202 



Applied Biophysics 



Value of the Conception of Volume Dose in Radiotherapy 



The volume dose might conceivably help in deciding on modi- 

 fications of technique, and might help in correlating physical 

 dose with general effects of radiation. 



It must be realized, however, that the physical methods hitherto 

 described for estimating volume dose suflfer from certain in- 

 accuracies. The chief of these are due to the fact that allowance 

 is not made, in the physical methods, for the variable tissues 

 and their densities in the human body, while biologically one 

 cannot expect uniform behavior of various tissues for a given 

 physical dose. 



Physical Factors 



The author has attempted elsewhere to show the effects of 

 certain physical factors on volume dose.^- ^ 



500 



FIG. 7. Relation of volume dose to field area for chest irradiation. The lower curve 

 is for the shorter FSD (40 centimeters). (From Boag.^) 



