The iodine is taken up by the active (abnormal) thyroid tissue, but not by any other tissues, resulting in a selective local accumulation of radioactive material in the abnormal tissues. (icatcare.org)
The more radioactive material in the vicinity, the more quickly the critical point is reached. (sciencedaily.com)
Mothers who received radioactive material for treatment or diagnostic purposes. (childdevelopmentinfo.com)