[Levels for discharge to home and return to general ward of patients who received therapeutic dose of 131I based on external exposure dose].

This paper describes levels for discharge from hospital and return to general ward of patients treated with 131I. The level was determined by comparing the possible exposure dose to those individuals whom the patients are in daily contact with the annual dose limit for the public. The external exposure dose was calculated by using the data on the distance between the patient and individuals, length of the time spent at each distance, and each individual's age. The following levels were obtained: (1) For the patient to be discharged from the hospital, the maximum residual radioactivity should be less than 0.51 GBq if the distance from the patient in bedroom is 50 cm or more and the ages of her children are all over one year. No restriction is needed for the patient with residual radioactivity of 0.20 GBq. (2) For the patient to be returned to the general ward, the maximum residual radioactivities should be 28 MBq and 41 MBq, corresponding to the distance from the patient of 2.0 m and 2.5 m respectively. We established a method to analyze the factors affecting the level.