| 摘要 |
A method for reducing ringing in nuclear magnetic resonance measurements i s disclosed. The method includes inducing a static magnetic field in a sensiti ve volume to orient nuclear magnetic spins of nuclei in the sensitive volume. The nuclear spins are reoriented by a first selected angle. An amplitude of the static magnetic field is then adjusted to cause a first selected phase shift in a spin echo signal measure d subsequently to the reorienting by the first angle. The spins are then reoriented by a second selected angle, and a first spin echo signal is detected. After a selected wait time, reorienting by the first selected angle is repeated. Adjusting the amplitude of the static magnetic field is then repeated to cause a second selected phase shift in a subsequently measured spin echo. The first and second selected phase shifts have a difference between them of an odd numbered multiple of 180 degrees. Reorienting by the second selected and detecting a second spin echo signal are then repeated. Finally, a difference between t he first spin echo signal and the second spin echo signal is determined. In one embodiment , the measuring of the first and second spin echoes is repeated a selected number of times, and the difference is calculated between time corresponding ones of the first an d second spin echoes.
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