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  • 1
    ISSN: 1435-1285
    Keywords: Key words Intravascular ultrasound – coronary artery disease – plaque tissue characterization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Previous studies correlating histomorphology with 20–30 MHz-derived intravascular ultrasound (IVUS) images showed that IVUS provides to some extent qualitative information on plaque composition. IVUS imaging proved to define calcifications with high sensitivity and specificity but was found to be less accurate in the assessment of soft components. Nevertheless previous studies on atherosclerotic plaque characterization were limited by use of low-frequency transducers that did not define accurately soft components. Our goal was to test the effectiveness of high frequency IVUS transducers in the identification of lipid/necrotic pools in atherosclerotic plaques. Methods: Forty MHz transducers were used for in vitro IVUS assessment of 12 arterial segments (10 coronary arteries and 2 carotid arteries dissected from 5 different autopsy cases). IVUS acquisition was performed at a 0.5 mm/s speed after ligature of the branching points to generate a closed system. Lipid necrotic areas were defined by IVUS as large echolucent intraplaque areas surrounded by tissue with higher echodensity. To obtain histopathologic sections corresponding to IVUS cross sections, vessels were divided into consecutive 3 mm-long segments using the most distal recorded IVUS image as the starting reference. Then, samples were fixed with 10% buffered formalin, processed for histopathologic study, serially cut, and stained with the Movat penthacrome method. Results: One hundred twenty-two sections were analyzed. Lipid pools were observed by histology in 30 cross sections (25%). IVUS revealed the presence of lipid pools in 19 of 122 cross sections with a sensitivity and specificity of 67% and 94%, respectively. Conclusions: High frequency transducers accurately identify lipid/necrotic pools and open new perspectives on future IVUS characterization of atherosclerotic plaques.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Doubly differential electron velocity spectra induced by 36Ar18 + (95 MeV/u) from thin target foils (C, Ni, Ag, Au) were measured at GANIL (Caen, France) by means of the ARGOS multidetector and the time-of-flight technique. The main features observed in the forward spectra are convoy electrons, binary-encounter electrons, and (for the Au target only) a high-velocity tail which we attribute to a “Fermi shuttle” acceleration mechanism. Backward spectra do not show distinct structures. The spectra allow us to determine absolute singly differential cross-sections as a function of the target material and the emission angle. The convoy electron yield increases with the target atomic number, but for C their yield is so small that our experiment is not able to detect them. Absolute doubly differential cross-sections for binary-encounter electron ejection from C targets are well described by a transport theory which is based on the relativistic electron impact approximation (EIA) for electron production and which accounts for angular deflection, energy loss and energy straggling of the transmitted electrons.
    Type of Medium: Electronic Resource
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