Unfortunately, DD your choice is a false one.
Physician-gating will be the limiting factor in the short run.
But once the bolus of patients is treated, demand for treatment will be the limiting factor.
My guess - and that is all it is - is that physician gating will limit use for the first 12-18 months and thereafter the limiting factor will be patient demand.
It is astonishing what foolish things one can temporarily believe if one thinks too long alone ... where it is often impossible to bring one's ideas to a conclusive test either formal or experimental. J.M. Keynes