It is demonstrated that the basic radiofrequency pulse train used to generate stimulated echoes (90x-τTE-90x-τTM-90x-τTE-Acq.) is in general characterized by strong amplitude and phase modulations of the transverse magnetization as a function of the resonance offset. Two dephasing techniques which eliminate the modulations are investigated both theoretically and experimentally, and a simple formula is derived for calculating the relative modulation across a spectrum as a function of gradient strength and duration, echo delay, and spectral linewidth.
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Acknowledgments-This research was supported in part by NIH grants #HL32427, #CA50703, and #R29CA43841.
- In vivo spectroscopy
- Resonance offset
- Spectroscopic localization
- Stimulated echo