Studies on Short-lived Internal α-emitters in Mice and Rats

Summary227Th is an interesting model for a short-lived bone ‘surface-seeker’ with α-emission. The distribution after intraperitoneal injection of 227Th-citrate in the different organs is described. About 70 per cent of the injected Th was retained in the skeleton. The total dose burden depends to a high degree on distribution of decay products, especially 223Ra. Calculations were done for the skeletal dose burden in mice. They yielded 200 rads per 1 µCi of 227Th injected. The highest skeletal dose-rate (7 rads/day per 1 µCi/kg) was reached at the third day after injection.The possibility of bone sarcoma induction is discussed by comparison with dose relationships after incorporation of 228Th.A provisional mechanical technique is described for estimation—to a certain extent—of the activity at bone surface and volume separately.