How accurate are thyroid imaging through ultra sound in determining cysts vs nodes?

Very accurate: One of the most accurate and specific determinations that an ultrasound can make.

Very: I don't have a percent for you but after doing this for over 30 years, that ultrasound is a great tool to determine if a lesion is solid (nodule) or fluid (cyst). The first use of ultrasound was to examine the gall bladder which is a fluid filled structure. Stones (solid) in the gall bladder were easily identified using U/S.