1. 旋进：它不仅用以诊断疾病,MRI是利用含奇数质子的原子核(如1H、13C、19F、23Na)自旋运动(Spin)的特点,置于外加的强大均匀磁场(称为主磁场)内,使原排列杂乱的原子核在磁力作用下而按周围磁场方向排列成行,这种原子核围绕主磁场轴旋转的现象,称为旋进(precession).

1. the act of preceding in time or order or rank (as in a ceremony)

    Synonym: precedenceprecedency

2. the motion of a spinning body (as a top) in which it wobbles so that the axis of rotation sweeps out a cone