Health concerns related to radiation exposure of the female nuclear medicine patient.

The female nuclear medicine patient is of special concern in evaluating radiation dose and risk in nuclear medicine. The female's overall body size and organ sizes generally are smaller than those of her male counterpart (thus her radiation doses will be higher, given the same amounts of administered activity and similar biokinetics); female gonads are inside the body instead of outside and are near several organs often important as source organs in internal dosimetry (urinary bladder, liver, kidneys, intestines); risk of breast cancer is significantly higher among females than males; and in the case of pregnancy, exposure to radiation of the embryo/fetus and the nursing infant are of special concern in such an analysis. All these concerns are addressed in this study through a comparative study of radiation doses for males and females over a large number (approximately 60) of nuclear medicine studies and through a study of what is known about radiation dosimetry in pregnancy and breast feeding. It was found that women's critical organ doses and effective doses (as defined by the International Commission on Radiological Protection 60 [ICRP 60] are about 25% higher than those for men across all these studies. Women's gonad doses, however, may be as much as 10 to 30 times higher than those in men, although 2- to 3-fold differences are common. Many radiopharmaceuticals are administered to women of childbearing age; however, little is known about how much activity crosses the placenta and about the biokinetics in the fetus should it occur. Nonetheless, dose estimates are provided at four stages of pregnancy (early, 3-month, 6-month, and 9-month gestation) for a large number of radiopharmaceuticals, whether or not quantitative estimates of placental crossover can be made. Many radiopharmaceuticals are also excreted in breast milk of nursing mothers. Breast feeding interruption schedules are suggested through analysis of the observed kinetics of these pharmaceuticals and an assumed dose limit of 1 mSv (effective dose equivalent) to the infant.