Dose Course 2018_Flipping book

10

The widening of the pencil is limited

❑ The pencil-beam width (

❑ This is due to the reduction or loss of the number of electrons in the beam at large depths due to range straggling

MCS ) as a function of depth agrees well with experiment at small and moderate depths.

❑ Then it continues to increase, whereas in reality it goes through a maximum and finally decreases.

❑ This is managed by the g(x) function or has to be managed in other ways in some systems

From Handbook of Radiotherapy Physics Ed Mayles, Nahum and Rosenwald

Dublin 2018