As far as I know they just give you a doppler at the 6 month check up - then you have to organise a second visit if it shows you have re-stenosed.
All rather a big hassle if you are located far away.
As for follow up before the 6 months is up - well so far that has proved to be a problem for me - I was liberated in April, never had miraculous results, but things improved little by little. Suddenly that disappeared and now I feel more or less as bad as before I started this journey, however I am not receiving any answers to my emails.
Therefore, seems to me that we'd all be better off looking for doppler's nearer to home, and only returning if we have a re-stenosis - easier said that done I fear! I am located in Ukraine, such a third world pit medically speaking I doubt it they've ever heard of a doppler!
Anyway, we can but live in hope