Re: RE Stress Test

["Charles Potter" <CAPOTTE@sandia.gov>]

     ICRP-30 says that 3% of thallium is retained in the kidneys while 97% 
     is uniformly distributed throughout all other organs and tissues.  
     When referring to uniform distribution, the ICRP assumes that 
     radionuclides are retained in organs or tissues with amounts 
     proportional to the mass of the particular organ or tissue.  Since the 
     kidneys weigh 310g and the total body is 70kg (Reference Man), the 
     kidneys would contain 0.44% of the thallium if they were included in 
     the uniform distribution.  Since 3% of thallium is retained in the 
     kidney, the ICRP is assuming that thallium is relatively 
     _concentrated_ there.
     
     As far as inferring a major excretion pathway, perhaps one could infer 
     that urine is the main pathway due to the above argument and the high 
     solubility described in ICRP-30.  Nureg/CR-4884 which has fu and ff 
     values for some elements does not include those for thallium.
     
     However, to contradict myself, ICRP-23 does describe the daily balance 
     of thallium.  The intake pathways and amounts are 1.5 ug and 0.05 ug 
     from food/fluids and airborne respectively (I wonder where airborne 
     thallium comes from).  The losses are 0.5 ug and 1.0 ug through urine 
     and feces respectively.  Since the f1 for thallium is 1, all thorium 
     deposited in the lung and stomach would find its way into the transfer 
     compartment, and from there to the other organs and tissues.  
     Therefore, the excretion values would imply that approximately 1/3 of 
     an uptake of thallium is excreted via urine and the rest via feces 
     (with trace excretion by hair, sweat and milk).
     
     This is probably overkill, but I hope it's interesting.
     
     Gus Potter
     Sandia National Laboratories
     CAPOTTE@sandia.gov
     (505) 844-2750


______________________________ Reply Separator _________________________________
Subject: RE  Stress Test
Author:  VERNIG.PETER@FORUM.VA.GOV at hubsmtp
Date:    5/17/96 8:57 AM


Radsafers,
I did not study the original message about the basketball player 
and his stress test.  There are exercising EKGs that some might 
interpret as a "stress test".  There are also heart studies using 
Tc-99m, I believe.  But generally, I think, a "stress test" would
be "stress thallium [201] study.  In that the dose is about 4 mCi and 
it is injected when the patient is at "maximum" stress or exertion, 
while exercising on a treadmill.  Since this is done to a moving 
patient, who is fatigued, mishaps are not, shall we say uncommon.
     
ICRP didn't yeild much about ellimination except a biological half 
life of 10 days [physical half life is 73 hours].  ICRP says the 
thallium is uniformly distributed to all organs except the kidneys.
     
Would one infer that urine is not a major route of excretion from that?
     
Peter G. Vernig, VA Medical Center, vernig.peter@forum.va.gov