Abstract
My co-authors and I appreciate the interest of Drs. Beasley, Moore, and Wagner in our publication, “Radiation Safety in the Treatment of Patients with Thyroid Diseases by Radioiodine 131I: Practice Recommendations of the American Thyroid Association” (1). They importantly emphasize the obligation to protect young and vulnerable children from radiation exposure when others receive 131I treatment for hyperthyroidism.
In response to the assertion that we did not fully address the in-depth counseling required for infants' exposure, we offer the following. 1) We agree that dosages greater than 15 mCi are often administered. In Tables 2A-1 and 2B-1, the list of dosages included: 10, 15, 20, and 30 mCi as examples. 2) Uptakes of 131I by hyperthyroid glands may exceed 50% of the administered activity, but how frequently depends upon, among other variables, the geographic region in which treatment is provided. 3) The effective half-life of 131I in hyperthyroid glands has varied in different investigations. The reference cited by Beasley et al. (2) recorded a mean effective half life of 6.2±1.2 days in 18 patients. However, in our paper (1) we reference a report on 224 patients in which the subgroups had mean effective half lives of 4.8–5.2 days (3). Moreover, effective half-lives of thyroidal 131I have varied when the disease was Graves' or toxic nodular goiter and whether anti-thyroid drugs had been administered (4,5). 4) We agree that exposure after the restriction period should be taken into account. See following text for discussion of our guiding principles. 5) Whether our recommendations insufficiently address the protection of the class of vulnerable very young children is a matter of opinion and depends upon the overall goals of the communication. Our report (1) aimed to cover major concerns in radiation protection. In Table 3, under Information gathering for radiation safety precaution planning and the subtitle Home, there is a line: “Special Household Situations…provide appropriate information and make an alternate arrangement” which is followed by “[when] Patient is responsible for the care of an infant or young child.”
We could not be all-inclusive in our recommendations, but we expressed broad principles (1). Thus, on pg 338, under Results and Discussion, the last sentence of the first paragraph reads: “Individualization is stressed in predicting, calculating, and measuring the retained activity in each patient.” And, at the beginning of Table 3, “It is incumbent upon the Radiation Treatment Team and the patient to agree upon a plan that, by environmental population assessments and by calculation, will not put others at risk of radiation exposure as identified in the NRC regulations (in a correction Thyroid
Also, the title of Table 2 states, “Examples of Precaution Requirements and Recommendations After Treatments with 131I.” Again, we could not be all-inclusive, but examples demonstrate individual-specific calculations. When available, data specific to the patient undergoing treatment should be used.
Of minor note, Beasley et al. refer to a report (6) describing children of ages 1 and 3 years who received doses of 3.3 and 7.2 mSv. Actually in that publication, 6 of 17 children under age 3 received greater than 1 mSv, but the maximum was 5.8 mSv.
Again, we welcome the reminder by Drs. Beasley, Moore and Wagner that, in designing protection from hazards of radiation, children, and especially those less than 3 years of age, require particular attention.