Total Energy Absorption in Radiotherapy 



205 



Quality of the Beam 



The effect of the quaHty of the beam as determined for whole- 

 body radiation has been mentioned already (see figures 9, 10). 

 Also Phillips ^^ demonstrated that for a given tumor dose, there 

 is a considerable difference in volume dose between techniques 

 using 200 kilovolts and 1,000 kilovolts (see table III). 



60^600 



50,000 



40,000 



30,000 



20,000 



10,000 



HalF-value layer mm Cu 

 FIG. 9.* 



