Direct simulation of spin echoes by summation of isochromats

• Published in: Concepts in magnetic resonance Vol. 8; no. 4; pp. 253 - 268
• Main Authors: Shkarin, Pavel, Spencer, Richard G. S.
• Format: Journal Article
• Language: English
• Published: New York John Wiley & Sons, Inc 1996
• ISSN: 1043-7347; 1099-0534
• DOI: 10.1002/(SICI)1099-0534(1996)8:4<253::AID-CMR2>3.0.CO;2-Y

Numerous methods have been used to illustrate and simulate complex spin‐echo phenomena for noninteracting spins. Our approach is to reconstruct the time domain signal by what amounts to a finite Fourier series, the terms of which correspond to spin isochromats. The coefficients of the series evolve in response to pulses and periods of free precession. This permits explicit calculation of echo timings and amplitudes for a sequence of strong pulses of arbitrary number, timing, flip angle, and phase. The effects of the shape and density of the isochromat distribution on echo formation are investigated, as are the effects of spin‐spin and spin‐lattice relaxation. In addition, we identify explicitly the magnetization components that contribute to echo formation in complex sequences. Further, the effect of pulse errors on echo amplitudes is readily simulated. © 1996 John Wiley & Sons, Inc.