@copyman

Outside early proton systems from way back, all the modern proton systems are generally considered "adaptive" with gantires allowing 6 degrees of freedom (x, y, z, roll, pitch, yaw) and so on.

HYPO-fractioning is delivering fewer but higher dose sessions.

Not all adaptive technology is perfect in any sense, for years people tried to get ultrasound to do roll, pitch, yaw, x, y, z into the ultrasound head and make a volume, just never worked super fast is the issue. Maybe the ETHOS system which is CT adaptive, has trouble processing things fast enough too, as it hasn't produced better results. The MR adaptive systems are great, but they won't beat proton which has been adaptive for some time and have only improved, the MR systems are still pretty new at it but are doing well and getting good reviews. Proton has negative views often from radiation oncology because way back proton was expensive and caused departments to lose money, now the technology is there but doesn't have their confidence yet, but for my money I will look for a real good proton system.

@copyman
MRI-guided proton therapy is an emerging, cutting-edge technology that combines real-time MR imaging with proton beam delivery, though it is currently in the experimental/prototype phase rather than standard clinical use. This integration provides superior soft-tissue contrast, allowing for real-time tracking of moving tumors (e.g., liver, lung) to improve precision.
ScienceDirect.com

Proton therapy machines commonly use CT guidance to ensure accuracy, though the approach differs from conventional X-ray (photon) machines. Modern proton centers use in-room, cone-beam CT (CBCT), or CT-on-rails systems for daily image guidance to verify patient position and adapt to anatomical changes.
National Institutes of Health (.gov)