Measurement of external radiation level in the process of ¹³¹I-treated thyroid carcinoma patients

Objective: To measure the spatial distribution of radiation field and how it changes over time in the process of therapy thyroid carcinoma with ¹³¹I, and also to offer a meaningful reference for the shielding design of ward and radiation environment management of related projects. Methods: Active measurement combining with the passive measurement. Results: The radiation dose rate of the position 1 meter in front of the patients' chest reached 393 μGy/h after taking the drug for 5 minutes. And the dose rate attenuated significantly with the increase of treatment time. During the whole treatment, the cumulative dose generated from patients to the nearest monitoring point was 2.6 mSv. For each cumulative dose monitoring points in the ward, dose generated in the first 24 hours was 57%∼80% of the total dose generated in the entire treatment process; dose generated in the first 48 hours accounted for 80%∼95%; but the dose later only contributed a little part to the total dose. Conclusion: The measurement results have a good reflection of the source intensity and distribution of the radiation field in the whole ¹³¹I therapy for differentiated thyroid carcinoma metastases. (authors)