Frieze - How on EARTH do you get those wear patterns out?

I've had some frieze carpets that clean right up no problem. Then the are the ones that somebody had their sofa on their spot and in front of the sofa was a lot of foot traffic....

I've had several homes like this now, and literally I'm getting SICK because the wear patterns REALLY look like embedded dirt.

I stuck my Rotovac on each spot for well over a minute and hit it with a lot of heat and chems and it still didn't look much better - perhaps some improvement.

I hate it because I keep...

Frieze - How on EARTH do you get those wear patterns out?