RADON SEED IMPLANTS 



79 



strength after any subsequent time, and the column labeled millicurie- 

 hours (mc-hr) indicates the percentage of the radiation used up to the 

 time of removal of the seed. If the seed is 4 days old, it will possess a 

 potential activity of 48.42 per cent of its original maximum strength 

 of 1 mc. In this time interval it has emitted 68.60 mc-hr. If this seed 

 is used during the next 6 days on a second patient, its activity will reduce 

 to 16.32 per cent of its initial value, and during these 6 days it has de- 

 livered 42.8 mc-hr to the second patient. 



TABLE 11-14 



Decay of Radon 



The number of millicuries (mc) available after any lapse of time if the 

 original strength at time zero is 1 mc 



