A pressure tourniquet having a window transparent to ultrasound is wrapped around a leg or another anatomical structure containing veins. An ultrasound transducer is placed in contact with the window of the tourniquet. The window is adjacent the anatomical structure and the transducer probes a dilated vein with ultrasound. The transducer can measure the size of the vein and detect reflux. A pneumatic bladder on the tourniquet is inflated to apply pressure to the anatomical structure so that the vein is compressed by the tissue of the surrounding anatomical structure. As pressure from the tourniquet reduces the diameter of the vein, competency of the vein valve can be temporarily restored to indicate the proper reduced diameter required to restore venous function. An electrode catheter is introduced into the vein to apply energy for durably molding the vein to the reduced diameter.