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It is an efficient protocol to use the refocusing flip angle pulse optimization technique to solve special engineering technical problems in nuclear magnetic resonance (NMR) measurements. By reducing RF pulse duration, the low refocusing flip angle pulses can consume lower power, satisfy specific absorption rate of samples, and improve signal-to-noise ratio as well. To further analyze the function mechanism of pulse angles, the dependence of signal intensity on RF pulse is studied in homogenous magnetic field and constant gradient magnetic field respectively. Afterwards, echo amplitudes with various tip angles and flip angles ranging from 0° to 180° are compared with conventional sequence of 90° pulse followed by 180° pulses theoretically and experimentally. For the constant gradient field, the refocusing pulse of flip angle can be as low as 140°, defined as the optimum herein, to obtain the strongest signal intensity, enhanced by 13% compared with that of 180°. Moreover, T1 distributions measured by the conventional and optimal sequences for distilled water at room temperature are compared, and good conformances of T1 between the two pulse sequences are obtained, which demonstrates the optimal refocusing pulse can be directly applied to T1 measurement. The results provide constructive suggestion for designing pulse sequences for signal intensity enhancement in NMR logging while drilling and NMR online quick analysis.
[1] Hennig J, Friedburg H 1988 Magn. Reson. Imaging 6 391
[2] Alsop D C 1997 Magn. Reson. Med. 37 176
[3] Hennig J, Nauerth A, Friedburg H 1986 Magn. Reson. Med. 3 823
[4] Haase A, Frahm J, Matthaei D, Hänicke W, Merboldt K D 1986 J. Magn. Reson. 67 258
[5] McIntyre D J O, Hennel F, Morris P G 1998 J. Magn. Reson. 130 58
[6] Andrade F D, Netto A M, Colnago L A 2011 Talanta 84 84
[7] Andrade F D, Netto A M, Colnago L A 2012 J. Magn. Reson. 214 184
[8] Hrlimann M D, Griffin D D 2000 J. Magn. Reson. 143 120
[9] Song Y Q 2002 J. Magn. Reson. 157 82
[10] Reiderman A, Itskovich G, Krugliak Z, Beard D R 2001 Magn. Reson. Imaging 19 569
[11] Li X, Xiao L Z, Liu H B 2011 Well Logging Technol. 35 200 (in Chinese) [李新, 肖立志, 刘化冰 2011测井技术 35 200]
[12] Coates G R, Xiao L Z, Prammer M G 1999 NMR Logging Principles and Applications (Houston: Halliburton Energy Services) p101
[13] Zu D L 2004 Magnetic Resonance Imaging (Beijing: Higher Education Press) p83 (in Chinese) [俎栋林 2004 核磁共振成像学(北京: 高等教育出版社) 第83页]
[14] Bloch F 1946 Phys. Rev. 70 460
[15] Chen J F, Liu W Q, Zhong W X 2006 Acta Phys. Sin. 55 884 [陈杰夫, 刘婉秋, 钟万勰 2006 55 884]
[16] Casanova F, Perlo J, Blmich B 2011 Single-Sided NMR (Berlin Heidelberg: Springer-Verlag) p12
[17] Anferova S, Anferov V, Rata D G, Blmich B, Arnold J, Clauser C, Blmler P, Raich H 2004 Concepts Magn. Reson. B 23B 26
[18] Anferova S, Anferov V, Arnold J, Talnishnikh E, Voda M A, Kupferschlager K, Blmler P, Clauser C, Blmich B 2007 Magn. Reson. Imaging 25 474
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[1] Hennig J, Friedburg H 1988 Magn. Reson. Imaging 6 391
[2] Alsop D C 1997 Magn. Reson. Med. 37 176
[3] Hennig J, Nauerth A, Friedburg H 1986 Magn. Reson. Med. 3 823
[4] Haase A, Frahm J, Matthaei D, Hänicke W, Merboldt K D 1986 J. Magn. Reson. 67 258
[5] McIntyre D J O, Hennel F, Morris P G 1998 J. Magn. Reson. 130 58
[6] Andrade F D, Netto A M, Colnago L A 2011 Talanta 84 84
[7] Andrade F D, Netto A M, Colnago L A 2012 J. Magn. Reson. 214 184
[8] Hrlimann M D, Griffin D D 2000 J. Magn. Reson. 143 120
[9] Song Y Q 2002 J. Magn. Reson. 157 82
[10] Reiderman A, Itskovich G, Krugliak Z, Beard D R 2001 Magn. Reson. Imaging 19 569
[11] Li X, Xiao L Z, Liu H B 2011 Well Logging Technol. 35 200 (in Chinese) [李新, 肖立志, 刘化冰 2011测井技术 35 200]
[12] Coates G R, Xiao L Z, Prammer M G 1999 NMR Logging Principles and Applications (Houston: Halliburton Energy Services) p101
[13] Zu D L 2004 Magnetic Resonance Imaging (Beijing: Higher Education Press) p83 (in Chinese) [俎栋林 2004 核磁共振成像学(北京: 高等教育出版社) 第83页]
[14] Bloch F 1946 Phys. Rev. 70 460
[15] Chen J F, Liu W Q, Zhong W X 2006 Acta Phys. Sin. 55 884 [陈杰夫, 刘婉秋, 钟万勰 2006 55 884]
[16] Casanova F, Perlo J, Blmich B 2011 Single-Sided NMR (Berlin Heidelberg: Springer-Verlag) p12
[17] Anferova S, Anferov V, Rata D G, Blmich B, Arnold J, Clauser C, Blmler P, Raich H 2004 Concepts Magn. Reson. B 23B 26
[18] Anferova S, Anferov V, Arnold J, Talnishnikh E, Voda M A, Kupferschlager K, Blmler P, Clauser C, Blmich B 2007 Magn. Reson. Imaging 25 474
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