Different performance of the power Doppler ultrasound modality of two machines in one patient. (A) Machine B, presence of a positive power Doppler signal (arrow) within the region of synovial proliferation. (B) Machine A, this signal is absent. Arrowhead, vessel; *noise on cortical surface.
Ten Cate et al. Arthritis Research & Therapy 2013 15:R162 doi:10.1186/ar4345