Tl SPECT fetal doses

[scherer@uiuc.edu (David Scherer)]

>The following message was forwarded to me from a RadSafe user.  If
>you think it is useful, would you please post the attached response? 
>Thanks.
>
>Mike Stabin
>
>-------------------------------------------------------------------------------
>Does anyone know of any dosimetry references which may be useful
>for 
>determining fetal doses for Thallium SPECT heart studies?  Early
>estimates 
>suggested moderate to low doses. However recently I have heard that 
>Tl readily crosses the placenta, a point that these estimates did not take 
>into account.
>
>Any help would be appreciated.
>
>Geoff Clarke
>
>---------------------------------------------------------------------------
----------
>
>Our best estimates of the fetal doses are as follows:
>
>Planar study, 150 MBq (4 mCi)
>Early pregnancy - 15 mGy (1.5 rad)
>3 months pregnant - 8.7 mGy (0.87 rad)
>6 months pregnant - 7.1 mGy (0.71 rad)
>9 months pregnant - 4.1 mGy (0.41 rad)
>
>SPECT imaging, 110 MBq (3 mCi)
>Early pregnancy - 11 mGy (1.1 rad)
>3 months pregnant - 6.4 mGy (0.64 rad)
>6 months pregnant - 5.2 mGy (0.52 rad)
>9 months pregnant - 3.0 mGy (0.30 rad)
>
>Thyroid imaging, 80 MBq (2.2 mCi)
>Early pregnancy - 7.8 mGy (0.78 rad)
>3 months pregnant - 4.6 mGy (0.46 rad)
>6 months pregnant - 3.8 mGy (0.38 rad)
>9 months pregnant - 2.2 mGy (0.22 rad)
>
>These numbers for administered activity are just typical values used per
>study - they may vary.  The values DO account for placental crossover,
>with data taken from studies performed on guinea pigs by Wegst (1992).
>
>All of the above data taken from the master's thesis of Joy Russell,
>University of Tennessee, 1995, Radiation Absorbed Dose to the
>Embryo/Fetus from Nuclear Medicine Procedures.  Article being prepared
>for HPJ, Russell and Stabin, 1995.
>
>Mike Stabin
>Radiation Internal Dose
>  Information Center
>Oak Ridge Institute for 
>  Science and Education
>P.O. Box 117
>Oak Ridge, TN  37831-0117
>423-576-3449  ph
>423-576-8673  fax
>stabinm@orau.gov  Internet
>