Abstract
I, and I am sure my co-authors, appreciate the kind words of Drs. Hennessey, Parker, and Garber and Radiation Safety Officer Kennedy in their comments on our publication, “Radiation Safety in the Treatment of Patients with Thyroid Diseases by Radioiodine (131I): Practice Recommendations of the American Thyroid Association” (1). They raised three important concepts that deserve discussion.
Patients whose thyroid glands and tissues exhibit differing fractional uptakes and effective half-lives of 131I will expose other people to varying levels of radiation after radioiodine treatments. In Table 2A-1 of our article (1), we provided examples of restriction durations for hyperthyroid patients in whom the assumed uptake was 50% at 24 hours and the effective half-life was 5 days, but the administered activities of 131I were varied. The footnote for Table 2 states that “Examples should be modified to meet local and specific needs.” Inherent in this explication is the assumption that radiation treatment teams will calculate radiation exposure according to the variables found in a given patient. The values for the variables that are commonly encountered are included in Table 2A-1 and with minor adjustments may be applied to the majority of patients. However, for some, the variables will be skewed from the usual. In appraisals of unusual patients, measurements of effective half-lives may be difficult to accomplish in a busy clinic, but a literature search should be helpful. For example, although effective half-lives in patients with nodular thyroid glands are especially difficult to assess, useful data can be gleaned from a publication by Nielsen et al. (2). For patients with nontoxic and toxic nodular goiters, this article reports that effective half-lives were estimated from 24- and 96-hour thyroid uptakes. The extremes recorded can be used to calculate the maximum durations of retained activities over time for patients with similar disorders. Then, with measurements of thyroid uptake and the proposed treatment in megabecquerel (millicuries), maximum levels of radiation exposure to others can be reasonably determined over subsequent days.
Disposal of radioactive trash can be vexing. The concerns are not solely for the risk of radiation exposure to others, but also for the possibility that terrorists may be using radioactivity. In our publication (1), in Table 4, Step 4, under “Outside the Home,” the possibility of setting off radiation detectors at national borders, airports, and elsewhere is addressed: radiation treatment teams should issue a letter or card that explains the low levels of radioactivity involved. Although, this action was not proposed in Table 4 for disposing radioactive trash, it offers a reasonable solution. If the radiation treatment team projects that the level of radiation in the trash of a patient at a given time is unlikely to threaten others, then a letter stating this conclusion should be given to the patient; copies can then be provided to the company that picks up the trash and to the disposal site.
The general status and disabilities of a patient should be assessed before any treatment is given. Limitations in activities should be advised not only for patients with hypothyroidism, but also for those with hyperthyroidism, Graves' eye disease, stroke, dementia, etc. Whereas disabilities must be taken into account when administering 131I, these should have previously been confronted by physicians responsible for overall care of the patient. Nevertheless, because of its importance, our recommendations (1) discuss the concept of disability. In Table 3 see: under “Consider inpatient 131I therapy … ,” 2. The patient is unable to comply …; and under “Information gathering for radiation precaution planning, travel.” More instruction appears in Table 4, Step 2 under “For your travel.”
Again, we are pleased to hear from readers of Thyroid and to have the opportunity to discuss their perturbations. We hope that the above information allays their concerns.