CT is an X-ray based imaging, which can produce ionizing radiation for the human body. The human body receives ionizing radiation, which can produce random effects, so CT exams are hazardous. The occurrence of random effects is positively correlated with the dose; CT examinations may cause cancer, and the chance of cancer is also positively correlated with the radiation dose required for CT examinations. However, the risk is relatively low when CT examinations are performed with good protection. Therefore, patients should have CT examinations as needed for their medical conditions.