Re: Tl-201 contaminated by Tl-202

[stabin@esper.com (Mike Stabin)]

>     Is contamination by Tl-202 relatively common for Tl-201 scans?  
>     Should we expect that contamination by Tl-202 is significant 
>     enough that it remains easily detectable for some period 
>     afterward?
>     

Yes, Liz Brackett is right, the levels are usually about 0.5-1% of the
Tl-201 activity, *when the drug is administered*.  As time goes by (decay
it, Sam) the relative levels change, so the % changes, but as noted by
Carol, the actual levels change slowly, and can be detectable by many
in-vivo counters for some time.  There is an article in HPJ on the general
subject of contaminants (Health Physics 61(3):427-430, 1991) - might be some
more data of interest to you there.

Mike Stabin
Oak Ridge