RE: Thyroid radiation doses are much too high

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

>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



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