210 



Applied Biophysics 



The discrimination now possible between volume . dose and 

 surface dose should permit of new standards. That limiting the 

 permissible general radiation should be a volume dose, and that 

 limiting the local radiation a surface dose, which might presum- 

 ably be higher than the figure used hitherto, which, in effect, 

 has no real value for those working with radium. 



Correlation of Biological Eflferts with Volume Dose 



The ultimate practical value of the conception of volume dose, 

 will depend on the possibility of using it as a criterion for modify- 

 ing technique, and as a means of obtaining more knowledge of 

 the action of radiation. The physical factors hitherto discussed 

 indicate the manner of influencing volume dose by technical 

 variations. 



Modification of technique will be considered by a radiotherapist 

 only if the general effect of the radiation is of such magnitude 

 as to interfere with the delivery of a local dose. General effects, 



3000 



UJ 



> 



O 

 O 



I 



a. 

 > 



2000- 



1000- 



5 10 15 20 25 50 35 



FIG. 13. Lymphocyte Counts in IxnivinuAL Patients 



Abscissae = days after commencement of radiation. The volume doses received 

 are indicated on the curves. Note that althouRh the trend is marked, each curve 

 shows a rise at some time during treatment. (From Ellis."*) 



