RE: A Question for Power Reactor Types and others with portal monitors.

["Flood, John" <FloodJR@NV.DOE.GOV>]

-----Original Message-----

From: John Jacobus [mailto:crispy_bird@YAHOO.COM] 

Sent: Thursday, April 08, 2004 10:51 AM



"If a patient is given a bone scan

with 30 mCi of Tc-99m, after 3 days there may still be

7 microcuries of activity present."



Actually, there may be AS MUCH AS 7 uCi remaining.  The effective half-life

will also include the biological elimination rate, and varies greatly from

individual to individual.



"Tl-201 is only used for heart scans.  While it is has

a half life of 3 days, there are Tl-202 and Tl204

contaminates.  However, you do not retain thallium

chloride."



Again, this is heavily related to biological elimination rates.  Our

experience is that Tc-99m is rarely detectable for more than 10 days and

usually undetectable in a week or less, but Tl-201 cases remain detectable

longer.  The longest lived of our cases (a month each) were both Tl-201

stress tests.



And our experience probably mimics others - the overwhelming majority of

detectable medical uses are Tc-99m, with Tl-201 second - the stress test

business is booming (thanx to baby boomers, no doubt).



The other big player is therapeutic I-131 thyroid treatments - not only can

they last a long time, they are detectable from a great distance.



Bob Flood

Nevada Test Site





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