The fluoride mixes with enamel, the hard surface on teeth, to help prevent holes, or cavities,from forming.

VOA: special.2009.03.11

Rather than by forming an image or a picture you put electrodes on the surface of the body and measure the electrical potential as a function of position on the body.

它并不对人进行直接的造影,而是将电极放到身体表面,通过测量该位置电势能,表征该部位的生理状态

耶鲁公开课 - 生物医学工程探索课程节选