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

Summary

²²⁷Th 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.