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Nuclear Science, IEEE Transactions on

Issue 4 • Date Aug 1990

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Displaying Results 1 - 8 of 8
  • Calculation of the rotational centers in computed tomography sinograms

    Publication Year: 1990 , Page(s): 1525 - 1540
    Cited by:  Papers (8)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1044 KB)  

    An efficient method for accurately calculating the center-of-rotation, or projection center, for parallel computed tomography projection data, or sinograms, is described. This method uses all the data in the sinogram to estimate the center by a least-squares technique and requires no previous calibration scan. The method also finds the object's center-of-mass without reconstructing its image. Since the method uses the measured data, it is sensitive to noise in the measurements, but that sensitivity is relatively small compared to other techniques. Examples of its use on simulated and actual data are included. For fan-beam data over 360°, two related methods are described to find the center in the presence or absence of a midline offset View full abstract»

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  • A precision synchrotron radiation detector using phosphorescent screens

    Publication Year: 1990 , Page(s): 1502 - 1505
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    A precision detector to measure synchrotron radiation beam positions is described. It has been designed and installed as part of the beam energy spectrometers at the Stanford Linear Collider (SLC). The distance between pairs of synchrotron radiation beams is measured absolutely to better than 28 μm on a pulse-to-pulse basis. This contributes less than 5 MeV to the error in measuring SLC beam energies (approximately 50 GeV). A system of high-resolution video cameras viewing precisely aligned fiducial wire arrays overlaying phosphorescent screens has achieved this accuracy View full abstract»

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  • Coping with complexity

    Publication Year: 1990
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (84 KB)  

    The author presents a short talk on intentional complexity, a form of complexity self-created by individuals such as occurs in experimental set ups View full abstract»

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  • A new approach to the measurement of resolution and sampling on a positron emission tomograph

    Publication Year: 1990 , Page(s): 1506 - 1513
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (436 KB)  

    Two technical difficulties underlie the accurate determination of spatial resolution in positron emission tomography (PET): (1) measuring the full-width half-maximum (FWHM) and full-width tenth-maximum (FWTM) from undersampled profiles; (2) measuring axial resolution from multiple reconstructed data sets. To address the first problem, a technique that involves a quadratic estimation of the peak of the profile distribution was developed. This method was compared with the standard technique of Gaussian fitting and was found to be as accurate for constant background distributions. For axial resolution, a second method involving a single scan and imaging of line sources oriented 45 degrees to the axis of the scanner was proposed. Axial FWHM estimations were achieved by deconvolving the values obtained with line spread functions from sources placed parallel to the axis of the scanner. This technique was validated by comparing the results with those obtained by others using a multiple-scan technique on a similar machine View full abstract»

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  • CT image correction for beam hardening using simulated projection data

    Publication Year: 1990 , Page(s): 1520 - 1524
    Cited by:  Papers (10)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (756 KB)  

    A general beam-hardening correction technique is presented. Knowledge of the CT (computerized tomography) scanner X-ray spectrum is necessary. This postreconstruction method does not require the original projection data. Simulated projections through an uncorrected reconstructed image are used to correct for beam hardening. Errors in the mean linear attenuation coefficient are decreased from 30% to 5% with virtual elimination of the visual streaking artifact. The theoretical image improvement equals that of projection linearization postreconstruction methods using the original projection data. The correction is limited to cases where the material causing the beam hardening is contained within the reconstruction space View full abstract»

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  • Planar double delay-line readout technique for microchannel plate detectors

    Publication Year: 1990 , Page(s): 1548 - 1549
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    A two-dimensional position-sensitive electrical readout system for microchannel plate detectors in spectroscopic applications has been devised. Two adjacent parallel coplanar delay lines are used. The difference in time of arrival of the electron event signal between the ends of the delay lines gives one coordinate of the centroid of each event pulse. The ratio of the event amplitudes on the two delay lines gives the orthogonal coordinate by means of charge partitioning. The performance characteristics of operational double delay lines for systems of this type are presented View full abstract»

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  • A VME multiprocessor data acquisition system combining a UNIX workstation and real-time microprocessors

    Publication Year: 1990 , Page(s): 1514 - 1519
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (504 KB)  

    A data acquisition system combining a UNIX workstation and one or several real-time microprocessors has been designed and built for the tandem accelerator. The hardware and software options chosen for reading, processing, storing, and displaying real-time experimental data are detailed. The fixed components of the hardware architecture are the VME bus for data processing and the CAMAC system for transferring digital data. A multitask multiprocessor software based on shared memory and message passing has been developed around a mixed UNIX/pSOS kernel View full abstract»

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  • Comparison of photocurrent enhancement and upset enhancement in CMOS devices in a medium-energy X-ray environment

    Publication Year: 1990 , Page(s): 1541 - 1547
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (628 KB)  

    Radiation-induced upset levels in SA3001 static random access memories (SRAMs) and SA3246 clock integrated circuits (ICs) have been measured in a medium-energy flash X-ray environment (average photon energy ~100 keV), where dose-enhancing effects are very important. By comparing device responses using a non-dose-enhancing ceramic package lid and a dose-enhancing Kovar/gold lid, dose-enhancement factors for photocurrent and upset were generated. The observed upset enhancement factors of 3.0±0.5 (SRAM) and 2.2±0.2 (clock IC) are in excellent agreement with measurements of photocurrent enhancement factors (2.5±0.5) in diodes processed with the same diffusions as the complementary metal-oxide-semiconductor (CMOS) ICs irradiated in a steady-state X-ray environment. These results indicate that upset is dominated by the radiation-induced transient supply current in these ICs, and that steady-state diode photocurrent measurements are a good predictor of both photocurrent and upset enhancement for ICs made with this technology View full abstract»

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IEEE Transactions on Nuclear Science focuses on all aspects of the theory and applications of nuclear science and engineering, including instrumentation for the detection and measurement of ionizing radiation; particle accelerators and their controls; nuclear medicine and its application; effects of radiation on materials, components, and systems; reactor instrumentation and controls; and measurement of radiation in space.

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