Ellen Herron, BSRT(T)
We set up the same way as Floortje. Works really well going to FB first then to the DIBH reference. We have learned to tighten our rotations (rot, roll and pitch) to a 2 degree tolerance. The tighter these bottom rotations are then the better your patient will setup and less room for variance. We get the rot, roll and pitch as close to zero as we possible can on FB reference setup. Then usually when switching to DIBH they fall right into tolerance. If a minimal lng or lat shift is needed then we do make that shift. Like Floortje said vrt should only be manipulated on DIBH scan by coaching patients breath not moving table.
We’ve also learned during films to look at your spine and sternum (along with breast). If there is a difference from original DRR then you may need to coach them to take more or less of a breath.
Then lastly, check to make sure you have a good ROI drawn. If ROI is not sufficient then parameters on AlignRT computer may flicker, which can make if very difficult to treat a DIBH patient. If you need any examples, then let me know!
Hope this helps!