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AbstractAbstract
[en] In positron emission tomography (PET), the annihilation radiation is usually detected as a coincidence occurrence that localizes the position of the annihilation event to a straight line joining the detectors. The measure of the difference between the time of flight (TOF) of the annihilation photons between their inception and their detection permits the localization of the position of the annihilation event along the coincidence line. The incorporation of TOF information into the PET reconstruction process improves the signal-to-noise ratio in the image obtained. The utilization of scintillation detectors utilizing cesium fluoride scintillators, fast photomultiplier tubes, and fast timing circuits allows sub-nanosecond coincidence timing resolution needed for the effective use of TOF in PET. Mathematical considerations and pilot experiments show that with state-of-the-art electronic components and through the application of proper reconstruction algorithms, the combination of TOF and PET positional data improves severalfold the signal-to-noise ratio with respect to conventional PET image reconstruction at the cost of increasing the amount of data to be processed. The construction of a TOF-assisted PET device is within the capability of state-of-the-art technology
Primary Subject
Record Type
Journal Article
Journal
Journal of Computer Assisted Tomography; v. 5(2); p. 227-239
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INIS VolumeINIS Volume
INIS IssueINIS Issue
AbstractAbstract
[en] A feasibility study was carried out to determine whether image quality can be improved by the use of time-of-flight (TOF) information in positron emission tomography (PET). The experiment used two fast cesium fluoride detectors followed by constant-fraction discriminators for coincidence-timing resolutions of 600 to 800 psec full width at half maximum, depending on the energy discrimination level. A point source was scanned to study the spatial response of the point spread function with and without the TOF information for nonfiltered back-projected data. Back-projected images of a simplified chest phantom, 42 cm in diameter and filled with relative activity concentrations of 1, 0, and 5, are presented for the unfiltered data to demonstrate the improvement in image quality obtained with the use of TOF. Filtered and reconstructed images of this phantom are also presented to show the relative differences in the images obtained with PET and TOF-PET techniques for similar filter functions
Primary Subject
Secondary Subject
Source
28. annual meeting of the Society of Nuclear Medicine; Las Vegas, NV, USA; 16 Jun 1981
Record Type
Journal Article
Literature Type
Conference
Journal
Journal of Nuclear Medicine; ISSN 0022-3123; ; v. 21(11); p. 1095-1097
Country of publication
Reference NumberReference Number
INIS VolumeINIS Volume
INIS IssueINIS Issue
AbstractAbstract
[en] A comparison of several reported methods for detection and quantitation of left-to-right shunts by radionuclides was performed in 50 children. Count ratio (C2/C1) techniques were compared with the exponential extrapolation and gamma function area ratio techniques. C2/C1 ratios accurately detected shunts and could reliably separate shunts from normals, but there was a high rate of false positives in children with valvular heart disease. The area ratio methods provided more accurate shunt quantitation and a better separation of patients with valvular heart disease than did the C2/C1 ratio. The gamma function method showed a higher correlation with oximetry than the exponential method, but the difference was not statistically significant. For accurate shunt quantitation and a reliable separation of patients with valvular heart disease from those with shunts, area ratio calculations are preferable to the C2/C1 ratio
Primary Subject
Record Type
Journal Article
Journal
Circulation; v. 51(6); p. 1136-1143
Country of publication
ANIMALS, BETA DECAY RADIOISOTOPES, BETA-MINUS DECAY RADIOISOTOPES, BODY, CARDIOVASCULAR SYSTEM, COUNTING TECHNIQUES, DIAGNOSTIC TECHNIQUES, DISEASES, HOURS LIVING RADIOISOTOPES, INTERMEDIATE MASS NUCLEI, ISOMERIC TRANSITION ISOTOPES, ISOTOPES, MAMMALS, MAN, MEDICINE, NUCLEAR MEDICINE, NUCLEI, ODD-EVEN NUCLEI, ORGANS, OXYGEN COMPOUNDS, PATHOLOGICAL CHANGES, PRIMATES, RADIOISOTOPE SCANNING, RADIOISOTOPES, TECHNETIUM COMPOUNDS, TECHNETIUM ISOTOPES, TRANSITION ELEMENT COMPOUNDS, VERTEBRATES, YEARS LIVING RADIOISOTOPES
Reference NumberReference Number
INIS VolumeINIS Volume
INIS IssueINIS Issue
AbstractAbstract
[en] A new radiopharmaceutical, 68Ga ion hydroxide colloid, for hepatic imaging by positron emission tomography was prepared from the eluate of a 68Ge-68Ga solvent extraction generator. In rats, 84% of the administered dose of colloid localized in the liver and 4.6% accumulated in the spleen. Initial imaging studies in normal dogs showed close correspondence of the findings by positron tomography and transmission computed tomography. Emission tomography with 68Ga-colloid was performed in 10 patients with hepatic metastases demonstrated by conventional 99mTc sulfur colloid scintigraphy. All focal defects noted on the conventional scintigrams were easily identified and generally were seen more clearly by positron tomography. In one patient, additional lesions not identified on the initial 99mTc sulfur colloid images were demonstrated. The positron tomographic images were compared with those obtained by transmission computed tomography in seven patients; the two studies showed comparable findings in five patients, whereas positron tomography more clearly showed multiple lesions in two. Our results suggest that positron emission tomography is a suitable technique for obtaining high contrast, cross-sectional images of large abdominal organs
Primary Subject
Secondary Subject
Record Type
Journal Article
Journal
American Journal of Roentgenology; v. 136(4); p. 685-690
Country of publication
ANIMALS, BETA DECAY RADIOISOTOPES, BETA-MINUS DECAY RADIOISOTOPES, BETA-PLUS DECAY RADIOISOTOPES, BODY, COLLOIDS, COMPUTERIZED TOMOGRAPHY, COUNTING TECHNIQUES, DIAGNOSTIC TECHNIQUES, DIGESTIVE SYSTEM, DISPERSIONS, DRUGS, EMISSION COMPUTED TOMOGRAPHY, GALLIUM ISOTOPES, GLANDS, HOURS LIVING RADIOISOTOPES, INTERMEDIATE MASS NUCLEI, ISOMERIC TRANSITION ISOTOPES, ISOTOPES, LABELLED COMPOUNDS, NUCLEI, ODD-EVEN NUCLEI, ODD-ODD NUCLEI, ORGANS, RADIOACTIVE MATERIALS, RADIOISOTOPE SCANNING, RADIOISOTOPES, SYNTHESIS, TECHNETIUM ISOTOPES, TOMOGRAPHY, YEARS LIVING RADIOISOTOPES
Reference NumberReference Number
INIS VolumeINIS Volume
INIS IssueINIS Issue
AbstractAbstract
[en] Quantitation of regional myocardial blood flow (MBF) in absolute terms with positron emission tomography (PET) has been difficult to achieve in part because of errors induced by the relatively low spatial resolution of current tomographic instruments. We previously demonstrated that MBF could be accurately measured over a wide range of flows after intravenous administration of H2 15O when the arterial input function and myocardial radiotracer content were measured directly. To extend this quantitative approach for noninvasive estimates of MBF with PET. We recently developed and implemented a novel mathematical approach whereby partial volume and spillover effects were estimated along with flow within the operational one-compartment flow equation. Noninvasive estimates of flow correlated closely with flow measured directly with radiolabeled microspheres. In the present study, with the use of a commercially available cardiac phantom, we assessed our ability to obtain true time-activity curves from observed PET data contaminated by partial volume and spillover effects. Computer simulations demonstrated that the approach developed is relatively insensitive to most potential sources of error, but is sensitive to timing discrepancies between the arterial input function and the tissue time-activity curve. Implementation of this approach provides accurate quantitation of regional MBF in absolute terms and should be useful in noninvasive evaluation of the efficacy of treatments designed to enhance nutritional perfusion in human subjects
Primary Subject
Record Type
Journal Article
Journal
Country of publication
BETA DECAY RADIOISOTOPES, BETA-PLUS DECAY RADIOISOTOPES, BODY, CARDIOVASCULAR SYSTEM, COMPUTERIZED TOMOGRAPHY, EMISSION COMPUTED TOMOGRAPHY, EVEN-ODD NUCLEI, HYDROGEN COMPOUNDS, ISOTOPE APPLICATIONS, ISOTOPES, LIGHT NUCLEI, MINUTES LIVING RADIOISOTOPES, MOCKUP, MUSCLES, NUCLEI, ORGANS, OXYGEN COMPOUNDS, OXYGEN ISOTOPES, POLAR SOLVENTS, RADIOISOTOPES, RESOLUTION, SOLVENTS, STRUCTURAL MODELS, TOMOGRAPHY
Reference NumberReference Number
INIS VolumeINIS Volume
INIS IssueINIS Issue
AbstractAbstract
[en] All tracer-kinetic models currently employed with positron-emission tomography (PET) are based on compartmental assumptions. Our first indication that a compartmental model might suffer from severe limitations in certain circumstances when used with PET occurred when we implemented the Kety tissue-autoradiography technique for measuring CBF and observed that the resulting CBF estimates, rather than remaining constant (to within predictable statistical uncertainty) as expected, fell with increasing scan duration T when T greater than 1 min. After ruling out other explanations, we concluded that a one-compartment model does not possess sufficient realism for adequately describing the movement of labeled water in brain. This article recounts our search for more realistic substitute models. We give our derivations and results for the residue-detection impulse responses for unit capillary-tissue systems of our two candidate distributed-parameter models. In a sequence of trials beginning with the simplest, we tested four progressively more detailed candidate models against data from appropriate residue-detection experiments. In these, we generated high-temporal-resolution counting-rate data reflecting the history of radiolabeled-water uptake and washout in the brains of rhesus monkeys. We describe our treatment of the data to yield model-independent empirical values of CBF and of other parameters. By substituting these into our trial-model functions, we were able to make direct comparisons of the model predictions with the experimental dynamic counting-rate histories, confirming that our reservations concerning the one-compartment model were well founded and obliging us to reject two others. We conclude that a two-barrier distributed-parameter model has the potential of serving as a substitute for the Kety model in PET measurements of CBF in patients, especially when scan durations for T greater than 1 min are desired
Primary Subject
Record Type
Journal Article
Journal
Country of publication
Reference NumberReference Number
INIS VolumeINIS Volume
INIS IssueINIS Issue
AbstractAbstract
[en] In positron emission tomography (PET), the annihilation radiation is usually detected as a coincidence occurrence that localizes the position of the annihilation event to a straight line joining the detectors. The measure of the difference between the time of flight (TOF) of the annihilation photons between their inception and their detection permits the localization of the position of the annihilation event along the coincidence line. The incorporation of TOF information into the PET reconstruction process improves the signal-to-noise ratio in the image obtained. The utilization of scintillation detectors utilizing cesium fluoride scintillators, fast photomultiplier tubes, and fast timing circuits allows sub-nanosecond coincidence timing resolution needed for the effective use of TOF in PET. Mathematical considerations and pilot experiments show that with state-of-the-art electronic components and through the application of proper reconstruction algorithms, the combination of TOF and PET positional data improves severalfold the signal-to-noise ratio with respect to conventional PET image reconstruction at the cost of increasing the amount of data to be processed. The construction of a TOF-assisted PET device is within the capability of state-of-the-art technology
Primary Subject
Secondary Subject
Record Type
Journal Article
Journal
Journal of Computer Assisted Tomography; v. 5(2); p. 227-239
Country of publication
Reference NumberReference Number
INIS VolumeINIS Volume
INIS IssueINIS Issue
AbstractAbstract
[en] The tissue autoradiographic method for the measurement of regional cerebral blood flow (rCBF) in animals was adapted for use with positron emission tomography (PET). Because of the limited spatial resolution of PET, a region of interest will contain a mix of gray and white matter, inhomogeneous in flow and in tracer partition coefficient (lambda). The resultant error in rCBF, however, is less than 4%. Although the tissue autoradiographic method requires a monotonically increasing input function to ensure a unique solution for flow, the PET adaptation does not, because of an additional integration in the operational equation. Simulation showed that the model is accurate in the presence of ischemia or hyperemia fo the gray matter. Inaccuracy in timing of the arterial input function will result in large errors in rCBF measurement. Propagation of errors in measurement of tissue activity is largely independent of flow, reflecting the nearly linear flow compared with activity relationship
Primary Subject
Record Type
Journal Article
Journal
Journal of Nuclear Medicine; ISSN 0022-3123; ; v. 24(9); p. 782-789
Country of publication
BETA DECAY RADIOISOTOPES, BETA-PLUS DECAY RADIOISOTOPES, BODY, CENTRAL NERVOUS SYSTEM, COMPUTERIZED TOMOGRAPHY, DIAGNOSTIC TECHNIQUES, EMISSION COMPUTED TOMOGRAPHY, EVEN-ODD NUCLEI, HYDROGEN COMPOUNDS, ISOTOPES, LIGHT NUCLEI, MINUTES LIVING RADIOISOTOPES, NERVOUS SYSTEM, NUCLEI, ORGANS, OXYGEN COMPOUNDS, OXYGEN ISOTOPES, RADIOISOTOPES, RESOLUTION, TOMOGRAPHY
Reference NumberReference Number
INIS VolumeINIS Volume
INIS IssueINIS Issue
AbstractAbstract
[en] The proceedings of the Sixth Nordic Meeting of the Biological Engineering Society held in Aberdeen in July 1984 on computer-aided biomedical imaging and graphics and physiological measurement and control are presented. The summaries of the papers presented cover the use of computer imaging and graphics in ultrasonic imaging, nuclear medicine, radiology, biomedical radiography, tomography and NMR imaging. The papers on the use of computers in physiological measurement and control cover subject headings including computer-based instrumentation, transducers, monitoring and control, assessment and therapy, clinical measurement, blood flow and signal processing and analysis. (U.K.)
Primary Subject
Secondary Subject
Source
1984; 2e 238 p; Biological Engineering Society; London (UK); ISBN 0 904716 27 9; ; Price Pound22.00. Summaries of papers.
Record Type
Book
Country of publication
Reference NumberReference Number
INIS VolumeINIS Volume
INIS IssueINIS Issue
AbstractAbstract
[en] The well-known tissue autoradiographic technique for the measurement of regional cerebral blood flow (CBF), originally proposed by Kety and his colleagues has been adapted for the measurement of CBF in human subjects using positron emission tomography (PET) and intravenously administered oxygen-15-labeled water. This report describes the steps necessary for the implementation of this PET/autoradiographic technique. In order to establish the accuracy of the method, we measured CBF with intravenously administered oxygen-15-labeled water and PET in anesthetized adult baboons and compared the results with blood flow measured by a standard tracer technique that uses residue detection of a bolus of oxygen-15-labeled water injected into the internal carotid artery. The correlation between CBF measured with PET and the true CBF for the same cerebral hemisphere was excellent
Primary Subject
Record Type
Journal Article
Journal
Journal of Nuclear Medicine; ISSN 0022-3123; ; v. 24(9); p. 790-798
Country of publication
ANIMALS, BETA DECAY RADIOISOTOPES, BETA-PLUS DECAY RADIOISOTOPES, BODY, CENTRAL NERVOUS SYSTEM, COMPUTERIZED TOMOGRAPHY, DIAGNOSTIC TECHNIQUES, EMISSION COMPUTED TOMOGRAPHY, EVEN-ODD NUCLEI, HYDROGEN COMPOUNDS, ISOTOPES, LIGHT NUCLEI, MAMMALS, MINUTES LIVING RADIOISOTOPES, NERVOUS SYSTEM, NUCLEI, ORGANS, OXYGEN COMPOUNDS, OXYGEN ISOTOPES, PRIMATES, RADIOISOTOPES, TOMOGRAPHY, VERTEBRATES
Reference NumberReference Number
INIS VolumeINIS Volume
INIS IssueINIS Issue
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