In order for the radiation oncologist to design your treatment, the exact size and location of the tumor must first be determined. This is usually done by using scans to create a detailed 3-D image of the treatment area. The scans usually include a CT scan, but they can also include an MRI, PET scan, and ultrasound scan. Your oncologist can rotate the image on his computer screen in order to view the tumor from every angle.
It is very important that the position in which you are scanned is reproduced at the time of treatment. Sometimes temporary skin marks or even tiny tattoos (about the size of a freckle) are made on your body to help the radiation therapist (RT) position you correctly each day for treatment. The radiation therapist, or RT, may position you lying on your stomach, using a special couch-top that allows the breast to fall away from the body. You may also be positioned on your back, with a pad to hold your arm above your head out of the beam’s path. You may be asked to hold still in that position for up to 20 minutes each day.
For some cancers of the left breast, radiation oncologists may use respiratory gating technology. To use this treatment technique, your team studies the motion of your chest as you breathe to evaluate the targeted area's movement in and out of the beam's path. The RT can then turn the beam on only when the targeted area is in a specific position. The RT may ask you to hold your breath (if that is comfortable) while a small cube on your chest broadcasts the position of the ribcage to the control room. Holding your breath while your lungs are expanded creates more space between your heart and breastplate, so that the radiation can target the surgical site while minimizing exposure to the heart and lung tissue. If you don't feel comfortable holding your breath, talk to your RT, and ask if it is possible for you to continue to breathe normally. It is often possible, but it may take a little longer for the treatment since the beam will only turn on when your target is in position.