. Phantom lungs are made from lung tissue substitutes whose constituents are foaming plastics and various adjuvants selected to make the lung tissue substitute similar to normal healthy lung tissue. Some of the properties of phantom lungs cannot be readily controlled by phantom lung manufacturers. Some, such as density, are a complex function of the manufacturing process, while others, such as elemental composition of the bulk plastic are controlled by the plastics manufacturer without input, or knowledge of the phantom manufacturer. Despite the fact that some of these items cannot be controlled, they can be measured and accounted for. This report describes how manufacturing processes can influence the performance of phantom lungs. It is proposed that a metric that describes the brightness of the lung be employed by the phantom lung manufacturer to determine how well the phantom lung approximates the characteristics of a human lung. For many purposes, the linear attenuation of the lung tissue substitute is an appropriate surrogate for the brightness.
Date: October 1, 2008
Creator: Traub, Richard J.
Partner: UNT Libraries Government Documents Department

Final Scientific/Technical Report

Description: Boeing Phantom Works and its team originally proposed a three-year Phase III SPI project to develop a 30-kWh flywheel with a 100 kW power capability as a power risk management system (RMS) for power users and providers. The chief objectives for the Risk Management System Flywheel were to (1) demonstrate its ability to protect a critical load such as a small data center from swings in power availability, cost, and power factor and (2) show that the RMS flywheel can perform these functions with reduced noise, emissions, and operating costs when compared with non-HTS competitors including batteries, diesel generators, and microturbines.
Date: June 29, 2007
Creator: Strasik, Dr. Michael
Partner: UNT Libraries Government Documents Department

Sandia National Laboratories results for the 2010 criticality accident dosimetry exercise, at the CALIBAN reactor, CEA Valduc France.

Description: This document describes the personal nuclear accident dosimeter (PNAD) used by Sandia National Laboratories (SNL) and presents PNAD dosimetry results obtained during the Nuclear Accident Dosimeter Intercomparison Study held 20-23 September, 2010, at CEA Valduc, France. SNL PNADs were exposed in two separate irradiations from the CALIBAN reactor. Biases for reported neutron doses ranged from -15% to +0.4% with an average bias of -7.7%. PNADs were also exposed on the back side of phantoms to assess orientation effects.
Date: September 1, 2011
Creator: Ward, Dann C.
Partner: UNT Libraries Government Documents Department

Recent upgrade of the in vivo neutron activation facility at Brookhaven National Laboratory

Description: The in vivo neutron activation facility at Brookhaven National Laboratory consists of a delayed- and a prompt-gamma neutron activation (DGNA and PGNA) system and an inelastic neutron scattering (INS) system. The total body contents of several basic elements, including potassium, calcium, chlorine, sodium, and phosphorus are measured at the DGNA system; total body carbon is measured at the INS system; and the nitrogen-tohydrogen ratio is measured at the PGNA system. Based on the elemental composition, body compartments, such as total body fat and total body protein can be computed with additional independently measured parameters, such as total body water, body size, and body weight. Information on elemental and compartmental body composition obtained through neutron activation analysis is useful, if not essential, for research on growth, malnutrition, aging diseases, such as osteoporosis and acquired immunodeficiency syndrome in which the progression of the illness is closely related to changes in major body compartments, such as bone, adipose tissue, and muscle. The DGNA system has been modified and upgraded several times since it was first built. Recently, all three systems underwent major upgrades. This upgrading and some preliminary studies carried out with the modified facilities are reported here.
Date: October 1, 1993
Creator: Ma, R.; Dilmanian, F. A..; Rarback, H.; Meron, M.; Kamen, Y.; Yasumura, S. et al.
Partner: UNT Libraries Government Documents Department

Characterizing Tissue with Acoustic Parameters Derived from Ultrasound Data

Description: In contrast to standard reflection ultrasound (US), transmission US holds the promise of more thorough tissue characterization by generating quantitative acoustic parameters. We compare results from a conventional US scanner with data acquired using an experimental circular scanner operating at frequencies of 0.3 - 1.5 MHz. Data were obtained on phantoms and a normal, formalin-fixed, excised breast. Both reflection and transmission-based algorithms were used to generate images of reflectivity, sound speed and attenuation.. Images of the phantoms demonstrate the ability to detect sub-mm features and quantify acoustic properties such as sound speed and attenuation. The human breast specimen showed full field evaluation, improved penetration and tissue definition. Comparison with conventional US indicates the potential for better margin definition and acoustic characterization of masses, particularly in the complex scattering environments of human breast tissue. The use of morphology, in the context of reflectivity, sound speed and attenuation, for characterizing tissue, is discussed.
Date: January 23, 2002
Creator: Littrup, P; Duric, N; Leach, R R; Azevedo, S G; Candy, J V; Moore, T et al.
Partner: UNT Libraries Government Documents Department

Practical, computer-aided registration of multiple, three-dimensional, magnetic-resonance observations of the human brain

Description: Researchers working with MR observations generally agree that far more information is available in a volume (3D) observation than is considered for diagnosis. The key to the new alignment method is in basing it on available information on surfaces. Using the skin surface is effective a robust algorithm can reliably extract this surface from almost any scan of the head, and a human operator`s exquisite sensitivity to facial features is allows him to manually align skin surfaces with precision. Following the definitions, we report on a preliminary experiment where we align three MR observations taken during a single MR examination, each weighting arterial, venous, and tissue features. When accurately aligned, a neurosurgeon can use these features as anatomical landmarks for planning and executing interventional procedures.
Date: December 31, 1992
Creator: Diegert, C.; Sanders, J. A. & Orrison, W. W. Jr.
Partner: UNT Libraries Government Documents Department

Microdosimetry of monoenergetic neutrons

Description: Tissue spheres 0.25, 0.5, 1.0, 2.0, 4.0, and 8.0 {mu}m in diameter were simulated using a wall-less spherical counter filled with a propane-based tissue-equivalent gas. Microdosimetric spectra corresponding to these site sizes were measured for five neutron energies (0.22, 0.44, 1.5, 6, and 14 MeV) and the related mean values {bar Y}{sub F} and {bar Y}{sub D} were calculated for several site sizes and neutron energies. An elaborate calibration technique combining soft x-rays, a {sup 55}Fe photon source, and a {sup 244}Cm collimated source of alpha particles was used throughout the measurement. The spectra and their mean values are compared with theoretically calculated values for ICRU tissue. The agreement between the calculated and the measured data is good in spite of a systematic discrepancy, which could be attributed, in part, to the difference in elemental composition between the tissue-equivalent gas and plastic used in the counter, and the ICRU standard tissue used in the calculations.
Date: December 31, 1993
Creator: Srdoc, D. & Marino, S. A.
Partner: UNT Libraries Government Documents Department

Monochromatic computed tomography of the human brain using synchrotron x rays: Technical feasibility

Description: A monochromatic computed tomography (CT) scanner is being developed at the X17 superconducting wiggler beamline at the National Synchrotron Light Source (NSLS), Brookhaven National Laboratory, to image the human head and neck. The system configuration is one of a horizontal fan beam and an upright seated rotating subject. The purpose of the project are to demonstrate improvement in the image contrast and in the image quantitative accuracy that can be obtained in monochromatic CT and to apply the system to specific clinical research programs in neuroradiology. This paper describes the first phantom studies carried out with a prototype system, using the dual photon absorptiometry (DPA) method at energies of 20 and 39 Kev. The results show that improvements in image contrast and quantitative accuracy are possible with monochromatic DPA CT. Estimates of the clinical performance of the planned CT system are made on the basis of these initial results.
Date: December 31, 1991
Creator: Nachaliel, E.; Dilmanian, F. A.; Garrett, R. F.; Thomlinson, W. C.; Chapman, L. D.; Gmuer, N. F. et al.
Partner: UNT Libraries Government Documents Department

The development of early pediatric models and their application to radiation absorbed dose calculations

Description: This presentation will review and describe the development of pediatric phantoms for use in radiation dose calculations . The development of pediatric models for dose calculations essentially paralleled that of the adult. In fact, Snyder and Fisher at the Oak Ridge National Laboratory reported on a series of phantoms for such calculations in 1966 about two years before the first MIRD publication on the adult human phantom. These phantoms, for a newborn, one-, five-, ten-, and fifteen-year old, were derived from the adult phantom. The ``pediatric`` models were obtained through a series of transformations applied to the major dimensions of the adult, which were specified in a Cartesian coordinate system. These phantoms suffered from the fact that no real consideration was given to the influence of these mathematical transformations on the actual organ sizes in the other models nor to the relation of the resulting organ masses to those in humans of the particular age. Later, an extensive effort was invested in designing ``individual`` pediatric phantoms for each age based upon a careful review of the literature. Unfortunately, the phantoms had limited use and only a small number of calculations were made available to the user community. Examples of the phantoms, their typical dimensions, common weaknesses, etc. will be discussed.
Date: December 31, 1989
Creator: Poston, J. W.
Partner: UNT Libraries Government Documents Department