The Experts below are selected from a list of 210 Experts worldwide ranked by ideXlab platform

N. S. Aly - One of the best experts on this subject based on the ideXlab platform.

Eugene Druker - One of the best experts on this subject based on the ideXlab platform.

  • Airborne gamma-ray spectra processing: Extracting Photopeaks.
    Journal of environmental radioactivity, 2018
    Co-Authors: Eugene Druker
    Abstract:

    The acquisition of information from the airborne gamma-ray spectra is based on the ability to evaluate photopeak areas in regular spectra from natural and other sources. In airborne gamma-ray spectrometry, extraction of Photopeaks of radionuclides from regular one-second spectra is a complex problem. In the region of higher energies, difficulties are associated with low signal level, i.e. low count rates, whereas at lower energies difficulties are associated with high noises due to a high signal level. In this article, a new procedure is proposed for processing the measured spectra up to and including the extraction of evident Photopeaks. The procedure consists of reducing the noise in the energy channels along the flight lines, transforming the spectra into the spectra of equal resolution, removing the background from each spectrum, sharpening the details, and transforming the spectra back to the original energy scale. The resulting spectra are better suited for examining and using the Photopeaks. No assumptions are required regarding the number, locations, and magnitudes of Photopeaks. The procedure does not generate negative Photopeaks. The resolution of the spectrometer is used for the purpose. The proposed methodology, apparently, will contribute also to study environmental problems, soil characterization, and other near-surface geophysical methods.

  • Processing of Airborne Gamma-Ray Spectra: Extracting Photopeaks
    ASEG Extended Abstracts, 2016
    Co-Authors: Eugene Druker
    Abstract:

    Receiving information from airborne gamma-ray spectra is based on the ability to estimate the photopeak areas in the regular spectra of natural and other sources. In the airborne gamma-ray spectrometry, extracting the Photopeaks of radionuclides from regular one-second spectra is a complicated problem. In the region of higher energies, e.g., above 1.6 MeV, the difficulties are associated with low count rates, while in the region of lower energies, difficulties are due to a significant background level and its statistical noise. In this article a new procedure is proposed to process the measured spectra up to extracting evident Photopeaks. The procedure consists of decreasing noises in energy channels along the flight lines, transforming spectra to equal resolution spectra, removing baselines from each spectrum, sharpening details, and transforming spectra back to original channel scale. The resulting spectra are better suited for examining and using the Photopeaks. No assumptions regarding the number, positions and magnitudes of Photopeaks are needed. Non-negativity of photopeak areas is ensured by the procedure. The proposed technique is likely to contribute to studies of environmental issues, soil characterization and other near surface geophysical methods.

Kholud. S. Almugren - One of the best experts on this subject based on the ideXlab platform.

Michael A. King - One of the best experts on this subject based on the ideXlab platform.

  • Window Selection for Dual Photopeak Window Scatter Correction in Tc-99m
    1994
    Co-Authors: Daniel J. De Vries, Michael A. King
    Abstract:

    Abstmct-The width and placement of the windows for the dual photopeak window (DPW) scatter subtraction method for Tc-99m imaging is investigated in order to obtain a method that is stable on a multihead detector system for single photon emission computed tomography (SPECT) and is capable of providing a good scatter estimate for extended objects. For various window pairs, stability and noise were examined with experiments using a SPECT system, while Monte Carlo simulations were used to predict the accuracy of scatter estimates for a variety of objects and to guide the development of regression relations for various window pairs. The DPW method that resulted from this study was implemented with a symmetric 20% photopeak window composed of a 15% asymmetric photopeak window and a 5% lower window abutted at 7 keV below the peak. A power function regression was used to relate the scatter-to-total ratio to the lower window-to-total ratio at each pixel, from which an estimated scatter image was calculated. DPW demonstrated good stability, achieved by abutting the two windows away from the peak. Performance was assessed and compared with Compton window subtraction (CWS). For simulated extended objects, DPW generally produced a less biased scatter estimate than the commonly used CWS method with k = 0.5. In aquisitions of a clinical SPECT phantom, contrast recovery was comparable for both DPW and CWS; however, DPW showed greater visual contrast in clinical SPECT bone studies.

  • Window selection for dual photopeak window scatter correction in Tc-99m imaging
    IEEE Transactions on Nuclear Science, 1994
    Co-Authors: Daniel J. De Vries, Michael A. King
    Abstract:

    The width and placement of the windows far the dual photopeak window (DPW) scatter subtraction method for Tc-99m imaging is investigated in order to obtain a method that is stable on a multihead detector system for single photon emission computed tomography (SPECT) and is capable of providing a good scatter estimate for extended objects. For various window pairs, stability and noise were examined with experiments using a SPECT system, while Monte Carlo simulations were used to predict the accuracy of scatter estimates for a variety of objects and to guide the development of regression relations for various window pairs. The DPW method that resulted from this study was implemented with a symmetric 20% photopeak window composed of a 15% asymmetric photopeak window and a 5% lower, window abutted at 7 keV below the peak. A power function regression was used to relate the scatter-to-total ratio to the lower window-to-total ratio at each pixel, from which an estimated scatter image was calculated. DPW demonstrated good stability, achieved by abutting the two windows away from the peak. Performance was assessed and compared with Compton window subtraction (CWS). For simulated extended objects, DPW generally produced a less biased scatter estimate than the commonly used CWS method with k=0.5. In acquisitions of a clinical SPECT phantom, contrast recovery was comparable for both DPW and CWS; however, DPW showed greater visual contrast in clinical SPECT bone studies. >

  • A Monte Carlo investigation of the dual photopeak window scatter correction method (SPECT)
    IEEE Transactions on Nuclear Science, 1993
    Co-Authors: George Hademenos, M. Ljungberg, Michael A. King, S.j. Glick
    Abstract:

    Results from a Monte Carlo investigation of the dual photopeak window (DPW) scatter correction method are presented for point and extended sources of Tc-99m in both homogeneous and nonhomogeneous attenuating media. The DPW method uses the ratio of counts in two nonoverlapping energy windows within the photopeak region as input to a regression relation. A pixel-by-pixel estimate of the scatter in the summed windows is obtained and subtracted to yield an estimate of the primary. An approximately tenfold decrease in the scatter fraction and an excellent agreement with the shape of the true scatter distribution were observed. >

  • A dual-photopeak window method for scatter correction.
    Journal of nuclear medicine : official publication Society of Nuclear Medicine, 1992
    Co-Authors: Michael A. King, George Hademenos, Stephen J. Glick
    Abstract:

    The imaging of scattered photons degrades contrast and is a major source of error in the quantitation of activity. It was hypothesized that, if the photopeak was divided into two nonoverlapping energy windows, a regression relation could be obtained between the ratio of counts within these windows and the scatter fraction for counts within the total region. This idea was tested by acquiring dual photopeak window acquisitions of a 99mTc point source in an elliptical attenuator, and at the same locations in air. From these, a regression between the scatter fraction and window ratio was determined. When this regression was applied to estimate the scatter distribution for acquisitions in both uniform and nonuniform elliptical attenuators, the residual scatter fraction was reduced approximately ten-fold and the estimated scatter line spread functions matched very closely the tails of the total line spread functions. In SPECT acquisitions, dual-photopeak window scatter correction was observed to significantly increase the contrast of "cold" spheres, improve the accuracy of estimating activity at the center of "hot" spheres, and return the three-dimensional modulation transfer function for point sources in an elliptical attenuator to near their in-air shape.

  • Implementation and testing of the dual photopeak window scatter correction method on a multi-headed SPECT system
    IEEE Conference on Nuclear Science Symposium and Medical Imaging, 1
    Co-Authors: Michael A. King, George Hademenos, D. J. Devries, B.c. Penney, Hugh T. Morgan, G.g. Jarkewicz
    Abstract:

    The authors describe the implementation and testing of the dual photopeak window (DPW) scatter correction method on a multiheaded single photon emission computed tomography (SPECT) system. The DPW scatter correction method assumes that variations in the ratio of counts within two abutted energy windows which span the photopeak region is due solely to changes in the scatter fraction, and that there is a unique relationship between the ratio and the scatter fraction which is stable with time and location across the face of the cameras. A small variation in the window count ratio was observed across the camera faces, with rotation, and with time. The regression relation between window count ratio and scatter fraction was determined to have significant variation with time and location across the camera faces at large scatter fractions. The method was observed to give significant improvement in the contrast of spheres in acquisitions of a SPECT phantom. The variation in the regression relations at large scatter fractions raises concern for the quantitative accuracy of the contrast improvement when the DPW method is applied to energy windows which split the photopeak at the emission energy. >

Mahmoud I. Abbas - One of the best experts on this subject based on the ideXlab platform.