Re: Dose Rates from Patients

["Mike Bohan" <mike.bohan@yale.edu>]

        Reply to:   RE>Dose Rates from Patients

Hi Mike,

In answer to your question, the following statistics are from a large medical
school affiliated hospital which performed 19 I-131 therapies in 1995.  The
average administered dose was 99.4 mCi (Range 5 - 202 mCi, includes some
in-house hyperthyroidism cases).  The average dose rate at 1 meter was 15.2
mR/hr (21.3 mR/hr excluding hyperthyroidism cases) (Range 0.4 - 38 mR/hr @ 1
meter).  The average dose rate after 16 hours (excluding 6 hyperthyroidism
cases) was 7.3 mR/hr (Range 3.5 - 15.4 mR/hr).  Consequently, the percent dose
rate reduction among the thyroid cancer cases was 66% after 16 hours.

In addition to the I-131 therapies, the medical staff assigned (Nurses & Nurses
Aides) to care for these patients also care for all temporary low dose rate
brachytherapy patients. In 1995, the following cases were performed: (37)
Cs-137, average implanted activity ~175 mCi for 48 hrs, (2) Ir-192, average
implanted activity 74.3  mCi, (5) Ra-226, average implanted activity 76 mg for
48 hrs, and (2) Am-241, average implanted activity 7.5 Curies (Sealed, partial
internally shielded sources with 60 keV energy - typical dose rate at 1 meter
less than 4 mR/hr).  

Of 58 monitored caregivers in 1995, (28) received minimal (monthly film badge),
(24) received between 10 - 50 mR/yr, (4) received between 60 - 100 mR/yr, and
(2) received between 110 - 200 mR/yr.


For medicolegal reasons, if not for regulatory compliance, I believe
occupational monitoring should be provided for personnel who care for I-131
patients, but the most important health physics concern for these personnel is
to ensure they are properly trained to avoid internal contamination and to
practice appropriate ALARA techniques to ensure the occupational dose statistics
noted above.

Hope this answers your questions,

Mike Bohan

<><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><
Michael J. Bohan, RSO   |  e-mail: mike.bohan@yale.edu
Yale-New Haven Hospital |    Tele: (203) 785-2950
Radiological Physics    |     FAX: (203) 737-4252
20 York St. - WWW 204   |    As usual, everything I say may be plausibly
New Haven, CT    06504  |    denied at my employer's convenience ...
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--------------------------------------
Date: 09/07/96 3:22 PM
To: Mike Bohan
From: radsafe@romulus.ehs.uiuc.edu

     Here's a question for the medical HPs.

     A patient is given 175 mCi I-131 (thyroid cancer?), what is the
     occupational dose to the attending medical staff?


     What dose rate at 1 meter from the patient?

     Is occupational dose monitoring normally required for medical
     personnel?

     Thanks.

     Mike Russell
     russelmj@songs.sce.com