HISTOPATHOLOGY OF CNS RADIATION 



167 



Such proiiiession of lesions apparently does not take place in response to 

 beta radiation, at least not to the same decree as with roentijen radiation 

 (Campbell and Novick, 1949: Edwards and Bao;t>;. 192'3). 



More recently, interest in the neuropatholo2;y of radiation has tended to be 

 focused on the acute phase of the reaction (Haymaker ft al., 1958; Voy;el 

 ct al., 1958). By the use of relatively large doses of gamma radiation, it has 

 been possible to characterize the acute lesion as seen by conventional 

 methods of light microscopy as one of acute inflammatory changes and de- 

 generati\e alterations in the cerebellum ( Vogel it al., 1958). These changes 

 are the direct eflfect of radiation on the brain, since they do not appear when 

 the whole body of the animal is radiated and the head shielded. While the 

 acute changes are definite, they are mild in comparison with those which 

 develop as time after radiation is increased. 



In personal studies, the experimental procedure precludes critical evalua- 

 tion ot the acute phases of radiation reaction. 1 antalum'''- deli\ers radiation 

 at a rate such that se\eral days are recjuired to accumulate the dosages 

 necessary. When Ta'^- wire, shielded with polyethylene to prevent beta 

 radiation fiom complicating the picture, is inserted into the cerebrum of 



Fig. 1. tloronal section of monkey brain, showing representati\e lesion induced by 

 insertion of Ta"'" wire. Dosage. 600 r in 5^ days. Left hemiplegia developed aftei 

 3 months. Sacrifice 1 year after radiation. Lesion measured 7x4 mm. 



