Answer to Question #8879 Submitted to "Ask the Experts"

Category: Nuclear Medicine Patient Issues — Diagnostic Nuclear Medicine

The following question was answered by an expert in the appropriate field:


I was wondering how safe it is for a small child, infant, or pregnant woman to be in close contact with a patient who has been injected with one or more radioactive isotopes. When I say close contact, I mean within three feet or less. Is there a time frame in which they should avoid contact? I work in a hospital and we tell all our patients to keep contact to a minimum but they don't all do that.


There are no recommendations to patients to restrict time or distance from infants and children from any diagnostic nuclear medicine exam, only from therapy procedures. The doses from diagnostic exams are so small as to be of no concern. The dose drops off rapidly with distance from the patient. The only possible restriction after a diagnostic exam is possibly to restrict breastfeeding for a period of time.

The Nuclear Regulatory Commission had a study performed to see how much activity would have to be given for all the common nuclear medicine drugs that would result in a dose of 1 millisievert to a family member. This is the dose limit for the public for licensed activities and it is one-third the average dose to Americans from natural background radiation from the earth, food and water, and cosmic radiation.

The amount of the drug needed to be given to reach that dose was as much as 5 to more than 20 times the amount a patient is given for typical exams. That is why no one gives directions to restrict time and distance after nuclear medicine exams.  

The dose to family members is extremely low and the majority of drugs decay away and are eliminated from the body in urine in a day or less.

Marcia Hartman, MS

Answer posted on 17 February 2010. The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, materials, and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.