52 



BIOLOGICAL EFFECTS OF RADIATION 



may be found which specifies the radiation more closely. This is per- 

 fectly justifiable, since the radiation not passing through the filter is 



lost. 



Standard Absorption Curves from 60 to 180 Kv.—The specification of 

 X-ray quahty, by using the complete absorption curve, has been recom- 

 mended by the X-ray Standardization Committee of the Radiological 

 Society of North America.^ (56). 



Table 3. — Absorption of General X-radiation in Aluminum 



(Tube wall, 1.29 mm. cerium glass) 



/o = incident radiation; / = transmitted radiation; IOO///0 percentage transmission 



Note: All second-place decimal figures given in italics are approximate values 



Table 1 gives the copper absorption values for radiation from a thin 

 tube in which the wall absorption is about the same as for 0.02 mm. Cu. 

 In the first column are given filter thicknesses at practical intervals. 

 In the other double columns headed by the applied tube voltage are given 

 respectively the percentage transmission of the filter and its corresponding 

 logarithm to the base 10. 



Similar data for a thick pyrex tube having a wall absorption about 

 the same as for 0.1 mm. Cu are given in Table 2. 



2 Quotation from Par. 7 of the 1933 Committee report: "For most practical pur- 

 poses, the quality of the X-radiation may be satisfactorily specified in terms of the 

 copper or aluminum absorption curve combined with a statement of the initial 

 filtration. In lieu of an absorption curve, the equivalent constant potential apphed 

 to the tube terminals to yield the same curve may be stated as a single numerical 

 magnitude. Up to 100 kv. (constant) aluminum absorption curves and above 

 100 kv. (constant) copper absorption curves shall be used to establish the equivalent 

 potential." 



