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RE: I-131 Tx to pregnant patient
Jeffery
I'm not familiar with the reference that you have, and haven't done fetal
iodine dosimetry for decades. If I remember correctly, the fetal thyroid
dose not concentrate iodine until it is ~ 90 days old. I recommend you look
at an old publication of mine.
FETAL THYROID DOSE FROM INTAKES OF RADIOIODINE BY THE MOTHER
J.R. Johnson
AECL-7694, Health Physics 43 No. 4 (1982) 573-582.
Best of the holidays to you and yours.
John
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-----Original Message-----
From: owner-radsafe@list.vanderbilt.edu
[mailto:owner-radsafe@list.vanderbilt.edu]On Behalf Of JGarrett@mbhs.org
Sent: December 22, 2003 1:00 PM
To: 'radsafe@list.vanderbilt.edu'
Subject: I-131 Tx to pregnant patient
Dear Rad Safers:
I was just informed that there was a patient a couple of weeks ago who
received an I-131 treatment for residual thyroid disease post
thyroidectomy. The pregnancy test on the day of the therapy was negative.
However, a few days later, 5 -6, the patient's period was late. The
subsequent serum test demonstrated a positive test for pregnancy. I have
done some initial calculation for the dose to the uterus/embryo. The amount
of I-131 administered was 75 mCi. The calculations I have performed are
given below. My first question is what method would yall use since there is
such a drastic difference between the two methods? Thanks for your help.
NRC Guide 8.36 Radiation Dose to the Embryo/Fetus Method
Dose = I x f1 x DF, where I = initial activity in uCi = 75 mCi=75000 uCi,
f1 is fractional uptake to the blood = 1.00, and DF is the dose factor =
3.64E-3 rem/uCi
Dose = (75000 uCi)*(1.00)*(3.64E-03 rem/uCi) = 273 rem => 273 rads to the
embryo.
Using Tabular values from internaldosimetry.com
Dose to Uterus = 2.2E-01 rad/mCi
Dose = (75 mCi)*(2.2E-01 rad/mCi) = 16.5 rad to the embryo
Jeffrey A. Garrett, MS, DABR
Chief Physicist
Mississippi Baptist Medical Center
1225 North State Street
Jackson, MS 39202
Office: 601-968-1725
Cancer Center: 601-968-1416 or 1420
Fax: 601-960-3317
The information contained in this email is confidential and is intended for
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