Some embodiments of a device comprise a tubular flexible body that includes a channel though a longitudinal axis; a first sensor that is located in a distal end of the tubular flexible body; a second sensor that is located in the distal end of the tubular flexible body; and wiring that connects to the first sensor and the second sensor and that extends to a proximal end of the tubular flexible body, wherein a sensed orientation of the first sensor is oriented opposite to a sensed orientation of the second sensor.