[ RadSafe ] Energies used in Breast Irradiation

[Rees, Brian G]

I have a friend that had Milk Duct In Situ Carcinoma (breast cancer), she had a lumpectomy and is now going to have breast irradiation.  Since I had the opportunity for her to ask, I had her ask about the treatment.  The energy of the x-rays will be 6 and 18 Mev, these seem awfully high since the probability of interaction is pretty low for an 18 Mev x-ray in tissue... can somebody help me to understand this?  They also mentioned a "boost" of 10 Gy, what does that refer to? ("whole breast dose is reached at 4256 cGy, boost delivers an additional 1000 cGy")

Thanks,
Brian Rees, CHP, RRPT