Real-time three-dimensional flexible needle tracking using two-dimensional ultrasound

Needle insertion is one of the most commonly performed minimally invasive procedures. Visualization of the needle during insertion is key for either successful diagnosis or therapy. This work presents the real-time three-dimensional tracking of flexible needles during insertion into a soft-tissue simulant using a two-dimensional (2D) ultrasound transducer. The transducer is placed perpendicular to the needle tip to measure its position. During insertion the transducer is robotically repositioned to track the needle tip. Positioning of the transducer is accomplished by a compensator, that uses the needle insertion velocity corrected by needle tip velocities to determine out-of-plane motion. Experiments are performed to validate the needle tip pose during tracking. The maximum mean errors in needle tip position along the x-, y- and z-axes are 0.64 mm, 0.25 mm and 0.27 mm, respectively. The error in tip orientations (θ-about the y-axis and φ-about the z-axis) are 2.68° and 2.83°, respectively. This study demonstrates the ability to compute the needle tip pose using a 2D ultrasound transducer. The tip pose can be used to robotically steer needles, and thereby improve accuracy of medical procedures.