Colleen,
We've actually had many discussions about scan safety and radiation exposure from them

Go to this link and click on "Radiation Exposure Levels" http://www.oralcancerfoundation.org/facts/radiation.htm

CT is definitely radiographic and has the highest exposure of any diagnostic scanning modality.

Gary Allsebrook
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Dx 11/22/02, SCC, 6 x 3 cm Polypoid tumor, rt tonsil, Stage III/IVA, T3N0M0 G1/2
Tx 1/28/03 - 3/19/03, Cisplatin ct x2, IMRT, bilateral, with boost, x35(69.96Gy)
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"You are a mist that appears for a little while and then vanishes" (James 4:14 NIV)