Hi Xue,
I think it is important to understand the role of ultrasound in such a case.
The RA is obvious clinically and the erosions are best monitored radiographically.
In these patients I feel like the role I play is to give an update as to the severity of active inflammation (synovitis) as this will given symptoms and also management.
If we see with the colour / power Doppler that there is not much evidence of flow in the joints there will be no real reason to change the medications. If we see reduction in flow over serial scans that is reassuring and if we see a rapid escalation in flow then there is often an associated exacerbation of symptoms and the medications need to reviewed / increased / changed.
Steve