What monitoring technique should be used to rule out internal contamination after handling a radioiodine solution?

The recommended monitoring technique to rule out internal contamination after handling a radioiodine solution is a thyroid uptake measurement taken 24 hours after the handling. This approach is effective because the thyroid gland has a high affinity for iodine, particularly radioiodine isotopes, which are commonly used in diagnostic and therapeutic procedures in nuclear medicine.

If a worker has been exposed to a radioiodine solution, any internal contamination would typically lead to increased uptake of radioiodine in the thyroid. By performing a thyroid uptake measurement, clinicians can gauge how much of the radioactive iodine has been absorbed into the thyroid tissue. A significant uptick in uptake would indicate potential internal contamination, allowing for timely intervention if necessary.

In contrast, other monitoring techniques either do not directly measure thyroid activity or are not as effective in determining internal contamination with radioiodine. For instance, urine counts may reflect the elimination of radioiodine rather than confirming its uptake by the thyroid. Plasma counts would measure radioiodine distributed in the bloodstream rather than its localization within the thyroid itself. Pocket dosimeters measure external radiation exposure rather than internal contamination and are not suitable for assessing the specific risk of radioiodine uptake in the body.