VOA标准英语2016.07.14
[audio]http://sound.yywz123.com/tingbbs/voab/voab20160714.mp3[/audio]_______________________________ . An alternating magnetic field created inside the MRI\'s tube excites hydrogen atoms in the body’s tissues, making them emit radio waves. Those waves can be turned into pictures, similar to X-ray images.自20世纪80年代，医生就开始用核磁共振成像机器，或者核磁共振扫描仪，来检查病人的身体。这种方法可以使得病人不必遭受有害的X射线辐射。核磁共振成像管内的交变电场，会激活人组织内部的氢原子，使它们释放无线电波。_______________________________。
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