The radiation from liver enhancement ct is gone the moment the exam is over. The principle of liver enhancement ct is different from that of tests such as emission computed tomography (ECT). The principle of the former is to conduct imaging by energizing the bulb during the examination, and the radiation disappears at the same time after the examination; the latter is to conduct imaging by means of radioisotopes, which have a certain metabolic cycle, and therefore the examiner is still exposed to a certain amount of radiation for a period of time after the examination. Whether it is enhanced ct or emission computed tomography, as a regular means of medical examination in the clinic, the amount of radiation is controllable and will not cause significant harm to the examiner under normal use. It is recommended that those who need to undergo liver enhancement ct should improve the preparation before the examination under the guidance of a professional physician in order to obtain the best examination results.