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Geographic information system for Long Island: An epidemiologic systems approach to identify environmental breast cancer risks on Long Island. Phase 1

Description: BNL is developing and implementing the project ``Geographic Information System (GIS) for Long Island`` to address the potential relationship of environmental and occupational exposures to breast cancer etiology on Long Island. The project is divided into two major phases: The four month-feasibility project (Phase 1), and the major development and implementation project (Phase 2). This report summarizes the work completed in the four month Phase 1 Project, ``Feasibility of a Geographic Information System for Long Island.`` It provides the baseline information needed to further define and prioritize the scope of work for subsequent tasks. Phase 2 will build upon this foundation to develop an operational GIS for the Long Island Breast Cancer Study Project (LIBCSP).
Date: December 1, 1995
Creator: Barancik, J.I.; Kramer, C.F. & Thode, H.C. Jr.
Partner: UNT Libraries Government Documents Department

Preliminary experience with monoenergetic photon mammography

Description: We are using a beam port at the National Synchrotron Light Source facility at Brookhaven National Laboratory as a source of monoenergetic photons. The photon source is radiation from a bending magnet on the X-ray storage ring and provides a usable X-ray spectrum from 5 keV to over 50 keV. A tunable crystal monochromotor is used for energy selection. The beam is 79mm wide and 0.5 mm high. We imaged the ACR mammography phantom and a contrast-detail phantom using a phosphor plate as the unaging detector. Phantom images were obtained at 16, 18, 20 and 22 keV. Phantom thickness varied from 15 mm to 82 mm. These images were compared to images obtained with a conventional dedicated mammography unit. Subjective preliminary results show that image contrast of the monoenergetic images is similar to those obtained from the conventional x-ray source with somewhat sharper and cleaner images from the monoenergetic source. Quantitative analysis shows that the monoenergetic images have improved contrast compared to the polyenergetic derived images. Entrance skin dose measurements show a factor of 5 to 10 times less radiation for the monoenergetic images with equivalent or better contrast Although there remain a number of technical problems to be addressed and much more work to be done, we are encouraged to further explore the use of monoenergetic imaging.
Date: December 31, 1995
Creator: Johnston, R.E.; Washburn, D.; Pisano, E.; Thomlinson, W.C.; Chapman, D.; Gmur, N.F. et al.
Partner: UNT Libraries Government Documents Department

Synchrotron radiation applications in medical research

Description: The medical projects employing synchrotron radiation as discussed in this paper are, for the most part, still in their infancies and no one can predict the direction in which they will develop. Both the basic research and applied medical programs are sure to be advanced at the new facilities coming on line, especially the ESRF and Spring- 8. However, success is not guaranteed. There is a lot of competition from advances in conventional imaging with the development of digital angiography, computed tomography, functional magnetic resonance imaging and ultrasound. The synchrotron programs will have to provide significant advantages over these modalities in order to be accepted by the medical profession. Advances in image processing and potentially the development of compact sources will be required in order to move the synchrotron developed imaging technologies into the clinical world. In any event, it can be expected that the images produced by the synchrotron technologies will establish ``gold standards`` to be targeted by conventional modalities. A lot more work needs to be done in order to bring synchrotron radiation therapy and surgery to the level of human studies and, subsequently, to clinical applications.
Date: December 31, 1995
Creator: Thomlinson, W.
Partner: UNT Libraries Government Documents Department

Data acquisition and analysis of mammography images at the NSLS June--August 1995

Description: At Brookhaven National Laboratory mammography experiments are being carried out at the X27C R and D beamline of the National Synchrotron Light Source using a monochromatic x-ray beam in order to explore the potential of monoenergetic photons for mammographic imaging. In two different periods of beamtime the authors have performed preliminary studies of mammographic imaging using a monochromatic synchrotron radiation source. They used both phantom objects and real tissue samples. Qualitative studies with the contrast-detail phantom show good agreement when compared with the theoretical contrast. As expected, the contrast is higher if the energy is lower. The results show an improved contrast with energies 18 keV and lower compared to images obtained from conventional polyenergetic x-ray imaging systems. The results also show that for similar imaging conditions the monoenergetic mean glandular dose is less than that from polyenergetic sources. This is due both to the increased sensitivity of the image plate detectors and to actual reductions of dose for truly monochromatic beams.
Date: December 31, 1995
Creator: Arfelli, F.; Burns, C. & Chapman, D.
Partner: UNT Libraries Government Documents Department

Detecting circumscribed lesions with the Hough transform

Description: We have designed and implemented a circumscribed lesion detection algorithm, based on the Hough Transform, which will detect zero or more approximately circular structures in a mammogram over a range of radii from a few pixels to nearly the size of the breast. We address the geometrical behavior of peaks in Hough parameter space (x,y,r) for both the true radius of a circular structure in the image (r = r{sub o}), and for the parameter r as it passes through this radius. In addition, we evaluate peaks in Hough parameter space by re-analyzing the underlying mammogram in the vicinity of the circular disk indicated by the peak. Discs suggested by the resulting peaks are accumulated in a feature image, scaled by a measure of their quality. These results are then rectified with respect to image contrast extremes and average value. The result is a feature with a continuously scaled pixel level output which suggests the likelihood that a pixel is located inside a circular structure, irrespective of the radius of the structure and overall mammogram contrast. These features are evaluated fast qualitative and quantitative performance metrics which permit circumscribed lesion detection features to be initially evaluated without a full end-to-end classification experiment.
Date: January 11, 1996
Creator: Groshong, B. R & Kegelmeyer, W. P., Jr.
Partner: UNT Libraries Government Documents Department

Human radiation studies: Remembering the early years. Oral history of biophysicist Cornelius A. Tobias, Ph.D., January 16, 1995

Description: Dr. Cornelius A. Tobias was interviewed by representatives of US DOE Office of Human Radiation Experiments (OHRE). He was chosen for this interview because of his extensive biophysics and medical physics research activities while he was employed by the University of California, Berkeley and San Francisco and at the Donner Laboratory. He discusses his involvement in wartime studies of effects of high altitude on aviators, carbon monoxide with radioactive tracers, blood studies with radioactive iron, human use committees, heavy-ion research with the Bevatron, boron isotope research, classified research involving human subjects, heavy-particle radiography, heavy- particle beams and medical research, and pituitary irradiation studies,.
Date: July 1, 1995
Partner: UNT Libraries Government Documents Department

Mammography imaging studies using a laue crystal analyzer

Description: Synchrotron based mammography imaging experiments have been performed with monochromatic x-rays in which a laue crystal placed after the object being imaged has been used to split the beam transmitted through the object. The X27C R&D beamline at the National Synchrotron Light Source was used with the white beam monochromatized by a double crystal Si(111) monochromator tuned to 18 keV. The imaging beam was a thin horizontal line approximately 0.5 mm high by 100 mm wide. Images were acquired in line scan mode with the phantom and detector both scanned together. The detector for these experiments was an image plate. A thin Si(l11) laue analyzer was used to diffract a portion of the beam transmitted through the phantom before the image plate detector. This ``scatter free`` diffracted beam was then recorded on the image plate during the phantom scan. Since the thin laue crystal also transmitted a fraction of the incident beam, this beam was also simultaneously recorded on the image plate. The imaging results are interpreted in terms of an x-ray schliere or refractive index inhomogeneities. The analyzer images taken at various points in the rocking curve will be presented.
Date: December 31, 1995
Creator: Chapman, D.; Thomlinson, W. & Arfelli, F.
Partner: UNT Libraries Government Documents Department

Science & Technology Review, December 1997

Description: Serial publication produced by Lawrence Livermore National Laboratory regarding the institution's research in technology to address concerns about energy, bioscience, and the environment. "Science & Technology Review is published ten times a year to communicate, to a broad audience, the Laboratory's scientific and technological accomplishments in fulfilling its primary missions. The publication's goal is to help readers understand these accomplishments and appreciate their value to the individual citizen, the nation, and the world" (inside cover).
Date: December 1997
Creator: Lawrence Livermore National Laboratory
Partner: UNT Libraries Government Documents Department

Automated analysis for microcalcifications in high resolution digital mammograms

Description: Digital mammography offers the promise of significant advances in early detection of breast cancer. Our overall goal is to design a digital system which improves upon every aspect of current mammography technology: the x-ray source, detector, visual presentation of the mammogram and computer-aided diagnosis capabilities. This paper will discuss one part of our whole-system approach -- the development of a computer algorithm using gray-scale morphology to automatically analyze and flag microcalcifications in digital mammograms in hopes of reducing the current percentage of false-negative diagnoses, which is estimated at 20%. The mammograms used for developing this ``mammographers assistant`` are film mammograms which we have digitized at either 70 {mu}m or 35 {mu}m per pixel resolution with 4096 (12 bits) of gray level per pixel. For each potential microcalcification detected in these images, we compute a number of features in order to distinguish between the different kinds of objects detected.
Date: January 1, 1993
Creator: Mascio, L.N.; Hernandez, J.M. & Logan, C.M.
Partner: UNT Libraries Government Documents Department

Single fiber beta detector for stereotactic biopsy and intraoperative lumpectomy of breast cancer

Description: We have developed an intraoperative probe for use in early detection of breast cancer and aiding lumpectomy. The probe consists of a small plastic scintillator, 0.8mm dia and 3mm long, coupled to a single clear optical-fiber strand, and solid state photomultiplier. Due to the small size of the probe, it can be placed inside of a small gauge biopsy needle. The scintillator is very efficient in detecting betas and positrons while being very in efficient to energetic gammas due to small size and low density. High quantum efficiency, 80%, and high gain obtainable, solid state photomultiplier makes the probe very low noise device in detecting beta particles. Intrinsic resolution of the probe is expected to be around 1 mm. Preliminary results using beta sources and a rat bearing R320 adenocarcinoma tumor were very successful.
Date: October 1, 1996
Creator: Atac, M.; Nalcioglu, O. & Roeck, W.W.
Partner: UNT Libraries Government Documents Department

Current status and perspectives of synchrotron radiation in medicine

Description: The high flux and brightness, tunable beams, time structure and polarization of synchrotron radiation provide an ideal x-ray source for many medical applications. The present status of synchrotron angiography, multiple energy computed tomography, mammography and radiation therapy at laboratories around the world is reviewed and some future projections for these applications are addressed.
Date: November 1, 1996
Creator: Thomlinson, W.
Partner: UNT Libraries Government Documents Department

Front-End Data Reduction in Computer-Aided Diagnosis of Mammograms: A Pilot Study

Description: This paper presents the results of a pilot study whose primary objective was to further substantiate the efficacy of front-end data reduction in computer-aided diagnosis (CAD) of mammograms. This concept is realized by a preprocessing module that can be utilized at the front-end of most mammographic CAD systems. Based on fractal encoding, this module takes a mammo-graphic image as its input and generates, as its output, a collection of subregions called focus-of-attention regions (FARs). These FARs contain all structures in the input image that appear to be different from the normal background tissue. Subsequently, the CAD systems need only to process the presented FARs, rather than the entire input image. This accomplishes two objectives simultaneously: (1) an increase in throughput via a reduction in the input data, and (2) a reduction in false detections by limiting the scope of the detection algorithms to FARs only. The pilot study consisted of using the preprocessing module to analyze 80 mammographic images. The results were an average data reduction of 83% over all 80 images and an average false detection reduction of 86%. Furthermore, out of a total of 507 marked microcalcifications, 467 fell within FW, representing a coverage rate of 92%.
Date: February 20, 1999
Creator: Gleason, S.S.; Nishikawa, R.M. & Sari-Sarraf, H.
Partner: UNT Libraries Government Documents Department

A novel approach to computer-aided diagnosis of mammographic images

Description: This is a work-in-progress report of a research endeavor that deals with the design and development of a novel approach to computer-aided diagnosis (CAD) of mammographic images. With the initial emphasis being on the analysis of microcalcifications, the proposed approach defines a synergistic paradigm that utilizes new methodologies together with previously developed techniques. The new paradigm is intended to promote a higher degree of accuracy in CAD of mammograms with an increased overall throughput. The process of accomplishing these goals is initiated by the fractal encoding of the input image, which gives rise to the generation of focus-of-attention regions (FARs), that is, regions that contain anomalies. The primary thrust of this work is to demonstrate that by considering FARs, rather than the entire input image, the performances of the ensuing processes (i.e., segmentation, feature extraction, and classification) are enhanced in terms of accuracy and speed. After presenting the proposed approach to CAD of mammographic images, the paper describes the generation of FARs. Furthermore, an experimental study is included that demonstrates the impact of this front-end procedure on the process of microcalcification segmentation. Specifically, the experimentation reveals a dramatic decrease (increase) in the amount of input data (throughput), as well as a reduction in the number of false detections.
Date: August 1, 1996
Creator: Sari-Sarraf, H.; Gleason, S.S.; Hudson, K.T. & Hubner, K.F.
Partner: UNT Libraries Government Documents Department

Dual-energy subtraction imaging utilizing indium as a contrast agent

Description: The purpose of our current work is to establish the minimum detection, of indium contrast agent using dual-energy subtraction imaging above and below indium K-edge. Experiments were performed on the X12 and X17B2 beamlines at the National Synchrotron Light Source using the same method but with two different set-ups. Experiments were first carried out on InCl{sub 3} solutions, then on V79 Chinese hamster cells and on BALB/c mice excised tumors, labeled with indium. For each experiment, several layers of Lucite were placed in front of the phantom to ensure a 43 mm thickness, dose to that of a mammography examination. Results were the same on X12 and X17B2. As expected, indium-free materials disappeared on subtracted images (water, steel reference and screw). Indium samples were easily distinguishable for the following concentrations: 10-5-2-1 mg/cm{sup 2}. Smaller concentrations were not clearly distinguishable and we were unable to see cell samples and tumors. To conclude, the lowest concentration we can image is around 1 mg/cm{sup 2}. These results agree with theoretical results. Such results also suggest that indium concentration in both cells and tumors is lower than 0.5 mg/cm{sup 2}. Since the current detection is dose to optimum, we conclude that dual energy subtraction imaging using indium to label tumors cells and tumors is not possible unless the indium uptake is increased by more than an order of magnitude.
Date: October 1, 1997
Creator: Le Duc, G.; Zhong, Z.; Warkentien, L.; Laster, B. & Thomlinson, W.
Partner: UNT Libraries Government Documents Department

Decision trees and integrated features for computer aided mammographic screening

Description: Breast cancer is a serious problem, which in the United States causes 43,000 deaths a year, eventually striking 1 in 9 women. Early detection is the only effective countermeasure, and mass mammography screening is the only reliable means for early detection. Mass screening has many shortcomings which could be addressed by a computer-aided mammographic screening system. Accordingly, we have applied the pattern recognition methods developed in earlier investigations of speculated lesions in mammograms to the detection of microcalcifications and circumscribed masses, generating new, more rigorous and uniform methods for the detection of both those signs. We have also improved the pattern recognition methods themselves, through the development of a new approach to combinations of multiple classifiers.
Date: February 1, 1997
Creator: Kegelmeyer, W.P. Jr.; Groshong, B.; Allmen, M. & Woods, K.
Partner: UNT Libraries Government Documents Department

Diffraction enhanced x-ray imaging

Description: Diffraction enhanced imaging (DEI) is a new x-ray radiographic imaging modality using synchrotron x-rays which produces images of thick absorbing objects that are almost completely free of scatter. They show dramatically improved contrast over standard imaging applied to the same phantoms. The contrast is based not only on attenuation but also the refraction and diffraction properties of the sample. The diffraction component and the apparent absorption component (absorption plus extinction contrast) can each be determined independently. This imaging method may improve the image quality for medical applications such as mammography.
Date: September 1, 1997
Creator: Thomlinson, W.; Zhong, Z.; Chapman, D.; Johnston, R.E. & Sayers, D.
Partner: UNT Libraries Government Documents Department

Analysis of differential protein expression in normal and neoplastic human breast epithelial cell lines

Description: High resolution two dimensional get electrophoresis (2DE) and database analysis was used to establish protein expression patterns for cultured normal human mammary epithelial cells and thirteen breast cancer cell lines. The Human Breast Epithelial Cell database contains the 2DE protein patterns, including relative protein abundances, for each cell line, plus a composite pattern that contains all the common and specifically expressed proteins from all the cell lines. Significant differences in protein expression, both qualitative and quantitative, were observed not only between normal cells and tumor cells, but also among the tumor cell lines. Eight percent of the consistently detected proteins were found in significantly (P < 0.001) variable levels among the cell lines. Using a combination of immunostaining, comigration with purified protein, subcellular fractionation, and amino-terminal protein sequencing, we identified a subset of the differentially expressed proteins. These identified proteins include the cytoskeletal proteins actin, tubulin, vimentin, and cytokeratins. The cell lines can be classified into four distinct groups based on their intermediate filament protein profile. We also identified heat shock proteins; hsp27, hsp60, and hsp70 varied in abundance and in some cases in the relative phosphorylation levels among the cell lines. Finally, we identified IMP dehydrogenase in each of the cell lines, and found the levels of this enzyme in the tumor cell lines elevated 2- to 20-fold relative to the levels in normal cells.
Date: July 1, 1997
Creator: Williams, K.; Chubb, C.; Huberman, E. & Giometti, C.S.
Partner: UNT Libraries Government Documents Department

A compact Compton backscatter X-ray source for mammography and coronary angiography

Description: This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The project objective is to generate a large flux of tunable, monochromatic x-rays for use in mammography and coronary angiography. The approach is based on Compton backscattering of an ultraviolet solid-state laser beam against the high-brightness 20-MeV electron beams from a compact linear accelerator. The direct Compton backscatter approach failed to produce a large flux of x-rays due to the low photon flux of the scattering solid-state laser. The authors have modified the design of a compact x-ray source to the new Compton backscattering geometry with use of a regenerative amplifier free-electron laser. They have successfully demonstrated the production of a large flux of infrared photons and a high-brightness electron beam focused in both dimensions for performing Compton backscattering in a regenerative amplifier geometry.
Date: November 1998
Creator: Nguyen, D. C.; Kinross-Wright, J. M.; Weber, M. E.; Volz, S. K.; Gierman, S. M.; Hayes, K. et al.
Partner: UNT Libraries Government Documents Department

Radiogenic neoplasia in thyroid and mammary clonogens. Final progress report, 1 January 1987--31 December 1997

Description: The induction of cancer by ionizing radiation is a matter of great practical importance to the nuclear industry, to national defense, to radiological medicine and to the general public. It is increasingly apparent that carcinogenesis is a leading dose-limiting effect of radiation exposure. The thyroid and mammary glands are among the most sensitive human tissues to radiogenic initiation of cancer, and there is a profoundly higher risk of neoplastic initiation in these glands among individuals irradiated before or during puberty than among those exposed in later life. The authors developed unique quantitative experimental models to investigate and characterize the cells of origin of thyroid and mammary cancers and the effects of radiation on them (C185). To study these progenitor cells in vivo it is necessary to have a system by which their concentrations, total numbers and responses to radiation and other factors can be measured. It is a truism that not all cells in a tissue are equally sensitive to neoplastic initiation. They reasoned that the progenitor cells are most likely members of that subpopulation that is necessary to maintenance of normal tissue cell numbers and to repair and replacement after tissue damage. They further reasoned that such cells would likely be responsive to specific mitogenic stimulation by hormones. On the basis of these considerations, they developed quantitative rat thyroid and mammary epithelial cell transplantation systems.
Date: July 10, 1998
Creator: Clifton, K.H.
Partner: UNT Libraries Government Documents Department

Development of a small field-of-view scintimammography camera: Measurements and simulations

Description: The authors report on studies of a small field of view scintimammography camera based on a position sensitive PMT and a crystal scintillator array. A 5-inch R3292 Hamamatsu PMT was coupled to a variety of scintillators, including pixelized NaI(TI), Csi (Na) and YAP. Laboratory and phantom studies were performed to compare performances of the above scintillator sensors with special emphasis on spatial resolution and scatter rejection. The results of Monte Carlo simulations for different pixel sizes are also presented.
Date: October 1, 1997
Creator: Steinbach, D; Goode, AR; Farzanpay, F; Majewski, S; Weisenberger, AG; Williams, MB et al.
Partner: UNT Libraries Government Documents Department

Comparison of organochlorine chemical body burdens of female breast cancer cases with cancer free women in Rio Grande do Sul, Brazil--Pilot Study

Description: This pilot study collected preliminary data to examine known and suspected breast cancer risk factors among women living in rural and urban areas in the state of Rio Grande do Sul, Brazil by questionnaire. In addition, the body burden levels of a panel of organochlorines was measured in a small clinic-based prospective sample.
Date: December 1999
Creator: Erdmann, C. A.; Petreas, M. X.; Caleffi, M.; Barbosa, F. S. & Goth-Goldstein, R.
Partner: UNT Libraries Government Documents Department

A Combined Scintimammography/Stereotactic Core Biopsy Digital X-ray System

Description: Jefferson Lab, Hampton University and the Riverside Regional Medical Center are collaborating in a clinical study employing a dual modality imaging system utilizing scintimammography and digital radiography. The purpose of the study is to obtain clinical data on the reliability of scintimammography in predicting the malignancy of suspected breast lesions with the ultimate goal to reduce the number of false positives associated with conventional x-ray mammography. The scintimammography gamma camera is a custom built mini gamma camera with an active area of 5.3 cm x 5.3 cm based on a 2x2 array of Hamamatsu R7600-C8 position sensitive photomultiplier tubes. The spatial resolution of the gamma camera at the collimator surface is &lt;4 mm FWHM and the sensitivity is 4000 cps/mCi. Preliminary results are that of the six cases that indicated a lesion with high uptake of MiraLuma ({sup 99m}Tc-sestamibi) five were positive for cancer. Out of a total of 25 patients in the study, all cases negative for MiraLuma uptake were confirmed negative via the biopsy pathology. The scintimammography results indicate that the lesions become visible with the mini gamma camera within 3 minutes post injection of MiraLuma.
Date: October 20, 2000
Creator: Weisenberger, A. G.; Barbosa, F.; Green, T. D.; Hoefer, R.; Keppel, C.; Kross, B. et al.
Partner: UNT Libraries Government Documents Department

Analysis of Factors Affecting Positron Emission Mammography (PEM) Image Formation

Description: Image reconstruction for positron emission mammography (PEM) with the breast positioned between two parallel, planar detectors is usually performed by backprojection to image planes. Three important factors affecting PEM image reconstruction by backprojection are investigated: (1) image uniformity (flood) corrections, (2) image sampling (pixel size) and (3) count allocation methods. An analytic expression for uniformity correction is developed that incorporates factors for spatial-dependent detector sensitivity and geometric effects from acceptance angle limits on coincidence events. There is good agreement between experimental floods from a PEM system with a pixellated detector and numerical simulations. The analytic uniformity corrections are successfully applied to image reconstruction of compressed breast phantoms and reduce the necessity for flood scans at different image planes. Experimental and simulated compressed breast phantom studies show that lesion contrast is improved when the image pixel size is half of, rather than equal to, the detector pixel size, though this occurs at the expense of some additional image noise. In PEM reconstruction counts usually are allocated to the pixel in the image plane intersected by the line of response (LOR) between the centers of the detection pixels. An alternate count allocation method is investigated that distributes counts to image pixels in proportion to the area of the tube of response (TOR) connecting the detection pixels that they overlay in the image plane. This TOR method eliminates some image artifacts that occur with the LOR method and increases tumor signal-to-noise ratios at the expense of a slight decrease in tumor contrast. Analysis of image uniformity, image sampling and count allocation methods in PEM image reconstruction points to ways of improving image formation. Further work is required to optimize image reconstruction parameters for particular detection or quantitation tasks.
Date: November 1, 2001
Creator: Smith, Mark F.; Majewski, Stan; Weisenberger, Andrew G.; Kieper, Douglas A.; Raylman, Raymond R. & Turkington, Timothy G.
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