Radioactive iodine (radioiodine) is given to patients with some forms of thyroid cancer in order to destroy the cancer cells. 131I has a half-life of 8 days. Women who have been treated with 131I are advised to not become pregnant for 180 days (approximately 6 months) to avoid the radioactive contamination of a developing fetus. If a woman has been given a dose of 10 mCi (millicurie, a measurement of radiation), how much 131I will still be in her system when she can safely become pregnant? a.3.125% of the original isotope

b. There will be no iodine-131 left in her system after 180 days.

c.1.7 x 10-6 mCi

d.22.5 x 10-6 mCi