442 FARR ET AL. 



The underlying purpose has been to determine whether the reaction was 

 capable of destroying neoplastic cells and whether surrounding and distant 

 structures were affected by the procedure. To make this evaluation, a com- 

 parison series of cases was collected to determine the spontaneous alterations 

 which occur in untreated cases, e.g., the amount of necrosis occurring in the 

 development of a neoplasm of the glioblastoma multiforme type, the most 

 commonly investigated neoplasm in this study. In addition, forms of irradia- 

 tion other than neutron capture therapy, such as that occurring in x-ir- 

 radiation, have been considered for comparative purposes. Thus, in the 

 nonirradiated and irradiated brain, the whole brain was embedded in 

 celloidin, with whole brain sections being cut in coronal, horizontal, or 

 sagittal planes at 25 ^ and mounted on slides for low power survey. In addi- 

 tion, representative sections were cut at 7 /x and mounted with thin cover 

 slips for detailed microscopic examination. A variety of special stains de- 

 signed for studying the cellular details of the central nervous system with 

 the nerve tracts weie used for detailed obsei'vations. 



The major series comprised 16 patients to whom neutron capture therapy 

 was given in 1 to 4 exposures with, in the various patients, a total thermal 

 neutron exposure ranging from 0.44 X 10^" to 6.31 X 10^' per square cm 

 at the skin surface. An additional patient was treated at the new medical 

 research reactor in a single exposure with a total thermal neutron penetra- 

 tion of 1.73 X 10'" per square cm at the cortical surface. Studies are still in 

 progress on another patient who, in a similar fashion, received over 10'^ 

 neutrons per square cm on the cortical surface. In contrast to these cases 

 with neutron capture therapy, one patient received thermal neutrons only, 

 and this data provides comparison material. 



Neutron capture therapy is accompanied by radiation other than that 

 specifically provoked. Thus, it becomes necessary to establish the levels of 

 these ancillary radiations and to evaluate whether they contribute to or 

 detract from the clinical picture. The several contaminating radiations 

 include ( 1 ) gamma radiations from the reactor core and gamma rays 

 induced when neutrons are lost through capture in the shielding and reflect- 

 ing materials, (2) the remaining small fraction of the emergent neutrons 

 which retain energies in the kilovolt range which may possibly cause tissue 

 damage in their own right, and (3) the effects of the passage of the great 

 quantities of slow neutrons through tissue, wherein, through thermal neutron 

 capture by hydrogen and carbon, there is produced appreciable induced 

 gamma emission; and by nitrogen, energetic protons. The first two factors 

 are approached chiefly as engineering design problems; the third is the sub- 

 ject of this essay. 



Neutrons are elementary nuclear particles which have essentially unit 

 mass, about the size of an hydrogen nucleus or proton, but no electrical 



