Releasing thyroid cancer patients from the hospital based on dose rate measurement after 131I activity administration

The treatment of thyroid cancer generally comprises total thyroidectomy and oral administration of radioiodine (131I). One consideration in this therapy is the radiation exposure risks, which have led the Sri Lankan Regulatory Authority to lay down criteria on releasing patients from hospitals when the therapy procedure involves 131I activities greater than 1.85 GBq (50 mCi). This study was carried out to assess the time dependent dose rate following the administration of 131I activities and estimate the radioiodine effective half-life (Teff) inside the patient’s body, which would be useful for releasing patients from hospitals and guide radiation protection recommendations as well. External whole body dose rates at 1.0 m from 60 patients were measured immediately after 131I administration and at 24 hour intervals up to 5 days. These dose rates were used to estimate the Teff . The results demonstrated a bi-exponential radioiodine clearance pattern up to 5 days with Teff values of 15.9 and 25.3 hours in the first and second phase, respectively. Also, majority of the patients could be released from the hospital after 72 hours post-therapy administration as they reach the permissible dose rate limit recommended by the regulatory authority of Sri Lanka by this time.

DOI: http://dx.doi.org/10.4038/jnsfsr.v42i2.6993

J.Natn.Sci.Foundation Sri Lanka 2014 42 (2): 137-141