Re: medical misadministration to child

["Michael G. Stabin" <michael.g.stabin@vanderbilt.edu>]

Two technical problems here:



> From: "William V Lipton"

> Thus, the dose estimate would be:

> (5.72 E-3 mrem/pCi)*(400 uCi)*(1 E6 pCi/uCi) = 2.3 E6 mrems = 2300 rems



At this level, dose equivalent has no scientific meaning, one should report

absorbed dose (Gy preferably, or rad in antediluvian units). Also, "Sv" and

"rem" are already plural, in my understanding.



There are more up-to-date and detailed dose estimates in ICRP 53 for the

10-year-old for I-131 NaI of:



790 mGy/MBq at 35% uptake

1500 mGy/MBq at 45% uptake

1900 mGy/MBq at 55% uptake



which would suggest doses of 11700, 22000, or 28000 mGy (1170, 2200, or 2800

rad). That's pretty good agreement with the older Reg Guide numbers.

Hyperthyroid individuals will have higher uptakes than euthyroid

individuals, but generally with faster washout. I have not seen a well

characterized kinetic model for I-131 NaI in hyperthryoid children, so it's

hard to get much more accurate with the dosimetry.



> The nonstochastic occupational limit for a minor would be 5 rems.  It

> seems like the patient could expect a "significant adverse" health

> effect.



We know that the nonstochastic occupational limit of 500 mGy is pretty low

for most organs, where a threshold of 10's of Gy are needed to show a

nonstochastic effect (as per experience with radiation therapy). The testes

can show transient effects at the 500 mGy level, so we set it this low for

all organs. It is not reasonable to expect a nonstochastic effect at 51 mSv

(5.1 rem) because we have set an administrative level of 50 mSv (5 rem), 10

times lower than the low numbers for adults. Children may be more

radiosensitive, but this low level is based on administrative concerns, not

radiobiology. Dr. Marcus can probably enlighten us about what, if any,

nonstochastic effects might be expected from these doses.



Mike



Michael G. Stabin, PhD, CHP

Assistant Professor of Radiology and Radiological Sciences

Department of Radiology and Radiological Sciences

Vanderbilt University

1161 21st Avenue South

Nashville, TN 37232-2675

Phone (615) 343-0068

Fax   (615) 322-3764

Pager (615) 835-5153

e-mail     michael.g.stabin@vanderbilt.edu

internet   www.doseinfo-radar.com







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