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Anisotropy of the ultrasonic backscatter of myocardial tissue: II. Measurements in vivo 总被引:2,自引:0,他引:2
E I Madaras J Perez B E Sobel J G Mottley J G Miller 《The Journal of the Acoustical Society of America》1988,83(2):762-769
The purpose of this investigation was to determine the angular dependence of the backscatter from canine myocardial tissue in vivo and to compare it with the variation of backscatter over the cardiac cycle that has been recognized and reported previously. The backscatter was measured from regions of left ventricular wall in canine hearts in which the fibers of the muscle lay parallel to the surface of the heart and were oriented predominantly in a circumferential fashion. Because of technical considerations, the angle of insonification was varied systematically through two cycles in which the angle relative to the muscle fiber axes ranged from 60 degrees-120 degrees. Backscatter was maximum at angles of interrogation perpendicular to the myocardial fibers and minimum at those most acute (60 degrees) relative to the orientation of the fibers. The previously observed variation of integrated backscatter over the heart cycle was evident at each angle of interrogation. At end systole, the average maximum-to-minimum angular variation of integrated backscatter as 5.0 +/- 0.4 dB. At end diastole, the average maximum-to-minimum angular variation was 3.2 +/- 0.4 dB. Thus, even though angular dependence of the backscatter from tissues with directionally oriented structures is substantial, the anisotropy does not account for cardiac-cycle-dependent variation of backscatter. Accordingly, the angular dependence should be incorporated in approaches to quantitative tissue characterization with ultrasound. 相似文献
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Aihara H Alston-Garnjost M Avery RE Barbaro-Galtieri A Barker AR Barnes AV Barnett BA Bauer DA Bengtsson H Bintinger DL Bobbink GJ Bolognese TS Bross AD Buchanan CD Buijs A Caldwell DO Clark AR Cowan GD Crane DA Dahl OI Derby KA Eastman JJ Eberhard PH Edberg TK Eisner AM Enomoto R Erné FC Fujii T Gary JW Gorn W Hauptman JM Hofmann W Huth JE Hylen J Kamae T Kaye HS Kees KH Kenney RW Kerth LT Ko W Koda RI Kofler RR Kwong KK Lander RL Langeveld WG Layter JG Linde FL Lindsey CS Loken SC Lu A Lu X 《Physical review letters》1987,59(7):751-754
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Aihara H Alston-Garnjost M Avery RE Barbaro-Galtieri A Barker AR Barnes AV Barnett BA Bauer DA Bengtsson H Bintinger DL Blumenfeld BJ Bobbink GJ Bross AD Buchanan CD Buijs A Cain MP Caldwell DO Chamberlain O Chien C Clark AR Cowan GD Crane DA Dahl OI Derby KA Eastman JJ Eberhard PH Eisner AM Enomoto R Erné FC Fujii T Gabioud B Gary JW Gorn W Hauptman JM Hofmann W Huth JE Hylen J Joshi UP Kamae T Kaye HS Kees KH Kenney RW Kerth LT Ko W Koda RI Kofler RR Kwong KK Lander RL Langeveld WG Layter JG 《Physical review letters》1986,57(4):404-407
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Bauer DA Belcinski R Berg RC Bingham HH Bloom ED Buchanan CD Caldwell DO Chun SB Clark AR Dahl OI Eastman JJ Eberhard PH Eisner AM Fairfield KH Godfrey G Greenbaum GS Hauptman JM Hofmann W Holtzapple RL Khacheryan S Knöpfle KT Kofler RR Lambert DJ Loken SC Lu A Lynch GR Lys JE Madaras RJ Marsiske H Masek GE Miller ES Nicol NA Nygren DR Oyang YT Paar HP Palounek AP Pellett DE Ronan MT Ross RR Shapiro G Stephens RW Stevenson ML Strauss MG Sullivan MK Vernon W Wang EM Wang YX Wenzel WA Yamamoto H 《Physical review D: Particles and fields》1994,50(1):R13-R17
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Shell Filling and Spin Effects in a Few Electron Quantum Dot 总被引:1,自引:0,他引:1
Tarucha S Austing DG Honda T van der Hage RJ Kouwenhoven LP 《Physical review letters》1996,77(17):3613-3616
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We study graphs whose vertices possess the same value of betweenness centrality (which is defined as the sum of relative numbers of shortest paths passing through a given vertex). Extending previously known results of S. Gago, J. Hurajová, T. Madaras (2013), we show that, apart of cycles, such graphs cannot contain 2-valent vertices and, moreover, are 3-connected if their diameter is 2. In addition, we prove that the betweenness uniformity is satisfied in a wide graph family of semi-symmetric graphs, which enables us to construct a variety of nontrivial cubic betweenness-uniform graphs. 相似文献