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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European journal of nuclear medicine 11 (1985), S. 127-131 
    ISSN: 1619-7089
    Keywords: Positron emission tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A simple Monte Carlo program was constructed for the purpose of calculating absorbed fractions of relevance to neurologic positron-emission-tomography studies. The caudate, putamen, and cerebellum regions of the brain were mathematically modeled to serve as source regions for the absorbed-fraction calculations for positron-annihilation photons. The target organs were the caudate, putamen, cerebellum, brain, spine portion in the head, skull, and head. Absorbed fractions were also calculated for a uniform ring source which encircled the head phantom.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1619-7089
    Keywords: Fourier filtering ; Positron emission tomography ; Ramp ; only filtering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Positron emission tomography (PET) images are characterized by both poor spatial resolution and high statistical noise. Conventional methods to reduce noise, such as local weighted averaging, produce further deteriorations in spatial resolution, while the use of deconvolution to recover resolution typically amplifies noise to unacceptable levels. We studied the use of two-dimensional Fourier filtering to simultaneously increase quantitative recovery and reduce noise. The filter was based on inversion of the scanner's measured transfer function, coupled with high frequency roll-off. In phantom studies, we found improvements in both “hot” and “cold” sphere quantification. Compared with ramp-only filtering, improvements in hot spot recovery for the highest accuracy filter averaged 13.6%±6.6% for spheres larger than 15 mm; improvements in cold spot recovery averaged 30.7%±4.7%. At the same time, the noise was reduced by a factor of 3 compared with ramponly filtering. Fourier-based image restoration filtering is thus capable of improving both accuracy and precision in PET.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1619-7089
    Keywords: Positron emission tomography ; Fluorine18-fluoro-2-deoxy-D-glucose ; Local cerebral glucose utilization ; Factor analysis ; Healthy men
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Cerebral glucose utilization measured with fluorine-18-fluoro-2-deoxy-D-glucose is characterized by considerable variability both among different persons and for the same person examined on different occasions. The goal of this study was to explore whether some regions of the brain were more variable than others with respect to glucose utilization and whether there was a pattern in their covariance. The global and regional cerebral utilization of glucose was measured in 12 healthy young volunteers on 3 or 4 occasions. In all, 24 regions were examined. The interrelation of the glucose utilization rates of the brain regions was investigated by factor analysis of the metabolic rates. Some 70% of the total variance was attributable to only 1 factor, while 80% of the total variance could be attributed to 2 factors. Regions making up the first factor were the frontal and temporal cortex, cingulate gyrus, caudate nucleus, thalamus and putamen. These regions are functionally related to the limbic system. Regions of the second factor were the parietal cortex, occipital cortex and cerebellum, regions more clearly related to sensory and motor functions. The 2-factor pattern was highly reproducible, being found with different algorithms for factor extraction and rotation. Under resting conditions, the variance of cerebral metabolism seems to be primarily related to regions which are closely involved with the limbic system. Cortical regions involved primarily in motor and sensory functions have less influence on the variance.
    Type of Medium: Electronic Resource
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