Hello, Adam or anyone else, have you found any answer to your above questions? I have similar concerns and questions.
Concern 1: For deep inspiration or expiration breath-holding patient, majority of the patient use belly to control their breathing. And for generally speaking, for the comfortable breath-holding (not deep inspiration) cases, upper torso/chest above sternum exhibits small motion. Given that the AlignRT practice guide generally ask user to contour the “stable” area and avoid “belly” area, how do we know if the magnitude number being monitored through the system is accurately reflecting the true tumor position during breath-holding? For example, if we assume the tumor position moves 1cm between the regular breathing to deep inspiration breathing, but the reference ROI that is mostly above sternum area only moves 3-5mm because the patient is belly breather?
Concern 2: Without Active Breath Control system, how do we ensure the patient is holding the exact same breath depth during CBCT acquisition and during treatment beam delivery? Imagine a workflow, where you setup patient initially based on FB ROI (or BB), then you ask patient to hold breath while acquiring CBCT. Now based on the acquired breath hold CBCT, you calculate the required shift by comparing the CBCT to planning breathold CT. After you move the couch, you now have to acquire another reference surface image due to large shift in couch. At this point, how do we ensure, the new reference surface is going to be acquired at the right depth of breath hold as was done for the breath hold CBCT that was used to allow couch shift?
I would greatly appreciate if anyone can share some information/documentation/research papers. Thank you!