196 Applied Biophysics 



Mayneord approached the problem on different Hnes, and 

 has done a great deal of work alone, and with his collabo- 

 rators, on the theoretical and practical aspects of the problem. 

 His original paper ^- described a method of integrating the dose 

 by measuring the volume of rotation between the isodose sur- 

 faces of a beam by practical measurement of the moment of the 

 area, and gives values for volume doses of different types of 

 radiation which throw into sharp contrast their differences in 

 this respect. (See table I.) 



He discusses ^^ the mathematical theory of volume dose and 

 derives the following interesting generalizations. For a beam 

 in which the dose contours in a given plane-section are straight 

 lines perpendicular to the axis of the beam, and the dose falls 

 linearly with depth, the integral dose is given by the product 

 of the mass of the body concerned and the dose at its center 

 of gravity. From investigations made in collaboration with 

 Clarkson, ^^ on a wax model of a man, tables were constructed 

 giving the "average" dose throughout a patient of a given thick- 

 ness and a given quality of beam. (A body of mass M receives 



an average or mean dose D when the Integral or Volume Dose 



2: — D.M.) This ''average dose," corrected for focus-skin 

 distance and multiplied by the mass of the patient gives the 

 "integral dose." 



Mayneord further ^'^ discusses the mathematical theory of 

 integral dose in radium therapy. It appears that, for concentric 

 shells about a radium source, the volume dose of each shell 

 is proportional to its thickness and the number of milligram- 

 hours (mgh) at the center. Moreover, there is a reciprocal 

 relationship between the source emitting radiation and the vol- 

 ume receiving it. "The integral dose throughout any volume 

 whatever, due to a finite source, uniformly filled with radio- 

 active material, is equal to the integral dose throughout the 

 original source if the 'receiver' be filled with radiating material 

 of the same uniform density." A graph is given from which the 

 integral dose per mgh for point sources near the center of an 

 absorbing mass, may be read (figure 2). For a sphere of radius 



