Well, I am afraid that all of us will be confronted with problems with abdomen setups. This is inherently related to the technology used. If you have a flat surface, or one with few structures in it, like a flat belly, then your system cannot find a proper solution (in longitudinal direction) and you always have to caution the proposed solution. But “fortunately” not all bellies are flat… But even then it is probably still near impossible to provide universal guidelines on how to draw you ROIs.
I try to provide a few hints that might help….
– Don’t include in your ROI any clothing or hairy regions.
– Don’t include in your ROI any “artefacts” or parts of body structures which might not be contoured in a coherent way in your ROI, e.g. stoma
– Important. Try to move your patient to the proper treatment position without using AlignRT. You need to have a good undertstanding of the location of your isocenter. Then, with the help of anatomical landmarks and your room laser you can find the position within a few cm. Use AlignRT for the final fine tuning of the position. But be aware that the longitudinal position might be wrong by even >10cm. So always use “common sense” to validate the final position and it might be best to verify with kV-kV imaging.
If you provide me your email, I can send you a few sample ROIs.