Re: Tl-201

["Carol S. Marcus" <csmarcus@ucla.edu>]

At 04:25 PM 8/1/02 -0400, Kurt R. Geber wrote:

> Does anybody have info on the
>
> biological half-live of Tl-201 used in stress tests.  Does the
>
> inability to pass a portal monitor for 30 days seem excessive?
>
>
> Kurt R. Geber
>
> NASA Project Radiation Safety Officer 
Dear

Kurt:


According to ICRP #63, p. 371, 80% of Tl-201 is excreted by the GI tract,

and 20% by the kidneys.  The whole body retention curve can be

represented by a two-exponential function with half-times equal to 7 days

for 63% and 28 days for 37% of the injected activity.


Tl-201 has a halflife of 3.044 days, so the effective halflife for 63% of

the dose is 2.1 days and for 37% is 2.7 days.  I don't know how

sensitive your portal monitors are, but the usual administered activities

are 2-4 mCi.  This ought to give you all the information you need to

figure out whether 30 days is too long, presuming you know the minimum

detectable activity of Tl-201 for your monitor.


Ciao, Carol


Carol S. Marcus, Ph.D., M.D.

<csmarcus@ucla.edu>