Re: Thallium 201

[Elizabeth Brackett <ebracket@freenet.columbus.oh.us>]

On Fri, 17 May 1996, Darryl Kaurin wrote:

> 
> Dear Radsafers,
> 
> Regarding the stress test, I had one and they did use 4 mCi of thallium-201. 
> The health physics personal where I worked measured me daily, and the half
> life was 3 days, equal to the physical decay.  I couldn't work in radiation
> areas for 3 weeks.  I was told by the hp staff latter that you might be able
> to request they use Tc-99m insted, which has a much shorter half life, and
> less dose of course too.  I haven't calculated my dose, but it is certainly
> more than the dose I get at work.
> 
> Darryl Kaurin
> dkaurin@eden.rutgers.edu

If you're all not too sick of this thread, I'd like to mention that you
need to be aware of the impurities in the administered material also if
you're monitoring someone at work.  I received a frantic phone call from a
power plant several years ago because they were getting a rather large
peak while performing a body count (an NRC inspector was on site at the
time, the primary reason for their panic).  The peak was identified by the
software as a secondary peak of cerium (I don't recall if it was 144 or
141) and it proceeded to calculate an activity. Upon questioning, the
employee remembered he had had a stress test 6 weeks prior to the body
count.  The peak was due to Tl-202, which has a 12 day half life. 
Percentage-wise the impurity is small (I think it was 1% or less) but body
counters are very sensitive (this was a germanium based system) so it can
cause interferences for quite some time.

Liz Brackett, CHP
ebracket@freenet.columbus.oh.us