RE: Thyroid radiation doses are much too high

[John Jacobus <crispy_bird@yahoo.com>]

Mike,

Thanks for the reply.  My comments were toward trying

to understand the logic behind the risk in the paper

under discussion, not it the specifics assoicated with

your calculations.  In reviewing your comments I

realized I may not have been that clear.  



Basically, what I was trying to say is that if we

remove the thyroid for the computed EDE, as you

suggest and I forgot to mention, then the risk to the

other tissues (as such) is only a few rem.  Again,

there is not demonstrated risk below 10 rem.  



--- "Stabin, Michael"

<michael.g.stabin@Vanderbilt.Edu> wrote:

> >I think the risk comes from secondary cancers from

> other organs, not

> thyroid cancer.  If you give a patient 30 mCi of

> I-131, the effective

> dose equivalent is 1170 mrem.  See "Radiation Dose

> Estimates for I-131

> Sodium Iodide" in

> http://www.orau.gov/reacts/DOSETABLES.doc  

> 

> John - two problems with this calculation. First,

> the quantity effective

> dose should not be used in therapy applications.

> Second, this effective

> dose is dominated by the thyroid contribution (340

> mSv/MBq x 0.03 = 10.2

> mSv/MBq, and the ED is 11 mSv/MBq, or 39 rem/mCi, as

> you used). If the

> thyroid is ablated, as the discussion has assumed,

> this contribution is

> removed. However, again, this calculation does not

> make sense in a

> therapy situation.

> 

> 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

> 







=====

+++++++++++++++++++

""A fanatic is one who cannot change his mind and won't change the subject."  Winston Churchill



-- John

John Jacobus, MS

Certified Health Physicist

e-mail:  crispy_bird@yahoo.com



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