LESIONS WITH ACCELERATED PARTICLES 



339 



Rabbit #2-9 



BEAM MONITOR 



1 2 3 4 5 6 



Seconds 



Fig. 7. Typical record of stimulation of blinking reflex. 



would not wish to use such large dose stimulation in humans. In animals 

 this may be a different problem. We know that needles used in stimulation 

 inflict permanent traiuna on brain tissue. It may well be that radiation- 

 induced trauma will actually be less. 



Looking into the futme. one might \ isualize some of the advantages of 

 hea\y ion pidses for stinudation and study of the cerebral cortex. One should 

 probably try to stimulate with hea\ier ions than alpha particles; perhaps 

 e\en a single accelerated hea\y nucleus of some ion such as iron might be 

 capable of stimulating, owing to its sreat linear energy tiansfer. It seems 

 quite possible to produce microbeams of heavy ions, perhaps 10 /x in diameter, 

 then direct pulses of such beams to arbitrarily selected spots in the brain, and 

 to vary the depth of penetration at will. One must admit that due to scatter- 

 ing and straggling the resolution becomes poorer as the beam reaches to 

 greater depth in the brain. Thinking about future possibilities for radiation 

 stimulation of the brain. I wish to present a preliminary scheme of the Heavy 

 Ion Scanning Stimulator i HISS ) . shown in Fig. 8. which is in construction 

 at Berkeley. Here magnetic fields pro\ide a pre-coded scan pattern, as the 

 beam is pulsed at some predetermined sequence. The response of the brain 

 to such space and time coded radiation "messages'" to the surface of the 

 cerebral cortex might prove to be illuminating to our knowledge of cerebral 

 cortical function and behaxiour. 



Summary 



The chronological development of techniques for use of accelerated ions 

 in neurologv are described. Methods for deep localization of lesions, produc- 

 tion of laminar lesions, and knife-edge lesions are described. The stimulation 

 of reflex action by alpha particles is demonstrated. 



