[ RadSafe ] Energies used in Breast Irradiation

[Dixon, John E. (CDC/ONDIEH/NCEH)]

Hmm. I am not a medical physicist, but I agree with your statement that these photons are of a very high energy for this purpose. I don't know the stopping power of breast tissue, but this looks like the teletherapy might involve charged particles (given the energy). A related example using photons can be illustrated using mammography done with 30-40 kev photons. Higher shallow doses in tissue with photons can be obtained using lower photon energies (lower than 18 Mev anyway) and higher currents (more photons per unit time). I don't know what "boosting" means; but it might have something to with enhancing the effectiveness of radiation on the tissue by using oxygen enhancement.

Please send the answers to your questions once you get them.

Regards,
John Dixon

-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu [mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Rees, Brian G
Sent: Monday, January 24, 2011 3:45 PM
To: The International Radiation Protection (Health Physics) Mailing List
Subject: [ RadSafe ] Energies used in Breast Irradiation

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
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