Fig. 3.

Schematic diagram of sensor-based probe normal positioning. Sensor2 and sensor4 are mounted in the US imaging plane; Sensor1 and sensor3 are mounted co-plane, orthogonal to the US imaging plane.

Schematic diagram of sensor-based probe normal positioning. Sensor2 and sensor4 are mounted in the US imaging plane; Sensor1 and sensor3 are mounted co-plane, orthogonal to the US imaging plane.