| 摘要 |
<p>In magnetic resonance spectroscopy or imaging, e.g. n.m.r. or e.s.r., a method of localizing the region of a sample from which a resonance signal is obtained by modulating the component Mz of magnetization in the Bo direction according to position in the sample. This is achieved by flipping the spins away from the Bo direction, applying a gradient magnetic field so that they lose or gain phase according to their position, refocussing the effects of any resonance offsets including chemical shifts and subsequently returning them to the Bo direction whereupon Mz depends on the phase lost or gained and thus the position. This may be repeated, possibly with different gradient fields or different phase pulses, to further localize the region before a resonance signal is finally detected. The contribution to the resonance signal varies with Mz and so is localized to regions of greater Mz.</p> |
