Showing papers in "IEEE Transactions on Nuclear Science in 1979"
TL;DR: In this article, features of accelerators, microwave tubes, and free electron lasers are discussed in such a way as to bring out essential similarities and differences, and two classes of waveparticle interaction are distinguished.
Abstract: Some features of accelerators, microwave tubes, and free electron lasers are discussed in such a way as to bring out essential similarities and differences. Two classes of wave-particle interaction, and two regimes of operation are distinguished.
160 citations
TL;DR: In this article, a cyclic subgradient projection (CSP) method was proposed to calculate simultaneously attenuation and activity concentration coefficients, and some experimental results in its favor are presented.
Abstract: In order to obtain truly quantitative reconstruction of gamma-emitter concentration in Emission Computerized Tomography (ECT) the attenuation within the region of interest has to be accounted for. In this report we propose to calculate simultaneously attenuation and activity concentration coefficients. Starting from the system of non-linear equations which describes the model of single photon gamma-ray emission in a discretized form we show how to reduce it to a mixed convex-concave feasibility problem and apply to it our method of Cyclic Subgradient Projections (CSP). This approach is discussed and some experimental results in its favor are presented.
151 citations
TL;DR: In this article, the cause of the upsets is most probably a multi-MeV alpha particle created by an (n, alpha) or (p, alpha), or similar nuclear reaction.
Abstract: Dynamic 16K random access memories (RAMs) have been irradiated with neutrons having mean energies of 6.5, 9 and 14 MeV and with 32 MeV protons and have been found to undergo single event upset. For both particles, one upset is expected for approximately 108 particles/cm2. The upsets are statistical and the affected cells can be reset and continue normal operation. Both HIGH and LOW storage elements are upset though at different rates. The cause of the upsets is most probably a multi-MeV alpha particle created by an (n, alpha) or (p, alpha) or similar nuclear reaction. The alpha particle discharges either the storage capacitor, the floating bit line, or the reference capacitor used by the sense amplifier.
128 citations
TL;DR: In this article, the authors compare the noise properties of conventional and energy selective X-ray computed tomography (XCT) images and show that the conventional image is a subset of the energy selective data and demonstrate that if this is done at the optimal display energy, the resulting conventional image will have the same noise as that produced by a conventional system with the same dose.
Abstract: We compare the noise properties of conventional and energy selective X-ray computed tomography. The images produced by the systems are not directly comparable so we discuss their relationship and show that the conventional image is a subset of the energy selective data. We describe how to form a conventional image from the energy selective images and demonstrate that, if this is done at the optimal display energy, the resulting conventional image will have the same noise as that produced by a conventional system with the same dose. But the energy selective system also extracts all the energy dependent information so it produces more information for the same dose than a conventional system.
128 citations
TL;DR: In this article, soft errors have been induced in solid-state static RAM's by iron nuclei from the Lawrence Berkeley Laboratory (LBL) Bevalac, in experiments designed to prove the ability of iron-roup cosmic rays to generate such errors.
Abstract: Soft errors have been induced in solid-state static RAM's by iron nuclei from the Lawrence Berkeley Laboratory (LBL) Bevalac, in experiments designed to prove the ability of iron-roup cosmic rays to generate such errors. Subsequently, various de-lidded device types were tested in beams of argon and krypton ions from the LBL 88-inch Cyclotron, at energies near 2 MeV/nucleon. The latter tests showed that some devices are essentially immune to bit error while others are quite susceptible. Good agreement was obtained with model predictions in cases where the latter exist. Latchup, whose cause we attribute to individual heavy ions, was also observed in some device types.
115 citations
TL;DR: An inexpensive, high-speed multiple section computed-tomographic X-ray transmission scanner has been designed that will be used to determine regional myocardial perfusion and to quantify the volume of ischemic and infarcted tissue.
Abstract: An inexpensive, high-speed multiple section computed-tomographic X-ray transmission scanner has been designed. This scanner utilizes a novel multipleanode, scanning-electron-beam, X-ray source to obtain scan times of 50 msec for two adjacent tomographic sections. Up to 8 sections may be scanned in sequence in 200 msec. A conventional stationary detector array and data processing system is used. Dynamic scanning at a rate of 1/sec for 20 seconds (up to 160 images) in combination with intravenous contrast media injections will be used to determine regional myocardial perfusion and to quantify the volume of ischemic and infarcted tissue. Image quality comparable to conventional body scanners is expected.
106 citations
TL;DR: In this article, general properties as well as specific configurations of a new family of strong Rare Earth Cobalt quadrupoles are discussed, and the work prepared by Lawrence Berkeley Laboratory and funded by Los Alamos Scientific Laboratory for the Department.
Abstract: General properties as well as specific configurations of a new family of strong Rare Earth Cobalt quadrupoles are discussed. Work prepared by Lawrence Berkeley Laboratory and funded by Los Alamos Scientific Laboratory for the Department.
103 citations
TL;DR: In this paper, an algorithm is developed to compensate for the effect of attenuation of?-rays within the body using a constant attenuation coefficient and a known body contour.
Abstract: Correction for internal ?-ray absorption is an important aspect in single photon emission computed tomography. An algorithm has been developed to compensate for the effect of attenuation of ?-rays within the body. This algorithm consists of two correction steps and assumes a constant attenuation coefficient and a known body contour. The correction steps are applicable for both parallel beam and fan beam geometries. Computer simulations and experimental results have shown that this method provides a simple and effective correction for attenuation. The incomplete projection problem arises in whole body emission CT imaging, especially when fan beam collimators are used. It has been shown that fan beam geometry provides better spatial resolution than parallel beam geometry. For small organs inside the thoracic and abdominal cavities, however, fan beam geometry often produces incomplete projections which are caused by a decreased field of view of gamma cameras equipped with fan beam collimators. Two methods are described to reduce the artifacts generated from reconstruction of incomplete (truncated) projections.
101 citations
TL;DR: The Risk Assessment Review Group was organized by the U.S. Nuclear Regulatory Commission on July 1, 1977, with four elements to its charter: (1) Clarify the achievements and limitations of WASH-1400, the "Rasmussen Report." (2) Assess the peer comments thereon, and responses to those comments.
Abstract: The Risk Assessment Review Group was organized by the U.S. Nuclear Regulatory Commission on July 1, 1977, with four elements to its charter: (1) Clarify the achievements and limitations of WASH-1400, the "Rasmussen Report." (2) Assess the peer comments thereon, and responses to those comments. (3) Study the present state of such risk assessment methodology. (4) Recommend to the Commission how (and whether) such methodology can be used in the regulatory and licensing process.
100 citations
TL;DR: The health hazards of NMR imaging are not likely to become important if the RF power densities are less than 10 mW/cm2, static magnetic fields were less than 0.3 tesla and the temporal variation of fields is less than 3 T/sec.
Abstract: The health hazards of NMR imaging are not likely to become important if the RF power densities are less than 10 mW/cm2, static magnetic fields are less than 0.3 tesla and the temporal variation of fields is less than 3 T/sec.
95 citations
TL;DR: It is concluded that the fan-beam collimator system, when compared with conventional parallel-hole collimators, produces simultaneous improvements in SP/ECT system sensitivity and resolution, which results in improved visualization of small centrally located organs.
Abstract: Scintillation camera systems using parallel collimation have been used for single-photon emission computed tomography (SP/ECT). A major problem is the limited resolution of present parallel-hole collimators. We have built and evaluated collimators for a SP/ECT system, consisting of two opposing LFOV scintillation cameras and a gantry, which have parallel collimation along the cranial-caudal axis of the patient and converging collimation in a direction perpendicular to this axis. The collimator converges to a line of focus located 58 cm from the collimator face and parallel to the cranial-caudal axis of the patient. Two converging collimators combined with opposing LFOV cameras are capable of simultaneously imaging 11 contiguous, 2.6 (or 1.3) cm thick, transverse sections from data collected during a single revolution of the cameras about the patient. A fan beam convolution algorithm reconstructs the transverse slices and provides partial compensation for ?-ray attenuation. It is concluded that the fan-beam collimator system, when compared with conventional parallel-hole collimator systems, produces simultaneous improvements in SP/ECT system sensitivity and resolution. This results in improved visualization of small centrally located organs.
TL;DR: In this paper, a design procedure for the elimination of all second-order transverse geometric and chromatic aberrations in a particular class of static magnetic transport systems for charged-particle beams is given.
Abstract: A design procedure is given for the elimination of all of the second-order transverse geometric and chromatic aberrations in a particular class of staticmagnetic transport systems for charged-particle beams.
TL;DR: A new image reconstruction technique for computed tomography using projection data obtained by a smaller angle rotation less than 180 degrees around the object to estimate missing region in the Fourier transformed domain by extrapolation employing analytic continuity.
Abstract: A new image reconstruction technique for computed tomography is described. Projection data obtained by a smaller angle rotation less than 180 degrees around the object are used to make the image. The main feature of the method is the estimation of missing region in the Fourier transformed domain by extrapolation employing analytic continuity. Numerical simulations were carried out using computer generated pattern data. The results show strong effects of the content of noisy component on the reconstructed image. The method might be, however, practically applied to some real fields for medical diagnosis.
TL;DR: The design and performance characteristics of ECAT-II, a second generation whole-body positron imaging system, providing high contrast, high resolution, quantitative images in two-dimensional and tomographic formats is presented in this paper.
Abstract: The design and performance characteristics of ECAT-II, a second generation whole-body positron imaging system, providing high contrast, high resolution, quantitative images in two-dimensional and tomographic formats is presented. Discussed are: (i) a description of ECAT-II; (ii) the design criteria and implementation for maximizing image quality by minimizing effects such as random coincidence and scattered radiation, and by additionally performing dynamic background correction; and (iii) phantom studies to illustrate the implemented system resolution, efficiency, linearity, and field uniformity.
TL;DR: In this paper, Teflon, Mylar and Kapton H are compared from the point of view of charged-area scaling of discharge current pulse properties, and the experimental observations are used to motivate a theory of discharge arc propagation in which the propagation velocity is controlled by the rate of removal of excess charge via wave propagation along a filamentary tunnel filled with an overdense plasma.
Abstract: FEP Teflon, Mylar and Kapton H are compared from the point of view of charged-area scaling of discharge current pulse properties. The properties measured are peak current, pulse duration, released charge and energy dissipated in a load resistor, all for 20 keV incident electrons at a current density of 80 nA/cm2. In general it is found that the three materials are more similar than dissimilar, and furthermore that this similarity extends to discharge damage as well, the damage being identified as a combination of subsurface filamentary tunnels and surface grooves. The experimental observations are used to motivate a theory of discharge arc propagation in which the propagation velocity is controlled by the rate of removal of excess charge via wave propagation along a filamentary tunnel filled with an overdense plasma.
TL;DR: In this paper, two high-purity germanium coaxial detectors were irradiated simultaneously with fast neutrons from an unmoderated 252Cf source, and it was shown that the detector with the conventional electrode configuration was about 28 times more sensitive to radiation damage than was the detector having the p+ contact on the coaxial periphery.
Abstract: Two high-purity germanium coaxial detectors, having opposite electrode configurations from one another, but fabricated from the same germanium crystal, were irradiated simultaneously with fast neutrons from an unmoderated 252Cf source. Both detectors were 42 mm diam. The detector having the conventional electrode configuration was about 28 times more sensitive to radiation damage than was the detector having the p+ contact on the coaxial periphery. These results prove that germanium coaxial detectors having the conventional electrode configuration should not be used in any situation subject to significant radiation damage. This conclusion was anticipated because the defects produced by neutron and proton irradiation of germanium act predominantly as hole traps.
TL;DR: In this paper, two types of 4K dynamic RAM devices have been shown to exhibit soft errors when exposed to energetic protons, and the types of errors observed and their locations in memory depend on the beam energy.
Abstract: Two types of 4K dynamic RAM devices have been shown to exhibit soft errors when exposed to energetic protons. Considerable variation in sensitivity was found among devices, even those of the same model. For individual devices the soft error cross section increased with proton energy over the range of proton energies of from 18 to 130 MeV. The types of errors observed and their locations in memory were also found to depend on the beam energy.
TL;DR: In this article, a DC-to-200MHz, CCD-based transient data recorder is presented, which is designed to acquire 512 samples of data at intervals as small as one nanosecond (±25ps) and to an amplitude accuracy of eight bits (±0.2%).
Abstract: A DC-to-200MHz, CCD-based transient data recorder is currently under development. Multiple recorders will be operated via a conventional computer interface. Each recorder is designed to acquire 512 samples of data at intervals as small as one nanosecond (±25ps) and to an amplitude accuracy of eight bits (±0.2%). Developmental data is presented.
TL;DR: In this paper, the mean drift time interval from subsequent single ionization clusters of a relativistic particle in the TEC can be made large enough compared to the width of the anode signal to allow the recording of the clusters separately.
Abstract: The time expansion chamber (TEC), a new type of drift chamber, allows the measurement of microscopic details of ionization. The mean drift time interval from subsequent single ionization clusters of a relativistic particle in the TEC can be made large enough compared to the width of the anode signal to allow the recording of the clusters separately. Since single primary electrons can be detected, the cluster counting would allow an improved particle separation using the relativistic rise of primary ionization. In another application, very high position accuracy for track detectors or improved energy resolution may be obtained. Basic ionization phenomena and drift properties can be measured at the single electron level.
TL;DR: The performance of a new positron imaging device designed for high resolution dynamic studies on the human brain is described, which is the first to exploit the high photoelectric efficiency of bismuth germanate (BGO) detectors which are almost 3 times as dense as NaI.
Abstract: The performance of a new positron imaging device designed for high resolution dynamic studies on the human brain is described. This unit is the first to exploit the high photoelectric efficiency of bismuth germanate (BGO) detectors which are almost 3 times as dense as NaI. In the first 4 months of clinical use some 300 patient studies have been performed. The detector performance and design criteria are discussed. The principles of operation of the coincidence circuit and computer programs are described. Finally some clinical studies are presented to demonstrate its imaging capabilities.
TL;DR: In this paper, a convolutional formula is obtained for the direct reconstruction of a three-dimensional structure function from cone-beam projection measurements, where the cone apex is assumed to move on a circle to generate the two-dimensional projected images.
Abstract: A convolutional formula is obtained for the direct reconstruction of a three-dimensional structure function from cone-beam projection measurements. The cone apex is assumed to move on a circle to generate the two-dimensional projected images. The derivation starts from the three-dimensional form of the Radon inversion formula. A transformation of variables is applied to adapt this formula to the cone-beam projection geometry.
TL;DR: In this paper, the authors describe a stationary positron tomooraph desifier for the rapid, accurate, three-dimensional imaging of positron-labeled compounds anywhere in the human body.
Abstract: We describe a stationary positron tomooraph desiqned for the rapid, accurate, three-dimensional imaging of positron-labeled compounds anywhere in the human body. The system consists of a large gantry containing lead shieldinq and a 92 cm diam ring of 280 closely-packed rectanqular NaI(Tl) crystals, lightpipes and phototubes; coincidence and address circuits; semiconductor histogram memory; a hard-wired reconstructor; and a gray-level CRT. Event rates, backgrounds and resolution test images are presented.
TL;DR: Design considerations indicate that a clinically useful proton CT scanner is eminently feasible.
Abstract: The use of protons or other heavy charged particles instead of x rays in computed tomography (CT) is explored. The results of an experimental implementation of proton CT are presented. High quality CT reconstructions are obtained at an average dose reduction factor compared with an EMI 5005 x-ray scanner of 10:1 for a 30-cm-diameter phantom and 3.5:1 for a 20-cm diameter. The spatial resolution is limited by multiple Coulomb scattering to about 3.7 mm FWHM. Further studies are planned in which proton and x-ray images of fresh human specimens will be compared. Design considerations indicate that a clinically useful proton CT scanner is eminently feasible.
TL;DR: In this paper, a survey of latch-up control methods for VLSI-integrated CMOS is presented, and the extent of their applicability to VLSIs is discussed.
Abstract: The potential for latch-up, a pnpn self-sustaining low impedance state, is inherent in standard bulk CMOS-integrated circuit structures. Under normal bias, the parasitic SCR is in its blocking state but, if subjected to a large voltage spike or if exposed to an ionizing environment, triggering may occur. This may result in device burn-out or loss of state. The problem has been extensively studied for space and weapons applications. Prevention of latch-up has been achieved in conservative design (~9 ?m p-well depths) by the use of minority lifetime control methods such as gold doping and neutron irradiation and by modifying the base transport factor with buried layers. The push toward VLSI densities will enhance parasitic action sufficiently so that the problem will become of more universal concern. This paper will survey latch-up control methods presently employed for weapons and space applications on present (~9 ?m p-well) CMOS and will indicate the extent of their applicability to VLSI designs.
TL;DR: In this paper, the results of the initial studies of CT imaging are presented, and preliminary computer simulations are described and discussed, with the following advantages: (1) reduced biological hazard, (2) less expensive hardware, (3) easily extended to full 3D image, (4) very high data rates, and ability to make unique physiological measurements.
Abstract: The results of our initial studies of a new method of CT imaging are presented. The technique does not use x rays, but rather employs a weak electrical current to map out the electrical properties of the tissues in a tomographic slice. Results of preliminary computer simulations are described and discussed. Compared to x-ray CT, we expect ICT to have the following advantages: (1) reduced biological hazard, (2) less expensive hardware, (3) easily extended to full 3-D image, (4) very high data rates, (5) ability to make unique physiological measurements.
TL;DR: In this article, a thorough investigation has been done about the behavior of natural diamond as a radiation detector material for a wide temperature range, and the average energy required to create an electron-hole pair and energy resolution have been measured in the 100 K - 400 K interval.
Abstract: A thorough investigation has been done about the behavior of natural diamond as a radiation detector material for a wide temperature range. Drift velocities and mean free drift time have been determined at temperatures ranging between 85 K and 700 K and with electric fields up to 60 KV/cm. Average energy required to create an electron-hole pair and energy resolution have been measured in the 100 K - 400 K interval. The spectroscopic features of diamond detectors have also been analyzed on a broad temperature interval. It was found that as T approaches 500 K polarization phenomena begin, thus establishing the upper temperature limit for the detector operation.
CERN1
TL;DR: In this paper, it was shown that the self-forces caused by space charge and inductive wall impedances are proportional to the external force, making calculation of bucket area reduction and bunch lengthening easy.
Abstract: This distribution fits well with distributions observed in proton synchrotrons and makes several analytical calculations for bunched beams in longitudinal phase space possible. For any shape of the focusing force the line density becomes proportional to the potential well. Self-forces caused by space-charge and inductive wall impedances are thus proportional to the external force, making calculation of bucket area reduction and bunch lengthening easy. The microwave instability threshold, as given by the Keil-Schnell criterion with local values for current and energy spread, is independent of the azimuthal position along the bunch, and again analytical formulae are possible even for strongly non-linear focusing forces. The relative magnitude of the self-force and the microwave threshold turn out to be closely related, as the self-force is always 40% of the external force when the microwave threshold is reached. The classical longitudinal space-charge limit can therefore only be reached within a factor of 0.4. Other calculations with this "natural" distribution include analytical formulae for the rigid dipole mode threshold, and creation of flat-topped bunches with reduced peak line density resulting in a higher transverse space-charge limit.
TL;DR: In this paper, it was shown that a circular arrangement of detectors, i.e., a ring, provides optimum detection efficiency for positron emission tomography, but with insufficient sampling of rays.
Abstract: Detector Motion. Recent study has shown that a circular arrangement of detectors, i.e., a ring, provides optimum detection efficiency for positron emission tomography1. However, with a stationary ring there is insufficient sampling of rays (Fig. 1). Note that the ray spacing for central rays is equal to the circumferential detector spacing d, and is less for peripheral rays. This sampling limitation means a loss of frequency response and spatial resolution. It can also lead to aliasing artifacts2.
TL;DR: In this paper, a generalized method for the reconstruction of a region of interest within a slice in the presence of beam hardening is introduced, which is based on variable sampling of the projection data and a post-reconstruction correction scheme.
Abstract: A generalized method for the reconstruction of a region of interest within a slice in the presence of beam hardening is introduced. The method, limited field of reconstruction (LFV), is based on variable sampling of the projection data and a post-reconstruction correction scheme. An initial reconstruction of the whole slice is performed using the coarsely sampled projections. The low resolution reconstructed image is used to estimate the bone and tissue thicknesses along each ray. The bone and tissue lengths obtained from the first low resolution image are then used in subtracting the contribution of the external region from the region of interest and to correct for beam hardening. The finely sampled corrected projections are used in reconstructing a high resolution image of the region of interest without artifacts from the external region and beam hardening. Computer simulation results are presented and applicability of the present correction method to practical scanners is discussed.
TL;DR: In this article, the evolution of gamma-ray imaging is traced and a new gamma ray transverse section tomographic instrument is described which matches the favorable properties of wide-aperture focusing collimators to a form of the Radon equation which requires only angular averages of line integrals for reconstructions.
Abstract: The evolution of gamma-ray imaging is traced and a new gamma-ray transverse section tomographic instrument is described which matches the favorable properties of wide-aperture focusing collimators to a form of the Radon equation which requires only angular averages of line integrals for reconstructions. Single slice scans of less than 5 minutes are accomplished with amounts of radioactivity that are standard for procedures using gamma cameras.