[Is the post-therapeutic dosimetry of patients with short-term hospitalization after 131I therapy sufficiently reliable?]

According to the new recommendations of the Federal German Radiation Protection Committee (SSK) for patient discharge, that were published in April 1997, patients can be discharged after radioiodine therapy with a radiation exposure of less than 1 mSv per year in 2 m distance. The aim of this study was to evaluate whether the measurement of the achieved dose was different 48 hours after application of I-131 and after an interval of one week. The study was planned in order to ensure quality management in the follow-up of the patients.

In a prospective study 115 patients were followed, that were treated for a benign thyroid disease. The patients were discharged 48 hours after the intake of I-131 after falling short of the exposure limit. All patients were measured at discharge and about 8 days later with the same uptake facility.

Because of similar results focal and disseminated forms of benign thyroid diseases could be analysed together. The calculated doses 8 days after the discharge were higher than the values at the time of discharge. The doses were underestimated about 4% with an standard error of 15%.

The error in early dosimetric measurements is small in comparison to the overall uncertainty in therapy and uptake dosimetry. A valid dosimetry and sufficient quality management can be guaranteed even for an early discharge.