doppler ultrasouns

I haven't quite figured out how this group works yet, but I have a question:I had surgery for a brain infection 3 months ago and then developed DVT and put on warfarin for 6 months.  The neurosurgeon wonders if I should have a doppler ultrasound before  stop using the coumadin so make sure the DVT has resolved.Does anybody have any experience or opinions about this?Thanks.