来自《耶鲁大学开放课程：生物医学工程探索 第20集 第20集》

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  you're seeing a projected image.
  你看到的只是投影
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  You're only looking in one direction, really,
  实际上你只是从单一的方向来看
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  and you're seeing a projection of all the things
  你看到的是物体的投影
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  that the X-rays could pass through.
  所有X射线能穿过的物体的投影
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  I can't tell for example if the aortic arch
  比如 我不能分辨出
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  is in front of or behind the spine.
  脊柱前面的主动脉弓
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  I can't even tell where the boundary them of are
  我甚至分辨不清它们的边界
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  because it's all just-- they're absorbing X-rays
  因为它们都吸收X射线
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  and so I can't see it.
  所以我们看不见
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  What if I wanted to look at this in more detail,
  如果我想看到更多的细节
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  or I wanted to distinguish what part of this is this aortic arch
  或者说我想分辨出哪部分是主动脉弓
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  and what part is the spine, how would I change the imaging?
  哪部分是脊椎 我该怎样改进呢