Is this the situation? You measured the dose at 1 meter from a patient's thyroid after he (she) was administered the I-131, and somehow determined that the maximum total dose at 1 meter would be 75 mrem. I find this difficult to believe for an administered activity in the therapeutic range. Could you fill in some of the details of the administered activity and your measurement and calculation methods?
Putting that aside, consider the dose to other organs in the patient, for an administered activity of 120 mCi. NCRP Report No. 70, "Nuclear Medicine - Factors Influencing the Choice and Use of Radionuclides in Diagnosis and Therapy," lists the following organ dose factors for I-131 administered orally as iodide (all quanties are in mrad/uCi):
liver = 0.35
ovaries = 0.14
red marrow = 0.20
stomach wall = 1.6
testes = 0.085
total body = 0.47
For an administered activity of 120 000 uCi, this would result in organ doses of:
liver = 42.0 rads
ovaries = 16.8 rads
red marrow = 24.0 rads
stomach wall = 192 rads
testes = 10.2 rads
total body = 56.4 rads
The event report seems to imply that, since the purpose of the treatment was to kill the thyroid, the misadministration resulted in "no effects to patient." However, this seems to overlook the potential significant unnecessary exposure to other organs of the patient.
The opinions expressed are strictly mine.
It's not about dose, it's about trust.
Curies forever.
Bill Lipton
liptonw@dteenergy.com
"Larson, Kaye M BAMC-Ft Sam Houston" wrote:
Interesting question brought up while I am sitting here with this table of data, 2001 effective dose estimates for the ablation treatment room, in front of me.
Using the length of treatment hours a patient spends in our ablation room, initial exposure measurements taken at 1 meter, and a calculated decay constant for each patient. I find the total treatment exposures, calculated, for the year is less than 75 mrem, at one meter (we had 19 ablation patients last year.). I don't have nureg 1556, vol 9, in front of me to look at the calculated criteria for release. I don't have patient information which can matter so much in a situation like this (small children at home...). I don't excuse a mistake like what occurred. Just some interesting numbers. Very course, but interesting.
Kaye Larson
Health Physicist
Brooke Army Medical Center, Fort Sam Houston
Kaye.Larson@amedd.army.mil-----Original Message-----
From: William V Lipton [mailto:liptonw@DTEENERGY.COM]
Sent: Friday, June 14, 2002 7:17 AM
To: radsafe@list.vanderbilt.edu
Subject: "Oops, I did it, again." (medical misadministration)
My question: Was the patient released, in accordance with 10 CFR 35.75,
on the basis of a 32 mCi administration? If so, the 500 mrem exposure
limit for a member of the public was probably exceeded.