来自《耶鲁大学开放课程：生物医学工程探索 第21集 第21集》

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  that radio frequency wave has to be exactly right
  必须选用恰当的电磁波频率
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  for the atoms that you want to move.
  来激发那些特定的原子
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  It has to be radio waves
  这些电磁波必须有
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  that are at the correct frequency or wavelength
  正确的频率 或者说是波长
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  to stimulate these particular atoms.
  来激发这些特定的原子
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  That's one of the things that makes MR so versatile,
  这使得磁共振无所不能
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  in that if you stimulate them with one frequency,
  因为如果用某个波长的电磁波激发原子
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  you can manipulate hydrogen atoms.
  你就能操纵这些氢原子
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  If you stimulate them with another frequency,
  如果用另一些波长的电磁波来激发
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  you can stimulate other atoms.
  你就能激发其它原子
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  Now, the reason why most of the images you'll see
  你现在看到的图像大多
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  are based on protons or hydrogen nuclei is because
  来源于质子 即氢原子核 这是因为