Is it feasible to treat craniospinal fields with new generation scanning beam-only proton machines?

Yes, it is feasible to treat craniospinal fields with scanning beam-only technology. Scanning beam proton therapy delivers one discrete Bragg peak "spot" at a time. Large fields require many spots; so treating large fields such as craniospinal fields with scanning beam techniques requires more time ...

I'd also mention that although craniospinal looks cool with protons, there are many common diseases in which dropping the integral dose volume by up to 1/2 (due to lack of exit dose) makes lots of sense. Esophagus is one, lung, left breast and CNS are others, given what we now know about dose baths ...

Pencil beam scanning (PBS) is not only feasible for craniospinal, I would say it's preferable over passive scatter, for efficiency of delivery. Dose rates are now faster for pencil beam than passive scatter, which saves beam time, anesthesia time, room time, therapist time, etc.

One reason to prefer...