I-131 Bioassay, Requirements vs Recommendations

[VERNIG.PETER@FORUM.VA.GOV]

Group,
 
10 CFR 35.315 currently requires measurement of the thyroid burden of per-
sonnel that prepare or administer doses of I-131 requiring isolation IAW
35.75.  That used to mean doses over 30 mCi.  With the recent revision of
35.75 patients that have received large doses may be released
wo/isolation based on case specific calculations of dose to the public.
Personnally, I have a problem sending a patient home to excrete 100 mCi
of I-131 under uncontrolled conditions, but that is not the issue I want
to discuss.
 
In the proposed 35.315 there is no staff thyroid measurement requirement
at all.  On the other hand, The Guidance in NUREG 1556, appendix L, page
L-7 says that personnel preparing ANY therapy dose SHOULD have their 
thyroid burden measured.  Further guidance in appendix L says that 1 uCi
should be the evaluation level meaning the level at which evaluation
beyond the initial measurement should be done.  
 
At our facility we'd never get to the evaluation level.  We typically do
2-4 high dose [100-200] therapies and maybe twice that low dose [10-30 mCi]
in a year.  We don't do case specific early releases so currently we do
bioassay only on the personnel doing the high dose administrations.
 
So how do people feel about thyroid bioassay?  On one hand we will likely
have no requirement and on the other guidance requiring more bioassays be
done.  Oh, I forgot typically we're seeing single digit to maybe a twenty
nanocuries [0.001-0.02 uCi] on the bioassays for the high doses.
 
This has been the senders thoughts only, and does not reflect the opinion
or policy of the Denver VA Medical Center, the Department of Veterans
Affairs, or the US Government.
 
Peter G. Vernig, VA Medical Center, Denver, vernig.peter@forum.va.gov
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