Should you change an ROI during a fraction due to camera blockage, without taking imaging to confirm alignment. Once you have an ROI specified and that is tied to an image alignment, i.e., captured after shifts are made from a cbct, does expanding or changing and ROI introducing an offset. Basically, how much can you change the ROI without re imaging, if any? With respect to different treatment site and techniques (3D, DIBH, SBRT, BH SBRT, etc. ), how big of a change is okay?