If the patient is just having a normal X-ray or CT film, then only during the examination and the radiation emitted will have some radiation to the human body, and the radiation from the instrument will disappear after the examination. If the patient is having PET-CT, the radiation will last for a few days before it disappears because some radioactive substances are used on the human body before use and the residue of radioactive substances in the human body after the examination is over. The radiation only penetrates the body and causes some damage to the body in an instant, for example, it may damage the reproductive system, the blood system, or even affect the chromosomes, but this can only happen if the patient is frequently, and for a long time, under the radiation. Occasionally, this does not happen because the dose of radiation used each time is controlled by the state and is very safe. Before taking the film, you need to remove all kinds of objects in and around the examination area, wipe off the ointment and iodophor from the film area, and wear less clothes without buttons and decorative items.