LOCAL IRRADL\TION OF CXS WITH HIGH ENERGY PROTONS 355 



Fig. 8. Horizontal section of the right hemisjjhere of a goat's brain showing a 

 sharply deHmited lesion in the internal capsule 7 weeks after cross-fire irradiation with 

 20 krad. Gros-thionin. X 5. The photographs are published by courtesy of Acta 

 Radiolosica. 



and measured 13-16 mm. 7 he histopathologic picture of the brain lesions of 

 these 2 coats corresponded closely to each other. Within the white matter the 

 lesion was sharply limited, and its central part was completely necrotic. The 

 capillaries were destroyed, and aroimd them were seen shadows of erythro- 

 cytes and plasma exudate. There were no lar^e hemorrhaues inside the lesion 

 or around it. A narrow zone smroundino- the definite lesion showed desjener- 

 atino axons and myelin sheaths. Slight cellular proliferation was noted. In the 

 lesion examined 7 weeks after irradiation, a few macrophages were seen 

 around distended vessels at the margin of the damaged resion. Outside the 

 lesion there were no signs of pathologic processes in the brain. 



A dose of about 40 krad given by cross fire irradiation to 1 goat produced 

 a different lesion. The volume of necrotic tissue was large. The tissue around 

 the necrotic area in some places contained wide, thin-walled, newly fonned 

 vessels and was densely infiltrated with lymphocytes and macrophages. The 

 affected region surroimdino- the necrosis was at least the size of the necrotic 

 area itself. Onlv minimal hemorrhages were noted in the outer zone. The 

 irradiated hemisphere was swollen, but did not show any other pathological 

 chano;es outside the lesion. 



