Hi there Hillbilly,
I've just finished 21 radiotherapy sessions to left breast. I had mine at hospital in Melbourne where they do Deep Inspiration Breath Hold for radiation on left breast. Basically you just take a big deep breath in and hold it while they shoot the rad beam through. Apparently it's so targeted the breath hold gives clear pathway that means rads miss the heart. Truly amazing, just a breath hold can make all the difference. If you google Deep Inspiration Breath Hold you can check it out. Ask your radiation oncologist about it. I don't know if all hospitals do it like that but I reckon it's worth checking out. Our bodies go through enough as it is, we don't need further complications like rad injuries to the heart.
Good luck with it all,
Jennie