Purpose of CT scan before rads

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Houndmommy
Houndmommy Member Posts: 377
edited June 2014 in Radiation Therapy - Before, During, and After

I know they do a CT scan as part of the setup for rad treatment but what exactly are they looking at?  I assume they can't see any leftover cancer cells from the MX.  Is it used to avoid as much lung and bone as possible?  I thought they used my other breast and my scar to determine the area.

Thanks, Kim

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  • Mouser
    Mouser Member Posts: 245
    edited June 2010

    I don't *think* i had a CT scan before rads in 2007 -- i thought they took X-rays to figure out how to aim the machine. Of course, my diagnosis was somewhat different, since i had only 2 foci (1 DCIS, 1 IDC); i did not have a mx then either. They did do an MRI, because i wanted to avoid the mx, and with 2 foci they wanted to be sure nothing else was going on  -- in the affected breast. It may also depend on age - i was postmenopausal (63).

    Not sure how they'd use the mx scar -- i don't think that would differ between women by where the tumor was, would it? But if you had clean margins from the mx, they wouldn't see anything anyway!

    One thing i've noticed on these boards -- strategies really differ.My sister says some of it is regional -- that  they do more chemo in the east and more rads in the midwest (i think i have that right). And her onc does a yearly MRI, at the 6 months mark between yearly mammos. My onc only does yearly mammos. Some of that may be insurance - mine pays for 1 and only 1 mammo per year, barring "cause" - and you'd better not have it after 364 days, either!!!

    Can you *ask*?  Or maybe someone will come along who knows...

     all the best!

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  • waltersren1
    waltersren1 Member Posts: 17
    edited June 2010

    I actually just had this done yesterday.You're right.It is to avoid as much lung as possible.I asked the tech why they did the CT and thats what she told me.

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  • Houndmommy
    Houndmommy Member Posts: 377
    edited June 2010

    Thanks waltersren1!  And thanks for your post as well Mouser.  

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  • redsox
    redsox Member Posts: 523
    edited June 2010

    The purpose of the CT is to give them a complete picture of the geometry of your body in the area they are going to treat, e.g. breast, chest wall, and/or nodes.  They are looking for lung, heart, and other areas they want to avoid including in the radiation fields.  Also, they are looking for indications of the site of the cancer that they want to target, such as clips placed by the surgeon or seroma in the surgical cavity.  Then they do the treatment planning which means they plan the path of the radiation beams, location, angle, dose.  They look at various arrangements of the beams and the dose pattern on your body to find the one the best hits the target and avoids critical structures such as heart and lungs.  Some of the lung is included in any breast plan, but they try to minimize it. 

    The scar is usually a target area because it has higher risk of recurrence than other areas.  The other breast is not similar enough to guide planning except to keep it out of the line of the radiation beams.

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  • faithfulc
    faithfulc Member Posts: 284
    edited July 2010

    When you start your treatment, ask for your file and there will be printouts of your CT scan with the treatment plan (color lines).  Ask your radiation oncologist to go over this with you.  (I even asked for a copy).

    Redsox explained it so well! But if you can see it in pictures it becomes even clearer.

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