Is it feasible to use MV fluoroscopy to monitor the treatment port for left-sided breast cancer with DIBH?

Absolutely. When we first started doing DIBH, I used to stand at the machine with the MV fluoro on to watch the treatment. It was indeed very reassuring. As I recall, I was able to see the beating heart beneath the block, or maybe was just able to see the edge of the beating heart at the field edge....