208 



Applied Biophysics 



h. Using two wedge fields as described by Ellis and Miller ^ 

 (see figure 12) , the volume dose for 1,000 r tumor dose calculated 

 by me from measurements made by Boag/ is 1,42 megagram- 

 rontgens. An appropriate technique to achieve the same treat- 

 ment without wedge fields would be to use two lateral 10 X 8 

 square centimeter fields and one 6 X ■+ square centimeter, e.g., 

 to the skull. Under these conditions, the volume dose for 1,000 r 

 tumor dose is 2.4 megagram-rontgens — obviously higher than 

 that for the wedge fields. 



FIG. 12. Diagram of the isodose distributions produced by combining two X-ray 

 beams at right angles, using wedge filters. (From Ellis and Miller. s) 



Volume Dose and Tolerance Dose 



Mayneord and Clarkson ^•'' by their work on whole-body ir- 

 radiation have put the energy absorption by the body under such 

 conditions in true perspective, and a new aspect of the concep- 

 tion "tolerance dose" has emerged. For whole-body irradiation, 

 the volume dose relationships for 40 kilovolt, 200 kilovolt, and 



