206 



Applied Biophysics 



0-1 0-2 0-5 0-4 



HalF-vafue layer mm. Cu. 

 FIG. 10.* 



* Figures 9 and 10 show a comparison of the values of integral dose obtained in a 

 model patient constructed wholly of wax and in a model constructed of Spiers' mix- 

 ture for various radiation qualities. (From Mayneord and Clarkson.^^) 



a. Using Ungar's ^^ conception of the economy quotient, 

 it can be shown that the greater the homogeneity of dosage, the 

 smaller the volume dose. Ungar gives examples of arrange- 

 ments of fields for treating a case of carcinoma of the cervix 

 in relation to the "economy quotient" and the volume dose. The 

 economy quotient is the ratio of the minimum tumor dose to the 

 difference between the maximum and minimum tumor doses, 

 and is a measure of the efficiency of the technique. It seems that, 

 other things being e(|ual. the arrangement which gives the greater 

 economy quotient gives the smaller volume dose. Since the 

 economy quotient is highest when tlie difference between the 

 maximum and minimum tumor doses is smallest, it follows that 

 the greater the homogeneity, the smaller the volume dose (see 

 figure 11). 



