RE: I-131 therapy capsules

[Dave Derenzo <dave@uic.edu>]

Dear David,

Thank you for your answer.  I am pretty sure that you are correct in your 
assumption that the material would have been absorbed through the skin had 
you not taken some action.  And had you not conducted a bioassay, you might 
never have known how effective your decontamination efforts were.

Since stomach contents are acidic, do you think that a significant amount 
of I-131 vapor could be released by a burping patient?  If you are 
downwind, you might inhale a dose that way.  I guess what I am trying to 
say is that there might be some very good reasons for doing thyroid 
bioassays, even if stabilized I-131 or I-131 in capsules is 
administered.  Can anyone think of other possible but credible exposure 
pathways?

Dave Derenzo

At 03:39 PM 04/24/2000 -0500, you wrote:
>Our physicians administer the I-131 dose in liquid form only very rarely,
>say to a pediatric patient who doesn't swallow capsules well. A long time
>ago, probably before the capsules got better, I remember a case or two when
>a patient didn't digest the capsule and it was found in a bedpan the next
>day.
>
>Years ago I somehow got a small quantity of liquid I-131 on the skin of my
>finger, about 8 mCi. I know that because I stuck my finger into a dose
>calibrator in the nuclear medicine department and saw that reading. I
>immediately washed my hands very thoroughly with Betadine iodinated surgical
>scrub, which is notorious (along with iodinated x-ray contrast media) for
>interfering with diagnostic nuclear medicine thyroid exams. A check of my
>thyroid the following day revealed no uptake. I'm sure that without the
>blocking by the Betadine I would have accumulated some uptake. Stabilized or
>not, I-131 is readily absorbed through the skin, so a bioassay is definitely
>indicated.
>
>David L. North, Sc.M. DABR
>Associate Physicist
>Department of Medical Physics
>Rhode Island Hospital
>593 Eddy St.
>Providence, RI 02903
>ph: (401)444-5961
>fax: (401)444-4446
>dnorth@lifespan.org
>
>
> > ----------
> > From:         Dave Derenzo
> > Reply To:     radsafe@romulus.ehs.uiuc.edu
> > Sent:         Monday, April 24, 2000 10:07
> > To:   Multiple recipients of list
> > Subject:      RE: I-131 therapy capsules
> >
> > Since we are still on the subject of I-131 therapy capsules, I have heard
> > that there are two reasons why some physicians prefer to administer the
> > solution:
> >
> > 1.  It is much easier to specify a custom dose
> >
> > 2.  A small spot in the stomach of the patient who gets a capsule can
> > receive a high dose before and while the capsule is dissolving.  An
> > attempt
> > to mitigate this dose is usually performed by having the patient drinking
> > a
> > lot of water.  In contrast, the solution mixes readily with stomach
> > contents.
> >
> > Also, with regard to thyroid bioassays, what happens if a person involved
> > with administering the stabilized liquid gets some on his or her
> > skin?  Will it absorb?  If so, do you feel that a bioassay would then be
> > needed?
> >
> > All comments are welcome and I promise not to flame anyone for their
> > opinion.  Others please follow suit.
> >
> > Dave Derenzo
> >
> > At 07:42 AM 04/24/2000 -0500, you wrote:
> > >Does the tech who administers the sample continue with some follow-up on
> > the
> > >patient?
> > >
> > >We had an HP tech visit his mother in the hospital, not a nuclear
> > medicine
> > >patient.  He came back with I-131 (~100 mREM CDE).  Yes, less than 10% of
> > >the limit (50 REM) requiring monitoring, but throw a few of these into
> > the
> > >mix and some #s begin to add up.
> > >
> > >One needs to look at the annual picture when deciding not to monitor.
> > >
> > >Matt Williamson
> > >Indian Point Unit 3
> > >Williamson.m@nypa.gov <mailto:Williamson.m@nypa.gov>


Dave Derenzo, RSO (dave@uic.edu)
UIC Radiation Safety Section, M/C 932
Phones: Voice (312) 996-1177  Fax: (312) 996-8776

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