How long it takes for the radiation from the film to disappear depends mainly on what kind of examination is done. In the case of ordinary X-ray or CT, a certain dose of radiation may be produced to the human body during the filming and examination process, and the auxiliary radiation will disappear after the filming is completed, and the dose of such radiation is low and meets the national standard for radioactive examination, so there is basically no harm to human health. Patients who are concerned about radiation damage can also use lead plates to shield important parts during the filming process. However, if the patient is taking PET-CT, usually some radioactive substances need to be used in the body for imaging before taking the film, and the radioactive substances will remain in the human body for a period of time after the examination is finished, and the radiation will disappear completely only after a few days of metabolism.