[ RadSafe ] Energies used in Breast Irradiation

??µ?t???? ???a??d?? od at tlmq.com
Tue Jan 25 02:26:11 CST 2011

This is standard breast tumor radiotherapy. 6 MV have a Dmax in a depth of 
about 1.5 cm, while 18 MV in about 3.5 cm. The point is to irradiate, 
homogeneously, the whole breast gland and spare (to a certain degree) the 
skin. The opposing, 6 MV irradiating fields are placed tangential to the 
chest wall, so the maximum tissue distance to be traveled by the photons can 
often be more than 20 cm. Our problem is usually to get enough dose to the 
center of the target volume, so sometimes 6 MV dose is supplemented by the 
more penetrating 18 MV fields.

Now, we are prescribing 50 Gy to the breast as a whole. In some centers this 
is split in two parts: 40 Gy to the whole breast and 10 Gy to the site of 
the tumor (which is called "boost")


THEAGENEION Anticancer Hospital



----- Original Message ----- 
From: "Rees, Brian G" <brees at lanl.gov>
To: "The International Radiation Protection (Health Physics) Mailing List" 
<radsafe at health.phys.iit.edu>
Sent: Monday, January 24, 2011 10:44 PM
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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