| 摘要 |
<p>In a magnetic resonance imaging apparatus 1 there is a region of good i.e. uniform field between A and B but, where the field falls off, say, at D, the r.f. excitation pulse can produce an alias image of D which overlies the desired image of say, B. To reduce this effect, the r.f. excitation coil 4 comprises an array of small coils, the amplitude and phase of the excitation of which is controlled so that the r.f. field collapses rapidly outside the region of good field. <IMAGE></p> |
