204 



Applied Biophysics 



method ^^ and it should be pointed out that Boag's graph (figure 

 7), for a similar technique, shows no appreciable difference with 

 the two FSD and gives a rather higher value (36 megagram- 

 rontgens) than either of the two techniques compared above. 



The Arrangenieiit and Number of Fields 



The author has discussed ^ the effect of these factors for two 

 sets of conditions : 



0.05 r 



D. 40 kv 



ic 0.0 99 r 

 O.lr 



yO.lr 



->0.5r 

 >0.6r 



^ 0.8r 

 $^0.9r 



1.1 r 



1.2 r 

 'l.5r 

 'l.4r 



FIG. 8. Isodose distributions in a cross-section of the trunk for various qualities 

 of radiation. (From Mayneord & Clarkson.^'^) 



