THE HUMAN RESPONSE TO A SINGLE DOSE OF X-RAYS THE LATENT PERIOD 



Three known factors influence the length of the latent period, the dose of 

 radiation, the body size and the particular anatomical site irradiated. It 

 has been found that for a sjiven anatomical site of irradiation, i.e. the whole 



300 



I 



I 



800 



Irradiation of wtiole length of spine 

 (Anl(yiosing spondylitis) 



\ 



Figure 2 



ioo\_ 



3 15 



Latent period 



10 



"h. 



length of the spine, or the whole abdomen, or the whole pelvis, a distinct 

 relationship exists between the dose of radiation expressed in terms of body 

 size and the length of the latent period, and that this relationship is a curvi- 

 linear one {Figure 1). If the log dose per unit of body size is plotted against 

 the latent period, the relationship is linear provided only that a restricted 

 range of time is used [Figure 2). By plotting the dose against the reciprocal 



7cV 





Figure 3 % 



i 



20 



30 



SO 



7-5 



Irradiation of tyhoie iengiii of spme 

 ( An l<y losing spond/lifisj 



to 80 120 ISO 200 210 280 



Surface dose (v)/ tola/ body surface area 



of the latent period, the relationship is a linear one over the whole range of 

 observed values [Figure 3). This behaviour is in keeping with the usual 

 pharmacological dose response relationships^ and the reasons for viewing 



230 



