PRODUCTION OF HIGH PuRIm 1231 FOR CLINICAL AND RESEARCH PURPOSES

D F R I E S E L, J Blue, H Wellman, M Kavuula, Wayne Smith
unpublished
The advantages of t h e use of 1 2 3 ~ over o t h e r ,o~Tr.-A 1 radio-isotopes f o r c l i n i c a l d i a g n o s t i c procedures i n n u c l e a r medicine, i t s s h o r t h a l f-l i f e (13.1 hours) and t h e s u i t a b i l i t y of i t s only emitted r a d i a t i o n (159 keV y r a y) t o e x i s t i n g d e t e c t i o n methods, have been known f o r many y e a r s. 3, I n s p i t e of t h e s e i d e a l p r o p e r t i e s , however, i t has n o t come i n t o general c l i n i c
more » ... l use because of t h e complexity of i t s production v i a p a r t i c l e ac-c e l e r a t o r s and r e s u l t i n g high c o s t. A review of t h e various r e a c t i o n mechanisms used t o produce 1 2 3 ~ i s provided by Sodd e t a1.495) ~ o s t commercial s u p p l i e r s of 1 2 3 ~ use low energy r e a c t i o n s (5 35 MeV) on expensive, i s o t o p i c a l l y enriched 1 2 2 ~ e o r 1 2 4 ~ e t a r g e t s. The p u r i t y of t h e r e s u l t i n g 1231 depends on t h e p u r i t y of t h e Te t a r g e t , t h e primary contaminant being 1241, a b e t a e m i t t e r w i t h a 4.2 day h a l f-l i f e. A program t o develope an on-line f a c i l i t y Figure 2. f o r t h e production of an 1 2 3 ~ i s o t o p e f r e e o f any o t h e r r a d i o a c t i v e contaminants v i a t h e l2 7~ (p, 5n) B+ 12%e + 1231 h a s begun using t h e proton beam from t h e Indiana Isochronous Cyclotron. The o b j e c t i v e i s t o demonstrate t h a t a pure 1 2 7 ~ "Liquid-Vapor" t a r g e t assembly u t i l i z i n g a continuous helium gas flow generator i s n o t only f e a s i b l e , b u t has a h i g h e r production r a t e than o t h e r t a r g e t s using t h i s r e a c t i o n , while y i e l d i n g a contaminant-free isotope. I n a d d i t i o n , i t i s r e q u i r e d t h a t t h e t a r g e t assembly be usable f o r many i r r a d i a t i o n s with no maintainance o r recharging , while being quickly and e a s i l y placed i n t o o r o u t of s e r v i c e on t h e beam l i n e i n t h e i s o t o p e production room. The c r o s s s e c t i o n f o r t h e 1271 (p,5n) 12%e re-a c t i o n h a s been measured by s e v e r a l groups6)and is found t o peak a t about 57 MeV, a s i l l u s t r a t e d i n Figure 1. The 1 2 7 ~ (p, 3n) r e a c t i o n c r o s s s e c t i o n i s a l s o shown and i s a p o s s i b l e contaminant source, i.e., 125=. From t h e s e d a t a , t h e c a l c u l a t e d y i e l d of 40 60 80 mo I eo Proton Energy (MeV) Figure 1.
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