There have been a number of interesting studies with ultrasound and carpal tunnel. There was a reasonably recent RCT from a group in Taiwan [Chang et al. (2014). "Comparative effectiveness of ultrasound and paraffin therapy in patients with carpal tunnel syndrome: a randomized trial." BMC Musculoskelet Disord 15(1): 399] which gave good results (especially for pain and function) using ultrasound 2 x weekly at a fairly typical dose of 1MHz, 1.0 W cm^2 Pulse 1:4, 5 mins. The US treatment was compared with paraffin wax therapy and the US came out more effective.