Million-Volt Therapy 259 



the upper limit and it is doubtful if many patients would survive 

 65 Mgr. 



Similar conclusions can be arrived at for other lesion sites, 

 and as a matter of routine all cases are isodosed at a million 

 volts, each case being treated as an individual case with its 

 individual problems. 



Effect of the Variation of Density through the Body 



Considerable investigation has shown that at 200 kilovolts the 

 isodose curves calculated for treatments have always erred on 



20 



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FIG. 6. Pin-anu-Akc Device 



the optimistic side, particularly where beams have had to pass 

 through bone. At 200 kilovolts, a particular skull absorbed 15% 

 more than the same thickness of tissue, while at 1,000 kilovolts 

 there was only 4.5% more absorption. This would mean that 

 in the treatment of a brain tumor at 200 kilovolts, the lesion 

 dose might be at least 15% lower than calculated. A particularly 



