A small amount of radioactive substances used for scintigraphy of bones, heart, or other areas, will remain in the body at the point the examination is finished. However, data shows that the exposure dose to family members that live with the patient after the examination is only a few micro sieverts after 24 hours (source: Reasonable and Unreasonable Medical Radiation Protection, Innervision ; written in Japanese). At that dose level, there should be no problems with going home and interacting normally with family members. However, since higher energy levels are used for FDG-PET examinations than for scintigraphy, patients should wait about one hour within the hospital after FDG-PET examinations, but typically an hour elapses while processing payments and so on, so it should not be a problem for patients to leave the examination room immediately after examinations. Also, the half-life of the radioactive drug used for FDG-PET examinations is only two hours, so its radioactivity decreases quickly. Injected drugs are discharged from the body in urine, so radioactive drugs can be eliminated from the body more quickly by drinking lots of water and urinating.
Patient Exposure During Radiological Procedures