Abstract
To estimate the dose equivalent (H1cm) of a person who may come into close contact with patients exposed to 201T1, dose rates around 15 adult patients (rest group: 8, exercise group: 7) have been measured with ionization survey meters. Measurements were carried out at 30min, 24h, 72h, 144h (or 120h) and 216h after the administration of 201T1Cl. Survey meters were set up at the height of the first cervical vertebrae (I), xiphoid process (II) and anterior superior iliac spines (III) with the patient in a standing posture, and at distances of 0.05, 0.5, 1.0 and 1.5m from the patient. The maximum H1cm rate of 18.37μSv/h per 74MBq was recorded at level II in the anterior projection. Doses in the posterior projection were similar to those at the anterior projection, however, in the right- and left-lateral projections the doses were lower than the anterior dose. The difference in doses between the rest and exercise groups was slight. The calculated effective half-life was 63.0h. H1cmS were 891, 196, 77 and 42μSv/w per 74MBq at distances of 0.05, 0.5, 1.0 and 1.5m, respectively. These H1cmS correspond to 84% of the total H1cmS (μSv/∞h). The family of a patient given 201T1 was one-third of the total H1cm at 0.05m, the dose did not exceed the dose limit described in recommendations-1990 of ICRP. However, it was a substantial dose for them. Staff doses in general wards and in special wards (ICU or CCU) were one-fourth of a total H1cm at 0.5m, these doses were the result of contact with 17 201T1 patients and 257 201T1 patients for one year. The dose of patient in the same room as patients given 201T1 were 42μSv/w at 1.5m; this dose did not exceed his dose limit of 100μSv/w. These results do not suggest that radiation protection is necessary when exposed to a patient given 201T1, but in the case of close contact with many 201T1 patients, it would be necessary when the radiation dose exceeds the limit.
